US3615371A

US3615371A - Aluminum alloy for electric conductor

Info

Publication number: US3615371A
Application number: US712357A
Authority: US
Inventors: Katsuhisa Nakajima; Sadao Inoue
Original assignee: Furukawa Electric Co Ltd
Current assignee: Furukawa Electric Co Ltd
Priority date: 1967-04-08
Filing date: 1968-03-12
Publication date: 1971-10-26
Anticipated expiration: 1988-10-26
Also published as: FR1563317A; GB1166415A

Abstract

This aluminum alloy for electric conductor consists of a ternary Al-Mg-RE alloy containing less then 0.6 weight percent of one or more of rare earth metals and has improved castability, weldability, fatigue strength and antisoftening characteristics on heating at a high temperature and is applicable to the continuous casting and rolling method and the rolling method using large ingots for the purpose of easily manufacturing aluminum alloy conductor having excellent characteristics.

Description

ited States 1 atent Inventors Appl. No.

Priority Katsuhisa Nakajima;

Yasuo Maeda; Sadao lnoue, all of Kiyotalti, Nilrko, Japan Mar. 12, 1968 Oct. 26, 197 1 The Furukawa Electric Company Limited Tokyo, Japan Apr. 8, 1967 Japan ALUMINUM ALLOY FOR ELECTRIC CONDUCTOR 1 Claim, No Drawings US. Cl

Int. Cl

Primary Examiner-Richard 0. Dean Attorney-Stevens, Davis, Miller & Miosher ABSTRACT: This aluminum alloy for electric conductor consists of a ternary Al-Mg-RE alloy containing less then 0.6 weight percent of one or more of rare earth metals and has improved castability, weldability, fatigue strength and antisoftening characteristics on heating at a high temperature and is applicable to the continuous casting and rolling method and the rolling method using large ingots for the purpose of easily manufacturing aluminum alloy conductor having excellent characteristics.

1 ALUMKNUM ALLOY FOR ELECTlRll C CONDUTOR This invention relates to improvements in aluminum alloys for electric conductors, more particularly to electric conductive aluminum alloys having electric conductivity equivalent to that of the conventional electric conductive aluminum (hereafter abridged as ECAl) and more excellent mechanical strength, fatigue strength and antisoftening characteristic at a high temperature than ECAl, and electric conductivity and mechanical strength equivalent to those of the conventional electric conductive binary Al-Mg alloy or ternary Al-Mg-Si alloy and higher castability, weldability, fatigue strength and antisoftening characteristic at a high temperature than these alloys and applicable to the continuous casting and rolling method or the rolling method using large ingots for the pur pose of manufacturing electric conductive wires having im proved characteristics.

Aluminum and aluminum alloys have recently been used not only for wires of transmission lines and distribution lines, but also for electric alloy conductive materials in various fields. Various characteristics which have not heretofore been considered are required for the aluminum and alloys thereof, in addition to such basic characteristics as electric conductivity, tensile strength, elongation and bendability, etc. For example, the conventional electric conductive aluminum (ECAl) used for transmission line and distribution line is deficient in fatigue strength and antisoftening characteristic at a high temperature so that improved electric conductive materials are desired. The electric conductive binary Al-Mg alloy and ternary Al-Mg-Si alloy have been used for special transmission line and distribution line, rotor bars for generator, windings for transformer, bus bars for electric resistance heating furnace, etc. These alloys, however, are deficient in weldability, fatigue strength and antisoftening characteristic at a high temperature and thus could not be used for a long duration and applied to welding operation for obtaining highly reliable welds. Thus, excellent weldability, fatigue strength and antisoftening characteristic at a high temperature have recently been required for the aluminum alloys.

