U.S. patent application number 11/377125 was filed with the patent office on 2006-08-24 for expandable core for use in casting.
Invention is credited to Koichi Anzai, Youji Yamada, Jun Yaokawa.
Application Number | 20060185815 11/377125 |
Document ID | / |
Family ID | 34372754 |
Filed Date | 2006-08-24 |
United States Patent
Application |
20060185815 |
Kind Code |
A1 |
Yaokawa; Jun ; et
al. |
August 24, 2006 |
Expandable core for use in casting
Abstract
A salt core (2) is formed by casting a mixed material of a salt
material and a ceramic material. Any one of a chloride, bromide,
carbonate, and sulfate of potassium or sodium is used as the salt
material. As the ceramic material, granular one having a density
falling within a range of 2.2 g/cm.sup.3 (exclusive) to 4
g/cm.sup.3 (inclusive) is used.
Inventors: |
Yaokawa; Jun; (Miyagi,
JP) ; Anzai; Koichi; (Miyagi, JP) ; Yamada;
Youji; (Shizuoka, JP) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
34372754 |
Appl. No.: |
11/377125 |
Filed: |
March 16, 2006 |
Current U.S.
Class: |
164/137 ;
164/5 |
Current CPC
Class: |
B22C 9/105 20130101 |
Class at
Publication: |
164/137 ;
164/005 |
International
Class: |
B22C 5/18 20060101
B22C005/18; B22D 33/04 20060101 B22D033/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 17, 2004 |
WO |
PCT/JP04/13669 |
Sep 17, 2003 |
JP |
324778/2003 |
Claims
1. A core for use in casting which is formed by casting a mixed
material of a salt material and a ceramic material, said salt
material comprising any one of a chloride, a bromide, a carbonate,
and a sulfate of any one of potassium and sodium, and said ceramic
material comprising artificially synthesized granular one having a
density falling within a range of 2.2 g/cm.sup.3 (exclusive) to 4
g/cm.sup.3 (inclusive).
2. A core for use in casting according to claim 1, wherein said
ceramic material comprises synthetic mullite having a density of
2.79 g/cm.sup.3 to 3.15 g/cm.sup.3.
3. A core for use in casting according to claim 1, wherein said
ceramic material comprises aluminum borate having a density of 2.93
g/cm.sup.3.
4. A core for use in casting which is formed by casting a mixed
material of a salt material and a ceramic material, said salt
material comprising any one of a chloride, a bromide, a carbonate,
and a sulfate of any one of potassium and sodium, and said ceramic
material comprising artificially synthesized granular one having a
particle size of not more than 150 .mu.m.
5. A core for use in casting which is formed by casting a mixed
material of a salt material and a ceramic material, said salt
material comprising any one of a chloride, a bromide, a carbonate,
and a sulfate of any one of potassium and sodium, and said ceramic
material comprising any granular one of synthetic mullite, aluminum
borate, boron carbide, silicon nitride, silicon carbide, aluminum
nitride, aluminum titanate, cordierite, and alumina.
6. A core for use in casting which is formed by casting a mixed
material of a salt material and a ceramic material, said salt
material comprising any one of a chloride, a bromide, a carbonate,
and a sulfate of any one of potassium and sodium, and said ceramic
material comprising whiskers of any one of aluminum borate, silicon
nitride, silicon carbide, potassium hexatitanate, potassium
octatitanate, and zinc oxide.
7. A core for use in casting according to claim 6, wherein said
ceramic material comprises aluminum borate whiskers.
8. A core for use in casting which is formed by casting a mixed
material of a salt material and a ceramic material, said salt
material comprising a mixed salt obtained by adding any one of a
carbonate and a sulfate of any one of potassium and sodium to a
chloride of any one of potassium and sodium, and said ceramic
material comprising artificially synthesized granular one having a
density falling within a range of 2.2 g/cm.sup.3 (exclusive) to 4
g/cm.sup.3 (inclusive).
9. A core for use in casting according to claim 8, wherein said
ceramic material comprises synthetic mullite having a density
falling in a range of 2.79 g/cm.sup.3 to 3.15 g/cm.sup.3.
10. A core for use in casting according to claim 8, wherein said
ceramic material comprises aluminum borate having a density of 2.93
g/cm.sup.3.
11. A core for use in casting which is formed by casting a mixed
material of a salt material and a ceramic material, said salt
material comprising a mixed salt obtained by adding any one of a
carbonate and a sulfate of any one of potassium and sodium to a
chloride of any one of potassium and sodium, and said ceramic
material comprising artificially synthesized granular one having a
particle size of not more than 150 .mu.m.
12. A core for use in casting which is formed by casting a mixed
material of a salt material and a ceramic material, said salt
material comprising a mixed salt obtained by adding any one of a
carbonate and a sulfate of any one of potassium and sodium to a
chloride of any one of potassium and sodium, and said ceramic
material comprising any granular one of synthetic mullite, aluminum
borate, boron carbide, silicon nitride, silicon carbide, aluminum
nitride, aluminum titanate, cordierite, and alumina.
13. A core for use in casting which is formed by casting a mixed
material of a salt material and a ceramic material, said salt
material comprising a mixed salt obtained by adding any one of a
carbonate and a sulfate of any one of potassium and sodium to a
chloride of any one of potassium and sodium, and said ceramic
material comprising whiskers of any one of aluminum borate, silicon
nitride, silicon carbide, potassium hexatitanate, potassium
octatitanate, and zinc oxide.
14. A core for use in casting according to claim 13, wherein said
ceramic material comprises aluminum borate whiskers.
15. A core for use in casting according to any one of claims 8 to
14, wherein said mixed salt is made from potassium chloride and
sodium carbonate.
Description
TECHNICAL FIELD
[0001] The present invention relates to expendable salt-core for
use in casting, which is loaded in a mold used for forming
non-ferrous alloy castings, particularly a high pressure
die-casting mold as well, can withstand a high casting pressure
environment, and is formed from a salt material.
BACKGROUND ART
[0002] Conventionally, high pressure die-casting can afford to
manufacture with high volume production for complicated-shape
components with high dimensional accuracy at a low cost. Although,
depending on the shape restriction of the components, an expendable
core for use in casting may have to be used. Conventionally, as an
expendable core, in addition to expendable sand cores formed using
sand, a so-called salt core is available. The salt core is a very
attractive choice in the light of the productivity.
[0003] More specifically, after casting process is finished, the
salt core can be removed by dissolving it with hot water or steam.
When the salt core is used, as compared to a case wherein a sand
core (e.g., a shell mold core) is used, cumbersome sand removing
operation can be eliminated to improve the productivity. With a
sand core, chiefly because a so-called metal penetration phenomenon
occurs, that is, the melt enters gaps among sand grains in the
boundary with the core and accordingly the sand cannot be easily
removed.
[0004] Therefore, after the product is extracted from the mold, the
product must be subjected to several knock-out machines to
discharge the sand in the product. Furthermore, sand that does not
fall readily due to metal penetration must be dropped by shot
blasting. Hence, the sand removing operation is cumbersome, leading
to an increase in cost.
[0005] A salt core of this type is formed from sodium chloride
(NaCl) or potassium chloride (KCl) as a main material (salt
material), as disclosed in, e.g., Japanese Patent Publication No.
48-17570 (to be merely referred to patent reference 1 hereinafter),
U.S. Pat. No. 3,963,818 (to be merely referred to as patent
reference 2 hereinafter), U.S. Pat. No. 4,361,181 (to be merely
referred to as patent reference 3 hereinafter), and U.S. Pat. No.
5,165,464 (to be merely referred to as patent reference 4
hereinafter).
[0006] The salt core shown in each of patent references 1 to 3 is
formed by molding a chloride such as granular (powder) sodium
chloride or potassium chloride into a predetermined shape by press
molding and sintering the molded material.
[0007] The salt core described in patent reference 4 uses sodium
chloride as the salt material and is molded into a predetermined
shape by die-casting.
[0008] Each of U.S. Pat. No. 4,446,906 (to be merely referred to as
patent reference 5 hereinafter), U.S. Pat. No. 5,803,151 (to be
merely referred to as patent reference 6 hereinafter), Japanese
Patent Publication No. 49-15140 (to be merely referred to patent
reference 7 hereinafter), Japanese Patent Publication No. 48-8368
(to be merely referred to as patent reference 8 hereinafter),
Japanese Patent Publication No. 49-46450 (to be merely referred to
as patent reference 9 hereinafter), and U.S. Pat. No. 4,840,219 (to
be merely referred to as patent reference 10 hereinafter) discloses
a salt core in which ceramic is mixed as a filler in the salt
material.
[0009] The salt core shown in patent reference 5 uses silica
(SiO.sub.2) or alumina (Al.sub.2O.sub.3) as reinforcement and is
molded into a predetermined shape by die-casting. The tensile
strength of the salt core is described as 150 psi to 175 psi which
corresponds to 1.03 MPa to 1.2 MPa. With a sand core which is also
a expendable core, the strength of the core is generally evaluated
from the value of the bending strength obtained by a bending
strength test. With the salt core as well, an evaluating method
using the bending strength can be employed.
[0010] The bending strength is a barometer that indicates the
strength of an expendable core when a bending stress acts on the
expendable core. A bending stress supposedly acts, for example,
when a melt flows from a gate into a mold cavity at a high speed to
collide against an internal salt core, or when an impact acts on a
core as the core is being attached in a mold. The bending stress
which is generated in this manner is the main factor that breaks
the core in high pressure die-casting at a high speed injection.
Patent reference 5 has no description on the bending stress.
Although the specification of patent reference 5 describes that an
engine block is produced by die-casting using the salt core, it has
no commercial record. Therefore, it is estimated that the salt core
did not have a bending stress that could stand the high melt and
high injection speed of high pressure die-casting.
[0011] The salt core shown in patent reference 6 uses particles,
fibers, and whiskers of alumina, silica sand, boron nitride (BN),
boron carbide (BC), as reinforcement. The salt core is formed by
molding a mixture of the reinforcement and salt material into a
predetermined shape by pressurized molding and sintering the molded
material. This patent suggests that the salt core is reinforced by
various types of ceramics, although the process is different.
[0012] The salt core shown in each of patent references 7 and 8
uses alumina as reinforcement. The salt core shown in patent
reference 9 uses silica, alumina, zirconia (ZrO.sub.2), or the like
as reinforcement. The salt cores shown in patent references 7 to 9
are formed by casting.
[0013] The salt core shown in patent reference 10 is formed by
mixing two types of alumina having different particle sizes as
reinforcement in a salt material and molding the mixture into a
predetermined shape by die-casting. The salt material used for the
salt core is a mixed salt obtained by mixing sodium carbonate
(Na.sub.2CO.sub.3) in sodium chloride.
[0014] A salt core which uses a mixed salt as the salt material in
this manner is also described in U.S. Pat. No. 5,303,761 (to be
merely referred to as patent reference 11 hereinafter) and Japanese
Patent Laid-Open No. 50-136225 (to be merely referred to as patent
reference 12 hereinafter) in addition to the above patent
references.
[0015] Patent reference 11 shows a mixed salt which is made from
sodium chloride and sodium carbonate in the same manner as in
patent reference 10. Patent reference 12 discloses a mixed salt
obtained by mixing potassium chloride and sodium chloride in sodium
carbonate.
[0016] A salt material obtained by mixing ceramic in a mixed salt
is shown in Japanese Patent Publication No. 48-39696 (to be merely
referred to as patent reference 13 hereinafter) and Japanese Patent
Laid-Open No. 51-50218 (to be merely referred to as patent
reference 14 hereinafter).
[0017] Patent reference 13 shows a salt material obtained by mixing
a metal oxide such as alumina or zinc oxide (ZnO) and a siliceous
granular material such as silica sand, talc, or clay in a mixed
salt made from sodium carbonate, sodium chloride, and potassium
chloride.
[0018] Patent reference 14 shows a salt material obtained by mixing
silica, alumina, fiber, or the like in a mixed salt made from
potassium carbonate, sodium sulfate (Na.sub.2SO.sub.4), sodium
chloride, and potassium chloride.
[0019] When a salt material is used as a mixed salt in this manner,
the melting point of the salt material can be relatively decreased
more as compared with a case wherein the salt material is made from
a single type chloride, carbonate, or sulfate.
DISCLOSURE OF INVENTION
Problem to be Solved by the Invention
[0020] The salt core shown in each of patent references 1 to 3 and
6 described above is formed by press molding and accordingly cannot
be formed into a complicated shape. This problem can be solved to a
certain degree by forming the salt core by casting such as
die-casting, as shown in patent references 4, 5, 10, and 11. The
salt core shown in patent reference 4, however, has a low bending
strength. When a product is to be cast using this salt core,
limitations and conditions in casting increase.
[0021] More specifically, in the salt core shown in patent
reference 4, the material itself of the core is made from a brittle
material (e.g., with a bending strength of 1 MPa to 1.5 MPa) such
as sodium chloride or potassium chloride. Hence, this core can only
be used in, e.g., parmanent mold casting or low pressure die
casting (LP) in which the melt supply pressure is low and the melt
flow rate is suppressed so the core will not be damaged during
product casting, and cannot be used in high pressure, high speed
die-casting generally called die-casting. Conventional die-casting
requires a higher melt pressure of 40 MPa to 100 MPa during casting
and a higher injection speed (a gate rate of 20 m/sec to 100 m/sec)
than in permanent mold casting and low pressure die casting. Even a
core different from a salt core is difficult to use in conventional
die-casting. In laminar flow die-casting, squeeze die-casting, or
the like in which the melt supply pressure is high but the supply
rate is low, a shell core {with a bending strength of 3 MPa to 6
MPa (the present maximum value: 6 MPa)} with an improved strength
may be used. In this case, however, the time required for sand
removal after casting becomes excessively long, and the
manufacturing cost increases greatly.
