JPH08319552A - Plasma torch and plasma thermal spraying device - Google Patents

Abstract

PURPOSE: To improve the utilization efficiency and energy efficiency of a thermal spraying material by forming the cathode of a plasma torch having an anode enclosing the cathode to an annular form and to decrease deviation of spray pattern and to improve use life of electrodes. CONSTITUTION: This plasma torch 100 consists of a cathode block 2 coaxially arranged at the center of a cylindrical housing 1 made of a heat resistance material and a cylindrical anode block 3 held on the inner peripheral wall of this housing 1. A discharge space 4 is formed between the cathode block 2 and the anode block 3. The cathode block 2 has the ring cathode 25 having the ring discharge part. A pipe 5 for supplying the thermal spraying material is coaxially fixed to the center of the ring cathode 25. The anode block 3 consists of the cylindrical anode 34 disposed to enclose the discharge space 4 apart this space between the ring cathode 25 and its discharge part and ring magnets 35, 36 continuously arranged to enclose the discharge space 4 so as to form the magnetic fluxes intersecting with each other within the plane inclusive of the central axis in the discharge space 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma torch and a plasma spray apparatus for performing thermal spraying for surface treatment of members and welding for members.

[0002]

2. Description of the Related Art In a conventional plasma torch, as shown in FIG. 3, a cathode 101 has a rod shape and an anode 102 has a cathode 101.
Are arranged so as to surround. Due to the discharge energy generated between the cathode 101 and the anode 102, the discharge space 103
The plasma gas supplied to is discharged as a high temperature, high energy plasma jet 104 from a hole 105 provided in the center of the anode 102.

When a thermal spray material or a welding material (hereinafter referred to as a thermal spray material) is sent toward the central axis of the plasma jet 104, the thermal spray material touches the plasma jet 104 and melts. The molten thermal spray material is sprayed and ejected from the central hole 105 of the anode. As a result, a thermal spray plasma torch that forms an adhesion film on the surface of the member placed on the front surface or a plasma torch that fills the material while melting the joining end of the member is used.

[0004]

In the conventional plasma torch, the thermal spray material is fed only in a specific direction from the side of the axisymmetric plasma jet. Therefore, there are the following drawbacks. B) The thermal spray material cannot be directly supplied to the region with the highest temperature and the highest energy near the center of the plasma jet, and the utilization efficiency and energy efficiency of the thermal spray material are poor.

(B) The spray pattern of the spray material sprayed in a spray form is biased in a specific direction. C) Since the positions of the discharge points on the cathode and the anode are fixed with the passage of time, that part is intensively consumed and the life of the electrode is shortened.

An object of the present invention is to provide a plasma torch and a plasma spraying apparatus which can improve the utilization efficiency and energy efficiency of the spraying material, have less unevenness of the spray pattern, and extend the life of the electrode.

[0007]

The plasma torch of the present invention is surrounded by a ring cathode having a ring-shaped discharge part and a discharge part of the ring cathode with an annular discharge space therebetween. An anode, a magnet continuously installed in the discharge space so as to form a magnetic flux that intersects in a plane including a central axis in the discharge space, and a hollow portion of the ring cathode that substantially defines the discharge space. It is characterized in that a thermal spray material supply port for feeding the thermal spray material along the central axis is provided.

A plasma torch according to a second aspect of the present invention is characterized in that the magnet is a pair of ring magnets arranged in a row so that the same poles abut each other. A plasma torch according to a third aspect of the present invention is characterized in that the magnet is a pair of ring magnets arranged so as to abut different poles. The plasma spraying apparatus of the present invention includes the above plasma torch,
It comprises a power supply for applying a voltage between the ring cathode and the anode, and a thermal spray material transporting means for transporting the thermal spray material to the thermal spray material supply port.

[0009]

In this plasma torch or plasma spraying apparatus, the spraying material is supplied from the center of the ring cathode to the center of the annular discharge gap. Therefore, it is possible to improve the utilization efficiency and energy efficiency of the thermal spray material, reduce the bias of the spray pattern, and increase the life of the electrode.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on an embodiment shown in the drawings. The plasma torch 100 comprises a cylindrical housing 1 made of a heat-resistant material, a cylindrical cathode block 2 coaxially arranged at the center of the housing 1, and a cylindrical anode block held on the inner peripheral wall of the housing 1. 3 and 3. A discharge space 4 is formed between the front end of the cathode block 2 and the front end of the anode block 3.

The housing 1 has an outer cylinder 13 having a central circular opening 11 at the front end (the left end in the drawing) and a flange 12 at the rear end, an inner cylinder portion 14 inserted into the outer cylinder 13, and the inner cylinder portion. A main body 16 having a body portion 15 provided at the rear end of the main body 14 and a connection joint plate 17 fastened to the rear surface of the main body 16. A plasma gas supply channel (not shown) is formed on the inner wall of the main body 16.

The cathode block 2 has a cylindrical cathode casing 21 whose rear end is held on the inner circumference of the body portion 15,
An electrical insulator 22 filled in the rear part of the cathode casing 21, a thermal insulator 23 filled in the front part of the cathode casing 21, and a cylindrical cathode holder 24 held in the rear part by the thermal insulator 23, A ring cathode 25 having a ring-shaped discharge portion fixed to the tip of the cathode holder 24.

