Effect of rolling parameters on microstructure and mechanical properties of 460 MPa grade low yield ratio fire-resistant weathering steel

doi:10.13251/j.issn.0254-6051.2020.09.011

Abstract

Abstract: Microstructure of low yield ratio fire-resistant weathering steel after cooling at different rates was determined by thermal simulation method.By comparing the effects of post-rolling relaxing process or not and final cooling temperature after hot rolling on mechanical properties of the steel,the effect of different processes on microstructure was investigated by using OM,SEM and TEM.The results show that with cooling rate increasing,the microstructure of the steel plates changes from polygonal ferrite to (acicular ferrite+granular bainite) duplex microstructure.Due to the transformation of undercooled austenite into polygonal ferrite during relaxation treatment,the yield strength and yield ratio of the steel plates decrease.With the decrease of final cooling temperature,the yield strength and yield ratio of the steel plates increase,which is due to the refinement of acicular ferrite and the dispersion strengthening of M/A constituent.Good match of high strength and low yield ratio of the steel plates are successfully achieved by the combination of direct water-cooling after hot rolling and controlled final cooling temperature between 500 ℃ to 560 ℃.

Key words: low yield ratio fire-resistant and weathering steel, relaxing, thermo-mechanical simulation, final cooling temperature, M/A

CLC Number:

TG335

Ma Longteng, Wang Yanfeng, Yang Yongda, Han Chengliang, Ma Changwen, Tian Zhihong. Effect of rolling parameters on microstructure and mechanical properties of 460 MPa grade low yield ratio fire-resistant weathering steel[J]. Heat Treatment of Metals, 2020, 45(9): 66-70.

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