JP5223570B2 - Manufacturing method of composite sintered body, composite sintered body, and fuel injection valve - Google Patents

Description

  The present invention relates to a method for manufacturing a composite sintered body, a composite sintered body, and a fuel injection valve.

When producing a metal product by sintering a compact containing a metal powder, for example, as a method for producing the compact, for example, a metal powder and an organic binder are mixed and kneaded, and the metal powder is injection molded using the kneaded product. An injection molding (MIM: Metal Injection Molding) method is known.
The molded body manufactured by the MIM method is subjected to degreasing treatment (debinder treatment) and the organic binder is removed, and then subjected to sintering. As a result, a target metal product (sintered body) is obtained. can get.

  By the way, by using two kinds of metal powders having different compositions, it has been performed to obtain a composite sintered body composed of different kinds of metal materials for each part. For example, among the long sintered bodies, one side is composed of an austenitic stainless steel sintered body, and the other side is composed of a ferritic stainless steel sintered body. Various application examples are assumed as functional parts in which portions having different magnetic characteristics are adjacent to each other.

In Patent Document 1, a first member molded body and a second member molded body made of metal powders of different materials are temporarily attached, followed by primary firing, and then hot isostatic pressing (HIP). ) A method for obtaining a composite sintered body by performing a treatment is disclosed.
However, when the metal powder in the molded body of the first member and the metal powder in the molded body of the second member are different materials, thermal expansion occurs between the sintered body of the first member and the sintered body of the second member. The rate is different. This difference in coefficient of thermal expansion is mainly caused by the difference in the crystal structure of the metal material constituting each member. And this thermal expansion coefficient difference will surface as a deformation | transformation and a remarkable fall of dimensional accuracy in the composite sintered compact after a baking process, and had become a problem on utilization.
From the above, it has been difficult to produce a high-quality composite sintered body using two types of metal powders having different compositions and crystal structures.

JP 2001-355005 A

  An object of the present invention is to provide a method for producing a composite sintered body capable of efficiently producing a high-quality composite sintered body composed of different kinds of metal materials for each part by setting an atmosphere gas during sintering. Another object of the present invention is to provide a composite sintered body having high mechanical characteristics and high dimensional accuracy manufactured by the method for manufacturing such a sintered body, and a fuel injection valve including a component made of the composite sintered body.

The above object is achieved by the present invention described below.
The method for producing a composite sintered body according to the present invention includes a first composition comprising a first metal powder composed of a first metal material having a crystal structure of a Fe-based alloy having a face-centered cubic lattice and an organic binder. And a second composition comprising an organic binder and a second metal powder having a composition different from that of the first metal material and having a crystal structure made of a Fe-based alloy having a body-centered cubic lattice . And a molding process for obtaining a composite molded body of different metals,
Rukoto said composite compact was sintered in an atmospheric gas containing nitrogen atom, the crystal structure Yusuke a firing step to obtain a composite sintered body made of a metallic material consisting of Fe based alloy of face-centered cubic lattice, the It is characterized by.
Thereby, a high-quality composite sintered body composed of different types of metal materials for each part can be efficiently manufactured.

In the method for producing a composite sintered body according to the present invention, the atmospheric gas containing nitrogen atoms is preferably nitrogen gas or ammonia gas.
Thereby, the crystal structure of the Fe-based alloy can be reliably transferred to the face-centered cubic lattice. In addition, by firing the degreased body under a gas atmosphere containing nitrogen atoms, the surface of the obtained composite sintered body is subjected to the same treatment as the nitriding treatment, so the surface hardness is improved, A composite sintered body having excellent wear resistance can be obtained.

In the manufacturing method of the composite sintered compact of this invention, it is preferable that the baking conditions in the said baking process are the temperature of 1000-1500 degreeC x 0.2-7 hours.
Thereby, sintering of a defatted body can be optimized and the crystal structure can be prevented from being enlarged more than necessary. As a result, a composite sintered body having a finer crystal structure can be obtained.

In the method for producing a composite sintered body according to the present invention, the composite molded body is two-color formed by supplying the first composition and the second composition into the same mold and performing two-color molding. It is preferable that the molded body or an insert molded body formed by insert molding using a molded body of one of the first composition and the second composition as an insert work.
Thereby, while preventing the first composition and the second composition from mixing with each other, it is possible to easily produce a composite molded body in which they are adjacent to each other.

In the method for producing a composite sintered body of the present invention, the average particle size of the metal powder having the higher solidus temperature among the first metal powder and the second metal powder is low in the solidus temperature. It is preferable that the average particle size of the metal powder is smaller.
Since the surface energy of the particles increases as the average particle size decreases, the particles can be sintered at a temperature lower than the normal sintering temperature, and the sintering temperature of the first metal powder and the sintering of the second metal powder can be reduced. The crystallization temperature can be approached.

In the method for producing a composite sintered body of the present invention, the average particle diameter of the first metal powder and the average particle diameter of the second metal powder are preferably 1 to 30 μm, respectively.
Thereby, the surface energy of each particle becomes particularly large, and this surface energy is manifested as a driving force for sintering. As a result, even when different types of metal powders having different solidus temperatures are used, the sintering temperatures of the metal powders approach each other, so the first metal powder and the second metal powder The time difference of sintering can be further reduced. As a result, it is possible to more reliably prevent the occurrence of uneven sintering in the composite sintered body.

In the method for producing a composite sintered body according to the present invention, the organic binder content in the first composition and the second composition is preferably 2 to 20% by mass, respectively.
Accordingly, each composition has excellent fluidity and shape retention, and the content of the organic binder is not excessively increased, and the sintered density of the finally obtained composite sintered body can be increased. In addition, the dimensional accuracy of the composite sintered body can be increased.

In the method for producing a composite sintered body according to the present invention, the composite molded body is configured such that one of the first composition and the second composition includes or sandwiches the other composition. It is a molded product,
It is preferable that the composition located outside the composite molded body has a larger shrinkage rate in the firing step than the composition located inside.
Thereby, at the time of degreasing or baking, since the 2nd composition contracts more compared with the 1st composition, the 1st composition is compressed by the 2nd composition. . As a result, a gap is hardly generated between the first composition and the second composition after compression, and a higher-density composite sintered body is obtained.

In the method for producing a composite sintered body of the present invention, the molding step is preferably performed by a metal powder injection molding method.
This makes it possible to produce relatively compact and complex and detailed composite molded bodies with a near net (shape close to the final shape), eliminating or minimizing subsequent machining. be able to.

The composite sintered body of the present invention is manufactured by the method for manufacturing a sintered body of the present invention,
The sintered body of the first metal powder and the sintered body of the second metal powder are integrated.
As a result, the composite sintered body becomes dense as a whole, that is, has a low porosity and a high density, and has excellent mechanical properties as a whole.

In the composite sintered body of the present invention, it is preferable that the sintered body of the first metal powder and the sintered body of the second metal powder are joined based on mutual diffusion.
As a result, a composite sintered body particularly excellent in mechanical properties can be obtained.
In the composite sintered body of the present invention, the first metal powder before sintering is composed of a γ-Fe alloy, and the second metal powder before sintering is composed of an α-Fe alloy. And
The sintered body of the second metal powder preferably contains a γ solid solution containing the composition of the first metal powder and the component of the atmospheric gas in the firing step.
As a result, a composite sintered body having excellent mechanical properties and dimensional accuracy can be obtained.

