JPH04246160A - Thermal-spraying torch - Google Patents

Abstract

PURPOSE:To provide a thermal-spraying torch, which can form film by high quality plasma-spraying over the whole inner face of a pipe by traveling the thermal-spraying torch of a base material only at one time in a longitudinal direction of the pipe in the case of executing the thermal-spraying treatment for protecting the inner wall of large diameter pipe. CONSTITUTION:Arc is generated between electrodes composed of a pair of a cathode pole 15 and a anode pole 17 having faced end faces of cutting shape of cylindrical tube bodies and magnetic field is generated so that the faced electrodes become the same pole and the above arc is circularly shifted on the round cutting face of tube body to be the electrode end faces by magnetic driving. Then, by supplying the plasma gas 23 into the arc generated range, ring shaped arc plasma 28 is formed on periphery of the electrodes and thermal- spraying powder is supplied into the plasma in circular direction of the tube body from a thermal-spraying power introducing hole 25.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal spraying torch used for forming a protective film, particularly on the inner wall of a pipe, by thermal spraying.

0002

[Prior Art] Traditionally, thermal spraying technology has been used to improve wear resistance,
It has been used for a long time as a method for forming films with properties such as heat resistance, and is broadly classified into gas spraying, which uses combustion gas as the melting means, and electric spraying, which uses electrical energy as the melting energy. Further, electric thermal spraying generally includes arc spraying, plasma spraying, etc., and plasma spraying has recently been attracting attention in particular due to the quality of the sprayed coating.

FIG. 3 shows a conventional example of a plasma spray torch. Water-cooled cathode 1 and water-cooled anode 2
During this period, power is supplied by a power source 3 to generate a DC arc 4, and a plasma working gas 5 fed from the rear is supplied to the arc 4.
The plasma is heated by heating and ejected from the nozzle 7 as arc plasma 6. The thermal spraying material is a powder that is placed on a carrier gas 8, blown into a plasma jet, heated and melted, and then accelerated to collide with the surface of a substrate (base material) 9 to be thermally sprayed at high speed to form a film. At this time, the plasma working gas is often argon or nitrogen, or helium or hydrogen added to these gases.

0004

However, in the plasma spray torch as described above, as shown in FIG. 3, the centers of the cathode 1 and the anode 2 are coaxial, and the nozzle 7
The area of the nozzle varies depending on the output, but the maximum is 2 to 3.
mm2, and when carrying out thermal spraying for the purpose of protecting the inner wall of a large-diameter pipe, the distance between the torch and the base material 9 may be increased to expand the spraying area, or the base material 10 may be rotated as shown in Fig. 4. It was necessary to form the film forming region 12 while moving the torch 11 or scanning the torch 11 in the circumferential direction inside the tube.

However, when the distance between the torch and the base material 9 is increased, the collision speed of the molten particles reaching the base material 9 slows down and the temperature of the molten particles decreases. This results in poor adhesion between the material and the film. Also, as shown in Fig. 4, the base material 10 or the torch 1
The method of scanning 1 has the disadvantage that the scanning device becomes expensive. Further, it has the disadvantage that it takes a long time to form a film, making it unsuitable for mass production.

[0006] In view of these points, the present invention provides a plasma spray coating that can be applied to a base material, or a thermal spraying torch that can form a high-quality coating on the entire surface of a pipe by running the torch once in the longitudinal direction of the base material. The purpose is to provide

[0007]

[Means for solving the problem] In order to achieve the above object, an arc discharge is generated between a pair of electrodes having cut-shaped end surfaces of opposing cylindrical tubes, and the polarity becomes the same between the opposing electrodes. A ring-shaped arc plasma is formed around the electrode by generating a magnetic field and moving the arc around the circular cut end of the tube that is the end face of the electrode by magnetic drive and supplying plasma working gas to the arc generation area. Thermal spray powder is then supplied into the plasma in the circumferential direction of the tube.

[0008]

[Operation] According to the above means, a magnetic field is applied to the pair of electrodes whose opposing end surfaces have the cut shape of a cylindrical tube so that the opposing electrode surfaces have the same polarity, and the magnetic field is applied between the electrodes. Since the arc is generated by direct current, the arc receives a force according to Fleming's left-hand rule due to the magnetic field, and the arc tends to move between the end faces of the electrodes. In the above means, since the magnetic fields applied to the opposing electrodes are of the same polarity, there is no magnetic flux penetrating between the two electrodes, and all the magnetic flux is suddenly directed outward from the inside of the opposing electrode end faces. It bends, intersects with the arc created by the DC current, and provides driving force to the arc. On the end face of the electrode having a circular tube shape, the arc receives a driving force in the same circumferential direction, so that the arc moves around along the cut shape of the circular tube on the end face of the electrode. Since the orbiting speed of this arc is very fast, when plasma working gas is supplied to the arc from inside the torch, high temperature arc plasma is generated so as to radiate toward the circumference of the tube. When powder is supplied as a film forming material to this high temperature arc plasma, the inner surface of the tubular member can be thermally sprayed at high speed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a longitudinal cross-sectional view of a thermal spray torch for use on a cylindrical surface, showing a first embodiment of the present invention. 13a and 13b are cooling water inlets, 14a and 14b are cooling water outlets, 15 is a cathode, 16 is a high melting point conductive material forming the cathode tip, 17
is an anode, 18a and 18b are excitation coils that generate a magnetic field within the electrodes, and 19a and 19b are excitation coils 18a and 18b.
20a and 20b are thermal insulators, 21 is a nozzle made of a heat-resistant material, 22 is a tubular member made of a heat-insulating and electrically insulating material, and 23 is a plasma A working gas, 24 is an introduction path for this gas 23, 25 is a thermal spray powder inlet, 26 is an arc, 27 is a DC power supply, and 28 is a plasma jet.

