Key points of forging process design in forging production

The task of forging process design

Forging process design is the most important technical preparation in the production of forgings. Its main tasks are the following four:

(A) Design process

• (1) Select the main forming method of forging and the main processing method of each process.
• (2) Calculate the work steps, design the graphics and structural elements of the work steps or process parts and put forward the technical requirements.
• (3) Calculate the size and weight of the billet and determine the variety and specification of raw materials.
• (4) To determine the specifications and quantity of processing equipment.
• (5) Propose the technical requirements, specifications and quantity of the tooling.
• (6) Determine the auxiliary materials, auxiliary series of work content and management requirements, etc.

(2) Propose quality standard and guarantee measures

• (1) According to the quality control level specified in the forging drawing, determine the key processes and their control accuracy range, sampling rules, sampling methods, etc.
• (2) Hot set the quality standard of the process parts.
• (3) propose process measures to ensure quality during processing.
• (4) Determine acceptance rules and select inspection methods.

(3) Determine the process route

• (1) Before the process design, the leading process route should be proposed according to the product design drawings, forging drawings and forging technical conditions.
• (2) After the process design is completed, design the process route in detail.

(4) Prepare process specifications

• (1) Select the diagram and table paper sample of the process specification.
• (2) Draw sketches of process parts.
• (3) Prepare textual terms.
• (4) Draw the base diagram and organize text proofreading, auditing and loquatting.

The basis of forging process design

The forging process is mainly based on product design drawings and forging drawings, technical conditions, on-site production conditions and production batch for the design.

(A) Product drawings

Product drawings are the main technical basis for designing forgings and their forging process. It puts forward the shape, size, organization, performance and other technical requirements of the forgings, so before the development of the process, the product drawings must be carefully analyzed to master the technical points and key items to ensure.

(B) Forging drawing

The forging drawing is the direct basis for the design of the forging process. It not only comprehensively reflects the requirements of the product drawings for forgings, but also reflects the selected main forming methods, other processes (such as heat treatment, surface cleaning, etc.) processing methods and inspection methods.

(C) Forging technical standards

Forging technical standards are and product design drawings have the same effect of directive documents. It specifies in detail the technical requirements and acceptance methods of forgings, so it is also the main basis for the design of the forging process.

(D) On-site production conditions

The forging process must be realized through on-site production conditions. If necessary, it can also be achieved through appropriate technical transformation, such as updating the old equipment, promoting the application of new technologies, new technologies, new equipment, etc.

(E) Production batch

Process must be designed according to the given amount of production loquat, because the size of the production batch determines the type of production, and directly affect the selection of process methods, equipment and tools.
Different types of production, the process over the sound of the degree of detail is also different, and even the process methods selected are different. Single production, in addition to the need to ensure the organization and performance of the product, should be used as far as possible to simplify the processing of common process methods such as free forging instead of die forging, with rough forging instead of finish forging, etc.. Batch production, we must design all the processes in detail, and the use of fully formal process methods. When the batch is not large, generally to ensure product quality; batch is very large, but also take into account to improve production efficiency and save metal materials and other issues.

The forging process design steps

(A) Technical analysis of the process

According to the product drawings. Forgings buried samples and technical standards given by the original conditions and technical requirements, combined with the production conditions and absorb the latest scientific and technological achievements and experience, to identify technical difficulties, to discuss and confirm the program, determine the process parameters, estimate the technical and economic indicators, and put forward technical transformation advice.

(B) Determine the leading process

According to the results of the technical analysis of the process, in the forging drawings and the relevant technical standards on the basis of the provisions, determine the leading process of manufacturing forgings, that is, to determine the type of billet (round bar, square bar or forging billet), heating (flame heating, electric heating or protective heating), the main forming method (hammer forging, press forging or special forging) and the type of heat treatment (stress relief treatment, preparatory heat treatment or final heat treatment), etc.. For precision forgings should also determine the surface protection method (compound cover, atmosphere or vacuum protection) and surface processing methods (sand blowing, mechanical polishing or chemical processing).

(C) Design work steps

In addition to a few special documents or simple processes, all other processes and work steps need to be calculated and designed in detail, including work steps and process sketches; quality standards and inspection methods for work steps and process parts; blank specifications and weights; process parameters; equipment models and specifications; specifications and accuracy levels of common tools; shoving rules; and general documents used.
The work step design starts with the forging and forming work step design, then calculates the blank and designs the preparation, heating, trimming, heat treatment processes and work steps, and finally designs other processes.

