微观组织对Q460高强耐火钢高温屈服强度的影响

Effects of microstructure on the high temperature yield strength of Q460 high-strength fire-resistant steel

采用不同冷却参数的TMCP工艺对同一成分的Q460高强耐火钢进行处理,得到微观组织分别为全贝氏体和贝氏体+铁素体复相组织的两种钢,借助OM、SEM、TEM、EBSD等手段,对两种钢在600℃高温拉伸后的显微组织及析出相进行表征。结果表明,全贝氏体Q460钢的高温屈服强度明显高于贝氏体+铁素体复相钢,且全贝氏体钢的600℃屈服强度为其室温屈服强度的70.4%,符合耐火钢的要求。造成两种钢屈服强度差异的主要原因是全贝氏体钢在高温拉伸时组织受力均匀,贝氏体的屈服强度决定了该钢的屈服强度;而复相钢在高温拉伸时组织受力不均匀,软相铁素体的屈服强度决定了该钢的屈服强度。

The TMCP technique with different cooling parameters was used to treat the Q460 high-strength fire-resistant steel of the same composition,and two kinds of steels with the microstructure of full bainite and bainite+ferrite dual-phase were obtained.By means of OM,SEM,TEM and EBSD,the microstructure and precipitates of two steels after high-temperature tensile test at 600℃were characterized.The results show that the high-temperature yield strength of full bainite Q460 steel is significantly higher than that of bainite+ferritic dual-phase steel,and the yield strength of full bainite steel at 600℃is 70.4%of its room-temperature yield strength,which satisfies the requirement of fire-resistant steel.The main reason for the difference in yield strength of two steels is that the microstructure of full bainite steel is uniformly stressed when it’s stretched at high temperature and the yield strength of bainite determines that of the steel,while the stress of dual-phase steel is not uniform and the yield strength of the soft phase ferrite determines that of the steel.