US3811846A

US3811846A - Aluminum alloy electrical conductor

Info

Publication number: US3811846A
Application number: US00259722A
Authority: US
Inventors: R Schoerner; E Chia
Original assignee: Southwire Co LLC
Current assignee: Southwire Co LLC
Priority date: 1970-12-01
Filing date: 1972-06-05
Publication date: 1974-05-21
Anticipated expiration: 1991-05-21

Abstract

Aluminum alloy electrical conductors are produced from aluminum base alloys containing from about 0.20 to about 1.60 weight percent cobalt, from about 0.30 to about 1.30 weight percent iron, up to about 0.40 weight percent magnesium, up to about 0.40 weight percent copper, from about 99.50 to about 97.00 weight percent aluminum and up to about 0.45 weight percent each of additional alloying elements, the total weight percent of additional alloying elements not exceeding about 0.70 percent; the total weight percent of magnesium and copper not exceeding about 0.40 percent and the total weight percent of additional alloying elements not exceeding about 0.40 percent when the total weight percent of cobalt and iron exceeds about 1,80 percent. The alloy conductors have an electrical conductivity of at least 57 percent, based on the International Annealed Copper Standard (IACS), and improved properties of increased thermal stability, tensile strength, percent ultimate elongation, ductility, fatigue resistance and yield strength as compared to conventional aluminum alloys of similar electrical properties.

Description

United States Patent 1191 Schoerner et al.

1 ALUMINUM ALLOY ELECTRICAL CONDUCTOR [75] Inventors: Roger J. Schoerner; Enrique C.

- Chia, both of Carrollton, Ga.

[73] Assignee: Southwire Company, Carrollton,

[22] Filed: June 5, 1972 [21] Appl. No.: 259,722

Related U.S..Applicati0n Data [63] Continuation-in-part of Ser. No. 94,193, Dec. 1, 1970, abandoned, which is a continuation-in-part of Ser. No. 54,563, July 13, 1970, abandoned.

[52] US. Cl 29/193, 29/527.7, 75/138, 75/143, 148/2, 148/32, 164/76 [51] Int. Cl B2lc 1/00, C22f 1/04 [58] Field of Search 29/183, 183.5, 193, 527.7; 75/138-148; 148/2, 3, 11.5 A, 32; 164/76 [56] References Cited UNITED STATES PATENTS 1,579,481 4/1926 Hybinette 75/138 1,932,795 10/1933 McCullough 75/142 1,932,838 10/1933 Dean et al. 75/147 1,945,297 1/1934 Sterner-Rainer 75/147 3,160,513 12/1964 Westerveld et al. 75/138 3,670,401 6/1972 Schoerner 148/2 FOREIGN PATENTS OR APPLICATIONS 498,227 1/1939 Great Britain 706,721 6/1931 France OTHER PUBLICATIONS Kruptokin et al., The Mechanical Properties of AVOOO Aluminum with Small Additions of Different 1 51 May 21, 1974 Elements, Metals Abstract, December, 2,291.

Kruptokin, Influence of Small Additions of Iron, Nickel and Cobalt on Mechanical Properties and Conductivity of Aluminum, Slavic Library, November 30, 1965, Battell Memorial Institute.

Primary ExaminerRichard 0. Dean Attorney, Agent, or FirmHerbert M. Hanegan; Van C. Wilks 5 7 ABSTRACT Aluminum alloy electrical conductors are produced from aluminum base alloys containing from about 0.20 to about 1.60 weight percent cobalt, from about 0.30 to about 1.30 weight percent iron, up to about 0.40 weight percent magnesium, up to about 0.40 weight percent copper, from about 99.50 to about 97.00 weight percent aluminum and up to about 0.45 weight percent each of additional alloying elements,

, the total weight percent of additional alloying ele- 32 Claims, N0 Drawings l ALUMINUM ALLOY ELECTRICAL CONDUCTOR CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of our copending application, Ser. No. 94,193, filed Dec. 1,

1970, now abandoned, which in turn is a continuation-- in-part of our copending application, Ser. No. 54,563, filed July 13, 1970, now abandoned.

The present invention concerns an aluminum base alloy especially suited for producing high strength lightin the marketplace of today because of their light weight and low cost. One area where aluminum alloys have found increasing acceptance is in the replacement of copper in the manufacture of electrically conductive wire. Conventional electrically conductive aluminum alloy wire(referred toas EC) contains a substantial amount of pure aluminum and trace amounts of impurities such as silicon, vanadium, iron, copper, manganese, magnesium, zinc, boron, and titanium.

Even though desirable in terms of'weight andcost, aluminum' alloys have received far less than complete acceptance in the electrical conductor marketplace. One of the chief reasons for the lack of complete acceptance is the range of physical properties available with conventional EC aluminum alloy conductors. If the physical properties, such as thermal stability, tensile strength, percent elongation, ductility and yield strength,could be improved significantly without substantially lessening. the electrical conductivity of the finished product, a very desirable improvement would be achieved. lt is accepted, however, that addition of alloying elements, as in other aluminum alloys, reduces conductivity while improving the physical properties. Consequently, only those additions of elements which improve physical properties without substantially lessening conductivity will yield an acceptable and useful product.

