JP2012201940A - Apparatus and method for producing metal powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and a method for producing a metal powder, which are capable of stably producing the high-quality metal powder with low oxygen content and fine, uniform grain size, regardless of the composition of the metal powder to be produced.SOLUTION: The apparatus 1 for producing the metal powder includes: a supply unit; a storing unit 2 that stores molten metal 90 and is arranged below the supply unit; and an atomizing nozzle arranged below the storing unit. The apparatus 1 further includes, in the storing unit 2: a heat-radiating means 5 that lowers temperature of the molten metal 90 and is arranged on a liquid surface of the molten metal 90 stored; and a heating means that heats the molten metal 90 and is arranged below the heat-radiating means 5. The storing unit 2 includes a storing container 21, wherein an induction heating coil 81 is installed inside a wall thereof. The heating means includes the induction heating coil 81 and a controller including a power source for applying voltage to the induction heating coil 81. The heat-radiating means 5 is constituted of the wall in which the induction heating coil is not installed.

Description

  The present invention relates to a metal powder production apparatus and a metal powder production method.

Conventionally, in order to produce a metal powder, a metal powder production apparatus (atomizer) for pulverizing molten metal by an atomizing method has been used. As this metal powder manufacturing apparatus, Patent Document 1 includes a container for holding molten metal, an orifice for passing molten metal flowing down from the container, and a slit for injecting a fluid jet to the molten metal passing through the orifice. And an apparatus having a nozzle. In this device, by the action of gas that passes through the orifice at high speed along with the fluid jet, the molten metal flowed down from the container is split and further made fine by colliding with the fluid jet, thereby making fine metal A powder can be produced.
However, depending on the composition of the metal powder to be manufactured, the oxygen content of the metal powder is increased, leading to a reduction in the quality of metal products manufactured using the metal powder. In addition, even if the oxygen content can be lowered, it is difficult to produce a metal powder having a fine and uniform particle size because the particle size of the metal powder becomes large or the particle size distribution becomes wide. was there.

Japanese Patent No. 3858275

  An object of the present invention is to provide a metal powder production apparatus and a metal powder production method capable of stably producing a high-quality metal powder having a low oxygen content and a uniform particle size regardless of the composition of the metal powder to be produced. It is to provide.

The above object is achieved by the present invention described below.
The metal powder production apparatus of the present invention includes a storage unit for storing molten metal,
A flow path provided below the storage section, through which the molten metal flowing down from the storage section can pass, and a slit that opens to the lower end of the flow path and injects a fluid into the flow path. A nozzle comprising,
A supply unit provided above the storage unit and configured to supply molten metal to the storage unit;
Of the storage part, provided in the liquid surface portion of the stored molten metal, a heat dissipating means for lowering the temperature of the molten metal, a heating means provided below the heat dissipating means and heating the molten metal, It is characterized by having.
As a result, a metal powder production apparatus capable of stably producing a high-quality metal powder having a low oxygen content and a fine particle size is obtained regardless of the composition of the metal powder to be produced.

In the metal powder manufacturing apparatus of the present invention, the supply unit is provided so as to extend downward from a lower surface of the supply unit container and a supply unit container for storing the molten metal, and the molten product stored in the supply unit container A supply tubular member through which the metal can pass,
It is preferable that the lower end of the supply portion cylindrical member is configured to be positioned below the liquid level of the molten metal stored in the storage portion.
Thereby, the molten metal supplied from a supply part will be transferred to a storage part, hardly touching external air. As a result, the temperature drop of the molten metal accompanying the transfer can be minimized, and the temperature control of the molten metal can be made easier.

In the metal powder manufacturing apparatus of the present invention, the storage section has a bottomed cylindrical shape, is provided so as to extend downward from a storage section container that stores molten metal, and a lower surface of the storage section container, and the storage section A reservoir cylindrical member that allows the molten metal stored in the container to pass through, and
It is preferable that the heating means is composed of an induction heating coil disposed in a wall portion of the reservoir container, and the heat radiating means is composed of the wall portion where no induction heating coil is provided.
Thereby, since the temperature of a molten metal can be finely controlled, the temperature of the molten metal which fluctuates greatly in a short time can be reliably maintained constant. In addition, the structure of the heat dissipation means can be simplified.

In the metal powder manufacturing apparatus of the present invention, it is preferable that the heat dissipating means has a refrigerant flowing through a pipe provided in the storage section.
As a result, the amount of oxygen taken into the molten metal can be further reduced, and particularly high-quality metal powder can be stably produced.
In the metal powder manufacturing apparatus of the present invention, it is preferable that the heat dissipating means injects a gas toward the liquid surface of the molten metal stored in the storage section.
As a result, sufficient heat dissipation is achieved without considering the insulation and thermal conductivity of the reservoir, so there are no restrictions on the choice of material for the reservoir, and materials are selected with the highest priority on mechanical properties and cost. It becomes possible to do.

In the metal powder manufacturing apparatus of the present invention, it is preferable that the heating means is configured to gradually increase the heating temperature in accordance with an elapsed time from when the molten metal starts to be stored in the storage unit.
Thereby, the control which maintains the temperature of a molten metal constant immediately after starting the storage of a molten metal can be performed easily.

In the metal powder manufacturing apparatus of the present invention, a temperature measurement unit that measures the temperature of the molten metal stored in the storage unit, and
It is preferable to have a control unit that controls the heating temperature by the heating unit based on the measured temperature of the molten metal.
Thereby, regardless of the composition of the metal powder to be manufactured, a metal powder manufacturing apparatus capable of stably and easily manufacturing a high-quality metal powder having a low oxygen content and a fine particle size is obtained.

In the metal powder manufacturing apparatus of the present invention, a liquid level measuring unit that measures the height of the liquid level of the molten metal,
It is preferable to have a control unit that controls the amount of molten metal supplied by the supply unit based on the measured height of the liquid level.
Thereby, regardless of the composition of the metal powder to be manufactured, a metal powder manufacturing apparatus capable of stably and easily manufacturing a high-quality metal powder having a low oxygen content and a fine particle size is obtained.

