Residuai stress variation and redistribution of SSAW tube before and after hydrostatic testing

Because of processing procedure, the residual stresses are created in spiral seam submerged arc welded(SSAW) tubes. Especially, the remarkabl e tensile residual stresses exist on the inner surface of the heat affected zone(HAZ), and in this way the service reliability of SSAW tube will be reduced. During pressured water test the pressured water induced stress(≈ 0.9 ~ 0.95σs) is superimposed on the existing residual stresses and produces plastic deformation in the high tensile residual stress region. Therefore, the magnitude of residual stress will be reduced and the residual stress will be redistributed in more homogeneous way. The present paper demostrates the residual stress variation and redistribution in one kind of SSAW tubes before and after hydrostatic test. The residual stresses are obtained by means of both hole drilling and grooving separation methods.