US3711339A - Aluminum alloy conductor - Google Patents

Abstract

AN IMPROVED ALUMINUM ALLOY CONDUCTOR. THE CONDUCTOR IS CHARACTERIZED BY A COMBINATION OF GOOD MECHANICAL AND ELECTRICAL PROPERTIES AND CONTAINS FROM 0.04 TO 1.0% IRON, 0.02 TO 0.2% SILICON, 0.1 TO 1.0% COPPER, 0.001 TO 0.2% BORON, BALANCE ESSENTIALLY ALUMINUM.

Description

United States Patent 3,711,339 ALUMINUM ALLOY CONDUCTOR Fred A. Besel, Southbury, and William C. Setzer, Hamden, Conn., assignors to Olin Corporation No Drawing. Continuation-impart of application Ser. No. 66,067, Aug. 21, 1970, which is a continuation-in-part of application Ser. No. 885,315, Dec. 15, 1969, which in turn is a continuation-in-part of application Ser. No. 715,552, Mar. 25, 1968, all now abandoned. This application Nov. 23, 1970, Ser. No. 92,289

Int. Cl. C22c 21/02 US. Cl. 148--32.5 7 Claims ABSTRACT OF THE DISCLOSURE An improved aluminum alloy conductor. The conductor is characterized by a combination of good mechanical and electrical properties and contains from 0.04 to 1.0% iron, 0.02 to 0.2% silicon, 0.1 to 1.0% copper, 0.001 to 0.2% boron, balance essentially aluminum.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of copending application Ser. No. 66,067, by Fred A. Besel and William C. Setzer for Aluminum Alloy Conductor, which in turn is a continuation-in-part of copending application Ser. No. 885,315, by Fred A. Besel for High Conduc tivity Aluminum Alloys, which in turn is a continuationin-part of Ser. No. 715,552, by Fred A. Besel for Super- Strength, High Conductivity Aluminum Alloys, all of which are now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to the art of electrical conductors.

It is highly desirable to obtain high strength and high conductivity aluminum alloy conductors with excellent formability, that is, with the capability of taking many reverse plastic bends and manipulations, etc. without cracking. One may readily appreciate that it is highly desirable commercially to obtain wire having the foregoing characteristics and to obtain it at a reasonable cost.

The foregoing is particularly important in communication wire. In this application, high conductivity is important; however, electrical grade (EC grade) aluminum having high conductivity often has low low strength or is susceptible to elevated temperature strength degradation and room temperature creep and relaxation. This naturally has an adverse effect on mechanical electrical contacts.

The higher strength alloys which overcome the foregoing strength deficiencies are generally deficient with respect to electrical conductivity.

High purity aluminum can only be moderately strengthened by cold working; likewise, cold working causes a loss in formability.

However, there are many applications where the excellent formability is not critical, as, for example, in overhead electric transmission lines. In these applications, it is important to achieve a combination of high strength and high conductivity in order to reduce the number of supporting line poles or line towers. Thus, in these applications, it is important to achieve a combination of high strength and high conductivity.

Accordingly, it is a principal object of the present invention to provide improved aluminum base alloy conductors.

3,711,339 Patented Jan. 16, 1973 SUMMARY OF THE INVENTION In accordance with the present invention it has now been found that the foregoing objects and advantages may be readily obtained. The present invention provides improved conductors comprising an aluminum base alloy conductor having a diameter between 0.002 and 0.375 containing from 0.04 to 1.0% iron, from 0.02 to 0.2% silicon, from 0.1 to 1.0% copper, from 0.001 to 0.2% boron, balance essentially aluminum.

The iron, silicon and boron alloying additions are substantially contained in the matrix in a dispersion of extremely fine precipitate.

The copper addition is substantially present in solid solution.

Thus, the conductor of the present invention has itnpurity and the alloying elements, except for copper, precipitated throughout the matrix. The copper addition is present as a solid solution addition to provide some solid solution strengthening of the matrix rather than a dispersion or precipitation hardening agent as is normally the case for this addition.

One conductor of the present invention achieves high strength and high conductivity in combination with excellent formability. In this case, the diameter would generally be between 0.002 and 0.125" and the copper content should be maintained between 0.1 and 0.4% and the boron content should be maintained between 0.001 and 0.1%.

It has been found that the foregoing conductor readily achieves the objectives of the present invention and attains high strength and high conductivity in combination with excellent formability. Formability may be characterized as a combination of ductility and bendability at a sufliciently high strength level such that the material may be distorted from its original shape or formed into a new shape without fracture. Thus, in its most flexible form, i.e., the fully annealed condition, the conductor of the present invention has a minimum IACS conductivity of 60% and readily obtains a minimum tensile strength of 16,000 p.s.i. and an elongation in excess of 10%. Further, the tensile strength of the wire in the annealed condition can be increased to 18,000 p.s.i., the yield strength to 16,000 p.s.i., by an additional wire reduction with almost no measurable loss in conductivity or formability, and with an elongation in excess of 2%. This reduction is limited to about 25%. Greater reductions cause a decrease in formability in the cold worked wire.

