Microstructure characteristics and mechanical properties of X80 pipeline steels

Abstract

The relation between microstructure characteristics and mechanical properties of X80 pipeline steels was investigated using optical microscopy, scanning electron microscopy, etc. It is shown that the structure consists of polygonal ferrite (PF), quasi-polygonal ferrite (QPF), acicular ferrite (AF), and granular bainitic ferrite (GF). With increasing volume fraction of M-A islands (below 3%), the yield strength increases. With increasing content of higher angle grain boundaries(HAGBs), the yield strength, elongation, and DWTT properties at −15° increase, and the volume fraction of M-A islands reaches its highest point in the steel containing the most volume fraction of GF.

Keywords

X80 pipeline steel / mechanical properties / higher angle grain boundaries / effective grain size

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