In the fuel injection valve of the present invention, the first metal powder before sintering is made of a nonmagnetic material, and the second metal powder before sintering is made of a magnetic material,
Using these metal powders, an electromagnetic fuel injection valve provided with a tubular part manufactured by the method for manufacturing a composite sintered body of the present invention,
The tubular part is characterized in that a sintered body of magnetic material powder and a sintered body of nonmagnetic material powder are integrated.
As a result, the connection strength between the sintered body of the magnetic material powder and the sintered body of the non-magnetic material powder is high and the mechanical characteristics and dimensional accuracy are excellent without going through complicated steps such as welding and brazing. An electromagnetic fuel injection valve having a tubular part is obtained.

Hereinafter, a method for producing a composite sintered body, a composite sintered body, and a fuel injection valve of the present invention will be described in detail with reference to the accompanying drawings.
The method for producing a composite sintered body according to the present invention is a method for efficiently producing a high-quality composite sintered body composed of different kinds of metal materials for each part using a plurality of kinds of metal powders having different compositions and crystal structures. It is. Since the composite sintered body manufactured by such a method has partially different electromagnetic characteristics, thermal characteristics, mechanical characteristics, chemical characteristics, etc. It is suitably used as a functional component.

<First Embodiment>
First, 1st Embodiment of the manufacturing method of the composite sintered compact of this invention is described.
1 and 2 are diagrams for explaining a first embodiment of a method for producing a composite sintered body according to the present invention.
In the method for producing a composite sintered body according to the present embodiment, [1] a first kneaded product (first composition) 21 containing a first metal powder and an organic binder, and the first metal powder are: A composition preparation step of preparing a second kneaded product (second composition) 22 containing a second metal powder having a different composition and crystal structure and an organic binder, and [2A] a first kneaded product 21 A primary molding step for obtaining a primary molded body 3 by molding, and [2B] using the obtained primary molded body 3 as an insert work, the second kneaded product 22 is insert-molded to form a secondary molded body (composite molded body) 4. [3] degreasing the obtained secondary molded body 4 to obtain a degreased body 6, and [4] firing the obtained degreased body 6 in a predetermined atmosphere to obtain a composite And a firing step for obtaining the sintered body 1. Hereinafter, these steps will be described in detail.

[1] Composition Preparation Step First, a first metal powder and an organic binder are prepared and kneaded with a kneader to obtain a first kneaded product (first composition) 21.
In the first kneaded material (compound) 21, the first metal powder and the organic binder are uniformly dispersed.
A second metal powder and an organic binder are prepared and kneaded with a kneader to obtain a second kneaded product (second composition) 22.

The second metal powder is composed of a metal material (second metal material) having a composition and a crystal structure different from that of the metal material (first metal material) constituting the first metal powder. Therefore, by using such a first metal powder and a second metal powder, the composite sintered body 1 having a different material for each portion can be manufactured.
Also, in the second kneaded material (compound) 22, the second metal powder and the organic binder are uniformly dispersed.

These metal powders may be composed of any metal material, and the metal material is any one of Ti-based alloy, Fe-based alloy, Ni-based alloy, Co-based alloy and Cu-based alloy. Is preferred. With these metal material powders, a composite sintered body 1 having a high sintering density can be produced by powder metallurgy. For this reason, it is suitable as a metal powder for producing a composite sintered body.
In addition, since these metal materials have relatively close solidus temperatures, the timing at which the first metal powder is sintered and the second metal powder are sintered in the temperature rising process of the firing step described later. The timing is close and the diffusion phenomenon between them can be promoted. As a result, it is possible to obtain the composite sintered body 1 having more excellent mechanical characteristics.

Of these, Fe-based alloys are preferably used as the metal powder.
Examples of the Fe-based alloy include low carbon steel, carbon steel, die steel, high speed tool steel, Fe—Ni alloy, Fe—Ni—Co alloy, and the like.
As the Fe-based alloy, stainless steel is particularly preferably used. Since the stainless steel powder is excellent in sinterability, a sintered body produced using this powder is particularly excellent in mechanical characteristics and chemical characteristics.
Specific examples of the stainless steel include SUS304, SUS316, SUS317, SUS329, SUS410, SUS430, SUS440, SUS630, and the like.

The crystal structure of the metal material refers to the arrangement structure of metal atoms, and includes types such as a simple cubic lattice, a body-centered cubic lattice, a face-centered cubic lattice, and a hexagonal close-packed lattice. In general, the composition and crystal structure of a metal material are uniquely determined, but some metal materials have a plurality of crystal structures depending on the temperature range.
For example, as a metal material whose crystal structure is a body-centered cubic lattice, for example, in addition to simple substances such as Cr, α-Fe, Mo, β-Ti, V, etc., ferritic stainless steel such as SUS405, SUS410, SUS430, and SUS434. Examples include various alloys such as steel.

  In addition, examples of the metal material whose crystal structure is a face-centered cubic lattice include SUS301, SUS302, SUS303, SUS304, SUS305, SUS309, SUS310, and SUS316 in addition to simple substances such as Al, Co, Cu, γ-Fe, and Ni. , SUS317, SUS321, SUS347, SUS384, austenitic stainless steel, SUH31, SUH35, SUH36, SUH37, SUH38, SUH309, SUH310, SUH330, SUH660, SUH661, austenitic heat resistant steel, low carbon steel, permalloy, -Various alloys, such as a Cr-Mo type alloy, are mentioned.

Furthermore, examples of the metal material whose crystal structure is a hexagonal close-packed lattice include α-Ti and Zn.
Low carbon steel generally refers to carbon steel having a carbon content of about 0.02 to 0.3% by mass.
Moreover, as a permalloy, the iron nickel soft magnetic material etc. which are prescribed | regulated to JISC2531 etc. are mentioned, for example.

  On the other hand, examples of the organic binder include polyolefins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer, acrylic resins such as polymethyl methacrylate and polybutyl methacrylate, styrene resins such as polystyrene, polyvinyl chloride, and polyvinyl chloride. Various resins such as polyesters such as vinylidene, polyamide, polyethylene terephthalate, polybutylene terephthalate, polyether, polyvinyl alcohol, or copolymers thereof, various waxes, paraffin, higher fatty acids (eg stearic acid), higher alcohols, higher alcohols A fatty acid ester, a higher fatty acid amide, etc. are mentioned, Among these, it can use 1 type or in mixture of 2 or more types.

  In addition, the content of the organic binder is preferably about 2 to 20% by mass, and more preferably about 5 to 10% by mass, of each of the first kneaded product and the second kneaded product. When the content of the organic binder is within the above range, each kneaded product has excellent fluidity and shape retention, and the content of the organic binder is not excessively increased, and finally obtained composite sintered body. 1 sintering density can be increased. In addition, the dimensional accuracy of the composite sintered body 1 can be increased.

Further, a plasticizer may be added to each of the kneaded materials 21 and 22. Examples of the plasticizer include phthalic acid esters (eg, DOP, DEP, DBP), adipic acid esters, trimellitic acid esters, sebacic acid esters, and the like, and one or more of these are mixed. Can be used.
Furthermore, in addition to each metal powder, organic binder, and plasticizer, for example, various additives such as an antioxidant, a degreasing accelerator, and a surfactant are added to each kneaded product 21 and 22 as necessary. Can do.

The kneading conditions vary depending on various conditions such as the constituent material and particle size of each metal powder to be used, the composition of the organic binder, and the blending amount thereof. For example, kneading temperature: about 50 to 200 ° C., kneading time : About 15 to 210 minutes.
Moreover, each kneaded material 21 and 22 is pelletized (small lump) as needed. The particle size of the pellet is, for example, about 1 to 15 mm.

