Nb-Ti微合金化热轧多相钢的组织和性能

通过两阶段控轧和随后的三段冷却,获得了14mm厚的Nb-Ti微合金化热轧多相钢板.利用光学显微镜、扫描电镜、透射电镜、X射线衍射(XRD)、电子背散射衍射(EBSD)和力学性能测试等手段对其组织和性能进行了研究.结果表明,试验钢的显微组织由铁素体、贝氏体和少量马氏体组成;其平均屈服强度为518MPa,抗拉强度为616MPa,延伸率高达41%;组织中大量的铁素体大角度晶界、近似等轴状铁素体晶粒和较小尺寸贝氏体束的存在,大大提高了试验钢的塑性;铁素体和贝氏体组织的细化,细小的(Nb,Ti)C粒子以及铁素体晶粒和贝氏体板条内的位错提高了试验钢的强度.

On the Microstructure and Mechanical Properties of Hot-Rolled Nb-Ti Microalloyed Multiphase Steel

The 14mm-thick Nb-Ti microalloyed hot-rolled multiphase steel plate was developed by two-stage rolling and subsequent three-step cooling, then it was characterized by optical microscopy, SEM, TEM, XRD, EBSD (electron back-scattered diffraction) and other tests to investigate its microstructure and mechanical properties. The results indicated that the microstructure of the steel specimen is composed of ferrite, bainite and small amount of martensite, and that the mean yield strength, tensile strength and percentage elongation are 518MPa, 616MPa and 41%, respectively. The existence of lots of big-angle ferrite grain boundaries, near-equiaxial ferrite grains and small bainitic beams significantly improves the ductility. The refinement of ferrite grains and bainitic structures, fine (Nb, Ti)C particles and the dislocations in ferrite and lath bainite increase the strength.