Technical Field
[0001] The present invention relates to a method of cooling a metal part by immersing the
metal part in a cooling liquid, a manufacturing method of a metal part by using this
cooling method, and a cooling apparatus for a metal part.
Background Art
[0002] Quenching treatment and solid solution treatment are heat treatments which involve
immersing a metal part heated to a high temperature into cooling liquids consisting
of a mineral oil (a quenching oil), water or an aqueous solution of water-soluble
coolant and the like, to rapidly cool the metal part. Although these cooling liquids
are excellent in the stability of cooling and cost efficiency, the following point
can be mentioned as a problem. That is, the instant a metal part heated to a high
temperature is immersed in these cooling liquids, these cooling liquids vaporize at
an interface with the metal part, generating a film of vapor (hereinafter called a
"vapor film") on the surface of the metal part. Because this vapor film retards the
cooling of the metal part, in particular, when the vapor film becomes partially stable
due to the shape of the metal part, the arrangement of the metal part in a cooling
tank, and the like, the metal part is not uniformly cooled and deformation and soft
spots (hardness difference) occur in the metal part.
[0003] To solve this problem, a conventional practice has been to stir a cooling liquid
with a metal part immersed by means of convection as strongly as possible, so that
positive heat exchange occurs at the interface between the vapor film and the cooling
liquid and the temperature of the surface of the metal part is lowered, thereby rapidly
breaking a vapor film.
[0004] In
JP2003-286517A (hereinafter referred to as Patent Document 1), there is proposed a method by which
a cooling liquid in which a metal part is immersed is stirred by oscillations and
jet flows, and horizontal and vertical flows are generated in the cooling liquid,
whereby a vapor film is broken and bubbles generated from the broken vapor film are
caused to diffuse in the cooling liquid and disappear.
[0005] However, in the method described in Patent Document 1 above, the cooling liquid is
stirred when the vapor film is broken and, therefore, strong flows are generated in
the cooling liquid and uniform breakage of the vapor film is apt to be hindered. Therefore,
this method described in Patent Document 1 has room for further improvement in that
a metal part is uniformly cooled.
[0006] From SU 815 048 A a quenching tank is known that contains a vibration generator to
produce vibrations in the quenching tank. A cooling method for cooling metal parts,
such as spindles and main axles for automatic lathes, is disclosed. A repeatedly varying
pressure is applied by a vibration generator to a vapor film which is formed when
the cooling liquid vaporizes on a surface of the metal part.
[0008] Hence, the present invention has been made in view of the above circumstances and
has as its object the provision of a method of uniformly cooling a metal part by uniformly
breaking a vapor film which is generated by the vaporization of a cooling liquid on
a surface of the metal part.
Disclosure of the Invention
[0009] To solve this problem, the present inventors earnestly devoted themselves to investigations
and as a result they found out that a vapor film formed by the vaporization of a cooling
liquid on the surface of a metal part is kept in a stable manner by the pressure in
the interior of the film, and that the vapor film can be effectively broken by shattering
the stability of this vapor film.
[0010] That is, the present invention provides a cooling method of cooling a metal part
by immersing the heated metal part in a cooling liquid and by applying a repeatedly
varying pressure to a vapor film which is formed when the cooling liquid vaporizes
on a surface of the metal part, the vapor film is broken without stirring the cooling
liquid.
[0011] According to the invention, the cooling method comprises the features as comprised
by the characterizing part of claim 1.
[0012] According to this cooling method, when a repeatedly varying pressure is applied to
a vapor film, the vapor film repeats expansion and contraction and fluctuates, and
the vapor film is broken, with a portion where the film thickness has decreased due
to this fluctuation serving as an initiation point. At this time, by applying a repeatedlyvarying
pressure to the vapor film without stirring the cooling liquid, weak flows like natural
convection are generated in the cooling liquid, but strong flows are not generated
as would be the case when the cooling liquid is stirred. For this reason, the vapor
film can be uniformly broken.
[0013] In the cooling method of the present invention, examples of a method of applying
a repeatedly varying pressure to the vapor film include a method of applying oscillations
to the cooling method, a method of changing the liquid-level pressure of the cooling
liquid, and a method of performing the application of a repeatedly varying pressure
by combining these two methods. As a method of applying a repeatedly varying pressure
to the vapor film, it is possible to mention also a method by which the metal part
is caused to swing. Furthermore, the pressure applied to the vapor film may be continuously
varied or it may be intermittently varied like pulse oscillation.
[0014] In the cooling method of the present invention, a method of applying oscillations
to the cooling liquid is not especially limited so long as it does not generate strong
flows in the cooling liquid, and examples of methods of applying oscillations to the
cooling liquid include, for example, a method which involves providing an oscillator,
such as an oscillating plate and a rotating body, in a cooling tank, and causing the
oscillatingplate to perform reciprocating motions or causing the rotating body to
perform rotational motions. Examples of a method of applying oscillations to the cooling
liquid also include a method which involves providing multiple oscillators in the
cooling tank and causing these oscillators to oscillate. According to this method,
it is possible to apply oscillations due to the resonance by the multiple oscillators
to the cooling liquid and to apply oscillations which are partially different within
the cooling tank.
[0015] Also in the cooling method of the present invention, when the method which involves
applying oscillations to the cooling liquid is adopted as a method of applying a repeatedly
varying pressure to the vapor film, at least either of the amplitude and frequency
of the vibrations may be adjusted according to the thickness of the vapor film.
[0016] The thickness of the vapor film changes depending on the size, temperature and shape
of the metal part, the kind and temperature of the cooling liquid, the pressure applied
to the liquid and the like. For example, when the vapor film is thick, it is preferred
to make the amplitude larger, and when the vapor film is thin, it is preferred to
make the frequency higher.
[0017] Furthermore, in the cooling method of the present invention, when the method which
involves applying oscillations to the cooling liquid is adopted as a method of applying
a repeatedly varying pressure to the vapor film, at least either of the amplitude
and frequency of the oscillations may be adjusted according to the condition of the
cooling liquid.
