JPS63230807A - Rotary disk for centrifugal atomization - Google Patents

Abstract

PURPOSE:To quickly transmit rotation of a disk to molten metal and to prevent slipping of the molten metal on the upper face of the disk by forming the upper face of the disk to concave face and burying a core material made of the same material as the molten metal at the center of the upper face of the disk. CONSTITUTION:The upper face of the disk 2 for centrifugal atomization is formed to continuous concave face and at the center the core material 3 composing of the same or >=90% of the same composition as the molten metal 5 flowed down. An explosure area of the core material 3 to the upper face of the disk 2 is desirable to the ratio of <=1/10 of total area of the upper face of the disk 2. This core material 3 intermittently forms solidified skull 6 of the molten metal 5 on the upper face of the disk 2. By this method, the rotation of the disk 2 is surely transmitted to the flowed molten metal 5 and can prevent from the slipping. Therefore, the efficiency of disintegration is improved and the fine powder can be produced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention stabilizes the spraying phenomenon of molten metal and improves the powdering effect by improving the material and structure of the main part of the centrifugal spraying process, the one-rotation disk. It is about an invention that improves.

[Background of the Invention] Usually, a molten metal atomization method is employed to produce high-purity alloy powder, and among these, an inert gas atomization method and a centrifugal atomization method have been industrialized. The former is a high-pressure gas such as Ar or N2, etc.
This method involves spraying, atomizing, and solidifying hot water droplets, but the solidification rate is relatively slow.On the other hand, the latter applies centrifugal force to the molten metal by some means [physical property constants such as the thermal conductivity of the coolant]. It is convenient to increase the solidification rate of Alloy 9 powder, refine the powder structure, and make it appear amorphous.

Among these centrifugal spray methods, the method in which the molten metal falls onto a disk rotating at high speed and uses the centrifugal force to scatter and solidify the molten metal can apply a large centrifugal force.

Moreover, it is advantageous because the pouring temperature can be set appropriately.

On the other hand, increase the rotational speed of the disc to 10,000 rpm+e or more.

In addition, a special structural design is required to stabilize the rotation.

On the other hand, the powdering efficiency of this centrifugal spraying method is determined by how efficiently centrifugal force is applied to the molten metal, but according to the research results of the present inventors on the centrifugal spraying method, the most frequently occurring particle size of the powder produced The relationship between (da) and the disk rotation speed (R) is approximated by the following equation, where dn+ is expressed by μts and R is expressed by rpa+.

d m= 4 XIO'

This is mentioned in the interrogation paper "Tetsu to Hagane" 71 (1985).

[Problems with the prior art] In this case, ideally the so-called pulverization point at the moment when the molten metal leaves the edge of the rotating disk is important, and its speed (peripheral speed of the pulverization disk) determines the powder particle size. When the molten metal is on the disk surface, the speed is not necessarily increased to the circumferential speed of the disk. In an extreme case, the molten metal slides on the disk surface from the center to the periphery, hardly rotating, and therefore scattering without being subjected to centrifugal force, resulting in a speed of 50 m/s.
There was a problem in that even if sprayed at a disk circumferential speed higher than ee, only break-shaped metal pieces could be obtained.

In response to this problem, the present inventors extensively investigated the relationship between the molten metal and the disk material, and found that it is important to increase the wettability with the molten metal. It has already been found that it is advantageous to use materials of low densities as materials of construction for the disks. (Refer to Japanese Patent Application Laid-open No. 116704/1983).

However, even in this case, there was a problem that materials with poor thermal conductivity could not be used at high speeds, leading to destruction.

In the centrifugal spraying method, the upper surface of the disk is formed into a concave shape, and the molten metal and its composition are 90%
This rotary disk for centrifugal spraying is characterized by having the same core material buried so that its upper surface is exposed.

Further, in the present invention, the exposed area of the core material on the top surface of the disk is set to be 1/10 or less of the total area of the top surface of the disk, and the materials other than the core material constituting the top surface of the disk have a thermal conductivity of 0. .3cal/am sec” 0 or more substance,
In this embodiment, a cooling medium is brought into contact with the lower surface of the disk.

[Function] When the molten metal that falls at the center of the disk, which is formed in a continuous concave shape, moves to the periphery of the disk due to centrifugal force, friction is forcibly created between the top surface of the disk and the disk surface at this inclined part. cause This allows the rotation of the disc to be quickly transmitted to the molten metal.

Slippage between the molten metal and the upper surface of the disk is prevented. [Embodiment] Next, an embodiment of the present invention will be described with reference to the drawings.

