U.S. patent application number 09/683185 was filed with the patent office on 2003-05-29 for method and apparatus for heat treating material.
This patent application is currently assigned to United Technologies Corporation. Invention is credited to Rabinovich, Albert, Ward, William J. JR..
Application Number | 20030098106 09/683185 |
Document ID | / |
Family ID | 24742903 |
Filed Date | 2003-05-29 |
United States Patent
Application |
20030098106 |
Kind Code |
A1 |
Rabinovich, Albert ; et
al. |
May 29, 2003 |
Method and apparatus for heat treating material
Abstract
A method and apparatus for quenching a material. The apparatus
includes a support for receiving the material; and an outlet
adjacent the support for impinging a fluid against a first section
of the material. The apparatus increases a cooling rate of the
first section relative to a cooling rate of a second section of the
material, preferably minimizing a differential between the cooling
rate of the first section and the cooling rate of the second
section.
Inventors: |
Rabinovich, Albert; (West
Hartford, CT) ; Ward, William J. JR.; (Marlborough,
CT) |
Correspondence
Address: |
PRATT & WHITNEY
400 MAIN STREET
MAIL STOP: 132-13
EAST HARTFORD
CT
06108
US
|
Assignee: |
United Technologies
Corporation
Hartford
CT
|
Family ID: |
24742903 |
Appl. No.: |
09/683185 |
Filed: |
November 29, 2001 |
Current U.S.
Class: |
148/712 ;
266/134 |
Current CPC
Class: |
C21D 9/0068 20130101;
C21D 1/667 20130101; C22F 1/10 20130101; C21D 2221/00 20130101 |
Class at
Publication: |
148/712 ;
266/134 |
International
Class: |
C21D 001/667 |
Claims
1. A method of quenching a material, comprising the steps of:
providing a material having a first section and a second section;
and propelling a fluid against said first section to increase a
cooling rate of said first section relative to a cooling rate of
said second section.
2. The method as recited in claim 1, wherein said fluid comprises a
gas.
3. The method as recited in claim 1, wherein said propelling step
generally minimizes a gradient between a temperature of said first
section and a temperature of said second section.
4. The method as recited in claim 1, wherein the propelling step
comprises impinging said fluid against said first section to
provide impingement cooling at said first section.
5. The method as recited in claim 1, wherein the propelling step
remains constant during quenching.
6. The method as recited in claim 1, wherein the propelling step
varies during quenching.
7. The method as recited in claim 6, wherein the propelling step
varies by adjusting a pressure of said fluid.
8. A method of adjusting the cooling rate of a forging during
quenching, comprising the steps of: providing a forging having a
first section with a first cooling rate and a second section having
a second cooling rate; and propelling a fluid against said first
section in order to minimize a differential between said first
cooling rate and said second cooling rate.
9. The method as recited in claim 8, wherein said fluid is a
gas.
10. The method as recited in claim 8, wherein said propelling step
generally minimizes a gradient between a temperature of said first
section and a temperature of said second section.
11. The method as recited in claim 8, wherein the propelling step
comprises impinging said fluid against said first section to
provide impingement cooling at said first section.
12. The method as recited in claim 8, wherein the propelling step
remains constant during quenching.
13. The method as recited in claim 8, wherein the propelling step
varies during quenching.
14. The method as recited in claim 13, wherein the propelling step
varies by adjusting a pressure of said fluid.
15. An apparatus for quenching a material, the material having a
first section and a second section, said apparatus comprising: a
support for receiving the material; and an outlet adjacent said
support for impinging a fluid against the first section of the
material, so that a cooling rate of the first section increases
relative to a cooling rate of the second section.
16. The apparatus as recited in claim 15, wherein said outlet has a
diameter (d) and is positioned a distance (Z) from the material
placed in said support, and Z/d is between approximately 1.0 and
6.0.
17. The apparatus as recited in claim 15, wherein said outlet
comprises a plurality of outlets each having a diameter (d),
adjacent outlets having a spacing (s) therebetween, and s/d is less
than approximately 26.0.
18. The apparatus as recited in claim 17, wherein said spacing is a
circumferential spacing (X) and X/d is less than approximately
26.0.
19. The apparatus as recited in claim 17, wherein said spacing is a
radial spacing (Y) and Y/d is less than approximately 24.0.
20. The apparatus as recited in claim 15, wherein said outlet
comprises a plurality of outlets in an annular pipe.
Description
BACKGROUND OF INVENTION
[0001] This invention relates to a method and an apparatus for heat
treating a material. Specifically, the present invention relates to
a method and apparatus for fluid impingement quenching a
forging.
