High Pressure Die CastingThe metal liquid is driven by the compression injection punch to fill the precision cavity at a high speed with the inner gate speed of 50~100m/s and the specific pressure of ≥70MPa, and the filling time is only 0.01~0.2 seconds, and after solidification, the high-precision thin-walled parts of CT4~6 grade are obtained; however, due to the difficulty of the cavity gas to be completely discharged, the castings are generally characterized by the presence of diffuse porosity, which makes it impossible to carry out the solution heat treatment, and the elongation rate of δ＜5%.
Low-pressure castingDry compressed air (0.02~0.08MPa) acts on the liquid surface of the sealed crucible, driving the metal liquid through the ascending liquid pipe from bottom to top along the pouring system laminar flow filling, the filling speed can be controlled at 0.05~0.5m/s; the crystallization process applies the pressure preservation pressure (0.1~0.3MPa) in order to force the filling contraction, obtaining the casting of the organization of the dense, non-involved porosity, and it is possible to carry out the T6 heat treatment, the tensile strength ≥300MPa, elongation δ up to 7%~12%. Tensile strength ≥300MPa, elongation δ up to 7%~12%.
Gravitational castingMetal liquid only relies on the gravitational potential energy generated by the pouring ladle to fill the metal mold or resin sand mold, and the flow pattern is determined by the geometrical parameters of the pouring system; it realizes the sequential solidification and shrinkage through the setting of risers, and the tendency of shrinkage and loosening of the thick-walled parts is low, and the casting airtightness can be up to Grade Ⅰ (no leakage in 30 seconds of pressure holding at 0.02MPa), but the dimensional tolerances are usually only CT7~10, and the machining allowances are large.
