U.S. patent application number 15/037235 was filed with the patent office on 2016-10-13 for pulling-up-type continuous casting method and pulling-up-type continuous casting apparatus.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Naoaki SUGIURA, Yusuke YOKOTA.
Application Number | 20160296999 15/037235 |
Document ID | / |
Family ID | 51894175 |
Filed Date | 2016-10-13 |
United States Patent
Application |
20160296999 |
Kind Code |
A1 |
SUGIURA; Naoaki ; et
al. |
October 13, 2016 |
PULLING-UP-TYPE CONTINUOUS CASTING METHOD AND PULLING-UP-TYPE
CONTINUOUS CASTING APPARATUS
Abstract
A pulling-up-type continuous casting method according to an
aspect of the present invention includes disposing a shape defining
member (102) above a molten-metal surface of molten metal (M1) held
in a holding furnace (101), the shape defining member (102) being
configured to define a cross-sectional shape of a cast-metal
article (M3) to be cast, submerging a starter (ST) into the molten
metal (M1) while making the starter (ST) pass through the shape
defining member (102), and pulling up the molten metal (M1) by
pulling up the starter (ST) while making the molten metal (M1) pass
through the shape defining member (102) after a temperature of the
shape defining member (102) reaches a predetermined reference
temperature. The reference temperature is equal to or higher than a
solidification completion temperature of the molten metal (M1).
Inventors: |
SUGIURA; Naoaki;
(Takahama-shi, JP) ; YOKOTA; Yusuke; (Toyota-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOYOTA JIDOSHA KABUSHIKI KAISHA |
Toyota-shi, Aichi |
|
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi, Aichi
JP
|
Family ID: |
51894175 |
Appl. No.: |
15/037235 |
Filed: |
October 8, 2014 |
PCT Filed: |
October 8, 2014 |
PCT NO: |
PCT/JP2014/077623 |
371 Date: |
May 17, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22D 11/20 20130101;
B22D 11/01 20130101; B22D 11/041 20130101; B22D 11/145
20130101 |
International
Class: |
B22D 11/20 20060101
B22D011/20; B22D 11/041 20060101 B22D011/041; B22D 11/14 20060101
B22D011/14 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 26, 2013 |
JP |
2013-244004 |
Claims
1-11. (canceled)
12. A pulling-up-type continuous casting method comprising:
disposing a shape defining member above a molten-metal surface of
molten metal held in a holding furnace, the shape defining member
being configured to define a cross-sectional shape of a cast-metal
article to be cast; submerging a starter into the molten metal
while making the starter pass through the shape defining member;
and pulling up the molten metal by pulling up the starter while
making the molten metal pass through the shape defining member
after a temperature of the shape defining member reaches a
predetermined reference temperature, wherein the reference
temperature is equal to or higher than a solidification completion
temperature of the molten metal and wherein the temperature of the
shape defining member is measured by a contact-type temperature
sensor fixed on a top-side main surface of the shape defining
member.
13. The pulling-up-type continuous casting method according to
claim 12, wherein the reference temperature is equal to or higher
than a solidification start temperature of the molten metal.
14. The pulling-up-type continuous casting method according to
claim 12, wherein in the step of disposing the shape defining
member, a bottom-side main surface of the shape defining member is
brought into contact with the molten-metal surface.
15. The pulling-up-type continuous casting method according to
claim 12, wherein the shape defining member comprises a heating
unit that heats the shape defining member itself, and in the
pulling-up the molten metal, the shape defining member is heated by
the heating unit until the temperature of the shape defining member
reaches the reference temperature.
16. A pulling-up-type continuous casting apparatus comprising: a
holding furnace that holds molten metal; a shape defining member
disposed above a molten-metal surface of the molten metal, the
shape defining member being configured to define a cross-sectional
shape of a cast-metal article to be cast; a temperature sensor that
measures a temperature of the shape defining member; a pulling-up
machine that pulls up the molten metal by pulling up a starter
while making the molten metal pass through the shape defining
member; and a casting control unit that starts the pulling-up by
the pulling-up machine after the temperature of the shape defining
member measured by the temperature sensor reaches a predetermined
reference temperature, wherein the reference temperature is equal
to or higher than a solidification completion temperature of the
molten metal and wherein the temperature sensor is a contact-type
temperature sensor fixed on a top-side main surface of the shape
defining member.
17. The pulling-up-type continuous casting apparatus according to
claim 16, wherein the reference temperature is equal to or higher
than a solidification start temperature of the molten metal.
18. The pulling-up-type continuous casting apparatus according to
claim 16, wherein the shape defining member is disposed so that its
bottom-side main surface is in contact with the molten-metal
surface.
