Effect of homogenization on sulphide morphology and mechanical properties of rolled AISI 4340 steel

Abstract

The modification that sulphide inclusions undergo during homogenization of hot-rolled AISI 4340 low-alloy steel, and its effect on mechanical properties were evaluated. Transverse ultimate tensile strength and 0·2% offset yield strength did not change with homogenization time, whereas transverse ductility exhibited a minor improvement. Charpy V-notch impact strength was higher in the rolling direction than in the transverse direction and in both cases it improved appreciably with homogenization. Reversed bending fatigue strength first increased, then reached a maximum, and subsequently decreased with homogenization time. Fatigue life at a given stress level decreased with increasing mean overall sulphide size.