Heating and dissolving device

Abstract

To provide a heating-melting device that can produce fine metal powder stably and efficiently.SOLUTION: A heating-melting device 100 has a cylindrical body 31 that has a hollow shape having openings 31 at both ends and is formed of a conductive material, an induction coil 32 wound around the outer face of the cylindrical body 31, and a third voltage supply circuit 44 for feeding an AC voltage to pass a high-frequency current through the induction coil 32. The cylindrical body 31 is disposed between a crucible 21 and a storage part 15 with the openings pointing up and down. The cylindrical body 31 generates ultrasound by a current passed through the induction coil 32, so that the dissolved raw material passing through the cylindrical body 31 is powderized.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a technique for micronizing metallic raw materials. [Background technology]

[0002] Patent Document 1 describes a heating and melting apparatus in which metallic raw materials melted in a crucible are discharged from a tapping port into a chamber, where the raw materials are atomized and recovered. Specifically, a vibrator that irradiates ultrasonic waves is provided in the chamber, and the raw materials discharged from the tapping port of the crucible are atomized by the ultrasonic waves irradiated from the vibrator. The atomized raw materials are cooled before reaching a storage section, and are then recovered as metal powder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 1-208407 Summary of the Invention [Problem to be solved by the invention]

[0004] When pulverizing a molten raw material, the smaller the size of the desired metal powder, 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 of less than several tens of μm, the vibration energy required to pulverize the raw material becomes significantly large, which raises concerns that metal powder of the desired size cannot be produced stably and efficiently.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to provide a heating and melting apparatus that can stably and efficiently produce fine metal powder. [Means for solving the problem]

[0006] 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 cylindrical body made of a conductive material and having openings at both ends thereof; an induction coil wound around the outer circumferential surface of the cylindrical body; 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 disposed with its opening facing up and down, below the discharge part, at a passage position where the melted raw materials pass inside the opening of the cylinder. and, When an electric current flows through the induction coil, ultrasonic waves are generated, which atomize the molten raw material passing through the cylinder.

[0007] In the above configuration, the melting material flowing downward passes through the inside of the opening of the cylinder. 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 the eddy currents, generating an electromagnetic force that vibrates the cylinder radially. As a result, the radial vibration of the cylinder irradiates the melting material passing through the cylinder with ultrasonic waves, thereby atomizing the 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 atomization profile of the melting material passing through the cylinder. This allows for greater vibration energy to be applied to the melting material than, for example, when vibrating the cylinder using a vibrator such as a piezoelectric element. Furthermore, because the cylinder is directly vibrated, no amplifier or other device is required to amplify the vibration, and vibration energy loss is minimal. This allows for stable and efficient production of fine metal powder. [Effects of the Invention]

[0008] According to the present invention, fine metal powder can be produced stably and efficiently. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing the configuration of a heating and melting device. [Figure 2] A top view of the cylinder. [Figure 3] FIG. 4 is a configuration diagram of a third voltage supply circuit. [Figure 4] Waveform diagram of oscillating voltage. [Figure 5] 1 is a diagram illustrating magnetic flux generated around a cylindrical tube in a dynamic magnetic field. [Figure 6] 1 is a diagram illustrating vibration of a cylindrical body. [Figure 7] 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. DETAILED DESCRIPTION OF THE INVENTION

[0010] (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 that can produce metal powder from raw material 150. Specifically, the melting apparatus 100 produces metal powder of 20 μm or less. The raw material 150 is a high-melting-point metal, such as a titanium alloy, zirconium, or tantalum.

[0011] In the following, the horizontal direction, which is the direction parallel to the installation surface when the thermal melting apparatus 100 is installed, will be referred to as "D1," and the up-down direction will be referred to as "D2." The up-down direction D2 is also a direction perpendicular to the horizontal direction D1.

[0012] 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.

[0013] 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 melting point unit 20 and the atomizing unit 30 is formed inside the chamber 10. Specifically, the chamber 10 has a cylindrical upper container portion 11 and a conical lower container portion 12 located below the upper container portion 11. The upper container portion 11 is provided with partition plates 16 and 18 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 melting point unit 20 and the atomizing unit 30 are held. Specifically, the melting point unit 20 is accommodated in the holding space 13 above the partition plate 16 within the chamber 10. Inside the chamber 10, the atomizing unit 30 is housed in a holding space 14 defined by a partition plate 16 and a partition plate 18. Inside the lower container portion 12, a housing portion 15 is formed, which is a space for housing the produced metal powder. Specifically, inside the chamber 10, the space below the partition plate 18 constitutes the housing portion 15.

[0014] The discharge unit 20 is a unit that melts the raw material 150 and causes the melted 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.

[0015] The crucible 21 is a container that accommodates the raw material 150. The crucible 21 is formed, for example, from 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 the bottom plate 25 form a space in which the raw material 150 is accommodated.

[0016] The side wall 24 is a cylindrical part that is open at the top. The side wall 24 is divided into multiple segments by slits formed on the inner circumferential surface. Each segment has a cooling flow path inside, and a coolant such as water can pass through the cooling flow path. A thin insulating plate is embedded in the slits that divide the segments.

