JP4804854B2 - Composite torch type plasma spraying equipment - Google Patents

Description

  The present invention uses a large current flowing in a gas and a high-temperature plasma arc of about 10,000 degrees generated thereby to melt a material such as metal or ceramics and spray it on an object. The present invention relates to a so-called composite torch type plasma spraying apparatus that forms a strong film.

  In the composite torch type plasma generator having a main torch and a sub-torch, the inventor of the present invention requires that the main cathode of the main torch has a high temperature in order to generate thermoelectrons, whereas the sub-torch that receives the thermoelectrons. The sub-cathode is cooled and maintained at a low temperature, and a composite torch type plasma generator in which the arrangement of the cathode and anode of the main torch is reversed has been developed (for example, Patent Documents). 1, see).

  This composite torch type plasma generator includes a main torch having a main anode and a sub torch having a sub cathode. The main anode includes a powder material supply pipe penetrating through a central portion thereof, a cooling passage provided on the outside thereof, and a tip edge located outside the cooling passage and protruding from the tip of the material supply pipe. I have. The front end surface of the main anode is formed in a substantially bowl shape, that is, in a truncated cone shape protruding inward, and the front end edge serves as an anode point of the main anode.

  In this apparatus, a hairpin arc from the sub-cathode of the sub-torch to the main anode of the main torch is generated, and in this state, plasma gas is supplied from the gas inlets of both torches to generate plasma. Thereafter, the material to be treated is discharged from the powder material supply pipe of the main torch along the central axis of the plasma and plasma arc.

  As a result, the material to be processed proceeds while being melted along the central axis of the plasma arc, so that the thermal plasma energy can be fully enjoyed.

Japanese Patent Laid-Open No. 2002-231498

When the conventional composite torch type plasma generating apparatus is used as a composite torch type plasma spraying apparatus, the following problems occur.
That is, most of the powder material is fed into the plasma arc at the anode end of the plasma arc that does not interfere with each other and the tip of the anode portion having the powder material supply hole (the tip opening portion of the powder material supply pipe) to form molten particles. The sprayed coating is formed, but the others are present as molten particles and unmelted particles inside and outside the main torch without being fed into the plasma arc.

  Here, the problem is that the spray particles that could not be fed into the plasma arc adhere to the wall surface inside the main torch and hinder the operation. The particularly problematic part is the tip surface of the anode portion, that is, the inner surface of the tip of the truncated cone that protrudes inward, and when molten particles adhere to this tip surface, the anode point and the powder material supply hole and the vicinity thereof Will be damaged. And as the supply amount of the powder sprayed material increases, the degree of damage increases, and finally the powder material feed hole is closed or the seal part of the anode part having water cooling means is burned out. , Spraying can not be done.

  Here, the time for causing the trouble depends on the properties of the powder material, the supply amount, etc., but is, for example, within 20 minutes, and during this time, the thermal spraying operation cannot be stably performed.

  In view of the above circumstances, an object of the present invention is to enable a stable thermal spraying operation.

  The present invention comprises a composite torch comprising a main torch having a plasma gas supply means and a sub-torch, wherein a material discharge hole is provided in an anode portion of the main torch, and a powder spray material is fed from the material discharge hole onto a plasma central axis. In the type plasma spraying apparatus, a gas ejection hole for preventing adhesion of spray particles is provided in the anode portion.

  The gas ejection hole according to the present invention is characterized in that it is disposed at a position where it does not interfere with the anode point of the plasma arc and the material discharge hole. One or a plurality of gas ejection holes of the present invention are provided on the radiation centering on the material ejection holes. The gas ejection holes according to the present invention are characterized in that they are provided in equal divisions at positions offset from the radiation centering on the material ejection holes.

  The gas discharged from the gas ejection holes of the present invention is a plasma gas. The main anode of the present invention has a material feed pipe penetrating through the central portion thereof, a cooling passage provided on the outside thereof, a tip edge located outside the cooling passage and protruding from the tip of the material feed pipe And. The tip surface of the main anode of the present invention is formed in a truncated cone shape projecting inward, and the tip edge thereof serves as an anode point of the main anode.

  According to the present invention, the gas spray holes for preventing the spray particles from adhering to the anode portion are provided, so that it is possible to prevent the molten particles and unmelted particles of the powder spray material from adhering to the anode portion. Therefore, since the anode part, in particular, the anode point and the material discharge hole can be kept clean, the thermal spraying operation can be performed stably.

  The present inventor believes that a major factor that prevents stable operation of spraying is that unmelted or melted sprayed particles adhere to the wall surface inside the main torch, so a device for forcibly blowing off with gas is provided. I thought it was necessary. However, it is difficult to provide a new device in terms of structure and cost.

