Plasma torch, plasma spraying device and method for controlling a plasma torch

Abstract

The plasma torch of the present application rotates the generated plasma (P) along the central axis (T) while ejecting it in the axial direction, and emits the sprayed material powder melted by the plasma (P) to the outside from the front nozzle opening. The vector of the current flowing between the first discharge surface (39) of the cathode (36) and the second discharge surface (49) of the second electrode (41) for generating the plasma (P) is orthogonal to the vector of the magnetic flux of the magnetic field synthesized by the first magnet (37), the second magnet (42), the above-mentioned third magnet (M3), and the fourth magnet (M4).

Description

Technical Field

[0001] This invention relates to a plasma torch, a plasma spraying apparatus, and a method for controlling the plasma torch. Background Technology

[0002] Plasma spraying and other methods have been put into practical use as a way to form a film on the surface of a substrate that imparts heat resistance, corrosion resistance, wear resistance, etc. In this method, the radiant heat of the plasma arc generated by a plasma torch melts powder of spraying materials such as metals, alloys, inorganic materials or ceramics, and sprays it onto the surface of an object such as a metal substrate, thereby creating a film on the surface of the object.

[0003] A plasma torch may have, for example, a ring cathode; an anode disposed around the ring cathode with a discharge space spaced apart from it; and a plurality of magnets forming magnetic fluxes intersecting in a plane containing a central axis in the discharge space.

[0004] In this plasma torch, while supplying plasma-generating gas to the area around the ring cathode, a columnar plasma arc is generated by applying voltage between the electrodes inside the plasma torch and causing discharge between the electrodes. Multiple magnets are used to make the generated plasma arc rotate at high speed in the circumferential direction of the plasma torch, thereby generating a plasma flow.

[0005] Here, for example, in the plasma flow, powder of the spraying material is supplied from the hollow of the ring cathode along the approximate central axis of the discharge space using a gas medium, and the spraying material is melted by the generated plasma arc and sprayed onto the surface of the object (for example, see Patent Documents 1 and 2).

[0006] As described in Patent Documents 1 and 2 above, in a plasma torch that only rotates the plasma arc, if a plasma-generating gas is supplied during plasma jetting, the powder of the spray material introduced from the spray material supply port at the center of the annular cathode will deviate from the central axis of the discharge space due to the influence of the airflow of the rotating plasma-generating gas, and the molten spray material may adhere to the inner surface (discharge surface) of the anode. In particular, depending on the properties of the spray material, such as the specific gravity and particle size of the powder, the molten spray material is more likely to adhere to the discharge surface of the anode due to the influence of the swirling airflow. Furthermore, in such conventional plasma torches, the melting efficiency of the spray material is low, and the spray material may not be fully utilized for film formation. In addition, melting efficiency refers to the proportion of molten spray material emitted from the plasma torch.

[0007] Therefore, the plasma torch is required to further improve the efficiency of forming a film composed of various spraying materials on the substrate surface using plasma, while also being able to stably improve the melting efficiency of the spraying materials and suppress electrode consumption.

[0008] Therefore, for example, a plasma torch as described in Patent Document 3 has been proposed. In the configuration of the electrodes and magnets for generating plasma in the plasma torch described in Patent Document 3, the vectors of the current and the magnetic flux of the magnetic field, which determine the rotation direction and magnitude of the force of the discharge poles, are not orthogonal. Therefore, the vector product of the current and the magnetic flux of the magnetic field becomes unstable, resulting in problems such as the pole rotation direction reversing, the pole not rotating, or the pole being fixed and heat concentrating.

[0009] Furthermore, in the plasma torch described in the aforementioned Patent Document 3, when the vector product of the current and the magnetic flux of the magnetic field is unstable, there is a problem that the spray material inlet pipe (jet) that supplies spray material to the discharge space briefly becomes a discharge path, and the discharge current flows into the spray material inlet pipe, causing the spray material inlet pipe to melt.

[0010] Existing technical documents

[0011] Patent documents

[0012] Patent Document 1: Japanese Patent Application Publication No. 8-319552

[0013] Patent Document 2: Japanese Patent Application Publication No. 2011-071081

[0014] Patent Document 3: Japanese Patent No. 5799153 Summary of the Invention

[0015] The problem that the invention aims to solve

[0016] The present invention was made in view of the above-mentioned problems, and its object is to provide a plasma torch, a plasma spraying device, and a control method for the plasma torch, which can maintain the orthogonality of the vector product of the current used to generate plasma and the magnetic flux of the magnetic field to stabilize the rotation of the discharge poles, and can suppress the consumption of the spraying material inlet tube.

[0017] Methods for solving problems

[0018] To address the aforementioned issues, the plasma torch of the present invention generates plasma that rotates along a central axis while being ejected axially. The plasma melts the powder of the coating material, which is then emitted to the outside from the front nozzle.

[0019] The plasma torch is characterized by having:

[0020] The first electrode is formed as a cylinder having a first through hole extending along the axial direction in the center, and has a first discharge surface continuously formed around the end of the first through hole on the front side.

[0021] The second electrode is formed as a cylinder having a second through hole extending along the axial direction in the center, and is located in front of the first electrode, having a second discharge surface continuously formed around the end of the second through hole in a manner opposite to the first discharge surface of the first electrode.

[0022] The first magnet is disposed on the rear side of the first electrode opposite to the first discharge surface;

[0023] A second magnet is disposed on the outer periphery of the second electrode;

[0024] The third magnet is disposed on the front side of the second electrode opposite to the second discharge surface;

[0025] A fourth magnet is disposed on the outer periphery of the first electrode and is opposite to the second magnet in the axial direction;

[0026] A spray material inlet pipe, slidably disposed along the central axis in the first through hole, supplies spray material powder from the supply port into the discharge space formed between the first electrode and the second electrode; and

[0027] A plasma-generating gas supply passage supplies plasma-generating gas from the outer periphery of the first electrode to the discharge space.

[0028] The vector of the current flowing between the first discharge surface of the first electrode and the second discharge surface of the second electrode to generate the plasma is orthogonal to the vector of the magnetic flux of the magnetic field synthesized by the first magnet, the second magnet, the third magnet, and the fourth magnet.

