Triaxial residual stresses in thermomechanically rolled seamless tubes characterized by high-energy synchrotron X-ray diffraction

Abstract

Residual stresses in seamless steel tubes have a significant influence on the mechanical stability and reliability of industrial constructions. In this contribution, triaxial residual stresses in seamless rolled tubes with an outer diameter of 82 mm and a wall thickness of 9.8 mm were analyzed at synchrotron source PETRA III at DESY in Hamburg using the HZG beamline HEMS (P07) with a photon energy of 75 keV. The position-resolved measurements were performed using a conical-slit measurement technique with a spatial resolution in the direction of the X-ray beam of 0.8 mm. The tubes were produced under dedicated thermal conditions resulting in complex microstructure and residual stress profiles across the tube walls. The (experimental) measurements allowed determining axial, tangential and radial residual stress profiles. The results reveal tensile stresses up to 150 MPa on the outer wall side and compressive stress of about −120 MPa on inner wall side. The measurements document the importance of the cooling process control during the thermo-mechanical rolling, which represents a key factor for the design of dedicated microstructure and residual stress levels in the tubes.