How to choose precision stamping raw materials

Precision stamping is a technology that uses punches and dies to deform or fracture plates and dissimilar materials such as iron, aluminum, copper, etc. to achieve a certain shape and size.
However, there are many people who do not understand the raw materials of precision stamping and how to choose the raw materials of precision stamping.


Selection of raw materials in precision stamping

At present, the materials that can be stamped are not only low carbon steel, but also stainless steel, aluminum and aluminum alloy, copper and copper alloy. Generally, materials with carbon content <0.25% and tensile strength less than 650N/mm² are the main materials. For example, cold rolled steel SPCC (JIS) or 1010 (SAE).

The 4 requirements for precision metal stamping materials mainly include the following.
1. Chemical composition of the material: Generally speaking, the lower the carbon content of the steel, the lower the impurity content, the better the plasticity and the lower the hardness.
2. Material surface quality: the material of stamping parts is mostly steel plate, commonly used thin plate.
When stamping dies work, they have to bear impact, vibration, friction, high pressure and deep drawing, bending and twisting, and even work under higher temperature, so the working conditions are complicated and prone to wear, fatigue, fracture and deformation; therefore, the requirements for the materials of the working parts of dies are higher than those of ordinary parts. The country has certain regulations and requirements for the surface quality of steel plates. The surface of the material must be smooth, without scratches, impurities, pores and shrinkage; there is no delamination in the cross-section of the material and no obvious damage to the mechanical properties; the surface of the material should be free from rust, oxide and other adhesions. In the stamping process, a material with good surface quality can obtain smooth surface and high quality stamping parts, but it is not easy to break and damage the die in the process of deformation.
3. Microstructure: The mechanical properties of metal materials depend not only on their chemical composition, but also on their microstructure. Generally speaking, the microstructure of metal is very fine, but the plasticity is very large, which is beneficial to the deformation of the material in the stamping process. However, if the microstructure of the metal is too fine, the strength and hardness of the material will increase.
4. Thickness tolerance: In the stamping process, the requirements for thickness tolerance are relatively strict. In the process of stamping and forming, there will be high pressure and even damage to the parts.
How to choose metal stamping materials for your products
For any kind of metal stamping parts, the selected material should be able to form stable and qualified products without cracking or wrinkling according to the requirements of its stamping process, which is a more basic and very important requirement for material selection.
1、Rational selection of materials according to the requirements of metal stamping parts
The selected material should enable the stamping parts to work normally in the machine or parts and have a certain service life. For this reason, the selected material should meet the requirements of strength, stiffness, toughness, corrosion resistance and heat resistance according to the conditions of use of the stamped parts.
2、Rational selection of materials according to the requirements of stamping process
For any kind of metal stamping parts, the selected material should be able to form a qualified product without cracking or wrinkling in a stable manner according to the requirements of the stamping process, which is a more basic and very important requirement for material selection. For this reason, the following methods can be used to reasonably select materials.
(1) Test punching. According to the previous production experience and possible conditions, select several kinds of sheet materials that can basically meet the requirements of stamping parts for test punching, and then select the one that has no cracks or wrinkles and has low scrap rate. The result of this method is more intuitive, but with a greater blindness.
(2) Analysis and comparison. On the basis of the analysis of the nature of stamping deformation, the degree of maximum deformation during stamping and forming and the ultimate degree of deformation allowed by the sheet stamping and forming properties are compared and used as a basis for selecting the plate suitable for the requirements of the stamping process of the part.
In addition, the same grade or the same thickness of the plate, there are cold-rolled and hot-rolled. Compared with the hot-rolled plate, cold-rolled plate size accuracy, small deviation, fewer surface defects, bright, dense internal organization, stamping performance is better.
3, reasonable selection of materials according to economic requirements
The selected materials should be as low as possible, convenient in origin and economical, in order to reduce the cost of the stamped parts, while meeting the requirements of service performance and stamping process.
The surface of the material should be smooth and flat, free from delamination and mechanical damage, and free from rust, oxide and other adhesions. The material should have: good formability, rigidity, extensibility, dent resistance, corrosion resistance and weldability and other process properties. The thickness tolerance of the material should be in line with the standards stipulated by the national jia. The material should have good adaptability to mechanical bonding and further processing such as welding, painting, plating, machining and riveting, etc. 1. Tensile parts should not use materials with small strain-hardening index
The strain hardening index has a very close relationship with the forming performance of the sheet metal. According to the theory of plastic deformation limit, the maximum elongation strain when the sheet is stretched centrally is twice as much as when it is stretched uniaxially. Under normal conditions, the material will rupture immediately after the occurrence of necking concentration. Therefore, the larger the strain hardening index of the material, the stronger the resistance of the material to local fracture, the more uniform the plastic strain distribution tends to be, and the peak strain becomes lower. Therefore, in the elongation-based molding parts, it is not advisable to use materials with small strain hardening index.
2. Compression forming process should not use materials with poor stability resistance
In compression molding, the deformation zone is mainly reached by the compressive stress and compressive strain to withstand the compressive deformation. Sheet under the action of compressive stress is easy to instability and wrinkling. In order to improve the stability of plastic deformation, it is not advisable to choose materials with poor resistance to instability.
3. The stretching process should not use poor plasticity materials
The material with low elongation should not be used in the stretching process. The better the plasticity of the material, the higher its uniform elongation, which means stretching and forming between stable deformation and uniform deformation.
4. Hardened materials should not be applied to the spinning process
The common spinning materials are mainly pure aluminum, mild steel and stainless steel, of which mild steel and stainless steel account for more than 60%. For common spinning, soft materials with good plasticity, low yield point, few impurities and uniform structure should be used.
5. Cold stamping process should not use high strength, low plasticity materials
High-strength, low plasticity materials should not be used in the cold stamping process to avoid increasing deformation resistance and crack resistance. The requirements for cold stamping and other volume forming of materials are that the materials should have high plasticity, low yield point and low work hardening sensitivity. The commonly used cold stamping materials are pure aluminum and aluminum alloy, copper and copper alloy, low carbon steel, medium carbon steel, low alloy steel, etc. Products stamped with these materials have smooth surface, dimensional accuracy and can withstand large pressure. A plastic deformation, punching out products with complex shapes.
6. Bending process should not use highly elastic materials
Stamping and bending steel needs to have good plasticity, low yield strength and low elasticity. Steel with good plasticity in the bending process is not easy to bend and crack, it is low yield, high strength, low elasticity of steel, bending after forming the rebound deformation is small, easy to obtain the exact shape of the bend.
7. Elongation forming should not use poor plasticity materials
In the stamping process, flaring, reaming, bulging, bending, outward turning of the tube and part of the stretching belongs to the extension type deformation. Since the deformation zone is mainly subject to tensile deformation by normal stress and normal strain, the material in the deformation zone is easy to over-elongate. When this elongation exceeds the ultimate elongation of the material, it is easy to fracture, so it is not suitable to use materials with poor plasticity in the elongation formation process.


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