U.S. patent application number 12/889299 was filed with the patent office on 2011-01-20 for phosphorus-copper base brazing alloy.
This patent application is currently assigned to J.W. HARRIS CO., INC.. Invention is credited to Joseph W. HARRIS.
Application Number | 20110011920 12/889299 |
Document ID | / |
Family ID | 31950508 |
Filed Date | 2011-01-20 |
United States Patent
Application |
20110011920 |
Kind Code |
A1 |
HARRIS; Joseph W. |
January 20, 2011 |
PHOSPHORUS-COPPER BASE BRAZING ALLOY
Abstract
A solid phos-copper base or silver-phos-copper base brazing
alloy component for forming a brazed joint with a raised shoulder,
little to no black oxide, and improved corrosion resistance. The
brazing alloys of the present invention are visually
distinguishable from copper and copper alloy parts. The solid
brazing components of the present invention may be used in forming
brazed joints at low brazing temperatures and result in a joint
that is strong, ductile, smooth and corrosion resistant. The solid
brazing components are provided in the form of wire, strip, foil or
preform, and thus are advantageously used in a wide variety of
brazing applications including copper tubing. The brazing
components of the present invention are made of an alloy having a
liquidus temperature above 840.degree. F. and consist essentially
of about 4-9% phosphorus, about 0.1-10% tin, up to about 4%
antimony, about 0.1-15% nickel, up to about 3% silicon, up to about
18% silver, up to about 3% manganese, with the balance being
copper. Exemplary embodiments include about 6-15% silver and/or
5-8% nickel.
Inventors: |
HARRIS; Joseph W.;
(Cincinnati, OH) |
Correspondence
Address: |
Lincoln Electric Company/Perkins COIE LLP
607 Fourteenth Street , NW
Washington
DC
20005-2003
US
|
Assignee: |
J.W. HARRIS CO., INC.
Mason
OH
|
Family ID: |
31950508 |
Appl. No.: |
12/889299 |
Filed: |
September 23, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10628651 |
Jul 28, 2003 |
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12889299 |
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10226672 |
Aug 23, 2002 |
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10628651 |
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60452255 |
Mar 5, 2003 |
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Current U.S.
Class: |
228/176 ;
164/459; 164/462; 164/476 |
Current CPC
Class: |
B23K 35/0222 20130101;
B23K 35/30 20130101; B23K 35/0244 20130101; B23K 35/0227 20130101;
B23K 35/0233 20130101; B23K 35/302 20130101 |
Class at
Publication: |
228/176 ;
164/462; 164/459; 164/476 |
International
Class: |
B23K 1/20 20060101
B23K001/20; B22D 11/00 20060101 B22D011/00; B23K 31/02 20060101
B23K031/02 |
Claims
1. A method of forming a solid brazing component having a liquidus
temperature above 840.degree. F. comprising the steps of: forming
an alloy melt consisting essentially of, in weight percent: (a)
about 4-9% phosphorus; (b) about 0.1-10% tin; (c) about 0.1-15%
nickel; (d) up to about 18% silver; (e) up to about 3% silicon; (f)
up to about 4% antimony; (g) up to about 3% manganese; and the
balance copper; continuously casting the alloy melt into a billet;
fabricating the billet into a solid brazing component selected from
the group consisting of wire, strip, foil and preform.
2. The method of claim 1 wherein the billet is fabricated into a
wire by extrusion, the method further comprising drawing the wire
one or more times to a final desired thickness.
3. The method of claim 2 further comprising forming the wire into a
preform.
4. A method of forming a brazed joint comprising the steps of:
forming a solid brazing component by the method of claim 1; placing
the solid brazing component between two metal parts; heating the
solid brazing component to melt at least a major portion of the
alloy to cause the alloy to wet and flow between the two metal
parts; cooling the alloy to form a brazed joint with a raised cap
between the two metal parts, wherein the brazed joint is
substantially free of black metal oxide.
5. The method of claim 4 wherein the solid brazing component is
placed between two copper alloy parts and the brazed joint is
visually distinguishable from the parts.
6. The method of claim 4 wherein the solid brazing component is
placed between two tubular shaped parts.
7. The method of claim 4 wherein the solid brazing component is
heated to a temperature less than 1410.degree. F. to melt the major
portion.
