JPH05263211A - Induction plasma torch for pressure reduction - Google Patents

Abstract

PURPOSE:To execute homogeneous thermal spraying without damaging torch constituting members in melting and thermal spraying of powder by an induction plasma torch. CONSTITUTION:The outer pipe 3, intermediate pipe 4 and carrier gas introducing pipe 5 of the torch 1 constituted by disposing the carrier gas introducing pipe 5, the intermediate pipe 4 and the outer pipe 3 in this order from the inner side and disposing a high-frequency induction coil 13 on the outer periphery of the cooling pipe 6 are made of silicon nitride sintered bodies. The damage of the outer pipe 3 is thereby prevented even if cooling water is supplied to the cooling medium passage between the cooling pipe 6 and the outer pipe In addition, the mounting and moving of the high-frequency induction coil 13 is facilitated by supporting and fixing a torch supporting lower flange 7 and upper flange for supporting the torch 1 by means of three pieces of rods 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction plasma torch which is capable of efficiently heating and melting powder of ceramics or metal in an inductively coupled plasma under reduced pressure and jetting the powder, which is mainly used for thermal spraying. Is.

[0002]

2. Description of the Related Art Heretofore, as an induction plasma torch, a torch having a water-cooled induction coil provided in a triple structure of an outer tube made of transparent quartz, an intermediate tube, and a carrier gas introducing tube is often used. Originally, in order to form a satisfactory molten coating on an object to be sprayed using an induction plasma torch, it is necessary to generate a plasma flame in a perfectly balanced manner on the left and right to completely melt the supplied powder. In order to do this, it is necessary for the tubes to be perfectly concentric in the torch configuration.

However, a quartz outer tube, an intermediate tube,
It is said that it is very difficult to construct a completely concentric torch by using each carrier gas introduction pipe.

In view of such circumstances, the present inventors have proposed a completely concentric induction plasma torch using a sintered body of boron nitride as a raw material. That is, a carrier gas introduction pipe, an intermediate pipe and an outer pipe made of a boron nitride sintered body are sequentially fitted into a cylindrical support made of a sintered boron nitride body and having a multi-stage concentric insertion hole formed therein. An induction plasma torch having a structure in which a gas supply tube for introducing gas in a tangential direction to the tubes is fitted and screwed to the tips of the intermediate tube and the outer tube in the support.

The structure of this torch will be described with reference to the longitudinal sectional view of FIG. 4. In the figure, reference numeral 41 is a cylindrical support obtained by processing a boron nitride sintered body. Inside the support body 41, multi-stage insertion holes 41a to 41e are concentrically provided by repeatedly drilling and threading the support body 41 with a lathe or the like, and the carrier holes are inserted into these insertion holes. Gas introduction pipe 4
4, the intermediate pipe 43, and the outer pipe 42 are fixed by fitting screwing.

The insertion hole is formed in the cylindrical support body 41 by first forming an insertion hole 41a for inserting the carrier gas introducing pipe 44 through the support body 41, and then forming the intermediate pipe 43. The insertion hole 41b is formed concentrically with the insertion hole 41a at a position approximately in the middle of the support 41, and then the insertion hole 41c of the outer tube 42 is formed. Next, an insertion hole 41d having the same or slightly smaller inner diameter than the intermediate tube 43 is provided above the intermediate tube 43 supporting insertion hole 41b, and the outer tube 42 supporting insertion hole 4 is provided.
An insertion hole 41e having the same or slightly smaller diameter as the inner diameter of the outer tube 42 is formed above 1c.

In this way, the concentric circles 41a ...
Cylindrical support 4 made of sintered boron nitride having 41e formed thereon
1, an outer tube 42, an intermediate tube 43, and a carrier gas introducing tube 4 each made of a boron nitride sintered body to have a cylindrical shape.
4 and plasma gas supply pipe 45, sheath gas supply pipe 4
In order to attach 6, the carrier gas introducing pipe 44 is first passed through the insertion hole 41a from below, and is fixed by screwing with the screw 49. After that, similarly, the intermediate pipe 43 is inserted into the insertion hole 41b,
The outer tube 42 is sequentially screwed into the insertion hole 41c, and then the plasma gas supply pipe 45 and the sheath gas supply pipe 46 are provided tangentially to the insertion holes 41d and 41e, respectively.
Insert into g and screw. A small gap of about 1 mm is provided between the inner peripheral surface of the outer pipe 42 and the outer peripheral surface of the intermediate pipe 43 in order to increase the speed of the supplied gas and enhance the cooling efficiency.

