U.S. patent application number 09/934100 was filed with the patent office on 2002-02-21 for method of making a flux, a brazing wire, and a brazing paste.
Invention is credited to Jossick, Daniel J., Schuster, Jerry L..
Application Number | 20020020468 09/934100 |
Document ID | / |
Family ID | 26838851 |
Filed Date | 2002-02-21 |
United States Patent
Application |
20020020468 |
Kind Code |
A1 |
Schuster, Jerry L. ; et
al. |
February 21, 2002 |
Method of making a flux, a brazing wire, and a brazing paste
Abstract
A method of making a brazing flux compound including the steps
of dispensing a desired amount of each of a plurality of
ingredients. Adding potassium bifluoride to a bowl and adding boric
acid on top of the potassium bifluoride. Mixing the boric acid and
potassium bifluoride to form a substantially smooth wet first
paste. Adding potassium tetraborate to the first paste and mixing
the potassium tetraborate with the first paste to form a
substantially creamy second paste. Adding potassium fluoroborate to
the second paste and mixing the potassium fluoroborate with the
second paste to form a third paste. Adding potassium carbonate to
the third paste and mixing until the potassium carbonate is
completely dissolved thus forming a fourth paste. Heating the
fourth paste for a predetermined time at a predetermined
temperature such that the said fourth paste is substantially dried
into a substantially solid flux and then reducing the substantially
solid flux to a powder flux.
Inventors: |
Schuster, Jerry L.;
(Newfields, NH) ; Jossick, Daniel J.; (Exeter,
NH) |
Correspondence
Address: |
Lawson, Philpot & Persson, P.C.
Suite 110
67 Water Street
Laconia,
NH
03246
US
|
Family ID: |
26838851 |
Appl. No.: |
09/934100 |
Filed: |
August 21, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09934100 |
Aug 21, 2001 |
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09603317 |
Jun 24, 2000 |
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6277210 |
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60141165 |
Jun 25, 1999 |
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Current U.S.
Class: |
148/26 ;
148/23 |
Current CPC
Class: |
B23K 35/0244 20130101;
B23K 35/3006 20130101; B23K 35/0227 20130101; B23K 35/3606
20130101; B23K 35/3605 20130101 |
Class at
Publication: |
148/26 ;
148/23 |
International
Class: |
B23K 035/34 |
Claims
What is claimed is:
1. A method of making a brazing flux compound comprising the steps
of: dispensing a desired amount of each of a plurality of
ingredients; first adding potassium bifluoride; second adding boric
acid on top of the potassium bifluoride; first mixing the boric
acid and potassium bifluoride to form a substantially smooth wet
first paste; third adding potassium tetraborate to the first paste;
second mixing the potassium tetraborate with the first paste to
form a second paste; fourth adding potassium fluoroborate to the
second paste; third mixing potassium fluoroborate with the second
paste to form a third paste; fifth adding potassium carbonate to
the third paste; fourth mixing until potassium carbonate is
completely dissolved thus forming a fourth paste; heating the
fourth paste for a predetermined time at a predetermined
temperature such that the said fourth paste is substantially dried
into a substantially solid flux; and reducing the substantially
solid flux to a powder.
2. The method of claim 1 further comprising the step of adding an
amount of non-reactive liquid to at least one of said mixing steps
as the paste in the corresponding mixing step begins to stiffen,
said amount of non-reactive liquid being sufficient to cause the
paste to retain a substantially smooth consistency.
3. The method of claim 2 wherein said non-reactive liquid is
deionized water.
4. The method of claim 1 wherein said predetermined temperature of
said heating step is between about 600 and about 700 degrees
Fahrenheit.
5. The method of claim 4 wherein said predetermined temperature of
said heating step is about 650 degrees Fahrenheit.
6. The method of claim 1 wherein the predetermined time of said
heating step is between about 2 hours and about 6 hours.
7. The method of claim 6 wherein the predetermined time of said
heating step is about 4 hours.