8. The method of claim 4 wherein the solid brazing component is
heated to a temperature less than 1300.degree. F. to melt the major
portion.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional application of and claims
the benefit of priority to U.S. application Ser. No. 10/628,651
filed Jul. 28, 2003 which claims the benefit of and priority to
U.S. Provisional Application Ser. No. 60/452,255, filed Mar. 5,
2003, and is also a continuation-in-part of commonly owned, U.S.
patent application Ser. No. 10/226,672, filed Aug. 23, 2002, which
is now abandoned. Each of the above-identified applications is
incorporated by reference herein in their entirety.
FIELD OF THE INVENTION
[0002] This invention relates to a solid copper brazing component
and method for forming a brazed joint, and in particular, a brazing
component for joining copper and copper alloys.
BACKGROUND OF THE INVENTION
[0003] Copper and copper alloys have been brazed successfully for
many years with metals comprising the phosphorus-copper alloys,
also known as phos-copper alloys. Silver is often added to the base
metals to accomplish special features for a wide variety of
applications. These alloys are generally known as
silver-phos-copper alloys. Silver brazing alloys, composed
primarily of silver, copper, zinc, tin, nickel, manganese, and
cadmium, are used to braze ferrous and non-ferrous metals and
alloys. These silver brazing alloys are designed to work at low
temperatures and to provide strong, ductile joints.
[0004] Additions of other elements, such as tin, antimony, nickel
or silver, to phos-copper and silver-phos-copper alloys have been
made in an effort to lower the melting range temperatures or to
reduce the phosphorus content to increase ductility. For example,
U.S. Pat. No. 5,066,456 discloses that the addition of tin and
antimony up to six percent each to a phos-copper based alloy lowers
brazing temperatures.
[0005] Air conditioning coils, heat exchangers, water coolers and
other copper coils are manufactured by connecting copper tubing and
fittings by brazing with phos-copper or silver-phos-copper brazing
alloys. These alloys produce strong, ductile brazes, but the
industry has long experienced a relatively high percentage of leaks
after brazing, particularly with BCuP-2 alloys. Most leaks are
caught on the production floor during testing and are repaired.
This double work of brazing and testing is very costly. More
damaging, very tiny leaks can evade factory testing and end up as
warranty work in the field, which is both expensive and damaging to
the company's brand image.
[0006] The phos-copper alloys now on the market all range within a
solidus temperature of 1310.degree. F. to a liquidus temperature of
1500.degree. F. Alloys of even higher phosphorus content, up to 8%,
are now in use to enhance productivity because of their lower
operating temperature cost considerations. The non-silver alloys in
this group are the most commonly used in industry and contain 7% to
7.4% phosphorus, the balance being copper. The fact that these
phos-copper alloys flow and join very well is problematic in that
they also flow very thinly. Torch and furnace brazing is performed
as rapidly as possible to achieve good productivity. While these
alloys are quick to braze, they are difficult to observe for
soundness. The entire 360.degree. of the brazed joint must be
carefully viewed by the operator, for it is here that a correction,
if needed, should be made. These thin-flowing alloys produce only a
very small cap, or shoulder, around the pipe at the fitting
junction. The alloys are thin-flowing in that they flow like a
heavy coating of paint, instead of more thickly as in a putty used
to seal a 1/8'' crack.
[0007] Even a skilled brazer cannot tell 100% of the time that he
has a totally leak-free connection by visually looking at his
completed braze. In some places on a given braze connection, the
brazing alloy can be seen to be in place as a shoulder between the
two parts, while in other places the alloy drops in the adjoining
area (the capillary) without forming any noticeable shoulder. When
viewing this very closely, the operator can often see that the
joint appears to be 100% sound, but he can't be certain of it. Most
air conditioning companies submerge each copper coil, which
comprises perhaps 100 brazes, into a water tank, and air pressure
is added to this coil to determine if there are any leaks. Wherever
leaks are found, brazing must be repeated.
[0008] The now-in-use phos-copper alloys, as described above, could
be modified to form an advantageous cap by lowering the phosphorus
content significantly. However, doing so is not feasible because
the liquidus temperature rises to a point of endangering the copper
being brazed. It is noteworthy that silver in the range of 6-15%,
when added to the phos-copper alloys described above, lowers the
solidus temperature to 1190.degree. F., allows the phosphorus
contents to be reduced as much as 2%, allows the alloy to flow in a
much thicker manner, and effects a noticeable cap or shoulder to
the brazed area. The popular 15% silver-phos-copper alloy has the
consistency of hot taffy when hot enough to braze, and easily forms
a large cap or shoulder at the joint area. This visible fillet is
quickly seen by the operator and any omission in the braze can be
remedied. However, the addition of silver is quite expensive.
