With the development of the machining industry, there are more and more parts manufactured by cold work moulds in production, and more and more types of cold deformation moulds are used. Cold bulk die forging (cold heading, cold extrusion, embossing, etc.); sheet metal stamping (such as drawing, blanking, trimming, punching, etc.); material rolling (cold rolling, roll forming, etc.). Although there are many types of cold deformation moulds, different working conditions, and different performance requirements, the basic working conditions are similar: that is, they all deform the metal in a cold state, and bear greater shear, pressure, and bending forces during work. Impact and friction.
Therefore, this type of die steel should have the following basic properties:
1) High hardness and high strength to ensure that it is not easy to produce slight plastic deformation or damage when subjected to high stress.
2) High wear resistance, which can ensure the dimensional accuracy of the mould under high wear conditions, which is more important for drawing dies and cold stamping dies.
3) Sufficient toughness, so that under impact load and dynamic load, it is not easy to peel off or collapse of working toughness.
4) Heat treatment deformation should be small. Because most moulds have complex cavities and precise precision, it is difficult to eliminate heat treatment deformation by grinding. In addition, some cold deformation moulds should also have sufficient heat resistance. How to choose the material of cold deformation mould and appropriate heat treatment methods to improve the service life of the mould is the most concerned issue in production. The normal failure of cold deformation mould should be abrasion, slight plastic deformation and fatigue failure. However, in actual production, in addition to wear failure, premature failure due to collapse, fracture, cracking, etc. is common. As we all know, it is a comprehensive factor that affects the service life of cold deformed moulds; the rationality of raw material selection, the internal metallurgical quality of the raw materials, the rationality of the design and manufacturing process, the use conditions and the technical level of the operators.
Material selection of cold deformed die steel
The following factors should be considered in the selection of cold deformed mould materials:
1) The working conditions of the mould, including equipment type, processing frequency, processed material, lubrication and environment, etc.;
2) The complexity of the mould shape and processing procedures;
3) Production batch and technical requirements of the product;
4) Difficulties and processing conditions of mould material sources. The material cost of large moulds often accounts for more than 50% of the mould cost. For moulds with complex shapes and high precision requirements, mould steel with small quenching deformation should be selected.
According to actual use, commonly used cold-deformed die steels include low-hardenability steel, low-deformation steel, micro-deformation steel, high-strength steel, high-toughness steel, and impact-resistant cold-deformation die steel.