8. The method of claim 1: wherein said first adding step comprises
adding potassium bifluoride ranging from approximately 19% to 29%
by weight; wherein said second adding step comprises adding boric
acid ranging from approximately 21% to 31% by weight; wherein said
third adding step comprises adding potassium tetraborate ranging
from approximately 15% to 25% by weight; wherein said fourth adding
step comprises adding potassium fluoroborate ranging from
approximately 21% to 31% by weight; and wherein said fifth adding
step comprises adding potassium carbonate ranging from
approximately 2.5% to 4.5% by weight
9. The method of claim 8: wherein said first adding step comprises
adding approximately 24% by weight of potassium bifluoride; wherein
said second adding step comprises adding approximately 26% by
weight of boric acid; wherein said third adding step comprises
adding approximately 20% by weight of potassium tetraborate;
wherein said fourth adding step comprises adding approximately 26%
by weight of potassium fluoroborate; and wherein said fifth adding
step comprises adding approximately 3.5% by weight of potassium
carbonate.
10. The method of claim 1 further comprising the step of sixth
adding boron and then fifth mixing said boron; said sixth adding
step being performed at any time after said second mixing step and
before said heating step
11. The method of claim 10 wherein said sixth adding step comprises
adding boron ranging from approximately 0.01% to 2.0% by weight
12. The method of claim 1 wherein said reducing step comprises
reducing the size of the flux to a powder of between about 20 mesh
and about 325 mesh.
13. The method of claim 12 wherein said reducing step comprises
reducing the size of the flux to a powder of between about 40 mesh
and about 200 mesh.
14. The method of claim 1 wherein said reducing step comprises
reducing the solid flux to a powder by a method selected from a
group consisting of three roll milling, hammer milling, crushing,
and pulverizing.
15. The method of claim 1 further comprising the steps of rolling
the fourth paste and fifth mixing the fourth paste prior to said
heating step.
16. The method of claim 1 further comprising the step of
transferring the fourth paste into a container prior to the heating
step such that the fourth paste fills the container to a height of
between about one inch and about two inches.
17. The method of claim 1 wherein at least one of said mixing steps
comprises the steps of first running a mixer, stopping the mixer,
scraping sides and a bottom of a bowl and a mixer blade, and second
running said mixer.
18. The method of claim 1 wherein said step of first adding
potassium bifluoride further comprises the step of separating at
least one clump of potassium bifluoride until only granules of
potassium bifluoride remain.
19. A method of making a wire brazing composition comprising the
steps of: making a brazing flux compound, wherein said step of
making a brazing flux compound comprises the steps of: dispensing a
desired amount of each of a plurality of ingredients; first adding
potassium bifluoride; second adding boric acid on top of the
potassium bifluoride; first mixing the boric acid and potassium
bifluoride to form a substantially smooth wet first paste; third
adding potassium tetraborate to the first paste; second mixing the
potassium tetraborate with the first paste to form a second paste;
fourth adding potassium fluoroborate to the second paste; third
mixing potassium fluoroborate with the second paste to form a third
paste; fifth adding potassium carbonate to the third paste; fourth
mixing until potassium carbonate is completely dissolved thus
forming a fourth paste; heating the fourth paste for a
predetermined time at a predetermined temperature such that the
said fourth paste is substantially dried into a substantially solid
flux; and reducing the substantially solid flux to a powder flux;
forming a silver brazing material into a desired shape; dispensing
the powder flux onto a silver brazing material; and forming the
silver brazing material and the powder flux into the wire brazing
composition.
20. A method of making a brazing paste comprising the steps of:
making a brazing flux compound, wherein said step of making a
brazing flux compound comprises the steps of: dispensing a desired
amount of each of a plurality of ingredients; first adding
potassium bifluoride; second adding boric acid on top of the
potassium bifluoride; first mixing the boric acid and potassium
bifluoride to form a substantially smooth wet first paste; third
adding potassium tetraborate to the first paste; second mixing the
potassium tetraborate with the first paste to form a substantially
creamy second paste; fourth adding potassium fluoroborate to the
second paste; third mixing potassium fluoroborate with the second
paste to form a third paste; fifth adding potassium carbonate to
the third paste; fourth mixing until potassium carbonate is
completely dissolved thus forming a fourth paste; heating the
fourth paste for a predetermined time at a predetermined
temperature such that the said fourth paste is substantially dried
into a substantially solid flux; and reducing the substantially
solid flux to a powder flux; forming a silver brazing material into
a silver powder; combining the silver powder, the powder flux and a
binder material; and mixing the silver powder, the powder flux and
the binder material together to form the silver brazing paste.
