高强钢激光-电弧复合焊接接头力学性能研究

为弥补高强钢在传统焊接中低效、变形严重、焊缝强度低等问题，采用6 kW光纤激光器和熔化极活性气体保护电弧焊复合焊接6 mm厚度的30CrNiMo钢板，在相同焊接工艺下使用ER50-6和ER308两种焊丝，焊后对两种焊缝的组织形貌和力学性能进行研究。研究结果表明：ER50-6焊丝焊缝为细小的针状马氏体组织，而ER308焊丝焊缝为粗大的柱状晶奥氏体；两种焊丝焊缝的硬度面分布也出现较大区别，ER50-6焊丝焊缝沿熔合线出现低硬度分布，ER308焊丝焊缝则在焊缝中心下部出现低硬度集中，二者对应拉伸断裂位置分别在熔合线处和焊缝中心；通过能谱分析得知，ER308焊丝中高含量的Cr元素在焊缝上部集中，导致焊缝上部淬硬性增强，硬度大幅上升，韧性急剧下降，并最终导致焊缝力学性能的薄弱。因此，采用复合焊接搭配ER50-6焊丝，可实现对6 mm厚30CrNiMo钢板以1.0 m/min速度的高效无变形焊接，焊缝强度高达1 197 MPa.

Research on Mechanical Properties of High-strength Steel Laser-arc Hybrid Welded Joints

6 kW fiber laser-MAG hybrid welding is used for 6 mm-thick 30CrNiMo high-strength steel plate.The microstructure and mechanical properties of the steel plate which were welded with ER50-6 and ER308 wires in the same welding process are studied.The result shows that the ER50-6 weld seam is an acicular martensite,and the ER308 weld seam is a coarse columnar austenite.The welded joints of diverse welding wires have significantly different hardness distributions.The low hardness distribution along the fusion line appears in the ER50-6 weld seam,and the low hardness of ER308 weld seam is concentrated in the lower part of the weld seam center.The corresponding tensile fracture positions are found in the fusion line and the weld seam center,respectively.The energy spectrum shows that the high content of Cr in ER308 weld seam is concentrated in the upper part of the weld seam center,which leads to the increase of hardenability and hardness,and sharp decline in toughness on this part,and finally leads to the weakness of the mechanical properties of the weld seam.The hybrid welding method and ER50-6 wire can be used to weld 6 mm-thick 30CrNiMo steel plate without distortion,and the weld strength is up to 1 197 MPa.