[0009] Another serious deterrent to being able to observe the
quality of copper tubing brazed with phos-copper or
silver-phos-copper brazing alloys is the formation of a black oxide
that is formed on the actual braze surface and on the adjacent
copper pipe. Because the braze and the copper pipe all turn black,
it is difficult to closely inspect the actual braze.
[0010] In addition to the initial soundness of the brazed joint,
the corrosion resistance of the joint is of great importance.
Brazed parts are used in corrosive environments of varying degree,
for example, the marine environment, sewer treatment facilities and
underground. The BCuP-5 alloy (80Cu-5P-15Ag) is typically used
whenever corrosion is a significant factor. However, further
improvement in corrosion resistance is desirable.
[0011] There is thus a need for a phos-copper base alloy system
that brazes at low temperatures, forms a noticeable cap or shoulder
to facilitate visual inspection, does not form black oxide to any
extent that will obscure visual inspection, and provides high
corrosion resistance.
SUMMARY OF THE INVENTION
[0012] The present invention provides a solid phos-copper base
brazing alloy component suitable for forming a brazed joint with a
raised shoulder and little to no black oxide, that is visually
distinguishable from copper or copper alloy parts, and provides
high corrosion resistance. The brazing filler metal of the present
invention incorporates an advantageously low brazing temperature
range and is both ductile, smooth and corrosion resistant. The
brazing alloys of the present invention can be extruded into wire
and optionally formed into various preforms or fabricated into
strips or foil, thereby providing a solid brazing component
suitable for numerous brazing applications, such as brazing large
copper pipe fittings. To this end, a brazing alloy is cast and then
fabricated into wire, strip, foil or preform. For example, a cast
billet may be extruded into wire, which may be further formed into
a preform. The component is made of an alloy having a liquidus
temperature above 840.degree. F. (449.degree. C.) and which
consists essentially of about 4% to about 9% phosphorus; about 0.1%
to about 10% tin; about 0.1 to about 15% nickel; up to about 3%
silicon; up to about 18% silver; up to about 4% antimony; up to
about 3% manganese, and the balance copper. In exemplary
embodiments, the alloy includes about 1% to about 18% silver and/or
about 3% to about 10% nickel, and advantageously 5-8% nickel.
[0013] The present invention further provides a method for forming
a brazing component of the composition described above, wherein a
molten alloy is continuously cast into a billet, which is then
fabricated into a wire or thick strip. The wire may then be drawn
to a desired diameter, and the strip may be rolled to a desired
thickness or to a thin foil. The wire may also be further formed
into a preform. To form a brazed joint, the solid brazing component
is placed between two metal parts, such as copper tubing, the
component is heated to a temperature to melt at least a major
portion of the brazing alloy, thereby causing it to wet and flow
between the parts, and then the alloy is cooled. The brazing
component of the present invention produces a substantial raised
shoulder or cap about the brazed joint, which is a visible sign to
the operator that the joint is sound.
[0014] The brazing component of the present invention further
produces a brazed joint with little to no black oxide that can
obscure the operator's view of the soundness of the joint. In
addition, the combination of alloying elements significantly
reduces the melting range of these brazing filler metals, thereby
providing a cost savings by reducing the use of expensive fuel
gases and the time required of the brazing process. The addition of
nickel in combination with tin may further provide an increase in
hardness and an improvement in corrosion resistance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and, together with a general description of the
invention given above, and the detailed description given below,
serve to explain the invention.
[0016] FIG. 1 is a graph depicting the improvement in corrosion
resistance for silver-phos-copper alloys of the present invention
containing 5-8% nickel in combination with tin, as compared to BCuP
alloys of the prior art.
[0017] FIG. 2 is a graph depicting the improvement in corrosion
resistance for phos-copper alloys of the present invention
containing 3-8% nickel in combination with tin, as compared to BCuP
alloys of the prior art.
