A Comprehensive Guide To Forgings: Everything You Need to Know About Forgings and Forged Products
Forging is a metalworking process that involves shaping metal using compressive forces. A hammer, die and anvil are used to deform the metal. Forging is the primary means of manufacturing wrought iron and steel for the purposes of creating objects or structures. In this comprehensive guide, you will learn about variations of forging and forged products.
Forging is a metal shaping technique using compressive, localized forces. The process involves hammering or pressing most often used to make parts out of a variety of metals and alloys. Forged parts may be machined after forging, but are more often machined before, as this can cause distortion of the part. Forging is common in the production of commercial and industrial equipment, such as automobile parts, tools, mechanical components for machines, and even musical instruments.
Forging has been a staple metal fabrication technique since the time of the ancient Mesopotamians. Since its origins in the fertile crescent, forging has experienced significant changes, resulting in a more efficient, faster and more durable process. This is because today, forging is most commonly performed with the use of forging presses or hammering tools powered by electricity, hydraulics or compressed air. Some of the common materials used for forging are carbon steel, alloy steel, microalloy steel, stainless steel, aluminum and titanium.
The earliest evidence for forging comes from copper smelting sites in Egypt around 5500 BCE where copper was hammered into shape by hand before being heated to form ingots.
Material of Forgings
What are forgings made of? Forging materials are mainly carbon and alloy steels of various compositions, followed by aluminum, magnesium, copper, titanium, etc. and their alloys. The original state of the metal material is steel bar, ingot, metal powder and liquid metal. The ratio of the cross-sectional area of the metal before deformation to the cross-sectional area after deformation is called the forging ratio. The correct choice of forging ratio, reasonable heating temperature and holding time, reasonable starting forging temperature and final forging temperature, reasonable deformation and deformation speed is very relevant to improve product quality and reduce costs.
Generally, small and medium-sized forgings are made of round bar or square bars as billets. The grain organization and mechanical properties of the bar are uniform and good, the shape and size are accurate, the surface quality is good, and it is easy to organize mass production. As long as the heating temperature and deformation conditions are reasonably controlled, forgings with excellent performance can be forged without large forging deformation.
Ingots are only used for large forgings. Ingot is cast organization, with large columnar crystal and loose center. Therefore, through large plastic deformation, the columnar crystals must be broken into fine grains and the sparse compacted to obtain excellent metal organization and mechanical properties.
The powder metallurgy precast billets are pressed and sintered, and powder forgings can be made in the hot state by die forging without flying edges. The forging powder is close to the density of general die forgings, with good mechanical properties and high precision, which can reduce the subsequent cutting process. Powder forgings have uniform internal organization, no segregation, and can be used to manufacture small gears and other workpieces. However, the price of powder is much higher than the price of general bars, and the application in production is somewhat limited.
By applying static pressure to the liquid metal poured in the die chamber and making it solidify, crystallize, flow, deform plastically and form under pressure, a die forged part of the desired shape and properties can be obtained. Liquid metal die forging is a forming method between die casting and die forging, especially suitable for complex thin-walled parts which are difficult to be formed by general die forging.
Forging materials in addition to the usual materials, such as various components of carbon steel and alloy steel, followed by aluminum, magnesium, copper, titanium and other alloys, iron-based high-temperature alloys, nickel-based high-temperature alloys, cobalt-based high-temperature alloys of deformation of the alloy also use forging or rolling to complete, but these alloys due to its plastic zone is relatively narrow, so the forging will be relatively more difficult, the heating temperature of different materials, open forging temperature and final forging temperature There are strict requirements for the heating temperature, opening forging temperature and final forging temperature of different materials.
ASTM / ASME A/SA 105 ASTM / ASME A 350 , ASTM A 181 LF 2 / A516 Gr.70 A36, A694 F42, F46, F52, F60, F65, F706.
Carbon steel forgings may contain many alloys such as chromium, titanium, nickel, tungsten, zirconium, cobalt, etc., but the carbon content determines hardness. For applications that do not require high operating temperatures or high strength, forged carbon steel parts are more economical than other forged metals.
ASTM / ASME A/SA 182 & A 387 F1, F5, F9, F11, F12, F22, F91
ASTM SB 61 , SB62 , SB151 , SB152 UNS No. C 70600 (Cu-Ni 90/10), C 71500
(Cu-Ni 70/30), UNS No. C 10100, 10200, 10300, 10800, 12000, 12200
ASTM SB564, SB160, SB472, SB162 Nickel 200 (UNS No. N02200), Nickel 201 (UNS No. N02201), Monel 400 (UNS
No. N04400), Monel 500 (UNS No. N05500), Inconel 800 (UNS No. N08800), Inconel 825 (UNS No. N08825), Inconel:
600 (UNS No. N06600), Inconel 625 (UNS No. N06625), Inconel 601 (UNS No. N06601), Hastelloy C 276 (UNS No. N10276), Alloy 20 (UNS No. N08020).
Different alloys are combined with steel to give forged alloy steel parts the desired quality. Alloys, including chromium, manganese, molybdenum and nickel, improve strength, toughness and wear resistance. The use of other alloying elements in forged steels allows the manufacture of parts with high corrosion and creep resistance and increased strength at high temperatures.
Open die steel forgings for general engineering purposes – alloy special steels
|W Nr.||EN 10250-3||C||Si||Mn %||P||S||Cr||Mo||Ni||Other %||Heat treatment|
|%||% Max.||% Max.||% Max.||% Max.||% Max.||% Max.|
|1.6311||20 MnMoNi 4-5||0,17-0,23||0,40||1,00-1,50||0,035||0,035||0,50||0,45-0,60||0,40-0,80||*||Q+T|
|1.6511||36 CrNiMo 4||0,32-0,40||0,40||0,50-0,80||0,035||0,035||0,90-1,20||0,15-0,30||0,90-1,20||*||Q+T|
|1.658||30 CrNiMo 8||0,26-0,34||0,40||0,30-0,60||0,035||0,035||1,80-2,20||0,30-0,50||1,80-2,20||*||Q+T|
|1.6582||34 CrNiMo 6||0,30-0,38||0,40||0,50-0,80||0,035||0,035||1,30-1,70||0,15-0,30||1,30-1,70||*||Q+T|
|1.6773||36 NiCrMo 16||0,32- 0,39||0,40||0,30-0,60||0,035||0,035||1,60-2,00||0,25-0,45||3,60-4,10||*||Q+T|
|1.6932||28 NiCrMoV 8-5||0,24-0,32||0,40||0,15-0,40||0,035||0,035||1,00-1,50||0,35-0,55||1,80-2,10||V 0,005-0,15||Q+T|
|1.6956||33 NiCrMoV 14-5||0,28-0,38||0,40||0,15-0,40||0,035||0,035||1,00-1,70||0,30-0,60||2,90-3,80||V 0,08-0,25||Q+T|
|1.7003||38 Cr 2||0,35-0,42||0,40||0,50-0,80||0,035||0,035||0,40-0,60||–||–||*||Q+T|
|1.7006||46 Cr 2||0,42-0,50||0,40||0,50-0,80||0,035||0,035||0,40-0,60||–||–||*||Q+T|
|1.7033||34 Cr 4||0,30-0,37||0,40||0,60-0,90||0,035||0,035||0,90-1,20||–||–||*||Q+T|
|1.7034||37 Cr 4||0,34-0,41||0,40||0,60-0,90||0,035||0,035||0,90-1,20||–||–||*||Q+T|
|1.7035||41 Cr 4||0,38-0,45||0,40||0,60-0,90||0,035||0,035||0,90-1,20||–||–||*||Q+T|
|1.7218||25 CrMo 4||0,22-0,29||0,40||0,60-0,90||0,035||0,035||0,90-1,20||0,15-0,30||–||*||Q+T|
|1.722||34 CrMo 4||0,30-0,37||0,40||0,60-0,90||0,035||0,035||0,90-1,20||0,15-0,30||–||*||Q+T|
|1.7225||42 CrMo 4||0,38-0,45||0,40||0,60-0,90||0,035||0,035||0,90-1,20||0,15-0,30||*||Q+T|
|1.7228||50 CrMo 4||0,46-0,54||0,40||0,50-0,80||0,035||0,035||0,90-1,20||0,15-0,30||–||*||Q+T|
|17243||18 CrMo 4||0,15-0,21||0,40||0,60-0,90||0,035||0,035||0,90-1,20||0,15-0,25||–||*||Q+T|
|1.7361||32 CrMo 12||0,28-0,35||0,40||0,40-0,70||0,035||0,035||2,80-3,30||0,30-0,50||0,60||*||Q+T|
|1.7707||30 CrMoV 9||0,26-0,34||0,40||0,40-0,70||0,035||0,035||2,30-2,70||0,15-0,25||0,60||V 0,10-0,20||Q+T|
|1.8159||51 CrV 4||0,47-0,55||0,40||0,70-1,10||0,035||0,035||0,90-1,20||–||–||V 0,10-0,25||Q+T|
|1.8523||40 CrMoV 13-9||0,35-0,45||0,15-0,40||0,40-0,70||0,035||0,035||3,00-3,50||0,80-1,10||–||V 0,15-0,25||Q+T|
* Can contain Al, Ti, V, Nb singly or in combination for grain refining.
Open die steel forgings for general engineering purposes – non alloy quality and special steels
|Nr.||EN 10250-2||C||Si||Mn %||P||S||Cr||Mo||Ni||Cr+Mo+Ni||Al||Heat treatment|
|%||% Max.||% Max.||% Max.||% Max.||% Max.||% Max.||% Max.||% Min.|
|1.0038||S 235 JRG 2||≤0,20||0,55||≤1,40||0,045||0,045||0,30||0,08||0,30||0,48||0,020||N|
|1.1133||20 Mn 5||0,17-0,23||0,40||1,00-1,50||0,035||0,035||0,40||0,10||0,40||0,63||0,020||N+T|
|1.1158||C 25 E||0,22-0,29||0,40||0,40-0,70||0,035||0,035||0,40||0,10||0,40||0,63||–||N+T|
|1.117||28 Mn 6||0,25-0,32||0,40||1,30-1,65||0,035||0,035||0,40||0,10||0,40||0,63||–||N+T|
|1.1203||C 55 E||0,52-0,60||0,40||0.60-0,90||0,035||0,035||0,40||0,10||0,40||0,63||–||N+T|
- Microalloyed steels
Microalloyed steels improve mechanical quality by adding trace amounts of alloying components to enhance the properties required for specific applications while reducing production costs. Forged microalloyed steels are widely used in automotive applications, including driveline components, crankshafts and connecting rods. Microalloyed steels are often used in conjunction with controlled cooling to eliminate the need to treat the part as a secondary operation.
ASTM A 182, A 240 F 304, 304L, 304H, 316, 316L, 316Ti, 310, 310S, 321, 321H, 317, 347, 347H, 904L.
ASTM / ASME A/SA 182 F 44, F 45, F51, F 53, F 55, F 60, F 61.
Stainless steels are iron alloys with a chromium content of at least 10.5%. They are known for their excellent corrosion resistance, durability, formability, recyclability, long life and resistance to extreme temperatures, making them suitable for a variety of applications.
Titanium alloys are more difficult to forge than other alloys and require close control of forging temperatures to achieve optimum mechanical properties. Forged titanium components are preferentially used in applications requiring high strength, corrosion resistance or operating temperatures. Parts made of forged titanium are also lighter than many other metals and alloys.
Depending on the choice of material, forged metal parts are suitable for a variety of applications in multiple industries. Each forged metal has many advantages when used to make mechanical parts.
Benefits of forged carbon, alloys and microalloys.
There are many benefits to forging with carbon, alloys and microalloys, including.
Benefits of carbon steel. Forging carbon steel produces parts that are resistant to wear, fatigue and abrasion.
Benefits of forging alloys. Forged alloys offer the following benefits: good availability, low cost, superior mechanical properties, and ease of machining.
Benefits of forged microalloys. Depending on the alloy and the forging and cooling temperatures, microalloys offer many advantages, such as improved high circumferential fatigue resistance and increased strength at higher static and dynamic loads.
Forging produces parts that are cost-effective, robust, reliable and can be formed into a variety of shapes. Machine forging processes combined with forged materials such as carbon, alloyed and micro-alloyed steels can provide excellent metallurgical properties suitable for a wide range of applications. Cornell Forge is proud to use all of these materials to meet our customers’ specifications and requirements.
Advantages for Steel Forgings
What makes forged products the first choice for various industries? Listed below are the benefits of using metal forging.
As a result, the potential for unexpected failure under stress or temperature differentials in mechanical forging is negotiated.
The use of steel forgings is the best way to ensure a product is made with high quality and durability. What makes forged products the first choice for various industries? Listed below are the benefits of using metal forging:
- Cost Effective
Forging offers significant cost advantages, especially in high-volume precision metal fabrication. Materials used in forging are cheaper than other materials used in metalworking processes. In addition, in most cases, it requires fewer auxiliary operations. In high-precision metal fabrication, it is possible to obtain finely machined materials with precise dimensions and good surface finish. Therefore, it requires very low machining, which results in cost efficiency.
- Different alloys
The great advantage of machine forging is that most metals can be forged into the desired shape. The forging process can be applied to any type of metal. Each metal has a unique set of properties that can be best used for a specific part as needed. Some common forged metals include aluminum, alloys, stainless steel, brass, carbon, titanium, copper, brass, etc. In industries that require high temperatures, alloys containing cobalt, molybdenum or nickel may be used. By using strong forged metals, industry can reduce the use of expensive alloys to obtain high strength parts.
- Better metallurgical properties
Sometimes, selective heating and uneven cooling that occurs in a machine can cause a specific part to fail. The final product obtained in the forging process is free of any internal voids and has good grain flow. The forging process reduces shrinkage and porosity, which are common in cast products.
Forged products are usually lightweight compared to castings, which makes it easy to transport, install, and move around. This also reduces cost since there will be less volume of material used in making these parts.
- High Strength
The strength of forged products can be as high as 70% compared to castings with the same dimensions. This is because the grain size in the metal is smaller compared to those in castings, allowing for better ductility or malleability when being shaped by tools during production.
The ductility or malleability of forged products allows them to withstand impact without breaking easily like castings do when struck with an object with a similar mass moving at high speeds. This property makes forged parts ideal for applications where high impact resistance is required such as shock absorbers and bumpers.
Forged products have a longer life span than other types of metal products. This is because they do not get worn out easily and can withstand high pressure, stress and strain.
- Ease of manufacture
Forged products can be made in different shapes and sizes according to the needs of customers. They can also be made with lower costs and faster production times than other types of metal products.
When compared to machined parts, forged parts have more tolerance in sizes and weights due to their uniformity throughout the process.
Lower manufacturing costs. The process of making forgings is quite simple, which means that it can be done with little or no waste of metal materials. This results in lower costs compared to other manufacturing processes.
- Improved dimensional accuracy
Forgings are much more accurate than castings when it comes to dimensions, especially in thin-walled parts that may become distorted during cooling. Forged parts can also be produced in complex shapes which cannot be achieved through other methods like casting or forging.
- PDF: Steel Forging Material Data (👈Click it to download)
Disadvantages of Forgings
The main disadvantages of forging are:
- The secondary finishing process requires.
- The size might be limited because of the press size.
- The maintenance cost is high.
- The metals gots distorted if works below the required temperature.
- The initial cost is high. In advantage, I have mentioned operation cost is low.
- Some material can not be forged in the forging process.
- The close tolerance is might not achieve in this process or difficult to maintain.
Characteristics of forgings
Compared with castings, metal can improve its organization and mechanical properties after forging processing. Casting organization after forging method of thermal processing deformation due to metal deformation and recrystallization, so that the original coarse dendritic and columnar grains into fine grains, uniform size of the equiaxial recrystallization organization, so that the ingot within the original segregation, loosening, porosity, slag and other compaction and welding, the organization becomes more compact, improve the plasticity and mechanical properties of the metal.
The mechanical properties of castings are lower than the mechanical properties of forgings of the same material. In addition, forging processing can ensure the continuity of metal fiber organization, so that the fiber organization of forgings and forging shape to maintain consistent, metal flow line integrity, can ensure that the parts have good mechanical properties and long service life using precision die forging, cold extrusion, warm extrusion and other processes to produce forgings, are incomparable to castings.
Forgings are objects in which metal is pressed and shaped by plastic deformation to the required shape or suitable compression force. This force is typically achieved through the use of a hammer or pressure. The forging process builds delicate grain structures and improves the physical properties of the metal. In the real world use of parts, a correct design enables the flow of particles in the direction of the main pressure. Casting is a metal forming object obtained by various casting methods, i.e., the smelted liquid metal is injected into a pre-prepared cast shape by pouring, pressure injection, inhalation or other casting methods, cooled, and after sand-fall, cleaning and post-treatment, the object with certain shape, size and properties is obtained.
What is the purpose of forging?
Forging is a process that uses heat and pressure to shape metal into various parts. It is one of the oldest methods of manufacturing steel, dating back to the Bronze Age. Forged parts are typically stronger than their cast counterparts because they have been worked from a solid piece of material rather than poured into a mold.
The purpose of forging is to create metal parts. Compared to other manufacturing methods, metal forging produces some of the sturdier manufactured parts available. As metal is heated and pressed, minor cracks are sealed, and any empty spaces in the metal close.
The hot forging process also breaks up impurities in the metal and redistributes such material across the metalwork. This vastly reduces inclusions in the forged part. Inclusions are compound materials implanted inside steel throughout manufacturing that cause stress points in the final forged parts.
While impurities should be managed during the initial casting process, forging further refines the metal.
Another way that forging strengthens metal is by alternating its grain structure, which is the metal material’s grain flow as it deforms. Through forging, a favorable grain structure can be created, making the forged.
The forging process is highly multipurpose and can be used on small parts just a few inches in size to large components that weigh up to 700,000 lbs. It is used to produce critical aircraft parts and transportation equipment. Forging is also used to fortify hand tools such as chisels, rivets, screws, and bolts.
The exact definition of forging depends on the type of material being forged. In general terms, it is working metal into shape by means of pressure without heating it above red heat (approximately 1,100°F). This process does not change the chemical composition of the metal but does change its mechanical properties.
There are three basic types of forges: open hearth, closed hearth and electric furnace. Open hearth is the oldest type of forge and uses charcoal as fuel in an open hearth fire pit with a water-cooled hood over it; closed hearth uses a controlled blast furnace with forced air circulation; electric furnace uses electricity as its power source and is used for making small forgings such as screws or bolts.
