终冷温度对(B+M/A)X80管线钢组织-性能的影响

Effect of Accelerated Cooling Stop Temperature on Microstructure and Mechanical Properties of the(B+M/A) X80 Pipeline Steel

通过HOP技术,使X80管线钢获取了(B+M/A)复相组织。采用力学性能测试、显微分析和X射线衍射方法研究了在不同终冷温度条件下(B+M/A)X80管线钢的组织演变规律,分析了显微组织对力学性能的影响。结果表明,随着终冷温度的升高,贝氏体的板条宽度增加,贝氏体的含量和位错密度减小以及残余奥氏体量增加,导致材料强度降低和塑性增加。在高的终冷温度条件下,马氏体的形成、碳化物的析出和残余奥氏体的分解是材料强度增加和塑性减小的内在因素。在不同终冷温度下,实验钢的屈强比都小于0.85,均匀伸长率大于0.8%,形变强化指数大于0.10,符合大变形管线钢的技术要求。

A new type of pipeline steel containing bainite（B）and M/A constituent was obtained through the heating online partitioning（HOP）.Effects of ACC stop temperature on microstructure evolution and mechanical properties of（B＋M/A）X80pipeline steel were researched by means of mechanical property test,microscopic analysis and X-ray diffraction.The results show that with increasing ACC stop temperature the strength decreases and the plasticity increase of the experimental steels This is ascribed to the coarsening of bainite laths,the decrease of both bainite content and dislocation density,and the increase of retained austenite content.When the ACC stop temperature is high,the formation of martensite,the precipitation of carbides and the decomposition of retained austenite consist the key factors influencing the strength and the plasticity.This（B＋M/A）dual-phase structure at different ACC stop temperature demonstrates the lower yield ratio,higher uniform elongation and strain hardening index for the experimental steel, which meets the technical requirements of high deformability linepipe.