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Wiklund, Greger
Publications (10 of 31) Show all publications
Wiklund, G., Akselsen, O. M., Sørgjerd, A. J. . & Kaplan, A. (2014). Geometrical aspects of hot cracks in laser-arc hybrid welding (ed.). Paper presented at . Journal of laser applications, 26(1), Article ID 12003.
Open this publication in new window or tab >>Geometrical aspects of hot cracks in laser-arc hybrid welding
2014 (English)In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 26, no 1, article id 12003Article in journal (Refereed) Published
Abstract [en]

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

National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-13192 (URN)10.2351/1.4827135 (DOI)c62385cd-69e7-4fba-8281-73299be94c1b (Local ID)c62385cd-69e7-4fba-8281-73299be94c1b (Archive number)c62385cd-69e7-4fba-8281-73299be94c1b (OAI)
Note
Validerad; 2014; 20140124 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Akselsen, O. M., Wiklund, G., Østby, E., Sörgjärd, A. & Kaplan, A. (2013). A first assessment of laser hybrid welding of 420 mpa steel for offshore structure application (ed.). In: (Ed.), Alexander Kaplan; Hans Engström (Ed.), 14th NOLAMP Conference: The 14th Nordic Laser Materials Processing Conference, August 26th – 28th 2013, Gothenburg, Sweden. Paper presented at Nordic Laser Materials Processing Conference : 26/08/2013 - 28/08/2013 (pp. 171-182). Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>A first assessment of laser hybrid welding of 420 mpa steel for offshore structure application
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2013 (English)In: 14th NOLAMP Conference: The 14th Nordic Laser Materials Processing Conference, August 26th – 28th 2013, Gothenburg, Sweden / [ed] Alexander Kaplan; Hans Engström, Luleå: Luleå tekniska universitet, 2013, p. 171-182Conference paper, Published paper (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2013
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-38823 (URN)d552e814-e923-451f-9cd7-50f5686d9f5f (Local ID)978-91-7439-688-1 (ISBN)978-91-7439-689-8 (ISBN)d552e814-e923-451f-9cd7-50f5686d9f5f (Archive number)d552e814-e923-451f-9cd7-50f5686d9f5f (OAI)
Conference
Nordic Laser Materials Processing Conference : 26/08/2013 - 28/08/2013
Note
Godkänd; 2013; 20131210 (andbra)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2017-11-25Bibliographically approved
Wiklund, G., Janiak, P. & Hedegård, J. (2013). Laser hybrid welding of alsi coated boron steel (ed.). In: (Ed.), Alexander Kaplan; Hans Engström (Ed.), 14th NOLAMP Conference: The 14th Nordic Laser Materials Processing Conference, August 26th – 28th 2013, Gothenburg, Sweden. Paper presented at Nordic Laser Materials Processing Conference : 26/08/2013 - 28/08/2013 (pp. 59-66). Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Laser hybrid welding of alsi coated boron steel
2013 (English)In: 14th NOLAMP Conference: The 14th Nordic Laser Materials Processing Conference, August 26th – 28th 2013, Gothenburg, Sweden / [ed] Alexander Kaplan; Hans Engström, Luleå: Luleå tekniska universitet, 2013, p. 59-66Conference paper, Published paper (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2013
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-35060 (URN)9710dcb6-c362-4e1c-82ed-5f7b18e01e4d (Local ID)978-91-7439-688-1 (ISBN)978-91-7439-689-8 (ISBN)9710dcb6-c362-4e1c-82ed-5f7b18e01e4d (Archive number)9710dcb6-c362-4e1c-82ed-5f7b18e01e4d (OAI)
Conference
Nordic Laser Materials Processing Conference : 26/08/2013 - 28/08/2013
Note
Godkänd; 2013; 20131210 (andbra)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Akselsen, O. M., Wiklund, G., Østby, E., Sørgjerd, A. & Kaplan, A. (2013). Properties of laser hybrid butt welds of 420 MPa steel (ed.). In: (Ed.), Jin S. Chung (Ed.), The proceedings of the Twenty-third (2013) International Offshore and Polar Engineering Conference: Anchorage, Alaska, June 30-July 5, 2013 : ISOPE-2013 Anchorage. Paper presented at International Offshore and Polar Engineering Conference : 30/05/2013 - 05/06/2013 (pp. 290-294). Cupertino, Calif.: International Society of Offshore and Polar Engineers
Open this publication in new window or tab >>Properties of laser hybrid butt welds of 420 MPa steel
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2013 (English)In: The proceedings of the Twenty-third (2013) International Offshore and Polar Engineering Conference: Anchorage, Alaska, June 30-July 5, 2013 : ISOPE-2013 Anchorage / [ed] Jin S. Chung, Cupertino, Calif.: International Society of Offshore and Polar Engineers , 2013, p. 290-294Conference paper, Published paper (Refereed)
Abstract [en]

