JPH01205004A - Method and apparatus for producing metal powder - Google Patents

Abstract

PURPOSE: To produce metal powder of fine, homogeneous and low oxygen content at a fixed particulate size by introducing a molten metal into a tight closure container, spraying the metal with an inert gas and cooling the formed metal particulate in the atmosphere consisting of an inert gas and sprayed water. CONSTITUTION: A molten metal contained in a storage container 3 is introduced into a tight closure tank 1 through a spray nozzle 2. By using an inert gas of Ar, etc., with the spray nozzles 2 arranged at an upper part of the tank 1, under a spray pressure of about 5-50×10<5> N/m<2> , the molten metal is sprayed to be turned to fine and uniform particulates. Cooling spray nozzles 4 are arranged in the tank 1 which sprays water with an inert gas. The spray nozzles 4, at every height divided into several in the vertical direction, are arranged along a peripheral direction of the tank 1, a distance X between the spray nozzle 4 at a most upper part and the spray nozzle 2 of molten metal is appropriately 20-30 cm. By this method, a fine metal particulate of a fixed particulate size is formed, is sent to a centrifugal settling device 8 by a tank bottom part pump 6 and is settled/ recovered.

Description

[Detailed Description of the Invention] Industrially Used Bone %1] The present invention involves introducing molten metal into a closed container or tank, atomizing it with a pressurized inert gas using a spray nozzle, and
metal powder by cooling the sprayed molten metal;
In particular, it relates to a method for producing aluminum powder. Furthermore, the invention relates to an apparatus for carrying out the method.

[Technical background] Several techniques for producing metal powders have been known for a long time, such as reducing oxide particles with gas, electrolyzing solutions of metal salts, and heating and spraying. There are methods to decompose gaseous metal substances. Each of these methods includes several additional methods and apparatus for producing metal powder. The most well-known method with respect to the atomization technology relevant to the present invention is to inject molten metal with a pressurized fluid through an atomization nozzle. It is sprayed using.

In such nozzles, air is conventionally used as the atomizing fluid, and the atomized molten metal is cooled in an air atmosphere. However, conventional devices that use air as the atomizing and cooling medium have a number of drawbacks.

Due to the oxygen contained in the air, the metal powder produced will be enriched with oxygen, some of which will have limited utility as a powder. There is also a risk of explosive mixtures forming when the reactive alloys are sprayed, ie hydrogen and oxygen mixing. Furthermore, a space-consuming cooling tower is required to cool the atomized molten metal.

Therefore, in recent years, other spray fluids have been used instead of air6, e.g., U.S. Pat. No. 4,080.126
No. 6,006,900 discloses a method and apparatus for producing metal powder using water as the atomizing fluid. The apparatus comprises a closed vessel, which is provided with a member for introducing an inert gas, and in whose upper region there is a flow of water into the vertical downward flow of molten metal. A spray nozzle is arranged to impinge on the In this way, the atomization of the molten metal is carried out in a non-oxygen atmosphere and the use of water ensures rapid cooling of the atomized molten metal as there is direct contact between the water and the molten metal under the atomization process. be able to. The produced metal 25) has a low oxygen content and has a homogeneous structure due to the rapid cooling process.

However, the shape of the resulting powder particles is irregular and, although suitable for powder metallurgical shaping, this method is completely unsuitable for purposes requiring fine (and uniform) particles. The average diameter of the particles obtained is
The diameter of the particles obtained by the method according to the invention is in the range of 75-100 microns, while in the range 150-175 microns. Furthermore, the use of water as the atomization medium results in a fairly irregular particle size and a fairly high water content in the resulting metal powder.

The use of inert gases as atomizing medium is also known, as described for example in U.S. Pat. No. 4,117,026 at. The disclosed apparatus for producing spherical metal powders With respect to the equipment used and the method of operation, it is essentially the same as that disclosed in the above-mentioned U.S. Pat. be. Although fine particles with a certain particle size can be obtained, cooling of the atomized metal in an inert gas atmosphere has a very slow cooling rate, so the particles produced are not homogeneous. Similar to the type of air introduced for cooling described above, the system also requires a cooling tower, which takes up a large amount of space.

[Object of the Invention] Therefore, the object of the present invention is to produce a metal powder having a small and constant particle size with a strong and homogeneous tFi structure and a low oxygen content.
It is another object of the present invention to provide a method for building a GJ without the aforementioned problems and disadvantages.Another object of the invention is to provide an improved device that requires less space.

[Summary of the Invention] According to the present invention, a method for producing metal powder includes cooling a sprayed molten metal in an atmosphere of sprayed water or in a spray atmosphere of an aqueous solution of chloride and an inert gas. be done. Further, an apparatus for producing metal powder according to this method includes a closed container into which the metal is sprayed, and the closed container is equipped with the sprayed water or an aqueous solution of nickel chloride and/or chromium chloride. A spray nozzle is provided for dispensing.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in detail with respect to specific embodiments, with reference to the accompanying drawings, which schematically show examples of the construction of a metal powder manufacturing apparatus according to the invention.

