JPH05247505A - Production of composite metal powder - Google Patents

Abstract

PURPOSE:To stably produce a high-quality composite metal powder in which the grains of the high-m.p. hard compd. such as a ceramic are uniformly dispersed by the atomization method. CONSTITUTION:When a molten metallic material is injected into a storage vessel 3 from a metal melting furnace 2, a composite of the hard powder of a ceramic, etc., and metal powder or a composite powder 7 obtained by depositing or fixing a metal powder on a hard powder is simultaneously injected. The composite powder is previously heated and then injected, and the molten metallic material is injected to the position shifted from the center of the storage vessel. Since the molten metallic material is agitated, the composite powder is efficiently and uniformly dispersed in the molten metallic material. Consequently, the molten metallic material is not cooled, the injection nozzle is not clogged, and the contamination of the molten metallic material with the gaseous impurities is prevented.

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 a composite powder of a high melting point, hard compound particles and a metal, which is suitable as a material for wear resistant materials, heat resistant materials and high strength materials.

[0002]

2. Description of the Related Art In recent years, in order to improve properties such as wear resistance, heat resistance and strength, composite materials of metal and carbide, oxide or nitride have been applied. This is because by dispersing hard particles made of carbide, oxide, or nitride having a high melting point with respect to the metal in the metal, heat resistance and wear resistance are significantly improved. On the other hand, when the hard particles are dispersed in a metal, the material becomes extremely hard, and in order to obtain a final product such as a tool or a roll, the powder raw material mixed with the hard particles is cold-formed and then sintered. The so-called powder metallurgy method is used. Therefore, in order to manufacture the composite material with the hard particles by the powder metallurgy method, it is important to manufacture the composite powder in which these are mixed as uniformly as possible.

Conventionally, as a method for producing the composite powder as described above, there are a composite powder production method to which a mechanical alloying method, a chemical alloying method and an atomizing method are applied. Among them, the atomizing method is used for mass production. It is said that it is possible to produce high quality composite powder in a short time. As a method for producing the composite metal powder by the atomization method, for example, a method of modifying the surface of the hard particles to be added to improve the wettability with the molten metal material (see JP-A-2-133502), the central hole of the spray nozzle Method of supplying high melting point particles from above (Japanese Patent Laid-Open No. 62-
No. 109905), a method of mixing and spraying ceramic powder preheated to a temperature 100 to 500 ° C. lower than the temperature of the molten metal material in a spray medium (JP-A-63-504).
No. 03), etc. are known.

[0004]

However, the above-described conventional method for producing a composite powder has the following problems and cannot be said to be an effective method. That is, in the method of adding the surface-modifying powder to the molten metal material, it takes time to disperse the added particles even in the molten metal material under stirring due to the strong surface tension of the molten metal material, and during this time, the surface-modifying substances do not interact with each other. There is a problem that melting and cohesion occur and uniform dispersion is hindered. Further, in the method of spraying particles such as ceramics in the vicinity of the molten metal material immediately before spraying, or by colliding the particles, a part of the sprayed gas soars upward due to the phenomenon of so-called winding, and the molten metal material flowing down is sprayed. Since the surface is covered, the addition particles are prevented from being dispersed in the molten gold material, and as a result, there is a problem that uncomposited ceramic particles are present in the produced composite powder. This is because the turbulent flow in the molten metal storage container prevents the powder from falling vertically downward.

On the other hand, it is not easy to form particles by spraying particles into the flowing molten metal flow unless it is a so-called free-fall atomizing method. In the free-fall method, a molten metal material does not require a blowing force of a spray gas, so that a pouring pipe is unnecessary and particles can be supplied from above the crushing point. However, small particle size for powder,
In the confined method used from the viewpoint of stable production, a method of injecting the spray gas near the tip of the pouring pipe is adopted because the blowing force of the spray gas is used. With this method, it is mechanically difficult to add particles so that they are incorporated into the molten metal material.For example, if a particle supply pipe is installed near the pouring pipe, the gas flow becomes unstable and powder quality is affected. In addition to the above-mentioned problems, the installation of the particle supply device complicates the steps of setting and removing before and after the operation, and the powder remains on the particle supply device, making maintenance after the operation difficult. Furthermore, since all of the atomized gas does not collide with the molten metal material and does not contribute to pulverization, all of the supplied particles do not form a composite with the metal powder.

