Specific Measures To Improve The Life Of Die-Casting Molds

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.


For the part of the cavity surface of the die-casting mold, which is prone to sticking and all the cores, nitriding, carbonitriding, KANUC in Japan, vapor deposition (PVD physical vapor deposition, CVD chemical vapor deposition), and nitriding should be used. Surface strengthening treatment by evaporation, laser, etc. to reduce sticking or erosion.

At present, there are more treatments using KANUC in Japan. If nitriding is required, the total depth of the nitrided layer of the profile should be smaller than the previous 0.2-0.3mm, and should be controlled from 0.04 to 0.08 to 0.12 mm depending on the thickness of the casting, and there should be no compound white bright layer. Prevent excessive cracking of the white bright layer and cause premature cracking of the mold. The higher the nitridation temperature, the higher the nitrogen potential concentration and the thicker the nitride layer, the more likely the white bright layer is to be produced. For parts that are easy to stick to the mold, a surface treatment such as nitriding can be performed once per 10,000 to 20,000 molds.

After the mold is die-casted from 8 to 100,000 times, the nitriding treatment can also be performed when the mold is easily formed due to the decrease in hardness. Note that the mold surface should be polished accordingly before and after annealing and nitriding. In order to prevent oxidation rust before the mold cavity is mass-produced, after the mold is passed, the mold should be oxidized in the electric furnace for 530-560 for 1 to 1.5 hours.

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