Effects of cooling processes on microstructure and susceptibility of hydrogen‐induced cracking of X80 pipeline steel

Abstract

The effects of three different kinds of cooling processes on the properties of the microstructure for hydrogen‐induced cracking (HIC) resistance and hydrogen atom diffusion on X80 pipeline steel have been investigated in the laboratory. The results show that Steel F after furnace cooling contains coarse polygonal ferrite (PF), quasi‐polygonal ferrite (QF), and a small amount of granular bainite (GB). Steel A after air cooling contains finer QF and GB. Steel W after water cooling quenching treatment contains a large amount of GB, lath bainite (LB), and a small amount of martensite (M) and ferrite. In addition, the results of hydrogen permeation test show that hydrogen atoms diffuse the fastest in Steel W with a finer microstructure and grains, and the content of dissolved hydrogen atoms is lowest in Steel F. After soaking corrosion tests, Steel A has the best HIC resistance properties, due to the role of more high‐angle grain boundaries (HABs) and fewer grain boundaries with the <100> orientation.