U.S. patent application number 13/119993 was filed with the patent office on 2011-08-04 for evaporating material and method of manufacturing the same.
This patent application is currently assigned to ULVAC, INC.. Invention is credited to Youichi Hirose, Kyoutoshi Miyagi, Hiroshi Nagata, Yoshinori Shingaki.
Application Number | 20110189498 13/119993 |
Document ID | / |
Family ID | 42100378 |
Filed Date | 2011-08-04 |
United States Patent
Application |
20110189498 |
Kind Code |
A1 |
Nagata; Hiroshi ; et
al. |
August 4, 2011 |
EVAPORATING MATERIAL AND METHOD OF MANUFACTURING THE SAME
Abstract
There is provided an evaporating material of thin plate shape
which can be manufactured at a reduced cost and at high
productivity, the evaporating material being adapted for use in
enhancing the coercive force of neodymium-iron-boron sintered
magnet by heat treatment while evaporating Dy in vacuum or in
reduced-pressure inert gas atmosphere. The evaporating material of
this invention has a core member la made of a fire-resistant metal
having a multiplicity of through holes, and is made by melting a
rare-earth metal or an alloy thereof so as to get adhered to, and
solidified on, the core member. In this case, the above-mentioned
adhesion is performed by dipping the core member into a molten bath
of the rare-earth metal or an alloy thereof, and pulling it out of
the molten bath.
Inventors: |
Nagata; Hiroshi; (Ibaraki,
JP) ; Shingaki; Yoshinori; (Ibaraki, JP) ;
Hirose; Youichi; (Ibaraki, JP) ; Miyagi;
Kyoutoshi; (Ibaraki, JP) |
Assignee: |
ULVAC, INC.
Chigasaki-shi, Kanagawa
JP
|
Family ID: |
42100378 |
Appl. No.: |
13/119993 |
Filed: |
October 6, 2009 |
PCT Filed: |
October 6, 2009 |
PCT NO: |
PCT/JP2009/005168 |
371 Date: |
April 18, 2011 |
Current U.S.
Class: |
428/596 ;
164/76.1 |
Current CPC
Class: |
C23C 2/04 20130101; H01F
41/0293 20130101; C21D 1/72 20130101; Y10T 428/12361 20150115; C21D
6/00 20130101; B22D 23/04 20130101 |
Class at
Publication: |
428/596 ;
164/76.1 |
International
Class: |
C25D 1/08 20060101
C25D001/08; B22D 23/04 20060101 B22D023/04; B22D 29/00 20060101
B22D029/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 8, 2008 |
JP |
2008-261772 |
Oct 22, 2008 |
JP |
2008-271904 |
Claims
1. An evaporating material comprising a core member made of a
fire-resistant metal and having a multiplicity of through holes,
the core member having a rare-earth metal or an alloy thereof that
is melted, adhered to, and solidified on, the core member.
2. The evaporating material according to claim 1, wherein the
rare-earth metal or the alloy thereof adhered to the core member is
formed by dipping the core member into a molten bath of the
rare-earth metal or of the alloy thereof, and by pulling up the
core member therefrom.
3. The evaporating material according to claim 1, wherein the
rare-earth metal is a member selected from the group consisting of
terbium, dysprosium, and holmium.
4. The evaporating material according to claim 1, wherein the
fire-resistant metal is a member selected from the group consisting
of niobium, molybdenum, tantalum, titan, vanadium, and
tungsten.
5. The evaporating material according to claim 1, wherein the core
member comprises one of a net member which is made by assembling a
plurality of wire materials into lattice shape, an expanded metal,
and a perforated metal.
6. The evaporating material according to claim 1, wherein the
evaporating material is heat-treated while evaporating the
evaporating material inclusive of dysprosium and terbium in vacuum
or in a reduced-pressure inert gas atmosphere, the evaporating
material being adapted for use in enhancing a coercive force of
neodymium-iron-boron sintered magnet or hot plastic working
magnet.
7. A method of manufacturing an evaporating material comprising the
steps of: forming a solidified body of a rare-earth metal or of an
alloy thereof by melting the rare-earth metal or the alloy thereof,
by dipping a base member made of a fire-resistant metal into a
molten bath of the rare-earth metal or of the alloy thereof in a
state of maintaining the base member at a temperature below the
melting temperature of the rare-earth metal or the alloy thereof,
and thereafter by pulling up the base member to thereby form on a
surface of the base member the solidified body; detaching the
solidified body off from the base member; and working the
solidified body thus detached into a plate shape.
8. The method of manufacturing the evaporating material according
to claim 7, wherein the base member is columnar shape or prismatic
shape.
9. The method of manufacturing the evaporating material according
to claim 7, further comprising increasing or decreasing the time of
dipping the base member into the molten bath, thereby controlling a
thickness of the solidified body.
10. The method of manufacturing the evaporating material according
to claim 7, further comprising changing the temperature of the base
member when dipping the base member into the molten bath, thereby
controlling the thickness of the solidified body.
11. The method of manufacturing the evaporating material according
to claim 7, wherein the rare-earth metal is a member selected from
the group consisting of terbium, dysprosium, and holmium.
12. The method of manufacturing the evaporating material according
to claim 7, wherein the fire-resistant metal is a member selected
from the group consisting of niobium, molybdenum, tantalum, titan,
vanadium, and tungsten.
Description
TECHNICAL FIELD
[0001] The present invention relates to an evaporating material and
a method of manufacturing the evaporating material. Particularly,
it relates to an evaporating material and the method of
manufacturing the evaporating material which is adapted for use in
manufacturing high-performance magnets to improve the coercive
force of neodymium-iron-boron sintered magnet or hot plastic
working magnet by carrying out heat treatment while evaporating
dysprosium or terbium in vacuum or in a reduced-pressure inert gas
atmosphere.
BACKGROUND ART
[0002] Conventionally, in order to obtain a high-performance magnet
having a dramatically enhanced coercive force, the following art
has been proposed (e.g., in Patent Document 1) by the applicant of
this patent application. The art in question discloses: to contain
in a processing box neodymium-iron-boron sintered magnets and
evaporating materials containing at least one of dysprosium (Dy)
and terbium (Tb) at a distance from each other; to heat the
processing box in a vacuum atmosphere to thereby evaporate the
evaporating materials; to adjust the amount of supply of the
evaporated metal atoms to the surfaces of the sintered magnets so
that the metal atoms get adhered; and to perform the processing
treatment to diffuse the adhered metal atoms into the grain
boundaries and/or grain boundary phases of the sintered magnets so
that a thin film made up of the metal evaporating material is not
formed on the respective surfaces of the sintered magnets (vacuum
vapor processing).
[0003] In the art of the above-mentioned Patent Document 1, as the
evaporating materials, small particles, for example, were used so
that they can be disposed around the sintered magnets that have
been disposed inside the processing box. When the evaporating
materials of this kind are used, the volumetric occupancy becomes
large and, as a result, the amount of charging of magnets into the
processing box cannot be increased. There was therefore a
disadvantage in that the cost becomes higher for the
above-mentioned processing treatment. In addition, there is another
disadvantage in that the work of manually disposing small particles
of evaporating materials into the processing box together with the
sintered magnets is troublesome.
[0004] As a solution, the applicant of the present patent
application has proposed to contain, inside the processing box,
plate-shaped evaporating materials and sintered magnets by
vertically stacking them while interposing spacers thereby
preventing them from coming into contact with one another and
thereby allowing for the metal atoms to pass therethrough (see
Japanese Patent Application No. 2008-41555).
[0005] As a method of manufacturing a thin plate of Dy or Tb, it is
considered to melt the ingots of Dy or Tb and cast them into slabs,
e.g., in an inert gas atmosphere, and then subject them to rolling
work. However, since Dy and Tb have high melting points and are
extremely active, they react with the furnace materials or casting
molds. It is therefore difficult to melt and cast them into slabs
without inclusion of impurities therein. Even conceding that the
melting and casting into slabs were possible, they have hexagonal
lattice structure and thus are poor in workability. In addition, in
order to roll them into thin plates, it becomes necessary to
subject them to heat treatments in an inert gas for several times
for annealing during the processing treatments. There was therefore
a problem in that the manufacturing costs of the plate-like
evaporating materials rapidly rise.
[Prior Art Document]
[Patent Document]
[0006] Patent Document 1: WO 2008/023731
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0007] In view of the above points, this invention has a first
problem of providing a plate-shaped evaporating material which can
be manufactured at low cost. It is a second problem to provide a
method of manufacturing an evaporating material which is capable of
manufacturing a plate-shaped evaporating material at a high
productivity and at a low cost.
Means for Solving the Problems
[0008] In order to solve the above-mentioned first problem, the
evaporating material according to this invention comprises a core
member made of a fire-resistant metal and having a multiplicity of
through holes. The core member has a rare-earth metal or an alloy
thereof that is melted, adhered to, and solidified on, the core
member.
[0009] According to this invention, the rare-earth metal or the
alloy thereof is melted, and the core member is dipped into the
molten bath of the rare-earth metal or of the alloy thereof, and
the core member is then pulled up or lifted. Alternatively, the
core member is sprayed with the molten rare-earth metal or the
molten alloy thereof (thermal spraying). At this time, since the
core member has the multiplicity of through holes, the molten
rare-earth metal or the molten alloy thereof gets adhered to the
surface of the core member through surface tension of the through
holes. By cooling the core member in this state down to the
temperature below the melting point of the rare-earth metal or the
alloy thereof, the molten rare-earth metal or the molten alloy
thereof gets solidified. There can thus be obtained an evaporating
material of plate shape, cylindrical shape, or the like in which
each of the through holes are occupied and also in which the
surface of the core member is coated with the rare-earth metal or
the rare-earth metal.
[0010] According to this invention, as described above, it is not
necessary to subject the rare-earth metal or the alloy thereof to
melting and casting into slabs. In addition, by making the core
member itself into the plate shape, there can be easily obtained an
evaporating material in a plate shape. In this manner, without
requiring particular cutting work, rolling work, or the like, it is
possible to eliminate the raw material losses due to the
occurrence, as a result of cutting work or the like, of portions
that cannot be utilized as the evaporating material. As combined
effects of the above, the evaporating material can be manufactured
at an extremely low cost.
[0011] In this invention, preferably the rare-earth metal or the
alloy thereof adhered to the core member is formed by dipping the
core member into a molten bath of the rare-earth metal or of the
alloy thereof, and by pulling up the core member therefrom.
According to this arrangement, as compared with the case in which
the rare-earth metal or the alloy thereof is caused to get adhered
by thermal spraying, the adhesion of the rare-earth metal or the
alloy thereof to the core member can be made easily. In addition,
since there will be no waste in the raw material, the productivity
can be further enhanced and further reduction in cost can be
attained.
[0012] In this invention, preferably the rare-earth metal is a
member selected from the group consisting of terbium, dysprosium,
and holmium.
[0013] Preferably, the fire-resistant metal is a member selected
from the group consisting of niobium, molybdenum, tantalum, titan,
vanadium, and tungsten.
[0014] Further, the core member preferably comprises one of a net
member which is made by assembling a plurality of wire materials
into lattice shape, an expanded metal, and a perforated metal.
[0015] The evaporating material according to the above-mentioned
arrangement is heat-treated while evaporating (sublimating) the
evaporating material inclusive of dysprosium and terbium in vacuum
or in a reduced-pressure inert gas atmosphere, the evaporating
material being adapted for use in enhancing a coercive force of
neodymium-iron-boron sintered magnet or hot plastic working
magnet.
[0016] In order to solve the above-mentioned second problem, the
method of manufacturing an evaporating material according to this
invention comprises the steps of forming a solidified body of a
rare-earth metal or of an alloy thereof by melting the rare-earth
metal or the alloy thereof, dipping a base member made of a
fire-resistant metal into a molten bath of the rare-earth metal or
of the alloy thereof in a state of maintaining the base member at a
temperature below the melting temperature of the rare-earth metal
or the alloy thereof, and thereafter pulling up the base member to
thereby form on a surface of the base member the solidified body;
detaching the solidified body off from the base member; and working
the solidified body thus detached into a plate shape.
[0017] According to this invention, the rare-earth metal or the
alloy thereof is melted, and the base member which is below the
melting temperature, e.g., at room temperature, and in a
predetermined shape is dipped into this molten bath. At this time,
if the base member having a large thermal capacity per unit volume
is dipped, the molten bath is rapidly cooled by the base member. As
a result, there will be formed on the surface of the base member a
film made of the rare-earth metal or the alloy thereof. By pulling
out the base member out of the molten bath, the film is immediately
cooled to a temperature below the melting point and is solidified.
There will thus be formed on the surface of the base member a
solidified body made of the rare-earth metal or the alloy thereof
having a predetermined thickness. Since the molten bath metal does
not react with the base member, the solidified body can be easily
peeled off from the base member only by adding vibrations or
shocks. Finally, the solidified body that has been detached is cut
off by cutting work into a plate shape or is formed into a plate
shape, after cutting work, by rolling or pressing work, thereby
obtaining an evaporating material in plate shape. In this
invention, in order to enable to adhere the molten bath to the base
member, the thermal capacity of the base member per unit volume is
required to be about at least 2 MJ/km.sup.3.
[0018] As described, according to this invention, it is not
necessary to subject the rare-earth metal or the alloy thereof to
casting by melting into slab shape. In addition, by performing
cutting work, rolling work or the like to the material that has
been detached off from the base member, there can be obtained an
evaporating material of plate shape with smaller number of steps.
Therefore, the evaporating material in plate shape can be
manufactured at a lower cost and with good productivity.
[0019] When the material that has been detached off from the base
member is subjected to cutting work or the like in plate shape, the
base member is preferably of columnar shape or of prismatic shape
in order to facilitate the working and also in order to eliminate
the loss in raw material.
[0020] Preferably, the time of dipping the base member into the
molten bath is increased or decreased, to thereby control the
thickness of the solidified body.
[0021] On the other hand, there may be employed an arrangement in
which the temperature of the base member is changed at the time of
dipping the base member into the molten bath, thereby controlling
the thickness of the solidified body.
[0022] According to this invention, preferably the rare-earth metal
is a member selected from the group consisting of terbium,
dysprosium, and holmium.
[0023] In addition, preferably the fire-resistant metal is a member
selected from the group consisting of niobium, molybdenum,
tantalum, titan, vanadium, and tungsten.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIGS. 1(a) and 1(b) are plan view and sectional view,
respectively, schematically showing an evaporating material
according to a first embodiment of this invention.
[0025] FIG. 2 is a schematic view showing a dipping apparatus used
in the manufacturing of the evaporating material according to the
above-mentioned first embodiment of this invention.
[0026] FIGS. 3(a) to 3(f) are views showing the manufacturing steps
of the evaporating material according to a second embodiment of
this invention.
[0027] FIG. 4 is a schematic view showing a dipping apparatus used
in the manufacturing of the evaporating material according to a
modified example of the above-mentioned second embodiment.
[0028] FIG. 5 is a view schematically showing a vacuum evaporating
processing apparatus in which the evaporating material of this
invention is used.
[0029] FIG. 6 is a view showing how the evaporating materials and
sintered magnets are housed into a processing box.
[0030] FIG. 7 is a table showing a volumetric ratio and weight of
the evaporating material manufactured according to example 1.
[0031] FIGS. 8(a) and 8(b) are photographs of external appearance
of the evaporating material manufactured according to Example
1.
[0032] FIG. 9 is a table showing whether the evaporating material
manufactured according to Example 2 is acceptable or not.
[0033] FIG. 10 is a table showing specific heat, specific weight,
and thermal capacity per unit weight of each of the materials of
base member used in Example 3.
EMBODIMENTS FOR CARRYING OUT THE INVENTION
[0034] A description will now be made of an evaporating material 1,
10 as well as of a method of manufacturing the evaporating material
1, 10 according to an embodiment of this invention, in which the
evaporating material is used in the manufacturing of a
high-performance magnet which enhances the coercive force of
neodymium-iron-boron sintered magnet or hot plastic working magnet
by heat-treating the magnet while evaporating Dy in vacuum or in a
reduced-pressure inert gas atmosphere.
[0035] With reference to FIG. 1, the evaporating material 1
according to a first embodiment is made: by melting a rare-earth
metal or an alloy thereof; by causing the molten metal of the
rare-earth metal or the alloy thereof to get adhered to a core
member 1a made of a fire-resistant material having a multiplicity
of through holes; and by solidifying the molten metal. As the core
member 1a, there is used a net member which is formed by assembling
wires W made of fire-resistant metal such as niobium, molybdenum,
tantalum, titan, vanadium, tungsten, or the like into a lattice
shape for further forming it into a plate shape. In this case, as
the wires W to constitute the net member 1a, the diameter shall
preferably be 0.1 to 1.2 mm, the apertures of the wire meshes 1b as
the through holes shall preferably be 8 to 50 meshes, more
preferably 10 to 30 meshes. The apertures larger than 50 meshes are
not suitable for mass productivity due to lack of strength as the
core member 1a. On the other hand, the apertures smaller than 8
meshes have a disadvantage in that, even if the core member 1a
dipped into the molten bath of the rare-earth metal is pulled up
out of the molten bath, the rare-earth metal can hardly be adhered
to the entire region of the core member 1a in a manner to fill the
meshes.
[0036] On the other hand, as the rare-earth metal or the alloy
thereof, aside from Dy, there can be used Tb or an alloy of Dy or
Tb with Nd, Pr, Al, Cu, Ga, or the like in order to further enhance
the coercive force. In the first embodiment, a description is made
of an example in which Dy is exemplified because the rare earth to
be used is for the purpose of manufacturing a high-performance
magnet. This invention is, however, not to be limited thereto, but
may also be applied to a case in manufacturing an evaporating
material made of other rare-earth metals such as holmium or the
like or the alloy thereof.
[0037] FIG. 2 shows a dipping apparatus M1 which is used in
manufacturing the evaporating material 1 according to the first
embodiment. The dipping apparatus M1 has a melting furnace 2 which
defines a dipping chamber 2a, and a vacuum chamber 4 which defines
a preparation chamber 4a connected through a gate valve 3 to an
upper side of the melting furnace 2.
[0038] At the bottom of the melting furnace 2, there is disposed a
crucible 5 for containing therein ingots of Dy. The crucible 5 is
made up of a fire-resistant metal such as molybdenum, tungsten,
vanadium, yttria, tantalum, or the like which does not react with
Dy. In addition, inside the melting furnace 2, there is provided a
heating means 6 for heating and melting Dy. The heating means 6 has
no particular limitation and anything may be used that can heat the
Dy inside the crucible 5 above the melting point (1407.degree. C.)
so that Dy inside the crucible 5 can be melted and can keep the
melted Dy in a state of molten bath. The heating means may thus be
of a known tungsten heater or a carbon heater. Otherwise, the
heating means may be constituted by a furnace of a high frequency
induction type or of an arc melting type. A side wall of the
melting furnace 2 has connected thereto a gas introduction pipe 7a
so that an inert gas such as argon, helium or the like can be
introduced into the dipping chamber 2a at a predetermined flow
amount. In addition, the melting furnace 2 has connected thereto a
vacuum pump P for reducing the pressure inside the dipping chamber
2a. The connection is made through an exhaust pipe P1 provided with
an on-off valve PV1 so that the dipping chamber can be evacuated to
a predetermined vacuum pressure and be held at that pressure.
[0039] On the other hand, the vacuum chamber 4 is also arranged to
be reduced in pressure inside the preparation chamber 4a. In this
case, the exhaust pipe P2 from the vacuum chamber is connected to
the exhaust pipe P1 on the side of the vacuum pump P of the on-off
valve PV1. It is thus so arranged that, by controlling the opening
and closing of another on-off valve PV2 which is interposed in the
exhaust pipe P2, the vacuum chamber can be evacuated by the same
vacuum pump P. In addition, the vacuum chamber 4 has connected to
the side wall thereof a gas introduction pipe 7b so that an inert
gas such as argon gas, helium gas or the like can be introduced
into the preparation chamber 4a at a predetermined flow amount.
[0040] One side wall of the vacuum chamber 4 is provided with an
open-close door 4b for use in bringing in, and taking out, the core
member 1a. On an inner surface of the upper wall, there is hung an
electronic type of hoist 8 so as to be positioned above the
crucible 5 in the dipping chamber 2a. The hoist 8 is provided with
a hoisting mechanism made up of: a drum 8b with a motor 8a and a
wire 8c wound around the drum 8b; and a hook block 8d mounted at
the front end of the wire 8c. It is so arranged that the core
member 1a can be moved between a mounting-dismounting position in
which the core member 1a is mounted on, or dismounted from, the
hook block 8d by the hoist 8 inside the preparation chamber 4a; and
a dipping position in which the core member 1a mounted on the hook
block 8d can be dipped in its entirety into the molten bath inside
the crucible 5 in the dipping chamber 2a.
[0041] Here, it is preferable that the hook block 8d is made of a
fire-resistant material such as molybdenum, tantalum or the like
which does not react with the molten Dy. Further, in place of the
hook block 8d, there may be disposed a holder of fire-resistant
make (not illustrated) for holding a plurality of core members 1a
arranged at a predetermined distance from one another so that a
plurality of core members 1a may be dipped into the molten bath of
Dy at the same time.
[0042] Next, a description will be made of the manufacturing of the
evaporating material 1 according to the first embodiment by using
the dipping apparatus M1 as shown in FIG. 2. First, ingots of Dy
are set in position in the crucible 5 in the dipping chamber 2a.
After having isolated the dipping chamber 2a by closing the gate
valve 3, the vacuum pump P is operated and also the on-off valve
PV1 is opened so as to start the evacuation of the dipping chamber
2a. Then, while maintaining the dipping chamber 2a at a
predetermined pressure (e.g., 1 Pa), Dy is heated. When the
temperature of Dy has reached a temperature at which Dy starts
sublimation (about 800.degree. C.), Ar gas is introduced through
the gas introduction pipe 7a into the dipping chamber 2a.
[0043] The reason why Ar gas is introduced is to prevent the Dy
from getting splashed as a result of sublimation. A loss of Dy is
thus prevented. Ar gas is introduced in such a manner that the
pressure inside the dipping chamber 2a becomes 15 to 200 kPa,
preferably 50 to 100 kPa. In this state the heating is continued.
Once the melting point has reached, Dy gets melted, and the
operation of the heating means 6 is controlled to maintain the
molten bath temperature (e.g., 1440.degree. C.) at a constant
temperature above the melting point.
[0044] In the preparation chamber 4a, on the other hand, the on-off
valve PV2 is opened in a state in which the open-close door 4b is
kept closed. The preparation chamber is thus once lowered by the
vacuum pump P down to a predetermined vacuum pressure (e.g., 1 Pa)
to thereby degas the preparation chamber 4a. At this time, the hook
block 8d is in the mounting-dismounting position. Once a
predetermined period of time has lapsed after the starting of the
evacuation, the on-off valve PV2 is closed and also Ar gas is
introduced until the preparation chamber 4a becomes an atmospheric
pressure so as to return the preparation chamber 4a back to the
atmospheric pressure. In this state, the open-close door 4b is
opened to bring in the core member 1a and set the core member to be
suspended by the hook block 8d. After closing the open-close door
4b, the on-off valve PV2 is opened once again to thereby evacuate
the preparation chamber 4a by the vacuum pump P. According to this
arrangement, the preparation for dipping the core member 1a is
finished.
[0045] Then, in a state in which the molten bath temperature is
maintained at the predetermined temperature, Ar gas is kept
introduced through the gas introduction pipe 7b into the
preparation chamber 4a until the preparation chamber reaches the
same pressure as that in the dipping chamber 2a. Once the dipping
chamber 2a and the preparation chamber 4a have attained the same
pressure, the gate valve 3 is opened. In this state, the motor 8a
of the hoisting means is rotated in the normal direction of
rotation so that the core member 1a is lowered from the preparation
chamber 4a toward the dipping chamber 2a through the hook block 8d.
When the core member 1a is lowered, the core member is sequentially
dipped into the molten bath of Dy and reaches the dipping
position.
[0046] When the core member has reached the dipping position, the
motor 8a of the hoisting means is rotated in the opposite direction
of rotation so as to sequentially pull the core member 1a out of
the molten bath through the hook block 8d. Here, since the core
member 1a is made up of wires W, when the core member 1a gets
dipped into the molten bath, the molten bath of Dy gets penetrated
into the wire meshes 1b of the core member 1a since the core member
1a has good wettability with the molten bath of Dy. Since the
thermal capacity per unit area of the core member 1a is small in
this state, the molten bath around the core member 1a is in a
liquid state. When the core member 1a is sequentially pulled up out
of the molten bath, the portion pulled up out of the molten bath
becomes a state in which the Dy gets adhered so as to fill each of
the meshes 1b due to its surface tension and so as to cover the
surface of the core member 1a. Immediately after being pulled up
out of the molten bath, the Dy is cooled to a temperature below the
melting point and gets solidified. When the core member 1a has been
completely pulled up out of the molten bath, there can be obtained
an evaporating material 1 of plate shape. The speed of pulling up
the core member out of the molten bath may appropriately be
determined considering the point: that Dy can be solidified in each
of the wire meshes 1b; and that the amount of adhesion of Dy
becomes as uniform and as large as possible; or the like.
[0047] Then, when the hook block 8d reaches the mounting position,
the gate valve 3 is closed. In this state, Ar gas (e.g., of 100
kPa) is further introduced into the preparation chamber 4a and the
evaporating material is cooled for a predetermined period of time.
After having cooled, Ar gas is further introduced into the
preparation chamber 4a to bring it back to atmospheric pressure.
The open-close door 4b is opened to thereby bring out the
evaporating material 1.
[0048] In this manner, in the first embodiment, it is not necessary
to subject Dy to melting and casting into slabs. Further, a
plate-shaped evaporating material made of Dy can be manufactured
only by making the core member 1a itself into plate shape.
Therefore, since no particular cutting work or rolling work is
required, it is possible to avoid the loss in raw material that may
happen as wastes by cutting work or the like. As a combined effect
thereof, it is possible to obtain the evaporating material 1 at an
extremely low cost.
[0049] Here, as described hereinafter, in case the evaporating
material 1 of the first embodiment is used in manufacturing a
high-performance magnet, with the progress of consumption of the Dy
adhered to the core member 1a, holes come to be formed in the
meshes 1b of the core member 1a. As a result, the conditions of
consumption of the evaporating material 1 can be visually
recognized, which is advantageous in judging when the evaporating
material 1 shall be replaced, or the like.
[0050] Further, when the evaporating material 1 has been consumed
as described above, this consumed evaporating material 1 can be
used again without any preliminary treatment. In other words, by
dipping the consumed evaporating material 1 into the molten bath of
Dy, and by pulling it up, the evaporating material 1 can be
regenerated. As a result, the Dy that remains adhered to the used
evaporating material 1 can be reused as it is without throwing it
away as a scrap. Expensive rare-earth atoms which are scarce as raw
materials such as Dy, Tb or the like can be effectively utilized in
an extremely effective manner.
[0051] In the above-mentioned first embodiment, a description has
been made of an example in which a core member 1a was formed into a
plate shape. However, without being limited to this example, a
cylindrical evaporating material may be manufactured by using a
wire net material formed into a cylindrical shape so as to be used
as an evaporating material for use in manufacturing a ring-shaped
sintered magnet or a hot plastic working magnet. In addition, the
core member 1a having formed a multiplicity of through holes of a
predetermined diameter may serve the purpose. In place of the wire
net material, an expanded metal or a perforated metal may be used
as well.
[0052] In the above-mentioned first embodiment, a description has
been made of an example in which the adhesion of Dy was performed
by dipping the core member 1a into a molten bath of ingots of Dy,
and by pulling the core member out of the molten bath. Instead, Dy
may get adhered to the core member 1a by spraying. Further, in the
above-mentioned first embodiment, a description has been made of an
example in which the core member 1a was manufactured by one time of
dipping operation. Instead, it may be so arranged that the dipping
is performed in plural times of operations by changing the
direction of dipping.
[0053] A description will now be made of a second embodiment of the
evaporating material 10 with reference to FIG. 3. The evaporating
material 10 is manufactured by the following steps, i.e.: a step in
which Dy is melted, and a base member 10a is dipped into the molten
bath of Dy in a state in which the base member 10a is maintained at
a temperature below the melting temperature of Dy, and the base
member is then pulled up or lifted out of the molten bath to
thereby form a solidified body 10b made of Dy on the surface of the
base member 10a (solidified body forming step); a step in which the
solidified body 10b is released or detached off from the base
member 10a (detaching step); and a step in which the detached
solidified body 10b is worked into a plate shape (working
step).
[0054] As the base member 10a, out of consideration that the
solidified body 10b is worked into a plate shape after having
formed the solidified body 10b, there is used a solid prismatic
shape or columnar shape, each being made of a fire-resistant metal
such as niobium, molybdenum, tantalum, titan, vanadium, tungsten or
the like. As the base member 10a, there is used one having a
thermal capacity of about 2.5 MJ/km.sup.3. If the thermal capacity
is below 2 MJ/km.sup.3, as described hereinafter, when the base
member is dipped into the molten bath of Dy, the base member 10a
itself will rapidly rise in temperature so that the Dy film formed
on the surface thereof will be melted once again and, as a result,
the solidified body 10b cannot be formed efficiently.
[0055] On the other hand, as the rare-earth metal or the alloy
thereof, aside from Dy, there may be used Tb or an alloy made by
compounding into Dy or Tb a metal which further enhances the
coercive force, such as Nd, Pr, Al, Cu, Ga or the like. Since this
second embodiment is also described with reference to the
evaporating material adapted for use in manufacturing a
high-performance magnet, Dy is used as an example. However, without
being limited thereto, this invention can be applied to the
manufacturing of other evaporating materials made of other
rare-earth metals such as holmium or the like, or of an alloy
thereof.
[0056] In the step of forming the solidified body, a dipping
apparatus M2 as shown in FIG. 4 may be used. The dipping apparatus
M2 has substantially the same construction as the one employed for
the dipping apparatus M1 (see FIG. 2) used in the above-mentioned
first embodiment. However, at the front end of a wire 81 of a hoist
80, there is provided, in place of the hook block 8d, a clamp 82
for holding one longitudinal end portion of the base member 10a. It
is thus so arranged that, by means of the hoist 80, the base member
10a can be moved between: a mounting-dismounting position in which
the mounting or dismounting of the base member 10a to and from the
clamp 82 is performed inside the preparation chamber 4a; and a
dipping position in which the base member 10a held by the clamp 82
is dipped into the molten bath in the crucible 5 inside the dipping
chamber 2a except for the portion that is being held by the clamp
82. In FIG. 4, the same reference numerals are assigned to the same
parts as in the dipping apparatus M1.
[0057] Preferably, the clamp 82 is formed, in a similar manner as
in the above-mentioned embodiment 1, of a fire-resistant metal such
as molybdenum, tantalum or the like which does not react with the
melted Dy. It may also be so arranged that a plurality of clamps 82
are disposed in line at a front end of the wire 8c through a jig
(not illustrated) so as to be able to dip a plurality of base
members 1a into the molten bath of Dy at the same time.
[0058] A description will now be made of a case in which, by using
the dipping apparatus M2 as shown in FIG. 4, a solidified body 10b
is formed on the surface of the base member 10a of prismatic shape,
and then the solidified body 10b is worked to thereby obtain a
plate-shaped evaporating material 10.
[0059] First, ingots of Dy are set in position in the crucible 5
inside the dipping chamber 2a. After having isolated the dipping
chamber 2a by closing the gate valve 3, the vacuum pump P is
operated and also the on-off valve PV1 is opened to start
evacuation. At the same time, the heating means 6 is operated to
start the heating. Then, heating is performed while maintaining the
dipping chamber 2a to a predetermined pressure (e.g., 1 Pa). When
the temperature of Dy has reached a temperature at which Dy starts
sublimation (about 800.degree. C.), Ar gas is introduced into the
dipping chamber 2a through the gas introduction pipe 7a.
[0060] Here, the purpose of introducing Ar gas is to keep the
evaporation of Dy under control. Ar gas is introduced so that the
pressure in the dipping chamber 2a becomes 15 to 105 kPa,
preferably 80 kPa. Heating is continued in this state and, when the
melting point has reached, Dy gets melted. The operation of the
heating means 6 is then controlled to maintain the molten bath
temperature (e.g., 1440.degree. C.) at a constant temperature which
is higher than the melting point.
[0061] On the other hand, in the preparation chamber 4a, the on-off
valve PV2 is opened in a closed state of the open-close door 4b to
thereby once reduce the pressure by the vacuum pump P to a
predetermined vacuum pressure (e.g., 1 Pa) to thereby degas the
preparation chamber 4a. At this time, the preparation chamber 4a is
at room temperature, and the clamp 82 of the hoist 80 is in the
mounting-dismounting position. When a predetermined period of time
has lapsed after starting the evacuation, the on-off valve PV2 is
closed and Ar gas is introduced until the preparation chamber 4a
becomes atmospheric pressure so as to return the preparation
chamber 4a back to the atmospheric pressure. In this state, the
open-close door 4b is opened to bring the base member 10a of room
temperature into the preparation chamber (see FIG. 3(a)). One
longitudinal end portion of the base member 10a is caused to be
held by the clamp 82 to thereby set the base member in position.
Then, after having closed the open-close door 4b, the on-off valve
PV2 is opened once again to thereby evacuate the preparation
chamber 4a by the vacuum pump P. According to this arrangement, the
preparation for dipping of the base member 10a is finished.
[0062] Then, in a state in which the molten bath temperature is
maintained at a predetermined temperature, Ar gas is introduced
into the preparation chamber 4a through the gas pipe 7b until the
preparation chamber 4a attains a pressure that is the same as the
dipping chamber 2a. Then, when the dipping chamber 2a and the
preparation chamber 4a have reached the same pressure, the gate
valve 3 is opened and, in this state, the motor 8a of the hoisting
means is rotated in the normal direction of rotation. The base
member 10a is thus lowered through the clamp 82 from the
preparation chamber 4a to the dipping chamber 2a. With the lowering
of the base member 10a, it sequentially gets dipped into the molten
bath of Dy, finally reaching the dipping position. The base member
is then held at the dipping position for a predetermined period of
time. In this case, the holding time is appropriately set depending
on the thermal capacity of the base member 10a and the thickness to
be obtained of the solidified body 10b. It is to be noted, however,
that dipping beyond the predetermined period of time will result in
melting again of the film once formed on the surface of the base
member 10a. The holding time shall therefore be set taking the
above circumstances into consideration.
[0063] When a predetermined period of time has lapsed in the
above-mentioned state, the motor 8a of the hoisting means is
rotated in the opposite direction of rotation to thereby
sequentially pull the base member 10a upward out of the molten
bath. Here, by dipping the base member 10a of about 2.5 MJ/km.sup.3
in thermal capacity per unit volume into the molten bath, the
molten bath will be rapidly cooled by the base member 10a when the
base member 10a is dipped into the molten bath, and gets adhered to
the surface of the base member 10a. As a result, a film made of Dy
is formed in a predetermined film thickness. By pulling up the base
member 10a out of the molten bath in this state, the film will
immediately be cooled down to a temperature below the melting point
and gets solidified. As a result, a solidified body 10b will be
formed on the surface of the base member 10a (see FIG. 3(b)). The
speed of pulling up the base member 10a is appropriately set
considering the time of dipping the jig into the molten bath.
