CA1055734A - Aluminum nickel alloy electrical conductor - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Aluminum alloy electrical conductors are produced from aluminum base alloys containing from about 0.20 percent to about 1.60 percent by weight nickel, from about 0.30 percent to about 1.30 percent iron, optionally up to about 2.00 percent of additional alloying elements, and from about 97.00 percent to about 99.50 percent by weight aluminum.
The alloy conductors have an electrical conductivity of at least fifty-seven percent (57%), 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

-- 105~734 The present invention concerns an aluminum base al10y especially suited for producing high strength light-weight electrical conductors including wire, rod and other such articles of manufacture. The present alloy is particularly well suited for use as a wire, rod, cable, bus bar, tube connector, termination, receptacle plug or electrical contact device for conducting electricity.
Aluminum base alloys are finding wider acceptance in the marketplace of today because of their light weigh~ 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 electrica~ly conductive aluminum a~loy wire (referred to as EC) cs~ntains 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 and cost, 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 13C aluminum alloy conductors. If the physical properties, such as thermal stab~lity, tensile strength, percent elongation, ductility and yield strength, could be improved significantly without substantia~ly lessening the electric~1 conductivity of the finished product, a very desirable improvement wouldbe achieved, It is accepted, however, that add~tion of alloying elements, as in other aluminum alloys, reduces conductivity wh;le improving the physical properties, Consequen1~1y, orily those additio~s oE elements which improve physioal properties without substantially lessening conductivity will yield an acceptable and useful product,

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It is an object of the present in~ention, therefore, to provide a new aluminum alloy electrical conductor which combines improved physical properties with acceptable electrical conductivity. These and other objects, features and advantages of the present invention wiLI 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 nickel, iron and optionally other a~loying elements with aluminum in a furnace to obtain a melt having requisite percentages of elements. It has been found that suitable results are o~tained with nickel preselIt in a weight percentage of from about 0. 20 percent to about 1. 60 percent. Superior results are achieved when nickel is present in a weigh~ percentage of Erom about 0. 50 percent to about 1. 00 percent and particularly superior and preferred results are obtained when nickel i9 present in a percentage by weight of from about 0. 60 ~
percent to about Oe80 percent. ~ `
Sui~able results are obtained with iron present in a weight perce~age of from about 0. 30 percent to abo~t 1. 30 percent. Superior - .~ .
results are achieved when iron is present in a weight percentage of Erom about 0. 40 percent to about 0. 80 percent and particularly superlor and preIerred results are obtained when iron is present in a percentage by - weight of from about 0. 45 percent to about 0. 65 percent. -The aluminum content of the present a~loy may vary frm about 97. 00 percent to about 99. S0 percent by weight with superior results being obtained when the aluminum c~tent varies between abou$ 97. 80%
and about 99. 20% by weight. Since the percentages for maximum and minimum aluminum do not correspond with the maximums- and minimums "; ' 1~55 1~3~
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for alloying elements, it should be apparent that sui~able results are not obtained if the maximum percentages for aL~ alloying elements are employed. 1~ commercial aluminum i~i employed in preparing the present mel$, 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.
Cptionally the presen~ aMoy may contain an additional - alloying element or group of alloying elements. The total concentration of the optional alloying elemen~s may be up to about 2. 00 percent by weight;
preferably from about 0.10 percent to about 1. 50 percent by weight is 10 employed. Particularly superior and preferred results are obtained when from about 0.10 percent to about 1. 00 percent by weight of total additional alloying elements is employed.
Additional alloying elements include the following:
ADDITIONAL ALLOYCNG ELEMENTS
Magnesium Scandium Dysprosium Cobalt Thorium Terbium Copper Tin Erbium Silicon Molybdenum Neodymium Zirconium Zinc Indium Cerium Tungsten Boron Niobium Chromium Thallium Hafnium Bismuth Rubidium Lanthanum Antimony Titanium Tantalum Vanadium Carbon Cesium Rhenium , Yttrium , , :- .. .