Description
RELATED APPLICATIONS
[0001] This application is a Continuation-in-Part of co-pending
U.S. patent application Ser. No. 09/603,317, filed on Jun. 24,
2000, which claims the priority of U.S. Provisional Patent
application Ser. No. 60/141,165, filed on Jun. 25, 1999.
FIELD OF THE INVENTION
[0002] The present invention relates to the field of brazing and,
in particular, to a method of making a flux for silver brazing that
is non-corrosive and non-hygroscopic in nature, and to a flux cored
silver brazing wire and silver brazing paste utilizing the
same.
BACKGROUND OF THE INVENTION
[0003] For many years, metal parts have been joined using
silver-based brazing compounds. As is well known in the art, it is
necessary to prepare the surfaces to be joined prior to applying
the brazing compounds in order to provide adhesion of the brazing
compound to the surfaces to be joined. This preparation is
typically performed by a flux material, which is applied to the
joint and activated by the application of heat to the joint. Once
activated, the flux thoroughly cleans the surfaces to the joined
and removes any oxides that will degrade the strength of the brazed
joint.
[0004] As they must aggressively clean the surfaces to be joined,
fluxes have typically been highly corrosive and hygroscopic in
nature. Accordingly, it is necessary in many applications to remove
any residual flux or flux residue from the joined parts in order to
prevent corrosion of the parts. This removal increases the overall
costs of the parts, due to the additional process steps and the
cost of waste disposal from the cleaning process. In addition, the
waste generated by this cleaning is hazardous to humans and harmful
to the environment.
[0005] Finally, because of their corrosiveness and affinity for
absorbing water, many typical fluxes have not been adapted for use
in flux cored wires. As this is the case, the use of these fluxes
has necessitated the additional step of applying the flux in a
paste form prior to heating and joining the parts. As was the case
with the cleaning step described above, the need to perform this
additional step increases the overall cost of the joined parts.
[0006] Accordingly, there is a need for a flux for use with silver
brazing compositions that effectively prepares the surfaces to be
joined, is non-corrosive and non-hygroscopic and, accordingly, does
not need to be cleaned from joined surfaces after they are joined,
and may be formed into a powder for disposal within a flux cored
wire.
SUMMARY OF THE INVENTION
[0007] The present invention is a silver brazing flux that is
non-corrosive and non-hygroscopic in nature, and a method of making
this flux. In its most basic form, the flux includes the following
compounds in the following percentages by weight:
1TABLE 1 Composition of Basic Flux Compound COMPOUND PERCENTAGE BY
WEIGHT Potassium Fluoroborate 21%-31% Boric Acid 21%-31% Potassium
Bifluoride 19%-29% Potassium Tetraborate 15%-25% Potassium
Carbonate 2.5%-4.5%
[0008] In addition the above materials, the preferred flux includes
boron in the range of 0.01% to 2.0% by weight. The addition of
boron in these amounts is preferred as such an addition has been
found to enhance the anti-oxidation properties of the flux.
However, it is recognized that the flux will work satisfactorily
without the addition of boron and, therefore, boron is not included
in all embodiments.
[0009] In some embodiments, the flux is combined with deionized
water, or other suitable binder materials, to form a flux paste. In
other embodiments, the flux is mixed and dried into a powder and
dispensed within a silver based filler material using, for example,
the process described in U.S. Pat. No. 5,781,846, which is
incorporated herein by reference, to form a U.S. Pat. No,
5,781,846.
[0010] The preferred flux includes the following compounds in the
following percentages by weight:
2TABLE 2 Composition of Preferred Flux Compound COMPOUND PERCENTAGE
BY WEIGHT Potassium Fluoroborate 26.3% Boric Acid 26.3% Potassium
Bifluoride 23.8% Potassium Tetraborate 20.2% Potassium Carbonate
3.3% Boron 0.2%
[0011] The method of making the flux includes the following
steps:
[0012] Dispensing the proper percentages of all ingredients by
weighing, volume, or other art recognized means. This dispensing
step may be performed prior to the mixing steps or contemporaneous
with each mixing step.
[0013] Adding boric acid on top of potassium bifluoride.
[0014] Mixing the boric acid and potassium bifluoride at medium-low
speed until a completely smooth wet paste is formed.