What are the different types of forgings?
The pounding action of forging deforms and shapes the metal, which results in unbroken grain flow. This causes the metal to retain its strength. Ancillary effects of this unique grain flow include the elimination of defects, inclusions, and porosity in the product. Another advantage of forging is the relatively low costs associated with moderate and long production runs. Once the forging tools have been created, products can be manufactured at relatively high speeds with minimal downtime.
Many different types of forgings are available. The main types of forging include:
- Preform Forging
What is preform forging? In preform forging, a blank is shaped to a desired shape by hammering. The finished product will have the same size and shape as the original blank. This type of forging is most commonly used for sheet metal or wire drawing.
- Flashless Forging
What is flashless forging? Flashless forging is similar to preform forging except that fewer blows are applied during the process, which means that there will be less material removed from the final product. Flashless forging can also be used with plastic and other materials that cannot withstand high temperatures during the forging process.
- Hammer Forging
What is hammer forging? Hammer forging uses hammers of various sizes and weights to shape material into desired shapes. Hammer forging usually takes place at room temperature but it can also be performed at elevated temperatures if necessary. This type of forging is most commonly used for making small parts such as fasteners and pins because it produces very precise dimensions without requiring expensive tooling equipment or skilled labor for its production.
- Press Forging
What is press forging? Press forging is a metalworking process that forms metal parts by applying pressure to a die. The metal is placed in the press with the die, and then the press is closed. Pressure is applied and the metal undergoes plastic deformation.
The advantage of press forging over other processes like extrusion is that it can be used to create complex shapes, with high-quality surfaces and tolerances. This means that more parts can be made at lower cost than through other methods. A disadvantage is that it requires expensive tooling and dies, which must be replaced after repeated use.
- Impact Forging
What is impact forging? Impact forging is a metalworking process that uses hammers or presses to shape hot metal stock into complex parts with very close tolerances (typically within 0.005 inches). It’s often used for mass production of small parts like fasteners or automotive components because it produces high volumes of identical parts quickly and cheaply.
- Open-Die Forging
What is open-die forging? This is the most common type of forging process, and it’s used to make parts that are too large or complex to be made by other methods. Open-die forgings are produced in a single operation. The part is placed into the die, which closes around it, and then the material is subjected to high pressure until it flows into the shape of the die. Open-die forgings are often used to make parts with features such as threads or holes.
- Closed-Die Forging
What is closed-die forging? Closed-die forging (also called closed-face forging) differs from open-die forging in that there is no gap between the punch and die faces during the forging process. Closed dies can produce more precise parts than open dies because there is no gap for material to escape through if something goes wrong during the forging process. Therefore, closed dies can produce better tolerance parts than open dies, but they require more time and energy to operate because they have fewer cycles per minute than open dies – typically only one or two compared with 10 or more for an open die.
- Net Shape Forging
What is net shape forging? Net shape forging is the process of making a part from a solid metal billet by using a press to shape it into its finished form. The term “net shape” refers to the fact that the dimensions of the billet are those of the final product, so no additional machining is needed to finish it. For example, if you wanted to make a shaft that was 10 mm in diameter and 100 mm long, you would buy or make a billet of steel that was 10 mm in diameter and 100 mm long. The resulting shaft would be “net shaped” because all of its dimensions are set by the size of the original billet.
- Isothermal Forging
What is isothermal forging? Isothermal forging is a method used to increase material quality and reduce stress concentration in metal parts. Isothermal forging uses controlled heating and cooling rates at specific temperatures over a range of time for each stage within a batch cycle. It provides uniformity in mechanical properties without warping, distortion or cracking due to temperature variations during heating and cooling processes. Isothermal forging reduces stresses caused by thermal cycling which occurs when metal parts are repeatedly heated and cooled during use or production processes such as extrusion, rolling or drawing operations.
- Near Net Shape Forging
What is near net shape forging? Near net shape forging involves taking a piece that has been machined into its near-finished form and then subjecting it to additional processing steps such as rolling or forging. This process produces parts that are more complex than those that can be produced through other methods such as extrusion or casting. Near net shape forging allows for parts with complex geometries to be produced using fewer processing steps than would otherwise be required by other processes such as cold rolling or hot forming operations. Near net shape forging allows for parts with complex geometries to be produced using fewer processing steps than would otherwise be required by other processes such as cold rolling or hot forming operations.
- Upset Forging
What is upset forging? Forging is a manufacturing process that uses forging presses to shape and form metal. The most common types of forging are upset forging and roll forging. Upset forging is used for making parts with flanges, shoulders or other features that are thicker than the base material, while roll forging is used to make thinner parts or complex shapes.
- Roll Forging (also called Ring Rolling)
What is roll forging? This is a manufacturing process where a cylindrical piece of steel is placed between two dies and hammered until it has been stretched into a different shape. This process requires less force than other types of forging because only one side of the metal needs to be stretched, while both sides are compressed during hot working processes such as extrusion or upsetting. Rolled products are typically uniform in thickness throughout their length and widths are determined by the diameter of the dies used during production.
- Hot Forging
What is hot forging? Hot forging is a metal shaping process that uses localized compressive heat and pressure to change the shape of a workpiece. The most common hot forging process is the upsetting process in which the end of the forging die has a smaller diameter than its base. This allows for the creation of male and female dies. The smaller diameter die is placed into a larger diameter die and compressed to form a mating surface. Once this occurs, the part is ejected from the dies and allowed to cool before being processed further.
- Cold Forging
What is cold forging? Cold forging is also known as cold working or cold heading. It involves using machines to deform metal without heating it. Cold forging can be used to create shapes that cannot be made by hot working alone, or where the metal must be cooled slowly to prevent cracking.
Hot Forging Vs. Cold Forging
In general, hot forging is done at a relatively high temperature to allow the material to flow and the tooling to work properly. Cold forging is done at room temperature or below.
The hot-forging process uses a heated die with a ram that pushes the workpiece against the die. The tooling is typically made of a material that can withstand the high temperatures required by this type of forging. The hot-forging process works well for materials that are ductile and have low tensile strength.
Cold-forging processes use dies made from tool steel or tungsten carbide, which are harder than normal dies used in hot-forging processes. They also use hardened punches that can withstand high temperatures if needed. The cold-forging process works well for materials that are more brittle and have high tensile strength.
When a piece of metal is hot forged, it must be heated significantly. The average forging temperatures required for hot forging of different metals are:
- Up to 1150°C for steel;
- 360 to 520°C for aluminum alloys;
- 700 to 800°C for copper alloys.
In the hot forging process, the billet or blank is heated by induction heating or in a forging furnace or oven to a temperature above the recrystallization point of the metal. This extreme heat is necessary to avoid strain hardening of the metal during the deformation process. Because the metal is in a plastic state, quite complex shapes can be produced. This metal remains ductile and malleable.
In order to forge certain metals, such as super alloys, a hot forging method called isothermal forging is used. Here, the die is heated to a temperature close to that of the billet to avoid surface cooling of the part during the forging process. Forging is also sometimes performed in a controlled environment to minimize the formation of oxide.
Traditionally, manufacturers choose hot forging to make parts because it allows the material to deform in a plastic state and the metal is easier to work with. Hot forging is also recommended for deforming metals with high formability ratios, which is a way to measure how much deformation the metal can withstand without creating defects. Other considerations for hot forging include:
- Production of discrete parts;
- Low to medium precision;
- Low stress or low work hardening;
- Homogeneous grain structure;
- Increased ductility;
- Elimination of chemical inconsistencies and porosity.
- Possible disadvantages of hot forging include:
- Less precise tolerances;
- Possible warpage of the material during cooling;
- Changing metal grain structure;
- Possible reactions between the surrounding atmosphere and the metal (fouling).
Cold Forging (or Cold Forming)
Cold forging deforms the metal below the recrystallization point. Cold forging significantly increases tensile and yield strengths while decreasing ductility. Cold forging is usually performed near room temperature. The most common metals used in cold forging applications are usually standard or carbon alloy steels. Cold forging is usually a closed-die process.
Cold forging is usually preferred when the metal is already soft (e.g., aluminum). This process is usually cheaper than hot forging and the end product requires little to no finishing work. Sometimes, when the metal is cold forged to the desired shape, residual surface stresses need to be removed after heat treatment. Because cold forging increases the strength of the metal, it may sometimes be possible to use a lower grade of material to produce usable parts that cannot be made from the same material by machining or hot forging.
Manufacturers may choose cold forging over hot forging for a number of reasons, as cold forged parts require little or no finishing, so this step in the manufacturing process is often optional, which saves money. Cold forging is also less susceptible to contamination issues and the final part has a better overall surface finish. Other benefits of cold forging include:
- Easier to give directional properties
- Improved reproducibility;
- Increased dimensional control;
- Handling high stresses and high die loads;
- Produces net shape or near net shape parts.
Some possible disadvantages include:
- Metal surfaces must be clean and free of oxidation prior to forging.
- This metal is less ductile.
- Residual stresses may be generated.
- Requires heavier, more powerful equipment.
- Requires more robust tools.
Warm forging is performed at temperatures below the recrystallization temperature but above room temperature to overcome the disadvantages and gain the advantages of hot and cold forging. Oxide formation is not an issue compared to hot forging and tolerances can be closer. Tooling costs are lower and the force required to manufacture is lower than with cold forging. Strain hardening is reduced and plasticity is increased compared to cold working.
What is the difference between forging and casting?
Forging is a process that involves heating a piece of metal and then shaping it into a desired shape by hammering or pressing. This can be done either on an anvil or on specialized machines called drop hammers. Forging allows for the creation of strong, high-quality pieces with complex shapes and intricate details that are impossible to make using traditional machining methods.
Casting is another method for creating metal parts by pouring molten metal into a mold. This process is used for low-cost parts such as gears and fasteners but does not produce high-quality parts since any defects in the casting will show up in your finished product.
Forged metals are stronger than cast metals because they have a grain structure that forms during the forging process. Grain structures are formed when atoms move differently when heated than when cooled down again, which results in crystals forming inside the metal during heating. This crystal structure resembles grains of sand, which makes the metal harder and more brittle than it would be without this grain structure.
Design of forgings
Forging design is the same as ordinary die forging, and precision forging drawings are developed based on product part drawings. It is the main basis for formulating precision forging processes, designing precision forging molds, and manufacturing and accepting forgings.
Selection of design program for forgings
The forging process program should be selected at the beginning of the work on the design of forgings. It should include the following:
- Selection of forging method: free forging, ordinary die forging, special forging or precision forging.
- Selection of forging equipment: hammer, press or special forging machinery.
- Selection of forging structure: die and the main profile shape, etc.
- Selection of heating method: flame heating, electric heating, non-oxidizing heating, etc.
The following issues should be considered comprehensively in the choice of forging process program and design of forgings.
(1) The material of forgings
Forging material is one of the main factors determining the forgings manufacturing process. Because the adaptability of various materials’ forging process and forging structural characteristics are different, they must be forged and process design, respectively, to be considered.
For example, nickel-based high-temperature alloy flow stress is larger than other materials, forming the ability to fill the groove is lower, and heating will cause chromium, nickel, aluminum, titanium and other elements of the depletion of the critical deformation of the sensitive response. Therefore, when selecting the forging process, choosing the forging equipment with lower deformation speed and the heating furnace with protection measures is necessary, etc. When designing forgings, the shape should be simple; the machining allowance should be larger than the forgings of other alloys and should be as far as possible to make the final forging a more uniform deformation.
(2) The shape and size of the parts features
The shape and size of the parts is to determine the shape and size of the forgings based on a comprehensive analysis of the structural characteristics of the parts will help to correctly determine the structural elements of the forgings and forging process reasonable choice.
The structural characteristics of the parts include the peripheral contour shape, the shape of the main axis, along the main axis of the cross-sectional dimensions of the relationship between the shape and size of the part of the off-axis proportion, the permissible skewness, rounded corners, ribs and the size of the belly plate, can be separated from the position of the mold, and so on.
(3) The use of parts requirements
The use of parts requirements include bearing mode (unidirectional load, multi-directional or composite load, cyclic load, continuous load or thermal load), load size and loading status (size, loading speed, temperature and environment), special mechanical physical or chemical performance requirements, expected service life and so on.
(4) The production batch of forgings
The size of the production batch and the possibility of repeated production are the basis for calculating the productivity of forgings and equipment load factor in various forging programs. The smaller the production of forgings, the use of die forging and complex processes, the more uneconomical. Conversely, the larger the output, the use of complex processes, mechanization and automation, the use of correction, fine pressure and other finishing processes, the more economical.
The forging method and the relationship between the production batch of forgings, see Table.
Table. Different forging methods used in forging production batches
|Single piece production||Free forging|
|Small batch production||Free forging+auxiliary tools, tire die forging|
|Batch and mass production||Free forging+die forging on a hammer or press, fixed multi groove die forging|
|Mass production||Fixed multi groove die forging|
(5) The choice of forging equipment
Forging equipment can be selected in Table.
Table. Adaptability of Forging Materials to Plating Equipment
|The Forging Materials||Explanation of equipment applicability|
|Aluminium alloy||When the forging deformation is large, a hydraulic press is preferred, otherwise it can be chosen at will.|
|Beryllium alloy||The preferred choice is a hydraulic press, as it has good malleability at slow speeds.|
|Copper alloy||Priority should be given to hammers, screw presses, or crank presses, but for bronze and high zinc brass that are sensitive to deformation speed, priority should be given to hydraulic presses.|
|Niobium alloy||Hammers, screw presses, and crank presses are preferred when alloys require high-temperature forging.|
|Magnesium alloy||Due to its poor malleability for rapid deformation, hydraulic presses should be preferred.|
|Molybdenum alloy||When high-temperature forging is required, a hammer, screw press, or crank press are preferred.|
|Nickel based alloy||Select according to the cross-sectional thickness of the forging; when forging thin section forgings (less than 12.7mm), priority should be given to using hammers, screw presses, or crank presses, otherwise they can be chosen at will.|
|Carbon steel and low alloy steel||When it is difficult to remove oxide skin from forgings with thin sections during forging, a hammer, screw press, or crank press are preferred, otherwise they can be chosen at will.|
|Stainless steel||Forgings with thin sections are preferred to use hammers, screw presses, or crank presses, otherwise they can be chosen at will.|
|Tantalum alloy||When forging at high temperatures, a hammer, screw press, or crank press are preferred.|
|Titanium alloy||Forgings with thin sections are preferred to use hammers, screw presses, or crank presses, otherwise they can be chosen arbitrarily.|
|Tungsten alloy||When forging at high temperatures, a hammer, screw press, or crank press are preferred.|
|Zirconium alloy||When the blank has a sleeve, a hydraulic press (above 760 ° c) is preferred. When the forging temperature is below 760 ° c, it can be chosen at will.|
(6) Forging production batch is different, should be used in the forging process and production costs are also different
The large production batch can only be used in forging programs with high production efficiency. Free forging generally consumes more material than die forging and precision forging, but precision forging and die forging one-time costs (tooling costs, equipment costs) than free forging, therefore, generally should be based on the production batch to determine the basis of the different forging programs and forging design options for a comprehensive cost comparison, under the premise of quality assurance, selected in the entire process of the most economical processing program. The figure is the relative relationship between the production batch, the forging process and the cost per piece.
Figure. Relative relationship between forging process and single piece cost
Drawing of forgings
1. The definition and basic characteristics of forging drawings
Forging drawing is a graphic, symbols and text describing the geometric features of forgings and technical requirements of the graphic and text documents. Therefore, the forging drawing is a complete embodiment of the structure of the forging, size and technical elements of the basic documents. Still, the main basis is the design process, design tooling, acceptance of forgings, and establishment of forging production.
Compared with other drawings, forging drawings have the following basic features:
- (1) As the forging drawing is the final result of the forging design, the drawing must accurately and comprehensively reflect the special content of the forging, such as parting line, flow line, rounded corners, slope, etc.
- (2) From product design to making finished products, forgings drawings comprehensively reflect the product’s internal technical requirements (such as performance, organization and internal continuity, etc.).
- (3) Reflects the product design drawings and subsequent processing requirements, such as flow lines and process residuals.
2. The forging drawings
According to the degree of simplicity in the drawing, forging pattern has three types:
Formal type is all the requirements of the forging; that is, all the results of the forging design are reflected in the drawing. In general, directly relying on the forging drawing can complete the forging of other technical work (such as the design process and process equipment, acceptance of forgings, etc.). Aviation free forgings and die forgings are used in this pattern.
Simple type, in the drawing only the main graphic of the forging, the basic contour size and technical elements (such as machining benchmarks, margin values and technical wood requirements, etc.), the use of product design drawings or other Kabuki documents. This type mainly applies to large forgings with complex shapes, especially forgings with many non-machining surfaces. It can simplify the design process. This pattern can also be used in the design of aviation forgings.
Temporary type, that is, in the product design drawings, specify the forging profile size of the relevant parts and then give the value of the machining allowance and the part of the residual material. This pattern is suitable for single-piece production of simple shape of free forgings design, not suitable for aviation forgings.
Third, the composition of the forging pattern
Forging and other design drawings, the same by the graphics and dimensions, technical requirements and additional instructions, title bar three parts:
(1) Graphics and dimensions
The graphics of forgings include all the structural elements of forgings (die line, die forging slope, rounded corners, web, ribs, holes and cavities, etc.), process residuals, test residuals, etc. The basic outline of the part is also drawn in the graphics to reflect the distribution of machining allowances. If necessary, some of the technical requirements should also be drawn in the graphic, such as flow lines take a test sample of the site.
The dimensions of the drawing include the size of the forging and its tolerance and the size of the relevant part two parts.
(2) Technical requirements and additional instructions
Most of the technical requirements of the forging are expressed in words, so often combined with additional instructions in the form of a note in the drawing. Its content includes the technical standard number of forgings, inspection and testing of the basic rules (number of samples, sampling sites and directions), forging category, flow direction, forging heat treatment requirements, surface cleaning requirements, surface defects standard, forging marking requirements and graphic requirements are not reflected in the content (such as unspecified radius of the corner, etc.).
(3) Title bar
In the title bar of the drawing of the original forging, such as part number, name, material grade, model number, etc., as well as the signature of the drawing, countersignature and approval column.
