U.S. patent number 3,770,515 [Application Number 05/253,335] was granted by the patent office on 1973-11-06 for high conductivity aluminum alloys.
Invention is credited to Fred A. Besel.
United States Patent |
3,770,515 |
Besel |
November 6, 1973 |
HIGH CONDUCTIVITY ALUMINUM ALLOYS
Abstract
A process for obtaining a high conductivity material comprising
the providing of a material from the group consisting of commercial
purity aluminum and aluminum alloys wherein the alloy contains at
least one alloying element in an amount of from 0.1 to 1.5 percent
weight, the total not exceeding 3.0 weight percent, cold deforming
the material at least 15 percent below 500.degree. F, heating for
at least 20 minutes in the range of 400.degree. to 800.degree. F
and cooling.
Inventors: |
Besel; Fred A. (Southbury,
CT) |
Family
ID: |
22959855 |
Appl.
No.: |
05/253,335 |
Filed: |
May 15, 1972 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
885315 |
Dec 15, 1969 |
|
|
|
|
715552 |
Mar 25, 1968 |
|
|
|
|
Current U.S.
Class: |
148/690;
148/697 |
Current CPC
Class: |
C22C
21/00 (20130101); H01B 1/023 (20130101) |
Current International
Class: |
H01B
1/02 (20060101); C22C 21/00 (20060101); C22f
001/04 () |
Field of
Search: |
;148/11.5A,159 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Metal Progress, May 1953; "Cond-Al"-a Tailor-Made Aluminum Alloy of
High Creep Strength and Conductivity; Harrington et al., pp.
90-93..
|
Primary Examiner: Stallard; W. W.
Parent Case Text
This is a continuation, of application Ser. No. 885,315 filed Dec.
15, 1969 now abandoned, which application is a continuation-in-part
of co-pending application Ser. No. 715,552, filed Mar. 25, 1968 now
abandoned.
Claims
What is claimed is:
1. A process for forming a high conductivity commercial purity
aluminum or aluminum alloy conductor comprising:
A. providing a material selected from the group consisting of
commercial purity aluminum and aluminum alloys containing at least
one alloying addition in an amount from 0.1 to 1.5 percent, said
alloying addition being selected from the group consisting of
magnesium, copper, silicon and mixtures thereof, the total amount
of said alloying additions not exceeding 3 percent;
B. cold deforming said material to rod at least 15 percent at a
temperature below 500.degree.F;
C. heating said material for at least 20 minutes at a temperature
from 400.degree.F to 800.degree.F, whereby nucleation occurs in the
alloy and electrical conductivity is increased;
D. cooling said material; and
E. further deforming said alloy to wire at a temperature less than
500.degree.F.
2. A process according to claim 1 wherein said material is an
aluminum alloy containing magnesium.
3. A process according to claim 1 wherein said material is an
aluminum alloy containing copper.
4. A process according to claim 1 wherein said material is an
aluminum alloy containing silicon.
5. A process according to claim 1 wherein said material is
commercial purity aluminum.
6. A process according to claim 1 wherein said heating step (C)
allows precipitation to approach equilibrium.
7. A process according to claim 1 wherein the resultant product has
an electrical conductivity of from 57 to 64 IACS.
Description
The present invention relates to a new and improved electrical
conductor. More particularly, the present invention resides in a
new and improved aluminum alloy or commercial purity aluminum
characterized by improved and surprisingly high electrical
conductivity.
High electrical conductivity is essential in electrical conductors
since electrical conductivity is the key characteristic of an
aluminum conductor.
Specifically, with respect to aluminum conductors, high purity
aluminum has an electrical conductivity somewhat in excess of 64
percent IACS; whereas, the industrial minimum conductivity
requirement for a commercial purity aluminum, such as EC grade, is
about 61 percent IACS, which is substantially lower than for high
purity aluminum.
Aluminum base electrical conductor alloys containing varying
alloying elements are well-known, such as, for example, aluminum
alloy 6201 containing 0.50 to 0.9 percent silicon, 0.6 to 0.9
percent magnesium, and a maximum of 0.06 percent boron, a maximum
of 0.50 percent iron, 0.10 percent copper, 0.03 percent manganese,
0.03 percent chromium and 0.10 percent zinc as impurities, other
impurities each not exceeding 0.03 percent and totaling less than
0.10 percent, the balance aluminum, and aluminum alloy 5005
containing 0.50 to 1.1 percent magnesium and a maximum of 0.40
percent silicon, 0.7 percent iron, 0.20 percent manganese 0.20
percent copper, 0.10 percent chromium and 0.25 percent zinc as
impurities, other impurities each not exceeding 0.05 percent and
totaling less than 0.15 percent, the balance aluminum.
