Hot work die steels refer to alloy tool steels suitable for making die for hot deformation of metal, such as hot forging die, hot extrusion die, die casting die, hot heading die, etc. Because the hot working die is under high temperature and high pressure for a long time, the die material is required to have high strength, hardness and thermal stability, especially high thermal strength, thermal fatigue, toughness and wear resistance.

Hot work die steel composition characteristics

1. Carbon content

It is generally medium carbon, and the mass fraction of carbon is 0.3% ~ 0.6%. Ensure that the material has higher strength and hardness, higher hardenability and better visibility, toughness.

2. Alloying elements

The added alloying elements are Cr, Mn, Si, Ni, W, Mo, V and other alloying elements. The Cr, Mn, Si and Ni alloying elements strengthen ferrite and improve hardenability. W, Mo alloying elements are to prevent temper brittleness, Cr, W, Si alloying elements can improve the phase change temperature, so that the die in the process of alternating heating and cooling will not change phase change and a large volume change, so as to improve its thermal fatigue resistance ability. In addition, W, Mo and V precipitate in the form of carbide during tempering and produce secondary hardening, so that the hot work die steel still maintains a high hardness at higher temperature, which is one of the important conditions for the normal operation of the hot work die steel. Cr and Si can improve the oxidation resistance of the steel.

Classification of hot work die steels

There are many classification methods of hot work die steels, which can be classified according to the content of alloying elements and the properties after heat treatment, and can be classified according to the use or alloying elements.

(1) according to the use can be divided into hot forging die steel, hot extrusion die steel, die casting die steel, hot punching die steel.

(2) according to the heat resistance can be divided into low heat resistance steel (350 ~ 370℃), medium heat resistance steel (550 ~ 600℃), high heat resistance steel.

(3) According to the unique properties, it can be divided into high toughness hot work die steel, high thermal strength hot work die steel and high wear resistance hot work die steel.

(4) according to alloying element classification can be divided into low alloy hot work die steel (tungsten, chromium and molybdenum), medium alloy hot work die steel and high alloy hot work die steel (tungsten molybdenum and chromium molybdenum); Or divided into tungsten hot die steel, chromium hot die steel and chromium tungsten molybdenum hot die steel. The high temperature strength and thermal stability of chromium-tungsten high alloy hot work die steels are lower than that of tungsten-molybdenum, but the cold and hot fatigue resistance and toughness are higher than that of tungsten-molybdenum.