The world’s first chemical tanker to use a combination of duplex stainless steel and stainless clad steel in the construction of its cargo tanks was successfully delivered to Oita-based Hiro Naviera S.A. on 15 November 2014 by Usuki Shipyard Co., Ltd. The application of the duplex steels in the vessel’s cargo tanks was made possible thanks to an expansive joint research program involving steel manufacturers, leading technical universities, and ship designer, as well as ClassNK (Chairman and President: Noboru Ueda) which supported the project as part of its Joint R&D for Industry Program.
The 12,500MT chemical tanker Sunrise Hope, owned by Hiro Naviera S.A., will be operated by Nippon Marine Co., Ltd (President: Shinichi Igata). The eco-ship design vessel is equipped with 14 cargo tanks, all which employ duplex stainless steel technology. Construction of the vessel was carried out in accordance with ClassNK’s Guidelines on Welding of Duplex Stainless Steels, which were released in January 2014, marking the first time the Guidelines have been used in the construction of an actual vessel.
Duplex stainless steel provides not only significantly greater strength and excellent corrosive resistance in comparison with the commonly used austenitic stainless steel SUS316LN, but its low nickel composition also makes it economical. Although duplex stainless steel technology has been used previously in shipbuilding internationally, this marks the first time in the world that a combination of both duplex and stainless clad steels have been used in the construction of a chemical tanker’s cargo tanks. It is also the first time that duplex stainless steels have been used in a Japanese shipyard, while the lean duplex stainless steel which contains lower nickel compared to duplex stainless steel have been used in some cases.
Duplex stainless steels consist of a mixture of both of austenite and ferrite phases and offer enhanced strength and corrosion resistance superior to that of commonly used austenitic stainless steels. On theSunrise Hope, duplex stainless steel KSUS329J3L replaces the commonly used SUS316LN for the bulkheads inside the cargo tanks, while the bulkheads adjacent to the cargo tanks were constructed using stainless clad steel, in which stainless steel and carbon manganese steels have been compression bonded together into a single plate. The stainless clad steel of the ballast tanks also ensures the coating quality of the tanks is protected.
The application of the steels in the construction of the Sunrise Hope was achieved as part of a joint research project carried out as part of the ClassNK Joint R&D for Industry Program by JFE Steel Corporation, Nippon Steel & Sumikin Stainless Steel Corporation (NSSC), Taseto Co., Ltd, and ClassNK, with the support of Professor Hiroshi Yajima and Associate Professor Tadakazu Tanino from Nagasaki Institute of Applied Science and Toshiaki Mori from Consultancy Juk Fnadyke. The team’s wealth of specialist knowledge and extensive expertise spanning from material development to ship construction ensured the technology was successfully applied to this first vessel.