US 3806326 A
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April 1974 I D. s. MEDlCK ETAL. 3,806,326
ELECTRICAL CONDUCTORS AND INSULATED CABLES COMPRISING THE SAME Filed May 24, 1971 I N VEN I 0R3 D. S. MEDRICK C. J. SNYDER and d ETEAGUE United States Patent O U.S. Cl. 29183-5 7 Claims ABSTRACT OF THE DISCLOSURE An electrical conductor with improved toughness and workability is made by adding about 0.01% tin to highiron content, zinc bearing aluminum to be hot-rolled from cast bars. Insulated cables are made comprising the improved conductors.
BACKGROUND OF THE INVENTION In Pat. 3,063,832, dated Nov. 13, 1962, C. J. Snyder, one of the applicants in the present case, disclosed a very high purity aluminum conductor in which the conductivity was maintained above 62% of the International Annealed Copper Standard (IACS) by the addition of tin. However, it was believed at that time that in order to achieve the advantage of the tin addition the aluminum content would have to be at least 99.5% and preferably 99.6%. Such high purity aluminum, is, however unduly expensive. R. J. Schoerner, in Pat. 3,512,221, issued May 19, 1970, taught the use in continuous cast bar of a high iron content aluminum for which he claimed superior elongation. We have found that high iron aluminum without the presently discovered addition of tin is deficiently brittle in such operations as compacting and does not provide consistent 62% conductivity in the V2 hard or fully annealed state.
SUMMARY We have invented an electric conductor which may take the form of bare rod suitable for cold drawing having a diameter of 0.25 to 1.00 inch, cold drawn wires, or standed pluralities of such wires, but is not limited thereto, and which has minimum 62% IACS conductivity at a 16,000 p.s.i. tensile strength, consisting essentially of 99.3 to 99.5 weight percent aluminum, 0.3 to 0.45 weight percent iron, at least 0.01 weight percent tin, at least 0.02 weight percent zinc, and the remainder impurities normally present in aluminum of electrical conductivity grade. We have also invented insulated conductors comprising the cold drawn wire of our invention and insulated cables comprising such wires. In making the conductor of our invention we prefer a method whereby an ingot is cast having the above composition, followed by cooling the entire mass to room temperature. The ingots are subsequently reheated to at least 600 F. and hot rolled to red having a diameter between 14 inch and 1 inch.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a pictorial view of a cable made to our invention.
FIG. 2 shows a diagram of the steps of a method of our invention.
FIG. 3 shows a pictorial view of an insulated wire made to our invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Example 1 Analysis by Weight: 0.058% silicon, 0.420% iron, 0.019% copper, 0.005% manganese, 0.015% boron,
3,806,326 Patented Apr. 23, 1974 0.002% vanadium, 0.001% chromium, 0.030% zinc, .009% nickel, 0.005% tin, 99.436% aluminum, by difference.
The aluminum of Example 1 was prepared by melting an EC grade aluminum and adding tin to bring the tin content to 0.01%. Thereafter the metal was melted in a crucible 11 (FIG. 2) poured into a mold 12 to form an ingot 13. A large number of the ingots 13 were stored for periods of time suflicient for them to come to room temperature and were stored at room temperature until needed. Thereafter the ingots 13 were transported to a rolling mill where they were heated in a preheating oven 14 to 650 F. From the oven 14 the ingots passed through a hot rolling mill 16, emerging therefrom as a rod 17 having a diameter from about 0.25 to 1.00 inch.
The rod 17 is subsequently cold drawn in a conventional manner to form a wire conductor 18 which may be insulated as shown in FIG. 3 with enamel 19 or with an extruded plastic, or stranded with other wires into a stranded conductor 21, insulated, and formed with other such insulated strands, into a cable 22.
When the conductor of Example 1 drawn to #12 AWG was batch annealed to half hard temper the following tensile and elongation measurements were made on three specimens: 15,730 p.s.i. and 19.5%, 16,100 p.s.i. and 18.0%, 16,300 p.s.i. and 20.0%. Conductivity of all specimens exceeded 62% IACS. A creep test was conducted by holding a specimen under a constant 10,000 p.s.i. tensile load for 833 hours at room temperature. The total extension so determined was 240 microinches per inch as compared to typical values of 2200 microinches per inch for EC grade aluminum extended similarly for 500 hours.
Example 2 Analysis by weight: 0.057% silicon, 0.440% iron, 0.015 copper, 0.005% manganese, 0.006% boron, 0.001% magnesium, 0.003% vanadium, 0.001% titanium, 0.001% chromium, 0.022% zinc, 0.011% nickel, 0.007% tin, 99.431% aluminum, by difference.
Conductor of Example 2 was cold drawn to #12 AWG and specimens found to have tensile strengths and elongation as follows after continuous annealing: 1 8,048 p.s.i. and 11.0%, 18,400 p.s.i. and 15.5%, 18,196 p.s.i. and 12.0%, 18,196 p.s.i. and 11.8%, 16,840 p.s.i. and 16.2%, 16,840 p.s.i. and 16.0%. Additional conductor was cold drawn to #10 AWG, continuously annealed, and found to have tensile strengths and elongation of 15,570 p.s.i. and 18.2%, and 16,060 p.s.i. and 12.0%. Conductivity was in excess of 62% IACS.