19. The pulling-up-type continuous casting apparatus according to
claim 16, wherein the shape defining member comprises a heating
unit that heats the shape defining member itself.
20. The pulling-up-type continuous casting apparatus according to
claim 19, wherein the heating unit is disposed on a periphery of a
molten-metal passage section through which the molten metal passes
in the shape defining member.
21. The pulling-up-type continuous casting apparatus according to
claim 19, wherein the casting control unit instructs the heating
unit to heat the shape defining member until the temperature of the
shape defining member measured by the temperature sensor reaches
the reference temperature.
Description
TECHNICAL FIELD
[0001] The present invention relates to a pulling-up-type
continuous casting method and a pulling-up-type continuous casting
apparatus.
BACKGROUND ART
[0002] Patent Literature 1 proposes a free casting method as a
revolutionary pulling-up-type continuous casting method that does
not requires any mold. As shown in Patent Literature 1, after a
starter is submerged under the surface of a melted metal (molten
metal) (i.e., molten-metal surface), the starter is pulled up, so
that some of the molten metal follows the starter and is drawn up
by the starter by the surface film of the molten metal and/or the
surface tension. Note that it is possible to continuously cast a
cast-metal article having a desired cross-sectional shape by
drawing the molten metal and cooling the drawn molten metal through
a shape defining member disposed in the vicinity of the
molten-metal surface.
[0003] In the ordinary continuous casting method, the shape in the
longitudinal direction as well as the shape in cross section is
defined by the mold. In the continuous casting method, in
particular, since the solidified metal (i.e., cast-metal article)
needs to pass through the inside of the mold, the cast-metal
article has such a shape that it extends in a straight-line shape
in the longitudinal direction.
[0004] In contrast to this, the shape defining member used in the
free casting method defines only the cross-sectional shape of the
cast-metal article, while it does not define the shape in the
longitudinal direction. As a result, cast-metal articles having
various shapes in the longitudinal direction can be produced by
pulling up the starter while moving the starter (or the shape
defining member) in a horizontal direction. For example, Patent
Literature 1 discloses a hollow cast-metal article (i.e., a pipe)
having a zigzag shape or a helical shape in the longitudinal
direction rather than the straight-line shape.
CITATION LIST
Patent Literature
[0005] PTL 1: Japanese Unexamined Patent Application Publication
No. 2012-61518
SUMMARY OF INVENTION
Technical Problem
[0006] The present inventors have found the following problem.
[0007] In the free casting method disclosed in Patent Literature 1,
when the shape defining member is not sufficiently heated, in
particular, at the start of casting and the like, the molten metal
that follows the bottom end of the starter being pulled up
solidifies as the molten metal comes into contact with the shape
defining member when the starter passes through the shape defining
member in some cases. In such cases, the solidified pieces get
snagged on the shape defining member, causing surface defects such
as peeling and curling in the cast-metal article near the boundary
between the starter and the cast-metal article.
[0008] The present invention has been made in view of the
above-described problem, and an object thereof is to provide a
pulling-up-type continuous casting method and a pulling-up-type
continuous casting apparatus in which the surface defects in the
cast-metal article near the boundary between the starter and the
cast-metal article is prevented.
Solution to Problem
[0009] A pulling-up-type continuous casting method according to an
aspect of the present invention includes: [0010] disposing a shape
defining member above a molten-metal surface of molten metal held
in a holding furnace, the shape defining member being configured to
define a cross-sectional shape of a cast-metal article to be cast;
[0011] submerging a starter into the molten metal while making the
starter pass through the shape defining member; and [0012] pulling
up the molten metal by pulling up the starter while making the
molten metal pass through the shape defining member after a
temperature of the shape defining member reaches a predetermined
reference temperature, in which [0013] the reference temperature is
equal to or higher than a solidification completion temperature of
the molten metal.
[0014] In the pulling-up-type continuous casting method according
to this aspect of the present invention, the molten metal is pulled
up by pulling up the starter while making the molten metal pass
through the shape defining member after the temperature of the
shape defining member reaches the predetermined reference
temperature. Note that the reference temperature is equal to or
higher than the solidification completion temperature of the molten
metal. Therefore, the solidification of the molten metal, which
would otherwise occur due to the contact between the molten metal
following the bottom end of the starter being pulled up and the
shape defining member, can be prevented, thus preventing the
surface defects in the cast-metal article near the boundary between
the starter and the cast-metal article.
