JPS6199606A - Production of composite powder - Google Patents

Abstract

PURPOSE:To obtain easily composite powder at a low cost by penetrating ceramics into a molten metal by using elements contributing to wetting and atomizing the molten metal under stirring. CONSTITUTION:>=1 Kinds of the elements which are selected from Ca, Ti, Cr, Mg, V, Zr, Nb, etc. and contribute to the wetting to ceramics are preliminarily incorporated into the molten metal or alloy thereof. The ceramic particles or ceramic fibers are then charged to the surface of the molten metal and are penetrated into the molten metal by improving the wetting between the particles or fibers and the molten metal. Carbide, oxide, nitride, etc. are used for the ceramics. A gaseous pressure or water pressure is acted to the molten metal column from a nozzle under stirring of such molten metal by which the atomized composite powder is obtd.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for producing a composite powder, and in particular, a method for producing a composite powder in which ceramic particles or ceramic fibers are uniformly dispersed in a metal or alloy powder thereof. Regarding.

[Background of the invention]

Conventionally, known methods for producing composite powders in which ceramic particles or the like are dispersed in metal powder include (1) a powder metallurgy method, (2) a solidification method, and (2) a casting method.

This powder metallurgy method is generally widely used as a method for producing dispersed reinforced alloys in which particles of non-metals such as ceramics are uniformly dispersed in a base metal. A surface oxidation method (SAP method) in which powder is molded and processed, or mechanical embedding of ceramic particles into metal particles.
i Composite powder is molded and processed by 1t, 1"25 canical alloying method. Furthermore, a composite powder in which the surface of ceramic powder is chemically or electrochemically coated with metal is used as a starting material, and metal powder is mixed with this composite powder. Examples include a method of molding and processing.

However, in the case of the SAP method or the mechanical alloying method, the treatment process takes a long time and there are difficulties in the method of mixing ceramic particles. Further, the process is complicated, and at the same time, it is difficult to uniformly disperse ceramic particles etc. in the metal, making it difficult to ensure quality stability.

Next, there are four representative examples of solidification methods.The first method is to hold the metal in a state in which solid and liquid phases coexist, increase the viscosity, and solidify the metal. The second method is to produce a composite powder by introducing ceramic particles into a slurry in a liquid coexistence zone and stirring the slurry until it solidifies (Japanese Patent Publication No. 58-48002, Japanese Patent Application Laid-Open No. 56-116851). The method involves forcibly injecting and dispersing ceramic particles together with gas into a falling column of molten metal and rapidly solidifying them to produce a composite powder (Japanese Patent Laid-Open No. 53-57).
101 Publication), or as a third method,
There is a method (Japanese Patent Publication No. 43-20883) of producing composite powder by adjusting the atmosphere through which metal particles are ejected from a nozzle to form an oxide film of an appropriate thickness.Furthermore, there is a fourth method. describes a method for producing composite powder in which an oxide-forming element is added to molten copper, the added element is selectively oxidized in the molten metal, and the molten metal is atomized without mechanical stirring (Japanese Patent Laid-Open No. 58-204106). (Government) etc.

In the first method of coagulation as described above, since the powder lacks fluidity, the final powder obtained becomes relatively coarse particles and becomes a composite powder in which ceramic particles are attached to the surface of metal particles. Also.

When a slurry is heated above the liquidus line.

Since the ceramic particles in the slurry are forced to be mechanically mixed, there is a drawback that the ceramic particles separate from the molten metal and float to the surface.

Next, in the second method, it is difficult to keep the content of ceramic particles in the metal powder constant.

The third method has the problem that it is difficult to form an oxide film with a uniform thickness on the surface of the powder, making it impossible to produce stable powder.

Furthermore, in the case of the fourth publication, the oxides generated in the molten metal have the property of floating to the surface of the molten metal as slap due to the difference in specific gravity, and in order to keep them dispersed as particles in the molten metal, forced stirring is required. In addition, forced stirring may make it impossible to obtain a healthy molten metal. Another disadvantage is that if the oxide is kept in the molten metal for a long time, it will grow and become coarse, and furthermore, when the stirring is stopped, the produced oxide will float and separate on the surface of the molten metal.

