TW201524640A - Method for bonding metal powder injection molded bodies - Google Patents

Abstract

According to this method for bonding metal powder injection molded bodies, a metal product is produced by: [1] bringing at least two metal powder injection molded bodies, each of which is obtained by kneading a metal powder and a binder and injection molding the kneaded material, into contact with each other; [2] applying a coating agent that contains nitrogen or chlorine to a bond part where the at least two metal powder injection molded bodies are in contact with each other; and [3] bonding the at least two metal powder injection molded bodies with each other at the bond part by means of degreasing or sintering. This bonding method is capable of improving the bonding strength at the bond part.

Description

Method for joining metal powder injection molded body

The present invention relates to a method for joining a metal powder injection molded article, and more particularly to a method for joining a metal powder injection molded body for joining a plurality of metal powder injection molded bodies to produce a metal product. .

MIM (Metal Injection Molding) is a method in which a metal powder and a binder are kneaded and then injection-molded in a predetermined shape to obtain a molded body (green part). The body is degreased and sintered in a vacuum or in a gas atmosphere to produce a metal product having a density of more than 95%. As the binder, a mixture of a plurality of resins and waxes is used. The shape of the molded body is maintained by sequentially scattering a plurality of binder components.

The binder is preferably a component that does not remain in the metal. For example, it is generally used in combination: a wax such as stearic acid, paraffin wax or palm wax which is easily volatilized at a temperature lower than 250 ° C, and a polyethylene, polypropylene, polystyrene which is easily decomposed and scattered at a temperature of 500 ° C or lower. EVA (ethylene vinyl acetate), EEA (ethylene-ethyl acrylate copolymer tree Resin such as grease).

However, the stator blade of the turbo compressor is disposed between the annular inner casing and the annular outer casing as disclosed in Patent Document 1 below. Further, the stator blade is formed of an alloy having a main component of Ti or Ni, and is configured by dividing a plurality of stator blade sectors in a circumferential direction. In general, a belt body constituting a part of the outer casing, an inner belt body constituting a part of the inner casing, and blades are separately formed, and the outer belt body and the inner belt body are welded to the blade to form a stator blade sector. .

In recent years, from the viewpoint of function improvement, there is a tendency to make the blade thinner and to make the blade surface into a complicated three-dimensional curved surface. However, it is difficult to ensure the shape accuracy of the blade by casting or plastic working. Therefore, regarding the method of manufacturing the blade, the above-described metal powder injection molding method is proposed.

The stator blade sector having a plurality of blades between the outer belt body and the inner belt body may be difficult to be formed by injection molding (a step of the metal powder injection molding method). Therefore, a split body of a stator blade sector is formed which has a blade between the outer tape body and the inner tape body, and a technique of joining a plurality of divided bodies to form a stator blade sector has been proposed.

Patent Document 2 listed below discloses a joining method of a metal powder injection molded body, which is intended to suppress a decrease in joint strength. In the joining method, a paste obtained by diluting a metal powder of the same kind as the metal powder constituting the molded body and a gelatinized soluble material with water is used. First, the above paste is applied to a molded body before sintering. The joint faces temporarily bond the molded bodies to each other by the paste. Then, the temporarily joined molded body is sintered, and the molded bodies are joined to each other by the metal powder contained in the paste. Further, Patent Document 2 listed below discloses a case where the paste is applied to the joint surface after degreasing, followed by sintering, and after the paste is applied to the joint surface, degreasing and sintering are performed.

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2004-197622

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2010-236042

The paste described in Patent Document 2 is a water-soluble paste-like material using starch as a raw material. Starch is a polymer composed of carbon (C), hydrogen (H), and oxygen (O), and is easily decomposed by heat. Further, in the metal powder injection molding method, a binder is formed by scattering a binder from a green body composed of a metal powder and a binder, and thus the size of the molded body is shrunk from the size of the green body. Here, it is difficult to control the deformation of the joint surface caused by the shrinkage. Therefore, when a paste (adhesive) which is susceptible to thermal decomposition is used, it is difficult to prematurely decompose and scatter the paste in the degreasing step or the sintering step, and it is difficult to maintain the adhesion state between the joined surfaces after shrinkage. Therefore, the effect of suppressing the decrease in the joint strength is not good.

