JPH01299777A - Structure of plasma torch - Google Patents

Abstract

PURPOSE:To prevent sudden consumption of a negative electrode by providing working gas blowout nozzles on the same axis as the negative electrode and arranging a magnet to the lower part of the negative electrode and bringing the Lorentz's force acting on the negative electrode in line with the turning direction of working gas. CONSTITUTION:The gas blowout nozzles of a working gas supply path 2 is provided on the same axis as the negative electrode 1 and further, the magnet 7 to generate a line of magnetic force is set up in the vicinity of the lower part of the negative electrode 1. At this time, in order to generate the turning flow of working gas to surround a plasma arc, the working gas blowout nozzles 8 are pierced and formed in the magnet 7. Since the working gas blowout nozzles 8 are provided in the magnet 7 itself and the magnet 7 is arranged in close vicinity to the negative electrode surface 1a, the acting force of the magnet 7 increases. By this method, the Lorentz's force on the negative electrode surface is brought in line with the turning direction of the working gas and the turning motion of a discharging point is stabilized. Accordingly, the sudden consumption of the negative electrode is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of a plasma torch used in a wide range of fields such as welding, cutting, and coating metals.

[Prior Art] As a technique for rotating the discharge point on the cathode surface in order to reduce rapid consumption of the cathode of a plasma torch, for example, as shown in Utility Model Application Laid-Open No. 62-41476, A structure is known in which a magnetic field line generating coil is disposed on the cathode surface and a rotating motion is caused at the discharge point by the Lorentz force acting on the cathode surface, and a magnet is used in addition to the magnetic field line generating coil as a means for applying the magnetic field.

Furthermore, as shown in Utility Model Application No. 62-41476, by combining a cathode with a concave surface and a magnetic field line generating coil,
A structure in which a discharge point is rotated on a concave surface of a cathode is known.

The cathode of a plasma torch includes a cathode body and a cathode part made of a material with higher heat resistance buried at the tip of the cathode body.The cathode can be buried by mechanical methods such as press-fitting or caulking, or by brazing or other methods. by metallurgical methods.

[Problem to be solved by the invention] In the magnetic field application type plasma torch according to the conventional technology,
As shown in FIG. 8, the magnetic field line generating coil or magnet is placed above the insulator 6, which has a working gas outlet at the bottom to generate a swirling flow of working gas. When using , the distance from the surface of the cathode l to the magnet 7 becomes long, and in order to secure the specified magnetic field strength on the cathode surface, the volume of the magnet must be increased or a strong magnet with a high residual magnetic flux density must be used. I needed to. Therefore, in order to reduce the rapid consumption of the cathode, there is a problem in that it is necessary to use magnets that are expensive or have extremely low mechanical strength.

Furthermore, in the plasma torch shown in Japanese Utility Model Application Publication No. 41476/1983, when the polarity of the magnetic field and the swirling direction of the working gas are arbitrarily selected, the Lorentz force acting on the surface of the cathode 1 having the concave surface 9 shown in FIG. There are cases where the direction of the force and the swirling direction of the working gas are contradictory, and in such cases, a force is generated that impedes the swirling movement of the discharge point on the cathode surface, so the effect of high-speed movement of the discharge point due to Lorentz force is reduced. There was a problem that the cathode was consumed early.

Next, in the bonded cathode of a plasma torch in which the cathode part is embedded in the tip of the cathode body, when the cathode part is joined by press-fitting, caulking, etc., the finishing accuracy of the joint surface of the cathode body and the cathode part is sufficiently improved. microscopically, the bonding surfaces are in point contact with each other, so there is no electricity or
It cannot be said that heat conduction is necessarily carried out perfectly.

On the other hand, in the case of joining by brazing, the joint surfaces are completely joined, but due to the shape of the cathode part, with brazing it is necessary to completely eliminate the hollow space that is created when gas generated during work does not escape and remains on the joint surface. is difficult, and the hollow portion reduces electrical and thermal conduction. No matter which method is used for bonding, poor electrical conductivity causes misfires and other problems, making it impossible to obtain stable functionality, while poor thermal conductivity causes the cathode to overheat and rapidly wear out. There was a point.

The present invention was made in view of the above-mentioned problems of the conventional technology.In order to reduce the rapid consumption of the cathode, the present invention uses a magnet with a small volume and high mechanical strength, and a swirling airflow of working gas to attach the cathode. The object of the present invention is to provide a magnetic field generating device in which the swirling movement of a discharge point on the surface is not hindered, and a bonded cathode that has good electrical and thermal conductivity and is easy to cool when an arc occurs.

[Means for Solving the Problems] In order to achieve the above object, the plasma torch of the present invention has a working gas outlet for generating a swirling flow of working gas surrounding the plasma arc, and has a working gas outlet that is connected to the cathode. A magnet is placed at the lower end of the cathode, which is coaxially arranged so that the magnetic field configuration is axially symmetrical, and which generates lines of magnetic force that form the magnetic field.

Further, the magnetic field generator is attached with the polarity selected so that the direction of the Lorentz force acting on the surface of the cathode having a concave surface coincides with the swirling direction of the working gas.

As for the bonded cathode, one or more ventilation holes are provided in the cathode body so that a part of the upper end surface of the cathode portion that is bonded to the cathode body is exposed.

[Function] The magnet installed at the lower end of the cathode generates magnetic lines of force at a predetermined magnetic field strength, causing swirling motion at the discharge point on the cathode surface, and the working gas ejected from the working gas outlet produces a swirling flow. and surround the arc.

In addition, by selecting the polarity of the magnetic field generator so that the direction of the Lorentz force generated on the concave cathode surface matches the swirling direction of the working gas, the discharge point can perform stable swirling motion on the cathode surface. be able to.

One or more ventilation holes penetrating the cathode body of the bonded cathode discharge the gas generated when the cathode part and the cathode body are joined by brazing to the outside, and also discharge part of the working gas that swirls when an arc occurs. passes through the ventilation hole to cool the cathode section.

[Example code] Examples will be described with reference to the drawings.

1 and 2 show an embodiment of claim (1), and the cathode l
The cathode part 1a is buried in the lower end of the cathode body lb,
An intermediate nozzle 3 is provided to form a working gas supply path 2 surrounding the cathode 1, and a nozzle 5 is provided to form a shield gas supply path 4 surrounding the intermediate nozzle 3. is surrounded by. An annular ferrite magnet 7 is disposed below the insulator 6, surrounding the lower part of the cathode 1, and coaxially with the cathode 1. The magnet 7 has an axially symmetrical magnetic field configuration, generates magnetic lines of force that form a magnetic field, and has a working gas outlet 8 for generating a swirling flow of working gas surrounding the plasma arc, as shown in FIG. have.

FIG. 3 shows an embodiment of claim (2), in which the cathode 1 has a cathode portion 1a that is axially symmetrical and has a concave surface 9 that is concave upwardly buried in the lower end of the cathode body ib. A magnetic field generator 10 is disposed coaxially above the cathode 1 so that the magnetic field configuration is axially symmetrical and generates magnetic lines of force that form a magnetic field, and a working gas supply path 2 that surrounds the cathode 1 is formed. A nozzle 5 is provided to form an intermediate nozzle 3 and a shield gas supply path 4 surrounding the intermediate nozzle 3. The magnetic field generating device 1.0 is made of a coil or a magnet. For example, when using a magnet, if the swirling direction of the working gas ejected from the working gas swirling device 11 is clockwise when viewed from the opening of the nozzle 5, The magnet is installed with the north pole facing downward, and the direction of the Lorentz force acting on the surface of the cathode 1 is made to coincide with the swirling direction of the working gas.

4 to 7 show embodiments of claim (3), the cathode body 1b and the cathode portion 1a are joined by brazing, and in FIGS. 4 and 5, the cathode body 1b and the cathode Part 1a
At the bottom of the hole into which the cathode part 1a is inserted, make two narrow ventilation holes 13 whose diameter is several times the thickness of the cathode part 12 or more, and after the brazing, a part of the end face of the cathode part 1a is exposed. Penetrate the line. A working gas swirling device 11 is located near the lower end of the bonded cathode 1.
A working gas supply path 2 and an intermediate nozzle 3 are provided on the inside, and a shielding gas supply path 4 and a nozzle 5 are provided on the outside so as to surround the bonding cathode 1.

The cathode main body 1b and the cathode portion 1a may be joined by a method such as press-fitting or caulking.

[Effects of the Invention] Since the present invention is configured as described above, it produces the following effects.

