U.S. patent application number 10/440148 was filed with the patent office on 2005-02-17 for molten metal supply device and aluminum titanate ceramic member having improved non-wettability.
This patent application is currently assigned to JAPAN FINE CERAMICS CENTER. Invention is credited to Kashiwagi, Kazumi, Kawamoto, Hiroshi, Kawasaki, Yuji, Kimura, Masaharu, Kimura, Masane, Kitaoka, Satoshi, Kume, Toshio, Nanjo, Fusayuki, Noda, Katsutoshi, Suzuki, Itsuo, Suzuki, Sadahiko.
Application Number | 20050035504 10/440148 |
Document ID | / |
Family ID | 26604303 |
Filed Date | 2005-02-17 |
United States Patent
Application |
20050035504 |
Kind Code |
A1 |
Kitaoka, Satoshi ; et
al. |
February 17, 2005 |
Molten metal supply device and aluminum titanate ceramic member
having improved non-wettability
Abstract
An electromagnetic type molten metal supply device having
superior accuracy in supplying molten metal. This device is
comprised of a rotary vane that rotates in accordance with the
movement of molten metal inside a molten metal transport conduit,
and the amount of molten metal being transported can be measured by
detecting the rotational frequency of the rotary vane.
Inventors: |
Kitaoka, Satoshi;
(Aichi-ken, JP) ; Kashiwagi, Kazumi; (aichi-ken,
JP) ; Nanjo, Fusayuki; (Aichi-ken, JP) ;
Kawamoto, Hiroshi; (Aichi-ken, JP) ; Noda,
Katsutoshi; (Aichi-ken, JP) ; Kimura, Masane;
(Aichi-ken, JP) ; Kimura, Masaharu; (Aichi-ken,
JP) ; Kawasaki, Yuji; (Aichi-ken, JP) ;
Suzuki, Itsuo; (Aichi-ken, JP) ; Suzuki,
Sadahiko; (Aichi-ken, JP) ; Kume, Toshio;
(Aichi-ken, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
JAPAN FINE CERAMICS CENTER
Nagoya-shi
JP
ROOT CO., LTD.
Nagoya-shi
JP
KIMURA CO., LTD.
Obu-shi
JP
YUSHIN KOSAN CO., LTD.
Nagoya-shi
JP
MARUSU GLAZE CO., LTD.
Seto-shi
JP
|
Family ID: |
26604303 |
Appl. No.: |
10/440148 |
Filed: |
May 19, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10440148 |
May 19, 2003 |
|
|
|
PCT/JP01/05571 |
Jun 28, 2001 |
|
|
|
Current U.S.
Class: |
266/237 |
Current CPC
Class: |
B22D 37/00 20130101;
B22D 39/006 20130101; C04B 2235/401 20130101; C04B 2111/1056
20130101; C04B 2235/3272 20130101; C04B 41/5029 20130101; C04B
2235/3217 20130101; G01F 1/06 20130101; C04B 41/009 20130101; C04B
41/5046 20130101; B22D 35/00 20130101; C04B 35/443 20130101; C04B
2111/00879 20130101; C04B 41/009 20130101; C04B 2235/72 20130101;
C04B 2235/94 20130101; C04B 41/5031 20130101; C04B 41/5029
20130101; C04B 2235/3418 20130101; C04B 41/4523 20130101; C04B
41/4558 20130101; C04B 41/4535 20130101; C04B 35/462 20130101; C04B
2235/9676 20130101; C04B 41/87 20130101; C04B 41/4537 20130101;
C04B 41/5031 20130101; C04B 35/478 20130101; C04B 41/4535 20130101;
C04B 2235/3206 20130101; C04B 41/5046 20130101 |
Class at
Publication: |
266/237 |
International
Class: |
B22D 019/00; C22B
009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 20, 2000 |
JP |
2000-353386 |
Feb 2, 2001 |
JP |
2001-27436 |
Claims
What is claimed:
1. A molten aluminum alloy supply device comprising: an
electromagnetic pump and a molten metal transport conduit provided
with said electromagnetic pump, wherein the transport conduit
compises aluminum titanate ceramic base material and has in at
least a part that come into contact with the molten aluminum alloy
a layer which Si content is less than that in said aluminum
titanate ceramic base material.
2. A supply device as in claim 1, wherein said layer contains one
or more components selected from the group consisting of
Al.sub.2O.sub.3, MgO and MgAl.sub.2O.sub.4.
3. A supply device as in claim 1, wherein said Si content of the
layer is equal to or less than 3 wt %.
4. A supply device as in claim 1, wherein said aluminum titanate
ceramic base material contains .alpha.-Al2O3.
5. A supply device as in claim 1 comprising: a rotary vane that is
provided inside the transport conduit and which rotates in
accordance with the movement of the molten aluminum alloy and a
detector that detects the rotational frequency of the rotary
vane.
6. A supply device as in claim 5, wherein said rotary vane has a
shaft and blades arranged on the shaft; the shaft is mounted in the
transport conduit via a cap member having a convex portion that is
fitted into a tapered fitting hole provided in the said transport
conduit and a throughhole that passes through the convex portion
and in which the shaft can be fitted.
7. A supply device as in claim 6, wherein said cap member is
pressure-fitted in said transport conduit by means of securing
member.
8. A supply device as in claim 7, wherein the tensile force
sufficient to compensate for the thermal expansion of said securing
member is applied to the said securing member.
9. A supply device as in claim 1, wherein said transport conduit
has a device detecting the volume of the molten aluminum alloy
inside the transport conduit.
10. A supply device as in claim 5, wherein said rotary vane
compises aluminum titanate ceramic base material and has in at
least a part that come into contact with the molten aluminum alloy
a layer which Si content is less than that in said aluminum
titanate ceramic base material.
11. A casting device comprising a molten aluminum alloy supply
devise as in claim 1.
12. A molten aluminum alloy contact member, the contact member
comprising aluminum titanate ceramic base material and having in at
least a part that comes into contact with the molten aluminum alloy
a layer which Si content is less than that in said aluminum
titanate ceramic base material.
13. A contact member as in claim 12, wherein said layer contains
one or more components selected from the group consisting of
Al.sub.2O.sub.3, MgO and MgAl.sub.2O.sub.4.
14. A contact member as in claim 12, wherein said layer contains
Al.sub.2TiO.sub.5.
15. A contact member as in claim 12, wherein said Si content of the
layer is equal to or less than 3 wt %.
16. A contact member as in claim 12, wherein said contact member
comprises one or more members selected from the group consisting of
ladle, transport conduit and mixing device.
17. A casting device comprising on or more molten aluminum titanate
alloy contact member as in claim 12.
18. A method of manufacturing aluminum alloy cast, using the molten
aluminum alloy contact member as in claim 12.
19. A method of manufacturing a molten aluminum alloy contact
member comprising steps: preparing a contact member comprising
aluminum titanate ceramic base material having in at least a part
of the contact member a layer containing one or more components
selected from the group consisting of Al.sub.2O.sub.3, MgO and
Al.sub.2TiO.sub.5, wherein the Si content of the layer is less than
that in the aluminum titanate ceramic base material; and
synthesizing MgAl.sub.2O.sub.4 in the layer by causing magnesium
and/or aluminum to act upon the layer.
20. A method of manufacturing a molten aluminum alloy contact
member comprising steps: preparing a contact member comprising
aluminum titanate ceramic base material having in at least a part
of the contact member a layer containing one or more components
selected from the group consisting of Al.sub.2O.sub.3, MgO and
Al.sub.2TiO.sub.5, wherein the Si content of the layer is less than
that in the aluminum titanate ceramic base material; and contacting
the layer of the contact member to a molten aluminum alloy
containing magnesium in at least a part of molten aluminum alloy
casting process and thereby synthesizing MgAl.sub.2O.sub.4 in the
layer.
21. A method of manufacturing an aluminium alloy cast comprising
steps: preparing a contact member comprising aluminum titanate
ceramic base material having in at least a part of the contact
member a layer containing one or more components selected from the
group consisting of Al.sub.2O.sub.3, MgO and Al.sub.2TiO.sub.5,
wherein the Si content of the layer is less than that in the
aluminum titanate ceramic base material; and contacting the layer
of the contact member to a molten aluminum alloy containing
magnesium in at least a part of molten aluminum alloy casting
process and thereby synthesizing MgAl.sub.2O.sub.4 in the layer.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a continuation of Application PCT/JP01/05571, filed
Jun. 28, 2001, now abandoned.
BACK GROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to a molten metal supply device that
transports/supplies molten metallic aluminum and molten metallic
sodium, for example. In addition, this invention relates to a
technology for conferring and retaining the non-wettability of a
ceramic member that comes into contact with a molten metal such as
a molten aluminum alloy.