Further, in the method in which the preheated ceramic particles are mixed and sprayed in the spray medium, the preheated ceramic particles are cooled immediately after mixing, so that the effect of preheating becomes small. That is, the spray medium ejected from the high-pressure gas container has been considerably cooled due to adiabatic expansion, and at an addition amount for producing a material that can be practically used as a composite material, the spray medium immediately flows in an overwhelming amount of spray medium flow. This is because the heat is taken away.

As described above, it is difficult to stably produce a completely complexed powder by the method of adding particles to the molten metal material flowing down from the molten metal material storage container or the pulverization point.

In view of such problems of the prior art, the present invention rapidly disperses particles in a molten metal material by a method of adding particles in a molten metal material storage container to stabilize a high quality composite metal powder. The present invention is intended to propose a method for producing a composite metal powder that can be produced as described above.

[0009]

The present invention relates to a method of pulverizing a molten metal stream by a fluid jet to obtain a metal powder, and when pouring a molten metal material from a metal melting furnace into a storage container A composite powder of a hard powder and a metal powder, or a composite powder in which a metal powder is adhered or fixed around a hard powder such as ceramics is simultaneously charged, and a molten metal material of the composite powder mixture is allowed to flow down from the storage container, It is also possible to preheat the composite powder into a storage container, and to inject the molten metal material into the storage container from the metal melting furnace at a position displaced from the center position of the storage container. It is a summary.

[0010]

In the present invention, the method of adding particles in the molten metal material storage container is adopted as the means for adding particles to the molten metal material for the following reason. When particles such as ceramics are added to the molten metal material, a method of continuously passing the particles through a supply pipe or a method of charging from a box can be considered, but poor wettability between the particles of ceramics and the molten metal material Because of the large difference in specific gravity, neither method can be easily combined. On the other hand, in the case of the method of adding in the molten metal material container, since the molten metal material is poured from the metal melting furnace, the molten metal material is stirred in the molten metal material container while rotating. Therefore, by simultaneously adding particles during this pouring, the molten metal material can be efficiently rolled up.
Furthermore, by making the particles or powders for addition into composite particles or powders in advance, the difference in specific gravity from the molten metal material can be reduced, so that homogeneous dispersion is facilitated.

The above-mentioned composite powder (hereinafter referred to as "first composite powder") is preheated and charged into the molten metal material storage container by preheating the first composite powder and inserting it into the melting atmosphere. The gas components adsorbed on the surface of the composite powder before being desorbed can be desorbed, the contamination of the molten metal material with the impurity gas components can be prevented, the temperature drop of the molten metal material can be suppressed, and the undissolved powder is melted by the molten metal nozzle. This is because the phenomenon of solidification and blockage inside can be suppressed. The heating temperature of the first composite powder is preferably a temperature at which the powders do not fuse before being charged. This is because if the powders are fused together, the uniform dispersion of the composite powder in the molten metal material is hindered. Further, the heating method of the first composite powder may be either heating by a heater or induction heating method. However, in the induction heating method, since the added powder can be heated to a high temperature in a short time, it is possible to perform heating by a heater for a long time. Induction heating is preferred because it can be heated under conditions that do not cause the sintering that tends to occur in some cases. The induction heating conditions are determined by the powder addition amount and the composition of the first composite powder. The heating temperature of the first composite powder may be a temperature at which the gas component is removed, for example, 200 ° C. or higher, but desirably, about 6/10 of the melting point does not progress the sintering and is close to the temperature of the molten metal material. The effect on the temperature of the molten metal material during addition is small. However, considering the heating upper limit temperature of the heating device, the cost increase due to the long heating time, and the increase in the number of processes, the temperature of about 300 to 500 ° C. is preferable. Moreover, the progress of sintering can be sufficiently suppressed by heating in this temperature range. However, if the particle size of the first composite powder is, for example, several μm, the sintering may proceed, so it is necessary to shorten the heating time. The appropriate heating time is preferably determined by investigating the conditions under which metallurgical sintering progresses from the composition and particle size of the first composite powder.