[0022] In order to increase the bending strength of the salt core,
ceramic may be mixed as a reinforcing material in the salt
material, as shown in patent references 5, 10, 13, and 14. With a
conventional ceramic-mixed salt core; however, a high expected
bending strength cannot be obtained. This may be due to the
following reasons. A versatile industrial material or natural
material (e.g., alumina or silica) may be mainly used as the
ceramic material, and accordingly the ceramic material may not
sufficiently disperse in the salt material. Alternatively, a
ceramic material having appropriate physical properties may not be
used.
[0023] The present invention has been made to solve the above
problem, and has as its object to provide a salt core which has
high fluidity, can be formed into a core with a complicated shape
by casting such as die-casting, parmanent mold-casting, and low
pressure die casting, has a high bending strength as a core, and
can be applied to die-casting as wall.
[0024] In recent years, artificially synthesized ceramic or the
like (which may be obtained by remelting, grinding, and classifying
kaolin and may be a ground product of, e.g., synthetic mullite; may
be obtained by granulating, sintering with a rotary kiln, and
classifying kaolin and may be a sintered product of, e.g.,
synthetic mullite; may be obtained by sedimentation by the flux
scheme, removing flux, and classification and may be, e.g.,
aluminum borate; or may be obtained by sedimentation by vapor
deposition and classification and may be, e.g., silicon carbide or
silicon nitride) has been under production.
[0025] These artificially synthesized materials are conventionally
used as a reinforcing material for a reinforced plastic material,
as a heat-resistant piston material, in a break shoe as an
alternative material to asbestos, or as an industrial material
developed for aviation and space technology. None of the
artificially synthesized materials is developed as salt core
reinforcing ceramic.
[0026] Such artificially synthesized materials are marketed with
various densities, particle sizes, shapes, and the like, and their
heat resistances and strength stabilities are greatly improved over
those of conventional ceramic. In view of this fact, the present
inventors re-examined the possibility of these materials as
salt-reinforcing ceramic materials, and reached the present
invention.
Means of Solution to the Problem
[0027] In order to achieve the above object, according to the
present invention, there is provided a core for use in casting
which is formed by casting a mixed material of a salt material and
a ceramic material, the salt material comprising any one of a
chloride, a bromide, a carbonate, and a sulfate of any one of
potassium and sodium, and the ceramic material comprising
artificially synthesized granular one having a density falling
within a range of 2.2 g/cm.sup.3 (exclusive) to 4 g/cm.sup.3
(inclusive).
[0028] According to claim 2 of the present invention, there is
provided a core for use in casting according to claim 1 of the
present invention, wherein the ceramic material comprises synthetic
mullite having a density of 2.79 g/cm.sup.3 to 3.15 g/cm.sup.3.
[0029] According to claim 3 of the present invention, there is
provided a core for use in casting according to claim 1, wherein
the ceramic material comprises aluminum borate having a density of
2.93 g/cm.sup.3.
[0030] According to claim 4 of the present invention, there is
provided a core for use in casting which in formed by casting a
mixed material of a salt material and a ceramic material, the salt
material comprising any one of a chloride, a bromide, a carbonate,
and a sulfate of any one of potassium and sodium, and the ceramic
material comprising artificially synthesized granular one having a
particle size of not more than 150 .mu.m.
[0031] According to claim 5 of the present invention, there is
provided a core for use in casting which is formed by casting a
mixed material of a salt material and a ceramic material, said salt
material comprising any one of a chloride, a bromide, a carbonate,
and a sulfate of any one of potassium and sodium, and said ceramic
material comprising any granular one of synthetic mullite, aluminum
borate, boron carbide, silicon nitride, silicon carbide, aluminum
nitride, aluminum titanate cordierite, and alumina.
[0032] According to claim 6 of the present invention, there is
provided a core for use in casting which is formed by casting a
mixed material of a salt material and a ceramic material, the salt
material comprising any one of a chloride, a bromide, a carbonate,
and a sulfate of any one of potassium and sodium, and the ceramic
material comprising whiskers of any one of aluminum borate, silicon
nitride, silicon carbide, potassium hexatitanate, potassium
octatitanate, and zinc oxide.
[0033] According to claim 7 of the present invention, there is
provided a core for use in casting according to claim 6 of the
present invention, wherein the ceramic material comprises aluminum
borate whiskers.
[0034] According to claim 8 of the present invention, there is
provided a core for use in casting which is formed by casting a
mixed material of a salt material and a ceramic material, the salt
material comprising a mixed salt obtained by adding any one of a
carbonate and a sulfate of any one of potassium and sodium to a
chloride of any one of potassium and sodium, and the ceramic
material comprising artificially synthesized granular one having a
density falling within a range of 2.2 g/cm.sup.3 (exclusive) to 4
g/cm.sup.3 (inclusive).
[0035] According to claim 9 of the present invention, there is
provided a core for use in casting according to claim 8 of the
present invention, wherein the ceramic material comprises synthetic
mullite having a density falling in a range of 2.79 g/cm.sup.3 to
3.15 g/cm.sup.3.
[0036] According to claim 10 of the present invention, there is
provided a core for use in casting according to claim 8 of the
present invention, wherein the ceramic material comprises aluminum
borate having a density of 2.93 g/cm.sup.3.
[0037] According to claim 11 of the present invention, there is
provided a core for use in casting which is formed by casting a
mixed material of a salt material and a ceramic material, the salt
material comprising a mixed salt obtained by adding any one of a
carbonate and a sulfate of any one of potassium and sodium to a
chloride of any one of potassium and sodium, and the ceramic
material comprising artificially synthesized granular one having a
particle size of not more than 150 .mu.m.
[0038] According to claim 12 of the present invention, there is
provided a cote for use in casting which is formed by casting a
mixed material of a salt material and a ceramic material, the salt
material comprising a mixed salt obtained by adding any one of a
carbonate and a sulfate of any one of potassium and sodium to a
chloride of any one of potassium and sodium, and the ceramic
material comprising any granular one of synthetic mullite, aluminum
borate, boron carbide, silicon nitride, silicon carbide, aluminum
nitride, aluminum titanate, cordierite, and alumina.
[0039] According to claim 13 of the present invention, there is
provided a core for use in casting which is formed by casting a
mixed material of a salt material and a ceramic material, the salt
material comprising a mixed salt obtained by adding any one of a
carbonate and a sulfate of any one of potassium and sodium to a
chloride of any one of potassium and sodium, and the ceramic
material comprising whiskers of any one of aluminum borate, silicon
nitride, silicon carbide, potassium hexatitanate, potassium
octatitanate, and zinc oxide.
[0040] According to claim 14 of the present invention, there is
provided a core for use in casting according to claim 13 of the
present invention, wherein the ceramic material comprises aluminum
borate whiskers.
[0041] According to claim 15 of the present invention, there is
provided a core for use in casting according to any one of claims 8
to 14 of the present invention, wherein the mixed salt is made from
potassium chloride and sodium carbonate.
Effect of the Invention
[0042] As has been described above, according to the present
invention, a salt core in which a ceramic material sufficiently
disperses in a salt material can be formed by casting.
[0043] Therefore, a core for use in casting according to the
present invention can be formed into a complicated shape by casting
while having such characteristics that it can be removed by water
(including hot water or steam) after casting, and its bending
strength is increased more than expected by a reinforcing material
made from a ceramic material. Hence, the core for use in casting
according to the present invention can also be used in, e.g., a die
cast machine which is conventionally difficult to use it. Moreover,
when mounting the core in another matrix, the core need not be
handled particularly carefully. Thus, the degrees of freedom of
casting can be increased.
[0044] According to claim 2 of the present invention, a salt core
in which synthetic mullite sufficiently disperses in a salt
material can be formed by casting.
[0045] According to claim 3 of the present invention, a salt core
in which aluminum borate sufficiently disperses in a salt material
can be formed by casting.
[0046] According to claim 4 of the present invention, a salt core
in which a salt material sufficiently disperses in a salt material
can be formed by casting.
[0047] Therefore, a core for use in casting according to the
present invention can be formed into a complicated shape by casting
while having such characteristics that it can be removed by water
(including hot water or steam) after casting, and its bending
strength is increased more than expected by a reinforcing material
made from a ceramic material. Hence, the core for use in casting
according to the present invention can also be used in, e.g., a die
cast machine which is conventionally difficult to use it. Moreover,
when mounting the core in another matrix, the core need not be
handled particularly carefully. Thus, the degrees of freedom of
casting can be increased.
[0048] According to claim 5 of the present invention, a salt core
which is sufficiently reinforced by a granular ceramic material can
be formed.
[0049] Therefore, a core for use in casting according to the
present invention can be formed into a complicated shape by casting
while having such characteristics that it can be removed by water
(including hot water or steam) after casting, and its bending
strength is increased more than expected by a reinforcing material
made from a granular ceramic material. Hence, the core for use in
casting according to the present invention can also be used in,
e.g., a die cast machine which is conventionally difficult to use
it. Moreover, when mounting the core in another matrix, the core
need not be handled particularly carefully. Thus, the degrees of
freedom of casting can be increased. As one type of ceramic
material is used, the salt core can be dissolved in water to
recover the ceramic material, so that the ceramic material can be
recycled.
[0050] According to claim 6 of the present invention, a salt core
which is sufficiently reinforced by whiskers made from a ceramic
material can be formed.
[0051] Therefore, a core for use in casting according to the
present invention can be formed into a complicated shape by casting
while having such characteristics that it can be removed by water
(including hot water or steam) after casting, and is sufficiently
reinforced by the whiskers made from a ceramic material, so that
its bending strength is increased more than expected. Hence, the
core for use in casting according to the present invention can also
be used in, e.g., a die cast machine which is conventionally
difficult to use it. Moreover, when mounting the core in another
matrix, the core need not be handled particularly carefully. Thus,
the degrees of freedom of casting can be increased. As one type of
ceramic material is used, the salt core can be dissolved in water
to recover the ceramic material, so that the ceramic material can
be reused.
[0052] According to claim 7 of the present invention, a salt core
which is sufficiently reinforced by aluminum borate whiskers can be
formed by casting.
[0053] According to claim 8 of the present invention, a salt core
in which a ceramic material sufficiently disperses in a salt
material made from a mixed salt can be formed by casting.
[0054] Therefore, a core for use in casting according to the
present invention can be formed into a complicated shape by casting
while having such characteristics that it can be removed by water
(including hot water or steam) after casting, and its bending
strength is increased more than expected by a reinforcing material
made from a ceramic material. Hence, the core for use in casting
according to the present invention can also be used in, e.g., a die
cast machine which is conventionally difficult to use it. Moreover,
when mounting the core in another matrix, the core need not be
handled particularly carefully. Thus, the degrees of freedom of
casting can be increased.
[0055] The salt material of the salt core is a mixed salt and its
melting point decreases relatively. Hence, the temperature required
when casting the salt core can be decreased, and the manufacturing
cost of the salt core can be decreased. Also, a salt core with
small unevenness formed on a core surface can be provided.
[0056] According to claim 9 of the present invention, a salt core
in which synthetic mullite sufficiently disperses in a salt
material made from a mixed salt can be formed by casting.
[0057] According to claim 10 of the present invention, a salt core
in which aluminum borate sufficiently disperses in a salt material
made from a mixed salt can be formed by casting.
[0058] According to claim 11 of the present invention, a salt core
in which a ceramic-material sufficiently disperses in a salt
material made from a mixed salt can be formed by casting.
[0059] Therefore, a core for use in casting according to the
present invention can be formed into a complicated shape by casting
while having such characteristics that it can be removed by water
(including hot water or steam) after casting, and its bending
strength is increased more than expected by a reinforcing material
made from a ceramic material. Hence, the core for use in casting
according to the present invention can also be used in, e.g., a die
cast machine which is conventionally difficult to use it. Moreover,
when mounting the core in another matrix, the core need not be
handled particularly carefully. Thus, the degrees of freedom of
casting can be increased.
[0060] The salt material of the salt core is a mixed salt, and its
melting point decreases relatively. Hence, the temperature required
when casting the salt core can be decreased, and the manufacturing
cost of the salt core can be decreased. Also, a salt core with
small unevenness formed on a core surface can be provided.
[0061] According to claim 12 of the present invention, a salt core
in which a granular ceramic material sufficiently disperses on a
salt material made from a mixed salt and which is sufficiently
reinforced by the ceramic material can be formed.
[0062] Therefore, a core for use in casting according to the
present invention can be formed into a complicated shape by casting
while having such characteristics that it can be removed by water
(including hot water or steam) after casting, and its bending
strength is increased more than expected by a reinforcing material
made from a granular ceramic material. Hence, the core for use in
casting according to the present invention can also be used in,
e.g., a die cast machine which is conventionally difficult to use
it. Moreover, when mounting the core in another matrix, the core
need not be handled particularly carefully. Thus, the degrees of
freedom of casting can be increased.
[0063] The salt material of the salt core is a mixed salt, and its
melting point decreases relatively. Hence, the temperature required
when casting the salt core can be decreased, and the manufacturing
cost of the salt core can be decreased. Also, a salt core with
small unevenness formed on a core surface can be provided.
[0064] According to claim 13 of the present invention, a salt core
in which ceramic whiskers sufficiently disperse in a salt material
made from a mixed salt and which is sufficiently reinforced by the
whiskers can be formed.
[0065] Therefore, a core for use in casting according to the
present invention can be formed into a complicated shape by casting
while having such characteristics that it can be removed by water
(including hot water or steam) after casting, and its banding
strength is increased more than expected by a reinforcing material
made from a granular ceramic material. Hence, the core for use in
casting according to the present invention can also be used in.
e.g., a die cast machine which is conventionally difficult to use
it. Moreover, when mounting the core in another matrix, the core
need not be handled particularly carefully. Thus, the degrees of
freedom of casting can be increased.