[0029] The characteristic is that, in the plasma torch, the first electrode is configured mirror-image of the second electrode with respect to a plane passing between the first electrode and the second electrode and perpendicular to the central axis.

[0030] The first discharge surface of the first electrode is a mirror image of the second discharge surface of the second magnet with respect to the plane.

[0031] The characteristic is that, in the plasma torch, the first magnet is arranged mirror-image of the third magnet with respect to the plane.

[0032] The vector of the magnetic flux of the first magnet is mirrored with respect to the plane as the vector of the magnetic flux of the third magnet.

[0033] The characteristic is that, in the plasma torch, the second magnet is arranged mirror-image of the fourth magnet with respect to the plane.

[0034] The vector of the magnetic flux of the second magnet's magnetic field is a mirror image of the vector of the magnetic flux of the fourth magnet's magnetic field with respect to the plane.

[0035] The characteristic is that, in the plasma torch, the first magnet is disposed in the region between the first through-hole and the outer periphery inside the first electrode.

[0036] The third magnet is disposed in the region between the second through hole and the outer periphery inside the second electrode.

[0037] The characteristic feature is that, in the plasma torch, the fourth magnet is continuously formed around the front end of the first electrode.

[0038] The second magnet is formed continuously around the rear end of the second electrode.

[0039] The characteristic is that, in the plasma torch, the first magnet is cylindrical with a through hole extending along the axial direction centered on the central axis.

[0040] The second magnet is cylindrical with a through hole extending along the axial direction centered on the central axis.

[0041] The third magnet is cylindrical with a through hole extending along the axial direction centered on the central axis.

[0042] The fourth magnet is cylindrical in shape and has a through hole extending along the axial direction with the central axis as the center.

[0043] The characteristic is that, in the plasma torch, the first discharge surface of the first electrode and the second discharge surface of the second electrode are inclined such that the gap between the first discharge surface of the first electrode and the second discharge surface of the second electrode extends toward the central axis.

[0044] The characteristic is that, in the plasma torch, the slope of the first discharge surface relative to the plane perpendicular to the central axis is the same as the slope of the second discharge surface relative to the plane.

[0045] The characteristic is that, in the plasma torch, the plasma generating gas supply passage supplies the plasma generating gas from between the outer periphery of the fourth magnet and the first electrode to between the first discharge surface of the first electrode and the second discharge surface of the second electrode.

[0046] The plasma torch is characterized by having a sheath gas supply passage through which sheath gas is supplied from the periphery of the supply port of the spray material inlet pipe toward the discharge space.

[0047] The characteristic is that, in the plasma torch, the sheath gas supply port of the sheath gas supply passage is provided at equal intervals around the supply port of the spray material inlet pipe.

[0048] The characteristic is that, in the plasma torch, the sheath gas is either the same gas as the plasma generating gas or a different gas from the plasma generating gas 45.

[0049] The characteristic feature is that, in the plasma torch, the sheath gas comprises one or more gases selected from the group consisting of rare gas elements, nitrogen, and hydrogen.

[0050] The characteristic is that, in the plasma torch, the position of the supply port of the spray material inlet pipe is adjusted according to the type of spray material.

[0051] The feature is that, in the plasma torch, the position of the supply port of the spray material inlet tube is adjusted to be within the discharge space.

[0052] To solve the above-mentioned problems, the plasma spraying apparatus of the present invention is characterized by having:

[0053] The plasma torch;

[0054] A power source that applies a voltage between the first electrode and the second electrode; and

[0055] A spray material delivery unit that delivers the spray material into the spray material inlet pipe.

[0056] To address the aforementioned issues, the plasma torch control method of the present invention is characterized by the following features:

[0057] Using the plasma torch, the spray material inlet tube is slid along the axial direction, and the position of the supply port of the spray material inlet tube is adjusted according to the type of spray material, so that the powder of the spray material is melted.

[0058] The effects of the invention

[0059] According to the present invention, the rotation of the discharge poles can be stabilized by maintaining the orthogonality of the vector product of the current used to generate plasma and the magnetic flux of the magnetic field, and the consumption of the spray material inlet tube can be suppressed. Attached Figure Description

[0060] Figure 1 This is a diagram showing the structure of a plasma torch according to an embodiment of the present invention.

[0061] Figure 2 yes Figure 1 A magnified view of region Q of the plasma torch shown.

[0062] Figure 3 It means Figure 1 A diagram showing the shape of the first magnet.

[0063] Figure 4 This is a diagram illustrating an example of the temperature distribution of a plasma flow.

[0064] Figure 5 It means that it has been produced. Figure 1 A diagram illustrating the state of the plasma in the plasma torch 11 shown.

[0065] Figure 6 It means Figure 1 A diagram illustrating the state of magnetic flux of the plasma torch 11 shown.

[0066] Figure 7A This is a diagram illustrating an example of a positive polarity electrode configuration.

[0067] Figure 7B This is a diagram illustrating an example of an electrode configuration with reverse polarity. Detailed Implementation

[0068] Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as embodiments) will be described in detail based on the accompanying drawings. In this embodiment, the application of a plasma torch to a plasma spraying apparatus will be described. It should be noted that the present invention is not limited to the following embodiments. That is, the plasma torch of the present invention can be widely applied to spraying, melting, gas heating, and other applications. In addition, the constituent elements in the following embodiments include elements that can be easily conceived by those skilled in the art and elements that are substantially the same. Furthermore, the constituent elements disclosed in the following embodiments can be appropriately combined.

[0069] <Plasma Spraying Device>

[0070] A plasma spraying apparatus for a plasma torch using an embodiment of the present invention will be described.

[0071] Figure 1This is a diagram illustrating the structure of a plasma torch according to an embodiment of the present invention. Additionally, Figure 2 yes Figure 1 A magnified view of region Q of the plasma torch shown. Additionally, Figure 3 It means Figure 1 A diagram showing the shape of the first magnet. Additionally, Figure 4 This is a diagram illustrating an example of the temperature distribution of a plasma flow. Additionally, Figure 5 It indicates that it has been generated. Figure 1 A diagram illustrating the state of the plasma in the plasma torch 11 is shown. Additionally, Figure 6 It means Figure 1 A diagram illustrating the state of magnetic flux of the plasma torch 11 shown.

[0072] For example, such as Figure 1 , 2 As shown, the plasma spraying apparatus 10 of this embodiment includes a plasma torch 11, a power supply 12, and a spraying material conveying device (spraying material conveying unit) 13.

[0073] [Plasma Torch]

[0074] The plasma torch 11 includes a torch body 21, a cathode block 22, an insulating part 23, an anode block 24, a spray material inlet pipe 25, a plasma generation gas supply passage 26, a cooling water supply passage 27-1 to 27-3, and a sheath gas supply passage 101. In addition, the torch body 21 and the cathode block 22 are electrically and thermally insulated from each other.

[0075] In addition, in this embodiment, the direction of the central axis of the cylindrical shape of the electrodes used in the cathode block 22 and the anode block 24 is set as "axial direction", and the direction of the diameter of the cylindrical shape of the electrodes is set as "radial direction".

[0076] Furthermore, plasma torch 11, for example, Figure 1 , Figure 2 , Figure 5 , Figure 6 As shown, the generated plasma P is rotated along the central axis T while being ejected axially, and the powder of the coating material is melted by the plasma P and emitted to the outside from the nozzle 21-a in front.

[0077] The torch body 21 is formed in a cylindrical shape. The torch body 21 has a section at its front end ( Figure 1 The torch body 21 (shown as the left end) has an outer cylinder 31 with a nozzle orifice 21a and an inner cylinder 32 disposed within the outer cylinder 31. The torch body 21 is formed of a copper alloy or the like, which has good thermal and electrical conductivity. An insulating layer may also be provided between the torch body 21 and the anode block 24. One end of the torch body 21 is covered by a cap 33.

[0078] The inner cylinder 32 has a plasma generation gas supply passage 26 and a cooling water supply passage 27-1 to 27-3 inside it.

[0079] For example, such as Figure 1 , Figure 2 As shown, the cathode block 22 has a cathode (first electrode) 36, a first magnet 37 and a fourth magnet M4.

[0080] Moreover, cathode 36, for example, Figure 1 , Figure 2 As shown, the cathode 36 is formed into a cylindrical shape with a first through hole K1 extending axially in the center. Furthermore, the cathode 36 has a first discharge surface 39 continuously formed around the end on the front side of the first through hole K1.

[0081] Additionally, the first magnet 37, for example, Figure 1 , Figure 2 As shown, it is positioned further back than the cathode 36. That is, the first magnet 37 is, for example, as shown... Figure 1 , Figure 2 As shown, it is disposed on the rear side of the cathode 36 opposite to the first discharge surface 39. In particular, the first magnet 37 is configured to be cooled by the cooling water of the surrounding cooling water passage in the region between the first through hole K1 and the outer periphery inside the cathode 36, such that the first magnet M1 does not exceed the Curie temperature.

[0082] exist Figure 1 , Figure 2 In the example, the first magnet 37 is cylindrical with a through hole extending axially around the central axis T.

[0083] Here, the first magnet 37 is, for example, Figure 3 As shown, it has a through hole in the center, forming a cylindrical (ring-shaped) structure. Additionally, in Figure 3 In the middle, along the central axis of the first magnet 37, one side is designated as the N pole and the other side as the S pole (the N pole is designated as the S pole). Figure 3 (The upper direction is set as the N pole and the lower direction as the S pole), but one side can be set as the S pole and the other side as the N pole.

[0084] In addition, such as Figure 1 , Figure 2 As shown, the fourth magnet M4 is disposed, for example, on the outer periphery of the cathode 36, and is arranged opposite the second magnet 42 in the axial direction. In particular, the fourth magnet M4 is formed continuously around the front end of the cathode 36. Moreover, multiple fourth magnets M4 may be arranged in a cylindrical (ring-shaped) configuration. In this embodiment, the fourth magnets M4 are arranged in one row in the radial direction, but the number can be set to any appropriate amount.

[0085] Alternatively, the fourth magnet M4 can also be formed into a cylindrical shape, similar to the first magnet 37. In this case, the fourth magnet M4 is cylindrical with a through hole extending axially around the central axis T.

[0086] In addition, the insulating part 23 is provided on the outer periphery of the spray material inlet pipe 25. As the insulating part 23, an insulating material with heat resistance is used.

[0087] In addition, the anode block 24 has an anode (second electrode) 41, a second magnet 42 and a third magnet M3.

[0088] Moreover, anode 41, for example, Figure 1 , Figure 2 As shown, a cylindrical anode 41 is provided on the inner peripheral wall of the torch body 21, and is formed with a second through hole K2 extending axially in the center, located in front of the cathode 36. Moreover, the anode 41 has a second discharge surface 49 continuously formed around the end of the second through hole K2 on the rear side, opposite to the first discharge surface 39 of the cathode 36.

[0089] Additionally, the second magnet 42, for example, Figure 1 , Figure 2 As shown, it is disposed on the outer periphery of the anode 41. In particular, the second magnet 42 is formed continuously around the front end of the anode 41. Moreover, multiple second magnets 42 may be arranged in a cylindrical (ring-shaped) configuration. In this embodiment, the second magnets 42 are arranged in one row in the radial direction, but the number can be set to any appropriate amount.

[0090] Alternatively, the second magnet 42 can also be cylindrical, similar to the first magnet 37. In this case, the second magnet 42 is cylindrical with a through hole extending axially around the central axis T.

[0091] In addition, Figure 1 , Figure 2 In the example, the inner diameter of the cylinder of the second magnet 42 and the fourth magnet M4 is the same.

[0092] Additionally, for example, such as Figure 1 , Figure 2 As shown, the third magnet M3 is disposed on the front side of the anode 41 opposite to the second discharge surface 49. In particular, the third magnet M3 is configured to be cooled by the cooling water of the surrounding cooling water passage in a manner that the third magnet M3 does not exceed the Curie temperature in the region inside the anode 41 and between the second through hole K2 and the outer periphery.

[0093] Alternatively, the third magnet M3 can also be cylindrical, similar to the first magnet 37. In this case, the third magnet M3 is cylindrical with a through hole extending axially around the central axis T.