Further, the reason why the molten metal to be injected from the metal melting furnace into the storage container is injected at a position deviated from the center position of the storage container is as follows. That is, when pouring the molten metal material into the molten metal material storage container, the pouring port of the metal melting furnace is usually located on the horizontal center line connecting the centers of the melting furnace and the molten metal material container. By arranging the pouring port diagonally with respect to the horizontal center line without placing it on the line, the molten metal material in the molten metal material storage container is rotated well and the effect of promoting stirring is obtained, and the added powder is This is because they are efficiently dispersed in the molten metal material.

It should be noted that the reason why the additive particles are made into a composite powder is that it is not easy to disperse the additive particles in the molten metal material if the additive particles are a single powder, and even if the additive particles are added to the molten metal material, they will float. This is because it becomes difficult to do so and dispersion becomes easy. The method for producing the first composite powder is not particularly limited, and for example, a method of mixing with a ball mill or the like can be used.

[0014]

1 is a schematic diagram showing an example of an atomizing apparatus for carrying out the method of the present invention, FIG. 2 is an enlarged schematic diagram showing a powder supplying apparatus in the same apparatus, and FIG. 3 is a molten metal material in the same apparatus. It is the schematic which shows the behavior at the time of adding a composite powder in a storage container, 1 is a molten metal material, 2 is a melting furnace, 3 is a molten metal material storage container, 4 is an induction heating device, 5
Is a stopper, 6 is a powder supply pipe, 7 is a first composite powder, 8
Is a powder supply device, 9 is a chamber, 10 is an atomizer, 11 is a tank, 12 is a cyclone, 13 is an exhaust valve,
14-1 and 14-2 are inert gas cylinders.

As shown in an enlarged scale in FIG. 2, the powder feeding device 8 has a filter 8 made of a sintered metal or a foam metal inside.
-1 is arranged, and the heating device 8-2 is built in the inner wall,
An inert gas of the same type as the melting atmosphere is made to flow from the lower part of the filter 8-1 to form a fluidized bed on the filter 8-1, and the temperature inside is measured by the thermocouple 15 to adjust the temperature. You can do it.

In the atomizing apparatus, the molten metal material 1 is poured from the melting furnace 2 into the molten metal material storage container 3.
Stirring with rotation occurs in the storage container 3, and the first composite powder 7 simultaneously added from the powder supply device 8 through the powder supply pipe 6 is efficiently entrained in the molten metal material and easily homogeneously dispersed. It The first composite powder 7 is an inert gas cylinder 1
4-1 is flown in the upper part of the filter 8-1 in the apparatus by the inert gas supplied and is added to the molten metal material storage container 3 by increasing the gas pressure of the inert gas cylinder 14-1 at the time of addition. To be done. The molten metal material 1 in which the first composite powder 7 is homogeneously dispersed in the molten metal material storage container 3 is
The composite metal powder produced by flowing down in a rod-like or plate-like manner from the bottom opening opened by raising the stopper 5 in the storage container 3 and pulverized by the atomizing medium sprayed from the atomizer 10 in the tank 11 is a cyclone. 12
Be recovered via.

Further, when the first composite powder is added, it is preheated by the heating device 8-2 in the powder supply device 8 to remove the gas component adsorbed before being charged into the melting atmosphere. Contamination of the molten metal material 1 with an impurity gas component is prevented, the temperature of the molten metal material is prevented from decreasing, and the molten metal nozzle is prevented from being clogged with unmelted powder, so that stable operation can be performed.

Next, when pouring the molten metal material 1 into the molten metal material storage container 3, the pouring port 2-1 of the melting furnace 2 connects the respective centers of the melting furnace 2 and the molten metal material storage container 3. When the molten metal material 1 in the molten metal material storage container 3 is rotated at a slant with respect to the horizontal center line, the rotation of the molten metal material 1 is further improved, and a large stirring effect is obtained. Dissolution and uniform dispersion into

When the molten metal material 1 is poured into the molten metal material storage container 3 and the molten metal material 1 is heated by the induction heating device 4 at the same time, the molten metal material in the container is agitated. The first composite powder is more efficiently dispersed in the molten metal material. The induction heating condition at this time may be selected such that the molten metal material is stirred depending on the structure of the molten metal material storage container 3, the amount of the molten metal material, and the like.

