材料期刊网

The purpose of this research is to quantify the effects of compositional and processing parameters on the microstructure and properties of dual phase steel produced directly by hot rolling and rapid cooling. Steels with the basecomposition of 0.1%C, 1.4%Si, and 1.0%Mn with additions of 0.5%Cr to influence hardenability, 0.04%Nb to retard recrystallization in the latter stages of rolling, or 0.02%Ti to inhibit grain growth during and after reheatingwere investigated. Investigation was made to predict microstructure evolution and to correlate microstructure withprocessing parameters. The effects of the important microstructure parameters such as ferrite grain size, martensitevolume fraction (VM) and morphology (polygonal or fibrous) on the tensile and impact properties are discussed.Multiple linear regression analysis of the ultimate tensile strength has shown that, increasing VM and martensitemicrohardness and grain refinement of ferrite are the major contributions to increase the strength of the steel. It wasfound that the dual-phase steel produced by controlled rolling process, with a microstructure which consisted of finegrained ferrite (4μm) and 35%～40% fibrous martensite, presented optimum tensile and impact properties becauseof enhanced resistance to crack propagation.