JPH0344409A - Method and apparatus for manufacturing spheroidal and fine metal powder - Google Patents

Abstract

PURPOSE:To manufacture fine and spheroidal metal powder with good product yield by setting the specific structure of cylindrical body at lower part of a nozzle for injection gas jet at the time of manufacturing the fine metal powder by injecting the gas jet against flowing-down stream of molten metal. CONSTITUTION:The molten metal 10 in a refractory-made vessel 5 is made to flow down as bar-like or plate-like molten metal stream from a nozzle 2 at bottom part of the vessel 5 and the gas jet 11 from an injection hole 9 of atomizing nozzle 1 is blown to finely cut the molten metal. In this case, a double cylindrical member 3 is fitted below the atomizing nozzle 1. This cylindrical member 3 is constituted of a cylindrical member 31 at inside and a cylindrical member 32 at outside and the inner diameter of the inside cylindrical member 31 is made >=5 times the inner diameter of circular or oval shape formed by connecting the gas injection holes 9 of atomizing nozzle 1 and the cross sectional area of annular part 33 formed with the inner and outer cylindrical members 31, 32 is made >=25% the cross sectional area of inside cylindrical member 31. The gas jet stream 11 and fine molten metal particles flows down in the inside cylindrical member 31 and the gas sucked with the gas jet is ascended in the annular part 33, and as this does not come into collision with the gas stream and the metal fine particles, the spherical metal fine powder can be manufactured with good yield.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method and apparatus for producing spherical fine metal powder. More specifically, the present invention allows a high-temperature molten metal material to flow down as a rod-shaped or plate-shaped molten metal flow,
The present invention relates to a method and apparatus for producing fine spherical metal powder, which is characterized in that the metal powder is refined by injecting and colliding it with a high-velocity gas jet.

(Prior art) The gas atomization method involves making a high-temperature molten metal flow down as a rod-shaped or plate-shaped molten metal stream, and then injecting and colliding a high-velocity gas jet at a certain angle with the molten metal stream from an atomizing nozzle. This method produces a large amount of spherical and fine metal powder by atomizing and cooling the molten metal flow.

In gas atomizing equipment for carrying out this gas atomizing method, the atomizing nozzle and the atomizing tank are commonly separated by a vacuum seal valve for convenience of melting in a vacuum atmosphere. The injected gas and the atomized molten metal material pass through a cylindrical member with a relatively small diameter, and then flow into an atomization tank provided below this member.

(Problem to be Solved by the Invention) By the way, as an atomizing nozzle used to carry out this gas atomizing method, a large number of independent injection holes are used in one.
There is a so-called pencil type which is oriented toward one focus (for example, Japanese Patent Laid-Open No. 49-41257). This type of atomizing nozzle has an excellent ability to further promote atomization of the molten metal flow, but when using this type of atomizing nozzle, the suction gas generated by the gas jet injection is transferred to the atomizing nozzle. Near the bottom of the molten metal flow, there is an upward gas flow that is in the opposite direction to the flow of the injected gas jet. Because of the collision, the gas jet becomes unstable, resulting in a problem that the molten metal flow cannot be effectively refined.

Another problem is that a large amount of fine powder generated from the molten metal flow is mixed into the surrounding gas flow induced by the gas jet, and the surrounding gas flow is sucked into the molten metal by the gas jet. Because of the collision with the material, the fine powder adheres to and integrates with the surface of the newly generated molten powder, and spherical powder may not be obtained.

Furthermore, as a method different from the above-mentioned method used in the gas atomization method, there is a method of injecting a gas jet using an annular nozzle (for example, Japanese Patent Publication No. 52-19181), but in this type of atomization nozzle, However, the suction gas induced by the gas jet injection mainly becomes an upward gas flow and collides near the finer part of the molten metal flow, which also makes the gas jet unstable. Similar to the method, there are problems in that the molten metal material cannot be effectively atomized and that spherical powder cannot be obtained.

