ClassNK approves lean duplex stainless steel

The new steel has been developed to have an equal to or greater resistance to pitting corrosion of sea water and acids than SUS304. In terms of strength, NSSC2120 is almost twice as strong as SUS304 at 0.2% proof stress under ClassNK regulations.

In addition, it also has weldability equivalent to that of SUS304 when CO2 gas shielded arc welding or submerged arc welding is applied.

The cargo tanks for use in chemical tankers built in Japan are usually constructed with austenitic stainless steel SUS304. But, with a nickel content of almost a quarter of SUS304, the newly approved austenitic-ferrite two phased stainless NSSC2120 can now also be applied to chemical tankers as a substitute for SUS304 for the first time in Japan.

The newly developed NSSC2120 has already been applied to two Japanese vessels, a chemical tanker and an oil tanker, built by Japanese shipyards Sasaki Shipbuilding Co Ltd and Hakata Shipbuilding Co Ltd.