HYBRID WELDING
Hybrid laser arc setup with an adaptive control vision developed at TWI
welding of these alloys, with improved fit-up gap tolerance when compared with conventional laser welding. Ytterbium fibre laser sources were used in the development of this process, owing to their high wall-plug efficiency, small footprint and the processing flexibility from their optical fibre beam delivery. Allen added: ‘Another driver for developing hybrid welding for this application was to reduce the distortion that would otherwise result if arc welds were made over the very long lengths of joint made in railcar seam welds.’ A series of welding trials
demonstrated that the process is capable of producing low porosity content, high-quality butt welds, at speeds of up to five metres per minute in 3mm thick material. Joint fit-up gaps of up to 1mm width with constant width gaps, or up to 1.5mm width with tapering gaps were also bridged successfully. Aluminium alloys are not the only materials
that can be used to reduce weight: TWI is also investigating using hybrid welding with alternative grades of higher strength carbon and stainless steels.
44 LASER SYSTEMS EUROPE ISSUE 31 • SUMMER 2016
reduces the distortion that would otherwise result if arc welds were made over very long lengths
[Hybrid welding]
Future tech Tere is still much research being done into both laser and hybrid welding. One hot topic is the development of real-time sensor systems to monitor and perfect the application of these joining processes. When laser or hybrid welds are being carried out, a change in a range of different signals generated by the process (for example, sounds, electrical charges or photo-emissions), can indicate that unacceptable defects are being produced in the welds, incorrect welding parameters are being used or joints are being welded that are out of tolerance. TWI is working with a
consortium of research and industrial partners in the Radicle project (
www.radiclelaser.com) – coordinated by the Manufacturing Technology Centre in the UK and standing for ‘Real-time dynamic
control system for laser welding’ – to develop new combinations of laser welding sensors to detect these changes at frequencies approaching tens of thousands of times a second. Te ultimate goal is to make such sensors fast and smart enough to adapt intelligently to control these processes in real time and improve the quality of the resulting welds. Te technology, although being targeted at laser welding, could then cross over to the hybrid laser
process, as Allen remarked: ‘As that monitoring and control capability improves, there is no reason why we couldn’t then apply it to the hybrid process, to have real-time quality assurance and control of that process as well.’ Industry also continues to drive hybrid laser
welding research and development in other directions. For example, the use of hybrid laser welding to clad surface layers onto substrates and, potentially, then additively manufacture structures, are possibilities. A number of industries, among them the nuclear
waste containment industry, are also pushing for more productive processes to weld thick-walled storage vessels for nuclear waste. Narrow gap multi-pass laser welding is one candidate for making such thick-walled welds, where a U-shaped joint profile can be filled with a number of overlapping passes. Allen said: ‘Existing narrow gap arc processes can be quite slow, and one way to increase the rate at which these joints can be made will be to hybridise the arc welding processes used with a beam from a suitable laser source.’ A great deal of research and development is being
carried out to bring improvements to the weld quality and productivity in these large-scale industrial applications. Hybrid welding clearly has a bright and interesting future ahead of it, in terms of the processes, materials and areas to which it could be applied.
@lasersystemsmag |
www.lasersystemseurope.com
TWI
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