The metal powder production method of the present invention produces a metal powder by storing molten metal in a storage part, causing the molten metal to flow down from the storage part, and then colliding with a fluid jet to split and solidify the molten metal. A method for producing metal powder comprising:
A solidified film is formed on the liquid surface of the molten metal stored in the storage part.
Thereby, regardless of the composition of the metal powder to be manufactured, it is possible to stably manufacture a high-quality metal powder having a low oxygen content and a fine particle size.

In the metal powder manufacturing method of the present invention, the formation of the solidified film may be performed by at least one of a method of dissipating heat from the liquid surface portion of the molten metal and a method of spreading the metal powder on the liquid surface of the molten metal. preferable.
As a result, the amount of oxygen taken into the molten metal can be further reduced, and particularly high-quality metal powder can be stably produced.

It is a longitudinal cross-sectional view which shows typically 1st Embodiment of the metal powder manufacturing apparatus of this invention. FIG. 2 is a partial detail view of FIG. 1. It is a longitudinal cross-sectional view which shows typically a part of 2nd Embodiment of the metal powder manufacturing apparatus of this invention. It is a longitudinal cross-sectional view which shows typically a part of 3rd Embodiment of the metal powder manufacturing apparatus of this invention. It is a longitudinal cross-sectional view which shows typically 4th Embodiment of the metal powder manufacturing apparatus of this invention.

Hereinafter, a metal powder production apparatus and a metal powder production method of the present invention will be described in detail with reference to the accompanying drawings.
<Metal powder production equipment>
<< First Embodiment >>
First, a first embodiment of the metal powder production apparatus of the present invention will be described.
FIG. 1 is a longitudinal sectional view schematically showing a first embodiment of the metal powder production apparatus of the present invention, and FIG. 2 is a partial detailed view of FIG.

  A metal powder manufacturing apparatus 1 shown in FIG. 1 is an apparatus used for obtaining a metal powder by pulverizing a molten metal 90 by an atomizing method and solidifying it. The metal powder manufacturing apparatus 1 includes a supply unit 6, a storage unit (tundish) 2 provided below the supply unit 6, and a nozzle 3 provided below the storage unit 2. The storage unit 2 is provided with a heating unit 8 for heating the molten metal 90 and a heat radiating unit 5 for radiating heat from the liquid surface portion of the molten metal 90.

Hereinafter, the configuration of each unit will be described.
(Supply section)
The supply unit 6 illustrated in FIG. 1 includes a supply unit container 61 having a bottomed cylindrical shape, and a supply unit cylindrical member 62 connected to the lower surface of the supply unit container 61. Among these, in the supply part container 61, the molten metal 90 which melt | dissolved the raw material of the metal powder to manufacture is temporarily stored. In addition, an opening 611 penetrating the bottom is provided in the center of the bottom of the supply container 61. The supply part cylindrical member 62 described above is connected to the lower surface of the supply part container 61 so that the hollow part and the opening 611 overlap each other. Accordingly, the molten metal 90 stored in the supply unit container 61 flows downward through the opening 611 and the supply unit cylindrical member 62, and subsequently stored in the storage unit 2.

Further, the supply container 61 may have a lid (not shown). By covering the lid, it becomes difficult for the stored molten metal 90 to come into contact with the atmosphere, so that oxidation of the molten metal 90, temperature reduction, and the like can be suppressed.
Furthermore, the inside of supply part container 61 can also be pressurized by putting a cover. In this case, since the molten metal 90 is discharged at a speed higher than the flow-down speed due to its own weight, the supply amount of the molten metal 90 per unit time can be controlled by appropriately adjusting the applied pressure.

  The constituent material of the supply section container 61 and the supply section cylindrical member 62 may be any material as long as it does not deform, melt, etc. by contact with the molten metal 90, for example, an iron-based material such as heat-resistant steel. Materials, various metal materials such as tungsten-based materials and molybdenum-based materials, various ceramic materials such as alumina and zirconia, various carbon materials such as graphite, and alumina / graphite materials which are composite materials of these materials Used.

(Reservoir)
The storage part (tundish) 2 shown in FIG. 1 has a storage part container 21 having a bottomed cylindrical shape, and a storage part cylindrical member 22 connected to the lower surface of the storage part container 21. Among these, the storage part container 21 receives the molten metal 90 supplied from the supply part 6, and stores this temporarily. In addition, an opening 211 penetrating the bottom is provided in the center of the bottom of the storage container 21. The reservoir cylindrical member 22 described above is connected to the lower surface of the reservoir container 21 so that the hollow portion and the opening 211 overlap.
Therefore, the molten metal 90 stored in the storage container 21 flows downward through the opening 211 and the storage tubular member 22.
The constituent materials of the reservoir container 21 and the reservoir cylindrical member 22 are the same as the constituent materials of the supply container 61 and the supply cylindrical member 62.

(nozzle)
The nozzle 3 shown in FIG. 1 is provided with a nozzle body 30, a flow path 31 through which the molten metal 90 flowing down from the reservoir 2 passes, and a slit that ejects fluid into the flow path 31. 32 and a cover 7 provided on the lower surface of the nozzle body 30. For example, water is used as the fluid.
The nozzle body 30 shown in FIG. 1 has, for example, a cylindrical shape, and is arranged so that the axis thereof and the flow path of the molten metal 90 flowing down from the storage portion 2 coincide.

The nozzle body 30 is provided with a flow path 31 formed so as to penetrate along the axis and a slit 32 formed so as to open near the lower end of the flow path 31.
The flow path 31 is a through-hole penetrating the nozzle body 30 in the vertical direction, and the inner diameter of the through-hole changes continuously. Specifically, the inner diameter of the flow path 31 is the largest at the upper end portion of the flow path 31, and is configured to continuously decrease downward therefrom. As a result, the inner wall surface of the flow path 31 in this region is a smooth curved surface. In the vicinity of the middle of the flow path 31, the internal diameter of the flow path 31 is the smallest, and continuously increases again downward from there.

An introduction path 321 disposed in the nozzle body 30 is connected to the slit 32 formed in the nozzle body 30. The introduction path 321 connects a fluid supply source (not shown) provided outside the nozzle 3 and the slit 32, and the fluid supplied from the supply source passes through the introduction path 321 and the slit 32. And jetted toward the flow path 31.
In addition, the introduction path 321 has a wedge-shaped partial longitudinal cross-sectional shape. With such a shape, the fluid introduced into the introduction path 321 can gradually increase the flow velocity in the wedge-shaped portion. For this reason, by disposing the wedge-shaped portion immediately before the slit 32, a high-speed fluid can be stably ejected from the slit 32. Further, since the fluid is supplied to the introduction path 321 in a pressurized state, the nozzle body 30 is required to have sufficient pressure resistance.