General principles of forging design
The design of forgings is the first part of the design of the product machining process. All the results of the forging design are described in the drawing. Forging drawing is the preparation of the forging process and design of forging molds or gauges of the main basis.
The forging drawing should meet the following requirements:
(1) Parts drawings of forgings proposed flow, non-processing surfaces, mechanical properties, internal organization and other requirements.
(2) Forgings should have good manufacturability.
(3) When the results of the forging design and subsequent machining process are directly related to the method, we must conduct a comprehensive analysis from the technical, economic and management coordination to provide good conditions for subsequent processing.
(4) Forging manufacturing process selection should be carried out first with technical and economic demonstration.
The main tasks of the design of forgings are the following:
- 1) According to the technical conditions of the parts, subsequent processing requirements and the possibility of production conditions, determine the forgings manufacturing program.
- 2) According to the parts drawings and the requirements of the relevant technical standards, determine the location of the forging die, die direction, profile shape, die forging slope and corner radius.
- 3) Determine the machining allowance of the forging, additional allowance, machining and measurement benchmarks, size and shape tolerances.
- 4) According to the technical standards of forgings and parts drawings, determine the specific technical requirements of forgings. These include surface quality standards, internal quality standards, flow distribution direction and mechanical properties.
- 5) According to the provisions of mechanical drawing standards, drawing forgings graphics, labeling dimensions and tolerances, fill in the technical requirements.
Process flow of forging
Different forging methods have different processes, including the longest process flow of hot die forging; the general order is:
Forging billet material → forging billet heating → roll forging billet preparation → die forging forming → cutting → punching → correction → intermediate inspection → inspection of the size of the forging and surface defects → forging heat treatment to eliminate forging stress, improve the cutting performance of the metal → clean up, mainly to remove the surface of oxidized skin → correction → check, the general appearance of the forging parts to be after the appearance and hardness check, important forging parts but also after the chemical composition analysis, mechanical properties, residual stress Inspection and non-destructive testing.
Volume calculation and sizing of blanks
The calculation of blank volume and cross-sectional area is mainly to determine the diameter and length of the original blank. Blank volume includes forgings (including even skin), burrs, fire consumption, etc., and some also include clamp clamp head.
(1) Disk type forging blank size determination
Vblank = (Vforging + Vedge) (1 + δ%)
In the formula:
- Vforging – forging volume (including continuous skin);
- Vedge – the volume of the burr, 40% – 60% of the volume of the burr bin, easy to fill the smaller value;
- δ – metal burning rate.
In order to prevent bending during upsetting, the ratio of blank length to diameter should be kept:
m = Lbillet/Dbillet = Lbillet/Abillet ≤ 3
In the formula:
- m – upsetting ratio, usually 1.5 – 2.2;
- Lbillet – the length of the burrs;
- Abillet – side length of square bar billet;
- Dbillet – the diameter of round bar blank.
Diameter of the blank:
Dbillet = 3√(4Vbillet/πm) or Dbillet = (0.95 – 0.84) 3√Vbillet
When using square bar blanks:
Abillet = (0.87 – 0.77) 3√Vbillet
Round bar stock or square bar blanks are then selected from the standard specifications.
Lbillet = 1.27Vbillet/D2billet or Lbillet = Vbillet/A2
(2) Shaft forgings blank size determination
Shaft forgings of the blank size can be calculated according to the blank cross-section combined with the work steps used to determine. Generally based on the maximum cross-section or average cross-section on the calculation of blank cross-section diagram.
From the table to find out the blank cross-sectional area, and then according to the following formula to find out the diameter of the round blank or the side length of the square blank:
Dbillet = 1.13√Fbillet or Abillet = √Fbillet
Then, select the round bar or square blank from the standard specification of the material.
Length of the blank:
Lbillet = 1.27Vbillet/D2 or Lbillet = Vbillet/A2
Fhead all is the average cross-sectional area of the head of the forging, i.e.
Fhead all = Vhead/Lhead
In the formula:
- Vhead – volume of the forging and burrs in the L head area.
Billet making process requires the use of clamping head, the length of the blank should be increased by a certain length. General clamping head length of (0.5 – 1.0) Dblank.
When using bar direct die forging, according to the maximum cross-sectional area of the forging (excluding burrs) to calculate the diameter of the blank.
When the length of the maximum cross-section area accounted for a small proportion of the blank diameter Dbillet < Dforging max (Dforging max – the maximum diameter of the forgings) can be taken
When the proportion of the length of the maximum cross-section area is large, then Dblank ≥ Dforging max should be taken.
When the cross-section area of each part of the forging is equal or similar, then according to the complexity of the forging, it is appropriate to increase the cross-sectional area of a part of the burr, namely
Fbillet = Fforging + a Fedge
- Fbillet, Fforging, Fside – blanks, forgings and the cross-sectional area of the burr side;.
- a – coefficient of complexity of forgings (0.5 – 0.8).
Length of the blank: when the head is at both ends, Lblank = Lforging;
When the head is at one end or in the middle, Lblank = Lforging – L;
In the formula:
- Lbillet, L forging – length of the blank and forging;
- L – the difference between the length of the blank and the length of the forgings.
The difference between blank length and forging length L
Forging Billet Unloading
Before forging, the size of raw materials required must be calculated according to the drawings, the profile, bar or rolled material, etc., cut into the required length and the large ingots or billets into the required size, such a process that is the material.
Preparation before discharging
In the forging of forging, the first need to carry out the preparation of the material. The material needs to select materials, calculate the size and demarcation of boundaries and other steps. At the same time, it is also necessary to determine the size and shape of the material according to the requirements of the forging process performance. The material should have good weldability, malleability, machinability and corrosion resistance. In addition, the cutting and cutting tools need to be inspected and maintained before undercutting to ensure their normal operation in the undercutting process.
Undercutting tools and methods
1. Undercutting tools
Undercutting tools mainly include manual shears, mechanical shears, planers, milling machines, saws, shears and so on. The specific choice of undercutting tools, depending on the type and size of the material used, etc..
Under the material of the common methods of shearing, sawing, turning, wheel cutting, hot chopping, cold folding, gas cutting and plasma cutting, etc., different methods of the material have their characteristics, the choice of what kind of under the material, mainly according to the nature of the material, under the material size, the batch of products and the quality of the material under the requirements.
2. Undercutting methods
Usually, there are shearing, cold folding, sawing, turning, wheel cutting, chopping and other discharging methods. And various methods of undercutting have their characteristics according to the nature of the material, size, batch and the requirements of the quality of undercutting. Their blank quality, material utilization processing efficiency are different. So, according to the above conditions choose the forging products suitable for the undercutting method.
a. shear materialization method
Shear material is characterized by high productivity, simple operation, low-cost molds and no material loss of the cut, but the quality of the end face is relatively poor. Shear material is suitable for mass production and is currently the main method of die-forging production material. Commonly used shearing equipment are punching and shearing machines, crank presses or screw presses.
b. sawing material method
Sawing can cut off the cross-section of the larger blanks; However, lower productivity sawing wear and tear, the cut is flat because of the precise material, especially in the precision forging process, which is a major discharging method. Commonly used under the material sawing machine has a disk, band saw and bow saw.
- (1) disc saw: sawing thickness is generally 3 – 8mm, saw pin wear and tear. And sawing speed is low, with a circumferential speed of about 0.5 – 1.0 m/s. Then the ordinary cutting speed is low, so the productivity is low. Sawing directly up to 750mm.
- (2) band saw: vertical, horizontal, can be oblique vertical, etc. Its productivity is 1.5 – 2 times the ordinary circular sawing machine, kerf wear 2 – 2.2mm, mainly used for sawing diameter of 350mm within the bar.
- (3) bow saw: a reciprocating sawing machine, bow arm and can get the reciprocating motion of the linkage mechanism and other components. Saw blade groove for 2 – 5mm, generally used for sawing diameter of 100mm within the bar. Use sawing material for the end face quality length accuracy requirements of high steel material.
Therefore, sawing is the most common in the forging factory. The metal can be sawn in the hot state or the cold state. Most forging production in cold sawing; only rolling mills use hot sawing.
c. turning material method
Turning under the material is characterized by good quality end face, high dimensional accuracy and high efficiency under the material, but the material has a certain loss. Turning is suitable for blanks with high requirements for section quality and dimensional accuracy. Turning under the use of equipment for the lathe.
d. wheel cutting method
Wheel cutting is characterized by good quality end face, high dimensional accuracy, simple operation and material loss; productivity is slightly higher than the sawing material but lower than the shear and cold folding material. The disadvantage of wheel cutting is that the consumption of abrasive wheels and the noise is large. Abrasive wheel cutting is suitable for small cross-section bars, pipe materials, shaped cross-section materials and difficult to cut metals, such as high temperature alloys. Abrasive wheel-cutting equipment for the use of a wheel cutting machine.
e. hot chopping cut material method
Hot chopping and cutting materials are characterized by a wide range of material, a simple operation, but hot chopping and cutting material needs to be heated, the worst quality of the end face, the labor conditions are not good and more dangerous, the size of the material is not easy to control. Hot chopping and cutting material are mostly used for free forging material. Commonly used equipment for free forging hammer, free forging hydraulic press and so on.
f. cold folding material method
No material loss characterizes cold folding material, but the operation is dangerous. The principle is to be broken at the material to open a small gap in the gap to produce stress concentration so that the billet breaks, in common parlance, the free forging hammer with a nibbler “nibbling shear”. Applicable to large cross-section rolled material, carbon content higher than 0.32% and unannealed medium and high carbon steel and alloy steel. Using cold folding machine or press, etc., opening the gap can be sawing, cutting or gas cutting.
g. gas-cutting method
Gas cutting is also known as oxygen cutting or flame cutting. It is characterized by low equipment costs, simple and portable operation, quick change in the cutting direction, can be operated manually or automatically and can be field work. However, the disadvantages are poor end face quality, high metal loss, low precision, low productivity and bad and dangerous labor conditions. Commonly used in cutting large cross-section blanks, mild steel or low alloy steel.
h. plasma cutting method
Plasma cutting is characterized by fast speed, high efficiency, good quality cutting surface, cutting size accuracy, small thermal deformation of the workpiece, and can cut various materials. In addition to being used for undercutting, it can also remove burrs. It is an important direction to effectively reduce the labor intensity of employees, automated production and development.
The plasma cutting current is generally below 100 A, theoretically can cut 120mm steel plate, with the best cutting range of 80mm.
Precautions for material discharging
1. Pay attention to the material loss of undercutting
The loss of material should be controlled within a reasonable range. Reasonable loss range can be determined according to the size of the forging and the type of material to avoid wasting costs and resources.
2. Accurate undercutting
The material size should be accurate to avoid influencing the subsequent forging work. Before discharging, the size can be verified and adjusted to improve the accuracy of discharging.
3. Protect the forging material
In the cutting and severing process, one needs to pay attention to protecting forging materials to avoid damage to the tool’s material or produce scratches and other adverse effects.
Forging material is an important step in the process of forging production, needs to focus on precision, efficiency and safety. Before discharging the need for adequate preparation, select the appropriate tools and methods, pay attention to the material loss, discharging to be accurate and protection of forging materials and other key points to ensure the smooth progress of forging production.
The quality requirements of the blanks under the material
The quality requirements of the blank, with the different forging process.
(1). the blank shape and dimensional accuracy control standards
1) blank length and weight tolerance
Hammer die forging without clamping the head of drop forging parts and upsetting parts; the blank can control the length tolerance and weight tolerance. General control of weight tolerance is more reasonable.
The weight tolerance of the blank can also be determined according to its weight G, which generally should be within the range of +0.03 – 0.1G.
2) various undercutting equipment undercutting tolerance:
The length tolerance of blanks varies with different undercutting equipment.
3) Inclination angle tolerance of sawmill undercutting:
When sawing undercutting, the end of the blank does not produce deformation, but the end face may be sawed oblique. Residual burrs are not allowed on the end face of the sawn blank.
(2). the blank surface quality requirements
1) the limitations of surface defects
The surface of the blank is not allowed to have defects such as cracks, folding, inclusions and large mechanical damage. For non-ferrous metals, such as aluminum alloys and magnesium alloys and other surfaces, it also does not allow bubbles, delamination, corrosion points and other defects. The coarse crystal ring on the surface of aluminum alloy and titanium alloy surface of the oxygen-rich layer should be removed before forging. The shear section should not have a serious shear tear crater; harder materials and brittle fracture zone cracks are required to be removed.
2) the requirements of surface roughness
Steel bar material after machining surface roughness should not be greater than Ra 10μm, the need for ultrasonic flaw detection of the gross surface roughness of Ra 2.5μm, some requirements to check the surface grain size of high temperature alloy blanks, the surface roughness should not be greater than Ra 1.25μm.
Non-ferrous metal forgings with a gross also, its surface roughness should not be less than Ra10μm; non – processing surface of the drop-forged parts with the blank, its surface roughness of Ra 5μm.
Aluminum alloys, magnesium alloys and other rough sawn surfaces of the blank may cause cracks when forging. When the sawn surface becomes the non-machining surface of the forging, in order to ensure the quality of the forging, the end face of the sawn blank needs to be turned and smoothed on the lathe again.
Aluminum alloy, magnesium alloy, titanium alloy, non-inductive steel and high-temperature alloys of the gross also need to be dun roughing; the sharp edges of the end face should be chamfered or round. Diameter less than 100mm of the blank, chamfering R1.5 – R5; diameter greater than 100mm of the gross also, chamfering R5 – R10.
What is forging process? Forging is the forming or deformation of metal in the solid state. Many forges are accomplished by an upsetting process in which a hammer or punch is moved horizontally to press against the end of a rod or bar, thereby widening and changing the shape of the end. The part usually passes through successive stations before reaching its final shape. High strength bolts are “cold headed” in this manner. Engine valves are also formed by header forging.
In drop forging, the part is hammered into the shape of the finished part in a die, much like a blacksmith’s open-die forging, in which the metal is hammered into the desired shape. A distinction is made between open-die forging and closed-die forging. In open die forging, the metal is never fully restrained by the die. In a closed die or press die, the forging metal is confined between the half-die. Repeated hammer blows on the die force the metal into the die shape and the two halves of the die eventually meet. The energy for the hydraulic hammer can be supplied by steam or pneumatic, mechanical or hydraulic pressure. In a true drop hammer forging, gravity alone drives the hammer down, but many systems use a combination of power assist and gravity. The hammer provides a series of relatively high speed, low force hammer blows to close the die.
In pressure forging, high pressure replaces high speed and the two halves of the die are closed in one stroke, usually provided by a power screw or hydraulic cylinder. Hammer forging is typically used to produce smaller volumes of parts, while pressure forging is typically used for high volume production and automation. The slow application of pressure forging tends to handle the interior of the part better than hammering and is often used for large, high-quality parts (e.g., titanium aircraft bulkheads). Other specialized forging methods vary depending on these basic topics: for example, bearing rings and large ring gears are made by a process called roll ring forging, which produces seamless round parts.
Different forging methods have different processes, including the longest process of hot die forging, the general order is: forging billet feeding; forging billet heating; roll forging preparation; die forging forming; cutting edge; punching; correction; intermediate inspection, inspection of forging size and surface defects; forging heat treatment, to eliminate forging stress, improve metal cutting properties; cleaning, mainly to remove surface oxidation; correction; inspection, general forgings to go through the appearance and hardness inspection, important forgings also after the chemical composition analysis, mechanical properties, residual stress and other tests and non-destructive testing.
Commonly used forging methods and their advantages and disadvantages
Free forging refers to using simple general-purpose tools or in the forging equipment between the upper and lower anvil iron directly on the billet to apply external forces so that the billet deformation and obtain the desired geometry and internal quality of the forgings processing methods. The forgings produced by the free forging method are called free forgings.
Figure. Free Forging
Free forging is based on producing small batches of forgings, using forging hammers, hydraulic presses and other forging equipment on the billet forming process to obtain qualified forgings. The basic processes of free forging include upsetting, elongation, punching, cutting, bending, twisting, misalignment and forging. Free forging adopts the hot forging method.
Free Forging Process
In the free forging process, the forgings are not restricted by molds or other external shapes but are shaped by workers using hammers or other forging tools. Below are some basic classifications of the free forging process:
These include basic processes, auxiliary processes, and finishing processes.
(1) The basic processes of free forging: upsetting, lengthening, punching, bending, cutting, twisting, shifting and forging, etc., while the most commonly used processes in actual production are upsetting, lengthening and punching.
Upsetting: This is a process to increase the diameter of the workpiece, which is commonly used to make the head or other parts that need to expand the diameter.
Drawing: In contrast to upsetting, drawing is the process of increasing the length of a part by decreasing its diameter. This is usually applied to workpieces that require slender sections.
Drawing is a necessary process in the forging of large shaft forgings, and it is also the main process that affects the quality of the forgings. Through the drawing process to make the billet cross-sectional area is reduced, the length increases, but it also plays a role in breaking up coarse crystals, forging the internal looseness and holes, refinement of the casting organization, so as to obtain a homogeneous dense high-quality forgings. In the study of flat anvil pulling long process at the same time, people gradually began to recognize the large forgings internal stress, strain state on the forging of internal defects of the importance of the upper and lower flat anvil pulling long, the development of flat anvil on the lower V anvil pulling long as well as up and down the V anvil pulling long, and then later on through the change of the pulling anvil shape and process conditions, and put forward WHF forging, KD forging method, FM forging method, JTS forging method, FML forging method, TER forging method, SUF forging method and the new FM forging method, these methods have been applied to the production of large forgings, and achieve better results.
- WHF forging method: A kind of wide flat anvil strong pressure down forging method, its forging principle is the use of upper and lower wide flat anvil, and the use of large pressure down rate, forging heart deformation is conducive to the elimination of internal defects in the ingot, widely used in large-scale water press forging.
- KD forging method: Developed on the basis of WHF forging method, its principle is to utilize the ingot in a long time under high temperature conditions have enough plasticity, can be in a limited number of equipment, with wide anvil large underpressure rate forging. The use of upper and lower V-type wide anvil forging is conducive to the improvement of the plasticity of the metal on the surface of the forging, increasing the three-way compressive stress state of the heart, and thus effectively forging the internal defects of the ingot.
- FM forging method: Using the upper flat anvil, the lower platform forging asymmetric deformation, as well as the lower platform on the deformation of the forging friction resistance, so that the forging from top to bottom gradually deformation, in order to make the tensile stress is transferred to the billet and the platform of the contact surface, the center of the hydrostatic compressive stress has been increased, which improves the deformation of the body of the stress state.