[0004] 2. Description of the Related Art
[0005] For example, a linear induction electromagnetic pump that
confers a thrust to a molten metal by means of the electromagnetic
induction effect is used to transport molten metals such as molten
metallic sodium in a fast breeder reactor or molten metallic
aluminum in a casting facility.
[0006] In a molten metal supply device, in particular a molten
metal supply device in a casting facility, it is important to
supply a predetermined amount of molten metal to the cavity used
for casting, in order to achieve casting accuracy.
[0007] A molten metal supply device having an electromagnetic pump
supplies molten metal to a casting cavity or a cylinder by
regulating the transfer velocity and the transfer time thereof, by
means of various types of current controls, to regulate the current
frequency supplied to the electromagnetic pump, the current
density, the current supply time, etc.
[0008] However, since an electromagnetic pump confers a thrust to
the molten metal, which is a fluid, it is difficult to accurately
control the transfer volume thereof by means of current
control.
[0009] Even when a discharge cylinder is provided for supplying a
molten metal to the cavity, the molten metal supply accuracy of the
electromagnetic pump ultimately becomes a problem. In addition,
even if an orifice or valve is provided in the supply path to the
cavity, the volume of molten metal supplied thereto will depend on
the molten metal supply accuracy.
[0010] Furthermore, the molten metal supply device, in particular
the members thereof that come into contact with the molten metal,
must be formed from a ceramic that has superior low thermal
expansion and thermal shock resistant properties. For example, in
aluminum alloy casting equipment, an aluminum titanate ceramic
ladle is often used as a measuring device in order to move a
predetermined amount of molten aluminum alloy from a molten metal
holding furnace to a molding machine. This ladle is formed from an
aluminum titanate ceramic that has superior low thermal expansion
and thermal shock resistant properties.
[0011] It is well known that aluminum titanate ceramic has low
thermal expansion and superior thermal shock resistant properties.
However, aluminum titanate ceramic only appears to possess low
thermal resistance because of cracks that appear at its grain
boundaries. Thus, the fact that the mechanical strength thereof is
considerably weakened by these cracks at the grain boundaries is a
problem.
[0012] Therefore, between several and 10 wt % of silica is
generally added to the ceramic in order to both retain the low
thermal expansion properties and increase the mechanical strength
thereof. In this way, grain growth during the sintering process for
the aluminum titanate is suppressed, and as a result, grain
boundary stress generated in the post-sintering cooling process is
reduced, and thus the mechanical strength of the ceramic is
improved because the generation of cracks is suppressed.
[0013] However, a significant reduction in the non-wettability of
the aluminum titanate ceramic ladle will occur after it has been
used continuously for about 1000 times to ladle molten metal, and
aluminum will remain on the inside of the ladle and its spout. As a
result, it will be difficult to supply a predetermined quantity of
molten metal to the forming machine, and this will cause an
increase in the defect rate caused by changes in the weight of cast
metal parts.
[0014] Furthermore, pieces of aluminum alloy that have been
deposited and hardened on the spout of the ladle will come into
contact with the casting system equipment, thus damaging the ladle
itself or the ladling machine.
[0015] At present, methods such as stopping the molten metal supply
ladle and mechanically stripping off the aluminum alloy that has
been deposited thereon are employed after the non-wettability
thereof has been reduced. In order to increase productivity, the
ladle must maintain its non-wettability for at least 10,000 ladling
cycles.
[0016] Because of the reasons stated above, there have been calls
for a molten metal supply device that has superior molten metal
supply accuracy. In particular, there have been calls for a molten
metal contact member that has superior molten metal supply accuracy
due to both its non-wettability with respect to molten aluminum
alloy and its ability to retain this non-wettability.
SUMMARY OF THE INVENTION
[0017] The present inventors have created the following inventions
as a means of solving the abovementioned problems.
[0018] The present inventors have developed a molten metal supply
device that uses an electromagnetic pump and which has good supply
accuracy.
[0019] In other words, the present invention is a molten metal
supply device, comprising:
[0020] a molten metal transport conduit provided with an
electromagnetic pump;
[0021] a rotary vane that is provided inside the transport conduit
and which rotates in accordance with the movement of the molten
metal; and
[0022] a detector that detects the rotational frequency of the
rotary vane.
[0023] According to this device, the amount of molten metal
transported by magnetic induction inside the transport conduit can
be measured based upon the rotational frequency of the rotary vane
that is detected by the detector. In addition, the amount of molten
metal transported can also be regulated based upon the rotational
frequency of the rotary vane. Because of this, the amount of molten
metal supplied can be accurately controlled. In this device, it is
preferred that a means for detecting the amount of molten metal
inside the transport conduit be provided in the transport conduit.
According to this aspect of the invention, accuracy and precision
in the detection and control of the amount of molten metal
transported, that are caused by changes in the amount of molten
metal inside the transport conduit, can be corrected.
[0024] In addition, one aspect of the present invention also
provides;
[0025] a method of manufacturing a cast metal object by supplying
molten metal using an electromagnetic pump;
[0026] that is provided with a rotary vane in a transport conduit
that transports molten metal to a cavity in a cast;
[0027] that detects the rotational frequency of the rotary vane
during the transportation of the molten metal; and
[0028] that controls the amount of molten metal supplied based on
the rotational frequency.
[0029] According to this method, a highly precise cast metal object
can be easily obtained.
[0030] In addition, another aspect of the present invention
provides,
[0031] a measuring device for a molten metal supply device that
uses an electromagnetic pump having:
[0032] a rotary vane that is provided in a molten metal transport
conduit and which is rotated in accordance with the movement of
molten metal; and
[0033] a detector that detects the rotational frequency of the
rotary vane.
[0034] In this measuring device, it is further preferred that a
means of detecting the amount of molten metal inside the transport
conduit be provided in the transport conduit.
[0035] According to this device, the amount of molten metal
transported can be measured with a high degree of accuracy.
[0036] In addition, the present inventors have studied the decrease
in the non-wettability of aluminum titanate ceramic with respect to
molten aluminum alloy, and have learned that silica added to
aluminum titanate ceramic is reduced by Al and Mg in the molten
aluminum alloy, synthesizing Si particles on the surface of the
aluminum titanate ceramic and the presence of these Si particles
reduces the non-wettability. Furthermore, it was learned that due
to the reduction of the silica, MgO and Al.sub.2O are produced on
the surface of aluminum titanate ceramic, and moreover because of
these compounds, MgAlO.sub.4 is produced on the surface of aluminum
titanate ceramic.
[0037] In other words, the present inventors have discovered that a
reduction in non-wettability can be controlled or avoided, and
non-wettability can be conferred and retained, by avoiding the
presence or generation of Si on the surface of aluminum titanate
ceramic that come into contact with the molten aluminum alloy.
[0038] Thus, according to the present invention, the following
means are provided due to the aforementioned discovery.
[0039] That is, a molten aluminum alloy contact member composed of
aluminum titanate ceramic having in at least the part that comes
into contact with the molten aluminum alloy:
[0040] a layer containing one or more components selected from the
group consisting of Al.sub.2O.sub.3, MgO, and MgAl.sub.2O.sub.4,
wherein the Si content of the layer is less than that in the
aforementioned aluminum titanate ceramic material.
[0041] In addition, a molten aluminum alloy contact member composed
of aluminum titanate ceramic having in at least the part that comes
into contact with the molten aluminum alloy:
[0042] an aluminum titanate layer having an Si content that is less
than that in the aforementioned aluminum titanate ceramic
material.
[0043] In addition, a molten metal supply device comprising these
contact members is provided.
[0044] The present invention provides a method of manufacturing a
molten aluminum alloy contact member composed of aluminum titanate
ceramic, having:
[0045] a process for forming, in at least the part of the aluminum
titanate ceramic member that comes into contact with the molten
aluminum alloy, a layer containing one or more components selected
from the group consisting of Al.sub.2O.sub.3, MgO, and
Al.sub.2TiO.sub.5, wherein the Si content of the layer is less than
that in the aforementioned aluminum titanate ceramic material; and
a
[0046] process for synthesizing MgAl.sub.2O.sub.4 by causing
magnesium and/or aluminum to act upon the layer containing
Al.sub.2O.sub.3, MgO, and/or Al.sub.2TiO.sub.5.
[0047] The present invention also provides a method of
manufacturing a molten aluminum alloy contact member, having:
[0048] a process for forming, in at least the part of the aluminum
titanate ceramic member at which two or more members are jointed
and which comes into contact with the molten aluminum alloy, a
layer containing one or more components selected from the group
consisting of Al.sub.2O.sub.3, MgO, and Al.sub.2TiO.sub.5, wherein
the Si content of the layer is less than that in the aforementioned
aluminum titanate ceramic material; and
[0049] a process for synthesizing MgAl.sub.2O.sub.4 by causing
magnesium and/or aluminum to act upon the layer containing
Al.sub.2O.sub.3, MgO, and/or Al.sub.2TiO.sub.5.