[2A] Primary Forming Step Next, the obtained first kneaded product 21 is formed into a predetermined shape to produce a primary formed body 3.
The production method (molding method) of the molded body is not particularly limited, and examples thereof include a metal powder injection molding (MIM) method, a compression molding (compact molding) method, and an extrusion molding method. The MIM method is preferred.
This MIM method can produce relatively compact and complex and fine shaped compacts with a near net (shape close to the final shape), making subsequent machining unnecessary or minimized. Has the advantage of being able to. For this reason, in applying this invention, the effect will be exhibited effectively.

Here, the case where the primary molded object 3 and the secondary molded object (composite molded object) 4 mentioned later are manufactured is demonstrated by taking MIM method as an example. Here, a case where a cylindrical (ring-shaped) primary molded body 3 and a secondary molded body 4 are manufactured will be described as an example.
First, as shown in FIG. 1 (a), a primary molding die 30 having a ring-shaped cavity 31 is used, and the first kneaded product 21 obtained in the above step is put into the cavity 31 by an injection molding machine. Injection molding. Thereby, the primary molded object 3 as shown in FIG.1 (b) is obtained. According to such injection molding, the primary molded body 3 having a complicated shape can be easily manufactured by selecting a molding die.

Moreover, the primary molded object 3 is a shape included by the secondary molded object 4 manufactured at the process mentioned later. That is, the primary molded body 3 is molded so as to be included in the second kneaded material 22 in a process described later (insert molding). As a result, the secondary molded body 4 includes the first kneaded material 21 with the second kneaded material 22.
Further, the shape and size of the manufactured primary molded body 3 is determined in consideration of the shrinkage of the primary molded body 3 due to the subsequent degreasing and sintering.
The molding conditions for injection molding vary depending on the constituent materials and particle size of the first metal powder to be used, the conditions of the composition of the organic binder and the blending amount thereof, and, for example, the material temperature is preferably About 80 to 200 ° C., and the injection pressure is preferably about ^{2 to} 30 MPa (20 to 300 kgf / cm ² ).

[2B] Secondary Molding Step Next, the obtained primary molded body 3 is placed in the cavity 41 of the secondary molding die 40. Here, as shown in FIG.1 (c), the primary molded object 3 is mounted in center vicinity of the longitudinal direction in the cavity 41 which makes | forms a long cylindrical shape.
Next, the second kneaded material 22 is injected into the space 42 other than the primary molded body 3 of the cavity 41 of the secondary molding die 40. As a result, the second kneaded product 22 spreads into the cavity 41 so as to cover (pinch) the primary molded body 3, and as shown in FIG. 1 (d), the secondary molded body containing the primary molded body 3. (Composite molded body of different metals) 4 is obtained. According to such an MIM method, since the second kneaded material 22 is pressed against the primary molded body 3 with a high pressure, the adhesion at these interfaces can be further enhanced. As a result, a composite sintered body 1 that is dense and excellent in mechanical properties is obtained.
Further, the shape and size of the manufactured secondary molded body 4 is also determined in consideration of the shrinkage of the secondary molded body 4 due to the subsequent degreasing and sintering.

The molding conditions for injection molding vary depending on the constituent material and particle size of the second metal powder to be used, the conditions of the composition of the organic binder and the blending amount thereof, and as an example, the material temperature is preferably About 80 to 200 ° C., and the injection pressure is preferably about ^{2 to} 30 MPa (20 to 300 kgf / cm ² ).
Further, the molding conditions in the secondary molding are preferably substantially the same as the molding conditions in the primary molding. Thereby, it is possible to prevent the primary molded body 3 placed in the cavity 41 from being deformed or altered due to the influence of heat or pressure during the secondary molding. That is, since the first kneaded material 21 and the second kneaded material 22 in the secondary molded body 4 go through substantially the same heat history, the secondary molded body 4 is degreased and degreased in the process described later. When firing, it is possible to make uniform the shrinkage rate, the degreasing rate, the sintering rate and the like in the entire secondary molded body 4. As a result, a composite sintered body 1 having a high sintering density and high dimensional accuracy is obtained.

  In the present embodiment, the second kneaded product 22 is injected so as to cover the primary molded body 3 (so as to be sandwiched), whereby the secondary molded body 4 is formed. In this case, it is preferable that the second kneaded material 22 positioned outside the secondary molded body 4 has a larger shrinkage rate in degreasing / firing described later than the first kneaded material 21 positioned inside. As a result, the second kneaded material 22 contracts more greatly than the first kneaded material 21 during the degreasing or firing, so that the first kneaded material 21 is compressed by the second kneaded material 22. Will be. As a result, it becomes difficult for a gap to be formed between the first kneaded material 21 and the second kneaded material 22 after compression, and a higher-density composite sintered body 1 can be obtained.

Thus, in order to provide a difference in shrinkage between the first kneaded product 21 and the second kneaded product 22, a difference may be provided in the organic binder content in each of the kneaded products 21 and 22.
Specifically, the content of the organic binder in the second kneaded material 22 may be made larger than the content of the organic binder in the first kneaded material 21. Thereby, the shrinkage rate of the second kneaded material 22 can be made larger than that of the first kneaded material 21.

[3] Degreasing step A degreasing treatment (debinding treatment) is performed on the secondary molded body 4 obtained in the above step to obtain a degreased body 6.
This degreasing treatment is performed, for example, in the atmosphere, an oxidizing gas such as oxygen, hydrogen, a reducing gas such as ammonia decomposition gas, an inert gas such as nitrogen, helium or argon, or one or more of these. Is performed by performing a heat treatment in an atmosphere containing a mixed gas containing or the like, or in a reduced-pressure atmosphere.
In this case, the conditions for the heat treatment are slightly different depending on the decomposition start temperature of the organic binder, etc., but are preferably about 100 to 750 ° C. for about 0.5 to 40 hours, more preferably about 150 to 600 ° C. It is about time.

Further, degreasing by such heat treatment may be performed in a plurality of steps (stages) for various purposes (for example, for shortening the degreasing time). Specifically, a method of degreasing the first half at a low temperature and a second half at a high temperature, a method of repeatedly performing a low temperature and a high temperature, and the like can be mentioned.
Further, the degreasing treatment may be performed by eluting a specific component in the organic binder or additive using a predetermined solvent (fluid such as liquid or gas).
In this way, the organic binder is removed, and the degreased body 6 is obtained.
Note that the organic binder may not be completely removed by the degreasing process. For example, a part of the organic binder may remain when the degreasing process is completed.

  In addition, the same kind of organic binder in the first kneaded product 21 and the organic binder in the second kneaded product 22 are preferably used. By using the same type of organic binder, the first kneaded product 21 and the second kneaded product 22 are softened or melted almost simultaneously in the degreasing step, and the organic binder in each kneaded product 21 and 22 is decomposed and decomposed. Degreased. As a result, the degreasing time lag is eliminated between the first kneaded product 21 and the second kneaded product 22, so that the decomposition product of the organic binder is efficiently removed from the secondary molded body 4. As a result, the entire secondary molded body 4 can be uniformly degreased.

[4] Firing step The degreased body 6 obtained in the above step is fired in a firing furnace (see FIG. 2 (e)). Thereby, the degreased body 6 is sintered, and the composite sintered body 1 shown in FIG.
By this sintering, diffusion at the interface occurs between the particles of the first metal powder and between the particles of the second metal powder, and the grains grow to form a crystal structure. Thereby, the composite sintered body 1 in which the sintered body portions 12 of the two second metal powders are integrated via the sintered body portion 11 of the first metal powder is obtained. Such a composite sintered body 1 is dense as a whole, that is, has a low porosity and a high density, and as a whole has excellent mechanical properties.

