Stainless steel surface processing types and comparison table
Stainless steel surface finish type
Table of Contents
|Abbreviation||Processing type||Surface state|
|NO.1||Hot rolling, heat treatment, pickling or descaling||Rough and dull|
|2E surface||Cold rolling, heat treatment and descaling with oxide scale||Rough and dull|
|2D surface||Cold rolling, heat treatment, pickling or descaling||The surface is uniform and smooth matte shape|
|2B surface||Cold rolling, heat treatment, pickling or descaling, bright processing（ Foggy surface ）||Smoother and straighter than 2D surface|
|Ba surface||Cold rolling, bright annealing（ Mirror ）||Smooth, bright and reflective|
|3. Surface||Brush or matt Polish one or both sides||No directional texture, no reflection|
|4. Surface||General purpose polishing for one or both sides||Non directional texture, reflective|
|6. Surface||Single or double Matte Satin Finish, tempico grind||The texture is Matt and non directional|
|7. Surface||High gloss surface processing||Smooth, high reflectance|
|8 surface||Mirror machining||No direction texture, high reflection, clear image|
|TR surface||Cold work hardening treatment: 1/4H、1/2H、3/4H、H||It should be changed according to the size of material and cold work|
|HL surface||Cold rolling, pickling, leveling and grinding||It is continuous grinding pattern, also known as hair plate|
Machining surface comparison table
|National standard||American Standard||Japanese standard||International standard||European standard|
Most people think that stainless steel will not rust. In fact, it is not. Like many other metals, it will be oxidized and rusted when it is exposed to the air or by hand. In addition, the surface of stainless steel workpiece will be oxidized and rusted after mechanical processing such as welding, stamping, curling, heat treatment, etc., and a black oxidation metamorphic hardening layer is formed, at the same time, a lot of meat is formed In general, it is difficult to remove the tiny burr and sharp edge by mechanical method, which affects the performance of the workpiece material. In order to solve these problems, people use various methods to grind and polish the surface of stainless steel and other metals.
Classification of grinding and polishing methods
1. Mechanical grinding and polishing:
- A: Grinding wheel polishing;
- B: Sand blasting polishing;
- C: Grinding polishing;
- D: Extrusion polishing.
2. Chemical grinding and polishing:
- A. Electrochemical chemical polishing;
- B. Chemical polishing.
3. Compound grinding and polishing: a combination of mechanical and chemical grinding methods
For different metal materials, different use occasions and different requirements on the surface of metal workpiece, different grinding methods or combination of several grinding methods must be used to grind the workpiece to meet the requirements of use.
Difference of different grinding and polishing methods
(1) There are essential differences between chemical grinding and mechanical grinding.
“Chemical grinding” is a process that makes the convex part dissolve preferentially, improves the metal surface roughness and obtains smooth and bright surface by comparing the tiny convex part and concave part on the ground surface.
“Mechanical grinding” is the process of removing the convex part of the ground surface by cutting, abrasion or plastic deformation to obtain a smooth and bright surface.
Therefore, there are two different ways to grind the surface of metal.
Due to the limitations of mechanical polishing, stainless steel and other metal workpieces can not play their due functions. It is difficult to solve these problems. In the 1980s, the electrochemical chemical grinding and polishing technology of stainless steel appeared, which has solved the difficult problems of mechanical polishing to a certain extent, and has obvious advantages. However, electrochemical polishing still has many disadvantages.
(2) Comparison between chemical grinding and electrolytic grinding.
Chemical grinding and polishing: the metal is immersed in a special chemical solution composed of various components, and the metal surface is naturally dissolved by chemical energy to obtain a smooth and bright surface.
Electrochemical chemical grinding and polishing: the metal is immersed in a special chemical solution composed of various components, and the metal surface is anodic dissolved by current energy to obtain a smooth and bright surface.
Chemical grinding is only impregnation operation, and the operation is simple; however, electrolytic grinding and polishing requires large capacity DC, reasonable setting of current polarity, accurate control of current and voltage, complex operation process, difficult quality control, and some special workpiece can not be processed. People have been looking forward to the emergence of better grinding methods. Although some pure chemical grinding and polishing technologies appeared during this period, compared with the electrolytic grinding method, the products meeting the important technical indicators such as luster, environmental protection and grinding effect have not appeared.
