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Galvanised Ultra High Strength Steel for Cold Formed Automotive Body in White Applications / JAMES AYRES

Swansea University Author: JAMES AYRES

  • E-Thesis – open access under embargo until: 17th May 2026

DOI (Published version): 10.23889/SUthesis.63588

Abstract

The requirement of automotive manufacturers to downgauge material to save weight and lower vehicular emissions has led to the development of ever more complex advanced and ultra-high strength steels (AHSS/UHSS). Dual Phase (DP) steels have come to the fore in recent years due to their high strength...

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Published: Swansea, Wales, UK 2023
Institution: Swansea University
Degree level: Doctoral
Degree name: EngD
Supervisor: Penney, David., Evans, Peter. and Underhill, Richard.
URI: https://cronfa.swan.ac.uk/Record/cronfa63588
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first_indexed 2023-06-05T14:49:53Z
last_indexed 2023-06-05T14:49:53Z
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spelling v2 63588 2023-06-05 Galvanised Ultra High Strength Steel for Cold Formed Automotive Body in White Applications 38642546577d778ff5eac1cb0f5baa58 JAMES AYRES JAMES AYRES true false 2023-06-05 The requirement of automotive manufacturers to downgauge material to save weight and lower vehicular emissions has led to the development of ever more complex advanced and ultra-high strength steels (AHSS/UHSS). Dual Phase (DP) steels have come to the fore in recent years due to their high strength and initial strain hardening whilst achieving good elongation. Microstructurally these properties are achieved with a combination of a hard martensitic phase combined with a soft and ductile ferrite phase.This thesis focusses on silicon’s role on the microstructure and mechanical properties of DP steels whilst also optimizing the processing windows at Tata Steel’s continuous annealing processing line (CAPL), and the galvanising line, ZODIAC. Lab casts of DP800 steel with 0wt%, 0.2wt% and 0.4wt% silicon were cast and rolled to match industrial specifications, it was found that the increased silicon content led to a refined hot rolled microstructure with an increased volume fraction of pearlite. The finely dispersed pearlite allows for an increase in nucleation sites where it can transform to austenite during the soak section of the annealing cycle. This led to a more finely dispersed and higher volume fraction of austenite which on cooling transforms to martensite in the final product. The result was an increase in tensile strength from 790MPa to 900MPa with no marked change in elongation.Additionally, a DP cast chemistry with an increase in silicon produced and used in Tata Steel’s IJmuiden plant was trialled to achieve a viable DP1000 product through Zodiac. Whilst the grade did achieve the requirements in some trials, the variability when scaling to industrial processing would likely lead to mechanical property failures, outweighing the benefits. Trialling the same cast chemistry using optimized CAPL cycles led to the development of a novel high yield variant of DP1000, and a potential successful replacement to the current cast chemistry used to produce DP1000 at Tata Steel’s UK site. E-Thesis Swansea, Wales, UK Steel, Dual Phase, Annealing, Microstructure, Mechanical Properties 15 5 2023 2023-05-15 10.23889/SUthesis.63588 COLLEGE NANME COLLEGE CODE Swansea University Penney, David., Evans, Peter. and Underhill, Richard. Doctoral EngD M2A, WEFO, EPSRC, Tata steel 2023-09-29T10:26:15.7502029 2023-06-05T15:43:17.2710122 Faculty of Science and Engineering School of Engineering and Applied Sciences - Materials Science and Engineering JAMES AYRES 1 Under embargo Under embargo 2023-06-05T15:53:33.0014152 Output 11323390 application/pdf E-Thesis – open access true 2026-05-17T00:00:00.0000000 Copyright: The Author, James Ayres, 2023. true eng
title Galvanised Ultra High Strength Steel for Cold Formed Automotive Body in White Applications
spellingShingle Galvanised Ultra High Strength Steel for Cold Formed Automotive Body in White Applications
JAMES AYRES
title_short Galvanised Ultra High Strength Steel for Cold Formed Automotive Body in White Applications
title_full Galvanised Ultra High Strength Steel for Cold Formed Automotive Body in White Applications
title_fullStr Galvanised Ultra High Strength Steel for Cold Formed Automotive Body in White Applications
title_full_unstemmed Galvanised Ultra High Strength Steel for Cold Formed Automotive Body in White Applications
title_sort Galvanised Ultra High Strength Steel for Cold Formed Automotive Body in White Applications
author_id_str_mv 38642546577d778ff5eac1cb0f5baa58
author_id_fullname_str_mv 38642546577d778ff5eac1cb0f5baa58_***_JAMES AYRES
author JAMES AYRES
author2 JAMES AYRES
format E-Thesis
publishDate 2023
institution Swansea University
doi_str_mv 10.23889/SUthesis.63588
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 0
active_str 0
description The requirement of automotive manufacturers to downgauge material to save weight and lower vehicular emissions has led to the development of ever more complex advanced and ultra-high strength steels (AHSS/UHSS). Dual Phase (DP) steels have come to the fore in recent years due to their high strength and initial strain hardening whilst achieving good elongation. Microstructurally these properties are achieved with a combination of a hard martensitic phase combined with a soft and ductile ferrite phase.This thesis focusses on silicon’s role on the microstructure and mechanical properties of DP steels whilst also optimizing the processing windows at Tata Steel’s continuous annealing processing line (CAPL), and the galvanising line, ZODIAC. Lab casts of DP800 steel with 0wt%, 0.2wt% and 0.4wt% silicon were cast and rolled to match industrial specifications, it was found that the increased silicon content led to a refined hot rolled microstructure with an increased volume fraction of pearlite. The finely dispersed pearlite allows for an increase in nucleation sites where it can transform to austenite during the soak section of the annealing cycle. This led to a more finely dispersed and higher volume fraction of austenite which on cooling transforms to martensite in the final product. The result was an increase in tensile strength from 790MPa to 900MPa with no marked change in elongation.Additionally, a DP cast chemistry with an increase in silicon produced and used in Tata Steel’s IJmuiden plant was trialled to achieve a viable DP1000 product through Zodiac. Whilst the grade did achieve the requirements in some trials, the variability when scaling to industrial processing would likely lead to mechanical property failures, outweighing the benefits. Trialling the same cast chemistry using optimized CAPL cycles led to the development of a novel high yield variant of DP1000, and a potential successful replacement to the current cast chemistry used to produce DP1000 at Tata Steel’s UK site.
published_date 2023-05-15T10:26:17Z
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score 11.012924

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