[0018] The condition of the cooling liquid changes in the order: (1) a vapor film stage
at which a vapor film is present on the surface of a metal part, (2) a boiling stage
at which this vapor film is broken and removed from the surface of the metal part,
with the result that the metal part is exposed and the cooling liquid which comes
into contact with this exposed surface boils, and (3) a convection stage at which
boiling comes to an end and convection starts. For example, it is preferred to make
the amplitude larger in the former period of the vapor film stage at which a vapor
film exists in a stable manner and to make the frequency higher from the latter period
of the vapor film stage at which the vapor film begins to be broken to before the
transition to the boiling stage.
[0019] In the cooling method of the present invention, the breakage effect of the vapor
film cannot be expected if the amplitude bf oscillations applied to the cooling liquid
is too small; on the other hand, if the amplitude is too large, the liquid surface
of the cooling liquid becomes wavy and in some cases strong flows are generated. From
this point of view, it is preferred that when oscillations are applied by use of an
oscillating plate, the amplitude expressed by the swing width of the oscillating plate
be not less than 2 mm. When oscillations are applied by a pressure, it is preferred
that the amplitude expressed by an amount of change in the pressure be not less than
1% (for example, not less than 100 Pa) of the pressure which is applied to the cooling
liquid in the state that the oscillations are not being applied.
[0020] If the frequency applied to the cooling liquid is too low, a change in the pressure
is gentle and the vapor film does not fluctuate, with the result that the breakage
effect of the vapor film cannot be expected. On the other hand, if the frequency applied
to the cooling liquid is too high, the fluctuation of the vapor filmbecomes too fine,
with the result that the breakage effect of the vapor film cannot be expected. From
this point of view, when an oscillating apparatus provided with a vibration motor
made by URAS TECHNO (trade name: URAS TECHNOVIBRATOR) is used, the frequencyof oscillations
applied to the cooling liquid is preferably 5 to 80 Hz, more preferably 20 to 30 Hz.
[0021] Furthermore, when oscillations applied to the cooling liquid have a low frequency
and a large amplitude, it is necessary to prevent the liquid surface of the cooling
liquid from becoming wavy and, therefore, the construction of the cooling tank becomes
complex. When oscillations having a small amplitude and a high frequency as ultrasonic
waves are applied to the cooling liquid, the fluctuation of the vapor film becomes
too fine and, therefore, the breakage effect of the vapor film cannot be expected.
[0022] In the cooling method of the present invention, it is mandatory that the cooling
liquid be stirred after the vapor film begins to be broken so that bubbles formed
by the breakage of the vapor film is caused to diffuse in the cooling liquid.
[0023] As a result of this, it is possible to cause the bubbles formed from the broken vapor
film to diffuse uniformly and rapidly in the cooling liquid and disappear, with the
result that the cooling for a metal part may be performed uniformly and rapidly. This
stirring of the cooling liquid is effective particularly when the rapid diffusion
of bubbles is required, for example, in a case where metal parts are cooled in a massive
amount at a time, in a case where metal parts having a large volume are cooled, and
the like.
[0024] Examplesof amethodof stirring the cooling liquid include jet stirring and it is preferable
to adopt a method by which a uniform flow is formed in the cooling liquid frombelow
upward. It is mandatory that the timing for starting the stirring of the cooling liquid
is synchronized with the point of time at which the vapor film begins to be broken.
[0025] The stirring may be performed either after stopping the application of a varying
pressure to the vapor film or while continuously applying a varying pressure. As for
which method is adopted, any one of the methods is selected according to the size,
kind, or quantity of a metal part to be cooled.
[0026] For example, when a metal part which is apt to be deformed is cooled, in order to
make gentle the cooling at the convection stage of the cooling liquid, it is preferable
to perform the stirring after the application of a varying pressure to the vapor film
is stopped. That is, it is preferable not to apply oscillations during the stirring
of the cooling liquid. On the other hand, in a case where metal parts are cooled in
a massive amount at a time and in a case where metal parts having a large volume are
cooled, in order to perform strong cooling even at the convection stage of the cooling
liquid, it is preferable to perform the stirring, with a varying pressure applied
to the vapor film. That is, it is preferable to apply oscillations simultaneously
with the stirring of the cooling liquid.
[0027] Furthermore, in the cooling method of the present invention, it is preferable to
adjust at least either of the intensity of the stirring and the direction of a flow
generated by the stirring according to the condition of the cooling liquid and the
condition of the metal part in the cooling liquid.
[0028] At the boiling stage of the cooling liquid, it is preferable to cause the bubbles
formed from the broken vapor film to diffuse uniformly and rapidly in the cooling
liquid and disappear. For this reason, it is preferable to perform strong stirring
from the later period of the vapor film stage at which the vapor film begins to be
broken to before the transition to the convection stage. Also, in a case where the
longitudinal direction of a metal part is arranged toward a vertical direction in
the cooling liquid, it is preferable to ensure that the direction of flows generated
by stirring is a vertical direction and in a case where the longitudinal direction
of a metal part is arranged toward a horizontal direction in the cooling liquid, it
is preferable to ensure that the direction of flows generated by stirring is a horizontal
direction.
[0029] Incidentally, the coolingmethod of the present invention can be favorably used in
the quenching treatment and solid solution treatment of metal parts.
[0030] The present invention also provides a method of manufacturing a metal part, which
is characterized in that the manufacturing method comprises a step of heating a metal
part and a step of cooing the metal part after the heating thereof by immersing the
metal part in a cooling liquid, and in that in the cooling step, by applying a repeatedly
varying pressure to a vapor filmwhich is formed when the cooling liquid vaporizes
on a surface of the metal part, the vapor film is broken without stirring the cooling
liquid.
[0031] According to this manufacturing method, the uniformity of the cooling of a metal
part is improved and the deformation or the soft spots thereof become less apt to
occur. Therefore, it is possible to obtain a high-accuracy and high-quality metal
part.
