GB829640A - Improvements relating to the manufacture of alloy strip - Google Patents

Abstract

Strip, or thin shaped pieces are made of an alloy that is inherently brittle at room temperature by compacting a mixture of metal powders corresponding to the composition of the alloy into a strip, sintering at a temperature which will relieve internal stresses but not be high enough to render the alloy homogeneous, cold rolling in one or more stages to the final thickness desired then carrying out any desired shaping operations, and finally homogenizing the strip or tin shaped pieces formed therefrom by further heating. Annealing steps may be interposed between the cold rolling stages, while the final homogenizing temperature should be higher than that used for sintering. The process is particularly applicable to binary Fe-Co alloys, but also to permanent magnet alloys of Ni-Fe-Al with or without Co. In an example Co powder size 5m obtained from the oxide and Fe powder size about 3m and of irregular shape obtained from the carbonyl are ball-milled to mix, and then heated in hydrogen at 400-450 DEG C. for 4 hours to improve their flowability and produce a light sintering. It is then crushed to between -100 and +60 mesh to the linear inch; compacted into strip 1 inch wide and 0.004 inch thick between rolls; sintered at 1150 DEG C. in hydrogen for 10-15 seconds; cold rolled in 3 stages to a thickness of 0.002 inch with inter-stage anneals at 1150 DEG C. in hydrogen for 10-30 seconds if desired; and finally homogenized in hydrogen at 1200 DEG C. for 10 minutes. In a further example powdered alloy of 70% Ni, 30% Al passing a 300 mesh, fibrous powdered Fe (from its carbonyl), and Co particles of 5m (from its oxide) were mixed to fine a resultant composition 12% Al, 28% Ni, 5% Co, remainder Fe, and rolled into strip 0.024 inch thick. This was sintered in hydrogen for 30 minutes at 700 DEG C. in a box sealed with a 50% alumina, 50% Ti powder mixture as a "getter", then cold rolled to 0.013 inch, annealed under the same conditions as those in which it was sintered, cold rolled to a final thickness of 0.009 inch, and finally (together with punched discs therefrom) homogenized by heating for 4 hours in hydrogen at 1300 DEG C., then cooled in 15 minutes to room temperature. Other treatable alloys referred to are Fe with 2-11% Si, and Fe with 5-15% Al.