JPS62139802A - Production of metallic powder - Google Patents

Abstract

PURPOSE:To produce extremely fine powder at a high yield by constituting a roll of a body part having collars in the state of bringing a molten metal into collision against the roll rotating at a high speed to grind the metal to pulverized powder. CONSTITUTION:The inside of a vacuum vessel 1 is evacuated to about <=1Torr pressure. A metallic material 3 to be ground is melted by the plasma generated by a plasma gun 2 so as to collide against the roll 4 rotating at a high speed, by which the material is splashed and ground. The collars (b) are attached to the positions approximately symmetrical with the body part a' of the roll 4 as a center. Ruggedness is preliminarily formed to the surfaces of the collars (b), then the material collides again against the collars (b) after the material is ground by the collision against the body part a'. The material is thereby resplashed and divided and the extremely fine metallic powder is obtd. The mush finer metallic powder is obtd. at a high yield if the surface of the body part a' is formed to a projecting shape (drum shape).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing powder of metal or alloy (hereinafter referred to as metal).

[Conventional technology]

The method for mass production of metal powder is (a) mechanically crushing solid raw materials. (b) Spraying molten metal using gas or liquid as a medium. (c) The molten metal collides with the surface of an object moving at high speed, forming fine molten droplets and solidifying them.

(and) other methods.

The present invention relates to the method (c), and has the advantage that the equipment can be simplified by using the roll surface as the object moving at high speed. Traditional rotating roll.

The mechanism of pulverization is to drop the molten metal onto the surface of a roll rotating at high speed, and create a negative pressure on the molten metal by using a peripheral speed of the roll that is significantly faster than the falling speed.
It generates capitivity and breaks the molten metal into fine pieces. The vacuum or low pressure in the present invention is 1T
This pressure, which refers to a force of about orr or less, is a pressure condition necessary to obtain high-quality powder properties. Under such low pressure.

Cavitake cannot be expected to occur due to the high-speed rotation of the rolls, and therefore, when applied to a continuous flow of molten metal flowing out from a nozzle, the conventional method is not effective enough to break up the fallen molten droplets into fine pieces. Of course, in order to prevent contamination of the molten metal by the nozzle, it is also sufficient to heat the solid raw material with a high energy density heat source to melt it and directly drop it as small molten droplets. It was not possible to obtain a good yield.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a method for producing sufficiently fine metal powder products at a high yield by improving the conventional powder production method using roll rotation.

[Means to solve the problem]

The present invention provides a roll that includes a body that atomizes the supplied molten metal by collision, and a soba that is integrally provided with the body that receives the molten droplets that have been atomized by the body and further atomizes the metal by colliding. It is characterized by consisting of parts.

[Effect]

The roll shape used in the conventional roll rotation method is a simple cylinder or disk, so for example, with a 1f cylindrical roll, the colliding molten droplets can only move in the direction perpendicular to the rotation axis, as shown in Figure 3. Since a large proportion of the powder is scattered in the left-right (axial) direction, and the angle between the direction of powder scattering and the direction of rotation of the roll is greatly different, a sufficient scattering speed cannot be obtained and it is difficult to divide the powder into fine pieces. This increases the frictional resistance between the roll surface and the molten droplet.

Conventionally, there have been examples in which the roll surface has been made uneven or has a concave (tsutsumi-shaped) roll shape, but this has not resulted in a sufficiently satisfactory effect.

According to the present invention, 1. For example, if the roll is provided with buckwheat at a symmetrical position with respect to the body where the molten droplets collide, the molten droplets that once collided with the body and scattered left and right will return to the brim. As they collide, they are further divided into smaller pieces.

The present invention further enhances the above-mentioned dividing effect.

The brim creates an uneven surface on which the molten droplets collide. Furthermore, the surface shape of the body is made convex (drum-shaped).

By increasing the probability that the molten metal droplet once collides with the surface of the body and then is accelerated and re-collides with the brim to be re-splattered and fragmented, it is possible to produce fine powder with a higher interlayer yield.

These effects will be explained with reference to FIGS. 1 and 3. As mentioned above, FIG. 3 shows the conventional method, and FIGS. 1A and 1B show how the molten droplets collide with the roll surface and scatter according to the method of the present invention. In the conventional method, the molten droplets that collide with the roll surface scatter to the left and right, and the breaking effect is small. On the other hand, in FIG. 1A, most of the molten droplets scattered left and right collide with the brim in an accelerated state, are scattered again, and are divided into thin pieces.

In FIG. 1B, by making the roll surface convex, the probability of scattering from side to side is increased, and fine powder can be produced at a higher yield.

〔Example〕

FIG. 2 is an example in which vacuum plasma is used as the heat source. In the vacuum chamber 1, there is a plasma gun 2 on the ceiling, a raw material drive device that chucks the raw metal 3 on the side wall so that its tip is in front of the plasma gun 2, and a raw material drive device directly below the tip of the raw material J/43. A powder recovery tank 6 is provided at the bottom of each roll 4.

The vacuum chamber 1 is connected to an exhaust system (not shown) via an exhaust lower. Note that 5 is a power supply device for the plasma gun 2. The effects of the present invention were confirmed using the above device.

The metal raw material 3 has a diameter of 40iIjI of material tN too.
φ, 7001m long bar, plasma output 30KW
The interior of the vacuum chamber was an Ar atmosphere with a pressure of TOTorr.

Roll 4 is copper water-cooled, diameter 300wRx 400 II
l + length without brim (Fig. 3), 11000R
Rotated with P. The metal powder obtained under these conditions was 100
The yield of less than μm was about 50%.

Next, roll 4 was made with a brim (No. 14A), and the other conditions were the same as described above, and the obtained metal powder was
The yield of xm or less was about 70%. Furthermore, when the roll 4 was made into a convex shape with a flange (Fig. 1-B) under the same conditions,
The yield of metal powder increased to about 80% when the diameter was 100 μm or less, confirming the effect of the collar and roll shape of the present invention 1.

In the above embodiment, the molten metal was supplied by melting the solid metal by local heating, but this method was carried out in a low pressure atmosphere at t7. In addition, there is no equipment in which the molten metal is composed of a refractory nozzle, tundish, etc., and it is effective for producing high-grade metal powder.

However, the effects of the present invention are not limited to these, and are also effective in solving the problem of insufficient splitting effect when molten metal is supplied through a nozzle or the like.

Further, in the above embodiments, plasma is used as the heat source, but the present invention is not limited to this.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the shape of the roll of the present invention. FIG. 2 is a diagram explaining the present invention in detail, and FIG. 3 is a diagram showing an example of a conventional roll shape and the flight of droplets due to it. 1: Vacuum chamber, 2: Plasma gun, 3: Raw metal. 4: Roll, 5: Power supply, 6: Powder collection tank, 7: Exhaust hole,
α, α: Body part, b nipper part. Figure 2

Claims (1)

[Claims] 1. A method for producing metal powder in which molten metal is made to collide with the surface of a roll rotating at high speed in a vacuum or low-pressure inert gas atmosphere to form fine molten droplets, the roll having a body and a metal powder in the body. 1. A method for producing metal powder, comprising: a brim portion integrally provided with the body portion that receives the micronized molten droplets and further micronizes them. 2. The method for producing metal powder according to claim 1, characterized in that the surface of the brim on the side that receives the molten droplets is made uneven. 3. A method for producing metal powder according to claim 1 or 2, characterized in that a roll having a convex body is used.