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In actual production, dissolution is only a part of the die-casting mold - 2020年11月05日(木)
In this example, the parts (cores and cavities) that are directly washed by the gate are prone to dissolution, and aluminum alloy sticky molds are prone to appear in places with soft hardness. In addition, the die-casting mold must be kept in a certain working temperature range during the die-casting production process to avoid early cracking failure. If the die-casting die fails at an early stage, it is necessary to find out which internal or external causes are in order to improve in the future. However, the crack propagation is very fast during brittle fracture, which is a very dangerous factor for the fracture failure of the die casting mold.).).There are many factors that cause the failure of die-casting molds, including external factors (for example, whether the casting temperature is high or low, whether the mold is preheated, the amount of spray coating, whether the tonnage of the die-casting machine is matched, the die-casting pressure is too high, the inner gate speed is too fast, The opening of the cooling water is not synchronized with the die-casting production, the type of die-casting material and the level of composition Fe, the size and shape of the casting, the wall thickness, the type of coating, etc. There are also internal factors (for example, the metallurgical quality wholesale cap mould Factory of the die-casting mold itself, the forging process of the blank, the rationality of the die-casting mold structure design, the rationality of the pouring system design, the internal stress generated during the processing of the mold machine (electric machining), the heat treatment of the die-casting mold Process, including various matching precision and finish requirements, etc. For this reason, on the one hand, the mold must be fully preheated at the beginning of die casting..
However, in actual production, dissolution is only a part of the die-casting mold. (2) Melting failure As mentioned earlier, the commonly used die-casting alloys include zinc alloy, aluminum alloy, magnesium alloy and copper alloy, as well as pure aluminum die-casting. It has a good affinity, especially Al is easy to bite. For this reason, on the one hand, all scratches and electrical machining marks on the mold surface must be polished, even if it is in the pouring system, it must be polished. When the hardness of the die-casting mold is high, the corrosion resistance is better, and if there are soft spots on the molding surface, the corrosion resistance is unfavorable. (1) Fragmentation failure Under the action of the injection force, the die-casting mold will initiate cracks at the weakest point, especially the scribe marks or electrical processing marks on the molding surface of the die-casting mold are not polished, or the corners of the molding are clear Small cracks will appear first in all areas, and when there is a brittle phase or coarse grains at the grain boundary, it is easy to break. In actual production, most of the die casting mold failures are thermal fatigue crack failure. Zn, Al, and Mg are more active metal elements, which are compatible with die-casting mold materials. During die-casting production, die-casting die is repeatedly affected by chilling and heating, and the molding surface and its interior are deformed, which are mutually involved, resulting in repeated cycles of thermal stress, resulting in damage and loss of organizational structure. Once the crack expands, molten metal squeezes in, and repeated mechanical stresses accelerate the crack growth. Toughness initiates the appearance of micro-cracks and continues to grow. (3) Die-casting die thermal fatigue cracking failure.
At the same time, it is necessary to ensure that the internal factors before and during the production of die-casting molds do not occur. In addition, the die-casting mold material used is required to have high strength, good plasticity, good impact toughness and fracture toughness
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