The tensile properties of heavily cold worked material are significantly higher than those of the annealed material; however, cold worked material has significantly less mechanical formability. Hence, with very large cold Alternatively, when excellent formability is not a prerequisite, another conductor of the present invention has an excellent work hardening rate which may be used to achieve a combination of higher strength and high conductivity. In this case one obtains an improved combination of strength and conductivity. Thus, one may obtain increased conductivity at strength levels comparable to conventional materials or conversely increased strength levels at conductivities comparable to conventional matenials or variations the'rebetween. For example, the conductivity is at least 57% IACS and the tensile strength may be, for example, at least 48,000 p.s.i. at 0.081" gage. The material having these properties is capable of passing the conventional wrap test (ASTM-B-39867). The material havingsaid excellent combination of strength and conductivity should be processed in the following manner:

(A) Provide an aluminum base alloy bar containing from 0.04 to 1.0% iron, 0.02 to 0.2% silicon, 0.1 to 1.0% copper, 0.001 to 0.2% boron, balance essentially aluminum;

(B) Deform said material at least ture of 400 F. up to 950 F.; and

(C) Cold deform said material to final gage with a reduction of at least 75% and preferably at least 90%.

DETAILED DESCRIPTION As stated hereinabove, the conductors of the present invention may be obtained having a good combination of strength and conductivity with excellent formability or alternatively some formability may be sacrificed in order to obtain an excellent combination of strength and conductivity.

The first portion of the specification will discuss that modification which obtains high strength and high conductivity with excellent formability.

CONDUCTOR HAVING HIGH STRENGTH, HIGH CONDUCTIVITY AND EXCELLENT FORMABILITY As stated hereinabove, this conductor of the present inat a temperavention contains iron in an amount from 0.04 to 1.0% and preferably from 0.1 to 0.3%. The silicon content ranges from 0.02 to 0.2%. Too high a silicon content causes loss in conductivity. The preferred silicon range is from 0.02 to 0.1%. The copper content may range from 0.1 to 0.4% and is preferably present in an amount from 0.25 to 0.35%. The boron is present in an amount from 0.00 1 to 0.1%. The balance of the alloy is essentially aluminum.

Small amounts of magnesium, zirconium, manganese and chromium or other elements may be added for particular reasons, such as added strength or thermal stability; however, these materials adversely afiect electrical conductivity and additions should be limited on this basis. Titanium maybe added as a grain refiner in amounts less than the stoichiometric quantity necessary to form T05 and in an amount such that electrical conductivity is not materially affected. Similarly, conventional impurities may be tolerated in amounts such that electrical conductivity is not materially affected.

In addition to the solid solution hardening provided by the copper, it is significant that the conductor of the present invention contains a dispersion of extremely fine precipitate of the iron, silicon and boron alloying additions. The precipitate acts as a hardening dispersion, at the same time depleting the matrix of solute to critical levels in order to retain high conductivity.

This conductor of the present invention is provided in wire form having a diameter of from 0.002" to 0.125. This conductor may be readily employed in industrial conductor sizes in the range of B and S gages including transmission, communication and building wire. The conductor may be readily employed advantageously as a single strand conductor, as a multi-stranded conductor or a stranded conductor in combination with alloys or EC grade aluminum or a steel wire core.

This conductor of the present invention may be prod essed in accordance with conventional techniques. Thus, the alloy may be cast in a conventional manner. The ascast billet may then be deformed to rod in a conventional manner, such as by rod rolling. The rod may then be drawn to gage or drawn, annealed and drawn to gage.

Thus, this conductor of the present invention can be processed in accordance with conventional or specialized techniques for processing communications wire, transmission wire, building wire, etc. The advantages of this conductor of the present invention resides in its critical chemistry which yields the desired combination of conductivity, strength and formability.

As indicated hereinabove, this conductor of the present invention is characterized by several advantages, especially a combination of good strength, conductivity and formability.

Formability may be measured or determined by a free loop bend test wherein a two inch length of, for example, 0.020" wire is pushed together and pulled apart repeatedly. If this can be done ten (10) times Without failing as by cracking, the wire'has satisfactory formability. The wire of the present invention has formability such that generally above 15 free loop bends can be performed even when the elongation is low. Normally a substantially higher number can be performed.

It is a particular advantage of the present invention that the highly desirable characteristics of the instant conductor are obtained with ease of manufacture.

