U.S. patent application number 13/295442 was filed with the patent office on 2012-03-08 for brazed aluminum laminate mold tooling.
This patent application is currently assigned to FLOODCOOLING TECHNOLOGIES, LLC. Invention is credited to Matthew T. Lowney, Anthony Nicholas Tanascu, Michael Wasylenko.
Application Number | 20120058364 13/295442 |
Document ID | / |
Family ID | 40998618 |
Filed Date | 2012-03-08 |
United States Patent
Application |
20120058364 |
Kind Code |
A1 |
Lowney; Matthew T. ; et
al. |
March 8, 2012 |
BRAZED ALUMINUM LAMINATE MOLD TOOLING
Abstract
A laminate aluminum block for forming an article includes a
series of aluminum laminate plates to collectively form a tool body
for forming an article in a forming operation. A series of aluminum
brazing layers are formed for brazing together adjacent aluminum
laminate plates. The series of aluminum laminate plates and the
series of aluminum brazing layers are deoxidized. Draining
apertures are formed through a plurality of the series of aluminum
laminate plates. The series of aluminum laminate plates are stacked
alternating with the aluminum brazing layers between adjacent
aluminum laminate plates without a flux. The stacked series of
alternating aluminum plates and aluminum brazing layers are
pressed. The stacked series of alternating aluminum plates and
aluminum brazing layers are heated in a vacuum furnace to a
temperature wherein the aluminum brazing layers braze the aluminum
laminate plates together and excess braze material drains from the
draining apertures.
Inventors: |
Lowney; Matthew T.;
(Davisburg, MI) ; Wasylenko; Michael; (Metamora,
MI) ; Tanascu; Anthony Nicholas; (Washington,
MI) |
Assignee: |
FLOODCOOLING TECHNOLOGIES,
LLC
Troy
MI
|
Family ID: |
40998618 |
Appl. No.: |
13/295442 |
Filed: |
November 14, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12393070 |
Feb 26, 2009 |
8079509 |
|
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13295442 |
|
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61031450 |
Feb 26, 2008 |
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Current U.S.
Class: |
428/654 ;
228/170; 428/156 |
Current CPC
Class: |
B23K 2101/18 20180801;
B32B 15/016 20130101; B22D 17/22 20130101; B21D 37/20 20130101;
B23K 2101/20 20180801; B23K 2103/10 20180801; B23K 3/087 20130101;
Y10T 428/24479 20150115; B23K 1/206 20130101; B23P 15/246 20130101;
Y10T 428/12764 20150115; B23K 1/008 20130101; B29C 2045/7318
20130101; Y10T 428/12736 20150115; Y10T 428/12639 20150115; B29C
33/301 20130101; B29C 45/7312 20130101 |
Class at
Publication: |
428/654 ;
228/170; 428/156 |
International
Class: |
B32B 15/01 20060101
B32B015/01; B23K 1/20 20060101 B23K001/20; B32B 3/00 20060101
B32B003/00; B23K 31/02 20060101 B23K031/02 |
Claims
1. A mold block comprising a tool body having a contoured finished
surface adapted to receive a tool insert having a forming surface
for forming a bottle neck in a molding operation, the tool body
defining an internal heat transfer channel for heat transfer with
the tool insert forming surface, wherein at least a portion of the
channel is offset generally equidistant from the finished surface
to provide a path contoured for conformal cooling of the insert,
and the tool body having a pair of ports, each port intersecting
the channel.
2. The mold block of claim 1 further comprising ribs within the
internal channel to provide structural support for the tool body
and enhance turbulent flow of a coolant through the channel.
3. The mold block of claim 1 wherein the tool body is formed from
aluminum plates.
4. A laminate aluminum mold block formed by a process comprising:
forming a series of aluminum laminate flat plates with channels to
collectively form a tool body; forming draining apertures through a
plurality of the series of aluminum laminate plates in a thickness
direction of the plates, the draining apertures being separate from
the channels; forming a series of aluminum brazing layers for
brazing together adjacent aluminum laminate plates; stacking the
series of aluminum laminate plates alternating with the aluminum
brazing layers between adjacent aluminum laminate plates; pressing
the stacked series of alternating aluminum plates and aluminum
brazing layers; heating the stacked series of alternating aluminum
plates and aluminum brazing layers to a temperature wherein the
aluminum brazing layers braze the aluminum laminate plates
together, wherein excess braze material drains out of the tool body
through the draining apertures during the heating; and forming a
finished surface in the tool body by the brazed series of aluminum
laminate plates.
5. The mold block formed by the process of claim 4, the process
further comprising forming the series of aluminum brazing layers
from aluminum foil sheets.
6. The mold block formed by the process of claim 4, the process
further comprising forming the series of aluminum laminate plates
and forming the series of aluminum brazing layers without a
flux.
7. The mold block formed by the process of claim 4, the process
further comprising deoxidizing the series of aluminum laminate
plates and the series of aluminum brazing layers prior to stacking
the series of aluminum laminate plates and the series of aluminum
brazing layers.
8. The mold block formed by the process of claim 4, the process
further comprising heating the stacked series of alternating
aluminum plates and aluminum brazing layers in a vacuum
furnace.
9. The mold block formed by the process of claim 8, the process
further comprising placing Magnesium within the furnace to minimize
oxidation of the series of alternating aluminum plates and aluminum
brazing layers during heating in the vacuum furnace.
10. The mold block formed by the process of claim 8, the process
further comprising heating at a temperature of at least 1040
degrees Fahrenheit.
11. The mold block formed by the process of claim 8, the process
further comprising heating at an atmosphere of 10-4 to 10-5
torr.
12. The mold block formed by the process of claim 4, the process
further comprising forming the series of aluminum laminate plates
with cooling channels.
13. The mold block formed by the process of claim 12, the process
further comprising piercing the aluminum brazing layers at
locations aligned with the cooling channels in the series of
aluminum laminate plates to expose the cooling channels to an
external environment during the heating of the series of aluminum
plates and the series of aluminum brazing layers.
14. The mold block formed by the process of claim 12, the process
further comprising stacking the series of aluminum laminate plates
and aluminum brazing layers upon a base plate with venting aligned
with the cooling channels so that the cooling channels are exposed
to an external environment during the heating of the series of
aluminum plates and the series of aluminum brazing layers.
15. The mold block formed by the process of claim 4, the process
further comprising applying a force to the series of alternating
aluminum plates and aluminum brazing layers during the heating of
the series of alternating aluminum plates and aluminum brazing
layers.
