JPS5948923B2 - Manufacturing method of metal fine powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing fine metal powder having finer particle size from powder or granular metal powder.

Many methods have been known for producing metal powders, and among these methods, mechanical crushing, molten metal pulverization, reduction, and electrolytic methods are common. The molten metal pulverization method for manufacturing powder is a method that is widely used for manufacturing metal powder because it is relatively easier and more efficient than pulverizing solid metals. However, it has the disadvantage that it is extremely difficult to produce fine powder because the pulverization time added to the molten metal to be crushed is short.

That is, the typical methods of pulverizing molten metal that are currently widely adopted include (a) a dropping method (Shotting) in which molten metal is dropped into water through pores, solidified, and granulated; (b)
(C) A molten metal agitation method (graining) in which the molten metal is cooled and solidified while being mechanically stirred vigorously in the atmosphere, and is granulated by utilizing oxidation of the metal; Examples of methods include atomization, in which the molten metal is dispersed finely by applying a compressed gas, a water jet, or a centrifugal force to a trickle, and at the same time is cooled and solidified to become powder.

The powder obtained by the above method (a) is coarse particles having a spherical or droplet shape, and it is difficult to produce powder with a particle size of 1 mm or less.

In addition, the powder obtained by the above method (b) is mostly coarse particles with amorphous or droplet-like shapes whose surfaces are covered with oxides, and whose particle size is coarse and in the range of 20 to 100 mesh. ing.

Furthermore, the powder obtained by the above method (C) has various shapes such as spherical and spherical depending on the manufacturing conditions, and has a wide particle size distribution of several tens of micrometers or more, but the surface may be oxidized or the cooling effect of the spray medium may be affected. Pores often form within the particles due to the entrainment of atmospheric gas due to the large size of the molten metal, or insufficient release of gas dissolved in the molten metal during solidification. Was.

For this reason, the same applicant had previously filed a patent application filed in
No. 156469 (hereinafter referred to as the prior invention) states,
Moreover, a solid powder with a higher melting point is allowed to coexist, and the solid powder is cooled and solidified while stirring to maintain a homogeneous state in which the solid powder is dispersed in the molten or semi-molten metal. A method for producing metal powder, comprising separating the solid powder from fine metal powder.

'', and it is true that this prior invention has no surface oxidation or pores, a wide particle size distribution from a few liters of mesh to about 325 mesh (of course, it also includes fine powder with a particle size of less than 325 mesh), and is spherical or irregularly shaped. Although it was possible to easily produce metal powders with various shapes, it was difficult to stably obtain fine metal powders with uniform shapes and particle sizes on the order of several tens of microns or smaller. Ta.

Therefore, from the granular or powdered metal powder produced by the above-mentioned known method, or the granular or powdered metal powder such as shavings and metal scraps, the above-mentioned However, the fine metal powder produced by this mechanical crushing method has a scale-like, plate-like, or dish-like shape, and the shape and particle size vary. Producing coherent metal powders was extremely difficult and required significantly longer milling times.