The firing temperature in this step varies depending on various conditions such as the constituent material and particle size of each metal powder used. For example, as the first metal powder and the second metal powder, the Ti-based alloy and Fe-based alloy described above, respectively, When a metal powder composed of any one of Ni-based alloy, Co-based alloy and Cu-based alloy is used, it is preferably about 1000 to 1500 ° C, more preferably about 1050 to 1400 ° C. Thereby, sintering of the degreased body 6 can be optimized, and the crystal structure can be prevented from being enlarged more than necessary. As a result, a composite sintered body 1 having a finer crystal structure can be obtained.
Moreover, especially when stainless steel powder is used as the first metal powder and the second metal powder, the firing temperature in this step is preferably about 1000 to 1400 ° C, more preferably about 1050 to 1350 ° C. Is done.

Further, the firing time is preferably about 0.2 to 7 hours, more preferably about 1 to 4 hours, when the firing temperature is within the above range. By performing firing for such a time at a firing temperature in the above temperature range, sintering of the degreased body 6 can be more reliably optimized and sintered while reliably preventing an increase in crystal structure. As a result, the composite sintered body 1 having excellent mechanical properties can be obtained.
The degree of sintering of the degreased body 6 can be slightly adjusted by increasing or decreasing the thermal energy applied to the degreased body 6 by changing the firing time within the above range.

As described above, the composite sintered body 1 in which the sintered body portion 11 of the first metal powder and the sintered body portion 12 of the second metal powder are integrated is obtained.
By the way, conventionally, a method of manufacturing a composite sintered body using two kinds of metal powders having different compositions and crystal structures has been known. However, if the crystal structure is different between the two types of metal powders, even if a composite sintered body is obtained, the difference in thermal expansion coefficient due to the difference in crystal structure may cause deformation and dimensional accuracy of the composite sintered body. As a result, the surface was reduced and the utilization of the composite sintered body was hindered.

Therefore, the present inventor has studied a method for producing a composite sintered body having a sufficient sintering density by a normal firing method using two types of metal powders having different crystal structures. In order to obtain a composite sintered body of dissimilar metals using dissimilar metal powders, a special method is used if firing conditions are set so that the crystal structures of the two types of metal materials are the same during sintering. The present inventors have found that a composite sintered body can be easily produced without any problems, and have completed the present invention.
Specifically, even if the two types of metal powders used have different crystal structures, the firing atmosphere is such that the crystal structure of one metal powder is transferred to the crystal structure of the other metal powder during sintering. By setting the gas, sintering in the secondary molded body 4 is promoted. As a result, it is possible to obtain a composite sintered body 1 that is dense and excellent in mechanical properties.

The composite sintered body 1 thus obtained has the same crystal structure of the sintered body portion 11 of the first metal powder and the sintered body portion 12 of the second metal powder. Thus, the thermal expansion coefficient can be reduced, and deformation of the composite sintered body 1 and reduction in dimensional accuracy can be prevented.
One of the reasons why the above phenomenon occurs is that atoms constituting the atmospheric gas enter the crystal structure of the metal powder, thereby changing the crystal structure and generating a solid solution of another crystal structure. Can be mentioned. Therefore, it is necessary to appropriately select the gas species that can form the metal powder and the solid solution in consideration of the crystal structure near the sintering temperature of the solid solution.

  Specifically, for example, an Fe-based alloy powder whose crystal structure is a face-centered cubic lattice, such as the austenitic stainless steel, austenitic heat-resisting steel, low-carbon steel, etc. described above, is used as the first metal powder. When the Fe-based alloy powder whose crystal structure is the body-centered cubic lattice such as the ferritic stainless steel described above is used as the powder, the body-centered cubic lattice of the second metal powder is changed to the face-centered cubic lattice during sintering. What is necessary is just to set atmospheric gas to do. In this case, nitrogen gas or ammonia gas is preferably used as the atmospheric gas. By using such a gas, atoms in the atmosphere gas enter the body-centered cubic lattice, and another crystal structure, that is, a γ solid solution (interstitial solid solution) having a face-centered cubic lattice is generated. As a result, the crystal structure of the first metal powder in the first kneaded material 21 and the crystal structure of the second metal powder in the second kneaded material 22 are aligned in a face-centered cubic lattice, respectively. Thus, the composite sintered body 1 is excellent in mechanical characteristics and dimensional accuracy.

  As described above, the crystal structure of the metal material includes simple cubic lattice, body-centered cubic lattice, face-centered cubic lattice, hexagonal close-packed lattice, and the like. When setting the atmosphere gas so as to align with the structure, it is preferable to be a close-packed lattice such as a face-centered cubic lattice or a hexagonal close-packed lattice, and more preferably a face-centered cubic lattice. . Close-packed lattice metal materials such as face-centered cubic lattice are excellent in mechanical properties such as hardness, so if you set the atmosphere gas as described above, you finally get a sintered body with excellent mechanical properties be able to. Further, there is a background that transition from the body-centered cubic lattice to the face-centered cubic lattice is likely to occur due to the high flexibility and low filling property of the body-centered cubic lattice.

As described above, a solid solution having another crystal structure is generated by incorporating atoms in the atmospheric gas. Examples of elements that promote the transition of the crystal structure include boron, carbon, and nitrogen.
Among the gases containing these elements, suitable as the atmosphere gas during sintering include the nitrogen gas as described above, a gas containing nitrogen atoms such as ammonia gas, carbon monoxide gas, and methane gas. Or a gas containing a boron atom such as diborane. These are all gases that can generate interstitial solid solutions, and can be said to be gases that can promote the transition of the crystal structure based on the atomic radius. Moreover, these gases suppress the oxidation and modification | denaturation of a metal powder at the time of sintering, and make it possible to obtain the high quality composite sintered compact 1. FIG.
Note that whether or not an interstitial solid solution with a crystal structure transition as described above is generated can be grasped from a state diagram of an alloy of a metal material and a component included in an atmospheric gas.

As an example of such a phase diagram, FIG. 3 shows a phase diagram of an Fe—N alloy.
According to this phase diagram, it is recognized that a γ phase is generated in the composite sintered body 1 when the nitrogen atom content is about 1 to 3% by mass at the sintering temperature. Therefore, for example, when a ferritic stainless steel powder is used as the second metal powder as described above, a calcination process is performed in a nitrogen gas atmosphere, so that nitrogen atoms enter the degreased body 6 to generate a γ phase. To do. As a result, when an austenitic stainless steel powder is used as the first metal powder, the crystal structure of the second metal powder can be transferred to a face-centered cubic lattice in accordance with the crystal structure of the first metal powder.

The crystal structure of the composite sintered body 1 thus obtained and the crystal structure of each metal powder before sintering are respectively X-ray diffraction (XRD), reflection high-energy electron diffraction (RHEED), and low-energy electron diffraction ( It can be identified by various crystal structure analysis such as (LEED).
In addition, it is preferable that all of the crystal structure of the second metal powder is transferred to the same crystal structure as that of the first metal powder at the time of sintering. The effects and effects are as follows. In this case, the composite sintered body 1 preferably contains 50% by mass or more of the crystal structure after the transition of the second metal powder.

  The average particle size of the first metal powder and the average particle size of the second metal powder are each preferably 1 to 30 μm, more preferably 1 to 10 μm, and more preferably 1 to 6 μm. Further preferred. By setting the particle size of the metal powder to such a relatively small particle size, the surface energy of each particle becomes particularly large, and this surface energy is manifested as a driving force for sintering. As a result, even when different types of metal powders having different solidus temperatures are used, the sintering temperatures of the metal powders approach each other, so the first metal powder and the second metal powder The time difference of sintering can be further reduced. As a result, the occurrence of uneven sintering in the composite sintered body 1 can be more reliably prevented.