  Therefore, the anode part of the main torch is provided with a gas ejection hole for preventing adhesion of spray particles near the anode point at the tip edge of the anode part and the material discharge hole, and the plasma existing in the hole is provided. By passing the gas, the sprayed particles were blown away, and the normal state of the anode point and the material discharge hole could be maintained.

  More specifically, the plasma spraying apparatus used in the present invention is a double torch type plasma composed of at least two main torches having a cathode and an anode and a sub-torch, and has a high temperature of about 10,000 ° C. as a major feature. The plasma arc is drawn out of the torch, and the sprayed powder material can be fed directly to the arc column.

  Here, the sprayed powder material is fed into the plasma arc column. From the viewpoint of thermal efficiency, it is best to feed the sprayed powder material coaxially with the plasma arc axis. Since the shaft center is extremely high temperature and high speed, the powder sprayed material is not fed into the shaft core, but is fed in the vicinity thereof. Also, some of the sprayed particles are not ejected out of the main torch, rather than being blown out by the plasma arc and not delivered, and even if delivered, they become unmelted particles. Adhere to the inner wall.

  Particularly problematic here is the adhesion to the anode spot and the material discharge hole and the adhesion to the vicinity thereof. As a result, the plasma arc and the thermal spraying become unstable, and the powder material eventually becomes clogged. No thermal spraying is possible. Therefore, a gas jet hole is provided at a position where it does not interfere with the anode spot at the tip of the anode section and the material discharge hole, and the sprayed particles near the anode spot and the material discharge hole are blown away by passing the existing plasma gas through the hole. Thus, the shape of the anode spot and the material discharge hole can be maintained. Therefore, a stable plasma arc was formed and stable spraying became possible.

  Here, it is effective to blow off the melted sprayed particles to effectively blow off the sprayed particles by the gas ejection holes. That is, the thermal spray particles are a high melting point material such as ceramics having a melting point exceeding 2,000 ° C., whereas the anode part is generally made of copper having good heat transfer. However, since copper has a lower melting point than the spray particles, if the spray particles melted by the plasma adhere to the anode part, the sprayed particles further melt on the attached wall surface, and the shape of the anode part having anode points and material discharge holes is damaged. The blow-off action has a great effect.

A first embodiment of the present invention will be described with reference to FIGS.
Overview of combined torch type plasma spraying equipment:
FIG. 1 shows a typical composite torch type plasma spraying apparatus characterized in that a powder spraying material can be fed coaxially with a plasma central axis.
In FIG. 1, a main anode 3 having a material inlet pipe 19 for supplying a powder sprayed material 20 together with an inert carrier gas 6 into a plasma 18 is a main mantle 4 having an emission port, and a main mantle having swirl flow forming means. The insulator 27 having the plasma gas inlet 5 is concentrically held.

  The positive terminal of the main power supply 7 is connected to the main anode 3, and the negative terminal of the main power supply 7 is connected to the main mantle 4 via the switch means 8, and these constitute the main torch 1 as a whole. .

  Next, there is a sub-torch activation electrode 10 disposed so as to intersect with the central axis of the main torch 1, a sub-mantle jacket 11 surrounding the sub-torch activation electrode 10 and having a discharge port at the tip, and the main torch 1. These insulators 27 are concentrically held by an insulator 28 similar to the insulator 27.

  The secondary power supply 14 has its positive terminal connected to the secondary mantle 11 via the switch means 15, and the negative terminal of the secondary power supply 14 is connected to both the secondary starting electrode 10 and the negative terminal of the main power supply 7. Constitutes the auxiliary torch 2 as a whole. The main torch 1 and the sub torch 2 are fixed by a connecting pipe 26, and each has a structure that can be easily detached and kept insulative.

  In FIG. 1, an inert gas such as argon is flowed from the main plasma gas inlet 5 as the main plasma gas 6, the switch means 8 is closed with the switch means 9 opened, and the main anode is driven by the high frequency of the main power supply 7. When applied between 3 and the main mantle 4, a main starting arc 16 is formed from the tip of the main anode 3 toward the outlet of the main mantle 4, whereby the main plasma gas 6 is heated and becomes plasma 18. It is discharged from the tip of the main mantle 4 toward the outside of the main torch 1.

  Next, the switch means 15 is closed and applied between the auxiliary torch starting electrode 10 and the auxiliary mantle 11 by the high frequency of the auxiliary power supply 14, and the auxiliary gas 13 is connected to the auxiliary gas 13 through the auxiliary gas inlet 12 as a secondary gas 13. When the active gas is sent in, the secondary starting arc 17 is generated, and the plasma 18 is ejected from the discharge port at the tip of the secondary mantle 11.

  In this way, each plasma 18 ejected from the tips of the main torch 1 and the sub-torch 2 intersects at the tips of the central axis of the main torch 1 and the central axis of the sub-torch 2. Since the plasma 18 is conductive, in this state, when the switch means 9 is closed and at the same time the switch means 8 and the switch means 15 are opened, a hairpin shape extending from the tip of the auxiliary torch starting electrode 10 to the anode point of the main anode 3 is formed. A conductive path is formed by the plasma 18.