16. The mold block formed by the process of claim 4, the process
further comprising forming the finished surface in the brazed
series of plates for forming an article with the finished
surface.
17. The mold block formed by the process of claim 4, the process
further comprising forming the finished surface for receiving an
insert for forming an article with the insert in a forming
operation.
18. The mold block formed by the process of claim 4, the process
further comprising inserting the insert into the finished
surface.
19. A method for forming an article comprising: providing a
laminate mold block according to claim 4; and forming an article
from the mold block.
20. A method for forming a laminate aluminum mold block for forming
an article in a forming operation comprising: forming a series of
aluminum laminate flat plates with channels to collectively form a
tool body; forming draining apertures through a plurality of the
series of aluminum laminate plates in a thickness direction of the
plates, the draining apertures being separate from the channels;
forming a series of aluminum brazing layers for brazing together
adjacent aluminum laminate plates; deoxidizing the series of
aluminum laminate plates and the series of aluminum brazing layers,
by submersion in an acetone solution, an alkali solution or an acid
solution; stacking the series of aluminum laminate plates
alternating with the aluminum brazing layers between adjacent
aluminum laminate plates; pressing the stacked series of
alternating aluminum plates and aluminum brazing layers; heating
the stacked series of alternating aluminum plates and aluminum
brazing layers to a temperature wherein the aluminum brazing layers
braze the aluminum laminate plates together, wherein excess braze
material drains out of the tool body through the draining apertures
during the heating; and forming a finished surface in the tool body
by the brazed series of aluminum laminate plates.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a division of U.S. application Ser. No.
12/393,070 filed Feb. 26, 2009, now U.S. Pat. No.______, which, in
turn, claims the benefit of U.S. provisional Application No.
61/031,450 filed Feb. 26, 2008, the disclosures of which are
incorporated in their entirety by reference herein.
TECHNICAL FIELD
[0002] Various embodiments of the invention relate to methods for
brazing aluminum laminate mold tooling, and tooling formed
thereby.
BACKGROUND
[0003] Various tools are conventionally utilized for forming
articles using various forming processes, such as injection
molding, blow molding, reaction injection molding, die casting,
stamping and the like. These tools often include a core block, a
cavity block and inserts. The blocks each having opposing forming
surfaces for collectively forming an article therebetween. The
blocks are often formed separately, and one block translates
relative to the other for closing, forming the article, opening,
removing the article, and repeating these steps. Often, the blocks
are each formed from a solid block of material that is capable of
withstanding the stresses, pressures, impacts and other fatigue
associated with the forming processes.
[0004] These tool components are commonly cooled using cooling
channels below the component surface. The cooling efficiency
typically determines the quality of the molded component, and how
much time it takes to mold the part into a finished solid
manufactured part. The cooling efficiency is dependent on the
following: thermal properties of the tool material; the geometry of
the cooling channels relative to the tool surface; the amount of
cooling surface area relative to molded tool or component surface
area; thermal properties of molded material; and molding process
environment or conditions.
[0005] Typical constraints of the molding processes are the thermal
properties of molded material, molding process environment or
conditions, and, for some applications, thermal properties of the
tool or tool component material. With these constraints considered,
opportunities to improve the cooling efficiency exist with the
geometry of the cooling channels relative to the tool or tool
component surface and the amount of cooling surface area relative
to molded tool, or component, surface area. Conventional machining
and manufacturing methods are limited to how the cooling channels
can be designed into the tool, because they are formed using a
drill and must consider tool geometry. Therefore, the laminate tool
process presents great opportunity to improve cooling efficiency
because of the ability to create large surface area conformal
cooling channels, and undulations in cooling channel surface to
induce turbulent flow.
[0006] Aluminum brazing is typically performed on small surface
areas required to be brazed and components that have a high
volume/mass ratio. The most common type of aluminum brazing is
performed in a nitrogen atmosphere using a flux braze process.
Other brazing processes are fluxless vacuum brazing. Braze filler
metals for flux atmosphere brazing includes foils and/or
pastes.
SUMMARY
[0007] An embodiment discloses a method for forming a laminate
aluminum mold block for forming an article in a forming operation.
A series of aluminum laminate plates are formed to collectively
form a tool body for forming an article in a forming operation. A
series of aluminum brazing layers are formed for brazing together
adjacent aluminum laminate plates. The series of aluminum laminate
plates and the series of aluminum brazing layers are deoxidized.
The series of aluminum laminate plates are stacked alternating with
the aluminum brazing layers between adjacent aluminum laminate
plates. The stacked series of alternating aluminum plates and
aluminum brazing layers are pressed. The stacked series of
alternating aluminum plates and aluminum brazing layers are heated
to a temperature wherein the aluminum brazing layers braze the
aluminum laminate plates together.
[0008] Another embodiment discloses a method for forming a laminate
aluminum mold block for forming an article in a forming operation.
A series of aluminum laminate plates are formed to collectively
form a tool body for forming an article in a forming operation. A
series of aluminum foil sheets are formed for brazing together
adjacent aluminum laminate plates. The series of aluminum laminate
plates are stacked alternating with the aluminum foil sheets
between adjacent aluminum laminate plates without a flux. The
stacked series of alternating aluminum plates and aluminum foil
sheets are pressed. The stacked series of alternating aluminum
plates and aluminum foil sheets are heated in a vacuum furnace to a
temperature wherein the aluminum foil sheets braze the aluminum
laminate plates together.
[0009] Another embodiment discloses a method for forming a laminate
aluminum mold block for forming an article in a forming operation.
A series of aluminum laminate plates are formed to collectively
form a tool body for forming an article in a forming operation. A
series of aluminum foil sheets are formed for brazing together
adjacent aluminum laminate plates. Draining apertures are formed
through a plurality of the series of aluminum laminate plates. The
series of aluminum laminate plates are stacked alternating with the
aluminum foil sheets between adjacent aluminum laminate plates. The
stacked series of alternating aluminum plates and aluminum foil
sheets are pressed. The stacked series of alternating aluminum
plates and aluminum foil sheets are heated to a temperature wherein
the aluminum foil sheets braze the aluminum laminate plates
together and excess braze material drains from the draining
apertures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a perspective view of a tool illustrating an
embodiment of the present invention;
[0011] FIG. 2 is a top plan view of the tool of FIG. 1;
[0012] FIG. 3 is a side elevation view of the tool of FIG. 1;
[0013] FIG. 4 is an exploded perspective view of the tool of FIG.
