Microstructural parameters, impact strength, and DWTT properties of coil steel X70 are governed to a considerable degree by a sufficiently high temperature for the start of rolling in 2000 mill finish stands (T sfr). Results are provided for a study of steel microstructure in relation to cold brittleness threshold during DWTT (T 90) and proportion of bainitic ferrite on T sfr. Rolling with T sfr close to a temperature for retarding recrystallization (T 5 or T NR) causes a difference in steel matrix grain size and an increase in volume fraction of bainitic transformation products with lath morphology (bainitic ferrite) due to partial austenite recrystallization. This structure leads to the worsening of steel impact strength and DWTT properties. The properties of coil steel may be improved by increasing steel niobium content and rolled product interim cooling.
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References
F. Haisterkamp, K. Hulka, Yu. I. Matrosov, et al., Niobium-Containing Low-Alloy Steels [in Russian], SP Intermet Engineering, Moscow (1999).
A. J. De Ardo, “Modern thermomechanical processing of microalloyed steels: a physical metallurgy perspective,” Proc. Microalloying’95 Conf., Pittsburgh, PA, June 11–14, 1995, The Iron and Steel Society, pp. 15–33.
N. V. Filatov, C. Yu. Nastich, A. V. Golovanov, et al., “Provision of property uniformity and cold resistance during DWTT in coil and sheet rolled product of steel X70 from the 20000 mill,” Metallurg, No. 8, 57–61 (2009).
G. Krauss and S. W. Thompson, “Ferritic microstructures in continuous cooled low- and ultralow-carbon steels,” ISIJ Int., 35, No. 8, 937–945 (1995).
K.-B. Kang, J. H. Bae, and W.-Y. Chu, “Effect of thermomechanical processing parameters on mechanical properties and microstructure of API-X80 grade hot-rolled strips,” Proc. 4th. Int. Conf. on Pipeline Technology, Ostend, Belgium, May 9–13, 2004, Vol. 4, pp. 1689–1699.
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Translated from Metallurg, No. 7, pp. 57–62, July, 2012.
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Nastich, S.Y., Soya, S.V., Molostov, M.A. et al. Effect of temperature for the start of finish rolling on coiled steel X70 microstructure and cold resistance. Metallurgist 56, 519–525 (2012). https://doi.org/10.1007/s11015-012-9608-6
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DOI: https://doi.org/10.1007/s11015-012-9608-6