JPH0441607A - Metal powder manufacturing method - Google Patents

Abstract

PURPOSE:To easily obtain fine metal powder by bringing conical shell type high pressure gas stream into contact with outer peripheral edge at lower end face of a molten metal nozzle and setting relation between suction pressure p2 for sucking molten metal and back pressure p1 of the molten metal in the molten metal nozzle to p2>=p1. CONSTITUTION:By acting the back pressure p1, the molten metal (m) is caused to flow out from a flowing-out hole 12 in the molten metal nozzle 91. Further, by passing the high pressure gas stream (g) through the outer peripheral edge 13a at the lower end face of molten metal nozzle 91, the inside space (s) is made to reduced pressure condition, and the molten metal (m) is sucked at the outer peripheral edge 13a side with the suction pressure p2 along the lower end face 13. In this case, the relation between the suction pressure p2 and the back pressure p1, is set to p2>=p1 and the molten metal (m) is caused to flow out toward the outer peripheral edge 13a along the lower end face 13. By this method, the molten metal (m) is cut into drips while being sucked with sucking action of the high pressure gas stream (g) and the molten metal quantity per one piece of powder is made to small. Further, the molten metal (m) existing on the outer peripheral edge 13a at the lower end face is cooled with the molten metal nozzle 91, which is cooled with the high pressure gas stream (g) to avoid the development of mutually rejoining the powders. In this way, the fine metal powder Pm is obtd.

Description

Detailed Description of the Invention A4 Purpose of the Invention (1) Industrial Field of Application The present invention relates to a method for producing metal powder, and in particular, to a method for producing metal powder, in particular, a method for producing a molten metal powder through an outlet opening at the lower end face of a molten metal nozzle. A method of forming a high-pressure gas flow from an annular gas nozzle disposed near the outlet into a conical shell shape so that it converges below the molten metal nozzle, and cutting the molten metal with the high-pressure gas flow to powder it. Regarding improvements.

(2) Conventional technology Conventionally, this type of manufacturing method involves making the molten metal flow down from the outlet of a molten metal nozzle in a substantially columnar shape, and colliding the molten metal with a high-pressure gas flow to turn the molten metal into powder. method is known.

(3) Problems to be Solved by the Invention However, according to the above manufacturing method, the amount of molten metal per powder cut by the high-pressure gas flow is large, and the cooling effect on the molten metal is insufficient. There is a problem in that it is difficult to obtain fine metal powder because the particle size distribution of the metal powder tends to be biased toward larger diameters. It is an object of the present invention to provide the above-mentioned manufacturing method capable of obtaining fine metal powder by employing suitable means.

B1 Structure of the Invention (1) Means for Solving the Problems The present invention provides a method for causing the molten metal to flow out from an outlet opening at the lower end face of a molten metal nozzle, and by an annular gas nozzle disposed near the outlet of the molten metal nozzle. forming a high-pressure gas stream in the shape of a conical shell so that it converges below the melt nozzle, and pulverizing the melt by cutting the melt by the high-pressure gas stream; A high-pressure gas flow is formed so that it contacts the outer circumferential edge of the lower end surface of the molten metal nozzle, and the high-pressure gas flow is generated by passing through the outer circumferential edge of the lower end surface, and the molten metal at the outlet is transferred to the lower end surface. By setting the relationship between the suction pressure p drawn toward the outer peripheral edge side and the back pressure 1)l for causing the molten metal in the molten metal nozzle to flow out from the outlet to 22≧p1, A first feature is that the flowing molten metal is cut at the outer peripheral edge of the lower end surface by the high pressure gas flow.

A second feature of the present invention is that the molten metal nozzle is provided with a restriction on the molten metal introduction side of the flow path for reducing the back pressure p.

(2) Effect According to the first feature, the molten metal existing on the outer periphery of the lower end surface of the molten metal nozzle is sucked out and cut by the suction action of the high-pressure gas flow, so the amount of molten metal per powder is reduced. It becomes less.

In addition, the molten metal existing on the outer periphery of the lower end surface has few lids, and is cooled by the molten metal nozzle and high-pressure gas flow, which heats the melt as it comes into contact with the high-pressure gas flow. It is possible to avoid the occurrence of rebonding.

