Variation of mechanical properties in large steel forgings

Abstract

In a continuing effort to reduce mechanical property variation in large, low alloy, steel forgings, the effects of forging reduction on mechanical and metallurgical properties were examined. This included tensile strength, ductility, impact energy and fracture toughness. Also examined were nonmetallic inclusion content and microstructure. In addition, the consequences of ingot solidification could not be ignored, therefore, the aspect of chemical homogeneity was considered. For these ingots and the range of forging reductions investigated (1.5:1 to 10:1), a reduction of approximately 3:1 produced optimum values in pct reduction of area, Charpy impact energy, and plane strain fracture toughness. The significant variations statistically determined in these parameters were accompanied by real variation in carbon concentration. Therefore, segregation of carbon on a macro scale was shown to be a major contributor to mechanical property variation in large steel forgings produced from statically cast ingots. Indeed, mechanical working alters segregation patterns but will not eliminate them.