Effect Of Oxide Fluxes Research Articles

Effect of Oxide Fluxes in Activated TIG Welding of Stainless Steel 316LN to Low Activation Ferritic/Martensitic Steel (LAFM) Dissimilar Combination

The aim of current work is to study the effect of different oxide fluxes in activated TIG welding process of dissimilar welding between LAFM and 316LN on weld dimensions, macro- and microexamination, and microhardness. Different oxide fluxes, namely TiO2, Fe2O3, CuO, Co3O4, and HgO, were used for the experiment, and its results were compared with convention TIG welding. Flux paste was applied over the area to be welded using a paint brush at the middle portion of the specimen. All welding experiments were carried out on a bead on a plate and under the same welding conditions and parameters. The experimental result reveals that full-length penetration was achieved with the use of Co3O4 and TiO2 fluxes. This enhancement in depth of penetration is attributed to the reverse Marangoni effect and arc constriction mechanism. In this study, insight was also revealed pertaining to the depth-enhancing mechanism present during ATIG welding of LAFM and SS316LN joints.

Effect of oxide fluxes on activated TIG welding of AISI 316L austenitic stainless steel

In this work, activated TIG (A-TIG) welding on 8 mm thick plates of AISI 316L stainless steel was carried out. The effect of various single component fluxes and a multi-component flux on weld bead geometries was analysed. The multi-component flux mixture resulted in though thickness penetration in a single pass. Metallography of different zones was observed and weld zone was found to exhibit austenitic-ferritic microstructure. Delta ferrite content was measured with Ferritoscope and increase in delta ferrite content was observed in A-TIG weld zones as compared to base metal. From microhardness measurements, weld zone was found to be harder than the base metal due to increase in delta ferrite fraction.

Effect of Oxide Fluxes on Depth of Penetration in Flux Bounded Tungsten Inert Gas Welding of AISI 304L Stainless Steel

Flux Bounded Tungsten Inert Gas (FBTIG) welding is a modified TIG welding process in which increased depth of penetration (DoP) can be achieved by laying thin flux coatings on either side of the weld centerline. The effect of three single component fluxes viz., SiO2, TiO2 and Cr2O3 on bead geometry of autogenous melt runs in AISI 304L stainless steel for the gap between the flux layers varying from 2 to 7 mm, is studied. Results show that DoP can be improved significantly in FBTIG process using single component fluxes. Nature of the flux and the gap between the flux layers influence the weld bead geometry. Among the three fluxes used, SiO2 is more efficient in improving the DoP. Arc constriction is the predominant mechanism operative in improving the DoP in FBTIG welding. Possibility of change in solidification mode in FBTIG weld metals of stainless steels is highlighted.

Effect of oxide fluxes on activation mechanisms of tungsten inert gas process

Activated tungsten inert gas (TIG) welding, which involves the deposition of an inorganic powder on the metal surface prior welding, improves TIG welding performances in terms of weld bead penetration. Most common commercial fluxes contain halides and oxides. The present paper focuses on fluxes made of oxides. It appears that oxides have two different effects: one on the fusion zone chemistry and the other on the electric arc behaviour. First, oxygen reverses the Marangoni convection movements that become centripetal, contributing thus to increase 'D' penetration. On the other hand, oxides may cause an increase in the energy flux density transferred by the arc to the metal. The characterisation of the arc plasma by optical emission spectroscopy suggests that oxides do not increase the arc temperature. It is established that the oxide effects by Marangoni convection appear for a critical value of the welding energy, whereas the oxide effects on the electrical arc exist irrespective of the welding energy value.

Effect of Oxide Fluxes on the Viscosity of Molten Aluminothermic Ferro-chrome Slags.

The viscous slag generated during aluminothermic reduction of metallic oxides for production of metals or alloys slows down the reduction process and obstructs clear separation of slag and metal. The fluxing constituents are added to bring down the viscosity.Hence the effect of variation of CaO and MgO contents on the viscosity of synthetically prepared ferrochrome slags having an approximate composition of industrial ferro-chrome slags resulting from aluminothermic reduction of chromium oxide has been studied at various temperatures. Increase of CaO and MgO contents is found to decrease the viscosity of the slags. The relative decrease in viscosity becomes very less beyond 40 mol% of CaO. It is further observed that both CaO and MgO additions do not decrease the viscosity appreciably at higher temperatures as they do at lower temperatures.The activation energy of viscous flow calculated from the viscosity data, is seen to obey the Arrhenius equation {μ=A0exp(Eμ/RT). The activation energy, Eμ decreases with increased flux addition. It is also observed that the activation energy of viscous flow is independent of temperature but is a function of the composition of the slag. Within the range of compositions studied, the net-work breaking ability of Mg++ ion is not as high as that of Ca++ ion. The possible ionic structure of the liquid slags and ionic interactions have been discussed in light of the calculated values of activation energy of viscous flow. Al2O3 does not behave as an amphoteric oxide as it does in silicate melts.