[0032] Incidentally, in the manufacturing method of the present invention, in the same way
as with the above-described cooling method, examples of a method of applying a repeatedly
varying pressure to the vapor film includes a method of applying oscillations to the
cooling method, a method of changing the liquid-level pressure of the cooling liquid,
a method of performing the application of a repeatedly varying pressure by combining
these two methods, and a method of fluctuating a metal part.
[0033] Also, as a method of applying oscillations to the cooling liquid, in the same way
as with the above-described cooling method, it is possible to mention a method by
which one or multiple oscillators are caused to oscillate.
[0034] Furthermore, in the manufacturing method of the present invention, when the method
of applying oscillations to the cooling liquid is adopted as a method of applying
a repeatedly varying pressure to the vapor film, in the same way as with the above-described
cooling method, at least either of the amplitude and frequency of the oscillations
may be adjusted according to the thickness of the vapor film and the condition of
the cooling liquid.
[0035] Moreover, in the manufacturing method of the present invention, it is mandatory that
the cooling method includes stirring the cooling liquid after the vapor film begins
to be broken so that bubbles formed by the breakage of the vapor film is caused to
diffuse in the cooling liquid. At this time, in the same way as with the above-described
cooling method, it is preferable to adjust at least either of the intensity of the
stirring and the direction of a flow generated by the stirring according to the condition
of the cooling liquid and the condition of the metal part in the cooling liquid.
[0036] Furthermore, the present invention provides a cooling apparatus for a metal part,
which is characterized in that the cooling apparatus comprises means for cooling a
metal part after the heating thereof by immersing the metal part in a cooling liquid,
and in that the cooling means applies a repeatedly varying pressure to a vapor film
which is formed when the cooling liquid vaporizes on a surface of the metal part,
and breaks the vapor film without stirring the cooling liquid.
[0037] According to this cooling apparatus, the uniformity of the cooling of a metal part
is improved and the deformation or the soft spots thereof become less apt to occur.
Therefore, it is possible to obtain a high-accuracy andhigh-qualitymetal part.
[0038] Incidentally, in the cooling apparatus of the present invention, in the same way
as with the above-described cooling method, examples of a method of applying a repeatedly
varying pressure to the vapor film includes a method of applying oscillations to the
cooling method, a method of changing the liquid-level pressure of the cooling liquid,
a method of performing the application of a repeatedly varying pressure by combining
these two methods, and a method of fluctuating a metal part. Furthermore, the pressure
applied to the vapor film may be continuously varied or it may be intermittently varied
like pulse oscillation.
[0039] Also, in the cooling apparatus of the present invention, as a method of applying
oscillations to the cooling liquid, in the same way as described above, it is possible
to mention a method by which one or multiple oscillators are caused to oscillate.
[0040] Furthermore, in the cooling apparatus of the present invention, when the method of
applying oscillations to the cooling liquid is adopted as a method of applying a repeatedly
varying pressure to the vapor film, in the same way as described above, at least either
of the amplitude and frequency of the oscillations may be adjusted according to the
thickness of the vapor film and the condition of the cooling liquid.
[0041] Furthermore, in the cooling apparatus of the present invention, it is mandatory that
the above-described cooling means stir the cooling liquid after the vapor film begins
to be broken so that the bubbles formed by the breakage of the vapor film is caused
to diffuse in the cooling liquid. At this time, it is preferable to adjust at least
either of the intensity of the stirring and the direction of a flow generated by the
stirring according to the condition of the cooling liquid and the condition of the
metal part in the cooling liquid.
Brief Description of the Drawings
[0042]
Figure 1 is a schematic configuration diagram showing an example of a cooling apparatus
used in a cooling method of a metal part related to the present invention;
Figure 2 is a diagram showing pressure changes occurring in the cooling liquid when
an oscillation device is actuated in the cooling apparatus of this embodiment;
Figure 3 is a diagram showing pressure changes occurring in the cooling liquid when
a stirrer is actuated in the cooling apparatus of this embodiment;
Figure 4 is a schematic configuration diagram showing another example of a cooling
apparatus used in a cooling method of a metal part related to the present invention;
Figure 5 is a diagram showing cooling curves on the side surfaces of round bar test
pieces made of stainless steel subjected to cooling treatments No. 1 to No. 4; and
Figure 6 is a diagram showing cooling curves on the side surfaces of round bar test
pieces made of stainless steel subjected to cooling treatments No. 5 and No. 6.
Best Mode for Carrying Out the Invention
[0043] An embodiment of the present invention will be described below with reference to
the drawings.
[0044] In this embodiment, a description will be given of a case where metal parts are manufactured
by using a cooling apparatus for a metal part related to the present invention.
[0045] Figure 1 is a schematic configuration diagram showing an example of a cooling apparatus
used in a cooling method of a metal part related to the present invention.
[0046] As shown in Figure 1, this cooling apparatus is equipped with a cooling tank 2 which
contains a cooling liquid 1, a container 3 which houses metal parts, two oscillation
devices 10, a stirrer 20, and a controller 30. In the upper part of this cooling apparatus,
there is arranged a heating device 40 which heats the metal parts. And the container
3 which houses metal parts heated by this heating device 40 is immersed in the middle
part of the cooling tank 2 by use of an elevator apparatus not shown in the figure.
[0047] The oscillation device 10 is equipped with one oscillating plate 11 and a drive unit
12 which oscillates this oscillating plate 11 with a prescribed amplitude and a prescribed
frequency. This oscillating plate 11 is disposed near the side surface of the container
3 in the cooling tank 2 perpendicularly, with the plate surface thereof facing the
container 3. When this oscillation device 10 is actuated, the oscillating plate 11
performs horizontal reciprocal motions and oscillations 4 are generated. The oscillations
4 are applied to the cooling liquid 1. By adjusting each of the frequencies and amplitudes
of the two oscillation devices 10, it is possible to apply oscillations generated
by the resonance of the two oscillating plates 11 or oscillations which differ on
both sides of the container 3.
