U.S. patent number 3,615,371 [Application Number 04/712,357] was granted by the patent office on 1971-10-26 for aluminum alloy for electric conductor.
This patent grant is currently assigned to The Furukawa Electric Company Limited. Invention is credited to Sadao Inoue, Yasuo Maeda, Katsuhisa Nakajima.
United States Patent |
3,615,371 |
Nakajima , et al. |
October 26, 1971 |
ALUMINUM ALLOY FOR ELECTRIC CONDUCTOR
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.
Inventors: |
Nakajima; Katsuhisa (N/A,
JA), Maeda; Yasuo (N/A, JA), Inoue; Sadao (N/A,
JA) |
Assignee: |
Limited; The Furukawa Electric
Company (JA)
|
Family
ID: |
12081027 |
Appl.
No.: |
04/712,357 |
Filed: |
March 12, 1968 |
Foreign Application Priority Data
|
|
|
|
|
Apr 8, 1967 [JA] |
|
|
42/22380 |
|
Current U.S.
Class: |
420/542;
148/437 |
Current CPC
Class: |
C22C
21/06 (20130101); H01B 1/023 (20130101) |
Current International
Class: |
H01B
1/02 (20060101); C22C 21/06 (20060101); C22C
021/00 () |
Field of
Search: |
;75/147,138,141,142,146
;148/32,32.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Dean; Richard O.
Claims
What we claim is:
1. Aluminum alloy for electric conductor consisting of from 0.02 to
2.0 weight percent of magnesium, from 0.04 to 0.57 weight percent
of one or more of rare earth metals, and remainder of aluminum.
Description
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
purpose of manufacturing electric conductive wires having improved
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.degree. 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 0.02-0.8
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
150.degree.-200.degree. C. We have this Al-Mg-RE alloy registered
as U.S. Pat. No. 3,278,300. This ternary alloy has an improved work
hardening effect owing to minute dispersion of the intermetallic
compound of Al-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 150.degree.-200.degree. C., but is not quite satisfactory
in antisoftening characteristic at a higher temperature in the
neighborhood of 500.degree. 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 above-mentioned
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 binary Al-Mg alloy or the ternary
Al-Mg-Si alloy, by adding to aluminum 0.02-2.0 weight percent,
preferably 0.05-1.5 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 difficulty 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 working.
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 0.05-0.1 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 0.15-0.5 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 electric conductivity 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 invention renders 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 casting the alloys of the invention in
molten state into a mould, solidifying by quenching the molten
metal until its temperature becomes 300.degree.-580.degree. C.,
subjecting to the solidified casting at least 70 percent of plastic
deformation while cooling at a cooling speed of at least 50.degree.
C./min. to a temperature of at most 250.degree. 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.degree.-580.degree. C. is that
in case of the temperature of more than 580.degree. 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.degree. 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.degree. C./min. to a temperature of at most 250.degree. 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.degree. 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.degree. C. at a
time immediately after the continuous rolling step it is impossible
to obtain not only sufficient 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.degree.-500.degree. C., a cooling speed of
200.degree.-600.degree. C./min. during plastic deformation, a
plastic deformation of at least 90 percent and a temperature
immediately after the working effect of 180.degree. 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 rolls to 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.degree.-500.degree. 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.degree. 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 0.5-1.3 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 alloys of the invention in order to
further improve the characteristics of the electric conductive
material manufactured.
The invention will be further explained in detail with
examples.
EXAMPLE 1
By the use of alloys of the invention, conventional binary Al-Mg
alloys for electric conductors (5005 alloy), conventional ternary
Al-Mg-Si alloys for electric conductor (6063 alloy), and ternary
Al-Mg-RE alloy containing excessive RE each having a composition
shown in table 1, billets were produced and extruded into 5
mm..times.10 mm. bars. The electric conductivity and tensile
strength of these bars were measured and the tension test at room
temperature was carried out after heating the bars at 500.degree.
C. for 50 hours. The results are shown in table 1. The RE was Misch
metal available in market and was directly added to the aluminum
base metal added with magnesium. ##SPC1##
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 conductive 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 1 that the alloys of the
invention have excellent tensile strength in case the electric
conductivity is equivalent to that of the binary Al-Mg alloy for
electric conductors such as 5005 alloy and that of the ternary
Al-Mg-Si alloy for electric conductors such as 6063 alloy and
extremely small rate of decrease in tensile strength after heating
at a high temperature for many hours. On the contrary the
conventional ternary Al-Mg-RE alloy for electric conductors, added
with at least 0.6 weight percent of RE, begins to increase its rate
of decrease of tensile strength after heating at a high temperature
for many hours in case the addition of RE reaches at about 1.0
weight percent and the advantageous effect caused by the addition
of RE could not be appreciated.
EXAMPLE 2
The alloys of the invention, conventional binary Al-Mg alloys for
electric conductors and ternary Al-Mg-RE alloys for electric
conductors containing excessive RE were made into billets which
were extruded into 8-mm. diameter wires to measure the tensile
strength at welds of each wire when the wire has been subjected to
butt weldings for 100 times. The results are shown in table 2.
##SPC2##
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 that
the range of values of the mechanical strength is also
decreased.
The weldability of the conventional ternary Al-Mg-RE alloy for
electric conductors containing excessive RE is better than that of
the conventional binary Al-Mg alloy for electric conductors, but is
worse than that of the alloys of the invention. It seems that the
addition of excessive RE causes bad influence upon welds owing to
the presence of magnesium, RE and intermetallic compound thereof in
aluminum.
