Profiling inclusion characteristics in submerged arc welded metals of EH36 shipbuilding steel treated by CaF 2 –TiO 2 fluxes

Abstract

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.