高强韧热轧贝氏体大H型钢性能及工艺研究

Research on characteristics and process of hot rolled bainitic large H-beam steel with high strength and toughness

设计了一种含Nb低CSiMnCuNi合金热轧贝氏体大H型钢。结合H型钢生产工艺,探讨了轧制温度、压下率与冷却方式对大H型钢组织及力学性能影响。结果表明:空冷条件下厚规格大H型钢获得粗大粒状贝氏体与少量铁素体、板条贝氏体,铁素体晶粒10~15μm,M/A岛尺寸3~5μm,屈服强度为531MPa,冲击功与温度呈陡峭下降趋势,-40℃时冲击功仅为40J。轧后水冷的厚规格大H型钢获得细小板条贝氏体、粒状贝氏体与少量铁素体,M/A相呈点状分布,铁素体晶粒在6~10μm之间,屈服强度达662MPa,冲击功随温度呈缓慢下降趋势,-40℃时冲击功为194J。薄规格大H型钢通过大压下得到更为细小的粒状贝氏体与铁素体,屈服强度为625MPa,冲击功与试验温度几乎呈水平直线,-40℃时冲击功高达262J。

A kind of the hot rolled large H-beam steel with low CSiMnCuNi alloy system bearing Nb was designed.Based on the production process of the hot-rolled large H-beam steel,the effects of rolling temperature,reduction rate,and cooling method on the microstructure and mechanical properties of large H-beam steel were explored.The results show that the microstructure consisting on coarse granular bainite with M/A island size of about 3-5μm,a small amount of ferrite with grain size of 10-15μm,lath bainite and the mechanical property with the yield strength of 531 MPa are obtained from thick gauge and large H-beam steel under air cooling condition.Furthermore,the impact energy shows a steep decline trend with the experimental temperature and the impact energy is only 40J at-40℃.However,the microstructure consisting on fine lath bainite,granular bainite with distributing M/A island like dotting shape,a small amount of ferrite with grain size of 6-10μm and the mechanical property with the yield strength of 662MPa are obtained from thick gauge and large H-beam steel under water cooling condition.In correspondingly,the impact energy slowly decreases with temperature and the impact energy is 194J at-40℃.The thinner specifications large H-beam steel with a large reduction ratio show a more fine-granular bainitic,ferrite microstructure and a more excellent comprehensive mechanical property with yield strength of 625MPa.Also,the impact energy is almost in a level straight line with the experimental temperature,and reaches 262 J at-40℃.