That is, in the conventional means, (i) When attempting to generate metal powder from molten metal material by the atomization method, the suction gas induced by the gas-shared injection mainly becomes an upward gas flow, and the molten metal is As the flow collides near the atomization part, the gas jet becomes unstable and cannot effectively atomize the molten metal material, and (ii) as another problem, the surrounding fluid attracted by the gas jet Fine powder generated from the molten metal material is mixed into the molten metal material, and the surrounding fluid is attracted by the gas jet and collides with the molten metal material, so the fine powder adheres to the surface of the newly generated molten powder and becomes integrated. There was a major problem in that spherical powder could not be obtained because of the spherical particles, and a solution to this problem was desired.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and apparatus for producing spherical and fine metal powder, which can solve the above problems.

(Means for Solving the Problems) In order to solve the above problems, the present inventors have made various studies and have completed the present invention.

Here, the gist of the present invention is to atomize the molten metal flow into spherical shapes by injecting a gas jet from an atomizing nozzle and colliding with the flowing molten metal flow.
A method for producing fine metal powder, wherein a double cylindrical member having the molten metal flow at its center is arranged downstream of the atomizing nozzle, and the gas jet and the fine molten metal are Metal flow is a method of producing spherical and fine metal powder, which is characterized by passing through an inner cylindrical member and passing suction gas induced by a gas jet through an outer annular part. be.

Further, in the above-described present invention, (i) the inner diameter of the inner cylindrical member is at least five times the diameter of the circle formed by connecting the gas injection holes of the atomizing nozzle or the long diameter of the ellipse. (ii) The cross-sectional area of the annular portion is 25% or more of the cross-sectional area of the inner cylindrical member.

In addition, from another aspect, it is an apparatus for generating spherical and fine metal powder by injecting a gas jet from an atomizing nozzle into a flowing molten metal flow and colliding with the flowing molten metal flow. an atomizing nozzle having at least one opening for downstream injection; (ii) from the periphery of the molten metal stream to be injected downstream from the opening;
(iii) a plurality of gas jet injection holes provided in the atomizing nozzle at an angle with respect to the molten metal flow; The present invention is an apparatus for producing spherical fine metal powder, comprising: a cylindrical member; and (iv) an atomization tank provided below the cylindrical member.

(effect) Hereinafter, the present invention will be explained in detail together with its effects.

In the present invention, by injecting a high-speed fluid jet from an atomizing nozzle and causing it to collide with a flowing molten metal stream,
A method of refining the molten metal material, more specifically, the method comprises: refining and cooling the molten metal material by jetting and colliding a gas jet against the molten metal material from around the flowing molten metal material. This method is an improved method of obtaining metal powder.

When injecting this gas jet, if the gas jet is arranged so as to surround the flowing molten metal stream and is injected at one focal point of the molten metal stream, the gas jet will be surrounded by the gas jet due to the suction action of the gas jet. The pressure in the region including the space in which the conical molten metal material flows is lower than that in the outer region of the gas jet, so that gas is drawn from the surrounding region of the gas jet into the inner region of the gas jet. The gas collides with the gas jet. In order to avoid this collision and improve the stability of the gas jet, the present invention divides the respective flow paths of the injected gas jet and the sucked gas by using double cylindrical members.

That is, the injected gas jet advances toward the center of the molten metal flow, and travels approximately vertically downward downstream from the point where the gas jet converges, that is, the aforementioned focal point.

In contrast, the gas flow sucked in by the gas jet is sucked in from around the propellant gas jet.

Therefore, in the present invention, a double cylindrical member is disposed below the atomizing nozzle, the inner cylindrical member containing the traveling direction of the molten metal flow.

The injected gas jet and the fine molten metal flow pass through the inner cylindrical member of this double cylindrical member, and mainly pass through the annular shape between the outer and inner cylindrical members. By arranging the double cylindrical member so that the gas sucked through the portion passes through, the collision of the gas in the vicinity of the focal point is reduced or prevented. In other words, all or part of the suction gas flow that collides with the injected gas jet flow passes through the annular portion, so that the gas jet flow is stabilized and the molten metal flow is reliably refined.

In addition, in the present invention, the "cylindrical member" is usually assumed to be a cylindrical member, but is not particularly limited to this, and as mentioned above, it can be used for injected gas jets and molten metal. Any cylindrical member that can separate the gas flow and the gas to be sucked may be used.

Furthermore, it is not necessary that all of the sucked gas passes through the annular portion, and only a portion of the gas may pass through the annular portion.