~5~734 Superior resul~s are obtained with the fo~lowing additional alloying elements in the percentages, by weight, as shown:
PREFERRED ADDITIONAL ALLOYCNG ELEMENTS
Magnesium 0. 001 to 1. 00%
Cobalt 0. 001 to 1. 00%
Copper 0. 05 to 1. 00%
Silicon 0. 05 to 1. 00%
Zirconium 0. 01 to 1. 00% -~
Niobium 0. 01 to 2. 00~0 -Tantalum 0~ 01 to 2. 00%
Yttrium 0. 01 to 1. 00%
Scandium 0. 01 to 1. 00%
Thorium 0. 01 to 1. 00%
Rare Earth Metals 0. 01 to 2. 0010 Carbon 0. 01 to 1. 00%
Particularly superior arIl preferred results are obtained with the use o~ cobalt or magnesium as the additional a~loying - element. Suitable results are obtained with magneium or cobal~ in a percentage range of from abou~ 0. 001% to about 1. 00% by weight with -~ 20 superior results being o~tained when from about 0. 025% to about 0. 50%
by weight is used. Particularly superior and preferred results are ~ ~
~; ~ obtained when from about 0. 03~o to about 0.10% by weight of magneeium ~;
or cobalt is employed. -~' ` The rare earth metals rnay be present either ~, individua~ly within the percentage range stated or as a partial or total .~ . .
group, the total percentage o~ the group being within the percentage range stated previously.
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It should be understood that the additional alloying elements may be present ei~her 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 abou~ 2. 00 percent by weight.
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 resul~s are obtained with continuous processing. Su~h 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 a~loy billets which are subsequently hot-worked to rod and drawn with ir~ermediate a~eals into wire.
CO~TINUOUS CAST~NG AND ROLL~G OPERATION
A continuous casting machine ss~rves as a means for solidifying the molten aluminum a~loy metal to provide a ca~t bar that 4, iS oonveyed in substantially the condition in which it solidified from the ~, .

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continuous casting machine to the rolling mill, which serves as a means for hot-forming the cast bar into rod or another hot-formed product in a manner which imparts substantial mc>vement to the cast bar along a plurality of angularly disposed axes.
The co~tinuous 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 iMer pulley. The casting wheel and the endless belt cooperate to provide a mold into one end of which molten metal is poured to solidify and from the other end of which the cast bar is emitted in substantia~ly that condition in which it solidified.
The rolling m~ll is of convention~l type having a plurality of roll stands arranged to hot-form the cast bar by a series of deor-mations. 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 subs$an~ially that condition in which it solidified. In this condition, the cast bar is at~a f hot-forming temperature within the range of temperatures for hot-forrning the cast bar at the initiation of hot-forming without heating between the casting machine f~nd the rolling mill. In the event that it is desired to closely control the hot-forming 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 casti~g machine and the rolling mil~ without departing from the inventive concept ~ disclosed herein.

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The roll stands each include a plurality of rolls which engage the cast bar. The rolls of each ro31 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 castmg wheel is rotated at a speed generally determined by its operating characteristics. The rolling miLI serves to hot-form the cast bar into a rod of a cross-sectional area substantially less than ~hat of the cast bar as i$ enters the rotling mill.
The peripheral surfaces of the rolls of adjacen~ ro31 stands in the ro~ling 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 of the 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 flll 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 thal: the space defined by the rolls of each roll stand not be overfilled so that the cast bar wi~ not bP forced i~to the gaps between the rolls. Thus, it is des~rable that the rod be fed toward each roll stand at a volume per unit of time which Is ~ .

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sufficient to fill, bu$ not overfill, the space defined by the ro~ls of the roll stand.
As the cast bar is received from the continuous casting machine, it usually has one large flat surface corresponding to the surface of the endless band and inwardly tapered side surfaces corresponding to the shape of 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 cross-sectional shape defined :
by the adjacent peripheries of the rolls of each roll stand.
Thus, it will be understood that with this apparatusJ cast aluminum alloy rod of an infinite number of different lengths iS prepared by simultaneous casting of the molten aluminwm 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 sma er cross-sectional ~ ~ -diameter.
To produc2 wire of various gauges, the continuous rod produced by the casting and ro~ling operation is processed in a reduction operation. The unannealed rod (i. e., as ro~led to f temper) iS cold-drawn through a series of progressively constricted dies, without intermediate anneals, to form a con~inuous wire of desired diameter. It has been found that the elimination of intermediate anneals is preferable during the procesSing of the rod and improves the physical properties of $he wire.
Processing wi$h intermediate anneals is acceptable when the requirements for physical properties of the wire peFmit reduced values. The _g_ ~o55~3~ ;

conductivity of the hard-drawn wire is at least 57 percent IACS. If grea~er 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 58 percent IACS. At the conclusion of the drawing operation and op~ional annealing operation, it is 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 450~ F.
to about 120Q F. may be employed with annealing times of about five minutes to about 1/10, 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 400 F7 to about 750 F. is employed with 20 residence times of about thirty ~30) minutes to about twenty-four (24) hours. As mentioned with respect to continuous annealing, in batch .
annealing the time,s and temperatures may be varied to suit the overa~
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 ~

