South Korean steelmaker POSCO and shipbuilder Hanwha Ocean have agreed to build a test ship whose main LNG cargo tanks are made of high-manganese steel, a POSCO-developed alloy that stays strong and tough at minus 163°C. Until now the steel has been used only in smaller LNG fuel tanks of about 1,000 tonnes; cargo tanks need more than 10,000 tonnes per ship. The alloy replaces costly, price-volatile nickel found in the Invar and nickel steels that conventional tanks use. The partners will study safety and durability in real service to win over shipowners, then aim to extend the material to bunkering ships, floating terminals and carriers for hydrogen, ethane and ammonia.