  When the average particle diameter of the first metal powder and the average particle diameter of the second metal powder are below the lower limit values, the surface energy of the particles of each metal powder becomes too large, There is a possibility that fluidity and filling property may be lowered. For this reason, the fluidity of the first kneaded material 21 and the second kneaded material 22 is lowered, and the cavity filling property at the time of molding may be lowered. On the other hand, when the average particle size of the first metal powder and the average particle size of the second metal powder exceed the upper limit values, the sintering temperatures of the metal powders may not be brought close enough. .

Of the first metal powder and the second metal powder, the metal powder having the higher solidus temperature has an average particle size smaller than the average particle size of the metal powder having the lower solidus temperature. It is preferable. If the average particle size is reduced, the metal material is activated and can be sintered at a temperature lower than the normal sintering temperature. Thus, the sintering temperature of the first metal powder and the sintering temperature of the second metal powder Can be further approached.
In addition, the first metal powder and the second metal powder used in the present invention can be produced by any method, for example, an atomizing method (for example, a water atomizing method, a gas atomizing method, etc.), Those produced by a reduction method, a carbonyl method, or a pulverization method can be used.

  Among these, those produced by the water atomizing method (including the high-speed rotating water stream atomizing method) can be preferably used. In the water atomization method, a fine metal powder can be efficiently produced by colliding a high-pressure water jet against a molten metal. The water jet used in this method has a larger specific gravity of the cooling medium and higher collision energy than the gas jet used in the gas atomization method, so that the molten metal can be more finely divided. In addition, a metal powder having a narrow particle size distribution and a uniform particle size can be produced.

  Moreover, many particles of the molten metal divided by the water atomizing method contain many different shapes as compared with the gas atomizing method. For this reason, each particle has a larger specific surface area than spherical particles. As a result, in the metal powder produced by the water atomization method, the surface energy of each particle is particularly large, and the sintering temperature of the first metal powder and the sintering temperature of the second metal powder as described above are close to each other. Becomes more prominent. That is, the metal powder obtained by the water atomization method is particularly suitable as the first metal powder and the second metal powder used in the present invention.

  Since the composite sintered body 1 manufactured as described above has a uniform crystal structure, it contains few structural defects and has excellent mechanical properties. In particular, when a metal powder having a particle size as described above is used, the particle size of the crystal structure becomes minute, and the mechanical characteristics are further improved. That is, when the crystal structure becomes minute, the main fracture mechanism of the composite sintered body 1 changes from the fracture inside the crystal structure to the fracture at the crystal grain boundary. Since the critical stress leading to generation of the composite sintered body 1 is particularly excellent in mechanical properties.

The mechanical properties of such a composite sintered body 1 vary depending on the composition of the metal powder used. For example, when the first metal powder and the second metal powder are stainless steel, respectively, JIS Z 2241 The specified tensile strength is as high as 500 MPa or more. The composite sintered body 1 having such tensile strength can be sufficiently used as various mechanical components.
Further, the composite sintered body 1 has a low surface roughness when the fine metal powder having a particle diameter as described above is used. Specifically, the composite sintered body 1 having a surface roughness Ra specified in JIS Z 0601 of 0.8 μm or less is obtained. It can be said that the composite sintered body 1 having such a surface roughness Ra has sufficiently high smoothness.
Further, when the degreased body is fired in a nitrogen gas atmosphere, the surface of the obtained composite sintered body 1 is subjected to a treatment equivalent to the nitriding treatment. For this reason, the surface hardness improves and the composite sintered compact 1 excellent in abrasion resistance is obtained.

  As described above, the composite sintered body 1 manufactured as described above is formed by integrating sintered bodies of dissimilar metals, so that it has excellent mechanical characteristics and is partially The electromagnetic characteristics, thermal characteristics, mechanical characteristics, chemical characteristics, etc. are different. Therefore, the composite sintered body 1 can be suitably used as various functional parts by utilizing such a difference in characteristics.

For example, functional parts having partially different magnetism, functional parts having partially different hardness, functional parts having partially different corrosion resistance, functional parts having partially different wear resistance, and the like can be manufactured.
In the present embodiment, the method of obtaining the composite molded body 4 by the insert molding method has been described. However, the insert molding prevents the first kneaded material 21 and the second kneaded material 22 from being mixed. However, it is possible to easily produce a composite molded body (insert molded body) 4 in which these are adjacent.

Second Embodiment
Next, 2nd Embodiment of the manufacturing method of the composite sintered compact of this invention is described.
4 and 5 are diagrams for explaining a second embodiment of the method for producing a composite sintered body of the present invention.
Hereinafter, although the second embodiment will be described, the description will focus on the differences from the first embodiment, and the description of the same matters will be omitted.

The manufacturing method of the composite sintered body according to the present embodiment is the same as that of the first embodiment except that the first kneaded material and the second kneaded material are two-color molded instead of insert molding. It is.
That is, the method for producing a composite sintered body according to the present embodiment includes: [1] a first kneaded product (first composition) 21 containing a first metal powder and an organic binder, and a first metal powder. Preparing a second kneaded product (second composition) 22 containing a second metal powder and an organic binder different from each other; [2] a first kneaded product 21 and a second kneaded product 21; The kneaded product 22 is two-color molded to obtain a two-color molded body 5, [3] a degreased step of degreasing the obtained two-color molded body 5 to obtain a degreased body 6, and [4] obtained. The obtained degreased body 6 is fired to obtain a composite sintered body 1. Hereinafter, these steps will be described in detail.

[1] Composition Preparation Step First, in the same manner as in the first embodiment, a first kneaded product (first composition) 21 and a second kneaded product (second composition) 22 are obtained.
[2] Molding Step Next, the first kneaded material 21 and the second kneaded material 22 are two-color molded.
The molding method is not particularly limited, and a metal powder injection molding (MIM) method, a compression (press) molding method, an extrusion molding method, and the like are used as in the first embodiment, and the MIM method is particularly preferably used. It is done.
Here, first, as shown in FIG. 4A, the space on the right side of the cavity 51 of the two-color molding machine 50 is closed with a pin 52. And the 1st kneaded material 21 is filled into the space of the left side of the cavity 51 produced by this. Next, as shown in FIG. 4B, the pin 52 is pulled out from the cavity 51, and the second kneaded material 22 is filled into the space on the right side of the cavity 51 generated thereby.
As a result, as shown in FIG. 4C, a two-color molded body (composite molded body of different metals) 5 obtained by two-color molding of the first kneaded material 21 and the second kneaded material 22 is obtained. .
In the present embodiment, the case where the two-color molding machine 50 capable of injecting two types of kneaded materials 21 and 22 into the same cavity 51 has been described. However, three or more types of kneaded materials are stored in the same cavity. Alternatively, a multicolor molding machine capable of injecting may be used.

