Effect of finish rolling temperature on the continuous cooling transformation of V-alloyed high strength hull steel

The dynamic continuous cooling transformation (CCT) diagrams of a kind of V-alloyed high strength hull steel were determined by the use of a thermo-simulating machine after multi-pass deformation designed to simulate the industrial controlled rolling procedures for the production of plates at different temperatures. The effects of finish rolling temperature and cooling rate on the microstructure, γ/α transformation and CCT diagrams of the hull steel were investigated. The results show that the dynamic CCT diagrams shift to left and upper, and the region of cooling rate to obtain ferrite and pearlite is widened with decreasing finish rolling temperature. With the increase of cooling rate, the onset of γ transformation (A_r3) is lowered gradually, and the bainite start temperature B_s changes in a parabolic way. As the finish rolling temperature decreases or the cooling rate increases, the grains of ferrite are refined.