[0017] The bottom plate 25 is a disk-shaped member. The bottom plate 25 has a cooling channel therein through which a coolant such as water can flow. A tapping port 26 for tapping the melted raw material 150 (i.e., the molten metal) is formed at the radial center of the bottom plate 25. 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 tapping port 26 in 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 having 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 therein through which a refrigerant flows, similar to the crucible 21 .

[0018] 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 by bolts. This allows the fixing portion 17 to fix the crucible 21 in a state where it is positioned and held within the chamber 10.

[0019] A melting coil 22 is wound around the outer periphery of the side wall 24 of the crucible 21. In this embodiment, the melting coil 22 is wound around the outer periphery of the side wall 24 so that the lower end of the melting coil 22 is higher than the bottom plate 25 in the up-down direction D2. A high-frequency melting voltage V1 is applied to the melting coil 22 from a first voltage supply circuit 42, which will be described later.

[0020] A discharge coil 23 is wound around the outer periphery of the discharge outlet 26. In this embodiment, the discharge coil 23 is wound above the lower end of the discharge outlet 26. A high-frequency discharge voltage V2 is applied to the discharge coil 23 from a 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 discharge outlet 26.

[0021] Inside the chamber 10, an atomizing unit 30 is held in the holding space 14 below the discharging unit 20. The atomizing unit 30 is a unit that atomizes the molten metal discharged from the discharging unit 20, and includes a cylinder 31, an induction coil 32, and a holding layer 33.

[0022] As shown in FIGS. 1 and 2 , the cylinder 31 is a hollow member having openings 31a formed by penetrating both end faces. In this embodiment, the cylinder 31 is formed of a conductive material such as copper. The cylinder 31 is disposed below the crucible 21 with the opening 31a facing the up-down direction D2. Specifically, the cylinder 31 is disposed at a position in the horizontal direction D1 where, when an imaginary line L is vertically extended downward from the tip of the outlet 26, the imaginary line L passes through the inside of 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 outlet 26, passes through approximately the 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.

[0023] An induction coil 32 is wound around the cylindrical body 31 along the outer circumferential surface of the cylindrical body 31. An oscillating voltage V3 is applied to the induction coil 32 from a third voltage supply circuit 44, which will be described later. In this embodiment, the induction coil 32 is fixed by a fixing part 19. Specifically, the fixing part 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 part 19 in a state where it is positioned and held below the water supply unit 20 (i.e., at the passing position).

[0024] 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 FIG. 2. The retaining layer 33 is a layer that holds the cylinder 31 so that it can vibrate relative to the induction coil 32. The retaining layer 33 is preferably 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.

[0025] The operation panel 40 is a user interface that includes operation keys, an operation screen, and the like, and receives operations from an 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 thermal melting apparatus 100. The control device 41 is a programmable controller that includes, for example, a CPU, a ROM, a RAM, and the like, and executes predetermined processes by the CPU executing a program stored in the ROM. In the control device 41, the CPU controls the operations 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.

[0026] 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 discharge coil 23 via a conductor and applies a high-frequency melting voltage V2 to the discharge 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.

[0027] The configuration of the third voltage supply circuit 44 will be described using Fig. 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, and therefore their description will be omitted. In Fig. 3, the induction coil 32 and the resistance component 102 in the atomizing unit 30 are illustrated as a load circuit 101. The resistance component 102 is a general term for circuit elements that act as resistance in the atomizing unit 30.

[0028] 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.

[0029] The forward converter circuit 51 is a circuit that rectifies and smoothes AC power supplied from the AC power supply 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 in which thyristors are combined, or a capacitor.

[0030] The DC voltage converted by the forward conversion circuit 51 is input to the inverter circuit 52. The inverter circuit 52 has a plurality of switching elements SW, and is a circuit that converts DC voltage into AC voltage by turning each switching element SW on and off in a predetermined sequence. Specifically, the inverter circuit 52 has a bridge circuit formed by a pair 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, and the switching element SW is switched 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.

[0031] 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, whereby the inverter circuit 52 outputs a positive oscillating voltage V3 with the voltage of the output line 57 as the high voltage side. In addition, one pair of switching elements is turned off and the other pair of switching elements is turned on, whereby the inverter circuit 52 outputs a negative oscillating voltage V3 with the voltage of the output line 58 as the high voltage side.

[0032] 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.

[0033] 4 shows the waveform of the oscillating voltage V3 applied to the load circuit 101 from the third voltage supply circuit 44. In FIG. 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 a 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.

[0034] The current sensor 53 is a circuit that outputs 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 a primary coil and a 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. The voltage detection resistor 61 is also connected to the secondary coil of the current transformer 60, and outputs a voltage corresponding to the current flowing through the secondary coil as a current detection signal Id. Therefore, the current detection signal Id corresponding to the current in the output line 58 is input from the current sensor 53 to the current detection port 50a of the controller 50 in accordance with the polarity of the oscillating voltage V3 output from the inverter circuit 52.

