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Influence of preheating temperature on cold lap formation in tandem GMAW
University West, Department of Engineering Science, Research Enviroment Production Technology West. (PTW)
University West, Department of Engineering Science, Division of Manufacturing Processes. (PTW)ORCID iD: 0000-0003-2560-0531
University West, Department of Engineering Science, Division of Manufacturing Processes. (PTW)ORCID iD: 0000-0002-9578-4076
2013 (English)Conference paper, Published paper (Refereed)
Abstract [en]

A cold lap is defined as a type of micro-lack of fusion in ISO standard (ISO 6520-1:2007) and have been found to influence fatigue properties of welds significantly. In the present study, the main purpose was to investigate the influence of preheating temperature on cold lap formation in tandem GMAW, both with respect to dimensions and occurrence probabilities.

Three different preheating temperatures were applied and cross-sections of welds were evaluated by light optical microscopy. The results showed that the cold lap occurrence frequency is a function of base metal temperature. However, the base metal temperature does not have a significant influence on cold lap depth.

Place, publisher, year, edition, pages
JOM-Institute , 2013.
Keywords [en]
Cold lap, GMAW, temperature, overflow, formation, overlap, lack of fusion, Work-integrated learning, WIL
Keywords [sv]
AIL
National Category
Manufacturing, Surface and Joining Technology
Research subject
Work Integrated Learning; ENGINEERING, Manufacturing and materials engineering
Identifiers
URN: urn:nbn:se:hv:diva-5561ISBN: 87-89582-21-7 (print)OAI: oai:DiVA.org:hv-5561DiVA, id: diva2:637989
Conference
JOM-17 - International Conference on Joining Materials. Helsingör, Denmark 5-8 May 2013
Projects
SUMAN SVETSAvailable from: 2013-07-24 Created: 2013-07-24 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
Keywords
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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