University of Oulu

Ari Saastamoinen, Antti Kaijalainen, Jouko Heikkala, David Porter, Pasi Suikkanen, The effect of tempering temperature on microstructure, mechanical properties and bendability of direct-quenched low-alloy strip steel, Materials Science and Engineering: A, Volume 730, 2018, Pages 284-294, ISSN 0921-5093, https://doi.org/10.1016/j.msea.2018.06.014

The effect of tempering temperature on microstructure, mechanical properties and bendability of direct-quenched low-alloy strip steel

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Author: Saastamoinen, Ari1; Kaijalainen, Antti1; Heikkala, Jouko1;
Organizations: 1University of Oulu, Centre for Advanced Steels Research, PL 8000, 90014 Oulu, Finland
2SSAB Europe Oy, Rautaruukintie 155, 92100 Raahe, Finland
Format: article
Version: accepted version
Access: embargoed
Persistent link: http://urn.fi/urn:nbn:fi-fe201903067353
Language: English
Published: Elsevier, 2018
Publish Date: 2020-06-05
Description:

Abstract

The tempering of re-austenized, quenched and tempered (RAQT) martensitic steels is an extensively studied and well understood field of metallurgy. However, a similar understanding of the effect of tempering on direct-quenched (DQ) high-strength steels has been lacking. Now, for the first time, the effect of tempering in the range of 250–650 °C on the strength, toughness, bendability, microstructure, crystallography and dislocation density of a DQ steel is reported. In the case of tempering at 570 °C, the effects of having a RAQ or DQ starting condition are compared. For the composition and thermal cycles studied, it was found that a peak tempering temperature in the range of 570–600 °C resulted in a DQT steel with an optimal balance of strength, bendability and toughness, i.e. a yield strength greater than 960 MPa, a minimum usable bending radius of 2 times the sheet thickness and T28J of − 50 to − 75 °C depending on the test direction. Crystallographic texture, dislocation density and the distribution of carbides are important factors affecting the bendability of DQT strip. Tempering had no effect on texture, but strongly influenced the size and distribution of carbides thereby resulting in differences in bendability and impact toughness transition temperature.

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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: 730
Pages: 284 - 294
DOI: 10.1016/j.msea.2018.06.014
OADOI: https://oadoi.org/10.1016/j.msea.2018.06.014
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Subjects:
Funding: The financial support of SSAB Europe Oy and The Finnish Funding Agency for Technology and Innovation (Tekes) is gratefully acknowledged (Grant no. 2137/31/2013).
Copyright information: © 2018. 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/