[0066] The salt material of the salt core is a mixed salt, and its
melting point decreases relatively. Hence, the temperature required
when casting the salt core can be decreased, and the manufacturing
cost of the salt core can be decreased. Also, a salt core with
small unevenness formed on a core surface can be provided.
[0067] According to claim 14 of the present invention, a salt core
in which aluminum borate whiskers sufficiently disperse in a salt
material made from a mixed salt and which is sufficiently
reinforced by the whiskers can be formed. Thus, a rigid salt core
having a low melting point can be formed by casting.
[0068] According to claim 15 of the present invention, potassium
chloride and sodium carbonate are easily available and inexpensive.
Thus, according to the present invention, the manufacturing cost of
a core for use in casting which is made of a salt material made
from a mixed salt can be decreased.
BRIEF DESCRIPTION OF DRAWINGS
[0069] FIG. 1 is a perspective view showing a cylinder block which
is cast using a core for use in casting according to the present
invention;
[0070] FIG. 2 is a graph showing the relationship between the
addition of synthetic mullite and the bending strength;
[0071] FIG. 3 is a graph showing the relationship between the
addition of synthetic mullite and the bending strength;
[0072] FIG. 4 includes views showing a bending sample;
[0073] FIG. 5 is a graph showing the relationship between the
bending sample; and the bending force;
[0074] FIG. 6 is a graph showing the relationship between the
addition of aluminum borate and the bending strength;
[0075] FIG. 7 is a graph showing the relationship between the
addition of silicon nitride and the bending strength;
[0076] FIG. 8 is a graph showing the relationship between the
addition of silicon carbide and the bending strength;
[0077] FIG. 9 is a graph showing the relationship between the
addition of aluminum nitride and the bending strength;
[0078] FIG. 10 is a graph showing the relationship between the
addition of boron carbide and the bending strength;
[0079] FIG. 11 is a graph showing the relationship between the
addition of aluminum titanate or spinel and the bending
strength;
[0080] FIG. 12 is a graph showing the relationship between the
addition of alumina and the bending strength;
[0081] FIG. 13 is a graph showing the relationship between the
addition of each of all the ceramic materials indicated in the
first to eighth embodiments and the bending strength:
[0082] FIG. 14 is a graph showing the relationship between the
addition of each of all the ceramic materials indicated in the
first to eighth embodiments and the bending strength;
[0083] FIG. 15 is a chart showing mixing conditions for potassium
chloride and the ceramic material;
[0084] FIG. 16 is a chart showing the relationship between the
mixing ratio of the granular ceramic material and the fluidity;
[0085] FIG. 17 is a chart showing the relationship between the
mixing ratio of the granular ceramic material and the fluidity;
[0086] FIG. 18 is a chart showing the relationship between the
mixing ratio of the granular ceramic material and the fluidity;
[0087] FIG. 19 is a graph showing the relationship between the
addition of aluminum borate whiskers and the bending strength;
[0088] FIG. 20 is a graph showing the relationship between the
addition of silicon nitride whiskers or silicon carbide whiskers
and the bending strength:
[0089] FIG. 21 is a graph showing the relationship between the
addition of potassium titanate whiskers and the bending
strength;
[0090] FIG. 22 is a graph showing the relationship between the
addition of zinc oxide whiskers and the bending strength;
[0091] FIG. 23 is a graph showing the relationship between the
addition of each of all the whiskers indicated in the ninth to 12th
embodiments and the bending strength;
[0092] FIG. 24 is a chart showing the relationship between the
mixing ratio of ceramic whiskers and the fluidity; and
[0093] FIG. 25 is a graph showing the relationship between the
addition of aluminum borate whiskers in potassium bromide or sodium
bromide and the bending strength.
BEST MODE FOR CARRYING OUT THE INVENTION
First Embodiment
[0094] A core for use in casting according to one embodiment of the
present invention will be described in detail with reference to
FIGS. 1 to 5.
[0095] FIG. 1 is a partially cutaway perspective view of a cylinder
block which is cast using a core for use in casting according to
the present invention. FIGS. 2 and 3 are graphs each showing the
relationship between the addition of synthetic mullite and the
banding strength, FIG. 4 includes views showing a bending sample,
and FIG. 5 is a graph showing the relationship between the weight
of the bending sample and the bending force.
[0096] Referring to FIG. 1, reference numeral 1 denotes an engine
cylinder block which is cast using a salt core 2 serving as a core
for use in casting according to the present invention. The cylinder
block 1 serves to form a motorcycle water-cooling 4-cycle
4-cylinder engine, and is formed into a predetermined shape by
die-casting. The cylinder block 1 according to this embodiment
integrally has a cylinder body 4 having cylinder bores 3 at four
portions and an upper crank case 5 extending downward from the
lower end of the cylinder body 4. A lower crank case (not shown) is
attached to the lower end of the upper crank case 5. The upper
crank case 5 cooperates with the lower crank case to rotatably
support a crank shaft (not shown).
[0097] The cylinder body 4 described above is of a so-called closed
deck type, and a water jacket 6 is formed in it using the salt core
2 according to the present invention. The water jacket 6 comprises
a cooling water inlet 8 which projects from one side of the
cylinder body 4 and is formed in a cooling water channel forming
portion 7 extending in a direction along which the cylinder bores 3
line up, a cooling water distribution channel (not shown) which is
formed in the cooling water channel forming portion 7, a main
cooling water channel 9 which communicates with the cooling water
distribution channel and is formed to cover all the cylinder bores
3, a communicating channel 10 which extends upward in FIG. 1 from
the main cooling water channel 9 and opens to a mating surface 4a
at the upper end of the cylinder body 4, and the like.
[0098] More specifically, the water jacket 6 is configured to
supply cooling water, flown into it from the cooling water inlet 8,
to the main cooling water channel 9 around the cylinder bores via
the cooling water distribution channel and guide the cooling water
from the main cooling water channel 9 to a cooling water channel in
a cylinder head (not shown) via the communicating channel 10. As
the water jacket 6 is formed in this manner, the cylinder body 4 is
covered with the ceiling wall (a wall that forms the mating surface
4a) of the cylinder body 4 except that the communicating channel 10
of the water jacket 6 opens to the mating surface 4a at the upper
end of the cylinder body 4 to which the cylinder head is connected,
thus forming a closed deck type structure.
[0099] The salt core 2 which serves to form the water jacket is
formed such that it is integrally connected to the respective
portions of the water jacket 6. Referring to FIG. 1, the cylinder
body 4 is partially cutaway to facilitate understanding of the
shape of the salt core 2 (the shape of the water jacket 6).
[0100] The salt core 2 is formed into the shape of the water jacket
6 by die-casting using a core material comprising a mixture of a
salt material and ceramic material (to be described later). In the
salt core 2 according to this embodiment, as shown in FIG. 1, a
channel forming portion 2a which forms the cooling water inlet 8
and the cooling water distribution channel, an annular portion 2b
which surrounds the four cylinder bores 3, and a plurality of
projections 2c which project upward from the annular portion 2b are
all integrally formed. The projections 2c form the communicating
channel 10 of the water jacket 6. As is conventionally known, in
casting, the salt core 2 is supported at a predetermined position
in a mold (not shown) by core prints (not shown). After casting,
the salt core 2 is removed by dissolving it with hot water or
steam.
[0101] To remove the salt core 2 after casting, the cylinder block
1 is dipped in a water tank (not shown) which stores hot water.
When the cylinder block 1 is dipped in the water tank in this
manner, the channel forming portion 2a in the salt core 2 and the
projections 2c exposed to the mating surface 4a are dissolved as
they come into contact with the hot water. The dissolved portion
gradually spreads to finally dissolve all the portions. In the core
removing process, hot water or steam may be blown with pressure
from a hole to promote dissolution of the salt core 2 left in the
water jacket 6. In the salt core 2, at portions where the
projections 2c are to be formed, core prints can be inserted in
place of the projections 2c.
[0102] For example, the salt core 2 according to this embodiment
uses synthetic mullite [3Al.sub.2O.sub.3.2SiO.sub.2 {MM-325 mesh
manufactured by ITOCHU CERATECH CORP., addition: 40 wt %}] to be
described later as the salt material. When forming the salt core 2
by die-casting, first, the mixture of the salt material and ceramic
material is heated to melt the salt material. The melt is stirred
such that the ceramic material disperses sufficiently, thus forming
a mixed melt. After that, the mixed melt is injected into a salt
core mold with a high pressure and solidified. After the mixed melt
solidifies, it is removed from the mold, thus obtaining the salt
core 2.
[0103] In selection of synthetic mullite as the ceramic material, a
plurality of products shown in Table 1 below were selected from
commercially available granular (powder) synthetic mullite
products. Among the selected products, those that could be used for
casting were sorted out in accordance with the following
experiment. TABLE-US-00001 TABLE 1 Particle Maximum Chemical Name
of Density size Addition in Sample Addition Name of Ceramic Name of
Product formulae Shape Manufacturer (g/cm.sup.3) (.mu.m) (wt %) (wt
%) Synthetic CeraBeads 3Al.sub.2O.sub.3.2SiO.sub.2 = Mullite
Particulate ITOCHU 2.79 53-106 20, 30, 40, 50, 60, x70 60
mullite/sintered #1700 CERATECH product CORP. Synthetic CeraBeads
3Al.sub.2O.sub.3.2SiO.sub.2 = Mullite Particulate ITOCHU 2.79
75-150 40, 50, 60, x70 60 mullite/sintered #1450 CERATECH product
CORP. Synthetic CeraBeads 3Al.sub.2O.sub.3.2SiO.sub.2 = Mullite
Particulate ITOCHU 2.79 106-300 s30, s40, s50, s60, x70 60
mullite/sintered #650 CERATECH product CORP. Synthetic MM-325mesh
3Al.sub.2O.sub.3.2SiO.sub.2 = Mullite Particulate ITOCHU 3.11 -45
10, 20, 30, 40, x50 40 mullite/ground CERATECH product CORP.
Synthetic MM-200mesh 3Al.sub.2O.sub.3.2SiO.sub.2 = Mullite
Particulate ITOCHU 3.11 -75 20, 30, 40 40 mullite/ground CERATECH
product CORP. Synthetic MM-150mesh 3Al.sub.2O.sub.3.2SiO.sub.2 =
Mullite Particulate ITOCHU 3.11 -100 20, 30, 40 40 mullite/ground
CERATECH product CORP. Synthetic MM-100mesh
3Al.sub.2O.sub.3.2SiO.sub.2 = Mullite Particulate ITOCHU 3.11 -150
20, 30, 40 40 mullite/ground CERATECH product CORP. Synthetic MM35-
3Al.sub.2O.sub.3.2SiO.sub.2 = Mullite Particulate ITOCHU 3.11
180-500 s30, s40 40 mullite/ground 100mesh CERATECH product CORP.
Synthetic MM-16mesh 3Al.sub.2O.sub.3.2SiO.sub.2 = Mullite
Particulate ITOCHU 3.11 -1000 s20, s30, s40, x50 40 mullite/ground
CERATECH product CORP. Synthetic MM-325mesh
3Al.sub.2O.sub.3.2SiO.sub.2 + 5-10% Particulate ITOCHU 3.15 -45 20,
30, 40 40 mullite + 57 Al.sub.2O.sub.3 CERATECH 10% corundum CORP.
xNo fluidity sSedimentation
[0104] In Table 1, the name of product is an expression which is
used by the manufacturer in marketing, and specifies corresponding
synthetic mullite. The addition in sample indicates the proportion
in weight of synthetic mullite added in potassium chloride.
[0105] The experiment to sort out from the synthetic mullite
products shown in Table 1 those that could be used for casting was
performed by heating the mixture of potassium chloride and
synthetic mullite to dissolve potassium chloride, stirring the
mixture sufficiently, turning the dissolution vessel upside down,
and checking the fluidity of the melt in accordance with whether or
not the melt in the vessel flowed out. By this experiment, as
described above, melts that had fluidity when the dissolution
vessel was turned upside down were selected as being castable. The
result is shown in Table 1 and FIGS. 16 and 17.
[0106] As the dissolving vessel described above, a crucible made of
INCONEL X-750 or a high-alumina Tammann tube was used. Potassium
chloride was dissolved by placing the dissolving vessel containing
potassium chloride in an electric resistance furnace and heating it
in an atmosphere. Casting was performed by injecting the melt at a
temperature of 800.degree. C. into a mold at a temperature of about
25.degree. C. After the casting, in order to prevent a sample from
being fixed to the mold by heat shrinkage, the sample was extracted
from the mold at a lapse of about 20 sea since the melt was
injected, and was cooled by air cooling at room temperature.
[0107] With this experiment, CeraBeads #650 was observed to have
fluidity when its addition was 30%, 40%, 50%, and 60%, as shown in
Table 1 and FIG. 15. From this result, as CeraBeads #650
sufficiently had fluidity if its addition was 60% or less, it was
supposedly castable, but could not be used for casting because it
sedimented on the bottom of the dissolving vessel (Table 1 and
FIGS. 15 and 16).
[0108] CeraBeads #1700 was observed to have fluidity when its
addition was 20%, 30%, 40%, 50%, and 60%. From this result,
CeraBeads #1700 sufficiently has fluidity if its addition is 60% or
less, and is thus supposed to be castable.
[0109] CeraBeads #1450 was observed to have fluidity when its
addition was 40%, 50%, and 60%. From this result, CoraBeads #1450
sufficiently has fluidity if its addition is 60% or less, and is
thus supposed to be castable. Both CeraBeads #1700 and #1450 were
also confirmed to disperse in a melt of potassium chloride (Table 1
and FIGS. 15 and 16).
