JPS63143228A - Manufacture of multicomponent metallic sintered body - Google Patents

Abstract

PURPOSE:To obtain a high density multicomponent metallic sintered body free from cracks by sintering and shaping a mixture of powder of an alloy having a eutectic structure with powder of other metal. CONSTITUTION:An alloy having a eutectic structure such as an alloy of rare earth elements is cooled at >=0.01 deg.C/sec cooling rate and crushed. The cooling may be carried out by direct contact with a cold medium. The same metal as one of the metals forming the eutectic structure or a metal different from the metals is also crushed. The resulting two kinds of powders are mixed, sintered and shaped to obtain a high density multicomponent metallic sintered body free from cracks and contg. metals capable of forming a eutectic structure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a multi-component metal sintered body.

[Conventional technology]

Generally, metal materials that crack during melting or casting, metal materials that react with crucibles during melting, etc. are once powdered and then sintered to obtain the desired shape.

The formation method includes a hot press (Hot
There is a pressing method, a ripping method, and a bonding method in which the compact is preformed by a pressing or shipping method, and then the green compact is fired and boxed.

[Problem that the invention seeks to solve]

However, even if the powder is sintered, it is difficult to obtain a complete high-density sintered body without porosity or cracks. For this reason, current methods include a liquid phase sintering method in which the temperature is raised to just above the melting point of the powder, and a method in which a binder or the like is mixed. In this liquid phase sintering method, it is difficult to remove the sintered body because liquid leaks from between the dies and the punch and the sintered dies, dies, and punch. Even if the sintered body can be taken out, it is necessary to control the temperature very strictly, which is a difficult method for industrial use.

On the other hand, the method of mixing a binder or the like has the problem of contamination of the obtained sintered body with impurities, which imposes various restrictions on the application and usage conditions of the product, and is not practical.

In view of the above-mentioned conventional problems, the present inventors conducted intensive research to obtain a sintered body of a multi-component metal with high density and no impurities without voids or cracks. If you obtain a metal powder having the following properties, then mix the same or other metal powders to obtain the desired target composition, and then perform normal sintering,
After learning that the desired sintered body could be obtained, the method was proposed (Japanese Patent Application No. 797, No. 1999-1999).

However, when such an improved method is implemented industrially, it is not always easy to crush the eutectic alloy, and an improvement is desired.

[Means for solving problems]

The present invention has been made in view of the above circumstances, and the gist thereof is to provide a method for manufacturing a multi-component metal sintered body containing a metal component capable of forming a eutectic structure, in which an alloy having a eutectic structure is prepared in advance. obtained, powdered by low-temperature pulverization, and then mixed with a metal powder having the eutectic structure and a metal powder that is the same as or different from the metal component constituting the eutectic structure, and then sintered. A method of manufacturing a multi-component metal sintered body is provided.

The present invention will be explained in detail below.

In the present invention, a multi-component metal material that can obtain a eutectic structure is used. For example, when obtaining a multi-component metal sintered body consisting of three types of single metals A, B, and O, if a eutectic structure is obtained in the ternary equilibrium phase diagram, the eutectic structure of the ternary metal is used. However, if a eutectic structure cannot be obtained in the ternary phase diagram, check whether a eutectic structure can be obtained in the co-element phase diagram between A and B, between B and 0, and between A and 0. The eutectic structure of the core metal is used. This is the same even when obtaining a multi-element metal sintered body of a metal element or more. In this case, it is preferable to have a eutectic composition near the eutectic composition where there is a large amount of eutectic structure, but it does not necessarily have to be a eutectic composition, and in consideration of grindability, etc. It is enough if you can obtain it.

The alloy with a eutectic structure is obtained by ordinary melting and casting methods, but in order to obtain a high-quality sintered body, it is preferable that the eutectic structure be fine and uniform, so cooling during casting is preferable. The speed is preferably 0.0/'C/sec or more.

In order to obtain a uniform and fine eutectic structure, it is especially important to
．． The arc melter method using a copper mold at /~25°C/sec is preferred.

In the present invention, the alloy thus obtained is pulverized by low-temperature pulverization. Low-temperature pulverization can be carried out either by lowering the temperature of the pulverizing equipment or by bringing the pulverized material into direct contact with a low-temperature medium.

In order to lower the temperature of the crushing equipment, it may be possible to use the Zimaquet method, or a cooling pipe may be wrapped around it. To bring the low-temperature medium into direct contact with the pulverized material, there is a method in which the low-temperature medium is directly poured into the powder material, and the material is pulverized while being poured.