The slit 32 is open over the entire circumference of the inner wall surface of the flow path 31. For this reason, the fluid ejected from the slit 32 having such a shape forms a conical fluid jet 33 as shown in FIG.
Such a constituent material of the nozzle body 30 may be the same as the constituent material of the supply section container 61 and the supply section cylindrical member 62, but a metal material is preferable. Thereby, the nozzle body 30 that achieves both heat resistance and pressure resistance applied to the fluid is obtained.

The cover 7 has a cylindrical shape, and is provided so that the axis thereof coincides with the axis of the flow path 31. By providing the cover 7 below the nozzle body 30, the falling metal powder can be prevented from being scattered, and the metal powder can be efficiently collected.
The cover 7 is preferably connected to the lower surface of the nozzle body 30 in an airtight manner. Thereby, it is possible to prevent outside air from flowing into the cover 7. As a result, when the molten metal 90 is pulverized and solidified to produce a metal powder, the molten metal 90 can be prevented from coming into contact with the outside air and the metal powder being oxidized and altered.

(Metal powder manufacturing method)
Next, a method for producing metal powder using the metal powder production apparatus 1 will be described.
First, the molten metal 90 is stored in the supply unit container 61. The stored molten metal 90 flows down into the storage container 21 below through the supply cylindrical member 62.
The molten metal 90 that has flowed into the storage container 21 is stored in the storage container 21 and flows down toward the nozzle 3 below through the storage tubular member 22.

At this time, high-speed fluid is ejected from the slit 32 of the nozzle 3 to form a fluid jet 33. When the fluid jet 33 is formed, an air flow G from the upper side to the lower side of the flow path 31 is generated accordingly. This air flow G reduces the pressure in the flow path 31.
When the molten metal 90 that has flowed down from the storage tubular member 22 reaches the flow channel 31 in this state, the molten metal 90 is split (primary split) due to the pressure drop in the flow channel 31. This is caused by the fact that the surrounding decompression force exceeds the force with which the molten metal 90 tries to close. Due to this primary division, the molten metal 90 becomes a large number of droplets 91.

  At this time, it is preferable that the reservoir cylindrical member 22 is disposed so that the lower end of the reservoir cylindrical member 22 is located at a position where the inner diameter of the flow path 31 is minimized. When arranged in this manner, the pressure in the vicinity of the lower end of the reservoir cylindrical member 22 becomes the lowest, so that the molten metal 90 can be particularly finely divided in the primary division. As a result, in particular, a particularly fine metal powder can be produced.

  The droplet 91 generated by the primary division subsequently collides with the fluid jet 33. Due to the impact accompanying the collision with the fluid jet 33, the droplet 91 is further finely divided (secondary division). At the same time, the secondary split droplet 91 is rapidly cooled by the large heat capacity of the fluid jet 33. As a result, the temperature of the droplet 91 is below the melting point and solidifies. A metal powder is obtained as described above.

(Heat dissipation and heating means)
Moreover, in this embodiment, since the storage part 2 is provided between the supply part 6 and the nozzle 3, the supply amount of the molten metal 90 to the nozzle 3 can be stabilized. That is, compared with the case where the molten metal 90 is directly supplied from the supply unit 6 to the nozzle 3, the molten metal 90 is temporarily supplied to the storage unit 2 and then flows down from the storage unit 2. It is easy to control the supply amount per unit time. For this reason, the manufacturing conditions of the metal powder are also constant, and a high-quality metal powder with a uniform particle size can be manufactured.

  Moreover, in this embodiment, since it was set as the structure which has the supply part 6 and the storage part 2 provided in the downward direction, even if the volume of the supply part container 61 is enlarged, it is hard to influence the quality of metal powder. There is an advantage. For this reason, the temperature drop of the molten metal 90 in the supply part container 61 can be suppressed by making the volume of the supply part container 61 sufficiently larger than the volume of the storage part container 21 (for example, 10 times or more). As a result, the quality of the finally obtained metal powder can be further improved.

By the way, in the metal powder manufacturing apparatus 1, as described above, the molten metal 90 is temporarily stored in the storage unit 2, and here a buffer function for making the supply amount per unit time constant is exhibited. For this reason, in order to ensure this buffer function, it is necessary to store a certain amount of molten metal 90 in the storage part 2.
However, in the conventional metal powder manufacturing apparatus, although the supply amount per unit time of the molten metal supplied to the nozzle is constant by temporarily storing the molten metal, the oxygen content of the metal powder finally obtained is There was a problem that it was extremely high. For this reason, the sinterability, magnetic characteristics, etc. of the metal powder are lowered, and the mechanical characteristics and electromagnetic characteristics of various metal products produced using the metal powder cannot be sufficiently improved. In particular, when an easily oxidizable element such as aluminum or titanium is included, the tendency is remarkable.

  Therefore, in the present invention, the storage unit 2 of the metal powder manufacturing apparatus 1 is provided with the heat dissipating means 5 that partially lowers the temperature of the liquid surface portion of the molten metal 90, and the molten metal 90 is disposed below the heat dissipating means 5. Heating means 8 for heating was provided. Thereby, in the metal powder manufacturing apparatus 1, the liquid surface of the molten metal 90 is partially solidified to form a solidified film, while the molten metal 90 is reliably maintained in a molten state below the solidified film. It will be heated. As a result, the molten metal 90 is prevented from contacting the atmosphere by the solidified film, and oxygen is prevented from being taken into the molten metal 90. And the raise of an oxygen content rate can be prevented in the metal powder finally obtained.

Hereinafter, the heating means 8 and the heat dissipation means 5 will be described in order.
Examples of the heating means 8 include those using various heating principles such as induction heating, resistance heating, microwave heating and the like, and are not particularly limited. Here, a case where induction heating is used will be described. . Since the heating by induction heating can directly generate heat from the molten metal 90, the heating efficiency is high, and the temperature of the molten metal 90 can be finely controlled. It is effective in maintaining a constant value.