Using the induction plasma torch thus concentrically formed of the boron nitride sintered body, the plasma gas supply pipe 45 to the carrier gas introduction pipe 4 are used.
A plasma gas such as argon gas is supplied at a rate of 5 liters / minute between the outer tube 4 and the intermediate tube 43, and a sheath gas such as argon gas is cooled from the sheath gas supply tube 46 between the intermediate tube 43 and the outer tube 42 for cooling the outer tube. When a high frequency of 5 KW and 13.56 MHz is applied to the induction coil 51 in a state of supplying 20 liters / minute as a gas and supplying 1 g / minute of powder having a particle size of 5 to 100 μm together with the carrier gas from the carrier gas introduction pipe 44, A well-balanced normal plasma flame 52 is generated and the powder is melted.
A film is formed on it.

[0009]

However, even if the molten powder is sprayed by the induction plasma torch manufactured by using the boron nitride sintered body as a raw material in a completely concentric structure as described above, Since the plasma flame is long and the sheath gas and plasma gas are mixed at the lower end of the torch and the outer tube is not sufficiently cooled by the sheath gas, the outer tube is overheated, resulting in nitridation of oxygen and oxygen outside the outer tube. It has the drawback that it combines with boron and sublimes, collapses from the outer wall of the boron nitride outer tube, and has holes on the outside.

In order to prevent the above-mentioned drawbacks, it is conceivable that a tube is further provided in the outer layer of the outer tube and a cooling gas such as argon gas is passed through the tube to cool the outer tube.
Inert gas such as argon gas is expensive and economically difficult. It is also conceivable to use cooling water in place of the inert gas, but in this case, there is a concern that the outer wall of the outer pipe may collapse due to oxygen or the like dissolved in the cooling water. In addition, an induction plasma torch made of a boron nitride sintered body has a small mechanical strength and has a problem that it breaks when it is mounted in a decompression chamber. Furthermore, when arranging the induction coil in such a torch, the sheath gas introduction pipe and the plasma dregs introduction pipe become an obstacle,
Its installation was difficult.

[0011]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted studies to solve the above-mentioned problems in the conventional induction plasma torch for decompression. As a result, the torch components such as the outer tube and the intermediate tube are sintered with silicon nitride. As a result, a decompression induction plasma torch has been obtained which is made of a body and has improved mechanical strength, can be cooled by cooling water, and is easily attached with an induction coil.

That is, the present invention comprises an outer tube made of a silicon nitride sintered body, an intermediate tube, a carrier gas introducing tube, a heat-resistant glass cooling tube, and a high-frequency induction coil arranged on the outer periphery of the cooling tube. A plasma torch,
The lower part of the outer tube is supported by the torch support lower flange and the outer tube support lower ring engaging with the lower part of the outer tube so that the lower end of the outer tube faces the decompression chamber connected to the lower part of the torch. The upper portions of the pipe, the carrier gas introduction pipe, and the cooling pipe are sequentially supported and sealed by respective support rings and O-rings, and these support rings engage with each other and are directly or indirectly supported by the torch support upper flange. It is an object of the present invention to provide an induction plasma torch for decompression having the above structure.

[0013]

The present invention has an outer tube, an intermediate tube, and
By making the carrier gas introduction tube made of silicon nitride sintered body, it is possible to improve the mechanical strength and cool with cooling water.
Further, an insulating ring for preventing frame earth is provided under the outer tube facing the decompression chamber to improve withstand voltage of high frequency power, and further, three rod rods for supporting the plasma torch are provided to facilitate installation of the induction coil. It is a thing.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a vertical cross-sectional view of a decompression induction plasma torch according to the present invention, in which reference numeral 1 denotes a torch body, and the torch body 1 is an outer tube 3, an intermediate tube 4, and a carrier gas made of a silicon nitride sintered body. The introduction pipe 5 and the heat-resistant glass cooling pipe 6 and a high-frequency induction coil 13 arranged on the outer periphery of the cooling pipe 6 are supported by a metal torch supporting lower flange 7 and an upper flange 17, The flanges 7 and 17 are screwed and fixed to the rod bar 14. The torch 1 is connected to the decompression chamber 2 in an airtight state below the torch 1 so that the lower end portion 3a of the outer tube 3 faces the decompression chamber 2.

Next, the structure of the torch 1 will be described in the order of the assembling steps. The lower part of the cylindrical torch 1 penetrates through the central portion of the metal torch supporting lower flange (hereinafter referred to as lower flange) 7. An opening hole 7a is provided, and a groove 7b is provided around the opening hole 7a from above or below.
And a metal lid 7c is brazed or welded to the groove 7b. A cooling water introduction hole 7d is provided in a tangential direction from a part of the groove toward the outer edge, and cooling water for cooling the lower flange 7 is introduced. It is discharged from the discharge hole provided.