As the low-temperature medium, ice, dry ice, liquid nitrogen, liquid argon, liquid helium, etc. can be used as long as it is not explosive or toxic even when vaporized. Preferably, in consideration of cooling efficiency, a liquefied gas such as liquid nitrogen, liquid argon, or liquid helium having a boiling point of minus 100 degrees or lower is suitable as the low-temperature medium.

In addition, if there is a risk of the pulverized material reacting with the low-temperature medium, the method is to flow the low-temperature medium through the pulverizer to avoid direct contact, or to use a heat exchanger to convert the non-reactive low-temperature medium (C) into the pulverized material. In particular, if the pulverized material is active in the atmosphere, it is necessary to carry out the pulverization in an inert atmosphere such as argon gas, for example in a dry box.

Moreover, if the pulverized material also reacts with nitrogen, a heat exchanger is set in a dry box, and inexpensive liquid nitrogen is used as a low-temperature medium to liquefy the argon gas in the dry box, and this liquid argon is directly used. It is also possible to pour it into the pulverized material, or to pulverize it while pouring it.

In this case, a bellows-type flexible pipe as a heat exchanger is sufficiently effective, and can be used inexpensively and easily as a low-temperature grinding method in an inert atmosphere.

More specifically, in the case of pulverization using a show crusher, for example, in order to keep the temperature of the pulverizer itself low, it is preferable to pulverize while pouring a low-temperature medium directly along with the pulverized material during pulverization. Choose a low-temperature medium that does not directly react with the material, and usually use an inert gas liquid.In the case of a cutter mill, it is also possible to use the container as jacket 2 and flow the low-temperature medium. However, it is more efficient to grind while pouring a low-temperature medium directly into the pulverized material. In this case, a low-temperature medium such as an inert gas liquid is selected so that the pulverized material and the low-temperature medium do not react directly.

In the case of a vibratory ball mill, if a low-temperature medium is placed in the container along with the pulverized material, the low-temperature medium will expand as it evaporates, so it is desirable not to completely seal the container. In this case as well, a low temperature medium such as an inert gas liquid is selected so that the pulverized material and the low temperature medium do not react directly.

Metal powder is added to and mixed with the alloy powder having the eutectic structure obtained as described above. As long as the composition after mixing becomes the composition of the desired metal sintered body, the metals to be added are not particularly limited, and for example, seven or more types of single metals, an alloy consisting of one or more types of metals, or a combination thereof. It may be.

In addition, in order to obtain a high-quality sintered body, it is preferable that 3% or more of eutectic structure exists after mixing, and furthermore, /0-
A range of JO1 or higher is preferable.

Alternatively, the alloy having a eutectic structure and the single metal to be added or the alloy may be combined and then crushed and mixed.Then, the powder is sintered and formed, but this may be done by a general method. As an example of the hot press method, the inner surface is coated with boron nitride (
The powder is filled into a die coated with a mold release agent such as BN), and similarly pressurized in an inert gas such as a canister gas or in a vacuum atmosphere. Although the temperature varies depending on the pressure, a temperature around ±300'C around the melting point of the eutectic structure is appropriate. The preferable pressing force varies depending on the material and the eutectic composition amount, but if it is too large, liquid phase leakage and damage to the die and punch will occur, so it should be 300 kg/ti or less, especially 700 to 700 kg/ti.
．． 200 kg/cnl is preferred. The material of the die and punch is usually graphite, but may also be made of heat-resistant steel or ceramics.

When performing the hilling method as a sintering forming method, for example, the powder is mixed with carbon steel, carbon steel, etc. in an inert atmosphere such as argon gas.
After filling a stainless steel or glass container, seal it under vacuum. It is sintered under pressure using a hip device.

The temperature is suitably lower than the hot press described above. However, in the case of a glass container, the temperature must be higher than the transition point of the glass. The pressure is not particularly limited as long as it can follow the deformation of the container at the temperature, but it is usually 200
It is 0 kg/air or less.

If it is too small, deformation will be insufficient and high density will not be obtained, so 1000 to /sookg7 (yl is preferred).

Furthermore, in the case of a sintering method, the powder is preformed into a predetermined shape using a hydraulic press or the like under an inert atmosphere such as argon gas, and then sintered in a sintering furnace. The atmosphere should be inert gas or vacuum. It is appropriate for the temperature to be higher than in the case of hot pressing.

