JP7741365B2 - Heating melting device - Google Patents

Description

The present invention relates to technology for micronizing metal raw materials.

Patent Document 1 describes a heating and melting device that discharges metallic raw materials melted in a crucible from a tapping port into a chamber, where the raw materials are atomized and recovered. Specifically, the chamber is equipped with a vibrator that emits ultrasonic waves, and the raw materials discharged from the crucible's tapping port are atomized by the ultrasonic waves emitted from the vibrator. The atomized raw materials are cooled before reaching the storage section, and are then recovered as metal powder.

Japanese Patent Application Publication No. 1-208407

When pulverizing molten raw materials, the smaller the desired metal powder size, the greater the vibration energy required to overcome the surface tension of the molten raw material and pulverize the raw material. For example, when producing metal powder smaller than a few tens of micrometers, the vibration energy required to pulverize the raw material becomes significantly greater, raising concerns that metal powder of the desired size may not be produced stably and efficiently.

The present invention was developed in consideration of the above-mentioned problems, and aims to provide a heating and melting device that can stably and efficiently produce fine metal powder.

In order to solve the above problems, the present invention provides a melting furnace comprising a discharge part for causing the melted raw materials to flow downward, a hollow cylinder formed of a conductive material and having openings at both ends, an induction coil wound around the outer periphery of the cylinder, and a voltage supply part for supplying an AC voltage for causing a high-frequency current to flow through the induction coil. The cylinder is positioned with its opening facing up and down, below the discharge part and at a passage position where the melted raw materials pass inside the opening of the cylinder, and current flowing through the induction coil generates ultrasonic waves that atomize the melted raw materials passing through the cylinder.

In the above configuration, the melted raw material flowing downward passes through the inside of the opening of the cylinder. At this time, a high-frequency current flows through the induction coil wound around the outer surface of the cylinder. This generates eddy currents on the outer surface of the cylinder, and the alternating magnetic flux flowing vertically around the cylinder interacts with each other to generate an electromagnetic force that vibrates the cylinder radially. As a result, the radial vibration of the cylinder irradiates the melted raw material passing through the interior of the cylinder with ultrasonic waves, thereby atomizing the melted raw material. Since the vibration frequency of the cylinder 31 caused by the electromagnetic force corresponds to the frequency of the high-frequency current, adjusting the frequency of the AC voltage supplied to the induction coil allows for control of the atomized outer shape of the melted raw material passing through the cylinder. As a result, it is possible to apply greater vibrational energy to the melted raw material than when, for example, a vibrator such as a piezoelectric element is used to vibrate the cylinder. Furthermore, because the cylinder is directly vibrated, there is no need for an amplifier or other device to amplify the vibration, and vibration energy loss is minimal. This enables stable and efficient production of fine metal powder.

The present invention makes it possible to produce fine metal powder stably and efficiently.

FIG. 1 is a diagram showing the configuration of a heating and melting device. A top view of the cylinder. FIG. 4 is a configuration diagram of a third voltage supply circuit. Waveform diagram of oscillating voltage. 1 is a diagram illustrating magnetic flux generated around a cylindrical tube in a dynamic magnetic field. 1 is a diagram illustrating vibration of a cylindrical body. 10A and 10B are diagrams illustrating an example of a frequency between a high-frequency current flowing through an induction coil and vibration of a cylindrical body.

(First embodiment)
The melting apparatus according to this embodiment will be described with reference to the drawings. The melting apparatus 100 shown in Fig. 1 is a water-cooled, cold crucible type melting apparatus capable of producing metal powder from raw material 150. Specifically, the melting apparatus 100 produces metal powder with a particle size of 20 μm or less. The raw material 150 is a high-melting-point metal, such as a titanium alloy, zirconium, or tantalum.

In the following, when the thermal melting apparatus 100 is installed, the horizontal direction, which is parallel to the installation surface, will be referred to as "D1," and the up-down direction will be referred to as "D2." The up-down direction D2 is also the direction perpendicular to the horizontal direction D1.

