JP2001226704A - Apparatus and method for producing metal powder - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide an apparatus and a method for obtaining metal powder having a smaller average particle diameter and a narrower particle size distribution width than in the conventional gas atomization method. A high-pressure gas ejection hole is directed downward and has a diameter.
The center line 5-1 of the jet is directed to the vertex 6 of the cone whose base is the circle where the jet hole 3 is located, and the apex angle α of the cone is 40 ° or less. And the molten metal nozzle 2 is inclined in a range β of 20 ° to 100 ° with respect to the vertically downward direction, and the distance L from the tip of the gas ejection hole at the position where the molten metal 4 first collides with the inner surface side of the cone is determined. An apparatus for producing atomized metal powder, the arrangement being 30 mm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus and a method for producing a metal powder or a metal alloy powder by a gas atomizing method.

[0002]

2. Description of the Related Art Metal powder is often used as a raw material for sintering for the purpose of forming a material having poor workability into a specific shape, reducing the number of finishing steps, improving the raw material yield, and forming a material having a unique function. Have been. There is an atomizing method as a method for producing powders of such metals and metal alloys. This is a method of injecting a liquid or gas such as high-pressure water at the nozzle part onto a molten metal by a natural falling flow from a nozzle or a nozzle to obtain a powder.
A large amount of metal powder can be produced at low cost.

[0003] However, the atomizing method has a limit in sufficiently reducing the particle size, and tends to be manufactured by mixing large to small particles. It is not always sufficient to obtain a fine metal powder having an appropriate particle size distribution. In order to obtain a high-density precision sintered part, the filling rate of the raw material powder must be increased, but in order to increase the filling rate, the powder must have an appropriate particle size distribution. For this reason, powders having different particle sizes are mixed and used as an appropriate particle size distribution. In order to mix and use, a raw metal powder having a narrow particle size distribution width is required, and a powder manufacturing method with a narrow particle size distribution width is important. For example, it is essential to obtain a composition that can only be obtained by sintering as dense as possible, especially for electrodes of new secondary batteries such as nickel-metal hydride batteries and lithium batteries, which have been remarkably developed in recent years. .

[0004] In response to such demands, various studies have been made to obtain metal powders having a particle size distributed in a narrow range by an atomizing method. For example, in Japanese Patent Application Laid-Open No. Hei 3-6308, a method of obtaining a metal powder having a uniform particle size by blowing a molten metal flow into a thin film by a nozzle having an inclined plane and spraying a gas jet such as a compressed air widely thereover. An apparatus is disclosed. Further, in the invention presented in Japanese Patent Application Laid-Open No. 5-59411, with respect to the production of fine metal powder having a narrow particle size distribution, the outer peripheral side surface of the tip of the nozzle is formed by an inverted conical curved surface with the center line of the nozzle as a symmetric axis. Formed and jets a plurality of linear jets along the side surface and in a direction deviated from the generatrix of the curved surface, and is generated at the intersection of the jets in the molten metal flowing out of the hole opened at the center of the nozzle tip surface. The upward flow of the spray gas is sprayed, the molten metal flows radially in a film form on the nozzle tip surface, and the jet ejected along the outer peripheral side of the tip end portion of the nozzle to the curtain flow at the periphery of the nozzle tip surface. Collision. In addition, Japanese Patent Publication No. 4-54721 discloses that after high-pressure gas is sprayed on a molten metal and then subjected to primary atomization, it is made to collide with a cup-shaped high-speed rotating plate on which a liquid film is formed to obtain finer metal particles to be secondary-atomized. An invention of a manufacturing method is disclosed.

However, these methods can reduce the average diameter of the obtained particles, but cannot always say that the width of the particle size distribution is sufficiently small.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus and a method for producing a metal powder having a smaller average particle diameter and a narrower particle size distribution than in the prior art in the production of metal powder by the gas atomization method. It is in providing the method.