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

Place, publisher, year, edition, pages
Cupertino, Calif.: International Society of Offshore and Polar Engineers, 2013
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-28262 (URN)2010a98a-ee73-45be-8932-b673bdaad5fc (Local ID)9781880653999 (ISBN)2010a98a-ee73-45be-8932-b673bdaad5fc (Archive number)2010a98a-ee73-45be-8932-b673bdaad5fc (OAI)
Conference
International Offshore and Polar Engineering Conference : 30/05/2013 - 05/06/2013
Note
Godkänd; 2013; 20130924 (andbra)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Norman, P., Wiklund, G., Janiak, P. & Kaplan, A. (2011). Comparison of 22MnB5-steel with and without AlSi-coating during laser hybrid arc welding (ed.). In: (Ed.), Einar Halmøy (Ed.), 13th NOLAMP Conference: 13th Conference on Laser Materials Processing in the Nordic Countries 27 - 29 June 2011. Paper presented at Conference on Laser Materials Processing in the Nordic Countries : 27/06/2011 - 29/06/2011. Trondheim: Department of Geography, Norwegian University of Science and Technology
Open this publication in new window or tab >>Comparison of 22MnB5-steel with and without AlSi-coating during laser hybrid arc welding
2011 (English)In: 13th NOLAMP Conference: 13th Conference on Laser Materials Processing in the Nordic Countries 27 - 29 June 2011 / [ed] Einar Halmøy, Trondheim: Department of Geography, Norwegian University of Science and Technology, 2011Conference paper, Published paper (Refereed)
Abstract [en]

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.

Place, publisher, year, edition, pages
Trondheim: Department of Geography, Norwegian University of Science and Technology, 2011
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-31954 (URN)6484da26-5cc8-4a4d-a396-71c2075c000d (Local ID)6484da26-5cc8-4a4d-a396-71c2075c000d (Archive number)6484da26-5cc8-4a4d-a396-71c2075c000d (OAI)
Conference
Conference on Laser Materials Processing in the Nordic Countries : 27/06/2011 - 29/06/2011
Note
Godkänd; 2011; 20110901 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Kaplan, A. & Wiklund, G. (2009). Advanced welding analysis methods applied to heavy section welding with a 15 kW fibre laser (ed.). Paper presented at International Conference on Welding of the IIW, International Institute of Welding : 12/07/2009 - 17/07/2009. Welding in the World, 53(Special issue), 295-300
Open this publication in new window or tab >>Advanced welding analysis methods applied to heavy section welding with a 15 kW fibre laser
2009 (English)In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 53, no Special issue, p. 295-300Article in journal (Refereed) Published
Abstract [en]

For butt joint welding of 8 mm and of 16 mm thick stainless steel a 15 kW fibre laser was applied, achieving full penetration for a welding speed of 7 m/min and 3 m/min, respectively. Optics with a focal length ranging from 500 mm to 150 mm focus the laser beam to a spot diameter of 0.65 to 0.2 mm with a focal depth of 18 to 4 mm and a cw-power density of 4 to 48 MW/cm2. Although narrow sound welds can be achieved, heavy spatter ejection along with underfill can take place at the top and root side, particularly for high power density and for low line energy. Various advanced analysis methods were developed. Spatter was observed by high speed imaging of the weld pool surface and of the keyhole. Quantitative evaluation of the drop size and flight trajectories enabled categorisation into four spatter modes, revealing favoured conditions for spatter suppression. Modelling subsequent to the drop evaluation provided additional analysis. An illustrative theoretical description and the formulation of a standard documentation methodology were developed. This aims to generalise and transfer knowledge as a guideline for spatter suppression in other laser welding situations.