Binary Al-Mg alloy and ternary Al-Mg-Si alloy used as the conventional-electric conductive material contain a comparatively large amount of Mg, which fact not only makes degassing in molten state considerably difficult but also enlarges the solidification temperature range with the result that excessive unstable gas remains in their ingots and causes fine defects even when a high level of technique and skill is used.

ingots having no defects could not be obtained by such method as the continuous casting and rolling method and the rolling method using large ingots wherein degassing of occluded gas becomes ineffective, which fact will decrease the fatigue strength of the final product. Thus, it is extremely difficult to apply the electric conductive binary Al-Mg alloys and ternary Al-Mg-Si alloys to the continuous casting and rolling method and the rolling method using large ingots. Moreover, the electric conductive binary Al-Mg alloy and ternary Al-Mg- Si alloy have disadvantages that they contain magnesium which is unstable and liable to be oxidized at high temperature and thus are inferior in weldability and could not be used for the conventional resistance welding in air for the purpose of obtaining highly reliable welds, and that they are difficult to use at a high temperature since their tensile strength remarkably decreases when they are heated at a high temperature of about 500 C. As the result of our studies of aluminum alloys for electric conductors to obviate the above disadvantages we found that a ternary aluminum alloy consisting of 0.020.8 weight percent of magnesium, 0.6-3.0 weight percent of one or more rare earth metals such as cerium, lanthanum, neodymium, praseodymium, samarium, etc., or of any composition thereof such as Misch metal (all these are hereafter abridged as RE), and the remainder, aluminum, had excellent electric conductivity and tensile strength and was superior in heat resistance at a comparatively low temperature of the order of l-200 C. We have this Al-Mg-RE alloy registered as U.S. Pat. No. 3,278,300. This ternary alloy has an nary Al-Mg alloy or the ternary Al-Mg-Si alloy,

improved work hardening effect owing to minute dispersion of the intermetallic compound of AlE-Mg-RE into the matrix of the aluminum solid solution, but has a disadvantage that it contains a comparatively large amount of expensive RE and makes the final product expensive. Moreover, this ternary alloy is comparatively difficult of degassing in casting and of application to the continuous casting and rolling method or the rolling method using large ingots for the purpose of obtaining ingots having no defects. This ternary alloy has good heat resistance at a comparatively low temperature of the order of 200 C., but is not quite satisfactory in antisoftening characteristic at a higher temperature in the neighborhood of 500 C., and moreover requires a fairly high level of technique to make good weld on it. Moreover, this ternary alloy has a disadvantage that its final product becomes hard and brittle when processed by a method in which its component inclusive of impurities, remain in the forced state of solid solution in the final product, such as continuous casting and rolling method, or by a method in which it is given a very high degree of cold working, such as rolling method using large ingots, thus making the manufacture of the electric conductive material by these two methods extremely difficult and increasing the working costs.

In order to obviate the above disadvantages, further researches were made on many aluminum alloys for electric conductors and the inventors have succeeded in obtaining excellent aluminum alloys for electric conductors, free from the abovementioned disadvantages.

The principal object of the invention is to provide aluminum alloys for electric conductors which are equal in electric conductivity and superior in mechanical strength, fatigue strength, and antisoftening characteristic at a high temperature to any conventional conductive aluminum.

Another object of the invention is to provide aluminum alloys for electric conductors which are equal in electric conductivity and mechanical strength and superior in castability, weldability, fatigue strength, and antisoftening characteristic at a high temperature to the binary Al-Mg alloy or the ternary Al-Mg-Si alloy for electric conductors.

A further object of the invention is to provide aluminum alloys for electric conductors having improved characteristics and applicable to the continuous casting and rolling method or the rolling method using large ingots.

In other words, the inventors have further investigated the ternary Al-Mg-RE alloy disclosed in the U.S. Pat. No. 3,278,300 and found out that reduction in quantity of RE added to this alloy improves its castability, weldability, fatigue strength, and antisoftening characteristic at a high temperature and that said alloy can easily be made into electric conductive materials having improved characteristics by the continuous casting and rolling method or the rolling method using large ingots.

The inventors have succeeded in obtaining aluminum alloys which are equal in electric conductivity and mechanical strength and superior to castability, weldability, fatigue strength and antisoftening characteristic at a high temperature to the conventional electric conductive aluminum or the biby adding to aluminum 0.02-2.0 weight percent, preferably 0.05-l.5 weight percent, of magnesium and less than 0.6 weight percent, preferably 0.1-0.5 weight percent, of RE.

