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

Cored wire welding is widely used for joining thick steel sections, where a high integrity weld is required. The shielding gases selected for cored wi re welding depend on the type of filling constituents of the wire. Weld pro perties, deposit chemistry, bean shape, deposition rates, and the operation al characteristics of welding are greatly affected by the shielding gases. In the present work, studies hare been carried out to observe the effects o f wide ranging shielding gases on the diffusible hydrogen contents of welds using cored and solid metal inert gas (MIG) welding wires. The hydrogen pr esent in the weld metal has been determined by the mehtod described in Brit ish Standard BS 6693: 1986. For flux and metal cored wires, it was observed that an increase in shielding gas CO2 content has a marked effect on diffu sible hydrogen and, for both consumables, the diffusible hydrogen content d ecreases as the CO2 content increases in Ar-CO2 mixtures. The effects of we ld penetration and metal transfer, by changing the shielding gas, on hydrog en content of the weld metal hare also been studied and reported.