Characteristics, Performance, and Applications of Hot Work Die Steel

Characteristics and applications of hot work die steel

Hot work die steel can be further divided into: die-casting die steel, hot forging die steel, and hot extrusion die steel. Ordinary hot work die steel cannot handle high-level die-casting dies, but high-level die-casting steel can be used in low-level hot work dies, with a huge difference in characteristics and prices between them.

The hot work die steel series can be divided into W series, Cr-Mo series, Cr-W-Mo series and other types according to their main chemical compositions. The 3Cr2W8V (H21) steel has high thermal strength, thermal stability, good wear resistance, and process performance. Its working temperature can reach 650°C. The disadvantages are serious carbide segregation, poor plasticity, toughness, thermal conductivity, cold and hot fatigue resistance and corrosion resistance.

The 4Cr5MoSiV (H11) and 4Cr5MoSiV1 (H13) steels have high quenching penetration and hardenability, high toughness, high thermal strength, and wear resistance. They are used at a temperature of 590°C, and the carbides in the steel are finely distributed and uniform, with good cold and hot fatigue resistance and corrosion resistance, as well as good cold and hot working performance.

H13 steel (an improved version of H11 steel) is currently the main material for hot die-forging steels and cold die sets in China. It is also a widely used hot work die steel, and an ideal substitute for 3Cr2W8V steel. Its service life can be increased by 2-3 times.

For molds that work under heavy loads and high-speed wear conditions, it is required that the surface of the die steel can form a thin and dense, good adhesion oxide film to maintain lubrication, reduce molten wear such as sticking and welding between the mold and the workpiece, and also reduce oxidation wear caused by oxidation on the surface of the mold. Therefore, the working conditions of the mold have a significant impact on the wear of the steel.

Properties of hot work die steel

Hardness is the main technical indicator of the die steel

In order to maintain the shape and size of the mold under high stress, it must have sufficient hardness. The hardness of cold work die steel generally remains around HRC60 at room temperature, while hot work die steel generally requires to maintain within the range of HRC40-55 depending on its working conditions. For the same type of steel, within a certain range of hardness values, hardness is proportional to deformation resistance. However, there could be significant differences in the deformation resistance of steel with the same hardness value but different compositions and structures.

Red hardness

For hot work dies that work in high-temperature conditions, it is required to maintain the stability of their structure and performance to maintain sufficient hardness, which is called red hardness. Carbon tool steel and low-alloy tool steel can generally maintain this property within the range of 180-250°C. Chromium-molybdenum hot work die steel usually maintains this property within the range of 550-600°C. The red hardness of the steel mainly depends on its chemical composition and heat treatment process.

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