SHIPBUILDING
SHAPE SHIP
Welding ship hulls is a relatively new application area for laser processing, but one where the laser can add value, as Rachel Berkowitz discovers
I
n the fourth millennium BC, sewing wooden planks together into a ship hull was the latest and greatest joining technology for Egyptian shipbuilders.
Jumping forward a couple of millennia, the Vikings honed ‘clinker built’ boat building, overlapping the edges of hull planks and riveting them together to construct a seaworthy vessel. But it wasn’t until the twentieth century that the maritime sector took up laser joining technologies. In 1992, the European shipbuilding
industry published a feasibility study about the use of laser welding in shipbuilding[1]
.
Meyer Werſt shipyard in Germany was, at the time, the only yard with industrial experience in laser welding techniques. Even then, CO2 laser welding was only used for pre- fabricating non-structural decks and internal walls for its enormous cruise liners. Strict regulatory requirements hindered its further adoption until research led to unified
guidelines for the approval of CO2 welding in shipbuilding[2]
. While a review from 2005[3] observed that
‘very few ship construction yards use laser welding, so it is clear that in shipbuilding the technology is still in its infancy’, the technology continues to gain popularity in shipyards. Now, research and development is bringing the advantages of laser welding systems to shipyards around the world.
Laser-arc hybrid welding Long before laser welding, arc welding offered the modern solution to joining in ship construction. By applying intense heat, metal at the joint between two parts is melted, and allowed to fuse together as it cools and solidifies. In arc welding, the heat to melt the metal is produced by an electric arc formed between the metal surface and an electrode. Still, arc welding is an energy-intense process and can lead to significant stress and
laser
distortion at the joints. Using a laser beam as the heat source offers
the advantages of lower distortion and higher welding speed. Hybrid laser-arc welding combines a laser beam with an arc welding process in a single weld pool. It provides the deep penetration of a thick metal offered by laser welds, along with better tolerance to joint fit and improved weld cap profile offered by arc welding. ‘Hybrid laser-arc welding is a joining
process that is beneficial for ship building applications, as it would reduce the costs associated with distortion, correction, and rework,’ said Paola De Bono, team manager of laser and sheet processes at TWI in Cambridge, UK. Over the last decade, numerous new laser concepts have been developed for materials processing. Fibre and disk laser sources are currently among the most promising in the materials laser welding market, thanks to their high beam quality, excellent scalability and high electrical-to- optical conversion efficiency, compared to CO2
and Nd:YAG lasers. ‘Hybrid laser-arc welding increases the
geometrical precision of the ship body sections,’ said Mikhail Kuznetsov, research assistant at the Institute of Laser Welding Technologies at Peter the Great Saint Petersburg Polytechnic University in Saint Petersburg, Russia. Along with Professor Gleb Turichin at the
Laser arc technological system adapted to weld shipbuilding steel 16 LASER SYSTEMS EUROPE ISSUE 37 • WINTER 2017
Saint Petersburg State Marine Technical University, Kuznetsov develops laser welding systems for a wide range of applications. Most
@lasersystemsmag |
www.lasersystemseurope.com
Turichin et al. 2017
By Novikov Aleksey/
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