| 1. |
- Akselsen, Odd M., et al.
(författare)
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A first assessment of laser hybrid welding of 420 mpa steel for offshore structure application
- 2013
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Ingår i: 14th NOLAMP Conference. - Luleå : Luleå tekniska universitet. - 9789174396881 - 9789174396898 ; , s. 171-182
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- For many years, laser hybrid welding has been used in various industries to increaseproductivity and reduce costs. One example is the adaption of the hybrid process inshipbuilding. The next natural step is to further develop the process for the oil and gasindustry, where the welded joint properties requirements are more severe, and the ability tohandle tolerance deviations is more critical. As a first attempt to develop hybrid laser processfor the use in offshore structures, the present investigation addresses preliminary weldingtrails carried out with 15 kW fibre laser with appropriate gas metal arc welding equipment,using double Y joint geometry and 20 mm thick 420 MPa steel plates. The subsequent weldtesting included both Charpy V notch impact and CTOD fracture mechanical testing at -30°C.The results indicate that the heat affected zone (HAZ) of the examined steel appeared withsatisfactory Charpy and CTOD toughness (> 200 J, > 0.2 mm) while the weld metal hadinsufficient toughness (20-40 J, < 0.2 mm). With a better welding wire, designed for lowtemperature applications, it is reasonable to suggest that laser hybrid arc welding can be usedfor applications even below a temperature of -30°C.
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| 2. |
- Akselsen, Odd Magne, et al.
(författare)
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Properties of laser hybrid butt welds of 420 MPa steel
- 2013
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Ingår i: The proceedings of the Twenty-third (2013) International Offshore and Polar Engineering Conference. - Cupertino, Calif. : International Society of Offshore and Polar Engineers. - 9781880653999 ; , s. 290-294
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Konferensbidrag (refereegranskat)abstract
- Laser hybrid welding has been used in European shipbuilding for many years due to its high productivity. In order to qualify the process for the oil and gas industry, an extensive welding and testing programme is needed, and the properties must satisfy more severe requirements than in shipbuilding. This is particularly the case when these activities are moving to the Arctic regions, where low temperature toughness may be the primary challenge. The present investigation addressed preliminary welding trials carried out with 15 kW fibre laser-gas metal arc (GMA) hybrid welding using double Y joint of 20 mm thick 420 MPa steel plates. Both Charpy V notch impact and CTOD fracture mechanical testing were included with test temperature of -30°C. The results indicate that the heat affected zone (HAZ) of the examined steel appeared with satisfactory toughness (> 200 J, > 0.2 mm) while the employed weld metal had insufficient impact properties. The weld metal CTOD toughness approached 0.2 mm. With a better welding wire, designed for low temperature applications, it is reasonable to suggest that laser hybrid arc welding can be used for applications even below -30 to -40°C
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| 3. |
- Norman, Peter, et al.
(författare)
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Comparison of 22MnB5-steel with and without AlSi-coating during laser hybrid arc welding
- 2011
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Ingår i: 13th NOLAMP Conference. - Trondheim : Department of Geography, Norwegian University of Science and Technology.
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Konferensbidrag (refereegranskat)abstract
- 22MnB5/Usibor1500 is a hot-dip aluminized manganese-boron steel grade that is used withinthe car manufacturing industry and as lasers are increasingly used for welding of the car bodythe amount of research concerning laser welding of this material follows. For thicker materialthe laser hybrid arc welding process has grown to a well-known tool to increase productivity,but for thinner materials the advantages are less obvious. In the present research the melt pooland wire drop transfer was observed with a high speed camera. Differences between welding,with and without the coating were clearly visible and are described and discussed in the paper.The resulting welds were examined microscopically and chemically to unveil the compositionof the material. It is aimed to avoid possible brittle inter-metallic phases directly during theprocess, hence by skipping the usual additional manufacturing step of removing the AlSicoatingin advance.
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| 4. |
- Wiklund, Greger, et al.
(författare)
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Geometrical aspects of hot cracks in laser-arc hybrid welding
- 2014
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Ingår i: Journal of laser applications. - : Laser Institute of America. - 1042-346X .- 1938-1387. ; 26:1
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Tidskriftsartikel (refereegranskat)abstract
- Hot cracks were frequently found in double sided laser-arc hybrid welding thick section (20 mm) low carbon steel. Other research has usually investigated the metallurgical resolidification mechanisms of the welded metal alloy, but here possible relationships between the hot cracks and geometrical aspects of their surrounding weld and heat-affected zone cross sections were studied. The motivation behind this research was to identify guidelines for laser-arc hybrid welding to avoid hot cracks. Weld cross sections were used to analyze hot cracking because they are rather easy to prepare and straightforward to alter through the process parameters. In this study, hot cracks were found in a preferred geometrical window, namely, in the middle of the narrow deep region of the weld which was generated by the laser beam. From the cross section analysis, a first indicator was that a more inclined, converging shape of the lower part of the weld cross section can avoid hot cracks, associated with different energy input and resolidification front geometry. Significant reduction of the welding speed has avoided hot cracks, being a second indicator
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| 5. |
- Wiklund, Greger, et al.
(författare)
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Laser hybrid welding of alsi coated boron steel
- 2013
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Ingår i: 14th NOLAMP Conference. - Luleå : Luleå tekniska universitet. - 9789174396881 - 9789174396898 ; , s. 59-66
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Several publications in the literature are stating that welding of AlSi coated boron steelwithout any pre-treatment often results in reduced weld strength and generally make the jointmore brittle. These problems are normally solved by locally removing the AlSi coating in aseparated process step before welding.One of the main goals of the experiments here presented was to join tailor weldedblanks (TWB) using only one process step without locally removing the AlSi coating and stillachieve the required weld strength needed for subsequent forming operations and good crashperformance.Laser-hybrid welding, a mixture of laser and MAG welding, were used for welding ofTWB’sThe experiments showed that correctly used, laser-hybrid can achieve welds in Usibor1500P materials that reach 95% of the strength of welds made on uncoated 22MnB5materials, in one process step without locally removing the AlSi coating.Optimized laser-hybrid welds were also tested on full scale B-pillars where theyperformed as good as conventionally laser-welded B-pillars (with coating removal) and nonweldedB-pillars. All welds were intact after both static and crash testing.In all, the experiments has successfully gathered knowledge on the determining factorsfor a sturdy process with high weld quality, approved crash performance, and improvedproductivity.
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