For orbital pipe welding,
reduced heat inputs and weld pools are needed to reduce the ID convexity around 12
o’clock and achieve the needed convexity around 6 o’clock.
To this end, a novel PAW mode,
namely the double-stage PAW,
is proposed that uses a keyhole stage to build a partially penetrated keyhole and then a melt-in stage to finally reach complete joint penetration.
While the keyhole stage helps reduce the heat inputs and weld pools,
the melt-in stage finishes the complete penetration at reduced impacts from the plasma jets producing the desired weld bead geometry and regularity