An object of the present invention is to provide a joining method of a metal powder injection molded body which can improve joint strength.

A feature of the present invention is to provide a joining method of a metal powder injection molded body, wherein the metal powder injection molded body is joined by a method in which at least two metal powders obtained by kneading the metal powder and the binder after injection molding are respectively obtained by injection molding. The injection molded bodies are in contact with each other, and a coating agent containing nitrogen or chlorine is applied to the joint portion where the at least two metal powder injection molded bodies are in contact with each other, and the at least two metal powders coated with the coating agent on the joint portion are emitted. The molded body is degreased or sintered, and the at least two metal powder injection molded bodies are joined at the joint portion to produce a metal product.

According to the above feature, by using a coating agent containing nitrogen or chlorine, the decomposition rate of the coating agent can be slowed, and when the metal powder injection molded body is degreased or fired, the metal powder can be injected into the molded body at the joint portion. The close contact state is maintained for a longer period of time, and the joint strength of the joint portion can be improved.

Preferably, the binder contains a wax which volatilizes in a predetermined temperature range and a resin which scatters in a temperature range higher than the predetermined temperature range, and at least a part of the coating agent is at least two When the metal powder injection molded body is degreased or sintered, it is more slowly volatilized than the above wax and scatters faster than the aforementioned resin.

Further preferably, the coating agent is applied to a contact surface or a circumferential side surface of the joint portion.

Further, it is preferable that the at least two metal powder injection molded bodies are degreased or sintered while the gap of the joint portion is maintained at 0.1 mm or less.

Further preferably, the metal product is provided with a plurality of And a blade segment of the blade body for supporting the plurality of blades, wherein the at least two metal powder injection molding bodies are each a segment of the blade sector having a single blade.

Further preferably, a rib extending in a direction intersecting the blade chord of the blade is formed on a back surface of one surface of the belt body on which the blade is vertically disposed.

Here, it is preferable that when the angle formed by the extending direction of the belt body portion and the extending direction of the rib portion in the divided body is θ , the angle θ is larger than 0° and is equal to or less than the stagger angle of the blade.

Or preferably when the angle between the extending direction of the strip portion and the divided body of the rib is defined as θ, 0 ° <θ ≦ 12 °.

1‧‧‧Metal products

2‧‧‧Metal powder injection molded body

3‧‧‧ joints

3a‧‧‧Contact surface

3b‧‧‧ week side

4‧‧‧ Coating agent

5‧‧‧Support block

6‧‧‧Metal powder injection molding board

7‧‧‧ spacers

11‧‧‧External body

11a‧‧‧Shell Department

11b‧‧‧ hooking

11c‧‧‧ ribs

11d‧‧‧ paragraph difference

12‧‧‧Inner body

12a‧‧‧Shell Department

12b‧‧‧Slits

13‧‧‧ stator blades

14‧‧‧Rotor blades

A‧‧‧ transverse width of the outer body

B‧‧‧ Height of the outer body

C‧‧‧Able to achieve sufficient joint strength gap

g‧‧‧Gap of the joint

h‧‧‧The height of the step of the outer body (the height of the edge of the inner body)

θ ‧‧‧An angle between the extension of the body and the direction in which the rib extends

λ‧‧‧Interlace angle

La‧‧‧ Turbine axis direction

Lc‧‧‧blade string

Le‧‧‧Extension of the outer body

Lr‧‧‧ extension of the rib

OH1, OH2‧‧‧ overhang

S1‧‧‧ mixing step

S2‧‧‧ injection molding step

S3‧‧‧ Coating step

S4‧‧‧ Degreasing step

S5‧‧‧Sintering step

Fig. 1 is a flow chart showing a method of joining metal powder injection molded articles of an embodiment.

