Reasonable selection of the most popular stamping

2022-08-03
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Reasonable selection of automobile stamping materials

1. Raising problems

generally speaking, product design and process personnel will be involved in the selection of materials when they encounter the following situations

a. when designing a new product, materials shall be selected according to the technical and economic indicators of the product, the effect on parts, stress conditions, working conditions and process requirements

b. when improving or imitating products, improvement schemes can be put forward on the basis of original products and imitations, and appropriate materials can be selected according to the requirements of restructuring and imitation

c. during the localization of imported products, technical analysis and performance test shall be carried out on their samples, and new materials with equivalent performance shall be proposed

d. when the process flow is changed, the raw materials are difficult to adapt and the materials are substituted. In the production process, the adoption of new materials, new processes, new technologies and cost saving and consumption reduction all involve the change of materials

e. in case of problems in raw material supply and demand, temporary or long-term material changes are required to ensure smooth production

therefore, the rational selection of materials for products and the selection of suitable materials are the basis for ensuring the usability, processability and economy of products. According to the statistics of the German Bureau of statistics, the cost of producing a car is allocated in proportion as raw materials accounting for 53%, manufacturing accounting for 30%, design and development accounting for 5%, and others accounting for 12%. It can be seen that the choice of raw materials directly determines the performance and economy of the automobile

a large number of cold stamping processes are used in automobile production. This process not only has high production efficiency and stable product quality, but also is very suitable for the needs of multi variety and mass production in the automobile industry. In medium and heavy-duty vehicles, most of the covering parts, such as the body outer plate, and some load-bearing and supporting parts, such as the frame, carriage and other parts are stamping parts. The steel used for cold stamping is mainly steel plate and steel strip, accounting for 72.6% of the steel consumption of the whole vehicle. The relationship between cold stamping materials and stamping production is very close. The quality of materials not only determines the performance of products, but also directly affects the process design of stamping process and the quality, cost and quality of stamping products Service life we can calculate the relative importance of the keyword and the relevance and production organization of some contents according to the keyword and the frequency of keyword appearing in the document call set. Therefore, it is an important and complex work to reasonably select automotive stamping materials

in automotive stamping parts, some stamping parts become automotive parts directly after stamping, while others can become automotive parts only after stamping, welding, or machining, or painting. Therefore, the selection of stamping materials should not only meet the requirements of product performance, but also meet the requirements of stamping process and subsequent processing (such as welding, machining, etc.)

generally, the following principles should be followed when selecting stamping materials:

a. the selected materials should first meet the service performance requirements of parts

b: the selected materials should have good process properties

c. the selected materials should be economical

the principles and precautions for material selection of stamping parts are discussed in the following from the use performance of parts and the requirements of different processing technologies for automotive stamping materials

2. Requirements of the service performance of automotive stamping parts on the performance of stamping materials

the so-called service performance refers to the mechanical, physical and chemical properties of mechanical parts under service conditions. Performance is the most important factor to be considered when selecting materials. Different parts require different performance. When selecting materials, the primary task is to accurately determine the main performance required by the parts

automotive stamping parts mainly include body covering parts, frame longitudinal beam and cross beam, car, wheel and engine covering parts, as well as some support parts and connectors. The use and working conditions of each specific auto part are different, and the load they bear is different, so the requirements for materials are also very different

2.1 requirements of automobile cab parts on material properties

most automobile cab parts are covering parts, with complex shape and forming, but little stress. The forming performance of materials has become the main contradiction with the use of die forming process. Therefore, the materials are required to have formability, tensile rigidity, extensibility, dent resistance, corrosion resistance and weldability. In product design, the variety of steel plate is usually selected according to the stress condition and shape complexity of plate parts. Generally, low-carbon cold-rolled steel sheet and ultra-low-carbon cold-rolled steel sheet with excellent drawing performance are selected. In recent years, phosphorous cold-rolled steel sheets, high bow cold-rolled steel sheets, cold-rolled dual phase steel sheets, bake hardened cold-rolled steel sheets, ultra-low carbon steel high-strength cold-rolled steel sheets and other types of steel sheets such as coated steel sheets, tailor welded steel sheets and TRIP steel sheets with excellent formability and higher strength have also been widely applied to car body parts such as door outer panels, door inner panels, door reinforcing panels, roof covers, trunk covers and bumpers. The commonly used material grades and drawing grades of Dongfeng heavy truck body are shown in Table 1

2.2 requirements for material properties of car compartment parts

the shape of car compartment parts is not very complex, and most of them adopt rolling forming process, which has certain requirements for the formability, rigidity, corrosion resistance and weldability of materials. High strength steel plates with good formability and weldability are generally selected. Generally, high-strength steel plate and ultra-fine grain steel with strength grade of MPA are used. See table 2

