A precipitation-hardenable, stainless steel comprises:- .Cr 7.- 18% .Ni 6.- 12% .Al 0.5.- 2.5% .Mn up to.1% .Si up to.1% .C up to.0.05% .P up to.0.015% .S up to.0.1% .N up to.0.05% the balance being iron. The steels may also optionally contain:- .Mo up to.8% .Ti up to.0.1% .B up to.0.003% and one half of the nickel may be substituted by Co in the ratio of three parts Co for each part of Ni replaced. The steel may be hot worked, annealed at 980-1093 DEG C., quenched in air, oil or water and then fabricated. It is then austenetized at 704-955 DEG C., cooled to between 150 DEG C. and - 129 DEG C. and tempered at 370 DEG - 650 DEG C. followed by cooling in air, oil or water.
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