Читать книгу Welding Metallurgy - Sindo Kou - Страница 34

PAW has several advantages over GTAW. With a collimated arc, PAW is less sensitive to unintentional arc length variations during manual welding. The short arc length in GTAW can cause a welder to unintentionally touch the weld pool with the electrode tip and contaminate the weld metal with tungsten. However, PAW does not have this problem since the electrode is recessed in the nozzle. As already mentioned, the keyhole is a positive indication of full penetration, and it allows higher welding speeds to be used in PAW.

However, the PAW torch is more complicated. It requires proper electrode tip configuration and positioning, selection of correct orifice size for the application, and setting of both orifice and shielding gas flow rates. Because of the need for a control console, the equipment cost is higher in PAW than in GTAW. The equipment for variable‐polarity PAW is much more expensive than that for GTAW. It cleans off oxide films during DCEP.