[0007]

Means for Solving the Problems The inventors of the present invention mainly applied a metal powder used for an electrode of a new type secondary battery by a gas atomization method to a particle size distribution as small as possible and having a uniform particle size. The means and conditions for obtaining a sized powder having a narrow particle size were studied. The metal powder used for the sintering raw material is required to have a sufficiently high packing density at the time of molding in view of the performance and yield of the obtained product. For that purpose, it is important that a sized powder can be produced first, and accordingly, the particle size configuration of the powder can be appropriately selected.

[0008] In the case of gas atomizing a molten metal of the same metal with the same gas jet, the average particle size of the powder generally obtained is almost proportional to the diameter of the molten metal stream, and becomes smaller as the gas mass supply rate to the molten metal increases. Have been. However, if the diameter of the molten metal stream is reduced, the nozzle is likely to be clogged, so that the diameter cannot be reduced so much.

Usually, in the case of gas atomization, the molten metal is powdered by a single collision with a gas jet. On the other hand, as described above, there is disclosed an invention in which the gas is injected into the high-speed rotating plate and then collides with the high-speed rotating plate to further reduce the size of the powder by performing the collision twice. However, installing a high-speed rotating plate in addition to the gas ejection device is complicated and difficult to implement. Therefore, among the conventional methods, the possibility of causing more than two collisions was examined.

[0010] There are many proposals for the form of gas or liquid ejection to the molten metal stream. Among them, we focused on a conical gas jet curtain in which the jet holes were arranged on the circumference and the jet directions of the gas were all collected at one point, as the jet form that could be used effectively. Normally, the molten metal stream that falls naturally is sprayed with this gas jet. However, in this conical gas jet curtain,
When the molten metal is poured at an angle from the inside, the molten metal that collided with the gas jet curtain is pulverized there, bounced back and collided with the gas jet curtain on the opposite side, further pulverized, and this is repeated twice or more As a result, they have found that it is possible to make the powder fine and to make the particle size uniform.

FIG. 1 shows an example of an embodiment in which this is incorporated in an actual manufacturing apparatus. The gas ejection holes 3 are arranged on a circumference, and the center line 5-1 in the gas ejection direction of the ejection holes is focused on any one of them. Assume that it is suitable for 6. In this case, all the gas jets ejected from the circumference go to the focal point 6, so that the conical gadget curtain 5 having the circle having the ejection hole as the bottom surface and the apex as the focal point is formed.

When the molten metal stream 4 having a certain angle from the molten metal nozzle 2 made of a heat-resistant material collides against the conical surface 5 of such a gas jet curtain, the powder which has been repelled into powder is repelled. The molten metal 7 can be further pulverized by hitting the gas jet curtain 5 on the opposite side. At that time, the primary collision is performed first as close as possible to the gas ejection hole, and the secondary and tertiary collisions are performed within a shorter time.

Examination of the metal powder thus obtained revealed that not only fine powder but also the effect of uniform particle diameter was obtained. This was thought to be because the collision with the secondary and tertiary gas jet curtains further subdivided the particles that were relatively large in the primary collision. The molten metal fragmented by collision with the gas solidifies in a short time in a short time as the particle diameter is small, but solidification is delayed when the particle diameter is large. Therefore, if a collision with a secondary or tertiary gas jet occurs in a short time, particles that did not become smaller in the primary collision are selectively fragmented, and as a result, the average particle size is reduced. It is considered that the diameter becomes smaller and the particle diameter becomes uniform.

Since the usefulness of gas atomization by the above-mentioned method has been clarified, the limit of the shape of the apparatus for more stably realizing the gas atomization was further studied. The present inventors have investigated and clarified the conditions under which finer grains can be obtained and the particle diameter can be made more uniform by using this apparatus, and the present invention has been completed. The gist of the present invention is as follows.

