Development of hot-rolled dual-phase weathering steel Cu–P–Cr–Ni–Mo

The continuous cooling transformation (CCT) diagrams of weathering steels Cu–P–Cr–Ni–Mo were constructed by means of a combined method of dilatometry and metallography. The diagram of weathering steel with 0.41% Mo exhibits an elongated polygonal ferrite C-curve with a delayed pearlite-start, and a metastable austenite gap between the polygonal ferrite/pearlite and the bainitic ferrite regions. Weathering steel with 0.41% Mo is possible to obtain a dual-phase microstructure directly by hot-rolling and appropriate cooling. Dual-phase microstructures with some bainite and pearlite have been obtained by hot-rolled simulating on hot-rolled dual-phase treatment procedures deduced by the CCT diagram. Hot-rolled dual-phase weathering steel with 0.41% Mo has more excellent comprehensive mechanical properties and formability than commercial weathering steel 09CuPCrNi.