Addition of magnesium to the alloys of the invention increases mechanical strength which is suitable for the electric conductive conductive material, while addition of RE serves to stabilize the gas occluded in the molten alloy to improve the castability, and make the alloy fit for continuous dynamic casting and casting into large ingots. Moreover, the alloys of the invention have an advantage that their fatigue strength becomes improved owing to improved soundness of ingots, that magnesium occluded therein in the solid solution becomes thermally stabilized to remarkably improve the weldability and antisoftening characteristic at a high temperature, that the state of compositions in forced solid solution or the severe working does not increase brittleness of the alloy after the cold working, and that the electric conductive material can be manufactured from the alloys of the invention in any easy manner with the aid of the continuous casting and rolling method or the rolling method of using large ingots.

The reason for limiting the amount of magnesium to 0.02-2.0 weight percent is that in the amount of less than 0.02 weight percent, magnesium becomes stable in aluminum at a high temperature irrespective of addition of RE and thus makes it possible to effect casting and welding, substantially without any difiiculty but the mechanical strength becomes insufficient for the electric conductive material and that in case magnesium content is more than 2.0 weight percent, the alloys become unsuitable as the electric conductive material because of remarkable decrease in electric conductivity.

The reason for limiting the amount of RE to less than 0.6 weight percent is that although even such small amount of RE as recognizable by the analysis can remarkably improve castability, weldability, fatigue strength and antisoftening characteristic at a high temperature, addition of 0.6 weight percent or more of RE does not present any improvements in proportion to its high cost, instead, it tends to deteriorate castability, weldability, fatigue strength and antisoftening characteristic at a high temperature and the work hardening effect of the alloys is increased to an unnecessary extent, thus making it very difficult to manufacture the electric conductive material by the continuous casting and rolling method or the rolling method .using large ingots and requiring a higher degree of cold work- In the alloys of the invention, any one or more of rare earth' metals such as Ce, La, Nd, Pr, Sm, etc., or any composition thereof, such as Misch metal (herein called RE") can produce the same effect. The alloys of the invention may contain impurities not more than 0.5 weight percent of copper, not more than 0.6 weight percent of silicon, not more than 0.6 weight percent of iron, not more than 0.2 weight percent of zinc and not more than 0.1 weight percent of manganese without substantially impairing the characteristics thereof.

The preferable composition of the alloys of the invention, which are equal in electric conductivity and superior in mechanical strength, fatigue strength and antisoftening characteristic at a high temperature to the conventional electric conductive aluminum (ECAl), is 0.05-0.l weight percent of magnesium, 0.1-0.3 weight percent of RE and the remainder, aluminum. The preferable composition of the alloys of the invention which are equal in electric conductivity and mechanical strength and superior in castability, weldability, fatigue strength and antisoftening characteristic at a high temperature to binary Al-Mg alloy for electric conductors, is 0.l5-0.5 weight percent of magnesium, 0.1-0.5 weight percent of RE and the remainder, aluminum. The preferable composition of the alloys of the invention which are equal in electricconductivity and superior in castability, weldability, fatigue strength and antisoftening characteristic at a high temperature to the ternary Al-Mg-Si alloy for electric conductors, is 1.0-1.5 weight percent of magnesium, 0.1-0.4-weight percent of RE and the remainder, aluminum.

The improved castability of the alloys of the inventionrenders it possible to manufacture from these alloys electric conductive materials having excellent characteristics in an easy manner with the aid of the continuous casting and rolling method. That is, the electric conductive material having more excellent characteristics may easily be manufactured by a continuous casting and rolling method comprising continuous v casting the alloys of the invention in molten state into a mould,

solidifying by quenching the molten metal until its temperature becomes 300-580 C., subjecting to the solidified casting at least 70 percent of plastic deformation while cooling at a cooling speed of at least 50 C./min. to a temperature of at most 250 C., and effecting subsequent cold working.