DETAILED DESCRIPTION
[0018] The present invention provides phos-copper base brazing
alloys that are materially improved in their properties by the
addition of specified amounts of tin and nickel, and further by
specified additions of silicon and/or silver. The melting range can
be lowered, narrowed or broadened. In other words, the specified
alloy additions lower one or more of the liquidus, major thermal
arrest (MTA) or solidus temperatures. As used herein, the liquidus
temperature refers to that temperature at which the alloy is
completely liquid, i.e. at which the alloy finishes melting upon
heating. The solidus temperature refers to that temperature at
which a metal is completely solid, i.e., at which the alloy begins
to melt upon heating. Thus, the brazing temperature range extends
from the solidus temperature to the liquidus temperature. The
brazing temperature, or melting temperature at which the alloy wets
and flows, is generally considered to be between the solidus and
liquidus temperatures. Some alloys exhibit thermal arrests between
the solidus and liquidus, which may be observed on the cooling
curve for a given alloy, with the major thermal arrest (MTA)
temperature indicating the melting temperature of a major portion
of the alloy. For alloys that do exhibit a MTA, the brazing
temperature is generally considered to be at or near the MTA. For
alloys that do not exhibit a MTA, the brazing temperature (i.e.,
temperature at which a major portion of the alloy is melted) is
generally considered to be at or near the liquidus temperature.
[0019] The alloys of the present invention form a large cap, or
shoulder, during the brazing process that is clearly visible, and
they do so at a brazing temperature that has not been possible with
phos-copper brazing alloys in the past without the addition of
silver to the composition of the alloys. In fact, the phos-copper
base alloys of the present invention which include tin and nickel,
and advantageously silicon, will form a cap or shoulder similar to
or superior to silver-phos-copper alloys of the prior art, and will
do so at lower brazing temperatures than the prior art
silver-containing alloys, and will exhibit greater corrosion
resistance. The phos-copper base alloys of the present invention
which include silver, tin and nickel, and advantageously silicon,
also form a cap or shoulder similar to or superior to
silver-phos-copper alloys of the prior art and will do so at
significantly lower brazing temperatures than the prior art
silver-containing alloys, particularly for high silver contents,
such as 6-18% and will exhibit greater corrosion resistance. The
liquidus and MTA temperatures of brazing alloys of the present
invention more closely represent the most important characteristic
of where the alloy flows (the working temperature). The filler
metal can readily fill loose connections and cap large copper
fittings. Specific formulations of this alloy can accommodate
near-eutectic melting characteristics to braze tight-fitting parts
and conversely, to fill loose connections as large as 0.050''.
[0020] The large caps formed by brazing with the phos-copper base
alloy compositions of the present invention (without silver
addition) are a bright tin or silver color, and their presence is
easily seen. This is an advantage over the phos-copper alloys of
the prior art that do not cap well and are black in color after
brazing. The brazing torch operator has great difficulty viewing
the previous copper brazes because the braze itself is black from
oxide as is the copper adjacent to the braze. This can contribute
to leaks in the manufacturing of such components as air
conditioning copper coils, leaks that can be avoided by the
operator's being able to see a bright metal braze (cap or seal)
that is contiguous and complete. The phosphorus-tin-nickel-copper
alloys and the phosphorus-tin-nickel-silicon-copper alloys of the
present invention cause no blackening on the braze or on the
adjacent copper.
[0021] To this end, a solid brazing component is provided as a
strip, foil, wire or preform, wherein the brazing component has a
liquidus temperature above 840.degree. F., thus making the
component suitable for brazing techniques. The brazing component is
made of an alloy consisting essentially of, in weight percent,
about 4-9% phosphorus, about 0.1-10% tin, and about 0.1-15% nickel.
In all alloy examples provided herein, the balance of the
composition is copper. Further, in all alloys described herein, all
or a portion of the tin may be replaced by antimony, which serves
the same or similar function in the alloy, but preferably the
antimony content does not exceed about 4%, and the sum of tin and
antimony does not exceed about 10% of the alloy composition. The
presence of nickel in combination with tin results in a lowering of
the solidus temperature, an increase in hardness, and an
improvement in corrosion resistance. Advantageously, nickel is
included in an amount of about 3-10%. It may be appreciated that as
nickel content increases, fabrication becomes increasingly more
difficult in proportion, namely extrusion and drawing into wire
becomes more difficult. Thus, to optimize corrosion resistance and
extrudability, the alloy advantageously includes about 5-8% Ni.