2 is a perspective view of a metal product produced by the above-described joining method of the metal powder injection molded body, wherein (a) is a first example, (b) is a second example, and (c) is a third example.

Fig. 3 (a) is a perspective view showing the metal powder injection molded body after injection molding, and Fig. 3 (b) is a perspective view showing the metal powder injection molded body coated with the coating agent.

Figure 4 is a cross-sectional view showing the coating method of the coating agent, (a) being the first For example, (b) is the second case, (c) is the third case, and (d) is the fourth case.

Fig. 5(a) is a front view of the outer band, and Fig. 5(b) is a view showing the relationship between the extending angle θ of the rib and the stability S.

Fig. 6 is a front view showing a modification of the outer belt body.

Fig. 7 is an explanatory view showing a gap test method of the joint portion, (a) showing a side view of the gap adjustment state, and (b) a side view showing the joint completion state.

Hereinafter, an embodiment of a joining method of a metal powder injection molded body will be described with reference to the drawings.

In the joining method of the metal powder injection molded body of the present embodiment, the metal powder injection molded body 2 obtained by kneading the metal powder and the bonding agent is joined to each other to perform degreasing (debinding) [debinding] ]) or sintering [sintering] (calcining) to produce metal product 1. Here, after the coating agent 4 containing nitrogen (N) or chlorine (Cl) is applied onto the joint portion 3 of the metal powder injection molded body 2, the metal powder injection molded body 2 is joined to each other and degreased or sintered.

Specifically, as shown in FIG. 1, the metal product 1 is produced through the kneading step S1, the injection molding step S2, the coating step S3, the degreasing step S4, and the sintering step S5. In the kneading step S1, the metal powder and the binder are kneaded; in the injection molding step S2, the kneaded material is heated and melted and then ejected into the mold; and the coating step S3 is to eject the metal powder taken out from the mold. The molded bodies 2 are combined with each other at the joint portion 3 The coating agent 4 is applied by a soldering iron or the like; the degreasing step S4 is to degrease the metal powder injection molded body 2 coated with the coating agent 4 by a heating furnace; and the sintering step S5 is to use the degreased metal powder to be molded into the molded body 2 The furnace is sintered.

The metal product 1 is, for example, part of a stator blade unit of a turbo compressor. The stator vane unit is composed of an annular inner casing, an annular outer casing, and a plurality of stator vanes disposed between the stator vane. The stator blade unit is produced by dividing a plurality of stator blade sector combinations in the circumferential direction. The above metal product 1 is a stator blade sector.

The metal product 1 (stator blade sector) shown in Fig. 2(a) is a belt body 11 which is a part of the outer casing, an inner belt body 12 which forms a part of the inner casing, and is disposed in the outer belt body 11 and The plurality of stator blades 13 are formed between the belt bodies 12. Further, the one-dot chain line in Fig. 2(a) indicates the joint portion 3.

The outer casing 11 has a casing portion 11a for forming an outer peripheral side flow surface of the stator blade 13, and a hook portion 11b formed at both end edges of the casing portion 11a. A step 11d is formed between the hook portion 11b and the casing portion 11a, and the step 11d is locked to the rail formed on the turbine casing. A rear surface (a surface opposite to the flow path surface) on one surface of the stator blade 13 is vertically provided on the outer tape body 11, and a concave portion is formed by the case portion 11a and the hook portion 11b. In the recess, a rib 11c for coupling the pair of hook portions 11b is formed on the casing portion 11a.

The inner belt body 12 has a casing portion 12a for forming an inner peripheral side flow surface of the stator blade 13, and a casing portion 12a formed in the casing portion 12a, respectively. The slit portion 12b at both end edges in the axial direction. The slit portion 12b is formed by folding back the side edge of the casing portion 12a. By inserting the plate member between the pair of slit portions 12b, the inner peripheral ends of the plurality of stator blade segments are connected to each other, and the inner band body 12 formed by the plurality of casing portions 12a is held in a ring shape. The rib portion 11c is for reinforcing the outer band body 11 to suppress the degreasing step S4 and the outer band body 11 is deformed in the sintering step S5. The effect of the rib 11c will be described later.