The heating and melting apparatus 100 includes a chamber 10, a melting unit 20, an atomizing unit 30, an operation panel 40, a control device 41, a first voltage supply circuit 42, a second voltage supply circuit 43, and a third voltage supply circuit 44.

The chamber 10 is a container whose upper and lower ends are closed in the vertical direction D2, and is filled with an inert gas to prevent oxidation of the product. A space capable of accommodating the discharge unit 20 and atomization unit 30 is formed within the chamber 10. Specifically, the chamber 10 has a cylindrical upper container section 11 and a conical lower container section 12 located below the upper container section 11. Partition plates 16 and 18 are provided within the upper container section 11, extending inward from the inner periphery of the chamber 10. The partition plates 16 and 18 define holding spaces 13 and 14 within the chamber 10, in which the discharge unit 20 and atomization unit 30 are held. Specifically, the discharge unit 20 is accommodated in the holding space 13 above the partition plate 16 within the chamber 10. Inside the chamber 10, the atomization unit 30 is housed in a holding space 14 defined by partition plates 16 and 18. Inside the lower container section 12, a storage section 15 is formed, which is a space for storing the produced metal powder. Specifically, inside the chamber 10, the space below the partition plate 18 forms the storage section 15.

The discharge unit 20 melts the raw material 150 and causes the molten raw material 150 to flow downward. The discharge unit 20 includes a crucible 21, a melting coil 22, and a discharge coil 23. In this embodiment, the discharge unit 20 is an example of a discharge section.

The crucible 21 is a container that contains the raw material 150. The crucible 21 is made of, for example, a copper material, and has a cylindrical side wall 24 and a bottom plate 25 provided below the side wall 24. The side wall 24 and bottom plate 25 form a space in which the raw material 150 is contained.

The side wall 24 is a cylindrical section that is open at the top. The side wall 24 is divided into multiple segments by slits formed on the inner surface. Each segment has a cooling flow path inside, through which a coolant such as water can pass. Thin insulating material is embedded in the slits that separate the segments.

The bottom plate 25 is a circular plate-shaped member. The bottom plate 25 has a cooling channel therein through which a coolant such as water can flow. A tapping port 26 is formed at the radial center of the bottom plate 25 for discharging the melted raw material 150 (i.e., the molten metal). The radial direction of the bottom plate 25 is also parallel to the horizontal direction D1. The tapping port 26 is a funnel-shaped member extending in the vertical direction D2 and has a through-hole penetrating the vertical direction D2. The inner diameter of the through-hole in the tapping port 26 is, for example, 3 to 5 mm. The tapping port 26 may be formed separately from the bottom plate 25. In this case, the tapping port 26 is preferably formed using a refractory or metal with a melting point higher than that of the raw material 150. The tapping port 26 may also be made of the same material as the crucible 21. Alternatively, the outlet 26 may have a flow path through which a refrigerant flows, similar to the crucible 21.

In this embodiment, the crucible 21 is fixed by a fixing portion 17 provided inside the chamber 10. Specifically, the fixing portion 17 is fixed to each of the partition plate 16 and the bottom plate 25 with bolts. This allows the fixing portion 17 to fix the crucible 21 while positioning and holding it within the chamber 10.

A melting coil 22 is wound around the outer periphery of the side wall 24 of the crucible 21. In this embodiment, the lower end of the melting coil 22 is wound around the outer periphery of the side wall 24 so that it is higher than the bottom plate 25 in the vertical direction D2. A high-frequency melting voltage V1 is applied to the melting coil 22 from the first voltage supply circuit 42, which will be described later.

A discharge coil 23 is wound around the outer periphery of the tap outlet 26. In this embodiment, the discharge coil 23 is wound above the lower end of the tap outlet 26. A high-frequency discharge voltage V2 is applied to the discharge coil 23 from the second voltage supply circuit 43, which will be described later. A protective member is provided around the discharge coil 23 to protect the discharge coil 23 from the molten metal discharged from the tap outlet 26.