[0015] Adding potassium tetraborate and mixing, preferably at
medium low speed;
[0016] Adding potassium fluoroborate and mixing, preferably at
medium low speed;
[0017] Adding potassium carbonate to the paste and mixing until it
is completely dissolved;
[0018] Adding boron and mixing, preferably at medium low speed;
[0019] Adding a non-reactive liquid, such a deionized water,
alcohol, or the like, to each step of the mixture as it begins to
stiffen in order to keep a loose, smooth consistency, similar to
that of cake frosting, and scraping the sides and bottom of the
mixing bowl as needed to keep the mix even.
[0020] Mixing the paste, preferably at medium speed.
[0021] Stopping the mixer and transferring the mixture into a
container, such as a pan. The transferring step preferably involves
transferring the mixture such that it fills the container to a
depth of between about one inch and about two inches, as filling to
this depth allows entrained moisture within the mixture to more
easily be exhausted from the mixture during the subsequent heating
step and also produces a solid flux that is more easily reduced to
powder form.
[0022] Drying the mixture by placing the container into an oven
preheated to between about 500 and about 700 degrees Fahrenheit and
leaving the mixture within the oven for a period of between about
two and six hours, such that substantially all moisture is dried
from the mixture;
[0023] Removing the dried flux and reducing the size of the flux
particles to a powder, such as by roll milling, hammer milling,
crushing, pulverizing, or the like, and screening to a desired
average particle size of between about 20 mesh and about 325
mesh.
[0024] The resulting flux powder is non-corrosive and
non-hygroscopic, and is readily adapted for suspension within a
paste or disposition within a brazing alloy to form a wire brazing
composition.
[0025] Therefore, it is an aspect of the invention to provide a
method of making a brazing flux that is non-corrosive.
[0026] It is a farther aspect of the invention to provide a method
of making a brazing flux that is non-hygroscopic.
[0027] It is a further aspect of the invention to provide a method
of making a brazing flux that promotes reaction between materials
during mixing that dries off moisture while causing dry materials
to combine to form a paste material.
[0028] It is a further aspect of the invention to provide a method
of making a brazing flux that prevents unwanted reactions between
materials during mixing.
[0029] It is a further aspect of the invention to provide a method
of making a brazing flux that does not leave a residue that must be
cleaned from surfaces after they are joined.
[0030] It is a further aspect of the invention to provide a method
of making a brazing flux that effectively prepares surfaces for
joining.
[0031] It is a further aspect of the invention to provide a method
of making a brazing flux that may be formed into a powder.
[0032] It is a further aspect of the invention to provide a method
of making a brazing flux that may be combined with a silver brazing
alloy to form wire brazing composition.
[0033] It is a still further aspect of the invention to provide a
method of making a brazing flux that may be combined with a binder
material to form a flux paste.
[0034] These aspects of the invention are not meant to be exclusive
and other features, aspects, and advantages of the present
invention will be readily apparent to those of ordinary skill in
the art when read in conjunction with the following description,
appended claims and accompanying drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0035] The present invention is a silver brazing flux that is
non-corrosive and non-hygroscopic in nature and a method of making
the flux. As set forth in the summary section above, the flux is a
mixture of potassium fluoroborate, boric acid, potassium
bifluoride, potassium tetraborate, and potassium carbonate and, in
some embodiments, boron. When combined in the percentages set forth
above, the resulting flux provides excellent surface preparation
characteristics and is both non-corrosive and non- hygroscopic.
[0036] In some embodiments, the flux is combined with deionized
water, or other suitable binder materials, to form a flux paste. In
these embodiments, the flux paste is applied to the faying surfaces
prior to the application of heat, and is subsequently heated until
it flows and wicks across the faying surfaces, effectively
preparing the surfaces for joining. Once the surfaces are prepared,
a solid wire of silver based brazing composition is brought into
contact with the heated surfaces, causing the brazing composition
to flow across the surfaces and, once cooled, to effectively join
the surfaces together.
[0037] In other embodiments, the flux is mixed and dried into a
powder and dispensed within a silver based filler material to form
a wire brazing composition. In some such embodiments, the filler
material may be formed into a sheath and filled using methods
similar to those described in the inventors U.S. Pat. No.
