Method and apparatus for semi-molten metal injection molding

A method of injection molding a semi-molten metal in a mold cavity to produce a thick molded article having thickness of not less than 5.0 mm in 50% or more of an area of a product portion corresponding to the mold cavity, wherein the semi-molten melt of a metal material is injected in a semi-melting state at a temperature of not more than a liquidus temperature of the metal material into the cavity of a mold through a product gate by using an injector which has an injection cylinder provided with a nozzle of a lower inner diameter than the inner diameter of the injection cylinder;

• the method comprising the steps of heating the material in the cylinder while being agitating by a screw into the semi-molten metal in which a solid fraction in the semi-molten melt is set to not less than 10%, pushing the semi-molten metal by means of the screw from the cylinder through the nozzle and injecting the semi-molten metal through the gate into the mold cavity, wherein a velocity Vg (mm/s) of the semi-molten melt passing through the product gate, a sectional area Sg (mm2) of the product gate portion of the thick molded article and a volume Vp (mm3) of the product portion are set so as to satisfy the following relationships:
• Vg≦8.0×104;
• and,
• Vg×Sg/Vp≧10.