Thus, this conductor of the present invention is useful in a wide variety of applications and is especially useful for building wire or communications wire where its high formability allows a high level of bendability. Furthermore, the presence of fine precipitate to stabilize the mechanical properties will provide a significant improvement in room temperature relaxation or creep which has been found to be troublesome in terminal connections involving spring or set screw clamping devices.

The precipitated particles present before annealing assist the nucleation of recrystallization during the anneal, hinder grain growth, and prevent exaggerated grain growth which would be particularly deleterious to formability. The alloy content (primarily that in solid solution) and fine grain size both serve to cause an initially higher strength level in the annealed wire, and both, together with the precipitated particles, an increased work hardening rate. Further the small grain size causes any local deformation to be redistributed over many small grains and thus over a greater volume of material. All of these factors interact synergistically to cause a significant increase in formability. 1

CONDUCTOR HAVING EXCELLENT COMBINA- TION OF STRENGTH AND CONDUCTIVITY As stated hereinabove, one of the conductors of the present invention may be obtained which achieves an excellent combination of strength and conductivity. This conductor contains iron in an amount from 0.04 to 1.0% and preferably from 0.5 to 1.0%. The silicon content ranges from 0.02 to 0.2% and preferably 0.02 to 0.1%. The copper content may range from 0.1 to 1.0% and preferably 0.35 to 0.5%. The boron is present in an amount from 0.001 to 0.2%. The balance of the alloy is essentially aluminum. Small amounts of zirconium, magnesium, manganese, and chromium or other elements may be added for particular improvements, such as added strength or thermal stability; however, these materials adversely affect electrical conductivity and additions. should be limited on this basis. Titanium is a preferred addition as a grain refiner in an amount less than the stoichiometric quantity necessary to form TiB and in an amount such that the electrical conductivity is not ma-- terially aifccted, in amounts generally less than 0.5%. Zirconium and magnesium are preferred additions for thermal stability. Magnesium also increases the work hardening rate. Zirconium is generally present in amounts less than 0.1% and magnesium less than .2%. Similarly, conventional impurities may be tolerated in amounts such that the electrical conductivity is not materially afl'ected.

In this modification, as in the previous modification, the conductor contains a dispersion of extremely fine pre cipitate of iron, silicon and boron alloying additions, with the copper addition being substantially present in solid solution.

For this modification, the conductor is provided in wire form having a diameter from 0.002 to 0.375", that is, improvement is obtained up to large diameters including redraw rod. Most often, the wire diameter is from 0.0 60 to 0.200".

As stated hereinabove, the particular advantage of this modification is that due to the high work hardening rate an excellent combination of strength and conductivity is obtained. Thus, by cold working, one may readily achieve improved strength at conductivity levels comparable to conventional materials or improved conductivity at strength levels comparable to conventional materials. In both cases, the material is capable of passing the standard wrap test referred to hereinabove which involves wrapping the wire around itself without fracture. In fact, the conductor of the present invention readily passes this test at high strength levels and is readily capable of being wrapped around itself a plurality of times.

The basis for the excellent characteristics of the conductor of the present invention is that the chemistry of the material provides an increased work hardening rate. Therefore, less work is required to achieve a given strength level. In addition, as will be apparent, the conductor of the present invention is subjected to a large amount of cold work.

Thus, in accordance with this modification, the alloy may be cast in a conventional manner. The as-cast billet or bar may or may not be homogenized, if desired, for example, at 930 F.i40 F. for eight hours or more.

The material is deformed at an elevated temperature above 400 F., preferably above 600 F. and at a temperature up to 950 F. This hot or warm deformation step has been found to be important in obtaining the desired properties.

The material is then cold deformed directly to gage. The material is cold deformed to a reduction of at least 75% and preferably at a reduction of at least 90% in order to obtain high mechanical properties. Naturally, the amount of cold reduction required to achieve a given strength level is dependent upon the particular chemistry and the hot rolling profile.

The present invention will be more readily apparent from a consideration of the following illustrative examples.

EXAMPLE I A 2" x 2" x 7" billet was prepared in a conventional manner having the following compositions: iron 0.18%, silicon 0.06%, boron 0.015%, copper 0.25%, balance essentially aluminum. The billet was hot rolled from 750 F. without reheating to redraw rod. The material was drawn to 0.29" and annealed for 24 hours at 550 F. The material was then drawn to wire having a diameter of 0.021" and given an anneal of short duration which fully recrystallized the material. Properties were determined on the fully recrystallized material which are given in the table below. The material was then given an additional small amount of cold workbetween about 4 and 12% and the properties determined on this material. These properties are also given in the table below.

Both the fully recrystallized material and the fully recrystallized and cold worked material were characterized by having a fine grain size, high strength, high conductivity and excellent formability. The iron, silicon and boron were substantially present as a dispersion of extremely fine precipitate and the copper was substantially present in solid solution.