Inside the chamber 10, an atomization unit 30 is held in the holding space 14 below the discharge unit 20. The atomization unit 30 atomizes the molten metal discharged from the discharge unit 20, and includes a cylinder 31, an induction coil 32, and a holding layer 33.

As shown in Figures 1 and 2, the cylinder 31 is a hollow member having openings 31a penetrating both end faces. In this embodiment, the cylinder 31 is formed of a conductive material such as copper. The cylinder 31 is positioned below the crucible 21 with the opening 31a facing in the vertical direction D2. Specifically, the cylinder 31 is positioned in the horizontal direction D1 where, when an imaginary line L is extended vertically downward from the tip of the tapping port 26, this imaginary line L passes inside the opening 31a of the cylinder 31. More specifically, the cylinder 31 is positioned and held so that, in the horizontal direction D1, the imaginary line L, which indicates the flow path of the molten metal flowing from the tapping port 26, passes through the approximate center S of the opening of the cylinder 31. That is, in this embodiment, the position where the cylinder 31 is held in the holding space 14 is an example of a passing position.

An induction coil 32 is wound around the outer periphery of the cylinder 31. An oscillating voltage V3 is applied to the induction coil 32 from a third voltage supply circuit 44 (described later). In this embodiment, the induction coil 32 is fixed by a fixing portion 19. Specifically, the fixing portion 19 is fixed to the partition plate 18 and the induction coil 32 with bolts. As a result, within the chamber 10, the induction coil 32 is fixed by the fixing portion 19 while being positioned and held below the water discharge unit 20 (i.e., at the passing position).

A retaining layer 33 is interposed between the outer periphery of the cylinder 31 and the induction coil 32. For convenience, the retaining layer 33 is not shown between the cylinder 31 and the induction coil 32 in Figure 2. The retaining layer 33 is a layer that holds the cylinder 31 so that it can vibrate relative to the induction coil 32. It is desirable that the retaining layer 33 be made of a material that can hold the cylinder 31 to the induction coil 32 without interfering with the vibration of the cylinder 31. For example, the retaining layer 33 can be made of silicone rubber, butadiene rubber, or the like.

The operation panel 40 is a user interface equipped with operation keys, an operation screen, etc., that receives operations from the operator. A signal corresponding to the operation received by the operation panel 40 is output to the control device 41. The control device 41 controls the operation of the heating and melting apparatus 100. The control device 41 is a programmable controller equipped with, for example, a CPU, ROM, RAM, etc., in which the CPU executes a program stored in the ROM to perform predetermined processing. In the control device 41, the CPU controls the operation of the first voltage supply circuit 42, the second voltage supply circuit 43, and the third voltage supply circuit 44 by executing the program stored in the ROM.

The first voltage supply circuit 42 is connected to the melting coil 22 via a conductor and applies a high-frequency melting voltage V1 to the melting coil 22. The second voltage supply circuit 43 is connected to the melting coil 23 via a conductor and applies a high-frequency melting voltage V2 to the melting coil 23. The third voltage supply circuit 44 is connected to the induction coil 32 via a conductor and applies a high-frequency oscillating voltage V3 to the induction coil 32. In this embodiment, the third voltage supply circuit 44 is an example of a voltage supply unit.

The configuration of the third voltage supply circuit 44 will be explained using Figure 3. In this embodiment, the first voltage supply circuit 42 and the second voltage supply circuit 43 have the same configuration as the third voltage supply circuit 44, so their explanation will be omitted. In Figure 3, the induction coil 32 and resistance component 102 in the atomization unit 30 are illustrated as the load circuit 101. The resistance component 102 is a general term for circuit elements that act as resistance in the atomization unit 30.

The third voltage supply circuit 44 is a resonant power supply circuit that oscillates at a switching period corresponding to a predetermined resonant frequency. Specifically, the third voltage supply circuit 44 includes a controller 50, a forward conversion circuit 51, an inverter circuit 52, a current sensor 53, a matching transformer 54, and matching capacitors 55 and 56.

