ClassNK approves duplex stainless steel applications

MARCH 27, 2013 — Classification society Nippon Kaiji Kyokai (ClassNK) has approved the first application of duplex stainless steel (NSSC 2120) on vessels in Japan.

The steel, manufactured by Nippon Steel and Sumikin Stainless Steel Corporation, was applied in tankers built by the Japanese shipyards Sasaki Shipbuilding Co., Ltd. and Hakata Shipbuilding Co., Ltd. were applied with the duplex stainless steel, which was . The two domestic vessels, a chemical tanker and an oil tanker, were launched in January 2013.

Cargo tanks in chemical tankers built in Japan are generally constructed with austenitic stainless steel SUS304. However, with a nickel content about one quarter of that of SUS304, the newly approved austenitic-ferrite two-phased stainless NSSC2120 can now be used in chemical tankers as a substitute for SUS304 for the first time in Japan.

Pitting corrosion resistance to sea water and corrosion resistance to acids of NSSC2120 are equal to or greater than those of SUS304. In terms of strength, NSSC2120 is almost twice as strong as SUS304 at 0.2 percent proof stress under NK Rules.

NSSC2120 has a weldability equivalent to that of SUS304 when CO2 gas shielded arc welding or submerged arc welding is applied.