[0110] MM-325 mesh was observed to have fluidity when its addition
was 10%, 20%, 30%, and 40%. From this result, MM-325 mesh
sufficiently has fluidity if its addition is 40% or less, and is
thus supposed to be castable. MM-325 mesh was also confirmed to
disperse in a melt of potassium chloride (Table 1 and FIGS. 15 and
17).
[0111] Each of MM-200 mesh, MM-150 mesh, MM-100 mesh, and SM-325
mesh was observed to have fluidity when its addition was 20%, 30%,
and 40%. From this result, each of MM-200 mesh, MM-150 mesh, MM-100
mesh, and SM-325 mesh has fluidity if its addition is 40% or less,
and is thus supposed to be castable. Each of MM-200 mesh, MM-150
mesh, MM-100 mesh, and SM-325 mesh was also confirmed to disperse
in a melt of potassium chloride (Table 1 and FIGS. 15 and 17).
[0112] Only MM35 to 100 mesh samples each with an addition of 30%
and 50% were subjected to experiment. With these additions,
although fluidity was observed, the sample-sedimented on the bottom
of the dissolving vessel (see Table 1 and FIG. 15) and was not
suitable as the material.
[0113] MM-16 mesh samples were observed to have fluidity when its
addition was 20%, 30%, and 40%, but sedimented on the bottom of the
dissolving vessel and were not suitable as the material. In Table
1, CeraBeads is a sintered product, and MM is a ground product.
[0114] Of these ceramic materials, those that sedimented were
excluded except MM-16 mesh, and the rest was used. As shown in
Tables 2, 3 and 4 below, bending samples were formed for respective
additions, and their bending strengths were measured. The results
shown in FIGS. 2 and 3 were obtained. TABLE-US-00002 TABLE 2
Composition Bending Composition wt % Bending Load N Strength MPa
pure KCl 0 186.255 1.55 pure KCl 0 250.024 2.08 pure KCl 0 226.274
1.89 pure KCl 0 308.725 2.57 pure KCl 0 225.850 1.88 KCl + 10%
MM325 10 588.125 4.90 KCl + 10% MM325 10 770.5 6.42 KCl + 10% MM325
10 655.099 5.46 KCl + 10% MM325 10 596.9 4.97 KCl + 10% MM325 10
545.775 4.55 KCl + 20% MM325 20 1010 8.42 KCl + 20% MM325 20 923.25
7.69 KCl + 20% MM325 20 569.7 4.75 KCl + 20% MM325 20 609.849 5.08
KCl + 20% MM325 20 910.325 7.59 KCl + 20% MM325 20 493.925 4.12 KCl
+ 20% MM325 20 680 5.67 KCl + 30% MM325 30 1122.59 9.35 KCl + 30%
MM325 30 1263.75 10.53 KCl + 30% MM325 30 1060.12 8.83 KCl + 30%
MM325 30 1089.57 9.08 KCl + 30% MM325 30 716.4 5.97 KCl + 40% MM325
40 1209.5 10.08 KCl + 40% MM325 40 1136.25 9.47 KCl + 40% MM325 40
1472.9 12.27 KCl + 40% MM325 40 1642 13.68 KCl + 40% MM325 40
1584.75 13.21 KCl + 40% MM325 40 1574.8 13.12 KCl + 40% MM325 40
1279.75 10.66
[0115] TABLE-US-00003 TABLE 3 Composition Bending Bending
Composition wt % Load N Strength MPa pure KCl 0 186.255 1.55 pure
KCl 0 250.024 2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725 2.57
pure KCl 0 225.850 1.88 KCl + 20% MM - 200 mesh 20 1143.19 9.53 KCl
+ 30% MM - 200 mesh 30 1083.25 9.03 KCl + 30% MM - 200 mesh 30
1216.25 10.14 KCl + 40% MM - 200 mesh 40 1132 9.43 KCl + 40% MM -
200 mesh 40 1740.25 14.50 pure KCl 0 186.255 1.55 pure KCl 0
250.024 2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725 2.57 pure
KCl 0 225.850 1.88 KCl + 20% MM - 150 mesh 20 922.075 7.68 KCl +
30% MM - 150 mesh 30 1119.9 9.33 KCl + 30% MM - 150 mesh 30 1102.84
9.19 KCl + 40% MM - 150 mesh 40 1674.25 13.95 KCl + 40% MM - 150
mesh 40 1822.5 15.19 pure KCl 0 186.255 1.55 pure KCl 0 250.024
2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725 2.57 pure KCl 0
225.850 1.88 KCl + 20% MM - 100 mesh 20 1072 8.93 KCl + 30% MM -
100 mesh 30 880.5 7.34 KCl + 30% MM - 100 mesh 30 1168.57 9.74 KCl
+ 40% MM - 100 mesh 40 1642.5 13.69 KCl + 40% MM - 100 mesh 40 1579
13.16 pure KCl 0 186.255 1.55 pure KCl 0 250.024 2.08 pure KCl 0
226.274 1.89 pure KCl 0 308.725 2.57 pure KCl 0 225.850 1.88 KCl +
20% MM - 16 mesh 20 267.875 2.23 KCl + 30% MM - 16 mesh 30 364.225
3.04 KCl + 40% MM - 16 mesh 40 485.649 4.05
[0116] TABLE-US-00004 TABLE 4 Composition Bending Bending
Composition wt % Load N Strength MPa pure KCl 0 186.255 1.55 pure
KCl 0 250.024 2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725 2.57
pure KCl 0 225.850 1.88 KCl + 20% SM - 325 mesh 20 1283.75 10.70
KCl + 30% SM - 325 mesh 30 1381.22 11.51 KCl + 30% SM - 325 mesh 30
1219.22 10.16 KCl + 40% SM - 325 mesh 40 1708.82 14.24 KCl + 40% SM
- 325 mesh 40 2029 16.91 pure KCl 0 186.255 1.55 pure KCl 0 250.024
2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725 2.57 pure KCl 0
225.850 1.88 KCl + 20% cerabeads#1700 20 802.75 6.69 KCl + 30%
cerabeads#1700 30 926 7.72 KCl + 40% cerabeads#1700 40 891.075 7.43
KCl + 50% cerabeads#1700 50 1070.02 8.92 KCl + 50% cerabeads#1700
50 977.5 8.15 KCl + 60% cerabeads#1700 60 650.75 5.42 KCl + 60%
cerabeads#1700 60 915.75 7.63 pure KCl 0 186.255 1.55 pure KCl 0
250.024 2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725 2.57 pure
KCl 0 225.850 1.88 KCl + 40% cerabeads#1450 40 798.575 6.65 KCl +
50% cerabeads#1450 50 729.799 6.08 KCl + 50% cerabeads#1450 50
977.75 8.15 KCl + 60% cerabeads#1450 60 739.75 6.16 KCl + 60%
cerabeads#1450 60 930.974 7.76 pure KCl 0 186.255 1.55 pure KCl 0
250.024 2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725 2.57 pure
KCl 0 225.850 1.88 KCl + 30% cerabeads#650 30 443.274 3.69 KCl +
40% cerabeads#650 40 379.625 3.16 KCl + 50% cerabeads#650 50
526.599 4.39 KCl + 60% cerabeads#650 60 519.125 4.33 KCl + 60%
cerabeads#650 60 550.924 4.59
[0117] The bending samples of MM-325 mesh were formed 5 pieces for
each of additions 0% and 10%, 7 pieces for an addition of 20%, 5
pieces for an addition of 30%, and 8 pieces for an addition of 40%.
Each of the bending samples shown in Tables 2, 3, and 4 was formed
by casting into a rod shape with a width of 18 mm, a height of 20
mm, and a length of about 120 mm to have a rectangular section.
Each bending sample was cast in the same manner as that performed
for checking the fluidity described above. Namely, potassium
chloride and synthetic mullite were placed in a crucible made of
INCONEL X-750 or a Tammann tube. The crucible or Tammann tube was
heated in a furnace to dissolve potassium chloride. After that, the
melt was sufficiently stirred and injected into a mold. The
temperature of the melt was set to 800.degree. C.
[0118] The bending strength was obtained on the basis of a load
that broke the bending sample, when the center of the bending
sample was supported at two points spaced apart by 50 mm and the
intermediate portion of the support points was pressed by a
pressing device having two pressing points spaced apart by 10 mm,
in accordance with the following equation: .sigma.=3 Pm/bh.sup.2
(1) where .sigma. is the bending strength [MPa], P is the bending
load [N], m=20 mm, b=18 mm, and h=20 mm.
[0119] The bending strength of synthetic mullite (MM-325 mesh)
increased to be substantially proportional to the addition, as
shown in FIG. 2. The solid line in FIG. 2 is an approximate curve
drawn by using the method of least squares. Even when the addition
was equal, the bending strength was different when a cavity of
about 10% was formed in the sample or the addition of the ceramic
material was slightly nonuniform. In order to confirm this, the
bending force of the sample against the weight was measured. The
bending force and the weight were substantially proportional to
each other, as shown in FIG. 5.
[0120] Therefore, as is apparent from FIG. 2, the salt core 2 which
is obtained by mixing synthetic mullite (MM-325 mesh) in potassium
chloride has a maximum bending strength of about 14 MPa if the
addition of synthetic mullite is in the range of 25% to 40%, and
has a bending strength (about 8 MPa) with which it can be used in
die-casting. This fact signifies that the salt core 2 according to
this embodiment can be used in most of the conventional casting
methods including die-casting.
[0121] As a result, when the salt core 2 is employed, the degrees
of freedom in casting, e.g., the pressure during melt injection and
the shape of the mold, can be increased. The present inventors set
the target bending strength of a salt core that can also be
employed in die-casting to at least 8 MPa, because the maximum
bending strength at the current technological level of a shell core
which is said to have a higher strength than the current salt core
is about 6 MPa.
[0122] As is apparent from FIG. 3, except MM-16 mesh, CeraBeads
#1700, CeraBeads #1450, and CeraBeads #650, ceramic materials made
of other synthetic mullite materials could also obtain high bending
strengths in the same manner as MM-325 mesh.
[0123] The salt core 2 could be formed to have a high bending
strength in this manner probably due to the following reason. The
density (2.79 g/cm.sup.3 to 3.15 g/cm.sup.3) of synthetic mullite
is appropriately higher than the density (1.57 g/cm.sup.3) of
potassium chloride in a molten state. When the individual grains of
synthetic mullite disperse substantially evenly in potassium
chloride in the molten state and solidify, crack progress in the
salt is suppressed. This is apparent from the fact that a
sufficient strength is not obtained with MM-16 mesh or CeraBeads
#650 which sediments.
[0124] Potassium chloride as the major component of the salt core 2
is dissolved in hot water, and accordingly the salt core 2 can be
removed by dissolving it in hot water after casting. More
specifically, when a cast product formed by using the salt core 2
is dipped in, e.g., hot water, the salt core 2 is removed. When
compared to a case wherein, e.g., a shell core, is used in the same
manner as the conventional salt core, the cost of the core removing
process can be decreased.
[0125] The ceramic material mixed in the salt core 2 is only one
type of synthetic mullite, and separates from potassium chloride
when the salt core 2 is dissolved in water (hot water), as
described above. If the separated ceramic material is collected and
dried, it can be recycled easily. More specifically, since the
ceramic material can be recycled, the manufacturing cost of the
salt core 2 can be decreased. If a plurality of ceramic materials
are used, even when the salt core is dissolved in hot water and
recovered, the mixing ratio of the recovered ceramic material
becomes unstable and cannot be managed. Thus, the ceramic material
is difficult to recycle.
Second Embodiment
[0126] A salt core according to the present invention can use
granular aluminum borate (9Al.sub.2O.sub.3.2B.sub.2O.sub.3) as a
ceramic material. When aluminum borate was mixed in potassium
chloride, a bending strength as shown in FIG. 6 was obtained.
[0127] FIG. 6 is a graph showing the relationship between the
addition of aluminum borate and the bending strength. The bending
strength shown in FIG. 6 is obtained by conducting the experiment
shown in the first embodiment by using aluminum borate as a ceramic
material. The lines in FIG. 6 are approximate curves drawn using
the method of least squares.
[0128] As aluminum borate to be used for the experiment, three
types shown in Table 5 below were selected from commercially
available granular products. TABLE-US-00005 TABLE 5 Particle
Maximum Name of Chemical Name of Density size Addition in Sample
Addition Name of Ceramic Product formulae Shape Manufacturer
(g/cm.sup.3) (.mu.m) (wt %) (wt %) Aluminum borate Albolite
9Al.sub.2O.sub.3.2B.sub.2O.sub.3 Particulate Shikoku 2.93 2.3 10,
15, x20, x30 15 PF03 Chemicals Corp. Aluminum borate Albolite
9Al.sub.2O.sub.3.2B.sub.2O.sub.3 Particulate Shikoku 2.93 7.3 10,
15, 20, x30 20 PF08 Chemicals Corp. Aluminum borate Albolite
9Al.sub.2O.sub.3.2B.sub.2O.sub.3 Particulate Shikoku 2.93 48.92 10,
20, 30, 35, x40 35 PC30 Chemicals Corp. xNo fluidity s:
Sedimentation
[0129] Of the three types of aluminum borate shown in Table 5,
judging from the presence/absence of fluidity, what could be used
for casting were Albolite PF03 with an addition of 10% and 15%,
Albolite PF08 with an addition of 10%, 15%, and 20%, and Albolite
PC30 with an addition of 10%, 20%, 30%, and 35% (see Table 5 and
FIG. 16). From this result, Albolite PF03 with an addition of 15%
or less, Albolite PF08 with an addition of 20% or less, and
Albolite PC30 with an addition of 35% or less sufficiently have
fluidity and are supposedly castable.
