The effect of TIG welding techniques on microstructure, properties and porosity of the welded joint of 2219 aluminum alloy

Five single oxide fluxes—MgO, CaO, TiO2, MnO2, and Cr2O3—were used to investigate the effect of active flux on the depth/width ratio in AZ31B magnesium alloy. The microstructure and mechanical property of the tungsten inert gas (TIG) welding seam were studied. The oxygen content in the weld seam and the arc images during the TIG welding process were analyzed. A series of emission spectroscopy of weld arc for TIG welding for magnesium with and without flux were developed. The results showed that for the five single oxide fluxes, all can increase the weld penetration effectively and grain size in the weld seam of alternating current tungsten inert gas (ACTIG) welding of the Mg alloy. The oxygen content of the welds made without flux is not very different from those produced with oxide fluxes not considering trapped oxide. However, welds that have the best penetration have a relatively higher oxygen content among those produced with flux. It was found that the arc images with the oxide fluxes were only the enlarged form of the arc images without flux; the arc constriction was not observed. The detection of arc spectroscopy showed that the metal elements in the oxides exist as the neutral atom or the first cation in the weld arc. This finding would influence the arc properties. When TIG simulation was carried out on a plate with flux applied only on one side, the arc image video showed an asymmetric arc, which deviated toward the flux free side. The thermal stability, the dissociation energy, and the electrical conductivity of oxide should be considered when studying the mechanism for increased TIG flux weld penetration.

Mechanism and Microstructure of Oxide Fluxes for Gas Tungsten Arc Welding of Magnesium Alloy

Mechanical properties and microstructures of a magnesium alloy gas tungsten arc welded with a cadmium chloride flux

Investigation of heat transfer and fluid flow in activating TIG welding by numerical modeling

Gas tungsten arc welding of magnesium alloy using activated flux-coated wire

Active fluxes that are deposited on the TIG torch path before alloy melting can significantly increase weld penetrations. Several mechanisms (arc constriction, surface-tension-driven flow) for the active-TIG or A-TIG welding process have been postulated. The A-TIG welding of magnesium is discussed here using a simple model for the surface tension over the weld pool, real-time monitoring data, and measured characteristics from the fusion zone region. The chlorides selected for this investigation incorporated simple-metal elements from different group numbers (LiiaCl, CaiiaCl2, CdiibC12, PbivbCl2 and CeCl3) so that correlations between their chemistry and their effects during A-TIG welding could be established. Video recordings showed that chlorides intensified the visible light emission from the arc and affected its profile. Measurements during arc welding at a constant current demonstrated that all chlorides increased the arc voltage (thus the heat input) and the arc temperature. A-TIG weld cross sections revealed that chlorides increased fusion zone dimensions, as could be expected from greater heat inputs. While calculations suggested that surface tension might have altered weld pool circulation, specially designed experiments with low-energy-density laser beams were inconclusive. Among all tested chlorides, cadmium chloride was the most effective during A-TIG welding due to the high first ionization potential of cadmium, which correlated to several observations such as: low chloride melting, boiling, and dissociation temperatures, high welding voltage, augmented arc temperature, increased fusion zone penetration, and greater depth-to-width ratio.

M. Marya

Papers

Theoretical and Experimental Assessment of Chloride Effects in the A-TIG Welding of Magnesium