[0050] Furthermore, the present invention provides a method of
manufacturing an aluminum alloy casting, having:
[0051] a process of synthesizing MgAl.sub.2O.sub.4 in a layer
containing Al.sub.2O.sub.3, MgO and/or Al.sub.2TiO.sub.5 by causing
a molten aluminum alloy contact member composed of an aluminum
titanate ceramic material, provided in at least the part that comes
into contact with the molten aluminum alloy with a layer containing
one or more components selected from the group consisting of
Al.sub.2O.sub.3, MgO, and Al.sub.2TiO.sub.5, and containing less Si
than that in the aforementioned aluminum titanate ceramic material,
to come into contact with a molten aluminum alloy containing Mg in
at least part of the casting process.
[0052] The present invention also provides a method of
manufacturing a molten aluminum alloy contact member, having:
[0053] a process of synthesizing MgAl.sub.2O.sub.4 in a layer
containing Al.sub.2O.sub.3, MgO and/or Al.sub.2TiO.sub.5 by causing
a molten aluminum alloy contact member composed of an aluminum
titanate ceramic material, provided in at least the part that comes
into contact with the molten aluminum alloy with a layer containing
one or more components selected from the group consisting of
Al.sub.2O.sub.3, MgO, and Al.sub.2TiO.sub.5, and containing less Si
than that in the aforementioned aluminum titanate ceramic material,
to come into contact with a molten aluminum alloy containing Mg in
at least part of the casting process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0054] FIG. 1 A figure illustrating the overall construction of a
molten metal supply device according to the present invention.
[0055] FIG. 2 A figure of a transport conduit and an
electromagnetic pump viewed from above.
[0056] FIG. 3 Cross sectional views (a) and (b) illustrating a
preferred disposition of the electromagnetic pump with respect to
the transport conduit.
[0057] FIG. 4 A cross sectional diagram illustrating the entire
measuring device in the molten metal supply device.
[0058] FIG. 5 A figure illustrating an example of the structure of
a rotary vane.
[0059] FIG. 6 FIG. 6(a) shows a cross sectional view of the
disposition of the rotary vane in the transport conduit in the
direction of the molten metal flow path. FIG. 6(b) shows a cross
sectional view of the disposition of the rotary vane in the
transport conduit in the direction that intersects the flow path.
FIG. 6(c) illustrates the disposition of the rotary vane in the
transport conduit as viewed from above.
[0060] FIG. 7 A figure illustrating a means to detect the amount of
molten metal in the transport conduit.
[0061] FIG. 8 A cross sectional view illustrating one example of a
structure for mounting the rotary vane inside the transport
conduit.
[0062] FIG. 9 A perspective view illustrating the structures of a
fitting hole and a cap for mounting the rotary vane into the
transport conduit.
[0063] FIG. 10 A cross sectional view illustrating one example of
how the cap is fastened to the transport conduit.
[0064] FIG. 11 A figure illustrating one example of a reverse flow
prevention device.
[0065] FIG. 12 A figure illustrating a method for controlling an
electromagnetic pump when the transport of molten metal is
initiated.
[0066] FIG. 13 FIGS. 13(a) and 13(b) illustrate the shape of a
ceramic ladle produced in an embodiment. FIG. 13(a) is a plan view,
and FIG. 13(b) is a cross sectional view taken along the line A-A
of FIG. 13(a).
[0067] FIG. 14 FIGS. 14(a) and 14(b) illustrate the shape of a
ceramic bonded set produced in an embodiment. FIG. 14(a) is a
vertical cross section showing the bonded set that has been
vertically separated, and FIG. 14(b) is a plan view of the lower
member thereof.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0068] Details of embodiments of the present invention will be
described below.
[0069] The molten metal supply device that uses an electromagnetic
pump according to the present invention is comprised of at least a
rotary vane that rotates in accordance with the movement of molten
metal that is transported inside a molten metal transport conduit
by the electromagnetic pump, and a detector that detects the
rotational frequency of the rotary vane. Said rotary vane and the
detector form a measuring device according to the present
invention.
[0070] In addition, the casting manufacturing method according to
the present invention should preferably employ this supply
device.
[0071] The molten metal supply device according to the present
invention will be illustrated below, and an embodiment of the
present invention will be described in detail.
[0072] The overall structure of a molten metal supply device 2 is
shown in FIG. 1. The molten metal supply device of the present
invention (hereinafter referred to as "the supply device") may be a
device for supplying molten metal for metal casting, or a device
for supplying molten metallic sodium to a fast breeder reactor, but
is preferably a molten metal supply device for metal casting.
[0073] The supply device 2 is a device for supplying molten metal
for metal casting, and comprises a transport conduit 4, an
electromagnetic pump 10 disposed along the conduit, and a measuring
device 20.
[0074] (Transport Conduit)
[0075] The shape of the transport conduit 4 provided in the supply
device 2 that transports molten metal is not particularly limited,
but preferably has a flat shape. When the transport conduit 4 has a
flat shape, an electromagnetic pump is efficiently formed, by
disposing an inductor adjacent to the long sides of the transport
conduit 4. In other words, sufficient drive torque can be obtained
with respect to the molten metal even if no core is provided inside
the conduit. More specifically, a flat rectangular pipe or an
elliptically shaped cylinder can be employed as the transport
conduit 4.
[0076] The transport conduit 4 may be made of a non-magnetic
material through which magnetic flux can pass, and ceramics can be
used. Preferably, a ceramic having a low thermal expansion, with
the coefficient of thermal expansion being
1.times.10.sup.-6/.degree. C. (room temperature to 1000 .degree.
C.) or lower should be used. If the coefficient of thermal
expansion exceeds this value, there are serious concerns that the
transport conduit 4 will be destroyed by the thermal shock that
occurs during the transport of the molten metal. Aluminum titanate
can be used for this material. It is necessary to prevent the
molten metal inside the transport conduit 4 from cooling and
hardening. Because of this, it is preferred that the transport
conduit 4 be insulated so that the metal therein is maintained at
its melting temperature. In particular, it is preferred that the
thermal conductivity of the transport conduit 4 be increased by
forming concave grooves in the surface of the transport conduit 4,
and that a tube-shaped heater be wrapped around the transport
conduit 4.
[0077] On the other hand, the electromagnetic pump 10 disposed on
the periphery of the transport conduit 4 must be cooled in order to
ensure its operation. Because of this, it is preferred that an
insulating layer be formed around the outer periphery of the
transport conduit, which is heated and insulated. The insulating
layer is preferably composed of an insulating material and a gas
(air) layer. A ceramic, glass or the like can be used as the
insulating material. In addition, the gas layer can be formed such
that air is forced to pass through a ventilation conduit. It should
be noted that it is preferred that the transport conduit 4 be
insulated along its entire length.
[0078] (Electromagnetic Pump)
[0079] A variety of structures can be employed as the
electromagnetic pump 10 in the supply device 2. The electromagnetic
pump 10 may be either an external type or an immersion type, or may
be a modified version of these.
[0080] An inductor 12 of the electromagnetic pump 10 is disposed
such that it generates movement torque in the molten metal inside
the transport conduit 4. The inductor 12 is comprised of at least a
stator core 14 and a coil 16.
[0081] FIG. 2 shows an upper view of the transport conduit 4 and
the electromagnetic pump 10.
[0082] Depending on the shape of the transport conduit 4,
sufficient drive torque may be produced in the molten metal inside
the transport conduit by the stator core 14 and the coil 16 only.
However, it is also possible to provide a core inside the transport
conduit 4 such that said core faces the stator core.
[0083] It is possible to use the stator core 14 and the coil 16 by
themselves if the inductor 12 comprising the stator core 14 and the
coil 16, which are provided facing each other across the transport
conduit 4, does not require a separate core inside the transport
conduit 4 because the transport conduit 4 is sufficiently
narrow.
[0084] In addition, the inductor 12 comprising the stator core 14
and the coil 16 can be provided inside the transport conduit 4. For
example, it is possible to use a type of transport conduit 4 that
has a double wall structure having an outer tube and an inner tube,
and to position the stator core 14 and the coil 16 inside the inner
tube and form the outer tube from a magnetic material to be used as
a core.