The forward converter circuit 51 is a circuit that rectifies and smoothes the AC power supplied from the AC power source 200 to convert it into DC power. In this embodiment, the forward converter circuit 51 is a voltage-type circuit, and is configured, for example, by a full-wave rectifier circuit combining thyristors or a capacitor.

The DC voltage converted by the forward conversion circuit 51 is input to the inverter circuit 52. The inverter circuit 52 has multiple switching elements SW, and converts the DC voltage into an AC voltage by turning each switching element SW on and off in a predetermined sequence. Specifically, the inverter circuit 52 has a bridge circuit composed of a set of switching elements SW. The switching elements SW may be bipolar transistors, FETs, IGBTs, thyristors, etc. A gate signal Sg output from the controller 50 is input to each switching element SW constituting the bridge circuit, switching it between an on state and an off state. The output side of the inverter circuit 52 is connected to the load circuit 101 via a matching transformer 54 and matching capacitors 55 and 56.

In response to the gate signal Sg output from the controller 50, one pair of switching elements is turned on and the other pair of switching elements is turned off, causing the inverter circuit 52 to output a positive oscillating voltage V3 with the voltage on output line 57 as the high voltage. Furthermore, by turning one pair of switching elements off and the other pair of switching elements on, the inverter circuit 52 outputs a negative oscillating voltage V3 with the voltage on output line 58 as the high voltage.

The matching transformer 54 is a transformer in which the primary coil and secondary coil can be magnetically coupled via a core. One end of the primary coil of the matching transformer 54 is connected to an output line 57 connected to the output side of the inverter circuit 52, and the other end is connected to an output line 58. One end of the secondary coil of the matching transformer 54 is connected to one side of the load circuit 101 via a matching capacitor 55 connected in series, and the other end of the secondary coil is connected to the other side of the load circuit 101 via a matching capacitor 56 connected in series. The matching capacitors 55 and 56 form a resonant circuit in combination with the induction coil 32. That is, the matching capacitors 55 and 56 and the induction coil 32 form a series resonant circuit connected in series to the load circuit 101.

Figure 4 shows the waveform of the oscillating voltage V3 applied to the load circuit 101 from the third voltage supply circuit 44. In Figure 4, the vertical axis represents voltage V, and the horizontal axis represents time. The oscillating voltage V3 is an AC voltage whose period T is determined according to the target frequency Ft, which will be described later. As a result, the oscillating voltage V3 is applied to the load circuit 101, and a high-frequency current flows through the induction coil 32.

The current sensor 53 is a circuit that extracts a current detection signal Id corresponding to the high-frequency current flowing through the induction coil 32. The current sensor 53 includes a current transformer 60 and a voltage detection resistor 61. The current transformer 60 is a circuit that allows magnetic coupling between the primary coil and secondary coil via a core. The primary coil is connected to an output line 58. One end of the secondary coil is connected to ground, and the other end is connected to a current detection port 50a of the controller 50. A voltage detection resistor 61 is also connected to the secondary coil of the current transformer 60, and a voltage corresponding to the current flowing through the secondary coil is extracted as a current detection signal Id. Therefore, depending on the polarity of the oscillating voltage V3 output from the inverter circuit 52, a current detection signal Id corresponding to the current on the output line 58 is input from the current sensor 53 to the current detection port 50a of the controller 50.

The controller 50 controls the frequency of the oscillating voltage V3 by adjusting the on-period and off-period of the gate signal Sg according to the frequency of the current detection signal Id detected by the current sensor 53. The on-period is the period during which the gate signal Sg has a waveform that turns on the switching element SW, and the off-period is the period during which the gate signal Sg has a waveform that turns off the switching element SW. Specifically, the controller 50 detects the number of zero-crossing points of the current detection signal Id over a predetermined period and determines the frequency of the current detection signal Id. A zero-crossing point is the timing at which the current detection signal Id crosses a reference current (e.g., 0 V). The number of zero-crossing points per cycle varies depending on the frequency of the current flowing through the load circuit 101. The controller 50 adjusts the on-period and off-period of the gate signal Sg so that the frequency of the current detection signal Id approaches the target frequency Ft. This adjusts the frequency of the oscillating voltage V3 to the target frequency Ft, thereby adjusting the frequency of the high-frequency current flowing through the induction coil 32.

