JPS62112710A - Production of metallic powder - Google Patents

Abstract

PURPOSE:To produce uniform and fine metallic powder by dropping molten metal flow onto a high speed rotating surface in a vacuum or non-oxidative atmosphere to splash the molten metal and further bringing the molten metal into collision against an outside wall provided above the rotating surface on the outside circumference thereof. CONSTITUTION:A metal in a vessel 1 in the vacuum or non-oxidative atmosphere is melted in a high-frequency heating furnace 2 and the molten metal 3 is admitted into a tundish 4. The molten metal is dropped from an aperture 9 in the base of the tundish 4 and is allowed to collide against the smooth surface of a rotating body 5 rotating at a high speed. The molten metal is made into unsolidified fine particles 7 by centrifugal force without sticking to the smooth high speed rotating surface and the particles further collide against the smooth surface of the outside peripheral wall 11 erected at 90-135 deg. angle with respect to the collision surface of the rotating body. The particles are thus splashed and solidified as the metallic powder 8 having the extremely fine and uniform grain size. Such powder accumulates on the bottom 12 of the vessel 1.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an improvement in a method for producing metal powder using a centrifugal atomization method.

<Prior Art> A centrifugal atomization method has been known as one of the methods for producing metal powder.

This method is a method in which the molten metal collides with a rotating body, causing the molten metal to be scattered and atomized by impact force and centrifugal force, and requires a larger amount of gas and energy than the gas atomization method or ultrasonic atomization method. This is a very advantageous method since it does not require boiling and therefore the equipment is relatively simple.

In such a centrifugal spraying method, the rotating body conventionally employed is mainly in the shape of a disk with a smooth surface or a convex or concave center.

However, all of these have the problem that the efficiency of transmitting centrifugal force to the molten metal is not good.

Therefore, in order to apply a large centrifugal force in a short period of time, the rotational speed of the rotating body should be increased to, for example, 10. It was necessary to increase the rpm to OOOrpm. However, in order to increase the rotational speed of the rotating body, the bearings and rotation opening grooves had to be complicated and rigid, which was a problem.

Therefore, in recent years, many methods have been studied to improve the impact force and centrifugal force transmission efficiency by forming fins or grooves on the surface of the disc-shaped rotating body.

However, these methods also have difficulty spraying the molten metal completely because the surface of the rotating body has a complicated shape, resulting in adhesion and solidification of the molten metal, resulting in uniform and fine metal powder being sprayed in one piece. Climbing up was difficult and rare.

<Means for Solving the Problems> In view of the above-mentioned problems in the conventional metal powder manufacturing method, the inventors of the present invention have conducted intensive studies to solve the problems, and as a result, the rotational speed of the rotating body has been increased from the conventional method. We have discovered a method that can increase the efficiency of transmitting centrifugal force to molten metal using a rotating body with a simple structure and obtain uniform and fine metal powder.

<Structure of the Invention> That is, the present invention is a rotating body having a collision surface that is smooth enough to prevent molten metal from adhering or solidifying, and a wall of a constant height above the outer periphery. metal flowing down,
The purpose is to produce metal powder by atomizing the powder by the impact force and centrifugal force of the rotating body, and then flying and colliding with the outer circumferential wall of the rotating body to form further fine particles.

According to the method of the present invention, the flowing molten metal is atomized by the impact force and centrifugal force from the rotating body with which it first collides. Then, the micronized particles in an unsolidified state collide again with the outer peripheral wall of the rotating body, where a large impact force and centrifugal force are applied, making it possible to further refine the particles.

<Effect> Hereinafter, details of the present invention will be explained based on the accompanying drawings.

FIG. 1 is a schematic diagram of an apparatus for carrying out the present invention, in which 1 is a container connected to a vacuum evacuation device and an atmospheric gas supply device (not shown), 2 is a high-frequency heating furnace provided in the container 1, and 3 is a Molten metal melted in the high-frequency heating furnace 2, 4 a tundish containing the molten metal, 5 a rotating body that atomizes the molten metal in the tundish 4 by centrifugal force, 6
is a rotational drive device for the rotating body 5.

When producing metal powder using the above-mentioned apparatus, the container 1 is evacuated by a vacuum evacuation device (not shown), and then atmospheric gas is supplied to the container 1 by an atmospheric gas supply device (not shown) to make the inside of the container 1 free. The atmosphere should be active or non-oxidizing.

On the other hand, after the molten metal 3 is heated and maintained at a predetermined temperature in the high-frequency heating furnace 2, the rotating body 5 is rotated at a predetermined speed by the rotation drive device 6, and the molten metal 3 is poured into the tundish 4.

The poured molten metal 3 is placed in the bottom opening 9 of the tundish 4.
As it flows further down, it first collides with the 1° collision surface of the rotating body 5.

