An experimental electro-thermo-mechanical characterization of plastic deformation of quenched and tempered pipe steel for oil country tubular goods

Abstract

Development, manufacturing, and optimization of Oil Country Tubular Goods (OCTG) are strongly related to thermo-mechanical behavior of quenched and tempered pipe steels. Threaded pipe connections consist of a pipe end with external thread (pin) and coupling with the internal thread (box). They are manufactured on seamless pipes made of typical OCTG steel grades like P110. Introduced residual stresses in the threaded connections due to cold preforming process as well as tension/ compression and torsion make-up tests lead to material degradation of the pipe steel. The complex geometry of thread and difficult access to the thread surface make conventional methods for residual stress measurement impossible. In this study, in-situ measurement of the strain, the temperature and the electrical resistivity of steel P110 during electro-mechanical coupled uniaxial tensile test was performed. The electro-thermo-mechanical properties of the investigated material were determined using a Matlab® code. The presented experimental method could be used for the experimental in-situ measurement of local plastic strains in threaded connections under make- up tests. Inanition, the obtained results of this research such as electro-thermo-mechanical properties of investigated pipe steel could be applied for material modelling of pipe steels.