1;
[0014] FIG. 5 is a perspective view of the tool of FIG. 1 in a
furnace fixture;
[0015] FIG. 6 is a perspective view of a tool illustrating another
embodiment of the present invention;
[0016] FIG. 7 is a perspective cross section view of a tool
illustrating another embodiment of the present invention;
[0017] FIG. 8 is an exploded perspective view of the tool of FIG.
7;
[0018] FIG. 9 is a top perspective view of the tool of FIG. 7;
[0019] FIG. 10 is a bottom perspective view of the tool of FIG.
7;
[0020] FIG. 11 is a perspective view of a braze fixture
illustrating an embodiment of the present invention;
[0021] FIG. 12 is a fragmentary perspective view of the braze
fixture of FIG. 11 illustrated in cooperation with a plurality of
the tools of FIG. 7;
[0022] FIG. 13 is another perspective view of the braze fixture of
FIG. 11 in cooperation with a plurality of the tools of FIG. 7;
[0023] FIG. 14 is a graph of time versus temperature for a braze
cycle illustrating another embodiment of the invention; and
[0024] FIG. 15 is a perspective view of another braze fixture
illustrating another embodiment of the invention.
DETAILED DESCRIPTION
[0025] As required, detailed embodiments of the present invention
are disclosed herein; however, it is to be understood that the
disclosed embodiments are merely exemplary of the invention that
may be embodied in various and alternative forms. The figures are
not necessarily to scale; some features may be exaggerated or
minimized to show details of particular components. Therefore,
specific structural and functional details disclosed herein are not
to be interpreted as limiting, but merely as a representative basis
for the claims and/or as a representative basis for teaching one
skilled in the art to variously employ the present invention.
[0026] The laminate tool process presents great opportunity to
improve cooling efficiency because of the ability to create large
surface area conformal cooling channels, undulations in cooling
channel surface to induce turbulent flow, and reduction in thermal
mass. Reduction in thermal mass can also improve the cooling
efficiency by reducing energy storage, with a drawback that the
design of the tool must still withstand the applicable structural
requirements. To utilize the laminate tool process for aluminum
tool applications, and achieve the mechanical properties required
for the molding processes, aluminum brazing of the laminated plates
is utilized.
[0027] Braze filler metals for fluxless vacuum brazing include
foils. A critical challenge in brazing aluminum is the prevention
of oxidation of the aluminum. Any form of oxidation may inhibit
brazing of the material. In the atmosphere flux brazing process,
the flux commonly contains Magnesium which is utilized to react
with any oxides that exist on the base aluminum, or that are
generated during the heating/brazing process. Some common problems
that are inherent with flux brazing is gas entrapment due to
out-gassing of the flux, potentially leaving porosity in the braze
joint. As a result, the atmosphere flux brazing is limited to small
surface areas that allow for a minimal amount of flux with minimal
resulting porosity, and also high volume/mass geometry to allow the
rapid heating and cooling of braze filler metal and flux in liquid
state to allow the flux to perform the deoxidizing function. In the
vacuum brazing process, the vacuum furnace allows for an oxygen
free environment. However, oxide formation can still occur due to
oxides being present within the base metal. Therefore, components
are deoxidized prior to vacuum brazing, and components are desired
to have a high braze surface area to mass ratio for rapid heating
and cooling to minimize any potential for oxidation of braze
surfaces.
[0028] The construction of aluminum laminated tooling presents
significant differences in braze requirements of typical aluminum
brazing applications. The laminate tooling process creates large
surface area requiring braze. For these reasons a fluxless vacuum
brazing process is provided that is specific to the laminate
tooling process.
[0029] The base material utilized in the exemplary laminated
tooling process is 6061 aluminum alloy. This alloy satisfies the
requirements of its end use. The laminate tooling process utilizes
an assembly of blanks or plates that are cut via laser, water, or
other precise methods to the specified design. With reference now
to FIGS. 1-4, a tool is illustrated and is referenced generally by
numeral 10. The tool 10 is a tool for forming an article in a
molding operation, such as in injection molding, blow molding,
reaction injection molding, roto-molding, die casting, stamping,
extruding, or the like. Alternatively, the tool 10 may be a mandrel
that is shaped similar to the article for forming a molding tool, a
die casting tool, a stamping tool, or the like, wherein the mandrel
is not employed for forming the article. Although one tool 10 is
illustrated, the invention contemplates that the tool 10 may be a
mold member, which is utilized in combination with one or more mold
members, such as an opposed mold half for forming an article
collectively therebetween. Although the item 10 is referred to as a
tool, the invention contemplates that this item may be a tool, a
tool component, or a tool insert.
[0030] The tool 10 includes a tool body 12, which has a forming
surface 14 for forming the article. The tool body 12 is formed from
a multiple layer process, for example, a laminate process, such as
that disclosed in U.S. Pat. No. 6,587,742 B2, which issued on Jul.
1, 2003 to Manuel et al.; and U.S. Pat. No. 5,031,483, which issued
on Jul. 16, 1991 to Weaver; the disclosures of which are
incorporated in their entirety by reference herein.
[0031] As illustrated, the tool body 12 is provided by a series of
aluminum laminate plates 16. As discussed in the incorporated
references, each of the laminate plates 16 may be formed
individually from a stock aluminum material by a cutting operation
that cuts each laminate plate 16 to a predetermined size such that
the series of laminate plates 16 provide a portion of the tool body
12. In one embodiment, each of the laminate plates 16 is cut by a
laser for providing a near net shape of the tool body 12 and the
forming surface 14, such that minimal machining is required once
the laminate plates 16 are assembled. After each of the laminate
plates 16 is cut, the plates 16 are stacked, aligned, and
assembled.
[0032] The tool 10 of one embodiment of the invention is a mold
block insert for molding and cooling a neck of a bottle from a blow
molding process of a polymer material. The forming surface 14
receives another insert that performs a portion of the mold cavity.
The mold cavity insert is engaged to the mold block insert 10 for
improved cooling characteristics due to conformal cooling provided
by the mold block insert 10. The laminate insert 10 is constructed
of thirteen 0.125 inch thick blanks 16. The thickness described is
an example for the depicted embodiment. Of course, various
thicknesses may be employed within the spirit and scope of the
invention. FIGS. 1-4 show the exploded and assembled views of the
laminated insert 10. The insert 10 is assembled in sequence with
braze foil placed between base metal blanks 16. In comparison to
prior art solid aluminum block inserts, the laminate aluminum mold
block insert 10 provides conformal cooling, which permits the end
user to control cooling of the neck of the bottle, thereby
enhancing quality of the bottle, improving cycle time and reducing
part failures.
