| 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. |
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| 4. |
- Engström, Hans, et al.
(författare)
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Robotiserad lasersvetsning : ett delprojekt inom RACER II - ett industristyrt utvecklingsprogram för laserbearbetning och abrasiv vattenstråleskärning
- 2001
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Kombinationen laser industrirobot har utvecklats till ett effektivt system för industriell produktion. Idag används till största delen Nd:YAG-laser tillsammans med olika industrirobotar för svetsning och skärning. Lasersvetsning med industrirobot inom bilindustrin utförs typisk på takkonstruktioner och huvar/bakluckor vilka till sin natur är enkla svetsgeometrier med relativt raka svetsar som normalt inte kräver komplicerade robotrörelser. Svetsning av överlappsfog dominerar. Denna fogtyp ställer betydligt mindre krav på toleranser på ingående komponenter samt noggrannhet hos laser/robot systemet än svetsning av stumfog. Målet med projektet är att hämta hem och vidareutveckla teknik för att kunna utföra och demonstrera avancerad robotiserad lasersvetsning, samt effektivt överföra denna kunskap till de industriella projektdeltagarna och övrig svensk industri. Projektet syftar också att lösa svetstekniska problem vid svetsning av svårsvetsade material som ferritiska Cr-stål och härdat specialstål, samt att svetsa industriella applikationer. Projektdeltagare har varit Faurecia Exhaust Systems AB, Motoman Robotics Europe AB och Hägglunds Vehicle AB. I projektet har vi utvecklat teknik för fogföljning och adaptiv styrning av svetsprocessen vid robotiserad lasersvetsning. Systemet har testats med bra svetsresultat för varierande spalter upp till 0.75 mm i 2 mm tjock stålplåt. Kallvalsad plåtyta med frästa kanter kräver en spalt på ca 0.15 mm för att fogföljaren ska kunna detektera spalten. Detta är det första adaptiva systemet i världen som har satts i drift av Motoman. Svetteknik har undersökts och utvecklats för ARMOX 500. Med lämplig eftervärmning erhålls svetsar av hög kvalitet med goda mekaniska hållfasthetsegenskaper. Svetsteknik har också utvecklats för 17% Cr-stål. För plåttjocklek 3 mm blir svetshastigheten med Nd:YAG-laser begränsad till ca 2 m/min, där högre hastigheter ger kraftiga genomrinningar. Porförekomsten kan elimineras genom att använda dubbelfokusoptik och nitrogen som skyddsgas men Faurecia Exhaust Systems AB menar att denna gas inte bör användas på grund av ökad risk för interkristallin korrosion samt att duktiliteten kan försämras. Även svetsteknik för en rör-fläns applikation där röret består av 17% Cr-stål och flänsen av ett C-Mn stål har utvecklats. Sprickbildning i svetsgodset har dock inte kunnat undvikas.
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| 5. |
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| 6. |
- Kaplan, Alexander, et al.
(författare)
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Advanced welding analysis methods applied to heavy section welding with a 15 kW fibre laser
- 2009
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Ingår i: Welding in the World. - 0043-2288 .- 1878-6669. ; 53:Special issue, s. 295-300
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 7. |
- Kaplan, Alexander, et al.
(författare)
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Imaging in cooperation with modeling of selected defect mechanisms during fiber laser welding of stainless steel
- 2008
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Ingår i: Congress proceedings. - Orlando, Fla : Laser institute of America. - 9780912035123 ; , s. 789-798
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 8. |
- Kaplan, Alexander, et al.
(författare)
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The impact of zinc-coating on laser hybrid welding of steel
- 2007
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Ingår i: Congress proceedings. - Orlando, Fla : Laser institute of America. - 9780912035888
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Konferensbidrag (refereegranskat)abstract
- 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.
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