  The metal powder manufacturing apparatus 1 includes a heating unit 8 including an induction heating coil 81 built in a wall portion of the storage container 21 and a control unit 82 electrically connected to the induction heating coil 81. Yes. By applying a voltage to the induction heating coil 81 from the control unit 82, the reservoir container 21 and the molten metal 90 are heated, and the condition of the molten metal 90 stored in the reservoir 2 is maintained at a condition suitable for the atomization method. can do. As a result, when the molten metal 90 undergoes primary splitting and secondary splitting, variation in conditions over time can be suppressed, so that it can be split under uniform conditions and a metal powder having a uniform particle size can be produced. it can.

Here, the configuration of each part of the heating means 8 will be described in detail.
The induction heating coil 81 shown in FIGS. 1 and 2 is built in the wall portion of the reservoir container 21. By being provided in the wall portion, it is possible to prevent the induction heating coil 81 and the molten metal 90 from contacting each other, prevent contamination of the molten metal 90, and prevent the induction heating coil 81 from deteriorating.

The constituent material of the induction heating coil 81 is not particularly limited as long as it is a conductive material, and examples thereof include copper, aluminum, and brass. The induction heating coil 81 is generally formed by forming a tubular body made of the above-described material into a coil shape, and cooling water is passed through the tubular body.
A control unit 82 is electrically connected to the induction heating coil 81. The control unit 82 includes a power source that applies a voltage to the induction heating coil 81 and a control circuit that controls the operation of the power source. As the power source, a high frequency power source is generally used, and an AC voltage having a frequency of about 1 kHz to 500 kHz is applied to the induction heating coil 81.

  The control circuit controls the operation of the power source based on a preset program or input information. Thereby, the temperature of the molten metal 90 is controlled within a predetermined range. As a specific example of the program, there is a program that gradually increases the heating temperature by the induction heating coil 81 according to the elapsed time from when the molten metal 90 starts to be stored in the storage container 21. By setting such a program, it is possible to easily perform control for maintaining the temperature of the molten metal 90 constant immediately after the storage of the molten metal 90 is started.

The heating temperature by the heating means 8 (temperature of the molten metal 90 at the heating center) is appropriately set according to the amount, composition, etc. of the molten metal 90. Specifically, when the melting point of the composition of the molten metal 90 is Tm [° C.], the heating temperature is preferably Tm + 50 [° C.] or higher, more preferably Tm + 100 [° C.] or higher and Tm + 300 [° C.] or lower. Preferably, it is Tm + 150 [° C.] or higher and Tm + 250 [° C.] or lower. By setting the heating temperature of the molten metal 90 within the above range, the fluidity of the molten metal 90 becomes uniform, and the molten metal 90 becomes optimal in primary splitting and secondary splitting. For this reason, by setting the heating temperature of the molten metal 90 within the above range, a fine metal powder having a uniform particle diameter can be reliably produced.
Further, when maintaining the temperature of the molten metal 90 constant, it is preferable to control the temperature range during the maintenance to be 30 ° C. or less, and it is more preferable to control to be 20 ° C. or less. .

  Although it is possible to measure the temperature of the molten metal 90 stored, it is possible to measure the temperature via the partition wall because of the harsh environment of measuring the temperature of the hot molten metal 90 or an infrared sensor. It is necessary to measure using For this reason, the temperature cannot be measured continuously in real time, or the temperature below the liquid level cannot be measured. From this point as well, the heating operation by the heating means 8 is based on a preset program. It is useful to do. In particular, in the storage unit 2 of the metal powder manufacturing apparatus 1 shown in FIG. 1, the molten metal 90 is caused to flow downward, while new molten metal 90 is supplied from above, so that the temperature of the molten metal 90 increases in a short time. Will fluctuate. For this reason, the program setting as described above is effective.

  Further, the installation position of the induction heating coil 81 may be the entire wall portion of the reservoir container 21 as long as it is below the heat dissipation means 5, but only a part of the wall portion directly below the heat dissipation means 5. May be. In the former case, the entire molten metal 90 being stored can be heated uniformly, and in the latter case, the temperature drop of the molten metal 90 can be efficiently prevented by heating only directly below the heat dissipating means 5 that tends to lower the temperature. Useful in terms. In addition, since the molten metal 90 is supplied to the reservoir container 21 shown in FIG. 1 from the supply unit 6 located above the reservoir container 21, the molten metal 90 being stored is located below the central portion of the reservoir container 21. The flow toward A part of the flow of the molten metal 90 hits the bottom of the storage container 21 and goes toward the wall. In the latter case, since only the liquid surface portion of the molten metal 90 is heated, the molten metal 90 moving downward is also slightly higher in temperature than the surroundings. For this reason, after heading for the wall part side, the flow which goes upwards again along a wall part is produced. As a result, in the latter case, convection is generated in the molten metal 90 being stored, and the effect that the temperature of the entire molten metal 90 tends to be uniform is also obtained.

  The liquid surface portion of the molten metal 90 is defined as follows. Although slightly different depending on the shape of the reservoir container 21, when the depth from the liquid surface of the molten metal 90 to the bottom surface of the reservoir container 21 is D1, a region having a depth of 0.4D1 or less from the liquid surface of the molten metal 90 Is the liquid surface. Therefore, the effect of the present invention described above can be enjoyed by providing the heating means 8 below this region.

  When the induction heating coil 81 is installed only in a part immediately below the heat radiating means 5, the setting range, that is, the distance D4 from the upper end to the lower end of the induction heating coil 81 is 0.05D1 or more and 0.5D1 or less. And is more preferably 0.1D1 or more and 0.3D1 or less. By setting D4 in the above range, the effects as described above are more remarkably exhibited. As a result, a high-quality metal powder having a uniform particle size can be produced more reliably.

  On the other hand, the heat dissipating means 5 is not particularly limited as long as it can partially reduce the temperature of the liquid surface portion of the molten metal 90, but in the present embodiment, of the wall portion of the reservoir container 21 The heat dissipating means 5 is constituted by a portion where no heating means such as an induction heating coil is provided. With such a heat radiating means 5, the liquid surface portion of the molten metal 90 is radiated through the wall portion or by contact with the atmosphere, and the solidified film 92 is formed by the temperature of the molten metal 90 being lower than the melting point. It is formed. Moreover, if it is the above structures, the structure of the thermal radiation means 5 can be simplified.