By the way, the dimensions, installation position, etc. of such a cylindrical body are as follows.
From the viewpoint of promoting spheroidization and refinement of the molten metal flow, there is a suitable range, and these suitable conditions will be described in detail below.

First, in the present invention, the inner diameter of the inner cylindrical member of the double cylindrical member is 5 times or more the diameter of the circle formed by connecting the gas injection holes of the atomizing nozzle or the long diameter of the ellipse. It is desirable that there be.

That is, this range is desirable because a stable gas jet injection state can be obtained within this range.

Furthermore, it is desirable that the cross-sectional area of the annular portion of the double cylindrical member be at least 25% of the cross-sectional area of the inner cylindrical member. By ensuring that suction gas passes through
This is to prevent gas collisions near the pulverization point and achieve stable spraying.

In the present invention, these preferable conditions are one or two.
Can be used in combination of two or more.

In this way, according to the present invention, spherical and fine metal powder can be reliably obtained.

Further, the present invention will be described based on the embodiments shown in FIGS. 1 and 2, but this is an illustration of the present invention, and the present invention is not limited thereby.

Embodiment FIGS. 1 and 2 are schematic diagrams of an embodiment according to the method of the present invention. In FIG. 2, 6 is a powder recovery tank (atomization tank), and the atomization nozzle 1 is installed in the upper part of the powder recovery tank 6. The atomizing tank 6 and the atomizing nozzle 1 are separated by a vacuum damper 41 and a movable vacuum damper valve body 42.In the center of the atomizing nozzle l, there is a molten metal material container installed above the atomizing nozzle 1. A downstream injection opening 8 is provided at the bottom of 5 (see Figure 1).
The molten metal material is supplied to the atomizing nozzle 1 through the downstream injection opening 8, and is turned into powder and collected in the powder recovery tank 6. In FIG. 2, the cylindrical member 3 is shown schematically. Details are as shown in FIG.

There are gas jet injection holes 9 arranged in an annular manner around the downstream injection opening 8 of the atomizing nozzle 1, and these injection holes 9 provide a gas jet injection hole 9 for the molten metal material 10 flowing down through the downstream injection opening 8. The molten metal material 10 is installed so as to have a predetermined intersection angle, and high-pressure nitrogen gas or the like is injected and collided with the molten metal material 10 to pulverize it into powder.

The shape of the injection hole 9 that injects this gas jet is not limited in any way, but a structure in which a large number of independent injection holes of the annular slit are arranged around the downstream injection opening 8 may also be used. I can do it.

Then, on the gas injection side of the atomizing nozzle 1 (directly above the atomizing tank 6), an opening 8 for flowing down injection of molten metal material is provided.
Centered on the center line (A-AvA in Figure 1),
A double cylindrical member 3 consisting of an inner cylindrical member 31 and an outer cylindrical member 32 is arranged. The inner diameter of the inner cylindrical member 31 of the double cylindrical member 3 is 5 times or more the diameter of the circle formed by connecting the gas injection holes of the atomizing nozzle l or the long diameter of the ellipse. and the cross-sectional area of the annular portion (33 in FIG. 1) of the double cylindrical member is 25% or more (in this example, 42% and 178%) of the cross-sectional area of the inner cylindrical member 31. A double cylindrical member 3 such as that shown in FIG.

Figures 3 to 5 and Table 1 show that under the above conditions,
1 shows the results of producing stainless steel powder using the method and apparatus according to the invention as well as conventional means. An example in which a single cylindrical body is provided is shown as a conventional example.

Table 2 shows the main specifications of the atomizing nozzle used in the experiment.

In addition, conditions for the molten metal material and atomizing gas are shown below.

Molten metal material composition SO53011 equivalent steel temperature 160
0'C Flow rate 10kg/min Type of injection gas High purity argon gas Pressure
50 kgf/cm'' In Table 1, methods 1 to 4 of the present invention all satisfy the constituent requirements of the present invention, the atomization situation is good, and fine powder is produced.

On the other hand, in the comparative method, the inner diameter of the inner cylindrical member is less than 5 times (120/30 = 4 times) the diameter of the circle formed by connecting the gas injection holes of the atomizing nozzle. ′
Eight drops adhered and accumulated on the cylindrical member, leading to blockage.