It is an object of the present invention, therefore, to provide a new aluminum alloy electricalconductor which combines improved physical properties with acceptable electrical conductivity. These and other objects, features and advantages of the present invention will be apparent from a consideration of the following detailed-description of an embodiment of the invention.

In accordance with the invention, the present aluminum base alloy is prepared by mixing cobalt, iron and optionally other alloyingelernents with aluminum in a furnace to obtain a melt having requisite percentages of elements. lt has been found that suitable results are obtained withcob'alt present in a weight percentage of from about 0.20 percent to about 1.60 percent. Superior results are achieved when cobaltis present in a weight percentage of from about 0.20 percent to about 1.00 percent and particularly superior and preferred results are obtained when cobalt is presentin a percentage by weightof from about 0.30 percent to about 0.80

percent. 7

Suitable results are obtained with iron present in a weight percentage of from about 0.30 percent to about 1.30 percent. Superior results are achieved when iron is present in a weight percentage of from about 0.30 percent to about 1.00 percent and particularly superior and preferred results are obtained when iron is present in a percentage by weight of from about 0.40 percen to about 0.70 percent.

The aluminum content of the present alloy may vary from about 97.00 percent to about 99.50 percent by weight with superior results being obtained when the aluminum content varies between about 97.90 percent and about 99.50 percent by weight particularly superior and preferred results are obtained when aluminum is present in a percentage by weight of from about 98.40 percent to about 99.30 percent. Since the percentages for maximum and minimum aluminum do not correspond with the maximums and minimums for alloyingelements, it should be apparent that suitable results are not obtained if the maximum percentages for all alloying elements are employed. If commercial aluminum is employed in preparing the present melt, it is preferred that the aluminum, prior to adding to the melt in the furnace, contain no more than 0.10 percent total of trace impurities.

Copper and magnesium'have a high solubility in aluminum at room temperature, consequently the electrical conductivity is decreased due to the known effect of atoms in solid solution on the electrical conductivity of aluminum. The present alloy may contain up to about 0.40 weight percent copper and up to about 0.40 weight percent magnesium.

The present alloy may contain up to about 0.45 percent by weight each of additional alloying elements, the total weight percent of additional alloying elements not exceeding about 0.70 percent. Superior results are obtained when the concentration of individual optional alloying elements is about 0.30 percent by weight or less and the total additional alloying elements not exceeding about0.60 weight percent. Particularly superior and preferred results are obtained when the concentration of individual optional alloying elements is about 0.20 percent by weight or less and the total additional alloying elements not exceeding about 0.40 weight percent.

Additional alloying elements include the following:

Superior results are obtained with the following additional alloying elements in the percentages, by weight, as shown:

PREFERRED ADDlTlONAL ALLOYING ELEMENTS Nickel 0.0005% to 0.45% Silicon 0.001% to 0.45% Zirconium 0.00l% to 0.45% Niobium 0.00l% to 0.45% Tantalum 0.00l% to 0.45% Yttrium 0.00l% to 0.45%

-Continued PREFERRED ADDlTlONAL ALLOYlNG ELEMENTS Mixtures of two or more of the above 0.001% to 0.70

Particularly superior and preferred results are obtained with the use of silicon in a percentage range of from about 0.001 to about 0.45 percent by weight, additional alloying elements in a percentage range of from about 0.0005 to about 0.25 percent by weight, and nickel or magnesium as additional alloying elements. Suitable results are obtained with magnesium or nickel in a percentage range of from about 0.0005 to about 0.40 percent by weight. Superior results are obtained with from about 0.025 to about 0.30 percent by weight magnesium or nickel, silicon in a percentage range of from about 0.001 to about 0.30 percent by weight, and from about 0.0005 to about 0.25 percent by weight additional alloying elements. Particularly superior and preferred results are obtained when from about 0.03 to about 0.10 percent by weight of magnesium or nickel is employed with from about 0.001 to about 0.20 percent by weight silicon and from about 0.0005 to about 0.20 weight percent additional alloying elements.

Superior and preferred results are also obtained with the use of cobalt and iron in the percentage ranges previously specified with additional alloying elements and optionally with silicon as the major additional alloying elements.

Suitable results are obtained with the use of silicon as the major additional alloying element in a percentage range of from about 0.001 to about 0.45 percent by weight and from about 0.0005 to about 0.25 weightpercent additional alloying elements with superior results being obtained with from about 0.001 to about 0.30 weight percent silicon and from about 0.0005 to about 0.25 weight percent additional alloying elements. Particular superior and preferred results are obtained with from about 0.001 to about 0.20 weight percent silicon and from about 0.0005 to about 0.10 weight percent additional alloying elements.

When silicon is not the major additional alloying element suitable results are obtained with the use of cobalt and iron in the percentage ranges previously specified and from about 0.0005 to about 0.70 weight percent additional alloying elements. Superior results are obtained with from about 00005 to 0.60 weight percent additional alloying elements with particular superior and preferred results obtained with from about 0.0005 to about 0.40 weight percent additional alloying elements.

The rare earth metals may be present either individually within the percentage range stated or as a partial or total group, the total percentage of the group being within the percentage range stated previously.

It should be understood that the additional alloying elements may be present either individually or as a group of two or more of the elements. It should be understood, however, that if two or more of the additional alloying elements are employed, the total concentration of additional alloying elements should not exceed about 0.70 percent by weight.

