Improvement of reliability and creep resistance in advanced low-alloy steels

The T23 and T24 steels were designed for welding membrane water walls without preheating and without post-weld heat treatment (PWHT). Results presented demonstrate that non-tempered weld joints of low-alloy creep-resistant steels T23 and T24 undergo a process of secondary hardening during long-term exposure at elevated temperatures. This process is accompanied by degradation of plastic properties, especially in the heat affected zone (HAZ). Therefore, PWHT of T23 and T24 welds is necessary to achieve suitable hardness and plastic properties of welds.