[3] Degreasing step The two-color molded body 5 obtained in the above step is subjected to a degreasing process (debinding process) in the same manner as in the first embodiment to obtain a degreased body 6 '.
[4] Firing Step The degreased body 6 ′ obtained in the above step is fired in a firing furnace in the same manner as in the first embodiment (see FIG. 5D). As a result, the degreased body 6 ′ is sintered, and a composite sintered body 1 ′ shown in FIG. 5 (e) is obtained.
A composite sintered body 1 ′ produced by this sintering is obtained by integrating a sintered body portion 11 ′ of a first metal powder of a different metal and a sintered body portion 12 ′ of a second metal powder. Therefore, in addition to being excellent in mechanical characteristics, the electromagnetic characteristics, thermal characteristics, mechanical characteristics, chemical characteristics, etc. are partially different. Therefore, by utilizing such a difference in characteristics, it can be suitably used as various functional parts of the composite sintered body 1.
In addition, since the crystal structure of the sintered body portion 11 ′ of the first metal powder and the crystal structure of the sintered body portion 12 ′ of the second metal powder are the same, the thermal expansion coefficient of both approaches and the composite firing It is possible to prevent deformation of the bonded body 1 ′ and decrease in dimensional accuracy.

In the second embodiment as described above, the same operation and effect as in the first embodiment can be obtained.
Further, according to the two-color molding, the first kneaded material 21 and the second kneaded material 22 are prevented from being mixed with each other, and a composite molded body (two-color molded body) adjacent to each other is easily produced. be able to.

<Fuel injection valve>
Next, the fuel injection valve provided with the components comprised by the composite sintered compact of this invention is demonstrated.
6 is a longitudinal sectional view showing an embodiment of the fuel injection valve of the present invention, and FIG. 7 is a partially enlarged view of the fuel injection valve shown in FIG. In the following description, the upper side in FIGS. 6 and 7 is referred to as “upper” and the lower side is referred to as “lower”.

An electromagnetic fuel injection valve 100 shown in FIG. 6 is an injection valve that injects fuel into a combustion chamber of a vehicle engine or the like, and has a composite magnetic pipe 120 (tubular component). The fuel flows through the composite magnetic pipe 120 from above to below.
The composite magnetic pipe 120 is divided into three regions, ie, a fuel connector part 121, a nonmagnetic part 122, and a valve accommodating part 123 from above.

The upper part of the composite magnetic pipe 120 is a fuel connector part 121 connected to a fuel pipe (not shown), and an O-ring 124 is attached to the outer periphery thereof. In addition, a fuel filter 125 that filters fuel sent from the fuel pipe is mounted inside the fuel connector portion 121.
An intermediate portion of the composite magnetic pipe 120 is a nonmagnetic nonmagnetic portion 122, and a ring-shaped coil 139 is provided so as to cover the outer periphery thereof. Further, a connector housing 143 is provided adjacent to the coil 139, and the winding of the coil 139 is connected to a terminal 144 that protrudes inside the connector housing 143. As a result, the coil 139 can be energized via the terminal 144. The coil 139 is covered with a magnetic housing 145.
A lower portion of the composite magnetic pipe 120 is a valve housing portion 123 that accommodates a fuel injection valve, and an O-ring 136 that seals a connection portion with an intake manifold (not shown) is attached to the outer periphery thereof.

  A bottomed cylindrical sheet holder 131 is provided so as to cover the outer periphery of the lower end portion of the composite magnetic pipe 120 and to extend downward. A valve seat 132 is fixed to the inner bottom portion of the seat holder 131, and an injection port 133 is formed in the valve seat 132. The fuel supplied to the inside of the composite magnetic pipe 120 is injected into the fuel chamber through the injection port 133.

A cylindrical fixed iron core 126 is fixed below the fuel filter 125 inside the composite magnetic pipe 120, and the lower end of the fixed iron core 126 extends to the vicinity of the nonmagnetic part 122 of the intermediate part of the composite magnetic pipe 120. .
A cylindrical adjuster 128 is provided inside the fixed iron core 126, and a spring 129 is provided below the adjuster 128. Inside the adjuster 128 and the spring 129 is a flow path through which the fuel filtered by the fuel filter 125 passes.

  A hollow movable iron core 138 is provided below the fixed iron core 126 inside the composite magnetic pipe 120, and the lower end surface of the spring 129 is in contact with the upper end surface inside the movable iron core 138. The movable iron core 138 is biased downward by the spring 129. Further, the lower end surface of the fixed iron core 126 and the upper end surface of the movable iron core 138 are opposed to each other with a slight gap as shown in FIG.

  A rod-shaped needle valve 130 is provided below the movable iron core 138, and the upper end portion of the needle valve 130 is fixed to the inner periphery of the movable iron core 138. On the other hand, the lower end of the needle valve 130 is located near the injection port 133. The needle valve 130 is movable up and down, and when the needle valve 130 is at the lower limit position of the movement width, the needle port 130 is closed to stop fuel injection. On the other hand, when the needle valve 130 is at a position other than the lower limit position, the injection port 133 is opened and fuel is injected from the injection port 133.

Next, the operation of the electromagnetic fuel injection valve 100 will be described.
In the electromagnetic fuel injection valve 100, when no current flows through the coil 139, the movable iron core 138 is biased downward by the spring 129, and the needle valve 130 fixed to the movable iron core 138 also moves downward. As a result, the lower end portion of the needle valve 130 closes the injection port 133 (closed state).

  When the coil 139 is energized after this closed state, a magnetic flux is generated around the coil 139, and the magnetic flux flows through a magnetic path surrounding the coil 139. The magnetic path is configured by a path that sequentially passes through the magnetic housing 145, the fuel connector portion 121, the fixed iron core 126, the movable iron core 138, the valve housing portion 123, and the magnetic housing 145. When a magnetic flux flows in such a magnetic path, a magnetic attractive force is generated between the fixed iron core 126 and the movable iron core 138, the movable iron core 138 is attracted upward, and the needle valve 130 also moves upward. As a result, the lower end portion of the needle valve 130 is separated from the injection port 133 (open state).

Incidentally, the composite magnetic pipe 120 included in the electromagnetic fuel injection valve 100 (the fuel injection valve of the present invention) is composed of the composite sintered body of the present invention.
That is, as described above, the composite magnetic pipe 120 is divided into three regions: the fuel connector portion 121, the nonmagnetic portion 122, and the valve housing portion 123. Of these, the fuel connector portion 121 and the valve housing portion 123 are magnetic. The non-magnetic portion 122 is made of a non-magnetic material different from the magnetic material, while being made of a material (for example, ferritic stainless steel such as SUS430).

As described above, the nonmagnetic portion 122 made of a nonmagnetic material is provided between the fuel connector portion 121 made of a magnetic material and the valve housing portion 123, so that the composite magnetic pipe 120 is likely to be formed. The magnetic path is interrupted at the nonmagnetic portion 122.
When the magnetic path is interrupted at the nonmagnetic portion 122, the magnetic flux flows preferentially between the fixed iron core 126 and the movable iron core 138. As a result, a magnetic attractive force can be reliably generated between the fixed iron core 126 and the movable iron core 138.

Further, the composite magnetic pipe 120 is constituted by the composite sintered body of the present invention, so that the above-described three regions are integrally connected. As a result, compared to the case where the three regions are connected by a method such as welding or brazing, the composite magnetism has high connection strength and excellent mechanical properties and dimensional accuracy without going through complicated steps such as welding. The pipe 120 can be manufactured efficiently.
In addition, such a composite magnetic pipe 120 is formed by collectively forming three regions by using a molding method such as insert molding or two-color molding, so that there is no positional deviation between the regions and dimensional accuracy is improved. A high composite magnetic pipe 120 is obtained. Therefore, it is not necessary to perform machining or the like for increasing the dimensional accuracy, and the cost of parts can be reduced.

  Furthermore, the composite magnetic pipe 120 composed of the composite sintered body of the present invention has a high surface hardness and excellent wear resistance by selecting an atmosphere gas during sintering. Here, when the movable iron core 138 moves in the electromagnetic fuel injection valve 100, the inner peripheral surface of the composite magnetic pipe 120 and the outer peripheral surface of the movable iron core 138 slide. Since the composite magnetic pipe 120 composed of the composite sintered body of the present invention has high dimensional accuracy and does not require post-processing, the surface having high hardness can be used as it is. However, it is highly durable.