[0002] Conventional quenching techniques include bath quenching and
fan quenching.
[0003] The bath quenching process immerses a forging within a
container of oil. The oil acts as a heat sink to cool the forging.
The process typically agitates the oil to increase the rate of heat
transfer.
[0004] The oil bath quenching process has numerous drawbacks. The
first drawback relates to the handling of the oil. Oil handling
must follow specific procedures for environmental and safety
concerns.
[0005] The second drawback relates to the waste stream. The used
oil must enter the waste stream properly. Environmental and safety
concerns demand the proper entry of the used oil into the waste
stream.
[0006] The third drawback relates to predictability. Oil bath
quenching is not a fully controllable process. For instance, the
oil bath quenching process lacks the ability to control local heat
transfer rates precisely. Generally speaking, oil bath quenching
produces an arbitrary heat transfer coefficient of between
approximately 70 and 140 BTU/hr ft.sup.2 .degree. F. uniformly
across the forging.
[0007] The final drawback relates to residual stress. Oil bath
quenching tends to produce high residual stress values due to the
arbitrary heat transfer coefficient. Such values can produce
cracking and distortion of the forging.
[0008] The second conventional quenching technique is fan
quenching. The fan quenching process uses forced convection to cool
a forging. One or more fans propel air against the forging to
increase the rate of heat transfer. While avoiding the
environmental issues encountered with oil bath quenching, the fan
quenching process does have several drawbacks. Notably, the fan
quenching process may not create the heat transfer rates needed to
produce the desired material properties in high temperature
aerospace alloy forgings. Second, the fan quenching process also
lacks the ability to control the heat transfer rates locally at
various locations on the forging.
[0009] New high temperature aerospace alloys have placed greater
demands on the quenching process. These new alloys require a high
lower limit of the cooling rate during quenching to achieve
metallurgical requirements (e.g. tensile strength). As a result,
fan quenching is no longer an option for these new high temperature
aerospace alloys.
[0010] These new high temperature aerospace alloys also demand that
the quenching process control the upper limit of the cooling rate
so as to avoid the formation of cracks in the forging. As a result,
oil bath quenching is no longer an option for these new high
temperature aerospace alloys.
[0011] In other words, the quenching process must remain within a
limited range of cooling rate values to produce the desired
material qualities in the forging. Unfortunately, conventional
quenching techniques do not appear to achieve these goals
satisfactorily for certain applications, such as these new high
temperature aerospace alloys.
SUMMARY OF INVENTION
[0012] It is an object of the present invention to provide an
improved quenching method and apparatus.
[0013] It is a further object of the present invention to provide a
quenching technique that reduces environmental concerns.
[0014] It is a further object of the present invention to provide a
quenching technique that produces less scrap during quenching
caused by cracking and distortion.
[0015] It is a further object of the present invention to provide a
quenching technique that produces less scrap during subsequent
manufacturing operations caused by residual stress effects.
[0016] It is a further object of the present invention to provide a
quenching technique that consumes less raw material.
[0017] It is a further object of the present invention to provide a
quenching technique that is controllable.
[0018] It is a further object of the present invention to provide a
quenching technique that can keep cooling rate values within a
limited range.
[0019] These and other objects of the present invention are
achieved in one aspect by a method of quenching a material,
comprising the steps of: providing a material having a first
section and a second section; and propelling a fluid against the
first section to increase the cooling rate of the first section
relative to a cooling rate of the second section.
[0020] These and other objects of the present invention are
achieved in another aspect by a method of adjusting the cooling
rate of a forging during quenching, comprising the steps of:
providing a forging having a first section with a first cooling
rate and a second section having a second cooling rate; and
propelling a fluid against the first section in order to minimize a
differential between the first cooling rate and the second cooling
rate.
[0021] These and other objects of the present invention are
achieved in another aspect by an apparatus for quenching a
material, comprising: a support for receiving the material; and an
outlet adjacent the support for impinging a fluid against a first
section of the material, so that a cooling rate of the first
section increases relative to a cooling rate of a second section of
the material.