[0094] In addition, Figure 1 , Figure 2 In the example, the cylindrical third magnet M3 and the first magnet 37 have the same inner diameter.

[0095] Here, for example, such as Figure 1 , Figure 2 , Figure 6 As shown, the cathode 36 is arranged mirror-image (face-symmetrically) with respect to the anode 41 about a plane R passing through the space between the cathode 36 and the anode 41 and perpendicular to the central axis T. Furthermore, as... Figure 2 As shown, the first discharge surface 39 of the cathode 36 is located relative to the plane R at a position mirror (plane symmetrical) to the second discharge surface 49 of the second magnet 41.

[0096] In the prior art, for example, to initiate a DC discharge between electrodes with a gap, a high-frequency voltage is first applied between the electrodes to break the insulation of the electrode space, causing a spark discharge. Then, a DC voltage is superimposed between the electrodes to transfer the DC discharge. Typically, the gap between the electrodes is set to a size matching the rated voltage of the DC power supply. However, if the gap is large, it is difficult to achieve a high-frequency spark discharge. Therefore, it is mechanically set to a small gap at ignition, and then transferred to a gap matching the rated voltage after the DC discharge begins.

[0097] However, in this embodiment, for example, as Figure 1 , Figure 2 As shown, the first discharge surface 39 of the cathode 36 and the second discharge surface 49 of the anode 41 are inclined in a manner that extends from the outer peripheral side toward the central axis T, such that the gap (in the radial direction) between the first discharge surface 39 of the cathode 36 and the second discharge surface 49 of the anode 41 is a size that matches the rated voltage, from the size that enables ignition based on high-frequency spark discharge.

[0098] Therefore, in this embodiment, the mechanical operation as in the prior art is not performed, and the transfer from ignition based on high-frequency spark discharge to the application of rated voltage is realized.

[0099] And, for example, such as Figure 1 , Figure 2 As shown, the slope of the first discharge surface 39 relative to the plane R perpendicular to the central axis T is the same as the slope of the second discharge surface 49 relative to the plane R.

[0100] Furthermore, for example, such as Figure 1 , Figure 2 , Figure 6As shown, the first magnet 37 is arranged in a mirror (face-symmetric) configuration with respect to the plane R and the third magnet M3. Furthermore, the vector of the magnetic flux of the first magnet 37 is located in a mirror (face-symmetric) position relative to the vector of the magnetic flux of the third magnet M3 with respect to the plane R.

[0101] In particular, for example, such as Figure 1 , Figure 2 , Figure 6 As shown, the second magnet 42 is arranged in a mirror (face-symmetric) configuration with respect to the plane R and the fourth magnet M4. In particular, the vector of the magnetic flux of the second magnet 42 is located in a mirror (face-symmetric) position relative to the vector of the magnetic flux of the fourth magnet M4 with respect to the plane R.

[0102] Through such a structure, for example, Figure 6 As shown, in order to generate plasma P, the vector of the current X flowing between the first discharge surface 39 of the cathode 36 and the second discharge surface 49 of the anode 41 is orthogonal to the vector of the magnetic flux of the magnetic field synthesized by the first magnet 37, the second magnet 42, the third magnet M3 and the fourth magnet M4.

[0103] Additionally, the spray material inlet pipe 25, for example, Figure 1 , Figure 2 As shown, powder of the spraying material is slidably disposed along the central axis T in the first through hole K1, and is supplied from the supply port 25-a to the discharge space S formed between the cathode 36 and the anode 41.

[0104] More specifically, the spray material inlet pipe 25, for example, Figure 1 , Figure 2 As shown, the spray material inlet pipe 25 is disposed on the inner periphery of the cathode 36 via the insulating part 23, and its axis is aligned with the axis of the cathode 36. The spray material inlet pipe 25 has a supply port 25-a at its front end for supplying spray material powder (spray powder) to the central axis T of the cathode 36. The spray material inlet pipe 25 is connected to the spray material conveying device 13, and the spray powder is supplied to the central axis T of the cathode 36 from the spray material conveying device 13 through the spray material inlet pipe 25 along with the conveying gas.

[0105] In addition, as a spraying material, it can use oxide ceramics such as alumina, zirconium oxide, and titanium dioxide, carbide ceramics such as tungsten carbide (WC), non-oxide ceramics such as silicon nitride, and metals such as aluminum, niobium, and silicon.

[0106] Furthermore, the spray material inlet pipe 25 is configured to slide axially relative to the through hole in the cathode 36. The position of the supply port 25a of the spray material inlet pipe 25 is adjusted according to the material used. The spray material inlet pipe 25 can be slid using a cylinder, electric cylinder, or the like. Therefore, the position of the supply port 25a of the spray material inlet pipe 25 can be easily and continuously maintained while the spray material inlet pipe 25 is sliding.

[0107] Furthermore, in order to allow the spray material inlet pipe 25 to slide axially relative to the spray material inlet pipe 25 within the through hole of the cathode 36 and the insulating portion 23, the spray material inlet pipe 25 is preferably pre-processed to reduce the sliding resistance of its surface. As surface processing methods, for example, grinding using a lathe, polishing, grinding using a grinding stone, electrolytic grinding, chemical cleaning, etc., can be used. Surface processing can be performed individually or in combination.

[0108] In this embodiment, the supply port 25-a of the spray material inlet pipe 25 is fixed by a fixing component after the position is determined by sliding the spray material inlet pipe 25 axially.

[0109] Here, the position of the supply port 25-a of the spray material inlet pipe 25 is adjusted according to the type, average particle size, and physical properties (e.g., melting point, specific heat, thermal conductivity, etc.) of the spray material. As described above, an example of the temperature distribution of the plasma flow is... Figure 4 As shown in the image. Figure 4 As shown, the central part of the plasma flow reaches an ultra-high temperature of over 10,000°C, while the surrounding part reaches a high temperature of around 1500~2000°C. Therefore, by adjusting the position of the supply port 25a according to the type, average particle size, and physical properties (e.g., melting point, specific heat, thermal conductivity, etc.) of the spraying material to enable the sprayed powder to melt efficiently, a film C of sprayed powder can be efficiently formed on the surface of the substrate M.

