等离子弧焊接中厚钢板时，常存在焊接工艺窗口窄问题. 在中厚不锈钢板小孔型等离子弧焊(keyhole plasma arc welding，K-PAW )中发现，离子气体流量较弱而使匙孔未打开，形成盲孔时，会在焊缝内产生平行于焊接方向的长条形气孔，形成条形气孔时，等离子弧形态发生明显变化，电弧面积增加且波动更为剧烈，出现向后的反射. 使用高速摄影装置研究了条形气孔的形成过程.结果表明，中厚板等离子弧焊中，条形气孔是在一定的焊接速度和较低的电弧能量下，熔池前壁倾角较大，等离子弧受熔池前壁反射作用冲击熔池后壁，使熔池后壁发生弯曲，并在一定的凝固条件下保留，产生平行长气孔. 对条形气孔的研究有助于为匙孔等离子弧焊接中匙孔形成条件及机制提供新认识.
Narrow welding process window often impedes plasma arc welding of medium - thick plate. In keyhole plasma arc welding (K-PAW), it is found that if the keyhole is not opened due to the weak ionic gas flow rate and the blind hole is formed, an elongated cavity parallel to the welding direction will be generated in the weld. When the cavity is formed, the morphology of plasma arc changes obviously. The arc area increases and fluctuates more violently, causing backward reflection. The formation process of elongated cavities was studied by high-speed camera. Experimental results show that the formation processs of elongated cavities is as follows: at a certain welding speed and a low arc energy, the dip angle of the front wall of the molten pool is enlarged, and the plasma arc reflected by the front wall will impact the back side, which would be bended and retained under solidification, then an elongated cavity exists. The study of elongated cavities is helpful to provide a new understanding of keyhole formation conditions and mechanism in keyhole plasma arc welding.
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