[0130] It was also confirmed that each of these aluminum borate
products dispersed in a melt of potassium chloride (see FIG. 15).
These aluminum borate products respectively have densities of 2.93
g/cm.sup.3. The particle sizes of Albolite PF03, Albolite PF08, and
Albolite PC30 are 2.3 .mu.m, 7.3 .mu.m, and 48.92 .mu.m,
respectively.
[0131] For each of the three types of aluminum borate having
different particle sizes described above, bending samples were
formed with the respective additions, as shown in Table 6 below,
and their bending strengths were measured. TABLE-US-00006 TABLE 6
Composition Bending Bending Composition wt % Load N Strength MPa
pure KCl 0 186.255 1.55 pure KCl 0 250.024 2.08 pure KCl 0 226.274
1.89 pure KCl 0 308.725 2.57 pure KCl 0 225.850 1.88 KCl + 10%
Albolite PF03 10 986.250 8.22 KCl + 10% Albolite PF03 10 984.750
8.21 KCl + 10% Albolite PF03 10 1027.250 8.56 KCl + 10% Albolite
PF03 10 1298.420 10.82 KCl + 10% Albolite PF03 10 981.000 8.18 KCl
+ 10% Albolite PF03 10 972.375 8.10 KCl + 10% Albolite PF03 10
1033.000 8.61 KCl + 10% Albolite PF03 10 1046.370 8.72 KCl + 15%
Albolite PF03 15 1343.84 11.20 KCl + 15% Albolite PF03 15 1187 9.89
pure KCl 0 186.255 1.55 pure KCl 0 250.024 2.08 pure KCl 0 226.274
1.89 pure KCl 0 308.725 2.57 pure KCl 0 225.850 1.88 KCl + 10%
Albolite PF08 10 897.000 7.48 KCl + 10% Albolite PF08 10 1173.070
9.78 KCl + 10% Albolite PF08 10 1017.250 8.48 KCl + 10% Albolite
PF08 10 1138.000 9.48 KCl + 10% Albolite PF08 10 991.275 8.26 KCl +
10% Albolite PF08 10 1199.750 10.00 KCl + 10% Albolite PF08 10
1032.090 8.60 KCl + 15% Albolite PF08 15 1075.500 8.96 KCl + 20%
Albolite PF08 20 1145.020 9.54 KCl + 20% Albolite PF08 20 1210.270
10.09 pure KCl 0 186.255 1.55 pure KCl 0 250.024 2.08 pure KCl 0
226.274 1.89 pure KCl 0 308.725 2.57 pure KCl 0 225.850 1.88 KCl +
10% Albolite PC30 10 793.474 6.61 KCl + 20% Albolite PC30 20
1126.25 9.39 KCl + 20% Albolite PC30 20 1320.4 11.00 KCl + 30%
Albolite PC30 30 1541.75 12.85 KCl + 30% Albolite PC30 30 1415.72
11.80 KCl + 35% Albolite PC30 35 1787.55 14.90
[0132] When aluminum borate was to be used as a ceramic material in
this manner, as shown in FIG. 6, if the addition was 10% to 20%,
the bending strength became higher than 8 MPa.
[0133] As shown in FIG. 6, the bending strength of aluminum borate
is rarely adversely affected by the particle size.
[0134] Therefore, when aluminum borate is used as a ceramic
material, as described above, the same effect as that obtained when
the first embodiment is employed can be obtained.
Third Embodiment
[0135] A salt core according to the present invention can use
granular silicon nitride (Si.sub.3N.sub.4) as a ceramic material.
When silicon nitride was mixed in potassium chloride, a bending
strength as shown in FIG. 7 was obtained.
[0136] FIG. 7 is a graph showing the relationship between the
addition of silicon nitride and the bending strength. The bending
strength shown in FIG. 7 is obtained by conducting the experiment
shown in the first embodiment by using silicon nitride as a ceramic
material. The lines in FIG. 7 are approximate curves drawn using
the method of least squares.
[0137] As silicon nitride to be used for the experiment, four types
shown in Table 7 below were, selected from commercially available
granular products. TABLE-US-00007 TABLE 7 Particle Maximum Name of
Name of Chemical Name of Density size Addition in Sample Addition
Ceramic Product formulae Shape Manufacturer (g/cm.sup.3) (.mu.m)
(wt %) (wt %) Silicon NP-600 Si.sub.3N.sub.4 Particulate DENKI
KAGAKU 3.18 0.7 20, 24, 33, 25, x30, x35, x40 25 nitride KOGYO K.K.
Silicon MM-5MF Si.sub.3N.sub.4 Particulate YAKUSHIMA 3.19 0.8 10,
20, 25, x30 25 nitride DENKO CO., LTD. Silicon SN-7 Si.sub.3N.sub.4
Particulate DENKI KAGAKU 3.18 4.3 20, 30, 40, x45 40 nitride KOGYO
K.K. Silicon SN-9 Si.sub.3N.sub.4 Particulate DENKI KAGAKU 3.18 5.7
20, 30, 35, 40 40 nitride KOGYO K.K. xNo fluidity s:
Sedimentation
[0138] Of the four types of aluminum borate shown in Table 7,
judging from the presence/absence of fluidity, what could be used
for casting were NP-600 with an addition of 20% and 25%, SN-7 with
an addition of 20%, 30%, and 40%, SN-9 with an addition of 20%,
30%, 35%, and 40%, and HM-5MF with an addition of 10%, 20%, and
25%. From this result, NP-600 with an addition of 25% or less, SN-7
with an addition of 40% or less, SN-9 product with an addition of
40% or less, and HM-5 MF with an addition of 25% or less are
supposedly castable.
[0139] It was also confirmed that each of the four ceramic
materials dispersed in a melt of potassium chloride (See FIG.
15).
[0140] NP-600, SN-7, and SN-9 respectively have densities of 3.18
g/cm.sup.3, and HM-5MF has a density of 3.19 g/cm.sup.3. The four
types of silicon nitride products have different particle
sizes.
[0141] For each of the four types of silicon nitride described
above, bending samples were formed with the respective additions,
as shown in Table 8 below, and their bending strengths were
measured. TABLE-US-00008 TABLE 8 Composition Bending Bending
Composition wt % Load N Strength MPa pure KCl 0 186.255 1.55 pure
KCl 0 250.024 2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725 2.57
pure KCl 0 225.850 1.88 KCl + 20% Si.sub.3N.sub.4 SN-9 20 1056.57
8.80 KCl + 20% Si.sub.3N.sub.4 SN-9 20 997.325 8.31 KCl + 30%
Si.sub.3N.sub.4 SN-9 30 1163.92 9.70 KCl + 30% Si.sub.3N.sub.4 SN-9
30 1038.25 8.65 KCl + 35% Si.sub.3N.sub.4 SN-9 35 1084.3 9.04 KCl +
40% Si.sub.3N.sub.4 SN-9 40 1470.5 12.25 pure KCl 0 186.255 1.55
pure KCl 0 250.024 2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725
2.57 pure KCl 0 225.850 1.88 KCl + 20% Si.sub.3N.sub.4 SN-7 20
1242.62 10.36 KCl + 20% Si.sub.3N.sub.4 SN-7 20 948.25 7.90 KCl +
20% Si.sub.3N.sub.4 SN-7 20 1254 10.45 KCl + 30% Si.sub.3N.sub.4
SN-7 30 1048.84 8.74 KCl + 40% Si.sub.3N.sub.4 SN-7 40 995 8.29 KCl
+ 40% Si.sub.3N.sub.4 SN-7 40 1144.25 9.54 pure KCl 0 186.255 1.55
pure KCl 0 250.024 2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725
2.57 pure KCl 0 225.850 1.88 KCl + 20% Si.sub.3N.sub.4 NP-600 20
787.75 6.56 KCl + 20% Si.sub.3N.sub.4 NP-600 20 712.424 5.94 KCl +
24.33% Si.sub.3N.sub.4 NP-600 24.33 833.174 6.94 KCl + 25%
Si.sub.3N.sub.4 NP-600 25 1030 8.58 pure KCl 0 186.255 1.55 pure
KCl 0 250.024 2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725 2.57
pure KCl 0 225.850 1.88 KCl + 10% Si.sub.3N.sub.4 HM-5MF 10 624.849
5.21 KCl + 20% Si.sub.3N.sub.4 HM-5MF 20 917.299 7.64 KCl + 20%
Si.sub.3N.sub.4 HM-5MF 20 914.224 7.62 KCl + 25% Si.sub.3N.sub.4
HM-5MF 25 992.9 8.27 KCl + 25% Si.sub.3N.sub.4 HM-5MF 25 1134.8
9.46
[0142] When silicon nitride was to be used as a ceramic material in
this manner, as shown in FIG. 7, if the addition was 20% or more,
the bending strength became higher than 8 MPa.
[0143] As shown in FIG. 7, the bending strength of silicon nitride
is rarely adversely affected by the particle size.
[0144] Therefore, when silicon nitride is used as a ceramic
material, as described above, the same effect as that obtained when
the first embodiment is employed can be obtained.
Fourth Embodiment
[0145] A salt core according to the present invention can use
granular silicon carbide (SiC) as a ceramic material. When silicon
carbide was mixed in potassium chloride, a bending strength as
shown in FIG. 8 was obtained.
[0146] FIG. 8 is a graph showing the relationship between the
addition of silicon carbide and the bending strength. The bending
strength shown in FIG. 8 is obtained by conducting the experiment
shown in the first embodiment by using silicon carbide as a ceramic
material. The lines in FIG. 8 are approximate curves drawn using
the method of least squares.
[0147] As silicon carbide to be used for the experiment, three
types shown in Table 9 below were selected from commercially
available granular products. TABLE-US-00009 TABLE 9 Particle
Maximum Name of Name of Chemical Name of Density size Addition in
Sample Addition Ceramic Product formulae Shape Manufacturer
(g/cm.sup.3) (.mu.m) (wt %) (wt %) Silicon OY-15 SiC Particulate
YAKUSHIMA 3.23 0.7 10, 20, 30, 40, 45 45 carbide DENKO CO., LTD.
Silicon OY-7 SiC Particulate YAKUSHIMA 3.23 2 10, 20, 30, 40, 45 45
carbide DENKO CO., LTD. Silicon OY-3 SiC Particulate YAKUSHIMA 3.23
3 10, 20, 30, 40, 45 45 carbide DENKO CO., LTD. x: No fluidity s:
Sedimentation
[0148] Of the three types of silicon carbide shown in Table 9,
judging from the fluidity, those with additions of 10%, 20%, 30%,
40%, and 45% could be used for casting (see FIG. 18). From this
result, any one of the three types of silicon carbide is supposedly
castable if the addition is 45% or less.
[0149] It was also confirmed that each of these silicon carbide
products dispersed in a melt of potassium chloride (see FIG. 15).
These silicon carbide products respectively have densities of 3.23
g/cm.sup.3 but different particle sizes.
[0150] For each of the three types of silicon carbide described
above, bending samples were formed with the respective additions,
as shown in Table 10 below, and their bending strengths were
measured. TABLE-US-00010 TABLE 10 Composition Bending Bending
Composition wt % Load N Strength MPa pure KCl 0 186.255 1.55 pure
KCl 0 250.024 2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725 2.57
pure KCl 0 225.850 1.88 KCl + 20% SiC OY-3 20 964 8.03 KCl + 30%
SiC OY-3 30 912.25 7.60 KCl + 30% SiC OY-3 30 1134.75 9.46 KCl +
45% SiC OY-3 45 1263.75 10.53 pure KCl 0 186.255 1.55 pure KCl 0
250.024 2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725 2.57 pure
KCl 0 225.850 1.88 KCl + 20% SiC OY-7 20 952.75 7.94 KCl + 30% SiC
OY-7 30 1292.5 10.77 KCl + 30% SiC OY-7 30 954.95 7.96 KCl + 40%
SiC OY-7 40 1206.75 10.06 KCl + 45% SiC OY-7 45 1185.69 9.88 pure
KCl 0 186.255 1.55 pure KCl 0 250.024 2.08 pure KCl 0 226.274 1.89
pure KCl 0 308.725 2.57 pure KCl 0 225.850 1.88 KCl + 20% SiC OY-15
20 669.75 5.58 KCl + 30% SiC OY-15 30 799 6.66 KCl + 30% SiC OY-15
30 673 5.61 KCl + 40% SiC OY-15 40 911.599 7.60 KCl + 45% SiC OY-15
45 991.5 8.26
[0151] When silicon carbide was to be used as a ceramic material in
this manner, as shown in FIG. 8, if the addition was 25% to 30% or
more, the bending strength became higher than 8 MPa.
[0152] As shown in FIG. 8, the bending strength of silicon carbide
is rarely adversely affected by the particle size.
[0153] Therefore, when silicon carbide is used as a ceramic
material, as described above, the same effect as that obtained when
the first embodiment is employed can be obtained.
Fifth Embodiment
[0154] A salt core according to the present invention can use
granular aluminum nitride (AlN) as a ceramic material. When
aluminum nitride was mixed in potassium chloride, a bending
strength as shown in FIG. 9 was obtained.
[0155] FIG. 9 is a graph showing the relationship between the
addition of aluminum nitride and the bending strength. The bending
strength shown in FIG. 9 is obtained by conducting the experiment
shown in the first embodiment by using aluminum nitride as a
ceramic material. The lines in FIG. 9 are approximate curves drawn
using the method of least squares.