In addition, as a casting method, a method of manufacturing composite powder by dispersing ceramic particles in molten metal has recently been attempted, but it is not clear how to disperse ceramics in molten metal or in the powder after solidification. A major problem is how to uniformly disperse ceramic particles.

In this way, conventional methods for producing composite powders have the problems of not being able to uniformly disperse ceramic particles or ceramic fibers in metal or metal alloy powders, but also complicating the production process and increasing production costs. had.

[Purpose of the invention]

An object of the present invention is to provide a method for producing a composite powder that is simple, has high industrial productivity, and can be obtained at low cost by uniformly dispersing ceramic particles or ceramic fibers in a metal or a powder of the metal. It is on offer.

[Summary of the invention]

In order to eliminate the conventional drawbacks, the present invention focuses on the fact that the conventional drawbacks can be overcome by using a composite powder in which ceramic particles or ceramic fibers are uniformly dispersed in a metal or its alloy powder as a starting material powder. More specifically, in producing a composite powder in which ceramic particles or ceramic fibers are uniformly dispersed in a metal or its alloy powder, a molten metal and a molten metal are mixed into a molten metal or its alloy. It is characterized in that an element that contributes to wetting with the ceramic particles or ceramic fibers is pre-impregnated, the ceramic particles or ceramic fibers are infiltrated into the molten metal, and then the molten metal is atomized while being stirred.

The present invention will be explained in detail below.

The structure of the present invention consists of a step of infiltrating ceramic particles or ceramic fibers into a metal or molten metal, a step of holding the particles or fibers in the molten metal, and a step of pulverizing the molten metal.

Next, each of these steps will be explained in detail. First, there is a method in which ceramic particles or fibers are infiltrated into a metal or a molten metal.1 In the normal casting method, particles or fibers are infiltrated into a molten metal or alloy. The present inventors investigated various methods of infiltration, and found that ceramic particles or fibers could float on the surface of the molten metal due to the difference in specific gravity and penetrate into the molten metal. It has been found that improving the wettability between the molten metal and the particle or fiber interface is an important point in order to prevent floating separation and agglomeration of particles.

In other words, Cn is added to the molten metal or its alloy in advance.
g T iy Cr * M g + ” r Z r
If ceramic particles or fibers are added to the surface of the molten metal after containing at least one element selected from pNb, the wettability between the particles or fibers and the molten metal will be improved and it will be easy to penetrate into the molten metal. Become. In this method, after solidifying a molten metal or its alloy impregnated with ceramic particles or ceramic fibers,
It has been confirmed that particles or fibers in the molten metal do not float to the surface of the molten metal and remain in the molten metal even when the molten metal is remelted or melted again.

As ceramic particles and ceramic fibers that are uniformly dispersed in metal or its alloy powder.

Graphite powder, SiC, TiC, VC, NbC carbide particles, A Q@031 Cr, O,, Z r Oss Y
xOs oxide particles and Si, N, A, N, Ti
N.

BN nitride particles, graphite, Sin, Aa, 0. Examples include fibers such as These carbide-based, oxide-based, and nitride-based particles and their fibers are pretreated with Ca e T
AJ or A containing at least one selected from x e Cr g M g g V g Z r or Nb
As a result of adding j1 alloy, Cu or Cu alloy, Ni or Ni alloy into the molten metal, any of the particles and fibers can permeate into the molten metal without floating to the surface of the molten metal.

The size of the ceramic particles and the 7 spectral ratio of the fibers that can penetrate into the hot water of the metal or its alloy are not particularly limited, and there is no need to pay special attention to their selection. As a result, the finer the dispersed particle diameter, the more effectively it affects the material properties.In the present invention, as a result of examining ceramic particles with a minimum particle diameter of up to 100 that can be obtained on a mass-produced scale, it was confirmed that all of them can penetrate into the molten metal. It has been confirmed that the amount that can penetrate into the molten metal is limited by the size of the penetrating particles.