The metal product 1 is not limited to the above configuration. As shown in Fig. 2(b), the metal product 1 may also be a stator blade sector having no ribs 11c. Further, as shown in FIG. 2(c), the metal product 1 may also be a part of a rotor blade unit of a turbo compressor, that is, a rotor blade sector. The metal product 1 as a rotor blade sector is composed of a plurality of rotor blades 14 that are a part of the outer casing and a plurality of rotor blades 14 that are coupled to the outer casing 11. Further, the one-dot chain line in FIGS. 2(b) and 2(c) indicates the joint portion 3.

Further, the metal product 1 is not limited to the stator blade sector and the rotor blade sector, and is a member including all of the members produced by joining a plurality of metal powder injection molded bodies 2. Further, the structures of the outer tape body 11 and the inner tape body 12 are merely examples, and are not limited to the above shapes.

The metal product 1 described above has a complicated shape, and it may be difficult to produce it by one injection molding in order to maintain the shape accuracy. Further, in the case where the metal product 1 is enlarged, its weight is increased, and deformation may occur in degreasing or sintering. Then, in the present embodiment, as shown in Fig. 3(a), a plurality of metal powder injection molded bodies 2 (divided bodies of blade sectors) are joined to each other, as shown in Fig. 2(a). Metal products 1. Various metals The powder injection molded body 2 has a single stator blade 13 between the outer tape body 11 and the inner tape body 12, and is formed into a relatively simple shape. Therefore, the powder injection molded body 2 can be produced by one injection molding while maintaining shape accuracy.

The metal product 1 produced by joining a plurality of metal powder injection molded bodies 2 is a blade including a plurality of blades (stator blades 13) and a belt portion (the outer belt body 11 and the inner belt body 12) for supporting the blades. Sector (eg, stator blade sector). The metal powder injection molded body 2 is a member that divides the blade sector into blades. Therefore, even if the metal product 1 has a complicated shape, the metal powder injection molded body 2 has a shape that is easily injection molded, and the shape accuracy can be maintained. In the following description, the metal powder injection molded body 2 is also the same as the respective portions of the metal product 1 (the outer tape body 11, the inner tape body 12, the stator blade 13, and the like).

The steps of the flowchart of Fig. 1 will be described. In the kneading step S1, the metal powder which is the raw material of the metal powder injection molded body 2 and the binder are kneaded and granulated. As the metal powder, for example, stainless steel (SUS), titanium, various alloys, various ceramics, or the like is used as a powder having a particle diameter of about 10 to 20 μm.

Further, the binder contains a wax which volatilizes in a predetermined temperature range, and a resin which scatters in a temperature range higher than the wax. The wax is, for example, stearic acid, paraffin wax, palm wax or the like which is easily volatilized at a lower temperature of 250 ° C or lower. Further, the resin is, for example, polyethylene, polypropylene, polystyrene, EVA (ethylene vinyl acetate), EEA (ethylene-ethyl acrylate copolymer resin) which is easily decomposed and scattered at a temperature of 500 ° C or lower (these may be mixed) use). In addition to the wax and resin in the bonding agent, it can be added as needed. Add a slip agent, a surfactant, and the like.

In the injection molding step S2, the metal powder injection molded body 2 shown in Fig. 3(a) is formed. The metal powder injection molded body 2 is also referred to as a green body. The metal powder injection molded body 2 contains a binder in addition to the metal powder constituting the metal product 1, and therefore the size of the metal powder injection molded body 2 is larger than that of the metal product 1.

