CA1071983A - Aluminum alloy electrical conductor - Google Patents

Abstract

ABSTRACT

This disclosure relates to a method of continuously preparing a heat-resistant aluminum base alloy electrical conductor that has a minimum electrical conduc-tivity of sixty-one percent (61%) IACS, improved properties of ultimate tensile strength, yield strength and elongation as compared with conventionally-prepared aluminum alloy electrical conductors, and superior thermal stability to continuously-processed aluminum alloy electrical conductors.
The conductor is prepared from an alloy melt containing from more than 0.15 to 1.00 weight percent silicon, from 0.10 to 0.95 weight percent iron with the balance of aluminum con-taining trace elements selected from the group consisting of copper, manganese, magnesium, titanium, vanadium and zinc wherein the individual concentrations of said trace elements do not exceed 0.05 weight percent and the total concentra-tion of said trace elements does not exceed 0.15 weight percent.

Description

10719~33 BACKGROIJND OF THE INVE~TION

This invention relates to an aluminum alloysuitable for use in fabricating an electrical conductor and more particularly concerns an aluminum alloy suitable for fabricating an electrical conductor for use in applications in which the electrical conductor is subjected to high temperatures for extended periods of time and therefore must have good thermal stabi}ity.
~ he use o~ various aluminum alloys, convention-ally re~erxed to as EC, to fabricate electrical conductors i8 well established in the art. Such alloys charaateristi~
cally have conducti~ities of at least 6~ percent of the International Annealed Copper Standard, hereinafter refer~ea to as IACS and chemical constituents consisting of a sub-stantial amount of pure aluminum and small amounts of impuri-ties such as iron, silicon, vanadium, copper, manganese, ~agnesium, zinc, boron and titanium. The lron content is;
generally less than 0.30 percent and the silicon content is generally less than 0.15 percent. Th~ physical properties of electrical conductors fabricated from prior aluminum ;~
alloys have proven less than satisfactory for many applica-tions which require that the electrical conductor used have -a high degree of thermal stability~ Generally desirable thermal stability has been obtainable only at less than desirable tensile strength, elongation or conductivity.
For example, it is generaily accepted that industrial purity aluminum has a recrystallization tempera- i ture of from about 300F to about 662F (150C to 350C) It is also accepted that such aluminum has a very low resis-

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~07~9~3 tance to heat and undergoes a softening phenomenon at a temperature of from about 212F to about 392F tlOOC to .;
200C). Much work has been done in t~e past to improve the heat resistance of alumlnum, however the majority of alloys -developed which have accepta~le electrical conductivity undergo a significant loss of strength upon being exposed to temperatures of from about 300~F to about 392~F (150C to 200C~ for several hours. Such alloys usually reta:in only from about 60 percent to about 80 percent of their original ;
tensile strength and elongation after exposure to tempera-tures in thls range for several hours.
Thus, it becomes apparent that a need has ;
arisen within the electrical industry for an aluminum alloy from which electrica] conductors might be fabricated which will have both improved thermal stability and tensile strength and acceptable conductivity, elongation and yield strength. ;
In the past aluminum alloys and rod for the fabrication of wire have been m~nufactured for commercial use by a plurality o separate steps which include casting an aluminum alloy ingot, reheating the ingot to a tempera~
ture which would permit hot rolling of the cast ingot into redraw rod, solutionizing the rod and water quenching the rod before cold drawing the rod into wire. After dra~in~
the wire fabricated by the aforementioned procedure is -generally annealed in order to obtain acceptable tensile strength. `Although wire produced by the aforementioned techniques has acceptable tensile strength, it is difficult and in fact almost impossible to produce an aluminum alloy ' ' ' :.

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~ ~17~ 33 wire having high thermal stability and acceptable elongation and electrical conductivity using this technique because the procedure inherently produces a structure which contains elements in solution because all the alloying elements are not removed from solution by the quenching steps and because large precipitates are formed if the alloy is processed at high temperatures. The cell structures of aluminun alloy wire fabricated from base metal so processed is unstable thereby promoting the formation of large cells when the wire is subjected to any heat treatment thereby leading to a finished product which has either poor thermal stability or poor physical and poor electrical properties.
In U.S. Patent No. 3,512,221 there is dlsclosed ~-an improved aluminum alloy electrical conductor prepared by continuously casting an alloy consisting essentially of less than about 99.70 weight percent aluminum, more than 0.30 weight percent iron, no more than 0.15 weight percent ~
silicon and trace quantities of typical impurities to form a c~nt~nuous aluminum alloy ~ar, hot-working the bar to form continuous rod which is subsequently drawn into wire without intermediate anneals, and thereafter final:Ly annealed. While this product yielded improved properties of increased ulti-mate elongation, bendability and fatigue resistance when compared with the conventional EC alloy, it still did not -yield a sufficient degree of thermalstability to permit use at elevated temperatures for extended periods of time.
~herefore it becomes apparent that there 1,. .
remains a need within the electrical industry for an e~fi-cient and economical method of fabricating an aluminum alloy ! ~

