The properties of the material itself must be achieved by proper heat treatment in mold making. Only good heat treatment can achieve our expected performance expectations. According to the performance requirements of mold materials, the heat treatment methods are mainly high temperature quenching, cryogenic treatment, high temperature tempering, and repeated many times. Go through these different heat treatments, to achieve the best mold performance.

1. High temperature quenching
In order to improve the rigidity and wear resistance of the mold material, generally, the materials need to be heated to above 1030 ° C. At high temperatures, various alloying elements are fully dissolved in the austenite to obtain high matrix hardness during quenching. Meanwhile, in order to ensure that the mold parts do not occur decarburization and oxidation, the vacuum treatment is used accordingly. At present, the high-rate gas quenching furnace used in the semiconductor industry can heat the mold steel material under high vacuum conditions by nitrogen protection, which not only ensures decarburization and oxidation of the mold material, but also prevents evaporation of alloying elements. At the same time, the adjustable gas pressure in the range of 200-500Kpa is used to quench the mold steel material to ensure sufficient hardening of the mold materials while reducing mold deformation.

2. cryogenic treatment and high temperature tempering
After quenching, high alloy steel has higher martensite transformation point (Ms point) than room temperature. In order to improve mold hardness and ensure dimensional stability, cryogenic treatment and high temperature tempering are usually required to ensure that the retained austenite can be fully transformed to stable tempering martensite. We calibrated the vacuum-quenched mold steel between room temperature and 100 ° C, and then placed it in a -140 ° C cryogenic tank for cryogenic cooling. The mold steel can be cooled and heated cycle between -140 ° C and 230 ° C without leaving the furnace to ensure that the mold steel does not deform or crack due to entering and exiting the furnace. At the same time, the oxidative cracking of the mold steel material during tempering is avoided due to the protection of nitrogen. At present, for D2 materials, we usually complete 3 cycles of -140 ° C deep cooling to 230 ° C tempering directly in the cryogenic equipment. For steels with tempering above 230 °C, such as SAM97, ELmax, ASP23, etc., we use a vacuum tempering furnace. After vacuuming, 99.999% of high-purity nitrogen is added as a medium to form convection through the change of blowing direction, ensuring the temperature uniformity of the mold material while saving tempering time.

3. Other auxiliary means
While improving the quality of quenching, tempering and cryogenic treatment, we have paid sufficient attention to other link of the injection mold making. In the past, the view that the cleanliness of the heat-treated mold material is irrelevant to the treatment has been abandoned, and the clean pretreatment is added. The parts that are not in the furnace are vacuumed, degreased and dried by a vacuum cleaner. It removes all kinds of processing oil and debris from the mold material, ensures that the mold material will not be brought into other impurities, avoids the decomposition of impurities during high temperature heating, pollutes the furnace environment and the mold material itself, and ensures the cleanliness of the mold material. The mold processing quality improves the service life of the injection.