University of Oulu

Ari Saastamoinen, Antti Kaijalainen, Tun Tun Nyo, Pasi Suikkanen, David Porter, Jukka Kömi, Direct-quenched and tempered low-C high-strength structural steel: The role of chemical composition on microstructure and mechanical properties, Materials Science and Engineering: A, Volume 760, 2019, Pages 346-358, ISSN 0921-5093, https://doi.org/10.1016/j.msea.2019.06.018

Direct-quenched and tempered low-C high-strength structural steel : the role of chemical composition on microstructure and mechanical properties

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Author: Saastamoinen, Ari1; Kaijalainen, Antti2; Nyo, Tun Tun2;
Organizations: 1Tampere University, Materials Science, Centre for Advanced Steels Research, 33720, Tampere, Finland
2University of Oulu, Centre for Advanced Steels Research, PL 8000, 90014, Oulu, Finland
3SSAB Europe Oy, Rautaruukintie 155, 92100, Raahe, Finland
Format: article
Version: accepted version
Access: embargoed
Persistent link: http://urn.fi/urn:nbn:fi-fe2019091928931
Language: English
Published: Elsevier, 2019
Publish Date: 2021-06-08
Description:

Abstract

The direct quenching of low-carbon steels after thermomechanical processing on hot strip mills is able to produce both strong and tough coiled plate without the need for subsequent tempering. The process is energy and time efficient with relatively low emissions when compared to conventional reheating, quenching and tempering. For some applications, however, it is desirable to combine direct quenching with tempering, and, bearing in mind the form of the semi-finished product, it is of interest to study the effect of tempering whole coils in a bell furnace. Here, the effects of boron, carbon, titanium, vanadium and tempering temperature on the microstructure, crystallography and mechanical properties of direct-quenched steels has been studied with the aid of simulated bell furnace heating and cooling cycles. All steels contained (in wt.%) 0.2Si–1Mn–1Cr-0.65Mo-0.03Al, while there were two levels of C (0.095 /0.140), V (0 /0.08), Ti (0 /0.025) and B (0 /0.0015). Tempering was performed with peak temperatures at 180 and 570 °C. The paper reveals several possible alloying and processing routes to strong and tough low-C steel. Carbon controls the strength and toughness, while titanium and boron affects the grain size of coarsest grains (d90%), Vanadium has a strong effect on strength retention during tempering at 570 °C: an addition of 0.08 wt% vanadium increases yield strength by 70 MPa and ultimate tensile strength by 100 MPa. The removal of boron from the steel is shown to have a huge impact not only on the microstructure but also on the impact toughness.

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Series: Materials science & engineering. A, Structural materials: properties, microstructure and processing
ISSN: 0921-5093
ISSN-E: 1873-4936
ISSN-L: 0921-5093
Volume: 760
Pages: 346 - 358
DOI: 10.1016/j.msea.2019.06.018
OADOI: https://oadoi.org/10.1016/j.msea.2019.06.018
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Subjects:
Funding: The financial support of SSAB Europe Oy, The Finnish Funding Agency for Technology and Innovation (Tekes) and Jenny and Antti Wihuri foundation is gratefully acknowledged.
Copyright information: © 2019 Elsevier B.V. All rights reserved. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/.
  https://creativecommons.org/licenses/by-nc-nd/4.0/