Effects of Reduction and Finishing Temperature on Microstructure and Mechanical Properties of Nb Bearing Si-Mn Hot-Rolled Dual-phase Steel

The effects of reduction(93.3%,85.0% and 81.7%)and finishing temperature(790,750 ℃ and 720℃) on microstructure and mechanical properties of 30 mm thickness Nb bearing Si-Mn hot-rolled dual-phase steel were studied at laboratory by 5 passes hot-rolled test.The results show that the uniform and small ferrite-martensite microstructure could be obtained through increasing the reduction with little influence on plasticity while strengthening the matrix.The high strength could be obtained through reducting the finishing temperature with considerable influence on plasticity,but the mischcrystal would appear.Under the present testing condition and when the reduction was around 85.0% and the finishing temperature was 790℃,the tensile strength could be ahove 700 MPa,yield ratio was 0.65 and the elongation was above 23%.