Effects of shielding gases on weld diffusible hydrogen contents using cored wires

Abstract

Cored wire welding is widely used for joining thick steel sections, where a high integrity weld is required. The shielding gases selected for cored wire welding depend on the type of filling constituents of the wire. Weld properties, deposit chemistry, bead shape, deposition rates, and the operational characteristics of weld ing are greatly affected by the shielding gases. In the present work, studies have been carried out to observe the effects of wide ranging shielding gases on the diffusible hydrogen contents of welds using cored and solid metal inert gas (MIG) welding wires. The hydrogen present in the weld metal has been determined by the method described in British Standard BS 6693: 1988. For flux and metal cored wires, it was observed that an increase in shielding gas CO₂ content has a marked effect on diffusible hydrogen and, for both consumables, the diffusible hydrogen content decreases as the CO₂ content increases in Ar–CO₂ mixtures. The effects of weld penetration and metal transfer, by changing the shielding gas, on hydrogen content of the weld metal have also been studied and reported.