Furthermore, in the conventional method, many coarse particles are produced.

FIG. 3 shows the relationship between the stability of gas spray and the ratio of the diameter of the inner cylindrical member of the double cylindrical member and the diameter of the gas injection hole installation circle. As is clear from Fig. 3, in order to produce a stable spray state and prevent the powder from depositing on the inner cylindrical member, the inner diameter of the inner cylindrical member must match the gas injection hole of the atomizing nozzle. It is desirable that the size is five times or more the diameter of the circle formed by tying or the long diameter of the ellipse.

Furthermore, Fig. 4 shows the relationship between the stability of gas spraying and the length of the double cylindrical member. In order to prevent deposition, the length of the double cylindrical member must be within a range where the gas jet and the inner cylinder do not intersect if the injected gas jet travels straight, i.e. The length of the double cylindrical member is preferably within a range in which the jetting direction of the gas jet and the inner cylindrical member do not intersect. This is because if the length of the cylindrical member exceeds this length, powder may be deposited within the inner cylindrical member, which may lead to blockage in severe cases.

Furthermore, FIG. 5 shows the relationship between the average diameter of the powder produced and the ratio of the cross-sectional area of the annular portion of the double-layered cylindrical member to the cross-sectional area of the inner cylindrical member. As is clear from FIG. 5, in order to generate a stable spray state and fine powder, the cross-sectional area of the annular portion of the double cylindrical member must be 25% of the cross-sectional area of the inner cylindrical member. The above is desirable.

(Effects of the Invention) As detailed above, according to the present invention, fine spherical metal powder can be stably produced in large quantities from molten metal material without causing any trouble such as equipment damage due to blow-up. Is possible.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing the positional relationship between the atomizing nozzle and the double cylindrical member in the present invention; FIG. A schematic horizontal diagram; Figure 3 is a graph showing the relationship between the stability of gas spraying and the ratio of the diameter of the inner cylindrical member of the double cylindrical member and the diameter of the gas spray hole installation circle; Figure 4 is , a graph showing the relationship between gas atomization stability and the length of the double tubular member: and. FIG. 5 shows the relationship between the average diameter of the produced powder and the ratio of the cross-sectional area of the annular portion of the double cylindrical member to the cross-sectional area of the inner cylindrical member. 1: Atomizing nozzle 2: Molten metal material supply nozzle 3: Double cylindrical member 31: Inner cylindrical member 32: Outer cylindrical member 33: Annular portion 41: 42: 5: 6 Near: 8: 9: 10: 11: Vacuum damper Vacuum damper Valve body Molten metal material container Atomization tank Cyclone Opening for injection of downstream injection hole Molten metal material gas jet (movable)

Claims (3)

[Claims] (1) A method of atomizing the molten metal flow and generating spherical and fine metal powder by injecting a gas jet from an atomizing nozzle and colliding with the flowing molten metal flow, the downstream side of the atomizing nozzle A double cylindrical member having the molten metal flow at its center is arranged, and the gas jet and the fine molten metal flow are passed through the inner cylindrical member, and the gas jet A method for producing spherical and fine metal powder, characterized in that the suction gas induced by the injection of is passed through an outer annular part. (2) In the method for producing spherical and fine metal powder according to claim 1, further: (i) the inner diameter of the inner cylindrical member is the diameter of a circle formed by connecting the gas injection holes of the atomizing nozzle; It satisfies one or more of the following conditions: (ii) the cross-sectional area of the annular portion is 25% or more of the cross-sectional area of the inner cylindrical member; A method for producing spherical and fine metal powder. (3) A device for generating spherical and fine metal powder by injecting a gas jet from an atomizing nozzle into a flowing molten metal stream and colliding with the flowing molten metal stream, (i) an opening for injecting the flowing molten metal stream; (ii) a plurality of gas jet injection holes provided in the atomizing nozzle at an angle with respect to the molten metal flow from the periphery of the molten metal flow injected downward from the opening; iii) a double cylindrical member provided below the atomizing nozzle with the molten metal flow at its center; and (iv) an atomizing tank provided below the cylindrical member. A device for producing spherical and fine metal powder.