Laser innovations for the maritime sector

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Keely Portway looks at how new laser technologies are optimising welding and cutting for shipbuilding

Ship under construction in a shipyard. (Image: Shutterstock.com)

After a relatively slow period between 2019 and 2020, the market for shipbuilding is steadily picking up, and, according to research firm Statista, is likely to grow from this year onwards, surpassing $160bn in 2023.

And the Ship Building Global Market Report 2021: Covid-19 Impact and Recovery to 2030 from ResearchAndMarkets.com would appear to agree, predicting that the market will reach $186.6bn by 2025, thanks largely to companies rearranging their operations and recovering from the impact of the pandemic.

Other factors include the increasing seaborne trade, rising population, surging purchasing power of consumers and therefore increasing demand for consumer goods.

In terms of markets, Europe is cited as crucial for the production of cruise vessels, however it is East Asia that is dominant in shipbuilding, with China, Japan and South Korea being the largest shipbuilding nations. According to Statista, China alone received 48 per cent of global shipbuilding orders in 2020.

The industry has certainly had its challenges over the last few years, pandemic-aside, with a shortage of skilled workers and various environmental regulations and policies changing the way that ships are built. Add to this the period of decline last year and the shipbuilding industry is becoming more reliant on quality, efficiency and accuracy than ever before. Enter stage-left, the laser! Laser cutting and welding are known for their high-precision and efficiency, so it’s little surprise that they are a mainstay of the shipbuilding industry.

100kW shipbuilding laser

Eyal Shekel, CEO at Civan Lasers, believes there is room to increase the use of lasers for cutting and welding in the sector, due to their ability to increase process efficiency. ‘It’s beneficial, for example, to be able to weld an outer panel just from the outside, instead of having to go both inside and outside. Being able to produce a high-quality, relatively fast weld on one side is a very big advantage,’ he said.

In terms of some of the most common uses for lasers in shipbuilding, Shekel highlighted the structure as a key area. ‘Particularly the T-joints and sealing welds,’ he said, ‘they present opportunities for laser welding. In general, we feel that with laser welding, and particularly with a high-power single-mode laser, you can perform quickly and accurately, even on thick materials.’ He added that the narrow beam of such a laser enables it to efficiently weld the very shallow angles of T-joints.

The company recently launched its 100kW single-mode, continuous-wave (CW) coherent beam combining (CBC) fibre laser, which Shekel said lends itself well to this purpose.

Civan’s 100kW single mode, continuous wave coherent beam combining fibre laser offers advantages for shipbuilding. (Image: Civan Laser)

The CBC technology is based on parallel amplification of a single seed signal that allows for coherent recombination, ramping the output power to a degree unobtainable by in-series amplifiers. Its dynamic beam shaping technology offers the ability to control beam shape, frequency, sequence and focus steering.

Power is a key point for Shekel, who highlighted 10kW or higher as the standout power needed for shipbuilding applications. ‘We now have 30kW and also 100kW available,’ he said. ‘The advantage is mainly in quality, because the more power you have, the faster you can go but when you’re trying to go faster without the higher power, you get the lower quality welds.’

A particularly important use-case for laser welding in shipbuilding, stressed Shekel, is in the joining of dissimilar metals together, for example in panel building. ‘You should not need a separate filler material or component,’ he said, ‘because with deep penetration laser welding, the coupling can go directly from one part to another. Another important part of the laser is the low heat-affected zone. A high quality of metal is required for shipbuilding, and you want to keep that quality with the weld. With a low heat-affected zone there is less residual stress on the weld.’

The power of diode lasers

Johannes Schäfer, technology and strategic key account manager at diode laser manufacturer Laserline, sees shipbuilding as a relatively conservative market, but one gradually taking on new technologies. ‘We see that there are still a lot of processes which have been used in the past, such as submerged arc welding – a laborious process that can involve workpiece distortion – but there is also laser technology now being used for cutting and for welding.’

Schäfer has noted a particular shift in the shipbuilding industry towards laser-gas metal arc hybrid welding, a combination of gas metal arc (GMA) welding and laser beam welding. ‘Despite the higher welding speed that laser GMA welding offers, there is less distortion in comparison to the old fashioned processes, which can help reduce production costs,’ he said. ‘It’s not going to be used for short seams or traditional GMA mouldings, but it can be useful for long seams, section weldings around different thicknesses, so around 5mm up to 15mm and special joints.’

He explained that diode lasers are different to other laser systems for shipbuilding, in that the combination of high power output and comfortable spot sizes can allow for optimal gap bridgeability. In addition, the energetic homogeneity of the spot and the high absorption capacity of a typical wavelength mix generate unusually calm melt pools, leaving almost no impurities on the areas adjoining the seams. As combined diode laser systems can reach powers of up to 60kW today, even ships’ sides of 50mm thickness can be welded with two welding runs (layer and opposite side). ‘That has an influence and impact on the properties like hardness,’ said Schäfer. ‘Typically, the hardness peaks in the heat-affected zone, that’s a normal point of welding. And we can decrease those hardness peaks for the types of steels used in shipbuilding industries.’