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Tensile % Yield Conductivity Strength, psi. _longation Strength, psi.
58%-63~% 12, 000-24, 000 12%-30% 8, 000-18, 000 A more complete unclerstanding of the invention will be obtained from the following examples:
EXAMPLE NO. 1 Various melts were prepared by adding the required - amount of alloying elements to 1816 grams of molten aluminum, con~aining less than 0.10% 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 sufficiellt times and at sufficient temperatures to allow complete solubility of the -a~loying 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 throug~ a ro~ling mill to 3/8 inch continuous rod. The hard (as ro:lled) rod was then drawn and annealed for five hours at 650 F. into soft (annealed) wireO
The final wire diameter obtained is 0.1019 inches, 10 gauge AWG.
The types of alloys employed and the results of the tests performed thereon are as fo31ows:
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, ,' l~S5734 TABL~ 1 Ni Fe UTS % Elong. % LACS
. 30 l.D0 17, 500 12. 5 60.49 . 80 . 70 18, 300 25. 6 59. 73 1. 00 . 60 17, 900 26. 1 59, 97 1. 50 . 40 17, 800 24. 8 59. 52 % Elong. = Percent ul~ima$e elongation UTS = Ultimate Tensile Strength % IACS = Conductivity in Percentage ~9CS

An additional alloy melt was prepared according to Example No. 1 so that the composition was as follows in weight percent:
Nickel - 0. 60%
Iron - 0. 90% -Magnesium- 0.15%
Aluminum - Remainder ~ .
The melt was processed to a No. 10 gauge soM wire. The physical properties of the wire were as follows~
Ultimate Tensile Strength - 18,200 psi ~ -Percent Ultimate Elongation - 25. 2%
Conductivity - 59.10% IACS
EXAMPLE NO. 3 An additional a~loy melt was prepared according to Example No. 1 so that the composition was as fo31ows in weight percent:

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Iron - 1.10%
Aluminum - Remainder The melt was processed to a No. 10 gauge soft wire.
The physical properties of the wire we:re as follows: :
l~ltimate Tensile Strength - 17, 400 psi Percent Illtimate Elongation - 14.1%
Conductivity - 60. 30% IACS -EXAMPLE NO. 4 An additional a~loy melt was prepared according to Example No. 1 so that the composition was as follows in weight percent:
Nickel - 1. 60%
:lron ~ - 30% `
Aluminum - Remainder The melt was processed to a No. 10 gauge soft wire. The physical pro-perties of the wira were as follows:
Ultimate Tensile S1;rength - 17, 200 psi Percent l)~timate Elongation - 27. 5%
Conductivity - 59.1% LACS ~ : .

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

Nickel - 0. 20%

Iron - 1. 30% ~

- Aluminum - Remainder : .
'''' ' : ~ -13-~5573~1 The melt was processed to a No. 10 gauge sof$ wire. The physical properties of the wire were as follows:
I~ltL~nate Tensile Strength - 17, 500 psi Percent Ultimate Elongation - 13. 5%
Conductivity - 61. 05% IACS

An additional alloy melt was prepared according to Example No. 1 so that the composition was as follows in weight percent:
Nickel - 0. 80%
Iron - 0. 45%
Cobalt - 0.10%
Aluminum - Remainder The melt was processed to a No. 10 gauge soft wire. The physical properties of the wire were as fol1ows:
Ultimate Tensile Strength - 17, 850 psi Percent l~ltimate Elongation - 2 3 . 6 %
Conductivity - 59. 8% IACS
Through testing and analysis of an alloy containing O. 80 weight percent nickel, 0. 30 weight percent iron, and the remainder aluminum, it has been found that the present aluminum base alloy after cold working incllldes intermetallic compound precipitates. One of the compounds is identified as nickel aluminate (NiAl 3) and the other is identified as iron aluminate (FeAl 3). The nickel intermetallic compound is found to be very stable and especially so at high tempera~ures. The nickel compound also has a low tendency to coalesce during annealing -of products formed from the alloy and the compound is genera~ly . . ' ~55'734 incoherent with the aluminum matrix. The mechanism of strengthening for this alloy is in part due to the dispersion of the nickel 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 nickel intermetallic compound precipit~te 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 can be rod-like, plate-like, or spherical in configuration.
Cther intermetallic compounds may also be formed depending upon the constituents of the melt and the relative concen~rations of the alloying elements. Those intermetallic compounds include the foll owing: Ni 2A1 3, MgCoAl, Fe 2A1 5, Co 2Al 9, Co 4A113~ CeAl 4, CeAl 2 ~
VAll~, VAl 7, VAl 6~ VAl 3, VA112, Zr 3Al, Zr 2Al, LaAl 4, LaAl 2~ -A13Ni2, A12Fes, Fe3NiAllo, Co2A15, FeNiAlg.
The iron aluminate intermetallic compound also con-tributes to the pinning of dislocation sites during cold working of the wire.
Upon examination of the iron intermeta~lic compound precipitate in a cold drawn wire, it is found that the precipitates are substantially evenly distributed through the a~loy and have a particle size of less than 1 micron.
If the wire is dra~vn without any intermediate anneals, the particle size of the iron intermetallic compounds is less than 2, 000 angstroms.
A characteristic of high conductivity aluminum a~loy - -wires which is not indicated by the historical tests for tensile strength, percent elongation and electrical conductiYity is the possible change in ~055~34 properties as a result of increases, decreases or Eluctua~ions 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 quiee significant from a manufacturing viewpoint since many insulation processes require high temperature thermal curesO
It has been found tha1; the aluminum alloy wire of the present invention has a characteristic of thermal stability which exceeds the thermal stability of conventional aluminum alloy wires, For the purpose of clarity, the following terminolog~r used in this applicai;ion is explained as follows:
Aluminum a~loy 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-sectionJ which is square or rectangular wi1h sharp or rounded corners or edges, or is round, a regular hexagon or a regular octagon, and whose diameter or greatest perpendicular distance be$ween para:llel faces is between 0. 374 inches and 0, 0031 inches, While this invention has been described in detail with particular reference to preferred ernbodiments thereof. it will be understood that variations and modifications can be effected within the .
spirit and scope of the invention as described hereinbefore and as defined in the appended claims.
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Claims (11)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE AS FOLLOWS:

