JPH0713288B2 - Induction plasma spraying equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction plasma spraying apparatus used for spraying alumina powder onto a sprayed object such as a metal plate to form an insulating layer on the sprayed object. is there.

[0002]

2. Description of the Related Art When an alumina (Al ₂ O ₃ ) powder is sprayed on a metal plate such as copper or iron to be sprayed to form an insulating layer on the metal plate, it is conventionally shown in FIG. Such as transparent quartz or boron nitride, which has a triple structure torch including an outer tube 1, an intermediate tube 2 and a carrier gas introducing tube 3, and an induction having a structure in which a water cooling induction coil is provided on the outer periphery of the lower opening of the torch. A plasma spray device is used.

In this apparatus, the outer pipe 1 is closed at the lower end and the upper end is joined to the upper outer periphery of the intermediate pipe 2, and the outer gas supply passage 5 is tangentially opened inside the upper end. The lower end of the intermediate pipe 2 is located above the lower end of the outer pipe 1, and the outer diameter of the lower end portion is enlarged so that the velocity of gas is increased between the inner pipe and the outer peripheral surface of the outer pipe 1 to improve cooling efficiency. In order to increase the height, an annular small gap 6 of about 1 mm is formed, the upper end of which is closed by being joined to the upper outer periphery of the carrier gas introducing pipe 3, and the intermediate gas supply passage 7 is connected to the outer gas supply passage 5 within the upper end thereof. The openings are tangential to the same circumferential direction.

The lower end of the carrier gas introducing pipe 3 is opened near the lower end in the intermediate pipe 2, and the upper end serves as a carrier gas supply passage 8. 9 is a plasma flame.

This apparatus supplies argon or nitrogen gas as an outer gas from the outer gas supply passage 5 and argon as an intermediate gas from the intermediate gas supply passage 7 in order to cool the outer pipe 1 from the high temperature caused by the plasma flame 9. Are used by operating the induction coil 4 by supplying argon as a carrier gas from the carrier gas supply passage 8.

Since the outer gas is introduced into the outer tube 1 from the outer gas supply passage 5 in the tangential direction, it flows out while rotating in a spiral shape. When a plasma flame is generated without flowing the carrier gas, a flat flame shape is formed, but when the carrier gas is flowed and the flow rate is increased, the center of the plasma flame becomes concave. At this time, when powder such as ceramics or metal is put into the carrier gas supply path, the powder is melted by the plasma flame, and a grounded support base (hot plate) provided under the plasma flame under the torch. The molten powder is sprayed by the force of the carrier gas on the metal plate 10 placed on 11 to form a coating.

[0007]

However, in such a thermal spraying apparatus, the support base 1 on which the metal plate 10 is mounted is mounted.
Induction coil 4 of metal plate 10 although 1 is grounded
Because of the long distance from, the spraying speed of the powder melted on the metal plate 10 becomes slower than that just below the tip of the torch, and therefore the alumina sprayed on the metal plate 10 has A continuous and uniform insulating layer 12 was not obtained, and as shown in FIG.
Is generated, and the molten metal 1 of the metal plate 10 is formed on the discharge mark 13.
However, there was a problem that insulation was not sufficiently obtained.

The discharge traces 13 are formed when the charges of the molten powder repel each other and a portion that cannot be sprayed is produced. Although it is conceivable to increase the spraying speed in order to reduce such discharge marks, the powder could not be completely melted by the plasma flame and optimum spraying could not be performed.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems in forming an insulating layer made of fused alumina powder on a metal plate, which is a material to be sprayed, and has an insulation property without a discharge mark. It was obtained as a result of investigations to obtain a coating with high quality.

That is, according to the present invention, a torch having a triple structure consisting of an outer tube, an intermediate tube and a carrier gas introducing tube, and an induction plasma spraying apparatus provided with an induction coil provided on the outer periphery of the opening of the torch have a plasma flame generation site around or at the site. It is characterized in that a ground member is provided therein.

[0011]

According to the present invention, as described above, the earth ring is provided as the earth member around the plasma flame generation portion of the thermal spraying device.
Alternatively, by providing a ground rod as a ground member in the plasma generation site, the stray capacitance of the electric charges existing in the plasma flame generated by melting of the powder during thermal spraying can be discharged to this ground ring or ground rod, As a result, it is possible to form an insulating film having no discharge mark on the metal plate.

