sometimes fail in the process of die-casting production. The causes of failure are mainly caused by the following three aspects. The following is a brief introduction:
1. Fragmentation failure
Under the action of the injection force, the die-casting mold will crack at the weakest point, especially the scribe marks or electrical machining marks on the molding surface of the mold are not polished, or the clear corners of the molding will be the first to appear. Crack, when there is a brittle phase at the grain boundary or the grain is coarse, it is easy to break. However, the cracks expand rapidly during brittle fracture, which is a very dangerous factor for the chipping 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 gating system part, it must be polished. In addition, the mold materials used are required to have high strength, good plasticity, good impact toughness and fracture toughness.
2. Dissolution failure
Commonly used die-casting alloys include zinc alloy, aluminum alloy, magnesium alloy and copper alloy, as well as pure aluminum die-casting. Zn, Al, and Mg are more active metal elements, and they have a good affinity with mold materials, especially Al is easy to bite. mold. When the hardness of the mold is higher, the corrosion resistance is better, and if there are soft spots on the molding surface, the corrosion resistance is unfavorable.
3. Thermal fatigue crack damage failure
During die-casting production, the die-casting mold
is repeatedly subjected to the action of cooling and heating, the molding surface and its interior are deformed, and they are involved in each other, resulting in repeated cycles of thermal stress, resulting in damage to the structure and loss of toughness, causing micro-cracks to appear and continue to expand. , once the crack expands, the molten metal squeezes in, and repeated mechanical stress accelerates the crack growth. To this end, on the one hand, the mold must be sufficiently preheated at the beginning of the die casting. In addition, the die-casting mold must be kept within 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 the mold is put into production and during the manufacturing process. In actual production, most mold failures are thermal fatigue crack failures.