In the lower part of the lower flange 7, a frame earth preventing insulating ring 8 made of an insulating material such as ceramics having an opening 8a in the central portion is similarly screw 8c.
It is fixed to the lower flange 7 by. The upper edge 8b of the opening 8a is countersunk and the torch 1
The lower end portion 3a of the outer pipe 3 can be engaged. This frame grounding insulation ring 8 is a torch 1
At the time of applying a high frequency power to the induction coil 13 to generate a plasma flame and perform thermal spraying, the plasma flame is directly grounded to the lower flange 7 to prevent the lower flange 7 from being damaged. is there.

Reference numeral 9 denotes a metal outer pipe supporting lower ring on the upper portion of the lower flange 7, which has an opening 9a formed at the center thereof, and four protrusions are formed on the upper portion of the opening 9a as shown in FIG. The portion 9b is formed. Further, the outer pipe supporting lower ring 9 has a cooling water introducing port 9c from the outside through an opening 9a.
Is provided at two locations in the tangential direction of the cooling water, and the cooling water is discharged from the drain port 16c while cooling the outer pipe 3 from the inlet 9c through the outer pipe 3 and the cooling pipe 6. This cooling water inlet 9c is provided at two places because the cooling water stagnates in the portion near the inlet and the flow is deteriorated at only one place, and the efficiency of the outer pipe cooling is reduced.

The outer tube 3 is formed such that its lower portion is wider than its central portion, and a protruding portion 3b is formed on its upper portion. The outer tube 3 having such a shape is first inserted into the above-described opening hole 7a of the lower flange 7, and the lower end portion 3a thereof is engaged with the upper end edge portion 8b of the frame earth preventing insulating ring 8. The outer tube supporting lower ring 9 is inserted from the upper end of the outer tube 3 engaged with the insulating ring 8 in this manner, and the projection 9b of the lower ring 9 and the projection 3b of the outer tube 3 are engaged with each other by the screw 9d. It is fixed to the lower flange 7 and O
Seal with ring 7e. Also, the lower flange 7
The outer tube 3 and the outer tube 3 are sealed with a metal C-shaped O-ring or a heat-resistant resin O-ring 10 provided on the lower portion of the protrusion 3b of the outer tube 3. This O-ring also serves as a cushion as a mechanical protection for the outer tube 3.

The upper edge 9 of the outer tube support lower ring 9
e is countersunk, and this countersunk upper edge 9e
The lower end of the cooling pipe 6 inserted from the upper end of the outer pipe 3 is engaged with the insulating ring 11 inserted onto the lower ring 9 from above the cooling pipe 6 by means of the screw 11a.
Made of silicon that is fixed to the cooling pipe 6 and abuts on the cooling pipe 6.
The ring 12 seals the lower ring 9, the insulating ring 11 and the cooling pipe. Next, a high-frequency induction coil 13 is arranged from above the cooling pipe 6 around the central portion thereof and is fixed by a supporting device (not shown).

Reference numeral 14 denotes a rod bar having a threaded upper end and a lower end screw for fixing the lower flange 7 and the upper flange 2a of the decompression chamber 2 and sealing with an O-ring 2b. The lower flange 7 and the decompression chamber 2 may be fixed to each other by the rod bar 14 not separately as shown in FIG. 1, but separately. Reference numeral 15 denotes a metal cooling pipe support ring, the central portion of which has an opening 15a through which the cooling pipe 6 can be inserted and is inserted from above the cooling pipe 6.

Reference numeral 16 designates an outer tube supporting upper ring made of metal,
The central portion has an opening 16a through which the outer tube 3 can be inserted, and is inserted from above the outer tube 3 and its lower end 16b.
Is countersunk so that it can be engaged with the upper end of the cooling pipe 6. Further, a drain port 16c for discharging the cooling water is provided in the middle of the opening 16a from the tangential direction to the opening 16a toward the outside. Reference numeral 17 denotes a metal torch-supporting upper flange (hereinafter referred to as an upper flange), the central portion of which has an opening 17a having the same inner diameter as the inner diameter of the outer tube 3 and is fitted from above the outer tube 3, and its lower end is It is countersunk to engage the upper end of the outer tube 3. Further, a hole 17b that can be engaged with the rod bar 14 is provided near the outer end of the upper flange 17.

