Review of Reheat Crack in Welded Joint of Low Alloy Heat-Resistant Steels

• Published in: Key Engineering Materials 2017-02, Vol.730, p.15-20
• Main Authors: Wang, Hai Bo, Chen, Zhong Bing, Shi, Wei, Lv, Yi Shi, Qi, Quan You
• Format: Article
• Language: English
• Subjects: Cracks; Grain boundaries; Heat resistant steels; Low alloy steels; Precipitation hardening; Segregations; Thickness; Welded joints
• ISSN: 1013-9826; 1662-9795; 1662-9795
• DOI: 10.4028/www.scientific.net/KEM.730.15

The current research status of reheat crack in welded joint of low alloy heat-resistant steels are outlined. Some new phenomena discovered in engineering in recent years are summarized, and related problems that remain to be studied are also presented. Reheat crack in welded joint is occurred frequently during postweld heat treatment (PWHT) or in service at elevated temperature. Mainly four mechanisms leading to reheat crack, respectively, impurity segregation grain boundary weakening, precipitation hardening, creep rupture and no-precipitation zone weakening have been generally accepted now. Several essential factors consist of parent material chemical composition, microstructure and thickness of welded joint, filler material, preheat and postheat procedures, welding energy input, PWHT parameter, and stress and strain and so on. Theoretical calculation methods, criterion of RoA (Reduction of Area) and several experimental methods are put forward to evaluate reheat crack susceptibility. Based on new issues emerged in engineering, problems of concerning reheat crack are necessary to be researched, which include at least mechanism and influence factors of new multi-element composite strengthening heat-resistant steels, the mitigation measures for increasing wall thickness weldment, the root cause analysis and prevention methods of conventional low alloy heat-resistant steels for long term service.