Example 1 A composite metal powder was produced by the atomizing apparatus shown in FIG. 1 in which the pouring port of the melting furnace was located on the horizontal center line connecting the molten metal storage container and the melting furnace. At that time, particle size 0.5 to 2
As a first composite powder obtained by mixing 500 g of 0 μm alumina powder and 1000 g of Cu powder having an average particle size of 150 μm with a size of 40 μm or more for 30 minutes in a ball mill having inner walls and balls made of alumina, and using a powder supply device for the first composite powder. The powder was held at 500 ° C for 1 hour. In this embodiment, after Cu, which is a molten metal material, is melted at 1350 ° C., it is poured into a molten metal storage container at a rate of about 30 kg / min, and at the same time as pouring, the total amount of the first composite powder is about 500 g from a powder supply device. All was fed at a rate of / min. Then, finally, 50 kg of the first composite powder and Cu were put together into a tundish, and the amount of dissolution was adjusted so that the amount of alumina contained was 1%.

Example 2 The pouring port of the melting furnace was arranged obliquely at an angle of 20 degrees with respect to the horizontal center line connecting the molten metal storage container and the melting furnace.
Others were atomized under the same conditions as in Example 1 to produce a composite metal powder.

Example 3 The pouring port of the melting furnace was disposed obliquely at an angle of 20 degrees with respect to the horizontal center line connecting the molten metal storage container and the melting furnace.
Alumina powder 5 having an average particle size of 50 μm as the first composite powder
A composite metal powder was manufactured by atomizing under the same conditions as in Example 1 except that 00 g was coated with 500 g of Cu powder having an average particle size of 20 μm by the mechanofusion method.

Comparative Example By the conventional pouring method in which the pouring port of the melting furnace was located on the horizontal center line connecting the molten metal storage container and the melting furnace, the first composite powder was made of only 0.5 to 20 μm alumina. Other than that, atomization was performed under the same conditions as in Example 1.

Table 1 shows the results of classifying the powders produced by the above four methods, measuring the amount of alumina contained, and comparing the amount of alumina of each particle size. Table 1 shows the analysis values (% by weight) of the powders having four particle sizes. As is clear from the results in Table 1, the analytical values of each particle size in Examples 1 to 3 to which the method of the present invention is applied are constant without deviating from the target of 1%. It is speculated that this is because the alumina was uniformly compounded. On the other hand, in the comparative example, the analysis value is considerably low, indicating that alumina is not incorporated in the molten metal material. This is because ceramics alone are not easily incorporated into the molten metal material.

[0025]

[Table 1]

[0026]

As described above, according to the method of the present invention, it is possible to easily and uniformly disperse the added composite powder in the molten metal material storage container. This is a great effect that a high quality composite metal powder in which high melting point and hard compound particles such as ceramics are extremely uniformly dispersed can be stably produced without complicating maintenance.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an atomizing device for carrying out the method of the present invention.

FIG. 2 is an enlarged schematic view showing a powder supply device in the same device.

FIG. 3 is a schematic view showing the behavior of the same apparatus when a composite powder is added in a molten metal material storage container.

[Explanation of symbols]

 1 Molten Metal Material 2 Melting Furnace 3 Molten Metal Material Storage Container 4 Induction Heating Device 5 Stopper 6 Powder Supply Pipe 7 Composite Powder 8 Powder Supply Device 9 Chamber 10 Atomizer 11 Tank 12 Cyclone 13 Exhaust Valve 14-1, 14-2 Inert Gas cylinder

Claims (3)

[Claims] 1. A method of pulverizing a molten metal flow by a fluid jet to obtain a metal powder, wherein when a molten metal material is poured from a metal melting furnace into a storage container, a composite powder of hard powder such as ceramics and metal powder. , Or a composite powder in which a metal powder is adhered or fixed around a hard powder such as ceramics and the molten metal material mixed with the composite powder is allowed to flow down from the storage container. Method. 2. A composite powder of hard powder such as ceramics and metal powder, or a composite powder in which metal powder is adhered or fixed around a hard powder such as ceramics is preheated and charged into a molten metal material storage container. Claim 1 characterized by the above-mentioned.
A method for producing the described composite metal powder. 3. The method for producing a composite metal powder according to claim 1, wherein the molten metal material to be poured from the metal melting furnace into the storage container is poured into a position displaced from the central position of the storage container. ..