Keyword
Laser welding, Materials science - Other processing/assembly, Lasersvetsning, Teknisk materialvetenskap - Övrig bearbetning/sammanfogning
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-11161 (URN)a1128af0-3b00-11df-a0f4-000ea68e967b (Local ID)a1128af0-3b00-11df-a0f4-000ea68e967b (Archive number)a1128af0-3b00-11df-a0f4-000ea68e967b (OAI)
Conference
International Conference on Welding of the IIW, International Institute of Welding : 12/07/2009 - 17/07/2009
Note
Validerad; 2010; Bibliografisk uppgift: 62. International Conference on Welding of the IIW, Singapore 12-17 July 2009; 20100329 (alka)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Kaplan, A., Westin, E., Wiklund, G. & Norman, P. (2008). Imaging in cooperation with modeling of selected defect mechanisms during fiber laser welding of stainless steel (ed.). In: (Ed.), Yongfeng Lu (Ed.), Congress proceedings: ICALEO, 27th International Congress on Applications of Lasers and Electro-Optics : October 20 - 23, 2008 Pechanga Resort & Casino, Temecula, CA, USA. Paper presented at International Congress on Applications of Lasers & Electro-Optics : 20/10/2008 - 23/10/2008 (pp. 789-798). Orlando, Fla: Laser institute of America
Open this publication in new window or tab >>Imaging in cooperation with modeling of selected defect mechanisms during fiber laser welding of stainless steel
2008 (English)In: Congress proceedings: ICALEO, 27th International Congress on Applications of Lasers and Electro-Optics : October 20 - 23, 2008 Pechanga Resort & Casino, Temecula, CA, USA / [ed] Yongfeng Lu, Orlando, Fla: Laser institute of America , 2008, p. 789-798Conference paper, Published paper (Refereed)
Abstract [en]

Fiber laser welding of stainless steel was studied for different joint configurations and gaps. The higher focusing capability of fiber lasers compared to traditional Nd:YAG and CO2 lasers creates different, usually smaller, keyhole and melt pool geometries. These geometrical aspects, accompanied by a different laser energy redistribution, are essential for the weld pool dynamics and the resulting joint, with or without defects. Typical defects identified during fiber laser welding were spatter, humping, or lack of material at the top or root. High-speed imaging enables observation of the geometry and motions of the melt pool surface and keyhole during welding. This is illuminated by an additional diode laser permitting spectral filtering and also the metal vapor dynamics can be visualized. Mathematical modeling provides the possibility to estimate and study additional phenomena that are difficult to measure, such as effects inside the melt volume or the impact of surface tension forces on dynamic melt motion. For recorded melt surface motion images, in particular, the corresponding surface tension forces and other mechanisms can be estimated by cooperative complementary modeling, enabling to draw conclusions. This advanced method was carried out for the different joint and defect cases studied, resulting in an illustrated theoretical description of the observed physical phenomena.

Place, publisher, year, edition, pages
Orlando, Fla: Laser institute of America, 2008
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-34018 (URN)81c41af0-c78a-11dd-941d-000ea68e967b (Local ID)978-0-912035-12-3 (ISBN)81c41af0-c78a-11dd-941d-000ea68e967b (Archive number)81c41af0-c78a-11dd-941d-000ea68e967b (OAI)
Conference
International Congress on Applications of Lasers & Electro-Optics : 20/10/2008 - 23/10/2008
Note
Godkänd; 2008; 20081211 (petern)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Vuorinen, E., Pino, G., Wiklund, G. & Kaplan, A. (2008). Laser surface hardening of steel with ausferritic structure (ed.). In: (Ed.), (Ed.), SMT22: 22nd international Conference on Surface Modification Technologies, Sept. 22-24, 2008, Trollhättan, Sweden. Paper presented at International Conference on Surface Modification Technologies : 22/09/2008 - 24/09/2008.
Open this publication in new window or tab >>Laser surface hardening of steel with ausferritic structure
2008 (English)In: SMT22: 22nd international Conference on Surface Modification Technologies, Sept. 22-24, 2008, Trollhättan, Sweden, 2008Conference paper, Published paper (Refereed)
Abstract [en]

High strength steels can be produced by austempering of Si-containing steels. High toughness and good wear resistance are properties possible to achieve. Surface hardening of this group of steels can give an additional increase of the surface hardness and wear resistance. Laser surface hardening has been used in order to increase the surface hardness of the steel 55Si7. The effect of surface hardening on the ferritic-austenitic carbide- free microstructure created for this steel has been studied. Optical as well as scanning electron microscopy has been used in the characterization of the micro-structural changes.

