Effect of high temperature holding time on microstructure and properties of coarse-grained zone of welded joint of X80 pipeline steel

doi:10.13251/j.issn.0254-6051.2020.07.024

Abstract

Abstract: Effect of high temperature holding time on microstructure and properties of X80 pipeline steel in the CGHAZ was studied by means of Gleeble-3500 thermal simulator, microstructure analysis, mechanical test and SEM. The results show that the coarse-grained zone of X80 pipeline steel is mainly composed of granular bainite, bainite ferrite and M/A component.With the increase of high temperature holding time, the diffusion rate of carbon and nitrogen atoms increases, the composition is tended to be more uniform, the cross distribution of granular bainite and bainite ferrite increases, the distribution of M/A island structure and carbon nitrogen compounds is more dispersed, and the toughness value of coarse-grained zone is also increased gradually.When the high temperature holding time is 18 s, the impact toughness of the coarse grain zone is the best, the impact absorbed energy of -10 ℃ is 288 J, and the moderate hardness value is 270 HV0.3. When the high temperature holding time is beyond 18 s, the impact absorbed energy of the coarse-grained zone decreases and the hardness value increases. When the high temperature holding time is 8 s, the impact toughness of coarse-grained zone is the lowest, the impact absorbed energy is only 49 J, the hardness value is the highest, is 283 HV0.3.

Key words: coarse-grained zone, high temperature holding time, M/A, granular bainitie ferrite, bainitic ferrite

CLC Number:

TG457.11

Ge Jialin, Zhang Xiaoyong, Ji Lingkang, Li Weiwei, He Xiaodong, Chen Qinglong, Yu Chenyang. Effect of high temperature holding time on microstructure and properties of coarse-grained zone of welded joint of X80 pipeline steel[J]. Heat Treatment of Metals, 2020, 45(7): 119-123.

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