Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Imperfections in narrow gap multi-layer welding: Potential causes and countermeasures
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.ORCID iD: 0000-0003-2596-5303
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.ORCID iD: 0000-0002-3569-6795
2020 (English)In: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 129, article id 106011Article in journal (Refereed) Published
Abstract [en]

Narrow Gap Multi-Layer Welding (NGMLW) using a laser as the main heat source and metal wire for material addition has been a growing topic of interest in the last decade. This is in part due to its potential for joining much thicker sheets of steel than what is usually considered possible when using autogenous laser welding. The process has shown great potential but improvements can still be made, e.g. through increased process control to decrease welding imperfections. Using closed-loop control, where the process is continuously monitored and regulated automatically, can help to account for variations during manufacturing. However, achieving functional closed loop control can be challenging due to limitations in data gathering and processing speeds. Important initial steps include identifying what data can be useful and how frequently this data has to be recorded. Too much data takes too long to process while too little causes risks of missing important details. In this study, 20 mm thick X80 pipeline steel sheets are joined together using this multi-layer approach; the samples are examined using 3D scanning and Computed Tomography (CT) analysis and the process is observed using High-Speed Imaging (HSI). The quality of the welded joint and welding imperfections are discussed and potential points of formation are identified. Suggestions on how to mitigate imperfections to improve the quality of the welded joint are presented, including the potential to use camera imaging for closed-loop process control and additional industrial uses of the HSI footage.

Place, publisher, year, edition, pages
Elsevier, 2020. Vol. 129, article id 106011
Keywords [en]
Narrow gap multi-layer welding (NGMLW), Laser welding, Narrow gap, High-speed imaging, Porosity, Cavities
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-74542DOI: 10.1016/j.optlaseng.2020.106011OAI: oai:DiVA.org:ltu-74542DiVA, id: diva2:1324812
Note

Validerad;2020;Nivå 2;2020-02-25 (alebob)

Available from: 2019-06-14 Created: 2019-06-14 Last updated: 2020-02-25Bibliographically approved
In thesis
1. Phenomena in wire based multi-layer laser welding and hybrid deposition
Open this publication in new window or tab >>Phenomena in wire based multi-layer laser welding and hybrid deposition
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Fenomen i trådbaserad, flerskiktad lasersvetsning och hybriddeposition
Abstract [en]

Several laser materials processing technologies using metal wire addition have been researched during the last decades. Especially in the field of joining, as well as in the field of Additive Manufacturing (AM), multiple major benefits have been reached, e.g. higher welding speeds and lower heat input. With laser and arc hybrid welding techniques, additional prospects become accessible. These can combine and improve both deep penetration of autogenous laser welding and gap bridging capabilities of traditional arc welding. In the field of AM, wire feed has been a much-appreciated way of supplying additional material. Reasons include clean and easy handling, high utilisation and availability. A high intensity heat source, e.g. a laser beam or an electrical arc, continuously melts a metal wire; the melt being deposited onto a substrate in one or multiple layers to generate a new surface or three dimensional structure. An alternative joining process is Narrow Gap Multi-Layer Welding (NGMLW). This technique utilises the former mentioned AM processes to fill a gap to join sheets together, instead of depositing on an open surface. NGMLW is a capable competitor to the above-mentioned joining processes due to its prospects of being able to join essentially any thickness of sheets, as long as the beam and wire can accurately reach the gap floor and a sufficient number of layers are used.

In this thesis, multiple types of NGMLW, Papers A – D, and hybrid material deposition, Papers E and F, using laser and hybrid heat sources with metal wire addition have been studied. Techniques such as High-Speed Imaging (HSI), 3D and Computed Tomography (CT) scanning have been used to gain greater insight into the workings of these modern manufacturing processes. The multi-layered way of material deposition within a gap to form a welded joint and onto a surface for AM have many similarities, e.g. wire melting behaviour and melt flow.

Paper A introduces the workings of NGMLW, highlighting possible welding imperfections and welded joint morphology. HSI of the process is analysed both qualitatively and quantitatively: qualitative analysis identifying possible causes for said imperfections; quantitative analysis highlighting the potential for using similar and lower frame rate camera footage for closed loop control to suppress the formation of such imperfections.

In Paper B, an alternative near-vertical building strategy for NGMLW is presented and compared to its more common horizontal counterpart. This upright strategy is found to be fully capable of producing sound welded joints, sporting less than 0.3% cavities. The near-vertical welded joints also have potential for unique material properties due to their much different thermal history.

Papers C and D return to the topic of horizontal NGMLW, but with resistance heating of the metal wire for easier processing, also referred to as Laser Hot-Wire Welding (LHWW). Process behaviour and the resulting morphology of welded joints are the main topics of Paper C. Theoretical reasoning for the formation of occasional centre-line cracks, relating to the shape of the melt pool during solidification, are presented. Arcing is observed in some of the experiments, although prior theory indicates that the applied wire voltage was too low for arcing to occur. This arcing phenomenon is further covered in Paper D, where HSI observations are used to correlate process parameters to arcing probability and a theoretical explanation of why arcing can occur is suggested.

Papers E and F take the step out of the gap, studying the impact of laser beam augmentation in different orientations on Wire-Arc Additive Manufacturing (WAAM). Paper E focuses on a method of quantifying melt pool movement. Fluctuations of the melt pool surface decreased by more than 35% with the introduction of a laser beam to the process. Paper F analyses the generated structures, evaluating the usable portion of the “as deposited” shapes and material composition. Surface irregularities decreased by more than 50% on application of a trailing laser beam. Additional aspects relating to the resulting morphology are also presented, including observations and reasoning for surface irregularities and sloping.

The knowledge gained and methods used in the presented work intertwine to form a strong insight into both laser and laser-hybrid materials processing with wire addition. They also introduce approaches for processing and quantifying HSI footage for process evaluation and improvement.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2019
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-74543 (URN)978-91-7790-407-6 (ISBN)978-91-7790-408-3 (ISBN)
Public defence
2019-10-23, E632, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2019-06-19 Created: 2019-06-14 Last updated: 2019-10-01Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full text

Authority records BETA

Näsström, JonasBrueckner, FrankKaplan, Alexander F.H.

Search in DiVA

By author/editor
Näsström, JonasBrueckner, FrankKaplan, Alexander F.H.
By organisation
Product and Production Development
In the same journal
Optics and lasers in engineering
Manufacturing, Surface and Joining Technology

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 10 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf