Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
TITLE OF INVENTION: METHOD FOR JOINTING METAL INJECTION
MOLDED PARTS
TECHNICAL FIELD
[0001] The present invention relates to a method for
jointing metal injection molded parts, especially to a method
for jointing metal injection molded parts in order to
manufacture a metal product by jointing plural metal
injection molded parts.
BACKGROUND ART
[0002] Metal injection molding (MIM) is a method for
manufacturing a metal product having density more than 95%
by degreasing and sintering, in vacuum or under a gas
atmosphere, a molded part (a green part) that is injection-
molded from mixtures of metal powders and binders, and then
injection-molding them to have a predetermined shape. As
the binders, mixtures of plural plastics and waxes are used.
The shape of the molded part is kept by dispersing plural
constituents of the binders sequentially.
[0003] A constituent not to be remained in metal is
preferably used for the binders. For example, it is common
to use mixtures of waxes such as stearin acid, paraffin wax
and carnauba wax that tend to vaporize at relatively low
temperature not more than 250 C, and plastics such as
polyethylene, polypropylene, polystyrene, EVA (ethylene
vinyl acetate) and EEA (ethylene-ethyl-acrylate copolymer
resin) that tend to decompose and disperse at temperature
not more than 500 C.
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[0004] And now,
stator blades of a turbine compressor
are disposed between an annular inner shroud and an annular
outer shroud, as disclosed in a Patent Document 1 listed
below. In
addition, stator blades are formed of alloy
containing Ti or Ni as a major ingredient, and constituted
by jointing plural stator blade sectors that are divided
along a circumferential direction. Generally, the stator
blade sector is formed by separately making an outer band
that constitutes a portion of the outer shroud, an inner
band that constitutes a portion of the inner shroud, and
blades, and then brazing the outer band and the inner band
with the blades.
[0005] Recently,
in view of functional improvement,
there are tendencies that a blade is made thinner and that
its blade surface has a complicated three-dimensional curved
surface, but it is hard to keep shape accuracy of a blade by
casting or plastic forming. Therefore, it is proposed to
use the above-mentioned metal injection molding as a
manufacturing method for a blade(s).
[0006] It may be
sometimes difficult to form the above-
mentioned stator blade sector provided with the plural blades
between the outer band and the inner band by injection
molding (one process in the metal injection molding).
Therefore, it is proposed to form a stator blade sector by
forming divided members of the stator blade sector each has
one blade between an outer band and an inner band, and then
jointing the plural divided members.
[0007] A Patent
Document 2 listed below discloses a
method for jointing metal injection molded parts, and its
object is to restrict decrease of jointing strength. In
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this jointing method, used are pastes that are made by
diluting, with water, metal powders akin to metal powders
that constitute a molded part and gelatinized soluble
materials. First, the above-mentioned pastes are pasted on
jointed surfaces of the molded parts that are not yet
sintered, and then the molded parts are temporarily jointed
with each other by the pastes.
Subsequently, the
temporarily-jointed molded parts are sintered, and thereby
molded parts are jointed with each other by the metal powders
contained in the pastes. Note that, in the Patent Document
2 listed below, disclosed are a case where the pastes are
pasted on the jointed surfaces after degreasing and then
sintering is done, and another case where degreasing and
sintering are done after the pastes are pasted on the jointed
surfaces.
Related Art Document
Patent Document
[0008] Patent
Document 1: Japanese Patent Application
Publication No. 2004-197622
Patent Document 2: Japanese Patent Application
Publication No. 2010-236042
SUMMARY OF INVENTION
Problems to be solved by the invention
[0009] The
gelatinized soluble materials made from
farinaceous materials are used in the pastes disclosed in
the Patent Document 2. The farinaceous materials are polymer
molecules made from carbon (C), Hydrogen (H) and oxygen (0),
and are easily decomposed by heats. In addition, since a
molded part is made by dispersing the binders from the green
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part constituted of the metal powders and the binders in the
metal injection molding, a size of the molded part is shrunk
from a size of the green part. Here, it is difficult to
control deformations of the jointed surfaces due to the
shrinkage. Therefore, if
pastes (adhesive agents) to be
easily decomposed by heats are used, the pastes are
decomposed and dispersed early in a degreasing process or a
sintering process, and thereby it becomes difficult to keep
a firmly-contacted state between the shrunk jointed surfaces.
Therefore, effects of restricting the decrease of jointing
strength are insufficient.
[0010] An object
of the present invention is to provide
a method for jointing metal injection molded parts that can
improve jointing strength.
[0011] An aspect of the
present invention provides a
method for jointing metal injection molded parts, the method
comprising: contacting at least two metal injection molded
parts with each other each of which is injection-molded from
mixtures of metal powders and binders; pasting paste agents
containing nitrogen or chlorine on a jointed portion at which
the at least two metal injection molded parts are contacted
with each other; and jointing the at least two metal
injection molded parts at the jointed portion to manufacture
a metal product by degreasing or sintering the at least two
metal injection molded parts of which the jointed portion is
pasted with the paste agents.
[0012] According
to the aspect, decomposition rate of
the paste agents can be made low by using the paste agents
containing nitrogen or chlorine, so that a firmly-contacted
state between the metal injection molded parts can be
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maintained further long during degreasing or sintering to
improve jointing strength of the jointed portion.
[0013] Here, it is preferable that the binders contain
waxes that vaporize at a predetermined temperature range,
and plastics that disperse at a higher temperature range
than the predetermined temperature range, and at least part
of the paste agents vaporize later than the waxes and
disperse earlier than the plastics during degreasing or
sintering of the at least two metal injection molded parts.
[0014] In addition, it is preferable that the paste
agents are pasted on a contact surface or a circumferential
side surface of the jointed portion.
[0015] In addition, it is preferable that the at least
two metal injection molded parts are degreased or sintered
in a state where a gap of the jointed portion is kept not
more than 0.1mm.
[0016] In addition, it is preferable that the metal
product is a blade sector that includes a plurality of blades
and a band portion that supports the plurality of blades,
and each of the at least two metal injection molded parts is
a divided member of the blade sector, the divided member
including a single blade.
[0017] Further, it is preferable that a rib that extends
in a direction intersecting with a chord line of the blade
is formed on a back surface, located on a back side of a
surface on which the blade is raised, of the band portion.
[0018] Here, it is preferable that, when an angle
between an extending direction of the band portion and an
extending direction of the rib in the band portion is denoted
by 6, the angle 8 is larger than 0 and not larger than a
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stagger angle of the blade.
[0019]
Alternatively, it is preferable that, when an
angle between an extending direction of the band portion and
an extending direction of the rib in the band portion is
denoted by 0, the angle e satisfies 0 <012 .
BRIEF DESCRIPTION OF DRAWINGS
[0020] [Fig. 1] It
shows a flowchart of a method for
jointing metal injection molded parts according to an
embodiment.
[Fig. 2] It shows perspective views of a metal product
manufactured by the method for jointing metal injection
molded parts, and (a) shows a first example, (b) shows a
second example and (c) shows a third example.
[Fig. 3] (a) shows a perspective view of metal
injection molded parts after injection molding, and (b) shows
a perspective view of the metal injection molded parts on
which paste agents are pasted.
[Fig. 4] It shows explanatory cross-sectional views of
a pasting method of the paste agents, and (a) shows a first
example, (b) shows a second example, (c) shows a third
example and (d) shows a fourth example.
[Fig. 5] (a) shows a front view of an outer band, and
(b) shows a graph showing relations between an extending
angle 0 of a rib and a stability S.
[Fig. 6] It shows a front view of a modified example
of the outer band.
[Fig. 7] It shows explanatory diagrams of a method for
testing a gap of a jointed portion, and (a) shows a side
view of a gap-adjustment state and (b) shows a side view of
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a joint-completion state.
DESCRIPTION OF EMBODIMENT
[0021] Hereinafter,
a method for jointing metal
injection molded parts according to an embodiment will be
described with reference to the drawings.
[0022] In the
method for jointing metal injection molded
parts according to the present embodiment, a metal product
1 is manufactured by jointing metal injection molded parts
2 each of which is injection-molded from mixtures of metal
powders and binders, and then degreasing (debinding) and
sintering (calcining) them. Here, after
paste agents 4
containing nitrogen (N) or chlorine (Cl) are pasted on
jointed portions 3 of the metal injection molded parts 2,
the metal injection molded parts 2 are jointed with each
other, and then degreased or sintered.
[0023]
Specifically, as shown in Fig. 1, the metal
product 1 is manufactured through a mixing process Si for
mixing the metal powders and the binders, an injection-
molding process S2 for heating and melting feedstock and
then injecting them into dies, a pasting process S3 for
coupling the metal injection molded parts 2 took out from
the dies with each other and then pasting the paste agents
4 on the jointed portions 3 by a soldering iron or the like,
a degreasing process S4 for degreasing the metal injection
molded parts 2 on which the paste agents 4 have been pasted
in a heating oven, and a sintering process 55 for sintering
the metal injection molded parts 2 that have been degreased
in a (the) heating oven.
[0024] The metal
product 1 is a portion of a stator
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blade unit of a turbine compressor, for example. The stator
blade unit is comprised of an annular inner shroud, an
annular outer shroud, and plural stator blades disposed
between them. The stator blade unit is manufactured by
assembling plural stator blade sectors divided along a
circumferential direction. The above metal product 1 is the
stator blade sector.
[0025] The metal product 1 (the stator blade sector)
shown in Fig. 2(a) is comprised of an outer band 11 that is
a portion of the outer shroud, an inner band 12 that is a
portion of the inner shroud, and plural stator blades 13
disposed between the outer band 11 and the inner band 12.
Note that dot-and-dash lines in Fig. 2(a) indicate the
jointed portions 3.
[0026] The outer band 11 includes a shroud portion lie
that forms a flow path surface on an outer circumferential
side of the stator blades 13, and hook portions 11b that are
formed along both end edges of the shroud portion 11a,
respectively. A stepped portion lid is formed between the
respective hook portions lib and the shroud portion 11a, and
the stepped portion lid is engaged with a rail formed on a
turbine housing. On a back surface, located on a back side
of a surface on which the stator blades 13 are raised, of
the outer band 11 (an opposite surface to the flow path
surface), a depressed portion is formed by the shroud portion
ha and the hook portions 11b. In the depressed portion,
ribs 11c each of which joints the pair of hook portions lib
are formed on the shroud portion 11a.
[0027] The inner band 12 includes a shroud portion 12a
that forms a flow path surface on an inner circumferential
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side of the stator blades 13, and slot portions 12b that are
formed along both end edges of the shroud portion 12a in an
axial direction, respectively. The slot portion(s) 12b is
formed by bending back a side edge of the shroud portion 12a.
Inner circumferential ends of plural stator blades are
jointed by inserting a plate part between the pair of slot
portions 12b, and thereby the inner bands 12 formed by the
plural shroud portions 12a are held to have an annular shape.
The above-mentioned ribs 11c reinforce the outer band 11,
and thereby they restrict deformations of the outer band 11
during the degreasing process S4 and the sintering process
S5.
[0028] Configuration of the metal product 1 is not
limited to the above configuration. As shown in fig. 2(b),
the metal product 1 may be a stator blade sector that
includes no rib 11c. In addition, as shown in Fig. 2(c),
the metal product 1 may be a rotor blade sector that is a
portion of the rotor blade unit. The metal product 1 as the
rotor blade sector is comprised of an outer band 11 that
constitutes a portion of an outer shroud, and plural rotor
blades 14 that are integrated with the outer band 11. Note
that dot-and-dash lines in Fig. 2(b) and Fig. 2(c) indicate
the jointed portions 3.
[0029] In addition, the metal product 1 is not limited
to a stator blade sector or a rotor blade sector, and
encompasses all parts each of which is manufactured by
jointing plural metal injection molded parts 2. In addition,
the above-mentioned configuration of the outer band 11 or
the inner band 12 is an example, and its shape is not limited
to the above-described shape.
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[0030] The above-described metal product 1 has a
complicated shape, and thereby it may be difficult to
manufacture it by one-time injection-molding while
maintaining its shape accuracy. In addition, if a size of
5 the metal product 1 is made larger, it may deform during
degreasing or sintering due to increase of its weight.
Therefore, in the present embodiment, the metal product 1 as
shown in Fig. 2(a) is manufactured by jointing the plural
metal injection molded parts 2 (divided members) as shown in
10 Fig. 3(a). Since each of the metal injection molded parts
2 has a single stator blade 13 between the outer band 11 and
the inner band 12, it can be manufactured by one-time
injection-molding while maintaining its shape accuracy.
[0031] The metal product 1 manufactured by jointing the
plural metal injection molded parts 2 is a blade sector (e.g.
the stator blade sector) provided with plural blades (the
stator blades 13) and band portions (the outer band 11 and
the inner band 12) that support the blades. The metal
injection molded part 2 is a part divided from the blade
sector to have a single blade. Therefore, even if the metal
product 1 has a complicated shape, the metal injection molded
part(s) 2 has a shape that can be injection-molded easily,
and its shape accuracy can be maintained. Note that, in
following descriptions for the metal injection molded
part(s) 2, identical reference numerals used for equivalent
elements of the metal product 1 will be used (such as the
outer band 11, the inner band 12 and the stator blade 13).
[0032] Respective processes of a flowchart shown in Fig.
1 will be described. In the mixing process Si, the metal
powders and the binders that become feedstock of the metal
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injection molded part 2 are mixed, and then pelletized. As
the metal powders, powders whose particle diameter is almost
to 20 pm made from stainless steel (SUS), titanium,
various types of alloys, various types of ceramics and so on
are used, for example.
[0033] In addition, the binders contain waxes that
vaporize at a predetermined temperature range, and plastics
that disperse at a higher temperature range than that of the
waxes. The waxes are stearin acid, paraffin wax, carnauba
wax and so on that tend to vaporize at relatively low
temperature not more than 250 C, for example. Further, the
plastics are polyethylene, polypropylene, polystyrene, EVA
(ethylene vinyl acetate), EEA (ethylene-ethyl-acrylate
copolymer resin) and so on that tend to decompose and
disperse at temperature not more than 500 C (these can be
used by being mixed). Note that lubricants, surfactants and
so on are added to the binders as needed in addition to the
waxes and the plastics.
[0034] In the injection-molding process S2, the metal
injection molded parts 2 shown in Fig. 3(a) are molded. The
metal injection molded part 2 is also called as a green part.
Since the binders are contained in the metal injection molded
part 2 in addition to the metal powders that will constitute
the metal product 1, a size of the metal injection molded
part 2 is larger than a size of the metal product 1.
[0035] In the pasting process S3, as shown in Fig. 3(b),
the plural metal injection molded parts 2 are assembled to
have a shape of the metal product 1, and then the paste
agents 4 are pasted on the jointed portions 3. The paste
agents 4 are waxes or plastics that contain nitrogen (N) or
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chlorine (Cl), for example. In addition, at least part of
the paste agents 4 contains materials that disperse later
than the waxes contained in the binders during degreasing or
sintering, and materials that disperse earlier than the
plastics contained in the binders during degreasing or
sintering. Here, the phrase "at least part of the paste
agents 4" means that one or some of constituents contained
in the paste agents 4 disperse later than the waxes contained
in the binders, and disperse earlier than plastics contained
in the binders.
[0036] Specifically, as the paste agents 4, waxes having
urethane group (-NH000-) or amide group (-CONH2), chlorinated
waxes and so on, or hot-melt adhesives having urethane group
can be used. As sold products, they are Hi-Bon (registered
trademark: Hitachi Kasei Polymer Co., Ltd.), Macromelt
(registered trademark: Henkel AG & Co. KGaA), EMPARA
(registered trademark: Ajinomoto Fine-Techno Co., Inc.), and
so on.
[0037] If the paste agents 4 disperse at early stage
during the degreasing process S4 or the sintering process S5
that will be described later, a gap may be generated at the
jointed portions 3 of the metal injection molded parts 2,
and thereby strength of the metal product 1 after being
sintered may degrade. However, since the paste agents 4 in
the present embodiment are materials that are not easily
decomposed by heats, i.e. waxes or resigns that contain
nitrogen (N) and/or chlorine (Cl), they don't disperse at
early stage during the degreasing process S4 or the sintering
process S5. Note that the paste agents 4 may be mixtures of
waxes that contain nitrogen (N) and/or chlorine (Cl) and
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resigns that contain nitrogen (N) and/or chlorine (Cl)
[0038] By using the above-described paste agents 4, at
least part of the paste agents 4 can be made dispersed later
than the waxes contained in the binders during degreasing or
sintering, and can be made dispersed earlier than the
plastics contained in the binders during degreasing or
sintering. Since the paste agents 4 contain materials that
disperse later than the waxes of the binders that are
degreased, the paste agents 4 can be restricted from
dispersing in the degreasing process S4, and thereby adhesion
(temporary jointing) function of the paste agents 4 can be
maintained for a long duration.
[0039] In addition, since the paste agents 4 contain
materials that disperse earlier than the plastics contained
in the binders during degreasing or sintering (i.e. at least
part of the paste agents 4 doesn't remain until almost a
time when the plastics of the binders disperse), dispersing
paths of the plastics of the binders are not blocked by the
paste agents 4 in the sintering process S5, and thereby the
metal powders can be sintered in a wholly-balanced manner.
As a result, deformations of the metal product 1 can be
restricted. (Note that the "deformation" used here doesn't
include shrinkage from the metal injection molded parts 2 to
the metal product 1 due to sintering.) In addition, since
the jointed portions 3 of the metal injection molded parts
2 (also called as a brown part(s)) are kept in a firmly-
contacted state after the degreasing process S4, strength of
the metal product 1 after being sintered is improved.
[0040] The above-described paste agents 4 are pasted,
in a heated-and-melted state, on the jointed portions 3 by
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a soldering iron, a roller, spraying, immersion coating and
so on. For
example, when using a soldering iron, paste
agents 4 having softening temperature not more than 330 C
that is an operating temperature of the soldering iron. The
paste agents 4 are pasted on contact surfaces 3a or
circumferential side surfaces 3b of the jointed portions 3.
[0041] In a first
example, shown in Fig. 4(a), the paste
agents 4 are pasted on the contact surfaces 3a. In a case
of pasting the paste agents 4 on the contact surfaces 3a,
adhesive strength (jointed strength) of the jointed portions
3 can be improved. However, it is preferable that a gap g
of the jointed portion 3 is kept not more than 0.1mm. If
the gap g becomes wide, it may cause strength degradation of
the jointed portions 3 in the metal product 1 and deformation
of the metal product 1.
[0042] In a second
example shown in Fig. 4(b), the paste
agents 4 are pasted on the contact surfaces 3a and the
circumferential side surfaces 3b. The contact surfaces 3a
are opposing surfaces at the jointed portion 3 of the metal
injection molded parts 2, and the circumferential side
surfaces 3b are side surfaces at the jointed portion 3 of
the metal injection molded parts 2. By pasting the paste
agents 4 on the circumferential side surfaces 3b in addition
to the contact surfaces 3a, a pasted amount on the contact
surfaces 3a can be reduced, and thereby the gap g can be
easily adjusted to be not more than 0.1mm. In
addition,
since an adhesive (jointed) area can be increased, adhesive
strength (jointed strength) of the jointed portions 3 can be
improved.
[0043] In a third
example shown in Fig. 4(c), the paste
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agents 4 are pasted on the circumferential side surfaces 3b.
Here, the paste agents 4 are pasted on whole circumferences
of the circumferential side surfaces 3b at the jointed
portion 3. By pasting
the paste agents 4 only on the
5 circumferential side surfaces 3b, the gap g can be easily
adjusted to be not more than 0.1mm. In addition, the paste
agents 4 pasted on the circumferential side surfaces 3b are
heated and then melted in the degreasing process S4 or the
sintering process S5, and infiltrate between the contact
10 surfaces 3a voluntarily. Therefore, the gap g can be kept
to have a desired value, and adhesive strength (jointed
strength) of the jointed portions 3 can be improved also by
the contact surfaces 3a.
[0044] In a fourth
example shown in Fig. 4(d), the paste
15 agents 4 are pasted on a portion of the circumferential side
surfaces 3b. In a case where the jointed portion 3 has a
complicated shape, the paste agents 4 may be pasted on areas
to be easily pasted. In
addition, in a case where the
contact surfaces 3a extend in a vertical direction as shown
in Fig. 4(d), the paste agents 4 pasted on the upper
circumferential side surfaces 3b infiltrate between the
contact surfaces 3a due to gravity.
[0045] As shown in
Fig. 3 (b), the metal injection
molded parts 2 on which the paste agents 4 are set on a
support block 5, and then sent to the degreasing process S4.
