The effect of tempering on the microstructure and mechanical properties of a novel 0.4C press-hardening steel |
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Author: | Haiko, Oskari1; Kaijalainen, Antti1; Pallaspuro, Sakari1; |
Organizations: |
1Materials and Mechanical Engineering, Centre for Advanced Steels Research, University of Oulu,90014 Oulu, Finland 2Raahe Works, SSAB Europe, 92100 Raahe, Finland |
Format: | article |
Version: | published version |
Access: | open |
Online Access: | PDF Full Text (PDF, 4.5 MB) |
Persistent link: | http://urn.fi/urn:nbn:fi-fe2019102134062 |
Language: | English |
Published: |
Multidisciplinary Digital Publishing Institute,
2019
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Publish Date: | 2019-10-21 |
Description: |
AbstractIn this paper, the effects of different tempering temperatures on a recently developed ultrahigh-strength steel with 0.4 wt.% carbon content were studied. The steel is designed to be used in press-hardening for different wear applications, which require high surface hardness (650 HV/58 HRC). Hot-rolled steel sheet from a hot strip mill was austenitized, water quenched and subjected to 2-h tempering at different temperatures ranging from 150 °C to 400 °C. Mechanical properties, microstructure, dislocation densities, and fracture surfaces of the steels were characterized. Tensile strength greater than 2200 MPa and hardness above 650 HV/58 HRC were measured for the as-quenched variant. Tempering decreased the tensile strength and hardness, but yield strength increased with low-temperature tempering (150 °C and 200 °C). Charpy-V impact toughness improved with low-temperature tempering, but tempered martensite embrittlement at 300 °C and 400 °C decreased the impact toughness at −40 °C. Dislocation densities as estimated using X-ray diffraction showed a linear decrease with increasing tempering temperature. Retained austenite was present in the water quenched and low-temperature tempered samples, but no retained austenite was found in samples subjected to tempering at 300 °C or higher. The substantial changes in the microstructure of the steels caused by the tempering are discussed. see all
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Series: |
Applied sciences |
ISSN: | 2076-3417 |
ISSN-E: | 2076-3417 |
ISSN-L: | 2076-3417 |
Volume: | 9 |
Issue: | 20 |
Article number: | 4231 |
DOI: | 10.3390/app9204231 |
OADOI: | https://oadoi.org/10.3390/app9204231 |
Type of Publication: |
A1 Journal article – refereed |
Field of Science: |
216 Materials engineering |
Subjects: | |
Funding: |
This research has been done within the program Steel Ecosystem for Focused Applications (StEFA). We gratefully acknowledge financial support from Business Finland and the companies participating in the program. |
Copyright information: |
© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). |
https://creativecommons.org/licenses/by/4.0/ |