Thereafter, the molten metal turns into unsolidified fine particles 7, collides with the outside of the rotating body and wall 11 again due to centrifugal force, where it becomes coarsely fine particles, flies away from the rotating body 5, and then becomes metal powder 8 into the container 1. It collects on the bottom 12.

As the molten metal is thrown off the collision surface 10 and outer wall 11 of the rotating body 5, a large impact force and centrifugal force are applied to the molten metal, resulting in very uniform and fine metal powder. can be obtained.

In this invention, if the particle diameter to be refined is d, the radius of the rotating body is D, and the rotational speed of the rotating body is ω, there is a gap between them of 1 1/2 −n doCD ・ω (however, O≦n≦1 > -(1)
There is a relationship between

When 100% of the centrifugal force from the rotating body is transmitted to the molten metal n
=1.

When the surface of the rotating body is smooth, the value of n becomes small, and the particle diameter d is difficult to become small. Therefore, we installed a wall around the outer circumference of the rotating body,
By creating a shape that can efficiently transmit centrifugal force, n
The value can be increased.

Here, it is preferable that the wall on the outer circumference of the rotating body is inclined at an angle of 90 to 135 degrees with respect to the collision surface of the rotating body. This is because when this angle is less than 90 degrees, the particles that collided with the outer peripheral wall return to the collision surface of the rotating body and cannot fly out of the rotating body. This is also because centrifugal force is not transmitted efficiently at 135 degrees or higher.

According to this invention, the particle movement is characterized by the fact that the particle changes direction continuously on the collision surface of the rotating body, but moves in a discontinuous direction (tangential direction) at the side wall, and the discontinuity point in the velocity There will be a huge impact.

If the side wall angle is 135 degrees or more, no large impact force will work.
Miniaturization is difficult to occur.

<Example> Hereinafter, an example of the present invention will be described based on the accompanying drawings.

In the apparatus shown in FIG. 1, the inside of the container 1 is evacuated using a vacuum device (not shown) and replaced with Ar gas to create an inert atmosphere.
An N alloy having a composition u-o, 4%- was heated to a temperature 250° C. higher than its melting point and poured into the tundish 4. Next, the molten metal was poured into the center of the rotating body 5 with a diameter of 300 mm through an opening 9 with a diameter of 3 # provided at the bottom of the tundish 4, and
Fine particles were formed by the rotating body collision surface 10 and the outer wall 11 having a height of 30 cm.

FIG. 2 is a diagram showing the relationship between the rotation speed of a rotating body and particle size. Curve A is a curve B when a rotating body without an outer wall is used.
2 is a diagram showing a case where the rotating body of the present invention having the same surface roughness is used.

As is clear from curve A in the same figure, when the rotating body does not have an outer wall, the centrifugal force transmission efficiency is poor, and the n value shown in the above formula (1) is approximately 0.3.

On the other hand, in the case of a rotating body in the apparatus used in the present invention, as shown by curve B, the particles are refined to the particle size shown by curve A before colliding with the outer wall by the rotating body collision surface, and then colliding with the outer wall. As a result, the n value shown in equation (1) is approximately n÷0.8, and the collision surface 10
Since the particles flying from the metal particles 8 are fine, the obtained metal particles 8 are extremely fine.

<Effects of the Invention> As described above, according to the method of the present invention, centrifugal force can be efficiently transmitted to molten metal in the centrifugal spraying method, and fine particles can be obtained by low-speed rotation. It can be produced at low cost using extremely simple equipment,
The industrial value is very large.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an apparatus used in the method of the present invention, and FIG. 2 is a diagram showing the relationship between the rotational speed of a rotating body and the particle size of metal powder particles. 1... Container 2... High frequency heating furnace 3... Molten metal 4... Tundish 5... Rotating body 6... Rotation drive device 7... Fine particles 8... Metal powder 9
...Tandish bottom opening 10...Collision surface of the rotating body 11...Rotating body outer wall 12...Bottom of the container Applicant's agent Patent attorney Kazu 1) Figure 1 of the Showa era Rotating Luro speed change (rpm)

Claims (2)

[Claims] (1) In a method for producing metal powder in which molten metal is made into fine particles by the impact force and centrifugal force of a rotating body, the rotating body is tilted at an angle of 90 degrees or more and 135 degrees or less above the collision surface and its outer periphery. It has a shape with high walls, and the molten metal is first flowed down onto the collision surface of the rotating body and is turned into unsolidified fine particles by the impact force and centrifugal force of the rotating body. A method for producing metal powder, which further refines the particles by impact force and centrifugal force by flying and colliding with the wall of a body. (2) The method for producing metal powder according to claim 1, wherein the collision surface of the rotating body and the inner surface of the outer peripheral wall are smooth enough to prevent molten metal from adhering or solidifying.