Optimizing Weldability of EH550 Offshore Engineering Steel via TiO2-Assisted Element Transfer During Submerged Arc Welding

The article delves into the optimization of weldability for EH550 offshore engineering steel through the use of MnO–SiO2–TiO2 fluxes during submerged arc welding. It systematically varies the TiO2 content in the flux to fine-tune elemental transfer behaviors, microstructural evolution, and mechanical properties. The study reveals that an optimal TiO2 content of 40 mass pct achieves the best balance between yield strength and impact energy, enhancing both the strength and toughness of the weld metal. The research also highlights the role of TiO2 in controlling the oxygen content gradient and promoting the formation of acicular ferrite, which significantly improves the mechanical properties. Additionally, the study provides a detailed analysis of the carbon equivalent or crack susceptibility index, demonstrating how the MnO–SiO2–TiO2 fluxes can significantly lower the risk of cracking and improve weldability. The findings offer valuable insights into the development of compatible fluxes for high-strength steel grades, paving the way for advanced applications in offshore engineering and shipbuilding.