- Shipbuilding – the low distortion of hybrid welding when compared with processes such as MAG welding or SAW reduces the amount of, and hence costs associated with, distortion correction and rework. Conversely, conventional joining methods and their associated re-work have been estimated to constitute up to 20-30% of overall manufacturing costs.
- Rail transport – as in shipbuilding, the low distortion that can result from hybrid railcar seam welding compared with conventional arc welding processes is of interest as a means of reducing fabrication costs, as well as the higher welding speeds reducing overall welding time.
- Oil and gas – hybrid orbital girth welding and longitudinal welding of pipes has been demonstrated, and with continuing developments in laser sources could be of interest as a means of increasing root pass and overall joint completion rates, depending on the pipe steel grades used and operating environment requirements.
TWI has over a decade of experience of hybrid laser-arc welding processes and their development. This includes experience of combining a variety of industrial lasers used for metals welding (principally CO2, Nd:YAG and, since their advent at the beginning of the last decade, Yb fibre lasers) with MIG/MAG and TIG arc welding.
Furthermore, TWI’s research and development in this area has covered a broad base of engineering alloys, including C-Mn steels used for structural and pipeline applications, conventional (austenitic) and higher strength (duplex and ferritic) stainless steels, as well as a wide range of aluminium alloys.
The chief benefits of hybrid laser-arc welding can be summarised
- Improved tolerance to joint fit-up: for example, hybrid welding can extend the tolerance to joint gap by a factor of at least 2-3 over laser welding, or greater with adaptive control of welding parameters.
- Improved weld quality: hot cracking (e.g. in some higher strength Al alloys) can be avoided, and internal porosity content reduced, with respect to laser welds.
- Increases in single pass penetration depth: this is controlled principally by the choice of laser and welding parameters used, but single pass penetrations of up to at least 6-12mm can be achieved using higher power lasers.
- Increases in welding speed: this is also dependent on the laser source used and materials being welded, but speeds of up to at least 5m/min are possible in thinner
- The increases in penetration depth and/or welding speed are particularly significant as the net heat input can be reduced. This results in lower distortion welding, suitable for long seam welds between plates, box sections, plates and attachments etc
Over the past decade, TWI has been carrying out developments of the hybrid welding process on a range of materials, within the Core Research Programme (CRP), Group Sponsored Projects and European-funded Collaborative Projects, as well as for its Industrial Members.
Examples of TWI’s work in hybrid welding include:
- CO2 laser-MAG welding of butt joints between C-Mn steel plates, including assessments of joint gap bridging ability and weld qualities and properties.
- Nd:YAG laser-MAG welding of T joints between C-Mn steels, and resulting properties, for shipbuilding applications.
- High speed, low distortion hybrid welding of aluminium alloys using latest generation fibre lasers.
- Low internal porosity content hybrid welding of aerospace aluminium alloys using fibre-delivered lasers.
- Hybrid welding of higher strength stainless steels.
- Real-time process control when hybrid welding butt joints in steels, stainless steels and aluminium alloys
If you require further information or have any questions please do not hesitate to contact us.
