Abstract: Low carbon ultra-fine grain steel was fabricated by multi-pass rolling at room temperature, total reduction is 50% and 70% respectively and annealing at 500 〜650 ℃ for 2 min, martensite microstructure of low carbon steel Q235B obtained quenching after austenitizing. The effect of rolling reduction on microstructure and properties of ultra-fine grain steel was studied. Microstructure evolution was examined by optical microscopy and scanning electron microscope. Chemical composition of precipitate particles have been analyzed by energy dispersive spectrometer and the mechanical property was measured by an Instron-5969 tensile tester. The results indicate that cold-rolling and annealing with martensite initial structure can fabricate ultra-fine grained steel, the strength is nearly the double of that of the original steel. In addition, with the increase of the reduction amount, the recrystallization temperature decreases, and cementite particles can grow up easily, which is not effective to the improvement of the mechanical properties of ultra-fine grained steel. Under the same annealing process, the grain sizes of ferrite and cementite increase, and the comprehensive mechanical properties of specimens decrease with the reduction amount increases.

摘要： 低碳钢Q235B奥氏体化后淬火得到马氏体组织,然后在室温下进行多道次轧制,总压下量分别为50%与70%,随后在500～650℃退火2 min制备低碳超细晶粒钢,研究轧制压下量对超细晶粒钢组织及性能的影响。采用光学显微镜和扫描电子显微镜观察显微组织演变,用能谱仪分析析出物颗粒化学成分,在Instron-5969拉伸试验机上进行拉伸实验。结果表明,冷轧+退火马氏体起始组织可以制备超细晶钢,强度相比原始钢强度提高近一倍。此外,随着压下量的增加,再结晶温度降低,渗碳体颗粒易长大,不利于超细晶钢机械性能的提高。相同退火工艺下,压下量增加,铁素体晶粒及渗碳体尺寸长大,其综合机械性能降低。