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1~7~33 :
and an aluminum alloy rod from which an electrical conductor having high thermal stability and acceptable physical and electrical properties can be fabricated.
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STATBMENT_OF THE INVENTION :
.1:1 .
There is provided in accordance with the inven-tion an aluminum alloy electrical conductor Eor use in -applications which require electrical conduc-tors with high thermal stability and which has an increased tensile strength when compared to prior heat^resistant aluminum alloys.
In the broadest aspect of thiR invention the electrical conductor is manufactured ~rom an aluminum alloy containing from more than 0.15 to 1.00 percent silicon, from 0.10 to 0.95 weight percent iron with the balance of the-alloy consisting of aluminum containing trace elements selected from the group consisting of copper, manganese, magnesium, titanium, vanadium and zinc whenthe concentra-tions of the individual trace elements do not exceed G.05' weight percent ~nd the total trace elemerts concentration does not exceed 0.15 weight percent.
More specifically, the invention resides in the method of preparing a heat-resistant aluminum alloy electri- -cal conductor comprising the steps of alloying ~rom more ¦
than 0.15 to 1.00 silicon, from 0.10 to 0.95 weight percent iron with from about 98.70 to about 99.92 weight percent aluminum when the aluminum contains trace elements selected from the group consisting of copper, mangagnese, magnesium2 : . . . .
titanium, vanadium and`zinc and the concentrations oE the individual trace elements do not exceed 0.05 weight percent -~

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~7~gt83 and the total trace element concentration does not exceed 0.15 weight percent; 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 to the groove for a portion of its length; hot-rolling the cast alloy sub-stantially immediately after casting while the cast alloy is in substantially that condition as cast to form a continuous :
rod; cold-drawing the rod into wire without intermediate anneals; and subsequently annealing or partially annealing ¦ ~.
the wire so that it has a minimum electrical conductivity o .
61 percent IACS.
In a first preferred embodiment o~ the invention the aluminum alloy consists of from more than 0.15 to l~00 weight percent silicon, from 0.10 to 0.30 weight percent iron with the balance o the alloy consisting o aluminum con-taining trace elements selected from the group consisting of copper, manganese, magnesium, titanium, vanadium and zinc;
when the individual concentrations of trace elements does not exceed 0.05 weight percent and the total trace elements ~: .
concentration does not exceed 0.15 weight percent. Good ;~ . t~nsile strength, yield strength, ultimate elongation, .. electrical pxoperties and thermal stability have been ob- ..
tained with an alloy which consists of from 0.16-to 0.40 .
weight percent silicon, no more than-0~30 weight percent iron, and the balance of the alloy consisting of aluminum ;
containing.trace elements selected from the group consisting l~:
of copper, manganese, magnesium, titanium, vanadium and zinc l ..
when the concentrations of the individual trace elements do not exceed o.05 weight percent and the to~al tr~ce element - 6 - ~ .

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concentration does not exceed 0.15 weight percent. Good results are also ob-tained when the silicon concentration of the alloy is from 0.50 to about 1.00 weight percent and the iron concentration of the alloy does not exceed 0.30 weight percent with the bala~çe consisting of aluminum con-taining the previously specified trace ~lements. Superior results are obtained when the silicon concentration of the present alloy consi&ts of from 0.40 to 0.49 weight percent and the iron concentration does not exceed 0.30 weight per-cent and the aluminum which makes up the balance of the al-loy contains trace elements of the type and amounts previ-ously recited.
In a second preferred embodiment of the inven-tion the aluminum alloy consists o~ from more than 0.15 to 0.85 weight percent silicon, from more than 0.30 to 0.95 weight percent iron with the balance of the alloy consisting or aluminum containing trace elements selected from the i group consisting of coppex, manganese, magnesium, titanium, vanadium and zinc when the individual concentrations of the trace elements does not exceed 0.05 weight pexcent and the total trace elements concentration does not exceed 0.15 weight percent. Good tensile strength, yield strength, ultimate elongation, electrical properties and thermal sta-bility have been obtained with an alloy-which consists of from moxe than 0.15 to 0.40 weight percent silicon, from more than 0.30 to 0.95 weight percent iron, and the balance of the alloy consisting of aluminum containing tracle elements seleated from the group consisting of copper, manganese, magnesium, titanium, vanadium and zinc when the concentra-'' ~,'. .