[0156] As aluminum nitride to be used for the experiment, two types
shown in Table 11 below were selected from commercially available
granular products. TABLE-US-00011 TABLE 11 Particle Maximum Name of
Name of Chemical Name of Density size Addition in Sample Addition
Ceramic Product formulae Shape Manufacturer (g/cm.sup.3) (.mu.m)
(wt %) (wt %) Aluminum -250mesh AlN Particulate K.K. TACHYON 3.25
-60 20, 30, 40 40 nitride Aluminum -150mesh AlN Particulate K.K.
TACHYON 3.25 -100 20, 30, 40 40 nitride x: No fluidity s:
Sedimentation
[0157] Of the two types of silicon carbide shown in Table 11,
judging from the fluidity, those with additions of 20%, 30%, and
40% could be used for casting (see Table 11 and FIG. 18). From this
result, both of the two types of aluminum nitride are supposedly
castable if the additions are 40%.
[0158] It was also confirmed that each of these aluminum nitride
products dispersed in a melt of potassium chloride (see FIG. 15).
These aluminum nitride products respectively have densities of 3.25
g/cm.sup.3 but different particle sizes.
[0159] For each of the two types of aluminum nitride described
above, bending samples were formed with the respective additions,
as shown in Table 12 below, and their bending strengths were
measured. TABLE-US-00012 TABLE 12 Composition Bending Bending
Composition wt % Load N Strength MPa pure KCl 0 186.255 1.55 pure
KCl 0 250.024 2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725 2.57
pure KCl 0 225.850 1.88 KCl + 20% AlN - 150 mesh 20 1237.5 10.31
KCl + 30% AlN - 150 mesh 30 1503 12.53 KCl + 30% AlN - 150 mesh 30
1649.5 13.75 KCl + 40% AlN - 150 mesh 40 1730.72 14.42 KCl + 40%
AlN - 150 mesh 40 2232.25 18.60 pure KCl 0 186.255 1.55 pure KCl 0
250.024 2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725 2.57 pure
KCl 0 225.850 1.88 KCl + 20% AlN - 250 mesh 20 1422.75 11.86 KCl +
30% AlN - 250 mesh 30 1848.75 15.41 KCl + 30% AlN - 250 mesh 30
1922.75 16.02 KCl + 40% AlN - 250 mesh 40 2775.5 23.13 KCl + 40%
AlN - 250 mesh 40 2092.89 17.44
[0160] When aluminum nitride was to be used as a ceramic material
in this manner, as shown in FIG. 9, if the addition wan 15% or
more, the bending strength became higher than 8 MPa.
[0161] As shown in FIG. 9, the bending strength of aluminum nitride
is rarely adversely affected by the particle size.
[0162] Therefore, when aluminum nitride is used as a ceramic
material, as described above, the same effect as that obtained when
the first embodiment is employed can be obtained.
Sixth Embodiment
[0163] A salt core according to the present intention can use
granular boron carbide (B.sub.4C) as a ceramic material. When boron
carbide was mixed in potassium chloride, a bending strength as
shown in FIG. 10 was obtained.
[0164] FIG. 10 is a graph showing the relationship between the
addition of boron carbide and the bending strength. The bending
strength shown in FIG. 10 is obtained by conducting the experiment
shown in the first embodiment by using boron carbide as a ceramic
material. The lines in FIG. 10 are approximate curves drawn using
the method of least squares.
[0165] As boron carbide to be used for the experiment, three types
shown in Table 13 below were selected from commercially available
granular products. TABLE-US-00013 TABLE 13 Particle Maximum Name of
Name of Chemical Name of Density size Addition in Sample Addition
Ceramic Product Formulae Shape Manufacturer (g/cm.sup.3) (.mu.m)
(wt %) (wt %) Boron carbide #I200 B.sub.4C Particulate DENKI KAGAKU
2.51 -3 20, 30, 33, 75, x35, x40 33.75 KOGYO K.K. Boron carbide S1
B.sub.4C Particulate DENKI KAGAKU 2.51 45-90 20, 30, 40 40 KOGYO
K.K. Boron carbide S3 B.sub.4C Particulate DENKI KAGAKU 2.51
125-250 s20, s30, s40 above 40 KOGYO K.K. xNo fluidity
sSedimentation
[0166] Of the three types of boron carbide shown in Table 13,
judging from the fluidity, what could be used for casting were
#1200 with an addition of 20%, 30% and 33.75% and S1 and S3 each
with an addition of 20%, 30%, and 40% (see Table 13 and FIG. 16).
From this result, #1200 is supposedly castable if the addition is
33.75% or less, and S1 and S3 are supposedly castable if the
additions are 40% or less. It was also confirmed that of each of
the three types of boron carbide, S3 sedimented in a melt of
potassium chloride while each of the remaining #1200 and S1
dispersed (see FIG. 15). These boron carbide samples respectively
have densities of 2.15 g/cm.sup.3 but different granular sizes.
[0167] For each of the three types of boron carbide described
above, bending samples were formed with the respective additions,
as shown in Table 14 below, and their bending strengths were
measured. TABLE-US-00014 TABLE 14 Composition Bending Bending
Composition wt % Load N strength Mpa pure KCl 0 186.255 1.55 pure
KCl 0 250.024 2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725 2.57
pure KCl 0 225.850 1.88 KCl + 20% B.sub.4C #1200 20 1260.84 10.51
KCl + 30% B.sub.4C #1200 30 1033 8.61 KCl + 30% B.sub.4C #1200 30
1579 13.16 KCl + 33.75% B.sub.4C #1200 33.75 2008 16.73 pure KCl 0
186.255 1.55 pure KCl 0 250.024 2.08 pure KCl 0 226.274 1.89 pure
KCl 0 308.725 2.57 pure KCl 0 225.850 1.88 KCl + 20% B.sub.4C S1 20
924.424 7.70 KCl + 30% B.sub.4C S1 30 1091.57 9.10 KCl + 30%
B.sub.4C S1 30 1281.5 10.68 KCl + 40% B.sub.4C S1 40 1627.19 13.56
KCl + 40% B.sub.4C S1 40 1265 10.54 pure KCl 0 186.255 1.55 pure
KCl 0 250.024 2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725 2.57
pure KCl 0 225.850 1.88 KCl + 20% B.sub.4C S3 20 352.149 2.93 KCl +
30% B.sub.4C S3 30 474 3.95 KCl + 30% B.sub.4C S3 30 482.424 4.02
KCl + 40% B.sub.4C S3 40 473.125 3.94
[0168] When boron carbide was to be used as a ceramic material in
this manner, as shown in FIG. 10, if the addition was set to 20% or
more in the sample with a sample name #1200 and the sample with a
sample name S1, the bending strength became higher than 8 MPa. As
shown in FIG. 10, with S3 which disperses, a high strength cannot
be obtained.
[0169] Therefore, when boron carbide is used as a ceramic material,
as described above, the same effect as that obtained when the first
embodiment is employed can be obtained.
Seventh Embodiment
[0170] A salt core according to the present invention can use
granular aluminum titanate (Al.sub.2TiO.sub.5) or spinal
(cordierite: MgO.Al.sub.3O.sub.3) as a ceramic material. When such
a ceramic material was mixed in potassium chloride, a bending
strength as shown in FIG. 11 was obtained.
[0171] FIG. 11 is a graph showing the relationship between the
addition of aluminum titanate or spinal and the bending strength.
The bending strength-shown in FIG. 11 is obtained by conducting the
experiment shown in the first embodiment by using aluminum titanate
or spinel as a ceramic material. The lines in FIG. 11 are
approximate curves drawn using the method of least squares.
[0172] As aluminum titanate and spinal to be used for the
experiment, those shown in Table 15 below were selected from
commercially available granular products. TABLE-US-00015 TABLE 15
Particle Maximum Name of Name of Chemical Name of Density size
Addition in Sample Addition Ceramic Product formulae Shape
Manufacturer (g/cm.sup.3) (.mu.m) (wt %) (wt %) Spinel NSP-70-
MgO.Al.sub.2O.sub.3 Particulate ITOCHU 3.27 75 20, 30, 40, x50 40
200mesh CERATECH CORP. Aluminum VCAT Al.sub.2TiO.sub.5 Particulate
Shinku 3.7- -1.0 10, 20, 30, 40, x50 40 titanate Ceramics K.K. xNo
fluidity s: Sedimentation
[0173] Of aluminum titanate shown in Table 13, judging from the
fluidity, those with additions of 10%, 20%, 30% and 40% could be
used for casting, and of spinel, judging from the fluidity, those
with additions of 20%, 30%, and 40% could be used for casting (see
Table 15 and FIG. 18). From this result, aluminum titanate and
spinel are supposedly castable if the additions are 40% or less. It
was also confirmed that each of the two ceramic materials dispersed
in a melt of potassium chloride (see FIG. 15).
[0174] Aluminum titanate has a density of 3.7 g/cm.sup.3 and a
particle size of 1 .mu.m, and spinel has a density of 3.27
g/cm.sup.3 and a particle size of 75 .mu.m.
[0175] For each of the ceramic materials described above, bending
samples were formed with the respective additions, as shown in
Table 16 below, and their bending strengths were measured.
TABLE-US-00016 TABLE 16 Composition Bending Bending Composition wt
% Load N Strength MPa pure KCl 0 186.255 1.55 pure KCl 0 250.024
2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725 2.57 pure KCl 0
225.850 1.88 KCl + 20% Al.sub.2TiO.sub.5 20 749.25 6.24 KCl + 30%
Al.sub.2TiO.sub.5 30 1336.55 11.14 KCl + 30% Al.sub.2TiO.sub.5 30
1270.07 10.58 KCl + 40% Al.sub.2TiO.sub.5 40 1137.19 9.48 KCl + 40%
Al.sub.2TiO.sub.5 40 1341.75 11.18 pure KCl 0 186.255 1.55 pure KCl
0 250.024 2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725 2.57 pure
KCl 0 225.850 1.88 KCl + 20% MgO.Al.sub.2O.sub.3 20 1111.07 9.26
KCl + 30% MgO.Al.sub.2O.sub.3 30 1541.87 12.85 KCl + 30%
MgO.Al.sub.2O.sub.3 30 1453 12.11 KCl + 40% MgO.Al.sub.2O.sub.3 40
1892.75 15.77 KCl + 40% MgO.Al.sub.2O.sub.3 40 1898.75 15.82
[0176] When aluminum titanate or spinel was to be used as a ceramic
material in this manner, as shown in FIG. 11, if the addition was
set to 20% or more, the bending strength became higher than 8 MPa,
as shown in FIG. 11.
[0177] Therefore, when aluminum titanate or spinel is used as a
ceramic material, as described above, the same effect as that
obtained when the first embodiment is employed can be obtained.
Eighth Embodiment
[0178] A salt core according to the present invention can use
granular alumina (Al.sub.2O.sub.3) as a ceramic material. When such
alumina was mixed in potassium chloride, a bending strength as
shown in FIG. 12 was obtained.
[0179] FIG. 12 is a graph showing the relationship between the
addition of alumina and the bending strength. The bending strength
shown in FIG. 12 is obtained by conducting the experiment shown in
the first embodiment by using alumina as a ceramic material. The
lines in FIG. 12 are approximate curves drawn using the method of
least squares.
[0180] As alumina to be used for the experiment, those shown in
Table 17 below were selected from commercially available granular
products. TABLE-US-00017 TABLE 17 Particle Maximum Name of Name of
Chemical Name of Density size Addition in Sample Addition Ceramic
Product formulae Shape Manufacturer (g/cm.sup.3) (.mu.m) (wt %) (wt
%) Alumina AL-160SG-3 Al.sub.2O.sub.3 Particulate SHOWA DENKO K.K.
3.92 0.6 20, 30, x35, x40 30 Alumina AL-45-1 Al.sub.2O.sub.3
Paritculate SHOWA DENKO K.K. 3.93 1 20, 30, 35, x40 35 Alumina
A-42-1 Al.sub.2O.sub.3 Particulate SHOWA DENKO K.K. 3.95 3-4 20,
30, x35, x40 30 Alumina A-12 Al.sub.2O.sub.3 Particulate SHOWA
DENKO K.K. 3.96 40-50 20, 30, x35 30 xNo fluidity s:
Sedimentation
[0181] Of alumina samples shown in Table 17, judging from the
fluidity, those with additions of 20%, 20%, 30% and 35% (AL-45-1)
could be used for casting (see FIG. 18). From this result, AL-45-1
is supposedly castable if the addition is 35% or less, and the
remaining samples are supposedly castable if the additions are 30%
or less.
[0182] It was also confirmed that any one of the above alumina
samples dispersed in a melt of potassium chloride (see FIG. 15).
These alumina samples have densities of about 4 g/cm.sup.3 and
particle sizes of 0.6 .mu.m (AL-160SG), 1 .mu.m (AL-45-1), 3 .mu.m
to 4 .mu.m (A-42-1), and 40 .mu.m to 50 .mu.m (A-12).
