Microstructures and textures comparison of conventional and high niobium API 5L X80 line pipe steel using EBSD

Abstract

The development of microstructure and crystallographic texture of conventional and high Niobium API 5L X80
line pipe steels has been studied using Electron Backscattered Diffraction (EBSD) technique. The selective
use of micro-alloying elements like niobium in alloy design, increases the recrystallization stop temperature,
which facilitates rolling at higher temperatures compared to conventional thermo-mechanical processing. The
measurement tools available with EBSD, such as image quality values and precise grain boundary misorientation
angles, provide new approaches to characterize and compare both microstructures. The texture analysis, in
addition, shows high intensification of {112}<110>, {554}<255> and rotated cube {001}<110> for both processes.
However, the Goss {110}<001> and the rotated Goss {110}<110> has been only observed in the conventional
processing which is a sign that the austenite was recrystallized prior to transformation. This shows the ease of
processing experienced with High Temperature Processing (HTP) chemistry compared to the conventional one.