[0064] When the clamp 82 has reached the mounting position, the
gate valve 3 is closed. In this state, Ar gas is introduced into
the preparation chamber 4a (e.g., 100 Pa), and the solidified body
is cooled for a predetermined period of time. After cooling, Ar gas
is further introduced into the preparation chamber 4a to bring the
preparation chamber 4a back to atmospheric pressure. The open-close
valve 4b is opened, and the base member 10a having formed the
solidified body 10b on the surface is taken out of the preparation
chamber.
[0065] Then, the solidified body 10b is released off from the base
member 10a. In this case, out of the base member 10a, that portion
which was held by the clamp 82 is kept free from formation of the
solidified body 10b. Therefore, in a state in which the solidified
body 10b is fixed in position, the above-mentioned portion of the
base member 10a is given a pulling force while subjecting it to
appropriate vibrations. The base member 10b can thus be pulled out.
On the other hand, as shown in FIG. 3(c), by cutting the solidified
body 10c on the longitudinally opposite side of the base member 10a
along a break line shown in chain line in the figure, by means of
cutting work or the like, the longitudinal side surface of the base
member 10a is exposed. Then as shown in FIG. 3(d), the base member
10a may be subjected to shocks, pushing forces or the like so that
the solidified body 10b pushes out the base member 10a. In this
manner, since the base member 10a and the metal of the molten bath
do not react with each other, the solidified body 10b can be easily
released off from the base member 10a only by giving vibrations,
shocks, or the like.
[0066] Finally, as shown, e.g., in FIG. 3(e), if the solidified
body 10b is cut along a break line shown in chain line in the
figure by means of cutting work or the like, there can be obtained
a plate-shaped evaporating material (see FIG. 3(f)). In this
manner, in the second embodiment, it is not necessary to melt and
cast Dy into slabs. In addition, since what has been released off
from the base member 10a is subjected only to cutting work, the
plate-shaped evaporating material 10 can be obtained at a low cost
and with good productivity.
[0067] Further, the evaporating material 10 manufactured as
mentioned above may be put to use by further subjecting it to
rolling work. It is to be noted here that, if the slabs are
manufactured and rolled into thin plates as in the conventional
art, the workability is poor due to the crystal structure of
hexagonal lattice that is present therein. In order to roll the
slabs into thin plates, it is necessary to subject them, in the
course of the processing treatments, to heat treatment for
annealing, thereby giving rise to the problem of jumping in
manufacturing cost. The product manufactured according to this
invention, on the other hand, is a thin plate of several mm in
thickness and has fine structure due to rapid cooling. Therefore,
it is rich in rolling characteristics so as to be capable of
rolling down to below 1 mm without the need for annealing.
[0068] In the above-mentioned second embodiment, a description has
been made of an example of prismatic shape as the base member 10a.
However, without being limited thereto, a columnar shape may also
be employed. In this case, a ring-shaped solidified body in cross
section which is detached from the base member 10a is cut along the
longitudinal direction so as to become semicircular in cross
section. What is thus obtained may then be subjected to rolling or
press working, thereby obtaining a plate-shaped evaporating
material.
[0069] Further, in the above-mentioned second embodiment, a
description has been made of an example in which the thickness of
the solidified body 10b is varied by changing the time of dipping
in the dipping position. Without being limited thereto, the
temperature of the base member 10a at the time of dipping into the
molten bath may be changed to thereby control the thickness of the
solidified body 10b. In this case, a known cooling means may be
disposed inside the vacuum chamber 4 to thereby control the
temperature of the base member 10a.
[0070] Still furthermore, in the above-mentioned second embodiment,
a description has been made of an example in which the base member
10a was dipped into the molten bath of melted ingots of Dy. Without
being limited thereto, e.g., Dy is evaporated inside the processing
chamber to thereby form a vapor atmosphere of Dy, and the base
member 10a of, e.g., normal temperature is brought into the vapor
atmosphere of Dy. Due to the difference in temperature between the
two, Dy may be caused to be adhered and deposited on the base
member. In this manner, the solidified body according to a modified
example can be formed by cooling. This kind of processing apparatus
was made the subject of an International Patent Application by the
applicant of this patent application and is described in
internationally laid-open No. WO2006/100968. Therefore, the details
thereof are omitted here.
[0071] Now, a description will be made of the manufacturing of
high-performance magnet in which was used the plate-shaped
evaporating material 1 or 10 manufactured according to the
above-mentioned first and the second embodiments. The
high-performance magnet was manufactured by performing a series of
processing treatments (vacuum vapor processing) at the same time,
i.e., the evaporating material 1 (10); was caused to be evaporated
and the evaporated Dy atoms were caused to get adhered to the
surface of known neodymium-iron-boron sintered magnet S that was
formed into a predetermined shape; and was diffused into the grain
boundaries and/or grain boundary phases of the sintered magnet S so
as to be spread uniformly. A description will hereinafter be made,
with reference to FIG. 5, of a vacuum vapor processing apparatus to
perform this kind of vacuum vapor processing.
[0072] As shown in FIG. 5, the vacuum vapor processing apparatus M3
has a vacuum chamber 12 which can be reduced in pressure down to a
predetermined pressure (e.g., 1.times.10.sup.-5 Pa) and can be
maintained thereat through an evacuating means 11 such as a turbo
molecular pump, a cryo-pump, a diffusion pump or the like. Inside
the vacuum chamber 12 there are provided an insulating material 13
which encloses the circumference of a processing box 20 (to be
described hereinafter), and a heat generating body 14 which is
disposed on the inside thereof. The insulating material 13 is made,
e.g., of Mo, and the heat generating body 14 is an electric heater
having a filament of Mo make (not illustrated). The filament is
energized by a power source (not illustrated) of an electrical
resistance heating system, and is enclosed by the insulating
material 13 and can heat the space 15 in which the processing box
20 is disposed. In this space 15 there is disposed a mounting table
16, e.g., of Mo make so that at least one processing box 20 can be
mounted thereon.
[0073] The processing box 20 is made up of a box portion 21 of
rectangular parallelepiped with an upper surface left open, and a
lid portion 22 which is detachably mounted on an upper surface of
the open box portion 21. The outer peripheral portion of the lid
portion 22 has formed a flange 22a around the entire circumference
thereof in a manner to be bent downward. When the lid portion 22 is
mounted on the upper surface of the box portion 21, the flange 22a
gets fit into the outer wall of the box portion 21 (in this case no
vacuum sealing such as metal seal is provided), whereby a
processing chamber 20a isolated from the vacuum chamber 12 is
defined. Then, when the vacuum chamber 12 is reduced in pressure
down to a predetermined pressure (e.g., 1.times.10.sup.-5 Pa) by
operating the evacuating means 11, the processing chamber 20a will
be reduced to a pressure which is higher (e.g., 1.times.10.sup.-4
Pa) than that in the vacuum chamber 12.
[0074] As shown in FIG. 6, the box portion 21 of the processing box
20 contains therein the sintered magnets S and the evaporating
materials 1 according to the above-mentioned embodiment. The
sintered magnets S and the evaporating materials 1 are vertically
stacked with spacers 30 interposed among them so as to prevent them
from coming into contact with one another. Each of the spacers 30
is constituted by arranging a plurality of wire materials (e.g.,
0.1 to 10 mm in diameter) into a lattice shape so as to become
smaller area in cross section than the lateral cross section of the
box portion 21. The outer peripheral portion of the spacer 30 is
bent upward substantially at right angles. The height of this bent
portion is set depending on the height of the sintered magnets S to
be subjected to vacuum vapor processing. On the horizontal portion
of this spacer 30, a plurality of sintered magnets S are mounted by
disposing at a uniform distance from one another. It is preferable
to dispose, among the sintered magnets, those portions having
larger surface areas to lie opposite to the evaporating materials 1
(10). In addition, the spacers 30 may be constituted by plate
members or bar members. By appropriately disposing the spacers
among the sintered magnets S, the sintered magnets S on the lower
stage can advantageously be prevented from being deformed under the
load of the sintered magnets S on the upper stage.