  From the viewpoint of increasing the efficiency of heat dissipation through the wall, or from the viewpoint of increasing the efficiency when the wall is heated by the induction heating coil 81 and indirectly heating the molten metal 90, the configuration of the reservoir container 21 A material having a relatively high thermal conductivity is preferably used. Among the above-described constituent materials, those containing a carbon material are preferable, and a composite material of ceramics and carbon is more preferably used in consideration of the insulation with respect to the induction heating coil 81. Examples of such composite materials include alumina / graphite materials.

  Here, when the distance from the liquid level of the molten metal 90 to the lower end of the heat dissipating means 5 (the distance from the upper end of the heating means 8) is D2, D2 is preferably 0.01D1 or more and 0.3D1 or less. 0.02D1 or more and 0.2D1 or less is more preferable. By setting D2 within the above range, a solidified film 92 having a thickness that can reliably prevent oxygen from being taken into the molten metal 90 is formed. As a result, it is possible to reliably suppress an increase in oxygen content in the manufactured metal powder. Also, a high-quality metal powder having a low oxygen content can be produced for the molten metal 90 that contains an element that easily oxidizes and easily generates a metal oxide.

  Further, by providing the heat dissipating means 5, a solidified film 92 is formed on the liquid surface of the molten metal 90. The thickness of the formed solidified film 92 is preferably about 1 μm to 500 μm, and more preferably It is about 20 μm or more and 300 μm or less. If the thickness of the solidified film 92 is within the above range, the amount of wasted molten metal 90 can be minimized while reliably preventing oxygen uptake. Note that the thickness of the solidified film 92 can be adjusted by D2. For example, the thickness can be increased by increasing D2.

  Further, the lower end of the supply portion cylindrical member 62 may be located above the liquid level of the molten metal 90 stored in the storage portion container 21, but is preferably located below the liquid level. preferable. By setting the position of the supply portion cylindrical member 62 in this way, the molten metal 90 supplied from the supply portion 6 is transferred to the storage portion container 21 with little contact with the outside air. As a result, the temperature drop of the molten metal 90 accompanying the transfer can be minimized, and the temperature control of the molten metal 90 can be made easier.

  In this case, when the distance from the liquid level of the molten metal 90 to the lower end of the supply portion cylindrical member 62 is D3, D3 may be larger than D2, but it is 0.01D2 or more and 0.8D2 or less. Preferably, it is 0.05D2 or more and 0.6D2 or less. By setting D3 within the above range, the temperature of the molten metal 90 can be kept more uniform and constant.

  Further, D3 is preferably larger than the thickness of the solidified film 92. As a result, the lower end of the supply-portion cylindrical member 62 extends below the solidified film 92 so as to penetrate the solidified film 92, so that the molten metal 90 is supplied via the supply-portion cylindrical member 62. At this time, it is possible to prevent the solidified film 92 from being caught in the flow of the molten metal 90. As a result, it is possible to prevent the quality of the metal powder from deteriorating.

  In addition, when manufacturing metal powder, the liquid level of the molten metal 90 stored in the storage container 21 is appropriately adjusted by appropriately adjusting the supply amount of the molten metal 90 supplied from the supply unit 6 to the storage unit 2. It is preferable to control so that the height is constant. Thereby, the temperature of the molten metal 90 can be controlled more strictly. In order to adjust the supply amount of the molten metal 90, for example, an opening / closing valve or the like may be provided in the middle of the supply portion cylindrical member 62, and this may be opened / closed. At this time, the vertical width of the height of the liquid surface is preferably 50 mm or less, and more preferably 30 mm or less.

As mentioned above, although the thermal radiation means 5 and the heating means 8 were demonstrated, these structures are not limited to the above. For example, the induction heating coil 81 may not be incorporated in the wall portion of the reservoir container 21 and may be provided outside the wall portion.
Further, the supply unit 6 may be replaced with another one (for example, a melting furnace or the like) as long as it can supply the molten metal 90 to the storage unit 2.
In addition, the output adjustment of the induction heating coil in the heating means 8 may be configured to be artificially adjusted, not only when it is made based on a program input in advance.

  The solidified film 92 can be formed not only by the method using the heat radiating means 5 as described above, but also by a method in which a metal powder is sprinkled on the liquid surface of the molten metal 90 stored in the storage container 21. By spreading the metal powder, a coating film made of the metal powder and a solidified film formed by solidifying the molten metal 90 by removing heat from the metal powder are formed on the upper surface of the molten metal 90. For this reason, the solidified film is strengthened, and the solidified film is rapidly formed, so that the amount of oxygen taken into the molten metal 90 is further reduced.

  The composition of the metal powder is not particularly limited, and examples thereof include Fe-based powders and Ni-based powders. Preferably, the same composition as that of the molten metal 90 is used. By spreading the metal powder having the same composition as the molten metal 90, even if the metal powder is taken into the molten metal 90, there is no possibility that the composition of the molten metal 90 will fluctuate. For this reason, the metal powder finally obtained also has the target composition.

The average particle diameter of the metal powder used is not particularly limited, but is preferably about 1 μm or more and 30 μm or less, and more preferably about 1 μm or more and 20 μm or less. By setting the average particle diameter of the metal powder within the above range, the metal powder can be floated on the liquid surface, and the solidified film 92 is reliably formed. Further, the solidified film 92 becomes dense, and the amount of oxygen taken into the molten metal 90 can be sufficiently reduced.
In addition, when using the method of spreading such a metal powder, you may abbreviate | omit the thermal radiation means 5 in the metal powder manufacturing apparatus 1. FIG.

<< Second Embodiment >>
Next, a second embodiment of the metal powder production apparatus of the present invention will be described.
FIG. 3 is a longitudinal sectional view schematically showing a part of the second embodiment of the metal powder production apparatus of the present invention.
Hereinafter, although the second embodiment will be described, the description will focus on the differences from the first embodiment, and the description of the same matters will be omitted.
The second embodiment is the same as the first embodiment except that the configuration of the heat dissipating means is different.

