The Effect of Cold Rolling on the Microstructure and Texture Evolution of API 5L X70 Steel in Normal and 45° Tilted Cross Section

Document Type : Original Articles

Authors

Department of Materials and Metallurgical Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran.

Abstract

In the present study, a combination of X-ray diffraction spectroscopy, field emission scanning electron microscopy (FESEM) and optical microscopy methods were used to investigate the microstructure and crystallographic texture changes of API 5L X70 pipeline steel following an extreme cold working process that resulted in reduce the thickness of 80% in the sample. All investigations were done on two different sections of the sample, including the surface and the inclined section rotated 45 degrees relative to the surface. In fact, these two cross-sections are chosen to show the angle between the two important crystallographic planes of {100} and {110}. FESEM and optical microscope analyzes showed that the microstructure of the primary steel includes granular bainite, conventional upper bainite, and martensite-austenite islands. The results showed that the morphology of the initial microstructure consisted of mostly equiaxed grains, which after applying cold work due to being subjected to severe pressure, turns into a microstructure with the morphology of elongated grains, especially in the rotated section. Analysis of crystal orientation changes by X-ray diffraction spectroscopy showed that the density of {100} crystallographic planes decreased due to applied cold work on the surface and at the same time the density of {110} crystallographic planes on the surface increased. Also, the results proved that {100} crystallographic planes were replaced by {110} crystallographic planes on the sample rotated by 45 degrees.

Keywords

Main Subjects


CAPTCHA Image