In the coating step S3, as shown in FIG. 3(b), a plurality of metal powder injection molded bodies 2 are assembled so as to have the shape of the metal product 1, and the coating agent 4 is applied onto the joint portion 3. The coating agent 4 is, for example, a wax containing N (N) or chlorine (Cl) or a resin. Further, at least a part of the coating agent 4 contains a material which scatters more slowly than the wax contained in the binder during degreasing or sintering, or a material which scatters faster than the resin contained in the binder during degreasing or sintering. Here, "at least a part of the coating agent 4" means that one of the components contained in the coating agent 4 is scattered faster than the wax contained in the binder or more slowly than the resin contained in the binder.

Specifically, as the coating agent 4, a wax having a urethane group (-NHCOO-), a guanamine group (-CONH ₂ ), a chlorinated wax, or the like, or a heat having a urethane group can be used. A fluxing agent. As a product, [Hi-Bon] (registered trademark: Hitachi Kasei Polymer Co., Ltd.), [Macromelt] (registered trademark: Henkel AG & Co. KGaA) can be used. [EMPARA] (registered trademark: Ajinomoto Fine-Techno Co., Inc.).

If the coating agent 4 is scattered at an earlier stage of the degreasing step S4 and the sintering step S5, which will be described later, the metal powder is injected into the molded body 2 The joint portion 3 generates a gap to lower the strength of the sintered metal product 1. However, the coating agent 4 of the present embodiment is a material which is not easily decomposed by heat, that is, a wax or a resin containing nitrogen (N) and/or chlorine (Cl), at an earlier stage of the degreasing step S4 and the sintering step S5. Will not fly. Further, the coating agent 4 may be a mixture of a wax containing nitrogen (N) and/or chlorine (Cl) and a resin containing nitrogen (N) and/or chlorine (Cl).

By using the above-mentioned coating agent 4, at least a part of the coating agent 4 can be more slowly scattered at the time of degreasing or sintering than the wax contained in the binder, or can be scattered faster than the resin contained in the binder at the time of degreasing or sintering. Since the coating agent 4 contains a material which scatters more slowly than the wax of the binder to be degreased, the scattering of the coating agent 4 can be suppressed in the degreasing step S4, and the subsequent (temporary bonding) function of the coating agent 4 can be maintained for a long period of time.

Further, since the coating agent 4 contains a material which disperses faster than the resin contained in the binder at the time of degreasing or sintering (that is, at least a part of the coating agent 4 can remain before and after scattering of the resin of the binder), it is sintered. In the step S5, the resin of the bonding agent does not block the scattering path, and the metal powder can be sintered in a well-balanced manner as a whole. As a result, the deformation of the metal product 1 (the "deformation" here) can be suppressed, and the shrinkage of the metal powder injection molded body 2 to the metal product 1 caused by the sintering is not included. Further, since the joint portion 3 of the metal powder injection molded body 2 (also referred to as a brown compact) after the degreasing step S4 can be kept in an adhered state, the strength of the sintered metal product 1 can be improved.

The coating agent 4 is heated and melted by a soldering iron, a brush, a roller, and a spray. [spraying], immersion [immersion coating] or the like is applied to the joint portion 3. For example, in the case of using a soldering iron, a coating agent 4 having a softening point at a use temperature of 330 ° C or lower of the soldering iron is used. The coating agent 4 is applied to the contact surface 3a or the circumferential side surface 3b of the joint portion 3.

In the first example shown in Fig. 4 (a), the coating agent 4 is applied onto the contact surface 3a. When the coating agent 4 is applied to the contact surface 3a, the adhesion (joining force) of the joint portion 3 can be improved. However, the gap g of the joint portion 3 is preferably kept at 0.1 mm or less. When the gap g is widened, the strength of the joint portion 3 of the metal product 1 is lowered, and the metal product 1 is deformed.