  In the present embodiment, the heat dissipating means 5 includes a cooling water circuit 51 built in the wall portion of the reservoir container 21 and a supply source (not shown) for supplying cooling water to the cooling water circuit 51. ing. Cooling water is continuously sent from the supply source to the cooling water circuit 51 and is distributed. For this reason, the periphery of the cooling water circuit 51 in the wall portion is efficiently cooled by the cooling water, and accordingly, the liquid surface portion of the molten metal 90 is indirectly cooled. As a result, the solidified film 92 can be efficiently formed in a short time, and the amount of oxygen taken into the molten metal 90 can be further reduced.

The cooling water circuit 51 is configured by a tubular hole formed in the wall portion of the storage container 21 or a tubular body made of a material having high thermal conductivity laid inside or outside the wall of the storage container 21. Is done. Examples of the material having high thermal conductivity include metal materials such as copper, aluminum, titanium, and stainless steel.
The cooling water circuit 51 is preferably formed in a spiral shape along the wall portion of the reservoir container 21. The cooling water can be replaced with other refrigerants (various liquids and various gases).
The flow rate of the cooling water varies depending on the size of the reservoir container 21, but as an example, it is preferably about 1 L / min to 100 L / min, and is about 3 L / min to 50 L / min. Is more preferable.
In such a second embodiment, the same operations and effects as in the first embodiment can be obtained.

«Third embodiment»
Next, a third embodiment of the metal powder production apparatus of the present invention will be described.
FIG. 4 is a longitudinal sectional view schematically showing a part of a third embodiment of the metal powder production apparatus of the present invention.
In the following, the third embodiment will be described. The description will focus on the differences from the first embodiment, and the description of the same matters will be omitted.
In addition to the structure which concerns on 1st Embodiment, the thermal radiation means 5 which concerns on 3rd Embodiment has the air supply part 52 which injects gas toward the liquid level of the molten metal stored by the storage part container 21. FIG. Other than the above, the second embodiment is the same as the first embodiment.

The air supply part 52 shown in FIG. 4 is mounted above the wall part. When gas is jetted from the air supply section 52 toward the liquid surface, the heat of the liquid surface is efficiently taken, and the temperature of the liquid surface portion rapidly decreases. As a result, the solidified film 92 can be efficiently formed on the liquid surface of the molten metal 90.
The gas injected from the air supply section 52 may be air, but is preferably an inert gas such as nitrogen gas or argon gas. If it is an inert gas, since the amount of oxygen taken into the molten metal 90 can be reduced, the oxygen content in the metal powder can be further reduced.

The air supply unit 52 may have any configuration, but preferably, a plurality of air supply ports 522 are evenly arranged in the air supply pipe 521 laid along the wall of the reservoir container 21. .
In such a third embodiment, the same operation and effect as in the first embodiment can be obtained. Moreover, in the heat radiating means 5 according to the third embodiment, sufficient heat dissipation is exhibited without considering the insulation and thermal conductivity of the wall portion of the reservoir container 21, so there are restrictions in the selection of the material of the wall portion. The material can be selected with the highest priority on mechanical characteristics and cost.

<< Fourth Embodiment >>
Next, a fourth embodiment of the metal powder production apparatus of the present invention will be described.
FIG. 5 is a longitudinal sectional view schematically showing a fourth embodiment of the metal powder production apparatus of the present invention.
In the following, the fourth embodiment will be described. The description will focus on the differences from the first embodiment, and the description of the same matters will be omitted.
The fourth embodiment is the same as the first embodiment except that the configuration of the heating means is different.

  In the present embodiment, the heating unit 8 includes a first temperature sensor (temperature measurement unit) 83 that measures the temperature of the molten metal 90 stored in the storage unit container 21 in addition to the induction heating coil 81 and the control unit 82. A liquid level monitor 84 that detects the height of the liquid level of the molten metal 90 stored in the storage container 21, and a second temperature sensor that measures the temperature of the molten metal 90 stored in the supply container 61. (Temperature measuring unit) 85 and an opening / closing valve 86 for adjusting the amount of molten metal 90 passing through the supply unit cylindrical member 62 per unit time. The first temperature sensor 83, the liquid level monitor (liquid level measuring unit) 84, and the second temperature sensor 85 are electrically connected to the control unit 82, and send the measurement result and the detection result to the control unit 82. It is configured as follows. In addition, the on-off valve 86 is also electrically connected to the control unit 82, and is configured such that its opening / closing operation is controlled by the control unit 82. The control unit 82 adjusts the output applied to the induction heating coil 81 and the opening / closing amount of the on-off valve 86 based on the measurement result and the detection result, thereby adjusting the temperature of the molten metal 90, the height of the liquid level, and the like. Control to keep the conditions constant can be performed more easily and reliably. In some cases, more strict control is possible by previously inputting conditions such as the composition of the molten metal 90, the temperature, and the capacities of the storage container 21 and the supply container 61 to the controller 82.

As described above, according to the present embodiment, the state of the molten metal 90 is centrally managed by the control unit 82, and the heating amount and the like are automatically controlled based on the centralized state. Quality metal powder can be produced reliably. That is, the control unit 82 according to the present embodiment is configured to perform feedback control.
In this case, since the measured values by the first temperature sensor 83 and the second temperature sensor 85 have a time lag with respect to the actual temperature change, the time lag is corrected based on the experience values inputted in advance. It is preferable to do this.
Moreover, in this embodiment, the induction heating coil 81 is divided into a plurality of parts, and is configured so that a voltage can be applied independently to each part. Thereby, a different voltage can be applied for every part, and, thereby, the amount of heating of the molten metal 90 can be made different for each depth from the liquid surface. As a result, the temperature of the molten metal 90 can be maintained more uniformly.

  As mentioned above, although the metal powder manufacturing apparatus and metal powder manufacturing method of this invention were demonstrated based on embodiment of illustration, this invention is not limited to these, For example, each part which comprises a metal powder manufacturing apparatus is It can be replaced with any structure capable of performing the same function. Moreover, arbitrary components may be added.

1. Production of metal powder (Example 1)
First, stainless steel SUS316L (melting point Tm: 1450 ° C.) was melted in a high frequency induction furnace to obtain a molten metal.
Next, the obtained molten metal was transferred into a supply container of the metal powder production apparatus shown in FIG. And while making molten metal flow down to a storage part and a nozzle, the molten metal was pulverized by injecting a water jet from the slit of a nozzle. Thereby, metal powder was obtained.

