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Effect of Laser Welding Parameters on Porosity of Weldsin Cast Magnesium Alloy AM50
University West, Department of Engineering Science, Research Enviroment Production Technology West. Swerea KIMAB, Kista, University West, Sweden. (PTW)ORCID iD: 0000-0001-8933-6720
The Welding Institute, Great Britain.
University West, Department of Engineering Science, Division of Welding Technology. (PTW)ORCID iD: 0000-0001-8822-2705
University West, Department of Engineering Science, Division of Welding Technology. (PTW)ORCID iD: 0000-0003-2560-0531
2018 (English)In: Modern Approaches on Material Science, ISSN 2641-6921, Vol. 1, no 2, p. 25-32Article in journal (Refereed) Published
Abstract [en]

Pores in the weld metal lower the mechanical properties of the weld. It is therefore important to understand the pore formation mechanisms and find procedures that could reduce porosity. This study focused on laser welding of 3 mm thick magnesium alloy AM50, investigating how different parameters affect porosity formation. Low levels of porosity content were achieved by either increasing the welding speed or using a two-pass welding approach. It was found that higher welding speeds did not allow pores,which were pre-existing from the die-casting process, to have sufficient time to coalesce and expand. In the two-pass welding technique, pores were removed as a result of a degassing process which occurred through the second pass.

Place, publisher, year, edition, pages
2018. Vol. 1, no 2, p. 25-32
Keywords [en]
Laser welding; Magnesium, Cast; Metallurgy; Porosity; Automotive; AM50
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
URN: urn:nbn:se:hv:diva-13754DOI: 10.32474/MAMS.2018.01.000106OAI: oai:DiVA.org:hv-13754DiVA, id: diva2:1301261
Available from: 2019-04-01 Created: 2019-04-01 Last updated: 2019-04-01Bibliographically approved
In thesis
1. Laser welding of ultra-high strength steel and a cast magnesium alloy for light-weight design
Open this publication in new window or tab >>Laser welding of ultra-high strength steel and a cast magnesium alloy for light-weight design
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There is a strong industrial need for developing robust and flexible manufacturing methods for future light-weight design. Better performing, environmental friendly vehicles will gain competitive strength from using light weight structures. In this study, focus has been on laser welding induced distortions for ultra-high strength steel (UHSS) where trials were performed on single hat and double hat beams simulating A-pillar and B-pillar structures. Furthermore, also laser welding induced porosity in cast magnesium alloy AM50 for interior parts were studied. For UHSS, conventional laser welding was done in a fixture designed for research. For cast magnesium, single-spot and twin-spot welding were done. Measurements of final distortions and metallographic investigations have been performed. The results show that the total weld metal volume or the total energy input were good measures for predicting the distortions within one steel grade. For comparing different steel grades, the width of the hard zone should be used. The relation between the width of the hard zone, corresponding to the martensitic area of the weld, and the distortions is almost linear. Additionally, compared with continuous welds, stitching reduced the distortions. For cast magnesium, two-pass (repeated parameters) welding with single-spot gave the lowest porosity of approximately 3%. However, two-pass welding is not considered production friendly. Twin-spot welding was done, where the first beam provided time for nucleation and some growth of pores while reheating by the second beam should provide time for pores to grow and escape. This gave a porosity of around 5%. Distortions and porosity are the main quality problems that occur while laser welding UHSS and cast magnesium, respectively. Low energy input seems to generally minimize quality issues. Laser welding shows high potential regarding weld quality and other general aspects such as productivity in light-weight design for both high strength steel and cast magnesium.

Place, publisher, year, edition, pages
Trollhättan: University West, 2019. p. 94
Series
PhD Thesis: University West ; 29
Keywords
Laser welding, ultra-high strength steel, cast magnesium alloy, light-weight design, automotive industry, distortion, porosity
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-13752 (URN)978-91-88847-29-4 (ISBN)978-91-88847-28-7 (ISBN)
Public defence
2019-04-24, F131, Trollhättan, 10:00 (English)
Opponent
Supervisors
Available from: 2019-04-02 Created: 2019-04-01 Last updated: 2019-04-01Bibliographically approved

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Fahlström, KarlKarlsson, LeifSvensson, Lars-Erik

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