Hydrogen Dissolution in the TiO2–SiO2–FeO and TiO2–SiO2–MnO Based Welding-Type Fluxes

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The hydrogen solubility of TiO2–SiO2–FeO and the TiO2–SiO2–MnO welding-type flux systems have been studied to identify and compare the hydrogen dissolution behavior in molten welding fluxes at high temperatures of 1823 K in a wide range of compositions. The dependence of the water vapor pressure and the hydrogen solubility showed a slope of 1/2 suggesting thermodynamic equilibrium was obtained. For an acidic slag composition, the hydrogen was found to be incorporated within the silicate network structure and decreased with higher TiO2 additions due to the dilution effect of SiO2 and subsequent decrease in incorporation sites. The additions of FeO and MnO, which acts as a basic component to the slag system, provided free oxygen ions, and decreased the incorporation sites for hydrogen dissolution. FTIR analysis of as quenched molten flux samples showed more pronounced bands for Si–OH bending vibrations when hydrogen solubility increased. For a basic slag composition, the hydrogen existed as a free hydroxyl and the addition of basic components such as FeO and MnO to the slag system increased the hydrogen solubility in the molten slag. Furthermore, it was observed that the hydrogen solubility was slightly lower for FeO than MnO containing fluxes.