- JTS forging method: Before forging, the ingot is heated to a high temperature, and then the surface is cooled rapidly, the surface of the ingot then forms a hard shell, the heart is still in a high temperature state, the hard shell of the billet deformation plays a fixed role, so that the deformation is mainly concentrated in the center of the forging, thus increasing the compaction effect of the heart and improving the qualification rate of the forging.
- FML forging method: On the basis of the FM method to reduce the press load of a forging method, the width of the anvil is narrower than the billet, the length direction and the billet axial direction to maintain consistency, the following auxiliary tool is still a large platform, and then the forging process, the amount of underpressure and forging ratio is relatively small, is to ensure that effective forging billet holes within the premise of reducing the loading of the press, loose defects.
- TER forging method: When forging and drawing length, a wide flat anvil is used to draw length in one direction, and a staggered anvil process is used to carry out multiple strong pressure drawing length, so that the maximum deformation of the billet is generated in one direction, effectively forging and closing the internal hole-type defects. When using this method of forging, the required pressure is smaller, and the forging cycle is shorter, which improves the labor productivity, reduces the production cost and increases the economic benefits.
- SUF Forging Method: Through the control of the anvil width ratio, the height of the ingot is fully reduced during forging, and finally the section is forged into a rectangular forging method, which is a kind of forging method with a wide flat anvil flattening, using a wide flat anvil flattening, which increases the width of the plastic flow range of the metal near the center of the ingot axis, which is more conducive to forging the heart of the billet defects.
- New FM Forging Method: According to the relationship between the transverse stress in the heart of the forging and the material width ratio, on the basis of the FM forging method, the control of the material width ratio is added to reduce the transverse tensile stress in the heart, and the application of the principles of the new FM forging method for the production of large forgings, significant economic benefits have been achieved.
- Punching: As the name suggests, punching is the process of making holes in a workpiece. This is usually done to make connections or holes for fixing.
Bending: To bend a workpiece to a specific curve or angle.
Cutting: Used to sever a workpiece or cut a part from it.
Twist: To distort the shape of a workpiece by rotating a part of it instead of the entire workpiece.
Misalignment: In forging, part of the workpiece is moved to another position, usually in combination with other processes.
Forge welding: This is a process of joining two or more workpieces together by heating and forging them together under a certain pressure.
(2) Auxiliary processes: Pre-deformation processes such as nip pressing, ingot prong pressing, shoulder cutting, etc.
- Jaw pressing: This is a process used to change the shape of a metal workpiece, usually in a cold or hot state. For example, when preparing a part or component of a specific shape, it may be necessary to pre-shape the metal for subsequent processing.
- COMPRESSING INGOT EDGES: After an ingot has been cast, it may have sharp or irregular edges. By compressing these edges, a more uniform and tidy ingot body is obtained, which facilitates subsequent machining processes such as forging or rolling.
- SHOULDER CUTTING: This is a process used to remove excess portions from a metal material. For example, one part of a workpiece may be higher or protruding than the rest, and it is necessary to remove this excess to obtain the desired shape.
(3) Finishing process: The process of reducing surface defects on a forging, such as removing unevenness and shaping the surface.
- Trimming: Removal of excess parts to improve dimensional accuracy.
- Leveling: Smooth the surface of the forging.
- Grinding: to further improve the surface quality of forgings.
- Forging is flexible and can produce small parts of less than 100kg and heavy parts of 300t or more;
- The tools used are simple general-purpose tools;
- Forging forming is to make the billet subregion gradually deform; therefore, forging the same forging equipment requires forging tonnage than the model forging is much smaller;
- Low precision requirements for equipment;
- Short production cycle.
Disadvantages and limitations:
- Production efficiency is much lower than model forging;
- Simple shape, low dimensional accuracy and rough surface of forgings; high labor intensity of workers, and also high technical level is required;
- It is not easy to realize mechanization and automation.
Die forging refers to using die forging equipment in the special die forging blank forming and obtaining forgings forging method. This method of production of forgings is accurate in size; the processing allowance is small; the structure is also more complex and high productivity.
Classified according to the equipment used: hammer die forging, crank press dies forging, flat forging machine die forging and friction press die forging.
The most commonly used equipment for die forging on the hammer is a steam-air die forging hammer, no anvil seat hammer and a high-speed hammer.
Forging die mold:
Its functions can be divided into the die forging and billet-making die chamber.
Figure. Dies used for die forging on the hammer
(1-hammer head; 2-upper die; 3-flying edge groove; 4-lower die; 5-die pads; 6, 7, 10-fastening wedge; 8-split die surface; 9-die hole) (-die chamber)
1) Die forging die chamber
(1) Pre-forging die chamber:
The function of the pre-forging die chamber is to deform the blank to a shape and size close to that of the forging so that when the final forging is carried out, the metal can easy to fill the die chamber and obtain the required size of the forging. The simple shape of the forgings or batch size needs to be set up pre-forging die chamber. The pre-forging die chamber has a round angle and slope; the final forging die chamber is much larger, and there is no fretting groove.
(2) Final forging die chamber:
The role of the final forging die chamber is to make the final deformation of the blank to the required shape and size of the forging. Therefore, its shape should be the same as the shape of the forging, but because the forging cooled to contraction, the final forging die chamber should be enlarged than the size of the forging contraction. The shrinkage of steel forgings is taken as 1.5%. In addition, along the die chamber around the fringe groove, to increase the resistance of the metal from the die chamber, prompting the metal to fill the die chamber while accommodating the excess metal.
2) Billet die chamber
For complex shapes of forgings, to make the blank shape basically in line with the shape of the forgings so that the metal can be reasonably distributed and well-filled with the die chamber, it is necessary to make blanks in advance in the blanking die chamber.
(1) Elongated die chamber:
It is used to reduce the cross-sectional area of a part of the blank to increase the length of that part. There are two types of elongation chambers: open and closed.
Figure. Drawing die chamber: (a) open type; (b) closed type
(2) Rolling die chamber:
It is used to reduce the cross-sectional area of one part of the blank to increase the cross-sectional area of another so that the metal is distributed according to the shape of the forging. Rolling die chambers are of two types: open and closed.
Figure. Rolling die chamber: (a) open type; (b) closed type
(3) Bending die chamber:
A bending die chamber is used to bend the blank for curved rod type drop-forged parts.
Figure. Bending die chamber
(4) Cut-off die chamber:
It is a pair of cutters in the corner of the upper and lower dies used to cut off the metal.
Figure. Cut off the die chamber
- Higher production efficiency. When die forging, the deformation of the metal is carried out in the die chamber so the desired shape can be obtained more quickly;
- Can forge complex shapes of forgings, and make the metal flow distribution more reasonable, improve the service life of parts;
- The size of the die-forging parts is more accurate, the surface quality is better, and the machining allowance is smaller;
- Save metal materials and reduce cutting and processing workload;
- Under the condition of sufficient batch, it can reduce the cost of parts.
Disadvantages and limitations:
- The weight of die forging parts is limited by the capacity of general die forging equipment, mostly below 70 Kg;
- The manufacturing cycle of forging dies is long and costly;
- The investment cost of die-forging equipment is larger than that of free forging.
Roll forging refers to a pair of rotating fan-shaped molds to produce plastic deformation of the billet to obtain the required forgings or forging billet forging process.
Figure. Schematic diagram of roll forging
The principle of roll forging deformation is shown above. Roll forging deformation is a complex three-dimensional deformation. Most deformed material flows along the length direction to increase the length of the billet, and a small portion of the material flows laterally to increase the width of the billet. The root cross-sectional area of the billet decreases during the roll forging process. Roll forging is suitable for shaft parts elongation, slab rolling and distribution of material along the length and other deformation processes.
Roll forging can produce connecting rods, twist drill bits, wrenches, nails, hoes, picks and turbine blades. The roll forging process utilizes the rolling forming principle to deform the blank gradually.
Compared with ordinary die forging, roll forging has a simpler equipment structure, smooth production, vibration and noise are small, easy to realize automation and high production efficiency.
Tire die forging
Tire die forging is the free forging method of making blanks, and then the final shape of the tire mold in a forging method is between free forging and die forging between a forging method. In the die forging equipment is less, most of the free forging hammers for small and medium-sized enterprises are commonly used.
Tire mold forging uses many types of molds commonly used in producing: type fall, buckle mold, set of molds, cushion mold, mold, etc.
Figure. Buckling die
Figure. Open type cylinder dies: (a) whole cylinder die; (b) block cylinder die; (c) cylinder die with cushion die.
Figure. Closed cylinder die
Closed-type cylinder die is mostly used in the forging of rotary forgings. Such as gears with tabs on both ends, sometimes also used for non-rotary forgings. Closed cylinder die forging is non-flying edge forging.
For the complex shape of the tire die forgings, it is necessary to add two half-molds in the cylinder die (i.e., increase a parting surface) made of a combination of cylinder die blanks in the two half-molds formed in the die chamber.
Figure. Combined cylinder die (1-cylinder die; 2-right half-die; 3-punch; 4-left half-die; 5-forging)
Figure. Combined die
Combined mold usually consists of two parts: upper and lower molds. They are often positioned with guide posts and pins to make the upper and lower dies coincide and avoid misaligning the forgings. The combined die mostly produces non-rotary forgings with complex shapes, such as connecting rods and fork forgings.
Tire die forging has the following advantages compared with free forging:
- Because of the billet forming in the die chamber, the forging size is more accurate, the surface is more polished and the distribution of streamlined organization is more reasonable, so the quality is higher;
- Tire die forging can forge a more complex shape of the forgings; because the die chamber controls the shape of the forgings, the billet forms faster with higher productivity than free forging 1 to 5 times;
- Fewer remaining blocks and thus less machining allowance can save metal materials and reduce machining hours.
Disadvantages and limitations:
- Need a larger tonnage of forging hammer;
- It can only produce small forgings;
- The service life of the tire mold is low;
- Work generally relies on manpower to move the mold, and therefore more labor-intensive;
- Tire die forging for the production of medium and small batch forgings.
Grinding ring refers to the production of ring-shaped parts of different diameters by a special equipment ring mill, also used to produce automobile wheel hubs, train wheels and other wheel-shaped parts.
Special forging includes roll forging, wedge cross rolling, radial forging, liquid die forging and other forging methods; these methods are more suitable for producing certain special shape parts. For example, roll forging can be used as an effective pre-forming process, significantly reducing the subsequent forming pressure; wedge rolling can produce steel balls, drive shafts and other parts; radial forging can produce large gun barrels, step shafts and other forgings.
What kind of equipment is used for forging?
The most popular forging equipment is the hammer and anvil. The idea behind the hammer and anvil is still used today in drop hammer forging equipment. The hammer is raised and then dropped or pushed into the workpiece, which rests on the anvil base. The main difference between drop hammers is the way the hammer is powered, most commonly air and steam hammers. Drop hammers are usually operated in a vertical position. This is because the excess energy is not released in the form of heat or sound, i.e., it is not the energy used to shape the workpiece that needs to be channeled to the base. A large machine base is also required to absorb the impact.
To overcome some of the drawbacks of the falling hammer, a counter-impactor or impactor is used. Both the hammer and the anvil move through the impactor with the workpiece sandwiched between them. Here, the excess energy becomes recoil, allowing the machine to work horizontally and with a smaller base. This will reduce noise, heat and vibration. It also creates a very different flow pattern. These machines are used for open-die forging or closed-die forging.
Presses are used for press forging. The two main types are mechanical and hydraulic presses. Mechanical presses use cams, cranks and switches to perform pre-set and reproducible hammer blows. Due to the characteristics of this type of system, different forces can be used at different stroke positions. As a result, these presses are up to 50 strokes per minute faster than hydraulic presses. Their capacities range from 3 million to 160 million. Hydraulic presses use fluid pressure and pistons to generate force. The advantage of hydraulics over mechanics is its flexibility and superior performance. The disadvantages are that they are slower to operate, larger and more costly.
Roll forging, automatic hot forging and upsetting processes all use specialized machinery.
Standard for forgings
|A 19||1936||Quenched-and-Tempered Carbon-Steel Axles, Shafts, and Other Forgings for Locomotives and Cars||Replaced by A 236 /no materials/|
|A 63||Alloy Steel Forgings for Locomotives and Cars||Replaced by A 237 /no materials/|
|A 105/A 105M||2005||Carbon Steel Forgings for Piping Applications||/1/|
|A 133||Alloy-Steel Forgings for Locomotives and Cars||Withdrawn 1941 /no materials/|
|A 136||Forge-Welded Steel Pipe||Withdrawn 1945 /no materials/|
|A 181/A 181M||2006||Carbon Steel Forgings, for General-Purpose Piping||/2/|
|A 182/A 182M||2009||Forged or Rolled Alloy and Stainless Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service||/88/|
|A 235||Carbon Steel Forgings for General Industrial Use||Replaced by A 668/A 668M /no materials/|
|A 236||Carbon Steel Forgings for Railway Use||Withdrawn 1981 /no materials/|
|A 237||Alloy Steel Forgings for General Industrial Use||Replaced by A 668/A 668M /no materials/|
|A 238||Forgings, Alloy Steel, for Railway Use||Replaced by A 730 /no materials/|
|A 243||Carbon and Alloy Steel Ring, Hollow Cylinder, and Disk Forgings for General Industrial Use||Replaced by A 668/A 668M /no materials/|
|A 266/A 266M||2008||Carbon Steel Forgings for Pressure Vessel Components||/4/|
|A 288||2008||Carbon and Alloy Steel Forgings for Magnetic Retaining Rings for Turbine Generators||/8/|
|A 289/A 289M||2008||Alloy Steel Forgings for Nonmagnetic Retaining Rings for Generators||/8/|
|A 290/A 290M||2005||Carbon and Alloy Steel Forgings for Rings for Reduction Gears||/19/|
|A 291/A 291M||2005||Steel Forgings, Carbon and Alloy, for Pinions, Gears and Shafts for Reduction Gears||/20/|
|A 292||Carbon and Alloy Steel Forgings for Turbine Generator Rotors and Shafts||Replaced by A 469/A 469M /no materials/|
|A 293||Steel Forgings, Carbon and Alloy, for Turbine Generator Rotors and Shafts||/no materials/|
|A 294||Alloy Steel Forgings for Turbine Wheels and Disks||/no materials/|
|A 336/A 336M||2009||Alloy Steel Forgings for Pressure and High-Temperature Parts||/45/|
|A 350/A 350M||2007||Carbon and Low-Alloy Steel Forgings, Requiring Notch Toughness Testing for Piping Fittings||/13/|
|A 369/A 369M||2006||Carbon and Ferritic Alloy Steel Forged and Bored Pipe for High-Temperature Service||/15/|
|A 372/A 372M||2008||Carbon and Alloy Steel Forgings for Thin-Walled Pressure Vessels||/48/|
|A 402||Forged or Rolled Alloy Steel Pipe Flanges, Forged Fittings, and Valves and Parts Specially Heat Treated for High-Temperature Service||Withdrawn 1958 /no materials/|
|A 404||1968||Forged or Rolled Alloy Steel Pip Flanges, Forged Fitings, and Valves and Parts Specially Heat Treated for High-Temperature Service||Withdrawn 1974 /no materials/|
|A 430/A 430M||1991||Austentic Steel Forged and Bored Pipe for Hi GH-Temperature Service||Replaced by A312/ A312M /11/|
|A 456/A 456M||2008||Magnetic Particle Examination of Large Crankshaft Forgings||/no materials/|
|A 461||Precipitation Hardening Alloy Bars, Forgings, and Forging Stock for High-Temperature Service||Replaced by A564/ A564M /no materials/|
|A 468||Method of Normal Magnetic Induction Characteristics of Carbon and Alloy Steel Generator Rotor Forgings||Replaced by A6/ A6M /no materials/|
|A 469/A 469M||2007||Vacuum-Treated Steel Forgings for Generator Rotors||/7/|
|A 470/A 470M||2005||Vacuum-Treated Carbon and Alloy Steel Forgings for Turbine Rotors and Shafts||/17/|
|A 471||2009||Vacuum-Treated Alloy Steel Forgings for Turbine Rotor Disks and Wheels||/11/|
|A 473||2009||Stainless Steel Forgings||/90/|
|A 477||Hot-Worked, Hot-Cold Worked and Cold-Worked Alloy Steel Forgings and Forging Billets for High Strength at Elevated Temperatures||Withdrawn 1991 /no materials/|
|A 508/A 508M||2005||Quenched and Tempered Vacuum-Treated Carbon and Alloy Steel Forgings for Pressure Vessels||/15/|
|A 521/A 521M||2006||Steel, Closed-Impression Die Forgings for General Industrial Use||/14/|
|A 522/A 522M||2007||Forged or Rolled 8 and 9% Nickel Alloy Steel Flanges, Fittings, Valves, and Parts for Low-Temperature Service||/2/|
|A 541/A 541M||2005||Quenched and Tempered Carbon and Alloy Steel Forgings for Pressure Vessel Components||/36/|
|A 579/A 579M||2009||Superstrength Alloy Steel Forgings||/27/|
|A 592/A 592M||2009||High-Strength Quenched and Tempered Low-Alloy Steel Forged Fittings and Parts for Pressure Vessels||/3/|
|A 594||Carbon Steel Forgings with Special Magnetic Characteristics||Withdrawn 1986 /no materials/|
|A 638/A 638M||2004||Precipitation Hardening Iron Base Superalloy Bars, Forgings, and Forging Stock for High-Temperature Service||/3/|
|A 649/A 649M||2009||Forged Steel Rolls Used for Corrugating Paper Machinery||/9/|
|A 654||1979||Special Requirements for Steel Forgings and Bars for Nuclear and Other Special Applications||Withdrawn 1983 /no materials/|
|A 668/A 668M||2004||Steel Forgings, Carbon and Alloy, for General Industrial Use||/13/|
|A 694/A 694M||2008||Carbon and Alloy Steel Forgings for Pipe Flanges, Fittings, Valves, and Parts for High-Pressure Transmission Service||/18/|
|A 695||1995||Steel Bars, Carbon, Hot-Wrought, Special Quality, for Fluid Power Applications||Withdrawn 2002 /2/|
|A 705/A 705M||2009||Age-Hardening Stainless Steel Forgings||/19/|
|A 707/A 707M||2007||Forged Carbon and Alloy Steel Flanges for Low-Temperature Service||/8/|
|A 711/A 711M||2007||Steel Forging Stock||/no materials/|
|A 723/A 723M||2008||Alloy Steel Forgings for High-Strength Pressure Component Application||/18/|
|A 727/A 727M||2009||Carbon Steel Forgings for Piping Components with Inherent Notch Toughness||/1/|
|A 730||1999||Forgings, Carbon and Alloy Steel, for Railway Use||Replaced by A668/668M /no materials/|
|A 765/A 765M||2007||Carbon Steel and Low-Alloy Steel Pressure-Vessel-Component Forgings with Mandatory Toughness Requirements||/6/|
|A 766/A 766M||Forgings||Withdrawn 1989 /1/|
|A 768/A 768M||2005||Vacuum-Treated 12 % Chromium Alloy Steel Forgings for Turbine Rotors and Shafts||/5/|
|A 769/A 769M||2005||Carbon and High-Strength Electric Resistance Forge-Welded Steel Structural Shapes||/8/|
|A 788/A 788M||2008||Steel Forgings, General Requirements||/no materials/|
|A 823||2008||Statically Cast Permanent Mold Gray Iron Castings||/14/|
|A 827/A 827M||2007||Plates, Carbon Steel, for Forging and Similar Applications||/6/|
|A 836/A 836M||2007||Titanium-Stabilized Carbon Steel Forgings for Glass-Lined Piping and Pressure Vessel Service||/1/|
|A 837/A 837M||2006||Steel Forgings, Alloy, for Carburizing Applications||/7/|
|A 859/A 859M||2009||Age-Hardening Alloy Steel Forgings for Pressure Vessel Components||/3/|
|A 891/A 891M||2008||Precipitation Hardening Iron Base Superalloy Forgings for Turbine Rotor Disks and Wheels||/2/|
|A 909/A 909M||2006||Steel Forgings, Microalloy, for General Industrial Use||/4/|
|A 940/A 940M||2006||Vacuum Treated Steel Forgings, Alloy, Differentially Heat Treated, for Turbine Rotors||/2/|
|A 952/A 952M||2002||Forged Grade 80 and Grade 100 Steel Lifting Components and Welded Attachment Links||/no materials/|
|A 965/A 965M||2006||Steel Forgings, Austenitic, for Pressure and High Temperature Parts||/43/|
|A 982/A 982M||2005||Steel Forgings, Stainless, for Compressor and Turbine Airfoils||/12/|
|A 983/A 983M||2006||Continuous Grain Flow Forged Carbon and Alloy Steel Crankshafts for Medium Speed Diesel Engines||/10/|
|A 986/A 986M||2006||Magnetic Particle Examination of Continuous Grain Flow Crankshaft Forgings||/no materials/|
|A 1021/A 1021M||2005||Martensitic Stainless Steel Forgings and Forging Stock for High-Temperature Service||/16/|
|A 1048/A 1048M||2006||Pressure Vessel Forgings, Alloy Steel, Higher Strength Chromium-Molybdenum-Tungsten for Elevated Temperature Service||/2/|
|A 1049/A 1049M||2006||Stainless Steel Forgings, Ferritic/Austenitic (Duplex), for Pressure Vessels and Related Components||/10/|
Welding and Filler materials
|A 205||Iron and Steel Filler Metal (Arc-Welding Electrodes and Gas-Welding Rods)||Replaced by A233 /no materials/|
|A 233||Mild Steel Covered Arc-Welding Electrodes||Withdrawn 1970 /no materials/|
|A 234/A 234M||2007||Piping Fittings of Wrought Carbon Steel and Alloy Steel for Moderate and High Temperature Service||/18/|
|A 316||Low-Alloy Steel Covered Filler Metal Arc-Welding Electrodes||Withdrawn 1970 /no materials/|
|A 371||Corrosion-Resisting Chromium and Chromium-Nickel Steel Welding Rods and Bare Electrodes||Withdrawn 1969 /no materials/|
|A 399||Surfacing Welding Rods and Electrodes||Withdrawn 1969 /no materials/|
|A 558||Bare Mild Steel Electrodes and Fluxes for Submerged Arc Welding||Withdrawn 1969 /no materials/|
|A 559||Mild Steel Electrodes for Gas Metal-Arc Welding||Withdrawn 1969 /no materials/|
Specification of forgings
Forging is the shaping of metal using a hammer or other tool. The process results in a permanent mold, and the metal shape becomes fixed.
