卷取温度对700 MPa热轧双相钢组织和性能的影响

Effect of Coiling Temperature on Microstructure and Properties of 700 MPa Hot-rolled Dual Phase Steel

采用Gleeble-2000热模拟试验机研究了热轧双相钢在连续冷却过程中的相变行为和组织演变规律,并绘制了试验钢的动态连续冷却转变(CCT)曲线。根据动态CCT曲线,在实验室采用控轧控冷工艺制备了在4种不同温度卷取的700MPa级热轧双相钢,通过光学显微镜(OM)、扫描电镜(SEM)、X射线衍射和拉伸试验对试验钢的组织和力学性能进行了观察和测试。结果表明:在300℃卷取的试验钢的力学性能最优,屈服强度为365MPa,抗拉强度为696MPa,断后伸长率为22.5%,组织组成为典型的铁素体加马氏体双相组织,并含有3.5%(体积分数)的残留奥氏体。

Phase transformation behavior and microstructure evolution of hot-rolled dual phase steel during continuous cooling process were studied by Gleeble-2000 thermal simulator,and the dynamic continuous cooling transformation (CCT) curve of the tested steel was drawn. According to the dynamic CCT curve, 700 MPa grade hot-rolled dual phase steels coiled at four different temperatures were prepared by controlled rolling and controlled cooling process in the laboratory. The microstructure and mechanical properties of the tested steels were observed and tested by optical microscopy(OM), scanning electron microscopy(SEM), X-ray diffraction and tensile test. The results showed that the mechanical properties of the tested steel coiled at 300 ℃ were the best, with yield strength being 365 MPa, tensile strength being 696 MPa and elongation being 22.5%, offering a typical dual-phase microstructure consisting of ferrite and martensite with 3.5%(volume fraction) retained austenite.