In addition, the structure of each part of a metal powder manufacturing apparatus is as follows.
・ Material of supply container: Alumina / graphite composite material ・ Material of storage container: alumina / graphite composite material ・ Inner diameter of supply tubular member: 5 mm
・ Inner diameter of reservoir cylindrical member: 5 mm
-Depth D1 from the liquid surface to the bottom surface of the molten metal in the reservoir container: 300 mm
・ Distance D2 from the liquid level of the molten metal in the reservoir container to the lower end of the heat dissipation means: 50 mm
-Distance D3 from the liquid level of the molten metal to the lower end of the supply tubular member: 40 mm
Moreover, the temperature of the molten metal in a metal powder manufacturing apparatus is as follows.
-Initial temperature of molten metal stored in the supply section container: 1720 ° C
-Heating temperature of molten metal stored in storage container: 1650 ° C

A solidified film having an average thickness of 120 μm was formed on the liquid surface of the molten metal stored in the storage container.
Further, during the production of the metal powder, the supply amount of the molten metal supplied from the supply unit is appropriately adjusted so that the liquid level of the molten metal in the storage container is constant. It was confirmed that the vertical height of the liquid level at the time of this adjustment was within 30 mm.

  In addition, in the heating means, since it was measured in advance that the temperature of the molten metal stored in the storage container was decreased by 1.5 ° C. per minute, based on this decrease rate, the temperature decrease should be canceled out. A program was input in advance so as to gradually increase the heating temperature according to the elapsed time after the start of storage of the molten metal. As a result, the temperature of the molten metal could be kept substantially constant at the above temperature from the start to the end of the production of the metal powder (temperature range: about 10 ° C.).

(Example 2)
A metal powder was obtained in the same manner as in Example 1 except that the heating temperature of the molten metal stored in the storage container was changed to 1575 ° C. The thickness of the obtained solidified film is shown in Table 1.
(Example 3)
A metal powder was obtained in the same manner as in Example 1 except that the heating temperature of the molten metal stored in the storage container was changed to 1720 ° C. The thickness of the obtained solidified film is shown in Table 1.

Example 4
A metal powder was obtained in the same manner as in Example 1 except that D2 was changed to 10 mm and the heating temperature of the molten metal stored in the storage container was changed to the temperature shown in Table 1. The thickness of the obtained solidified film is shown in Table 1.
(Example 5)
A metal powder was obtained in the same manner as in Example 1 except that D2 was changed to 80 mm and the heating temperature of the molten metal stored in the storage container was changed to the temperature shown in Table 1. The thickness of the obtained solidified film is shown in Table 1.

(Example 6)
In the metal powder manufacturing apparatus shown in FIG. 1, the induction heating coil is used so as to be laid throughout the reservoir container except for the portion provided with the heat dissipating means, and the molten metal stored in the reservoir container is heated. A metal powder was obtained in the same manner as in Example 1 except that the temperature was changed to the temperature shown in Table 1. The thickness of the obtained solidified film is shown in Table 1.
(Example 7)
A metal powder was obtained in the same manner as in Example 1 except that D3 was changed to 30 mm and the heating temperature of the molten metal stored in the storage container was changed to the temperature shown in Table 1. The thickness of the obtained solidified film is shown in Table 1.

(Example 8)
A metal powder was obtained in the same manner as in Example 1 except that D3 was changed to 0 mm and the heating temperature of the molten metal stored in the storage container was changed to the temperature shown in Table 1. The thickness of the obtained solidified film is shown in Table 1.
Example 9
A metal powder was obtained in the same manner as in Example 1 except that the configuration of the heat dissipation means was changed to the configuration shown in FIG. The cooling water was circulated at 5 L / min. Table 1 shows the thickness of the obtained solidified film.

(Example 10)
A metal powder was obtained in the same manner as in Example 1 except that the configuration of the heat dissipation means was changed to the configuration shown in FIG. Note that air (20 ° C.) was used as the cooling gas, and the gas pressure was 0.3 MPa. Table 1 shows the thickness of the obtained solidified film.
(Example 11)
At the start of the production of the metal powder, except that the stainless steel (SUS316L) powder with an average particle size of 5 μm was sprinkled on the liquid surface of the molten metal stored in the storage container, and a film (solidified film) was formed on the surface. In the same manner as in Example 1, a metal powder was obtained. The thickness of the obtained solidified film is shown in Table 1.

(Example 12)
A metal powder was obtained in the same manner as in Example 1 except that the metal powder production apparatus shown in FIG. 5 was used and the heating temperature of the molten metal stored in the storage container was changed to the temperature shown in Table 1. The thickness of the obtained solidified film is shown in Table 1.
Here, the heating means was controlled as follows. The first temperature sensor and the second temperature sensor were each attached near the bottom of the container.
First, the liquid level of the molten metal stored in the storage container is detected by the liquid level monitor, and the opening / closing amount of the on-off valve attached to the supply tubular member so that this height is constant Controlled. Thereby, the height of the liquid level could be maintained constant.

  Moreover, the output applied to the induction heating coil was controlled based on the measured value by the first temperature sensor, the measured value by the second temperature sensor, and the heating temperature. Specifically, the difference between the measured value by the first temperature sensor and the heating temperature was determined, and the output applied to the induction heating coil was controlled so that this was close to zero. In the calculation for obtaining the output, the measurement value by the second temperature sensor is used, and when this measurement value exceeds the heating temperature, the amount of heat is converted into the output, the output is reduced, When the temperature was lower than the heating temperature, the amount of heat was converted into an output, and control was performed to correct the calculation result so as to increase the output.

(Example 13)
A metal powder was obtained in the same manner as in Example 1 except that aluminum (melting point Tm: 660 ° C.) was used instead of stainless steel. The thickness of the obtained solidified film is shown in Table 1.
Here, the temperature of the molten metal in the metal powder production apparatus is as follows.
-Initial temperature of molten metal stored in the supply container: 950 ° C
-Heating temperature of molten metal stored in storage container: 900 ° C

  In addition, in the heating means, it was measured in advance that the temperature of the molten metal stored in the storage container decreased by 2 ° C. per minute. Therefore, based on this decrease rate, the melting was performed so as to counteract this temperature decrease. A program was input in advance so as to gradually increase the heating temperature in accordance with the elapsed time after the start of metal storage. As a result, the temperature of the molten metal could be kept substantially constant at the above temperature from the start to the end of the production of the metal powder (temperature range: about 10 ° C.).

