Hot working die bears great impact when working. The die cavity contacts with high temperature metal and is heated and cooled repeatedly. The working conditions of the die are extremely harsh. In order to meet the requirements of hot working die, hot working die steel should have the following basic characteristics:

1, good forming process performance, to meet the needs of processing and forming.

2, high hardenability. The general size of the hot die is relatively large, especially for the hot forging die. In order to make the mechanical properties of the whole die section uniform, it requires the hot die steel to have high hardenability.

3, good thermal conductivity. In order to make the die not accumulate too much heat, resulting in a decline in mechanical properties, as far as possible to reduce the temperature of the die surface, reduce the temperature difference inside the die, which requires that the hot work die steel should have a good thermal conductivity.

4, high temperature strength and good toughness. Hot working die, especially hot forging die, bears a lot of impact force when working, and the impact frequency is very high. If the die does not have high strength and good toughness, it is easy to crack.

5. Good wear resistance. Due to the friction and wear caused by the deformation of the blank when the hot work die is made, it is also subject to high temperature oxidation corrosion and grinding of iron oxide filings, so the hot work die steel needs to have high hardness and adhesion resistance.

6, high thermal stability. Thermal stability refers to the ability of steel to maintain its mechanical properties at normal temperature for a long time at high temperature. When the hot working mold works, the contact is hot metal, even liquid metal, so the mold surface temperature is very high, generally 400 ~ 700℃. This requires that the hot work die steel does not thermalize at high temperature and has high thermal stability, otherwise the die will undergo plastic deformation, resulting in heap collapse and failure.

7. Excellent heat-resistant fatigue. The working characteristics of the hot working die are repeated heat and cold. Under the action of repeated thermal stress, network cracks (cracking) will form on the surface of the die. This phenomenon is called thermal fatigue. The premature fracture of the die due to thermal fatigue is one of the main reasons for the failure of the hot working die. Therefore, the hot work die steel must have good thermal fatigue.