The forging process is often used to create metal parts that are stronger than those made by casting or machining. Also, forging can create shapes that are not possible with casting, such as thin-walled structures. The metal may be heated to make it easier to work with and then hammered into shape.
There are several types of forging processes: upsetting, swaging, upsetting and swaging, fullering, bending, drawing and upsetting and swaging.
Upsetting is a technique that increases the cross section of a bar stock by forcing it through dies with progressive force applied at right angles to the axis of the bar. The die has a series of steps that gradually increase in size so that each step pushes down into the previously formed portion and forces it down until it reaches its final size. When this process is completed, the diameter of the bar will be larger than its original size by an amount equal to all of the steps in the die set up combined. Swaging works similarly except there is only one step per punch instead of multiple steps as in upsetting.
Forgings are metal parts that are shaped by forging, which uses a hammer and metal-forming dies to shape metal. They can be created in many different shapes and sizes, from small metal pieces to large castings. The forging process is used to produce components for a wide variety of applications in industries such as aerospace, automotive and industrial manufacturing.
Forging specifications include the following:
- Material type – The material type is usually defined by the alloying element content or the material specification number (MS). For example, an ASTM A276 alloy steel has a specific composition and can be ordered by specifying ASTM A276 or by ordering the grade with a specific chemical analysis.
- Dimensions – Forgings can be ordered by specifying dimensions such as outside diameter (OD), inside diameter (ID), thickness and length. For example, an ASTM A563 forging may have dimensions of 1/16 inch OD x 3/8 inch ID x 3 inches long. Some forgings may have multiple diameters with different wall thicknesses (WT) so they can be used in several different applications within the same specification range.
Heat treatment of forgings
Heat treatment after closed die forging plays an important role in developing desired properties such as internal stress relief, refinement of grain structure, and improvement of mechanical and physical properties. For workability, Epower metals offers forgings in annealed, normalized, normalized and tempered, process annealed, spheroidized or fully annealed conditions. Steel forgings can then be quenched and tempered to achieve the final desired properties. Below we will describe some of the common post-forging heat treatments offered by Epowermetals.com.
The forging restores the softness of the metal. Forgings are heated to a specific temperature and then cooled in a furnace at specific time intervals to obtain uniform softness throughout the forging.
Involves heating the forging to a specific temperature and then allowing the forging to cool in still air. The result is a recovery of ductility. Normalized forgings are cheaper than fully annealed forgings because full annealing relies on furnace-controlled cooling.
Quenching and Tempering
Metal forgings are first quenched and then heated again to between 400 and 600°C. Tempering establishes the correct balance of strength and ductility within the forging.
Used for mild steel forgings. The forgings are heated to below the fully annealed or normalized temperature and then cooled in still air. This changes the grain size and flow of the forging.
Used for high carbon steel forgings as well as tool steel and alloy steel forgings. The process forms spheres throughout the structure of the forging, thereby improving machinability.
Quenching and tempering is the most widely used heat treatment, which is effective in improving the hardness of steel forgings, increasing their strength, and obtaining better wear resistance at a lower cost.
Heat treatment, through a heating process, changes the properties of steel forgings such as carbon steel or alloy steel. It is used to harden, soften or modify other properties of materials with different crystal structures at low and high temperatures. The type of transformation depends on the temperature to which the material is heated, the rate of heating, the time of heating, the temperature to which it is first cooled, and the rate of cooling. For example, quenching hardens steel by heating it to a high temperature and then quickly immersing it in room temperature oil, water or brine to prevent carbon atoms from moving through the crystal structure and forming carbides, thus softening the metal. The two main methods of softening metal (to restore its ductility) are annealing, in which the temperature is slowly increased, held for a period of time, and then slowly cooled, and tempering, in which the metal is slowly heated in an oil bath and held for several hours.
Machining of forgings
Machining of forgings is done by using a machining center and/or CNC lathe. The material to be machined is set in a chuck or collet and the tool is mounted on the spindle.
The main purpose of machining forgings is to finish and shape parts prior to heat treatment, to eliminate roughness, surface defects and other blemishes.
A forged part usually requires a certain degree of finishing before it can be used for its intended purpose. The same applies to cast parts that are machined after casting or sand castings that are finished by grinding or lapping.
The most common methods of machining forgings are turning, milling and drilling. There are several types of tools available for this purpose such as single point cutting tools and multiple point cutting tools (center drills).
Machining of forgings is done in the following steps:
- 1. Rounding and deburring – The outer surface of the forging is rounded with a lathe, followed by deburring (removal of sharp edges) using a grinder.
- 2. Drilling holes – Holes are drilled into the forging using drill presses or other machine tools.
- 3. Grooving – Grooves are machined into the forging to allow for oil flow through the part during operation. These grooves can be machined before or after heat treatment depending on the type of material being used in the forging process.
- 4. Heat treating – Forgings that undergo heat treatment require additional machining processes to prepare them for this process. The first step is to remove any scale from the parts after heat treatment has been completed and allow them to cool down completely before continuing with any further machine operations on them. Once they have cooled down, they are then ground down to remove any surface rust or scale that may have formed during processing and finally bead blasted or shot blasted to remove any remaining surface contaminants from the part as well as roughen up its surface slightly so that paint will adhere better when it is applied later on down into these grooves we just created earlier through our grinding process.
Measurement of forgings
The following are some of the most common methods of measuring hot forgings:
1. Measurement of the outer diameter and length of forgings.
Forging dimensions are established by the manufacturer or by the customer. The dimensions must be checked for accuracy before any further processing can be performed.
The inner diameter is measured with a micrometer, which is calibrated to read directly in thousandths of an inch (or mm). This measurement is taken from the centerline of the bore to the end face of the forging.
The outer diameter is measured with calipers, which are calibrated to read directly in thousandths of an inch (or mm). This measurement is taken from the outside surface of the forging to its inside surface where it contacts any other part. If there is no contact between parts, then this measurement may be taken from any convenient point on one side of the forging to any convenient point on another side parallel to it.
The length is measured with calipers which are calibrated to read directly in thousandths of an inch (or mm). This measurement is taken from one end face to another end face parallel to it at right angles to all other faces and surfaces.
2. Measurement of the weight and mass of forgings.
When measuring the weight and mass of forgings, the product must be in a state that is suitable for weighing. It is therefore necessary to check whether there are any inappropriate features (pits, cracks, etc.) on the surface of the article.
Depending on the material and its structure, it may be necessary to prepare the article for measurement by grinding or polishing.
If there are no distortions in the shape of a forging, it can be weighed directly using a digital scale. The accuracy of digital scales depends on their construction and design. In particular, they can vary significantly due to their sensitivity to vibration and the use of batteries. For example, if you have an impact hammer with a weight of 100 kg and decide to weigh it with a digital scale with accuracy ± 50 grams, then you will receive a value between 50 kg and 150 kg.
The weight and mass of forged parts can be calculated from the average density:
- Density (kg/m3) = Weight (g) / Volume (cm3).
3. Measurement of the inner diameter and thickness of forgings (including the measurement of holes).
Measurement of forgings is a separate area of measuring in which the diameter and thickness of forgings are measured. The measurement of holes in forgings is also an important part of the process. The hole diameter must be as small as possible, but also as large as possible to ensure that it can be used later.
Forging measurement methods are:
Forging inner diameter measurement method (forging ring measuring method). This method measures the inner diameter of forgings by using a special ring gauge with a constant radius that matches the outer diameter of the forging ring.
Forging outer diameter measurement method (forging disc measuring method). This method measures the outer diameter of forgings by using a forged disc with an inner diameter equal to or slightly smaller than the outer diameter of the forging ring.
4. Measurement of the hardness value and strength value of forgings.
The hardness value and strength value of forgings are measured by the Rockwell hardness tester, Brinell hardness tester, or Vickers hardness tester. Forging hardness is generally measured at a depth of about 0.5 mm from the surface of the forging. The smaller the depth at which measurements are made, the more accurate the results will be. However, if measurements are made too close to the surface of an object, it may be difficult to determine whether or not there is a problem with the surface condition of that object.
The Rockwell hardness tester measures the depth of indentation caused by a hardened steel ball pressed against the surface of an object under test. The Brinell hardness tester uses a diamond pyramid-shaped tip pressed against an indentation in an object under test to measure its hardness value. The Vickers hardness tester uses a hardened steel ball pressed against an indentation in an object under test at a fixed load until it reaches its maximum load capacity (force).
Inspection of forgings
The following is a list of inspection methods that may be used to detect defects in forged parts:
- Visual Inspection: Visual inspection is used to check the size and shape of forgings. It is also used to detect surface defects and cracks.
- Inspection by Magnification: Magnification is an effective method of inspection, especially when it is used in conjunction with other methods such as radiography and ultrasonic testing. Magnification allows the inspector to detect surface defects that may be difficult to find using other methods. A 10X magnification lens can be used to detect surface imperfections that are too small for the unaided eye to see. Magnification may also be useful in detecting internal flaws that cannot be detected by radiographs or ultrasonic testing.
- Surface Defects and Shrinkage Cracks: Surface defects are usually caused by the improper use of forging tools or by poor-quality material. If a forging is made from a poor quality material, it will have a greater number of surface defects than if made from a high-quality material. Sometimes surface defects can be removed by grinding but sometimes they cannot be removed and must be scrapped.
Shrinkage Cracks are often caused by the use of low quality steel or by improper heat treatment. Shrinkage cracks occur when metal cools unevenly due to poor heat treating methods or improper forge welds. Some shrinkage cracks can be repaired with welding but some cannot be repaired and must be scrapped.
The most common surface defects are:
- Scratches. These are caused by a variety of factors, such as improper handling, improper lubrication and abrasive particles in the metal. Scratches on the surface of a forging can be removed by grinding or shot blasting.
- Lines. These are caused by impurities in the metal, such as inclusions, oxides and other foreign matter. Lines can either be removed by grinding or shot blasting or they may remain on the forging surface after machining.
- Burns. Burns result when heat is applied to one section of the forging at a time instead of being evenly distributed throughout the forging. The area over which heat is applied becomes overheated and oxidizes, causing a discoloration on the surface of the forged part. This discoloration will not affect the strength or performance of the forged part but it may make it unattractive if it is visible after machining operations have been completed.
X-Ray Fluorescence Spectroscopy: X-ray fluorescence spectroscopy (XRF) detects the chemical composition of an object by using x-rays that interact with the elements present in it and then emitting wavelengths that correspond with their respective elements.
Inspection by Radiography: Radiography uses X-rays to evaluate the internal structure and surface of a forging. It is particularly useful for determining whether there are any internal flaws in a forging, such as porosity, voids or inclusions; however, radiographic examination is not always sufficient for evaluating surface imperfections because it does not provide magnification capabilities and does not reveal surface defects on flat surfaces as well as they would appear under magnification.
Nondestructive Testing (NDT) is a powerful tool used to perform inspections on structures, components and other items without causing any damage to the item being inspected.
Nondestructive Testing (NDT) is a powerful tool used to perform inspections on structures, components and other items without causing any damage to the item being inspected.
Engineers use NDT techniques to determine if an item meets design specifications and can be used as intended. NDT methods include ultrasonic testing (UT), magnetic particle testing (MT) and liquid penetrant testing (PT). NDT is also used for quality assurance tests in manufacturing processes.
Liquid Penetrant Testing (PT): Liquid Penetrant Testing (PT) is a non-destructive testing method that detects discontinuities in the surface of metal parts.
PT is commonly used to inspect welds, but it can also detect cracks in castings and forgings. The use of liquid penetrant testing is governed by ASTM F904, which covers the inspection of welds for discontinuities and defects.
Liquid penetrant testing (PT) is an inspection method that uses a solvent or dye to detect surface discontinuities in metal. The solvent/dye penetrates into small cracks and voids on the surface of the metal part being inspected and appears as a dark line when viewed against a background color such as white or black. PT is widely used on welded joints to detect defects such as porosity, undercuts and misalignment.
Magnetic Particle Testing: Magnetic particle testing (MT) is used to detect internal inclusion, porosity or voids in the metal. Magnetic particles are applied on the surface of the material; if there is an inclusion present, it will be detected.
Ultrasonic Testing: Ultrasonic testing (UT) involves sending ultrasonic waves through the material to detect internal defects and cracks. UT equipment can detect small cracks as well as large ones.
Determination of the cutting position of forging inspection specimens
The destructive (anatomical) inspection of important forgings is often carried out. These inspection items include streamline inspection, fracture inspection, low magnification acid immersion inspection, microstructure inspection, mechanical property inspection, etc.
The general principles for determining the inspection sites for these items are:
- (1) Parts with streamline requirements in the part drawing.
- (2) The high-stress areas specified in the part drawing, such as dangerous sections, are taken as longitudinal, transverse, and chordal specimens.
- (3) The main stress location specified in the part drawing (taking longitudinal specimens).
- (4) At the maximum cross-section of the forging, i.e., when the deformation is minimal.
- (5) For solid cylindrical forgings, the sample is taken at a radius of 1/3 from the surface; Take the hollow part at a thickness of 1/2; Take a solid rectangular piece at the 1/6 diagonal.
- (6) The low magnification metallographic sample should be taken at areas prone to overheating and areas with streamlined requirements, and the horizontal low magnification should be taken as much as possible at the maximum cross-section of the forging.
- (7) Take a high magnification metallographic sample at the maximum cross-section of the forging and check for non-metallic inclusions and grain size; Check non-metallic inclusions, grain size, and overheating in high-stress areas; Take the forging at the location with the most severe deformation and temperature rise, and check for overheating and grain size.
- (8) The tower-shaped specimen should be taken as much as possible at the minimum cross-section of the forging.
Quality control of forgings
Whenever our customers come to our company for the first time, after checking our production facilities, another concern is how we perform quality control, which will give them the confidence to place an order. Typically, we inspect new steel forging parts in terms of material, dimensions, mechanical properties and defect inspection.
Ordering material is the first step in manufacturing steel forgings. To ensure that the material meets our needs, we need a material certificate from the material factory.