From the above-mentioned viewpoints, the present invention has been made to produce metal powders of uniform shape and particle size from granular or powdered metal powders produced by known methods, or granular or powdered metal powders such as shavings and metal scraps. It provides a method for easily and quickly producing fine metal powder with a particle size on the order of several tens of microns or smaller. (A) Pure metals and alloys produced by known methods (hereinafter collectively referred to as these) (B) particles (shot) or powder, shavings, metal scraps, etc. (hereinafter collectively referred to as metal powder); (a) Al2O3, ZrO□, TiO2, Fe2O with a higher melting point and with an average particle size in the range of about IO to 10 μm which is further preferred for working and powdering purposes;
4. Aerosil (product name), Kaolinite and Co0
・Oxides such as 2A1203, (b) Carbides such as B4C, ZrC, WCl and TiC, (c) Nitrides such as Si3N4, BN, and TiN,
(d) Carbonitrides such as Ti (CN), and Ti
(e) CdS, Oyohi XcdS-ycdSe nanosulfides, (f) Fe2B, Ni2B, NbB, and A
One type of suitable solid powder appropriately selected from the above groups (a) to (g) according to the type of metal powder, such as borides such as lB2, (g) carbon flakes, and carbon such as graphite. or 2
(C) Next, a mixed powder consisting of a suitable metal powder as shown in item (A) above and a suitable solid powder as shown in item (B) above is charged into a container; The mixed powder is heated to a temperature at which the metal powder melts or semi-melts while stirring the metal powder and the solid powder to maintain a dispersed and homogenized state. The stirring may be carried out from the beginning of heating the mixed powder, or may be started at the time when the mixed powder is heated to a temperature just below the melting point of the metal powder, and the stirring may be performed using a mechanically or electromagnetically rotating or vibrating stirring blade The agitation may be applied by known means such as rotating or vibrating the container using the driving force described above.The degree of agitation cannot be generalized because it is affected by various factors, but for example, When stirring with a rotating plate stirring blade, the ingredients are heated with 100r,
It is sufficient to apply a rotational speed of at least 100 m, or more, and in the case of stirring by vibration of the container, the rotation speed is applied to the container 100 times per minute.
It is sufficient to apply vibrations of 1 minute or more, and furthermore, the heating melting is preferably performed to prevent oxidation of the metal powder heated to a molten or semi-molten state and the finer metal powder. (D) Next, the mixed powder consisting of the molten or semi-molten metal powder and the solid powder is cooled while continuing the stirring to semi-oxidize the metal powder. The metal powder in a semi-molten state is held in a molten state, and the semi-molten metal powder is divided into fine particles by the solid powder, and in this case, the average particle size of the solid powder is preferably in the range of 10 to 10 μm as described above. Often, if the average particle size is less than 10 people, it will be difficult to handle, impair workability, and become difficult to obtain economically, while if the average particle size exceeds 10 μm, it will be difficult to handle the metal powder efficiently. This is based on the reason that pulverization becomes difficult, and it is sufficient to perform the cooling to the solidus temperature of the metal powder, and the cooling rate is 0.1 to b to complete pulverization. is preferable, and on the other hand, it is preferable to rapidly cool the powder by transferring it to another container after completion of powdering to prevent agglomeration and sintering of the powder. (Of course 325m
A fine metal powder with a particle size of less than esh is formed, and this is separated from the solid powder by an appropriate means, and (F) further, if necessary, the particle size distribution is In order to obtain fine metal powder with a narrower range and finer shape and uniform shape, the above (3) to (
The steps shown in section D) may be repeated; By applying the metal powder to a mixed powder consisting of a solid powder, the metal powder can be formed into the metal fine powder shown in the above items (E) and (F). In this case, if necessary, an appropriate amount of solid powder can be added. A powder may be added to the mixed powder, and is characterized in that it consists of the above items (A) to 0.

Next, the present invention will be explained by examples.

Example 1 The experiment was carried out using an apparatus as shown in a schematic vertical cross-sectional view in FIG.

That is, 550 g of AI ingot with a purity of 99.99% was charged into a graphite crucible 2 which was rotatably provided around a vertical axis in an electric resistance furnace 1, and heated and melted to form a molten A at a temperature of 680°C.
16 was formed.

Next, when the molten AI was cooled to 670° C., the alumina-coated stainless steel stirring blade 4 rotated by the stirring motor 3 was rotated at a rotation speed of 250 r.
solid CdS having an average particle size of 0.5 μm while stirring the molten A1 by rotating the melter 2 with a motor 5.
Powder: Add 30g and melt A of such CdS powder addition
I at a cooling rate of about 0.1°C/min to the freezing point temperature (6
The mixture was cooled to 59° C.), kept at the freezing point temperature, kept stirring while maintaining a semi-molten state, and completely powdered, and then cooled to about 650° C. (first stage powdering treatment).

Next, according to the method of the present invention, 20 g of CdS powder as the solid powder was added to the resulting mixed powder of AI granules and CdS powder at a temperature of about 650° C. while continuing stirring. , again about 1℃/m
The mixture was heated to a temperature of 665° C. at a heating rate of 1.5 in, and then similarly cooled to a freezing point temperature at a cooling rate of about 0.1° C./min, and stirred while maintaining the semi-molten state at the freezing point temperature. By continuing, it was further finely powdered (
2nd stage powdering process).

Thereafter, the mixture was cooled to a temperature of 630° C. while stirring, and then transferred to another container and rapidly cooled.

Note that the above operations from melting to powdering were performed in a non-oxidizing atmosphere formed by spraying Ar gas from the nozzle 7 for inert gas spraying.

