Influence of Pilot Gas Composition on Convective Pattern of Weld Pool Surface in Plasma Keyhole Arc Welding

Abstract

This investigation is purposed to clarify the influence of pilot gas composition to convective pattern on the weld pool surface in Plasma keyhole arc welding process. In order to clarify this, the convective pattern on the top surface of weld pool was investigated in both cases of pilot gas: pure Ar and Ar mixture with 10% hydrogen. For estimating the convective pattern, the zirconia particles with diameter of 0.03 mm were utilized as tracers. After welding, using the software (Dipp-motion, Detect Co., Ltd) for analyzing the movement of zirconia particles, the convective pattern was estimated. In case of pure Ar, zirconia particles were in circulated motions just behind keyhole on the top surface of weld pool, and transported to rear part of weld pool on the bottom surface. In case of Ar mixture with 10% hydrogen, zirconia particles on both surfaces (top surface and bottom surface) of weld pool were in circulated motions behind keyhole. Furthermore, the weld bead shape was narrow on both top surface and bottom surface in case of pure Ar. Meanwhile, the weld bead shape was wide on both top surface and bottom surface in case of Ar mixture with 10% hydrogen.

Analysis of Eddy Formation and Heat Transfer Process in Weld Pool during Plasma Keyhole Arc Welding

“…Plasma keyhole arc welding (PKAW) is one of fusion welding processes [1,2]. PKAW process is characterized by a "keyhole" inside the weld pool caused by the plasma arc from the torch impinges on the entire thickness of base metal [3].…”

Behavior of Exit Keyhole Diameter during Switch off Period in Plasma Keyhole Arc Welding

“…Even though there are a lot of publications of PKAW process [13,14,15,16,17,18], the behavior of exit keyhole diameter has not been known yet, especially during the switch off period.…”