Quality evaluation and crack cause analysis of a type B sleeve service welding

Abstract Type B sleeve repair technology is important in service welding repair because the quality of fillet weld directly affects the sealing and bearing capacity of Type B sleeve repair. In this paper, a cover weld crack at 0 o ‘clocks of fillet weld found by non-destructive testing is analyzed. The tensile strength of fillet weld and longitudinal weld is much higher than the technical requirements of X80 steel grade pipe, the welding material belongs to a strong matching state, and its impact toughness value is low. At the same time, the hardness test was carried out at the fillet weld, and the hardness of the tube body at the welding position of the cover was higher than that at other positions, and there was a risk of cracking. The defects were dissected as hot cracks, and the reason was related to the strong matching of the selected welding material. It is suggested that when selecting welding materials for lap fillet welding, it is possible to try to reduce the matching strength level of the weld without affecting the sealing and bearing capacity.