Now, there are many multi-component metal materials that can obtain a eutectic structure, but some of them include rare earth metals, which have to be manufactured by sintering the powder due to problems such as cracking during casting and reaction with the mold. There is an alloy. In particular, combinations with transition metals have recently been in the spotlight as magnetic materials. According to the method of the present invention, such a multi-element metal sintered body containing rare earth metals, transition metals, etc. can be obtained in a high-density body without cavities or cracks, which is preferable.

[For production]

The reason why a high-density multi-component metal sintered body without cavities or cracks can be obtained by the method of the present invention is that the eutectic structure is uniform, fine, and has a low melting point, and that fine powder can be easily obtained by low-temperature grinding. There are many things that can be done. However, superplastic performance does not develop quickly even at fairly low temperatures and pressures during sintering.
As a result, the powder is filled with powder other than the eutectic structure,
And if a eutectic structure remains in the sintered body, it is uniform, 0.
It is thought that the ia structure also exhibits toughness and that a high-density sintered body without cavities or cracks can be obtained. There is also a possibility that the eutectic structure exhibits properties in a molten state and is filled with powder other than the eutectic structure.

Furthermore, as a secondary effect, since sintering can be performed at low temperatures and pressures, it is assumed that there are also effects such as suppressing reaction with punches and dies, and reducing cracking due to reduction in thermal contraction and expansion.

〔Effect of the invention〕

According to the method of the present invention as described above, it is possible to industrially advantageously produce a multi-component metal sintered body that is free from cavities, cracks, etc. and has no impurities, which has been difficult in the past. It is extremely excellent.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

In addition, in the following examples, melting and alloying were performed using an arc melter machine under vacuum @ (approximately o, / 771 torr)
This was done by injecting argon gas to 71) O@torr, and all crushing was done in an argon gas atmosphere in a glove box. A powder of less than 50 μm was obtained using a cutter mill.

In addition, the molding and sintering was done by hot press method in an argon gas atmosphere at a pressure of 100 to 9/ad, with an outer diameter of 30 mm,
Inner diameter/&1m, height soy, punch diameter/S size die (
(graphite) and boron nitride as a mold release agent.

The temperature was measured by attaching a PR-A-30 thermocouple to the side of the heating element (graphite), and the sintering state was determined by the amount of contraction of an extensometer attached to the cylinder that applied pressure. .

In actual sintering, the temperature is first set to 700°C, and once that temperature is reached, it is held for 70 minutes. If a large amount of shrinkage cannot be obtained, the temperature is further increased by 50°C, and after changing the temperature, it is held for 70 minutes. and observed changes in the amount of contraction. In this manner, hot pressing was terminated at the temperature at which a large amount of shrinkage was observed. After cooling, the sintered body was taken out and observed under an optical microscope to check for the presence of cavities, cracks, etc., and the test was repeated twice.

Example/ (Production of sintered body with atomic ratio Tb:Fe=/ :, 7) From the equilibrium diagram of terbium (Tb) and iron (Fe), if the eutectic composition of both is Tb? Coat% - Fecogat ratio, so Tb and Fe, both of which have a purity of 99.9%, were blended, melted, and alloyed with this composition to create a mass with a eutectic structure (
Approximately 201 mm x 20 t-mm) was obtained.

Next, a pair of crushing surfaces of the show crusher (size 2o
When pulverization was performed while pouring liquid argon as a low-temperature medium at the same time as the metal lump, the particles were pulverized to a particle size of 5 or less. Furthermore, liquid nitrogen was flowed through a steel pipe arranged like a bellows-type heat exchanger, and the argon gas in the glove box was liquefied, and the argon gas in the glove box was brought into direct contact with the pulverized material as a low-temperature medium. When crushed using a cutter mill machine with a steel crushing container at gOmm, the result was 7100 gOmm.
A powder with a particle size of 3 olim'J was obtained in an amount of yyio.

Iron powder with a particle size of 50 μm and the above eutectic structure powder with an atomic ratio Tb
: Fe = / : 3, and sintering was performed using the hot press method using this mixed powder.

A large amount of shrinkage is obtained at approximately / 000℃ during the sintering operation,
When taken out after cooling, a high-quality sintered body was obtained that did not react with the punch or die and was free of cavities and cracks.

