The United States of America As Represented by the Administrator of the

Walter R Witzke

Joseph R Stephens

An iron alloy is provided which exhibits excellent strength and toughness characteristics at cryogenic temperatures. The alloy consists essentially of about 10 to 16 percent by weight nickel, about 0.1 to 1.0 percent by weight aluminum, and 0 to about 3 percent by weight copper, with the balance being essentially iron. The iron alloy is produced by a process which includes using cold rolling at room temperature and subsequent heat treatment at temperatures ranging from 400.degree. to 650.degree. C., and possesses a fracture toughness ranging from 200 to 230 ksi .sqroot.in. and yield strengths up to 230 ksi.

High toughness-high strength iron alloy

A steel alloy is produced by a process which includes using cold rolling at room temperature and subsequent heat treatment at temperatures ranging from 500.degree. to 650.degree. C. The resulting alloy exhibits excellent strength and toughness characteristics at cryogenic temperatures. This alloy consists essentially of about 10 to 16 percent by weight nickel, to about 1.0 percent by weight aluminum, and 0 to about 3 percent by weight of at least one of the following additional elements: copper, lanthanum, niobium, tantalum, titanium, vanadium, yttrium, zirconium and the rare earth metals, with the balance being essentially iron. The improved alloy possesses a fracture toughness ranging from 200 to 230 ksi.sqroot.in. and yield strengths up to 230 ksi.

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Seven Hills, OH, United States of America

Walter R Witzke