In this study by Rak et al., the coarse-grained heat-affected zone (CGHAZ) microstructure and crack tip opening displacement (CTOD) toughness of grade StE 355 Ti-microalloyed offshore steels were investigated. Three parent plates of 40 mm thickness were studied: two were Ti-microalloyed with either Nb + V or Nb addition, and one conventional StE 355 steel without Ti addition was welded for comparison. Multipass tandem submerged arc welds (SAW) and manual metal arc welds (SMAW) were produced. Different heat-affected zone (HAZ) microstructures were simulated to evaluate the detrimental effect of welding on toughness. All HAZ microstructures were examined using optical and electron microscopy. The results showed that Ti addition, combined with proper steel processing to disperse fine TiN precipitates uniformly, a balanced proportion of other microalloying elements, and a Ti/N weight ratio of about 2.2, is beneficial for the HAZ properties of StE 355 grade steel.

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