For example, if more than 30% by volume of ceramic particles with a particle size of 100 particles are added to the molten metal, the molten metal will have almost no fluidity and cannot be pulverized by an atomization method or the like. In addition, in the case of fiber, the aspect ratio is 2
If you add more than 30% by volume of 00 or more, 1
The results are similar to those obtained when the particle size is 100 people. On the other hand,
For particles with a particle size of 10 μm and fibers with an aspect ratio of 20, powdering is possible even if the volume ratio is up to 45%.

On the other hand, Ca, Ti,
The amounts of Mg, V, Zr, and Nb added are based on the matrix of various metals or their alloys.

A range of 0.05 to 3.5 at/o is sufficient, and a powder in which ceramic particles or ceramic fibers are uniformly dispersed can be obtained. If the re-addition amount is less than 0.05a t/o, the effect of improving wettability is small, while if the addition amount is 3
If it exceeds a t/o, the additive element reacts with the matrix to form an intermetallic compound, which aggregates and coarsens in the matrix, which is undesirable because the mechanical strength of the material decreases. The amount of added element is 0.0
5-3 at/.

It is desirable to keep it within the range of .

t Next, we will explain how to make composite powder by atomization method from molten metal impregnated with ceramic particles or ceramic fibers.The feature of the single atomization method is that ceramic particles or ceramic fibers infiltrate into the molten metal or its alloy. Let me,
Next, while stirring the molten metal, the molten metal column from the nozzle is atomized by gas pressure or water pressure to obtain a composite powder.

FIG. 1 is a schematic sectional view showing an example of an apparatus for carrying out the method of the present invention. The molten metal impregnated with ceramic particles or ceramic fibers is melted directly from the base metal in the crucible 4, or R8 molten metal is melted separately in a melting furnace, and the molten metal is passed through the molten metal stoppers 1 and 7 and the molten metal stirring blades 2 and 6. At the same time, the ingot is injected into a crucible 4 that has been preheated by a heating element 3, or the infiltrated ingot is remelted in the crucible 4 and used as a raw material molten metal for composite powder. The raw material molten metal thus obtained is held in the crucible 4 with the molten metal stopper 7 inserted into the nozzle hole 9. The molten metal stopper 7 extends through the hollow molten metal stirring shaft 2 having a stirring blade 6 attached to its tip, and is installed so that it can move up and down even while stirring the molten metal. The nozzle hole 9 for dropping the molten metal can be opened and closed by moving the molten metal stopper 1°7 up and down. The stopper material is preferably made of hard graphite or the like.

The molten metal 5 held in the crucible 4 is passed through the molten metal falling nozzle hole 9
It is important to maintain a certain temperature to provide fluidity so that it can easily pass through the water.

This predetermined temperature is appropriately set in the range of 50 to 10'O<0>C, which is higher than the liquidus temperature for each type of matrix. If the temperature is below 50° C. above the liquidus line, the temperature is too low and the molten metal cannot pass through the molten metal drop nozzle hole 9. on the other hand,
When the temperature of the molten metal exceeds the liquidus line of 100°C, the ceramic particles or ceramic fibers in the molten metal will not agglomerate or float apart by holding the molten metal for a long time, but the composite metal particles will become crystallized or become particles. In order to achieve uniform dispersion of the molten metal, it is preferable to set the holding temperature of the molten metal at a temperature below 100° C. above the liquidus line.

In order to uniformly disperse the ceramic particles or ceramic fibers that have penetrated into the molten metal into the metal or its alloy powder, the molten fi 5 in the crucible is stirred using a stirring blade 6 and passed through the molten metal drop nozzle 8. The rotation speed of the molten metal stirring blade 6 should be adjusted appropriately so that the particles or fibers are uniformly dispersed in the molten metal.If the rotation speed is increased, the molten metal will become more turbulent, and the molten metal falling nozzle hole will not be smooth. The powder may not be able to pass through the powder, or casting defects such as pinholes may occur inside the resulting powder. It is desirable to set the appropriate rotational speed to about 60 to 80 rpm.