[0015] A pulling-up-type continuous casting apparatus according to
an aspect of the present invention includes: [0016] a holding
furnace that holds molten metal; [0017] a shape defining member
disposed above a molten-metal surface of the molten metal, the
shape defining member being configured to define a cross-sectional
shape of a cast-metal article to be cast; [0018] a temperature
sensor that measures a temperature of the shape defining member;
[0019] a pulling-up machine that pulls up the molten metal by
pulling up a starter while making the molten metal pass through the
shape defining member; and [0020] a casting control unit that
starts the pulling-up by the pulling-up machine after the
temperature of the shape defining member measured by the
temperature sensor reaches a predetermined reference temperature,
in which [0021] the reference temperature is equal to or higher
than a solidification completion temperature of the molten
metal.
[0022] The pulling-up-type continuous casting apparatus according
to this aspect of the present invention includes the casting
control unit that starts the pulling-up by the pulling-up machine
after the temperature of the shape defining member measured by the
temperature sensor reaches the predetermined reference temperature.
Note that the reference temperature is equal to or higher than the
solidification completion temperature of the molten metal.
Therefore, the solidification of the molten metal, which would
otherwise occur due to the contact between the molten metal
following the bottom end of the starter being pulled up and the
shape defining member, can be prevented, thus preventing the
surface defects in the cast-metal article near the boundary between
the starter and the cast-metal article.
Advantageous Effects of Invention
[0023] According to the present invention, it is possible to
provide a pulling-up-type continuous casting method and a
pulling-up-type continuous casting apparatus in which the surface
defects in the cast-metal article near the boundary between the
starter and the cast-metal article is prevented.
BRIEF DESCRIPTION OF DRAWINGS
[0024] FIG. 1 is a schematic cross section of a free casting
apparatus according to a first exemplary embodiment;
[0025] FIG. 2 is a plane view of a shape defining member 102
according to the first exemplary embodiment;
[0026] FIG. 3 is a block diagram of a casting control system
provided in a free casting apparatus according to the first
exemplary embodiment;
[0027] FIG. 4 is an enlarged cross section schematically showing a
state where a starter ST passes through a shape defining member 102
after the temperature of the shape defining member 102 reaches a
reference temperature;
[0028] FIG. 5 is an enlarged cross section schematically showing a
state where the starter ST passes through the shape defining member
102 before the temperature of the shape defining member 102 reaches
the reference temperature;
[0029] FIG. 6 is a macro-photograph showing a state where a starter
ST is pulled up through a shape defining member 102 when the
temperature of the shape defining member 102 is 650 degrees C.,
which is higher than a reference temperature;
[0030] FIG. 7 is a macro-photograph showing a state where the
starter ST is pulled up through the shape defining member 102 when
the temperature of the shape defining member 102 is 200 degrees C.,
which is lower than the reference temperature;
[0031] FIG. 8 is a plane view of a shape defining member 102
according to a modified example of the first exemplary
embodiment;
[0032] FIG. 9 is a side view of a shape defining member 102
according to a modified example of the first exemplary
embodiment;
[0033] FIG. 10 is an enlarged cross section schematically showing a
shape defining member 202 of a free casting apparatus according to
a second exemplary embodiment; and
[0034] FIG. 11 is a block diagram of a casting control system
provided in a free casting apparatus according to the second
exemplary embodiment.
DESCRIPTION OF EMBODIMENTS
[0035] Specific exemplary embodiments to which the present
invention is applied are explained hereinafter in detail with
reference to the drawings. However, the present invention is not
limited to exemplary embodiments shown below. Further, the
following descriptions and the drawings are simplified as
appropriate for clarifying the explanation.
First Exemplary Embodiment
[0036] Firstly, a free casting apparatus (pulling-up-type
continuous casting apparatus) according to a first exemplary
embodiment is explained with reference to FIG. 1. FIG. 1 is a
schematic cross section of a free casting apparatus according to
the first exemplary embodiment. As shown in FIG. 1, the free
casting apparatus according to the first exemplary embodiment
includes a molten-metal holding furnace 101, a shape defining
member 102, a support rod 104, an actuator 105, a cooling gas
nozzle 106, a cooling gas supply unit 107, a pulling-up machine
108, and a temperature sensor 110.
[0037] Note that needless to say, the right-hand xyz-coordinate
system shown in FIG. 1 is illustrated for the sake of convenience,
in particular, for explaining the positional relation among
components. In FIG. 1, the xy-plane forms a horizontal plane and
the z-axis direction is the vertical direction. More specifically,
the positive direction on the z-axis is the vertically upward
direction.