[0183] For each of alumina samples described above, bending samples
were formed with the respective additions, as shown in Table 18
below, and their bending strengths were measured. TABLE-US-00018
TABLE 18 Composition Bending Bending Composition wt % Load N
Strength MPa pure KCl 0 186.255 1.55 pure KCl 0 250.024 2.08 pure
KCl 0 226.274 1.89 pure KCl 0 308.725 2.57 pure KCl 0 225.850 1.88
KCl + 20% Al.sub.2O.sub.3 AL-45-1 20 1041.25 8.68 KCl + 30%
Al.sub.2O.sub.3 AL-45-1 30 1037.05 8.64 KCl + 35% Al.sub.2O.sub.3
AL-45-1 35 1116 9.30 KCl + 35% Al.sub.2O.sub.3 AL-45-1 35 1008.67
8.41 pure KCl 0 186.255 1.55 pure KCl 0 250.024 2.08 pure KCl 0
226.274 1.89 pure KCl 0 308.725 2.57 pure KCl 0 225.850 1.88 KCl +
20% Al.sub.2O.sub.3 A-42-1 20 871.75 7.26 KCl + 20% Al.sub.2O.sub.3
A-42-1 20 1432.5 11.94 KCl + 30% Al.sub.2O.sub.3 A-42-1 30 2118.07
17.65 KCl + 30% Al.sub.2O.sub.3 A-42-1 30 1660.75 13.84 pure KCl 0
186.255 1.55 pure KCl 0 250.024 2.08 pure KCl 0 226.274 1.89 pure
KCl 0 308.725 2.57 pure KCl 0 225.850 1.88 KCl + 20%
Al.sub.2O.sub.3 A-12 20 1093.52 9.11 KCl + 20% Al.sub.2O.sub.3 A-12
20 972.4 8.10 KCl + 30% Al.sub.2O.sub.3 A-12 30 1456 12.13 KCl +
30% Al.sub.2O.sub.3 A-12 30 1540 12.83 pure KCl 0 186.255 1.55 pure
KCl 0 250.024 2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725 2.57
pure KCl 0 225.850 1.88 KCl + 20% Al.sub.2O.sub.3 20 973.75 8.11
AL-160SG-3 KCl + 20% Al.sub.2O.sub.3 20 986.25 8.22 AL-160SG-3 KCl
+ 30% Al.sub.2O.sub.3 30 1166.34 9.72 AL-160SG-3 KCl + 30%
Al.sub.2O.sub.3 30 1183.75 9.86 AL-160SG-3
[0184] When alumina was to be used as a ceramic material in this
manner, as shown in FIG. 12, if the addition was set to 20% or
more, the bending strength became higher than 8 MPa.
[0185] Therefore, when alumina is used as a ceramic material, as
described above, the same effect as that obtained when the first
embodiment is employed can be obtained.
[0186] FIGS. 13 and 14 show the relationship between the additions
of all the ceramic materials indicated in the first to eighth
embodiments described above and the bending strengths. As is
apparent from FIGS. 13 and 14, of the ceramic materials described
above, what could form a salt core with the highest bending
strength was aluminum nitride.
[0187] Of the ceramic materials described above, the one with the
least expensive material unit cost is synthetic mullite, and the
one that requires the minimum material amount (addition) is
aluminum borate. More specifically, when synthetic mullite or
aluminum borate is used, a salt core having a high strength can be
manufactured while suppressing the manufacturing cost.
[0188] When the ceramic material indicated in any one of the first
to eighth embodiments was used, a salt core with excellent
castability and high strength could be formed probably because of
the following reason. A melt obtained by mixing such a ceramic
material in potassium chloride has fluidity. The density of the
ceramic material is appropriately higher than the density (1.57
g/cm.sup.3) of potassium chloride in a molten state. Such a ceramic
material disperses in potassium chloride in the molten state widely
and evenly to suppress crack progress in the salt.
[0189] More specifically, "fluidity" enabled casting, and
"dispersion" enabled sufficient strength. Of the two factors,
"fluidity" is influenced mainly by the addition (wt %) of the
ceramic material, and "dispersion" is influenced by the density.
Even a ceramic material different from those described in the first
to eighth embodiments is supposedly able to form a salt core having
the equal strength to those indicated in the embodiments described
above, as far as the different ceramic material has a density
approximate to those of the ceramic materials described above so
that it forms a melt having fluidity.
[0190] In order to investigate whether the ceramic material
disperses well in the salt material in the molten state, the
present inventors conducted an experiment on the mixing conditions
of potassium chloride and the ceramic material. According to this
experiment, as shown in FIG. 15, a ceramic material which dispersed
in molten potassium chloride had a minimum density which is higher
than 2.28 g.cm.sup.3 (boron nitride), a maximum density of 4
g/cm.sup.3 (alumina), and a maximum particle size of about 150
.mu.m.
[0191] This is because dispersion is closely related to the
solidification time of the melt and the sedimentation velocity of
the ceramic material. The theoretical equation of the sedimentation
velocity is: V=g(.rho.c-.rho.s)d.sup.2/18.mu. (2) where V is the
sedimentation velocity [m/s], g is the gravitational acceleration
9.80 [m/s.sup.2], .rho.c is the density [g/cm.sup.3] of the ceramic
material. .rho.s is the density [g/cm.sup.3] of the salt material
in the molten state, d is the particle size [m] of the ceramic
material, and .mu. is the coefficient of viscosity [Pas] of the
salt material.
[0192] According to equation (2), the sedimentation velocity V is
proportional to the density difference between the ceramic material
and the salt material in the molten state and to the square of the
particle size. Hence, regarding the particle size, if it is larger
than 150 .mu.m, the sedimentation velocity becomes very fast so the
ceramic material may not be able to be dispersed well. Regarding
the density of the ceramic material, it influences the
sedimentation velocity more than the particle size does. Thus, even
a ceramic material having a density higher than 4 g/cm.sup.3, which
is not subjected to the experiment this time, can be estimated to
be dispersed well.
[0193] The relationship between the additions of the respective
ceramic materials and the fluidities were as shown in FIGS. 16 to
18. The results of FIGS. 16 to 18 were obtained by an experiment of
placing the ceramic material and potassium chloride in a Tammann
tube, dissolving the mixture at 800.degree. C., stirring the
mixture sufficiently, and reversing the Tammann tube upside down.
Of the mixtures, one the melt of which flowed out from the Tammann
tube was determined as "with fluidity" and one the melt of which
did not was determined as "without fluidity".
[0194] Therefore, any ceramic material that has a density falling
within a range of 2.2 g/cm.sup.3 (=the density of boron nitride)
(exclusive) to 4 g/cm.sup.3 (inclusive) or/and a particle size of
about 150 .mu.m or less, forms grains, and disperses in a melt of
potassium chloride sufficiently can form a salt core having such a
strength that it can be used in die-casting as well.
Ninth Embodiment
[0195] A salt core according to the present invention can use
aluminum borate whiskers (9Al.sub.2O.sub.3.2B.sub.2O.sub.3),
silicon nitride whiskers (Si.sub.3N.sub.4), silicon carbide
whiskers (SiC), potassium hexatitanate whiskers
(K.sub.2O.6TiO.sub.2), potassium octatitanate whiskers
(K.sub.2O.8TiO.sub.2), or zinc oxide whiskers (ZnO) as a ceramic
material. Examples of the ceramic whiskers include those shown in
Table 19 below. TABLE-US-00019 TABLE 19 Particle Maximum Name of
Name of Chemical Name of Density size Particle Addition in Sample
Addition Ceramic Product formulae Shape Manufacturer (g/cm.sup.3)
(.mu.m) size (.mu.m) (wt %) (wt %) Aluminum Albolex
9Al.sub.2O.sub.3.2B.sub.2O.sub.3 whisker Shikoku 2.93 10-30 0.5-1.0
10, 15, 18.67, x20 15 borate M20 Chemicals Corp. Silicon SNW #1-S
Si.sub.3N.sub.4 alpha whisker Tateho 3.18 5-200 0.1-1.6 5, 7, x8 7
nitride Chemical Industries Co., Ltd. Silicon SCW SiC Beta whisker
Tateho 3.18 5-200 0.05-1.5 5, 7, x8, x10, x15 7 carbide #1-0.8
Chemical Industries Co., Ltd. Potassium Tismo N H.sub.2O.6TiO.sub.2
whisker Otsuka (3.4-3.6) 10-20 0.3-0.6 5, 7, x8, xI0 7 hexatitanate
Chemical 3.58 Co., Ltd. Potassium Tismo D K.sub.2O.8TiO.sub.2
whisker Otsuka (3.4-3.6) 10-20 0.3-0.6 5, 7, x8, x10 7 octatitanate
Chemical 3.58 Co., Ltd. Zinc oxide WZ-0501 ZnO whisker Matsushita
5.78 2-50 0.2-3.0 5, 10, 15, x16, 15 AMTEC K.K. x18, x20 xNo
fluidity s: Sedimentation
[0196] As shown in Table 19, of aluminum borate whiskers
(tradename: Albolex M20), judging from the fluidity, those with
additions of 10%, 15, and 18.67% could be used for casting (see
FIG. 24). From this result, aluminum borate whiskers are supposedly
castable if the addition is 18.67% or less.
[0197] Of silicon nitride whiskers (tradename: SNW #1-S), silicon
carbide whiskers (tradename: SCW #1-0.8), potassium hexatitanate
whiskers (tradename: Tismo N), and potassium octatitanate whiskers
(tradename: Tismo D), those with additions of 5% and 7% could be
used for casting (see FIG. 24). From this result, these whiskers
are supposedly castable if the addition is 7% or less.
[0198] Of zinc oxide whiskers (tradename: WZ-0501), those with
additions of 5%, 10%, and 15% could be used for casting (see FIG.
24). From this result, zinc oxide whiskers are supposedly castable
if the addition is 15% or less.
[0199] Of these whiskers, when aluminum borate whiskers were mixed
in potassium chloride, a bending strength as shown in FIG. 19 was
obtained.
[0200] FIG. 19 is a graph showing the relationship between the
addition of aluminum borate whiskers and the bending strength. The
bending strength shown in FIG. 19 is obtained by conducting the
experiment shown in the first embodiment by using aluminum borate
whiskers as a ceramic material. The line in FIG. 19 is an
approximate curve drawn using the method of least squares. When
conducting this experiment, bending samples were formed with the
respective additions, as shown in Table 20 below, and their bending
strengths were measured. TABLE-US-00020 TABLE 20 Bending
Composition Bending Strength Composition wt % Load N MPa pure KCl 0
186.255 1.55 pure KCl 0 250.024 2.08 pure KCl 0 226.274 1.89 pure
KCl 0 308.725 2.57 pure KCl 0 225.850 1.88 KCl + 10% Albolex M20 10
2485.750 20.71 KCl + 10% Albolex M20 10 2466.75 20.56 KCl + 10%
Albolex M20 10 2488.75 20.74 KCl + 10% Albolex M20 10 2832.25 23.60
KCl + 10% Albolex M20 10 2262.89 18.86 KCl + 10% Albolex M20 10
2758.00 22.98 KCl + 10% Albolex M20 10 2624.75 21.87 KCl + 10%
Albolex M20 10 2155.35 17.96 KCl + 15% Albolex M20 15 4101.05 34.18
KCl + 15% Albolex M20 15 3722.75 31.02 KCl + 15% Albolex M20 15
3763.50 31.36 KCl + 15% Albolex M20 15 3973.75 33.11 KCl + 15%
Albolex M20 15 3305.72 27.55 KCl + 15% Albolex M20 15 3783.02 31.53
KCl + 15% Albolex M20 15 3411.75 28.43 KCl + 18.7% Albolex M20 18.7
4346.25 36.22
[0201] When aluminum borate whiskers were to be used as a ceramic
material in this manner, as shown in FIG. 19, if the addition was
5% or more, the bending strength became higher than 8 MPa. If the
addition was 18% or more, a bending strength of as high as 35 MPa
was exhibited.
[0202] Therefore, when aluminum borate whiskers are used as a
ceramic material, as described above, the same effect as that
obtained when the first embodiment is employed can be obtained.
10th Embodiment
[0203] When silicon nitride whiskers or silicon carbide whiskers
were mixed in potassium chloride, a bending strength as shown in
FIG. 20 was obtained.
[0204] FIG. 20 is a graph showing the relationship between the
addition of silicon nitride whiskers or the addition of silicon
carbide whiskers and the bending strength. The bending strength
shown in FIG. 20 is obtained by conducting the experiment shown in
the first embodiment by using silicon nitride whiskers or silicon
carbide whiskers as a ceramic material. The lines in FIG. 20 are
approximate curves drawn using the method of least squares. When
conducting this experiment, bending samples were formed with the
respective additions, as shown in Table 21 below, and their bending
strengths were measured. TABLE-US-00021 TABLE 21 Composition
Bending Bending Composition wt % Load N Strength MPa pure KCl 0
186.255 1.55 pure KCl 0 250.024 2.08 pure KCl 0 226.274 1.89 pure
KCl 0 308.725 2.57 pure KCl 0 225.850 1.88 KCl + 5% SiC Whisker 5
718.75 5.99 KCl + 7% SiC Whisker 7 673 5.61 KCl + 5% SiC Whisker 5
581 4.84 KCl + 7% SiC Whisker 7 900 7.50 pure KCl 0 186.255 1.55
pure KCl 0 250.024 2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725
2.57 pure KCl 0 225.850 1.88 KCl + 5% Si.sub.3N.sub.4 Whisker 5
721.25 6.01 KCl + 5% Si.sub.3N.sub.4 Whisker 5 640 5.33 KCl + 5%
Si.sub.3N.sub.4 Whisker 7 881.025 7.34 KCl + 5% Si.sub.3N.sub.4
Whisker 7 975.799 8.13
[0205] When silicon borate whiskers or silicon carbide whiskers
were to be used as a ceramic material in this manner, as shown in
FIG. 20, if the addition was 7%, the bending strength became higher
than 8 MPa.
[0206] Therefore, when silicon borate whiskers or silicon carbide
whiskers are used as a ceramic material, as described above, the
same effect as that obtained when the first embodiment is employed
can be obtained.
11th Embodiment
[0207] When potassium hexatitanate whiskers or potassium
octatitanate whiskers were mixed in potassium chloride, a bending
strength as shown in FIG. 21 was obtained.