The target frequency Ft is a value determined according to the inductance (total inductance including the inductance of the loop path) resulting from the relationship between the cylindrical body 31 and the induction coil 32 and the resonant frequency of the series circuit of the matching capacitors 55 and 56, and is, for example, a value of 100 kHz or more and 400 kHz or less. In this embodiment, the target frequency Ft is determined so that one period T of the oscillating voltage V3 applied to the induction coil 32 has a length corresponding to the circumference (=2πr) of the cylindrical body 31. Specifically, the target frequency Ft can be calculated using the following (Equation 1).
Ft=1/{2πr×(E/ρ) ^1/2 }... (Formula 1)
r is the radius from the center of the cylinder 31. E is the Young's modulus of the cylinder 31. ρ is the density of the cylinder 31.

The third voltage supply circuit 44 configured as described above can control the frequency of the oscillating voltage V3 applied to the induction coil 32 to the target frequency Ft, regardless of external disturbances. For example, the impedance may change due to the adhesion of molten raw material 150 to the cylinder 31 or induction coil 32. Even in such cases, the controller 50 uses the current detection signal Id from the current sensor 53 to control the switching period of the inverter circuit 52 so that the frequency of the oscillating voltage V3 approaches the target frequency Ft. This allows a stable flow of high-frequency current to the induction coil 32.

Next, the operation of the heating and melting apparatus 100 when producing metal powder from the raw material 150 will be described.
When the heating and melting apparatus 100 processes metal powder from the raw material 150, the chamber 10 is filled with an inert gas atmosphere. The pressure inside the chamber is preferably set to approximately 0.5 to 2 atmospheres. When ultrasonic waves are used as in this embodiment, the chamber 10 is fabricated as a pressure vessel, and by pressurizing the chamber 10, it is possible to obtain a larger amplitude.

An operator operates the operation panel 40 to start the heating and melting apparatus 100. The control device 41 operates the first voltage supply circuit 42 to apply a high-frequency melting voltage V1 to the melting coil 22. This causes a high-frequency current to flow through the melting coil 22, generating an alternating magnetic field around the melting coil 22. The magnetic flux from the alternating magnetic field passes through the surface of the raw material 150 contained in the crucible 21, generating an induced electromotive force on the surface of the raw material 150. The induced electromotive force causes eddy currents to flow on the surface of the raw material 150, and the Joule heat generated by these eddy currents melts the raw material 150. At this time, the lower part of the raw material 150, which is in contact with the water-cooled bottom plate 25, does not melt and instead forms a skull (solidified layer) 151, blocking the opening of the tapping port 26 (Figure 1).

Next, the control device 41 operates the second voltage supply circuit 43 to apply a high-frequency tapping voltage V2 to the tapping coil 23. This causes a high-frequency current to flow through the tapping coil 23, generating an alternating magnetic field around the tapping port 26. The magnetic flux in the alternating magnetic field generates an induced electromotive force in the skull 151 inside the crucible 21. This causes an eddy current to flow in the skull 151 inside the crucible 21, melting the skull 151 and opening the tapping port 26. As a result, the molten metal in the crucible 21 is tapped from the tapping port 26.

When the control device 41 detects the discharge of molten metal from the tap outlet 26 via a signal from a monitoring device (not shown), it activates the third voltage supply circuit 44 to apply an oscillating voltage V3 to the induction coil 32. When the oscillating voltage V3 is applied from the third voltage supply circuit 44 to the induction coil 32, a high-frequency current flows through the induction coil 32. This generates a magnetic field around the cylinder 31.

