二次热循环对X100管线钢粗晶热影响区组织与性能的影响

Influence of secondary welding thermal cycle on microstructure and property of coarse grain heat-affected zone in an X100 pipeline steel

通过热模拟技术与显微分析方法研究了二次热循环对X100管线钢粗晶热影响区组织的影响规律,再热粗晶区的性能通过夏比V型缺口冲击试验表征。试验结果表明,当二次热循环的峰值温度处于(α+γ)两相温区,试验钢的临界粗晶热影响区出现局部脆化。局部脆化的原因主要有两个:一是临界粗晶热影响区组织粗化;另一是该区MA组元数量多,尺寸大,硬度高。

Influence of secondary thermal cycle on microstructure of coarse grain heat-affected zone（CGHAZ） in a X100 pipeline steel was investigated by means of thermal simulation technique and microscopic analysis method.The property of the reheated CGHAZ was characterized by Charpy V-notch impact test.The results indicate that the experimental steel exhibits local brittleness of intercritically reheated CGHAZ when the peak temperature of secondary thermal cycle is in the（α＋γ） range.There are two main reasons for the local brittleness.The first is the microstructure of intercritically reheated coarse-grained heat-affected zone（ICCGHAZ） is coarse.The second is ascribed to the large amount of coarse M-A lands with high hardness in the ICCGHAZ.