[0048] The stirrer 20 is equipped with a propeller 21 which is disposed, with a shaft thereof
facing a vertical direction, multiple flow regulating plates 22, and a drive unit
23 which controls the rotational motions of the propeller 21, all these three members
being present sideways from the oscillating plate 11 in the cooling tank 2. By actuating
this stirrer 20, the propeller 21 performs rotations and the cooling liquid 1 is stirred,
with the result that in the cooling liquid 1, upward flows are generated which move
along the flow regulating plate 22 from below the container 3 upward.
[0049] The controller 30 is disposed outside the cooling tank 2, and constructed so as to
control the timing for actuating the drive unit 12 of the oscillation device 10 and
the drive unit 23 of the stirrer 20. Also, the controller 30 is constructed so as
to control the drive unit 12 of the oscillation device 10 according to the thickness
of the vapor film or the condition of the cooling liquid 1 and, at the same time,
so as to control the drive unit 23 of the stirrer 20 according to the condition of
the cooling liquid 1 or the condition of metal parts in the cooling liquid 1.
[0050] A strain-gauge pressure sensor was installed in the cooling tank 2 of this cooling
apparatus and pressure changes occurring in the cooling liquid 1 within the cooling
tank 2 were measured in a case where the oscillation device 10 and the stirrer 20
are individually actuated.
[0051] Figure 2 is a graph showing pressure changes occurring in the cooling liquid when
the oscillating plate of the oscillation device is actuated under such a condition
that the frequency is 40 Hz. Figure 3 is a graph showing pressure changes occurring
in the cooling liquid when the stirrer is actuated under such a condition that upward
flows generated in the cooing liquid amount to a flow rate of 30 m
3/h. In this graph, the fluctuation width of the electromotive force of the sensor
on the ordinate indicates the magnitude of the amount of change in the pressure (a
relative value) and a numerical value of the electromotive force of the sensor indicates
the intensity of a flow generated in the cooling liquid (a relative value).
[0052] As shown-in Figures 2 and 3, when the oscillation device 10 was actuated, such pressure
changes that the electromotive force of the sensor became 0.02 V or so occurred repeatedly
in the cooling liquid, whereas pressure changes scarcely occurred in the cooling liquidwhen
the stirrer 20 was actuated.
[0053] Flows generated in the cooling liquid 1 by the oscillation device 10 were weak compared
to those occurred at the actuation of the stirrer 20. From this fact it could be ascertained
that when the oscillation device 10 is actuated, a repeatedly varying pressure is
applied to the cooling liquid 1 without the generation of strong flows, whereas by
the actuation of the stirrer 20, a varying pressure is not applied although strong
flows are formed in the cooling liquid 1.
[0054] Figure 4 is a schematic configuration diagram showing another example of a cooling
apparatus used in a cooling method of a metal part related to the present invention.
[0055] As shown in Figure 4, this cooling apparatus is equipped with a cooling tank 2 containing
a cooling liquid 1, a container 3 which houses metal parts to be subj ected to cooling
treatment, a gas introductionpipe 5 which introduces a gas into the cooling tank 2,
a gas exhaust pipe 6 which exhausts the gas from the cooling tank 2, a stirrer 20
in which a propeller 21 is disposed sideways in the cooling tank 2, with a shaft thereof
facing a vertical direction, and a controller 50 disposed outside the cooling tank
2. And in the same way as with the cooling apparatus shown in Figure 1 described above,
the container 3 which houses metal parts heated by a heating device 40 is immersed
in the middle part of the cooling tank 2. Incidentally, the same numerals refer to
the same parts as those of the cooling apparatus shown in Figure 1 described above,
and description of these parts are omitted.
[0056] The gas introduction pipe 5 can introduce a gas into the cooling tank 2 by use of
a solenoid valve 5a connected to the controller 50.
[0057] The gas exhaust pipe 6 can discharge the gas in the cooling tank 2 by use of a solenoid
valve 6a connected to the controller 50.
[0058] The controller 50 is constructed so as to continue introducing a gas into the cooling
tank 2 by opening the solenoid valve 5a of the gas introduction pipe 5 and repeatedly
perform the opening and closing the solenoid valve 6a of the gas exhaust pipe 6. As
a result of this, it is possible to change the pressure on the liquid level of the
cooling liquid 1 which has entered the cooling tank 2. Also, the controller 50 is
constructed so as to start the actuation of the stirrer 20 at the point of time when
the vapor film begins to be broken.
[0059] Furthermore, the controller 50 is constructed so as to control the gas volume introduced
from the gas introduction pipe 5 and the timing for the opening and closing of the
solenoid valve 6a of the gas exhaust pipe 6 according to the condition of the vapor
film and the cooling liquid 1 and so as to control a drive unit 23 of the stirrer
20 according to the condition of the cooling liquid 1 and metal parts in the cooling
liquid 1.
[0060] By use of the cooling apparatus of the above-described construction, the cooling
of metal parts was performed by a method corresponding to the embodiment of the present
invention and by a method corresponding to a conventional method.
[0061] Round bar test pieces made of stainless steel (metal parts) having a diameter of
12 mm, which had been heated to 830°C, were immersed in a quenching oil (a cooling
liquid) 1 at 70°C and cooled by the methods of No. 1 to No. 5 shown below. Incidentally,
in Nos. 1 to 3 and Nos. and 6, cooling was performed by use of the cooling apparatus
shown in Figure 1 described above (hereinafter called "the first cooling apparatus"),
and in No. 4, cooling was performed by use of the cooling apparatus shown in Figure
4 shown above. Incidentally, the amplitude of oscillations 4 applied to the quenching
oil 1 in the first cooling apparatus is expressed by the swing width of the oscillating
plate 11. Incidentally, each coolingmethod is automatically performed by the execution
of the arithmetic processing stored beforehand in the controllers 30, 50.
[0062] In No. 1, first, the oscillation device 10 was actuated, whereby the oscillating
plate 11 was caused to oscillate with a frequency of 40 Hz and an amplitude of 4 mm,
and the oscillations were applied to the quenching oil 1 for 2 seconds. Next, the
oscillation device 10 was stopped and simultaneously the stirrer 20 was actuated,
whereby the quenching oil 1 was jet-stirred by upward flows at a flow rate of 30 m
3/h.
