Profiling inclusion characteristics in submerged arc welded metals of EH36 shipbuilding steel treated by CaF2–TiO2 fluxes

EH36 shipbuilding steel has been submerged arc welded under 6 kJ mm−1 heat input employing CaF2–TiO2 fluxes. Ensuing weld metals have been examined with an emphasis on inclusion characteristics. Compositional-wise, the inclusion ensemble is largely categorised as a complex Ti-containing type. It is demonstrated that, as a function of TiO2 content, the average Ti content in the inclusions is gradually enhanced, which is compensated by the simultaneous reduction of Al and Mn. Meanwhile, inclusion size distribution curves show log-normal patterns with the frequency peaks ranging from 0.3 to 0.4 μm. Furthermore, inclusion number density and volume fraction show a definitive increasing trend, which are concurrent to the O uptake from 110 to 210 ppm enabled by TiO2 decomposition.