Here, by making a height level h of the stepped portion lid
of the outer band 11 identical to a height level h of the
inner band 12, the stator blades 13 can be set horizontally
in a state where the stepped portion lid is contacted with
corner of the support block 5.
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[0046] On the other hand, in a case where the above-
mentioned height levels h are not made identical to each
other, a gap may be generated between an end edge of the
inner band 12 and the support block 5 when setting the stator
blades 13 horizontally in a state where the stepped portion
lid of the outer band 11 is contacted with the corner of the
support block 5. In such a case, a supplemental support
block (not shown in the drawings) may be inserted into the
gap between the end edge of the inner band 12 and the support
block 5. Alternatively, a gap may be generated between the
stepped portion 11d of the outer band 11 and the corner of
the support block 5 when setting the stator blades 13
horizontally in a state where an end edge of the inner band
12 is contacted with the support block 5. In such a case,
a supplemental support block may be inserted into the gap
between the stepped portion 11d and (the corner of) the
support block 5.
[0047] Since the binders are removed during the
degreasing process S4 and the sintering process S5, a size
of the metal product 1 after being sintered shrinks wholly
from a side of the metal injection molded parts 2. Therefore,
the stator blades 13 can be shrunk almost horizontally by
setting the stator blades 13 horizontally. As a result, the
jointed metal injection molded parts 2 can be shrunk in a
wholly-balanced manner, and deformation due to distortion
upon shrinking can be restricted.
[0048] In the degreasing process S4, the waxes contained
in the binders are removed. Heating temperature for the
degreasing process S4 is generally lower than heating
temperature for the sintering process S5. Therefore, the
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metal injection molded parts 2 may be heated in a degreasing
apparatus other than a sintering oven used for the sintering
process S5. Of course, the metal injection molded parts 2
may be degreased by controlling temperature in a sintering
oven used for the sintering process S5.
[0049] In the sintering process S5, the plastics
contained in the binders are removed, and thereby the metal
powders are sintered. For example, in a case of using IN718
[IN: Inconel (registered trademark: Special Metals
Corporation)] that is Ni-base alloy as the metal powders, it
is preferable to carry out sintering under a non-oxidizing
atmosphere with more than 1200 C. With respect to the metal
product 1 after being sintered, as post processes, density
measurement may be done in order to confirm progress of
sintering, press-working may be done in order to adjust its
dimensions precisely, electro-discharge machining may be
done in order to treat its surfaces, and grinding or
polishing may be done in order to fix its surface roughness.
[0050] The above-mentioned ribs 11c (see Fig. 2(a), Fig.
3(a) and Fig. 3(c)) will be described. As shown in Fig.
5(a), the ribs 11c are extended on a back surface of the
outer band 11 (band portion). An extending direction Lr of
the rib(s) 11c intersects with a chord line Lc of the stator
blade 13. When an angle of the rib 11c to an extending
direction of the outer band Le (a vertical direction in a
case shown in Fig. 5(a)) is denoted by 0 (>0: magnitude of
the angle), a lateral width of the outer band 11 of the metal
injection molded part 2 is denoted as A, and its height is
denoted by B, shape stability S (dB: decibel) of the metal
injection molded parts 2 (the metal product 1) can be
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calculated by S=10.1ogio(B/A).
[0051] The metal injection
molded parts 2 each of which
has the above-mentioned angle 8 = 00, 6 or 12 are molded,
and then shapes of their outer bands 11 after being sintered
are measured three-dimensionally to compare them with ideal
shape of the metal injection molded parts 2 (the metal
product 1) that are uniformly shrunk. The comparison results
are shown in Fig. 5(b). If the stability S is high, shape
difference from the uniformly-shrunk metal injection molded
parts 2 is small. On the other hand, if the stability S is
low, shape difference from the uniformly-shrunk metal
injection molded parts 2 is large.
[0052] As shown in Fig. 5(b),
the stability S of 0 = 6'
and 12 is higher than that of 8 - 0 . Therefore, it is
preferable that the angle 8 of the rib 11c is made large
(i.e. an intersecting angle with the chord line Lc is made
large). However, also in a case of 0 = 0 , the stability S
can be made high enough to keep shape accuracy of the metal
product 1 according to conditions such as size, shape and
weight of the metal injection molded part(s) 2. Therefore,
the above case of 8 = 0 is not excluded.
