Effects of deformation and Mo, Nb, V, Ti on continuous cooling transformation in Cu–P–Cr–Ni–Mo weathering steels

The continuous cooling transformation (CCT) diagrams of the weathering steels Cu–P–Cr–Ni–Mo were investigated by means of a combined method of dilatometry and metallography. For five of the steels (B, C, D, E and F), since there is a metastable austenite gap completely open or half-open between the ferrite and the bainite transformation regions, it is possible to obtain dual-phase microstructure directly by hot-rolling and appropriate cooling. Hot deformation increased the transformation start temperature Ar3 significantly, enlarged the polygonal ferrite transformation temperature range, and shortened the gestation period of pearlite and polygonal ferrite transformation. Mo effectively retards the bainite and the pearlite transformations, elevates the pearlite-finish temperature, and induces the metastable austenite gap formed.