(D) Determine the process of work

In the determination of the leading process at the same time, according to the forging drawings and technical standards, the preliminary development of the basic process flow for production preparation. After the work step design is completed, all the processes and work steps will be combined and arranged in accordance with the processing order, and then properly adjusted with the existing production conditions of the plant, finally forming a complete forging process.

(E) Preparation of process procedures

The process procedure is a document that expresses the process flow, process content, natural condition of forgings, material consumption, labor quota, etc. in the form of words and charts. It is the processing and acceptance of forgings instructional documents.
There are three main types of forging process procedures:

• (1) Special process procedures. It is only applicable to a figure number or process the same several figure number forgings “which, with the manufacture of forgings complete process flow, in addition to a few processes can be processed according to special documents, other processes have the Ministry of gold work content.
• (2) General process procedures. It applies to a variety of forgings, and is generally used in the forging process of certain non-forging processes. When it is used for different forgings, in addition to the process parameters are different, there is no significant difference. Such as chemical milling, sand blowing and other process procedures are of this kind.
• (3) Type of process procedures. It is for the same or similar conditions (such as materials, basic process flow, shape), but because of some elements are different (such as size) and lead to individual process parameters different forgings prepared by the process procedures. Such documents in the process flow and basic work content, should be the same as the special process procedures, but for different drawing numbers of forgings, certain process parameters or process parts size is different, such as the same shape, different sizes of stainless steel ring forgings forging process procedures belong to such procedures.

The preparation of process procedures in accordance with the following general steps:

• (1) Select the appropriate style of chart paper type.
• (2) Write the text content according to the rules of writing, drawing according to the rules of charting
• (3) Prepare process and tool catalogs.
• (4) Conduct standardized inspection, technical proofreading and loquat review.

Key points of comprehensive design of the process

However, when designing the overall composition of the process, attention should be paid to the influence of various factors such as the original conditions of the forging (such as the material, shape and size of the forging), the actual situation on site (design, tools and personnel) and the matching of the preceding and following processes, and the necessary comprehensive analysis should be conducted in order to correctly select the process methods and parameters, so that the designed process can achieve advanced, reasonable, practical and economic purposes.

(A) Preparation process

The material preparation process includes the inspection of raw materials, cutting of blanks, removal of burrs and surface defects on blanks, and inspection of blanks. The following points should be noted when designing the preparation process.

• (1) The material preparation method should be selected according to the nature of the material, the accuracy of the blank and the production batch. For example, high temperature alloys. Magnesium alloy and titanium alloy billet should not be sheared or hot chopping and should be used to cut the wheel under the material; precision forgings should be used to precision under the material; small batch production with the material should also be used to general method under the material.
• (2) There are non-machined surface forgings or precision forgings of the blank, generally should be strict surface cleaning process.
• (3) Raw materials must have non-destructive testing and grade identification and other detailed inspection provisions. Material must be strictly controlled, do not allow mixed materials and unqualified materials into the production line.
• (4) Forging parts should be managed from the billet, which includes furnace number, ingot number, batch and file management, etc.

(B) Forging and forming process

The forging and forming process includes billet making, pre-forming, final forming and other processes. In addition to the design of these processes, the following points should be taken into consideration.

• (1) The size and deformation of each step of the forming process should be determined according to the allowable deformation of the forging material and the critical deformation range to prevent cracks and low coarse crystals.
• (2) Low plasticity materials should be selected with obvious three-way uneven compressive stress state of the forming method.
• (3) The metal flow line in the blank, should be free from the formation of obvious bending, cutting, vortex or through the flow defects.
• (4) Should be based on the plasticity of the forging material and forging temperature range, the requirements of the forging streamline and shape, as well as production conditions and production volume and other factors, the choice of free forging billet, special equipment bottle billet or die forging billet.
• (5) Free forging processes and work steps must be drawn and flooded line distribution, and specify specific operating rules, such as the size of the strike force, pulling the length of the billet turning order and direction, pressure shoulder tools and size, repeated upsetting order and direction and large free forgings should achieve the forging ratio, etc., should be made.
• (6) Must indicate the lubricant and its application method and application parts, etc.
• (7) Die forging direction of material release, the method of removing oxide, the size of the hammering force and the amount of underpressure and the method of removing the forging from the groove, etc., should be clearly specified.

(C) Heating and cooling process

Before forging billet heating should pay attention to the following points.