1. Aluminum base alloy electrical conductor wire characterized by the fact that it has a minimum conductivity of fifty-seven percent (57%) IACS and consists essentially of from about 0.20 to about 1.60 weight percent nickel, from about 0.30 to about 1.30 weight percent iron, from about 97.00 to about 99.50 weight percent aluminum and up to about 2.00 weight percent of an additional alloying element selected from the group consisting of:

2. Aluminum base electrical conductor wire of Claim 1 characterized by the fact that the additional alloying element is selected from the group consisting of:

3. Aluminum base alloy electrical conductor wire of Claim 1 characterized by the fact that nickel is present in a weight percentage of from about 0.50 percent to about 1.00 percent, iron is present in a weight percentage of from about 0.40 percent to about 0.80 percent, the additional alloying element is present in a weight percentage of from about 0.10 percent to about 1.50 percent, and aluminum is present in a weight percentage of from about 97.80 percent to about 98.92 percent.

4. Aluminum base alloy electrical conductor wire of Claim 1 characterized by the fact that the weight percentages of the constituents are as follows:

5. Aluminum base alloy electrical conductor wire of Claim 1 characterized by the fact that the weight percentages of the constituents are as follows:

6. Aluminum base alloy electrical conductor wire of Claim 1 characterized by the fact that the addi-tional alloying element is selected from the group consisting of the following elements and is present in a weight percentage as shown for each element:

7. Aluminum base alloy electrical conductor wire as claimed in Claim 1, 5 or 6 characterized by the fact that the alloy includes iron aluminate particles having a size of less than 2000 angstroms.

8. Process for preparing an aluminum alloy electrical conductor wire having a minimum conductivity of at least 58 percent IACS characterized by the steps of:
(1) Alloying from about 0.20 to about 1.60 weight percent nickel with from about 0.30 to about 1.30 weight percent iron, from about 97.00 to about 99.50 weight percent aluminum and up to about 2.00 weight percent of an additional alloying element selected from the group consisting of:

(2) 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;
(3) 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; and (4) Drawing the rod through wire-drawing dies, without annealing the rod between drawing dies, to form wire.

9. Process for preparing an aluminum alloy electrically conductive rod having a minumum conductivity of at least 57 percent IACS characterized by the steps of:
(1) Alloying from about 0.20 to about 1.60 weight percent nickel with from about 0.30 to about 1.30 weight percent iron, from about 97.00 to about 99.50 weight percent aluminum and up to about 2.00 weight percent of an additional alloying element selected from the group consisting of:

(2) 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; and (3) 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.

10. An aluminum base alloy electric wire conductor, having a minumum conductivity of 59 percent IACS, and consisting essentially of:
nickel from 0.2 to 1.5 weight percent iron from 0.3 to 1 weight percent magnesium from 0 to 0.35 weight percent and the balance aluminum.

11. A method of manufacturing an aluminum base alloy electric wire conductor, having a minumum conductivity of at least 59 percent IACS, comprising the steps of mixing an alloy consisting essentially of:
nickel from 0.2 to 1.5 weight percent iron from 0.3 to 1 weight percent magnesium from 0 to 0.35 weight percent and the balance aluminum, melting the mixture, casting the melted mixture, hot rolling the aluminum base alloy casting into a rod, cold drawing the rolled rod into a wire, and applying a continuous annealing treatment to the cold drawn wire.