保护气体对高氮钢焊接熔滴过渡模式和气孔缺陷的影响研究

采用激光-电弧复合热源对8 mm厚的高氮钢板进行焊接试验，研究不同保护气体组成对焊缝形貌、熔滴过渡特征和气孔缺陷的影响。结果表明，采用纯氩做保护气体时，熔滴过渡模式以射流过渡为主，并伴有少量排斥过渡；保护气体成分为Ar+N₂混合气体时，熔滴过渡模式为短路过渡；保护气体成分为Ar+N₂+O₂混合气体时，熔滴过渡模式为射流过渡。保护气体的组成对焊缝气孔缺陷也存在一定的影响，保护气体为纯氩时，焊缝气孔率最大，其值为2.52%；保护气体为90% Ar+10% N₂时，气孔率最低，仅为0.16%；Ar+N₂中添加1%的O₂后，气孔率略有升高，但与纯氩时相比，气孔率仍下降明显。采用Ar+N₂+O₂三元混合气作为保护气体时，能够有效抑制焊缝内气孔数量，同时可以改善熔滴过渡模式，提高焊接过程稳定性。

Study on the Impact of the Shielding Gas on the Droplet Transfer Mode and Blowhole Defect of High Nitrogen Steel Welding

High-nitrogen steel plates with a thickness of 8 mm are welded with a laser-arc composite heat source for experiment to study the impact of different shielding gas compositions on the welding joint profile, droplet transfer features and blowhole defect. The results show that when the pure argon is used as the shielding gas, the droplet transfer mode is mainly shown as spray transfer, accompanied by a small amount of repulsion transfer. When the shielding gas is mixed by Ar+N₂, the droplet transfer mode is short circuiting transfer; when the shielding gas is mixed by Ar+N₂+O₂, the droplet transfer mode is spray transfer. The shielding gas composition has some impact on the blowhole defect of the welding joint. When the shielding gas is pure argon, the blowhole defect rate of the welding joint is at its maximum and its value is 2.52%. When the shielding gas is 90% Ar+10% N₂, the blowhole defect rate is the lowest, only 0.16%; when 1% of the O₂ is added to the mixture of Ar+N₂, the blowhole defect rate slightly rises, but compared with that of pure argon, the blowhole defect rate still drops significantly. When the ternary mixture of Ar+N₂+O₂ is used as the shielding gas, the number of blowholes in the welding joint can be effectively contained, and the droplet transfer mode can be improved to better the stability of the welding process.