Chemical grinding ⇨ electrolytic chemical grinding ⇨ mechanical grinding
|Chemical grinding||Electrochemical chemical grinding||Mechanical grinding|
|The process of turning the ground workpiece surface into a smooth and bright surface by chemical reaction dissolution||The process of changing the polished workpiece surface into a smooth and bright surface by anodic dissolution of electrochemical reaction||By cutting, plastic deformation and wear, the surface of the workpiece is turned into a smooth and bright process|
|A protective film is formed on the ground surface after chemical reaction, which improves the corrosion resistance and wear resistance, and has a lasting luster.||Same as left||Due to the influence of plastic deformation, work hardening layer and lattice structure change on the surface, corrosion resistance and wear resistance are weakened, and it is easy to oxidize and blacken again, and the luster is not durable.|
|The grinding surface is smooth, continuous and uniform, and the flow resistance is small||Same as left||The grinding surface is smooth and continuous, and the flow resistance of concave convex part is large|
|There is no deposit on the ground surface||Same as left||The ground surface is stained with metal particles, sand, grinding paste, grease and other impurities|
|The micro burr and burr on the ground surface can be easily removed, and it can be removed below 100 μ M||Depending on the situation, the workpiece can not be processed sometimes||The micro burr and burr on the ground surface can not be removed more than 100 μ M|
|The ground surface has good reflective property, high reflection energy, and the positive and negative reflection rate is more than 90%||Same as left||Due to the random reflection of the ground surface, the reflection energy is low, and the positive reflectivity is 60%|
|The workpiece to be ground does not produce stress and deformation||Same as left||After processing, the workpiece produces processing stress and deformation|
|The fatigue strength increases by 10-20% due to the small surface concave convex difference||Same as left||It is easy to produce fatigue strength|
|For conductive materials, the contact surface is improved, cold radiation arc spark is not easy to generate, and the conductivity is increased||Same as left||Due to the influence of burr and burr, the contact surface is not in good contact and is easy to produce spark arc|
|Any complex shape of workpiece, linear thin plate, etc. can be ground and polished||Due to the influence of current distribution, some shapes of workpiece can not be processed, and the wire joint can not be processed||Workpieces with special shapes cannot be ground or are difficult to grind|
|Short grinding time||Long grinding time||Long grinding time|
|The operation technology is extremely simple||Requires considerable technical complexity||There is a gap between individuals in operation technology|
|Small workpieces can be processed in large quantities||Mass production of workpieces is not allowed||Mass production of workpieces is not allowed|
|Small equipment investment||It needs a lot of equipment investment and technical manpower investment||Some equipment investment is needed|
|No electricity is needed||A lot of electricity is needed||Less power is needed|
|Environmental pollution is minimal||Serious environmental pollution||Serious environmental pollution|
|Large concave convex and deep scratches on the ground surface cannot be removed||Same as left||The bumps and scratches on the ground surface can be removed by a certain time treatment|
|It is easy to be affected by the material of the workpiece, and some materials can not be processed||Same as left||Not affected by any material|
|It is difficult to handle large workpieces||It is also difficult to process large workpieces||Large size workpieces can be processed|
|Strong dependence on drugs||Chemical grinding fluid components are easy to buy||There is no left item defect|
|Medium cost||High cost||Low cost|
Mirror polishing of stainless steel surface
Mirror polishing of stainless steel surface is a type of surface treatment of stainless steel, which reflects the natural color of metal (similar to the effect of mirror reflection) by removing surface roughness and oxide scale. Generally, the surface roughness value RA ≤ 0.05 μ m and the surface finish greater than 10 can be called “mirror surface”.
According to the polishing methods, mirror polishing of stainless steel can be divided into mechanical polishing, chemical polishing and electrochemical polishing.
At present, the most commonly used mirror polishing equipment mainly uses stainless steel plate or other types of metal plate to rotate anticlockwise through an adjustable pressure grinding plate, the correction wheel drives the workpiece to rotate, and the gravity pressure is applied to the workpiece. In addition, the matching grinding emulsion (mainly composed of gold oxide, inorganic strong acid, organic lubricant and weak alkaline cleaning agent) is added to the grinding emulsion The grinding disc makes relative running friction to achieve the purpose of grinding and polishing. The mirror polishing machine can be divided into three steps: grinding, polishing and grinding; the matching abrasives, grinding materials and grinding fluids are also different according to different sections.
