JP3113639B2 - Manufacturing method of alloy powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an alloy powder used in powder metallurgy (a technique for producing a product by sintering a powder), and particularly relates to a soft metal (hereinafter referred to as a soft metal), The present invention relates to a method for producing an alloy powder from a raw material containing at least two or more types of hard metals (hard but brittle metals compared to soft metals (hereinafter, referred to as hard metals)).

[0002]

2. Description of the Related Art Powder metallurgy is used in various fields because of its advantages such as easy processing after sintering and production of alloys composed of insoluble metals. In powder metallurgy, powder production, powder molding, and sintering of the formed powder are performed. Since the properties such as the particle size distribution of the powder have a significant effect on the mechanical strength and the like of the metal product after sintering, various methods for producing powder have been developed. In the case of producing a powder composed of two or more insoluble layers, each layer is uniformly dispersed by performing a mechanical grinding (MG) method in which reagglomeration is repeated while performing mechanical pulverization. A method for obtaining a powder has been proposed.
JP-A-5-51663 discloses that an atomized powder containing aluminum as a main component containing ceramic particles is subjected to mechanical pulverization and reagglomeration treatment by the above-mentioned MG method to produce a powder in which ceramic particles are dispersed in aluminum. ing.

According to such a method, the molten metal is atomized into an atomized powder having a small particle size to some extent. It is described that this atomized powder is further pulverized mechanically and pulverized to the extent that reagglomeration occurs, thereby obtaining an aluminum-based composite alloy in which ultrafine ceramic particles are uniformly distributed without segregation. Note that reagglomeration is to obtain a powder in which particles are finely dispersed in a base material by recombining the base material with an additive such as fine ceramic particles. In other words, what has been once finely ground by pulverization is combined again to increase the particle size.

[0004]

However, the raw material powder
When a soft layer and a hard layer are included at the end , the soft layer is soft and excellent in ductility, so that it is difficult to be pulverized by mechanical pulverization. Conversely, the hard layer is hard and brittle, so that it is easily crushed as compared to the soft layer. In the technique described in JP-A-5-51663, mechanical pulverization reagglomeration requires a pulverization treatment of 10 hours or more by a ball mill, and the pulverization time is longer than ordinary pulverization, and the degree of reagglomeration is large. When crushed, the hard layer becomes an ultrafine powder.

Therefore, when such a powder is sintered, the powder mainly composed of a hard metal becomes an ultrafine powder and has a large specific surface area, so that the amount of oxygen absorbed during sintering increases. An increase in the oxygen content not only causes deterioration of sinterability, but also lowers mechanical properties such as elongation at break.

Accordingly, the present invention has been made to solve the above-mentioned problems, and an object thereof is to produce a sintered body having a small amount of oxygen absorption and excellent mechanical properties. It is another object of the present invention to provide a method for producing an alloy powder including a soft metal layer and a hard metal layer .

[0007]

To achieve the above object, the following method is provided. That is, the present invention provides :
A soft metal layer having one of Zn and Pb ;
It has either l-Ti compound or Al-Zr compound
And a hard metal layer that provides a process for producing the alloy powder, the raw material of the soft metal layer, by atomizing a molten metal by dissolving the raw material of the hard metal layer, a soft metal layer and hard metal layer And a mechanical pulverizing step of mechanically pulverizing the atomized alloy powder so that the atomized alloy powder does not re-aggregate. Further, according to the present invention, in the method, the soft metal layer is made of Sn, and the raw material is made of Si.
Production of alloy powder that is melted in a crucible containing C as a main component
Method. Further, in these methods, there is also provided a method for producing an alloy powder in which the maximum particle size of the alloy powder produced by the mechanical pulverization step is 45 μm or less.

In general, as a method for producing an alloy powder used for powder metallurgy, there is a method of producing an ingot by casting and mechanically pulverizing the ingot, and a method of producing a melt by dissolving a raw material and atomizing a molten metal. . Soft
When an ingot is manufactured by casting an alloy powder containing a metal layer and a hard metal layer and then manufactured by a method of mechanically pulverizing the same, when the ingot is converted from the molten metal, the cooling rate is slow, so that the soft There is a problem that the crystal of the metal is coarsened and coarse soft metal crystal remains in the powder after pulverization. Many soft metals have a low melting point, and are easily melted away during sintering to form coarse flowing holes. This coarse flow loss causes deterioration of mechanical properties such as elongation at break of the sintered body. In the case of the atomizing method, the problem of coarsening of the soft metal crystal when forming an ingot is solved, but it is difficult to atomize sufficiently by the atomizing method. There is a problem that large sieving is required and the yield is poor.

Therefore, in the present invention, first, atomized powder is prepared by an atomizing method, and then pulverized to such an extent that mechanical reagglomeration does not occur. According to the method of the present invention, since the molten metal is not formed into an ingot, the soft metal crystal does not become coarse when the ingot is formed. Further, since the atomized powder produced by the atomizing method is mechanically pulverized, the particle size becomes small and the yield is improved. Furthermore, since mechanical pulverization is performed to such an extent that reagglomeration does not occur, excessive pulverization of the hard metal can be suppressed. Here, as the soft metal,
For example, elements such as Sn, Zn, and Pb correspond thereto, and examples of hard metals include Al-Ti compounds and Al-Zr compounds. Examples of alloy powders containing both metals include Al-Sn. Alloy powders such as -Zr and Al-Sn-Zr-Mo correspond thereto.

As the atomizing method, various existing methods such as a gas atomizing method, a rotating disk method and a water atomizing method can be applied. However, the gas atomizing method can be used for reasons such as prevention of oxidation of atomized powder and production cost. preferable. The gas atomizing method is also advantageous in that the particle size of the produced atomized powder can be reduced. If the atomized powder has a small particle size, the time required for the subsequent mechanical pulverization step can be shortened, and pulverization can be sufficiently performed before reagglomeration. Note that it is preferable to use a gas atomization method using an inert gas such as argon, helium, or nitrogen as the spray medium.

The atomized powder produced by the atomizing method is pulverized by a mechanical method to such an extent that reagglomeration does not occur. As a mechanical pulverizing method, various devices such as an attritor, a ball mill, a vibrating ball mill, and a rod mill can be used. What is important here is that mechanical pulverization is performed to such an extent that reagglomeration does not occur. Hereinafter, the reason will be described in detail.

In general, when a powder composed of two or more layers is produced, each layer is uniformly dispersed by performing a mechanical grinding (MG) method in which reagglomeration is repeated while performing mechanical pulverization. A method has been proposed for obtaining a prepared powder. JP-A-5-51663 discloses that an atomized powder containing aluminum as a main component containing ceramic particles is mechanically pulverized and re-agglomerated by the above-mentioned MG method so that ultrafine ceramic particles can be uniformly distributed without segregation. It is said that the obtained aluminum-based composite alloy can be obtained. However, as described above, a soft metal layer and a hard metal layer are formed from a powder material containing a soft metal and a hard metal.
In the case of producing an alloy powder having the following formula , pulverization of the hard metal layer is promoted as compared with pulverization of the soft metal layer . For this reason,
When mechanical pulverization is performed to such an extent that reagglomeration occurs, the powder mainly composed of a hard metal becomes an ultrafine powder. Therefore, when such a powder is sintered, a powder containing a hard metal as a main component has a large amount of oxygen absorption, thus deteriorating the sinterability, and also has a problem that the mechanical properties of the sintered body are reduced. In the case of producing an alloy powder containing a soft metal layer and a hard metal layer as described above, if sufficient pulverization is performed to increase the mechanical properties by the conventional method, the mechanical properties of the sintered body will decrease. ,further,
It was found that there was a problem that the amount of oxygen absorption also increased. The present inventors have conducted intensive studies to solve such a problem, and found that when pulverized to the extent that reagglomeration does not occur, both mechanical properties and oxygen content can be satisfied at a satisfactory level. The present invention has been made based on the above.

In the present invention, the average particle size is reduced by atomization.
Alloy with soft metal layer miniaturized at the same time as miniaturization
A powder is obtained. For this reason, and by mechanical grinding,
Further, the powder particles are refined. In the mechanical grinding process
In this case, finer hard metal layers are promoted, but mechanical pulverization
Is performed to the extent that reagglomeration does not occur.
Is prevented from becoming ultrafine powder. For this reason, the obtained total
When sintering with gold powder, the oxygen absorption is low
It is. In addition, since the generation of ultrafine powder (1 μm or less) can be prevented, pulverization can be performed under the condition that the amount of ultrafine powder of 1 μm or less does not exceed 1%. Therefore, 1μ
The case where the ultrafine powder of m or less becomes 1% or more can be regarded as reagglomeration.

The mechanical pulverization is preferably performed by wet pulverization. This is because wet pulverization is easier to suppress reagglomeration. In addition, even in the case of dry pulverization, re-aggregation can be suppressed by adding an aggregation inhibitor such as ethanol.

The maximum particle size of the powder particles produced by mechanical pulverization is preferably 45 μm or less.
This is because if the particle size of the alloy powder exceeds 45 μm, the bonding force during sintering becomes weak. Therefore, if the maximum particle size is 45 μm or less and mechanically pulverized to the extent that reagglomeration does not occur, all the powders can be used for sintering, and the problems of both mechanical strength and oxygen absorption amount are reduced. Can be cleared.

The method according to the present invention is particularly suitable for producing an alloy powder containing a layer made of Sn as a soft metal layer . This is because Sn is one of the materials hard to be crushed as a soft metal, and the above-mentioned problem is remarkable. In addition, Sn is a typical element which raises the heat resistance of Ti alloy, and is mix | blended with the additive raw material powder of sintered Ti alloy.

When Sn is contained in the powder raw material, the powder raw material is preferably dissolved in a crucible containing SiC as a main component.
Generally, it is said that a crucible containing MgO as a main component or a crucible containing CaO as a main component has a small amount of contamination (contamination) with a molten metal. However, when the molten metal contains Sn and is melted in a crucible containing MgO and CaO as a main component, the amount of contamination to the molten metal increases. On the other hand, when a crucible containing SiC as a main component is used, the molten metal becomes molten. Contamination amount can be reduced.

After sintering the finished alloy powder, it is preferable to make it into a final mechanical part by processing such as extrusion or forging. This is because the particle size of the raw material powder is large as compared with the case where the raw material powder is pulverized to a degree of reagglomeration, so that many gaps in the sintered body are formed. Therefore, the gap can be filled by forging or the like, and the mechanical strength can be increased.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific examples embodying the present invention will be described.

(Invention Example) Composition (Al-25%, Sn-2)
A raw material composed of 5%, Zr-6%, Nb-6%, Mo-1%, and Si) is dissolved in an Ar atmosphere, and a tapping temperature is 1650.
Atomization was performed by spraying Ar gas on the molten metal at a temperature of ℃. In the crucible, 90% SiC, balance Al ₂ O ₃ , S
A crucible made of iO ₂ was used.

FIG. 1 shows a photograph of the metal structure of the atomized powder particles. The atomized molten metal was rapidly cooled and atomized, and the crystal grain size of Sn was 2-3 μm or less. FIG. 3 shows the particle size distribution of the atomized powder. As is apparent from this figure, the atomized powder had a small number of particles having a particle size of 45 μm or less, and approximately 60% of particles having a particle size exceeding 45 μm. This is because if the diameter of the molten metal discharged from the crucible is too small due to the relationship with the viscosity of the molten metal, smooth tapping cannot be performed, so the diameter of the molten metal must be increased, and as a result, the particle size of the atomized powder Will also be larger.

Next, the atomized powder was ground by an attritor to such an extent that reagglomeration did not occur. The particle size of the powder after pulverization was 45 μm or less for all powders. The grinding time was about 1 hour. FIG. 4 shows the particle size distribution after pulverization. As apparent from this figure, the average particle size is about 7 μm.
The pulverization was stopped at such a level that almost no powder with a particle size of about m or less than 1 μm was generated.

Next, in order to examine the sinterability, mechanical strength and workability of this alloy powder, the alloy powder was mixed with hydrogenated Ti powder,
A cylindrical test piece was manufactured. The manufacturing process at this time will be described with reference to FIG.