, ~7~983 tion does not exceed 0.15 weight percent. Good results are also obtained when the silicon concentration of the alloy is from 0.40 to 0.85 weight percent an~d the iron concentra-tion of the alloy is from more than 0.30 to 0.95 weight percent with the balance consisting of aluminum containing the previously specified trace elements. Superior results are obtained when the silicon concentration of the present alloy consists of fro~ 0.25 to 0.60 weight pexcent and the iron concentration is from more than 0.30 to 0.95 we,ight percent and the aluminum which makes up the balance o the alloy contains trace elements o~ the ~ype and amount~ previ-ously recited.
Good results are also obtained with an alloy which consists of from more than 0.15 to 0.85 weight per-cent silicon, from more than 0.30 to 0.60 weight percent ! iron with the balance of the alloy consisting of aluminum containing the previously recited trace elements within , their speciied concentration ranges. Superior results , have ~een obt~ined when the iron and silicon concentrations of the alloy are ~rom more than 0.30 to 0.57 weight percent `
'; 7 ' iron and from 0.25 to 0.60 weight percent silicon. Excep-tional results have been obtained when the iron and silico~
concentrations are from 0.25 to 0.60 weight percen~ silicon and from 0.40 to 0.57 weight percent iron.

For the purpose of clarity, the following terminology used in this application is explained as follows: 1~

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~', ~(:17~33 Rod - A solid product that is long in relation to its cross section. Rod ~ormally has a cross section of between 3 inches and 0.375 inches.
Wire - A solid wrought product that is long in xelation to its cross section, which is square or rectan~u-lar with sharp or rounded corners or edges or is round, a regular hexagon, or a regula~ octagon, and whose diameter or greatest perpendicular distance between parallel ~aces is between 0.374 inches and 0.0031 inches.
The aluminum alloy electrical conductor of this invention is prepared by initially melting and alloying aIuminum with the necessary amounts of iron, silicon and okher consti~uents to provide the xequisite alloy ~or pro-cessing. Typical impuritie~ or trace elements also present within the melt ! but only in trace ~uantities such as less i than 0.05 weight percent each with a total content of trace impurities gen~rally not exceeding 0.15 weight percent. Of course, when adjusting the amounts o~ trace elements due , -consideration must be given to the conductivity o~ ~he final alloy since some trace elements a~ect conductivity more ,' severely than others. The typical trace elements include vanadium, manganese, magnesium, zinc, boron and titanium~
If the content of the titanium is relatively high (but still quite low compared to the aluminum, iron and silicon con- ! -t~nt) t small amounts of boron may be added to tie up the excess titanium and keep it from reducing the conductivity o~ the wire.
Silicon and iron are the ma~or constituents added to the melt to produce the allcy of the present in-' I
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~ l ~L~7~L9~33 vention. Normally, in the first embodiment of the invention,about 0.40 weight percent silicon is aclded to the typical aluminum component used to prepare the present alloy. The iron is maintained at less than 0.30 percent. In practicing the second embodiment of the~invention, about 0.50 percent silicon and about 0.57 percent iron are added to the melt.
Of course, the scope of the present invention includes the addition of more or less silicon and iron together with the adjustment of the content of all alloying constituents.
After alloying, the melted aluminum composition is continuously cast into a continuous bar. The bar is then hot-worked in substantially that condition in which it i9 ..
received from ~he casting machine. A typical hot~working operation comprises rolling the cast bar in a rolling mi]l substantially immediately after being cast into a barr One example of a continuous casting and rolling oparation capable o producing continuous rod as specified in this application is as follows: I
A continuous casting machine sexves as a means ~or solidifying the molten aluminum alloy metal to provide a cast bar that is conveyed in substantially the condition in whlch it is solidi~ied from the continuous casting machine to the rolling mill, which serves as a means for hot-forming the cast bar illtO a rod or another hot-formed pro-duct in a manner which imparts substantial movement to ~he cast bar along a plurality of angularly disposed axes.
` The continuous casting machine is of conven- ~`
tional casting wheel type having a casting wheel w~Lth a casting groove partially closed by an endless belt supported by the casting wheel and at least one idler pulley. The I
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~L~37~L93 casting wheel and the endless belt cooperate to provide a mold into one end of which ~olten metal is poured to solidi-fy and from -the other end of which the cast bar is emitted in su~stantially that condition in which it is 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. ~he continuous casting machine and the rolling mill are positioned relative to each other so that the cast bar enters the rolling mill substantially i~mediately after solidification in substantially -that con- -dition in which it was solidified. In this condition the cast bar is at a hot~forming temperature within the ranye of temperatures fox hot~orming the cast bar at the initiation o hot-forming without heating between the casting machine and the rolling mill. In the event that it is desired to more closely control the hot-forming temperature of the cast -bar within the conventional range of hot-forming tempera-tures, means for adjusting the temperature of the cast bar may be placed b~tween the continuous casting machine and the rolling mill without departing ~rom 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 ~wo or more in number and arrangea dimetrically opposite from one another or arrànged at egually spaced posi-tions about the axis of movement of the cast bar through the rollin~ mill. The rolls of each roll stand of the rollin~ I
mill are rotated at a predetermined speed by a power means such as one or more electric motors and the casting wheel is .

