Abstract: A cryogenic pressure vessel of formed of an ASTM A553 Type 1 cryogenic steel alloy including in wt. %: C: 0.01-0.04; Mn: up to 2.0; P: up to 0.02; S: up to 0.15; Si: up to 1.0; Ni: 7-11; Cr: up to 1.0; Mo: up to 0.75; V: up to 0.2; Nb: up to 0.1; Al: up to 0.1; and N: up to 0.01. The steel alloy may have an ultimate tensile strength of at least 900 MPa, a total elongation of at least 20%; a microstructure including between 5 and 20 area % reverted austenite and the remainder tempered martensite; a transverse Charpy impact energy of at least 27 J at ?196° C.; and a lateral expansion of at least 0.381 mm at ?196° C.