Many people wonder: gravity casting can also form, why does die-casting require a three-step combination of high pressure, high speed, and holding pressure? The three underlying logics determine the quality of castings.
1. High speed filling: solving the problem of thin-walled forming
Aluminum alloy and zinc alloy have extremely fast cooling rates, and the metal liquid in the 0.5-1mm ultra thin wall area will solidify in a few seconds. Only high-speed filling at speeds above 30m/s can fill every detail of the mold cavity before the metal solidifies, avoiding material shortage, cold insulation, and grain defects.
2. High pressure boosting: eliminate shrinkage and increase density
Metal cooling and solidification will cause volume shrinkage. Without external pressure filling, loose holes will form inside, leading to gas leakage and insufficient strength of the casting. Continuous compression under high pressure above 60MPa, with additional metal liquid to supplement the shrinkage gap, significantly reducing porosity and improving air tightness and mechanical strength.
3. Continuous pressure maintenance: stabilize grain structure
During the pressure holding stage, the mold evenly dissipates heat, high-pressure suppresses grain coarsening, and the internal structure of the casting is dense and uniform. The tensile strength and hardness are much higher than those of ordinary gravity casting, meeting the mechanical requirements of automotive and new energy structural components.