Abstract:
Residual stresses of spiral submerged-arc welded pipe (SAWH pipe) and longitudinal submerged-arc welded pipes of UOE and JCOE in Grade X80,
φ1 219 mm×22.0 mm, were measured by cut-ring method and centre-hole drilling method. The testing results were compared and analyzed. The results show that after cut-ring test, the SAWH pipe had relatively large values of the circumferential opening, and the axial and radial displacements, indicating relatively high residual stresses; the average residual stress was 148.7 MPa. The UOE pipe and JCOE pipe had relatively small values of the circumferential opening and no axial and radial displacements, indicating relatively low residual stresses; the average residual stresses of the UOE pipe and JCOE pipe were 37.0, 69.3 MPa, respectively. The average circumferential and axial residual stresses on external surface of SAWH pipe by centre-hole drilling method were 132.1, 160.9 MPa, and those on internal surface were -218.0, -185.5 MPa, respectively. The overall residual stresses of SAWH pipe were higher than those of longitudinal submerged-arc welded pipes. It was suggested to set the control target of the residual stress of SAWH pipe in Grade X80,
φ1 219 mm×22.0 mm, as "the circumferential opening values shall not be larger than 80 mm".