US 1550508 A
Description (OCR text may contain errors)
I Patented Aug. 18 1925.
' HUGH S. COOPER,
OF CLEVELAND, O HIO, ASSIGNOR TO KEMET LABORATORIES GOM- PANY, INC., A. CORPORATION OF NEW YORK.
To all whom it may concern:
, Be it known that I, HUGH S. COOPER,
' a citizenofthe United States, residing at like. As. will appear hereinafter the .third' component imparts malleability to an otherwise unworkable binary. alloy, and it may therefore be conveniently designated a malleability component. Many of the compositions according tomy invention may be readily worked into wire, ribbon or the like suitable for use in electrical resistance elements and for like purposes.
It is known that certain iron-aluminum alloys, for example those containing about 9% of aluminum, exhibit high electrical resistance and good heat resistivity, but such binary alloys are of little practical value because their brittleness precludes the possi-- bility of their being used for most industrial purposes. Any increase in the aluminum content of such alloys accentuates their undesirable qualities. A decrease in aluminum content serves to improve the working properties; and if the aluminum content is -less than 5.6%, the alloy is malleable, ac-
cording to Hadfield. Such low-aluminum binary alloys are however deficient in the desired electrical resistance and heat resistivity.
I have discovered that a rather high aluminum content, for example 10 to 16%, may be maintained and surprising y good working qualities nevertheless imparted by suitable additions of manganese and chromium, or mixtures 'of these metals; and that, in addition, the electrical resistance is greatly increased over that exhibited by the corresponding binary alloys of aluminum and iron. The increase in workability and resistance is especially pronounced when chromium is the third metal of the alloy, and.
Application filed January 24, 1922. Serial No. 531,466.
chromium is accordinglymy preferred addition. However, iron-aluminum-manganese alloys within the range indicated have properties which render them valuable for many purposes. For example, an alloy of iron 70%, aluminum 20% and manganese 10% gives excellent heat resistant castings, showing a, fine silky fracture; while alloys of aluminum 12-15% and manganese 68%, with the balance iron, may even be rolled to some extent. i
For the preparation of attenuated members suitable for electrical resistance elements, I prefer iron-aluminum-chromium alloys, as intimated above. Compositions containing 12-16% aluminum with. additions of 5-10% ofchromium may be readily rolled, forged or swaged while hot, and may be formed into fine wire or ribbon, which,
after annealing, possesses suflicient flexibility and toughness for such purposes as are contemplated herein. In order to obtain maximum toughness, it is necessary to keep the carbon content low, and for this reason a carbon content of less than 0.20% is preferred when attenuated members are to be prepared.
Iron-aluminum-chromium alloys of certain composition have, as already indicated, a remarkably high electrical resistance, in fact a resistance which so far as I am aware is unprecedented in alloys heretofore investigated. The range of compositions for high resistance is somewhat broader than that indicated above for a high degree of workability, as the chromium may be in excess of the 10% there mentioned. However, the maximum electrical resistance falls within the range of compositions giving workable alloys, as demonstrated by the tabulation given below:
Composition Resistance (microhms per centimeter Chromium. Aluminum. cube) 6 1 150 a Z 14 Z 165 10 o 1 0 ms 1 1 D 176 10 a 14 a 172 1 c 12;, 14s 10 o 15 a 184 The highest resistances noted in the table are of the order of one hundred times that of copper.
With respect to both working and electrical qualities, my preferred composition is, chromium about 8%, aluminum about 14% with the balance predominantly iron, and carbon less than 0.20%. The presence of other elements in relatively small proportion is not excluded.
I am aware that it has been proposed to use for electric resistance elements, and for other purposes, alloys containing iron,
. aluminum and chromium, with'an addition of over 5% of titanium. It is my understanding that the function of the titanium, which may be present in quantities as high as 25%, is to harden the alloy; and I also understand that while these titanium-containing alloys are not too brittle to preclude their use as castings, they cannot be drawn and swaged as can the alloys of my invention. The appended claims are therefore not to be construed to cover alloys containing metals other than those described as suitable constituents for my alloys, in sufficient quantity materially to diminish the electrical resistance, resistance-to oxidation, or workability of the alloys.
The alloys of my invention are, for the most part, compositions in which the aluminum is present in excess of the manganese or chromium, or at least in substantially equal proportion therewith.
1. An alloy consisting predominantly of iron, aluminum, and chromium, the aluminum content being within the range of 10% to 16%, and the chromium content being greater than 5% and less than the aluminum content.
2. An alloy consisting predominantly of iron, aluminum, and chromium, with aluminum and chromium contents of about 14% and 8% respectively.
3. .An alloy consisting predominantly of iron, aluminum, and chromium, with aluminum and chromium contents of about 141% and 8% respectively, and containing not more than about 0.2% carbon.
4. An alloy consisting predominantly of iron, aluminum, and manganese, the aluminum content being Within the range of 10% to 16%, and the manganese content being greater than 5% and less than the aluminum content.
In testimony whereof, I afiix my signature.
HUGH S. COOPER.