  In this case, if the structure of the main torch 1 and the structure of the main plasma gas 6 and sub-torch 2 to be supplied and the amount of the sub-gas 13 supplied to the sub-torch 2 are appropriately selected, as shown in FIG. A plasma arc 23 that is substantially coaxial with the main torch 1 can be generated.

  The plasma 18 generated in this way is reliably held at the start point and the end point thereof at the auxiliary torch starting electrode 10 and the anode point 29 of the main anode 3, respectively, and the tip thereof is protected by an inert gas. Therefore, the amount of the main plasma gas 6 flowing to the main torch 1 can be set to an arbitrary amount from a small flow rate to a large flow rate over a very wide range.

  The material feed pipe 19 is provided through the center of the main anode 3, and a cooling passage 33 through which a cooling liquid, for example, cooling water W passes, is provided outside the material feed pipe 19. It has been. A tip edge 29 of the anode portion K is located at the tip of the outer periphery of the cooling passage 33, and the tip edge 29 protrudes from the material discharge hole 30 of the material feed pipe 19.

  The front end surface 3a of the main anode 3 is formed in a truncated cone shape projecting inward, and the front end edge 29 is an anode point. The distal end surface 3a is provided with a gas ejection hole 31 for preventing adhesion of spray particles. This gas ejection hole 31 is disposed at a position where it does not interfere with the anode point of the plasma arc 18 and the material discharge hole 30. The number and arrangement positions of the gas ejection holes 31 are appropriately selected as necessary. For example, one or a plurality of the gas ejection holes 31 are adopted.

  The powder sprayed material 20 fed from the material feed pipe 19 is provided so that the position of the anode point of the anode part is closer to the tip of the anode part than the position of the material discharge hole 30 of the material feed pipe 19. Thus, the thermal spray material 20 and the anode point 29 of the plasma 18 are reliably supplied to the high temperature plasma arc 23 in the direction coaxial with the central axis of the plasma 18 without interference.

  At this time, if the thermal spray material 20 is conductive, the anode point of the plasma 18 can be unstable through the thermal spray material 20 itself. However, by using a material such as ceramics having a heat resistance and a high insulation property for the material feeding tube 19, a conductive material such as a metal can be used.

  The thermal spray material 20 supplied from the material feed pipe 19 is immediately heated and melted by the high-temperature plasma 18 at about 10,000 ° C. regardless of the high-melting-point thermal spray material 20, and the molten particles 21 are shown in FIG. As shown in FIG. 4, the air travels toward the base material 25 without spreading so much while being accompanied by the plasma arc 23.

  In the plasma arc 23 including the molten particles 21, only the plasma 18 is separated by the plasma separation means 22 provided on the connecting pipe 26 immediately before the base material 25 in order to reduce the thermal load on the base material 25. Immediately thereafter, the molten particles 21 collide with the base material 25 to form a sprayed coating 24.

  The powder spray material 20 supplied from the material inlet tube 19 is fed onto the central axis of the plasma 18. When the thermal spray material 20 is fed in this way, the thermal spray material 20 can be sufficiently melted even at a low output as compared with the case where the thermal spray material 20 is fed so as to cross the plasma 18 and the plasma arc 23. The thermal spray coating 24 is obtained with high efficiency.

  Note that the main mantle 4, sub mantle 10, main anode 3, and sub starting electrode 10 all have a double structure and are cooled by circulation of water or the like. The description is omitted.

Measures to prevent thermal spray material adhesion:
The powder sprayed material 20 is optimally fed coaxially with the axis of the plasma arc 23, but as a matter of fact, the axis of the plasma arc 23 is extremely high temperature and high speed. It is not sent to the shaft center, but is sent to the vicinity thereof. In addition, some of the sprayed particles 20 are not sent by being repelled by the plasma arc 23, and some of the sprayed particles 20 are discharged out of the main torch 3 than those that become unmelted particles even if they can be sent. Instead, it tends to adhere to the inner wall surface of the main torch 3.

  At this time, since a part of the main plasma gas 6 fed from the main plasma gas inlet 5 is diverted and ejected from the gas ejection hole 31 of the anode part K, it tends to adhere to the tip surface 3a. The thermal spray material 20 is blown off by the gas 6 and cannot adhere to the tip surface 3a. Therefore, since the anode spot 29 and the material discharge hole 30 are not damaged, their shapes can be maintained normally, so that a stable plasma arc can be formed and stable spraying can be performed.