[0033] The laser cut aluminum plates 16 are formed from 6061-T6
aluminum. In order for the tolerance of the braze joint to be very
high, the base metal in the T6 (hardest) condition is utilized to
minimize and prevent any distortion and/or disruption to the
surfaces being brazed during the material handling and assembly
operations of the laminate tooling process. The braze alloy used
for brazing of 6061-T6 aluminum is 4047 aluminum alloy in foil
form. The selection of braze alloy material is determined by
material flow at liquid state, melting point temperature range,
metallurgical compatibility with base alloy, mechanical properties,
and commercial availability. Braze foil thickness is determined on
the mass of the laminate tool and also the resulting duration of
the braze process. A typical thickness for the foil used in a (five
inch by eight inch maximum plan view dimension) mold block preform
shown in FIGS. 1-5 is 0.003-0.008 inches. Alternatively, the
aluminum plates 16 could be clad with a thin layer of 4047 aluminum
alloy.
[0034] The design of the laminate tool 10 allows for the
opportunity to incorporate conformal cooling channels 18 (FIG. 4)
within the tool body 12 to improve end product cooling efficiency,
to improve internal features to reduce thermal mass of the
component for the brazing process and to further improve end
product cooling efficiency, and internal features to control the
flow of the molten braze alloy and prevent erosion of the braze
joints. Additionally, drain holes 19 are provided to drain excess
braze material from the tool 10 so as to not obstruct the internal
cooling passageways. The excess braze material is also drained to
prevent collection of the molten material which may create a
weakened void or a leak in the tool 10.
[0035] When the design of the laminate tool 10 is complete, data is
generated to build the component from 0.125 inch thick blanks 16 of
6061-T6 aluminum. The blanks 16 are cut (via laser, water, or other
precise methods) to the engineered shape. The braze foil is also
cut to the same shape as the outside profile of the base metal cut
blank. After cutting of the blanks 16 is complete, all base metal
cut blanks 16 receive mechanical abrasion of their surfaces. This
allows for deburring of the blanks, and increases the amount of
braze surface area. This operation may be done by dual action
sanding of the surfaces. In order to minimize oxidization during
abrasion, the media used for this operation should not include any
form of an oxide according to at least one embodiment. Silicon
Carbide abrasives can be utilized to prevent any introduction of
oxides to the surfaces to be brazed. Utilization of a coarse grit
sanding media increases the surface area for absorbing the braze
material. The blanks 16 may require deburring, which can be
performed as a separate process, or may be accomplished by the
sanding operation.
[0036] Upon completion of mechanical abrasion, the base metal
blanks 16 and braze foil are cleaned in an acetone solution, and
dried. The next step is to rack the base metal blanks 16 and braze
foil and submerge these components into a five percent alkali
solution for one to four minutes. The alkali solution allows the
base metal blanks 16 and braze foil to be cleaned and remove any
contamination. The base metal blanks 16 and braze foil are removed
from the alkali solution and rinsed with deionized water for
neutralization. The base metal blanks 16 and braze foil are then
submerged into an eight to twelve percent acid (hydrofluoric and
nitric) solution for two to six minutes. The acid solution provides
the deoxidation of the braze surfaces.
[0037] Upon removal of the base metal blanks 16 and braze foil from
the acid, the parts are rinsed with deionized water for
neutralization and then dried with clean dry compressed air. When
drying of the base metal blanks 16 and braze foil is complete, the
assembly of the laminate tool 10 is immediately performed. The
laminate tool 10 is assembled with the blanks 16 in a horizontal
plane. A first blank 20 is provided with alignment pins 22 fixtured
to the blank 20. The remaining plates 16 have clearance holes 24 to
align the blanks 16 together and allow floating, and no
interference, of the plates 16 at braze temperature. The clearance
holes 24 may also be provided with vents or notches to prevent
build-up of braze material and for outgassing during the brazing
process.
[0038] Starting with the first base metal blank 20, a piece of
braze foil is placed between each base metal blank 16 as it is
stacked up. The holes are punched through the braze foil in the
location of the internal features of the laminate tool 10 to allow
a path to the brazing environment (or the outside of laminate tool
10). When the assembly of the laminate tool 10 is completed, the
laminate tool 10 is immediately placed into a vacuum furnace. If
the laminate tool 10 cannot be immediately placed in the vacuum
furnace, the components can be stored in an inert environment
container which is free of oxygen.
[0039] Referring now to FIG. 5, the vacuum furnace set-up can be
optimized for the brazing process of the laminate tool 10. FIG. 5
illustrates one such set-up according to an embodiment of the
invention. A drip pan can be installed to catch any excess braze
and protect the furnace. A precision ground graphite plate 26 is
installed in the drip pan to provide a flat base for the laminate
tool 10 throughout the temperature range of the brazing cycle, and
allows for flatness of the part when brazing is completed. Ceramic
plates 27 are installed on top of the graphite plate 26 to insulate
the laminate tool from the high thermal conductive graphite and
isolate radiated furnace energy to laminate tool 10.
[0040] An aluminum vent/drain plate 28 is installed on top of the
ceramic plates 27. The vent/drain plate 28 is the same profile as
the laminate tool 10, and has passages 29 located in the location
of the drain holes 19 in the laminate tool 10, and extend to the
outside of the plate 28 so the brazing environment is allowed into
the internal features of the laminate tool 10. The vent/drain plate
28 is coated with Boron Nitride to prevent brazing of this plate 28
to the laminate tool 10.
[0041] The laminate tool 10 is placed on the vent/drain plate 28. A
weight plate 30 is then installed on top of the laminate tool 10.
It also has the same profile as the laminate tool 10 and contains
clearance holes 32 for the alignment pins 22. The weight plate 30
is coated with Boron Nitride to prevent brazing of this plate 30 to
the laminate tool 10. The function of this plate 30 is to allow
even weight distribution on the laminate tool surface 10 and not on
the alignment pins 22, which protrude through the top of the part
10. The braze area of the laminate tool is approximately twenty
square inches. The weight results in a clamping load of 1.3 to 1.5
pounds per square inch (psi). In this example, the clamp load was
1.3 psi. Rather than using a weight plate, high temperature springs
can apply the clamping load. This results in less thermal mass in
the furnace so heating can be faster or more parts can be loaded
into the furnace at one time. When high temperature springs are
used, loads of up to twenty psi can be achieved which in turn
enables thinner layers of foil, such as 0.002 to 0.003 inches.