By providing a working gas outlet in the magnet as a magnetic field generator and installing it close to the cathode surface, it is possible to use a magnetic material that is smaller in volume than before and has sufficient mechanical strength. The rotating movement of the discharge point on the surface is reliably performed, and rapid wear of the cathode can be reduced.

In addition, by selecting the polarity and attaching the magnetic field generator, the direction of the Lorentz force acting on the cathode surface always matches the swirling direction of the working gas, and the swirling motion of the discharge point on the cathode surface is maintained during steady operation. Since it becomes stable at times, rapid consumption of the cathode can be prevented.

The ventilation hole drilled in the cathode body of the bonded cathode facilitates the release of gas generated when the cathode body and cathode part are brazed, and prevents internal defects on the bonded surface, so there is no electricity or heat during operation. Since good conductivity is maintained and the working gas passes through the ventilation hole to cool the cathode section, rapid consumption of the cathode can be prevented and its service life can be extended. Furthermore, since the vent hole functions as an air vent when the cathode body and the cathode portion are joined by press-fitting, caulking, etc., it can be utilized in these cases as well.

[Brief explanation of the drawing]

1 to 7 are drawings showing embodiments of the present invention, and FIG. 1 is a cross-sectional view of a main part of a plasma torch in which the magnet described in claim (1) is provided at the lower end of the cathode, and FIG. is A- in Figure 1.
FIG. 3 is a cross-sectional view of the magnet along line A; FIG.
The figure is a sectional view of a bonded cathode provided with ventilation holes according to claim (3), FIG. figure,
Figure 7 is A- of Figure 6 showing cooling of the cathode by working gas.
A cross-sectional explanatory diagram of a working gas swirling device and a cathode along A&I, Fig. 8 is a cross-sectional view of main parts of a conventional magnetic field application type plasma torch, and Fig. 9 is an explanation of the configuration of a magnetic field application type plasma torch in which the cathode has a concave surface. It is a diagram. 1...Cathode 1a...Cathode part 1b...Cathode body 2...Working gas supply path 3...Intermediate nozzle 4... ... Shield gas supply path 5 ... Nozzle 6 ... Insulator 7 ... Magnet 8 ... Working gas outlet 9 ... Concave surface 10 ... Magnetic field generator 11 ... Working gas swirling device 12 ... Brazing part 13 ... Ventilation hole 14 ... Plasma Arc 15 war・φ・φ Skewer holder Fig. 2 Fig. 3 Fig. 412I Fig. 7

Claims (3)

[Claims] (1) A cathode 1, an intermediate nozzle 3 installed to surround the cathode 1 to form a working gas supply path 2, and further installed to surround the intermediate nozzle 3 to form a shield gas supply path 4. A plasma torch equipped with a nozzle 5 has a working gas outlet 8 for generating a swirling flow of working gas surrounding the plasma arc, and is arranged coaxially with the cathode 1 so that the magnetic field configuration is axially symmetrical. , and a magnet 7 that generates lines of magnetic force forming a magnetic field is installed at the lower end of the cathode 1. (2) A cathode 1 having an axially symmetrical cathode shape and a concave surface 9 concave upward, and a cathode 1 disposed coaxially above the cathode 1 and having an axially symmetrical magnetic field configuration and a magnetic field generating device 10 that generates magnetic lines of force to be formed, an intermediate nozzle 3 that surrounds the cathode 1 and is installed to form a working gas supply path 2, and further surrounds the intermediate nozzle 3 to form a shield gas supply path 4. The nozzle 5 and the cathode 1
In the plasma torch, the direction of the Lorentz force acting on the surface of the cathode 1 having the concave surface 9 and the working gas are determined. A structure of a plasma torch characterized in that the polarity of the magnetic field generator 10 is selected so that the rotation direction of the magnetic field generator 10 coincides with the rotating direction of the plasma torch. (3) A bonded cathode 1 having a cathode section 1a buried in the lower end of the cathode body 1b, an intermediate nozzle 3 surrounding the bonded cathode 1 and forming a working gas supply path 2, and furthermore, In a plasma torch equipped with a nozzle 5 that surrounds the nozzle 3 and is installed to form a shield gas supply path 4 , and a working gas swirling device 11 near the lower end of the bonded cathode 1 , the cathode body 1
A structure of a plasma torch characterized in that the cathode body 1b is provided with one or more ventilation holes 13 which are penetrated so that a part of the upper end surface of the cathode part 1a which is joined to the cathode body 1b is exposed.