In the working process, the mold bears the impact load, in order to reduce the damage in the process of breaking, falling edge and other forms, the mold steel is required to have a certain toughness. The chemical composition, grain size, purity, quantity, morphology, size and distribution of carbides and inclusions of die steel, as well as the heat treatment system of die steel and the metallographic structure obtained after heat treatment have a great impact on the toughness of steel.

In particular, the influence of steel purity and thermal deformation on its lateral toughness is more obvious. The toughness, strength and wear resistance of steel are often contradictory. Therefore, it is necessary to reasonably select the chemical composition of steel and adopt reasonable refining, hot processing and heat treatment processes to achieve the best match of wear resistance, strength and toughness of die materials.

The wear resistance of the die steel is very strong, in addition, the steel of the die steel also has the ability to resist thermal fatigue. In addition to the periodic change of load, hot work die steel is also affected by high temperature and periodic acute cooling.