Metal mold cavity surface thermal fatigue

Cavity surface metal thermal fatigue ( cracking ) . Hot mold work is characterized by intermittent . After each state of the metal forming the hot water to be cooled cavity surface oil, air and other media. Therefore . Hot mold working condition is repeated heating and cooling , so that the surface of the metal mold cavity to produce plastic container moldingthermal expansion and contraction , which repeatedly subjected to tensile and compressive stress . As a result, the cavity caused by surface cracks , called thermal fatigue phenomenon whereby hot die steel made for second basic performance requirements. That has a high thermal fatigue resistance . In general, the factors affecting the thermal fatigue resistance of steel are mainly : ① steel thermal conductivity. The high thermal conductivity of steel , a metal mold can reduce the degree of surface heating , thereby reducing the tendency of the steel to thermal fatigue . Thermalconductivity is generally believed that the amount of carbon steel and cooperation related to the high china plastic injection moldingthermal conductivity when the carbon content is low, it should not be hot die steel with high carbon steel. Commonly used in the production of carbon steel (C0.3% 5 ~ 0.6%) combined carbon content is too low. Causes decrease in the hardness and strength of steel .Isdisadvantageous.Critical point ② Steel. The critical point is usually steel (Acl) is higher. The lower steel thermal fatigue bias. Therefore . Usually by adding alloying elements Cr, W, Si, attracted improve the critical point of the steel. Thereby improving the thermal fatigue resistance of steel.