2.2.3 requirements for material performance of Dongfeng heavy truck carriage parts

the frame, carriage middle plate and some parts used for support and connection are important load-bearing parts. Most of them adopt the die forming process, requiring the materials to have high strength, good plasticity, fatigue durability, collision energy absorption capacity and weldability. Generally, high-strength steel plate, ultra-fine grain steel plate (strength level in MPA) and ultra-high strength steel plate (strength level in MPA) with good formability are selected. See Table 3 for common material grades and strength requirements of Dongfeng heavy truck frame and some parts used for support and connection

3.3.1 requirements of stamping process on the properties of stamping materials

stamping process is generally divided into separation process and forming process. According to the processing process, stamping parts can be roughly divided into blanking parts, bending parts, drawing parts, forming parts and cold extrusion parts

different structural types of stamping parts require different mechanical properties of materials, as shown in Table 4. When selecting stamping materials, firstly, metal materials with different mechanical properties are selected according to the type and use characteristics of stamping parts, so as to ensure product quality and save materials

3.1.1 separation process

the separation process generally includes cutting, blanking, punching, trimming and refurbishment. It mainly focuses on the blanking parts. The materials of the blanking parts are mainly based on meeting the use requirements. The process has no special requirements for materials. Only when the tensile strength is more than 600 MPa, the strength of the die shall be considered

3.1.2 forming process

the forming process mainly includes bending parts, drawing parts, formed parts and cold extruded parts. 4. Permanent deformation and temporary deformation - the part whose white height and arc height cannot be recovered after the leaf spring is unloaded is called permanent deformation

3.1.2.1 requirements for materials of bending parts

the materials of bending parts mainly meet the use requirements, and the process generally has two requirements for materials. When the tensile strength of the material is less than 600 MPa, it can be bent 180 degrees perpendicular to the rolling direction or 90 degrees parallel to the rolling direction; When the tensile strength is greater than 600 MPa, the bending method perpendicular to the rolling direction shall be adopted as far as possible to avoid cracking

3.1.2.2 requirements of drawing parts on materials

drawing parts have high requirements on material processability. Generally, the drawing parts used in automobiles are cold-rolled steel plates with a material thickness of less than 3.0 mm. The materials shall not only have good formability, but also have good dent resistance, sufficient structural stiffness and excellent surface morphology, as shown in table 5

3.1.2.3 requirements for materials of formed parts

most formed parts used in automobiles are mainly formed by composite processes such as drawing, bending and flanging. The material thickness is 0.6~9.0 mm. There are cold-rolled steel plate and hot-rolled steel plate. The material is required to have the following conditions. a. Appropriate yield strength is required. Low yield strength can ensure small elastic recovery and shape stability of parts after forming. However, for automotive beam parts, materials with high yield strength are required to ensure high safety warning performance. b. Good elongation (generally a 20%) can meet the needs of smooth forming. c. A low yield ratio (generally 0.75) is conducive to stamping, reducing the wrinkling trend of the material and improving the degree of ultimate deformation

3.2 requirements of welding process for stamping materials

the weldability of metal materials mainly depends on chemical composition, welding process conditions and structural rigidity. Different welding processes have different requirements for material properties and welding specifications. Therefore, the weldability of materials should be considered when selecting materials for stamping parts requiring welding processing. Table 6 lists the weldability and welding specifications of several steels

table 7 lists the common welding methods of main metal materials for reference by product design and process personnel

3.3 requirements of machining process on the performance of stamping materials

a small number of automotive stamping parts need to be machined after stamping, such as the oil reservoir seat on the transmission shaft, the brake disc for the chassis, and some parts on the engine. Therefore, the material requirements of machining should be considered when selecting these parts. Table 8 lists the processability of common materials

3.4 requirements of painting process on stamping materials

the painting quality of automobile directly affects the appearance quality of automobile and the improvement of automobile product grade. Besides the influence of painting material itself, the painting performance of steel plate is also a factor that cannot be ignored in the painting process. Generally speaking, the main factors affecting the coating performance of steel plate are the surface state of steel plate, the cleanliness of steel plate and the surface roughness of steel plate

the surface condition and cleanliness of steel plate directly affect the adhesion and appearance quality of paint, while the surface roughness of steel plate mainly affects the freshness of its surface. The painting of general automotive stamping parts requires that the steel plate surface has no obvious scratch, pit, pitting and other surface defects, and the steel plate with 03 surface is usually required; The exterior surface of the car body requires that the steel plate surface is uniform, and there are no defects such as pores, pits and scratches that affect the use. Generally, the steel plate with surface 05 is required, and the surface roughness Ra 0 2 forest M

4. Conclusion

whether the selection of stamping materials is reasonable or not directly affects the performance, quality and manufacturing cost of stamping products, and also determines the complexity of stamping process and continuous processing. Therefore, reasonable material selection is very important

through the analysis of the working conditions of automotive stamping parts and the requirements of different processing technologies on material properties, it can be seen that the following principles should be followed when selecting automotive stamping materials

a. meet the requirements for the use, stamping process and continuous processing of parts: the materials should have a smooth, uniform, flat and defect free surface quality with the continued and accelerated development of new material industry in our province; The material shall have excellent mechanical properties; The material shall have good formability, rigidity

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