Effects of Mo content on phase transformation behavior, microstructure and mechanical properties of high grade pipeline steel

doi:10.13251/j.issn.0254-6051.2021.05.001

Abstract

Abstract: By adjusting the Mo content in a high-strength pipeline steel, the effect of Mo content on dynamic phase transformation was studied. Under the same TMCP condition, the strength and toughness of the steels with 0.2% Mo and 0.3% Mo were studied comparatively, and two different complex acicular ferrite (AF) microstructures were analyzed by optical microscope, EBSD, TEM and other means. The relationship between the microstructures and the mechanical properties was investigated. The results show that the increasce of Mo content is beneficial to refinement of the microstructure and formation of the acicular ferrite, and move the dynamic CCT curves to the lower right. Under the same rolling conditions, the strength of the steel with 0.3% Mo is higher, the increase of Mo content helps to improve the effects of precipitation strengthening and fine grain strengthening, at the same time, the volume fraction of bainitic ferrite (BF), the size and number density of MA islands are increased, and the strength is further increased. In the case of the same proportion of high angle grain boundaries, the impact property of the steel with 0.3% Mo is worse, the size and number density of MA islands as well as their degree of irregularity are the main factors to affect the impact property.

Key words: pipeline steel, Mo, dynamic CCT curves, microstructure, bainitic ferrite

CLC Number:

TG142.1

Duan He, Shan Yiyin, Yang Ke, Shi Xianbo, Yan Wei, Ren Yi. Effects of Mo content on phase transformation behavior, microstructure and mechanical properties of high grade pipeline steel[J]. Heat Treatment of Metals, 2021, 46(5): 1-8.

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