A novel single wire indirect arc metal inert gas welding process operated in streaming mode

Dilution of a pad weld must be limited to a certain critical level to improve its wear and/or corrosion properties. To do that, a novel single wire indirect arc metal inert gas welding process operated in streaming mode was realized. A metal inert gas welding torch, arranged perpendicular to a substrate in vertical position, is fixed with an auxiliary tungsten electrode horizontally. The arc is ignited between a wire through the torch and the auxiliary electrode. The substrate is not electrically connected. The welding current is set in the range of streaming mode. 304 stainless steel was pad welded on Q235 substrates in vertical position by this process. Microstructures were analyzed with optical microscope. Dilution ratios were measured with stereo light microscope and calculated. The results show that, after eliminating interference of the massive torch setup, the dilution ratio of the pad weld with optimized parameters is 5.07%, much less than that with a metal inert gas welding process, which is 26.46%. The pad weld is bonded to the substrate without defects. Microstructures of the pad weld consist of columnar austenite and ferrite between the columns. The dilution ratio increases with increasing welding current or welding velocity, and decreases with increasing distance to the substrate.