The cutting stress generated during the mold processing, the stress of the spark discharge metamorphic layer, and the thermal fatigue stress generated during the die casting can be alleviated or eliminated by annealing. The mold should be periodically annealed to eliminate stress: the first stress relief annealing should be arranged before quenching (annealing temperature 700 °C ~ 750 °C), the second stress relief annealing should be arranged before the mass production after the test mold is qualified, and then in the die casting Each of the 10,000-mode and 30,000-mode anneal treatments is performed once, and the nitridation can be used instead of the one-time annealing treatment. The annealing temperature of H13 steel is 20 °C ~ 40 °C lower than the temperature of the last tempering at the time of quenching. For example, the stress relief annealing is performed by keeping the temperature of the module at 560±10°C for 1 to 1.5 hours.
Reasonable choice of mold hardness, US AISI H13 ESR material for die-casting mold, if the hardness is low, prone to sticking and early cracking, if the hardness is too high, it will increase the risk of cracking, so it is generally recommended: zinc alloy die-casting mold Use 47 ~ 52HRC; medium and small aluminum, magnesium alloy die-casting mold with 46 ~ 48HRC; large size aluminum, magnesium alloy castings and relatively thick or complex shapes of the mold, should be properly reduced hardness of 44 ~ 46HRC. Hitachi's DAC55, ZHD435 and ASSAB DIEVAR steels have good toughness and high temperature strength at high hardness, and the hardness can be increased by 2~4HRC compared with H13.