冷却速度对Ti微合金化Q355B屈服平台的影响研究

Research on Effect of Cooling Rate on Ti Microalloyed Q355B Yield Platform

为了研究冷却速度对Ti微合金化Q355B屈服平台的影响,选取某钢厂Q355B-Ti热轧钢卷,在终轧温度和卷取温度不变的情况下,分别测定在12℃/s、13℃/s、14℃/s、16℃/s、18℃/s、21℃/s、26℃/s、30℃/s冷却速度下拉伸性能曲线和金相组织。结果表明,冷却速度在12~16℃/s区间时无明显屈服平台,18~30℃/s区间时产生屈服平台,金相组织为贝氏体+铁素体,随着冷速增大,贝氏体组织形貌由不规则羽毛状向规则多边形转变,晶粒尺寸减小,晶粒度由10级增大到11级。分析认为,Q355B-Ti热轧钢卷产生屈服平台需要冷却速度达到18℃/s的临界值,在工艺设计范围内,通过控制冷却速度可以达到抑制或促进屈服平台的产生。

In order to study the effect of cooling rate on the yield platform of Ti microalloyed Q355B,Q355B-Ti hot-rolled steel coils from a certain steel plant were selected.The tensile performance curves and metallographic structure were measured at 12℃/s,13℃/s,14℃/s,16℃/s,18℃/s,21℃/s,26℃/s,and 30℃/s cooling rates,respectively,while the final rolling temperature and coiling temperature remained unchanged.The results show that there is no obvious yield platform in the cooling rate range of 12~16℃/s,and a yield platform is generated in the 18~30℃/s range.The metallographic structure is bainite+ferrite.As the cooling rate increases,the morphology of the bainite structure changes from irregular feather like to regular polygonal,the grain size decreases,and the grain size increases from level 10 to level 11.Analysis suggests that the production of yield platform in Q355B-Ti hot-rolled steel coils requires a critical cooling rate of 18℃/s.Within the process design range,controlling the cooling rate can suppress or promote the production of yield platform.