[0035] 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 a period during which the gate signal Sg has a waveform that turns on the switching element SW, and the off-period is a 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 in a predetermined period and determines the frequency of the current detection signal Id. The zero-crossing points are the timings at which the current detection signal Id crosses a reference current (e.g., 0 V). The number of zero-crossing points in one 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.

[0036] 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.

[0037] 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 the induction coil 32. Even in such a case, the controller 50 uses the current detection signal Id from the current sensor 53 to control the switching cycle 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.

[0038] 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 atmosphere inside the chamber 10 is replaced with an inert gas atmosphere. The pressure inside the chamber is preferably set to approximately 0.5 to 2 atmospheres. When using ultrasound 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.

[0039] An operator operates the operation panel 40 to start the operation of the heating and melting apparatus 100. The control device 41 activates 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 in the alternating magnetic field passes through the surface of the raw materials 150 contained in the crucible 21, generating an induced electromotive force on the surface of the raw materials 150. The induced electromotive force causes eddy currents to flow on the surface of the raw materials 150, and the Joule heat generated by these eddy currents melts the raw materials 150. At this time, the lower part of the raw materials 150 is in contact with the water-cooled bottom plate 25 and does not melt, forming a skull (solidified layer) 151 that blocks the opening of the tapping port 26 (FIG. 1).

[0040] 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 in the crucible 21. This causes an eddy current to flow in the skull 151 in the crucible 21, causing the skull 151 to melt and opening the tapping port 26. As a result, the molten metal in the crucible 21 is tapped from the tapping port 26.

[0041] When the control device 41 detects the tapping of molten metal from the tap outlet 26 based on 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.

[0042] 5 is a cross-sectional view of the cylinder 31 taken in the vertical direction D2, showing the magnetic flux around the cylinder 31 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 so as to avoid the cylinder 31.

[0043] When the direction of the current flowing through the induction coil 32 is counterclockwise when the cylinder 31 is viewed from above, the magnetic flux is directed upward. Therefore, eddy currents flow in the cylinder 31 due to the induced electromotive force in a direction that prevents the magnetic flux from increasing. Specifically, when the cylinder 31 is viewed from above in the vertical direction D2, the eddy currents flow in a clockwise direction. As a result, according to Fleming's left-hand rule, as shown in FIG. 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. Note that in FIG. 6, the displacement of the cylinder 31 due to vibration is indicated by a dashed line.

[0044] On the other hand, when 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 from the outside to the inside. That is, as shown in FIG. 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.

[0045] The applied electromagnetic force M causes the cylinder 31 to vibrate in the radial direction, generating ultrasonic waves that travel 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 toward 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 toward the inside in the radial direction), and then a reaction occurs in which the cylinder 31 itself tries to expand from the inside toward the outside, resulting in vibration of the cylinder 31. Therefore, as shown in FIG. 7, the cylinder 31 vibrates at a frequency (=2Ft) that is twice the frequency (=Ft) of the high-frequency current. Note that FIG. 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, resulting in the production of fine powder with smaller particle sizes.

[0046] The raw material 150 atomized by the atomization unit 30 falls toward the accommodation part 15 of the chamber 10. At this time, the atomized raw material 150 is cooled in the atmosphere and is accommodated in the accommodation part 15 as metal powder.

[0047] The present embodiment described above can achieve the following effects. The thermal 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 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 amount of 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.

[0048] Induction coil 32 is fixed by fixing part 19 in a passage position below discharge unit 20 within chamber 10. A retaining layer 33 is interposed between the outer circumferential surface of cylinder 31 and induction coil 32, which holds cylinder 31 to induction coil 32 so that cylinder 31 can vibrate. This allows cylinder 31 to be held in an appropriate position without impairing the vibration of cylinder 31 due to electromagnetic force M.

[0049] 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 cycle 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 disturbances, etc., and enables the molten metal to be atomized more stably.

[0050] (Other embodiments) The technology disclosed in this specification is not limited to the above-described embodiments, and can be modified into 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.

[0051] In the above-described embodiment, the cylinder 31 in the atomizing unit 30 is held by the induction coil 32 via the holding layer 33. Alternatively, the atomizing unit 30 may not include the holding layer 33 as long as the cylinder 31 is configured to be vibrated by the applied electromagnetic force M.

[0052] In the above-described embodiment, the thermal melting apparatus 100 is a cold crucible type. However, the thermal 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 discharging unit may include a hanging unit that hangs the ingot-shaped raw material vertically and a melting coil disposed 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 cylindrical body 31. [Explanation of symbols]

[0053] 15...accommodation section, 21...crucible, 26...tap port, 30...atomization unit, 31...cylindrical body, 32...induction coil, 44...third voltage supply circuit

Claims

1. 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 The opening is oriented in the vertical direction, and the opening is located below the outlet portion and at a passing position where the molten raw material passes through the inside of the opening of the cylindrical body. 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.

2. 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.

3. 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.

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