(1) In the atomizing method in which a molten metal is discharged from a nozzle and a high-pressure gas is sprayed from the nozzle to obtain fine metal powder, the high-pressure gas nozzle is directed downward and has a diameter of 50 mm or less. It is on the top, the center line of the ejection points toward the vertex of a cone whose bottom is the circle where the ejection hole is located, the apex angle of the cone is 40 ° or less, and the molten metal nozzle is oriented vertically downward. A metal atomized powder characterized in that the metal atomized powder is inclined in a range of 20 ° to 100 ° and the distance from the tip of the gas ejection hole at a position where the molten metal first collides with the inner surface side of the cone is 30 mm or less. manufacturing device. (2) above using atomized powder production apparatus (1), the ratio M _L of the ejection pressure of the gas 0.5～8MPa, the molten metal flow M _L (g / s) and gas flow rate M _G (g / s) / M _G 0.01 to 0.5, and method for producing a metal powder, characterized by.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to an apparatus used in a gas atomization method in which high-pressure gas is blown into a molten metal stream and pulverized, and a method of producing metal powder by using the apparatus. What is generally used is applied as it is.

FIG. 2 schematically shows the positional relationship between the molten metal stream 4 and the center line 5-1 of the gas jet curtain in the apparatus of the present invention. The gas ejection hole 3 is on the circumference of the diameter R, and ejects gas downward. In each of these gas ejection holes 3, the center line 5-1 in the gas ejection direction is directed to the focal point 6, and the conical surface of a cone having a circle having a diameter R as a base and an apex angle α having the focal point 6 as an apex is formed. It is assumed that a gas jet curtain 5-1 is formed. Here, R is 50 mm or less, and the cone apex angle α
Shall be 40 ° or less. The molten metal stream 4 is caused to flow out of the nozzle 2 at an angle of β with respect to the vertical direction, and collides with the conical gas jet curtain 5-1 from the inside at a distance L from the tip of the gas outlet 3. Where the angle β is 20 °
L is set to 30 mm or less.

The diameter R of the circumference where the gas ejection holes are arranged is 50 mm.
The reason for the following is that if it exceeds 50 mm, the time between the first and second collisions will be longer, and the effect of the second collision will be weakened,
This is because the distribution width of the particle diameter becomes large. Further, if R becomes too small, it becomes difficult to bring the molten metal nozzle portion close to the gas jet without contact with the gas jet curtain. Therefore, it is desirable that R is at least 15 mm or more. Preferred values of R are between 20 and 40 mm.

It is easy to arrange the gas ejection holes on the circumference so that the direction of each ejection hole can be set to the same focal point in the manufacture of the apparatus. However, if the apex angle α at the focal point described above is 40 ° or less, arranged within a diameter of 50 mm, and a gas curtain is formed, the arrangement of the orifices does not necessarily need to be circular, and may be elliptical, rectangular or It may be a polygon.

The shape of the high-pressure gas ejection hole may be a large number of small holes or slits arranged on the circumference of the diameter R. In the case of a small hole, its cross-sectional shape may be circular, elliptical or rectangular, but a circular shape is easiest to manufacture. The size of the hole
A sufficient gas curtain is formed if the distance between the centers of adjacent small holes is about 0.5 to 3 mm and the distance between the centers of adjacent small holes is about 1.0 to 6 mm. In the case of a slit, the width is preferably 3 mm or less, and the slit may be divided or all may be continuous. In any case, it is sufficient that a curtain-shaped high-pressure gas jet can be formed. The ejection direction of the gas jet, that is, the direction of the center line 5-1 of the ejection hole is all directed to the apex of an inverted cone having an apex angle α having a circle having a diameter R as a base. The reason for setting the angle α to 40 ° or less is that if the angle exceeds 40 °, the gas blow-up from the vicinity of the apex becomes large, hindering the secondary collision, and sometimes causing the molten metal to be blown up and block the molten metal nozzle. Because there is. But the apex angle is 0 °
That is, if the gas jet curtain is parallel, the distribution width of the particle diameter becomes large, so that α is preferably set to an angle other than 0 °. Desirable is in the range of 10-30 °.