For comparison, a lump having a eutectic structure was crushed in exactly the same manner as described above, except that liquid argon was not used as the low-temperature medium.
It could only be crushed to ~20 mm. Also, during the crushing process, sparks were generated from terbium acid (I think it was atomized), and the surface of the crushed product was discolored.The subsequent crushing process using a cutter/mill machine was able to crush 10 liters in 70 minutes, but the heat of the crushing If the container is not above 10O'C, 30 minutes of cooling time is required, resulting in /OF//L, and the particle size is 50μTrL in 0 minutes.
The following powder was obtained. In this way, productivity is extremely poor and actual production is difficult.

As another comparison, when a composition with an atomic ratio of Tb:Fe = /: 3 was directly blended, melted, and powdered from the single metal materials Tb and Fq, sintering was performed.
A large amount of shrinkage was obtained at 200°C.

When I took it out after cooling, the sample turned into liquid and leaked from the gap between the punch and the die, but the sample inside the die was completely intact.
It also reacted with the die and the sintered body could not be taken out.

Example 2 (Manufacture of sintered body with atomic ratio Gd:, Pe=/:3) From the equilibrium diagram of gadolinium (Ga) and iron (Pe), the eutectic composition of both is Gd: 7at%-Fe/, ?
at%, Gd and Fe, both of which have a purity of 99.9%, were blended, melted, and alloyed with this composition to create a eutectic structure (
2096B×20 tmm) was obtained. Show the resulting eutectic structure using a pair of crushing surfaces (size 20) of the crusher.
0×/AOmm) was cooled in advance with liquid nitrogen and then pulverized, and the particle size could be pulverized to a particle size of less than rnmJJ. Furthermore, using a cutter mill machine having a cylindrical crushing vessel made of steel with an inner diameter of 100 mm and a height of gO, and the cylindrical part being a jacket type, liquid nitrogen was poured into a steel pipe connected to the jacket. When the powder was pulverized while cooling the pulverization container, a powder having a particle size of SOμm or less was obtained at a production amount of qogyio.

The iron powder with a grain size of SOμm and the eutectic structure powder with an atomic ratio of Gd
: Fe = / : 3, and sintering was performed using the hot press method using this mixed powder.

During the sintering operation, a large amount of shrinkage was obtained at about qoo℃, and when it was taken out after cooling, there was no reaction with the punch or die.
Moreover, a high-quality sintered body without voids or cracks was obtained.

For comparison, a eutectic structure was crushed in exactly the same manner as in the example except that liquid nitrogen was not used as the low-temperature medium.
It could only be crushed up to m. In addition, sparks were generated during the crushing process, probably due to the oxidation of gadolinium, and some of the crushed surfaces were discolored. Grinding with cutter mill machine is 1
I was able to grind 10g in 0 minutes, but the heat of grinding caused the container to reach ioo℃.
Above all, 50 minutes of cooling time was required, and in the end it was 10g/
Powder with a particle size of 50 μm or less was obtained in 0 minutes. As described above, productivity is extremely poor and actual production is difficult.

As another comparison, when a composition with an atomic ratio of Gd:Fθ=/:3 was directly blended, melted, and powdered from the single metal materials Gd and Fs, sintering was performed at approximately /100°C.
A large amount of shrinkage was obtained.

When I took it out after cooling, the sample turned into liquid and leaked from the gap between the punch and the die, and the sample inside the die was completely punched and leaked.
It also reacted with the die and the sintered body could not be taken out.

Sender: Mitsubishi Chemical Industries, Ltd. Representative patent attorney for long diameter - (7 others)

Claims (5)

[Claims] (1) In a method for manufacturing a multi-component metal sintered body containing metal components capable of forming a eutectic structure, an alloy having a eutectic structure is obtained in advance, this is powdered by low-temperature grinding, and then the eutectic A method for producing a multi-component metal sintered body, which comprises mixing powder of an alloy having a structure and powder of a metal that is the same as or different from the metal component constituting the eutectic structure, and then sintering the mixture. (2) The manufacturing method according to claim 1, wherein the low-temperature pulverization is a method in which pulverization is carried out by bringing a low-temperature medium into direct contact with an alloy having a eutectic structure. (3) The manufacturing method according to claim 1 or 2, wherein the alloy having a eutectic structure is obtained under conditions of a cooling rate of 0.01° C./sec or more. (4) The manufacturing method according to claim 1, 2, or 3, wherein the alloy having a eutectic structure is a rare earth alloy. (5) The manufacturing method according to claim 4, wherein the rare earth alloy is an alloy consisting of a rare earth metal and a transition metal.