Influence of the Holding Thickness and Process in the Microstructure and Mechanical Properties of a Microalloyed 380 MPa Structural Steel

Abstract:

Flat low carbon microalloyed structural steels processed by controlled rolling have excellent mechanical properties, particularly regarding toughness, since austenite is rolled with full recrystallization between rolling passes (roughing stage at high temperatures), and, subsequently, with no recrystallization at all between passes (finishing stage at low temperatures), maximizing nucleation of ferrite grains during austenite transformation after hot rolling. However, rolling must be prompted in an intermediate temperature range where recrystallization of austenite between rolling passes occurs partially, as this can lead to great heterogeneity in the grain size distribution of the product, a potential condition to impairs its low temperature toughness. On the other hand, this holding period that is necessary to avoid rolling within this temperature range can last several minutes, reducing the productivity of the rolling line and, in this way, potentially harming the financial performance of the plant. This work was developed to analyze several proposed rolling conditions for the finishing stage during controlled rolling of 16 mm thick strips of a low C Nb-Ti microalloyed steel strip, 380 MPa structural grade, processed in a Steckel mill, to identify the best condition that provides maximum productivity without affecting the required microstructural, toughness and mechanical characteristics of the final product.

• Periodical: Materials Science Forum (Volume 1105)
• Pages: 167-172
• DOI: https://doi.org/10.4028/p-5bTKPK
• Online since: November 2023
• Authors: Jorge Adam C. Cohn*, Altair L. de Souza, Nerea Isasti, Pello Uranga, Paulo Haddad, Marcelo A. Rebellato, Antonio A. Gorni
• Keywords: Holding Thickness, Mechanical Properties, Productivity, Steckel Mill, TMCP

References

[1] ABNT, Norma Brasileira NBR 6656, Rio de Janeiro (Brazil), 2016, 7 p.

[2] K. Irvine, F. Pickering, T. Gladman, Grain-Refined C-Mn Steels, Journal of the Iron and Steel Institute, February 1967, 161-182.

[3] ABNT, Norma Brasileira NBR 6673, Rio de Janeiro (Brazil), 1981, 14 p.

[4] P. Uranga, J. Rodriguez-Ibabe, D. Stalheim, R. Barbosa, M.A. Rebellato. Application of Practical Modeling of Microalloyed Steels for Improved Metallurgy, Productivity and Cost Reduction in Hot Strip Mill Applications. In: Proceedings of the Iron & Steel Technology Conference - AISTech 2016, 2016; Pittsburgh. Warrendale: AIST; 2016. pp.1769-1778.

DOI: 10.1007/978-3-319-48767-0_33

[5] X. Yuan, Z. Liu, S. Jiao, L. Ma, G. Wang, The Onset Temperatures of γ to α-Phase Transformation in Hot Deformed and Non-Deformed Nb Micro-Alloyed Steels. ISIJ Int. 46 (2006) 579-585.

DOI: 10.2355/isijinternational.46.579