Figure 5 shows the magnetic flux around the cylinder 31 as a cross section of the cylinder 31 in the vertical direction D2, indicated by dashed lines. When a high-frequency current flows through the induction coil 32, a dynamic magnetic field is generated around the cylinder 31. In the dynamic magnetic field generated around the cylinder 31, the magnetic flux traces magnetic flux lines that flow in the vertical direction D2, avoiding the cylinder 31.

When the direction of the current flowing through the induction coil 32 is counterclockwise when viewing the cylinder 31 from above, the magnetic flux is directed upward. Therefore, the induced electromotive force causes eddy currents to flow in the cylinder 31 in a direction that prevents the magnetic flux from increasing. Specifically, when viewing the cylinder 31 from above in the vertical direction D2, the eddy currents flow clockwise. As a result, according to Fleming's left-hand rule, as shown in Figure 6, an electromagnetic force M acts on the cylinder 31 in a radial direction parallel to the horizontal direction D1, from the outside to the inside, displacing the cylinder 31 in the radial direction from the outside to the inside. In Figure 6, the displacement of the cylinder 31 due to vibration is indicated by a dashed line.

On the other hand, if the direction of the current flowing through the induction coil 32 is clockwise when the cylinder 31 is viewed from above, the magnetic flux flows downward. Therefore, when the cylinder 31 is viewed from above, the induced electromotive force causes eddy currents to flow counterclockwise. As a result, an electromagnetic force M acts on the cylinder 31 in the radial direction, from the outside to the inside, displacing the cylinder 31 in the radial direction. In other words, as shown in Figure 6, an electromagnetic force M acts on the cylinder 31 in the radial direction, from the outside to the inside, regardless of the direction of the high-frequency current flowing through the induction coil 32.

The applied electromagnetic force M causes the cylinder 31 to vibrate radially, generating ultrasonic waves from the inner circumferential surface of the cylinder 31 toward the center S. The electromagnetic force M acting on the cylinder 31 acts radially from the outside to the inside during each half cycle (= T/2) of the first and second halves of the high-frequency current flowing through the induction coil 32. The electromagnetic force M exerts a compressive force on the cylinder 31 in one direction (from the outside to the inside in the radial direction), followed by a reaction force that causes the cylinder 31 to expand from the inside to the outside, resulting in vibration of the cylinder 31. Therefore, as shown in Figure 7, the cylinder 31 vibrates at a frequency (= 2Ft) that is twice the frequency of the high-frequency current (= Ft). Note that Figure 7 illustrates the frequency relationship between the high-frequency current flowing through the induction coil 32 and the radial displacement (i.e., vibration) of the cylinder 31 as an example. This allows ultrasonic waves to be generated at twice the frequency of a high-frequency power supply, producing fine powder with smaller particle sizes.

The raw material 150 atomized by the atomization unit 30 falls toward the storage section 15 of the chamber 10. At this time, the atomized raw material 150 is cooled in the atmosphere and is stored in the storage section 15 as metal powder.

The present embodiment described above can achieve the following effects.
The heating and melting apparatus 100 includes a cylindrical body 31 made of a conductive material and an induction coil 32 wound around the outer periphery of the cylindrical body 31. An oscillating voltage V3 is supplied to the induction coil 32 from a third voltage supply circuit 44, causing a high-frequency current to flow through the induction coil 32. The cylindrical body 31 is positioned at a passage between the crucible 21 and the housing 15, with its opening 31a facing the vertical direction D2. When a high-frequency current flows through the induction coil 32, eddy currents generated on the outer periphery of the cylindrical body 31 interact with alternating magnetic flux, generating an electromagnetic force M that vibrates the cylindrical body 31. The vibration frequency of the cylindrical body 31 caused by the electromagnetic force M corresponds to the frequency of the high-frequency current. Therefore, the vibration energy applied to the cylindrical body 31 can be controlled by adjusting the frequency of the oscillating voltage V3 supplied to the induction coil 32. As a result, it is possible to apply a large vibration energy to, for example, the molten metal, i.e., the molten raw material 150. Furthermore, because the cylindrical body 31 is directly vibrated, no amplifier or other device is required to amplify the vibration, and vibration energy loss is minimal. As a result, even if the desired size of the metal powder is small, the raw material 150 can be pulverized stably and efficiently.