[0063] In No. 2, the oscillation device 10 was actuated, whereby the oscillating plate 11
was caused to oscillate with a frequency of 40 Hz and an amplitude of 4 mm, and the
oscillations were applied to the quenching oil 1.
[0064] In No. 3, the oscillation device 10 was actuated, whereby the oscillating plate 11
was caused to oscillate with a frequency of 40 Hz and an amplitude of 4 mm, and simultaneously
the stirrer 20 was actuated, whereby the quenching oil 1 was jet-stirred by upward
flows at a flow rate of 30 m
3/h.
[0065] In No. 4, the solenoid valve 5a was opened and the nitrogen gas from the gas introduction
pipe 5 was continued to be introduced into the cooling tank 2. With the liquid-level
pressure of the quenching oil 1 kept at 0.12 MPa, the opening and closing of the solenoid
valve 6a of the gas exhaust pipe 6 was performed twice per second for a duration of
15 seconds, whereby the pressure applied to the liquid level was repeatedly varied.
[0066] InNo. 5, the quenching oil 1 was allowed to undergo natural convection.
[0067] In No. 6, the stirrer 20 was actuated, whereby the quenching oil 1 was jet-stirred
by upward flows at a flow rate of 30 m
3/h.
[0068] And in the cooling process of Nos. 1 to 6, the temperature on the side surface of
a round bar test piece made of stainless steel was measured and a cooling curve of
each test piece was prepared. The results are shown in Figures 5 and 6.
[0069] Figure 5 shows cooling curves on the side surfaces of round bar test pieces made
of stainless steel cooled under the conditions of No. 1 to No. 4. Figure 6 shows cooling
curves on the side surfaces of round bar test pieces made of stainless steel cooled
under the conditions of No. 5 and No. 6.
[0070] As shown in Figure 5, in the No. 1 method which involves performing cooling by jet
stirring of the quenching oil 1 after the application of oscillations to the quenching
oil 1, in 1. 9 seconds after the immersion of a test piece in the quenching oil 1,
a change occurred from gentle cooling to abrupt cooling. This point of change is called
a "characteristic point."
[0071] In both the No. 2 method which involves performing cooling by applying oscillations
to the quenching oil 1 and the No. 3 method which involves performing cooling by jet
stirring the quenching oil 1 simultaneously with the application of oscillations to
the quenching oil 1, a characteristic point was observed in 2. 7 seconds after the
immersion of test pieces in the quenching oil 1.
[0072] In the No. 4 method which involves performing cooling by repeatedly varying the liquid-level
pressure of the quenching oil 1, a characteristic point was observed in 2.7 seconds
after the immersion of a test piece in the quenching oil 1.
[0073] It might be thought that because in No. 2, the quenching oil 1 is not jet-stirred
after the application of oscillations to the quenching oil 1, it takes time for the
bubbles formed by the breakage of a vapor film to diffuse, with the result that the
point of time at which a characteristic point is observed lags behind that of No.
1
[0074] Also, it might be thought that because in No. 3, cooling is performedbyjet-stirring
the quenching oil 1 simultaneously with the application of oscillations to the quenching
oil 1, strong flows are generated in the cooling liquid and uniform breakage of a
vapor film is impeded, with the result that the point of time at which a characteristic
point is observed lags behind that of No. 1.
[0075] Furthermore, it might be thought that because in No. 4, the quenching oil 1 is not
jet-stirred after the varying of the liquid-level pressure of the quenching oil 1,
it takes time for the bubbles formed by the breakage of a vapor film to diffuse, with
the result that the point of time at which a characteristic point is observed lags
behind that of No. 1.
[0076] On the other hand, as shown in Figure 6, in the No. 5 method which involves cooling
by the natural convection of the quenching oil 1, a characteristic point was observed
in 3. 8 seconds after the immersion of a test piece in the quenching oil 1. In the
No. 6 method which involves cooling by jet-stirring the quenching oil 1, a characteristic
point was observed in 3.5 seconds after the immersion of a test piece in the quenching
oil.
[0077] From the above results, it became apparent that a metal part can be rapidly cooled
by breaking a vapor film without the stirring of the quenching oil 1 and stirring
the quenching oil 1 after the vapor films begins to be broken.
[0078] The characteristic point of No. 1 was a temperature about 20°C higher than the characteristic
points of No. 2 to No. 4 and this temperature was about 50°C higher than the characteristic
points of Nos. 5 and 6. From the results, when cooling is performed under the condition
of No. 1, it could be ascertained that the breakage of a vapor film is caused by the
shattering of the stability of the vapor film, and is not due to a drop of the surface
temperature of a metal part.
[0079] Subsequently, metal parts were subjected to carburizing treatment and cooling thereafter
was performed by the method of the present invention and by a conventional method.
Dimensional changes of the metal parts before and after the heat treatment were investigated
as follows.
[0080] First, ring-shaped materials made of SCM420 (outside diameter: 70 mm, inside diameter:
55 mm, axial length: 40 mm) were prepared. The ring-shaped materials were arranged
in a furnace which had been brought into a reducing atmosphere by adding alcohol dropwise
at 920°C, with the axial direction of the materials aligned in a vertical direction.
Next, while propane gas being added into this furnace in a reducing atmosphere, carburizing
treatment was performed for 60 minutes, with the carbon concentration of the atmosphere
kept at 0.8%. Next, the temperature of the ring-shapedmaterials was lowered to 850°C
in the furnace in a reducing atmosphere.
[0081] Next, the ring-shaped materials were transferred from the heating device 40 shown
in Figure 1 into the cooling tank 2. This cooling tank 2 contains a quenching oil
(a cooling liquid) 1 at 70°C, and the area above the quenching oil 1 is held in a
nonoxidizing atmosphere. The ring-shaped materials were immersed in this quenching
oil 1. And cooling was performed under the conditions of No. 10 to No. 15.