• (1) Determine the heating specification should be based on the forging material, shape, size and machining allowance, but should also consider a fire time to complete the type of work step, the number and deformation amount. In the premise of meeting the forming requirements, the number of times the blank is heated should strive to reduce.
• (2) Forging heating temperature is the highest heating temperature allowed for the material. The specific heating temperature of each process or step of the blank should be adjusted according to the complexity of the operation, the principle is to ensure that the specified final forging temperature, because the final forging temperature is too high, there will be coarse organization, serious secondary oxidation and shrinkage and other problems; the final forging temperature is too low, will also lead to increased metal deformation resistance, plasticity, forming difficulties, cracking and other problems.
• (3) In the design of the heating process, in addition to the selected heating temperature, speed and time and other process parameters, should also be based on the characteristics of the furnace, material heating adaptability and the importance of forgings, to determine the amount of furnace and furnace loading and measures to maintain the cleanliness of the furnace, temperature control accuracy, protection methods, repeat heating (back to the furnace) the number of times and temperature, etc.
• (4) Cooling specification should be determined mainly according to the material characteristics, followed by the shape and size of the forgings and the influence of the workshop environment should be considered.

(D) Forging heat treatment process

Determine the heat treatment process of forgings, in addition to the provisions should be followed, should also pay attention to the following issues.

• (1) When the heat treatment of forgings have more than two processes to choose from, should be selected according to the specified technical requirements of one. And selected heat treatment process, should achieve as much as possible to eliminate stress, adjust the hardness and improve the organization of multiple projects.
• (2) Aluminum, magnesium alloy forgings must be forged after the final heat treatment, in order to meet the mechanical processing of Haet to. Blade and other heat treatment is easy to deformation of forgings, must have measures to prevent heat treatment deformation of the alloy structure of the forgings of the non-machined surface dimensions will change due to oxidation during heat treatment, heat treatment should also be preventive measures.
• (3) Before heat treatment, forgings should be cleared of oil and cracks.

(E) Surface cleaning and machining process of forgings

The H of this process is to remove the foreign matter, pollution layer and defects on the surface of forgings, or to reduce the excess metal and improve the accuracy of forgings.

• (1) Cleaning and processing methods, should be based on the accuracy of forgings, forgings with or without non-machining surface, forging materials, shapes and sizes, as well as the subsequent processing or finished parts requirements to be selected. For example, precision forgings should be selected to obtain precision size and smooth surface processing methods. Forgings with the need for electroplating of the non-machined surface, should be selected to keep the forging surface clean cleaning method. Thin long forgings should be chosen to use sand blowing cleaning, should not use roller cleaning, to avoid deformation of forgings after cleaning.
• (2) The process of removing foreign matter or defects on the surface should be carried out immediately after the process of generating foreign matter and defects.
• (3) Martensitic steel forgings before pickling, generally should be arranged first stress relief annealing process. Titanium alloy forging for chemical milling, hydrogen absorption phenomenon, generally in the chemical milling should be arranged after the annealing process to remove hydrogen.
• (4) For forgings with high surface quality requirements (precision forgings, forgings with non-machined surfaces) or forgings prone to rust in air (aluminum alloy and magnesium alloy forgings), rust prevention and oil seal treatment (including oxidation coverage) should be carried out after their final cleaning process is completed.

(F) Guarantee and quality inspection provisions

Quality assurance provisions in the forging process include quality assurance processes and work steps to ensure the quality of the shoving rules (such as upsetting to remove oxidation) and quality standards for process parts. Quality inspection provisions include inter-process inspection and final inspection provisions in determining these provisions, the following points should be noted.

• (1) The quality of forgings have a decisive impact on the process, or can only rely on the correct operation to ensure quality and difficult to find the quality of the final inspection process, should provide detailed operating instructions.
• (2) The quality standards of raw material quality level, equipment accuracy, tool accuracy and other production conditions should be selected according to the importance of forgings.
• (3) Reliable process parameters should be selected.
• (4) Try to shorten the time of the process defect survival, once found, should be promptly eliminated to prevent the expansion of the subsequent processing or lead to the creation of new defects. At the same time, it should be specified in the process for the specific situation.
• (5) Inter-process inspection and regular sampling should be set for the leading processes where quality is difficult to maintain stability. For important production conditions such as the fluctuation range of furnace temperature and composition of chemical milling solution, direct control should be implemented.
• (6) product defects should try to make the storm out first, and then the inspection. For example, aluminum alloy forgings shall first be anodized by sulfuric acid, and then test its surface defects.
• (7) Should try to expand the scope of application of nondestructive testing, and can directly assess the degree of process stability and forging quality level of inspection content. For example, the fracture inspection and forging regular comprehensive identification, including technical standards outside the project fatigue performance test and alloying elements depleted layer depth measurement and other inspection items.

Source: China Forgings 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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