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MHI First in Japan to Apply Laser-Arc Hybrid Welding to Commercial Ships
-- Nagasaki Shipyard Certified by Ship Classification Societies --

No.1309
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Tokyo, September 10, 2009 - Mitsubishi Heavy Industries, Ltd. (MHI) will soon become the first shipbuilder in Japan to apply a laser-arc hybrid welding system to the construction of commercial ships. The company's Nagasaki Shipyard & Machinery Works was recently certified in this advanced welding method by Lloyd's Register and Nippon Kaiji Kyokai (ClassNK). The new method is capable of significantly reducing heat deformation from welding, and for that reason it will not only enhance the quality of ships that require good visual appearance, such as passenger ships, but also contribute to improvement of shipbuilding efficiency for various types of vessels. The new method will also contribute to the company's target to enhance production efficiency by 30%, a goal being pursued under a companywide initiative known as "Production System Innovation." Going forward it will be further developed as the company's differentiated technology in shipbuilding, and will be applied at other MHI shipyards.

Because laser welding is highly efficient and offers deeper penetration than arc welding, its commercial application has become popular in the manufacture of products incorporating thin steel sheets, such as automobiles. However, commercial application of laser welding to large-scale products requiring thicker plates, such as ships, has been considered difficult due to the requirement for stringent precision control and concerns over deterioration of the quality of welding joints where a welding rod is not used.

Laser-arc hybrid welding is an automatic welding system that combines the advantages of conventional arc welding, which is highly suited to work processing, and laser welding, which is capable of reducing the total heat volume applied to material by concentrating the laser into one spot. In shipbuilding, hybrid welding will compensate for arc welding's disadvantage – heat deformation – and enhance the precision of the hull-block's finish, thereby reducing after-welding work such as cutting for adjustment and fairing at the assemble stage or dock. The new method will thus enhance both shipbuilding efficiency and quality as it simultaneously also provides a better finished appearance.

The Nagasaki Shipyard launched technological development of the new welding method in 2007 working in tandem with Technical Headquarters, which possesses advanced technology in laser processing. By integrating arc welding with laser welding, only the advantages of both methods have been synergize. To date the new method has demonstrated its superior quality in applications involving up to 13.0 millimeter thick plates, including quality of joints, toughness and fatigue strength, and its commercial viability in shipbuilding has been verified from the viewpoints of quality control and work processing.

MHI has already begun preparing for application of the new system in actual shipbuilding with installation of fiber laser oscillators at the Nagasaki Shipyard's Koyagi Plant. While promoting enhancement of quality and cost competitiveness here, the company will simultaneously focus on preparing to expand introduction of the technology to its other shipyards in the near future.