Example 3 Analysis by weight: 0.058% silicon, 0.420% iron, 0.019% copper, 0.005% manganese, 0.015% boron, 0.002% vanadium, 0.001% chromium, 0.030% zinc,
0.009% nickel, 0.005% tin, 99.436% aluminum, by difference.
Conductor of Example 3 was cold drawn to #10 and #12 AWG. Conductor was cold drawn to 0.097 in diameter, seven-stranded together and compacted to 2/ 0 AWG. No cracking was experienced during compacting. Wire drawn to 0.0975 inch diameter was annealed /2 hard and specimens found to have the following tensile strengths and elongation: 16,540 p.s.i. and 13.4%, 15,970 p.s.i. and 15.8%, 16,140 p.s.i. and 18.2%, 16,270 p.s.i. and 16.7%, 1 6,600 p.s.i. and 11.7%, 16,270 p.s.i. and 13.5%. The conductivity exceeded 62% IACS.
Example 4 Analysis by weight: 0.051% silicon, 0.437% iron, 0.016% copper, 0.006% manganese, 0.010% boron, 0.002% magnesium, 0.001% vanadium, 0.027% zinc,
3 0.004% nickel, 0.005% tin, 99.44l% aluminum, by difference.
Conductor of Example 4 was hard drawn to #13 and 19.5 AWG for use as magnet wire. In the hard drawn condition conductivity exceeded 62% IACS and after soft annealing the elongation was at least 23%.
Example 5 Analysis by weight: 0.053% silicon, 0.430% iron, 0.016% copper, 0.006% manganese, 0.011% boron, 0.002% magnesium, 0.002% vanadium, 0.028% zinc, 0.004% nickel, 0.007% tin, 99.441% aluminum, by difference.
Conductor of Example 5 was hard drawn to #13 and #19.5 AWG magnet wire. In the hard drawn condition the conductivity exceeded 62%, and after soft annealin the elongation was at least 23%.
Example 6 Analysis by weight: 0.055% silicon, 0.391% iron, 0.014% copper, 0.004% manganese, 0.006% boron, 0.001% magnesium, 0.001% vanadium, 0.001% titanium, 0.001% chromium, 0.025% zinc, 0.009% nickel, 0.010% tin, 99.482% aluminum, by difierence.
Conductor of Example 6 was'hard drawn into commercially useful wire, with electrical conductivity of 62% in the annealing condition.
The wire cold drawn in Examples 2-6 was all first cast into ingots, permitted to cool, reheated to at least 600 F., and hot rolled into rod prior to cold drawing. We believe that the cooling and reheating steps, when applied to the iron, zinc, tin bearing aluminum of our invention has a hitherto unsuspected effect, the exact mechanism of which is unknown that influences the toughness, high elongation, workability, high conductivity, and very low creep of our conductor. The toughness and workabilityare manifested by excellent performance of our conductor during manufacturing operations where it can be flipped over from one reel to another in high-speed wire drawing, without breaking and can be compacted readily without cracking.
We have invented a new conductor, composition, and
. 4 than definitive and for which-we desire an award of Letters Patent as defined in the following claims.
1. A drawn electric conductor annealed to half-hard temper, having a minimum conductivity at a tensile strength of 16,000 p.s.i. of 62% of the International Annealed Copper Standard, consisting essentially of 99.3 to 99.441 weight percent aluminum, 0.3 to 0.45 Weight percent iron, at least about 0.005 weight percent tin, at least 0.02 weight percent zinc and the remainder impurities normally present in aluminum of electrical conductivity grade, the amounts of each of said elements being so selected that said drawn and annealed conducvtor, held under a constant 10,000 p.s.i. tensile load for 833 hours at room temperature does not creep substantially more than 240 microinches per inch.
2. The conductor of claim 1 consisting of bare rod having a diameter of A to 1 inch and suitable for cold drawing into wire.
3. The conductor of claim 1 consisting of cold drawn wrre.
4. An insulated conductor comprising the wire of claim 3.
5. The conductor of claim 1 consisting of a plurality of stranded cold-drawn wires.
6. An insulated conductor comprising the stranded wires of claim 5.
7. An insulated electric cable comprising a plurality V of the conductors of claim 1.
examples and description have been illustrative rather References Cited UNITED STATES PATENTS 3,063,832 11/1962 Snyder -138 3,512,221 5/1970 Schoerner 75-143 X 3,515,796 6/ 1970 Schoerner 29-193 X 3,490,955 1/ 1970 Winter et al 75-148 X 2,075,090 3/1937 Bonsack 75-146 3,241,953 3/ 1966 Pryor et al. 29-193 X 3,607,151 9/ 1971 Pryor et al. 29-193 X ALLEN B. CURTIS, Primary Examiner us. 01. xn.