Effect of hot deformation and Nb precipitation on continuous cooling transformation of a high-Nb steel |
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| Authors: | G-Y Qiao Y-B Cao B Liao |
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| Affiliation: | 1. Key Lab of Metastable Materials Science &2. Technology and College of Materials Science &3. Engineering, Yanshan University, Qinhuangdao 066004, China;4. Key Lab of Applied Chemistry of Hebei Province and School of Environment and Chemical Engineering, Yanshan University, Qinhuangdao 066004, China;5. School of Materials Science and Engineering, Shijiazhuang Tiedao University, Shijiazhuang 050043, China |
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| Abstract: | In this work, the effects of hot deformation on continuous cooling transformation of a high-Nb steel were investigated on a Gleeble 3500 thermal simulator. The amounts of dissolved Nb were determined by inductively coupled plasma-atomic emission spectrometry. Furthermore, the effects of hot deformation and Nb precipitation on phase transformation were discussed. Results showed that high-Nb steel is suitable for acicular ferrite pipeline steels because the acicular ferrite microstructure can be obtained in a wide cooling rate range. Hot deformation strongly accelerates the polygonal ferrite transformation and increases the critical cooling rate to obtain a full acicular ferrite microstructure. Moreover, hot deformation markedly refines the final microstructure and improves the mechanical properties of acicular ferrite obtained at a high cooling rate. However, hot deformation can also promote Nb precipitation during holding and even cooling at low rates after hot deformation. Nb precipitation dramatically promotes the polygonal ferrite, weakens the effect of Nb in solution on phase transformation and strengthening, and decreases the microhardness. |
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| Keywords: | High-Nb steel Hot deformation Precipitation Continuous cooling transformation |
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