Method of molding low melting point metal alloy
The present invention relates to a method of molding a low-melting-point metal alloy which exhibits thixotropy properties in a solid-phase and liquid-phase coexisting temperature region. In this method, a temperature of a heating holding cylinder is increased to a liquidus temperature or higher at the start of a molding operation. Then a remaining material in the preceding molding remaining in the heating holding cylinder in a solid state is wholly melted. After that a temperature of the heating holding cylinder is lowered to a temperature in the solid-phase and a liquid-phase coexisting temperature region. At the same time a molding material is supplied and a provisional molding is carried out. After the temperature has reached the solid-phase and liquid-phase coexisting temperature region, a regular molding is started. By the present invention a problem of a remaining material in the heating holding cylinder, which becomes a trouble at the start of molding by injection, is solved.
1. A method of molding a low melting point metal alloy comprising the steps of,
supplying a metallic raw material that exhibits thixotropy properties in a solid-phase and liquid-phase coexisting temperature region as a first molding material,
heating said first molding material at a temperature in the solid-phase and liquid-phase coexisting temperature region to form a semisolid material in a solid-phase and liquid-phase coexisting state,
supplying, in a first regular molding operation, a required amount of said semisolid material to a heating holding cylinder to be accumulated, and
injecting said semisolid material into a mold by one shot from said heating holding cylinder,
wherein, at the start of a next regular molding operation, the method further comprises,
increasing a temperature of the heating holding cylinder to a liquidus temperature or higher,
wholly melting any remaining material from a preceding molding operation remaining in said heating holding cylinder in a solid state,
supplying additional first molding material to be temporarily molded in a temporary molding operation while lowering the temperature of the heating holding cylinder to a temperature in the solid-phase and liquid-phase coexisting temperature region, and then
starting a next regular molding operation after the cylinder temperature has reached the solid-phase and liquid-phase coexisting temperature region.
2. The method of molding a low melting point metal alloy according to claim 1 , wherein the melting of said remaining material is carried out while stirring the material.