At the center of the ring cathode 25, a spray material supply port pipe 5 is coaxially fixed, and the supply port pipe 5 is connected to a spray material introducing pipe 51 disposed at the axial center of the cathode holder 24. There is. The thermal spray material introducing pipe 51 is connected to the thermal spray material transport device 52. On the inner circumference of the cathode holder 24,
The cylindrical separator 26 is fitted, and the gap 27 between the inner periphery of the separator 26 and the thermal spray material introduction pipe 51 is the cooling water flow path 2
It is 8.

The anode block 3 includes a cylindrical portion 31 inserted and held at the tip of the inner cylindrical portion 14, a tip flange portion 32 having a tip surface fitted in the central circular opening 11, and an intermediate taper portion 33. And a ring magnet 35 and 36 which are mounted between the outer circumference of the tapered portion 33 and the inner circumference of the housing 1 and are arranged so as to repel each other.

The anode 34 is surrounded by the ring cathode 25 with the annular discharge space 4 interposed therebetween. The cylindrical portion 31 is provided with a plasma gas outlet 37 communicating with the plasma gas supply passage. A cooling water flow path 38 is formed around the ring magnets 35 and 36.

A thermal spray material supply joint 61 is connected to the center of the connection joint plate 17, and plasma gas introduction joints 62 and 63 are connected to the middle thereof. Further, a joint 64 that also serves as a cathode terminal and a cooling water inlet and a joint 65 that also serves as a cathode terminal and a cooling water outlet are connected to the intermediate portion of the connection joint plate 17, respectively, and are provided in the cathode block 2. It is connected to the cooling water channel 28.

Further, a joint 66 that also serves as an anode terminal and a cooling water inlet and a joint 67 that also serves as an anode terminal and a cooling water outlet are connected to the outer peripheral portion of the connection joint plate 17, respectively, and are provided in the anode block. Connected to the cooling water channel 38.

FIG. 2 is a principle diagram for explaining the operation and effect of the present invention. A discharge is generated in the discharge space 4 between the ring cathode 25 and the anode 34 by the voltage applied from the DC power supply 7. The plasma gas sent into the discharge space 4 is given energy, enters a plasma state, and a current I flows between the electrodes. Immediately after the plasma is generated, the ring cathode 25
Also, a columnar shape is formed on the surface of the anode 34 at a point where energy consumption is minimized.

On the other hand, when the two pole magnets 35 and 36 arranged so as to surround the discharge space 4 are arranged such that the same poles of the two ring magnets 35 and 36 abut against each other, the magnetic fluxes of the respective ring magnets 35 and 36 repel each other and the ring cathode 25 and the ring cathode 25. A magnetic flux H directed toward the center of the anode 34 is generated. A rotating force F acts on the columnar plasma through which the current I and the magnetic flux H intersect and the current I flows according to Fleming's law. As a result, the columnar plasma moves at the discharge point along the circular end surface of the ring cathode 25 and rotates.

The rotation is gradually accelerated after the start of the discharge and reaches several hundreds of rotations per second after several minutes. In this way, the columnar plasma rotating at a high speed generally exhibits one large plasma jet state generated from the circular end surface of the ring cathode 25,
It is ejected from a hole 30 provided at the center of the anode 34. Further, a material supply port is arranged at the center of the ring cathode 25, and the thermal spray material is supplied along the central axis of the one large plasma jet.

An example of thermal spraying conditions in this apparatus will be shown. Current (I) 500 amps Magnetic field strength (H) 1200 Gauss Plasma speed 800 / min Thermal spray material Alumina powder Thermal spray material supply rate 30 g / min Thermal spray efficiency 90% Electrode life 600 hours

According to the invention, the plasma is a ring cathode 2.
5. Since the electrode 34 continues to move without fixing the discharge point on the anode 34, these electrodes are not intensively consumed and the life is increased. Further, by feeding the thermal spray material to the central axis of the plasma, the utilization efficiency of the energy held by the plasma can be improved and the deviation of the spray pattern can be reduced.

In the above-mentioned embodiment, the ring magnets 35 and 36 are arranged so that the same poles abut against each other, and the magnetic flux of each magnet is repelled. However, the different poles abut against each other so that the ring magnets 35 and 36 are attracted to each other. You may arrange in a state. This case is effective in weakening the strength of the magnetic flux so as to prevent the plasma from being blown out by the excessively strong magnetic flux when the plasma current is small.

[Brief description of drawings]

FIG. 1 is a sectional view of a plasma torch.

FIG. 2 is a diagram showing the operating principle of the plasma torch.

FIG. 3 is a schematic view of a conventional plasma torch.

[Explanation of symbols]

 1 Housing 2 Cathode Block 3 Anode Block 4 Discharge Space 5 Supply Port Pipe for Thermal Spray Material 25 Ring Cathode 34 Anode 51 Thermal Spray Material Introduction Pipe

Claims (4)

[Claims] 1. A ring cathode having a ring-shaped discharge part, an anode surrounding the discharge part of the ring cathode with a discharge space therebetween, and a surface including a central axis in the discharge space. A magnet that is continuously installed so as to form a magnetic flux that intersects with the discharge space, and a spray material supply port that sends a spray material into the hollow portion of the ring cathode along substantially the central axis of the discharge space. A plasma torch characterized by being provided with. 2. The plasma torch according to claim 1, wherein the magnet is a pair of ring magnets arranged in a row so that the same poles abut each other. 3. The plasma torch according to claim 1, wherein the magnet is a pair of ring magnets arranged so as to abut different poles. 4. The plasma torch according to claim 1, a power source for applying a voltage between the ring cathode and the anode, and a thermal spray material for transporting the thermal spray material to the thermal spray material supply port. A plasma spray apparatus comprising a transfer means.