[0022] The alloys of the present invention may further include up
to about 3% silicon, and advantageously include silicon in an
amount of about 0.001-3%. In another exemplary embodiment of the
present invention, the alloys may further include up to 18% silver,
and advantageously contain silver in an amount of about 1-18%. In
yet-another exemplary embodiment of the present invention, the
alloy includes both silver and silicon additions. All alloys of the
present invention may further include up to about 3% manganese
without departing from the scope of the present invention.
Manganese is a known alloying addition for increasing the toughness
and hardness of the brazing alloy. Further, alloys including
impurity amounts of other elements are considered within the scope
of the present invention. Impurities may be present by virtue of
the raw materials used to make the alloys, and are to be
distinguished from elements intentionally added to the alloy melt
for the purpose of affecting the properties of the alloy.
[0023] As may be appreciated by one skilled in the art, variations
in the amounts of each of the alloying elements, within the
above-described ranges, will have an effect on the liquidus, MTA
and solidus temperatures of the brazing alloy, as well as hardness
and corrosion resistance. The following alloys are provided as
exemplary, in that they achieve desirable liquidus, MTA, and/or
solidus temperatures, achieve good corrosion resistance, form a
substantial cap or shoulder, and produce little to no blackening on
the braze or adjacent metal. In no way should the following
recitations be considered to limit the scope of the present
invention to the specific exemplary alloys. A first exemplary
embodiment of a brazing component of the present invention is made
of an alloy consisting essentially of, in weight percent: (a) about
4-9% phosphorus; (b) about 4-8% tin; (c) about 5-8% nickel, and the
balance copper. Optional additional elements may include up to 3%
silicon, up to 4% antimony, up to 18% silver and up to 3%
manganese.
[0024] A second exemplary embodiment of a brazing component of the
present invention is made of an alloy consisting essentially of, in
weight percent: (a) about 4-9% phosphorus; (b) about 4-8% tin; (c)
about 3-10% nickel, (d) about 2-18% silver, and the balance copper.
Optional additional elements may include up to 3% silicon, up to 4%
antimony and up to 3% manganese.
[0025] A third exemplary embodiment of a brazing component of the
present invention is made of an alloy consisting essentially of, in
weight percent: (a) about 4-7% phosphorus; (b) about 4-8% tin; (c)
about 5-8% nickel; (d) about 6-15% silver; (e) about 0.001-1%
silicon, and the balance copper. Optional additional elements may
include up to 4% antimony and up to 3% manganese.
[0026] A fourth exemplary embodiment of a brazing component of the
present invention is made of an alloy consisting essentially of, in
weight percent: (a) about 5-6% phosphorus; (b) about 6-7% tin; (c)
about 5-8% nickel; (d) about 6-10% silver, (c) about 0.015-0.02%
silicon, and the balance copper. Optional additional elements may
include up to 4% antimony and up to 3% manganese.
[0027] A fifth exemplary embodiment of a brazing component of the
present invention is made of an alloy consisting essentially of, in
weight percent: (a) about 5-6% phosphorus; (b) about 6-7% tin; (c)
about 5-8% nickel; (d) about 15% silver; (e) about 0.015-0.02%
silicon, and the balance copper. These alloys may exhibit a solidus
temperature on the order of 1034-1056.degree. F. and a liquidus
temperature on the order of about 1404.degree. F. or less, as well
as a MTA on the order of 1205-1296.degree. F. Optional additional
elements may include up to 4% antimony and up to 3% manganese.
[0028] The above-described alloy components are added to a melt in
desired amounts, and the resulting alloy melt is continuously cast
into a billet. The billet is then extruded into a wire or rolled
into strip or foil. The wire may be drawn one or more times to
produce a desired wire diameter. If desired, the wire may be
further formed into a preform.
[0029] A joint is brazed in accordance with the present invention
by placing the solid brazing component having one of the
compositions described above between two metal parts, heating the
solid brazing component to melt at least a major portion of the
alloy (i.e., heating to a brazing temperature at or near the MTA or
liquidus temperature) to cause the alloy to wet and flow between
the two metal parts, with flux if necessary, then cooling the alloy
to form the brazed joint, whereby a raised cap is visible between
the two metal parts, and the joint and adjacent metal parts are
substantially free of black metal oxide. In one embodiment, the
metal parts may be two copper or copper alloy parts and the brazed
joint will be visually distinguishable from the parts, having a
bright tin or silver color. The solid brazing components of the
present invention are suitable for brazing a wide variety of parts
of both simple and intricate shapes. For example, the brazing
components are suitable for brazing tubular shaped parts, whereas
powder brazing alloys of the prior art are not easily used in that
environment. In an exemplary embodiment of the method of the
present invention, the solid brazing component is heated to a
temperature less than 1410.degree. F., by virtue of the alloy
having a liquidus and/or MTA temperature below 1410.degree. F. In a
further exemplary embodiment of the present invention, the solid
brazing component is heated to a temperature less than 1300.degree.
