Low pressure die casting of metal, esp. non-ferrous metal - which is injected into evacuated die and then subjected to pressure during solidification

摘要

The die cavity is evacuated, molten metal is injected at low speed into the die and a riser or feeder head, and then pressure is exerted on the molten metal in the riser during solidification. A vacuum of 0.1-0.9 at. below the atmos. pressure is pref. applied, and the molten metal in the riser is pref. subjected to 2-10, esp. 5-6 bars. Pref. the molten metal is injected at max. 20, esp. max. 10 m/sec. into a die cavity located underneath a riser contg. a bell piston. The piston is connected by a pipe and valve to a vacuum pump, and is also mounted on the bottom end of a pneumatic cylinder. When a pressure sensor indicates that the metal has reached the riser, the vacuum is switched off and the bell piston is driven down the riser to exert 5-6 bars on the molten metal. Slow speed injection of the molten metal is combined with pressure exerted on the melt in the riser.