Heat Treatment Methods For Mold Materials

- Jul 12, 2019-

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

1.High temperature quenching
    In order to improve the rigidity and wear resistance of the material, the general materials need to be heated to above 1030 ° C. At high temperatures, various alloying elements are fully dissolved in the austenite to obtain a high matrix hardness during quenching, and in order to ensure that the parts do not undergo decarburization and oxidation, a vacuum treatment is employed. At present, the high-rate gas quenching furnace used in the semiconductor industry can heat the workpiece under high vacuum conditions by nitrogen protection, which not only ensures decarburization and oxidation of the workpiece, 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 workpiece to ensure the workpiece is fully hardened and the deformation is reduced.


design 042

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 hardness and ensure dimensional stability, cryogenic treatment and high temperature tempering are usually carried out to ensure the full transformation of retained austenite. For stable tempered martensite. We calibrated the vacuum-quenched workpiece between room temperature and 100 ° C, and then placed it in a -140 ° C cryogenic treatment tank for deep cooling. The workpiece can be cooled and cooled between -140 ° C and 230 ° C without leaving the furnace to ensure that the workpiece does not deform or crack due to entering and exiting the furnace. At the same time, due to the use of nitrogen protection, the oxidative cracking of the workpiece during tempering is avoided. 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 to ensure convection. The temperature uniformity of the workpiece 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 parts of the workpiece. The past view that the cleanliness of heat treated workpieces has nothing to do with processing has been abandoned, and clean pretreatment has been added. The parts that are not in the furnace are vacuumed, degreased and dried by a vacuum cleaner. The various types of processing oil and debris of the workpiece are removed, which ensures that the workpiece is not brought into other impurities, avoids the decomposition of impurities during high temperature heating, pollutes the furnace environment and the workpiece itself, and ensures the cleanliness of the workpiece microscopically. The perfection of the degree and processing quality improves the service life of the workpiece.

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