It is appropriate that the blade for stirring the molten metal be placed at a position approximately - from the height of the molten metal from the molten metal dropping nozzle 8 in the crucible. If the height of the molten metal is too high, the entire molten metal cannot be stirred uniformly, and if it is too low, the molten metal becomes turbulent and cannot smoothly pass through the molten metal falling nozzle hole.

The molten metal column that has passed through the molten metal drop nozzle hole 9 is immediately pulverized by gas or water pressure injected from the circular injection nozzle 10, but in order to obtain a uniform composite powder particle size in which particles and fibers are evenly dispersed, it is necessary to The diameter and injection pressure of the molten metal dropping nozzle, and the distance from the lower end of the molten metal dropping nozzle to the point where the water or gas stream collides with the molten metal column are important. For the molten metal drop nozzle hole diameter of 3 to 15 mm, the injection pressure is 4 to 50 kg/, -d for gas pressure, and 30 for water pressure.
~200 kg/aJ was appropriate. The distance from the bottom of the nozzle until the water or gas flow collides with the molten metal column is 3~
Low is appropriate. If the distance is long, the molten metal column is likely to be disturbed and cannot pass through the center of the circular injection nozzle/o, and an oxide film may be formed on the surface of the molten metal column.
As a solid layer occurs, ceramic particles or ceramic fibers in the molten metal column agglomerate, making it difficult to produce a composite powder in which one particle or fiber is uniformly dispersed.

On the other hand, when the distance is in the range of 3 to 10 square meters, the jetted pressure generates a suction force in the falling direction of the molten metal column, which has the advantage that the natural fall of the molten metal column becomes smooth.

The atomized composite powder is recovered by scattering it into a tank 11 filled with water 12 or argon, helium, nitrogen gas, or the like.

[Embodiments of the invention]

<Example 1> 900 g of pure An was melted in a graphite crucible in the atmosphere, the temperature was raised to 750°C, and the molten metal was held at 8IllIφ.
The mixture was stirred using an X600 jl alumina protection tube, and 100 g of SiC particles with a particle size of 0.5 μm were poured into the center of the vortex to examine the permeability of the SiC particles into the molten metal. As a result, the added SiC particles floated and separated on the surface of the molten metal and did not penetrate into the molten metal.

Molten copper held at 1180℃ in the same way, 1550℃
The permeability of SiC particles into the molten metal was also investigated for the molten Ni held in the molten metal.
The particles floated onto the surface of the molten metal and separated.

In addition to SiC fibers, Ti
Carbide particles and graphite particles of C, V C, N b C,
A jl103y Crxos* Z r O1+ y
, o, oxide particles and AA, 03 fiber, 5iiN4
Nitride-based particles such as AIN+TiN and BN were also investigated, but none of the particles or fibers penetrated into the molten metal in the AQ-based, copper-based, and Ni-based molten metals, and 0 or more particles floated and separated onto the molten metal surface. It can be seen that in the conventional casting method, none of the various ceramic particles or fibers penetrate into the molten metal or alloy.

<Example 2> After melting aluminum ingot using a graphite crucible in the atmosphere, 900 g of molten AJ-Ca alloy to which 1 st/o of metallic Ca was added was held at 750°C and SiC with a grain size of 0.5 μm was melted. 100 g of particles were added in the same manner as in Example 1, and the influence of the dispersion aid element on the permeability of SiC particles into the molten metal was investigated. As a result, the SiC particles permeated into the molten metal without floating to the surface of the molten metal.

Table 1 shows the results of examining the effects of dispersion aid elements on molten aluminum of various particles and fibers using a similar method. 1st
In the table, the x mark indicates that the material floated to the surface of the molten metal, and the 0 mark indicates that the material permeated into the molten metal.

As shown in the table, all ceramic particles or fibers can penetrate into the molten metal to which Ca and Zr have been added. However, when ceramic particles or fibers are infiltrated using a dispersion aid element other than Ca and Zr, it is understood that it is necessary to select the type of particles or fibers.

