Effect of microstructure and texture on the mechanical properties in high strength pipeline bend

Abstract

This paper focuses on the effect of microstructure and micro-texture on the mechanical properties in high strength pipeline bend. The transmission electron microscopy (TEM), and electron backscatter diffraction (EBSD) were performed on the microstructure and texture observation. Tensile tests and Charpy V-notch impact tests were used to measure the strength and impact toughness, respectively. After hot induction bending, the microstructure of both the inner arc side and the neutral axis position has some polygonal ferrite (PF) grains. High-density dislocations, M/A constituents in the bainite laths, and high frequency of high Taylor factor in the outer arc side result in the toughness lower than the other specimens. In addition, dynamic recovery and partial recrystallization occurred during hot induction bending, the recrystallized grains are small and scattered distribution in the inner arc side and the outer arc side. The results indicated that the mechanical properties of the outer arc side have anisotropy along with the longitudinal and transversal directions. Micro-texture results obtained by EBSD measurement show that the main texture components in the experimental specimens are Cube, Goss, Brass, Copper, R-cube, and {331} <1–10> possibly because of the same mother pipe. However, the Brass and {112} <110>component might be the major factor of the anisotropy for the experimental bend.