F., by virtue of the alloy having a liquidus and/or MTA temperature
below 1300.degree. F.
[0030] The alloys of the present invention, in their broadest form,
consist essentially of at least copper, phosphorus, tin (and/or
antimony) and nickel. Nickel, in combination with tin, achieves
benefits to a degree not obtainable by the addition of either
element alone to the phos-copper base alloys. Nickel, in
combination with tin and optionally silicon, in the phos-copper and
silver-phos-copper base alloys, is responsible for lowering the
melting range of the brazing alloy, increasing
corrosion-resistance, and smoothing the surface of the finished
braze area. The hardness of the phos-copper base alloys may also be
increased by nickel addition, particularly with respect to a
constant phosphorus content. However, if nickel content is
increased while decreasing phosphorus content, a decrease in
hardness may result. By way of example, an alloy of the present
invention consisting essentially of 7.1% phosphorus, 6% tin, and
1-8% nickel, balance copper, tests to a Rockwell B hardness of
85-91, whereas the BCuP-2 alloy of the prior art (alloy 1 in the
Table below) tests to a lower Rockwell B hardness of 78. The
resultant brazes from alloys of the present invention are also
ductile and strong. As with BCuP alloys of the prior art, it is
important for the base metal to fail rather than the brazed joint.
Several destructive tests on copper brazes made with
Cu--P--Sn--Ni--Si alloys of the present invention conducted by the
Edison Welding Institute did result in failure of the base metal,
rather than the brazed joint. Moreover, compared to Cu--P and
Cu--P--Ag alloys of the prior art, Cu--P--Sn--Ni and
Cu--P--Ag--Sn--Ni alloys of the present invention exhibit lower
liquidus, MTA and/or solidus temperatures and greater corrosion
resistance thereby allowing brazing to take place within a lower
temperature range and use to occur in more corrosive environments
with longer joint life. Silicon addition to these alloys also
creates the advantage of lowering the brazing temperature and
surface tension when they are in the molten state. This allows the
brazing alloys to better penetrate tightly fitting parts and to
achieve fuller coverage of the surfaces to be brazed. For example,
leaks in copper coils used in air conditioning systems are often
caused by small voids within a braze, connecting with one another,
to form a path wherein refrigerant gases escape.
[0031] Silicon additions in the presence of tin also offer the
advantage of changing the color and texture of phos-copper base
brazes from a dull, grainy, brown finish to a very smooth finish of
bright tin or silver color. To achieve this color and texture
change, these alloys require a tin or antimony content of not less
than 0.1% and not greater than 10% individually or in combination.
In particular, when added in the presence of tin (0.1% to 8.0%)
and/or antimony (up to 4.0%), a color change is effected to a
bright tin or silver color finish after brazing. Nickel addition
increases the degree of this color change, in particular, the
brightness. Silicon addition also increases the average tensile
strength of phos-copper alloys.
[0032] Cooling curves run on a phos-copper BCuP-2 braze alloy
(alloy 1), BCuP-4 braze alloy (alloy 2), and BCuP-5 braze alloy
(alloy 3) of the prior art and phos-copper base alloys of the
present invention containing tin and nickel additions with or
without silicon and/or silver additions are analyzed and the
results set forth the Table, showing solidus, MTA and liquidus
temperatures. Minor thermal arrests often appear in the cooling
curves but are not shown. All values are percents by weight.