[0038] The molten-metal holding furnace 101 contains molten metal
M1 such as aluminum or its alloy, and maintains the molten metal M1
at a predetermined temperature (e.g., about 720 degrees C.) at
which the molten metal M1 has fluidity. In the example shown in
FIG. 1, since the molten-metal holding furnace 101 is not
replenished with molten metal during the casting process, the
surface of molten metal M1 (i.e., molten-metal surface) is lowered
as the casting process advances. Alternatively, the molten-metal
holding furnace 101 may be replenished with molten metal as
required during the casting process so that the molten-metal
surface is kept at a fixed level. Note that the position of the
solidification interface SIF can be raised by increasing the
setting temperature of the molten-metal holding furnace 101 and the
solidification interface SIF can be lowered by lowering the setting
temperature of the molten-metal holding furnace 101. Needless to
say, the molten metal M1 may be a metal other than aluminum and an
alloy thereof.
[0039] The shape defining member 102 is made of ceramic or
stainless, for example, and disposed above the molten metal M1. The
shape defining member 102 defines the cross-sectional shape of cast
metal M3 to be cast. The cast metal M3 shown in FIG. 1 is a plate
or a solid cast-metal article having a rectangular shape in a
horizontal cross section (hereinafter referred to as "lateral cross
section"). Note that needless to say, there are no particular
restrictions on the cross-sectional shape of the cast metal M3. The
cast metal M3 may be a hollow cast-metal article such as a circular
pipe and a rectangular pipe.
[0040] In the example shown in FIG. 1, the shape defining member
102 is disposed so that its bottom-side main surface (bottom
surface) is in contact with the molten-metal surface. Therefore, it
is possible to prevent oxide films formed on the surface of the
molten metal M1 and foreign substances floating on the surface of
the molten metal M1 from entering the cast metal M3. Further, the
shape defining member 102 can be easily heated by the molten metal
M1.
[0041] Alternatively, the shape defining member 102 may be disposed
so that its bottom surface is a predetermined distance (e.g., about
0.5 mm) away from the molten-metal surface. When the shape defining
member 102 is disposed a certain distance away from the
molten-metal surface, the thermal deformation and the erosion of
the shape defining member 102 is prevented, thus improving the
durability of the shape defining member 102.
[0042] FIG. 2 is a plane view of the shape defining member 102
according to the first exemplary embodiment. Note that the cross
section of the shape defining member 102 shown in FIG. 1
corresponds to a cross section taken along the line I-I in FIG. 2.
As shown in FIG. 2, the shape defining member 102 has, for example,
a rectangular shape as viewed from the top, and has a rectangular
opening (molten-metal passage section 103) having a thickness t1
and a width w1 at the center thereof
[0043] Note that the temperature sensor 110, which is fixed on the
top-side main surface (top surface) of the shape defining member
102, is also shown in FIG. 2. Further, the xyz-coordinate system
shown in FIG. 2 corresponds to that shown in FIG. 1.
[0044] As shown in FIG. 1, the molten metal M1 follows the cast
metal M3 and is pulled up by the cast metal M3 by its surface film
and/or the surface tension. Further, the molten metal M1 passes
through the molten-metal passage section 103 of the shape defining
member 102. That is, as the molten metal M1 passes through the
molten-metal passage section 103 of the shape defining member 102,
an external force(s) is applied from the shape defining member 102
to the molten metal M1 and the cross-sectional shape of the cast
metal M3 is thereby defined. Note that the molten metal that
follows the cast metal M3 and is pulled up from the molten-metal
surface by the surface film of the molten metal and/or the surface
tension is called "held molten metal M2". Further, the boundary
between the cast metal M3 and the held molten metal M2 is the
solidification interface SIF.
[0045] The support rod 104 supports the shape defining member
102.
[0046] The support rod 104 is connected to the actuator 105. By the
actuator 105, the shape defining member 102 can be moved in the
up/down direction (vertical direction, i.e., z-axis direction)
through the support rod 104. With this configuration, it is
possible to move the shape defining member 102 downward as the
molten-metal surface is lowered due to the advance of the casting
process.
[0047] The cooling gas nozzle (cooling section) 106 is cooling
means for spraying a cooling gas (for example, air, nitrogen, or
argon) supplied from the cooling gas supply unit 107 on the cast
metal M3 and thereby cooling the cast metal M3. The position of the
solidification interface SIF can be lowered by increasing the flow
rate of the cooling gas and the position of the solidification
interface SIF can be raised by reducing the flow rate of the
cooling gas. Note that the cooling gas nozzle 106 can also be moved
in the up/down direction (vertical direction, i.e., z-axis
direction) and the horizontal direction (x-axis direction and/or
y-axis direction). Therefore, for example, it is possible to move
the cooling gas nozzle 106 downward in conformity with the movement
of the shape defining member 102 as the molten-metal surface is
lowered due to the advance of the casting process. Alternatively,
the cooling gas nozzle 106 can be moved in a horizontal direction
in conformity with the horizontal movement of the pulling-up
machine 108.