The properties are shown in the table below.

TABLE Fully recrystallized 00nd. percent IACS Free loop bends Grain slze (mm.)

(K s.i.) percent Fully recrystallized and cold worked EXAMPLE II 8 hours. All billets were then hot rolled to redraw rod with an entry temperature of 850 F. and an exit temperature of 375 F.

One billet was then given a cold deformation reduction of 75% from 0.365" to 0.182. The material had an ultimate tensile strength of 36,000 p.s.i. and a conductivity of over 59%. The second material was given a cold deformation of from 0.365 to 0.114" and had an ultimate tensile strength of 39,000 p.s.i. and a conductivity of over 59%. A third bar was given a cold deformation of from 0.365" to 0.081" and had an ultimate tensile strength of 48,000 p.s.i. and a conductivity of over 59% IACS.

All materials successfully passed the wrap test. In all cases the iron, silicon and boron were substantially present as a dispersion of extremely fine precipitate and the copper was substantially present in solid solution.

EXAMPLE III Two additional billets were prepared and processed in the same manner as Example II except that they were hot rolled to 0.660" gage instead of being hot rolled to redraw rod.

One sample billet was cold deformed from 0.660" to 0.182" and had resultant properties of 42,000 p.s.i. ultimate tensile strength and electrical conductivity over 59%.

A second billet was cold deformed from 0.660" gage to 0.135" gage and had an ultimate tensile strength of 46,000 p.s.i. with an electrical conductivity of over 59% IACS.

Both materials successfully passed the wrap test. The iron, silicon and boron were substantially present as a dispersion of extremely fine precipitate and the copper was substantially present in solid solution.

This invention may be embodied in other forms or carried out in other ways without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered as in all respects illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and all changes which come within the meaning and range of equivalency are intended to the embraced therein.

What is claimed is:

1. An improved aluminum base alloy conductor having high strength and high conductivity consisting essentially of an aluminum base alloy conductor having a diameter of between 0.002" and 0.375" containing as alloying additions from 0.04 to 1.0% iron, 0.02 to 0.2% silicon, 0.1 to 1.0% copper, 0.001 to 0.2% boron, balance essentially aluminum, wherein said copper is substantially present in solid solution and said iron, silicon and boron are substan tially present as a dispersion of extremely fine precipitate, wherein said precipitate acts as a hardening dispersion and depletes the matrix of solute.

2. An annealed conductor according to claim 1 having a minimum IACS conductivity of 60%, a minimum tensile strength of 16,000 p.s.i. and an elongation in excess of 10%.

3. A cold worked conductor according to claim 1 having a minimum IACS conductivity of 60% IACS, a minimum tensile strength of 18,000 p.s.i. and an elongation in excess of 2%.

4. A conductor according to claim 1 having a minimum IACS conductivity of 57% and a minimum tensile strength of 42,000 p.s.i.

5. A conductor according to claim 1 wherein iron is present in an amount from 0.5 to 1.0%, silicon from 0.02 to 0.1% and copper from 0.35 to 0.5%.

6. An improved aluminum base alloy conductor having a fine grain size, high strength, high conductivity and excellent formability consisting essentially of an aluminum base alloy conductor having a diameter of between 0.002" and 0.125" containing as alloying additions from 0.04 to 1.0% iron, 0.02 to 0.2% silicon, 0.1 to 0.4% copper, 0.001 to 0.1% boron, balance essentially aluminum, wherein said copper is substantially present in solid solution and said iron, silicon and boron are substantially present as a dispersion of extremely fine precipitate, wherein said References Cited UNITED STATES PATENTS 1,695,044 12/1928 Hallrnann 148+-11.S A 2,572,562 10/1951 Harrington 75147 3,104,189 9/1963 Wagner 148-32.5 3,397,044 8/1968 Bylund 29183 3,512,221 5/1970 Schoerner 29-4835 OTHER REFERENCES Alloy Digest: Aluminum EC, Filing Code Al-l04, June 1961.

WAYLAND w. STALLARD,1Primary Examiner NITED STATES PATENT GFEFKCE (1 ER? is FECA'EE U1 CQRR W7? HUN Patent No. 3,711,339 Dated January 16, 1973 lnventor( Fred A. Bese1 et a1.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Column 1, line &7, cancel the second occurrence of the word "low".

In Column 6, line 16, the composition "silicon 0. 1%," should read --si1icon .O 4%,--.

Signed and sealed this 3rd day of July 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR.

Rene Tegtmeyer Attesting Officer Acting Commissioner of Patents ORM PO-IOSO (10-69) USCOMM-DC 60376-P69 w u.s. covznumzfu PRINTING OFFICE: I969 0-366-334