What does the term "Activated Flux" mean in A-TIG welding? Why is it referred to as activated flux, and how does it differ from the flux used in other arc welding methods such as submerged arc welding or flux-cored arc welding?
Tungsten Inert Gas (TIG) welding continues to be one of the major welding processes used in the industry for high quality joints. Numerous developments have taken place in TIG welding technology over the past in power supply, shielding gas, tungsten electrode, and welding torches. Even though the developments such as addition of active elements to the electrode to increase the emissivity, the use of shielding gas mixtures, and the optimisation of the electrode-tip configuration enhanced the arc characteristics and improved the weld bead penetration profile, the productivity improvements were marginal. An increase in productivity can be achieved by increasing the penetration depth, as it helps reducing the number of welding passes. Activated TIG welding process known as A-TIG can be beneficial in this respect.
A-TIG welding process involves a method of increasing the penetration capability of the arc in TIG welding. This is achieved through the application of a thin coating of activating flux material onto the work piece surface prior to welding. The effect of flux is to constrict the arc which increases the current density at the anode root and the arc force on the weld pool. The actual mechanism by which the application of flux constricting the arc is not fully understood. Despite the productivity benefits of A-TIG welding, industry to date has been slow in exploiting this process. This is partially because the use of the flux is seen as an additional cost and its application an additional operation. Furthermore, the commercial fluxes tend to produce an inferior surface finish compared to conventional TIG welding and produce a surface slag residue which is required to be removed.
Activated flux in A-TIG welding is a granular mineral material that is melted by the heat of the arc and provides a layer of shielding gas to protect the weld. Unlike submerged arc and flux-cored arc welding, the flux in A-TIG welding is not pre-mixed with the welding wire as it is in these processes, so it must be separately fed into the weld pool. In addition, the flux used in A-TIG is typically more active, which means it releases greater amounts of gas to provide a more stable arc and a higher quality joint.
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