| 1. |
- Andersson, Joel Håkan, 1981, et al.
(author)
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Repair welding of wrought superalloys: Alloy 718, Allvac 718Plus and Waspaloy
- 2012
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In: Science and Technology of Welding and Joining. - 1743-2936 .- 1362-1718. ; 17:1, s. 49-59
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Journal article (peer-reviewed)abstract
- The ability to weld repair three precipitation hardening superalloys, Alloy 718, Allvac 718Plus and Waspaloy, with GasTungsten Arc Welding is compared in this study. Four different solution heat treatment conditions for each material were examined; Alloy 718 and Allvac 718Plus heat treated at 954 °C-1 h, 982 °C-1 h, 954 °C-15 h and 1020 °C-1 h and Waspaloy for 4 h at 996 °C, 1010 °C, 1040 °C and at 1080 . By metallography, the total number of cracks was evaluated both in the HAZ and in the FZ which made it possible to consistently rate the repair weldability of these three materials. Alloy 718 was significantly the best one with Allvac 718Plus slightly better than Waspaloy. As expected, the solution heat treatment conditions only affected the HAZ cracking behavior.
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| 2. |
- Andersson, Joel, 1981-, et al.
(author)
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Repair welding of wrought superalloys : Alloy 718, Allvac 718Plus and Waspaloy
- 2012
-
In: Science and Technology of Welding and Joining. - : Taylor & Francis Group. - 1362-1718 .- 1743-2936. ; 17:1, s. 49-59
-
Journal article (peer-reviewed)abstract
- The ability to weld repair three precipitation hardening superalloys, i.e. Alloy 718, Allvac 718Plus and Waspaloy, with gas tungsten arc welding, is compared in this study. Four different solution heat treatment conditions for each material were examined: Alloy 718 and Allvac 718Plus heat treated at 954uC–1 h, 982uC–1 h, 954uC–15 h and 1020uC–1 h and Waspaloy for 4 h at 996uC, 1010uC, 1040uC and at 1080uC. By metallography, the total number of cracks was evaluated in both the heat affected zone and the fusion zone, which made it possible to consistently rate the repair weldability of these three materials. Alloy 718 was significantly the best one, with Allvac 718Plus slightly better than Waspaloy. As expected, the solution heat treatment conditions only affected the heat affected zone cracking behaviour.
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| 3. |
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| 4. |
- Berglund, Daniel, et al.
(author)
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A two stage approach for the validation of welding and heat treatment models used in product development
- 2005
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In: Science and technology of welding and joining. - 1362-1718 .- 1743-2936. ; 10:6, s. 653-665
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Journal article (peer-reviewed)abstract
- Many components used in the aerospace industry have complex shape and are manufactured from high strength materials. Performing large scale tests is costly and time consuming, therefore, simulation tools are needed to support an effective product development process. Using manufacturing simulations during product development requires a validated model of the material and manufacturing process. In this paper, a validation scheme is proposed for thermomechanical models of welding and post-weld heat treatment. The scheme was investigated by comparing simulations using shell elements with experimental results, which showed good agreement when predicting residual stresses after welding, but an overestimation of the out-of-plane deformations when simulating both welding and heat treatment. However, the simulations showed that the outof-plane deformation is strongly influenced by the initial geometry. It can be concluded that the simulation model is adequately accurate to be used in concept evaluation.
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| 5. |
- Cederqvist, Lars, et al.
(author)
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Improved process stability during friction stir welding of 5 cm thick copper canisters through shoulder geometry and parameter studies
- 2009
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In: Science and technology of welding and joining. - London : Institute of Materials. - 1362-1718 .- 1743-2936. ; 14:2, s. 178-184
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Journal article (peer-reviewed)abstract
- The spent nuclear fuel from Swedish power plants will be placed in copper canisters that are sealed with friction stir welding and the stability and robustness of this process is now being optimised in three steps: first, the shoulder geometry was identified that produced the most stable weld cycle, then the welding parameters were optimised for that geometry with regards to stability, and finally, the chosen geometry and welding parameters were verified and evaluated during multiple weld cycles. The shoulder study showed that stable welds could be produced repeatedly with a convex scroll geometry which proved more stable than various concave and flat scroll geometries. In the subsequent parameter study, not only were the most stable values for the welding parameters derived, but a clear relationship was shown between power input and tool temperature. This relationship can be used to more accurately control the process within the parameter windows, not only for this application but for other applications where the welding temperature needs to be kept within a specified range. Similarly, the potential of the convex scroll shoulder geometry for use in applications with other metals and thicknesses is evident.