In the above-mentioned continuous casting and rolling method the reason for limiting the quenching temperature in case of solidifying the molten cast to 300-5 80 C. is that in case of the temperature of more than 580 C., the forced state of solid solution is not sufficient to improve the mechanical strength of the final product and that the temperature less than 300 C. is too low to effect the subsequent rolling step. The reason for giving the solidified casting at least 70 percent of plastic deformation while cooling at a cooling speed of at least 50 C./min. to a temperature of at most 250 C. is that in case of effecting the plastic deformation it is necessary to effect rolling at a high temperature at the beginning of the rolling step and effect rolling at a low temperature at the end of the rolling step in order to prevent the defects in the material and thus improve the mechanical strength thereof, that at a cooling speed of less than 50 C./min. the recovery of plastic strain takes place, thus decreasing the mechanical strength of wire rods, that less than 70 percent of plastic deformation makes it impossible to obtain mechanical strength necessary for the final product, and that at a temperature higher than 250 C. at a time immediately after the continuous rolling step it is impossible to obtain not only suflicient mechanical strength of the wire rod but also uniform characteristics of the wire owing to difference in cooling speeds at several locations of coiled wire rod.

The most preferable conditions for the continuous casting and rolling method are a quenching temperature range of 400-500 C., a cooling speed of 200-600 C./min. during plastic deformation, a plastic deformation of at least percent and a temperature immediately after the working effect of C. or under.

The alloys of the invention make also it possible to easily manufacture aluminum alloy conductors with the aid of the rolling method using large ingots, thereby improving the characteristics of the electric conductive material. That is, the aluminum conductor having improved characteristics such as tensile strength, fatigue strength, etc., may easily be manufactured by a rolling method using large ingots comprising casting the alloys of the invention in molten state into a large mold having a short side of at least 12.7 cm., reheating the casting obtained and subjecting hot rolling and subsequent cold rolling with flat rollsto sad casting to obtain a strip, and slitting said strip along the rolled direction thereof into bars or subsequently shaping said bars into wires of circular in section.

In the above-mentioned rolling method using large ingots the reason for limiting the dimension of the short side of the ingot to at least 12.7 cm. is that for the ingot having the short side of at least 12.7 cm. the characteristics of the electric conductive material are improved and the manufacturing cost becomes less expensive and that for the ingot having the short side of smaller than 12.7 cm. the characteristics of the electric conductive material are not improved and such small ingot can effectively be cooled by means of the mould to effect a proper degassing and thus obtain an ingot having substantially no defects, with the result that necessity of applying the alloys of the invention to such small ingot becomes meaningless.

The most preferable conditions for the above-mentioned rolling method using large ingots for the purpose of obtaining electric conductive material having improved characteristics in less expensive manner are a length of the short side of the ingot of 20.3-50.8 cm., a temperature for starting the hot rolling step of 400-500 C., a reduction of hot-rolling step of at least 90 percent, a temperature at the end of the hot-rolling step of at most 350 C., a reduction of cold rolling step of at least 30 percent, a size of the product at the end of the cold rolling step of 0.5-l.3 cm. and a reduction of shaping and drawing into wire is at least 50 percent.

It will be seen that the alloys of the invention have excellent castability so that they can be applied to the above-mentioned continuous casting and rolling method and rolling method using large ingots for the purpose of improving characteristics of the electric conductive materials manufactured. it is to be understood that the alloys of the invention may also be applied to the conventional hot working methods such as methods of extruding the alloys from billets rolling with grooved rolls.

from square bars, etc. for the purpose of obtaining wires or bars having any desired dimensions. However, the above-mentioned continuous casting and rolling methods and rolling method using large ingots are most preferably applied to the ductive aluminum (ECAl) and extremely small rate of decrease in tensile strength after heating at a high temperature for many hours.

It is also apparent from the table I that the alloys of the inalloys of the invention in order to further improve the haracvention have excellent tensile strength in case the electric conteristics ofthe electric conductive materialmanufactured. ductivity is equivalent to that of the binary Al-Mg alloy for The invention will be further explained in detail with examelectric conductors such as 5005 alloy and that of the ternary ples. Al-Mg-Si alloy for electric conductors such as 6063 alloy and extremely small rate of decrease in tensile strength after heat EXAMPLE 1 ing at a high temperature for many hours. On the contrary the By the use of alloys of the invention, conventional binary conventional ternary Al-Mg -RE alloy for electric conductors. Al-Mg alloys for electric conductors (5005 alloy), convenadded w at :3 weght l h f i to tional ternary Al-Mg-Si alloys for electric conductor (6063 al- 3 2 rate 0 :Crease o strengtha 3 f ag loy), and ternary Al-Mg-RE alloy containing excessive RE lg z z i 8 f l ours m il h 0 f each having a composition shown in table 1, billets were 23: r x s gg i T2 a s: e produced and extruded into 5 mm.Xl0 mm. bars. The electric e y e 0 ml no 6 apprecla e conductivity and tensile strength of these bars were measured EXAMPLE 2 and the tension test at room temperature was carried out after heating the bars at 500 C. for 50 hours. The results are shown 20 The alloys f the Invention, com'emlonal 'y E in table 1. The RE was Misch metal available in market and loys f" elecll'lc conductors n ternary Al-Mg-RE alloys for was directly added to the aluminum base metal added with i i conductors PQP excessive RE were made into magnesium.

