Analysis of the reasons affecting the failure of die casting

There are many reasons for the failure of die-casting, including external factors, such as the casting temperature, whether the mold is preheated, the amount of spray paint, whether the tonnage of the die-casting machine matches, and the die-casting pressure is too high. There are also internal reasons, such as The metallurgical quality of the material of the mold itself, the forging process of the blank, the rationality of the mold structure design, etc.,

If the mold fails early, it is necessary to find out which internal or external causes are in order to improve in the future. However, in actual production, dissolution is only a part of the mold. For example, the parts (core, cavity) that are directly washed by the gate are prone to corrosion, and the aluminum alloy is prone to sticking to the mold at soft hardness.

Under the action of the injection force, the die-casting mold will initiate cracks at the weak points, 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 first appear micro cracks. When there are brittle phases or coarse grains in 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 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 materials used are required to have high strength, good plasticity, good impact toughness and fracture toughness.

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 vivid metal elements, and they have a good affinity with mold materials, especially Al Easy to bite mold. When the mold hardness is higher, the corrosion resistance is better, and if there are soft spots on the molding surface, the corrosion resistance is bad.

Thermal fatigue, cracking, damage and failure. When the die-casting is produced, the die-casting mold is repeatedly subjected to the effect of cold and heat, and the molding surface and its interior are deformed, and they are drawn to each other to present repeated cycles of thermal stress, resulting in damage to the arrangement structure and loss of resistance, causing micro-cracks The appearance of the crack, and continue to expand, once the crack propagates, there will be molten metal squeezed in, coupled with repeated mechanical stress, the crack propagates faster.