First, the above-mentioned alloy powder (15 wt%)
And hydrogenated Ti powder (83 wt%), TiB_Two(2w
t%) (S1), and a molding surface pressure of 3 to 6 tonf / cm.^Two
(S2). Then, the compact is placed in a sintering furnace.
And the inside of the sintering furnace ^-FiveTorr. Soshi
And raise the temperature in the sintering furnace to the sintering temperature of 1300 ° C.
And maintained at that temperature for about 4 hours for sintering (S3).

FIG. 6 shows the relative density of the sintered body after sintering. According to this, the relative density of the sintered body was 3 to
It became about 93% or more at nf / cm ² or more. Also, the amount of oxygen absorbed by the sintered body was suppressed low as shown in Table 1. Further, the mechanical properties of the sintered body were satisfactory as shown in Table 1.

[0026]

[Table 1]

Next, the sintered body was extruded to form a long rod (S4). The relative density of the sintered body is about 93
% Or more, cracking did not occur during extrusion molding. If the material density of the sintered body is low, the elongation of the material is poor and cracks may occur. However, the alloy powder of (Invention Example) is pulverized until the particle size becomes 45 μm or less and the density is high. Did not occur. Next, a cylindrical test piece was formed by forging the sintered body formed into a long rod shape (S5). At this time, the material density of the coarse material is S
No cracking occurred during molding because of the rise in the extrusion process of No. 4.

Comparative Example 1 As Comparative Example 1, the same composition (Al-25%, Sn-25%, Zr-6%, Nb-6) was used.
%, Mo-1%, Si) are melted in an Ar atmosphere and ingots (φ300 × 30) at a pouring temperature of 1650 ° C.
Was manufactured. Observation of the metal structure in this case revealed that the crystal grain size of the ingot structure was several tens of μm. In addition, coarse Sn crystals (having a particle size of 10 μm or more) were present.

The above-mentioned ingot is roughly pulverized by press pulverization, and then the average particle size is reduced to 10 by an attritor.
It was pulverized to a size of not more than μm. The grinding time was 1 hour. FIG. 2 shows a photograph of the metal structure of the pulverized particles. In FIG. 2, what looks white inside is the Sn layer, and what looks black outside is the hard compound layer. As can be seen from this photograph, it was found that the particle size of the Sn crystal was large even after the pulverization, and the particle size did not change much by the pulverization. FIG. 7 shows the particle size distribution at this time. According to this, peaks occurred at about 0.2 μm and at about 6 μm. This is because the Sn layer is hardly pulverized, while the other compound layers are brittle and pulverization proceeds, so that such a layer becomes ultrafine powder.

Next, the alloy powder thus produced was mixed with a hydrogenated Ti powder in the same manner as in (Invention Example), molded in a mold, and sintered at 1300 ° C. The characteristic values of the sintered body at this time are shown in Table 1 together with the invention examples. The oxygen content of the sintered body was (invention example) (0.28 to 0.29
%) As compared to 0.45%. This is due to the fact that some of the alloy powders are ultrafine and the specific surface area is increased. Further, the elongation at break was as low as 0.6% as compared with that of (Inventive Example). Thus, although there is no significant difference in the high-temperature tensile strength between (Inventive Example) and (Comparative Example), it can be seen that the (Comparative Example) has a high oxygen content and thus a low elongation at break.

This sintered body was extruded in the same procedure as in (Example of the invention), and formed into a cylindrical test piece by forging. Some of the resulting test pieces had cracks. This is because coarse S
This is because the n-layer remains as it is, and a coarse flow loss hole was formed due to this.

Comparative Example 2 As Comparative Example 2, (Inventive Example)
Same composition as (Al-25%, Sn-25%, Zr-6
%, Nb-6%, Mo-1%, and Si) are dissolved in an Ar atmosphere, atomized by spraying Ar gas on a molten metal having a tapping temperature of 1650 ° C., and then sieved without pulverization. The particle size was reduced to 45 μm or less by division.