TABLE 1 Composition Electric 'Icnsllo conduestrength Mg RE Al tivity as (wt. (wt. (wt. (1.11.0.5. extruded Rate of Name 01 alloy percent) percont) percent) percent) (kg./111111.-) decrease 1 Aluminum alloy 01 the invention 0.12 0. 06 Remainden. 62. 3 0. 63 2.0 0.10 0.00 02.5 10.02 2.3 0. 10 0. 3O 61. 1 11. 2. 7 0.11 0.57 61.7 11.48 4.3 0. 37 0. 04 59. 2 12. 85 4. 2 0.32 0.12 59.2 13.20 4.0 0. 34 0. 28 58.9 13. 66 5. 0 0. 34 0. 52 58. 8 13. 71 5. 8 0. 51 0. 04 57. 2 13. 67 10. 6 0.48 0. t1 57.3 14.35 4.5 0.47 0. a3 57.0 14. 01 4.8 0.52 0.50 55.8 14.87 7.2 1.8 0.05 40.2 18.22 10.8 1.8 0.11 40.1 19.18 0.1 1.8 0.32 49.1 10.23 5.4 1.9 0.51 ..(.10 48.6 19.33 9.0

Well known alloy 62. 0 9. 57 36. 4 58.9 12. 09 41. 2 57. 1 13. 29 38. 2 49.3 18. 14 39. G 61.1 11. 00 16. 4 58. 6 13. 84 13. 2 56.4 15. 21 19. 2 48. 0 20. 00 1t). 2

ECAl 52.5 0.11 35. o 6063 alloy (Al-0.7% Mtg-0.4% Si alloy). 48. 0 17. 23 2i]. i) 5005 alloy (Al-0.6% Mg ttllOy) 55. 7 13. 33 37. 7

1 In tensile strength after heating at 500 C. for hours.

As seen from the table 1, the alloys of the invention consisting of the binary Al-Mg alloy and less than 0.6 weight percent of RE have excellent tensile strength in case the electric conductivity is equivalent to that of the conventional electric conbillets which were extruded into B-mm. diameter wires to measure the tensile strength at welds 011 each wire when the wire has been subjected to butt weldings for 100 times. The results are shown in table 2.

TABLE 2 Composition Rate Mg (wt. RE (wt. Al (wt. containing Range of Name of alloy percent) percent) percent) values 1 values (percent) (percent) Aluminum alloy 01 the invention 0. 20 0.15 Remaindcr. 87 26 0.18 0.46 do 92 29 0.43 74 35 0.42 78 37 O. 76 58 42 0.75 66 38 Well known alloy 0. 18 63 47 0. 40 31 59 0.75 4 63 0.22 78 41 0.45 59 38 0.68 42 44 X100% is at least 80%.

it is clearly shown in the above table 2 that the weldability of the alloys of the invention is far better than that of the conventional binary Al-Mg alloy for electric conductors, that the mechanical strength at the welds is remarkably improved, and

2. Method in which the alloys were continuously cast into 22 cm. bars which successively were hot rolled with the aid of grooved rolls into wire rods (hereinafter called CCR method).

that the range of values of the mechanical strength is also Metht?d in Which the alloys were cast while cooling y de a ed, water into 25.5 cm. 76 cm. large ingots which were hot- The weldability of the conventional ternary Al-Mg-RE alloy toned with the aid of flat and slit along the for electric conductors containing excessive RE is better than rolled direction into Square bars which were Subsequently h f h Conventional bi 1 M alloy f electric shaped into wires ofcircular in section (hereinafter called ductors, but is worse than that of the alloys of the invention. it R method'qseems that the addition of excessive RE causes bad influence The rods manlttfacntted by the abovefmehtloned three upon welds owing to the presence of magnesium, RE and inmethods w g 'h hamster means termetanic compound hereofin aluminum of cold wire-drawing. The specific gravity of each ingot and the tensile strength, bending limit and fatigue limit strength of EXAMPLE 3 each wire were measured. The results are shown in table 4.