EXAMPLE 3
Alloys of the invention, conventional binary Al-Mg alloys for
electric conductors and ternary Al-Mg-RE alloys containing
excessive RE each having a composition shown in table 3 and in
molten state were subjected to degassing with the aid of chlorine
gas and to holding and then cast into a metallic mold to obtain
ingots. Comparison was made of weldability of these ingots by
investigating the state of defects occurred in the ingots and by
measuring specific gravity at the optimum portion in the ingots.
The results are shown in table 3 in which A represents the sound
state, B, the presence of small blowholes, and C, the presence of
large blowholes. ##SPC3##
As seen from the table 3, the conventional occurrence Al-Mg alloys
produce ingots with defects while the alloys of the invention
containing small quantity of RE is capable of properly fixing gas
remained in the metals to decrease occurrence of defects during
solidification thus obtaining sound ingots without any defects. The
conventional ternary Al-Mg-RE alloys contain a large amount of gas
when they are in the molten state after the degassing treatment has
been completed so that it becomes difficult to fix all of the gas
by means of RE, thereby occurring blowholes.
EXAMPLE 4
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..times.10 cm. bars which were hot-rolled with the aid of
grooved rolls into wire rods (hereinafter called "WRR method").
2. Method in which the alloys were continuously cast into 22
cm..sup.2 bars which successively were hot rolled with the aid of
grooved rolls into wire rods (hereinafter called "CCR method").
3. Method in which the alloys were cast while cooling by water into
25.5 cm..times.76 cm. large ingots which were hot-rolled with the
aid of flat rolls and then slit along the rolled direction into
square bars which were subsequently shaped into wires of circular
in section (hereinafter called "SRS method").
The wire rods manufactured by the above-mentioned three methods
were made into wires of 3.5 mm. diameter by means of cold
wire-drawing. The specific gravity of each ingot and the tensile
strength, bending limit and fatigue limit strength of each wire
were measured. The results are shown in table 4. ##SPC4##
It is apparent from the table 4 that for the conventional binary
Al-Mg alloy for electric conductors the CCR and SRS methods make it
more difficult to obtain the sound ingot than the WRR method while
the bending characteristic of the worked wire becomes remarkably
bad. On the contrary the alloys of the invention ensure stabilizing
effect of the proper content of RE which permits of obtaining the
sound ingots without any defects by means not only of WRR method
but also of CCR and SRS methods. Moreover, the alloy wire of the
invention manufactured by the CCR and SRS methods has more
excellent fatigue limit strength than that of the alloy wire of the
invention manufactured by the WRR method.
The alloy wire of the invention manufactured by the WRR, CCR and
SRS methods has more excellent bending limit and fatigue limit
strength than the conventional binary Al-Mg alloy for electric
conductors. The conventional ternary Al-Mg-RE alloy containing
comparatively large quantity of RE and manufactured by the WRR, CCR
and SRS methods are capable of obtaining better ingots than the
conventional binary Al-Mg alloy and has more improved tensile
strength, bending limit and fatigue limit strength than the latter
alloy. Those characteristics of the former alloy are worse than
those 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 in the molten
state were subjected to the continuous casting 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 wire manufactured. The results are shown in
table 5. ##SPC5##
As seen from the table 5, the wire manufactured from the alloys of
the invention in accordance with the CCR method which lies within
the scope of the invention is capable of preventing defects from
occurring during the wire-drawing step and has excellent tensile
strength and bending limit. On the contrary the wire manufactured
from the alloys of the invention in accordance with the CCR method
which lies out of the scope of the invention, that is, in case the
casting temperature is too high or too low or the cooling speed
during the rolling is too low or the temperature of the material
immediately after the working is too high, is not capable of
preventing defects from occurring during the wire drawing and
deteriorates the tensile strength and bending limit thereof.
EXAMPLE 6
The alloys of the invention consisting of 0.4 weight percent of Mg,
0.1 weight percent of RE, and the remainder, aluminum in the molten
state were subjected to water-cooled casting step to obtain ingots
having dimensions shown in table 6. The ingots obtained were heated
again and made into strips by hot-rolling and cold rolling steps.
The strips were slit along the rolled direction into bars which
were shaped by grooved rolls into wires of circular in section to
measure the tensile strength and fatigue limit strength. The
results are shown in table 6. ##SPC6##
It is apparent from the table 6 that the wire manufactured from the
alloys of the invention in accordance with the SRS method which
lies within the scope of the invention has excellent tensile
strength and fatigue limit strength, and that the wire manufactured
from the alloys of the invention in accordance with the SRS which
lies out of the scope of the invention deteriorates the tensile
strength and fatigue limit strength owing to insufficient rate of
cold working.
As explained hereinbefore the alloys of the invention consisting of
the conventional binary Al-Mg alloy containing small quantity of RE
ensures remarkable improvement as aluminum alloy conductors in
castability, weldability, fatigue strength and antisoftening
characteristic at a high temperature without impairing their basic
characteristics such as electric conductivity, tensile strength,
bendability, etc. and are applicable to the continuous casting and
rolling method and rolling method using large ingots for the
purpose of easily manufacturing aluminum alloy conductor having
improved mechanical strength and antisoftening characteristic at a
high temperature and further provide the important advantage that
the alloy of the invention and the alloy conductor manufactured
from the alloy by means of the continuous casting and rolling
method and rolling method using large ingots are suitable not only
for transmission line and distribution line but also for windings
of dynamoelectric machine and transformer and for bus bars for
high-temperature application, that said alloy and alloy conductor
can effectively be manufactured without using a large amount of
expensive RE, and that said alloy and alloy conductor are so
excellent in weldability that reliable welds can be obtained.
* * * * *