Die steel can be roughly divided into three categories: cold rolled die steel, hot rolled die steel and ductile iron, which are used for forging, stamping, cutting and injection molding. Due to different uses, different shapes and difficult processing conditions, the steel used for dies and moulds must have high hardness, strength, wear resistance, sufficient impact strength and high hardenability, and hardening, hardness and other process properties according to the operating conditions of the die. Due to the different use and difficult working conditions, the performance requirements of cast steel are also different.

Cold rolled dies include cold forming dies, drawing dies, wire drawing dies, stamping dies, wire drawing dies, rolling dies, cold heading dies and cold extrusion dies. Steels for cold work dies must have high hardness, strength, wear resistance, adequate impact strength, and process properties such as high hardenability and hardenability, depending on the conditions of use of the tool. Alloy tool steels for such use are usually high-carbon alloy steels with a carbon mass fraction of more than 0.80%. An important alloying element in such steels is chromium, whose mass fraction usually does not exceed 5%. However, for some high requirements for wear resistance, quenched deformation of small steel, chromium content of up to 13%, and for the formation of a large number of carbide, the steel carbon content is also large, up to 2.0% to 2.3%. Cold work steel with high carbon content, its microstructure is mostly over-eutectic steel or Leyland steel. Commonly used steels are high-carbon low-alloy steel, high-carbon high-chromium steel, chromium-molybdenum steel, medium-carbon chromium-tungsten steel, etc.

Hot rolling dies are divided into several main types of hammer forging, stamping, extrusion and injection molding, including hot forging dies, press dies, stamping dies, hot extrusion dies and metal injection dies. In addition to the great mechanical stress, hot deformation dies must also be subjected to repeated heating and cooling, resulting in great thermal stress. In addition to its high hardness, strength, red-hardness, wear resistance and toughness, hot stamping die steel must also have good resistance to high temperatures, thermal fatigue stability, thermal and corrosion conductivity and hardenability to ensure constant mechanical properties throughout the cross section. For stamping steel, it must also have a surface layer that does not crack after repeated heating and cooling, as well as the ability to withstand the impact and scouring of liquid metal flow. This type of steel is generally carbon mass fraction of 0.30% to 0.60% of the medium carbon alloy steel, for sub-eutectic steel, part of the steel into eutectic steel or over-eutectic steel. Commonly used steel: chromium manganese, chromium nickel, chromium tungsten, etc.

Plastic moulds include thermoplastic moulds and thermosetting moulds. Steel for plastic moulds must have certain strength, hardness, wear resistance, thermal stability and corrosion resistance properties. In addition, it is also required to have good processability, such as small heat treatment deformation, good processing performance, good corrosion resistance, good grinding and polishing performance, good welding performance, high roughness, good thermal conductivity, stable size and shape under working conditions, etc. d. In general, hot stamping steel can be used for injection molding or extrusion molds; cold forming mold steel can be used for thermosetting molding and molds requiring high wear resistance and high strength.