BRIEF DESCRIPTION OF DRAWINGS
[0022] Other uses and advantages of the present invention will
become apparent to those skilled in the art upon reference to the
specification and the drawings, in which:
[0023] FIG. 1 is an exploded, perspective view of one embodiment of
the quenching apparatus of the present invention;
[0024] FIG. 2 is a cross-sectional view of the quenching apparatus
taken along line 11-11 in FIG. 1;
[0025] FIG. 3 is a plan view of one component of the quenching
apparatus shown in FIG. 1;
[0026] FIG. 4 is a detailed view of a portion of the component
shown in FIG. 3;
[0027] FIG. 5 is a cross-sectional view of the component taken
along line V-V in FIG. 4;
[0028] FIG. 6 is an elevational view of a second component of the
quenching apparatus shown in FIG. 1; and
[0029] FIG. 7 is an elevational view of a section of the quenching
apparatus shown in FIG. 1 with a forging placed therein.
DETAILED DESCRIPTION
[0030] FIG. 1 displays an exploded perspective view of one
embodiment of a quenching apparatus 100. The quenching apparatus
100 can receive an annular forging F (only partially shown in the
figure), such as a turbine disk or an air seal. Although
accommodating an annular shape, the apparatus could heat treat any
shape of forging F.
[0031] Similarly, the apparatus 100 could quench a forging made
from any material. The preferred material, however, is a high
temperature aerospace alloy. Generally speaking, such material must
have adequate performance characteristics, such as tensile
strength, creep resistance, oxidation resistance, and corrosion
resistance, at high temperatures. Course grained nickel alloys are
especially prone to quench cracking due to a ductility trough at
the upper temperatures (e.g. 1800-2100.degree. F.) of the quenching
process. Examples of high temperature aerospace materials include
nickel alloys such as IN100, IN1100, IN718, Waspaloy and IN625.
[0032] To achieve these characteristics, the aforementioned alloys
demand precise control of the quenching process. Precise control is
necessary to avoid cracking of the forging during quenching and to
avoid residual stress effects during subsequent manufacturing
operations on the forging. Typically, most forgings that exhibit
cracks during quenching are considered scrap.
[0033] The quenching apparatus 100 preferably can provide
impingement cooling to all surfaces of the forging F. The apparatus
100 includes a first cooling section 101, a second cooling section
103 and a central cooling section 105. Each section will now be
described in further detail.
[0034] FIG. 3 displays the first cooling section 101. The first
cooling section 101 preferably corresponds to a bottom of the
forging F. The first cooling section 101 includes one or more
supports 107 arranged around the apparatus 100. Although the figure
displays three, the present invention could use any suitable number
of supports 107.
[0035] The supports 107 have recesses in which a plurality of
concentric pipes 109 can reside. Although the figures show five,
the present invention could utilize any number of pipes 109. The
number of pipes 109 depends upon the geometry of the forging F. A
larger forging F requires more pipes 109.
[0036] A plurality of spacers 111 secure to the supports 107 with
conventional fasteners. The spacers 111 serve to retain the pipes
109 to the supports 107. Although the figures show each spacer 111
retaining multiple pipes 109, the spacer 111 could retain only one
pipe. This would allow the individual adjustment of pipes 109
without disturbing the other pipes 109. Another important function
of the spacers will be discussed below.
[0037] As seen in FIG. 2, the top of the forging F could have a
different shape than the bottom of the forging F. Accordingly, the
second cooling section 103 may not mirror the shape of the first
cooling section 101. Rather, the second cooling section 103
preferably conforms to the top of the forging F.
[0038] Similar to the first cooling section 101, the second cooling
section 103 includes one or more supports 115, concentric pipes 117
and spacers 119. When fastened to the supports 115, the spacers 119
secure the pipes 117 to the supports 115. The supports 107,115 and
the spacers 111,119 could be made from any material suitable to the
demands of the quenching process.
[0039] For versatility, the apparatus 100 should accommodates
forgings F of various shapes. For every forging F, the cooling
sections 101, 103 should generally conform to the specific shape.
This could be accomplished with conventional techniques. For
example, the apparatus could utilize supports 107, 115 specific to
each forging shape.
[0040] Alternatively, the same supports 107, 115 could be used for
every forging F. To accommodate different shapes, the universal
supports should include features (not shown) to allow selective
positioning of each of the pipes 109, 117. In one possible
arrangement, the universal supports could have height adjustable
platforms upon which the pipes 109, 117 rest. The platforms could
use a threaded shaft to adjust height.
[0041] In addition, either of the supports 107, 115 could be sized
and shaped to allow an outermost pipe 109,117 to surround the outer
diameter of the forging F. This arrangement allows the apparatus
100 to quench the outer diameter of the forging F. Not all forgings
F, however, require quenching at the outer diameter. As an example,
forgings F with thin sections at the outer diameter typically do
not require quenching.
[0042] FIGS. 4 and 5 display one of the pipes 109. The pipe 109 is
annular to provide axisymmetric cooling to the annular forging F.