When the total weight percent of cobalt and iron exceeds about 1.80 percent the total weight percent of magnesium and copper should not exceed about 0.40 percent and the total weight percent of additional alloying elements should not exceed about 0.40 percent in order to maintain the desired electrical conductivity and physical properties.

If the total weight percent cobalt and iron is about 2.90 percent the total weight percent of magnesium and copper should not exceed about 0.20 percent and the total weight percent of additional alloying elements should not exceed about 0.10 percent.

After preparing the melt, the aluminum alloy is preferably continuously cast into a continuous bar by a continuous casting machine and then substantially immediately thereafter, hot-worked in a rolling mill to yield a continuous aluminum alloy rod.

One example of a continuous casting and rolling operation capable of producing continuous rod as specified in this application is contained in the following paragraphs. It should be understood that other methods of preparation may be employed to obtain suitable results but that preferable results are obtained with continuous processing. Such other methods include conventional extrusion and hydrostatic extrusion to obtain rod or wire directly, sintering an aluminum alloy powder to obtain rod or wire directly, casting rod or wire directly from a molten aluminum alloy, and conventional casting of aluminum alloy billets which are subsequently hot-worked to rod and drawn with intermediate anneals into wire.

CONTINUOUS CASTING AND ROLLING OPERATION A continuous casting machine serves as a means for solidifying the molten aluminum alloy metal to provide a cast bar that is conveyed in substantially the condition in which it solidified from the continuous casting machine to the rolling mill, which serves as a means for hot-forming the cast bar into rod or another hotformed product in a manner which imparts substantial movement to the cast bar along a plurality of angularly disposed axes.

The continuous casting machine is of conventional casting wheel type having a casting wheel with a casting groove in its periphery which is partially closed by an endless belt supported by the casting wheel and an idler pulley. The casting wheel and the endless belt cooperate to provide a mold into one end of which the cast bar is emitted in substantially that condition in which it solidified.

The rolling mill is of conventional type having a plurality of roll stands arranged to hot-form the cast bar by a series of deformations. The continuous casting machine and the rolling mill are positioned relative to each other so that the cast bar enters the rolling mill substantially immediately after solidification and in substantially that condition in which it solidified. In this condition, the cast bar is at a hot-forming temperature within the range of temperatures for hot-forming the cast bar at the initiation of hot-forming without heating between the casting machine and the rolling mill. In the event that it is desired to closely control the hotforrning temperature of the cast bar within the conventional range of hot-forming temperatures, means for adjusting the temperature of the cast bar may be placed between the continuous casting machine and the rolling mill without departing from the inventive concept disclosed herein.

The roll stands each include a plurality of rolls which engage the cast bar. The rolls of each roll stand may be two or more in number and arranged diametrically opposite from one another or arranged at equally spaced positions about the axis of movement of the cast bar through the rolling mill. The rolls of each roll stand of the rolling mill are rotated at a predetermined speed by a power means such as one or more electric motors and the casting wheel is rotated at a speed generally determined by its operating characteristics. The rolling mill serves to hot-form the cast bar into a rod of a crosssectional area substantially less than that of the cast bar as it enters the rolling mill.

The peripheral surfaces of the rolls of adjacent roll stands in the rolling mill change in configuration; that is, the cast bar is engaged by the rolls of successive roll stands with surfaces of varying configuration, and from different directions. This varying surface engagement of the cast bar in the roll stands functions to knead or shape the metal in the cast bar in such a manner that it is worked at each roll stand and also to simultaneously reduce and change the cross-sectional area of the cast bar into that ofthe rod.

As each roll stand engages the cast bar, it is desirable that the cast bar be received with sufficient volume per unit of time at the roll stand for. the cast bar to generally fill the space defined by the rolls of the roll stand so that the rolls will'be effective to work the metal in the cast bar. However, it is also desirable that the space defined by the rolls of each roll stand not be overfilled so that the cast bar will not be forced into the gaps between the rolls. Thus, it is desirable that the rod be fed toward each roll stand at a volume per unit of time which is sufficient to fill, but not over fill, the space defined by the rolls of the roll stand.

As the cast bar is received from the continuous casting machine, it usuallyhas one large flat surface corresponding to the surface of the endless band and inwardly tapered side surfaces corresponding to the shaped the groove in the casting wheel. As the cast bar is compressed by the rolls of the roll stands, the cast bar is deformed so that it generally takes the crosssectional shape defined by the adjacent peripheries of the rolls of each roll stand.

Thus, it will be understood that with this apparatus, cast aluminum alloy rod of an infinite number of different lengths is prepared by simultaneous casting of the molten aluminum alloy and hot-forming or rolling the cast aluminum bar. The continuous rod has a minimum electrical conductivity of 57 percent IACS and may be used in conducting electricity or it may be drawn to wire of a smaller cross-sectional diameter.