In this way, refinement of the metal powder is achieved.

According to the second feature, it is possible to expand the control range of the back pressure p on the molten metal, thereby facilitating powder manufacturing work.

(3) Example 1. In FIG. 2, the metal powder manufacturing apparatus for carrying out the high-pressure He gas atomization method includes a powder manufacturing section 1 and a powder unrecovered section 2, and the powder manufacturing section 1 has an upper melting chamber 3 and a lower spray chamber. 4 and more, powder collection 8I! 2 consists of an upper cyclone 5 and a lower collection bot 6. The spray chamber 4 and the cyclone 5 are connected via a conduit 7.

A crucible 8 is disposed within the melting chamber 3, and the crucible 8
Molten metal nozzle attached to the bottom wall of 9. is spraying inside 4
Located at the inner upper part. The molten metal nozzle 91 has a flow path 10 extending in the vertical direction, an inlet 11 of which opens into the crucible 8, and an outlet 12 of the molten metal nozzle 9. Lower end surface 13 of
Open to.

An annular gas nozzle 14 is attached to the lower outer peripheral surface of the molten metal nozzle 91, and a gas introduction pipe 15 is connected to the gas nozzle 14. A stopper 16 is inserted into the crucible 8, and the stopper 16 can close the inlet 11 of the molten metal nozzle 91.

As also shown in FIG. 3A, the molten metal nozzle 9. is formed into a tapered surface 17 from its lower end surface 13 to a predetermined position on the lower outer peripheral surface. The high-pressure gas flow g from the gas nozzle 14 is formed into a conical shell shape so as to converge on the central extension line of the outlet 12 after passing along the tapered surface 16 . As a result, the high pressure gas flow g flows through the molten metal nozzle 9. Lower end surface outer rim 1
3a will be contacted.

In producing metal powder, a molten metal m is prepared in a crucible 8 as shown in FIGS. 3A and 3B, and the molten metal m is passed through a molten metal nozzle 9 by applying a back pressure P+ to it. It is made to flow out from the outlet 12 through the flow path 10 . Further, high pressure He gas is supplied to the gas introduction pipe 15 and the He gas is injected from the gas nozzle 14 to form a high pressure gas flow g.

Then, the high pressure gas flow g flows through the molten metal nozzle 9. When passing through the outer peripheral edge 13a of the lower end surface, the inner air space rjIs of the high-pressure gas flow g becomes depressurized, and a suction pressure Pt along the lower end surface 13 is generated.
This suction pressure P causes the molten metal m in the outlet 12 to be sucked toward the outer peripheral edge 13a of the lower end surface.

In this case, since the relationship between the suction pressure p2 and the front pressure p1 is set to pyo≧P+, the molten metal m flows out from the outlet 12 along the lower end surface 13 toward its outer peripheral edge 13a.

As a result, the molten metal m existing on the outer peripheral edge 13a of the lower end face of the molten metal nozzle 91 is sucked out by the suction action of the high-pressure gas flow g and is cut off, thereby reducing the amount of molten metal per powder.

In addition, the amount of molten metal m existing on the outer peripheral edge 13a of the lower end surface is small, and it is cooled by the molten metal nozzle 91 and the high-pressure gas flow g, whose temperature is lowered by contact with the high-pressure gas flow g.
It is possible to avoid the occurrence of re-bonding of the powders after they have been pulverized.

In this way, refinement of the metal powder Pm is achieved.

FIG. 4 shows a modification of the molten metal nozzle, and the molten metal nozzle 9
□ is a throttle 1 that reduces the back pressure P+ on the molten metal introduction side of the flow path 10
It is equipped with 8.

When such a molten metal nozzle 9□ is used, the control range of the back pressure P1 for the molten metal m can be expanded, and for example, the molten metal m can be directed to the inner periphery of the flow path 10 on the downstream side of the throttle 18 as shown by the chain line in FIG. By allowing the powder to flow out along the surface and easily establishing the relationship between the back pressure p and the suction pressure P2, it is possible to facilitate the powder manufacturing operation.