[0110] In this embodiment, the position of the supply port 25-a of the spray material inlet pipe 25 can be determined by using a pre-made graph (correlation graph) showing the relationship between the type, average particle size, physical properties (e.g., melting point, specific heat, thermal conductivity, etc.) of the spray material and the position where the spray material supplied from the spray material inlet pipe 25 is sprayed out in a molten state.

[0111] Such a correlation diagram can be obtained in the following way. First, based on the type, average particle size, and physical properties (such as melting point, specific heat, thermal conductivity, etc.) of the specific spraying material, the time required for the spraying material to melt to the core when the specific spraying material is put into the plasma is calculated.

[0112] Then, based on the time required for the spray material to melt, the position where the spray material supplied from the spray material inlet pipe 25 is sprayed out in a molten state is determined. Thus, the correlation diagram described above is obtained.

[0113] Furthermore, even when using spray materials other than those registered in the relevant diagram, the time required for the other spray materials to melt can be calculated. Based on the ratio of the obtained time to the time required for the spray materials to melt accumulated in the relevant diagram, the position where the spray materials are sprayed in a molten state can also be determined.

[0114] For example, when the coating material is metal powder, the melting point of metal is usually lower than that of ceramics, so the supply port 25-a of the coating material inlet pipe 25 is preferably located on the side of the anode block 24, which is closer to the plane R position.

[0115] In addition, when the spraying material is ceramic powder or the like, the melting point of ceramic is usually higher than that of metals, so the supply port 25-a of the spraying material inlet pipe 25 is preferably located on the side closer to the cathode block 22 than the plane R position.

[0116] In this way, by adjusting the position of the supply port 25-a of the spray material inlet pipe 25 according to the type of spray material, the spray powder can be melted and emitted more reliably.

[0117] Furthermore, the melting point of the metal powder used as the plasma torch 11 in this embodiment is, for example, about 650-2500°C. Examples of metal powders used include aluminum (melting point: about 660°C) and niobium (melting point: about 2468°C).

[0118] Furthermore, the melting point of the ceramic powder used in the plasma spraying apparatus 10 is, for example, around 2000~2450°C. Examples of ceramic powders used include alumina (melting point: approximately 2015°C) and zirconium oxide (melting point: approximately 2420°C).

[0119] Furthermore, the time it takes for the sprayed material to reach its melting point can be estimated by the material used, but this time varies depending on factors such as the average particle size of the sprayed material. The average particle size refers to the volume average diameter based on the effective diameter, and is determined, for example, by laser diffraction-scattering or dynamic light scattering methods.

[0120] In addition, the adjustment of the supply port 25-a of the spray material inlet pipe 25 can be performed only when the plasma spraying device 10 is running. However, in order to make the spray powder melt more efficiently and to form a film C of the spray powder on the surface of the substrate M more efficiently, it can also be performed periodically or continuously after operation, depending on the melting state of the spray powder, etc.

[0121] The plasma generating gas supply passage 26 is a passage for supplying plasma generating gas 45 from the outer periphery of the cathode 36 to the discharge space S formed between the anode 41 and the cathode 36. The plasma generating gas supply passage 26 is formed inside the inner cylinder 32 and the anode 41.

[0122] In particular, the plasma generation gas supply passage 26 is, for example, Figure 1 , Figure 2 As shown, plasma generating gas 45 is supplied from between the fourth magnet M4 and the outer periphery of the cathode 36 to between the first discharge surface 39 of the cathode 36 and the second discharge surface 49 of the anode 41.

[0123] Here, the plasma generating gas 45 can be one or more gases selected from the group consisting of rare gas elements, nitrogen (N2), hydrogen (H2), and CO2. Argon (Ar), helium (He), etc., can be used as rare gas elements. Gases containing components consisting of 2 atomic molecules, such as N2 or H2, cause severe damage to the cathode 36 or anode 41; therefore, from the viewpoint of suppressing a shortened lifespan of the cathode 36 or anode 41, they are generally preferred not to be used.

[0124] However, as described below, in this embodiment, the plasma arc is rotated radially so that the discharge points of the cathode 36 and the anode 41 are not concentrated at a single point. Therefore, as the plasma generating gas 45, gases containing components consisting of two atomic molecules, such as N2 gas and H2 gas, can also be used effectively.

[0125] Furthermore, the temperature of the plasma flow generated in the discharge space S decreases as it approaches the nozzle orifice 21a, and drops sharply in the region forward of the nozzle orifice 21a. However, the temperature decrease is slow compared to that of gases composed of rare gas elements, which are composed of monoatomic molecules, and other components such as N2 and H2, which experience a dramatic temperature drop during the process of returning from the plasma state to the original neutral gas.

[0126] Therefore, by using a gas composed of two atomic molecules as plasma generating gas 45, the heating area that effectively melts the sprayed powder can be expanded. Thus, the effective heating area of ​​the plasma that melts the sprayed powder can be extended while suppressing the loss of the cathode 36 and the anode 41.

[0127] Additionally, the sheath gas supply passage 101 is, for example, as follows Figure 1 , Figure 2 As shown, sheath gas SG is supplied from the sheath gas supply port 101a around the supply port 25-a of the spray material inlet pipe 25 toward the discharge space S.

[0128] Alternatively, multiple sheath gas supply ports 101a of the sheath gas supply passage 101 may be provided at equal intervals around the supply port 25-a of the spray material inlet pipe 25.

[0129] The sheath gas SG may, for example, contain one or more gases selected from the group consisting of noble gas elements, nitrogen, and hydrogen. That is, the sheath gas SG may be the same gas as the plasma generating gas 45 described above. However, the sheath gas SG may also be a different gas from the plasma generating gas 45.

[0130] In this way, the sheath gas supply passage 101 supplies sheath gas SG from the sheath gas supply port 101a around the supply port 25-a of the spray material inlet pipe 25 toward the discharge space S. Thus, even if the generated plasma is unstable, the spray material inlet pipe 25 can be prevented from becoming a discharge passage for a short time, the discharge current does not flow into the spray material inlet pipe, and the melting of the spray material inlet pipe 25 can be suppressed.