[0042] Ceramic plates 34 are installed on top of the laminate tool
10. A graphite plate 36 is installed on top of the ceramic plates
34, and a weight 38 with a calculated mass, specific for the
laminate tooling process, is placed on top of the graphite plate
36. The graphite plate 36 on top of the laminate tool 10 allows
even weight distribution across the surface of the laminate tool
10. The mass is determined using a calculation which considers
cross sectional surface area and the number of base metal blanks 16
of the laminate tool 10. The mass allows compression of the blanks
16 and maintains flatness and consistent braze joint thickness. For
the depicted embodiment, the weight 38 is twenty-five pounds.
[0043] Thermocouples are used during the brazing process that are
sheathed in an austenitic nickel-chromium-based superalloy, such as
Inconel.RTM., from Special Metals Corporation in Huntington, West
Va., USA. Each tool 10 has a passage 40 to install the thermocouple
to be in contact with the center, and/or last place to reach braze
temperature, of the laminate tool 10. Although the brazing process
occurs in high vacuum levels, the possibility of oxide is still
present due to oxides that may be existing within the base metal
and peripheral materials. To further prevent oxidation, high purity
Magnesium turnings are placed in a ceramic crucible within the
vacuum furnace hot zone. During the brazing cycle the Magnesium
heats up and reacts with any oxygen that may be present and prevent
oxidation of the aluminum. The required mass of Magnesium turnings
is dependent on the duration of the brazing cycle.
[0044] Prior to performing the aluminum brazing process in the
vacuum furnace, a vacuum furnace cycle is heated to 2000 degrees
Fahrenheit in a reducing, hydrogen, atmosphere to remove any oxides
that may be present in the furnace hot zone. The reducing vacuum
furnace cycle is performed without the aluminum laminate tool 10,
but with all braze set-up peripheral materials as previously
discussed, except the Magnesium, which is only introduced into the
furnace with the tool 10. The vacuum furnace brazing cycle also
employs specific high tolerance temperature control throughout the
brazing cycle.
[0045] With the reducing furnace cycle completed and the laminate
tool 10 braze set-up complete, the aluminum braze cycle for one
embodiment is initiated and is described as follows: the vacuum
furnace chamber is pumped down to 10-5 to 10-6 torr vacuum (this
vacuum is maintained throughout cycle); the heat is ramped to 750
degrees Fahrenheit at a rate of thirty degrees Fahrenheit per
minute until the laminate part 10 reaches 750 degrees Fahrenheit;
the heat is then ramped to 1020 degrees Fahrenheit at a rate of
thirty degrees Fahrenheit per minute until laminate part reaches
1020 degrees Fahrenheit; the temperature is held for a maximum of
ten minutes at 1020 degrees Fahrenheit; the heat is then ramped to
control thermocouple temperature of 1095 degrees Fahrenheit at a
rate of thirty degrees Fahrenheit per minute; when the laminate
part 10 temperature reaches 1095 degrees Fahrenheit, plus or minus
five degrees Fahrenheit a cooling rate is ramped at a maximum rate
permitted by the vacuum furnace to 985 degrees Fahrenheit; when
laminate part reaches 985 degrees Fahrenheit, turn off the heat and
cool at maximum rate to room temperature. Upon completion of the
furnace braze cycle, the part 10 is removed from the furnace, and
the set-up is disassembled. The vent/drain plate 28 and weight
plate 30 are then removed. The laminate tool 10 is then solution
heat treated and T6 hardening process is performed to final
material specifications.
[0046] Brazed parts 10 can be leak tested to verify success in the
brazing operation. If failures are detected, the failures can be
analyzed by X-Ray or ultrasonic testing for identifying the
failure. Repeat testing has found that prolonged exposure to the
brazing temperatures within the furnace, may result in seepage of
the brazing material away from an outer periphery of the part 10.
Referring to FIG. 2, a maximum degas distance is represented at
multiple locations labeled x, x' and x''. If the brazing material
withdraws past this maximum distance, then the braze cycle should
be modified to prevent excessive seepage. One way to reduce the
time required in the brazing operation, and therefore even out the
heat transfer, is to reduce the overall thermal mass in the
furnace. Reduction of thermal mass can be obtained by reduction in
the part 10 or in the furnace fixture.
[0047] FIG. 6 illustrates a portion of aluminum laminate tool 42
according to another embodiment. The tool 42 illustrates that
variations in cooling channels 44 and drain holes 46 can be
employed.
[0048] With reference now to FIGS. 7-10, another tool is
illustrated and is referenced generally by numeral 48. The tool 48
is a tool for forming an article in a molding operation. Although
the item 48 is referred to as a tool, the invention contemplates
that this item may be a tool, a tool component, or a tool
insert.
[0049] The tool 48 includes a tool body 50, which has a machined
surface 52 for receipt of the tool insert. As illustrated, the tool
body 50 is provided by a series of aluminum laminate plates 54.
Each of the laminate plates 54 may be formed individually from a
stock aluminum material by a cutting operation that cuts each
laminate plate 54 to a predetermined size such that the series of
laminate plates 54 provide a portion of the tool body 50. In one
embodiment, each of the laminate plates 54 is cut by a laser for
providing a near net shape of the tool body 50 and the finished
surface 52, such that minimal machining is required once the
laminate plates 54 are assembled. After each of the laminate plates
54 is cut, the plates 54 are stacked, aligned, and assembled.
[0050] The tool 48 of one embodiment of the invention is a mold
block insert for molding and cooling a neck of a bottle from a blow
molding process of a polymer material. The finished surface 52
receives another insert that performs a portion of the mold cavity.
The mold cavity insert is engaged to the mold block insert 48 for
improved cooling characteristics due to conformal cooling provided
by the mold block insert 48. The laminate insert 48 is constructed
of thirteen 0.125 inch thick blanks 54. The thickness described is
an example for the depicted embodiment. Of course, various
thicknesses may be employed within the spirit and scope of the
invention. FIGS. 7-10 show the exploded and assembled views of the
laminated insert 48. The insert 48 is assembled in sequence with
braze foil placed between base metal blanks 54. In comparison to
prior art solid aluminum block inserts, the laminate aluminum mold
block insert 48 provides conformal cooling, which permits the end
user to control cooling of the neck of the bottle, thereby
enhancing quality of the bottle, improving cycle time and reducing
part failures.