[0048] By cooling the cast metal M3 by the cooling gas while
pulling up the cast metal M3 by using the pulling-up machine 108
connected to the starter ST, the held molten metal M2 located in
the vicinity of the solidification interface SIF is successively
solidified from its upper side (the positive side in the z-axis
direction) toward its lower side (the negative side in the z-axis
direction) and the cast metal M3 is formed. The position of the
solidification interface SIF can be raised by increasing the
pulling-up speed of the pulling-up machine 108 and the position of
the solidification interface SIF can be lowered by reducing the
pulling-up speed. Further, the shape in the longitudinal direction
of the cast metal M3 can be arbitrarily changed by pulling up the
cast metal M3 while moving the pulling-up machine 108 in a
horizontal direction (x-axis direction and/or y-axis direction).
Note that the shape in the longitudinal direction of the cast metal
M3 may be arbitrarily changed by moving the shape defining member
102 in a horizontal direction instead of moving the pulling-up
machine 108 in a horizontal direction.
[0049] Note that in order to obtain a cast-metal article M3 having
an accurate size and excellent surface quality, the solidification
interface SIF is kept at an appropriate position (height). That is,
the casting is performed in a state where the solidifying speed in
the solidification interface SIF is substantially balanced by the
pulling-up speed. In view of productivity, it is desirable that the
pulling-up speed be greater. However, if the pulling-up speed is
increased while the solidifying speed is unchanged, the
solidification interface SIF rises, thus causing the held molten
metal M2 to be torn off. As described above, the solidifying speed
can be increased (i.e., the solidification interface SIF can be
lowered) by increasing the flow rate of the cooling gas and/or
lowering the molten metal temperature.
[0050] The temperature sensor 110 measures the temperature of the
shape defining member 102. In the example shown in FIG. 1, the
temperature sensor 110 is a thermocouple. As shown in FIG. 1, the
temperature sensor 110 is preferably fixed in the vicinity of the
molten-metal passage section 103 on the top surface of the shape
defining member 102. Note that the temperature sensor 110 is not
limited to the thermocouple. That is, other contact-type
temperature sensors may be used. Further, non-contact-type
temperature sensors may also be used. The contact-type temperature
sensor enables more accurate temperature measurement.
[0051] The free casting apparatus according to the first exemplary
embodiment can measure the temperature of the shape defining member
102 by the temperature sensor 110. Therefore, at the start of
casting, it is possible to start pulling up the starter ST after
the temperature of the shape defining member 102 reaches the
solidification completion temperature (solidus temperature) of the
molten metal M1 or a higher temperature. As a result, the
solidification of the held molten metal M2, which would otherwise
occur due to the contact between the held molten metal M2 following
the starter ST being pulled up and the shape defining member 102,
can be prevented, thus preventing the occurrence of the surface
defects in the cast metal M3 near the boundary between the starter
ST and the cast metal M3. Note that it is further preferable that
the pulling-up of the starter ST through the shape defining member
102 be started after the temperature of the shape defining member
102 reaches the solidification start temperature (liquidus
temperature) of the molten metal M1. Note that in the case of pure
metal, both the solidification completion temperature and the
solidification start temperature correspond to the melting point of
that metal and thus are equal to each other.
[0052] Next, a casting control system provided in a free casting
apparatus according to the first exemplary embodiment is explained
with reference to FIG. 3. FIG. 3 is a block diagram of a casting
control system provided in a free casting apparatus according to
the first exemplary embodiment. As shown in FIG. 3, this casting
control system includes a shape defining member 102, a pulling-up
machine 108, a temperature sensor 110, and a casting control unit
111. Note that the shape defining member 102, the pulling-up
machine 108, and the temperature sensor 110 have already been
explained with reference to FIG. 1, and therefore their detailed
explanation is omitted here.
[0053] The casting control unit 111 includes a storage unit (not
shown) that memorizes the reference temperature of the shape
defining member 102 which is used when the starter ST starts to be
pulled up from the molten metal M1. Then, when the temperature of
the shape defining member 102 measured by the temperature sensor
110 is lower than the reference temperature, the casting control
unit 111 does not start the pulling-up of the starter ST by the
pulling-up machine 108. On the other hand, when the temperature of
the shape defining member 102 measured by the temperature sensor
110 reaches the reference temperature, the casting control unit 111
starts the pulling-up of the starter ST by the pulling-up machine
108.