Table 2 summarizes the results of examining the influence of dispersion aid elements on the permeability of various ceramic particles or fibers into molten steel and molten Ni. Note that the amount of copper and Ni molten metal is 2.91 kK, and the amount of ceramic particles or fibers added is 90 g.

As can be seen from Tables 2 and 3, it is found that for both steel and Ni matrices, it is necessary to select the dispersion aid element depending on the type of ceramic particles or fibers.

<Example 3> 1.8 kg of molten aluminum containing metal Ca 1 at/o was held at 750°C, 200 g of SiC particles with an average particle size of 0.5 μm were added in the same manner as in Example 1, and the molten metal was heated. The molten metal was injected into the graphite crucible 4 shown in FIG. 1, and the molten metal was stirred by rotating the molten metal stirring blades 2.6 at 1100 rpm. In addition, the graphite crucible is heated to 75 by the heating furnace 3 along with the molten metal stirring blades and the molten metal stoppers 1 and 7.
First, the molten metal was preheated to 0° C. and stirred, and then the molten metal stopper was moved upward to allow the molten metal to fall from the nozzle hole 9 of 6 cylinders φ provided at the center of the bottom of the crucible. N gas was injected from the circular injection nozzle 10 at a pressure of 15 kg/aJ at a distance of 5 m from the lower end of the nozzle to the molten metal column for atomization. The obtained powder was immediately scattered into water 12 in tank 11. The particle size distribution of the atomite powder thus produced is shown in Table 4.

FIG. 2 is an optical micrograph showing a cross-sectional metallographic diagram of an atomized powder obtained by the method of the present invention.

As is clear from the figure, it can be seen that the SiC particles are uniformly dispersed in the aluminum powder.

FIG. 3 is an optical class I1 momme photograph showing a cross-sectional metal structure of an atomized powder in which SiC particles having an average particle diameter of 2 μm are infiltrated into an All-molten metal using a similar method. As in FIG. 2, it can be seen that the particles are uniformly dispersed in the powder.

〈Example 4〉 2.91) cg of molten copper containing 1 at/o Ti was heated to 1150°C and Si with an average particle size of 0.5 μm was heated.
90 g of C particles were added in the same manner as in Example 1, and injected into a crucible that had been preheated to 1200°C after penetrating into the molten copper, and while stirring the molten metal at a rotation speed of 200 rpm, a nozzle hole diameter of 10 mm was inserted. The molten metal is dropped from the N2 gas pressure of 25 kg.
Atomized with /J.

The particle size distribution of the produced atomized powder is shown in Table 4, and by optical microscope structure observation of the cross section of the atomized powder, S
As in Example 3, it was confirmed that the iC particles were uniformly dispersed in the copper powder.

<Example 5> 2.91 kg of Ni containing 1 at/o of Cr metal
The molten metal was maintained at 1550°C. 90 g of BN particles with an average particle size of 0.05 μm were added in the same manner as in Example 1, and Ni
The first infiltrated into the molten metal was poured into a crucible preheated to 1550°C, and the molten metal was stirred at 50 rpm for 12 hours.
Drop it through a nozzle hole diameter of diameter φ, and apply N gas pressure of 30 kg/
It was atomized with d.

The particle size distribution of the produced atomized powder is shown in Table 4, and the cross section and surface of the atomized powder were measured using an electron microscope.
As a result, it was confirmed that the BN particles were evenly dispersed in the Ni powder as in Example 3.

FIG. 4 shows an electron micrograph showing the metal structure of the powder surface and the line analysis results of element B by EDX. From FIG. 4, it can be seen that BN particles are uniformly present on the powder surface as well.

<Example 6> A 1.91-m aluminum molten metal containing l a t / o metal Zr was held at 750°C, and 100 SiC whiskers with an aspect ratio of 30 to 50 were formed in the same manner as in Example 1.
The melt was poured into a crucible preheated to 750°C, and the molten metal was heated at 500 r.
It was dropped through a nozzle hole diameter of 15 cm while being stirred at a rotation speed of pm, and totomized for 7 times at a N2 gas pressure of 30 kg/cwt.