However, the cooling pipe support ring 15 is screw 1
The outer pipe supporting upper ring 16 is fixed to the outer pipe supporting upper ring 16 by 5c, and the outer pipe supporting upper ring 16 is fixed to the upper flange 17 having the engaging surface spotted by a screw 16d. The upper flange 17 is provided with a hole 17b near the outer side thereof in the rod bar 14
And is fixed to the upper end screw of the rod bar 14 with a nut 22 via an insulator 18. The cooling pipe support ring 15, the outer pipe support upper ring 16 and the cooling pipe 6 are sealed by a silicon O-ring 15b, and the outer pipe support upper ring 16, the upper flange 17 and the outer pipe 3 are made of a silicon O ring 16e. Sealed by. The gap between the outer pipe 3 and the cooling pipe 6 is a passage for cooling water that cools the outer pipe 3, and is set to about 2 mm.

Reference numeral 19 is a metal intermediate pipe support ring, and the opening at the center thereof has the upper opening 19a the same size as the outer diameter of the intermediate pipe 4, and the lower opening 19b is about 1 mm wider than that, that is, the outer pipe. 3 is formed in a step shape with a wide lower opening 19b having an outer diameter dimension. And the lower opening 19
The sheath gas inlet 1 in the tangential direction from b to the outer edge portion
9c is provided and is connected to the sheath gas introducing pipe 19d. The intermediate pipe support ring 19 is fixed to the upper flange 17 whose engaging surface is spotted by a screw 19f, and is sealed by an O-ring 19e. This intermediate tube support ring 1
The intermediate pipe 4 is fitted into the opening of the upper end 9 and the upper end protruding portion 4a thereof is
Is supported on the support ring 19.

Reference numeral 20 is a convex carrier gas introducing pipe support ring, and the carrier gas introducing pipe 5 is provided in the opening 20a.
Is inserted. The opening 20a has a wide opening 20b equal to the inner diameter of the intermediate pipe from the lower end to the middle.
Plasma gas inlet port 2 in the tangential direction from 0b to the outside
0c is provided and is connected to the plasma gas introduction pipe 20g and serves as a plasma gas inlet passage between the carrier gas introduction pipe 5 and the intermediate pipe 4. The carrier gas introduction pipe support ring 20 is engaged with the counterbore upper surface of the intermediate pipe support ring 19 and fixed with screws 20d, and is sealed by a silicon O-ring 20e. As a result, the intermediate pipe 4 in which the protruding portion 4a is locked on the intermediate pipe supporting ring 19 is also fixed, but at this time, the silicon O-ring 20f is formed between the supporting ring 20 and the protruding portion 4a of the intermediate pipe 4. The mechanical pressure exerted on the intermediate pipe 4 is relieved by putting in. The carrier gas introduction pipe 5 to be inserted into the opening of the carrier gas introduction pipe support ring 20 has a projection 5a formed in the vicinity of the upper portion thereof, and the projection 5a is placed on the top of the carrier gas introduction pipe support ring 20. Then, the torch fixing ring 21 is fitted from above, fixed with screws 21a, and sealed with a silicon O-ring 21b. At this time, by inserting a silicon O-ring 21c between the protrusion 5a of the carrier gas introducing pipe 5 and the torch fixing ring 21, the pressure applied to the protrusion 5a can be relaxed.

The depressurization induction plasma torch of the present invention is obtained as described above, but the screws used at various places may be sequentially assembled by temporary fixing, and finally fixed firmly. Further, the torch normally supports the torch supporting upper flange 17 and the lower flange 7 with four rod rods 14, but as shown in the plan view of the upper flange 17 in FIG. The robot rod fixing holes 14a, 14b, 14c at the positions of the vertices of the right triangle may be supported by three rod rods. In this case, the induction coil 13 is provided between the rod rods having a large gap. It can be installed from the above, and the problem that the sheath gas introduction pipe and the plasma gas introduction pipe become an obstacle when the conventional induction coil is attached can be solved.
Even if it is necessary to change the direction of the attached induction coil, the distance between the rod rods is large, so that it can be easily changed.

In FIG. 1, projections 3b and 9b for engaging the outer tube 3 and the outer tube support lower ring 9 in the lower part of the torch are projections whose engagement surfaces are tapered. However, it is not necessarily limited to the tapered shape.

