Abstract
Tungsten inert gas (TIG) is a wide common process used in fabrication due to its low cost equipment, high quality and accuracy welds but has low productivity related to the low penetration depth in single pass. A new perspective, the Activated Tungsten Inert Gas (ATIG), in which the same equipment as TIG is used, except that a thin layer of activated flux is deposited on a workpiece surface. In this work, eight kinds of oxides were tested on 316L austenitic stainless steel. Three levels of welding current were used to study the effect of different activating fluxes on weld bead geometry and mechanical properties. X-ray Photoelectron Spectroscopy (XPS) was used for the first and the second level energy for different ATIG welds to analyze the relationship between the weld shape and oxygen content in welds. The experimental results showed that the weld profile is related to the thermodynamic stability of selected oxides and in relation to the energy provided. ATIG with TiO2, SiO2, MnO2 oxides presented the deepest welds followed by Cr2O3, Fe2O3, and ZnO. Finally ZrO2, CaO oxides had no effect on the weld depth. The ATIG welded joint showed better tensile strength than TIG. The ATIG hardness measurements carried out showed also better if not the same as TIG weld except for the Silicon oxide weld. Results of the impact test showed that, except for the titanium dioxide TiO2 which has a good benefit, the weldment using the other oxide fluxes exhibits worse withstanding to sudden shock than TIG welding.
Highlights
Tungsten inert gas (TIG) welding uses a non-consumable tungsten electrode and an inert gas
There are a few limitations of the TIG welding process, like low penetration depth, and if the workpiece thickness is greater than 3mm joint edge preparation and multiple passes are required to fill the joint completely
These limitations can be overcome by using Activated Tungsten Inert Gas (ATIG) welding
Summary
TIG welding uses a non-consumable tungsten electrode and an inert gas. In this process, an electric arc is formed between the tungsten electrode and the base metal. For acceptable penetration without a risk of crack, the sulfur range should vary from 0.005% to 0.030% for 316 stainless steel with the suggested Creq/Nieq ratio range from 1.43 to 1.9 [11] This element can be provided as pasted flux on the workpiece to improve the depth of welds [12]. Authors in [16] showed that oxygen as active element is active in pure liquid iron in the range of 150-300ppm This range the temperature coefficient of surface tension becomes zero or negative leading to shallow and wide weld bead. Eight different kinds of oxide fluxes (Cr2O3, Fe2O3, CaO, ZnO, ZrO2, SiO2, MnO2 and TiO2) were used to investigate the effect of single component flux on the morphology, and mechanical properties of 316L stainless steel TIG welds. This study contributes to the understanding of the phenomena that occur in the weld pool
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