[0054] Note that the reference temperature is equal to or higher
than the solidification completion temperature of the molten metal
M1. When the reference temperature is lower than the solidification
completion temperature of the molten metal M1, the held molten
metal M2 that follows the bottom end of the starter ST being pulled
up solidifies as the held molten metal M2 comes into contact with
the shape defining member 102. As a result, surface defects such as
peeling and curling tend to occur in the cast metal M3. On the
other hand, when the reference temperature is equal to or higher
than the solidification completion temperature of the molten metal
M1, the held molten metal M2 hardly solidifies even when the held
molten metal M2 comes into contact with the shape defining member
102. Further, when the reference temperature is equal to or higher
than the solidification start temperature, theoretically the held
molten metal M2 does not solidify even when the held molten metal
M2 comes into contact with the shape defining member 102.
Therefore, the reference temperature is preferably equal to or
higher than the solidification start temperature.
[0055] FIG. 4 is an enlarged cross section schematically showing a
state where the starter ST passes through the shape defining member
102 after the temperature of the shape defining member 102 reaches
the reference temperature. That is, FIG. 4 shows an example
according to the first exemplary embodiment. As shown in FIG. 4,
when the temperature of the shape defining member 102 is higher
than the reference temperature, the solidification of the held
molten metal M2, which would otherwise occur due to the contact
between the held molten metal M2 following the starter ST being
pulled up and the shape defining member 102, is prevented.
[0056] In contrast to this, FIG. 5 is an enlarged cross section
schematically showing a state where the starter ST passes through
the shape defining member 102 before the temperature of the shape
defining member 102 reaches the reference temperature. That is,
FIG. 5 shows a comparative example of the first exemplary
embodiment. As shown in FIG. 5, when the temperature of the shape
defining member 102 is lower than the reference temperature, a
solidified piece(s) M21 is generated in the boundary between the
starter ST and the shape defining member 102 as the held molten
metal M2 following the starter ST being pulled up comes into
contact with the low-temperature shape defining member 102.
[0057] Note that the xyz-coordinate systems shown in FIGS. 4 and 5
correspond to that shown in FIG. 1.
[0058] FIG. 6 is a macro-photograph showing a state where the
starter ST is pulled up through the shape defining member 102 when
the temperature of the shape defining member 102 is 650 degrees C.,
which is higher than the reference temperature. That is, FIG. 6
shows an example according to the first exemplary embodiment. As
shown in FIG. 6, when the temperature of the shape defining member
102 is higher than the reference temperature, the surface defects
in the cast metal M3, which would otherwise occur near the boundary
between the starter ST and the cast metal M3, is prevented.
[0059] In contrast to this, FIG. 7 is a macro-photograph showing a
state where the starter ST is pulled up through the shape defining
member 102 when the temperature of the shape defining member 102 is
200 degrees C., which is lower than the reference temperature. That
is, FIG. 7 shows a comparative example of the first exemplary
embodiment. As shown in FIG. 7, when the temperature of the shape
defining member 102 is lower than the reference temperature,
surface defects M22 such as peeling and curling in the cast metal
M3 occur near the boundary between the starter ST and the cast
metal M3.
[0060] Next, a free casting method according to the first exemplary
embodiment is explained with reference to FIG. 1.
[0061] Firstly, the starter ST is lowered by the pulling-up machine
108 and made to pass through the molten-metal passage section 103
of the shape defining member 102, and the tip (bottom) of the
starter ST is submerged into the molten metal M1.
[0062] Next, the starter ST starts to be pulled up at a
predetermined speed. Note that even when the starter ST is pulled
away from the molten-metal surface, the molten metal M1 follows the
starter ST and is pulled up from the molten-metal surface by the
surface film and/or the surface tension. That is, the held molten
metal M2 is formed. As shown in FIG. 1, the held molten metal M2 is
formed in the molten-metal passage section 103 of the shape
defining member 102. That is, the held molten metal M2 is shaped
into a given shape by the shape defining member 102.
[0063] As described above, in the free casting method according to
the first exemplary embodiment, the starter ST starts to be pulled
up after the temperature of the shape defining member 102 reaches
the solidification completion temperature of the molten metal M1 or
a higher temperature. As a result, the solidification of the held
molten metal M2, which would otherwise occur due to the contact
between the held molten metal M2 following the starter ST being
pulled up and the shape defining member 102, can be prevented, thus
preventing the occurrence of the surface defects in the cast metal
M3 near the boundary between the starter ST and the cast metal
M3.