The material certificate alone is not enough; once the material is delivered to our plant, our technicians will also cut a small piece, test the chemical composition with a spectral analyzer, and check that each tested component is within the elemental range.
In addition, after forging, we will also check the forged blanks to see if the material composition may have changed.
Dimensional inspection is the most important task for custom steel forgings. Any dimensional and tolerance errors may render the product unusable. To ensure final assembly, the dimensions and tolerances of the steel forgings should be as accurate as possible. Therefore, our quality inspectors will be responsible for the dimensional inspection of the finished product.
One method is to test instruments such as calipers, depth gauges, micrometers, inside micrometers, height gauges, etc. These will be done by manual operation. To get more accurate dimensions, CMM can be used. However, due to the high price, only a few companies have such instruments.
Since all of these custom steel forgings used will be assembled into the machine, it is sometimes difficult to check certain dimensions to ensure that the product will be usable when received by the customer, and a gauge/accessory will be made to test for any assembly issues.
Mechanical Properties Inspection
For some special uses or applications, the product will have some mechanical property requirements (such as hardness, tensile strength, etc.). Depending on the required properties, we will perform heat treatment service after closed die forging. We also confirm the expected properties and perform mechanical tests to prove the quality of the steel forgings. The following are some common mechanical property checks.
- Hardness test when steel forgings have hardness requirements. Hardness will be tested by Brinell or Rockwell hardness tester.
- Tensile test – A destructive test procedure that provides the ultimate tensile strength, yield strength, elongation and compression area ratio of the product.
Although steel forgings are much stronger than steel forgings, they may also have defects, which we can classify as surface defects and internal defects.
For surface defects such as trim, cold seal, dent, ECT, etc., they are mainly detected by 100% visual inspection or MPI (magnetic particle inspection). However, MPI is costly and this is done when requested by the customer, who will, of course, be responsible for the cost.
Internal inspection is required for safety and strength reasons, especially when steel forgings are used. The internal inspection of steel forgings includes:
- Non-destructive testing (NDT): X-ray, ultrasonic testing, etc. This is the most direct way to detect internal defects in products.
- Segmental testing: Another direct way to check the product for internal defects is to perform segmental testing and visually inspect the defects. In this way, the product is broken and can no longer be used.
Since all of these custom steel forgings used will be assembled into the machine, it is sometimes difficult to check certain dimensions to make sure the product is ready for use when the customer receives it, and we will make a gauge/fitting to test for any assembly issues.
Applications of Forgings
Forgings are made for a huge variety of applications.
In the automotive industry, forging is used to make suspension components, such as idler arms and axles, and driveline components, such as connecting rods and transmission gears. Forgings are often used for pipe stems, valve bodies and flanges, sometimes made of copper alloys for increased corrosion resistance. Hand tools such as wrenches are often forged, as are many wire rope fittings such as sockets and screw shackles. Forgings are widely used in shipbuilding, aerospace components, agricultural machinery and off-road equipment. Electrical transmission parts such as pendant clamps and base covers use copper alloy forgings to improve weather resistance.
Forging steels used for axles, connecting rods, pins, etc. usually contain 0.30-0.40% carbon to improve formability. Heat treatment after forging gives the parts better mechanical properties than low carbon steels. In heavy crankshafts and high-strength gears, the carbon content is sometimes increased to 0.50% and other alloying elements are added to improve hardenability.
Types of forged products
Forged products including custom forgings, forged bars, forged blocks, forged discs, forged shaft, forged cylinders, forged tubes – in stainless steel, titanium, Inconel, aluminum and more.
Forged products include forged bars and complex forged shapes in quality steel, titanium, Inconel and aluminum. These products are manufactured with high technical equipment and strict quality control system. Forged bars can be produced according to ASTM standards or customer’s drawing or sample. The forging process is used for producing complex forged shapes like crankshafts, connecting rods or other automotive parts.
What are custom forgings?
Custom forgings are created by compressing metals into specific shapes using high-pressure machinery. The forgings we create are considered custom because we can produce precise shapes according to customer specifications.
During the forging process, the material’s grain structure is retained and refined. The resulting forgings are durable and can outperform components that are made through other processes.
Forged parts are used in a variety of applications, including industrial equipment, automotive parts, medical devices and more. Our products include:
Forged gears — Gears manufactured using a forging process have superior strength and durability compared to those made from machined or cast parts. We produce gears with diameters ranging from 2 inches up to 48 inches (50 mm to 1,219 mm). Most commonly used materials include carbon steel alloys such as 1020 carbon steel and alloy tool steels such as D2 tool steel (1.5 percent carbon). Forged gears can also be made from stainless steels like 17-4PH stainless steel (0.75 percent nickel) or duplex 2205 stainless steel (13 percent nickel).
What are forged bars?
Forged Bar is made from a billet of steel. The billet is heated until it is malleable, then the bar is hammered or pressed into its final shape by a machine called a forge press.
The difference between hot rolled bar and forged bar is the way it’s processed from its raw state to the finished product.
Forged Bars are stronger than hot rolled bars because they have been hammered into their final shape and size, giving them more surface area than hot rolled bars. This also helps reduce warping and cracking during the heating process.
Forged bars are also more expensive than hot rolled bars because of their superior quality and strength, but they are an excellent choice for high-performance applications that require extra strength and durability such as heavy-duty equipment like tractors and other agricultural vehicles.
What are forged blocks?
Forged blocks are created through a manufacturing method that utilizes localized compressive force shaping processes. The forging process begins when forged steel blocks are compressed within a die and custom shaped to exact project specifications.
This manufacturing process is used primarily for its ability to produce strong, dense and durable materials with high tensile strength and high elasticity. The end product of this process is often called forgings or die forgings.
Forged blocks are constructed by taking a blank block of steel, which has been heated and softened, and hammering it into shape using a series of dies that have been designed specifically for this purpose. The hammering process produces an extremely strong block of material with a uniform density throughout the entire block. Forging creates an extremely strong material that can be used in many different industries such as construction, agriculture, transportation and more!
When a customer orders a forged block from a manufacturer, they will typically specify exactly what kind of metal they want and how large the finished item should be. They might also request additional features like holes or grooves that will help them use their new product more efficiently. It’s important for manufacturers to take these specifications into account when creating their products because they want to make sure that everything fits together perfectly when their customers receive their order.
The forging process begins when forged steel blocks are compressed within a die and custom shaped to exact project specifications. Forging is a manufacturing method that utilizes localized compressive force shaping processes. Forged steel blocks are subjected to high temperatures and pressures during the forging process, which results in increased strength and durability.
Forged Blocks vs. Cast Blocks
While cast blocks have been around for years, forged steel blocks are becoming increasingly popular for their superior strength, durability, and appearance. Cast blocks are typically produced using sand molds that require multiple steps and complex machinery to create the desired shape. Forged steel blocks can be created with just one pressurized step, resulting in a stronger product that requires less material than cast blocks do when manufactured with conventional means.
Forged Steel Blocks vs. Extruded Steel Blocks
Forged steel blocks offer many advantages over extruded steel blocks as well:
They can be bent into a variety of shapes without losing their integrity or strength through the bending process.
They have no grain direction like extruded shapes do. This makes them more resistant to cracking than extruded shapes can be in extreme temperatures or conditions (e.g., fireproofing).
What are forged discs?
Forged discs are a type of metal that is made by heating and pressing steel into a mold. The disc can be made from many different types of steel, but the most common type is carbon steel. Forging is done in a number of ways and it depends on the particular application for which the disc will be used.
Forging is one of the oldest methods used to make metal products. Forged discs are used for a variety of general industrial equipment and machinery used by the steel, power generation and power transmission industries. Forged discs are also used in valves, fittings, high pressure and oil field applications.
Forged discs have a number of advantages over other types of discs:
They can be made thicker than cast or rolled discs because they are formed from solid stock rather than poured molten metal. This means that forged discs can be made with very high structural strength ratings without increasing their weight significantly over cast or rolled versions of the same material grade and thickness.
The uniformity in size of forged parts is much greater than cast parts because there is no variation due to shrinkage during cooling as there is with casting processes.
What are forged rings?
Rolled ring forgings are metal parts that are created through a process referred to as ring rolling. These parts are often used in the manufacturing of machinery, but they can also be found in many other applications.
Ring rolling is a metalworking process that involves passing metal through rolls in order to flatten or stretch it. This process can be used to create flat sheets of metal and heated profiles, which can then be formed into complex shapes. The rolled ring forging process is also known as rotary forging or rotary rolling.
Rolling is an ancient metalworking technique that has been used for centuries. Modern industrial rolled rings can be made from many different elements including aluminum alloys, copper alloys, nickel-based alloys, steel alloys and titanium alloys.
Rolled rings are commonly used in machinery because they offer high strength at low cost compared to other types of forged discs such as solid discs that require more costly machining processes than rolled rings do. They also offer good fatigue resistance and long service life at low temperatures due to their high ductility and toughness properties.
What are forged shaft?
Forged steel shafts are created through a manufacturing process that involves the shaping of the shaft Forgings using localized compressive forces. The forging process is initiated when a piece of steel is struck repeatedly with a hammer or squeezed with a press.
The process of compression causes the metal to become work hardened, which means it has been made stronger through deformation. This process also causes cracks to form within the material, which can be repaired by filling them with molten metal.
Forging produces parts that are lighter and often more durable than those produced by casting or machining. Because of this, forged shafts are commonly used in high-end golf clubs and other sporting equipment where weight reduction is important.
Forged steel shafts are also used in other industries such as aerospace because they’re strong enough to withstand high amounts of stress while remaining lightweight.
What are forged cylinders?
Forged cylinders are the most common type of cylinder used in vehicles and industrial applications. A forged (cast) cylinder is made using a mold, but the forging process uses no molds. Instead, a blank piece of metal is compressed and shaped by a machine called a press to produce a cast-iron cylinder.
Forging is the process of shaping metal with force to make it stronger and more durable than it would be if it were cast or machined. The forging process involves heating the metal until it becomes malleable (soft enough to alter its shape). Then, the piece is placed in a die that has the desired shape and compressed under extreme pressure. The force applied to the metal during this process will cause it to take on the shape of the die cavity.
The main advantage of forged cylinders over cast cylinders is that they have greater strength and durability than machined parts because they are made from solid blocks of metal rather than from individual pieces welded together as they are in cast iron or steel blocks. This makes them stronger because there are no weak spots where welds might break off or cracks could form as in cast iron or steel blocks.
What are forged tubes?
Forged tubes are similar to seamless tubes in that they are formed by pushing a hot metal blank into a mold. However, they differ in that they are not made from one continuous piece of metal. Instead, they are made from several pieces that are welded together.
Forging is the process of creating a shape by compressing or squeezing a material between opposing forces. This can be done with simple machines such as levers and hammers, but it is more commonly done using specialized machines called presses that apply several tons of force at once.
In addition to being stronger than seamless tubes, forged tubes have certain advantages over other types of steel construction:
They can be made thinner than seamless tubing without compromising strength or durability
They tend to have lower weight per unit volume than solid round bars or square bars
Forged tubes are often used in high-pressure situations where there is significant risk of failure due to cracking or corrosion.
Forged tubes are often used in high-pressure situations where there is significant risk of failure due to cracking or corrosion. They are also used for high-temperature applications and for situations where great strength is needed. Forged tubes can be made of many different materials, including carbon steel, stainless steel, alloy steel and titanium.
Forged tubes are forged under extreme pressure within a die that has been heated to a high temperature to soften the metal. The process of forging the tube causes it to become stronger and more durable than an extruded tube of the same material. This is because the molecular structure of the material changes during this process, which makes it more resistant to breaking and cracking. Forged tubes are typically used when strength is important in addition to flexibility, such as in automobiles or aircraft engines.
What are forged lap joint flanges?
Lap Joint Flanges slide directly over a pipe and are used with Stub Ends. Typically, a pipe is welded to the Stub End leaving the Lap Joint Flange to rotate freely around the stub end, simplifying bolt hole alignment.
Lap Joint flanges are commonly used in piping systems where high pressure or vacuum is applied. They are also used in industrial applications such as oil refineries and chemical plants where they are exposed to high temperature and pressure.
The flange has two parts: An inner ring that fits into the pipe and an outer ring that attaches to other piping components. The two rings are held together by bolts or screws which may be threaded through holes in either one or both of the rings.
What are forged plate flanges?
A forged plate flange is a flat, circular disc welded to a pipe’s end enabling the flange to be bolted to another pipe. It is often referred to as flat flange, plain flange and flange slip, etc. Two plate flanges can be bolted together with a gasket in between them, usually used in fuel and water pipelines.
The surface of the plate is smooth and very flat with no holes or slots for bolts or screws. This design prevents leakage by eliminating any gaps between the joint face and mating surface.
Forged plate flanges are made from carbon steel, alloy steel or stainless steel materials. They are used in a variety of industries including oil refining and petrochemical processing plants, power generation plants, ship building yards and chemical processing facilities.
Forged Wind Power Flange
What are forged wind power flanges?
Forged wind power flanges are ring-shaped connectors that are used to assemble the bodies of the steel towers supporting the wind turbines. Tower flange is an important wind power component for tower connection which is installed with six or seven flanges in a wind turbine.
In addition, wind turbine tower flanges are used not only for connecting but also for connecting and supporting purposes in the construction of a large-scale wind power station.
The main parts of a tower flange include inner ring, outer ring, sealing plate and bolt holes. The inner ring mounts on the tower body and connects with other parts such as door hinges, bearing plate and so on. The outer ring is welded to the inner ring and provides support for vertical load transfer from the tower base to its upper part.
The sealing plate seals on both sides of the outer ring so as to prevent water or dust from entering into the tower body through bolt holes. It also prevents corrosion between steel surfaces through galvanized coatings or other protective materials bonded on both sides of the outer ring.
What are forged weld neck flanges?
A forged welding neck flange (“WN”) features a long tapered hub that can be welded with a pipe. This flange type is used, normally, in high-pressure and high/low temperatures applications that require an unrestricted flow of the fluid conveyed by the piping system (the bore of the flange matches with the bore of the pipe).
The main features of a WN Flange:
Face to Face Dimensions: ANSI B16.5, ASME B16.47, MSS-SP-43 & BS4504.
Face to Face Thickness: ANSI B16.5 Class 150#, 300#, 600#, 900#; ASME B16.47 Class 150#, 300#, 400#, 600#, 900#; EN 1092-1 Class 150# & EN 1092-2 Class 150#; DIN Standard 150# & 350.
What are forged threaded flanges?
Forged threaded flange is a type of flange that has taper pipe threads conforming to ASME B1.20.1 in its bore and can be used in piping systems.
Threaded flanges are mainly used for joining two pipes together or for connecting pipes to other components such as valves, pumps, etc., as per the requirements of the manufacturing process.
Flange is one of the most common types of joints used in piping systems. It is generally used to connect two pipes or tubes at an angle. However, there are many different types of flanges available on the market today and they all have their own unique features and characteristics.
The main purpose of a flange is to provide a secure connection between two pipes or tubes with different sizes, shapes, materials and diameters so that they can act as a single unit for safe transportation through pipelines or other means of transportation.
What are forged socket weld flange?
Forged socket weld flanges, also called welding flanges, are a type of flange that is used to connect two pieces of pipe together. Socket weld flanges are often used on smaller sizes of high pressure pipe and are attached to that pipe by inserting the pipe into the socket end and applying fillet weld around the top. This results in a smooth bore with excellent flow characteristics.
Socket weld flanges can be made from carbon steel or stainless steel. Carbon steel socket weld fittings come in three types: standard, low temperature and deep drawn. Standard socket weld fittings are used for low pressure applications where corrosion resistance is not needed or required. Low temperature socket weld fittings have a higher carbon content than standard socket weld fittings and are designed for use at temperatures up to 400° F (204° C). Deep drawn socket weld fittings are manufactured by drawing out the blank with a mandrel prior to welding; this process allows for greater thickness tolerances and improved dimensional stability than other types of socket weld fittings.
Socket weld flange sizes range from 1/2 inch to 12 inches in diameter with different materials available depending on your application requirements.
What are forged slip on flanges?
Forged slip-on flanges, SOF, are designed to slip over the outside of pipe, turnback KC, reducers and swages. They are available in both plain and weld neck styles. Slip-on flanges are often referred to as “sleeves” or “caps”.
Slip-on flanges are most commonly used in the process industry for connecting piping systems together in order to transport gases or liquids from one point to another. They can be made from carbon steel, stainless steel, cast iron or ductile iron materials according to customer specifications.
The slip on flange is designed so that a pipe can be slipped over the outside of it and then tightened down with bolts through holes in the flange. This makes assembly easy because you don’t have to fit any couplings or other parts together before connecting pipes together.
What are forged blind flanges?
A forged blind flange is a solid disk used to block off a pipeline or to create a stop. Similar to a regular flange, a blind flange has mounting holes around the perimeter and the gasket sealing rings are machined into the mating surface. The difference is that a blind flange has no opening for fluids to pass through.
Blind Flanges come in different configurations depending on their function. For example, some blind flanges have slotted holes that allow for passage of liquids while others are solid and have no slots for liquid flow.
Blind flanges can be constructed from carbon steel or stainless steel; depending on your application. Carbon steel has good corrosion resistance at low temperatures but is less resistant at high temperatures than stainless steel. Stainless steel, on the other hand, is more expensive but is resistant to most chemicals and has excellent corrosion resistance at high temperatures.
Blind flanges can also be made from other materials like aluminum or brass if they are being used in a corrosive environment such as oil or gas processing facilities where carbon steel may not hold up well over time due to its susceptibility to corrosion by certain chemicals like hydrogen sulfide (H2S) which forms when crude oil decomposes over time.
What are forged long weld neck flanges?
Forged long weld neck flanges are like weld neck flanges, except for the neck, which is extended and acts like a boring extension. Long weld neck flanges can be used in high pressure industrial applications, as well as high temperature situations. They are often utilized in the oil and gas or petrochemical industries.
Long Weld Neck Flange Advantages
Long weld neck flanges have some distinct advantages over their cousins, such as:
They have larger bore sizes than conventional weld neck flanges, which means they can handle more pressure before bursting.
They can handle higher temperatures than other types of flanges. This allows them to be used for extremely hot liquids or gases that would otherwise damage conventional materials due to extreme heat or pressure.
What are Forged Orifice Flanges?