[0082] InNo. 10, the oscillation device 10 was actuated, whereby the oscillating plate 11
was caused to oscillate with a frequency of 40 Hz and an amplitude of 4 mm, and the
oscillations were applied to the quenching oil 1 for 60 seconds.
[0083] In No. 11, the oscillation device 10 was actuated, whereby the oscillating plate
11 was caused to oscillate with a frequency of 60 Hz and an amplitude of 2 mm, and
the oscillations were applied to the quenching oil 1 for 60 seconds.
[0084] InNo. 12, the oscillation device 10 was actuated, whereby the oscillating plate 11
was caused to oscillate with a frequency of 40 Hz and an amplitude of 4 mm, and simultaneously
the stirrer 20 was actuated, whereby the quenching oil 1 was jet-stirred by upward
flows at a flow rate of 30 m
3/h for 60 seconds.
[0085] In No. 13, first, the oscillation device 10 was actuated, whereby the oscillating
plate 11 was caused to oscillate with a frequency of 40 Hz and an amplitude of 4 mm,
and the oscillations were applied to the quenching oil 1 for 2 seconds. Next, the
oscillation device 10 was stopped and simultaneously the stirrer 20 was actuated,
whereby the quenching oil 1 was jet-stirred by upward flows at a flow rate of 30 m
3/h for 60 seconds.
[0086] In No. 14, the stirrer 20 was actuated, whereby the quenching oil 1 was jet-stirred
by upward flows at a flow rate of 30 m
3/h for 60 seconds.
[0087] In No. 15, the quenching oil 1 was allowed to undergo natural convection and a ring-shaped
material was immersed in this quenching oil 1 for 5 minutes.
[0088] And for each of the ring-shapedmaterials after the cooling treatment, outside diameters
and out-of-roundness were measured in both end portions and middle portion in the
axial direction, and changes in the outside diameter and out-of-roundness before and
after the heat treatment were investigated. The results are shown in Table 1.
[0089] In Table 1, the numerical values of outside diameter marked with "+" mean that the
size increased after the heat treatment, and the numerical values marked with "-"
mean that the size decreased after the heat treatment. Maximum differences in dimensional
changes between top end, middle and bottom end are also shown in Table 1. The smaller
the maximum difference in outside diameter, the smaller the deformation difference
in the axial direction of a ring-shaped material after the heat treatment.
[0090] As shown in Table 1, in the methods of Nos. 10 to 13 which involve performing cooling
by applying oscillations to the quenching oil 1, the maximum difference in outside
diameter was small compared to the method of No. 14 which involves performing cooling
by the jet-stirring of the quenching oil 1 and the method of No. 15 which involves
performing cooling by the natural convection of the quenching oil 1.
[0091] Among the methods of No. 10 to No. 13, the maximum difference in outside diameter
was very small in No. 13 which involves performing cooling by the jet-stirring of
the quenching oil 1 after the application of oscillations to the quenching oil 1.
In No. 11 which involves performing cooling by the application of oscillations having
a high frequency and a small amplitude to the quenching oil 1, the effect of oscillations
was small and showed that the maximum difference in outside diameter was large compared
to Nos. 10, 12 and 13.
[0092] In Nos. 10 to 13, changes in out-of-roundness were small compared to No. 14 which
involves performing cooling by the jet-stirring of the quenching oil 1, and out-of-roundness
of the same degree as in No. 15 which involves performing cooling by the natural convection
of the quenching oil 1 was obtained.
[0093] From the above results, it became apparent that by breaking a vapor film without
stirring a quenching oil and by stirring the quenching oil after the vapor film begins
to be broken, the nonuniformity of axial deformation of an obtained metal part can
be improved.
[Table 1]
Method of quenching treatment |
Change in outside diameter (µm) |
Change in out-of-roundness (µm) |
Top end |
Middle |
Bottom end |
Difference |
Top end |
Middle |
Bottom end |
Difference |
10 |
+9 |
+1 |
+34 |
33 |
37 |
26 |
41 |
35 |
11 |
-14 |
-3 |
+25 |
39 |
43 |
29 |
35 |
36 |
12 |
+6 |
+4 |
+36 |
32 |
41 |
33 |
40 |
38 |
13 |
+12 |
+8 |
+31 |
23 |
42 |
29 |
36 |
36 |
14 |
-28 |
-7 |
+32 |
60 |
53 |
34 |
45 |
44 |
15 |
-27 |
-10 |
+21 |
48 |
45 |
27 |
37 |
36 |
Industrial Applicability
[0094] According to the present invention, a repeatedly varying pressure is applied to a
vapor film formed on the surface of a metal part and the vapor film is broken without
the stirring of a cooling liquid, with the result that strong flows are not generated
in the cooling liquid. Therefore, it becomes easy that the vapor film is uniformly
broken. Hence, the uniformity of the cooling of the metal part is improved and the
deformation or the soft spots thereof become less apt to occur. As a result of this,
it becomes easy to obtain high-accuracy and high-quality metal parts.
1. Verfahren zum Kühlen eines Metallteils durch Eintauchen des erhitzten Metallteils
in eine Kühlflüssigkeit (1), wobei das Verfahren umfasst:
Brechen einer Dampfschicht, die gebildet wird, wenn die Kühlflüssigkeit (1) auf einer
Oberfläche des Metallteils verdampft, durch Ausüben eines Drucks auf die Dampfschicht,
um den Druck wiederholt zu variieren, ohne die Kühlflüssigkeit (1) umzurühren,
dadurch gekennzeichnet, dass der Druck variiert wird durch eines von:
1) Anlegen von Schwingungen an die Kühlflüssigkeit (1) mit einer oszillierenden Platte
(11), die sich horizontal und hin und her in der Kühlflüssigkeit (1) bewegt; oder
2) Ändern des auf einen Flüssigkeitsoberflächenpegel der Kühlflüssigkeit (1) auszuübenden
Drucks durch Einführen eines Gases über dem Flüssigkeitsoberflächenpegel durch eine
Gaseinführungsleitung (5); oder
3) Kombinieren des Anlegens von Schwingungen an die Kühlflüssigkeit (1) mit der oszillierenden
Platte (11), die sich horizontal und hin und her in der Kühlflüssigkeit (1) bewegt,
und des Änderns des Drucks, der auf den Flüssigkeitsoberflächenpegel der Kühlflüssigkeit
(1) durch Einführen des Gases über dem Flüssigkeitsoberflächenpegel durch eine Gaseinführungsleitung
(5) ausgeübt wird; und
Umrühren der Kühlflüssigkeit (1) mit einem Rührer (20), nachdem die Dampfschicht zu
brechen beginnt.
