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 mu m. 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.

Automated summary

This study investigated inclusions in EH36 shipbuilding steel submerged arc welded with CaF2-TiO2 fluxes. The inclusions were found to be mainly of a complex Ti-containing type, with an increase in Ti content and a reduction in Al and Mn content with increasing TiO2 content. The size distribution of inclusions followed a log-normal pattern, with frequency peaks ranging from 0.3 to 0.4 μm. The number density and volume fraction of inclusions showed a definite increasing trend, which was attributed to the uptake of O from 110 to 210 ppm enabled by TiO2 decomposition.