107~98;3 rotated at a speed generally determinecl by its operating characteristics. The rolling mill serves to hot-form the cast bar into a rod of a cross-sectional area substantially -less than that of the cast bar as it ente~s the rolling mill.
Thus, it will b~ understood that with this apparatus cast aluminum rod of an indefinite number of dif-ferent lengths is prepared by simultaneous casting of the molten aluminum alloy and hot-forming or rollin~ the cast aluminum bar.
The continuous rod produced by the casting and rolling operation i5 then processed in a xeduct~on ope~ation designed to produce continuous wlre o~ various gau~es. The annealed rod ~i.e., as rolled to F. temper) is drawn through a series of progressively constricted dies, without inter-mediate anneals, to form a continuous wire of desired diame- ~ -ter. At the conclusion of this drawing operation, the alloy wire wlll have an excessively high tensile strength, yield strength and unacceptably low ultimate elongation, plus a conductivity below that which is industry-accepted as a mini-mum for the electrical conductor, l.e., 61 percent of IACS.
The wire is then annealed or partially annealed to obtain the desired tensile strength, ultimate elongation and con-ductivity and is subsequently cooled. At the conclusion of the annealing operation, it is found that the annealed alloy wire has the properties of acceptable conductivity and im- -proved tensile strength together with unexpectedly improved -percent ultimate elongation and a surprisingly increased thermal stability as specified preYiously in this applica-tion. The annealing operation may be continuous as in re-: ' ~:

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~'7~ 3 sistance annealing, induction annealing, convection anneal-ing by con-tinuous furnaces or radiation annealing by contin-uous furnaces, or preerably, may be batch annealing in a batch furnace. Continuous annealing temperatures of from -~
about 900F to a~out 1200F may be employed with annealing times of rom about 0.001 seconds to about one ~1.0) second.
Batch annealing temperatures of from about 350F to about 800F may be employed with annealing times of from about 8 hours to about 0.5 hours. Generally, however, annealing times and temperatures may be adjusted to ~eet the require-ments of the particular overall processing operation so long as the desired tensile strength, elongation, conductivity and thermal stability i9 achieved.
During the continuous casting of this alloy, a substantial portion of the iron and silicon present in the alloy precipitates out of solution as an aluminum-iron-sili-con intermetallic compound. Thus, after casting the bar conr tains a dispersion of fine particles of the above mentioned ;
intermetallic compound in a super-saturated solid solution matrlx. As the bar is rolled in a hot-working operation immediately after casting, the intermetallic particles are broken up and dispersed through the matrix thereby i~hibit-ing large cell ormation. When the rod is drawn to its fi-nal size without intermediate anneals and then aged in a ~inal annealing opexation, the tensile strength, elongation and thermal stability are increased due to the small c~
size and the additional pinning of dislocations by the preferential precipitation of the aluminum-iron-silicon in-termetallic c~mpound on the dislocations sites. Therefore, - 13 ~
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these dislocation sources must be activated under the ap-plied stress of the drawing operation and this causes both the tensile strength, yield strength, lelongation and thermal -stability to be further improved. The properties o~ the present aluminum alloy wire a~e significantl~ affected by the size of the aluminum-iron-silicon particles in the ma-trix. Coarse precipitates reduce the percent elongation and thermal stability of the wire by enhancing nucleation and thus, formation of large cells which, in turn lowers the re-crystalization temperature of the wire. Fine precipitates imp~ove the precent elongation, tensile strength, conduc-tivit~, and thermal ~tability o~ the wire by reducin~ nu-cleation and increasing the recrystaliæation temperature.
Grossly coarse precipitates of the iron-aluminum-silicon in- ¦
termetallic compound cause the wire to become brittle and i generally unuseful. Coarse precipitates have a particl~ size of above one micxon, measured along the transverse axis of the particle, and fine precipitates have a particle size of below one micron, measured along the trdnsverse axis of the particle.
~' ~ more complete understanding of the invention will be obtained ~rom the following examples.

