JPS6247412A - Production of metallic powder - Google Patents

Abstract

PURPOSE:To produce metallic powder having excellent powder metallurgical characteristics by using pencil type nozzles to form atomizing water flow groups having inverted circular conical appearance and dropping a molten metal toward the convergent intersection parts thereof. CONSTITUTION:Plural atomizing water flows 1 ejected independently from each other are concentrated toward the falling column 2 of the molten metal by using the pencil type nozzles and the molten metal is pulverized by a water atomization method. The injection directions of the respective atomizing water flows 1 are shifted toward the same rotating direction (counterclockwise when viewed from the ejection points in the figure) around the axial center 2a of the falling column 2 of the molten metal to incline the flows 1, by which the rotating moment in the counterclockwise direction as shown by an arrow A is generated to the falling column 2 and the pulverous metallic powder suitable as a raw material for powder metallurgy is obtd.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention uses a so-called pencil nozzle to form a group of atomized water streams having an inverted conical appearance, and drops molten metal toward the concentrated intersection of these streams. The method relates to a method of manufacturing metal powder by causing the metal to melt, and in detail, a method of manufacturing metal powder that can exhibit excellent powder metallurgy properties by adjusting the jetting direction of each atomized water so as to give a rotational moment to the molten metal. It is related to.

[Prior art] When obtaining metal products using metal powder, first (
It is common to go through the following steps: 1) prepare metal powder, then (2) fill the metal powder into a mold and compression mold it, and then (3) perform a sintering operation. The quality and appearance of the obtained metal product are significantly influenced by the various properties of the metal powder prepared in (1) above. The characteristics of the metal powder include (a) apparent density, (b) particle size, (
C) Particle size.

(d) Particle shape, etc. can be mentioned.

By the way, among the characteristics (a) to (d) above, research is underway to improve (d) the particle size in the direction of making it as small as possible. This is because if the particle size is reduced to make the metal powder into fine particles, this will work advantageously in the sintering process and the like in (3) above, ultimately improving the quality of the metal product. Examples of such atomization techniques include a reduction method, an electrolytic method, a carbonyl method, an a-mechanical pulverization method, and an atomization method, among which the atomization method is dominated by a liquid atomization method (mainly a wood atomization method).

Since it has various advantages such as being able to produce fine metal powder at low cost, it has come to occupy an extremely important position in pulverization technology. The water atomization method can be roughly divided into V-type and conical type depending on the spraying mode of the atomized water, and into band-shaped spraying type (or film-shaped spraying type) and pencil-type spraying type depending on the type of the spraying part.

Among these wood atomization methods, the particle size that meets the requirements (for example, under 10 lumen) is achieved by using the conical and belt-shaped jetting method.
In order to produce fine metal powder, (A) increase the source pressure of the atomized water (for example, 500 kg/cm2 or more when forming a conical membrane-shaped water jet) to increase the injection speed of the atomized water; (B) It is necessary to use a method such as increasing the angle between the atomized water and the molten metal flow (hereinafter referred to as the apex angle).

However, if the ejection pressure of the atomized water at the ejection nozzle section is increased in an attempt to increase the ejection speed of the atomized water as in (A) above, the pressure on the injection nozzle section or the pressure tank provided directly above the nozzle section will increase. The load will increase. As a result, deformation occurred in the injection nozzle part or the pressure tank part.

This causes turbulence in the sprayed atomized water, making the shape of the conical film unstable and causing variations in the properties of the product powder. Additionally, nozzles for forming conical films are generally required to have strict processing and assembly accuracy, but the reality is that it is extremely difficult to maintain such strict precision all the time. It was originally difficult to make it a reality. On the other hand, in the method (B) of increasing the apex angle, there is a strong tendency for upward flow to occur in the concentrated part of the atomized water, resulting in the so-called blockage phenomenon.The disadvantages of methods (A) and CB) are that , injecting atomized water from a plurality of so-called pencil-type injection nozzles to form an atomized water stream group with an inverted conical appearance, and causing molten metal to fall toward the concentrated intersection of the atomized water stream group (hereinafter referred to as "pencil"). This also applies to the production of metal powder using a water jet conical injection method (sometimes referred to as a water jet conical injection method).

[Problems to be Solved by the Invention] The present invention has been made in consideration of these circumstances, and in producing metal powder using the conical injection method using the pencil-type water stream group as described above, Rather than sticking to the method of increasing the injection speed as in (A) or increasing the apex angle as in (B) above, and making improvements within these frameworks, Based on a different point of view, the present invention aims to provide a method for producing fine metal powder that can promote the pulverization of metal powder without suffering the drawbacks that seem to be inevitable in the methods (A) and CB). It is something.

[Means for Solving the Problems] The method for producing fine metal powder according to the present invention is to produce fine metal powder by concentrating a plurality of atomized water streams ejected independently of each other toward a falling column of molten metal. This is a method for manufacturing a method of manufacturing a molten metal, and its gist lies in changing the rotational moment of the falling column by shifting the injection direction of each atomized water stream in the same direction around the axis of the falling column of molten i. .

[Operations and Examples] In manufacturing metal powder using the conical jetting method using the pencil-type water jet group, the present invention provides that the jetting direction of each atomized water jet is directed in the same direction around the axis of the molten metal falling column. Its greatest feature is that it imparts a rotational moment to the falling column by shifting it. FIG. 1 is a schematic diagram conceptually showing the features of the present invention.

Metal powder is produced by concentrating a plurality of atomized water streams 1 toward a falling column of molten metal (the falling column of molten metal is shown thicker than it actually is in order to clarify the characteristics of the present invention) 2. , the injection direction of each atomized water stream 1 is set in the same circular direction (
In the figure, the requirement is to shift the atomized water flow counterclockwise as seen from the spouting point.If the atomized water flow is made to be inclined as shown in the figure, the molten metal falling column 2 will have an arrow A. A counterclockwise rotational moment is generated as shown in . Of course, it may also be rotated clockwise. For this reason, a centrifugal force acts on the molten metal, and a blowing force acts on the molten metal, and the energy generated by the wood jet jet is not canceled out like in the case of a concentrated type, so it is efficiently used to refine the molten metal. . Incidentally, such a blowing effect prevents the molten metal fine powder from recondensing. In addition, since the one-point concentration method is no longer used, the upward velocity component of each atomized water flow after the cross-collision of the atomized water flows 1 becomes extremely small, making it possible to prevent the occurrence of the so-called blockage phenomenon.
Along with this, the flowing water of each atomizing water stream is also stabilized, which contributes to the miniaturization of the atomized powder.

[Effects of the Invention] Since the present invention is configured as described above, it can exhibit the following excellent effects.

(1) Rotational moment is applied to the molten metal at the intersection of the atomized water flow and the molten metal to generate centrifugal force, and the kinetic energy of the atomized water flow can be efficiently used for pulverization, making it possible to improve the pulverization of metal powder. Further pulverization can be promoted.

(2) Since the upward velocity component of atomized water after each atomized water flow cross-collides can be reduced,
The so-called blockage phenomenon can be prevented from occurring, and the atomized water flow can be stabilized.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram conceptually showing the features of the present invention.

Claims (1)

[Claims] A method for producing metal powder by concentrating a plurality of atomized water streams ejected independently from each other toward a falling column of molten metal, the injection direction of each atomized water stream being directed around the axis of the falling molten metal column. A method for producing metal powder, the method comprising applying a rotational moment to the falling column by shifting the falling column in the same circumferential direction.