To produce wire of various gauge, the continuous rod produced by the casting and rolling operation is processed in a reduction operation. The unannealed rod (i.e., as rolled to f temper) is cold-drawn through a series of progressively constricted dies, without interme diate anneals, to form a continuous wire of desired diameter. lt has been found that the elimination of intermediate anneals is preferable during the processing of the rod and improves the physical properties of the wire. Processing with intermediate anneals is acceptable when the requirements for physical properties of the wire permit reduced values. The conductivity of the hard-drawn wire is at least 58 percent IACS. If greater conductivity or increased elongation is desired, the wire may be annealed or partially annealed after the desired wire size is obtained and cooled. Fully annealed wire has a conductivity of at least 59 percent IACS. At the conclusion of the drawing operation and optional annealing operation, itis found that the alloy wire has the properties of improved tensile strength and yield strength together with improved thermal stability, percent ultimate elongation and increased ductility and fatigue resistance as specified previously in this application. The annealing operation may be continuous as in resistance annealing, induction annealing, convection annealing by continuous furnaces .or radiation annealing by continuous furnaces, or, preferably, may be batch annealed in a batch furnace. When continuously annealing, temperatures of about 450F to about l,200F may be employed with annealing times of about 5 minutes to about U 10,000 of a minute. Generally, however, continuous annealing temperatures and times may be adjusted to meet the requirements of the particular overall processing operation so long as the desired physical properties are achieved. In a batch annealing operation, a temperature of approximately 400F to about 750F is employed with residence times of about 30 minutes to about 24 hours. As mentioned with respect to continuous annealing, in batch annealing the times and temperatures may be varied to suit the overall process so long as the desired physical properties are obtained.

It has been found that the properties of a Number 10 gauge (American wire gauge) fully annealed soft wire of the present alloy vary between the following figures:

A more complete understanding of the invention will be obtained from the following examples.

EXAMPLE NO. 1

Various melts are prepared by adding the required amount of alloying'elements to 1,816 grams of molten aluminum, containing less that 0.1 percent trace element impurities, to achieve a percentage concentration of elements as shown in the accompanying table; the remainder being aluminum. Graphite crucibles are used except in those cases where the alloying elements are known carbide formers, in which cases aluminum oxide crucibles are used. The melts are held for sufficient times and at sufficient temperatures to allow complete solubility of the alloying elements with the base aluminum. An argon atmosphere is provided over the melt to prevent oxidation. Each melt is continuously cast on a continuous casting machine and immediately hot-rolled through a rolling mill to inch continuous rod. Wire is then drawn from the rod in both the asrolled condition (hard rod) and after being annealed for 5 hours at 650F (soft rod). The final wire diameter obtained is 0.107 inches, 10 gauge AWG. Wire from each type rod is tested in both the as-drawn condition (hard wire) and after being annealed for 5 hours at 650F (soft wire).

The types of alloys employed and the results of the tests performed thereon are as follows:

TABLE 1 Co Fe Mg Ni HR SR HW-HR HW-SR SW-HR SW-SR Properties .80 .80 .08 2.1 25.5 2.0 2.5 17.8 24.5 7: Elong.

31.450 19.400 38.040 34.045 19.790 18.978 UTS 58.38 59.63 58.03 58.79 59.76 59.98 70 IACS .80 .80 4.3 22.0 3.0 3.0 21.0 22.0 70 Elong.

27.800 18.340 31.700 27.450 17.590 15.750 UTS 59.01 61.42 58.37 59.88 60.48 60.63 [AC 1.0 .80 3.3 20.1 4.2 2.3 25.0 27.7 Elong.

28.150 17.875 32.135 26.685 17.200 16.275 UTS 58.38 59.90 58.37 59.29 59.86 60.06 lACS .80 .80 .10 1.1 14.5 3.4 2.0 20.5 24.5 Elong.

34.395 19,650 40.360 36.700 20.280 19,240 UTS 57.56 59.38 56.80 58.07 59.02 59.33 lACS .40 .80 .10 .40 2.8 20.0 2.0 2.5 22.9 24.5 Elong.

30.340 17.110 37.935 32.500 18,350 17,245 UTS 59.19 60.65 58.64 59.66 60.65 60.72 lACS HR Hard Ro SW-SR Soft Wire drawn from Soft Rod SR Soft Rod Elong. Percent ultimate elongation HW-HR Hard Wire drawn from Hard Rod UTS Ultimate Tensile Strength HW-SR Hard Wire drawn from Soft Rod lACS Conductivity in Percentage lACS SW-HR Soft Wire drawn from Hard Rod Soft wire and soft rod are the fully annealed forms of the products.

EXAMPLE NO. 2

An additional alloy melt is prepared according to Example No. 1 so that the composition is as follows in weight percent:

Cobalt 0.60%

lron 0.90% Magnesium 0.15% Aluminum Remainder The melt is processed to a No. 10 gauge soft wire from hard rod. The physical properties of the wire are as fol lows:

Ultimate Tensile Strength 20.040 psi Percent Ultimate Elongation 18.50% Conductivity 59.05% lACS EXAMPLE NO. 3

Cobalt 0.80%

lron 0.50% Misch Metal 0.40% Aluminum Remainder Ultimate Tensile Strength 18,500 psi Percent Ultimate Elongation 19% Conductivity 59.2% lACS EXAMPLE NO. 4

Cobalt 0.80? lron 0.40"- Niohium 0.20% Tantalum 0.20% Aluminum Remainder The melt is processed to a No. 10 gauge soft wire from hard rod. The physical properties of the wire are as follows:

Ultimate Tensile Strength 19.380 psi Percent Ultimate Elongation 19.5% Conductivity 59.171 lACS EXAMPLE NO. 5

Cobalt 0.80% Iron 0.35% Copper 0.40% Silicon 0.30% Aluminum Remainder The melt is processed to a No. 10 gauge soft wire from hard rod. The physical properties of the wire are as follows:

Ultimate Tensile Strength 17,000 psi Percent Ultimatc Elongation 19.5% Conductivity 59.7% lACS EXAMPLE NO. 6

Cobalt 0.80% lron 0.45% Zirconium 0.30% Aluminum Remainder The melt is processed to a No. 10 gauge soft wire from hard rod. The physical properties of the wire are as follows: I

Ultimate Tensile Strength 18,600 psi Percent Ultimate Elongation 18.5% Conductivity 59.3% lACS ADDITIONAL EXAMPLES I Additional alloy melts are prepared according to Example No. l. The composition and the physical properand a majority are less than 2 microns in length and less than one-half micron in width.