[0085] Note that the inductor 12 can be disposed in a variety of
configurations with respect to the transport conduit 4, but it is
preferred that it be disposed as shown in FIG. 3. In other words,
when the stator core 14 and the coil 16 are disposed on the
exterior of the transport conduit 4, it is preferred that they be
disposed such that they are in the same horizontal position (i.e.,
at the same height) on two sides of the transport conduit 4 having
a rectangular shape that is longer in the vertical direction, or
that they be inclined from horizontal up to 15 degrees. If they
exceed 15 degrees, there is a great deal of concern that elements
of the electromagnetic pump 10 may be damaged, should molten metal
leak from the transport conduit 4. More preferably, the inductor 12
is inclined in an angular range between the horizontal and 6
degrees from the horizontal. Note that as shown in FIGS. 3(a) and
3(b), it is preferred that the horizontal central line of the
transport conduit 4 match the horizontal central line of the
inductor 12 on both sides thereof when viewed from a perpendicular
cross section in the axial direction of the transport conduit
4.
[0086] The supply device 2 can further be provided with a molten
metal holding furnace 18 that maintains molten metal in its molten
state. In this situation, it is preferred that the transport
conduit 4 be arranged such that it is connected to the molten metal
holding furnace 18 from near the bottom thereof and extends upward.
Furthermore, in the case of a casting device, the front end of the
transport conduit is connected to a cavity 5 used for metal
casting.
[0087] (Measuring Device)
[0088] A measuring mechanism (device) for the molten metal
transported by the electromagnetic pump 10 in the supply device 2
comprises a rotary vane 22 that rotates in accordance with the
movement of the molten metal, and a detector 32 that detects the
rotational frequency of the rotary vane. The detailed structure of
the measuring device 20 is shown in FIG. 4.
[0089] (Rotary Vane)
[0090] One embodiment of the rotary vane 22 is shown in FIG. 5. The
rotary vane 22 is formed into a shape and structure that is capable
of being rotated by the molten metal that moves inside the
transport conduit 4. The shape of the vane is not particularly
limited, and can be a screw type or an impeller type. It is
preferable that the vane be the impeller type.
[0091] In the device 2, the rotary vane 22 is formed from a shaft
24 and blades 26 arranged on the shaft 24. Pressure is applied to
the blades 26 by the movement of the molten metal, and in this way
the blades 26 and the shaft 24 are rotated.
[0092] It is preferred that the rotary vane 22 be formed from a
material having such characteristics as non-wettability, corrosion
resistance, and thermal shock resistance, with respect to the
molten metal applied to the supply device 2. In particular, it is
preferred that the coefficient of thermal expansion be
1.times.10.sup.-6/.degree. C. (room temperature to 1000.degree. C.)
or lower if the vane 22 is to be used for molten metallic aluminum.
If the coefficient of thermal expansion exceeds this value, there
will be a conspicuous increase in the possibility that the rotary
vane 22 will be damaged. Ceramic is a non-magnetic material that
has such a coefficient of thermal expansion, and in particular, a
ceramic that is composed primarily of aluminum titanate
(TiAl.sub.2O.sub.5) or Sialon can be used. Note that Sialon is a
type of solid solution of Si.sub.3N.sub.4, and can be one of two
types: .beta.'-Sialon and .alpha.-Sialon. .beta.'-Sialon is a
compound represented by the formula
Si.sub.6-zAl.sub.zO.sub.zN.sub.6-z with z being 0 or greater up to
a maximum value of 4.2. In addition, .alpha.-Sialon is a compound
represented by the formula M.sub.x(Si, Al).sub.12(N, O).sub.16,
with x being 0 or greater up to 2.0. M is one or more selected from
the group consisting of Li, Mg, Ca, and the rare earth elements
(including Y, Nd, Yb or the like).
[0093] It is preferable that the rotary vane 22 be disposed inside
the transport conduit 4 such that the rotary shaft 24 is
perpendicular with respect to the direction in which the molten
metal moves. More preferably, the rotary shaft 24 should be
vertical. This is particularly preferable in situations in which
the inductor 12 is disposed on both sides of the transport conduit
4.
[0094] FIG. 6 shows the rotary vane 22 disposed inside the
transport conduit 4. As shown in FIG. 6(a) and FIG. 6(b), when the
rotary shaft 24 of the rotary vane 22 is perpendicular to the
direction in which the molten metal flows and is disposed
vertically, it is preferable that the rotary shaft 24 be disposed
such that it is eccentric with respect to the vertical center of
the transport conduit 4, as shown in FIG. 6(b). In other words, it
is preferable that the rotary shaft 24 be disposed such that the
width of the flow path of the molten metal formed between the
rotary vane 22 and the sidewall of the transport conduit 4 are not
uniform. When such a configuration is used, the rotation of the
rotary vane 22 will be smoothly initiated and maintained because a
non-uniform differential pressure will be applied to the rotary
vane 22 by the movement of the molten metal. In this situation, a
greater pressure will be applied to the blades 26 located on the
side where the molten metal flow path is wider, and the rotary vane
22 will be rotated such that the blades 26 on said side will move
in the downstream direction.
[0095] In addition, it is preferable that the inductor 12 also be
disposed in the position in which the rotary vane 22 is disposed.
In this situation, it is preferable that the inductor 12 be
disposed such that it is on both sides of the rotary shaft 24 of
the rotary vane 22, and it is more preferable that the rotary vane
22 be eccentric inside the transport conduit 4 between the
inductors 12 facing each other. When disposed in this manner, the
molten metal being driven by the inductors 12 will effectively
rotate the rotary vane 22.
[0096] Furthermore, in order to make it easer to rotate the rotary
vane 22, it may be directly driven by an external motor 40 (see
FIG. 4). In this way, sufficient rotary force can be supplied to
the rotary vane 22, and the rotary vane can be reliably rotated to
transport the molten metal. In particular, it is preferred that the
external motor 40 be used to initiate the rotation of the rotary
vane 22.
[0097] (Rotational Frequency Detector)
[0098] A rotational frequency detector serves to directly or
indirectly detect the rotations that are transmitted to the shaft
24 of the rotary vane 22. Any of the variety of known methods can
be employed as the detection mechanism.
[0099] For example, as shown in FIG. 4, the rotational frequency
detector can be a pulse generator 32 that is arranged such that
when the rotation of the shaft 24 inside the transport conduit 4 is
transmitted, the pulse generator 32 detects the rotation and
generates a pulse. Note that by transmitting the pulses generated
by the pulse generator 32 to a device equipped with a pulse counter
mechanism, the rotational frequency can be easily detected.
[0100] The amount of molten metal transported when the rotary vane
22 arranged in this manner is rotated once can be calculated.
However, the amount of molten metal transported can fluctuate based
on differences in the structure of the device or operating
conditions. Thus, it is preferable to establish the parameters that
cause this fluctuation based upon actual measurements, so that the
amount of molten metal being supplied can be expressed based upon
these parameters during actual measurement.
[0101] Furthermore, as shown in FIG. 4, the drive force of the
external motor 40 can be transmitted to the shaft 24, and the
rotary vane 22 can be formed so that it is rotatively driven from
the exterior thereof. In this way, sufficient rotational force can
be conferred to the rotary vane.
[0102] In situations in which the rotary vane 22 is rotatively
driven by the external motor 40 or the like, a rotor 34 that
rotates in accordance with the rotation of the shaft 24
(preferably, a plate-shaped member), and a sensor 36 that remotely
detects the rotation of the rotor 34, can be arranged on the
exterior of the transport conduit 4. In this situation, by
providing a rotation detection hole in the rotor 34, its rotations
(frequency) can be detected by means of a photoelectric sensor 36.
When this type of rotor 34 and sensor 36 are provided, an
abnormality is generated in the rotation of the exterior rotor 34
when an abnormality is generated in the rotary vane 22 because the
rotary vane 22 inside the transport conduit 4 and the rotor 34 are
formed to be integral with each other. At this time, abnormalities
in the rotary vane 22 can be detected by comparing the rotational
frequency detected by the sensor 36 and the expected rotational
frequency being generated by the motor. Thus, when the rotary vane
22 is driven by an external motor, the rotor 34 and the sensor 36
effectively function as a sensor for detecting any abnormality in
the rotary vane 22 and/or the transport conduit 4.
[0103] Note that even if the rotary vane is not driven by the
external motor 40, the rotor 34 and the sensor 36 function as a
mechanism to check the rotational state of the rotary vane 22.
[0104] The rotor 34 can also serve as an insulating member. In this
situation, the rotor 34 is preferably formed from a material having
high thermal insulation performance and a large surface area.
Furthermore, the rotor 34 can function as a more effective
insulator if a nozzle 38 for a cooling means such as air or the
like that is supplied from a gas supply source blows the cooling
means such as air onto the rotor 34.
