激光深熔焊接X65油气管线钢焊缝的成形机理及性能分析

Forming Mechanism and Performance Analysis of X65 Oil and Gas Steel Pipeline Weld Fabricated by Laser Deep-Penetration Welding

采用Nd:YAG激光器开展X65管线钢激光深熔焊接实验,通过光学显微镜、扫描电镜、硬度仪,观察焊缝形貌,表征焊缝区域的微观组织,测量焊缝区域的硬度变化。结果表明:由于焊接偏转角度的变化影响了激光在空间中的能量分配,焊缝深度从8mm下降至4mm,且沿焊接厚度方向,焊缝形貌沿激光偏转角度发生了偏转;由于焊接裂纹与温度、温度梯度等相关,通过降低焊接速度,在焊缝收尾处观察到了裂纹;随着焊接速度的增加,焊接热影响区的宽度变窄,焊缝区最大硬度由472.1HV增大到565.5HV;熔凝区硬度分布的非对称性随着焊接速度的增大而增强。

In this study,a laser deep-penetration welding experiment was conducted on an X65 steel pipeline using a Nd:YAG laser.The morphology of the created weld was observed using a optical microscope.The microstructure of the weld area was characterized by a scanning electron microscope and its hardness was measured by a hardness tester.Results show that the weld depth of the steel sample decreases from 8 mm to 4 mm because of the variation in welding deflection angle,which affects the energy distribution of the laser in space.It is also observed that the weld profile deflects along the laser deflection angle in the direction of welding thickness.At the end of the welding process,a crack associated with temperature and temperature gradient is observed on the weld due to reduction in welding speed.However,as the welding speed increases,the width of the weld heat-affected zone narrows,and the maximum hardness of the weld zone increases from 472.1 HV to 565.5 HV.The asymmetry in the hardness distribution of the fusion zone increases with the increasing welding speed.