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| 6. |
- De Backer, Jeroen, 1987-, et al.
(author)
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Thermoelectric method for temperature measurement in friction stir welding
- 2013
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In: Science and technology of welding and joining. - 1362-1718 .- 1743-2936. ; 18:7, s. 541-550
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Journal article (peer-reviewed)abstract
- Previous research within friction stir welding (FSW) has demonstrated that online control of welding parameters can improve the mechanical properties and is necessary for certain applications to guarantee a consistent weld quality. One approach to control the process is by adapting the heat input to maintain a stable welding temperature, within the specified operating boundaries. This requires accurate in-process temperature measurements. This paper presents a novel method to measure the temperature at the interface of the FSW tool and workpiece. The method is based on the thermoelectric effect between dissimilar materials. The measurements are compared to thermocouple measurements and to a physical model and show good correspondence to each other. Experiments demonstrate that the method can quickly detect temperature variations, due to geometrical variations of the workpiece or due to parameter changes. This allows use of the method for online control of robotic FSW.
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| 7. |
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| 8. |
- Eriksson, Ingemar, et al.
(author)
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Measurements of fluid flow on keyhole front during laser welding
- 2011
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In: Science and technology of welding and joining. - 1362-1718 .- 1743-2936. ; 16:7, s. 636-641
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Journal article (peer-reviewed)abstract
- This paper presents the results of a high speed video survey of melt flow on the front face of a keyhole created during fibre laser welding. Using fast Fourier transform techniques, quantitative values of fluid flow velocities down the keyhole front have been established. The results have led to a phenomenological understanding of some of the quality problems which arise at excess welding speeds. The downward flow velocity on the keyhole front is found to be generally independent of welding speed, and proportional to laser power
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| 9. |
- Fahlström, Karl, 1986-, et al.
(author)
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Correlation between laser welding sequence and distortions for thin sheet structures
- 2017
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In: Science and technology of welding and joining. - : Informa UK Limited. - 1362-1718 .- 1743-2936. ; 22:2, s. 150-156
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Journal article (peer-reviewed)abstract
- Thin ultra-high strength steel shaped as 700 mm long U-beams have been laser welded in overlap configuration to study the influence of welding sequence on distortions. Three different welding directions, three different energy inputs as well as stitch welding have been evaluated, using resistance spot welding (RSW) as a reference. Transverse widening at the ends and narrowing at the centre of the beam were measured. A clear correlation was found between the weld metal volume and distortion. For continuous welds there was also a nearly linear relationship between the energy input and distortion. However, the amount of distortion was not affected by a change in welding direction. Stitching and RSW reduced distortion significantly compared to continuous laser welding.
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| 10. |
- Fahlström, Karl, 1986-, et al.
(author)
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Metallurgical effects and distortions in laser welding of thin sheet steels with variations in strength
- 2017
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In: Science and technology of welding and joining. - : Informa UK Limited. - 1362-1718 .- 1743-2936. ; 22:7, s. 573-579
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Journal article (peer-reviewed)abstract
- Geometrical distortions occur while welding, but the understanding of how and why they occur and how to control them is limited. The relation between the weld width, weld metal volume, total energy input, width of hard zone and distortions when laser welding three different thin sheet steels with varying strength has therefore been studied. Weld metal volume and total energy input show a good correlation with distortion for one steel at a time. The best correlation with the when including all three steel grades was the width of the hard zone composed of weld metal and the martensitic area in the heat affected zone. © 2017 Institute of Materials, Minerals and Mining.
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