The heat treatment is to change the metallographic structure of the die-casting mold material by heating and cooling, and to obtain the necessary strength, hardness, toughness, dimensional stability at high temperature, thermal fatigue resistance, machinability and the like. When heat treatment of die-casting molds, attention should be paid to the same material and the same hardness requirements after heat treatment. If different heat treatment methods are used, the quality performance will be completely different.
The heat treatment process of H13 die steel and the metallographic structure after heat treatment shall be in accordance with the regulations of the North American Die Casting Society (NADCA 207-2003). It is recommended that the company that sells the mold steel be responsible for the heat treatment of the mold to avoid quality disputes caused by different materials and heat treatment manufacturers.
H13 steel adopts high-pressure liquid nitrogen-cooled high-vacuum furnace to quench high quality, which can effectively prevent decarburization, oxidation, deformation and cracking of the mold surface. Increase the quenching temperature to 1020 ° C ~ 1050 ° C (DIEVAR steel in 1000 ~ 1030 ° C), according to the size of the module material, and the strength and toughness required by each component, properly control the temperature and holding time, so that the alloy carbide is sufficient Dissolving austenite, which can reduce the mold crack caused by insufficient heat treatment of the heat-dissolved carbide and remaining between the grain boundaries.
However, attention should be paid to the critical points Ac1 and Ac3 of steel and the holding time to prevent austenite roughening. After quenching the die-casting mold, tempering with a minimum of 3 times at different temperatures, according to 2 to 3 hours/time of heat preservation, paying special attention to the temperature and hardness effect of tempering, H13 steel can not be at 425-550 °C, DIEVAR steel can not be returned at 500-550 °C Fire to avoid temper brittleness. If nitriding is to be performed, a tempering treatment can be reduced.