[0131] Additionally, cooling water supply passages 27-1 to 27-3, for example... Figure 1 , Figure 2 The diagram shows a passage for cooling the components constituting the plasma torch 11. In this embodiment, a cooling water supply passage 27-1 is formed inside the inner tube 32, inside and outside the anode 41, and between the outer cylinder 31 and the inner cylinder 32. A cooling water supply passage 27-2 is formed inside the inner cylinder 32 and inside the cathode 36. A cooling water supply passage 27-3 is formed inside the spray material inlet pipe 25.

[0132] Additionally, for example, such as Figure 1 As shown, at the other end of the torch body 21, there are plasma generating gas inlet connector 51 for supplying plasma generating gas 45 to the radial outer periphery of the spray material inlet pipe 25, a first water supply connector 52 for supplying cooling water W to the anode 41, a first drain connector (not shown) for discharging the cooling water W used for heat exchange at the anode 41, a second water supply connector (not shown) for supplying cooling water W, a second drain connector (not shown) for discharging the cooling water W used for heat exchange at the cathode 36, a water supply passage 53 for supplying cooling water W into the spray material inlet pipe 25, and a drain passage 54 for discharging the cooling water W used for heat exchange at the spray material inlet pipe 25.

[0133] The cooling water W supplied to water supply connector 52-a, after passing through the interior of inner cylinder 32, the exterior of anode 41, and between outer cylinder 31 and inner cylinder 32 for heat exchange, is discharged through drain connector 52-b. Similarly, the cooling water W supplied to water supply connector 52-c, after passing through the interior of inner cylinder 32 and cathode 36 for heat exchange, is discharged through drain connector 52-d. Furthermore, the cooling water W supplied to water supply passage 53, after passing through the interior of coating material inlet pipe 25 for heat exchange, is discharged through drain passage 54.

[0134] [power supply]

[0135] Power supply 12 is a DC power supply that applies voltage between cathode 36 and anode 41.

[0136] [Spraying Material Conveying Device]

[0137] The spraying material conveying device 13 conveys the powder of the spraying material to the spraying material inlet pipe 25, so that the spraying powder is supplied to the spraying material inlet pipe 25 along with the conveying gas G.

[0138] In the plasma torch 11 of such a plasma spraying apparatus 10, an arc discharge is generated in the discharge space S by applying a voltage between the cathode 36 and the anode 41 via a power supply 12. By supplying plasma generating gas 45 to the discharge space S, the plasma generating gas 45 is energized and becomes a plasma state, generating a current (discharge current) X between the electrodes. Immediately after the generation of the discharge current X, a columnar plasma arc is generated at the point of least energy consumption on the surfaces of the cathode 36 and the anode 41.

[0139] For example, the plasma arc between the cathode 36 and the anode 41 is as follows: Figure 5 As shown, magnetic flux is generated on the surfaces of the cathode 36 and the anode 41. On the other hand, magnetic flux is generated between the cathode 36 and the anode 41 by the first to fourth magnets 37, 42, M3, and M4 arranged radially outside the discharge space S. If this current intersects with the magnetic flux, according to Fleming's left-hand rule, the magnetic field acts on the current, generating a rotational force. Through this rotational force, the plasma arc moves along the first discharge surface 39 of the cathode 36, rotating at its discharge point (cathode point), and similarly, the discharge point (anode point) of the anode 41 moves along the second discharge surface 49 of the anode 41, rotating accordingly.

[0140] In this way, the generated plasma arc rotates circumferentially relative to the central axis T of the plasma torch 11 due to the magnetic field.

[0141] Here, as described above, the cathode 36 is arranged mirror-image (face-symmetrically) with respect to the anode 41 about a plane R passing through the space between the cathode 36 and the anode 41 and perpendicular to the central axis T. Furthermore, as... Figure 2 As shown, the first discharge surface 39 of the cathode 36 is located relative to the plane R at a position mirror (plane symmetrical) to the second discharge surface 49 of the second magnet 41.

[0142] Furthermore, regarding plane R, the first magnet 37 and the third magnet M3 are arranged in a mirror (face-symmetric) configuration. Also, the vector of the magnetic flux of the first magnet 37 is located relative to plane R in a position mirror (face-symmetric) with the vector of the magnetic flux of the third magnet M3.

[0143] Furthermore, regarding plane R, the second magnet 42 and the fourth magnet M4 are arranged in a mirror (face-symmetric) configuration. Also, the vector of the magnetic flux of the second magnet 42 is located relative to plane R in a position mirror (face-symmetric) with the vector of the magnetic flux of the fourth magnet M4.

[0144] Through such a structure, for example, Figure 6 As shown, the vector of the current X flowing between the first discharge surface 39 of the cathode 36 and the second discharge surface 49 of the anode 41 in order to generate plasma P is orthogonal to the vector of the magnetic flux of the magnetic field synthesized by the first magnet 37, the second magnet 42, the third magnet M3 and the fourth magnet M4.

[0145] As a result, the plasma arc can rotate continuously and more stably. That is, it can maintain the orthogonality of the vector product of the current used to generate plasma and the magnetic flux of the magnetic field, thereby stabilizing the rotation of the discharge poles, and can prevent the discharge current from flowing into the spray material inlet pipe, thus suppressing the consumption of the spray material inlet pipe.

[0146] Through the function of such a plasma torch 11, a stable, high-speed rotating plasma arc becomes a plasma flow generated from the circular end face of the cathode 36 and ejected from the nozzle 21a.

[0147] Furthermore, the plasma torch 11 is adjusted so that the supply port 25-a of the spray material inlet pipe 25 is located on the central axis of the cathode 36. Spray powder is supplied from the supply port 25-a to the central axis T of the plasma flow, thus enabling the supply of spray powder to the central axis T of the plasma flow. As described above, the temperature distribution of the plasma flow is such that the central portion of the plasma flow reaches an ultra-high temperature of over 10,000°C, while the surrounding portion reaches a high temperature of approximately 1500-2000°C. Therefore, by supplying spray powder from the rear of the plasma flow to the central axis of the plasma flow, the spray powder enters the center of the vortex of the high-speed rotating plasma arc. This allows the spray powder to be melted by the ultra-high temperature heat of the central portion of the plasma flow and emitted from the nozzle port 21a.

