Investment casting pattern and method for making the same

• Main Authors: VIHTELIC, JOSEPH M, JACKSON, PHILIP D, FRISCH, KURT C, KRESTA, JIRI E
• Format: Patent
• Language: English; French; German
• Published: 02.08.2000
• Edition: 7
• Subjects: CASTING; CHEMISTRY; COMPOSITIONS BASED THEREON; FOUNDRY MOULDING; MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONSONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS; METALLURGY; ORGANIC MACROMOLECULAR COMPOUNDS; PERFORMING OPERATIONS; POWDER METALLURGY; THEIR PREPARATION OR CHEMICAL WORKING-UP; TRANSPORTING

Method of making a shell mold for casting molten metals or alloys involves forming a thermally collapsible, low density reaction injection molded (RIM) thermosetting polyurethane foam pattern having a shape corresponding to the casting to be made. The pattern is formulated to have an aggregate density (pattern outer skin and pattern cellular core) in the range of about 10 to 15 lbs/ft and a smooth continuous as-molded surface devoid of surface connected open cells, dimensional stability over a range of temperatures, and ready, ashless burnout from the shell mold formed thereon without cracking the shell mold. The pattern is free of organometallic catalysts that should not be present in the casting of aerospace superalloys, such as nickel and cobalt base superalloys and titanium. The pattern then is invested without the need for any surface polymer or other film or layer in a shell mold.