Texture Dependent Mechanical Anisotropy of X80 Pipeline Steel

Pipeline steel grades API X80 are used for oil and gas transport. The most important mechanical properties of these steel grades are strength and fracture toughness. A remarkable directional anisotropy of toughness and strength were often observed in the plates. The effect of the thermo-mechanical processing parameters on the mechanical properties and texture of several commercial pipeline API X80 plates were investigated with a particular emphasis on the effect of the slab reheating temperature and the finish cooling temperature on the directional anisotropy. The crystallographic texture gave rise to a specific anisotropy profile in yield strength and in Charpy fracture energy in the ductile-brittle transition temperature domain. The observed anisotropy pattern could be understood on the basis of crystal plasticity and crystal fracture principles.