Die casting in investment mold

Abstract

Method and apparatus for casting a metallic material involves the steps of providing a non-metallic mold in a mold-receiving chamber disposed in at least one of relatively movable first and second members, communicating a mold cavity in the mold to a gating passage disposed in at least one of the first and second metallic members, communicating the gating passage to a shot sleeve, and flowing metallic material from the shot sleeve to the gating passage and into the non-metallic mold.

Description

FIELD OF THE INVENTION [0001] The present invention relates to casting of metals and alloys and, more particularly, to casting of metals, alloys, and intermetallics under pressure in a non-metallic investment mold. BACKGROUND OF THE INVENTION [0002] Titanium based alloys (e.g. Ti-6Al-4V) and intermetallics (e.g. TiAl) are used as cast components in the aerospace industry. Many such cast components are made by the well known gravity investment casting process wherein an appropriate melt is cast into a preheated ceramic investment shell mold formed by the lost wax process. [0003] Although commonly used, investment casting of complex shaped components of such titanium based materials can be characterized by relatively high costs and low yields. Low casting yields are attributable to several factors, in particular inadequate filling of certain mold cavity regions such as especially thin wall mold cavity regions. For example, filling of thin wall mold cavity regions having a thickness of...

AI Technical Summary

Benefits of technology

[0014] Moreover, the invention can be used to cast complex investment molds having backlocks, undercuts, or other features that can not be cast using metal dies. Practice of the invention permits complex mold geometries to be cast, without the need for significant chemical and / or mechanical rework of the die cast component.

Problems solved by technology

Although commonly used, investment casting of complex shaped components of such titanium based materials can be characterized by relatively high costs and low yields.

Low casting yields are attributable to several factors, in particular inadequate filling of certain mold cavity regions such as especially thin wall mold cavity regions.

For example, filling of thin wall mold cavity regions having a thickness of less that 0.050-0.060 inch with a titanium alloy or titanium aluminide melt is difficult due to melt fluidity, low superheat, and out-gassing problems.

However, such an approach is disadvantageous in that the molten titanium alloy or titanium aluminide can react with the mold at such high temperatures to form deleterious phases on the surface of the castings produced in such shell molds.

Moreover, it is oftentimes necessary to increase the thickness of one or more thin wall mold cavity regions when the mold is being made in order to subsequently achieve satisfactory mold filling during casting.

Drawbacks of using metal die casting molds include the high cost of the metal dies and the presence of die parting line between the metal dies, which parting line sometimes limits the complexity of the die cavity and thus the casting that can be die cast.

A further drawback of using metal dies when die casting titanium aluminide material is the generation of cracking in the casting as a result of rapid solidification of the melt in the metal mold.

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