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The joining of advanced high strength steels using resistance spot welding. / Christopher Carl Edward Miller

Swansea University Author: Christopher Carl Edward Miller

Abstract

Weight reduction of the automotive body-in-white structure is increasingly necessary to improve fuel efficiency and reduce the carbon emissions and environmental impact of motor vehicles. This must be achieved without compromising the strength of the body-in-white structure. Steel manufacturers are...

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Published: 2008
Institution: Swansea University
Degree level: Doctoral
URI: https://cronfa.swan.ac.uk/Record/cronfa42252
first_indexed 2018-08-02T18:54:15Z
last_indexed 2018-08-03T10:09:39Z
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recordtype RisThesis
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spelling 2018-08-02T16:24:28.5733830 v2 42252 2018-08-02 The joining of advanced high strength steels using resistance spot welding. 3bcb91b45372b75ee6ccf8709ac41d2f NULL Christopher Carl Edward Miller Christopher Carl Edward Miller true true 2018-08-02 Weight reduction of the automotive body-in-white structure is increasingly necessary to improve fuel efficiency and reduce the carbon emissions and environmental impact of motor vehicles. This must be achieved without compromising the strength of the body-in-white structure. Steel manufacturers are continuing to develop advanced high strength steels (AHSS) which not only exhibit high strength and excellent energy absorbing characteristics but also retain a comparable degree of formability to low alloy grades. The specific properties of advanced high strength steels such as dual phase and TRIP are derived via the addition of specific alloying elements and careful control of thermomechanical processing routes in order to develop the required microstructures in the final product. The utilisation of such grades could yield significant reductions in the weight of body-in-white structures since they offer the automotive design engineer the opportunity to fabricate components out of thinner sheet whilst retaining or even improving on the structural strength and impact performance of components fabricated from thicker mild steel sheets. A major barrier to the widespread acceptance and implementation of AHSS by the automotive industry is the perceived complexities associated with the joining of these materials using resistance spot welding, which remains the dominant joining process in modem automobile construction. The complex alloy chemistries of these grades coupled with the extremely high cooling rates generated by the resistance welding process can give rise to weld microstructures with properties differing greatly from the parent microstructure. Of particular concern for automotive manufacturers is the potential for the formation of martensite in the weld nugget and heat affected zones, since its high hardness and low ductility are thought to result in poor weld performance. This research programme has investigated the weldability of six AHSS grades in comparison to low alloy grades typical of those currently used in the automotive industry, using a basic single pulse weld schedule. Simple modifications to welding parameters such as increasing electrode force and electrode tip diameter were investigated as well as the effects of advanced weld schedules on weld microstructures, microhardness and strength. The effect of joining selected advanced high strength steels to low carbon mild steel has also been studied. E-Thesis Materials science. 31 12 2008 2008-12-31 COLLEGE NANME Engineering COLLEGE CODE Swansea University Doctoral 2018-08-02T16:24:28.5733830 2018-08-02T16:24:28.5733830 Faculty of Science and Engineering School of Engineering and Applied Sciences - Uncategorised Christopher Carl Edward Miller NULL 1 0042252-02082018162439.pdf 10797960.pdf 2018-08-02T16:24:39.9300000 Output 30309708 application/pdf E-Thesis true 2018-08-02T16:24:39.9300000 false
title The joining of advanced high strength steels using resistance spot welding.
spellingShingle The joining of advanced high strength steels using resistance spot welding.
Christopher Carl Edward Miller
title_short The joining of advanced high strength steels using resistance spot welding.
title_full The joining of advanced high strength steels using resistance spot welding.
title_fullStr The joining of advanced high strength steels using resistance spot welding.
title_full_unstemmed The joining of advanced high strength steels using resistance spot welding.
title_sort The joining of advanced high strength steels using resistance spot welding.
author_id_str_mv 3bcb91b45372b75ee6ccf8709ac41d2f
author_id_fullname_str_mv 3bcb91b45372b75ee6ccf8709ac41d2f_***_Christopher Carl Edward Miller
author Christopher Carl Edward Miller
author2 Christopher Carl Edward Miller
format E-Thesis
publishDate 2008
institution Swansea University
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 - Uncategorised{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Engineering and Applied Sciences - Uncategorised
document_store_str 1
active_str 0
description Weight reduction of the automotive body-in-white structure is increasingly necessary to improve fuel efficiency and reduce the carbon emissions and environmental impact of motor vehicles. This must be achieved without compromising the strength of the body-in-white structure. Steel manufacturers are continuing to develop advanced high strength steels (AHSS) which not only exhibit high strength and excellent energy absorbing characteristics but also retain a comparable degree of formability to low alloy grades. The specific properties of advanced high strength steels such as dual phase and TRIP are derived via the addition of specific alloying elements and careful control of thermomechanical processing routes in order to develop the required microstructures in the final product. The utilisation of such grades could yield significant reductions in the weight of body-in-white structures since they offer the automotive design engineer the opportunity to fabricate components out of thinner sheet whilst retaining or even improving on the structural strength and impact performance of components fabricated from thicker mild steel sheets. A major barrier to the widespread acceptance and implementation of AHSS by the automotive industry is the perceived complexities associated with the joining of these materials using resistance spot welding, which remains the dominant joining process in modem automobile construction. The complex alloy chemistries of these grades coupled with the extremely high cooling rates generated by the resistance welding process can give rise to weld microstructures with properties differing greatly from the parent microstructure. Of particular concern for automotive manufacturers is the potential for the formation of martensite in the weld nugget and heat affected zones, since its high hardness and low ductility are thought to result in poor weld performance. This research programme has investigated the weldability of six AHSS grades in comparison to low alloy grades typical of those currently used in the automotive industry, using a basic single pulse weld schedule. Simple modifications to welding parameters such as increasing electrode force and electrode tip diameter were investigated as well as the effects of advanced weld schedules on weld microstructures, microhardness and strength. The effect of joining selected advanced high strength steels to low carbon mild steel has also been studied.
published_date 2008-12-31T01:40:29Z
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score 11.04748

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