A second embodiment of the present invention will be described with reference to FIGS. 3 and 4. The same reference numerals as those in FIGS. 1 and 2 have the same names and functions.
The differences between this embodiment and the first embodiment are as follows.
(1) The tip part of the anode part 3 is formed in a truncated cone shape, and the gas ejection hole 31 is provided in the truncated cone shaped tip part.
(2) Six gas ejection holes 31 are provided at equal intervals in the circumferential direction, and each gas ejection hole 31 is located on the radiation centering on the material ejection holes 30. That is, as shown in FIG. 3, the axis of the gas ejection hole 31 is located on a straight line (radiation) L passing through the center of the material discharge hole 30 in the front view.

A third embodiment of the present invention will be described with reference to FIGS. 5 and 6. The same reference numerals as those in FIGS. 3 and 4 have the same names and functions.
The difference between this embodiment and the second embodiment is the position of the gas ejection hole 31. In this embodiment, the gas ejection hole 31 is made to be a material ejection hole so that the traveling axis of the plasma gas 6 discharged from the gas ejection hole 31 and the traveling axis of the powder sprayed material 20 from the material ejection hole 30 do not intersect. 30 is offset by an interval A.

  That is, as shown in FIG. 5, the axial center of the gas ejection hole 31 is arranged in parallel with a distance A from a straight line (radiation) L passing through the center of the material ejection hole 30 in the front view. Such an offset is effective as a means for blowing off spray particles that are more likely to adhere to the vicinity.

An experimental example of the present invention will be described.
As a specific spraying example,
Thermal spray output: 180A × 100v = 18kW
Plasma gas: Ar ――― 71 / min
Secondary gas: Ar ――― 21 / min
Carrier gas: Ar ――― 41 / min
Thermal spraying distance: 100mm
The sprayed material was sprayed at a supply rate of 30 g / min together with a carrier gas using a sprayed steel plate (50 × 50 × 5) washed and blasted to the sprayed material.

  As a result, the stable spraying time was around 10 minutes in the case where there was no gas ejection hole of the conventional example, whereas in the case of having the gas ejection hole 31 of the present invention, the normal continuous spraying conditions were the same. A few hours, the stable spraying time, could be sprayed stably without any problem, and practical spraying became possible.

Also, here, compared to spraying with a general-purpose single torch,
First, as typical spraying conditions,
Thermal spray output: 600A × 60v = 36kW
Plasma gas: Ar ――― 501 / min
Carrier gas: Ar ――― 41 / min
Thermal spraying distance: 100mm
Under the same spraying conditions, the same sprayed material and the same sprayed material were sprayed at the same supply amount.

  As a result, although the thermal spray output was half, the thermal spray efficiency was improved by several tens of percent and all the thermal spray coating properties were good. In particular, the hardness of the sprayed coating exceeded 1000 in terms of micro Vickers hardness, and showed good wear resistance.

It is a longitudinal cross-sectional view which shows 1st Example of this invention. It is a principal part enlarged view of FIG. It is an enlarged front view which shows 2nd Example of this invention. It is the IV-IV sectional view taken on the line of FIG. It is an enlarged front view which shows 3rd Example of this invention. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5.

Explanation of symbols

1 main torch
2 Deputy torch
3 Main anode
6 Plasma gas
13 Secondary gas
18 Plasma
19 Material feed pipe
20 Thermal spray material
21 Molten particles
23 Plasma flame
29 Anode
30 Material discharge hole
31 Gas ejection hole K Anode

Claims (7)

A composite torch type plasma spraying apparatus comprising a main torch having a plasma gas supply means and a sub torch, wherein a material discharge hole is provided in an anode portion of the main torch, and a powder spraying material is fed from the material discharge hole onto a plasma central axis. In
A composite torch type plasma spraying apparatus provided with a gas ejection hole for preventing adhesion of spray particles in the anode part   2. The composite torch type plasma spraying apparatus according to claim 1, wherein the gas ejection hole is disposed at a position where the anode point of the plasma arc and the material discharge hole do not interfere with each other.   2. The composite torch type plasma spraying apparatus according to claim 1, wherein one or a plurality of the gas ejection holes are provided on the radiation centering on the material discharge hole.   3. The composite torch type plasma spraying apparatus according to claim 1, wherein the gas ejection holes are provided in equal divisions at positions offset from the top of the radiation centering on the material ejection holes.   5. The composite torch type plasma spraying apparatus according to claim 1, wherein the gas discharged from the gas ejection hole is a plasma gas.   The main anode has a material feed pipe penetrating through the center thereof, a cooling passage provided on the outside thereof, and a tip edge located outside the cooling passage and projecting from a material discharge hole of the material feed pipe The composite torch type plasma spraying apparatus according to claim 1, 2, 3, 4, or 5   7. The composite torch type plasma spraying apparatus according to claim 6, wherein a front end surface of the main anode is formed in a truncated cone shape projecting inward, and a front end edge thereof serves as an anode point of the main anode.

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