As a result, a mixed powder in which CdS powder was attached to Al fine powder was obtained, and this mixed powder was ultrasonically cleaned in acetone and separated into Al fine powder and OS powder.

The resulting Al fine powder has a spherical shape, the degree of surface oxidation is extremely small, and its particle size distribution is as shown in Figure 2.
The following were the most minor ones.

For comparison purposes, FIG. 2 also shows the particle size distribution before the second-stage powdering treatment in Example 1, that is, at the time of completion of the first-stage powdering treatment.

As shown in the figure, it is clear that the AI granule powder after the first stage pulverization treatment is further refined by performing the second stage pulverization treatment according to the method of the present invention. It is.

Example 2 Into a bottomed quartz tube with an inner diameter of 20 mmφ, 100 g of pure copper shot (granular pure copper powder) having a particle size of about several mm and Al2O3 powder (trade name: Aerodinol) with an average particle size of 20 people were charged together, After sealing with Ar at 173 atm, the tube was placed in a heating furnace.

Note that protrusions were provided on the inner surface of the quartz tube to ensure sufficient stirring.

Next, the quartz tube was tilted almost horizontally in the heating furnace and heated to a temperature of 11°C while rotating at a rotational speed of 20 or more pom.
After heating the pure copper powder to 00°C to a semi-molten state,
Cooling was performed while continuing rotation at a cooling rate of 0.5° C./min.

The resulting mixed powder was ultrasonically cleaned in acetone to separate the pure copper powder and the A1゜03 powder, but most of the pure copper powder was spherical and had a particle size of several tens of micrometers. It contained many things.

Example 3 100 g of Cu-13.5% Sn alloy cutting pieces (shavings) prepared in advance and 10 g of carbon black of 80 people with an average particle size were charged into the same quartz tube as used in Example 2, Similarly, after being sealed with Ar at the same pressure, the quartz tube was charged vertically into a heating furnace, and the quartz tube was heated 150 times/year in the heating furnace.
The temperature is approximately 1050℃ while vibrating up and down at a rate of min.
, then cooled to a temperature of 800° C. while mixing and stirring, then reheated to a temperature of 900° C., which is the half-melting temperature of the alloy, while continuing mixing and stirring, and then cooled to a temperature of 800° C. It was then rapidly cooled down.

In this way, according to the method of this invention, the powdering treatment is carried out in two steps.
When the mixed powder obtained by repeating the application several times was similarly subjected to ultrasonic cleaning using acetone, it was found that the above composition had a particle size distribution in which most of the particles had a diameter of several tens of micrometers or less, and had a shape close to a spherical shape. An alloy powder was obtained.

Example 4 Cutting pieces (shavings) of stainless steel (SUS304) 50
0g and average particle size: 8μm titanium nitride powder 50g
were charged into an aluminum crucible, and this crucible was placed into a vacuum induction furnace.

Next, the alumina stirring blade was rotated at a rotation speed of 500 r, p,
m, to rotate the stainless steel cutting piece at about 1420 m.
The mixture was heated to a temperature of 1380° C. to a semi-molten state, and then cooled to a temperature of 1380° C. at a cooling rate of 10° C./min while continuing stirring, and then rapidly cooled.

Most of the stainless steel powder obtained by ultrasonic cleaning with acetone had a spherical shape with a particle size of about several tens of micrometers.

As described above, according to the present invention, powdery or granular metal powder can be easily produced, efficiently produced, at low cost, without pores or surface oxidation, and with uniform particle shape and size. This makes it possible to produce fine metal powder with specific properties.

[Brief explanation of the drawing]

Fig. 1 is a schematic vertical cross-sectional view showing an apparatus for implementing the present invention;
The figure is a graph showing the particle size distribution of a fine metal powder obtained by the method of the present invention and a comparative metal powder. In the drawings, 1... electric resistance furnace, 2...
...graphite crucible, 3,5...motor, 4...
... Stirring blade, 6... Molten metal, 7...
··nozzle.

Claims (1)

[Claims] 1 In a non-oxidizing atmosphere, a solid powder that is difficult to dissolve in the metal powder to be refined, has a higher melting point, and has an average particle size within the range of 10 μm to 10 μm, and a semi-molten powder. A mixed powder consisting of a metal powder held in a state,
A method for producing fine metal powder, characterized in that the metal powder in a semi-molten state is divided into fine particles by the solid powder by stirring using a rotating stirring blade or vibration in a container.