[0105] (Detection of the Amount of Molten Metal Inside the
Transport Conduit)
[0106] When calculating the amount of molten metal transported
inside the transport conduit 4 from the rotational frequency of the
rotary vane 22, the amount of molten metal transported per rotation
will change according to the amount of molten metal inside the
transport conduit 4. A means to detect the volume of molten metal
inside the transport conduit 4 is provided in order to compensate
for fluctuations in the transported amount caused by the volume of
the molten metal. This means is not particularly limited, but is
preferably a means to detect the volume of molten metal by
detecting the surface level of the molten metal inside the
transport conduit 4. For example, a float that floats on the molten
metal can be provided inside the transport conduit 4, and the
magnitude of the displacement of this float can be detected from
outside. A detection member that is linked to the displacement of
the float can be provided on the float to detect the amount of
fluctuation of the float from outside.
[0107] A preferred structure is illustrated in FIG. 7. FIG. 7 shows
a float 28 installed on the transport conduit 4 via a mounting unit
30. In this example, the float 28 includes a catch 28a that is
caught on the upper edge of the mounting unit 30, and a contact
member 28b that comes into contact with the molten metal inside the
transport conduit 4. The catch 28a includes an indicator 29 that
indicates the displacement of the float 28. The catch 28a of the
float 28 is engaged with the upper edge of the mounting unit 30 to
enable the float 28 to rock, and at the same time, the mounting
unit 30 has a space 30a that can accommodate the maximum
displacement of the float 28 without hindering its rocking
movements. In this example, the float 28 itself serves as a
detection member, and the displacement produced by the contact
member 28b is transmitted as is to the catch 28a and the indicator
29, and thus is easily comprehended from outside. Note that it is
of course possible to use a separate detection member to transmit
the displacement of the float to the outside.
[0108] The displacement magnitude of the float that is transmitted
to the outside can be detected by a variety of known detection
means, switching means, or the like, and can be detected as the
volume of molten metal. For example, the displacement magnitude of
the float can be detected with a differential transformer, a
magnetic sensor, or the like. Furthermore, the amount of molten
metal transported that is ascertained from the rotational frequency
of the rotary vane 22 can be corrected based on the volume of
molten metal obtained from the sensor.
[0109] Preferably, the float, the mounting unit, and the detection
member all have superior non-wettability and thermal shock
resistance, and have a coefficient of thermal expansion (room
temperature to 1000 degrees C.) of 1.times.10.sup.-6/.degree. C. or
less. More specifically, it is preferable that these members be
formed primarily of aluminum titanate.
[0110] (Rotary Vane Securing Structure)
[0111] The rotary vane 22 must be disposed inside the transport
conduit 4 with excellent sealing performance, and is preferably
mounted such that it can easily be removed from the transport
conduit 4 for maintenance or replacement. In addition, it is
preferred that the rotary vane 22 be mounted such that the effects
of thermal expansion can be avoided as much as possible.
[0112] Because of this, as shown in FIG. 8 and FIG. 9, it is
preferred that the rotary vane 22 be snapped into the transport
conduit 4, primarily using tapered concave and convex members. More
specifically, a tapered fitting hole 42 is provided in the
transport conduit 4 in which the caliber thereof grows smaller
toward the interior of the conduit, a cap 44 is employed that has a
tapered convex portion 46 that is fitted to and matches the fitting
hole 42, and a through hole 48 in which the shaft 24 can be mounted
is provided in the convex portion 46. In this way, the rotary vane
22 can be mounted inside the transport conduit 4 by fitting the
aforementioned cap 44 into the aforementioned fitting hole 42, and
thus the precision of the seal on the conduit 4 can be improved and
maintained by means of a mechanical fitting.
[0113] If thermal expansion is taken into consideration, the
transport conduit 4 and the cap 44 are preferably formed from a
material that has a coefficient of thermal expansion of
1.times.10.sup.-6/.degree. C. (room temperature to 1000.degree.
C.), and more specifically, are preferably formed primarily from
aluminum titanate. In addition, it is preferable that the rotary
vane also be formed from a material having a coefficient of thermal
expansion of 1.times.10.sup.-6/.degree. C. (room temperature to
1000.degree. C.) or less, and preferable that this material be
aluminum titanate ceramic.
[0114] Note that the means of securing the cap 44 to the transport
conduit 4 is not particularly limited. The cap 44 can be secured to
the transport conduit 4 by means of a thermal resistant material,
e.g., a stainless steel fastener (a stainless steel band) or a
screw member. For example, as shown in FIG. 10, one of the end
loops of an endless stainless steel band 50 is placed on the edge
of the cap 44, and the other end loop of the band 50 can be secured
by latching it to a band latch unit 52 fixed at a predetermined
position.
[0115] The securing member preferably has a coefficient of thermal
expansion of 2.times.10.sup.-5/degrees C. (room temperature to
800.degree. C.) or less, but in order to avoid the loosening of the
secured state that may be caused by the thermal expansion of the
securing member, it is preferred that a constant tensile force be
added to the securing member. For example, in the aforementioned
band latching unit 52, the securing member 50 that is latched by
the latch unit 52 can be mounted such that it can be maintained in
a constant-pressure fitted state that is not affected by thermal
expansion. More specifically, the band latch unit 52 is disposed in
a predetermined position via an elastic body 54 that expands and
contracts. In this situation, the band latch unit 52 is
continuously energized in the direction that the elastic body 54
attempts to return to by means of the restoring force of the
elastic body 54. Here, the direction in which the band latch unit
52 is energized is the same direction that can strengthen the
pressure fitting by the securing member 50. By latching the
securing member 50 to the band latch unit 52, the securing member
50 is energized in a constant pressure fitting direction. As a
result, even if the securing member 50 thermally expands, the
effects of this are avoided and a stable pressure-fitted state can
be maintained.
[0116] In addition, for example, a compressed elastic body can also
be used to energize the securing member 50 in the pressure-fitting
direction. In this situation, the restoring force that attempts to
expand or contract the elastic body is used to energize the
securing member. More specifically, the elastic body is secured in
the compressed state onto the inner side of the loop of said looped
securing member, the restoring force of the elastic member is
resisted, and the securing member is mounted thereby. When made in
this manner, even if the securing member thermally expands, the
restoring force of the elastic body can compensate for the
loosening of the pressure-fitted state. Note that not only a
variety of shapes of coil springs can be used for the elastic body,
but an elastomer can be used as well. However, the elastic body
preferably has thermal resistance and low thermal expansion.
[0117] Note that this type of securing structure is particularly
preferable in situations in which the shaft 24 is inserted into the
transport conduit 4 from above.
[0118] Also note that the position of the rotary vane 22 can be
made adjustable by a height adjustment means arranged on the
portion of the shaft 24 outside of the top of the conduit 4. For
example, the adjustment means may be a screw mechanism, and may be
a structure formed to use interchangeable roller bearings of
different heights.
[0119] Furthermore, it is preferable that the shaft 24 comprises an
insulating material so that the heat of the rotary vane 22 is not
transmitted outside the transport conduit 4.
[0120] (Reverse Flow Prevention Device)
[0121] A reverse flow prevention device can be provided in order to
prevent the reverse flow of molten metal due to the rotation of the
rotation vane 22. The reverse flow prevention device can be
provided as a wall-shaped body 60 on the downstream side of the
rotary vane and to the rear in the rotational direction of the
rotary vane. In other words, as shown in FIG. 11, the reverse flow
prevention device is on the downstream side of the rotary vane 22
at a point that corresponds to approximately 1/4 of one rotation of
the blades 26 in the opposite direction from the flow of the molten
metal, and extends approximately along the rotation track of the
tip of the blades 26. This wall-shaped body 60 prevents the molten
metal held between the rotating blades 26 from moving in the
reverse direction with the rotation of the rotary vane 22, and
ensures that the molten metal held between the rotating blades 26
moves in its intended downstream direction.
[0122] The shape of the wall-shaped member is not particularly
limited, but may be comprised of a wall that runs approximately
along the rotation track of at least the tip of the blades 26.
[0123] Next, a method of using this type of molten metal supply
device 2 to supply molten metal to a cavity or the like of a metal
cast and manufacture a cast metal object will be described.
[0124] First, molten metal in the molten metal holding furnace 18
is supplied to a cavity for a metal cast by operating the
electromagnetic pump 10. As the molten metal is transported, the
rotary vane 22 provided inside the transport conduit 4 rotates, and
the rotational frequency thereof is detected by the detector 32. If
the relationship between the rotational frequency and the amount of
molten metal has been established, the operating time of the
electromagnetic pump 10 and the power supply are adjusted based on
the rotational frequency, such that the desired time of rotation of
the rotary vane 22 and/or the rotational frequency thereof are
obtained in order to supply a predetermined amount of molten metal
to the cavity. In this way, a constantly accurate amount of molten
metal can be supplied to the cavity of the metal cast, and a cast
metal object can be manufactured with a high degree of
precision.
