Influence of pilot gas composition on convective pattern of weld pool surface in plasma keyhole arc welding

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. © 2017 Japan Welding Society. All rights reserved.