As mentioned above, although the manufacturing method of the composite sintered compact of this invention, the composite sintered compact, and the fuel injection valve were demonstrated based on suitable embodiment, this invention is not limited to this.
For example, in the method for producing a composite sintered body, an arbitrary step can be added as necessary.

1. Production of composite sintered body (Example 1)
<1> First, a mixture of stainless steel SUS304L powder (PF-3F, manufactured by Epson Atmix Co., Ltd.) having an average particle size of 2.9 μm and a specific surface area of 650 m ² / kg, manufactured by a water atomization method, and polypropylene and wax. (Organic binder) was weighed to a mass ratio of 91: 9 to obtain a mixed raw material. Note that SUS304L is austenitic stainless steel, and the unit cell of the crystal structure is a face-centered cubic lattice.

<2> Next, this mixed raw material was kneaded with a kneader to obtain a compound (first kneaded product).
<3> Next, this compound was injection molded with the injection molding machine for primary molding shown in FIG. 1 under the molding conditions shown below to produce a primary molded body. In addition, the obtained primary molded object was a ring shape of outer diameter 7mm x thickness 3mm.
<Molding conditions>
-Material temperature: 150 ° C
Injection pressure: 11 MPa (110 kgf / cm ² )

<4> Next, stainless steel SUS430L powder (manufactured by Epson Atmix Co., PF-2F) having an average particle size of 2.3 μm and a specific surface area of 820 m ² / kg, manufactured by a water atomization method, and polypropylene and wax The mixture (organic binder) was weighed so as to have a mass ratio of 90:10 to obtain a mixed raw material. Note that SUS430L is ferritic stainless steel, and the unit lattice of the crystal structure is a body-centered cubic lattice.

<5> Next, this mixed raw material was kneaded with a kneader to obtain a compound (second kneaded product).
<6> Next, using the obtained primary molded body as an insert work, this compound was insert-molded with the injection molding machine for secondary molding shown in FIG. (Composite molded body) was produced. In addition, the obtained secondary molded body was a cylindrical shape having an outer diameter of 7 mm and a length of 30 mm.
<Molding conditions>
-Material temperature: 150 ° C
Injection pressure: 11 MPa (110 kgf / cm ² )

<7> Next, the obtained secondary molded body was subjected to heat treatment (degreasing treatment) under the following degreasing conditions to obtain a degreased body.
<Degreasing conditions>
-Heating temperature: 500 ° C
・ Heating time: 2 hours ・ Heating atmosphere: Nitrogen gas

<8> Next, the obtained degreased body was fired under the firing conditions shown below. Thereby, a composite sintered body was obtained.
<Baking conditions>
・ Baking temperature: 1200 ℃
-Firing time: 3 hours-Firing atmosphere: nitrogen gas-Firing furnace: Continuous furnace

(Examples 2-9)
A composite sintered body was obtained in the same manner as in Example 1 except that the type of metal powder, average particle size, organic binder content and firing temperature were changed as shown in Table 1.

(Example 10)
Instead of insert molding, a composite sintered body is produced in the same manner as in Example 1 except that a two-color molded body is manufactured by the following two-color molding and the two-color molded body is degreased and fired. Obtained.
<1> First, a mixture of stainless steel SUS304L powder (PF-2F, manufactured by Epson Atmix Co., Ltd.) having an average particle size of 2.3 μm and a specific surface area of 820 m ² / kg, produced by a water atomizing method, and polypropylene and wax. (Organic binder) was weighed to a mass ratio of 90:10 to obtain a mixed raw material. Note that SUS304L is austenitic stainless steel, and the unit cell of the crystal structure is a face-centered cubic lattice.

<2> Next, this mixed raw material was kneaded with a kneader to obtain a compound (first kneaded product).
<3> Next, a stainless steel SUS430L powder (manufactured by Epson Atmix Co., PF-2F) having an average particle size of 2.3 μm and a specific surface area of 820 m ² / kg, manufactured by a water atomizing method, and polypropylene and wax The mixture (organic binder) was weighed so as to have a mass ratio of 90:10 to obtain a mixed raw material. Note that SUS430L is ferritic stainless steel, and the unit lattice of the crystal structure is a body-centered cubic lattice.

<4> Next, this mixed raw material was kneaded with a kneader to obtain a compound (second kneaded product).
<5> Next, this compound was injection-molded with the two-color molding machine shown in FIG. 4 under the molding conditions shown below to produce a two-color molded body. In addition, the obtained two-color molded object was a cylindrical shape of outer diameter 7mm x length 30mm.
<Molding conditions>
-Material temperature: 150 ° C
Injection pressure: 11 MPa (110 kgf / cm ² )

<6> Next, the obtained two-color molded body was subjected to heat treatment (degreasing treatment) under the following degreasing conditions to obtain a degreased body.
<Degreasing conditions>
-Heating temperature: 500 ° C
・ Heating time: 2 hours ・ Heating atmosphere: Nitrogen gas

<7> Next, the obtained degreased body was fired under the firing conditions shown below. Thereby, a composite sintered body was obtained.
<Baking conditions>
・ Baking temperature: 1200 ℃
-Firing time: 3 hours-Firing atmosphere: nitrogen gas-Firing furnace: Continuous furnace

(Example 11)
A composite sintered body was obtained in the same manner as in Example 10 except that the average particle size of the metal powder was changed as shown in Table 1.
(Comparative Examples 1-4)
A composite sintered body was obtained in the same manner as in Example 1 except that the average particle diameter, firing temperature and firing atmosphere of the metal powder were changed as shown in Table 1. In particular, in Comparative Examples 1 to 4, the firing atmosphere was a reduced pressure atmosphere.

(Comparative Example 5)
A composite sintered body was obtained in the same manner as in Example 10 except that the average particle diameter, firing temperature and firing atmosphere of the metal powder were changed as shown in Table 1. In particular, in Comparative Example 5, the firing atmosphere was a reduced pressure atmosphere.
(Comparative Example 6)
After obtaining the secondary compact, the secondary compact was subjected to primary sintering, and then subjected to hot isostatic pressing (HIP) to increase the density of the primary sintered compact. A molded body was obtained in the same manner as in Example 1, and then degreased and fired to obtain a composite sintered body. The primary sintering was performed in a reduced pressure atmosphere.
(Comparative Examples 7-8)
Except for changing the average particle size and firing temperature of the metal powder as shown in Table 1, the primary sintered body was subjected to HIP treatment in the same manner as in Comparative Example 6 and then degreased and fired to perform composite firing. A ligature was obtained.

2. 2. Evaluation of Composite Sintered Body 2.1 Evaluation of Tensile Strength The tensile strength of the composite sintered body of each Example and each Comparative Example was measured by a method according to the method prescribed in JIS Z2241.
2.2 Evaluation of Relative Density Specific gravity of the composite sintered bodies of each Example and each Comparative Example was measured by Archimedes method. And the relative density of each composite sintered compact was computed from the true density of the metal material which comprises each metal powder. The calculated relative density was evaluated according to the following evaluation criteria.
<Relative density evaluation criteria>
◎: 97% or more ○: 95% or more and less than 97% △: 93% or more and less than 95% ×: less than 93%

2.3 Evaluation of Dimensional Accuracy As the dimensional accuracy of the composite sintered bodies of the examples and the comparative examples, the deviation from the target size was evaluated according to the following evaluation criteria.
<Evaluation criteria for dimensional accuracy>
◎: Dimensional accuracy is particularly high ◯: Dimensional accuracy is high △: Dimensional accuracy is low ×: Dimensional accuracy is particularly low Table 1 shows the evaluation results of 2.1 to 2.3.