[0125] Furthermore, in situations in which a detection means for
detecting the volume of molten metal (molten metal level) that
flows inside the transport conduit 4 is provided, fluctuations in
the amount of molten metal supply obtained from the rotational
frequency of the rotary vane 22 (caused by the volume of molten
metal (molten metal level)) are compensated for based on the
detected volume of molten metal, thereby making a more accurate and
precise supply volume control possible.
[0126] Note that when the driving of the electromagnetic pump 10 is
initiated, it is preferable that the operation of the
electromagnetic pump 10 be controlled such that pressure is applied
to the rotary vane 22 by the non-uniform movement of the molten
metal so that the rotary vane 22 rotates smoothly inside the
transport conduit 4. In other words, it is preferable that a
uniform thrust not be applied on the blades 26 arranged on the
rotary vane 22 by the movement of the molten metal. More
specifically, the inductors 12 disposed opposite each other with
respect to the shaft 24 of the rotary vane 22 are not operated
simultaneously. In particular, as shown in FIG. 12, when the shaft
24 is eccentrically disposed inside the transport conduit, the
inductor 12 on the side having the large gap between the rotary
vane 22 and the inner wall of the transport conduit 4 is operated
first, and the rotation of the rotary vane 22 due to the operation
of this inductor 12 is confirmed by the detector 32. Here, after
the stable rotation of the rotary vane 22 is confirmed, for example
after 10 rotations (10 pulses) or more are confirmed, the inductor
12 on the opposite side is operated next, thereby placing the
electromagnetic pump 10 into normal operation. This differential
system is particularly effective in situations where the thrust due
to electromagnetic induction is small.
[0127] Note that each element of the present invention described
above can be employed separately or in combination with the molten
metal supply device, the measurement device, the method of
manufacturing a cast metal object, and the casting device of the
present invention.
[0128] As described above, the present invention can adopt each of
the following aspects.
[0129] (1) A molten metal supply device that uses an
electromagnetic pump, the molten metal supply device
comprising:
[0130] a molten metal transport conduit provided with an
electromagnetic pump;
[0131] a rotary vane that is provided inside the transport conduit
and which rotates in accordance with the movement of the molten
metal; and
[0132] a detector that detects the rotational frequency of the
rotary vane;
[0133] wherein the rotation shaft of the aforementioned rotary vane
is eccentrically disposed inside the aforementioned transport
conduit.
[0134] (2) A molten metal supply device that uses an
electromagnetic pump, the molten metal supply device
comprising:
[0135] a molten metal transport conduit provided with an
electromagnetic pump;
[0136] a rotary vane that is provided inside the transport conduit
and which rotates in accordance with the movement of the molten
metal; and
[0137] a detector that detects the rotational frequency of the
rotary vane;
[0138] wherein the aforementioned rotary vane includes a shaft and
blades arranged on the shaft;
[0139] the aforementioned shaft is mounted in the transport conduit
via a cap member having a convex portion that is fitted into a
tapered fitting hole provided in the aforementioned transport
conduit and a throughhole that passes through the convex portion
and in which the shaft can be fitted.
[0140] It should be noted that, in this device, it is preferred
that the shaft, the rotary vane, the transport conduit, and the cap
member all be formed primarily of aluminum titanate.
[0141] (3) A molten metal supply device that uses an
electromagnetic pump, the molten metal supply device
comprising:
[0142] a molten metal transport conduit provided with an
electromagnetic pump;
[0143] a rotary vane that is provided inside the transport conduit
and which rotates in accordance with the movement of the molten
metal; and
[0144] a detector that detects the rotational frequency of the
rotary vane;
[0145] wherein the aforementioned cap member is pressure-fitted in
the aforementioned transport conduit by means of a securing
member.
[0146] In this aspect, it is preferred that the aforementioned
securing member be a low thermal expansion metal such as stainless
steel.
[0147] (4) A molten metal supply device that uses an
electromagnetic pump, the molten metal supply device
comprising:
[0148] a molten metal transport conduit provided with an
electromagnetic pump;
[0149] a rotary vane that is provided inside the transport conduit
and which rotates in accordance with the movement of the molten
metal; and
[0150] a detector that detects the rotational frequency of the
rotary vane;
[0151] wherein the aforementioned cap member is pressure-fitted in
the transport conduit by means of a securing member; and
[0152] a tensile force of a degree that can compensate for the
thermal expansion of said securing member is applied to the
aforementioned securing member.
[0153] In this aspect, the tensile force is preferably applied by
an elastic body such as a coil spring.
[0154] (5) A molten metal supply device that uses an
electromagnetic pump, the molten metal supply device
comprising:
[0155] a molten metal transport conduit provided with an
electromagnetic pump;
[0156] a rotary vane that is provided inside the transport conduit
and which rotates in accordance with the movement of the molten
metal; and
[0157] a detector that detects the rotational frequency of the
rotary vane;
[0158] wherein the aforementioned rotary vane is primarily a low
thermal expansion ceramic such as aluminum titanate or Sialon.
[0159] According to the present invention, the accuracy of the
supply of molten metal can be improved in an electromagnetic pump
type molten metal supply device. In addition, a metal casting
device having superior molten metal supply accuracy can be
provided.
[0160] Furthermore, according to the device of the present
invention, a cast metal object having superior accuracy can be
manufactured.
[0161] (6) A molten metal supply device that uses an
electromagnetic pump according to any of the devices (1) to (5)
described above, the molten metal supply device comprising:
[0162] a device to detect the volume of molten metal inside the
transport conduit.
[0163] According to this device, the supply of molten metal can be
controlled with a high degree of accuracy.
[0164] (Molten Aluminum Alloy Contact Member)
[0165] Next, a molten aluminum alloy contact member will be
described.
[0166] The aluminum alloy in the present invention is defined as an
alloy whose primary component is aluminum. More specifically, other
than aluminum, the aluminum alloy can contain at least one or more
metals that can form an alloy with aluminum, such as Cu, Si, Mg,
Zn, Fe, Mn, Ni, or Ti. Preferably, the alloy contains Mg. The
aluminum alloy preferably contains 20 wt % or less of Mg relative
to the whole.
[0167] Examples of the aluminum alloys that can be used in the
present invention are illustrated in Table 1 (units: wt %)
1TABLE 1 Cu Si Mg Zn Fe Mn Ni Ti Al 2.0 7.0 0.5 1.0 1.0 0.5 0.3 0.2
remaining to to or or or or or or portion 4.0 10.0 less less less
less less less
[0168] The molten alloy contact member of the present invention is
preferably applied to a member for molten metal having a part that
may come into contact with the molten metal alloy. Specific
examples include a ladle, a molten metal transport conduit, and an
agitator. Maintenance of these parts is made easier, and the
accuracy of the handling of the molten metal is improved. It is
particularly preferable that the molten alloy contact member of the
present invention be applied to ladles.
[0169] In addition, the molten alloy contact member of the present
invention can be preferably applied even to a member comprising an
aluminum titanate ceramic bonded section, such as a conduit and
molding die. The effect of increasing the non-wettability of the
bonded section interface is that the intrusion of molten metal into
gaps in the bonded section due to capillarity can be effectively
suppressed. In this way, the maintenance of the junction is made
easier.
[0170] Note that the molten alloy contact member of the present
invention is preferably applied to a molten metal supply device
that uses an electromagnetic pump. It is particularly preferable to
apply the molten alloy contact member to the rotary vane, the
blades, the shaft, the cap member, the float and the float-mounting
unit of the molten metal supply device of the present
invention.
[0171] The aluminum titanate ceramic that is the base material of
the contact member of the present invention is a ceramic that is
primarily composed of aluminum titanate (Al.sub.2TiO.sub.5), and
contains Si. Note that the Si contained therein is typically in the
form of silica (SiO.sub.2), but is not limited to this form. Si may
be in the form of a metallic element or a complex oxide of other
metals. The amount of silica contained in the aluminum titanate
ceramic is not particularly limited, but is normally between 1 to
10 wt % and preferably, 4 to 8 wt %. Note that the aluminum
titanate ceramic may also contain Fe.sub.2O.sub.3, MgO, or the
like.
[0172] A layer containing one or two or more compounds selected
from the group consisting of Al.sub.2O.sub.3, MgO, and
MgAl.sub.2O.sub.4 is provided at least at the position in which the
aluminum titanate ceramic contact member comes into contact with
the molten alloy. By providing this layer, the dispersion of the Si
in the aluminum titanate ceramic toward the side that is in contact
with the molten alloy is effectively suppressed when the contact
member comes into contact with the molten aluminum alloy.