[0012]

Embodiments of the present invention will be described in detail below with reference to FIGS. In addition, the reference numeral 1 attached in these drawings
Reference numerals 1 to 11 denote the same parts as the reference numerals 1 to 11 in FIG.

In FIG. 1, a ground ring 15 is provided as a ground member connected to the induction coil 4 around the plasma flame 9 generation site above the metal plate 10 placed on the support 11 below the induction coil 4. It is the device of the present invention. As described above, the earth ring 1 is provided around the portion where the plasma flame 9 is generated.
By providing 5, the stray capacitance 16 of the electric charge existing in the plasma flame 9 generated by the melting of the alumina powder introduced together with the carrier gas during the thermal spraying can be discharged to the earth ring 15 and removed. Therefore, the insulating layer 12 having no discharge mark can be obtained on the metal plate 10. The earth ring 15 is preferably made of a heat resistant material such as tungsten or nickel-chromium alloy.

FIG. 2 shows an earth member in which a plurality of earth wires 17 are suspended below the earth ring 15 of FIG. 1, and the stray capacitance of electric charges existing in the plasma flame is earthed to the earth ring 15. Since the electric discharge can be removed by both of the wires 17, the insulating layer 12 having no further discharge trace can be formed on the metal plate 10.

In FIG. 3, a grounding rod 18 is directly inserted as a grounding member into the plasma flame 9 generation portion of the thermal spraying apparatus. Also by this, the charge of the molten powder in the plasma flame can be removed by discharge, and the insulating layer 12 having a high insulating property without a discharge mark can be formed on the metal plate 10.

[0016]

As described above, according to the present invention, when the alumina powder is melt-sprayed on the metal plate, an earth ring is provided around the plasma flame generating portion of the thermal spraying apparatus or inside the plasma generating portion. By installing a grounding rod on the metal plate, the electric charge of the molten powder floating in the plasma flame during thermal spraying can be discharged to these grounding rings or grounding rods and removed, and there is no discharge mark on the metal plate. A high insulating layer can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of an induction plasma spraying apparatus of the present invention.

FIG. 2 is a sectional view showing another embodiment of the induction plasma spraying apparatus of the present invention.

FIG. 3 is a sectional view showing another embodiment of the induction plasma spraying apparatus of the present invention.

FIG. 4 is a sectional view of a conventional induction plasma spraying device.

FIG. 5 is an enlarged partial sectional view showing a state of an insulating layer formed on a metal plate.

[Explanation of symbols]

 1 Outer Pipe 2 Intermediate Pipe 3 Carrier Gas Introducing Pipe 4 Induction Coil 9 Plasma Flame 10 Metal Plate 12 Insulating Layer 15 Earth Ring 17 Earth Wire 18 Earth Rod

Front page continuation (72) Inventor Emilio Fujiwara, 2-3-14 Awaji, Higashiyodogawa-ku, Osaka-shi, Osaka Prefecture Sansha Electric Manufacturing Co., Ltd. Sansha Electric Co., Ltd. (72) Inventor Hidehisa Tachibana 2-14-3 Awaji, Higashiyodogawa-ku, Osaka City, Osaka Prefecture Sanja Electric Co., Ltd. (56) Reference JP-A-5-21194 (JP, A) )

Claims (4)

[Claims] 1. An outer gas is introduced tangentially from one end,
An outer pipe discharged from the opening at the other end, coaxially provided inside the outer pipe, and provided coaxially in the intermediate pipe and the intermediate pipe that introduces an intermediate gas tangentially from one end and discharges from the opening at the other end , A torch having a triple structure including a carrier gas introduction pipe for discharging the carrier gas supplied from one end through an opening at the other end, and an induction coil provided on the outer periphery of the opening of the torch. Is applied to generate a plasma flame, and an induction plasma spraying apparatus for spraying a molten powder onto a metal plate arranged below the torch is characterized in that a ground member is provided around or inside the plasma flame generation site. And induction plasma spraying equipment. 2. The induction plasma spraying apparatus according to claim 1, wherein the earth member is an earth ring. 3. The induction plasma spraying apparatus according to claim 1, wherein the earth ring has a plurality of earth wires below the earth ring. 4. The induction plasma spraying apparatus according to claim 1, wherein the ground member is a ground rod.