National Category
Other Materials Engineering Manufacturing, Surface and Joining Technology
Research subject
Engineering Materials; Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-28680 (URN)28f530a0-c788-11dd-941d-000ea68e967b (Local ID)28f530a0-c788-11dd-941d-000ea68e967b (Archive number)28f530a0-c788-11dd-941d-000ea68e967b (OAI)
Conference
International Conference on Surface Modification Technologies : 22/09/2008 - 24/09/2008
Note
Godkänd; 2008; 20081211 (petern)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-03-05Bibliographically approved
Wiklund, G., Nilsson, T. & Kaplan, A. (2007). Laser hybrid welding of Zinc-coated ultra high strength steel (ed.). In: (Ed.), Veli Kujanpää (Ed.), 11th NOLAMP Conference: 11th NOLAMP Conference in Laser Processing of Materials ; Lappeenranta, August 20 - 22, 2007. Paper presented at Conference on Laser Materials Processing in the Nordic Countries : 20/08/2007 - 22/08/2007. Lappeenranta: Lappeenranta University of Technology Press
Open this publication in new window or tab >>Laser hybrid welding of Zinc-coated ultra high strength steel
2007 (English)In: 11th NOLAMP Conference: 11th NOLAMP Conference in Laser Processing of Materials ; Lappeenranta, August 20 - 22, 2007 / [ed] Veli Kujanpää, Lappeenranta: Lappeenranta University of Technology Press, 2007Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Lappeenranta: Lappeenranta University of Technology Press, 2007
Series
Acta Universitatis Lappeenrantaensis, ISSN 1456-4491 ; 273
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-29363 (URN)2d0cb520-f24e-11db-bb1b-000ea68e967b (Local ID)978-952-214-412-6 (ISBN)2d0cb520-f24e-11db-bb1b-000ea68e967b (Archive number)2d0cb520-f24e-11db-bb1b-000ea68e967b (OAI)
Conference
Conference on Laser Materials Processing in the Nordic Countries : 20/08/2007 - 22/08/2007
Note

Godkänd; 2007; 20070424 (cira)

Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Kaplan, A., Wiklund, G. & Nilsson, T. (2007). The impact of zinc-coating on laser hybrid welding of steel (ed.). In: (Ed.), Yongfeng Lu (Ed.), Congress proceedings: 2007 ICALEO, 26th International Congress on Applications of Lasers & Electro-Optics : October 29 - November 1, 2007. Paper presented at International Congress on Applications of Lasers & Electro-Optics : 29/10/2007 - 01/11/2007. Orlando, Fla: Laser institute of America
Open this publication in new window or tab >>The impact of zinc-coating on laser hybrid welding of steel
2007 (English)In: Congress proceedings: 2007 ICALEO, 26th International Congress on Applications of Lasers & Electro-Optics : October 29 - November 1, 2007 / [ed] Yongfeng Lu, Orlando, Fla: Laser institute of America , 2007Conference paper, Published paper (Refereed)
Abstract [en]

Hybrid Nd:YAG/MAG welding of ultra high strength steel is studied for 1,5 mm thick sheets in I-, T- and overlap joint type configuration. Untreated and zinc-coated steels were compared, causing distinct differences in terms of process stability and welding result. For zinc coating it can be distinguished between domains of trapped zinc layers like in overlap and T-joints and free surface zinc coatings. While the former situation is critical for violent evaporation and in turn spatter in the absence of a gap, in the latter case a zinc domain outside the weld pool area evaporates due to its low boiling point, thus not disturbing the laser welding process. However, during hybrid welding arc instabilities and short circuiting were observed when changing to zinc coated steel, even for butt joints. One hypothesis is an impact of the zinc vapour atoms on the plasma, with an ionisation energy 20% higher than iron, but 40% lower than Ar. The influence was calculated by Saha's equation. The process window is much narrower than for uncoated steel. Moreover, an enhanced generation of spatter and fume can be observed. A theory for the impact of zinc-coating on hybrid welding is postulated.

Place, publisher, year, edition, pages
Orlando, Fla: Laser institute of America, 2007
National Category
Manufacturing, Surface and Joining Technology
Research subject
Manufacturing Systems Engineering
Identifiers
urn:nbn:se:ltu:diva-34630 (URN)8e20e9d0-fd34-11db-b816-000ea68e967b (Local ID)978-0-912035-88-8 (ISBN)8e20e9d0-fd34-11db-b816-000ea68e967b (Archive number)8e20e9d0-fd34-11db-b816-000ea68e967b (OAI)
Conference
International Congress on Applications of Lasers & Electro-Optics : 29/10/2007 - 01/11/2007
Note
Godkänd; 2007; Bibliografisk uppgift: CD-ROM; 20070508 (alka)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
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