The iron aluminate intermetallic compound also contributes to the pinning of dislocation sites during cold ties of a 10 gauge ft Wire ffom'hafll rod of the 5 working of the wire. Upon examination of the iron inalloy melts are as follows:

termetallic compound precipitate in a cold drawn wire,

TABLE 2 Example UTS lACS 0. Co Fe Mg in psi Elongation Conductivity 1176 .8 .5 17,430 24.7 60.68 1177 .8 .5 1 17,410 24.8 60.43 1183 .8 .3 17,785 26.6 61.65 11114 .8 .5 17,700 28.0 61.54 1185 .6 .9 18,485 23.7 60.76 1186 .8 .9 17,930 26.5 59.97 1187 .4 1.1 19,355 19.8 60.19 11811 .6 1.1 20,400 17.5 59.87 1196 .2 1.1 18,515 20.5 60.41 1 I97 .4 .9 I 17,495 22.4 60.40 1198 .4 1.1 18,695 21.5 60.02 1199 .6 .9 18,975 20.3 60.99 1200 .2 .7 .1 17,775 22.8 60.83 1216 .8 Graphite .05 17,635 27.3 61.84

. .01 1219 .8 .53 17,180 29.2 61.62 1220 .8 .4 17 ,480 29.0 61.31 1221 .8 .5 .051 18,965 26.4 61.28 1227 .8 .5 .05 18,785 17.1 60.72 1228 .8 .5 .2 17,140 27.2 60.56 1237 .7 .5 17,030 24.5 61.49 1238 .8 .7 17,295 26.4 60.96 1239 .6 .5 .05 17,975 22.7 61.29 1201 .6 .9 .1 20,898 20.7 59.15 1240 .8 .3 .05 17,630 23.3 61.25 1293 1.40 .49 17,120 24.5 59.52 1313 .20 1.10 12 17,400 24.2 60.01 1316 .22 .96 .15 17,425 22.0 59.92 1317 .23 1.20 .14 18.333 23.7 59.47 1321 .43 .70 .054 17,200 26.5 61.12 1322 .40 1.05 .05 17,830 22.0 60.12 1325 .40 .68 .10 17.792 25.5 60.44 1327 .38 1.10 .11 19,004 25.2 59.52 1328 .42 .35 .15 17,000 24.0 60.88 1329 .41 .50 .16 17,000 24.0 60.47 1330 .44 .70 .16 18,100 25.0 59.80 1331 .42 .91 .16 18,690 22.0 60.51 1343 .33 .95 M54 20,874 16.4 49.90 1.0HF

Through testing and analysis of an alloy containing 0.80 weight percent cobalt, 0.30 weight percent iron, and the remainder aluminum, it has been found that the present aluminum base alloy after cold working includes intermetallic compound precipitates. One of the compounds is identified as cobalt aluminate (Co A1 and the other is identified as iron aluminate (FeAl The cobalt intermetallic compound is found to be very stable and especially so at high temperatures. The cobalt compound also has a low tendency to coalesce during annealing of products formed from the alloy and the compound is generally incoherent with the aluminum matrix. The mechanism of strengthening for this alloy is in part due to the dispersion of the cobalt intermetallic compound as a precipitate throughout the aluminum matrix. The precipitate tends to pin dislocation sites which are created during cold working of the wire formed from the alloy. Upon examination of the cobalt intermetallic compound precipitate in a cold drawn wire, it is found that the precipitates are oriented in the direction of drawing. In addition, it is found that the precipitates are rod-like or plate-like in configuration it is found that the precipitates are substantially evenly distributed through the alloy and have a particle size of less than 1 micron. If the wire is drawn without any intermediate anneals, the particle size of the iron intermetallic compounds is less than 2,000 angstroms.

A characteristic of high conductivity aluminum alloy wires which is not indicated by the historical tests for tensile strength, percent elongation and electrical conductivity is the possible change in properties as a result of increases, decreases or fluctuations of the temperature of the strands. It is apparent that the maximum operating temperature of a strand or series of strands will be affected by this temperature characteristic. The characteristic is also quite significant from a manufacturing viewpoint since many insulation processes require high temperature thermal cures.

1t has been found that the aluminum alloy wire of the present invention has a characteristic of thermal stability which exceeds the thermal stability of other aluminum alloy wires. In order to demonstrate this feature a group of wires is prepared for testing decrease in tensile and yield strength in response to ageing at established temperatures and times. The samples have compositions and are processed as shown in the following table:

TABLE ll] tion as described hereinbefore and as defined in the appended claims.