Actually, using the plasma torch of the present invention, a plasma gas such as argon gas is spirally formed between the plasma gas introduction pipe 20g and the carrier gas introduction pipe 5 and the intermediate pipe 4 at 10 liters / minute. Further, argon gas as a sheath gas is helically supplied at a rate of 30 liters / minute from the sheath gas introducing pipe 19d between the intermediate pipe 4 and the outer pipe 3, and the cooling water introducing port 9c is provided between the cooling pipe 6 and the outer pipe 3. Is supplied with cooling water at a rate of 5 liters / minute, and while further supplying cooling water at a rate of 5 liters / minute from the cooling water inlet 7d to cool the lower flange 7, argon gas is used as a carrier gas from the carrier gas introduction pipe 5. 20 kW for the induction coil 13 in a state of supplying a sprayed material of Cu or Si powder having a particle size of 10 to 20 μm together with 5 liter / min.
When a high frequency power of 56 MHz is applied, it is uniformly and excellent in thermal conductivity and insulation on the object to be sprayed such as glass, metal, ceramics, etc. placed in the decompression chamber by the plasma flame well balanced on the left and right. A film with high voltage can be formed, and since the outer tube is sufficiently cooled by cooling water, it is not overheated, and the fact that it is made of a silicon nitride sintered body also contributes to the outer tube. No damage was observed.

[0028]

As described above, in the induction plasma torch for decompression of the present invention, the outer tube, the intermediate tube, the carrier gas introducing tube, etc. constituting the decompression induction plasma torch are made of a silicon nitride sintered body so that the mechanical strength is improved. In addition, since it is less likely to be affected by oxygen, even if cooling water is supplied as a medium for cooling the outer pipe between the outer pipe and the cooling pipe provided on the outer side of the outer pipe, the outer pipe is sufficiently damaged without being damaged. It is possible to cool and thus to achieve satisfactory plasma spraying. Furthermore, by installing a frame grounding insulating ring below the torch support lower flange and supplying cooling water into the torch support lower flange, plasma spraying of the sprayed object placed on the decompression chamber is possible. It is possible to prevent the plasma flame from being grounded to the lower flange and to prevent the lower flange from being damaged by excessive heat, so that a uniform sprayed coating can be formed.

[Brief description of drawings]

FIG. 1 is a partial vertical cross-sectional view showing the structure of a decompression induction plasma torch of the present invention.

2 is a plan view of an outer tube support lower ring in FIG. 1. FIG.

FIG. 3 is an explanatory view showing a fixed position of a rod bar on the torch support upper flange in FIG.

FIG. 4 is a vertical cross-sectional view of a conventional induction plasma torch.

[Explanation of symbols]

 1 torch 2 decompression chamber 3 outer tube 4 intermediate tube 5 carrier gas introduction tube 6 cooling tube 7 torch support lower flange 8 frame earth prevention insulation ring 9 outer tube support lower ring 13 high frequency induction coil 14 rod rod 15 cooling tube support ring 16 Outer pipe support upper ring 17 Torch support upper flange 19 Intermediate pipe support ring 20 Carrier gas introduction pipe support ring 21 Torch fixing ring

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Okada 2-14-3 Awaji, Higashiyodogawa-ku, Osaka City, Osaka Prefecture Sansha Electric Manufacturing Co., Ltd. (72) Hidehisa Tachibana 2-chome, Awaji, Higashiyodogawa-ku, Osaka City, Osaka Prefecture Sanyo Denki Seisakusho Co., Ltd. (72) Inventor Hiroyasu Murata 2-14-3 Awaji, Higashiyodogawa-ku, Osaka City, Osaka Prefecture Sansha Denki Seisakusho Co., Ltd.

Claims (4)

[Claims] 1. A plasma comprising an outer tube made of a silicon nitride sintered body, an intermediate tube, a carrier gas introducing tube, a heat-resistant glass cooling tube, and a high-frequency induction coil arranged on the outer periphery of the cooling tube. A torch, the lower part of the outer tube is supported by a torch support lower flange and an outer tube support lower ring engaging with the lower part of the outer tube so that the lower end of the outer tube faces the decompression chamber connected to the lower side of the torch. The upper portion of the outer pipe, the intermediate pipe, the carrier gas introduction pipe, and the cooling pipe are sequentially supported and sealed by respective support rings and O-rings, and these support rings engage with each other to directly or indirectly support the torch. An induction plasma torch for decompression, which is supported by an upper flange. 2. The outer pipe has a protrusion in the vicinity of a lower portion thereof, and the protrusion is engaged with the protrusion of the outer pipe supporting lower ring, and a C-shape is provided below the protrusion of the outer pipe supporting lower ring. The decompression induction plasma torch of claim 1, wherein an O-ring is provided to engage the torch support lower flange and the outer tube support lower ring. 3. The decompression induction plasma torch according to claim 1, wherein the outer tube supporting lower ring has a cooling water inlet for introducing cooling water from the outside between the outer tube and the cooling tube. 4. The decompression induction plasma torch according to claim 1, wherein the torch supporting lower flange and the upper flange are supported by three rod rods.