Hot ductility of Nb-V microalloyed steels

Microalloyed steel has become a good option in industry application for its high strength and low weight. However hot ductility problems exist during high temperature deformation which limit the commercial usage. Therefore, in this study, the hot ductility behavior of Niobium and Vanadium contained microalloyed steel with as cast structure and hot rolled structure were investigated by hot tensile test in the temperature region from 800℃ to 1000℃, followed by fracturing and rapid quenching. Reduction of Area was recorded as an important parameter representing the hot ductility. High temperature yield strength, Ultimate tensile strength and elongation were obtained for study the hardening effect of microalloyed elements. Analyses of microstructure damage during tensile test were performed with optical microscope. Cracks were observed to understand the detrimental influence of Niobium and Vanadium on hot ductility. It was detected that the critical temperature zone for this microalloyed steel is between 850℃ and 950℃, the rolled steel has better ductility performance than as cast steel, and rolling procedure may reduce the negative effect of Nb and V on hot ductility.