The tubes 113 can be made from any suitable material, such as
tooling steel (e.g. AMS5042, AMS5062, AIS14340), stainless steel
(AISI310, AISI316, 17-4HP), copper and brass. As an example, the
pipes 109 could have an inner diameter of between approximately
0.7" and 1.3" and have a suitable thickness. The specific values
will depend upon the demands of the quenching process.
[0043] The pipes 109,117 each have an inlet (not shown) attached to
a fluid source 127 using conventional techniques. The source 127
could use conventional valves (not shown) to control fluid flow to
each pipe 109,117. The valves could either be manually or
computer-controlled. The benefits of having such control will
become clear below.
[0044] The pipes 109,117 have an arrangement of openings 131
therein. Preferably, the openings are regularly arranged around the
pipes 109,117 to provide axisymmetric cooling to the forging F.
However, non-symmetric arrangements are possible. As seen in FIG.
5, The openings 131 span an angle .alpha. of between approximately
25.degree. and 270.degree. of the circumference of the pipe
109,117. Preferably, the angle .alpha. is approximately
90.degree..
[0045] The openings 131 in the pipes 109,117 define outlet nozzles
for the fluid to exit the cooling sections 101,103. The fluid
propels from the openings 131 to cool the forging F. The openings
131 could have either sharp edges or smooth edges in order to
provide a desired nozzle configuration. Specific geometric aspects
of the openings 131 will be discussed in detail below.
[0046] FIG. 6 displays the central cooling section 105. The central
cooling section 105 preferably resides within the inner bore of the
forging F. As with the outer diameter, the inner diameter of the
forging F may not require quenching. Forgings F with thin sections
at the inner diameter typically do not require quenching.
[0047] Similar to the pipes 109,117, the central cooling section
105 is a pipe that includes an inlet 133 attached to the fluid
source 127 using conventional techniques. The central cooling
section 105 also includes a plurality of openings 135 at an outlet
end. The size and shape of the central cooling section 105 depends
upon the geometry of the forging F.
[0048] Assembly of the apparatus 100 proceeds as follows. The
assembled first cooling section 101 receives the forging F.
Specifically, the forging F rests on the spacers 111.
[0049] Then, the second cooling section 103 is placed over the
forging F. Likewise, the spacers 111 rest on the forging F. Next,
the central cooling section 105 is placed inside the central bore
of the annular forging F. The central cooling section 105
preferably rests on the supports 107 of the first cooling section
101, and is spaced from the forging F by abutting the distal ends
of the spacers 111. Other arrangements, however, are possible. The
apparatus 100 is now ready to begin the quenching operation. The
apparatus could utilize any suitable fluid, such as a gas, to
quench the F. Preferably, the present invention uses air. The
source 127 could have a diameter of between approximately 2.5" and
3.5". The source 127 could also supply approximately 12 lb/sec of
ambient (e.g. 65-95.degree. F.) air to the apparatus 100 at a
pressure of between approximately 45 and 75 psig. Again, the
specific values will depend upon the demands of the quenching
process.
[0050] Generally speaking, one goal of the present invention is to
control the cooling rate of the forging F precisely. This precise
control allows the use of impingement cooling on the forging F.
Impingement cooling is a subset of forced convection cooling that
produces significantly higher heat transfer coefficients than the
remainder of the forced convection regime. For example,
conventional forced air convection can achieve heat transfer
coefficients of approximately 50 BTU/hr ft.sup.2 .degree. F. with
typical equipment. Impingement cooling, on the other hand, can
achieve heat transfer coefficients up to approximately 300 BTU/hr
ft.sup.2 .degree. F.
[0051] FIG. 7 provides the spatial relationship between the pipes
109,117 and the forging F. Although displaying the first and second
cooling sections 101,103, the spatial relationships shown in this
figure are also applicable to the central cooling section 105. As
seen in the figure, the spacers 111 provide a gap between the
forging F and the pipes 109,117.
[0052] The openings 131 in the pipe preferably have a diameter d
adequate to propel a sufficient amount of fluid against the forging
F to perform the quenching process. As an example, the diameter d
of the openings 131 could be between approximately 0.55" and 0.75".
At this diameter d, preferably between approximately 0.002 lb/sec
and 0.01 lb/sec of fluid flows through each opening 131 at a
velocity of between approximately 200 ft/sec and 1000 ft/sec.