[0064] Next, since the starter ST or the cast metal M3 is cooled by
a cooling gas, the held molten metal M2 is indirectly cooled and
successively solidifies from its upper side toward its lower side.
As a result, the cast metal M3 grows. In this manner, it is
possible to continuously cast the cast metal M3.
Modified Example of First Exemplary Embodiment
[0065] Next, a free casting apparatus according to a modified
example of the first exemplary embodiment is explained with
reference to FIGS. 8 and 9. FIG. 8 is a plane view of a shape
defining member 102 according to a modified example of the first
exemplary embodiment. FIG. 9 is a side view of the shape defining
member 102 according to the modified example of the first exemplary
embodiment. Note that the xyz-coordinate systems shown in FIGS. 8
and 9 also correspond to that shown in FIG. 1.
[0066] The shape defining member 102 according to the first
exemplary embodiment shown in FIG. 2 is composed of one plate.
Therefore, the thickness t1 and the width w1 of the molten-metal
passage section 103 are fixed. In contrast to this, the shape
defining member 102 according to the modified example of the first
exemplary embodiment includes four rectangular shape defining
plates 102a, 102b, 102c and 102d as shown in FIG. 8. That is, the
shape defining member 102 according to the modified example of the
first exemplary embodiment is divided into a plurality of sections.
With this configuration, it is possible to change the thickness t1
and the width w1 of the molten-metal passage section 103. Further,
the four rectangular shape defining plates 102a, 102b, 102c and
102d can be moved in unison in the z-axis direction.
[0067] As shown in FIG. 8, the shape defining plates 102a and 102b
are arranged to be opposed to each other in the y-axis direction.
Further, as shown in FIG. 9, the shape defining plates 102a and
102b are disposed at the same height in the z-axis direction. The
gap between the shape defining plates 102a and 102b defines the
width w1 of the molten-metal passage section 103. Further, since
each of the shape defining plates 102a and 102b can be
independently moved in the y-axis direction, the width w1 can be
changed.
[0068] Note that the temperature sensor 110 is fixed in the
vicinity of the molten-metal passage section 103 on the top surface
of the shape defining plate 102b.
[0069] Further, as shown in FIGS. 8 and 9, a laser displacement
gauge S1 and a laser reflector plate S2 may be provided on the
shape defining plates 102a and 102b, respectively, in order to
measure the width w1 of the molten-metal passage section 103.
[0070] [0038] Further, as shown in FIG. 8, the shape defining
plates 102c and 102d are arranged to be opposed to each other in
the x-axis direction. Further, the shape defining plates 102c and
102d are disposed at the same height in the z-axis direction. The
gap between the shape defining plates 102c and 102d defines the
thickness t1 of the molten-metal passage section 103. Further,
since each of the shape defining plates 102c and 102d can be
independently moved in the x-axis direction, the thickness t1 can
be changed.
[0071] The shape defining plates 102a and 102b are disposed in such
a manner that they are in contact with the top sides of the shape
defining plates 102c and 102d.
[0072] Next, a driving mechanism for the shape defining plate 102a
is explained with reference to FIGS. 8 and 9. As shown in FIGS. 8
and 9, the driving mechanism for the shape defining plate 102a
includes slide tables T1 and T2, linear guides G11, G12, G21 and
G22, actuators A1 and A2, and rods R1 and R2. Note that although
each of the shape defining plates 102b, 102c and 102d also includes
its driving mechanism as in the case of the shape defining plate
102a, the illustration of them is omitted in FIGS. 8 and 9.
[0073] As shown in FIGS. 8 and 9, the shape defining plate 102a is
placed and fixed on the slide table T1, which can be slid in the
y-axis direction. The slide table T1 is slidably placed on a pair
of linear guides Gil and G12 extending in parallel with the y-axis
direction. Further, the slide table T1 is connected to the rod R1
extending from the actuator A1 in the y-axis direction. With the
above-described configuration, the shape defining plate 102a can be
slid in the y-axis direction.
[0074] Further, as shown in FIGS. 8 and 9, the linear guides G11
and G12 and the actuator A1 are placed and fixed on the slide table
T2, which can be slid in the z-axis direction. The slide table T2
is slidably placed on a pair of linear guides G21 and G22 extending
in parallel with the z-axis direction. Further, the slide table T2
is connected to the rod R2 extending from the actuator A2 in the
z-axis direction. The linear guides G21 and G22 and the actuator A2
are fixed on a horizontal floor surface or a horizontal pedestal
(not shown). With the above-described configuration, the shape
defining plate 102a can be slid in the z-axis direction. Note that
examples of the actuators A1 and A2 include a hydraulic cylinder,
an air cylinder, and a motor.