[0051] The laser cut aluminum plates 54 are formed from 6061-T6
aluminum. In order for the tolerance of the braze joint to be very
high, the base metal in the T6 (hardest) condition is utilized to
minimize and prevent any distortion and/or disruption to the
surfaces being brazed during the material handling and assembly
operations of the laminate tooling process. The braze alloy used
for brazing of 6061-T6 aluminum is 4047 aluminum alloy in foil
form. The selection of braze alloy material is determined by
material flow at liquid state, melting point temperature range,
metallurgical compatibility with base alloy, mechanical properties,
and commercial availability. Braze foil thickness, (0.003-0.010
inches for this example), is determined on the mass of the laminate
tool and also the resulting duration of the braze process.
Minimizing braze foil thickness reduces excess braze material, and
minimizes resulting braze joint thickness for enhanced mechanical
integrity.
[0052] The design of the laminate tool 48 allows for the
opportunity to incorporate conformal cooling channels 56 (FIGS. 7
and 8) within the tool body 50 to improve end product cooling
efficiency, to improve internal features to reduce thermal mass of
the component for the brazing process and to further improve end
product cooling efficiency, and internal features to control the
flow of the molten braze alloy and prevent erosion of the braze
joints. The cooling channels 56 may be formed with projections 57
and structural ribs 59 for causing turbulence within the flow of
coolant in the channel 56. Further, the ribs 59 enhance the
strength of the channels 56 and the tool 48. Additionally, mass
reduction holes 58 are provided to reduce mass, reduce thermal
mass, and drain excess braze material from the tool 48.
[0053] When the design of the laminate tool 48 is complete, data is
generated to build the component from 0.125 inch thick blanks 54 of
6061-T6 aluminum. The thickness of the blanks 54 is not limited to
0.125 inch thickness. Blank 54 thickness is driven by the design
factors for a particular application and an ability to achieve near
net shape of the cooling channels 56, when applicable. The blanks
54 are cut (via laser, water, or other precise methods) to the
engineered shape. During the cutting of the blanks 54, the number
of each blank 54 may be etched into a surface of the blank 54 to
assist in assembling the blanks 54 in the correct order. The braze
foil is also cut to the same shape as the outside profile of the
base metal cut blank.
[0054] After cutting of the blanks 54 is complete, all base metal
cut blanks 54 receive mechanical abrasion of their surfaces. This
allows for deburring of the blanks, and increases the amount of
braze surface area. This operation is done by dual action sanding
of the surfaces. In order to minimize oxidization during abrasion,
the media used for this operation should not include any form of an
oxide according to at least one embodiment. Silicon Carbide
abrasives can be utilized to prevent any introduction of oxides to
the surfaces to be brazed.
[0055] Upon completion of mechanical abrasion, the base metal
blanks 54 and braze foil are cleaned in an acetone solution, and
dried. The next step is to rack the base metal blanks 54 and braze
foil and submerge these components into a five percent alkali
solution, which is at a temperature of 130 degrees Fahrenheit, for
four to six minutes. The alkali solution allows the base metal
blanks 54 and braze foil to be cleaned and remove any
contamination. The base metal blanks 54 and braze foil are removed
from the alkali solution and rinsed with deionized water for
neutralization. The base metal blanks 54 and braze foil are then
submerged into an ten to twelve percent acid (hydrofluoric and
nitric) solution for four to six minutes. The acid solution
provides the deoxidation of the braze surfaces.
[0056] Upon removal of the base metal blanks 54 and braze foil from
the acid, the parts are rinsed with deionized water for
neutralization and then dried with clean dry air. Optimum drying
conditions can be performed in a recirculating air oven at a
temperature of 300 degrees Fahrenheit to reduce moisture. When
drying of the base metal blanks 54 and braze foil is complete, the
assembly of the laminate tool 48 can be immediately performed. If
assembly of the laminate component 48 is not immediately performed,
the components 48 are stored in containers to minimize exposure to
the air for minimizing oxidation of the prepared components.
[0057] The laminate tool 48 is assembled with the blanks 54 in a
horizontal plane as in FIG. 8. The assembly of the components 48
may be performed in a dust free area. Manual handling of the blanks
48 and foil may be performed with rubber gloves to minimize
contamination introduced on any of the brazing surfaces of the
components 48.
[0058] Beginning with a first base metal blank 60 placed upon a
work surface, a piece of braze foil 62 is placed between each base
metal blank 54 as it is stacked up. During the assembly of the
laminate component, the braze foil 62 is pierced at piercings 64,
(or punched out in relief at apertures 66 shown in phantom), in the
location of the internal features of the laminate tool 48. The
piercings 64 minimize, and may potentially eliminate, excess braze
material. The piercings 64 prevent trapped air in the assembled
component 48, thereby eliminating an opportunity for the braze
material to blowout during phase change to liquidus state. The
piercings 64 also allow all internal features of the component 48
to be in equilibrium with the brazing environment or atmosphere.
When the assembly of the laminate component 48 is completed as
illustrated in FIGS. 9 and 10, the laminate component 48 is ready
to be installed onto a brazing fixture and then immediately placed
into a vacuum furnace. If the laminate component 48 cannot be
immediately placed in the vacuum furnace, the components 48 can be
stored in an inert environment container which is free of
oxygen.
[0059] Referring now to FIG. 11, a brazing fixture 68 may be
employed for the laminate tooling 48, or component, aluminum
brazing process. The brazing fixture 68 is designed and built with
materials that have excellent high strength properties and at high
temperatures, utilizes a low mass design to prevent a heat sink
effect yet providing structural strength, and provides a system to
apply distributed forces to the brazed components 48 for
compression throughout the braze cycle while maintaining a fixed
position of the component 48 on the fixture 68.
[0060] The braze fixture 68 includes a base 70, a frame 72, and a
top 74. The base 70 is manufactured from an austenitic
nickel-chromium-based superalloy sheet, such as Inconel.RTM. 750X
sheet, from Special Metals Corporation in Huntington, West Va.,
USA. The sheet is welded yielding a honeycomb construction. The
base 70 is then solution heat treated, age hardened, and top and
bottom surfaces machined parallel. Gussets 71 are manufactured from
304 stainless steel, and are welded to the bottom of the base 70
creating an X-brace and perimeter frame for additional structural
strength. The base 70 is then stress relieved at a temperature
below the age hardening temperature of the sheet material, so the
required properties of the sheet material are not affected. The top
and bottom of the base 70 are then precision ground on top and
bottom to provide flat and parallel surfaces.