TABLE-US-00001 % % % % % Liquidus MTA Solidus Alloy P Ag Sn Ni Si
.degree. F. .degree. F. .degree. F. 1* 7.1 -- -- -- -- 1475 -- 1310
2** 7.2 6 -- -- -- 1335 1246 1190 3*** 5 15 -- -- -- 1480 1194 1190
4 5 15 6 5 0.02 1343 1293 1037 5 5 15 6 5 -- 1352 1211 1037 6 5 15
6 6 0.02 1352 1205 1038 7 5 15 6 7 0.02 1353 1251 1034 8 5 15 6 8
0.02 1384 1296 1034 9 5 15 6 6 0.015 1404 1212 1056 10 7 6 6 6
0.015 1240 1114 1037 11 5 6 6 0.015 1134 -- 1134 12 7.1 -- 6 1 --
1241 -- 1241 13 7.1 -- 6 3 -- 1264 1210 1098 14 7.1 -- 6 5 -- 1290
1178 1116 15 7.1 -- 6 8 -- 1359 1133 1098 *Prior art phos-copper
brazing alloy known as BCuP-2 **Prior art silver-phos-copper
brazing alloy known as BCuP-4 ***Prior art silver-phos-copper
brazing alloy known as BCuP-5
[0033] The Table illustrates significant reductions in temperature
across the melting range of the phos-copper base alloys of the
present invention as compared with the BCuP-2 brazing alloy (alloy
1) of the prior art. Brazing temperatures for the phos-copper
alloys with tin and nickel additions are significantly lower than
the phos-copper BCuP-2 brazing alloys. The higher the nickel
content, the lower the brazing temperature. The substantial
reduction of required brazing temperatures effects considerable
savings of both fuel gases and cycle time of brazing operations.
The lower brazing temperatures also lessen the degree of annealing
caused to parent copper and brass metals with the phos-copper base
alloys. Such annealing causes the metal to soften and to become
very weak. Also, in some very hot brazing furnaces, slight melting
of the copper or brass base parts can occur.
[0034] A comparison of alloys 12-15 of the present invention show
the effect of adding 6% tin in combination with 1-8% nickel to the
BCuP-2 alloy. The combination of 6% tin and 1% nickel drops both
the liquidus and solidus temperatures to 1241.degree. F. As nickel
content increases, the solidus temperature drops further, and the
liquidus increases, but a MTA occurs, and brazing occurs at or near
the MTA.
[0035] A comparison of alloy 11 of the present invention with the
BCuP-2 alloy (alloy 1) of the prior art demonstrates the
synergistic effect achieved by the addition of silicon, tin and
nickel in accordance with the present invention. The BCuP-2 alloy
does not exhibit a MTA, and so brazing occurs at or near the
liquidus temperature of 1475.degree. F. Addition of 6% tin in
combination with 6% nickel and 0.015% silicon achieves a lowering
of both the solidus and liquidus temperatures to 1134.degree.
F.
[0036] A reduction in brazing temperature is also generally
apparent in the silver-phos-copper alloys containing tin and
nickel, in particular those further containing silicon, and more in
particular for those alloys containing about 6-15% silver. Alloy 10
of the present invention in comparison to the BCuP-4 alloy (alloy
2) demonstrates that the addition of tin, nickel and silicon lowers
the MTA, solidus and liquidus temperatures of the brazing alloy.
Alloys 4-9 of the present invention in comparison to the BCuP-5
alloy (alloy 3) further demonstrate a decrease in the liquidus and
solidus temperatures while maintaining or slightly increasing the
MTA temperature. In each of the alloys of the present invention,
the liquidus temperature is below 1410.degree. F. and the solidus
temperature is below 1250.degree. F. Many of the alloys also
exhibit an MTA temperature less than 1300.degree. F. Exemplary
alloys of the present invention have a brazing temperature (MTA or
liquidus temperature) below 1300.degree. F., and advantageously,
below 1250.degree. F.