As is apparent from Table 1, the composite sintered bodies obtained in each example had high tensile strength and excellent mechanical properties.
In addition, the composite sintered body obtained in each example had good relative density and dimensional accuracy. In particular, when a metal powder having an average particle size of 10 μm or less was used, this tendency was remarkable.
Moreover, although the improvement of the tensile strength of the composite sintered compact was recognized by HIP processing, it did not reach the tensile strength of the composite sintered compact obtained in each Example.
In addition, the external appearance photograph is shown in FIG. 8 about the composite sintered compact obtained in Example 3, and the composite sintered compact obtained in the comparative example 1. FIG.

As is clear from FIG. 8, the composite sintered body obtained in Example 3 has a linear outer peripheral surface of the portion of the SUS304L sintered body and the portion of the SUS430L sintered body. A cylindrical body having a uniform outer diameter was obtained.
On the other hand, the composite sintered body obtained in Comparative Example 1 is a cylindrical body in which the outer peripheral surfaces of the SUS304L sintered body portion and the SUS430L sintered body portion are distorted, and the outer diameter is particularly near the boundary of each portion. Was uneven.
Further, for the composite sintered body obtained in Example 3 and the composite sintered body obtained in Comparative Example 1, element mapping images and Ni concentration distribution spectra were obtained for the cross section of the joint. The obtained element mapping image and Ni concentration distribution spectrum are shown in FIG. In FIG. 9, the light color portion indicates a region where the Ni concentration is high, and the dark color portion indicates a region where the Ni concentration is low.

As is clear from FIG. 9, in the composite sintered body obtained in Example 3, it is recognized that Ni is diffused from the SUS304L side originally containing Ni to the SUS430L side not originally containing Ni. Thereby, in the composite sintered compact of Example 3, it is guessed that the site | part of a SUS304L sintered compact and the site | part of a SUS430L sintered compact couple | bond together firmly and become a composite sintered compact.
On the other hand, in the composite sintered body obtained in Comparative Example 1, almost no diffusion of Ni from the SUS304L side to the SUS430L side is observed.

It is a figure for demonstrating 1st Embodiment of the manufacturing method of the composite sintered compact of this invention. It is a figure for demonstrating 1st Embodiment of the manufacturing method of the composite sintered compact of this invention. It is a phase diagram of a Fe-N type alloy. It is a figure for demonstrating 2nd Embodiment of the manufacturing method of the composite sintered compact of this invention. It is a figure for demonstrating 2nd Embodiment of the manufacturing method of the composite sintered compact of this invention. It is a longitudinal cross-sectional view which shows embodiment of the fuel injection valve of this invention. It is the elements on larger scale of the fuel injection valve shown in FIG. 3 is an appearance photograph of the composite sintered body obtained in Example 3 and the composite sintered body obtained in Comparative Example 1. FIG. It is the element mapping image acquired about the cross section of the junction part of the composite sintered compact obtained in Example 3, and the composite sintered compact obtained in the comparative example 1, and the density | concentration distribution spectrum of Ni.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 1 '... Composite sintered body 11, 11' ... Sintered body part of 1st metal powder 12, 12 '... Sintered body part of 2nd metal powder 21 ... 1st kneaded material 22 …… Second kneaded product 3 …… Primary molded body 30 …… Primary molding mold 31 …… Cavity 4 …… Secondary molded body 40 …… Secondary molding mold 41 …… Cavity 42 …… Space 5 ... Two-color molding 50 ... Two-color molding machine 51 ... Cavity 52 ... Pin 6, 6 '... Degreasing body 100 ... Electromagnetic fuel injection valve 120 ... Composite magnetic pipe 121 ... Fuel connector section 122 …… Nonmagnetic part 123 …… Valve housing part 124 …… O-ring 125 …… Fuel filter 126 …… Fixed iron core 128 …… Adjuster 129 …… Spring 130 …… Needle valve 131 …… Seat holder 132 …… Valve Bush sheet 133 ... Injection port 136 ... O-ring 138 ... Movable iron core 139 ... Coil 143 ... Connector housing 144 ... Terminal 145 ... Magnetic housing

Claims (13)

A first composition comprising a first metal powder composed of a first metal material made of a Fe-based alloy having a face-centered cubic lattice and an organic binder, and the composition is different from that of the first metal material ; Using a second metal powder composed of a second metal material made of an Fe-based alloy having a body-centered cubic lattice and a second composition containing an organic binder, a composite molded body of different metals A molding process to obtain;
Rukoto said composite compact was sintered in an atmospheric gas containing nitrogen atom, the crystal structure Yusuke a firing step to obtain a composite sintered body made of a metallic material consisting of Fe based alloy of face-centered cubic lattice, the A method for producing a composite sintered body characterized by the above. The method for producing a composite sintered body according to claim 1 , wherein the atmospheric gas containing nitrogen atoms is nitrogen gas or ammonia gas. The firing conditions in the firing step, method for producing a composite sintered body according to claim 1 or 2 at a temperature 1000 to 1500 ° C. × 0.2 to 7 hours. The composite molded body is a two-color molded body formed by two-color molding by supplying the first composition and the second composition into the same mold, or the first composition and The method for producing a composite sintered body according to any one of claims 1 to 3 , which is an insert molded body formed by insert molding using a molded body of one of the second compositions as an insert work. The average particle size of the metal powder having a higher solidus temperature among the first metal powder and the second metal powder is smaller than the average particle size of the metal powder having a lower solidus temperature. The manufacturing method of the composite sintered compact in any one of 1-4 . The method for producing a composite sintered body according to any one of claims 1 to 5 , wherein an average particle diameter of the first metal powder and an average particle diameter of the second metal powder are 1 to 30 µm, respectively. The method for producing a composite sintered body according to any one of claims 1 to 6 , wherein the content of the organic binder in each of the first composition and the second composition is 2 to 20% by mass. The composite molded body is formed such that one of the first composition and the second composition includes or sandwiches the other composition,
The method for producing a composite sintered body according to any one of claims 1 to 7 , wherein the composition located outside the composite molded body has a larger shrinkage rate in the firing step than the composition located inside. It said forming step The method of producing a composite sintered body according to any one of claims 1 to 8 carried by a metal powder injection molding method. It is manufactured by the method for manufacturing a sintered body according to any one of claims 1 to 9 ,
A composite sintered body, wherein the sintered body of the first metal powder and the sintered body of the second metal powder are integrated. The composite sintered body according to claim 10 , wherein the sintered body of the first metal powder and the sintered body of the second metal powder are joined based on mutual diffusion. The first metal powder before sintering is composed of a γ-Fe based alloy, and the second metal powder before sintering is composed of an α-Fe based alloy,
The composite sintered body according to claim 10 or 11 , wherein the sintered body of the second metal powder includes a γ solid solution containing the composition of the first metal powder and a component of the atmospheric gas in the firing step. body. The first metal powder before sintering is composed of a non-magnetic material, and the second metal powder before sintering is composed of a magnetic material,
An electromagnetic fuel injection valve comprising a tubular component manufactured by the method for manufacturing a composite sintered body according to any one of claims 1 to 9 , using these metal powders,
The fuel injection valve according to claim 1, wherein the tubular part is formed by integrating a sintered body of magnetic material powder and a sintered body of nonmagnetic material powder.

Images