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Cold laps - micro-lack of fusion defects in steel arc welds: a review
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik.
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik. (PTW)ORCID-id: 0000-0003-2560-0531
Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för maskinteknik. (PTW)ORCID-id: 0000-0002-9578-4076
Högskolan Väst, Institutionen för ingenjörsvetenskap.ORCID-id: 0000-0001-8822-2705
(engelsk)Manuskript (preprint) (Annet vitenskapelig)
Emneord [en]
Review, cold lap, micro defect, lack of fusion, oxides, formation, NDT, magnetic field, weld pool, arc, welding
HSV kategori
Forskningsprogram
TEKNIK, Produktions- och materialteknik
Identifikatorer
URN: urn:nbn:se:hv:diva-5613OAI: oai:DiVA.org:hv-5613DiVA, id: diva2:651268
Tilgjengelig fra: 2013-09-25 Laget: 2013-09-25 Sist oppdatert: 2016-02-11bibliografisk kontrollert
Inngår i avhandling
1. Cold lap formation in Gas Metal Arc Welding of steel: An experimental study of micro-lack of fusion defects
Åpne denne publikasjonen i ny fane eller vindu >>Cold lap formation in Gas Metal Arc Welding of steel: An experimental study of micro-lack of fusion defects
2013 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
Trollhättan: University West, 2013. s. 54
Serie
PhD Thesis: University West ; 2
Emneord
Tandem GMAW, old laps, lack of fusion, Spatter, Overlap, Overflow, Manganese, Silicon, Oxides, Temperature
HSV kategori
Forskningsprogram
TEKNIK, Produktions- och materialteknik
Identifikatorer
urn:nbn:se:hv:diva-5596 (URN)978-91-977943-6-7 (ISBN)978-91-977943-5-0 (ISBN)
Disputas
2013-09-24, C118, Högskolan Väst/University West, Trollhättan, 11:10 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2013-09-17 Laget: 2013-09-17 Sist oppdatert: 2015-10-02bibliografisk kontrollert

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