In the second example shown in Fig. 4(b), the coating agent 4 is applied onto the contact surface 3a and the circumferential side surface 3b. The contact surface 3a is an opposing surface of the joint portion 3 of the metal powder injection molded body 2, and the circumferential side surface 3b is a side surface of the joint portion 3 of the metal powder injection molded body 2. In addition to the contact surface 3a, the coating agent 4 is also applied to the circumferential side surface 3b, and the amount of application to the contact surface 3a can be reduced, and the gap g can be easily adjusted to 0.1 mm or less. Further, since the subsequent (joining) area can be increased, the adhesion (joining) of the joint portion 3 can be improved.

In the third example shown in Fig. 4(c), the coating agent 4 is applied to the peripheral side surface 3b. Here, the coating agent 4 is applied to the entire circumference of the circumferential side surface 3b of the joint portion 3. The coating agent 4 is applied only to the circumferential side surface 3b, and the gap g is easily adjusted to 0.1 mm or less. Further, the coating agent 4 applied to the circumferential side surface 3b is heated and melted in the degreasing step S4 or the sintering step S5, naturally Will penetrate into the contact surface 3a. Therefore, the gap g can be maintained below the desired value, and the adhesion force (joining force) of the joint portion 3 can also be increased by the contact surface 3a.

In the fourth example shown in Fig. 4(d), the coating agent 4 is applied to a part of the circumferential side surface 3b. When the joint portion 3 has a complicated shape, the coating agent 4 can be applied only at a place where coating is easy. Further, as shown in FIG. 4(d), when the contact surface 3a extends in the vertical direction, the coating agent 4 applied to the upper circumferential side surface 3b can penetrate the contact surface 3a by gravity.

As shown in Fig. 3 (b), the metal powder injection molded body 2 coated with the coating agent 4 is placed on the support block 5 and sent to the degreasing step S4. Here, by matching the height h of the step 11d of the outer band 11 and the height h of the end edge of the inner band body 12, the stator blade 13 can be placed in a state where the step 11d is brought into contact with the corner portion of the support block 5. Placed horizontally.

Further, when the height h does not match, the stator blade 13 is placed horizontally in a state where the step 11d of the outer tape 11 abuts against the corner portion of the support block 5, and the end edge of the inner tape body 12 is A gap may occur between the support blocks 5. In this case, an auxiliary support block (not shown) for filling the gap can be inserted between the end edge of the inner band body 12 and the support block 5. Alternatively, if the stator blade 13 is horizontally placed in a state where the end edge of the inner tape body 12 is brought into contact with the support block 5, a difference may occur between the step 11d of the outer tape body 11 and the corner portion of the support block 5. gap. In this case, an auxiliary support block (not shown) for filling the gap can be inserted between the step 11d and the corner portion of the support block 5.

In the degreasing step S4 and the sintering step S5, because of the combination The agent is removed, and the size of the sintered metal product 1 is contracted as a whole as compared with the size of the metal powder injection molded body 2. Therefore, by placing the stator blades 13 horizontally, the stator blades 13 can be contracted substantially horizontally. As a result, the entire metal powder injection molded body 2 can be contracted in a well-balanced manner, and deformation due to strain at the time of shrinkage can be suppressed.

In the degreasing step S4, the wax contained in the binder is removed. The heating temperature of the degreasing step S4 is generally lower than the heating temperature of the sintering step S5. Therefore, the metal powder can be injected into the molded body 2 by heating, which is different from the sintering furnace used in the sintering step S5. Of course, in the sintering step S5, the metal powder may be injected into the molded body 2 by controlling the temperature of the sintering furnace to be used for degreasing.

In the sintering step S5, the resin contained in the binder is removed to sinter the metal powder. For example, in the case of using a Ni-based alloy IN718 [IN: [Inconel] (registered trademark: Special Metals Corporation)] as the metal powder, it is preferred to carry out sintering in a non-oxidizing atmosphere exceeding 1200 °C. Regarding the metal product 1 after sintering, as the post-treatment, the density can be measured in order to confirm the progress of the sintering, or the press processing can be performed for fine-tuning the size, or the electric discharge machining can be performed for the end surface treatment, or the surface roughness can be adjusted. The grinding or grinding treatment can be carried out.

