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TRIP assisted press hardened steel by the anisothermal bainitic ferrite transformation

T. Taylor, K. Kim, J. Zhang, David Penney Orcid Logo, J. Yanagimoto

Journal of Materials Processing Technology, Volume: 289, Start page: 116950

Swansea University Author: David Penney Orcid Logo

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Abstract

A new steel chemical composition is combined with a new press hardening process, in which die-quenching is interrupted by opening the forming tool to permit slow cooling of the hot formed part through the anisothermal bainitic ferrite transformation. This promotes carbon partitioning to austenite be...

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Published in: Journal of Materials Processing Technology
ISSN: 0924-0136
Published: Elsevier BV 2021
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URI: https://cronfa.swan.ac.uk/Record/cronfa55601
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The final microstructure is predominantly bainitic ferrite with dispersions of martensite and up to 11 % retained austenite. Retained austenite can undergo stress induced transformation to martensite in an automobile crash event. The steel exhibits up to 25 % elongation and 930 MPa tensile strength. In contrast to traditional cold formable Transformation Induced Plasticity assisted steels, where retained austenite is consumed during work hardening of cold forming, here, the desired microstructure is achieved after hot forming meaning the retained austenite is more uniformly distributed within the formed part, which enhances energy absorption. The new steel chemical composition is carefully designed to provide optimal microstructural evolution within the constraints of the new press hardening process, yet relatively lean and manufacturer friendly. The new press hardening process is energy efficient as secondary heating is not required since retarded cooling through the bainitic ferrite transformation is provided by residual heat accumulation of the newly developed titanium alloy forming tool. Development of the new technology is demonstrated by press hardening experiments, tensile testing, microstructural analysis, transversal &amp; axial crush testing of formed parts and numerical simulation of crush testing, including a new modelling technique that more accurately simulates deformation of hot versus cold formed parts. 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spelling 2022-08-15T15:11:41.1498060 v2 55601 2020-11-05 TRIP assisted press hardened steel by the anisothermal bainitic ferrite transformation 869becc35438853f2bca0044df467631 0000-0002-8942-8067 David Penney David Penney true false 2020-11-05 MTLS A new steel chemical composition is combined with a new press hardening process, in which die-quenching is interrupted by opening the forming tool to permit slow cooling of the hot formed part through the anisothermal bainitic ferrite transformation. This promotes carbon partitioning to austenite before the forming tool is re-closed and die-quenching is resumed to near-ambient temperature. The final microstructure is predominantly bainitic ferrite with dispersions of martensite and up to 11 % retained austenite. Retained austenite can undergo stress induced transformation to martensite in an automobile crash event. The steel exhibits up to 25 % elongation and 930 MPa tensile strength. In contrast to traditional cold formable Transformation Induced Plasticity assisted steels, where retained austenite is consumed during work hardening of cold forming, here, the desired microstructure is achieved after hot forming meaning the retained austenite is more uniformly distributed within the formed part, which enhances energy absorption. The new steel chemical composition is carefully designed to provide optimal microstructural evolution within the constraints of the new press hardening process, yet relatively lean and manufacturer friendly. The new press hardening process is energy efficient as secondary heating is not required since retarded cooling through the bainitic ferrite transformation is provided by residual heat accumulation of the newly developed titanium alloy forming tool. Development of the new technology is demonstrated by press hardening experiments, tensile testing, microstructural analysis, transversal & axial crush testing of formed parts and numerical simulation of crush testing, including a new modelling technique that more accurately simulates deformation of hot versus cold formed parts. Results show a 22 % increase to energy absorption under axial crushing compared to traditional cold formed Transformation Induced Plasticity assisted steels owing to greater work hardening capacity in formed radii of the part, which are shown to be exposed to the highest stresses during crushing. Journal Article Journal of Materials Processing Technology 289 116950 Elsevier BV 0924-0136 Retained austenite, Stress induced transformation, Electron back scattered diffraction, Hot stamping, Crush testing, Numerical simulation 1 3 2021 2021-03-01 10.1016/j.jmatprotec.2020.116950 COLLEGE NANME Materials Science and Engineering COLLEGE CODE MTLS Swansea University Japan Society for the Promotion of Science (JSPS). 