Sample Co Fe Al Processing No. l 0.60 0.05 Remainder Continuous casting and immediate hot rolling; drawing to flat magnet wire with no intermediate anneals and then partially annealed No. 2 0.045 Remainder Billet casting; homogenization and rolling; drawing with intermediate anneals to flat magnet wire and then partially annealed.

0.045 Remainder Billet casting; homogenization and rolling; drawing with intermediate anneals to form flat magnet wire and then partially annealed.

No. 4 0.80 0.60 Remainder Continuous casting and immediate hot rolling; drawing to flat magnet wire with no intermediate anneals and then partially annealed The results of the test are reproduced in the following table:

TABLE IV 160C-AGE1NG TEMP. 190-200C AGEING TEMP. DECREASE DECREASE DECREASE SAMPLE TIME IN YS 1N UTS TlME IN YS lN UTS No. l 100 hrs. 0 100 hrs. 600 psi I200 psi 500 hrs. 1,800 psi 0 670 hrs. 4,200 psi I200 psi No. 2 100 hrs. 0 0 100 hrs. 2,700 psi 2300 psi 500 hrs. 1,800 psi 0 550 hrs. 9,300 psi 5000 psi No. 3 100 hrs. 1,400 psi 0 480 hrs. 2,800 psi 0 NO TEST No. 4 H hrs. 0 (l 500 hrs. (1 550 hrs. (1 0 YS Yield Strength UTS Ultimate Tensile Strength A significant aspect shown by the results of these tests is the lack of thermal stability obtainable with several aluminum alloys. The test sample wires identified as No. 2 and 3 show a significant decrease in thermal stability in the yield and tensile strength tests and alloy No. 2 has almost completely softened after a 550 hour soak period at 190-200C. On the other hand, the wire fabricated from the present alloy demonstrates a high degree of thermal stability by exhibiting zero decreases in yield and tensile strength.

For the purpose of clarity, the following terminology used in this application is explained as follows:

Aluminum alloy rod A solid product that is long in relation to its cross-section. Rod normally has a cross-section of between three inches and 0.375 inches.

Aluminum alloy wire A solid wrought product that is long in relation to its cross-section, which is square or rectangular with sharp or rounded corners or edges, or is round, a regular hexagon or a regular octagon, and whose diameter or greatest perpendicular distance between parallel faces is between 0.374 inches and 0.00- 31 inches.

While this invention has been described in detail with particular reference to preferred embodiments thereof, it will be understood that variations and modifications can be effected within the spirit and scope of the invensentially of from about 0.20 to about 1.60 weight percent cobalt, from about 0.30 to about 1.30 weight percent iron, the remainder being aluminum with asso ciated trace elements, said aluminum alloy electrical conductor having the following properties when measured as a No. 10 A.W.G. fully annealed wire:

Tensile strength: 12,000 24,000 psi Elongation: l2 30 percent Yield strength: 8,000 18,000 psi.

2. The aluminum alloy electrical conductor according to claim 1 further including an additional alloying element selected from the group consisting of magnesium, copper, silicon and mixtures thereof; the combined weight percentage of magnesium and copper not to exceed about 0.8 percent, and the silicon weight percentage not to exceed about 0.45 percent.

3. The aluminum alloy electrical conductor according to claim 2 wherein the combined weight percentage of magnesium, copper and silicon not to exceed about 0.8 percent when the combined weight percentage of cobalt and iron is 1.8 percent or greater.

4. The aluminum alloy electrical conductor according to claim 2 wherein the combined weight percentage of magnesium and copper does not exceed about 0.20 percent, the combined weight percentage of additional alloying elements does not exceed about 0.10 percent,

8. The aluminum alloy electrical conductor according to claim 2 wherein cobalt is present in a weight percentage of from about 0.20 to about 1.0 percent and iron is present in a weight percentage of from about 0.3 percent to about 1.0 percent.

9. The aluminum alloy electrical conductor according to claim 2 wherein cobalt is present in a weight percentage of from about 0.30 percent to about 0.80 percent.

10. The aluminum alloy electrical conductor according to claim 1 wherein the weight percentages of the constitutents are as follows:

Cobalt Iron 0.50% Misch Metal 0.40% Aluminum remainder.

11. The aluminum alloy electrical conductor according to claim 1 wherein the weight percentages ,of the constituents are as follows:

Cobalt 0.110% Iron 0.40% Niobium 0.20% Tantalum 0.2071 Aluminum remainder.

12. The aluminum alloy electrical conductor according to claim 2 wherein the weight percentages of the constituents are as follows:

Cobalt 0.80% Iron 0.35% Copper 0.40% Silicon 0.30% Aluminum remainder.

13. The aluminum alloy electrical conductor according to claim 1 wherein the weight percentages of the constituents are as follows:

Cobalt 0.80% Iron 0.45% Zirconium 0.30% Aluminum remainder.

14. The aluminum alloy electrical conductor according to claim 1 wherein said conductor is in the form of a rod.

15. The aluminum alloy electrical conductor according to claim 1 wherein said conductor is in the form of a wire.

16. Aluminum alloy electrical conductor having a minimum conductivity of 58 percent IACS consisting essentially of from about 0.20 to about '1 .60 weight percent cobalt, from about 0.30 to about 1.30 weight percent iron, the remainder being aluminum with associated trace elements, said aluminum alloy electrical conductor having the following properties when measured as a fully annealed wire:

Tensile strength: at least 12,000 psi Yield strength: at least 8,000 psi.