The induction coil 32 is fixed by a fixing part 19 within the chamber 10 at a passing position below the water discharge unit 20. A holding layer 33 is interposed between the outer surface of the cylinder 31 and the induction coil 32, holding the cylinder 31 to the induction coil 32 so that it can vibrate. This allows the cylinder 31 to be held in the appropriate position without impairing the vibration of the cylinder 31 due to the electromagnetic force M.

The controller 50 of the third voltage supply circuit 44 determines the frequency of the high-frequency current flowing through the induction coil 32 based on the current detection signal Id output from the current sensor 53, and adjusts the switching period of the inverter circuit 52 so that the determined frequency of the high-frequency current approaches the target frequency Ft. This prevents large changes in the vibration energy applied to the raw material 150 due to external disturbances, etc., and enables the molten metal to be refined more stably.

(Other embodiments)
The technology disclosed in this specification is not limited to the above-described embodiments, and can be modified in various forms without departing from the spirit thereof, for example, the following modifications are also possible.
A bias voltage may be superimposed on the oscillating voltage V3. In this case, the oscillating voltage V3 whose polarity changes with respect to the bias voltage is applied to the induction coil 32.

In the above-described embodiment, the cylinder 31 in the atomizing unit 30 was held by the induction coil 32 via the holding layer 33. Alternatively, if the cylinder 31 is configured to be vibrated by the applied electromagnetic force M, the atomizing unit 30 does not need to have the holding layer 33.

In the above-described embodiment, the heating and melting apparatus 100 was a cold crucible type. However, the heating and melting apparatus 100 may have any configuration for melting the raw material 150, as long as it includes the atomizing unit 30. For example, the dispensing unit may include a hanging section that suspends the ingot-shaped raw material vertically, and a melting coil that is arranged around the suspended raw material. In such a configuration, the raw material is melted by Joule heat generated by electromagnetic induction using the melting coil, etc., and the molten metal flows downward. The molten metal is converted into fine powder as it passes through the inside of the cylinder 31.

15...accommodation section, 21...crucible, 26...tap port, 30...atomization unit, 31...cylindrical body, 32...induction coil, 44...third voltage supply circuit

Claims (3)

a tapping section for allowing the melted raw materials to flow downward;
a hollow cylindrical body made of a conductive material, the hollow cylindrical body having openings at both end faces;
an induction coil wound around the outer circumferential surface of the cylindrical body;
a voltage supply unit that supplies an AC voltage to the induction coil to cause a high-frequency current to flow,
The cylindrical body is
With the opening facing up and down, the melting raw material is disposed below the tapping portion and at a passing position where the tapped melted raw material passes through the inside of the opening of the cylindrical body, and
A heating and melting apparatus in which ultrasonic waves are generated by passing a current through the induction coil, and the raw material to be melted is powdered as it passes through the cylindrical body.
a fixing portion that fixes the induction coil at the passing position;
2. The heating and melting apparatus according to claim 1, further comprising: a retaining layer interposed between an outer peripheral surface of the cylindrical body and the induction coil, for retaining the cylindrical body on the induction coil so as to be vibrable. The voltage supply unit
a sensor that outputs a signal corresponding to the current flowing through the induction coil;
an inverter circuit having a switching element for converting a DC voltage into the AC voltage;
a controller that controls a switching period of the inverter circuit,
The controller
determining the frequency of the high frequency current flowing through the induction coil based on the signal output by the sensor;
3. The heating and melting apparatus according to claim 1, wherein the switching period of the inverter circuit is adjusted so that the determined frequency of the high-frequency current approaches a predetermined target frequency.