[0075] After having disposed an evaporating material 1 (10) on the
bottom surface of the box portion 21, the spacer 30 on which the
sintered magnets S are disposed in lines is mounted on top thereof,
and another evaporating material 1 (10) is disposed thereon. In
this manner, the evaporating materials 1 (10) and the spacers 30
having disposed thereon in lines a plurality of sintered magnets S
are alternately stacked with each other in layers to the upper end
of the processing box 20. Since the lid portion 22 is positioned
close to the spacer 30 on the uppermost stage, the evaporating
material 1 may be omitted.
[0076] In this manner, the sintered magnets S and the evaporating
materials 1 (10) are first disposed in the box portion 21. After
having mounted the lid portion 22 on the opened upper surface of
the box portion 21, the processing box 20 is disposed on the
mounting table 16. Then, the vacuum chamber 12 is reduced in
pressure by evacuating through the evacuating means 11 until it
reaches a predetermined pressure (e.g., 1.times.10.sup.-4 Pa). When
the vacuum chamber 12 has reached the predetermined pressure, the
heating means 14 is operated to heat the processing chamber
20a.
[0077] When the temperature in the processing chamber 20a under
reduced pressure has reached a predetermined temperature, the Dy in
the processing chamber 20a is heated to substantially the same
temperature as that of the processing chamber 20a. As a result, Dy
starts evaporating and Dy vapor atmosphere is formed in the
processing chamber 20a. At this time, an inert gas such as Ar or
the like is introduced into the vacuum chamber 3 at a constant
amount of introduction from a gas introduction means (not
illustrated). According to this arrangement, the inert gas is also
introduced into the processing box 20 and, by means of the inert
gas, the metal atoms that have been evaporated in the processing
chamber 20a get diffused. The introduction pressure of the inert
gas such as Ar or the like shall preferably be 1 kPa to 30 kPa,
more preferably 2 kPa to 20 kPa.
[0078] In order to control the evaporating amount of Dy, the
heating means 14 is controlled to set the temperature in the
processing chamber to a range of 800 to 1050.degree. C., preferably
of 850 to 950.degree. C. (for example, when the temperature in the
processing chamber is 900.degree. C. to 1000.degree. C., the
saturated vapor pressure of Dy will be about 1.times.10.sup.-2 to
10.sup.-1 Pa).
[0079] According to the above arrangement, the amount of
evaporation of Dy can be controlled by adjusting the partial
pressure of the inert gas such as Ar or the like, and the Dy atoms
that have been evaporated by the introduction of the inert gas are
diffused inside the processing chamber 20a. As a result of combined
effects in that the Dy atoms are caused to get adhered to the
entire surfaces of the sintered magnets S while controlling the
amount of supply of Dy atoms to the sintered magnets S, and that
the diffusion speed becomes faster by heating the sintered magnets
S in a predetermined temperature range, the Dy atoms that have been
adhered to the surfaces of the sintered magnets S can be
efficiently diffused and uniformly spread into the grain boundaries
and/or grain boundary phases before being deposited on the surfaces
of the sintered magnets S, thereby forming a Dy layer (thin
film).
[0080] As a result, the magnet surfaces can be prevented from
getting deteriorated. In addition, it is restrained for the Dy to
be excessively diffused into the grain boundaries in the regions
closer to the surfaces of the sintered magnets. Since the grain
boundary phases have Dy-rich phases (phases having Dy in the range
of 5 to 80%) and, furthermore, Dy is diffused only near the
surfaces of the grain boundaries. Consequently, the magnetizing
force and the coercive force can effectively be enhanced or
recovered. In addition, there can be obtained high-performance
magnets which do not require finish working and which are superior
in productivity.
[0081] Finally, after having carried out the above-mentioned
processing treatments for a predetermined period of time (e.g., 4
to 48 hours), the operation of the heating means 14 is stopped and
also the introduction of the inert gas by the gas introduction
means is stopped once. Successively, the inert gas is introduced
once again (100 kPa) to stop the evaporation of the evaporating
materials 1, 10. Then, the temperature in the processing chamber
20a is once lowered to, e.g., 500.degree. C. Thereafter, the
heating means 14 is operated once again. By setting the temperature
in the processing chamber 20a to a range of 450.degree. C. to
650.degree. C., heat treatment is performed to further enhance or
recover the coercive force. Then, the processing chamber is rapidly
cooled down to about room temperature to thereby take out the
processing box 20 out of the vacuum chamber 12.
EXAMPLE 1
[0082] In Example 1, the evaporating materials 1 were manufactured
by using the dipping apparatus M1 as shown in FIG. 2. As the core
members 1a there were prepared ones that were formed into a plate
shape of 100 mm.times.100 mm in size, each by varying the quality
of material of the wire and the diameter and meshes of the wire
(samples 1 to 9 in FIG. 7). As a comparative example, there was
prepared a plate member (sample 10) of Mo make which is 100
mm.times.100 mm in size and 0.5 mm in thickness. As the rare-earth
metal for deposition, Dy (composition ratio 99%) was used. The same
processing treatments were performed on samples 1 to 10 under the
same conditions.
[0083] First, 160 kilograms of ingots were set in position inside
the crucible (300 mm in diameter.times.300 mm). After having
isolated the dipping chamber 2a by closing the gate valve 3, the
vacuum pump P was operated to start evacuation. At the same time,
the heating means 6 was operated to start heating. Then, heating
was performed while maintaining the pressure inside the dipping
chamber 2a to 1 Pa. When the temperature of Dy has reached
800.degree. C., Ar was introduced into the dipping chamber 2a
through the gas introduction pipe 7a.
[0084] On the other hand, in the preparation chamber 4a, the
pressure therein was once reduced to 1 Pa by the vacuum pump P in a
state of closing the open-close door 4b, and maintained the
pressure for one minute to thereby degas the preparation chamber
4a. Thereafter, Ar gas was introduced until the preparation chamber
4a attained the atmospheric pressure. Then, the open-close door 4b
was opened and the above-mentioned samples 1 to 10 were brought
into the preparation chamber, and were respectively set in position
to the hook block 8d of the hoist 8. Then, after having closed the
open-close door 4b, the preparation chamber 4a was evacuated once
again by the vacuum pump P.
[0085] In the dipping chamber 4a, when the temperature of Dy
exceeded 1400.degree. C. as a result of heating, Dy ingots got
melted. By controlling the heating means, an attempt was made to
keep the temperature of the molten bath at 1440.degree. C. Then, Ar
gas was introduced through the gas introduction pipe 7b into the
preparation chamber 4a until the pressure therein attained the same
pressure as that in the dipping chamber 2a. Once the dipping
chamber 2a and the preparation chamber 4a attained the same
pressure, the gate valve 3 was opened. In this state, the motor 8a
of the hoisting means was rotated in the normal direction of
rotation to thereby lower the core member 1a through the hook block
8d from the preparation chamber 4a toward the dipping chamber 2a.