(Example 14)
A metal powder was obtained in the same manner as in Example 13 except that the heating temperature of the molten metal stored in the storage container was changed to 800 ° C. The thickness of the obtained solidified film is shown in Table 1.
(Example 15)
A metal powder was obtained in the same manner as in Example 13 except that the heating temperature of the molten metal stored in the storage container was changed to 950 ° C. The thickness of the obtained solidified film is shown in Table 1.

(Comparative Example 1)
A metal powder was obtained in the same manner as in Example 1 except that the installation of the heat dissipating means and the heating means was omitted.
(Comparative Example 2)
A metal powder was obtained in the same manner as in Comparative Example 1 except that aluminum (melting point Tm: 660 ° C.) was used instead of stainless steel.
In addition, the temperature of the molten metal in a metal powder manufacturing apparatus is as follows.
-Initial temperature of molten metal stored in the supply container: 950 ° C

2. Evaluation of metal powder 2.1. Evaluation of oxygen content About the metal powder obtained by each Example and each comparative example, the oxygen content was measured with the oxygen-nitrogen simultaneous analyzer (the LECO company make, TC-136). The measurement results are shown in Table 1.
2.2. Evaluation of Particle Size The average particle size and standard deviation of the metal powder obtained in each example and each comparative example were measured using a laser diffraction particle size distribution measuring device. The average particle diameter is the particle diameter (μm) when the cumulative amount is 50% on a volume basis. The standard deviation is defined by the following equation and serves as a guide for the width of the particle size distribution.
(Standard deviation) = (d84% −d16%) / 2
However, d84% is the particle size (μm) when the cumulative amount is 84% on the volume basis, and d16% is the particle size (μm) when the cumulative amount is 16% on the volume basis.
These results are shown in Table 1. In addition, about the standard deviation of the metal powder obtained in Examples 1-12, it shows by a relative value when the standard deviation of the metal powder obtained in Comparative Example 1 is set to 1, and is obtained in Examples 13-15. The standard deviation of the metal powder is shown as a relative value when the standard deviation of the metal powder obtained in Comparative Example 2 is 1.

As shown in Table 1, it was revealed that the metal powder obtained in each example had a low oxygen content. Moreover, it became clear that the metal powder obtained in each Example is a powder having a smaller particle diameter and a uniform particle diameter as compared with the metal powder obtained in each Comparative Example.
In particular, such tendency was remarkable in the metal powders obtained in Examples 1, 7, 9, 10, 12, and 13.

  DESCRIPTION OF SYMBOLS 1 ... Metal powder manufacturing apparatus 2 ... Storage part 21 ... Storage part container 211 ... Opening 22 ... Storage part cylindrical member 3 ... Nozzle 30 ... Nozzle main body 31 ... Flow path 32 ... Slit 321 ... ... Introduction path 33 …… Fluid jet 5 …… Heat dissipation means 51 …… Cooling water circuit 52 …… Air supply part 521 …… Air supply pipe 522 …… Air supply port 6 …… Supply part 61 …… Supply part container 611 …… Opening 62 …… Supply section cylindrical member 7 …… Cover 8 …… Heating means 81 …… Induction heating coil 82 …… Control section 83 …… First temperature sensor 84 …… Liquid level monitor 85 …… Second temperature Sensor 86 ... Open / close valve 90 ... Molten metal 91 ... Droplet 92 ... Solidified film G ... Air flow

Claims (10)

A reservoir for storing molten metal;
A flow path provided below the storage section, through which the molten metal flowing down from the storage section can pass, and a slit that opens to the lower end of the flow path and injects a fluid into the flow path. A nozzle comprising,
A supply unit provided above the storage unit and configured to supply molten metal to the storage unit;
Of the storage part, provided in the liquid surface portion of the stored molten metal, a heat dissipating means for lowering the temperature of the molten metal, a heating means provided below the heat dissipating means and heating the molten metal, The metal powder manufacturing apparatus characterized by having. The supply unit is provided so as to extend downward from a lower surface of the supply unit container and a supply unit container that stores the molten metal, and the supply of the molten metal stored in the supply unit container is allowed to pass therethrough A cylindrical member,
The metal powder manufacturing apparatus of Claim 1 comprised so that the lower end of the said supply part cylindrical member may be located below the liquid level of the molten metal stored in the said storage part. The storage part has a bottomed cylindrical shape, and is provided so as to extend downward from a storage part container for storing molten metal and a lower surface of the storage part container, and the molten metal stored in the storage part container A storage tubular member capable of passing,
The said heating means is comprised by the induction heating coil arrange | positioned in the wall part of the said storage part container, The said thermal radiation means is comprised by the said wall part which does not provide an induction heating coil. Metal powder manufacturing equipment.   The metal powder manufacturing apparatus according to any one of claims 1 to 3, wherein the heat radiating means includes a refrigerant that circulates in a pipe provided in the storage section.   4. The metal powder manufacturing apparatus according to claim 1, wherein the heat radiating unit is configured to inject gas toward a liquid level of molten metal stored in the storage unit. 5.   The metal powder according to any one of claims 1 to 5, wherein the heating unit is configured to gradually increase the heating temperature according to an elapsed time from when the molten metal starts to be stored in the storage unit. Manufacturing equipment. Furthermore, a temperature measurement unit that measures the temperature of the molten metal stored in the storage unit,
The metal powder manufacturing apparatus according to claim 1, further comprising: a control unit that controls a heating temperature by the heating unit based on the measured temperature of the molten metal. Furthermore, a liquid level measuring unit for measuring the height of the liquid level of the molten metal,
The metal powder manufacturing apparatus according to claim 1, further comprising: a control unit that controls a supply amount of the molten metal by the supply unit based on the measured height of the liquid level. It is a metal powder production method for producing a metal powder by storing molten metal in a reservoir, causing the molten metal to flow down from the reservoir, and then colliding with a fluid jet to split and solidify the molten metal,
A metal powder manufacturing method comprising forming a solidified film on a liquid surface of a molten metal stored in the storage unit.   The method for producing a metal powder according to claim 9, wherein the formation of the solidified film is performed by at least one of a method of dissipating heat from the liquid surface portion of the molten metal and a method of spreading metal powder on the liquid surface of the molten metal.

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