双面激光打底焊根部熔合模拟及组织演变分析

Root fusion simulation and microstructure evolution analysis of double-sided laser backing welding

提出了一种双面摆动激光错位同步焊接新工艺,用于厚板大钝边的自熔打底焊接,开展了不同激光间距下打底焊接试验,建立了双面激光打底焊接有限元模型,获取熔池形貌,并与试验焊缝形貌进行对比验证,在此基础上分析了接头粗晶区的焊接热过程及组织演变.结果表明,双面摆动激光错位同步焊接可以实现大钝边打底焊缝的良好熔透成形;与单面激光打底焊接相比,双面激光焊接粗晶区800~500℃的冷却时间(t8/5)和800~300℃的冷却时间(t8/3)延长;当激光间距不低于50 mm时,粗晶区发生重新奥氏体化.单面摆动激光焊接粗晶区的显微组织为板条马氏体,双面摆动激光焊接粗晶区的显微组织为板条马氏体和板条贝氏体,而且随着激光间距的缩短,板条贝氏体含量逐渐增加;双面摆动激光错位同步焊接利于改善接头性能,降低冷裂倾向.

A new process of double-sided oscillation laser dislocation synchronous welding was proposed for autogenous laser welding of thick plates with big root face height. The backing welding experiments with different laser spacings were carried out, the finite element model of double-sided laser backing welding was established. The morphology of the molten pool was obtained and verified by comparison with the morphology of the test weld. On this basis, the welding thermal process and microstructure evolution of the coarsegrained region of the joint were analyzed. The results show that, the double-sided oscillation laser dislocation synchronous welding could achieve good penetration and forming of big root face height backing weld. Compared with single-sided laser backing welding, t8/5 and t8/3 of double-sided laser welding in the coarse-grained area increased;when laser spacing was not less than 50 mm, the coarse-grained region was re-austenitized. The microstructure of single-sided laser welding in coarse-grained area was lath martensite, the microstructure of double-sided welding was lath martensite and lath bainite, and the content of lath bainite gradually increased with the shortening of laser spacing. The double-sided oscillation laser dislocation synchronous welding was beneficial to improve the joint performance and reduce the tendency of cold cracking.