[0061] The frame 72 of the fixture 68 is manufactured from 304
stainless steel sheet that has been formed to create angles and
structure for optimal strength. The components of the frame 72 are
welded together then stress relieved. The frame 72 is then fastened
to the fixture base 70 utilizing high strength stainless steel
fasteners. The top 74 of the fixture 68 is manufactured from 304
stainless steel sheet that has been formed into u-shaped channels
76 for structural strength. Tabs 78 are welded on each end of the
u-channels 76 to create a hook. The components of the top 74 are
stress relieved. Several of the u-channels 76 are used to create
the top 74 of fixture 68, and hook on to the frame 72 of the
fixture 68 to maintain position.
[0062] As discussed above, reduction in mass results in reduction
of thermal mass, thereby providing a reduction in throughput of the
vacuum furnace. Referring now to FIGS. 12 and 13, additional mass
can be reduced by utilizing high temperature alloy springs, such as
ribbon springs 80 manufactured from an austenitic
nickel-chromium-based superalloy sheet, such as Inconel.RTM. 750X
sheet. The ribbon springs 80 generate a force to be applied to the
laminate component 48, instead of applying a weight as in the
previous embodiment. The ribbon springs 80 are manufactured from
0.060 inch thick sheet stock and are formed to a specific shape,
then solution heat treated and age hardened to maximize mechanical
properties and high temperature strength. The ribbon springs 80
maintain their strength and applied force during brazing because
the brazing temperatures for aluminum are well below the heat
treatment temperatures that would affect the properties of the
material. Although ribbon springs 80 are illustrated and described,
various spring types may be employed such as coil springs or the
like to design to a fixture size and load rate for a specific
brazing application.
[0063] The ribbon springs 80 provide a force of approximately
thirty-five pounds per square inch of the laminated component 48.
In order to prevent the ribbon springs 80 from providing point
loads upon the laminate component 48, additional supports are
employed to distribute the force uniformly over the surface of the
laminate component 48. As a result load u-channels 82 manufactured
from 304 stainless steel are used, typically 0.7-1.5 inches wide by
0.5 inches tall by desired length. The load u-channels 82 are
placed on top of the part 48 with edges facing down. The ribbon
springs 80 are placed between the top 74 of the braze fixture 68
and the load u-channels 82 on top of the part 48.
[0064] The set-up of the laminate components 48 to be brazed, on
the brazing fixture 68 can be optimized for the brazing process.
Dependent on the size of laminate component 48, multiple components
48 can be set-up on the fixture 68 for a single furnace run. To
determine the layout of multiple components 48, a minimum of 1.5
inches spacing can be maintained between components 48. The
following describes a method, for example, for preparing each
laminate component 48 for brazing on the braze fixture 68. A
rectangular 0.060 inch thick 304 stainless steel sheet base plate
84 is provided 0.25 inch wider than the profile of the component 48
to be brazed. The base plate 84 is placed on the base 70 of the
fixture 68 in the determined location. The base plate 84 has been
stress relieved, painted with Magnesium Hydroxide, and dried before
being used in the set-up. The base plate 84 provides a flat surface
for the laminate component 48 and load distribution to the
honeycomb base 70.
[0065] An aluminum vent/drain plate 86 is installed on top of the
base plate 84. The vent/drain plate 86 is the same profile as the
laminate component 48, and has passages 88 located in the location
of the drain holes 58 in the laminate component 48 and to the
outside of the vent plate 86 so the brazing environment/atmosphere
is allowed into the internal features of the laminate component 48.
The vent/drain plate 86 is painted with Magnesium Hydroxide to
prevent brazing of this plate 86 to the laminate component 48. The
laminate component 48 is placed on the vent/drain plate 86. Another
base plate 84 is then installed on top of the laminate component
48. The base plate 90 in this location, provides a flat surface for
load distribution on the laminate component 48 surface.
[0066] The load u-channels 82 are placed with the edges on top of
the base plate 90 so that the u-channels 82 cover the entire
surface of the laminate component 48 and extend just beyond the
component 48 in length. A minimum force is determined using a
calculation which considers cross-sectional surface area and the
number of base metal blanks 84 of the laminate component 48. The
force allows compression of the blanks 54, maintaining flatness,
constraining the location of the laminate component 48 on the
fixture 68, and consistent braze joint thickness. The ribbon
springs 80 are installed between the load u-channels 82 and the top
74 of the braze fixture 68. The ribbon springs 80 are compressed to
install into the braze fixture 68, and total force is determined by
the measurable pre-load of the spring 80 multiplied by the spring
rate multiplied by the total number of springs 80 per laminate
component 48. This total force is designed to be greater than or
equal to the calculated force required during the brazing
operation.
[0067] Load thermocouples are used during the brazing process that
are sheathed in an austenitic nickel-chromium-based superalloy,
such as Inconel.RTM., from Special Metals Corporation in
Huntington, West Va., USA. A minimum of two load thermocouples are
used and the first is installed in the laminate component 48
closest to center of the fixture 68, and a second in another
laminate component 48 on a peripheral region of the fixture 68.
Although the brazing process occurs in high vacuum levels, the
possibility of oxide is still present due to oxides or oxide
bearing medium that may be existing within the base metal and
peripheral materials. To further prevent oxidation of the aluminum
laminate component 48, high purity Magnesium turnings are placed on
top of the braze fixture 68. During the brazing cycle the Magnesium
vaporizes in the brazing environment then allowing reaction with
any oxygen that may be present and prevent or reduce oxidation of
the aluminum. The required mass of Magnesium turnings is dependent
on the braze furnace volume and duration of the brazing cycle.
[0068] Once all the laminate components 48 are installed on the
braze fixture 68 as discussed, the loaded braze fixture 68 can be
installed on a furnace load cart. When loading the braze fixture 68
on the furnace load cart, the braze fixture 68 can be installed on
a plurality of support cross bars 92. A small amount of Magnesium
turnings is also placed into each of the support cross bars 92. The
loaded braze fixture 68 is subsequently installed in the vacuum
furnace.