[0148] Furthermore, according to this embodiment, the plasma torch 11 adjusts the position of supplying the sprayed powder into the discharge space S according to the type of sprayed powder. Thus, regardless of the melting difficulty of the sprayed material, more than 90% of the sprayed material supplied from the sprayed material conveying device 13 can be emitted from the nozzle 21a in a completely molten state without adhering to the inner wall of the discharge space S, so that it can be used in the formation of the film towards the substrate M.

[0149] In this way, the plasma torch 11 has a spray material inlet pipe 25 installed in the cathode 36, and the position of the front end of the spray material inlet pipe 25 is adjusted based on the position of the completed melting of the spray powder, which is predetermined according to the type of spray material.

[0150] Then, the spraying material is supplied from the supply port 25a located on the central axis of the cathode 36 to the central axis T of the plasma flow while the plasma is rotated. As a result, the plasma torch 11 can cause the spraying powder supplied to the central axis T of the plasma flow to enter the center of the vortex of the high-speed rotating plasma arc and melt, and can prevent the molten spraying powder from adhering to the discharge surface 41-a of the anode 41, while simultaneously being emitted from the nozzle port 21-a to form a film.

[0151] Therefore, the plasma torch 11 can increase the melting efficiency of the spraying powder supplied from the spraying material conveying device 13 to, for example, more than 90%, regardless of the difficulty of melting the spraying material. Thus, it can stably improve the melting efficiency of the spraying material and suppress the consumption of the cathode 36 and the anode 41.

[0152] In addition, the anode and cathode points of the plasma arc are forced to move, which can suppress damage to the cathode 36 and anode 41 due to the concentration of the poles, thereby improving the lifespan of the cathode 36 and anode 41 and suppressing the generation of contamination that accompanies the consumption of the cathode 36 and anode 41.

[0153] Furthermore, since the plasma arc rotates, the concentration of poles can be suppressed. Therefore, even if a gas composed of two atomic molecules, such as N2 gas or H2 gas, is used as the plasma generating gas 45, operating costs can be reduced, while damage to the cathode 36 and anode 41 can be suppressed.

[0154] In addition, by using a gas composed of 2 atomic molecules as plasma generating gas 45, the plasma torch 11 can expand the area where the sprayed powder melts, thus suppressing the loss of the cathode 36 and anode 41 while extending the effective heating area of ​​the plasma that melts the sprayed material.

[0155] Thus, the plasma spraying device 10 with plasma torch 11 can utilize plasma to more efficiently form a film of various spraying materials on the surface of the substrate M, thereby further improving the spraying efficiency.

[0156] Furthermore, as described above, regarding the plane R passing through the space between the cathode 36 and the anode 41 and perpendicular to the central axis T, the cathode 36 and the anode 41 are arranged in a mirror image (face-to-face symmetry). Furthermore, the first magnet 37 and the third magnet M3 are arranged in a mirror image (face-to-face symmetry), with the vector of the magnetic flux of the magnetic field of the first magnet 37 and the vector of the magnetic flux of the magnetic field of the third magnet M3 located in mirror image (face-to-face symmetry). Furthermore, the second magnet 42 and the fourth magnet M4 are arranged in a mirror image (face-to-face symmetry), with the vector of the magnetic flux of the magnetic field of the second magnet 42 and the vector of the magnetic flux of the magnetic field of the fourth magnet M4 located in mirror image (face-to-face symmetry).

[0157] Here, use Figure 7A , Figure 7B The reason why the shape configuration of the electrodes and magnets in this embodiment is related to the stability of the vector product of the current and the magnetic field of the plasma space will be explained.

[0158] For example, the mirror-image composite magnetic fields generated by the first, fourth, and third and second magnet groups respectively arranged in the cathode and anode sections collide closely on the left and right symmetrical planes of the cathode-anode gap, and are directed upwards ( Figure 7A ) or below ( Figure 7B The currents flowing between the two electrodes intersect orthogonally. Furthermore, if a voltage is applied between the electrodes, discharge begins at the smallest gap at the upper end of the electrodes. The current flowing through the generated plasma is pushed downwards by the gas pressure flowing above the electrodes, but is pushed back by the pressure of the sheath gas and powder transport gas flowing below the electrodes, remaining at a pressure equilibrium position, maintaining the discharge, and rotating under the force represented by the vector product of the current and magnetic field at that position. Figure 7A In the example, the force rotates clockwise from the plane of the paper toward the front, i.e., when viewed from the left. Figure 7B In the example, the polarities are reversed, but the magnetic field is also reversed, while the magnitude and direction of the force remain unchanged, and the rotation direction is clockwise.

[0159] With this structure, the vector of the current X flowing between the first discharge surface 39 of the cathode 36 and the second discharge surface 49 of the anode 41 in order to generate plasma P is orthogonal to the vector of the magnetic flux of the magnetic field synthesized by the first magnet 37, the second magnet 42, the third magnet M3 and the fourth magnet M4.

[0160] As a result, the plasma arc can rotate more continuously and stably. That is, it can maintain the orthogonality of the vector product of the current used to generate plasma and the magnetic flux of the magnetic field, thereby stabilizing the rotation of the discharge poles, and can prevent the discharge current from flowing into the spray material inlet pipe, thus suppressing the consumption of the spray material inlet pipe.

[0161] Furthermore, as described above, the sheath gas supply passage 101 supplies sheath gas SG from the sheath gas supply port 101a around the supply port 25-a of the spray material inlet pipe 25 toward the discharge space S. Thus, even if the generated plasma is unstable, the spray material inlet pipe 25 is prevented from becoming a discharge passage for a short time, and the discharge current does not flow into the spray material inlet pipe, thereby suppressing the melting of the spray material inlet pipe 25.

[0162] As described above, the present invention can maintain the orthogonality of the vector product of the current and magnetic flux used to generate plasma, thereby stabilizing the rotation of the discharge poles. It can also suppress the consumption of the spray material inlet tube, and can make the spray material ejected from the spray material inlet tube without adhering to the discharge surface of the anode, thus improving the melting efficiency of the spray material. Therefore, it can be appropriately applied, for example, to wear-resistant spray coatings on the surface of calender rolls, the refining of silicon for solar cells, and insulating coatings for large plasma display panels.