5,781,846. In others, the filler material is formed with a notch,
groove or other surface detail that allows the filler material to
accepting the flux and allows the filler material and the flux to
be formed into a U.S. Pat. No. 5,781,846. Regardless of the shape
taken by the filler material prior to disposition of the flux, in
each of these embodiments the faying surfaces are heated and the
wire brazing composition is brought into contact with the heated
surfaces, causing the flux to melt and flow and subsequently
causing the brazing composition to melt and flow.
[0038] All embodiments of the flux may be utilized with all
American Welding Society (AWS) standard industrial
silver/copper/zinc alloys. Accordingly, the preferred brazing alloy
will vary depending upon the particular application in which it
will be used.
[0039] As noted above, the preferred flux includes the following
compounds in the associated percentages by weight:
3 COMPOUND PERCENTAGE BY WEIGHT Potassium Fluoroborate 26.3% Boric
Acid 26.3% Potassium Bifluoride 23.8% Potassium Tetraborate 20.2%
Potassium Carbonate 3.3% Boron 0.2%
[0040] The preferred method includes the following steps:
[0041] Weighing each solid and liquid ingredient in separate clean,
dry containers.
[0042] Adding potassium bifluoride into a stainless steel mixing
bowl and separating any clumps such that until only granules less
than 300 microns in size remain;
[0043] Adding boric acid on top of the potassium bifluoride;
[0044] Mixing the boric acid and potassium bifluoride at medium-low
speed until a completely smooth wet paste is formed;
[0045] Adding deionized water to the paste as it begins to stiffen
in order to keep a loose, smooth consistency, similar to that of
cake frosting, and scraping the sides and bottom of the mixing bowl
as needed to keep the mix even;
[0046] Adding potassium tetraborate and mixing at medium low speed
until the mixture becomes smooth and creamy, adding additional
deionized water to the mixture as it beings to stiffen, and
scraping the sides and bottom of the mixing bowl as needed to keep
the mix even;
[0047] Adding potassium fluoroborate and mixing at medium to medium
low speed until smooth, adding additional deionized water to the
mixture as it beings to stiffen, and scraping the sides and bottom
of the mixing bowl as needed to keep the mix even;
[0048] Adding potassium carbonate to the paste and mixing until it
is completely dissolved;
[0049] Adding boron and mixing, preferably at medium low speed
[0050] Stopping the mixer, scraping the sides and bottom of the
bowl and the mixer blade, mixing again at medium speed;
[0051] Stopping the mixer and pouring the mixture into a stainless
steel pan;
[0052] Drying the mixture by placing the stainless steel pan into a
pre-heated oven at approximately 650 degrees Fahrenheit for a
period of about four hours such that substantially all moisture is
dried from the mixture;
[0053] Removing the dried flux and milling to a powder and
screening to a desired particle size of between about 40 mesh and
about 200 mesh.
[0054] It has been found that the order in which the potassium
bifluoride, boric acid and potassium tetraborate are added is
important in obtaining the desired result. Namely, by adding these
materials in this order, a smooth paste having the desired
properties is formed, while adding in other orders does not produce
the desired smoothness or properties. However, it is noted the
order of addition of the remaining component compositions has no
substantial effect on the final product and, therefore, the order
of addition of these components may altered to achieve similar
results.
[0055] In each of the mixing steps, it is preferred the that mixing
be performed using a planetary mixer of the food preparation type,
such as those marketed by the Hobart company under part number
V1401. Such a mixer is preferred due to its ease of cleaning, range
of mixing speeds, and completeness of mixing. However, it is noted
that mixers of other types may be substituted to achieve similar
results.
[0056] In some embodiments, it is desirable to mill the wet mixture
after it has been initially mixed and prior to drying, and then
remixing the wet mixture to eliminate any inhomogeneities. Such an
intermediate milling step may be performed more than once, or not
at all, depending upon the consistency of the mixture.
[0057] As noted above, the resulting flux powder is non-corrosive
and non-hygroscopic, and is readily adapted for suspension within a
paste or disposition within a brazing alloy to form a wire brazing
composition.
[0058] Although the present invention has been described in
considerable detail with reference to certain preferred versions
thereof, other versions would be readily apparent to those of
ordinary skill in the art. Therefore, the spirit and scope of the
appended claims should not be limited to the description of the
preferred versions contained herein.
* * * * *