Sample alloy specimens were prepared containing 0.12 percent iron, 0.003 percent copper, 0.001 perce~ mang- !
anese, 0.001 percent magnesium, 0.001 percent titanium, 0.001 percent vanadium and 0.015 percent zinc with the bal-ance being aluminum. Each sample also included a silicon content which varied in a range from 0.04 percent to 0.98 -~ - 14 - ~

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1983 ' percent silicon. The samples containing less than 0.15 per-cent silicon are considered conventional EC alloys, while the samples containing more than 0.15 percent silicon are in accordance with the first embodiment: of this invention wherein iron is less than 0.30 percent. All samples were continuously cast into continuous bars and hot-rolled into continuous rod in similar fashion. The samples were then cold drawn through successively constricting dyes to yield ;
a wire having a diameter of 0.102 inches. Sections of the wire were collected on separate bobbins and batch furnace annealed at various temperatures and for various lengths o~ time to yield sections of varying tensile strengths.
Several samples o each section were tested in a device designed to measure the ultimate tensile strength oE each sec~ion, the elongation of each section, the electrical conductivity of each section and the yield tensile strength o each section. The results are tabulated in Tables I and II.

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Thermal Stability Test: :' Other samples, prepared as above, were annealed .
-' in a batch furnace at 525F for a period of two hours and , allowed to cool. After the cooling period, the samples were . .~. ~
tested to determine ultimate tensile st:rength and yield j.
tensile strength and similar samples were then,aged for four hours at 482F to determine'the thermal stability of samples having different concen~rations. The results are as follows:
,' , TABLE III .
Bar 9~ % ' No. Fe Si UT~ X 10 % Retention Y~S X 103 ~ Retention .
~1 0.12 .0~ 16.3 90 15~3 87 ~2 0.12 .08 17.4 89 15.~ 90 ~3 0.12 .13 17.2 90 15.7 90 ~4 0.12 .lg 17.6 gO 16.2 91 0.12 .32 17.6 94 16.0 94 , 6 0.12 .41 18.1 96 16.1 96 7 0.12 .44 1~.1 99 15.7 101 8 0.12 .49 18.6 99 16.5 98 9 0.12 .7~ 2~.~ 98 17.~ 97 ~10¦ 0.12 ¦.sa 1 .7 97 14.1 93 As seen in Table III, Bar Nos. 4-10, which con~
tained more than 0.15 percent silicon and were thus prepared ,, i, in accordance with this invention, generally exhibited a .~ .
greater percent Retention of both ultimate tensile strength (UT~) and yield tensile strength (YT~) after being aged fvr '~.
four hours at 48~F than Bar Nos. 1-3 which were con~ention~

al ~C alloys. It can be concluded, therefore, that the wire ~' ~
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107~ 33 !

of the present invention has surprisingly improved thermal stability when compar~d with conventional EC aluminum alloy wire.

Sample alloy specimens were ~repared containin~
0.57 percent iron, 0.003 percent copper, 0.001 percent manganese, 0.001 percent magnesium, 0.001 percent titanium, 0.001 percent vanadium and 0.015 percent zinc with the bal-ance being aluminum. Each sample also included a silicon content which vaxied in a range ~rom 0.04 percent to 0.8.
percent silicon. The samples containing less than 0.15 per-cent silicon are considered in accordance with prior axt U.S. Patent No. 3,512,221, while the samples containing more than 0.15 percent silicon are in accordance with the second 1 embodiment of this invention wherein the iron is from 0.30 to 0 95 percent. A11 samples were then processed and tested as set forth in Examples I-10 and the results are tabulated in Tables IV and V.