The rib 11c (see FIGS. 2(a), 3(a), and 3(b)) will be described. As shown in Fig. 5 (a), a rib portion 11c is provided on the back surface of the outer tape body 11 (belt portion). The extending direction Lr of the rib 11c is intersected with the chord line Lc of the stator blade 13. The angle of the rib 11c is θ (>0: angular size) with respect to the extending direction Le of the outer tape 11 (in the case of the vertical direction of FIG. 5(a)), and the metal powder is emitted from the outer body 11 of the molded body 2. When the width is set to A and the height is set to B, the dimensional stability S (dB: decibel) of the metal powder injection molded body 2 (metal product 1) can be S = 10. Log ₁₀ (B/A) to find out.

The metal powder injection molded body 2 in which the angle θ of the rib 11c is 0°, 6°, and 12° is formed, and the shape of the outer belt 11 after sintering is three-dimensionally measured, and the desired metal powder is uniformly shrunk. The shape of the molded body 2 (metal product 1) was compared. The comparison results are shown in Figure 5(b). When the stability S is high, the difference in size from the metal powder injection molded body 2 after uniform shrinkage is small. On the other hand, when the stability S is low, the difference in size from the metal powder injection molded body 2 after the uniform shrinkage is large.

As shown in Fig. 5(b), the stability S of θ = 6° or 12° is higher than in the case of θ =0°. Therefore, it is preferable to increase the above-described angle θ of the rib 11c (that is, to increase the crossing angle with respect to the blade string Lc). However, even when θ =0°, the condition of the size, shape, weight, and the like of the metal powder injection molded body 2 may be a high degree of stability S in which the shape accuracy of the metal product 1 can be maintained. Therefore, the case where the above angle θ = 0° is not excluded.

Further, if the angle θ of the rib 11c is excessively large, the weight of the rib 11c itself may promote deformation at the time of sintering. Therefore, it is preferable to set an upper limit for the above angle θ. In view of this, the upper limit of the above-described angle θ is preferably the stagger angle λ (>0: angular size) of the stator blade 13. As shown in Fig. 5(a), the "staggered angle λ" is an angle of the blade string Lc with respect to the turbine axis direction La (in the case of Fig. 5(a), which is parallel to the extending direction Le). Specifically, the upper limit of the angle θ is preferably a value within a range of 6° to 12° based on the above test results. However, the upper limit of the angle θ is not limited to the numerical value (range), and each of the metal powder injection molded bodies 2 can be set in accordance with the weight of the rib 11c itself.

That is, the angle θ between the extending direction Le of the outer tape body 11 and the extending direction Lr of the rib portion 11c is preferably larger than 0° and equal to or less than the stagger angle λ . In particular, if only the deformation caused by the contraction is considered, the angle θ is preferably set to be the same as the size of the stagger angle λ . Here, since the stagger angle λ of the stator blade 13 is constant to some extent, it is preferably 0° < θ ≦ 12°. Further, the direction of the angle θ from the extending direction Le of the outer belt body 11 to the extending direction Lr of the rib portion 11c is opposite to the direction of the stagger angle λ from the turbine axis direction La toward the blade string line Lc.

In the modification shown in FIG. 6, the end surface of the metal powder injection molded body 2 is inclined with respect to the turbine axis direction La. As shown in Fig. 6, the rib 11c may be formed to have such a tilt in accordance with the stagger angle λ of the stator blade 13. In the present modification, the extending direction Le of the outer band 11 and the turbine axis direction La are not parallel. In the case shown in Fig. 6, the difference between the overhanging portions OH1 and OH2 of the outer tape body 11 with respect to the rib portion 11c can be reduced, and the deformation caused by the strain at the time of shrinkage of the metal powder injection molded body 2 (metal product 1) can be effectively suppressed. .