[0053] The gaps formed between the pipes 109,117 and the forging F
created by the spacers 111 are an essential aspect of the present
invention. The spacers 111 define a distance Z between the pipes
109,117 and the forging F. The distance to diameter ratio (Z/d)
should range between approximately 1.0 and 6.0.
[0054] A circumferential spacing X exists between adjacent openings
131 in the pipes 109,117. The circumferential spacing of the
openings 131 ensures adequate fluid flow to the forging F to
achieve the desired cooling rate. The circumferential arrangement
of the apertures 131 also ensures axisymmetric cooling of the
forging F. The circumferential spacing to diameter ratio (X/d)
should be between approximately 0.0 and 24.0.
[0055] Finally, a radial spacing Y exists between adjacent openings
131 in the pipes 109. Similarly, the radial spacing of the openings
131 ensures adequate fluid flow to the forging F to achieve the
desired cooling rate. The radial spacing to diameter ratio (Y/d)
should be between approximately 0.0 and 26.0.
[0056] Using these parameters, the present invention can treat all
sections of the forging using impingement cooling. Impingement
cooling is preferred because of the combined effect of increased
turbulence and increased jet arrival velocity significantly
increases the heat transfer coefficient of the apparatus 100.
[0057] By varying the aforementioned parameters within the suitable
ranges, the present invention can achieve another goal of the
present invention--to reduce any differential between the cooling
rates of different areas of the forging F. Ideally, the present
invention seeks to equalize the cooling rates across all areas of
the forging.
[0058] The present invention reduces temperature gradients within
the forging F by providing more impingement cooling to one area of
the forging F compared to another area of the forging F. In terms
of heat transfer, the volume of an object equates to thermal mass
and the surface area of the object equates to cooling capacity.
Objects exhibiting a low surface area to volume ratio cannot
transfer heat as readily as objects with higher surface area to
volume ratios.
[0059] The present invention seeks to increase the heat transfer of
areas of the forging F that exhibit low surface area to volume
ratios. Practically speaking, the present invention provides more
cooling to surfaces of the forging F located adjacent larger
volumetric sections than surfaces of the forging F located adjacent
smaller volumetric sections.
[0060] The present invention can locally adjust impingement cooling
by varying any of the aforementioned characteristics. For example,
one can selectively adjust cooling to desired areas of the forging
F by adjusting the diameters of the pipes 109,117, by adjusting the
diameter of the openings 131, by adjusting the size of the spacer
111 or by adjusting the density of the openings 131 (ie. adjust
spacing distances X or Y) during the system design stage. During
operation of the apparatus 100, one can selectively adjust the
cooling to desired areas of the forging F by adjusting pressure in
each pipe 109,111,133. The aforementioned valves on the supply 127
could be used to adjust pressure. Any other technique to adjust
pressure could also be used.
[0061] The present invention could leave these characteristics
static during the quenching process. In other words, the apparatus
100 could keep the selected pressures in the pipes 109,111,133
constant throughout the entire temperature range of the quenching
process. Alternatively, the present invention could dynamically
adjust the pressures in the pipes 109,111,133 during the quenching
process. For example, the apparatus 100 could operate at a desired
pressure until the course grain nickel alloy forging F exits the
temperature range of the ductility trough (e.g. 1800-2100.degree.
F.). Thereafter, the apparatus could operate at a reduced pressure
for the remainder of the quenching process. Other variations are
also possible.
[0062] The present invention can produce heat transfer coefficients
greater than those created by oil bath quenching (e.g. 70-140
BTU/hr ft.sup.2 .degree. F.) or fan quenching (e.g. 50 BTU/hr
ft.sup.2 .degree. F.). The present invention can produce a heat
transfer coefficient of approximately 300 BTU/hr ft.sup.2 .degree.
F.
[0063] Despite the higher heat transfer coefficient, the quenched
products that the present invention produces exhibit lower residual
stress values than those products created by oil bath quenching.
The arbitrary cooling rate of oil bath quenching produces high
residual stress values. The present invention, on the other hand,
achieves lower residual stress values because of the ability to
differentially cool the forging F (i.e. control the temperature
gradients across the forging). Note that reference to the residual
stress values produced by fan quenching is not appropriate because
fan quenching cannot meet the cooling requirements needed to quench
high temperature aerospace alloys.
[0064] The present invention has been described in connection with
the preferred embodiments of the various figures. It is to be
understood that other similar embodiments may be used or
modifications and additions may be made to the described embodiment
for performing the same function of the present invention without
deviating therefrom. Therefore, the present invention should not be
limited to any single embodiment, but rather construed in breadth
and scope in accordance with the recitation of the appended
claims.
* * * * *