[0208] FIG. 21 is a graph showing the relationship between the
addition of potassium hexatitanate whiskers or the addition of
potassium octatitanate whiskers and the bending strength. The
bending strength shown in FIG. 21 is obtained by conducting the
experiment shown in the first embodiment by using potassium
hexatitanate whiskers or potassium octatitanate whiskers as a
ceramic material. The lines in FIG. 21 are approximate curves drawn
using the method of least squares. When conducting this experiment,
bending samples were formed with the respective additions, as shown
in Table 22 below, and their bending strengths were measured.
TABLE-US-00022 TABLE 22 Composition Bending Bending Composition wt
% Load N Strength MPa pure KCl 0 186.255 1.55 pure KCl 0 250.024
2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725 2.57 pure KCl 0
255.850 1.88 KCl + 5% K.sub.2O.6TiO.sub.2 5 661 5.51 KCl + 5%
K.sub.2O.6TiO.sub.2 5 856 7.13 KCl + 5% K.sub.2O.6TiO.sub.2 5 976
8.13 KCl + 5% K.sub.2O.6TiO.sub.2 5 799 6.66 KCl + 5%
K.sub.2O.6TiO.sub.2 5 900 7.50 KCl + 7% K.sub.2O.6TiO.sub.2 7
1140.5 9.50 KCl + 7% K.sub.2O.6TiO.sub.2 7 905.2 7.54 KCl + 7%
K.sub.2O.6TiO.sub.2 7 778.7 6.49 KCl + 7% K.sub.2O.6TiO.sub.2 7
1082 9.02 KCl + 7% K.sub.2O.6TiO.sub.2 7 972.474 8.10 KCl + 7%
K.sub.2O.6TiO.sub.2 7 870.25 7.25 KCl + 7% K.sub.2O.6TiO.sub.2 7
1134.25 9.45 KCl + 7.05% K.sub.2O.6TiO.sub.2 7.05 1052.4 8.77 KCl +
7.05% K.sub.2O.6TiO.sub.2 7.05 952.375 7.94 KCl + 8%
K.sub.2O.6TiO.sub.2 8 997.75 8.31 KCl + 8% K.sub.2O.6TiO.sub.2 8
557.7 4.65 KCl + 8% K.sub.2O.6TiO.sub.2 8 1019 8.49 KCl + 8%
K.sub.2O.6TiO.sub.2 8 922.7 7.69 KCl + 8% K.sub.2O.6TiO.sub.2 8
578.875 4.82 KCl + 8% K.sub.2O.6TiO.sub.2 8 1048.72 8.74 KCl + 8%
K.sub.2O.6TiO.sub.2 8 646.15 5.38 pure KCl 0 186.255 1.55 pure KCl
0 250.024 2.08 pure KCl 0 226.274 1.89 pure KCl 0 308.725 2.57 pure
KCl 0 255.850 1.88 KCl + 5% K.sub.2O.8TiO.sub.2 5 715 5.96 KCl + 5%
K.sub.2O.8TiO.sub.2 5 697 5.81 KCl + 5% K.sub.2O.8TiO.sub.2 5 555
4.63 KCl + 5% K.sub.2O.8TiO.sub.2 5 909 7.58 KCl + 5%
K.sub.2O.8TiO.sub.2 5 761 6.34 KCl + 5% K.sub.2O.8TiO.sub.2 5
794.25 6.62 KCl + 7% K.sub.2O.8TiO.sub.2 7 1088 9.07 KCl + 7%
K.sub.2O.8TiO.sub.2 7 993.599 8.28 KCl + 7% K.sub.2O.8TiO.sub.2 7
1350 11.25 KCl + 8% K.sub.2O.8TiO.sub.2 8 1079.5 9.00 KCl + 8%
K.sub.2O.8TiO.sub.2 8 1163 9.69 KCl + 8% K.sub.2O.8TiO.sub.2 8
1188.25 9.90 KCl + 8% K.sub.2O.8TiO.sub.2 8 1182 9.85 KCl + 8%
K.sub.2O.8TiO.sub.2 8 1175.77 9.80
[0209] When potassium hexatitanate whiskers or potassium
octatitanate whiskers were to be used as a ceramic material in this
manner, as shown in FIG. 21, if the addition was 7%, the bending
strength became higher than 8 MPa.
[0210] Therefore, when potassium hexatitanate whiskers or potassium
octatitanate whiskers are used as a ceramic material, as described
above, the same effect as that obtained when the first embodiment
is employed can be obtained.
12th Embodiment
[0211] When zinc oxide whiskers were mixed in potassium chloride, a
bending strength as shown in FIG. 22 was obtained.
[0212] FIG. 22 is a graph showing the relationship between the
addition of zinc oxide whiskers and the bending strength. The
bending strength shown in FIG. 22 is obtained by conducting the
experiment shown in the first embodiment by using zinc oxide
whiskers as a ceramic material. The line in FIG. 22 is an
approximate curve drawn using the method of least squares. When
conducting this experiment, bending samples were formed with the
respective additions, as shown in Table 23 below, and their bending
strengths were measured. TABLE-US-00023 TABLE 23 Bending
Composition Bending Strength Composition wt % Load N MPa pure KCl 0
186.255 1.55 pure KCl 0 250.024 2.08 pure KCl 0 226.274 1.89 pure
KCl 0 308.725 2.57 pure KCl 0 225.850 1.88 KCl + 5% ZnO Whisker 5
401.45 3.35 KCl + 5% ZnO Whisker 5 487.35 4.06 KCl + 10% ZnO
Whisker 10 654 5.45 KCl + 10% ZnO Whisker 10 510.899 4.26 KCl + 15%
ZnO Whisker 15 612.75 5.11 KCl + 15% ZnO Whisker 15 532.375
4.44
[0213] When zinc oxide whiskers are to be used as a ceramic
material in this manner, as shown in FIG. 22, if the addition is
15%, a salt core with a high bending strength can be formed.
[0214] Therefore, when zinc oxide whiskers are used as a ceramic
material, as described above, the same effect as that obtained when
the first embodiment is employed can be obtained.
[0215] FIG. 23 is a graph showing the relationship between the
addition of each of all the whiskers shown in the ninth to 12th
embodiments described above and the bending strength. As is
apparent from FIG. 23, of the whiskers described above, the one
that could form a salt core with the highest bending strength was
aluminum borate whiskers.
[0216] The relationship between the additions of the respective
ceramic whiskers and the fluidities were as shown in FIG. 24. The
result of FIG. 24 was obtained by an experiment of placing the
ceramic whiskers and potassium chloride in a Tammann tube,
dissolving the mixture at 800.degree. C., stirring the mixture
sufficiently, and reversing the Tammann tube upside down. Of the
mixtures, one the melt of which flowed out from the Tammann tube
was determined as "with fluidity" and one the melt of which did not
was determined as "without fluidity".
[0217] The respective embodiments described above exemplified cases
wherein potassium chloride was used as a salt material. Other than
potassium chloride, a sodium chloride, or any one of a bromide,
carbonate, and sulfate of potassium or sodium can be used as a salt
material. As the sodium chloride, sodium chloride (NaCl) can be
used. As the bromide of potassium or sodium, potassium bromide
(KBr) or sodium bromide (NaBr) can be used. As the carbonate,
sodium carbonate (Na.sub.2CO.sub.2) and potassium carbonate
(K.sub.2CO.sub.3) can be used. As the sulfate, potassium sulfate
(K.sub.2SO.sub.4) can be used.
13th Embodiment
[0218] When potassium bromide or sodium bromide was used as a salt
material and aluminum borate whiskers were mixed in the salt
material, a bending strength as shown in FIG. 25 was obtained.
[0219] FIG. 25 is a graph showing the relationship between the
addition of aluminum borate whiskers in potassium bromide or sodium
bromide and the bending strength. FIG. 25 also describes the
bending strength obtained when aluminum borate whiskers are mixed
in a different salt material. As the different salt material,
potassium chloride and sodium chloride were employed. FIG. 25
describes a density .rho. of each salt material in a solid state. A
density .rho. of potassium bromide in the solid state is 2.75
g/cm.sup.3. A density .rho. of sodium bromide in a solid state is
3.21 g/cm.sup.3. A density .rho. of potassium chloride in a solid
state is 1.98 g/cm.sup.3. A density .rho. of sodium chloride in a
solid state is 2.17 g/cm.sup.3.
[0220] The bending strength shown in FIG. 25 is obtained by
conducting the experiment shown in the first embodiment by using
aluminum borate whiskers as a ceramic material. The lines in FIG.
25 are approximate curves drawn using the method of least squares.
When conducting this experiment, bending samples were formed with
the respective additions, as shown in Tables 24 to 27 below, and
their bending strengths were measured. Table 24 shows the bending
strength obtained when aluminum borate is mixed in potassium
bromide, and Table 25 shows the bending strength obtained when
aluminum borate is mixed in sodium bromide.
[0221] Table 26 shows the bending strength obtained when aluminum
borate is mixed in potassium chloride. Table 26 is obtained by
adding the results of two experiments, that is, a case wherein the
addition of aluminum borate whiskers is 0 and a case wherein the
addition of aluminum borate whiskers is 3 wt %, to Table 20. Table
27 shows the bending strength obtained when aluminum borate is
mixed in sodium chloride.
[0222] The type of aluminum borate whiskers employed in practicing
this embodiment is identical to that described in the ninth
embodiment (see FIG. 19 and Table 19). TABLE-US-00024 TABLE 24
Bending Composition Bending Strength Composition wt % Load N MPa
KBr 0 296.45 2.47 KBr + 3% Albolex M20 3 1735.25 14.46 KBr + 3%
Albolex M20 3 1197.82 9.98 KBr + 3% Albolex M20 3 1206.42 10.05 KBr
+ 3% Albolex M20 3 1291.00 10.76 KBr + 3% Albolex M20 3 1389.52
11.58 KBr + 5% Albolex M20 5 1845.25 15.38 KBr + 10% Albolex M20 10
2715.50 22.63 KBr + 12% Albolex M20 12 3304.75 27.54
[0223] TABLE-US-00025 TABLE 25 Bending Composition Bending Strength
Composition wt % Load N MPa NaBr 0 227.20 1.89 NaBr + 3% Albolex
M20 3 1210.75 10.09 NaBr + 3% Albolex M20 3 1424.50 11.87 NaBr + 3%
Albolex M20 3 1527.07 12.73 NaBr + 3% Albolex M20 3 2041.42 17.01
NaBr + 5% Albolex M20 5 2098.85 17.49 NaBr + 8% Albolex M20 8
2531.25 21.09 NaBr + 10% Albolex M20 10 2554.40 21.29
[0224] TABLE-US-00026 TABLE 26 Bending Composition Bending Strength
Composition wt % Load N MPa KCl 0 186.255 1.55 KCl 0 250.024 2.08
KCl 0 226.274 1.89 KCl 0 308.725 2.57 KCl 0 225.850 1.88 KCl 0
214.600 1.79 KCl 3 748.000 6.23 KCl + 10% Albolex M20 10 2485.75
20.71 KCl + 10% Albolex M20 10 2466.75 20.56 KCl + 10% Albolex M20
10 2488.75 20.74 KCl + 10% Albolex M20 10 2832.25 23.60 KCl + 10%
Albolex M20 10 2262.89 18.86 KCl + 10% Albolex M20 10 2758.00 22.98
KCl + 10% Albolex M20 10 2624.75 21.87 KCl + 10% Albolex M20 10
2155.35 17.96 KCl + 15% Albolex M20 15 4101.05 34.18 KCl + 15%
Albolex M20 15 3722.75 31.02 KCl + 15% Albolex M20 15 3763.50 31.36
KCl + 15% Albolex M20 15 3973.75 33.11 KCl + 15% Albolex M20 15
3305.72 27.55 KCl + 15% Albolex M20 15 3783.02 31.53 KCl + 15%
Albolex M20 15 3411.75 28.43 KCl + 18.7% Albolex M20 18.7 4346.25
36.22
[0225] TABLE-US-00027 TABLE 27 Bending Composition Bending Strength
Composition wt % Load N MPa NaCl 0 319 2.66 NaCl 0 253 2.11 NaCl 0
413 3.44 NaCl + 3% Albolex M20 3 285.825 2.38 NaCl + 3% Albolex M20
3 468.95 3.91 NaCl + 3% Albolex M20 3 429.924 3.58 NaCl + 5%
Albolex M20 5 434.424 3.62 NaCl + 10% Albolex M20 10
[0226] When aluminum borate whiskers were to be mixed in potassium
bromide or sodium bromide in this manner, the bending strength
became higher than 8 MPa if the addition was 3 wt % or more, as
shown in FIG. 25. In FIG. 25, when aluminum borate whiskers are
mixed in sodium chloride, a salt core with a high bending strength
can be formed.
[0227] Therefore, when potassium bromide or sodium bromide is used
as a ceramic material, as described above, the same effect as that
obtained when the first embodiment is employed can be obtained.
[0228] As described above, in addition to use of chloride, bromide,
or salt alone, as a salt material, a mixed salt of a potassium
chloride or sodium chloride and a carbonate or sulfate of potassium
or sodium can be used. For example, a mixed salt of potassium
chloride and sodium carbonate, a mixed salt of sodium chloride and
sodium carbonate, a mixed salt of sodium chloride and potassium
carbonate, or a mixed salt of potassium chloride and potassium
sulfate can be used.
[0229] When a mixed salt is employed as a salt material in this
manner, a salt core with a low melting point can be formed, as is
conventionally known. Therefore, the temperature required for
casting the salt core can be decreased. The power consumption of
the casting device can be decreased accordingly, and the cost for
manufacturing the salt core can be decreased. When any one of the
four types of mixed salts described above was used to form a salt
core, unevenness did not readily form on the surface of the cast
core.
INDUSTRIAL APPLICABILITY
[0230] A core for use in casting according to the present invention
is usefully employed in a mold for die-casting.
* * * * *