The lowering speed at this time was set to 0.1 m/s. The core member
was sequentially dipped into the molten bath of Dy and reached the
dipping position. When the core member reached the dipping
position, the motor 8a of the hoisting means was rotated in the
opposite direction of rotation to thereby sequentially pull the
core member 1a out of the molten bath. The pull-up speed at this
time was set to 0.05 m/s.
[0086] Then, when the hook block 8d reached the
mounting-dismounting position, the gate valve 3 was closed. In this
state, Ar gas was introduced so that the pressure in the
preparation chamber 4a was maintained at 100 kPa, and cooled for
one minute. After cooling, Ar gas was further introduced into the
preparation chamber 4a to bring it back to the atmospheric
pressure. The open-close door 4b was opened to bring out the
evaporating materials 1.
[0087] FIG. 7 is a table showing the volumetric ratio (regions free
from adhesion of Dy) and the weight of Dy by varying, respectively,
the material of the wire, as well as the diameter and meshes of the
wire. FIG. 8 are photographs showing appearances of sample 2 (FIG.
8(a)), and sample 5 (FIG. 8(b)). According to them, samples 1 and 2
show that Dy failed to effectively adhere and, therefore, they were
found unfit for forming into evaporating materials. On the other
hand, in samples 3 and 9, Dy can be seen to have adhered to the
core member 1a in such a manner that each of the meshes was filled
over the entire region of the core member 1a and also that Dy got
adhered to the entire region of the core member 1a. Especially, in
samples 4 to 6, it can be seen that Dy got adhered in weight over
45 grams.
EXAMPLE 2
[0088] In Example 2, by using the dipping apparatus M1 shown in
FIG. 2 and by using sample 5 in Example 1 as the core member 1a,
the evaporating materials 1 were manufactured under the same
conditions as those in Example 1, except that the pull-up speed at
the time of pulling up the core member 1a from the dipping position
was varied.
[0089] FIG. 9 is a table showing the result of judging the
availability as to whether the product obtained can be used as the
evaporating material when the pull-up speed at the time of pulling
up was varied at 0.005 to 1 m/sec. In FIG. 9, those that have been
judged, in a visual inspection, to be unfit for mass production due
to the occurrence of splashes on the external surfaces are marked
with "x." According to this inspection, it has been confirmed that
the evaporating materials 1 could be manufactured at good
efficiency if the speed range falls within 0.01 to 0.5 m/sec.
EXAMPLE 3
[0090] In Example 3, by using the dipping apparatus M2 as shown in
FIG. 4, solidified bodies 10b have been manufactured on the
surfaces of the core members 10a. As the core members 10a there
were prepared, respectively, a Mo make of columnar shape (sample 1)
worked into 200 mm in diameter.times.300 mm, and of a prismatic
shape (sample 2) worked into 150 mm in square shape.times.300 mm.
Regarding sample 1, as the core member 10a, there was prepared one
made of C, Si, Mg, Nb, Ta, Ti, W, Mo, V or Cu. Further, as the
rare-earth to get adhered, there was used Dy (composition ratio
99%). Processing treatments were carried out on samples 1 and 2
under the following same conditions.
[0091] First, ingots (100 g) of Dy were set in position into the
crucible (300 mm in diameter.times.500 mm). After closing the gate
valve 3 and isolating the dipping chamber 2a, the vacuum pump P was
operated to thereby start evacuation and, at the same time, the
heating means 6 was operated to start heating. Then, heating was
performed while maintaining the dipping chamber 2a at 1 Pa. When
the temperature of Dy reached 800.degree. C., Ar was introduced
into the dipping chamber 2a through the gas introduction pipe
7a.
[0092] On the other hand, the preparation chamber 4a was once
reduced in pressure by the vacuum pump P down to 1 Pa in a state of
closing the open-close door 4b and was left for 2 minutes to
thereby degas the preparation chamber 4a. Thereafter, Ar was
introduced until the preparation chamber 4a reached atmospheric
pressure. Then, the open-close door 4b was opened to bring the
above-mentioned samples 1 and 2 into the preparation chamber. The
samples were respectively set to the clamp 82 of the hoist 8. Then,
after having closed the open-close door 4b, the preparation chamber
4a was once again evacuated by the vacuum pump P.
[0093] In the dipping chamber 4a, when the temperature of Dy has
reached 1407.degree. C. as a result of heating, the ingots of Dy
started to get melted. By controlling the heating means, the molten
bath temperature was maintained at 1500.degree. C. . Then, Ar gas
was introduced into the preparation chamber 4a through the gas
introduction pipe 7b until the same pressure as that in the dipping
chamber 2a was reached. When the dipping chamber 2a and the
preparation chamber 4a attained the same pressure, the gate valve 3
was opened. In this state, the motor 8a of the hoisting means was
rotated in the normal direction of rotation to lower the base
member 1a through the clamp 82 from the preparation chamber 4a
toward the dipping chamber 2a. The lowering speed at this time was
set to 0.05 m/sec. In this manner, the base member 10a was
sequentially dipped into the molten bath of Dy so as to reach the
dipping position. Once the base member has reached the dipping
position, it was held for 5 seconds and thereafter the motor 8a of
the hoisting means was rotated in the opposite direction of
rotation so as to pull out the base member 10a out of the molten
bath through the clamp 82. The pull-up speed at this time was set
to 0.02 m/sec.
[0094] Then, when the clamp 82 reached the mounting-dismounting
position, the gate valve 3 was closed. In this state, Ar gas was
introduced into the preparation chamber 4a so that the pressure
therein can be maintained at 100 kPa and cooled the base member for
2 minutes. After cooling, Ar gas was further introduced into the
preparation chamber 4a to bring the preparation chamber back to
atmospheric pressure. The open-close door 4b was opened and brought
out the base member.
[0095] FIG. 10 is a table showing the specific heat, specific
weight, and thermal capacity per unit volume of each of the
materials of the base member 1a of sample 1. According to this
table, in the case of base member 10a made of Nb, Ta, Ti, W, Mo or
V and sample 2, those portions, out of the base member 10a, which
are dipped into the molten bath can be recognized to have formed a
solidified body of Dy in a substantially uniform thickness.
According to this result, it has been found that the material whose
thermal capacity (specific heat x specific weight) per unit volume
was 2 to 3 MJ/km.sup.3 is suitable. On the other hand, in the case
of base member made of C, Si or Mg, little or no Dy was found to
have adhered. In addition, in the case of base member made of Cu,
the molten bath of Dy was solidified. Further, when a pulling force
was applied to the base member 10a with the solidified body having
been fixed, the base member could be easily pulled out of the
solidified body. The thickness of the solid was measured to be 2.0
mm. In addition, when this product was subjected to rolling work in
a known direction, it could be worked into 0.3 mm.
DESCRIPTION OF REFERENCE NUMERALS AND CHARACTERS
[0096] 1, 10 evaporating material
[0097] 1a, 10a core member
[0098] 1b wire mesh (through hole)
[0099] 10b solidified body
[0100] W wire material
[0101] Dy (rare-earth metal)
[0102] M1, M2 dipping apparatus
* * * * *