| 摘要 |
Precision castings, such as brake calipers and other parts requiring a fine finish and having complex internal geometries, can be produced by casting a shot of a semi-solid thixotropic metal alloy about a core, preferably a hot-chamber die-cast core, having a lower melting point than the solid-to-semi-solid transition temperature of the thixotropic alloy. Then, after the shot solidifies to form a casting with a captured core, the core is melted from the casting in a liquid bath, in an air furnace, or during other heat treatment of the part. The process dramatically reduces or even eliminates machining requirements for cast metal parts because the inner surface of the casting is of extremely low porosity and meets stringent tolerance requirements and because the melt-away core can be formed with protrusions that prevent mechanical removal of the core from the casting and that form undercuts, threads, bores, etc. in the casting. Process robustness, speed, and versatility can be enhanced by coating the core with a thin, uniform, abrasion-resistant, and thermally resistant coating that prevents excessive heat from being transferred to the core from the shot and that prevents the core from alloying with the casting.
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