[0173] In addition, when the molten alloy contains Si, contact
between that Si and the aluminum titanate ceramic can be
avoided.
[0174] The layer containing one or two or more compounds selected
from the group consisting of Al.sub.2O.sub.3, MgO, and
MgAl.sub.2O.sub.4 can be a layer substantially formed from one of
these compounds, or a layer that is substantially formed from a
combination of these compounds. In either case, it is preferred
that the layer be substantially formed from these compounds or
consist of only these compounds. It is even more preferable that
the layer be single-phase ceramic that is substantially free of
other ceramics. In addition, the layer can have a laminated
structure that includes a plurality of layers.
[0175] The Al.sub.2O.sub.3 is preferably .alpha.-Al.sub.2O.sub.3.
An .alpha.-Al.sub.2O.sub.3 layer can be obtained by forming an
alumina film by dip-coating with Aluminasol, and then baking this
alumina film in the presence of air (preferably at 1100 to
1500.degree. C.).
[0176] The MgO layer can be obtained by dissolving a magnesium salt
in water, dip coating, and then baking the layer in the presence of
air (preferably at 1100 to 1500.degree. C.). The layer is
preferably obtained using dip-coating in an aqueous solution of
magnesium nitrate, and then baking it in the presence of air
(preferably at 1100 to 1500.degree. C.).
[0177] The MgAl.sub.2O.sub.4 layer is obtained by forming an
Al.sub.2O.sub.3 layer and/or a MgO layer, and then applying Mg or
MgO, and/or Al or Al.sub.2O.sub.3, to the coating film. In
addition, the MgAl.sub.2O.sub.4 layer can also be obtained by
forming the raw materials prepared to obtain MgAl.sub.2O.sub.4 and
then baking them to produce a spinel in the layer. It is preferable
that after the .alpha.-Al.sub.2O.sub.3 layer or the MgO layer is
formed, the contact member be formed in place by immersing it in
molten magnesium or a molten metal containing Mg (for example, a
molten aluminum alloy) for a fixed period of time. It is most
preferable that the MgAl.sub.2O.sub.4 layer be formed in place
after the .alpha.-Al.sub.2O.sub.3 layer is formed.
[0178] The layer containing one or two or more compounds selected
from the group consisting of Al.sub.2O.sub.3, MgO, and
MgAl.sub.2O.sub.4 contains less Si than the aluminum titanate
ceramic material. Preferably, the amount of Si contained therein is
3 wt % or less, and more preferably 1 wt % or less. Furthermore, it
is preferable that the layer be substantially free of Si. Here,
"being substantially free of Si" is defined as a Si content of 0.1
wt % or less, and more preferably 0.01 wt % or less.
[0179] The layer containing Al.sub.2O.sub.3, MgO, and
MgAl.sub.2O.sub.4 preferably has one dispersion suppression
function selected from amongst the three following types
(1)-(3).
[0180] (1) The layer containing Al.sub.2O.sub.3, MgO, and
MgAl.sub.2O.sub.4 can suppress the diffusion of Si (other than Si,
silica (SiO2) being typical) in the aluminum titanate ceramic. More
specifically, it provides a degree of compaction and/or film
thickness that can exhibit said diffusion suppression function.
[0181] Note that the diffusion of Si in the aluminum titanate
ceramic is defined as diffusion of Si out of the aluminum titanate
ceramic (toward the molten metal).
[0182] (2) In addition, said layer can control the diffusion of Al
and Mg in the molten aluminum alloy toward the aluminum titanate
ceramic. More specifically, the layer provides a degree of
compaction and/or film thickness that can exhibit said diffusion
suppression function.
[0183] (3) When the molten aluminum alloy contains Si, the
diffusion of Si toward the aluminum titanate ceramic can be
suppressed. More specifically, the layer provides a degree of
compaction and/or film thickness that can exhibit said diffusion
suppression function.
[0184] From amongst the above, it is more preferable to have two or
more types. In particular, it is preferable to have (1) and (2). In
addition, (3) is preferred when the molten aluminum alloy contains
Si. It is most preferable that the layer comprises all of the
diffusion suppression functions.
[0185] To exhibit this type of diffusion suppression function, a
film thickness of 0.1 .mu.m to 1000 .mu.m is preferred. When the
thickness is less than 0.1 .mu.m, the coating film will be quickly
worn away due to repeated contact with the flow of molten alloy,
and will basically lose its diffusion suppression function and
non-wettability. In addition, when the thickness exceeds 1000
.mu.m, the difference in the coefficient of thermal expansion
between the aluminum titanate ceramic and the coating film will
cause cracks and peeling in the coating film during the cooling
process that occurs after the coating is baked, and thus a
diffusion suppression effect cannot be exhibited. Preferably, the
layer has a film thickness of 1 .mu.m to 500 .mu.m, and more
preferably a film thickness of 10 .mu.m to 100 .mu.m.
[0186] In addition, from the viewpoint of a degree of compaction,
the layer containing Al.sub.2O.sub.3, MgO, and MgAl.sub.2O.sub.4
preferably has a porosity of 30% or less. When the porosity exceeds
30%, the diffusion of Al, Mg, and Si in the molten aluminum alloy,
and the diffusion of Si in the aluminum titanate ceramic, are
difficult to suppress.
[0187] An aluminum titanate (Al.sub.2TiO.sub.5) layer containing
less Si than the aluminum titanate ceramic material may be used as
a protective layer. By forming this layer, .alpha.-Al.sub.2O.sub.3,
MgO, and MgAl.sub.2O.sub.4 will be generated on the surface of the
layer due to contact with the molten alloy, and a protective layer
that can confer and maintain non-wettability will be produced in
place.
[0188] The Si content is preferably 3 wt % or less, and more
preferably 1 wt % or less; it is even more preferable that the
layer be substantially free of Si.
[0189] It is preferable that the aluminum titanate layer also be
formed such that it has a compaction and/or film thickness that can
suppress the diffusion of Al, Mg, or Si in the molten aluminum
alloy, and can suppress the diffusion of Si in the aluminum
titanate ceramic. In other words, it preferably has a thickness of
0.1 to 1000 .mu.m and more preferably 1 to 500 .mu.m, and
preferably has a porosity of 30% or less. An aluminum titanate
layer being substantially free of Si means that the Si content is
preferably 0.1 wt % or less, and more preferably 0.01 wt % or less.
Note that it is preferable that the aluminum titanate be
substantially single phase, but it may contain one or more
compounds selected from the group consisting of Al.sub.2O.sub.3,
MgO and MgAl.sub.2O.sub.4.
[0190] In the present invention, by providing a surface layer
containing Al.sub.2O.sub.3, MgO and MgAl.sub.2O.sub.4 and/or
Al.sub.2TiO.sub.5, regardless of the covering film used, diffusion
of Si toward the surface of the aluminum titanate ceramic due to
contact with the molten aluminum alloy can be suppressed,
non-wettability can be maintained, and the non-wettability of the
contact portion can be effectively retained by the
MgAl.sub.2O.sub.4 that is ultimately obtained through contact with
the molten aluminum alloy. Thus, non-wettability can be retained
over the long term.
[0191] In addition, the MgAl.sub.2O.sub.4 layer that is ultimately
obtained can stably retain non-wettability because the infiltration
and diffusion of Si is suppressed.
[0192] Thus, when a member that provides any of these layers at the
contact position with the molten aluminum alloy is employed and a
cast aluminum alloy object is manufactured, a highly accurate
casting can be efficiently achieved.
[0193] In addition, by forming a layer containing Al.sub.2O.sub.3,
MgO and/or Al.sub.2TiO.sub.5 at predetermined positions of the
contact member, and using these positions in the process of casting
aluminum alloy by bringing them into contact with a molten aluminum
alloy containing Mg and/or MgO to form a MgAl.sub.2O.sub.4 layer,
the aluminum titanate ceramic member comprising a MgAl.sub.2O.sub.4
layer according to the present invention can be obtained. In this
way, a MgAl.sub.2O.sub.4 layer can be easily obtained by forming
only an Al.sub.2O.sub.3 layer, and without specifically forming a
MgAl.sub.2O.sub.4 layer.
[0194] In addition, during the casting process, the non-wettability
due to the Al.sub.2O.sub.3 layer and the like is retained in the
beginning, and a MgAl.sub.2O.sub.4 layer is continuously formed in
place as the contact time increases. Since this MgAl.sub.2O.sub.4
layer retains the non-wettability, the non-wettability lifespan of
the aluminum titanate ceramic member can be efficiently
extended.
[0195] [Embodiments]
[0196] Embodiment 1: Production of the Aluminum Titanate
Ceramic
[0197] The aluminum titanate (Al.sub.2TiO.sub.5) base powder that
was used was Marusu Yuuyaku's TA-2 (containing 5 wt % SiO.sub.2) .
