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采用２０ｋＷＣＯ２激光加工系统焊接低碳钢，研究了辅助气体对等离子体屏蔽临界功率密度的影响。研究结果表明，辅助气体不同时等离子体屏蔽临界功率密度由小到大的排列顺序为：Ａｒ→Ｎ２→ＣＯ２→Ｈｅ。Ａｒ作为辅助气体时，等离子体屏蔽的临界功率密度可以低至１．８５×１０６Ｗ／ｃｍ２。辅助气体对等离子体屏蔽临界功率密度的影响主要取决于气体的导热性和解离能，相比而言，气体电离能的影响是次要的。采用Ａｒ作为辅助气体时，等离子体屏蔽临界功率密度低的原因主要在于Ａｒ的导热性能差，激光支持的燃烧波（Ｌａｓｅｒ－ｓｕｐｐｏｒｔｅｄＣｏｍｂｕｓｔｉｏｎＷａｖｅｓ—ＬＳＣ）波容易过热和扩展。
Low-carbon steel was welded by 20kW CO2 laser processing system. The effect of auxiliary gas on the critical power density of plasma shielding was studied. The results show that the order of the critical power density of the plasma shielding plasma with different auxiliary gases is Ar → N2 → CO2 → He. When Ar is used as an auxiliary gas, the critical power density of the plasma shield can be as low as 1.85 × 10 6 W / cm 2. The influence of the assisting gas on the critical power density of the plasma screen depends mainly on the thermal conductivity and the dissociation energy of the gas, in contrast, the influence of the gas ionization energy is secondary. The reason why the critical power density of the plasma shielding is low when Ar is used as an auxiliary gas mainly lies in that the thermal conductivity of Ar is poor and the Laser-supported Combustion Wave-LSC wave easily overheats and expands.