2. Verfahren zum Kühlen eines Metallteils nach Anspruch 1, dadurch gekennzeichnet, dass die an die Kühlflüssigkeit (1) angelegten Schwingungen durch mehrere oszillierende
Platten (11) gegeben sind.
3. Verfahren zum Kühlen eines Metallteils nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass die Amplitude und/oder die Frequenz der Schwingungen gemäß der Dicke der Dampfschicht
angepasst wird.
4. Verfahren zum Kühlen eines Metallteils nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass die Amplitude und/oder die Frequenz der Schwingungen gemäß dem Zustand der Kühlflüssigkeit
(1) angepasst wird.
5. Verfahren zum Kühlen eines Metallteils nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass die Kühlflüssigkeit (1) umgerührt wird, nachdem die Dampfschicht zu brechen beginnt,
und bewirkt wird, dass durch das Brechen der Dampfschicht gebildete Blasen in die
Kühlflüssigkeit (1) diffundieren.
6. Verfahren zum Kühlen eines Metallteils nach Anspruch 5, dadurch gekennzeichnet, dass die Intensität des Rührens und/oder die Richtung eines durch das Rühren erzeugten
Stroms gemäß dem Zustand der Kühlflüssigkeit (1) und des Zustands des Metallteils
in der Kühlflüssigkeit (1) angepasst wird.
7. Verfahren zum Herstellen eines Metallteils, wobei das Verfahren umfasst:
Erhitzen eines Metallteils;
Kühlen des Metallteils durch Eintauchen des Metallteils in eine Kühlflüssigkeit (1)
nach dem Erhitzen des Metallteils;
wobei das Kühlen umfasst:
Brechen einer Dampfschicht, die gebildet wird, wenn die Kühlflüssigkeit (1) auf einer
Oberfläche des Metallteils verdampft, durch Ausüben eines Drucks auf die Dampfschicht,
um den Druck wiederholt zu variieren, ohne die Kühlflüssigkeit (1) umzurühren,
dadurch gekennzeichnet, dass der Druck variiert wird durch eines von:
1) Anlegen von horizontalen Schwingungen an die Kühlflüssigkeit (1) mit einer oszillierenden
Platte (11), die sich horizontal und hin und her in der Kühlflüssigkeit (1) bewegt;
oder
2) wiederholtes Ändern eines auf einen Flüssigkeitsoberflächenpegel der Kühlflüssigkeit
(1) auszuübenden Drucks durch Einführen eines Gases über dem Flüssigkeitsoberflächenpegel
durch eine Gaseinführungsleitung (5); oder
3) eine Kombination des Anlegens der horizontalen Schwingungen an die Kühlflüssigkeit
(1) durch die oszillierende Platte (11) und des Änderns des Drucks, der auf den Flüssigkeitsoberflächenpegel
der Kühlflüssigkeit (1) durch Einführen des Gases über dem Flüssigkeitsoberflächenpegel
durch die Gaseinführungsleitung (5) auszuüben ist; und
Umrühren der Kühlflüssigkeit (1) mit einem Rührer (20), nachdem die Dampfschicht zu
brechen beginnt.
8. Kühlvorrichtung für ein erhitztes Metallteil durch Eintauchen des erhitzten Metallteils
in eine Kühlflüssigkeit (1), wobei die Vorrichtung umfasst:
eine oszillierende Platte (11);
einen Rührer (20); und
eine Steuereinheit (30),
wobei eine Dampfschicht, die gebildet wird, wenn die Kühlflüssigkeit (1) auf einer
Oberfläche des erhitzten Metallteils verdampft, durch Ausüben eines Drucks auf die
Dampfschicht, um wiederholt den Druck zu variieren, ohne die Kühlflüssigkeit (1) umzurühren,
gebrochen wird,
dadurch gekennzeichnet, dass der Druck variiert wird durch eines von:
1) Anlegen von Schwingungen an die Kühlflüssigkeit (1) mit der oszillierenden Platte
(11), die sich horizontal und hin und her in der Kühlflüssigkeit (1) bewegt; oder
2) Ändern des auf einen Flüssigkeitsoberflächenpegel der Kühlflüssigkeit (1) auszuübenden
Drucks durch Einführen eines Gases über dem Flüssigkeitsoberflächenpegels durch eine
Gaseinführungsleitung (5); oder
3) Kombinieren des Anlegens von Schwingungen an die Kühlflüssigkeit (1) mit der oszillierenden
Platte (11), die sich horizontal und hin und her in der Kühlflüssigkeit (1) bewegt,
und des Änderns des Drucks, der auf den Flüssigkeitsoberflächenpegel der Kühlflüssigkeit
(1) durch Einführen des Gases über dem Flüssigkeitsoberflächenpegel durch die Gaseinführungsleitung
(5) ausgeübt wird; und
wobei der Rührer (20) die Kühlflüssigkeit (1) umrührt, nachdem die Dampfschicht zu
brechen beginnt.