The outflow angle β of the molten metal flow is set to 20 ° or more and 100 ° or less. If the angle is less than 20 °, the particle diameter increases and the distribution width increases. This is probably because secondary and tertiary collisions are less likely to occur. If it exceeds 100 °,
Particles due to the primary collision may be directed toward the molten metal nozzle, and smooth atomization may not be performed, such as particles adhering to the nozzle. Preferred is 30-80 °.

The primary collision position at which the molten metal collides with the gas jet curtain is defined by the gas ejection hole at the tip of the ejection hole.
It should be within 30mm. That is, L (mm) in FIG.
<L ≦ 30. This is because the farther the position where the molten metal collides with the gas jet is away from the gas ejection hole, the more the primary and micronizing effects, as well as the secondary and tertiary collision effects decrease, This is because a metal powder having a narrow particle size distribution width cannot be obtained.

The apparatus for producing atomized powder of metal has the above configuration. To effectively produce metal powder having a narrow particle size distribution width by using this apparatus, the gas ejection pressure must be 0.5 to 8MPa.
a, Flow rate of molten metal _ML (g / min) and gas flow rate _MG (g / mi
The ratio M _L / M _G with n), preferably set to 0.01 to 0.5.

The gas ejection pressure is detected by providing a pressure regulating valve if necessary in the middle of the pipe from the high-pressure gas source and arranging a pressure gauge near the gas ejection hole to detect the pressure. This pressure is 0.
In the case of less than 5 MPa, the proportion of powder having a large particle diameter increases,
The particle size distribution width expands. This is considered to be because the supersonic region of the gas jet becomes narrow. Even if the ejection pressure is higher than 8 MPa, the refinement of the particle diameter is saturated, and it is useless to increase the pressure further.
For stable operation, the pressure is preferably 3 to 7 MPa.

The ratio M _L / M _G between the flow rate of the molten metal and the flow rate of the gas is 0.
If it exceeds 5, the proportion of powder having a large particle diameter increases, and the tendency for the particle diameter distribution width to widen increases. Further, even if it is less than 0.01, the refinement of the particle diameter is not further improved, and M _L /
Since in order to reduce the ratio of M _G must squeezed the melt flow, it becomes prone to clogging of the melt nozzle by it. Therefore, M _L / M _G preferably set to 0.01 to 0.5, but desirable is to the 0.05 to 0.4.

The gas is preferably argon or nitrogen which does not normally react with the molten metal. If necessary, the gas may be reacted with the metal at the time of gas atomization, and the gas is not particularly limited.

[0027]

EXAMPLE Metal fine powder was produced using the apparatus shown in FIG. 1 or FIG. The gas ejection hole 3 of the device has a center position R in the ejection direction as a circle having a diameter of 30 mm, and a small hole having a diameter of 1 mm inclined at 10 ° to the center of the circle with respect to the vertical direction as a center-to-center distance of about 1.5 mm. It was arranged on the circumference. In other words, the bottom surface of the gas jet curtain 5 by gas ejection is 30 mm in diameter.
Is a conical surface having a vertical angle α of 20 °. The molten metal nozzle 2 was a round hole having a diameter of 3.5 mm and was inclined at an angle of 30 ° with respect to the vertical direction, and the first collision with the molten metal flow was performed at a position where the distance L from the tip of the gas ejection hole was 10 mm. With this apparatus, the jet gas is argon, and Fe-4.5C% alloy, Misch metal (Mm) alloy (Ni: 49.4%, Co: 10.5%, M
n: 5.2%, Al: 1.9%, balance Mm) or Ni-55% S
Using the i-alloy, the ratio of the flow rate of the molten metal to the flow rate of the jet gas M _L / M _G
Was changed to produce metal fine powder. For comparison,
When the R at the outlet position is 60 mm, the apex angle α of the cone is
For the case of 45 ° or the case where the primary collision position L was 35 mm, metal fine powder production using an Fe-4.5% alloy was also performed. Table 1 shows the specifications and production conditions of the apparatus for producing these metal powders.