These alloys however are in general characterized by electrical
conductivity values considerably lower than high purity aluminum.
For example, aluminum alloy 6201 wire possesses an electrical
conductivity of only about 53 to 55 percent IACS.
It is therefore, highly desirable to conveniently obtain high
electrical conductivity values more favorably comparable to high
purity aluminum. Conventional mill processing of the aluminum base
alloys employed as electrical conductors, e.g., conductor wire, bus
bar etc. does not achieve the aforementioned increased conductivity
however, and so it is highly desirable that a process be
accomplished which meets this goal.
It is also highly desirable to conveniently obtain high electrical
conductivity values in combination with high strength in electrical
conductors such as wire and strip, for use as, for example,
overhead electrical transmission lines in order to reduce the
number of supporting line poles or towers. At present it is
necessary to employ, for example, strands of EC H-19 temper
aluminum wire reinforced with a high strength steel core, or to
include additions of varying alloying elements in aluminum in order
to achieve the requisite tensile strength but with an attendant
loss in electrical conductivity.
It is therefore a principal object of the present invention to
provide a process for obtaining commercial purity aluminum or an
aluminum alloy with increased electrical conductivity, and the
alloy produced thereby.
It is a further object of the present invention to provide a
process for obtaining an aluminum alloy having increased electrical
conductivity as well as increased strength, and the alloy produced
thereby.
It is a further object of the present invention to provide a
process to achieve the foregoing objectives simply and conveniently
at relatively low cost.
It has now been found that in accordance with the present invention
the foregoing objectives may be readily achieved.
In general, the present invention is applicable to the broad class
of aluminum alloys in which:
A. the equilibrium solid solubility of the alloying additions is
relatively small at room temperature with increasing solubility
thereof with increasing temperature;
B. the amounts of the alloying additions in the alloy are above the
solubility limit thereof at room temperature
The present invention is also equally applicable to commercial
purity aluminum, i.e., at least 99.3 purity, as aforementioned,
wherein the electrical conductivity is substantially increased to a
value more closely approximating that for high purity aluminum.
Briefly, the process of the present invention comprises:
A. providing a material selected from the group consisting of
commercial purity aluminum and aluminum alloys, wherein said alloys
contain at least one alloying addition in an amount from 0.1 to 1.5
weight percent, the total thereof not exceeding 3.0 weight percent,
wherein said alloying addition is soluble in an amount greater than
0.25 percent in said alloy, and wherein there is no eutectic
transformation in said aluminum alloy below 400.degree.F;
B. cold deforming said material to at least 15 percent
reduction;
C. heating said material to 400.degree. to 800.degree.F for at
least 20 minutes; and
D. cooling said material.
For applications requiring increased strength as well as increased
electrical conductivity the alloy, as distinguished from commercial
purity aluminum, is further deformed following step(D) at a
temperature of from that of room to less than 500.degree.F. This
may be accomplished after cooling to room temperature and
reheating, or upon or after cooling down from the temperature range
of step C. The amount of deformation is naturally dependent upon
the strength required and may range up to 99.8 percent or more.
Generally, the more common alloying additions employed in the
alloys of the invention are copper, magnesium, silicon, cadmium,
antimony, bismuth, tin, zirconium, tantalum, titanium, and/or
chromium, although others may also be employed and naturally
various elements as impurities may also be present.
The alloy provided may contain the alloying additions substantially
in solution prior to the cold deforming step (B), should a direct
chill of the billet after casting be employed, although the present
invention is equally applicable to alloys wherein the alloying
additions are to a degree not in solution. That is, it is
immaterial to the present invention whether the alloying
substituents are substantially in solution, and hence a direct
chill or normal air cool of the casting may be readily employed
after casting and/or after homogenizing, should homogenizing be
required prior to the practicing of the present invention.
In addition the material provided may readily be in the cast
condition or in the wrought condition, i.e., the casting may first
be reduced prior to the cold deforming of step (B).
The cold deforming of step (B) normally refers to deformation
carried out at room temperature although deformation may also be
carried out at higher temperatures so long as the temperature
remains below the recrystallization temperatureof the particular
alloy being deformed and in general ranges from room up to less
than about 500.degree.F. Deforming at temperatures above that of
room however, requires amount of reduction in order to provide the
requisite internal deformation of the alloy. Although the maximum
amount of cold reduction is not critical and may range up to 99.8
percent or more, the minimum amount of reduction required is at 15
percent.