This alloy powder was mixed with hydrogenated Ti powder under the same conditions as in (Example of the invention) and sintered. As a result, the relative density of the sintered body was 3% higher than that of (invention example) as shown in FIG.
To some extent. This is because sinterability is low in the powder that has just been atomized because the particle diameter is large.
In addition, the ratio of particles having a size of 45 μm or less was as low as about 40% as shown in FIG. 3, and the yield was poor.

Such a sintered body was extruded in the same manner as in (Example of the present invention) and formed into a cylindrical test piece by forging.
In such a test piece, cracks occurred during shaft forming. This is because the material density of the sintered body is low and the elongation of the material is poor.

(Comparative Example 3) Same composition (Al-25%, S
n-25%, Zr-6%, Nb-6%, Mo-1%, S
The raw material of i) was melted by changing the material of the crucible into two types, a crucible containing MgO as a main component and a crucible containing CaO as a main component, to produce an alloy powder under the same conditions as in (Example of the invention).
When the crucible containing SiC as the main component (invention example) was used, almost no fume was generated, whereas Mg was used.
When a crucible containing O and CaO as a main component was used, fumes (evaporation of metal components of the crucible) occurred during melting, and it was difficult to grasp the state of the molten metal surface. Table 2 shows the amount of contamination of the alloy powder and the life of the crucible at this time.

[0036]

[Table 2]

As is clear from Table 2, the crucible containing MgO and CaO as the main components has a large amount of contamination with the alloy powder.
Crucible life is short. On the other hand, the crucible containing SiC as a main component had a small amount of contamination with alloy powder and a long crucible life.

As described above, the above-mentioned invention examples and comparative examples are made of Al—Sn
Although the case where the alloy powder of -Zr is manufactured has been described,
The present invention is not limited to this. For example, Al-V, Al-T
It can also be used for the production of alloy powder using i, Fe-V, Fe-Mo or the like as a raw material.

[0039]

According to the method for producing an alloy powder of the present invention,
An alloy powder having a small amount of oxygen absorption during sintering and having excellent mechanical properties of the sintered body after sintering can be produced.

[Brief description of the drawings]

FIG. 1 shows the metallographic structure of the atomized powder in the invention example 1
It is a micrograph shown at 0,000 times.

FIG. 2 is a photomicrograph showing the metallographic structure of the powder after pulverizing an ingot manufactured by casting at a magnification of 1,000.

FIG. 3 is a diagram showing the particle size distribution of atomized powder after atomization in the invention example.

FIG. 4 is a drawing showing the particle size distribution of the atomized powder after mechanical pulverization in the inventive examples.

FIG. 5 is a drawing for explaining a process of manufacturing a cylindrical test piece by powder metallurgy.

FIG. 6 is a drawing showing the relative densities of the sintered bodies of the invention example and comparative example 2.

FIG. 7 is a drawing showing the particle size distribution of the alloy powder of Comparative Example 1.

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Tadahiko Furuta 41-Cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central R & D Laboratories Co., Ltd. 41, Yokomichi 1 Inside Toyota Central Research Laboratory, Inc. (56) References JP-A-1-180901 (JP, A) JP-A-64-56802 (JP, A) (58) Fields investigated (Int. Cl. ⁷⁾ , DB name) B22F 9/04 B22F 9/08 B22F 1/00

Claims (3)

(57) [Claims] 1. It has any one of Sn, Zn and Pb
And the soft metal layer that, Al-Ti compounds and Al-Zr compound
A hard metal layer having any one of the above-described materials, wherein the soft metal material and the hard metal material are melted by melting a molten metal. A method for producing an alloy powder, comprising: a step of producing an atomized alloy powder having a layer and a hard metal layer; and a mechanical pulverization step of mechanically pulverizing the atomized alloy powder so as not to re-agglomerate. 2. The method according to claim 1, wherein the soft metal layer is made of Sn.
Is dissolved in a crucible composed mainly of SiC, claim 1
A method for producing the described alloy powder. 3. The method for producing an alloy powder according to claim 1 , wherein the maximum particle diameter of the alloy powder produced by the mechanical pulverization step is 45 μm or less. .