To produce an Fe- and Ni-base heat resistant alloy extremely excellent in strength and capable of being easily worked, which is so far considered to be difficult in working in the case of a refined material and also deficient in strength at high temp. in the case of a powdered heat resistant alloy.

The Fe- and Ni-base heat resistant alloy can be produced by using an alloy powder, prepared by gas atomizing and containing ≥15%, by weight, of Cr, and solidifying and forming this alloy powder by means of hot forging, hot rolling, or hot extrusion. Further, this heat resistant alloy has a composition contains, by weight, 50-300ppm B and in which the contents of O, Al, and Ti and controlled to ≤100ppm, ≤0.5%, and %h0.5%, respectively.