超高强度钢激光焊接工艺与接头力学性能

摘要

Based on the experiments using the Yb:YAG laser welding system,the welding process and joint mechanical properties of hot-forming ultra-high strength steel under butt and lap joint designing types are investigated,and the microstruetures of different zones are observed by laser confocal microscope.The experimental results indicate that the welding speed has a significant effect on the joint mechanical properties in the condition that the laser power and defocusing amount keep constant.For the lap joint,the fractured load decreases with the increasing of the welding speed and the specimens were all fractured in the lap interface;for the butt joint,the joint tensile strength increases with the increasing of the welding speed and the specimens were all fractured in the heat affected zone.Microstructures of the fusion zones are martensite, and some soft ferrite appeared in the heat affected zone causing the tensile strength decrease, therefore the fracture occurred in this region.%采用Yb:YAG激光焊接系统对热成形超高强度钢搭接和对接两种接头形式下的焊接工艺和接头力学性能进行了研究,并采用激光共焦显微镜观察接头各部分的微观组织.试验结果表明,在激光功率和离焦量保持不变的条件下,焊接速度对两种接头形式下的接头力学性能影响显著.搭接接头抗剪力随焊接速度的增加而减小,且试样均断裂于焊缝搭接面处；对接接头抗拉强度随焊接速度的增加而增大,试样断裂于热影响区.焊缝微观组织为板条马氏体,热影响区有部分铁素体析出,导致此处强度降低,因而断裂发生在热影响区处.