In terms of wavelengths, Schäfer explained that Laserline generally produces infrared lasers for welding in shipbuilding. ‘We produce diode lasers up to a very high power, up to 45kW or even more, but of course, for the shipbuilding industry we have the special 60kW laser. It depends on the volume and thickness of the sheets that the customer demands.’

Developing lasers for the maritime sector

The 60kW power for lasers in shipbuilding is the focus of a research project in which Laserline has been involved for several years. Based in Germany, Thick Metal Sheet Welding by High-Power Diode Lasers for Maritime Applications (DIOMAR), involves a consortium of experts working to develop new diode laser beam sources with a maximum output of up to 60kW in continuous-wave mode.

This is with the aim of ensuring high-quality laser welding processes for steel sheet thicknesses of up to 30mm are available for use in shipbuilding and other maritime applications.

Laserline has been responsible for the development of the new high-power laser diode sources. Other organisations in the group include German research institute Laser Zentrum Hannover, shipbuilding firm Meyer Werft, and electronics manufacturer Held Systems. DIOMAR is funded by the German Federal Ministry for Economic Affairs and Energy.

The latest laser welding processes can make the welding of thick materials in ship building more efficient. (Image: Meyer Werft/M. Wessels)

The overarching aim of the project is to establish new laser welding processes based on high-power lasers in the maritime sector. It is hoped that, by achieving high-quality joints with high welding speeds, costs can be reduced for edge preparation, as well as the amount of additional material compared to existing joining methods. The application development has been taking place in both a laser laboratory and in a shipyard-like test environment for the past three years. This makes it possible to quickly test, evaluate and optimise the new processes, which the group says could complement, or replace, existing processes.

The consortium is particularly keen to ensure laser safety for very high laser outputs, including the handling of expected large quantities of emitted hazardous substances. The release of hazardous substances from the laser processing zone is also being thoroughly investigated under the project.

The metal sheet thickness is an important issue, as the project demonstrates. Schäfer went on to detail the sheer variety of thicknesses used in shipbuilding. ‘It depends on the construction of the ships, the rudders and the lower bottom of the ships have some very high thicknesses up to 15mm, or sometimes even more. Every ship is different, and some use thinner material, but when you’re going upwards on the ships, the thicknesses also decrease, so it’s mostly a range of 5 to 15mm.’ In terms of the material itself, Schäfer explained that there is a high quantity of sheets used. ‘That sheet material is mostly plex steel,’ he said.

Laserline has been supplying and developing lasers for maritime for some years now, and Schäfer offered some insight into how manufacturers can get involved in shipbuilding projects. ‘The industry has its own qualification process,’ he said. ‘They have to qualify the process and they have to make sure that the process and the weld is secure. That’s the point at which they have to do a qualification which is done by a third party – here in Germany, that’s an organisation which controls the welders for the shipbuilding industry. When they are looking at the paperwork, we introduce the laser processing and we give some samples for analysis.’

Cutting on the XXL scale

The use of lasers for cutting in the maritime industry is equally well recognised for the high-quality, high-precision results achieved, not to mention its green credentials. With steel plates used as the main raw material in shipbuilding, laser cutting plates can replace some die-cutting methods that require large moulds, thereby reducing production times and costs.

Steel processing firm Otto Klostermann has realised the benefits as a specialist processor of ‘XXL’ formats for its shipbuilding clients, as well as the vehicle construction, waggon production, bridge construction and crane manufacture sectors. The company recently invested in a LaserMat II machine from Messer Cutting Systems, which is available with either a 4kW or 6kW CO2 laser. ‘Our old laser cutting system was getting on in years,’ said Philipp Klostermann, managing director of Otto Klostermann. ‘It was no longer state of the art, and there were no spare parts available for it any longer. As the laser machine is totally loaded all year round, it was clear that we needed a new one.’

Steel processing firm Otto Klostermann uses a LaserMat II system from Messer Cutting Systems for XXL formats. (Image: Messer Cutting Systems)

The new cutting machine was selected because it is specifically designed for large plate processing, being capable of processing large steel sheets weighing many tonnes. The company is now able to cut components out of mild steel up to 25mm thick, or from stainless steel up to 20mm thick. The on-board laser beam source (resonator) additionally means that plates up to 4.5m wide and up to 30m long can be processed. Klostermann explained: ‘These are exactly the XXL sizes which we had in mind. To achieve this, we were happy to extend the length of the vibration damped foundations of the old laser system by 4m.’

An optical beam path length compensation keeps the length of the laser beam constant during transverse axis movements and ensures the highest laser beam and cut quality over the entire cutting area. The high positioning and repetitive accuracy of the system is achieved by a series of harmonised functional factors such as a track construction suitable for laser and robust linear guidance. In addition, accelerations of up to 0.5g and a simultaneous positioning speed of 100m/min also ensure high levels of performance and speed. There is no need for a full enclosure with the CO2 laser, as an on-board laser beam protection hood complies with class 1 laser safety, with the additional benefit of easy access for loading and unloading, even during operation.

‘What is more,’ said Klostermann, ‘the infinitely rotating bevel head enables us to perform continuous bevels from -45° to +45°. Furthermore, we cannot only prepare countersinks with the highest surface quality directly during the cutting process, but we can also cut and mark with the same tool – a saving in costs and time.’

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