EFFECT OF PROCESSING HISTORY ON FRACTURE OF MATERIALS AT HIGH STRENGTH LEVELS

摘要

The influence of melting and solidification variables on the fracture toughness of AISI 4340 steel at a yield strength of 240,000 psi was studied In this initial part of the program, four different ingot structures were obtained by casting air-melted 4340 steel into four different types of molds: (a) a sand mold, (b) a cast iron chill mold, (c) a "hot" mold lined with exothermic material, and (tip a mold producing unidirectional solidification. Ingots of these structures were evaluated as described below, as were comparable vacuum cast ingot of types (a) and (d).