[0163] Furthermore, as mentioned above, the plasma torch of the present invention is not limited to spraying devices, but can be widely used in melting, gas heating and other applications.

[0164] In addition, in this embodiment, the cathode (first electrode) and the anode (second electrode) are used as the cathode and anode, respectively, but the polarity of the power supply can also be changed to switch the polarity of these electrodes.

[0165] Furthermore, this embodiment describes the application of a plasma torch to a plasma spraying apparatus, but it is not limited thereto; the present invention can also apply a plasma torch to a microparticle manufacturing apparatus.

[0166] Explanation of the label

[0167] 10 Plasma Spraying Equipment

[0168] 11 Plasma Torches

[0169] 12 DC power supply

[0170] 13. Spraying material conveying device (spraying material conveying unit)

[0171] 21 Torch Body

[0172] S discharge space

Claims

1. A plasma torch, wherein generated plasma is rotated along a central axis and ejected axially, and the plasma melts powdered coating material, which is then emitted to the outside from a front nozzle. The plasma torch is characterized by having: The first electrode is formed as a cylinder having a first through hole extending along the axial direction in the center, and has a first discharge surface continuously formed around the end of the first through hole on the front side. The second electrode is formed as a cylinder having a second through hole extending along the axial direction in the center, and is located in front of the first electrode, having a second discharge surface continuously formed around the end of the second through hole in a manner opposite to the first discharge surface of the first electrode. The first magnet is disposed on the rear side of the first electrode opposite to the first discharge surface; A second magnet is disposed on the outer periphery of the second electrode; The third magnet is disposed on the front side of the second electrode opposite to the second discharge surface; A fourth magnet is disposed on the outer periphery of the first electrode and is opposite to the second magnet in the axial direction; A spray material inlet tube is slidably disposed along the central axis in the first through hole, and supplies powder of spray material from the supply port to the discharge space formed between the first electrode and the second electrode; as well as A plasma-generating gas supply passage supplies plasma-generating gas from the outer periphery of the first electrode to the discharge space. The vector of the current flowing between the first discharge surface of the first electrode and the second discharge surface of the second electrode to generate the plasma is orthogonal to the vector of the magnetic flux of the magnetic field synthesized by the first magnet, the second magnet, the third magnet, and the fourth magnet.

2. The plasma torch according to claim 1, characterized in that, The first electrode is configured mirror-image of the second electrode with respect to a plane passing through the space between the first electrode and the second electrode and perpendicular to the central axis. The first discharge surface of the first electrode is a mirror image of the second discharge surface of the second magnet with respect to the plane.

3. The plasma torch according to claim 2, characterized in that, The first magnet is configured as a mirror image of the third magnet with respect to the plane. The vector of the magnetic flux of the first magnet is mirrored with respect to the plane as the vector of the magnetic flux of the third magnet.

4. The plasma torch according to claim 3, characterized in that, The second magnet is arranged as a mirror image of the fourth magnet with respect to the plane. The vector of the magnetic flux of the second magnet's magnetic field is a mirror image of the vector of the magnetic flux of the fourth magnet's magnetic field with respect to the plane.

5. The plasma torch according to any one of claims 2 to 4, characterized in that, The first magnet is disposed in the region between the first through hole and the outer periphery inside the first electrode. The third magnet is disposed in the region between the second through hole and the outer periphery inside the second electrode.

6. The plasma torch according to claim 5, characterized in that, The fourth magnet is formed continuously around the front end of the first electrode. The second magnet is formed continuously around the rear end of the second electrode.

7. The plasma torch according to claim 6, characterized in that, The first magnet is cylindrical with a through hole extending along the axial direction centered on the central axis. The second magnet is cylindrical with a through hole extending along the axial direction centered on the central axis. The third magnet is cylindrical with a through hole extending along the axial direction centered on the central axis. The fourth magnet is cylindrical in shape and has a through hole extending along the axial direction with the central axis as the center.

8. The plasma torch according to any one of claims 2 to 4, characterized in that, The first discharge surface of the first electrode and the second discharge surface of the second electrode are inclined such that the gap between the first discharge surface of the first electrode and the second discharge surface of the second electrode extends toward the central axis.

9. The plasma torch according to any one of claims 2 to 4, characterized in that, The slope of the first discharge surface relative to the plane perpendicular to the central axis is the same as the slope of the second discharge surface relative to the plane.

10. The plasma torch according to any one of claims 1 to 4, characterized in that, The plasma generating gas supply passage supplies the plasma generating gas from between the outer periphery of the fourth magnet and the first electrode to between the first discharge surface of the first electrode and the second discharge surface of the second electrode.

11. The plasma torch according to any one of claims 1 to 4, characterized in that, It also has a sheath gas supply passage, from which sheath gas is supplied from the sheath gas supply port around the supply port of the spray material inlet pipe toward the discharge space.

12. The plasma torch according to claim 11, characterized in that, The sheath gas supply port of the sheath gas supply passage is provided at equal intervals around the supply port of the spray material inlet pipe.

13. The plasma torch according to claim 11, characterized in that, The sheath gas is either the same gas used to generate plasma or a different gas used to generate plasma.

14. The plasma torch according to claim 11, characterized in that, The sheath gas is a gas selected from the group consisting of rare gas elements, nitrogen, and hydrogen.

15. The plasma torch according to any one of claims 1 to 4, characterized in that, The position of the supply port of the spray material inlet pipe is adjusted according to the type of spray material.

16. The plasma torch according to claim 15, characterized in that, The position of the supply port of the spray material inlet pipe is adjusted so that it is within the discharge space.

17. A plasma spraying apparatus, characterized in that, have: The plasma torch according to any one of claims 1 to 16; A power source that applies a voltage between the first electrode and the second electrode; and A spray material delivery unit that delivers the spray material into the spray material inlet pipe.

18. A method for controlling a plasma torch, characterized in that, Using the plasma torch according to any one of claims 1 to 16, the spray material inlet tube is slid along the axial direction, and the position of the supply port of the spray material inlet tube is adjusted according to the type of spray material, so that the powder of the spray material is melted.

Images