In the figure, 1 is a rotating shaft that is vertically supported and rotates at high speed;
2 is a disk fixed horizontally to the upper end of the spindle 1. Disk 2 is made of high-strength Cu alloy such as Cu Be, or other materials, and has a thermal conductivity of 0.3 cal at room temperature.
/csec ``It is manufactured from a substance of C or higher.The upper surface of the disk 2 is formed into a continuous concave shape such as a concave spherical shape, and the upper surface of the disk 2 is the same as or 90% or more of the molten metal 5 flowing down at the center. A core material 3 having the same composition is buried.The exposed area of the core material 3 on the upper surface of the disk 2 is
The ratio should be 1/10 or less of the total area of the upper surface. The spindle 1 and the disk 2 are formed in a hollow shape, and cooling water is jetted onto the inner surface of the disk 2 at a pressure of several kg/am'' from a nozzle 4 provided in the spindle 1 to forcibly cool the disk 2.

The geometrical shape of the disk 2 may be a continuous concave shape having an inwardly inclined surface at a dust-proof angle as described above. Under high-speed rotation, it is necessary to configure an axially symmetrical concave surface, and if the contact with the molten metal is too steep, the impact load during skull dispersion, which will be described later, will be large and have a negative effect on the spindle rotation system. A spherical surface with a radius of curvature of 20 cm and a diameter of 9 c+s produced good effects. This geometrical improvement alone made it possible to spray molten metal to some extent even with a disk with poor wettability, but in order to further increase powdering efficiency, the core material 3 is buried in the center as described above. This core material 3 causes solidified skulls 6 of molten metal to be intermittently formed on the upper surface of the disk. The role of this solidification skull 6 is to prevent heat conduction from the top surface of the disk, keep the skull 6 itself in a moderately heated state, and improve wettability with the molten metal. At the same time, the unevenness of the skull surface increases the frictional force of the molten metal on the skull surface. let That is.

A core material 3 made of the same or similar material as the molten metal is buried in the center of the disk in advance, and the flowing molten metal is fused to form a skull 6 at an appropriate pouring temperature, and this skull 6 grows to some extent (thickness). When it becomes fleshy), it cannot follow the rotational movement and breaks and becomes separated at the fused part, and a new solidified skull is generated and grows. The situation is shown in FIGS. 1 to 4 in order.

It was found that the fused part at the base of the skull became stronger, delaying the skull's breakage and dispersion, and increasing the probability of vibration generation and eccentric loading, which could easily damage the spindle rotation system. On the other hand, if the area ratio is too small, it will be difficult to generate skulls;
The limit seems to depend on the material of the molten metal, the pouring temperature, the number of rotations of the disk, etc. In addition, the disk surface other than the core material, including the inner part, is made of high-strength Cu alloy such as CuBe, or other material with a thermal conductivity of 0.3 cal/am at room temperature.
5ecTl: It is preferable to be composed of a substance with a thermal conductivity much lower than this. If the thermal conductivity is significantly lower than this, the water cooling effect will be weakened, causing seizure with the molten metal, and interfering with the solidification skull generation mechanism. Additionally, due to the structure of the spindle rotation system that circulates around the shaft, excessively increasing the cooling water pressure increases the friction between the fixed and rotating shafts.

This is undesirable because it impedes high-speed rotation of the disk.

Ideally, the core material 3 is made of the same material as the molten metal, but in reality it is determined by the impurity tolerance limit of the sprayed powder. According to experiments, molten metal −′ at the initial stage of pouring: 90
It has been found that if the composition is the same, the powder stain amount can be suppressed to 0.05% or less.

[Effects of the Invention] As explained in the embodiments above, the rotating disk according to the present invention has a concave shape and a core material that is a co-material with the molten metal is embedded in the center of the concave shape, so that solidified skulls are intermittently generated. Since the rotation of the disk can be more reliably transmitted to the molten metal flowing down to prevent smearing, it is useful for improving the powdering efficiency and making it possible to manufacture fine powder.

[Brief explanation of the drawing]

Claims (2)

[Claims] (1) In the centrifugal spraying method, in which molten metal flows down the center of the upper surface of a disk that rotates at high speed in a horizontal plane, and the molten metal is powdered by the centrifugal force, the upper surface of the disk is formed into a concave shape, and the center of the molten metal is A rotating disk for centrifugal spraying, characterized in that a core material whose composition is 90% or more identical to that of the molten metal is embedded so that its upper surface is exposed. (2) The exposed area of the core material on the top surface of the disk should be one-tenth or less of the total area of the top surface of the disk, and the materials other than the core material that make up the top surface of the disk have a thermal conductivity near room temperature. A substance with a temperature of 0.3 cal/cm sec°C or higher,
The rotating disk for centrifugal spraying according to claim 1, wherein a cooling medium is brought into contact with the lower surface of the disk.