The effect of MnO on the hydrogen solubility in the CaF 2-CaO-SiO 2 based welding flux system at 1823 K has been studied. At an acidic slag composition of CaO/SiO 2 molar ratio or basicity of 0·8 and below, MnO addition decreased the hydrogen solubility. At an intermediate slag composition of CaO/SiO 2 molar ratios of 1·1 and 1·3, the hydrogen solubility as a function of MnO additions resulted in a parabolic behaviour showing a minimum and then increasing with higher MnO content. MnO was found to behave as a basic oxide, which decreases the hydrogen solubility when the incorporation hydroxyl mechanism is dominant for an acidic slag and increases the hydrogen solubility when the free hydroxyl mechanism is dominant for a basic slag. This change in the dominant hydrogen dissolution mechanism was also apparent from the hydrogen solubility results at various CaO/SiO 2 molar ratios and fixed MnO contents. A higher hydrogen solubility in the slag is likely to lower the diffusible hydrogen content in the weld metal, and optimum MnO additions were suggested depending upon the basicity of the slag. Fourier transformed infrared analysis of as quenched slags showed that MnO depolymerised the slag network structure and correlated well with the effect on the hydrogen solubility in slags.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics