Measurement and Control of Residual Stress of High-Grade and Large-Diameter Welded Pipe for Oil and Gas Transportation

It was discussed that the research progress and technical achievements had been obtained in the field of residual stress measurement and control of high-grade and large-diameter welded pipe for oil and gas transportation in China. (1) The layout scheme of measuring points and the requirements of spaces between measuring points, hole depth, etc., for residual stress measurement of welded pipe using hole drilling strain-gage method were proposed. On which, the residual stress measurement technology for welded pipe was proposed. (2) The measurement results indicate that the characteristics and distribution of residual stress of SAWH pipes with different grades and sizes were quite different. In general, the residual stress of SAWH pipe was highest, followed by JCOE pipe and UOE pipe. After the ring splitting test, SAWH pipe section usually had relative displacement in circumferential, axial and radial directions, and the degree of deformation varies greatly; But SAWL pipe section usually only occurs circumferential opening, without axial and radial stagger, and the circumferential opening of JCOE pipe was usually larger than that of UOE pipe. (3) Based on the mechanical analysis of the complex deformation of SAWH pipe after the ring splitting test and the superposition principle of elastic mechanics, a prediction model of the residual stress of the high-grade and large-diameter welded pipe suitable for SAWH pipe was established, which overcame the deficiency of the existing prediction models of the residual stress of the welded pipe only considering the circumferential deformation. (4) The key forming parameters affecting the residual stress of SAWH pipe were analyzed and determined as the reduction and forming angle. Combined with the finite element simulation analysis, field adjustment and residual stress analysis, the forming technology and residual stress control technology of low residual stress SAWH pipe were developed.