Alloys of the invention, conventional binary Al-Mg alloys it is apparent from the table 4 that for the conventional bifor electric conductors and ternary Al-Mg-RE alloys containy E for electric Conductors the and 5R5 i excessive RE each h i a composition Shown i table 3 methods make it more difficult to obtain the sound ingot than and in molten state were subjected to degassing with the aid of the WRR method While the bending Characteristic of the chlorine gas and to holding and then cast into a metallic mold 2O worked becomes remarkably on the Contrary the to obtain ingots. Comparison was made of weldability of these y of the ihvehtioh ehsul'e Stabilizing effeCt of the Proper ingots by investigating the state of defects occurred in the incontent of RE which PermitS of Obtaining the Sound 'hgots g'ots and by measuring specific gravity at the optimum portion without y defects y means not y of WRR method but in the ingots. The results are sh i m 3 i hi h A also ofCCR and SRS methods. Moreover, the alloy wire ofthe represents the sound state. B, the presence ofsmall blowholes, invention manufactured by the R n R m thods has d C, h presence oflarge b| h 1 more excellent fatigue limit strength than that ofthe alloy wire As seen from the table the oonventiorial bcctn'rrieifl Ofthe invention manufactured y the WRR method Mg alloys produce ingots with defects while the alloys of the The alloy wire of the invention manufactured y the R invention containing small quantity of RE is capable of CCR and SRS methods has more excellent bending limit and properly fixing gas remained in the metals to decrease occurfatigue limit Strength than the conventional binary S rence of defects during solidification thus obtaining sound infor electric CondUCtOIS- The COn e t OnHl ternary Algots without any defects. The conventional ternary Al-Mg-RE Mg-RE alloy containing comparatively large quantity of RE alloys contain a large amount of gas when they are in the moland manufactured y the CCR and SR5 methods are ten state after the degassing treatment has been completed so pable of Obtaining better ingots than the conventional bithat it becomes difficult to fix all of the gas by means of RE, nary Al-Mg alloy and has more improved tensile strength. thereby occurring blowholes. bending limit and fatigue limit strength than the latter alloy.

TABLE 3 Composition State of Specific. Mg (wt. RE (wt. Al (wt. defects gravity Name of alloy percent) percent) percent) occurred (g./c1n.

Alloy oi the invention. 0.05 0.04 Remainder" A 2.70 0.11 0.50 d0..... 2 A 2.70 0.52 0.12 do 2.69 1.8 0.50 (10 A 2.68

Well known alloy 0. Roiuainden. BO 2. 62 1.8 ..d0 BC 2.48 0.42 .dO C 2.67 1.7 do C 2.62

EXAMPLE 4 Those characteristics of the former alloy are worse than those The alloys of the invention, conventional binary Al-Mg alloys for electric conductors, and ternary Al-Mg-RE alloys containing comparatively large quantity of RE, each having a composition shown in table 4 were by the following methods.

1. Method in which the alloys were cast while cooling by water into 10 cm. l0 cm. bars which were hot-rolled with the aid of grooved rolls into wire rods (hereinafter of the alloy of the invention. it seems that the addition of excessive RE causes deterioration of the above-mentioned characteristics.

EXAMPLE 5 The alloys of the invention consisting of 0.1 weight percent of Mg, 0.5 weight percent of RE and the remainder, aluminum called WRR method"). in the molten state were subjected to the continuous casting TABLE 4 Composition Cimruclt-ristics of wire Specific Fatigue Munniacgravity Tensile Bending limit Mg (\vt. RE (wt. Al (wt. hiring of ingot strength limit (D: Strength Name of alloy percent) percent) percent) method (gjcmfi) (kg/mm?) Wire's din.) (kg/mm!) WRR 2. 60 27.1 ll) 7. 7 0.4 0.2 Remainder" CCR 2. 68 28.7 1D 8.:

