Factors affecting the service life of die casting molds
The service life of a die-casting mold is a key indicator of its economic viability. It is influenced by multiple factors, including material properties, design rationality, manufacturing process, and maintenance. Properly controlling these factors can extend mold life by over 50%, significantly reducing production costs. Mold life is typically measured by the number of molds required to maintain die-casting quality. Typical zinc alloy molds have a lifespan of approximately 50,000 to 100,000 cycles, aluminum alloy molds have a lifespan of 100,000 to 300,000 cycles, and copper alloy molds typically have a lifespan of less than 50,000 cycles.
Material quality and heat treatment level are inherent factors affecting mold life. Inclusions (such as sulfides and oxides) or forging defects (such as porosity and cracks) in mold steel can become sources of premature failure, leading to premature cracking of the mold during use. For example, if the non-metallic inclusion level in H13 steel exceeds Level 2, mold life can be reduced by 30% to 40%. Improper heat treatment can also be fatal. Excessively high quenching temperatures lead to coarse grains and reduced toughness; insufficient tempering leaves excess austenite, resulting in reduced hardness and accelerated wear during use. In one case, when the tempering temperature of H13 steel was 50°C lower than the standard, the mold life dropped from 250,000 cycles to 120,000 cycles.
Mold structural design significantly impacts mold life. A cavity corner radius that is too small (
The rationality of die-casting process parameters directly impacts mold performance. Excessively high pouring temperatures can exacerbate mold thermal fatigue. When aluminum alloy pouring temperatures exceed 700°C, mold surface oxidation accelerates, and thermal cracks appear 50% earlier. Improper mold temperature control is equally detrimental. Excessively low temperatures (<150°C) can cause the molten metal to chill, increasing filling resistance and causing increased force in the mold cavity. Excessively high temperatures (>300°C) can reduce mold strength and predispose to plastic deformation. Excessive injection speed and pressure increase the impact of the molten metal on the mold cavity. For example, after one die-casting plant increased its injection speed from 4m/s to 5m/s, mold cavity wear increased 1.8 times, significantly shortening its lifespan.
Maintenance and upkeep are key to extending mold life. Preheating the mold before production begins can cause thermal shock due to the dramatic temperature difference, leading to cavity cracking. The correct preheating method is to gradually raise the mold temperature to operating temperature (at a rate of ≤50°C/h). Improper application of release agent can also affect mold life. Excessive application can cause a sudden drop in mold surface temperature, exacerbating thermal fatigue. Uneven application can lead to localized sticking, increase release forces, and cause cavity strain. Regular maintenance can identify potential problems. For example, every 10,000 molds, clean the vents and inspect the core for wear. Every 50,000 molds, regrind the cavity surface to restore its roughness to Ra ≤ 0.8μm. These measures can extend mold life by 20%-30%.