Stainless steel plates of various materials and thicknesses can be processed to different degrees of mirror effect; due to the macro unevenness of the base metal (the surface roughness Ra value is generally DA), the surface roughness should be first ground to a certain value (RA ≤ 0.8 μ m) by grinding, and then the surface roughness can be ground to “mirror” by polishing and grinding.
There are many kinds of surface states of stainless steel. Generally, the surface used as master batch for mirror grinding mainly includes 2B, 2BB, 2D, Ba, No.1, etc. the materials suitable for mirror grinding are SUS304, 304j1, 316L, 201202430, The final mirror surface effect of 441 austenitic and ferritic stainless steel is also determined by the material and surface of its base metal; generally speaking, the grinding effect of 300 series stainless steel is slightly better than that of other series materials, Ba surface grinding effect is the best, 2b is the second, No.1 is the worst.
In addition, polishing emulsion, polishing machine and polishing emulsion circulation system contact, coupled with the corrosion of various acidic and alkaline substances, the polishing emulsion and polishing machine should have good corrosion resistance. In addition, due to the high-speed rotation of the polishing machine and the friction of the metal plate, a lot of heat is generated (especially the thermal conductivity of austenitic stainless steel is very poor); due to the grinding work, a lot of heat will be generated in the same area, which will cause the change of metal surface stress, thus affecting the metal physical state, and finally leading to the metal flatness, so the polishing equipment and polishing environment are required Have good heat dissipation conditions.
What should we pay attention to when using stainless steel polishing machine?
After turning on the machine, put the workpiece from less to more into the polishing barrel. The number of the workpiece has a close relationship with the weight and the shape of the workpiece. Therefore, the workpiece is slowly put in to increase, and the rotation of the inverted workpiece slows down, but the workpiece can not be stationary. When the workpiece does not rotate, the polishing liquid will be uneven, and the polishing time will be lengthened unnecessarily.
When using stainless steel polishing machine, do not splash liquid and water on wires and plugs. Over current switch should be installed in the power supply of W type machine, and it is recommended to select more than 10A. After turning on the power supply, check whether the cooling fan of the rear cover works normally. P-type machine should not work under low frequency for a long time. Lightning may damage the machine.
If you want to prolong the service life of stainless steel polishing machine, daily maintenance is very important. The polishing barrel has water leakage, and there is a polishing needle on the bottom of the polishing barrel. You can remove the polishing needle with pliers. Add some glue. The timer does not flash. If you do not press the start switch, press it to time. When the water in the polishing barrel is overheated, please change the water in time (the normal temperature range is 50 ° C). The vibration of the machine is big. Check whether each corner of the machine is in the stressed position and adjust the length. The indication is normal, but the machine does not work. Check whether the voltage is lower than 220 V and whether the polishing needle is placed excessively.
The most important point of super mirror polishing is the size of polishing. The distance from whetstone grinding to mirror polishing is the most basic principle (the most ideal is 1500 oilstone to start grinding). Before the next step of operation, the mold must be thoroughly cleaned to achieve good results. Be very careful not to modify it repeatedly (repeated modification will affect quality problems).
Due to the time limit, time pressure, excessive fatigue, the decline of concentration, these factors are easy to affect the work, which should be paid great attention to. Experts point out that polishing is a time-consuming and expensive process, and following certain rules can reduce the cost of polishing. Every step of polishing must be kept clean, which is the most important point.
- 1. Polishing must be carried out in a clean, dust-free room. Because hard dust particles can contaminate the abrasive material and damage the near finished mold surface.
- 2. Only one grade of polished diamond paste is used for each polishing tool and stored in a dust-proof or sealed container.
- 3. When converting a finer sand number, both hands and workpiece must be cleaned.
- 4. At the beginning of polishing, it is necessary to deal with corners, corners and fillets which are difficult to polish.
- 5. Special care should be taken in the treatment of sharp corners and corners. Care should be taken not to form rounded corners or round edges. Hard polishing tools should be used to grind and polish the mould.
Source: China Stainless Steel Plate Manufacturer – Yaang Pipe Industry (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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