Development of cast high strength microalloyed steels

Cast microalloyed steels containing 1(.)25-1(.)3%Si and >2(.)0%Mn plus small quantities of nickel, chromium and microalloying elements (Nb, V, Ti) may be adequately strengthened by air cooling from 950degreesC. After a tempering treatment at 500-550degreesC, these low carbon (0.15-0.20%C) cast steels can exhibit YS 520725 MPa, UTS 690-820 MPa, 20-40% El and impact toughness up to 30 J at -40degreesC. The air cooled microstructures in these steels consist of precipitation strengthened ferrite+ bainite. The tempering treatment induces transformation of retained austenite to pearlite and improves mechanical properties. (C) 2004 W. S. Maney Son Ltd.