Weld Repair of 1-1/4Cr-1/2Mo Steel Piping Girth Welds

Abstract

Weld repairs have been performed to 1-1/4Cr-1/2Mo steel girth weldments from a hot reheat pipe returned from service at 1000°F (538°C) for 244,000 h. Shielded metal arc weld (SMAW) repairs were performed to excavated portions of the ex-service welds with post weld heat treatment (PWHT) and using a temperbead technique. The welds were evaluated prior to and after repair to study the effects of degradation on repairability, the effectiveness of temperbead repairs and the remaining life achievable by weld repair. Temperbead repairs result in higher peak hardness compared to the PWHT repairs (320 Hv versus 230 Hv). Both PWHT and temperbead repairs resulted in increased yield strength compared to the ex-service base metal and weld at both room temperature and at 1050°F (565°C), the maximum benefits being realized for the temperbead repairs. Effects on tensile strength were more marginal. Both PWHT and temperbead repairs resulted in improved toughness at room temperature as measured by Charpy impact energy. The temperbead repair produced a greater enhancement of toughness compared to the PWHT repair in composite weldment specimens. Larson-Miller parameter extrapolations of stress rupture data indicate a remaining life of about 46 yr for temperbead repairs and 28 yr for PWHT repairs under design conditions of 1000°F (538°C) and 6.6 ksi (46 MPa). Other isostress extrapolation procedures yield lower lives, but the temperbead repairs are consistently superior regardless of the extrapolation procedure used. [S0094-9930(00)01502-X]