In addition to the throttle 18, the back pressure p is adjusted by the molten metal nozzle 9. ．． 9. Examples include the inner diameter of m, the viscosity of the molten metal m, etc.

[Example] The table below shows the case where aluminum alloy powder was manufactured under various manufacturing conditions using the molten metal nozzle 9I shown in FIG. 2.

The molten metal m is an aluminum alloy molten metal containing 6% by weight Cr, 2% by weight Zr, and 3% by weight Fe, the material of the crucible 8 and the molten metal nozzle 9I is graphite, the amount of raw material charged into the crucible 8 is about 2 kg, and the molten metal temperature is The temperature was 1200°C and the He gas pressure was 100 kgf/d.

In the table, the present inventions 1 to 2 are based on the above-mentioned manufacturing method, while the conventional examples I to 2 are the ones in which the molten metal m is flowed into a substantially columnar shape from the outlet 12 of the molten metal nozzle 9I as shown by the chain line in FIG. 3A. This applies when the water is allowed to flow down. In this case, the back pressure p1 is set to be larger than the suction pressure p:, that is, P+>Pl.

FIG. 5 shows the particle size distribution of aluminum alloy powder, and FIG. 5(a) corresponds to the present invention (■) in the table, and FIG. 5(b) corresponds to the conventional example (■) in the table.

As is clear from the above table and FIG. 5, the present inventions ■ to ■
According to , it can be seen that the particle size distribution of aluminum alloy powder is biased toward smaller powder diameters, and the average diameter is also smaller.

C1 Effect of the Invention According to the invention described in claim (1), fine metal powder can be obtained by specifying the back pressure P+ and suction pressure Pz acting on the molten metal as described above.

According to the invention recited in claim (2), the back pressure p.

and suction pressure Pg can be easily established to improve the production efficiency of fine metal powder.

[Brief explanation of drawings]

Fig. 1 is an overall front view of the metal powder manufacturing equipment, Fig. 2 is a longitudinal sectional front view of the main part of Fig. 1, Fig. 3A is an explanatory diagram of the powder manufacturing method using a molten metal nozzle, and Fig. 3B is a 3A 4 is a longitudinal sectional front view showing a modified example of the 18iJi nozzle, and FIG. 5 is a particle size distribution diagram of aluminum alloy powder. and...high pressure gas flow, m...molten metal, Pl...back pressure, p
2... Suction pressure, Pm... Metal powder, 95.9z... Molten metal nozzle, 10... Channel, 12... Outlet, 13...
... lower end surface, 13a ... lower end surface outer periphery, 14 ... annular gas nozzle, 18 ... aperture

Claims (2)

[Claims] (1) Lower end surface (13) of molten metal nozzle (9_1, 9_2)
Let the molten metal (m) flow out from the outlet (12) that opens at
In addition, the outlet (12) of the molten metal nozzle (9_1, 9_2)
) The annular gas nozzle (14) disposed near the molten metal nozzle (9_1, 9_
2) Formed into a conical shell shape so as to converge below,
In pulverizing the molten metal (m) by cutting it with the high-pressure gas stream (g), the conical shell-shaped high-pressure gas stream (g) is connected to the molten metal nozzle (9_1, 9_
2) is formed so as to contact the outer peripheral edge (13a) of the lower end surface, and the high pressure gas flow (g) is formed so as to contact the outer peripheral edge (13a) of the lower end surface.
suction pressure p_2 that is generated by passing the molten metal (m) at the outlet (12) and sucks the molten metal (m) toward the outer peripheral edge (13a) of the lower end face; By setting the relationship between the back pressure p_1 and the back pressure p_1 for causing the molten metal ( ) to flow out from the outlet (12) to be p_2≧p_1, the molten metal (
m) at the outer peripheral edge (13a) of the lower end surface of the high pressure gas flow (
A method for producing metal powder, which comprises cutting by g). (2) As the molten metal nozzle (9_2), its flow path (1
0) on the molten metal introduction side to reduce the back pressure p_1.
8), the method for producing metal powder according to item (1).