Mechanical Anisotropy of Hot Rolled Line Pipe Steel Coil

Abstract

The mechanical anisotropy of hot rolled coils for linepipe grades in the range between X52 and X80 have been investigated in terms of tensile strength and Charpy impact toughness. Samples were taken in different orientations with respect to the strip rolling direction: 0, 30, 45, 60 and 90 degrees. Tensile tests were performed on round tensile specimens to avoid the need for strip levelling. Results from this investigation reveal that the hot rolled coils display different degrees of anisotropy varying as function of strength level and thickness. The material anisotropy is reflected in variations in yield, tensile strength and ovality of the gauge section after fracture. At the same time, variations of the CVN absorbed energy in the upper shelf energy and in the ductile to brittle transition temperature were also observed. Finally, detailed texture studies revealed a relation between mechanical anisotropy and crystallographic texture.