Second Exemplary Embodiment
[0075] Next, a free casting apparatus according to a second
exemplary embodiment is explained with reference to FIG. 10. FIG.
10 is an enlarged cross section schematically showing a shape
defining member 202 of a free casting apparatus according to the
second exemplary embodiment. The free casting apparatus according
to the second exemplary embodiment is equipped with a heating unit
(heater) 20 disposed inside the shape defining member 202. The rest
of the configuration is similar to that of the free casting
apparatus according to the first exemplary embodiment. Note that
the xyz-coordinate system shown in FIG. 10 also corresponds to that
shown in FIG. 1.
[0076] The heating unit 20 is disposed inside the shape defining
member 202 so as to surround the molten-metal passage section 103.
As a result, the heating unit 20 can effectively heat the periphery
of the molten-metal passage section 103, which comes into contact
with the held molten metal M2. Therefore, the free casting
apparatus according to the second exemplary embodiment can increase
the temperature of the shape defining member 202 to the reference
temperature in a shorter time than that of the free casting
apparatus according to the first exemplary embodiment. That is, the
productivity of the free casting apparatus according to the second
exemplary embodiment is better than that of the free casting
apparatus according to the first exemplary embodiment. Note that
the heating unit 20 may be disposed on the top surface of the shape
defining member 202 instead of being disposed inside the shape
defining member 202.
[0077] Next, a casting control system provided in a free casting
apparatus according to the second exemplary embodiment is explained
with reference to FIG. 11. FIG. 11 is a block diagram of a casting
control system provided in a free casting apparatus according to
the second exemplary embodiment. As shown in FIG. 11, this casting
control system includes a shape defining member 202, a pulling-up
machine 108, a temperature sensor 110, and a casting control unit
111. Note that the shape defining member 202 includes a heating
unit 20. Details of the shape defining member 202 are the same as
those explained above with reference to FIG. 10. Further, the
pulling-up machine 108 and the temperature sensor 110 are similar
to those of the first exemplary embodiment, and therefore their
detailed explanations are omitted.
[0078] The casting control unit 111 starts heating the shape
defining member 202 by the heating unit 20 before starting the
pulling-up of the starter ST from the molten metal M1. Then, when
the temperature of the shape defining member 202 measured by the
temperature sensor 110 is lower than the reference temperature, the
casting control unit 111 does not start the pulling-up of the
starter ST by the pulling-up machine 108 and continues the heating
of the shape defining member 202 by the heating unit 20. On the
other hand, when the temperature of the shape defining member 202
measured by the temperature sensor 110 reaches the reference
temperature, the casting control unit 111 starts the pulling-up of
the starter ST by the pulling-up machine 108. At this point, the
casting control unit 111 stops the heating of the shape defining
member 202 by the heating unit 20. Note that the heating of the
shape defining member 202 by the heating unit 20 may be continued
when the pulling-up of the starter ST is started. However, by
stopping the heating, the power consumption can be reduced.
[0079] Note that the present invention is not limited to the
above-described exemplary embodiments, and various modifications
can be made without departing from the spirit and scope of the
present invention.
[0080] This application is based upon and claims the benefit of
priority from Japanese patent application No. 2013-244004, filed on
Nov. 26, 2013, the disclosure of which is incorporated herein in
its entirety by reference.
REFERENCE SIGNS LIST
[0081] 20 HEATING UNIT [0082] 101 MOLTEN METAL HOLDING FURNACE
[0083] 102, 202 SHAPE DEFINING MEMBER [0084] 102a-102d SHAPE
DEFINING PLATE [0085] 103 MOLTEN-METAL PASSAGE SECTION [0086] 104
SUPPORT ROD [0087] 105 ACTUATOR [0088] 106 COOLING GAS NOZZLE
[0089] 107 COOLING GAS SUPPLY UNIT [0090] 108 PULLING-UP MACHINE
[0091] 110 TEMPERATURE SENSOR [0092] 111 CASTING CONTROL UNIT
[0093] A1, A2 ACTUATOR [0094] G11, G12, G21, G22 LINEAR GUIDE
[0095] M1 MOLTEN METAL [0096] M2 HELD MOLTEN METAL [0097] M21
SOLIDIFIED PIECE [0098] M3 CAST METAL [0099] R1, R2 ROD [0100] S1
LASER DISPLACEMENT GAUGE [0101] S2 LASER REFLECTOR PLATE [0102] SIF
SOLIDIFICATION INTERFACE [0103] ST STARTER [0104] T1, T2 SLIDE
TABLE
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