Design and development of submerged arc welding fluxes using TiO2-SiO2-CaO and SiO2-CaO-Al2O3flux system

Abstract

Submerged arc welding is widely used in pipeline manufacturing due to higher efficiency as compared to the other welding processes. In present study, TiO2-SiO2-CaO and SiO2-CaO-Al2O3–based submerged arc welding fluxes were developed for joining of linepipe steel. Twenty-one fluxes were formulated based on mixture design methodology. Fluxes were analysed using X-ray florescence (XRF), thermogravimetric, differential-scanning calorimetry, Hot-disc and X-ray diffraction (XRD) techniques. The structural behaviour of rutile basic fluxes were analysed using Fourier transformed infrared spectroscopy (FTIR). Thermo-gravimetric analysis and differential scanning calorimetry were performed from 25 ℃ to 900 ℃ in order to determine the thermal stability and change in enthalpy of fluxes. Thermal conductivity, thermal diffusivity and specific heat of each flux were evaluated by hot disc technique. The density and grain fineness number for flux particles was evaluated at room temperature. Multi objective optimisation was performed to derive the optimised flux formulations. Individual effect of all the mixture constituents is rarely observed on the physicochemical properties of fluxes as compared to the binary and ternary mixture effects. The binary compositions significantly affect the density. TiO2-CaO is the most effective binary mixture which has increasing effect on density while all remaining binary mixture constituents have decreasing effect. The weight loss of fluxes observed during thermogravimetric analysis is affected by binary and ternary mixture constituents. Both binary and ternary flux mixtures affect change in enthalpy observed during differential scanning calorimetry. SiO2.Al2O3is the only most effective binary mixture constituent of flux having increasing effect on thermal conductivity. Binary mixture constituents TiO2.CaF2, SiO2.Al2O3and CaO.Al2O3are the most effective and having synergistic effect on thermal diffusivity.