GTAW, also called Tungsten Inert gas welding, is a process which uses an arc between non-consumable tungsten electrode and the workpiece. Molten pool is protected by inert atmosphere which is by supplying external shielding gas. Argon or Helium gas can be used as shielding gas.
TIG welding produces high quality welding joint compared to other processes, however productivity remains its main concern. It is slow process and thus it is only used for root pass and for the jobs where stringent quality requirement is demanded. If current is increased to increase productivity rate, then penetration in the weld joint will be poor which again will need proper attention.
To overcome such problem of conventional TIG welding process, new technique which is developed uses active flux layer and thus process is titled as A-TIG welding process.
This process had been developed over decades but its use is very rare. Activated fluxes are mixture of inorganic material suspended in a volatile medium. The theory on the effect of activating flux on penetration is that the flux changes the surface tension in the weld pool so that the fluid flow is changed, thereby increasing the penetration.
The other factor which increased penetration was arc constriction. Because the conductivity of the flux was much lower than that of the metal vapour and the melting & boiling points of the flux were higher than those of the weld metal, the metal evaporation would be only generated in the central regions of the welding arc, where the temperature was higher than the dissociation temperature of the flux compounds, thereby leading to a reduction in the conductivity area of the anode spot. Thus constricting the plasma column and reducing the anode spot tend to increase the energy density of the heat source and electromagnetic force of the weld pool, resulting in a relatively narrow and deep weld morphology compared with the conventional TIG welding.
Different fluxes had been tried and experimented. Among those CaO, TiO2, Cr2O3, SiO2 and MoO2 had proven to give better penetration compared to conventional TIG welding process.
Reference : Welding of 304L Stainless steel with Activated Tungsten Inert Gas Process (A-TIG), E.Ahmadi, A.R.Ebrahimi, R. azari Khosroshahi
Keep Reading, Happy Welding…