What problems will affect the failure of die casting?
Die-casting molds sometimes fail during the production process of die-casting. The failure causes are mainly caused by the following three aspects
1. Fragmentation failure Under the action of the injection force, the die-casting mold will have cracks in the weakest part, especially the scribe marks or electrical processing marks on the molding surface of the mold are not polished, or the clear corners of the molding are not polished. Micro cracks will appear first, and when there are brittle phases or coarse grains at the grain boundaries, it is easy to break. However, the crack propagation is very fast during brittle fracture, which is a very dangerous factor for the fracture and failure of the mold. 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. In addition, the mold material used is required to have high strength, good plasticity, good impact toughness and fracture toughness.
2. Commonly used die-casting alloys for corrosion failure include zinc alloy, aluminum alloy, magnesium alloy and copper alloy, as well as pure aluminum die-casting. Zn, Al, Mg are more active metal elements, and they have good affinity with mold materials, especially It is Al easy to bite mold. When the mold hardness is high, the corrosion resistance is better, and if there are soft spots on the molding surface, the corrosion resistance is unfavorable.
3. Thermal fatigue, cracking, damage and failure. During the production of die-casting, the die-casting mold is repeatedly subjected to the effect of chilling and heating, and the molding surface and its interior are deformed. Microcracks appear and continue to grow. Once the cracks expand, molten metal squeezes in, and repeated mechanical stresses accelerate the cracks.
For this reason, on the one hand, the mold must be fully preheated at the beginning of die casting. 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. At the same time, it is necessary to ensure that there are no problems with the internal factors before and during the production of the mold. In actual production, most mold failures are thermal fatigue cracking failures.
