27SiMn高强钢激光-MAG复合焊接头组织和性能

Microstructures and Properties of 27SiMn High-Strength Steel Joints by Laser-MAG Hybrid Welding

利用光纤激光-金属活性气体(MAG)复合焊接方法焊接了25mm厚的27SiMn高强钢,分析了焊接接头的微观组织和力学性能。结果表明,接头钝边焊道焊缝和热影响区主要为马氏体;填充焊道的焊缝主要由晶内针状铁素体、少量先共析铁素体和上贝氏体组成,其热影响区组织以马氏体为主。焊接接头硬度分布不均匀,钝边焊道硬度的最高值出现在焊缝;填充焊道硬度的最高值出现在粗晶区,母材的硬度最低。拉伸时接头均断于母材。冲击试验结果表明,钝边焊道焊缝的冲击断口存在脆性断裂区和韧性断裂区,填充焊道焊缝的冲击断口仅观察到韧性断裂区。

25 mm thick 27 SiMn high strength steels are welded with the fiber laser-metal active gas（MAG）hybrid welding method,and the microstructures and mechanical properties of the welding joints are analyzed.The results show that the weld seam and heat affected zone of the root-face pass of the joints are mainly composed of martensite.The weld seam of the filler pass mainly consists of intragranular acicular ferrite,a small amount of pre-eutectoid ferrite and upper bainite,and the microstructure of the heat affected zone is mainly martensite.The microhardness distribution of welding joints is not uniform and the highest microhardness of the root-face pass is at the weld seam.The highest microhardness of the filler pass is in the coarse grain area,and the lowest microhardness is in the base metal.Tensile specimens are all broken in base metals.The impact experimental results show that the brittle fracture zone and toughness fracture zone exist in the impacted fracture of the weld at the root-face pass,while the toughness fracture zone is observed in the impacted fracture of the weld at the filler pass.