17. The aluminum alloy electrical conductor according to claim 16 further including an additional alloying element selected from the group consisting of magnesium, copper, silicon and mixtures thereof; the combined weight percentage of the magnesium and copper not to exceed about 0.8 percent, and the silicon weight percentage not to exceed about 0.45 percent.

18. Method of preparing an aluminum alloy conductor having a minimum conductivity of at least 58 percent IACS comprising the steps of:

A. alloying from about 0.20 to about 1.60 weight percent cobalt with about 0.30 to about 1.30 weight percent iron, the remainder being aluminum with associated trace elements;

B. casting the alloy in a moving mold formed between a groove in the periphery of a rotating casting wheel and a metal belt lying adjacent said groove for a portion of its length;

C. hot rolling the cast alloy substantially immediately after casting while the cast alloy is in substantially that condition as cast to form a continuous rod;

said aluminum alloy conductor having the following properties as a fully annealed wire:

Tensile strength: at least 12,000 psi Yield strength: at least 8,000 psi.

19. Method of preparing an aluminum alloy conductor in accordance with claim 18 including the further step of drawing said conductor through wire-drawing dies, without annealing the conductor between drawing dies, to form wire..

20. The method according to claim 18 wherein the alloying stepalso includes the addition of alloying elements selected from the group consisting of magnesium, copper, silicon and mixtures thereof, in amounts sufficient to yield said alloy wherein the combined weight percentage of magnesium and copper does not exceed about 0.8 percent, and thesilicon weight percentage does not exceed about 0.45 percent.

21. The method according to claim 18 wherein the alloying step includes the addition of magnesium, copper and silicon in amounts sufficient to yield said alloy wherein the combined weight percentage does not exceed about 0.8 percent when the combined weight percentage of cobalt and iron is 1.8 percent or greater.

22. The method according to claim 18 wherein the alloying step includes the addition of magnesium and copper in amounts sufficient to yield said alloy wherein the combined weight percentage does not exceed about 0.20 percent and the combined weight percentage of cobalt and iron is about 2.90 percent or less.

23. The method according to claim 18 wherein the additional alloying element added is magnesium in an amount sufficient to yield up to about 0.40 weight percent magnesium.

24. The method according to claim 18 wherein the additional alloying element added is copper in an amount sufficient to yield up to about 0.40 weight percent copper.

25. The method according to claim 18 wherein the additional alloying element added is silicon in an amount sufficient to yield up to about 0.45 weight percent silicon.

26. The method according to claim 18 wherein cobalt is added in an amount sufficient to yield a weight percentage of from about 0.20 percent to about 1.0 percent cobalt and iron is added in an amount sufficient to yield a weight percentage of from about 0.3 percent to about 1.0 percent iron.

27. The method according to claim 18 wherein cobalt is added in an amount sufficient to yield a weight percentage of from about 0.30 percent to about 0.80 percent cobalt and iron is added in an amount sufficient to yield a weight percentage of from about 0.40 percent to about 0.70% iron.

28. The method according to claim 18 wherein cobalt, iron and misch metal are added in amounts sufficient to yield an alloy having the following weight percentages:

Cobalt 0.80% lron 0.50% Misch metal 0.40% Aluminum remainder.

29. The method according to claim 18 wherein cobalt, iron, niobium and tantalum are added in amounts sufficient to yield an alloy having the following weight percentages:

Cobalt 0.80% Iron 0.40% Niobium 0.20%

0.20% remainder.

Tantalum Aluminum 30. The method according to claim 18 wherein cobalt, iron, copper and silicon are added in amounts sufficient to yield an alloy having the following weight percentages:

Cobalt 0.80% Iron 0.35% Copper 0.40% Silicon 0.30% Aluminum remainder.

31. The method according to claim 18 wherein cobalt, iron, and zirconium are added in an amount sufficient to yield an alloy having the following weight percentages:

Cobalt 0.80% Iron 0.45% Zirconium 0.30% Aluminum remainder.