. 0 Alloy of the invention g 4 l 0.2 0.5 .d0. {COR 2.60 27.5 1D 8.2 SE8 2. 70 27. 7 1D 8.5 WRR 2. 68 26. 0 1D 6. 0 0.7 d0 CCR 2.53 11.7.9 5D

v it R Egg 5%,; 3 7:9 0.2 2 0 do CCR 2.66 29.5 3D 7.2 SR8 2.68 28.4 2D 8.0

and rolling method based on the manufacturing conditions of the CCR method shown in table 5 and then cold-drawn into 4.0 mm. diameter wires to measure numbers of detecting defects during the wire drawing step and characteristics of the ill strength and fatigue limit strength. The results are shown in table 6.

It is apparent from the table 6 that the wire manufactured from the alloys of the invention in accordance with the SRS wire manufactured. The results are shown in table 5. 5 method which lies within the scope of the invention has excel- TABLE 5 I Characteristic of wire Coohflg Temperature Number of Ingot speed R educof material detecting Bending temperduring tion of immediately defects Tensile limit ature rolling tolling after rollduring wire strength (D.W1res Manufacturing condition C.) C./min.) (percent) ing 0.) drawing (kg/mm!) dia.) Within the scope of the invention... 500 300 95 150 26. 2 1D 400 200 90 200 0 25.9 1D 600 250 90 300 13 21.3 2D Out of the scope of the 1nventl0n 450 200 60 260 0 22. 2 ID 250 40 80 200 49 27.7 5D

As seen from the table 5, the wire manufactured from the lent tensile strength and fatigue limit strength, and that the alloys of the invention in accordance with the CCR method wire manufactured from the alloys of the invention in acwhich lies within the scope of the invention is capable of cordance with the SRS which lies out of the scope of the inpreventing defects from occurring during the wire-drawing 2O vention deteriorates the tensile strength and fatigue limit step and has excellent tensile strength and bending limit. On strength owing to insufficient rate ofcold working. the contrary the wire manufactured from the alloys of the in- As explained hereinbefore the alloys of the invention convention in accordance with the CCR method which lies out of sisting of the conventional binary Al-Mg alloy containing the scope of the inv n i that in 0886 the Casting p r small quantity of RE ensures remarkable improvement as aluture is too high or too low or the cooling speed during the minum alloy conductors in castability, weldability, fatigue rolling is too low or the temperature of th material strength and antisoftening characteristic atahigh temperature mediately after the Working is too high, is not capable of without impairing their basic characteristics such as electric preventing defects from occurring during the wire drawing conductivity il Strength, b d bim d are and deteriorates the tensile strength and bending limit thereof. li abl to the continuous casting and rolling method and rolling method using large ingots for the purpose of easily EXAMPLE6 manufacturing aluminum alloy conductor having improved The alloys f the invention Consisting f weight percent mechanical strength and antisoftening characteristic at a high of Mg, 0.1 weight percent of RE, and the remainder, amtemperature and further provide the important advantage that minuin in the molten state were subjected to water-cooled the alloy of the mvemlo" and the alloy Cqnductor i tured from the alloy by means of the continuous castlng and casting step to obtain ingots having dimensions shown in table m d d mod Sin lat e in ms are Suita 6. The ingots obtained were heated again and made into strips 3 m nd djigstribgutiog line but also by hot-rolling and cold rolling steps. The strips were slit along 8 y or ransmlsslon i a for windings of dynamoelectric machine and transformer and the rolled direction into bars which were shaped by grooved for bus bars for hightemperature application, that said alloy rolls into wires of circular in section to measure the tensile 40 and alloy conductor can effectively be manufactured without TABLE 6 using a large amount of expensive RE, and that said alloy and Fan ue alloy conductor are so excellent in weldability that reliable Tensile i welds can be obtained. Dimension strength strength w we claim Manufacturin condition of in (it c k k g g m) g/mm g/mm 1. Aluminum alloy for electric conductor consisting offrom 254 X 75.2 0.02 to 2.0 weight percent of magnesium, from 0.04 to 0.57 15-24 X weight percent of one or more of rare earth metals. and Out of the scope of the invention 10.16 x 50.8 23.6 6.7 remamder Ofalummum'