[0028]

[Table 1]

The particle size of the obtained metal powder was measured by an optical diffraction method, and the particle size having a cumulative weight of 50% was defined as the average particle size. Further, a geometric standard deviation was obtained from the obtained particle diameters, and used as an index of the width of the particle diameter distribution. The smaller the deviation value, the smaller the width of the particle size distribution. Table 1 also shows the measurement results of the average particle size and the standard deviation.

As can be seen from these results, numbers 5 to
The shapes of the gas jet curtains 9 and 13 to 18, the angle of the nozzle of the molten metal, and the position where the molten metal collides with the gas jet curtain are within the range defined by the present invention, and the flow ratio of the molten metal to the jet gas is appropriate. At one time, even with the same molten metal flow rate, a metal powder having a small average particle size and a narrow particle size distribution is obtained. However, when the diameter of the circle where the gas ejection holes are installed is large, as in the case of No. 2, 3, or 4, or when the collision position of the molten metal stream with the gas jet curtain is too large, the outflow angle of the molten metal is 0. °
The average particle size is large and the deviation is large, although it is improved as compared with No. 1. In addition, the conical shape formed by the gas jet curtain has a large apex angle of 10
Although the obtained particle size is preferable, the clogging of the melt nozzle occurred in a short time. This was presumed to be due to the large gas blow-up.

Even when the apparatus of the present invention is used, the pressure of the jet gas is too low, or the ratio M _L / M
When the M _G is too large, as seen in No. 10 or 11, the average particle size is not smaller, the greater standard deviation.

[0032]

According to the apparatus for producing metal powder by the atomizing method of the present invention, it is possible to obtain a metal powder having a smaller average particle size and a narrower particle size distribution at the same molten metal flow rate and jet gas flow rate. By regulating the gas pressure and the flow ratio between the molten metal and the ejected gas, the effect can be more remarkably realized. These greatly contribute to the supply of inexpensive and high-quality metal powders for sintering materials and electrode materials for secondary batteries.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an example of a metal powder production state with a longitudinal section of an apparatus of the present invention.

FIG. 2 shows the direction of gas ejection, the direction of molten metal flow of the apparatus of the present invention,
It is a figure which illustrates typically the collision position etc. of a molten metal flow and jet gas.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molten metal 2 Molten nozzle 3 Molten flow 4 Gas ejection hole 5 Gas ejection flow 5-1 Center line of gas ejection flow 6 Focus of gas ejection direction 7 Powder flow after collision

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kazutaka Asabe 1-8 Fuso-cho, Amagasaki City, Hyogo Prefecture Within Sumitomo Metal Industries, Ltd. Electronics Technology Research Laboratories (72) Inventor Koichi Kashiro 1-8 Fuso-cho, Amagasaki City, Hyogo Prefecture No. Sumitomo Metal Industries, Ltd. Electronics Technology Laboratory Co., Ltd. F-term (reference) 4K017 AA04 BA03 BA06 BB06 BB12 CA07 DA01 EB03 EB12 EB17 FA06 FA10 FA11 FA14

Claims (2)

[Claims] In an atomizing method in which a molten metal is discharged from a nozzle and a high-pressure gas is blown out of the nozzle through an ejection hole to obtain finely divided metal powder, the ejection hole of the high-pressure gas faces downward and has a diameter of 50 mm or less. , The center line of the jet is directed to the vertex of a cone whose bottom is the circle where the jet hole is located, the apex angle of the cone is 40 ° or less, and the molten metal nozzle is 20 ° away from the vertical downward direction. Inclined from 100 ° to 100 °, the distance from the tip of the gas ejection hole at the position where the molten metal first collides with the inner surface side of the cone is 30 mm or less,
An apparatus for producing metal atomized powder, wherein the apparatus is arranged. 2. Using the atomized powder production apparatus as claimed in claim 1, 0.5～8MPa the ejection pressure of the gas, molten metal flow rate M _L
(G / s) and 0.01 the ratio M _L / M _G of the gas flow rate M _G (g / s)
0.5, wherein the metal powder is produced.