The purpose of the cold deforming of Step (B) and subsequent
heating of Step(C) is to effect precipitation of those alloying
constituents and impurities which exceed their solubility limit in
the alloy at room temperature, and which a portion thereof has
remained in solution after a normal air cool, or wherein the
substituents have remained substantially in solution due to a rapid
cool of the material. Cold deformation of the alloy produces an
unstable alloy structure containing these alloying constituents in
solid solution. Subsequent heating of the deformed structure at the
temperature range of 400.degree. to 800.degree.F of Step (C) and
preferably from 400.degree. to 600.degree.F, allows nucleation to
occur in the unstable alloy and precipitation to approach
equilibrium, whereby electrical conductivity increases.
The initial degree of cold deformation of Step (B) will effect the
requisite temperature and the time of the intermediate heat
treatment of Step (C) required for any particular alloy and will
also determine the resultant level of electrical conductivity and
strength. For example, a severely cold deformed alloy will respond
at a lower temperature, but will require a longer time at said
temperature in order to develop electrical conductivity
substantially equal to that of an alloy having a lesser amount of
cold deformation and a correspondingly lesser time at a higher heat
treating temperature. Although the heating of Step (C) must be for
at least 20 minutes the maximum time of heating is not especially
critical but generally, although not necessarily, is about 48
hours.
In general, in accordance with the present invention, electrical
conductivity values of the alloys of aluminum are raised to within
the range of 57 percent to 64 percent IACS, and of commercial
purity aluminum to the range of 62.5 to 64 percent IACS.
Following the aforementioned heat treatment of Step (C) and cooling
of step (D) the alloy may then be further deformed, or reduced, to
the desired gage at room temperature in order to develop the
requisite tensile strength e.g., to a range of 37,000 to 55,000
psi., since the alloy is now essentially annealed.
The present invention thus provides for a high conductivity
material more nearly comparable to high purity aluminum and, if
desired, coupled with improved strength for application wherein
high strength is requisite.
The present invention will be more readily apparent from a
consideration of the following illustrative examples:
EXAMPLE I
A 2 .times. 2 .times. 7 inches billet containing 0.49 percent
copper, 0.17 percent iron, 0.06 percent silicon -- by analysis in
weight percent, was cast, solution heat treated at 1150.degree.F
for 2 hours and water quenched. The as-cast solution heat treated
billet had a conductivity of 57.5 percent IACS measured on a
Magnatest FM-100 Conductivity Meter. The as-cast solution heat
treated billet was then processed to determine the properties
attainable by normal processing, i.e., the billet was then cold
rolled down to 3/8 inch diameter redraw rod with the only heating
being that which is normally evolved during cold working, and then
drawn durther to 0.145 inch diameter wire--a total reduction of
99.6 percent from the casting. At this reduction the wire had a
conductivity of only 56.67 percent IACS (measured on a Kelvin
Bridge) and a UTS of 47,000 psi.
EXAMPLE II
A 2 .times. 2 .times. 7 inches billet containing 0.48 percent
copper, 0.15 percent iron, 0.06 percent silicon -- by analysis in
weight percent, was cast, solution heat treated at 1150.degree.F
for 2 hours and water quenched. The as-cast solution heat treated
billet had a conductivity of 57.5 percent IACS measured on a
Magnatest FM-100 Conductivity Meter. The as-cast solution heat
treated billet was processed according to the invention as follows:
the billet was cold rolled 77 percent in four passes to a
hexagonal-shaped rod with a cross sectional area equivalent to a
diameter of 1.08 inch. The cold work reduced the conductivity to
55.7 percent IACS. The cold worked rod was then heat treated at
525.degree.F for 25 hours and water quenched. This treatment caused
the conductivity to increase to 59.4 percent IACS. After cooling,
the alloy was then cold rolled to 3/8 inch diameter redraw rod with
the only heating being that which is normally evolved during cold
working, and then drawn to 0.145 inch diameter wire and tested.
This wire had a conductivity of 59.96 percent IACS (measured on a
Kelvin Bridge) and a UTS of 37,600 psi at this gage.
Additional wire was drawn to 0.064 inch diameter and tested. This
data indicates that for a cold reduction of 99.6 percent, i.e.,
that achieved in reducing a 2.25 inch diameter casting to 0.145
inch diameter wire, the wire had a conductivity of 59.5 percent
IACS and a UTS of 47,000 psi.