[0037] FIGS. 1 and 2 visually demonstrate the synergistic effect of
tin and nickel in the silver-phos-copper alloys and the phos-copper
alloys. FIG. 1 depicts the corrosion resistance for silver
phos-copper alloys of the present invention compared to the BCuP-5
alloy (alloy 3), and also to the BCuP-4 (alloy 2) and BCuP-2 (alloy
1) alloys. The graph includes data for alloy 4 and alloys similar
to alloys 6-8 of the Table. It is noted that the silicon content
varies from that listed for alloys 6-8 in the Table. Nonetheless,
the alloys in FIG. 1 will be referred to as alloys 6-8. Alloys 4
and 6-8 are similar to BCuP-5, but modified with 6% tin; 5, 6, 7
and 8% nickel; and 0.02% silicon addition (or 0 or 0.015), i.e.,
Cu-5P-15Ag-6Sn-5-8Ni-0.02Si. To simulate a brazed joint in a
corrosive environment, a sample of each of the braze alloys was
agitated in a 10% HCl solution for 64 hours, and the weight loss
measured. The results were extrapolated to predict the extent of
corrosion after a period of one year. If a sample was made of a
silver-phos-copper brazing material, the thickness of the sample
would be reduced through corrosion by the amount shown in on year's
time. It is noted, however, that each surface of the sample was
exposed to acid in this test and thereby subject to corrosion,
whereas only one surface of a braze is likely exposed in actual
use. Therefore, the extent of corrosion is exaggerated in this
test. Nonetheless, for purposes of comparison, if alloy 4 (5% Ni)
were completely exposed to a 10% hydrochloric acid (HCl) solution
for one year, the thickness of the braze would decrease by 0.127
inch. A braze of an alloy similar to alloy 8 (8% Ni) would decrease
in thickness by 0.105 inch. So, the 8% Ni alloy 8 is about 17% more
corrosion resistant than the 5% Ni alloy 4 when exposed to HCl. The
BCuP-5 alloy would decrease in thickness by 0.147 inch, and thus,
the 5% Ni alloy 4 is about 14% more corrosion resistant than BCuP-5
when exposed to HCL, and 8% Ni alloy 8 is about 29% more corrosion
resistant than BCuP-5. FIG. 1 also compares the silver phos-copper
alloys having 5-8% Ni to the BCuP-2 and BCuP-4 alloys of the prior
art. In addition to the 14% improvement over BCuP-5, a braze of a
BCuP-4 alloy would decrease in thickness by 0.17 inch, such that
the 5% Ni alloy 4 is about 25% more corrosion resistant. A braze of
a BCuP-2 alloy would decrease in thickness by 0.173 inch. So, the
5% Ni alloy 4 is about 27% more corrosion resistant than BCuP-2
when exposed to HCl.
[0038] FIG. 2 depicts the corrosion resistance for phos-copper
alloys 13-15 of the present invention, as set forth in the Table,
compared to the BCuP-2 alloy (alloy 1), as well as the BCuP-4
(alloy 2) and BCuP-5 (alloy 3) alloys, of the prior art. The 3% Ni
alloy 13 would decrease in thickness by about 0.065 inch, and thus,
is about 62% and 56% more corrosion resistant than 13CuP-2 and
BCuP-5, respectively, when exposed to HCL. The 8% Ni alloy 15 would
decrease in thickness by about 0.023 inch, and thus, is about 87%
and 84% more corrosion resistant than BCuP-2 and BCuP-5,
respectively.
[0039] FIGS. 1 and 2 thus demonstrate that high nickel additions
may be added to the silver-phos-copper base alloys and phos-copper
base alloys when accompanied by tin to provide an alloy suitable
for brazing that forms a smooth, solid, visually distinguishable
brazed joint with significantly increased corrosion resistance.
[0040] The Table and Figures show meaningful reductions in
liquidus, MTA and solidus temperatures and increases in corrosion
resistance for the Cu--P--Sn--Ni and Cu--P--Sn--Ni--Si alloys of
the present invention compared to the BCuP-2 alloy (alloy 1), and
for the Cu--P--Ag--Sn--Ni--Si and Cu--P--Ag--Sn--Ni alloys of the
present invention compared to the BCuP-4 (alloy 2) and BCuP-5
(alloy 3) alloys. Further, the brazed joints using alloys of the
present invention have substantial raised shoulders or caps about
the brazed joint which are visually distinguishable from adjacent
copper and copper alloys. There is a further absence of black
oxide, which can obscure the operator's view of the soundness of
the joint. A synergistic effect is achieved with the combined
additions of tin and nickel and with tin, nickel and silicon in
both phos-copper and silver-phos-copper alloys.
[0041] While the present invention has been illustrated by the
description of an embodiment thereof, and while the embodiment has
been described in considerable detail, it is not intended to
restrict or in any way limit the scope of the appended claims to
such detail. Additional advantages and modifications will readily
appear to those skilled in the art. The invention in its broader
aspects is therefore not limited to the specific details,
representative apparatus and method and illustrative examples shown
and described. Accordingly, departures may be made from such
details without departing from the scope or spirit of the general
inventive concept.
* * * * *