[0069] The vacuum furnace used for the aluminum brazing process of
the laminate tooling 48, or components, may be designed
specifically for aluminum brazing. Typically aluminum brazing
vacuum furnaces possess the following functionality: a nickel
chrome based hot zone which can endure the thermal stress of
backfilling and opening at brazing temperatures at approximately
1100 degrees Fahrenheit; a recirculation cooling system for the
chamber to allow and maintain an elevated temperature of
approximately 140 degrees Fahrenheit; an oversized vacuum system
achieving 10-4-10-5 torr; high tolerance temperature control of
plus or minus five degrees Fahrenheit through a 1000-1200 degrees
Fahrenheit range; while satisfying AMS 2750 standard.
[0070] Prior to performing the aluminum brazing process in the
vacuum furnace, a vacuum furnace pre-heat cycle is performed
heating the chamber to 1000 degrees Fahrenheit at a pressure less
than 10-4 torr. The furnace chamber water temperature may be
increased between 100 and 130 degrees Fahrenheit so that relative
humidity is decreased to reduce or prevent moisture in the furnace.
The furnace chamber water temperature can be increased during the
furnace pre-heat cycle.
[0071] With the furnace pre-heat cycle complete and the braze
fixture set-up complete, the aluminum braze cycle, is initiated as
illustrated in FIG. 14 with the temperatures of the furnace, and
the load thermocouples TC1, TC2 graphed versus time. The vacuum
furnace chamber is backfilled with nitrogen. Then, the furnace door
is opened and the braze fixture 68 is loaded in the furnace. The
furnace door is closed, and the furnace chamber is pumped down to
100 .mu.m. Then the chamber is backfilled with nitrogen to a ten
inch vacuum, which is repeated three times. Next the chamber is
pumped down to less than 10-4 torr. Subsequently the furnace
temperature is ramped to 300 degrees Fahrenheit and maintained for
one minute. The furnace temperature is then ramped to 1040 degrees
Fahrenheit plus or minus five degrees Fahrenheit at a rate of
twenty degrees Fahrenheit per minute. This temperature is
maintained until the load thermocouples reach 1040 degrees
Fahrenheit plus or minus five degrees Fahrenheit. The furnace
temperature is then ramped to 1100 degrees Fahrenheit at a rate of
twenty degrees Fahrenheit per minute until the load thermocouples
reaches 1080 degrees Fahrenheit plus or minus five degrees
Fahrenheit. The heat is disabled and the chamber is backfilled with
nitrogen until the furnace door is opened. The load thermocouples
are removed and the braze fixture 68 is removed from the furnace.
The furnace door is closed, and the brazed laminate components 48
are air cooled in the braze fixture 68 under load until the
component temperature is less than 500 degrees Fahrenheit. While
cooling to room temperature, when the laminate parts 48 reaches 985
degrees Fahrenheit, the heat can be turned off for cooling at
maximum rate to room temperature. The braze fixture is disassembled
and the brazed laminate components 48 are removed.
[0072] Additional heat treatment of the brazed laminate components
48 may be employed, depending on the final material specifications.
Solution heat treatment of the 6061 laminate components 48 may be
utilized, and a standard water quench process can be used to
achieve the T4 condition of the 6061 aluminum. The 6061 laminate
components 48 may then be age hardened to a T6 condition.
[0073] Of course various brazing fixture variations may be employed
under the spirit and scope of the invention. The varying geometries
of tools may result in various configurations of the brazing
fixture. Referring now to FIG. 15, a brazing fixture 94 is
illustrated for fixturing another laminate tool 96. The laminate
tool 96 depicted utilizes more plates 98 than previous embodiments
resulting in a larger height to width ratio and a larger height to
depth ratio. The fixture 94 includes a lower platen 100 formed from
304 stainless steel. The laminate tool is placed upon the lower
platen. A plurality of threaded rods 102 are fastened to the lower
platen 100 about the perimeter of the laminate tool 96 and extend
above the height of the laminate tool 96. The threaded rods 102 may
also be formed from 304 stainless steel. An upper platen 104 is
placed upon the laminate tool 96 in sliding engagement with the
threaded rods 102. The upper platen 104 is also formed from
stainless steel. A plurality of coil springs 106 are each placed
about one of the threaded rods 102 in engagement with the upper
platen 104. The coil springs 106 are each formed from a high
temperature alloy such as Inconel.RTM. 750X.
[0074] A stainless steel tube 108 is placed about each spring 106.
The tubes 108 may each provided at a length that is less than the
overall spring 106 length and that is equivalent to the designed
load per spring 106 rate. Subsequently, a nut 110 and washer 112
(both may also be formed from stainless steel) are placed upon each
threaded rod 102. The nuts 110 are tightened until the washers 112
engage the tubes 108, thereby compressing the springs 106 to
collectively provide the desired load to the laminate tool 96.
[0075] The management, and/or minimization, of braze alloy flow
during brazing process, for large braze surface areas, via design
of internal passages, thermal mass, geometry, and vent/drain plate
prevents erosion of base metal due to control of braze alloy flow
in liquid state. As a result, porosity free braze joints and
superior braze joint quality are obtained. Therefore, the process
allows the manufacturing of conformal cooling channels (pressure
vessels) required for the described tooling.
[0076] Optimization of laminate component 48 cooling efficiency by
conformal cooling with undulations in conformal cooling channels
induces turbulent cooling flow, with a reduction in thermal mass
resulting in reduced energy storage.
[0077] An aluminum braze fixture with low thermal mass
minimizes/prevents heat sink with brazed components, maintains high
temperature strength to ensure flatness of parts and uniform
distribution of forces.
[0078] Engineered weight distribution on the laminate tool 48
throughout the braze process generates uniform braze joint
thickness and maintains flatness, resulting in uniform mechanical
and thermal properties.
[0079] The utilization of the mechanical and chemical cleaning
process to deoxidize the base metal and the braze alloy enhances
brazability of required surfaces.
[0080] The utilization of Magnesium turnings prevents oxide
formation on brazed surfaces during the vacuum furnace brazing
cycle.
[0081] The aluminum brazed laminate tool provides mechanical
properties near or equivalent to that of the base metal.
[0082] While embodiments of the invention have been illustrated and
described, it is not intended that these embodiments illustrate and
describe all possible forms of the invention. Rather, the words
used in the specification are words of description rather than
limitation, and it is understood that various changes may be made
without departing from the spirit and scope of the invention.
* * * * *