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Factors influencing fusion of spatter to the base metal during tandem GMAW
University West, Department of Engineering Science. (PTW)
University West, Department of Engineering Science, Division of Production Engineering. (PTW)ORCID iD: 0000-0003-2560-0531
University West, Department of Engineering Science, Division of Production Engineering. (PTW)ORCID iD: 0000-0002-9578-4076
2012 (English)In: Proceedings of The 5th International Swedish Production Symposium: 6th-8th of November 2012 Linköping, Sweden / [ed] Mats Björkman, Linköping, Sweden, 2012, p. 233-239Conference paper, Oral presentation only (Refereed)
Abstract [en]

Tandem gas metal arc welding (tandem GMAW) is, as a high productivity welding method of manufacturing process, utilized broadly in modern Swedish industry. Spatter is more or less an inevitable flaw in GMAW, especially for the high efficiency processes. Recently, spatter was found as a potential source of cold laps, which negatively influences fatigue life. The main objectives of this paper are to investigate the spatter/base metal interface and identify the primary factors for formation of cold laps.

Tandem GMAW was performed in a sealed chamber filled with either pure argon or pure dioxide. Cross sections of spatter and base metal were prepared and evaluated by Light optical microscopy and Scanning Electron Microscopy (SEM) with an attached Energy Dispersive Spectroscope (EDS).

Mn-Si oxides were found to enhance the lack of fusion occurrence in the spatter/base metal. The oxide of Mn and Si mostly came from oxidation of the droplets in the welding process. Spatter diameter and spatter distance was evaluated with respect to lack of fusion in spatter/base metal interface for welds using pure Ar shielding gas. From this it was concluded that temperature is another important factor for lack of fusion formation in the spatter/base metal interface.

Place, publisher, year, edition, pages
Linköping, Sweden, 2012. p. 233-239
Keyword [en]
tandem GMAW, cold lap, spatter, lack of fusion, SEM, EDS, oxide
National Category
Engineering and Technology Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
URN: urn:nbn:se:hv:diva-4664ISBN: 978-91-7519-752-4 (print)OAI: oai:DiVA.org:hv-4664DiVA, id: diva2:556197
Conference
5th International Swedish Production Symposium, SPS12
Available from: 2012-09-24 Created: 2012-09-24 Last updated: 2016-02-11Bibliographically approved
In thesis
1. 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. p. 54
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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Svensson, Lars-ErikMarkocsan, Nicolaie

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