Causes of die-casting mold failure
Publish Time: 2024-05-07
① Thermal fatigue cracking of the mold fails. During die-casting production, the mold is repeatedly subjected to the effects of cold and heat shocks, causing deformation of the molding surface and its interior. They are involved in each other and cause repeated cycles of thermal stress, resulting in damage to the organizational structure and loss of toughness, causing micro cracks. appear and continue to expand. Once the crack expands, molten metal squeezes in, and repeated mechanical stress accelerates the expansion of the crack. For this reason, on the one hand, the mold must be fully preheated when die casting starts. In addition, during the die-casting production process, the mold must be maintained within a certain operating temperature range to avoid early cracking failure. At the same time, it is necessary to ensure that there are no internal problems before the mold is put into production and during manufacturing. Because in actual production, most mold failures are thermal fatigue cracking failures.
② Fracture failure Under the action of injection force, the mold will develop cracks at the weakest point, especially if the scribing marks or electrical machining marks on the molding surface have not been polished, or the clear corners of the molding will be the most vulnerable. Fine cracks appear first, and when there is a brittle phase at the grain boundary or the grains are coarse, it is easy to break. In brittle fracture, the crack expands very quickly, which is a very dangerous factor for the mold to break and fail. For this reason, on the one hand, all scratches and electrical machining marks on the mold surface must be polished, even if they are in the pouring system, they must be polished. In addition, the mold materials used are required to have high strength, good plasticity, impact toughness and fracture toughness.
③ Melting failure As mentioned before, 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 better interaction with mold materials. The affinity, especially Al, is easy to mold. When the hardness of the mold is higher, the corrosion resistance is better, but if there are soft spots on the molding surface, the corrosion resistance is unfavorable. However, in actual production, corrosion only occurs in local parts of the mold. For example, corrosion occurs easily in areas where the gate is directly washed away (core, cavity), and aluminum alloy mold sticking occurs in areas with softer hardness.
