Variation of microstructures and mechanical properties in the post-weld heat-treated HAZ of Cu containing HSLA steel welds

The present study focuses on the effect of Cu and post-weld heat treatment (PWHT) on the microstructure and mechanical properties in the coarse grained heat affected zone (CGHAZ) of Cu containing high strength low alloy (HSLA) steel welds. For this study, HSLA steels with and without Cu were prepared in laboratory. Mechanical properties were estimated by Vickers hardness and Charpy impact tests. As a result, despite PWHT, the Vickers hardness did not change noticeably; however, the impact toughness deteriorated significantly with increasing PWHT time. In case of Cu added steel, intergranular brittle fractures occurred after PWHT, due to the strengthening of the grain interior by precipitation of Cu particles. Additionally, the formation of a soft denuded grain boundary zone also played a significant role in lowering the fracture toughness during PWHT.