TIG Welding Stainless SteelTIG welding is a high quality process ideally suited for welding of stainless steels, particularly thin sheet up to about 5mm thick. Standard TIG equipment is suitable and stainless steels are welded using DCEN polarity. The process is capable of giving very high quality welds with very low defect rate. A thoriated tungsten electrode is normally used but health scares have promoted use of ceriated or lanthanated instead. The filler rod used depends on the type of stainless being welded but, in general, is matching for austenitic grades, enriched in nickel for duplex grades, and may be matching or an austenitic type for ferritic and martensitic grades. Shielding gas is conventionally pure argon, but other gases are available to provide specific properties and these include argon-hydrogen, argon-helium-hydrogen, and argon-nitrogen mixtures. When welding pipes an inert gas purge is required inside the pipe to prevent oxidation on the underside of the weld. Gas purging may also be used to protect the root side of butt welds in plate or sheet materials too. The main safety issues are electrical, radiation, and inert compressed gases. Welding fume is not normally a concern but at high currents ozone gas may be produced.
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