Characterizing Phase Transformations in the Coarse-Grained Heat-Affected Zone of EH550 Offshore Engineering Steel Subjected to Varied High Heat Inputs

The study focuses on characterizing phase transformations in the coarse-grained heat-affected zone (CGHAZ) of EH550 offshore engineering steel subjected to different high heat inputs. Using advanced confocal scanning laser microscopy (CSLM), the researchers document the microstructural evolution and quantify the kinetic processes of phase transformations. The article highlights the significant differences in bainite growth rates and start temperatures under varying heat inputs, as well as the transformation of bainite laths from slender to blocky morphologies. The findings have important implications for optimizing the mechanical properties and toughness of welded joints in high-strength steels. The study also includes Charpy impact tests to assess toughness, revealing that lower heat inputs result in superior toughness. The article concludes with a schematic continuous cooling transformation (CCT) diagram and inverse pole figures, illustrating the relationship between heat input, microstructure, and mechanical properties. This comprehensive analysis offers valuable insights for fine-tuning the performance of welded structures in the offshore engineering industry.