Strength increase in the coarse-grained heat-affected zone of a high-strength, blast-resistant steel after post-weld heat treatment

The microstructure and precipitation behaviors in the coarse-grained heat-affected zone (CGHAZ) of a blast-resistant steel during post-weld heat treatment (PWHT) were investigated. It was found that using PWHT at 650 °C for 1 h is beneficial for the strength recovery in the softened CGHAZ in the as-welded condition. This is attributed to the re-precipitation of strengthening phases during the PWHT process that are dissolved in the CGHAZ during heating to the high temperature and do not re-precipitate completely during cooling. The strength change in the CGHAZ is therefore related with the change in microstructure after PWHT and rationalized by the model used in the present study.