以低碳钢为研究对象, 采用高功率CO₂激光焊接设备, 通过抛切焊缝断面统计气孔数量, 并观测焊缝中气孔位置和形貌, 研究了非熔透性深熔焊接过程中保护气体流量、激光束倾角、激光功率及焊接速率等工艺参数对低碳钢激光焊接气孔形成规律的影响. 结果表明, 在低碳钢CO₂激光非熔透性深熔焊接过程中, 气孔的形成主要源于焊接过程中匙孔的不稳定塌陷所形成的工艺型气孔, 在熔池中气泡逸出熔池的速率低于熔池金属凝固速率的情况下会产生气孔. 随着气体流量的增加, 气孔数量呈现先增加后减少的过程, 流量为35 L/min时气孔数量最少; 随着激光束倾角的增加, 气孔数量呈现先增加后减少的趋势,在满足较大熔深条件下, 倾角22.5°时可以获得较少的气孔数量. 激光功率为4 kW时气孔数量最少, 在0.75 m/min的低焊速下气孔得到较好抑制.

The porosity in the welded seam can be generated easily during the CO₂ laser nonpenetration deep welding of low carbon steel, which affects the quality of welding. This research uses the mild steel as the object for the high quality requirements of welding. The advanced high-power CO₂ laser generator was used for the welding experiment. The method of cutting cross-section of weld seam was used to analyze the porosity number and observe the morphology and location of porosity in the weld. The effects of such process parameters as shielding gas flow, laser beam inclination, laser power and welding speed on porosity generating were discussed. The research results show that the generating of porosity is due to the unstable collapse of the keyhole in the process of CO₂ laser nonpenetration welding of low carbon steel. The porosity would be formed when the speed of bubble escaping form the weld pool is lower than the speed of melting metal solidifying. The results also show that with the increase of shielding gas flow, the porosity number presents a curve of increase firstly and then decrease. The lowest porosity number can be obtained at a 35 L/min of gas flow. With the increase of laser beam inclination angle, the porosity number shows a trend of decrease after increase. Under the condition of deeper penetration welding, the relatively lower porosity number can be obtained at the inclination angle of 22.5°.When the laser power is 4 kW, the porosity number is lowest. At the condition of lower welding speed, the bubble can escape easily for the longer existence period of melting weld pool. Thus lower porosity number and porosity number can be achieved. The porosity can be inhibited effectively at a welding speed of 0.75 m/min.