Heat Treatment of Metals ›› 2023, Vol. 48 ›› Issue (6): 130-135.DOI: 10.13251/j.issn.0254-6051.2023.06.024

• Process Research • Previous Articles     Next Articles

Effect of cooling process on microstructure and mechanical property of Q500qE bridge steel

Wu Fengjuan,Yang Hao, Qu Jinbo   

  1. Institute of Research of Iron and Steel, Shagang, Jiangsu Province, Zhangjiagang Jiangsu 215625, China
  • Received:2022-11-29 Revised:2023-05-05 Published:2023-08-11

Abstract: Taken high-strength bridge steel Q500qE as the object, the influence of different cooling processes on its microstructure and properties were studied. The results show that under the low speed cooling process (5 ℃/s), the microstructure mainly consists of granular bainite with coarse M/A islands, which exhibits a low strength and poor toughness, in spite of a low yield ratio. The high speed cooling process (25 ℃/s) leads to a lath bainite dominant microstructure with spherical and rod-like M/A islands, with a much improved strength and toughness, but a high yield ratio. Upon the interrupted cooling process (20 ℃/s+air cooling+20 ℃/s), a multiphase microstructure, containing polygonal ferrite, lath bainite and granular bainite, with fine and dispersed M/A islands, is obtained, which results in the lowest yield ratio, highest toughness, and best overall properties.

Key words: Q500qE bridge steel, cooling process, M/A island, yield ratio, low temperature toughness

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