32. The method according to claim 18 wherein said

Claims

2. The aluminum alloy electrical conductor according to claim 1 further including an additional alloying element selected from the group consisting of magnesium, copper, silicon and mixtures thereof; the combined weight percentage of magnesium and copper not to exceed about 0.8 percent, and the silicon weight percentage not to exceed about 0.45 percent.
3. The aluminum alloy electrical conductor according to claim 2 wherein the combined weight percentage of magnesium, copper and silicon not to exceed about 0.8 percent when the combined weight percentage of cobalt and iron is 1.8 percent or greater.
4. The aluminum alloy electrical conductor according to claim 2 wherein the combined weight percentage of magnesium and copper does not exceed about 0.20 percent, the combined weight percentage of additional alloying elements does not exceed about 0.10 percent, and the combined weight percentage of cobalt and iron is about 2.90 percent or less.
5. The aluminum alloy electrical conductor according to claim 2 wherein the additional alloying element is magnesium in an amount up to about 0.40 weight percent.
6. The aluminum alloy electrical conductor according to claim 2 wherein the additional alloying element is copper in an amount up to about 0.40 weight percent.
7. The aluminum alloy electrical conductor according to claim 2 wherein the additional alloying element is silicon in an amount up to about 0.45 weight percent.
8. The aluminum alloy electrical conductor according to claim 2 wherein cobalt is present in a weight percentage of from about 0.20 to about 1.0 percent and iron is present in a weight percentage of from about 0.3 percent to about 1.0 percent.
9. The aluminum alloy electrical conductor according to claim 2 wherein cobalt is present in a weight percentage of from about 0.30 percent to about 0.80 percent.
10. The aluminum alloy electrical conductor according to claim 1 wherein the weight percentages of the constitutents are as follows:
11. The aluminum alloy electrical conductor according to claim 1 wherein the weight percentages of the constituents are as follows:
12. The aluminum alloy electrical conductor according to claim 2 wherein the weight percentages of the constituents are as follows:
13. The aluminum alloy electrical conductor according to claim 1 wherein the weight percentages of the constituents are as follows:
14. The aluminum alloy electrical conductor according to claim 1 wherein said conductor is in the form of a rod.
15. The aluminum alloy electrical conductor according to claim 1 wherein said conductor is in the form of a wire.
16. Aluminum alloy electrical conductor having a minimum conductivity of 58 percent IACS consisting essentially of from about 0.20 to about 1.60 weight percent cobalt, from about 0.30 to about 1.30 weight percent iron, the remainder being aluminum with associated trace elements, said aluminum alloy electrical conductor having the following properties when measured as a fully annealed wire: Tensile strength: at least 12,000 psi Yield strength: at least 8,000 psi.
17. The aluminum alloy electrical conductor according to claim 16 further including an additional alloying element selected from the group consIsting of magnesium, copper, silicon and mixtures thereof; the combined weight percentage of the magnesium and copper not to exceed about 0.8 percent, and the silicon weight percentage not to exceed about 0.45 percent.
18. Method of preparing an aluminum alloy conductor having a minimum conductivity of at least 58 percent IACS comprising the steps of: A. alloying from about 0.20 to about 1.60 weight percent cobalt with about 0.30 to about 1.30 weight percent iron, the remainder being aluminum with associated trace elements; B. casting the alloy in a moving mold formed between a groove in the periphery of a rotating casting wheel and a metal belt lying adjacent said groove for a portion of its length; C. hot rolling the cast alloy substantially immediately after casting while the cast alloy is in substantially that condition as cast to form a continuous rod; said aluminum alloy conductor having the following properties as a fully annealed wire: Tensile strength: at least 12,000 psi Yield strength: at least 8,000 psi.
19. Method of preparing an aluminum alloy conductor in accordance with claim 18 including the further step of drawing said conductor through wire-drawing dies, without annealing the conductor between drawing dies, to form wire.
20. The method according to claim 18 wherein the alloying step also includes the addition of alloying elements selected from the group consisting of magnesium, copper, silicon and mixtures thereof, in amounts sufficient to yield said alloy wherein the combined weight percentage of magnesium and copper does not exceed about 0.8 percent, and the silicon weight percentage does not exceed about 0.45 percent.
21. The method according to claim 18 wherein the alloying step includes the addition of magnesium, copper and silicon in amounts sufficient to yield said alloy wherein the combined weight percentage does not exceed about 0.8 percent when the combined weight percentage of cobalt and iron is 1.8 percent or greater.
22. The method according to claim 18 wherein the alloying step includes the addition of magnesium and copper in amounts sufficient to yield said alloy wherein the combined weight percentage does not exceed about 0.20 percent and the combined weight percentage of cobalt and iron is about 2.90 percent or less.
23. The method according to claim 18 wherein the additional alloying element added is magnesium in an amount sufficient to yield up to about 0.40 weight percent magnesium.
24. The method according to claim 18 wherein the additional alloying element added is copper in an amount sufficient to yield up to about 0.40 weight percent copper.
25. The method according to claim 18 wherein the additional alloying element added is silicon in an amount sufficient to yield up to about 0.45 weight percent silicon.
26. The method according to claim 18 wherein cobalt is added in an amount sufficient to yield a weight percentage of from about 0.20 percent to about 1.0 percent cobalt and iron is added in an amount sufficient to yield a weight percentage of from about 0.3 percent to about 1.0 percent iron.
27. The method according to claim 18 wherein cobalt is added in an amount sufficient to yield a weight percentage of from about 0.30 percent to about 0.80 percent cobalt and iron is added in an amount sufficient to yield a weight percentage of from about 0.40 percent to about 0.70% iron.
28. The method according to claim 18 wherein cobalt, iron and misch metal are added in amounts sufficient to yield an alloy having the following weight percentages:
29. The method according to claim 18 wherein cobalt, iron, niobium and tantalum are added in amounts sufficient to yield an alloy having the following weight percentages:
30. The method according to claim 18 wherein cobalt, iron, copper and silicon are added in amounts sufficient to yield an alloy having the following weight percentages:
31. The method according to claim 18 wherein cobalt, iron, and zirconium are added in an amount sufficient to yield an alloy having the following weight percentages:
32. The method according to claim 18 wherein said alloy conductor is formed into a wire having the following properties when measured as a No. 10 A.W.G. fully annealed wire: Tensile strength: 12,000 - 24,000 psi Elongation: 12 - 30 percent Yield strength: 8,000 - 18,000 psi.