9% Nickel steel

9 percent nickel steel is a quenched-and-tempered low-alloy plate for cryogenic service, specified as ASTM A553 Type I. It keeps high toughness down to minus 196 C, the boiling point of liquid nitrogen and below the minus 163 C of LNG, with a minimum yield of 585 MPa and 690 to 825 MPa tensile. The 9 percent nickel stabilizes a fine ferritic microstructure with retained austenite that resists brittle fracture at cryogenic temperatures. It is the standard material for IMO Type B and Type C self-supporting LNG tanks and for land LNG storage; liquid-hydrogen and ammonia service push toward austenitic stainless or aluminum instead.