Hot die steel Including forging die, hot extrusion die and die three. As mentioned before. The main characteristics of hot working die working conditions is in contact with hot metal, which is the main difference with the cold die working conditions. It will have the following two problems:
(L) cavity heated metal surface. Usually die forging work. The cavity surface temperature can reach 300 ~ 400 DEG C hot extrusion die above can reach 500 to 800 DEG C; die casting mold cavity temperature and type of material and the casting temperature. Such as black metal die-casting mold cavity temperature can reach 1000 DEG C. This high temperature causes the surface hardness and strength of the cavity was significantly lower in the use of prone play crib. Therefore. The basic performance of hot die steel is hot plastic deformation resistance is high, including high hardness and high temperature strength, high thermal deformation resistance, actually reflects the high tempering stability of steel. The first way so we can find the hot die steel alloy, namely Cr, W and Si. added alloy elements can improve the stability of tempering steel.
(2) the cavity surface of the metal have Gelau (Gui Lie). Hot mold work is characterized by intermittent. Every time after the hot metal forming to the surface of water, oil and air cooling medium cavity. So hot.
The mould state is repeatedly heated and cooled, so that the cavity surface of the metal have repeated expansion and contraction, the tension and compression under repeated stress. The results of surface cracks caused by the cavity, the phenomenon known as thermal fatigue, thus, hot die steel for proposed second basic use with performance requirements. High thermal fatigue resistance. Generally speaking, the main factors affecting the thermal fatigue resistance of steel: the thermal conductivity of steel. High thermal conductivity of steel, can minimize heat the metal mold surface, thereby reducing the tendency of thermal fatigue of steel. Is generally believed that the thermal conductivity of steel and carbon content, carbon content of high thermal conductivity is low, so not hot work die steel with high carbon steel. Commonly used in the production of carbon steel (C0.3%5 ~ 0.6%) carbon content is too low. Leads to the decrease of the hardness and strength of steel is also unfavorable. The critical point of steel. Usually the critical point of steel (Acl steel). The higher the lower the tendency of thermal fatigue.Usually by the addition of alloying elements Cr, W, Si, critical point lead to increase of steel. In order to improve the thermal fatigue resistance of steel.