EXAMPLE III
A 2 .times. 2 .times. 7 inches billet containing 0.40 percent
magnesium, 0.10 silicon, 0.18 percent iron -- by analysis in weight
percent, was solution heat treated at 1150.degree.F. 2 hours and
water quenched. The as cast solution heat treated billet had a
conductivity of 56.1 percent IACS measured on a Magnatest FM-100
Conductivity Meter. The as-cast solution heat treated billet was
then processed to determine the porperties attainable by normal
processing, i.e., the billet was cold rolled to 3/8 inch diameter
redraw rod with the only heating being that which is normally
evolved during cold working, and then a section was drawn to 0.145
inch diameter wire (a reduction of 99.6 percent) and tested. It had
a conductivity of only 55.9 percent IACS (measured on a Kelvin
Bridge) and a UTS of 42,400 psi.
EXAMPLE IV
A section of the 3/8 inch diameter redraw rod as described in
Example III was then drawn to 0.325 inch diameter rod (97.9 percent
reduction from the casting). The drawn 0.325 inch diameter rod had
conductivity of 56.40 percent IACS (measured on a Kelvin Bridge).
The rod was then further processes according to the invention as
follows: the rod was given an intermediate temperature heat
treatment of 650.degree.F for 100 minutes and water quenched. This
treatment raised the conductivity to 60.12 percent IACS. The rod
was then drawn to fine wire (between 0.145 inch and 0.064 inch
diameters) and tested. The interpolated data indicates that for a
99.6 percent reduction, the alloy would have a conductivity of 58.7
percent IACS and a UTS of 45,600 psi.
EXAMPLE V
A 2 .times. 2 .times. 7 inches ingot containing 0.18 percent iron,
0.06 percent silicon, 0.015 percent boron, nominal composition in
weight percent, balance essentially aluminum was heat treated at
740.degree.F for 4 hours and air cooled before processing according
to this invention. After this treatment the ingot had a
conductivity of 62.8 percent IACS when measured on a Magnatest
FM-100 conductivity meter. The heat treated ingot was then cold
rolled to 1.08 inch diameter rod. The conductivity after this 77
percent reduction was 62.3 percent IACS. The rod was then heated at
540.degree.F for 24 hours and cooled. The conductivity was found to
increase to 63.9 percent IACS.
EXAMPLE VI
A 2 .times. 2 .times. 7 inches ingot containing 0.10 percent
copper, 0.18 percent iron, 0.06 percent silicon nominal
composition, in weight percent, balance essentially aluminum, had a
conductivity of 60.0 percent IACS in the cast condition, measured
on a Magnatest FM-100 conductivity meter. The ingot was homogenized
at 1150.degree. F for 2 hours and water quenched. The conductivity
after this treatment was 59.8 percent IACS. According to this
invention the heat treated ingot was then cold rolled to 1.08 inch
diameter rod (a reduction of 77 percent) in which condition it had
a conductivity of 59.2 percent IACS. The cold rolled rod was then
heat treated at 540 .degree.F for 24 hours. The rod was
subsequently rolled and drawn 90 percent to 0.325 inch diameter rod
when it had a conductivity of 61.8 percent IACS measured on a
Kelvin Bridge.
EXAMPLE VII
A 2 .times. 2 .times. 7 inches ingot containing 0.20 percent
magnesium, 0.18 percent iron, 0.6 percent silicon nominal
composition in weight percent, balance essentially aluminum, had a
conductivity of 58.3 percent measured on Magnatest FM-100
conductivity meter in the cast condition. The conductivity after
the ingot was homogenized at 940.degree.F 8 hours and air cooled
was 59.1 percent IACS. The heat treated ingot in accordance with
this invention was then cold rolled 77 percent to 1.08 inches
diameter after which the conductivity was reduced to 59.1 percent
IACS. The cold rolled rod was then heat treated at 517.degree.F for
24 hours and subsequently conventionally rolled and drawn 98
percent to 0.145 inch diameter wire where the conductivity was 61.5
percent IACS measured on a Kelvin Bridge.
EXAMPLE VIII
As an example of the prior art for comparison to Example V, a 2
.times. 2 .times. 7 inches ingot of the composition of Example V
was heat treated at 750.degree.F for 1/2 hour and then hot rolled
in 13 passes without further heating to 3/8inch diameter redraw
rod. At this diameter the alloy had a conductivity of 62.4 percent
IACS measured on a Kelvin Bridge.
It is thus seen that the present invention readily provides for
surprisingly increased electrical conductivity values which more
closely approximate that of high purity aluminum as well as high
strength, if desired.
This inventon 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 be embraced therein.
* * * * *