[Example] The metal powder manufacturing apparatus according to the present invention has a closed container, that is, tank 1.
Equipped with: Molten metal is transferred from reservoir 3 to tank 1
The atomized metal is sent to a spray nozzle 2 provided at the top of the tank 1.

The US 8 (ultrasonic gas atomization) type nozzle 2 is effective, and this atomizes the molten metal with an inert gas such as nitrogen or argon. However, other types of nozzles are also applicable.

The spray pressure applied is on average 5-50X 10'N/
The average diameter of the metal powder particles is 75 to 100 μm, which is preferably in the range of 15 to 30×10′N/m 2 .

A cooling spray nozzle 4 to which water as a cooling medium is supplied via a line 5 is provided inside the tank 1 . The nozzles 4 that spray this water are arranged along the circumferential direction of the tank 1 at several vertically divided heights. In this way, the water spray jet is directed radially towards the central part of the tank 1 and effective mixing is achieved within the tank 1.

Of the water atomizing atomizing nozzles 4 shown, the one in the most extreme position is intentionally located at a constant distance X from the atomizing nozzle 2 to which the molten metal is applied. This distance X is important in order to effect supercooling of the molten particles before the metal reaches the solidification zone by the water spray jet.

Supercooling of the molten particles reduces the solidification time so that the metal particles have a very fine and homogeneous structure. According to actual tests, the distance 1x of 20~: l Oc m
The result was favorable from this point of view.

Then, during the axial movement 'LJJ of the metal particles through the tank 1, solidification and cooling of the metal particles takes place by impact with the atomized water particles moving (radially) across the tank 1. In this way, the "steam film" (3Leasri1m) formed around the metal particles is effective!
The solidification and cooling are achieved at high speeds.

The inert gas used for atomization of molten metal is -f
i is sufficient to maintain the required inert atmosphere within tank 1. In order to keep the required pressure constant, which is higher than the atomization pressure, a collection member 9 for the spent inert gas is provided in the lower part of the tank 1, which in particular is used for water atomization. It is arranged between the spray nozzle 4 and the surface of the accumulated metal powder or the liquid surface of the water. Collection member 9 comprising an inwardly recessed skirt 11
extends along the circumference of the tank 1 and is connected to exhaust means (not shown) by a pipe 10. Spent inert gas also contains water particles and steam. Some of this steam and water particles are '111? ! It settles in the collecting member 9, is discharged, and is returned to the tank 1, for example, by a pipe.

The metal powder and water collected at the bottom of the tank 1 are sent by a pump 6 through a conduit to a centrifugal settler (separation means) 8, which separates the liquid phase from the metal powder. After settling, the metal powder containing 1-7% water is sent to a secondary heated drying drum to reduce the water content to acceptable levels.

In the above yJJ manufacturing process arrangement of metal powder according to the invention, water is used as a cooling medium.

However, in the process of manufacturing aluminum powder or aluminum alloy powder, it is considered effective to use an aqueous solution containing nickel chloride and/or chromium chloride as a cooling medium. The particles obtained in the actual tests were coated with a thin layer of nickel and/or chromium. This coating has a beneficial effect on oxidation control and moisture pickup.

Co-extrusion of fiber reinforcement (composites) can be said to be a typical application of aluminum powder. That is, the nickel/chromium coating on the particle surface is
, ^! , 05 etc. to improve the interface between the fiber and the ground.

Moreover, the metal powder produced by the method and apparatus according to the invention is particularly effective and suitable for plasma spraying onto articles.

It goes without saying that the produced metal powder can be used for other purposes, such as powder compaction, post-extrusion processing, forging, and field processing of articles.

[Brief explanation of the drawing]

The drawing is a schematic explanatory diagram showing one embodiment of the metal powder manufacturing apparatus according to the present invention.
...Reservoir 4...Spray nozzle 6...
Pump 8...Centrifugal sedimentator (separation means) 9...Collection member

Claims (1)

[Claims] 1. Molten metal is introduced into a closed container (1) and a spray nozzle (2
), wherein the metal particles are cooled in an atmosphere consisting of an inert gas and atomized water. 2. The metal powder is aluminum powder or aluminum alloy powder, and the atmosphere for cooling consists of an aqueous solution of nickel chloride or an aqueous solution of nickel chloride and chromium chloride sprayed, and an inert gas. The method for producing metal powder according to claim 1. 3. A manufacturing apparatus for manufacturing metal powder by the method for manufacturing metal powder according to claim 1 or 2, which comprises a closed container (1) and a spray nozzle (1) for supplying an inert gas to the closed container. 2) a means for supplying molten metal into the closed container fitted with a spray nozzle (4) for supplying a sprayed cooling medium;
are disposed circumferentially within said closed container (1) at one or more predetermined heights, and have an outlet communicating with a pump (6) for separating the cooling medium and formed particles from the separating means (8). )
An apparatus for producing metal powder, characterized in that the apparatus is disposed at the bottom of the closed container for sending the metal powder to the container. 4. The topmost spray nozzle (4) that sprays the cooling medium,
20 to 30 from the spray nozzle (2) that sprays molten metal
Claim 3 characterized in that the power is distributed at a distance of cm.
An apparatus for producing the metal powder described above.