1. Procédé de refroidissement d'une pièce métallique par immersion de ladite pièce métallique
une fois chauffée dans un liquide de refroidissement (1), ledit procédé comportant
la rupture d'une couche superficielle de vapeur qui est formée quand ledit liquide
de refroidissement (1) se vaporise sur une surface de ladite pièce métallique, par
l'application d'une pression sur ladite couche superficielle de vapeur de façon à
faire varier la pression de façon répétée sans agiter ledit liquide de refroidissement
(1),
caractérisé en ce qu'on modifie ladite pression par l'une quelconque des actions:
1) appliquer des oscillations audit liquide de refroidissement (1) avec une plaque
oscillante (11) se mouvant horizontalement et en va-et-vient dans ledit liquide de
refroidissement (1); ou
2) changer la pression à appliquer à un niveau de surface liquide dudit liquide de
refroidissement (1) par introduction d'un gaz au-dessus dudit niveau de surface liquide
par un tuyau d'introduction de gaz (5); ou
3) combiner l'application des oscillations audit liquide de refroidissement (1) avec
la plaque oscillante (11) se mouvant horizontalement et en va-et-vient dans ledit
liquide de refroidissement (1), et le changement de la pression à appliquer au niveau
de surface liquide dudit liquide de refroidissement (1) par introduction du gaz au-dessus
dudit niveau de surface liquide par ledit tuyau d'introduction de gaz (5); et
agiter ledit liquide de refroidissement (1) avec un agitateur (20) après le début
de ladite rupture de ladite couche superficielle de vapeur.
2. Procédé de refroidissement d'une pièce métallique selon la revendication 1, caractérisé en ce que lesdites oscillations appliquées audit liquide de refroidissement (1) sont générées
par une pluralité de dites plaques oscillantes (11).
3. Procédé de refroidissement d'une pièce métallique selon la revendication 1 ou 2, caractérisé en ce qu'on ajuste au moins, ou bien l'amplitude, ou bien la fréquence, des oscillations en
fonction de l'épaisseur de ladite couche superficielle de vapeur.
4. Procédé de refroidissement d'une pièce métallique selon la revendication 1 ou 2, caractérisé en ce qu'on ajuste au moins, ou bien l'amplitude, ou bien la fréquence, des oscillations en
fonction de l'état dudit liquide de refroidissement (1)
5. Procédé de refroidissement d'une pièce métallique selon l'une des revendications 1
à 4, caractérisé en ce qu'on agite ledit liquide de refroidissement (1) après le début de ladite rupture de
ladite couche superficielle de vapeur, et après que des bulles formées par ladite
rupture de ladite couche superficielle de vapeur sont amenées à diffuser dans ledit
liquide de refroidissement (1).
6. Procédé de refroidissement d'une pièce métallique selon la revendication 5, caractérisé en ce qu'on ajuste au moins, ou bien l'intensité de ladite agitation, ou bien la direction
du flux généré par ladite agitation, en fonction de l'état dudit liquide de refroidissement
(1) de l'état de ladite pièce métallique dans ledit liquide de refroidissement (1).
7. Procédé de fabrication d'une pièce métallique, comportant:
le chauffage d'une pièce métallique ;
le refroidissement de ladite pièce métallique par immersion de ladite pièce métallique
une fois chauffée dans un liquide de refroidissement (1), ledit refroidissement comportant
la rupture d'une couche superficielle de vapeur qui est formée quand ledit liquide
de refroidissement (1) se vaporise sur une surface de ladite pièce métallique, par
l'application d'une pression sur ladite couche superficielle de vapeur de façon à
faire varier la pression de façon répétée sans agiter ledit liquide de refroidissement
(1),
caractérisé en ce qu'on modifie ladite pression par l'une quelconque des actions:
1) appliquer des oscillations audit liquide de refroidissement (1) avec une plaque
oscillante (11) se mouvant horizontalement et en va-et-vient dans ledit liquide de
refroidissement (1); ou
2) changer, de façon répétée, la pression à appliquer à un niveau de surface liquide
dudit liquide de refroidissement (1) par introduction d'un gaz au-dessus dudit niveau
de surface liquide par un tuyau d'introduction de gaz (5); ou
3) combiner l'application des oscillations audit liquide de refroidissement (1) avec
une plaque oscillante (11) se mouvant horizontalement et en va-et-vient dans ledit
liquide de refroidissement (1), et le changement de la pression à appliquer à un niveau
de surface liquide dudit liquide de refroidissement (1) par introduction d'un gaz
au-dessus dudit niveau de surface liquide par ledit tuyau d'introduction de gaz (5);
et
agiter ledit liquide de refroidissement (1) avec un agitateur (20) après le début
de ladite rupture de ladite couche superficielle de vapeur.
8. Appareil de refroidissement d'une pièce métallique par immersion de ladite pièce métallique
une fois chauffée dans un liquide de refroidissement (1), ledit appareil comportant:
une plaque oscillante (11),
un agitateur (20), et
un moyen de commande (30),
et où une couche superficielle de vapeur, qui est formée quand ledit liquide de refroidissement
(1) se vaporise sur une surface de ladite pièce métallique, est rompue par l'application
d'une pression sur ladite couche superficielle de vapeur de façon à faire varier la
pression de façon répétée sans agiter ledit liquide de refroidissement (1),
caractérisé en ce que ladite pression est modifiée par :
1) ou bien l'application d'oscillations audit liquide de refroidissement (1) avec
une plaque oscillante (11) se mouvant horizontalement et en va-et-vient dans ledit
liquide de refroidissement (1) ;ou
2) ou bien le changement de la pression à appliquer à un niveau de surface liquide
dudit liquide de refroidissement (1) par introduction d'un gaz au-dessus dudit niveau
de surface liquide par un tuyau d'introduction de gaz (5); ou
3) ou bien la combinaison de l'application des oscillations audit liquide de refroidissement
(1) avec une plaque oscillante (11) se mouvant horizontalement et en va-et-vient dans
ledit liquide de refroidissement (1), et le changement de la pression à appliquer
à un niveau de surface liquide dudit liquide de refroidissement (1) par introduction
d'un gaz au-dessus dudit niveau de surface liquide par ledit tuyau d'introduction
de gaz (5); et
où ledit agitateur (20) agite ledit liquide de refroidissement (1) après le début
de ladite rupture de ladite couche superficielle de vapeur.