The forged orifice flanges are used with orifice meters for the purpose of measuring the flow rate of either liquids or gases in the respective pipeline. Orifice meters are commonly used to measure the flow rate and total volume of liquids, gases and steam.
The Forged Orifice Flange is designed to withstand high pressure, as well as high temperature conditions. This type of flange is manufactured from carbon steel or stainless steel material, depending on your specific requirements. The material used for manufacturing this type of flange is chosen based on the application requirement and end user’s requirement which may vary from one industry to another industry.
The Forged Orifice Flange comes in various forms such as single hole, double hole and four hole. The flange is available in different sizes ranging from ½ inch to 2 inches according to your needs. It is also available in various sizes according to the diameter of pipe that it needs to be mounted on (i.e.: 1 inch diameter pipe will have a ½ inch sized flange). The main purpose of using this type of flange is to connect pipes together by applying pressure onto both sides simultaneously thus ensuring maximum strength during installation process.
What are Forged Spectacle Flanges?
Forged spectacle flanges are specialty flanges made of two metal discs attached in the middle by a small section of steel. The discs can be flat or curved and are designed to fit into a matching groove on your frame. The groove is usually found on the temples of your glasses, but can also be used in other areas such as the nosepiece.
The purpose of this component is to strengthen and reinforce your frames, which helps prevent them from breaking or bending when you put them on or take them off. It also adds a nice aesthetic touch to your glasses and helps provide a sturdy base for attaching other elements like hinges.
Forged spectacle flanges are made using a special type of metal forging process called hot drop forging, which involves heating up the metal until it’s malleable enough to be shaped with heavy presses (or drops). The result is an extremely strong part that can hold up to years of wear and tear without bending out of shape or breaking apart like some cheaper substitutes might do over time.
What are Forged Loose Flanges?
A Loose Flange (Lap Joint flange) is a device which consist of two pieces , it looks like a weld neck flange together, and it is butt welded with the pipes, it also like a loose slip-on flange.
A Lap Joint Flange has one or more holes through its face to allow a pipe to be inserted into the gap between the two pieces of the flange.
It is used when there is no need for pressure or vacuum in the system and the pipes are not subjected to high loads.
Forged Oval Flange (DIN)
What are Forged Oval Flanges?
The forged oval flange is a special shape of the flange, mainly used for valves and other special equipment parts. Oval flange are reliable, safe and convenient, with the advantages of compatibility and practicability.
There are many types of oval flanges in the market: such as straight oval flange, knuckle oval flange, and inclined oval flange. The straight oval plate is mainly applied to packing machines, and it has a large bearing capacity and a long life span. In addition to this type of plate, there are also other types such as knuckle plates (K-type), inclined plates (I-type), double angle plates (D-type), etc., which have different specifications according to their functions.
What are Forged Tube Sheets?
Tube sheets are used to support and isolate tubes in heat exchangers, boilers or to support filter elements.
Tube sheets are typically made from high-strength steel plate with holes drilled to accept the tubes or pipes in a accurate location and pattern relative to one another. The tube sheets are used to support and isolate tubes in heat exchangers and boilers or to support filter elements. Tubes are attached to the tube sheet by hydraulic pressure.
Tube sheets are available in a variety of shapes and sizes that can be customized for your application’s specific needs. Tube sheets come in standard diameters ranging from 4″ to 12″, but can be produced up to 36″ diameter. We also offer custom tube sheet fabrication services on any size sheet up to 48″ x 96″.
What are Custom Forged Flanges?
Custom forged flanges are used for specialty projects. For a custom ring flange, all we need is the OD, ID, thickness, bolt pattern, and grade of material.
Custom forged flanges are available in all materials and pressure ratings up to Class 3000. Custom flanges can be made from carbon steel, alloy steel or stainless steel materials. We have a large selection of standard flange sizes such as ANSI/ASME B16.5, B16.47 and NACE MR0175/ISO 15608 ring flanges ready for immediate shipment!
Forged Steel Flanges can be made with any combination of flat face or raised face flanges to meet your specifications. They can also be made with no center hole (blind), two holes (blind), four holes (blind) or six holes (blind). Blind flanges are ideal for applications where the piping system needs to be concealed from view inside machinery or other equipment. Our forged steel blind flanges are fabricated from carbon steel or stainless steel materials depending on your requirements. We also manufacture a variety of pressure ratings for customized applications ranging from 1500 PSI to 3000 PSI (10 bar).
Custom forged flanges are available with metric and inch bolt patterns as well.
We offer a wide range of forged products such as:
Bar stock – round bar (DIN 17100) up to 6000mm length; square bar (DIN 17102) up to 2400mm length; hexagonal bar (DIN 17103) up to 3000mm length; flat bar (DIN 17130) up to 3000mm length; rectangular tube (DIN 17135) up to 6000mm length; oval tube (DIN 17136) up to 2000mm length; pipe fittings and tubes – round pipes from Ø12mm to Ø300mm and oval tubes from Ø30mm.
Why Forgings are Considered Superior to Other Metalworking Processes?
Forgings are a popular metalworking process that can be used to make a wide range of products. Forgings are generally considered superior to other metalworking processes because they provide better strength and durability than other types of manufacturing methods.
For example, castings are made from molten metal poured into a mold. The castings may be solid or hollow but there is no way to control the exact composition of the final product. This may result in weak areas or seams where two parts join together.
Another problem with casting is that it is difficult to achieve uniform thickness throughout an object because there is no way to measure until after it has cooled down and solidified. A large amount of material must be removed from the inside or outside of the part so that it can be machined or drilled afterwards.
The best way to avoid these problems is by using forgings instead. Forgings are made from a solid piece of metal which has been shaped using powerful presses and other equipment such as forging hammers and forging dies. Forging hammers press against dies that have been shaped like a mold so that when force is applied in one direction, it will cause the metal to flow outwards into a shape desired by the forging manufacturer.
Why Custom Forgings are Better?
Custom Steel Forgings are a solution for your part needs when design, material and cost are all important factors.
Custom forgings offer a high degree of reliability and tolerance capabilities.
Custom steel forgings offer uniformity of composition and structure. With many metal forgings made from one “heat” of steel, steel forgings have minimum variation in machinability and mechanical properties.
Custom forged steel parts are stronger and more reliable than machined or cast parts due to the fact that the grain flow of the steel is altered, conforming to the part’s shape. Grain flow strengthening in steel forgings is analogous to the cross grain strength of wood.
Custom forgings make possible designs that accommodate high loads and stresses. Forgings are free from internal gas pockets, voids, or cooling defects that can cause unexpected fatigue or impact load failure. Custom Steel forgings are used when quality cannot be questioned.
Steel forging is the application of thermal and mechanical energy to steel bars, billets, and ingots to cause the material to change shape while in the solid state. This is a different process than casting, where metal is melted and poured into a mold in the liquid or molten state.
The general forging defects are:
- Unfilled sections – This is a common defect where the metal has not been fully displaced by the punch. This can result in an open area on your part that may be unacceptable for use.
- Cold shut – Cold shut is a crack that occurs at the end of the forging process. It occurs when the metal cools too quickly and does not have time to flow properly. This can also result in an open area on your part that may be unacceptable for use.
- Scale pits – Scale pits are small indentations on the surface of your forged product that are caused by impurities present during forging or from oxidation after forging. These imperfections do not affect performance but do reduce appearance quality.
- Die shift – The die shifts during the forging process and this produces an uneven cross section. This can be avoided by using a proper lubrication system.
- Flakes – Flakes form on the surface of the forgings due to improper grain flow. This is caused by high temperatures and improper lubrication.
- Improper grain flow – Improper grain flow may be due to low temperature, uneven pressure, or poor lubrication. In all these cases, the metal will not flow properly into the mold cavity.
- Surface cracking – Surface cracking occurs when an unsupported surface is subjected to high impact loads from the dies or hammers that produce it. It also results from improper mold design or defective tooling materials such as hardened steel dies that have been allowed to wear out during their use.
- Residual stresses – Residual stresses are built up when there is a difference between the temperature at which fusion takes place and that at which solidification occurs in a casting process such as lost wax casting or sand casting (which use hot metal).
- Incomplete forging penetration – Incomplete forging penetration is a defect that occurs when the entire cross section of the tool does not enter the die. The result is a hole in the sheet metal that is smaller than desired and may be up to 1/16″ (1.6 mm) in diameter.
Forging defects can be caused by a number of factors including:
- When properly set up, dies should be able to reach maximum depth within the die within one full stroke. Improperly set up dies allow too much space between the ram and anvils causing the ram to bottom out before reaching maximum depth within a die. This condition is most prevalent with longer tools such as punches, dies, etc., which must travel a greater distance within a die before reaching maximum depth relative to shorter tools such as chisels, shears and rolls which only travel half as far within a die before reaching maximum depth relative to longer tools.
- Improperly set up dies can also cause excessive tool wear along with poor tool performance and premature tool failure. Improperly set up dies will cause excessive wear on both sides of your cutting edge due to improper force distribution throughout the cut. This excessive wear will result in premature failure of your cutting tool while increasing cycle time due to increased force requirements needed to achieve full depth within dies.
Risk factors of forging production
Forging production risk factors and the main causes:
In the forging production, easy to occur in the trauma accident, according to its cause can be divided into three kinds.
First, mechanical injuries – scrapes and bruises caused directly by machines, tools or workpieces.
Third, electric shock injuries.
Second, from the point of view of safety and technical labor protection, the characteristics of the forging workshop are:
- 1. Forging production is carried out in the state of scorching metal (such as mild steel forging temperature range between 1250 – 750 ℃), due to a large number of manual labor, the slightest carelessness may occur burns.
- 2. The heating furnace and scorching ingots, billets and forgings in the forging shop constantly emit a lot of radiation heat (forgings at the end of forging, still have a fairly high temperature), workers are often subject to heat radiation.
- 3. The forging workshop heating furnace in the combustion process generated by the smoke and dust into the air of the workshop, not only affect the health, but also reduce the visibility of the workshop (for the burning of solid fuel heating furnace, the situation is more serious), and therefore may also cause work-related accidents.
- 4. The equipment used in forging production, such as air hammers, steam hammers, friction presses, etc., are issued when working with impact forces. Equipment under such impact loads, itself prone to sudden damage (such as the sudden breakage of the forging hammer piston rod), and cause serious injury accidents.
- Presses (such as hydraulic presses, crank hot die forging presses, flat forging machines, precision presses) shear bed, etc., in the work, although the impact is smaller, but the sudden damage to the equipment and other circumstances also occur, the operator is often caught off guard, may also lead to work-related accidents.
- 5. Forging equipment in the work of the force is very large, such as crank presses, tensile forging presses and water presses such as forging equipment, their working conditions are more smooth, but the force of its work parts is very large, such as China has manufactured and used 12,000t forging presses. It is the common 100 – 150t press, the force issued is already large enough. If the die is installed or operated slightly incorrectly, most of the force is not acting on the workpiece, but on the die, the tool or the parts of the equipment itself. In this way, some kind of installation and adjustment errors or improper operation of the tool may cause damage to the machine and other serious equipment or personal accidents.
- 6. The tools and auxiliary tools of the forger, especially the hand forging and free forging tools, clamps, etc. have a wide range of names, and these tools are put together in the workplace. In the work, the tools are replaced very often, and storage is often disorganized, which is bound to increase the difficulty of checking these tools, when the forging needs to use a tool and often can not be quickly found, sometimes “make up” the use of similar tools, which often cause accidents at work.
- 7. Because of the noise and vibration of the forging workshop equipment in operation, the workplace is noisy and unpleasant to the ear, affecting the human hearing and nervous system, distracting the attention, thus increasing the possibility of accidents.
Analysis of the causes of work accidents in forging workshop:
- 1. The need to protect the area, equipment lack of protective devices and safety devices.
- 2. The protective devices on the equipment are not perfect, or not used.
- 3. The production equipment itself is defective or faulty.
- 4. Damage to equipment or tools and inappropriate working conditions.
- 5. The forging die and anvil are defective.
- 6. Confusion in the organization and management of the workplace.
- 7. Process operation methods and repair of auxiliary work is not done properly.
- 8. Personal protective equipment such as protective glasses are faulty, work clothes and work shoes do not meet the working conditions.
- 9. When several people work together on an operation, they do not coordinate with each other.
- 10. Lack of technical education and safety knowledge, resulting in the use of incorrect procedures and methods.
Forging process should pay attention to the place:
- 1. The forging process includes: cutting the material to the required size, heating, forging, heat treatment, cleaning and inspection. In small manual forging, all of these operations are performed by several forgers overhand and underhand in a small place. Exposure to the same hazardous environment and occupational hazards; in large forges, the hazards vary with the job.
- Working conditions Although working conditions vary depending on the form of forging, they have certain common features: moderately intense physical labor, dry and hot microclimate environment, noise and vibration generation, and air contaminated by fumes.
- 2. Workers are exposed to both hot air and thermal radiation, resulting in heat accumulation in the body. heat plus metabolic heat can cause heat dissipation disorders and pathological changes. the amount of sweating for 8 hours of labor will vary with the small gas environment, physical exertion, and degree of thermal adaptability generally between 1.5 and 5 liters, or even higher. In smaller forging shops or far from heat sources, the Behar II heat stress index is usually 55 to 95; however, in large forging shops, the working point near the heating furnace or drop hammer machine may be as high as 150 to 190. susceptible to salt deficiency and heat cramps. During the cold season, exposure to changes in the microclimate environment may promote its adaptability to some extent, but rapid and too frequent changes may constitute a health hazard.
Atmospheric pollution: The air in the workplace may contain soot, carbon monoxide, carbon dioxide, sulfur dioxide, or also acrolein, the concentration of which depends on the type of heating furnace fuel and the impurities contained, as well as the combustion efficiency, airflow and ventilation conditions.
Noise and vibration: Type forging hammers necessarily produce low frequency noise and vibration, but may also have some high frequency components with sound pressure levels between 95 and 115 decibels. Exposure of staff to forging vibrations may cause temperamental and functional disorders that can reduce work capacity and affect safety.
Common defects and solutions in large forgings
The defects in large forgings can be divided into five categories: chemical composition, unqualified tissue performance, second-phase precipitation, porosity defects, and cracks. They can be divided into raw material defects in smelting, steel output, ingot injection, mold release cooling or heat delivery, and forgings defects in heating, forging, post-forging cooling, and heat treatment.
Due to the large section size of forgings, the large change and distribution of temperature during heating and cooling, the forging deformation, and the large metallurgical defects of steel ingot, it is easy to form some defects different from small and medium-sized forging. Such as severe segregation and loose, dense inclusions, developed columnar crystals and large uneven crystallization, sensitive cracking and white spot tendency, grain heritability and tempering brittleness, serious inhomogeneity of tissue performance, shape and size super difference, and so on.
The following are some main defects found in large forgings and potential forging solutions:
The uneven distribution of chemical composition and impurities in steel is called segregation. Generally, those above the average component are called positive segregation, and those below the average component are called negative segregation. There is still macro segregation, such as regional segregation, microsegregation, dendrite segregation, and intercrystal segregation.
Segregation in large forgings is closely related to steel ingot segregation, and the degree of steel ingot segregation is also related to steel type, ingot type, smelting quality, and pouring conditions. Alloy elements, impurity content, and gas in steel all aggravate the development of segregation. The larger the ingot, the higher the pouring temperature, the faster the pouring speed, and the more serious the segregation degree.
(1) Regional segregation
It belongs to macroscopic segregation, caused by the change of crystallization, the difference. For example, the gas in steel drives the bar trajectory in the rising process, forming whisker segregation. The crystal crystallized at the top, and the impurities at the high melting point sink, as if the axis segregation formed by the falling of crystal rain. Precipitation at the bottom of the ingot forms a negative segregation sedimentation cone. Finally, the upper area is solidified, and carbon, sulfur, and phosphorus are enriched, becoming the positive segregation area with more defects.
Figure.1-1 is a schematic diagram of the 55T 34CrMolA ingot in China.
Figure.1-1 Schemram of ingot ingot
① “∧” segregation zone; ② “V” type; ③ Negative segregation zone.
The solutions to prevent regional segregation are:
- 1) Reduce the content of sulfur, phosphorus, and other segregation elements and gases in steel, such as furnace refining, vacuum carbon deoxygenation (VCD) treatment, and ingot bottom-blowing argon process.
- 2) Adopt multi-furnace pouring, bursting pouring, vibration pouring, and heat insulation outlets, and enhance the ability to burst and contract.
- 3) Strictly control the injection temperature and speed, and use the short crude ingot type to improve the crystallization conditions.
On the transverse low power piece of the forging, the frame features corresponding to the ingot outline, also known as frame segregation. Figure.1-2 is ingot segregation shown on low-power test strips of 30CrMnSiNiA steel die forging. Because the segregation band in the ingot expands along the mold surface when deformation. The segregation zone comprises small pores and enriched elements, negatively affecting forgiving uniformity.
With its high purity and reasonable crystal structure, electroslag remelting has become an important method for producing large forgings and billet. However, ripple segregation will be formed if the current and voltage are unstable in the remelting process. When the current and voltage increase, the steel liquid overheats, the crystallization speed slows down, and the concentration band increases; when the current and voltage decrease, the concentration degree of the melting element decreases, and the periodic changes form ripple gradient bands, as shown in Figure.1-3.
Regional segregation showed scattered dark puncta on the transverse low acid extract, called punctate segregation. Figure. 1 – 4 are dot segregation distributed over the entire transverse section.
Figure.1-2 30CrMnSiNiA the area segregation shown on the low power piece
1:1 hydrochloric acid solution
Figure.1-3 30CrMnSiNiA ripple segregation on refused steel
1:1 hydrochloric acid solution
Figure.1-4 Point segregation of 45# steel forging die to low test
1:1 hydrochloric acid solution
(2) The dendrite segregation
It belongs to the microscopic segregation. The inhomogeneity of the components of dendrite crystallization and intercrystalline microregions may cause an uneven distribution of tissue properties. Using a scanning electron microscope (SEM), spectrometer (WDS), and energy spectrometer (EDS) for microregion observation and composition analysis can detect and clarify the cause. Generally, high temperature diffusion heating, reasonable deformation, and homogenizing heat treatment can eliminate or reduce its adverse effects.
2. Inclusion of substances and harmful trace elements
According to their source, the inclusion can be divided into endogenous and foreign.