2022-08-15T15:11:41.1498060 2020-11-05T13:20:08.9469047 Faculty of Science and Engineering School of Engineering and Applied Sciences - Materials Science and Engineering T. Taylor 1 K. Kim 2 J. Zhang 3 David Penney 0000-0002-8942-8067 4 J. Yanagimoto 5 55601__18615__998d723978fe4c3d9291506a7f9ae1ab.pdf 55601.pdf 2020-11-09T12:26:17.5041764 Output 4408224 application/pdf Accepted Manuscript true 2022-10-22T00:00:00.0000000 © 2020. This manuscript version is made available under the CC-BY-NC-ND 4.0 license true eng http://creativecommons.org/licenses/by-nc-nd/4.0/
title TRIP assisted press hardened steel by the anisothermal bainitic ferrite transformation
spellingShingle TRIP assisted press hardened steel by the anisothermal bainitic ferrite transformation
David Penney
title_short TRIP assisted press hardened steel by the anisothermal bainitic ferrite transformation
title_full TRIP assisted press hardened steel by the anisothermal bainitic ferrite transformation
title_fullStr TRIP assisted press hardened steel by the anisothermal bainitic ferrite transformation
title_full_unstemmed TRIP assisted press hardened steel by the anisothermal bainitic ferrite transformation
title_sort TRIP assisted press hardened steel by the anisothermal bainitic ferrite transformation
author_id_str_mv 869becc35438853f2bca0044df467631
author_id_fullname_str_mv 869becc35438853f2bca0044df467631_***_David Penney
author David Penney
author2 T. Taylor
K. Kim
J. Zhang
David Penney
J. Yanagimoto
format Journal article
container_title Journal of Materials Processing Technology
container_volume 289
container_start_page 116950
publishDate 2021
institution Swansea University
issn 0924-0136
doi_str_mv 10.1016/j.jmatprotec.2020.116950
publisher Elsevier BV
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Engineering and Applied Sciences - Materials Science and Engineering{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Engineering and Applied Sciences - Materials Science and Engineering
document_store_str 1
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description A new steel chemical composition is combined with a new press hardening process, in which die-quenching is interrupted by opening the forming tool to permit slow cooling of the hot formed part through the anisothermal bainitic ferrite transformation. This promotes carbon partitioning to austenite before the forming tool is re-closed and die-quenching is resumed to near-ambient temperature. The final microstructure is predominantly bainitic ferrite with dispersions of martensite and up to 11 % retained austenite. Retained austenite can undergo stress induced transformation to martensite in an automobile crash event. The steel exhibits up to 25 % elongation and 930 MPa tensile strength. In contrast to traditional cold formable Transformation Induced Plasticity assisted steels, where retained austenite is consumed during work hardening of cold forming, here, the desired microstructure is achieved after hot forming meaning the retained austenite is more uniformly distributed within the formed part, which enhances energy absorption. The new steel chemical composition is carefully designed to provide optimal microstructural evolution within the constraints of the new press hardening process, yet relatively lean and manufacturer friendly. The new press hardening process is energy efficient as secondary heating is not required since retarded cooling through the bainitic ferrite transformation is provided by residual heat accumulation of the newly developed titanium alloy forming tool. Development of the new technology is demonstrated by press hardening experiments, tensile testing, microstructural analysis, transversal & axial crush testing of formed parts and numerical simulation of crush testing, including a new modelling technique that more accurately simulates deformation of hot versus cold formed parts. Results show a 22 % increase to energy absorption under axial crushing compared to traditional cold formed Transformation Induced Plasticity assisted steels owing to greater work hardening capacity in formed radii of the part, which are shown to be exposed to the highest stresses during crushing.
published_date 2021-03-01T04:09:56Z
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