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iO71983 Thermal Stability Test:
Other samples, prepared as above, were annealed - in a batch furnace at 525F for a period of two hours and allowed to cool. After the cooling period, the samples were tested to determine ultlmate tensile strength and yield tensile strenth and similar samples were then aged for four . hour~ at 482~F to determine th~e thermal stability of samples :
-- having different silicon concentrations. The result.s are as -follows:

TABLE VI

Ear ~ ~ .
~_ O ~ No. Fe Si UT~ X 10 % Retention YTS X 103 % Retention .
11 0.57 0.4 15.3 93 12.9 88 l2 0.57 .11 16.5 93 14.~ 89 - ~13 0.57 .22 16.8 93 15.2 88 14 0.57 .25 16.9 94 15.4 '92 .~15 0.57 .34 17.6 93 15~6 94 ;
~ 16 0.57 .43 17.9 94 15~7 9g H 17 0.57 .50 18.9 94 16~4 95 8 0.57 .60 19.6 94 17.1 94 9 0.57 .67 20.4 94 17.5 93 As seen in Table.VI, Bar Nos. 13-19~ which con- ¦
tained more 0~15 percent silicon and were thus prepar~d in accordance with this invention, generally exhibited a great-e~ percent;Retention o~ both ultimate tensile strength ~UT~
and yield kensile strength (YTS) after being aged or four hours at 482F than Bar Nos. 11 and 12 which were prepared in accordance with the prior ark U.S. Patent No. 3,512,221.
It can be concluded, therefore~ tha~ the wire of the present ~:
j '' 10~1983 invention has surprisingly improved thermal stability when compared with the conventiDnal prior art aluminum alloy wire.

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Claims (8)

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

1. A method of preparing a heat-resistant aluminum base alloy electrical conductor having a minimum electrical conductivity of sixty-one percent (61%) IACS
characterized by:
(a) alloying from more than 0.15 to 1.00 weight percent silicon, from 0.10 to 0.95 weight percent iron with the balance of aluminum containing trace elements selected from the group consisting of copper, manganese, magnesium, titanium, vanadium and zinc wherein the individ-ual concentrations of said trace elements do not exceed 0.05 weight percent and the total concentrations of said trace elements does not exceed 0.15 weight percent;
(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 to said groove for a portion of its length to form a continuous aluminum, base alloy bar having iron-aluminum-silicon intermetallic precipitates formed therein; and (c) hot-rolling the continuous bar sub-stantially immediately after casting while the bar is in substantially that condition as cast to form a continuous rod, said rolling operation breaking-up and evenly dispers-ing said precipitates throughout the aluminum matrix and forming precipitate particles having a diameter of less than one micron when measured along the transverse axis of said particles.

2. A method according to claim 1, charac-terized by maintaining the iron content of the alloy no greater than 0.30 weight percent.

3. A method according to claim 2, further characterized in a preferred form by maintaining the silicon from 0.40 to 0.49 weight per cent.

4. A method according to claim 1, charac-terized in that the iron content of the alloy is from more than 0.30 to 0.95 weight percent, and the silicon content is from more than 0.15 to 0.85 weight percent.

5. A method according to claim 4, further characterized in a preferred form by maintaining the silicon from 0.25 to 0.60 weight percent.

6. A method according to claim 1, 2 or 3, characterized by including the further steps of drawing said continuous rod through a series of wire-drawing dies without any preliminary or intermediate anneals to form a wire, and thereafter annealing or partially annealing said wire.

7. A heat-resistant aluminum base alloy electrical conductor having a minimum electrical conduc-tivity of sixty-one percent (61%) IACS comprising from more that 0.15 to 1.00 weight percent silicon, from 0.10 to 0.95 weight percent iron with the balance of aluminum con-taining trace elements selected from the group consisting of copper, manganese, magnesium, titanium, vanadium and zinc wherein the individual concentrations of said trace elements do not exceed 0.05 weight percent and the total concentrations of said trace elements does not exceed 0.15 weight percent.

8. A heat-resistant aluminum base alloy electrical conductor as claimed in claim 7, characterized as retaining at least ninety percent (90%) of its original ultimate tensile strength after heat aging at a temperature of 482°F. for a period of four hours.