The common endogenous inclusions include sulfide, silicate, oxide, etc. Their quantity and composition in steel are related to the composition of steel, smelting quality, pouring process, and deoxygenation method. The endogenous inclusions with high melting points solidify before the matrix metal, and the crystallization is not hindered, presenting a regular angular shape; the endogenous inclusions with low melting points are mostly distributed along the grain boundary due to the limitation of the solidified metal. Sulfide and better plastic silicate group, when the ingot, through forging deformation, extends along the main deformation direction in a strip. Figure. 1-5 shows an elongated MnS inclusion shape in a 34CrNi3Mo rotor steel. When forging deformation, oxide and poor plastic silicate are mixed and broken into small particles in a chain ball distribution. Figure. 1 – 6 are the chain oxides distributed along the direction of deformation. Small size, diffuse distribution of endogenous inclusion, mostly microscopic defects, the harm degree is small. Large or dense clouds constitute macroscopic defects, which greatly impact the use of forgings and can easily cause serious failure accidents.
Figure.1-5 Deformed MnS mixed with morphology SEM 500X
Figure.1-6 Deformed broken oxide mixed with LM 500X
External inclusion refers to the slag, protective slag, oxide film, refractory material, and special metal block in the mixed human steel. Usually, the external inclusion is coarse, and serious distribution will destroy the continuity of steel and scrap.
With the development of high parameters and large-scale machinery and equipment, more stringent requirements are put forward for the quality of large forgings. Therefore, trace elements such as lead, antimony, tin, bismuth, and arsenic in steel need to be controlled to improve the toughness level of forgings.
The general solution to reducing the inclusions in steel is:
- 1) Vacuum treatment of liquid steel, refining outside the furnace, and control of liquid steel quality;
- 2) Clean pouring to prevent external inclusion contamination and special-metal entry;
- 3) Reasonable forging and deformation, and improve the inclusion distribution.
3. Retraction hole and loose hole
These pore defects destroy the metal continuity, form the stress concentration and crack source, and belong to the disallowed defects.
When the ingot is opened, the resection amount is insufficient, and the residual shrinkage hole and loose, manifested as the forging end, has a tubular hole or serious central loose. As shown in Figure.1-7 is the refrigeration roll of 9Cr2Mo steel. Due to the low pouring temperature of the ingot, the shrinkage hole goes deep into the spindle area, is not completely removed during forging, and forms the residual of the shrinkage hole. The center of the transverse test film showed the characteristics of branch and fork holes. Further dissection revealed the presence of loose tissue at the end.
Figure.1-7 Macroscopic morphology on the transverse specimen of the residual in the forging
The solutions to prevent such defects are:
- 1) Strictly control the pouring temperature and speed to prevent low temperature and slow ingot injection;
- 2) Use heating or adiabatic outlet to improve the shrinkage conditions and move the shrinkage hole to the outlet area to prevent the shrinkage hole from being deep into the ingot;
- 3) Control the cutting rate of the ingot during forging, fully cut, and shrink the defects. Reasonable forging and pressing deformation, compaction, and loose defects.
The bubbles are divided into internal and subcutaneous bubbles:
The furnace charge, gas, and air import the gas in the steel. When smelting, the deoxygenation is poor, and the boiling exhaust is insufficient; the gas content in the steel liquid is too much. During the solidification process, as the temperature decreases, the gas solubility declines and emerges from the steel liquid, forming internal bubbles. When the ingot mold wall is wet corroded, and the coating contains moisture or volatile substances, the gas will permeate into the surface layer of the ingot, forming subcutaneous bubbles.
The bubbles will be flattened or expanded into cracks after forging and deformation.
The solution to prevent air bubbles is:
- 1) Fully baking the furnace material and pouring system;
- 2) Fully degassing during smelting and adopt the protective pouring process;
- 3) Defects of high temperature diffusion, forging welding, and holes;
- 4) Timely burning and peeling of the surface cracks.
5. Forge cracks
In large forging, when the raw material quality is bad or the forging process is not then, it is often easy to produce forging cracks. The following are a few forging cracks caused by poor material failure.
(1) Forging crack caused by steel ingot defect
Most ingot defects may cause cracking during forging. Figure.1-8 shows the central crack of the spindle forging in 2Cr13. This is because the 6T ingot solidifies when the narrow crystallization temperature range and the line shrinkage coefficient are large. Inadequate condensation, the temperature difference between inside and outside is large, and the axial tensile stress is large along the dendrite cracking, forming the steel spindle intercrystal crack; the crack is further expanded in forging into the spindle forging has been cracked. The following measures can eliminate the defect:
- ① Improve the purity of molten steel;
- ② Ingot cooling slowly to reduce thermal stress;
- ③ Adopts good heating agent and insulation cap to increase the replenishment and shrinkage capacity;
- ④ Adopts central compaction forging process.
Figure.1-8 Forging cracking caused by intercrystalline shaft core cracks
(2) Forging cracks caused by the precipitation of harmful impurities in steel along the grain boundary.
The sulfur in steel often emerges along the crystal boundary in the form of FeS, and its melting point is only 982℃. At the forging temperature of 1200℃, the FeS on the grain boundary will melt and surround the grain in the liquid film, destroying the combination between grains and producing thermal fragility, and the slight forging will crack.
When copper-containing copper in steel is heated in the peroxide atmosphere at 1100-1200℃, a copper-rich zone will be formed in the surface layer due to selective oxidation. When the solubility exceeds copper in austenite, copper is distributed at the grain boundary in liquid film, forming copper brittle, which cannot be forged and formed. If there is also tin and antimony in the steel, it will also seriously reduce the solubility of copper in the austenite, exacerbating this embrittlement tendency. Figure.1-9 are the mesh cracks of 16Mn steel forgings. Due to the high copper content, the surface is selectively oxidized during forging and heating so that the copper is enriched along the grain boundary, and the forged cracks are formed along the copper-rich phase core of the grain boundary and expanded.
Figure.1-9 16Mn steel forged mesh crack LM 4% dilute sulfuric acid aqueous solution erosion
(3) Forged cracks caused by different phase (second phase)
The mechanical properties of the second phase in steel are often very different from the metal matrix, so it will cause additional stress during deformation and flow, leading to the plastic decline of the overall process. The separation will form holes once the local stress exceeds the binding force between the different phases and the matrix, for example, in steel oxide, nitride, carbide, boride, sulfide, silicates, etc. If these phases are dense, chain distribution, especially in the weak binding force along the grain boundary, high-temperature forging will crack. Figure.1-10 is the macroscopic morphology of 20SiMn steel 87t ingot caused by the precipitation of fine AlN along the grain boundary, whose surface has been oxidized, showing polyhedral columnar crystal. Microscopic analysis shows that forging cracking is related to the massive precipitation of fine granular AlN along the primary crystal boundary.
The solution to prevent forging cracking caused by crystal precipitation of aluminum nitride is:
- 1) Limit the amount of aluminum added in steel, remove nitrogen gas in steel, or inhibit the amount of AlN precipitation by titanium addition method;
- 2) Using heat delivery steel ingot, overcooling phase change treatment process;
- 3) Improve the heat delivery temperature (> 900℃) to directly heat the forging;
- 4) Fully uniform annealing before forging to diffuse the crystal boundary precipitation phase.
6. Overheating, overburning, and uneven temperature
If the heating temperature is too high or the temperature stay time is too long, it is easy to cause overheating too burning. Overheating significantly reduces the plasticity and impact toughness of the material. When over-burning, the grain boundary of the material is violently oxidized or melted, completely losing its deformation ability.
When the heating temperature distribution is seriously uneven, the temperature difference between inside and outside, front and negative, along the length is too large, causing uneven deformation during forging, eccentric forging, and other defects, also known as under heat.
Figure.1-11 is the overheating tissue of 5t PCrNi3Mo steel forging billet caused by high heating temperature. The sample was corroded by 10% (volume fraction) nitric acid water and 10% (volume fraction) sulfuric acid water and observed by a gold phase microscope (LM). The grain was thick, the grain boundary was black, and the matrix was gray-white, showing overheating characteristics.
Figure.1-12 shows the cracks caused by overburning of GCr15SiMn forgings of bearing steel, with melting traces and low melting point drama on the grain boundary, and the crack expands along the grain boundary. The sample was eroded with a 4% (volume fraction) nitric acid alcohol solution with a black grain boundary, which was burned out, and the forging billet was overburned and scrapped.
Figure.1-11 PCrNi3Mo Steel forgings overheated tissue 100X
Figure.1-12 GCr15SiMn Steel forgings with overburned tissue 100X
The solutions to prevent the heating defects are:
- 1) Strictly implement the correct heating specifications;
- 2) Pay attention to the furnace installation method to prevent local heating;
- 3) Adjust the temperature measuring instrument, careful heating operation, and control the furnace temperature gas flow to prevent uneven heating.
7. White point
A white dot is an internal defect produced by forgings during post-forging cooling. Its morphology in the transverse low power test film is fine hair silk sharp angle crack; the fracture is silvery white spots. Figure.1-13 are the white dots on the longitudinal breaks of the Cr-Ni-Mo steel forgings. Its shape is irregular, the size disparity, the minimum long axis size is only 2mm, and the largest is 24mm.
Figure.1-13 The morphology of the white dots on the macroscopic breaks
White dot essence is a kind of brittle, sharp-edge crack with great harm and is a dangerous defect in martensite and pearlescent steel.
The cause of the white spot is the enrichment of hydrogen in steel to the tensile stress area under the action of stress so that the steel produces the so-called hydrogen embrittlement and brittle fracture of steel. Hence, the combined action of hydrogen and additional stress is the cause of the white spot.
The solution to prevent the white spots is mainly:
- 1) Reduce the hydrogen content in the steel, such as paying attention to the baking furnace material, smelting fully boiling, vacuum gas removal, refining and degassing from the furnace, etc.
- 2) Using the heat treatment to eliminate the white spots, the main task is to diffuse the hydrogen in the steel, stress elimination, such as the expanded hydrogen annealing heat treatment, etc. See the common defects in the forging process and those often caused by improper post-forging cleaning.
8. Uneven tissue performance
Because of their large size, large process, long cycle, uneven process, and many unstable factors, large forgings often cause serious uneven tissue performance, so they can not pass the mechanical properties test, metallographic tissue inspection, and nondestructive testing. Due to the segregation of chemical components in ingots, the aggregation of inclusions, the influence of various pore defects, slow temperature change, uneven distribution, large internal stress, many defects, high temperature long time forging, local deformation, plastic flow condition, compaction degree, deformation distribution; cooling diffusion process is slow, the tissue transformation is complex, and the additional stress is large. The above factors may lead to serious uneven tissue performance and unqualified quality.
Measures to improve the uniformity of large forgings:
- 1) Adopt advanced metallurgical technology to improve the metallurgical quality of steel ingot;
- 2) Adopt control forging, control cooling technology, optimize the process, and improve large forgings production’s technical and economic level.
9. Quenched crack and tempering embrittlement
Many large forgings with high mechanical properties and surface hardness requirements should be roughly processed after forging and undergo thermal heat treatment or surface quenching. A great temperature stress will occur during heat treatment due to the sharp temperature changes. Because the phase transition also produces tissue stress and the residual stress present in the forging, if the resultant tensile stress value exceeds the tensile strength of the material and there is no plastic deformation relaxation, various forms of cracking and cracking will occur – for example, longitudinal, transverse, surface and central cracks, surface cracking and stripping, etc. Due to large forging section size, heating, cooling temperature distribution, the uneven phase change process is complex, with residual stress, and different degrees of various macro and micro defects, poor plasticity, low toughness; it can increase crack initiation and expansion process, often form immediate or delay of cracking damage, even crack and natural crack, etc., cause significant economic losses.
Figure.1-14 is a 9Cr2Mo steel roller surface quenching transverse crack, in the quality quenching heating overheating, and insufficient tempering, retaining high residual internal stress; in the future, the heart tensile stress and residual stress overlap, exceeding the strength limit of the steel, causing the fracture of three sections. The illustrated fracture shows that the crack originates from the heart of the superheated coarse crystal along the radial, radial tear edge, and the surface layer is a fine porcelain surface quenching layer.
Figure.1-14 Transateral cracking during roll surface quenching
The general solution to prevent quenching cracks is:
- 1) Adopt reasonable heat treatment specifications to control the heating speed and cooling process and reduce the heating defects and temperature stress;
- 2) Avoid the serious metallurgical defects and residual stresses existing in the forgings;
- 3) Return the fire in time after quenching.
The tendency of increased fragility is caused by the precipitation of tempering fragile carbide or the aggregation of harmful trace elements such as phosphorus, tin, antimony, and arsenic along the grain boundary.
The solution to prevent tempering embrittlement is:
- 1) Reduce the content of harmful elements in steel;
- 2) Reduce the segregation in steel;
- 3) Avoid heat treatment in the tempering brittle temperature area, and make appropriate fast cooling to prevent the enrichment of harmful groups.
Where to buy high quality forgings
To get high quality forgings, you need to know where to buy them.
There are several ways to get high quality forgings. It depends on what you are looking for and how much you are willing to spend.
The best way to get a quality forging is to buy it directly from the manufacturer. Most of the big name companies that make forgings will have them on their website for sale. If you can’t find what you need here, then go to their local distributor and see if they have it in stock. If not, then ask them where else they might be able to find it for you.
The forging process is more complex than the machining process. Because forging processes include many steps, it is easy for the manufacturer to make mistakes. The following are some tips for choosing a good forging manufacturer:
How to evaluate the quality of forgings?
To evaluate the quality of forgings, you can check it from the following aspects:
Checking the surface finish. The surface finish of forgings should be smooth, not rough, especially for forging parts with complex geometries.
Inspecting forging parts for cracks. If there are no obvious defects on forgings, you can use a magnifying glass to check if there are any small cracks on the surfaces or in the holes.
Checking the surface texture and color of forgings. Forging parts with different types of materials have different colors and textures. For example, aluminum alloys have a white color and relatively smooth texture; while steel has a gray color and coarse texture after forging processing.
Looking at whether there are any burrs or weld marks on forged components. These defects may affect the performance of parts after assembly into an end product.
How to choose the supplier of forgings?
In order to buy high quality forgings, we need to know where to buy them. There are different ways that can help us to find a good supplier of forgings.
1. Recommendation from friends or relatives
If you have a friend or relative who works in the field of forging industry, they can recommend their own suppliers. They will surely recommend those suppliers who have been providing good service and products for their customers.
2. Searching on the internet
If you have an internet connection at home, then this is the easiest way to search for the best supplier of forgings. You just need to type “forgings manufacturers” in your search engine and you will get plenty of results from which you can select one as per your requirement. However, before selecting any particular manufacturer make sure that he/she has a website where you can see their products and also read customer reviews about them.
3. Personal visit to the factory site
This is another way to find out whether the company manufactures good quality forgings or not. It is always better if you visit the company by yourself instead of taking someone else’s recommendation on face value because sometimes people may be misleading you by telling.
If you are looking for a quality source of forgings, you need to do your homework.
- 1. The supplier’s track record and reputation should be considered as well.
- 2. The supplier’s facilities should be inspected before making any purchase agreement.
- 3. The quality of their products should be compared with those of other suppliers for reference purposes.
- 4. It is recommended that you ask for samples from the suppliers before ordering high quality forgings from them.
Here are some things to consider:
- 1. Is the supplier certified?
- 2. Does the supplier offer a warranty?
- 3. What guarantees does the supplier offer?
- 4. How long has the supplier been in business?
- 5. Does the supplier have experience working with similar materials and processes as yours?
What kind of forging manufacturers can we choose?
Forging manufacturers are divided into two categories:
The first category is the forging manufacturer that provides product design, mold making and production. This type of manufacturer has its own mold shop and can also provide customized designs and products.
The second category is the forging manufacturer that only provides the product design and mechanical processing of forging parts after receiving customer orders. There are many manufacturers who offer this kind of service, but it must be noted that not all manufacturers can provide good quality products.
If you want to buy high quality forgings, then we recommend buying from the first category of manufacturers because they have more experience than second-tier manufacturers. If you choose to buy from second-tier manufacturers, then make sure you understand their strengths and weaknesses so that your needs can be met as much as possible.
What should we pay attention to when buying forgings?
When you want to buy forgings, you should pay attention to a lot of aspects. First of all, you need to look at the material and size of the forgings. Secondly, you should choose a forging manufacturer with a good reputation. Thirdly, you need to choose a reliable forging supplier who can provide all kinds of forging products according to your requirements. In fact, these three factors are very important factors affecting the quality of forgings.
Secondly, when choosing a forging manufacturer with good reputation, we must pay attention to its certifications and experience in this industry. Thirdly, choosing a reliable forging supplier who can offer all kinds of forgings according to our requirements is also very important because different customers have different needs for their products.
Epower metalsis the premier supplier of steel forgings in China. We have six production lines to meet various production requirements with an annual capacity of 10,000 tons. With forging facilities ranging from 300 to 2500 tons in our forging plant, we can supply you with small or large steel forgings. In addition, we can offer the following value-added services.
With in-house tooling shop, forging shop and machining shop. We can provide in-house products that meet drawing specifications. No matter what type of product is required, we have the ability to meet all needs for any application. We also have extensive experience in delivering dollies from prints or samples only, compared to other steel forging companies.
Redesign Services – Sometimes the original design is too costly for additional machining operations, or doesn’t work very well. Contact our company and our engineering team can combine our extensive forging experience with our usage experience to help you redesign your part. To improve our customer service, our redesign services are always free of charge.
Converting casting to forging – defects often occur in the casting process. So if you want to convert a casting design into a forging, Epower metals will be your smart partner for this job. We will re-evaluate your current design and provide you with a new steel forging solution for approval.
Our company also offers castings – we also have our own foundry, so if you need castings, feel free to contact us as well. Of course, we can also help with sourcing other products, such as stampings, metal products, etc. This allows us to be a comprehensive service company.
If you are looking for high quality forgings, then you have landed on the right page. We are the leading manufacturers and suppliers of top quality forgings in India.
Our product range includes forged steel shafts, forged steel flanges, forged steel spindles, forged steel gears and many others.
The best thing about our products is that they are made from superior quality raw materials which ensures their durability at every step of production process. The other factors that contribute towards producing longer lasting products are our skilled workforce and state-of-the-art manufacturing facilities. Our professionals use the latest technology to manufacture these products at an affordable price range so that our customers can buy these at an affordable price.
Source: China Forgings Manufacturer: www.epowermetals.com
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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