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采用20kWCO2激光加工机焊接st37－2钢，研究了辅助气体种类、气体流量以及聚焦激光束的离焦状态对等离子体屏蔽的影响。结果表明，不同辅助气体时等离子体屏蔽临界功率密度存在很大差异，由小到大的顺序为：Ar→N2→CO2→He。He良好的控制等离子体的能力不仅在于He高的电离能不易形成LSC波，更主要地在于He良好的导热性能抑制了LSC波的扩展。增大辅助气体流量或采用负离焦均可以在一定程度上减小等离子体屏蔽对焊接过程的影响。
Welding of st37-2 steel with a 20kW CO2 laser machine was used to study the influence of the assisting gas type, gas flow rate and defocused state of the focused laser beam on the plasma shielding. The results show that the plasma shielding critical power density varies greatly with different auxiliary gases, in descending order: Ar → N2 → CO2 → He. He’s ability to control the plasma well is not only that the He ionization can not easily form the LSC wave but more importantly that He’s good thermal conductivity suppresses the propagation of the LSC wave. Increasing the flow of auxiliary gas or adopting negative defocus can all reduce the influence of the plasma shielding to the welding process to a certain extent.