2 - Casting and Solidification

Abstract

This chapter discusses casting and solidification techniques. Casting operation includes pattern design and pattern fabrication, selection of the mold and core materials and molding process, selection of the melting technique, selection of pouting technique, control of the solidification process, part separation from the mold, cleaning, finishing, and inspection, and secondary treatment of cast components. The chapter describes various types of casting, which include: expendable-mold casting and green sand casting, investment casting, lost-foam casting, die casting and semisolid casting, squeeze casting, centrifugal casting, and continuous casting. The interactions between molten-metals and atmospheric gases cause defects in castings. Melt-cleaning processes aim to eliminate such defects in castings through special pouting and gating techniques, and prior treatment of the melt. The chapter illustrates a simplified practical method to design the gating system developed by the American Foundry Society (AFS). It further describes solidification rate. The rate at which a casting solidifies depends on the rate of heat dissipation, which influences the casting production rate and the metallurgical structure of the part.