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Influence of oxides on cold lap formation in tandem GMAW
University West, Department of Engineering Science, Division of Mechanical Engineering. (PTW)
University West, Department of Engineering Science, Division of Mechanical Engineering. (PTW)ORCID iD: 0000-0003-2560-0531
University West, Department of Engineering Science, Division of Mechanical Engineering. (PTW)ORCID iD: 0000-0002-9578-4076
2012 (English)In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, ISSN 1362-1718, Vol. 17, no 8, 643-648 p.Article in journal (Refereed) Published
Abstract [en]

The connection between the formation of cold laps and the presence of Mn‐Si oxides was studied. The underlying purpose is to understand the fundamental mechanisms of cold lap formation and to avoid it. Tandem gas metal arc welding (GMAW) was used to produce welded specimens in two different shielding gases (pure Ar and pure CO2) with base metal S355 MC (EN-10149-2) and wire G3Si1 (EN ISO 14341-A). Cross-sections of welds in the cold lap location were evaluated by light optical microscopy and scanning electron microscopy combined with energy dispersive spectroscopy. The results showed that the Mn‐Si oxides significantly enhanced cold laps formation, especially the overlap type cold lap formation. The Mn‐Si oxides originated from oxidation of the droplets. These oxides transfers to the surface of the weld pool at the weld toe, where they contributed to the formation of the cold laps.

Place, publisher, year, edition, pages
2012. Vol. 17, no 8, 643-648 p.
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
URN: urn:nbn:se:hv:diva-3826DOI: 10.1179/1362171812Y.0000000057ISI: 000309661300006Scopus ID: 2-s2.0-84867507729OAI: oai:DiVA.org:hv-3826DiVA: diva2:452599
Available from: 2011-10-31 Created: 2011-10-31 Last updated: 2016-02-11Bibliographically approved
In thesis
1. Experimental study on cold lap formation in tandem gas metal arc welding
Open this publication in new window or tab >>Experimental study on cold lap formation in tandem gas metal arc welding
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Göteborg: Chalmers, 2011. 87 p.
Series
Technical report / Department of Materials and Manufacturing Technology, Chalmers University of Technology, ISSN 1652-8891 ; 69/2011
Keyword
GMAW, Cold lap, oxide, Tandem arc welding
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-3828 (URN)
Presentation
2011-09-09, Lecture Room MB, Chalmers University of Technology, Göteborg, 10:00 (English)
Opponent
Supervisors
Projects
KOST/LOST project and WIQ project
Available from: 2011-10-31 Created: 2011-10-31 Last updated: 2011-10-31Bibliographically approved
2. Cold lap formation in Gas Metal Arc Welding of steel: An experimental study of micro-lack of fusion defects
Open this publication in new window or tab >>Cold lap formation in Gas Metal Arc Welding of steel: An experimental study of micro-lack of fusion defects
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cold laps are defined as micro-lack of fusion defects at the weld toe more or less parallel to the surface of the parent plate. These defects are known to negatively influence the fatigue properties of weldments. Previous studies suggest that cold lap formation can not be avoided completely in Gas Metal Arc Welding (GMAW). Therefore, a better understanding of formation mechanisms is imperative to be able to minimize the number and size of these defects. The main objective of this work has been to provide a more comprehensive understanding of cold laps, including categorising, characterisation and defining the most significant factors for formation. GMAW was used to produce welds that were investigated by metallographic methods using light optical microscopy, scanning electron microscopy and energy dispersive spectrometry. A novel classification of cold laps was introduced and three types of cold laps were identified: spatter cold laps, overlap cold laps and spatter-overlap cold laps. It was shown that cold laps are partially or fully filled by oxides. The most common oxides are manganese silicon oxides which were concluded to be formed primarily by oxidation of droplets. The presence of oxides was found to significantly increase the tendency to form spatter cold laps as well as overlap cold laps. Particularly for overlap cold laps, it was found that the depth (in transverse direction of weld) is reduced when welding in a non-oxidising environment. Welding on blasted surfaces increased the cold lap formation by entrapment of gas. The droplet and base metal temperatures were also found to be significant factors in cold lap formation. For overlap cold laps the occurrence frequency decreased with increased preheating temperature of the base metal. Mechanisms of overflowing resulting in overlap cold laps were discussed based on an extensive literature review. Several phenomena are believed to contribute to overflow including Rayleigh instability, the balance of forces, transfer of lateral momentum by droplets and an outward Marangoni fluid flow of the weld pool.

The present studies suggest that cold lap formation can be suppressed by ensuring that the welding process (arc) is as stable as possible and by welding on a preheated work piece in a non-oxidising environment.

Place, publisher, year, edition, pages
Trollhättan: University West, 2013. 54 p.
Series
PhD Thesis: University West, 2
Keyword
Tandem GMAW, old laps, lack of fusion, Spatter, Overlap, Overflow, Manganese, Silicon, Oxides, Temperature
National Category
Mechanical Engineering
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-5596 (URN)978-91-977943-6-7 (ISBN)978-91-977943-5-0 (ISBN)
Public defence
2013-09-24, C118, Högskolan Väst/University West, Trollhättan, 11:10 (English)
Opponent
Supervisors
Available from: 2013-09-17 Created: 2013-09-17 Last updated: 2015-10-02Bibliographically approved

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Publisher's full textScopushttp://dx.doi.org/10.1179/1362171812Y.0000000057

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