The operation of the thermal spraying torch of this embodiment constructed as described above will be explained below.

First, an arc 2 is generated in the gap between the electrodes using a pulse current generator or the like installed separately or built into the DC power supply 27.
6 is generated, and then low voltage and high current power is supplied from the power source 27 to maintain the arc 26 stably. after that,
Excitation coils 18a and 18b provided on electrodes 15 and 17 are energized to generate a magnetic field in each electrode. At this time, if the magnetic field is of the same type on the end faces of both opposing electrodes, the magnetic flux will be directed outward from the inside of the tube-shaped electrode, and a magnetic flux component perpendicular to the direction of the arc current will be generated. According to the law, a driving force is applied to the arc, and the arc moves at high speed around the end faces of both electrodes in the cut shape of an endless cylindrical tube.

At this time, the circular driving force F of the arc is expressed by the following equation, and is proportional to the product of magnetic flux density B, arc current I, and arc length L.

F=B×I×L From the above equation, in order to increase the arc rotation driving force, the arc current,
Although the arc length can be increased, in the present invention, it is better to increase the magnetic flux density in order to perform film formation with as low a current as possible. The plasma working gas 23 is supplied from the introduction path 24 to the arc region generated in the region formed by the opposing electrodes in this manner. At this time, argon, nitrogen, hydrogen, helium, etc. are used as the plasma working gas. The plasma working gas supplied into the arc is heated to a high temperature and becomes a plasma state, and the energy density increases due to the thermal pinch effect, resulting in an ultra-high temperature arc plasma 28 that is ejected from the ejection port at high speed.

[0014] At this time, when the spraying material is supplied into the arc plasma through the spray powder inlet 25 provided in the nozzle, it is heated and melted, and is carried by a high-velocity plasma jet and collides with the inner wall of the tube, flattening it. to form the desired film.

FIG. 2 is a detailed view showing an example of thermal spraying inside a cylinder using a thermal spraying torch according to a second embodiment of the present invention. 30 is a cathode, 31 is an anode, 32, 33 are excitation coils that generate a magnetic field within the electrodes, 34, 35 are power sources for supplying excitation current to the excitation coils 32, 33, 36,
37 is a thermal spraying torch drive mechanism, 38 and 39 are working gas introduction pipes, 40 is a DC power supply, 41 is a driver for the drive mechanism, 42
Reference numeral denotes a DC power supply, a control device for a thermal spray powder supply device, a plasma working gas, etc., 43 a plasma jet, 44 a tube to be thermally sprayed, and 45 a nozzle.

The operation of the thermal spraying torch according to the embodiment constructed as described above will be explained below.

First, the cathode 3 is prepared in the same manner as in the first embodiment.
0. An arc is generated between the anodes 31, and the arc is moved around according to the shape of the electrode end face by the magnetic field generated by the excitation coils 32 and 33, and plasma working gas is introduced into the arc generation area and heated to a high temperature to generate plasma. The liquid is then ejected in the radial direction at high speed from the nozzle. At the same time, when materials for film formation are supplied into the plasma from the thermal spray powder introduction port provided inside the nozzle 45, they are heated and melted, and are carried by the high-velocity plasma jet 43 and collide with the inner wall of the tube, flattening and forming the desired film. form. Further, the thermal spraying torch is configured to be moved in the longitudinal direction within the tube by drive means 36 and 37, thereby making it possible to thermally spray the inside of the cylinder at high speed in the circumferential and longitudinal directions.

It should be noted that the present invention is not limited to the above embodiments, and various modifications can be made based on the gist of the present invention.

[0019]

[Effects of the Invention] As is clear from the above explanation, according to the present invention, it is possible to obtain arc plasma that matches the internal shape and dimensions of the tubular member, so that thermal spraying, which has been done pointwise up to now, can now be done linearly. It is possible to spray the inside of the pipe in a planar manner with one run of the film forming device or the base material, and it is possible to provide a thermal spraying torch with extremely high productivity.

[Brief explanation of the drawing]

[Fig. 1] Cross-sectional view of a thermal spraying torch of the present invention

[Figure 2] Detailed view of thermal spraying treatment on the inner surface of a cylinder using the thermal spraying torch of the present invention

[Figure 3] Longitudinal cross-sectional view of a conventional thermal spray torch

[Fig. 4] An explanatory diagram of a conventional example in which the inner surface of a cylinder is thermally sprayed by rotating a thermal spraying torch.

[Explanation of symbols]

15 Cathode 17 Anode 18a, 18b Excitation coil 21 Nozzle 23 Plasma working gas 24 Working gas introduction route 25 Thermal spray powder inlet

Claims (2)

[Claims] 1. An electrode consisting of a pair of cathode and anode having cut-shaped end surfaces of circular tube bodies facing each other with a gap therebetween;
An excitation coil provided around the electrode to generate a magnetic field in which the opposing end surfaces of the electrodes have the same polarity, and working gas introduction paths provided inside the cylinders constituting a cathode and an anode for supplying plasma working gas to the gap, respectively. and a thermal spraying torch comprising a plurality of thermal spraying powder inlets provided at appropriate pitches around the gap. 2. An electrode consisting of a pair of cathode and anode having cut-shaped end surfaces of circular tubes facing each other with a gap therebetween;
an excitation coil provided around the electrode that generates a magnetic field in which opposing end surfaces of the electrodes have the same polarity; a nozzle provided to cover between the pair of electrodes; and a cathode that supplies plasma working gas to the gap. 1. A thermal spraying torch comprising: working gas introduction paths provided inside a cylinder constituting an anode; and a plurality of thermal spray powder introduction ports provided at appropriate pitches in the nozzle.