An Fe--Ni alloy for use as a part 10 of an electron-gun 4 is press-blanked by a punch to form minute apertures 10a, 10b, 10c for passing an electron beam 3. The burrs 10 formed around the minute apertures 10a, 10b, 10c are detrimental to such part 4. The Fe--Ni alloy according to the present invention essentially consists of from 30 to 55 wt % of Ni, not more than 0.5 wt % of Si, not more than 1.5 wt % of Mn, and the balance being Fe and unavoidable impurities. The alloy includes from 10 to 1,000 of A type or B type non-metallic inclusions of 10 .mu.m or more in length per 1 mm.sup.2 of longitudinal cross section, and from 100 to 50,000 of C type non-metallic inclusions having a diameter of 5 .mu.m or less.