Water and an alumina ball were added to the base powder, the weight
ratio of raw material : alumina ball : water was adjusted to
1:1:0.7, and this mixture was mixed in a ball mill for 63 hours.
After that, the Al.sub.2TiO.sub.5 slurry was passed through a sieve
(200 mesh), and water was extracted therefrom with a filter press
to obtain an Al.sub.2TiO.sub.5 press cake.
[0198] To this press cake were added suitable amounts of water, a
deflocculating agent (manufactured by Chukyo Yushi, product name:
D-305), a binder (manufactured by Chukyo Yushi, product name:
WE-518), and the slurry density was adjusted to 2.1 to 2.3
g/cm.sup.3.
[0199] After this, this slurry was poured into a plaster mold, and
after it was cast, it was dried at room temperature to obtain a
green compact. Two types of green compact were produced, the ladle
shape shown in FIG. 13 and the vessel shaped bonded set (2 members)
that comprise the bonded portion shown in FIG. 14. As shown in
FIGS. 13(a) and (b), a ladle-shaped body 102 is a hemispherical
vessel comprising one sprue; and the bonded set, as shown in FIG.
14(a), is a vessel 106 consisting of 2 members vertically disposed
with respect to each other, that has as shown in FIG. 14(b), a
tapered inner circumferential surface 110 in the opening of the
lower member 108, and an upper member 112 that is formed into an
approximately annular body that comprises an outer circumferential
surface 114 that fits into the inner circumferential surface 110.
The two vertically arranged members 112, 108 form an integral
vessel when fitted together.
[0200] Furthermore, by baking the green compacts for one hour at
1600.degree. C. in the presence of air, an Al.sub.2TiO.sub.5
ceramic sintered compact was obtained.
[0201] Embodiment 2: Forming the Al.sub.2O.sub.3 Layer and the
MgAl.sub.2O.sub.4 Layer
[0202] The Al.sub.2TiO.sub.5 ceramic sintered compacts obtained (a
total of three types) were dip-coated in Aluminasol (manufactured
by Nissan Chemical, product name: Aluminasol 200 or Aluminasol
520), and then dried at room temperature. After that, an
.alpha.-Al.sub.2O.sub.3 layer having a thickness of 5 .mu.m was
formed over the entire surface of each Al.sub.2TiO.sub.5 ceramic
sintered compact by baking each at 1100.degree. C. for one hour in
the presence of air.
[0203] After that, each compact was immersed for one hour in a
molten aluminum alloy (A4C: composition shown in Table 1),
700.degree. C.) that contains a trace amount of Mg (0.5 wt %). In
this way, the .alpha.-Al.sub.2O.sub.3 layer on the surface of the
Al.sub.2TiO.sub.5 ceramic reacts with the Mg in the molten A4C, and
a monophase MgAl.sub.2O.sub.4 layer is formed on the surface of the
Al.sub.2TiO.sub.5 ceramic. The thickness of the MgAl.sub.2O.sub.4
layer is the same as the 5-.mu.m thickness of the
.alpha.-Al.sub.2O.sub.3 layer before being immersed in the molten
A4C.
[0204] Note that the presence of .alpha.-Al.sub.2O.sub.3 (before
immersion in the molten metal) or MgAl.sub.2O.sub.4 (after
immersion in the molten metal) on the surface of the
Al.sub.2TiO.sub.5 ceramic sintered compacts was confirmed by X-ray
diffraction analysis. In addition, the thickness of each layer was
measured by energy dispersion type X-ray diffraction analysis.
[0205] Embodiment 3: Evaluation of Non-wettability
[0206] (1) Wetting Angle
[0207] The wetting angle is measured in order to evaluate the
non-wettability of the Al.sub.2TiO.sub.5 ceramic sintered compact
with respect to the molten aluminum alloy (A4C).
[0208] The following three types of Al.sub.2TiO.sub.5 ceramic test
pieces were used. In other words, i) a test piece in which the
surface of the sintered compact produced in Embodiment 1 was cut
into a 25 mm.times.25 mm.times.6 mm piece, surface-finished to 25
mm.times.25 mm (thickness of 5 mm) by means of a #800 diamond
grindstone, and had a surface roughness (center line average
roughness) of approximately 3 .mu.m; ii) a test piece with the same
surface finish, on whose surface an .alpha.-Al.sub.2O.sub.3 layer
having a thickness of 5 .mu.m was formed according to Embodiment 2;
and iii) a test piece obtained by immersing an Al.sub.2TiO.sub.5
ceramic sintered body on which an .alpha.-Al.sub.2O.sub.3 layer had
been formed in a molten aluminum alloy (A4C, 720 degrees C.) for 50
hours in order to change the surface of the .alpha.-Al.sub.2O.sub.3
layer to an MgAl.sub.2O.sub.4 layer.
[0209] An MH-type guided interlock observation device produced by
Union Optical was used to measure the wetting angle. The
aforementioned test pieces were placed on the device's heater with
their final processed surfaces (25 mm.times.25 mm surfaces) facing
upward, and then cylindrical pieces of aluminum alloy (A4C) that
were 10 mm in diameter and 10 mm in length were placed on these
surfaces. After that, the temperature was raised 5.degree. C./min
from room temperature to 700.degree. C. in an argon gas atmosphere
(flow volume 2500 cc/min), and was maintained at that point for 30
seconds. After that, at 700.degree. C., a lamp light was radiated
onto the aluminum alloy and test pieces, the images produced were
projected onto a screen, and the contact angle between the surface
of each test piece and the aluminum alloy was measured from these
images.
[0210] The wetting angle at 700.degree. C. was as noted below. The
Al.sub.2TiO.sub.5 sintered compact=120 degrees, the
.alpha.-Al.sub.2O.sub.3 coated Al.sub.2TiO.sub.5 sintered
compact=135 degrees, and the MgAl.sub.2O.sub.4 coated
Al.sub.2TiO.sub.5 sintered compact=128 degrees; thus, it is clear
that the non-wettability of the Al.sub.2TiO.sub.5 sintered compact
with respect to the aluminum alloy increases due to the
.alpha.-Al.sub.2O.sub.3 coating and the MgAl.sub.2O.sub.4
coating.
[0211] (2) Non-wettability Lifespan
[0212] Two kg of 700.degree. C. molten aluminum alloy (A4C) was
poured into a ladle-shaped Al2TiOO5 ceramic sintered compact
(comprising an .alpha.-Al.sub.2O.sub.3 layer), and after holding it
there for 50 seconds, the molten metal inside the ladle was
discharged. This process was repeated until the molten metal stuck
to the inner wall of the ladle and remained there, even after the
molten metal had been discharged. The results were that the ladle
produced in the embodiment had absolutely no molten metal stuck
thereto after 12,000 repetitions of this process. Because of this,
it is clear that this ladle possesses and can retain excellent
non-wettability. In addition, the presence of the MgAl.sub.2O.sub.4
layer on the inner wall of the ladle was confirmed after 12,000
repetitions of the process.
[0213] In contrast, subjecting an Al.sub.2TiO.sub.5 ceramic ladle
not having an Al.sub.2O.sub.3 layer formed thereon resulted in
molten metal sticking thereto after 2000 repetitions of the
aforementioned process.
[0214] (3) Sealing Characteristics of a Bonded Body Comprising
Bonded Sections
[0215] Each member of the Al.sub.2TiO.sub.5 ceramic bonded set
having an .alpha.-Al.sub.2O.sub.3 layer thereon was fitted together
at the bonding positions to form a bonded body, and the outer
circumference of the bonding position was secured with a stainless
steel band (width 20 mm) via an alumina fiber sheet (manufactured
by Mitsui Mining Materials, product name: Almax). A piece of
aluminum alloy (A4C) was placed inside the bonded body, and then
its temperature was raised (20.degree. C./min) in an argon gas
atmosphere (flow volume 100 cc/min) until the temperature reached
720.degree. C. and the aluminum alloy melted. After melting, the
temperature was maintained at 720.degree. C. for one hour, and then
the temperature was reduced (20.degree. C./min). This process was
repeated 50 times.
[0216] The result of this was that absolutely no molten metal was
observed leaking from the bonded position while the process was
being repeated. In addition, absolutely no molten metal stuck to
the molten metal contact positions on the inner wall of the bonded
body, thus confirming that the bonded body retained excellent
non-wettability. Note that the formation of an MgAl.sub.2O.sub.4
layer on the surface of the molten metal contact portions inside
the bonded body was confirmed.
[0217] According to the present invention, conferring and retaining
the non-wettability of aluminum titanate ceramic with respect to
molten aluminum alloy can be easily achieved.
* * * * *