Coetsee, TheresaDe Bruin, Frederik Johannes2023-09-212023-09-212022-05-11Coetsee, T.; De Bruin, F. In Situ Modification of CaF2-SiO2-Al2O3-MgO Flux Applied in the Aluminium-Assisted Transfer of Titanium in the Submerged Arc Welding of Carbon Steel: Process Mineralogy and Thermochemical Analysis. Minerals 2022, 12, 604. https://DOI.org/10.3390/min12050604.2075-163X (online)10.3390/min12050604http://hdl.handle.net/2263/92354DATA AVAILABILITY : The data sets presented in this study are available upon request from the corresponding author.Flux formulations are specified to target chemical and physico-chemical parameters. Chemical parameters set flux element transfer behaviours and weld metal oxygen contents. Physicochemical parameters such as slag viscosity, surface tension and melting range are targeted to ensure an acceptable weld bead profile and surface appearance. Slag detachability is an important physicochemical property required to ensure high welding productivity, smooth weld bead surface and no slag entrapment. Here, bead-on-plate welding tests were made with and without metal powder additions, including aluminium powder as a de-oxidiser. Difficult slag detachability was observed in weld runs made with metal powder additions. Mineralogy of the post-weld slags, and thermochemical calculations, show that the flux was modified due to the aluminothermic reduction of MnO and SiO2 from the slag to form alumina. Increased quantities of spinel phase were identified in the post-weld slag samples, at the weld pool–slag interface. The combined effect of increased slag viscosity, from increased spinel in the slag, and lowered weld pool solidus temperature, resulted in the formation of a rough bead surface morphology, which, in turn, caused mechanical fixation of the slag to the weld bead. Flux modification to higher CaF2 content should ensure that higher quantities of spinel phase can be tolerated in the slag.en© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license.SlagFluxPhase chemistryFluorideSpinelMineralogyOxy-fluorideGlassEngineering, built environment and information technology articles SDG-07SDG-07: Affordable and clean energyEngineering, built environment and information technology articles SDG-09SDG-09: Industry, innovation and infrastructureEngineering, built environment and information technology articles SDG-12SDG-12: Responsible consumption and productionEngineering, built environment and information technology articles SDG-13SDG-13: Climate actionArticle