processes for general shapes

Refractory Molds - Of the several refractory-mold-based methods, the Shaw process is probably the best known. Here, the wood or metal pattern halves are dipped into an aggregate slurry containing a methyl silicate binder, forming a shell. After stripping the pattern, the shell is fired at a high temperature to produce a strong refractory mold. Metal is introduced into the mold while it is still hot. This aids feeding but it also produces the relatively slow cooling rates and coarse-grained structures that are typical of the process.

Dimensional accuracy as good as + 0.003 in (_+ 0.08 mm) is attainable in castings smaller than about one inch (25 mm), while tolerances as close as + 0.045 in (+1.1 mm) are claimed in castings larger than 15 in (630 mm) in cross-section. Additional allowances of about 0.010-0.020 in (0.25-0.5 mm) must be included across the parting line. Surface finishes are typically better than 80 gin (2 gm) rms in nonferrous castings.