Next, the gap g (see FIG. 4(a)) of the joint portion 3 will be described. As shown in Fig. 7 (a), two metal powder injection molding sheets 6 are prepared, and one of the metal powder injection molding sheets 6 is used. The spacer 7 causes the other metal powder injection molding plate 6 to be inclined, and a gap is formed between the two metal powder injection molding plates 6. The gap size can be adjusted by changing the horizontal position of the spacer 7. After the application of the coating agent 4 to the gap, the metal powder is injected into the molding plate 6 to perform degreasing and sintering, and the gap C when the two metal powders are injected into the molding plate 6 at a sufficient strength is measured. The gap C capable of achieving sufficient joint strength was 0.1 mm. Therefore, the gap g of the joint portion 3 is preferably 0.1 mm or less.

Further, the gap C can be changed in accordance with the metal powder, the binder, and the like which are the raw materials of the metal powder injection molding plate 6. That is, the gap g of the joint portion 3 is not necessarily limited to 0.1 mm or less, and empirically preferably 0.1 mm to 0.5 mm or less.

According to the bonding method of the present embodiment, since the coating agent 4 contains nitrogen (N) or chlorine (Cl), the decomposition rate of the coating agent 4 can be made slow. Therefore, at the time of degreasing or sintering, the adhesion state of the metal powder injection molded body 2 can be maintained for a longer period of time, and the joint strength of the joint portion 3 can be improved.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit and scope of the invention. For example, the inner band body 12 may be formed with a rib. Further, the rib 11c is provided to improve the shape accuracy of the metal product 1 (metal powder injection molded body 2) at the time of degreasing or sintering, and may be subjected to cutting before the stator blade unit is completed (even if the rib 11c is cut) The angle θ of the rib 11c can also be determined based on the cutting marks. Further, the ribs 11c may be provided in plural in one metal powder injection molded body 2.

Claims (8)

A joining method of a metal powder injection molded body, wherein at least two metal powder injection molding bodies obtained by injection molding after kneading the metal powder and the binder are mutually abutted, and the at least two metal powder injection molding bodies are offset a coating agent containing nitrogen or chlorine is applied to the joint portion, and the at least two metal powder injection molded bodies coated with the coating agent at the joint portion are degreased or sintered, and the at least two metal powders are injected into the molded body. The joint portion is joined to produce a metal product. The bonding method of the metal powder injection molded body according to claim 1, wherein the bonding agent contains a wax which volatilizes in a predetermined temperature range, and which scatters in a temperature range higher than the predetermined temperature range. The resin, at least a part of the coating agent, is more slowly volatilized than the wax and diffuses faster than the resin when the at least two metal powder injection molded articles are subjected to degreasing or sintering. The bonding method of the metal powder injection molded body according to the first or second aspect of the invention, wherein the coating agent is applied to a contact surface or a circumferential side surface of the joint portion. The joining method of the metal powder injection molded body according to the first or second aspect of the invention, wherein the at least two metal powder injection molded bodies are degreased while maintaining a gap of the joint portion of 0.1 mm or less. Or sintered. The joining method of the metal powder injection molded body according to the first or second aspect of the invention, wherein the metal product is a blade sector including a plurality of blades and a belt portion for supporting the plurality of blades, The at least two metal powder injection molded bodies are each a divided body of the aforementioned blade sectors having a single blade. The joining method of the metal powder injection molded body according to the fifth aspect of the invention, wherein the back surface of the side of the belt body on which the vane is vertically formed is formed to intersect the blade string of the vane. Ribs extending in the direction. The joining method of the metal powder injection molded body according to the sixth aspect of the invention, wherein the angle formed by the extending direction of the belt body portion and the extending direction of the rib portion in the divided body is θ , The angle θ is greater than 0° and is below the stagger angle of the aforementioned blade. The joining method of the metal powder injection molded body according to the sixth aspect of the invention, wherein the angle between the extending direction of the belt body portion and the extending direction of the rib portion in the divided body is θ , 0° < θ ≦ 12 °.