The particle size distribution of the produced atomized powder is shown in Table 4.

As can be seen from Figure 5, Figure 5 shows an optical micrograph showing the cross-sectional metal structure of the atomized powder.

It can be seen that the SiC whiskers are uniformly dispersed in the aluminum powder.

<Example 7> 1.8 kg of molten aluminum containing 1 at/o of metal V was held at 750°C, 200 g of graphite particles with an average particle size of 1 μm were added in the same manner as in Example 1, and the molten aluminum was The molten metal was injected into a crucible preheated to 750°C, and the molten metal was dropped through a nozzle hole diameter of 8 mm while stirring at a rotational speed of 30 rpm, and N2 gas was added to the crucible for 25 min.
Atomized at kg/cd.

The particle size distribution of the produced atomized powder is shown in Table 4. Further, as a result of optical BJ microstructure analysis of the cross section of the atomized powder, it was confirmed that the graphite particles were uniformly dispersed in the aluminum powder.

〔Effect of the invention〕

As mentioned above, Hon J! According to the present invention, a composite powder in which ceramic particles or ceramic fibers are uniformly dispersed in a metal or alloy powder thereof can be easily and inexpensively produced on an industrial scale, which is a remarkable effect.

Furthermore, by using the composite powder produced by the method of the present invention, there is no need to mix metal powder and ceramic powder, which has the advantage of making it easy to mold various products.
It is growing.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing an example of an atomized device used in the method of the present invention, Fig. 2 is an optical microscope photograph showing a cross-sectional metallographic diagram of the atomized composite powder obtained by the method of the present invention, and Fig. 3
The figure is an optical microscope photograph showing a cross-sectional metallographic diagram of aluminum atomized composite powder with 22m5ic particle decomposition.
The figure shows an electron micrograph showing metal ff1m on the powder surface and EDX, : , k 6 B element 0
Line segment jJ? (/l Connection 1'/5111f This is an optical V & photo diagram showing the cross-sectional gold dust structure of the SiC whisker-dispersed aluminum atomized composite powder. 1... Molten metal stopper shaft, 4... Crucible, 5... Molten metal, 6--Blade for stirring molten metal, 9... Molten metal falling nozzle hole.

Claims (1)

[Claims] 1. In producing a composite powder in which ceramic particles or ceramic fibers are uniformly dispersed in a metal or its alloy powder, the molten metal and the ceramic powder or ceramic fibers are mixed in the molten metal or its alloy. A method for producing a composite powder, which comprises preliminarily impregnating an element that contributes to wetting with a molten metal, infiltrating the molten metal with ceramic particles or ceramic fibers, and then atomizing the molten metal while stirring the molten metal. 2. A method for producing a composite powder according to claim 1, wherein the metal or its alloy is Al, Cu, Ni, or an alloy thereof. 3. In claim 1, the element contributing to wetting of the molten metal or its alloy and the ceramic particles or ceramic fibers is Ca, Ti, Cr, Mg.
, V, Zr, and Nb. 4. In claim 3, the Ca, Ti,
The addition amount of one or more elements selected from Cr, Mg, V, Zr, and Nb is 0.05 to 0.05 in total of one or two or more elements.
3.0 at/o range. 5. Claims 1 and 3, wherein the ceramic particles are one type selected from graphite particles, carbide-based, nitride-based, or oxide-based particles with a particle size of 0.01 to 10 μm; Ceramic fiber has an aspect ratio of 20 to 20
1. A method for producing a composite powder, characterized in that: 6. A method for producing a composite powder according to claims 1 to 5, characterized in that the ceramic particles or ceramic fibers account for 0.05 to 45% of the total volume. 7. A method for producing a composite powder according to claim 1, characterized in that the atomization involves stirring the molten metal and pulverizing it into powder by gas pressure or water pressure immediately after it falls.