[0053] In addition, if the
angle 0 of the rib 11c is
too large, it is concerned that deformation during sintering
due to its weight is fomented. Therefore, it is preferable
to set an upper limit for the angle O. In view of the above-
mentioned matters, it is preferable to set the upper limit
of the angle 0 to a stagger angle A (>0: magnitude of the
angle) of the stator blade 13. The "stagger angle A" is an
angle of the chord line Lc to a turbine-axis direction La
(which is parallel to the extending direction Le in the case
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shown in Fig. 5(a)), as shown in fig. 5(a). Specifically,
it is preferable to determine the upper limit of the angle
e within a range 6 to 12 based on the above-described test
results. However, the upper limit of the angle 0 is not
restricted by these values (range), but can be determined
with respect to each metal injection molded part 2 according
to weight of the rib 11c.
[0054] Namely, it is
preferable that the angle 0 between
the extending direction Le of the outer band 11 and the
extending direction Lr of the rib 11c is set larger than 0
and not larger than the stagger angle A. Especially, only
in view of deformation due to shrinkage, it is further
preferable that the angle 0 has identical magnitude to that
of the stagger angle A. Here, since the stagger angle A of
the stator blade 13 is determined in some measure, it is
specifically preferable that 0 <1912 . Note that a
direction of the angle 0 from the extending direction Le of
the outer band 11 to the extending direction Lr of the rib
11c is opposite to a direction of the stagger angle A from
the turbine-axis direction La to the chord line Lc.
[0055] Fig. 6 shows a
modified example in which end
surfaces of the metal injection molded part(s) 2 are inclined
to the turbine-axis direction La. As shown in Fig. 6, there
may be a case where the rib(s) 11c is inclined in this manner
according to relation with the stagger angle A of the stator
blade 13. In the present modified example, the extending
direction Le of the outer band 11 is not parallel to the
turbine-axis direction La. In the case as shown in Fig. 6,
difference between overhangs OH1 and 0H2 of the outer band(s)
11 to the rib(s) 11c can be made small, so that the
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deformation of the metal injection molded parts 2 (the metal
product 1) due to distortion upon shrinking can be also
restricted effectively.
[0056] Next, the
above-mentioned gap g of the jointed
5 portion 3 (see Fig. 4(a)) will be described. As shown in
Fig. 7(a), two metal injection molded plates 6 are prepared
to form a gap between the two metal injection molded plates
6 by inclining one of the two metal injection molded plates
6 on another of the two metal injection molded plates 6 b
10 use of a spacer 7. By changing a horizontal position of the
spacer 7, a size of the gap can be adjusted. The paste
agents 4 are pasted on this gap and then the metal injection
molded plates 6 are degreased and sintered to measure a gap
C that can joint the metal injection molded plates 6 with
15 sufficient jointing strength. The cap C
realizing
sufficient jointing strength is 0.1mm. Therefore, it is
preferable that the gap g of the jointed portion 3 is not
more than 0.1mm.
[0057] Note that
the gap C may vary according to the
20 metal powders, the binders and so on that become feedstock
of the metal injection molded plate(s) 6. Namely, the gap
g of the jointed portion 3 is not necessarily limited to be
not more than 0.1mm, but it is preferable, on an empirical
basis, that it is not more than 0.1mm-0.5mm.
[0058] According to the
jointing method in the present
embodiment, since the paste agents 4 contain nitrogen (N) or
chlorine (Cl), decomposition rate of the paste agents 4 can
be made low. Therefore, a firmly-contacted state between
the metal injection molded parts 2 can be maintained further
long during degreasing or sintering, and thereby jointing
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21
strength of the jointed portion(s) 3 can be improved.
[0059] The present invention is not limited to the
present embodiment, and can be modified variedly within a
scope that does not extend beyond the subject matter of the
present invention. For example, ribs may be formed on the
inner band 12. Note that, since the ribs 11c are provided
in order to improve the shape accuracy of the metal product
1 (the metal injection molded parts 2) during degreasing or
sintering, there may be a case where they are cut away before
completion of the stator blade unit (even if the ribs 11c
are cut away, the angle e of the rib(s) 11c are recognizable
from their cut-away marks). In addition, the plural ribs
11c may be provided on a single metal injection molded part
2.
