JPH0523859A - Plasma cutting device and plasma cutting torch therefor - Google Patents

Abstract

PURPOSE:To simplify constitution of a plasma cutting device, to lighten a burden of an operator in nozzle exchange work of a plasma cutting torch and to realize plasma cutting in a spent fuel pool. CONSTITUTION:In the plasma cutting torch 20, the plasma cutting device provided with an electrode 1 and a nozzle 2 adopting a natural cooling system by external water is provided and an arc restraining plate 2d'' is provided on the tip of the nozzle 2 to suppress consumption of the nozzle 2 tip to improve a nozzle service life. In addition, the nozzle exchange work is simplified by dividing the nozzle 2 into a nozzle main body 2a and the nozzle tip 2b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma cutting apparatus and a plasma cutting torch for realizing underwater plasma cutting work as a waste cutting work, and a nozzle and an electrode rod used for the plasma cutting torch.

[0002]

2. Description of the Related Art As examples of conventional plasma cutting apparatus and plasma cutting torch, a plasma cutting machine UR-CTY and a plasma cutting torch UW-51Y (including nozzle and electrode rod) manufactured by Hitachi Seiko Co., Ltd. have been put into practical use. ing. This plasma cutting machine requires a cooling water device for cooling the torch nozzle and the electrode rod. In addition, the structure of the torch is complicated because the nozzle and the electrode rod are cooled by cooling water, and the nozzle consists of two parts because it is necessary to provide a groove for flowing cooling water, and it is manufactured by brazing it. It was difficult to make. In addition, since the nozzle material has high electrical conductivity and uses copper as a material with good thermal conductivity, when used in a spent fuel pool of a nuclear power plant, etc., copper ions will dissolve in the pool water. Ions can attach to the reactor fuel and cause corrosion.

[0003]

In the conventional general plasma cutting apparatus as shown in the above example, since the cutting (or welding) work in the air was originally developed, the plasma cutting The torch had to be forcibly cooled with a cooling water device or the like. Therefore, a cooling water device was required as an auxiliary equipment of the plasma cutting device. Further, in order to forcibly cool the nozzle and electrode rod of the torch with cooling water, cooling is performed while maintaining insulation between the nozzle and electrode rod, and
Since it was necessary to efficiently cool the structure, the structure of the torch portion including the nozzle and the electrode rod was complicated.

An object of the present invention is to use an external water such as pool water around the torch for cooling the torch when the underwater plasma cutting is performed by providing a cutting pool or the like, thereby eliminating the need for a cooling water device. Alternatively, the structure of the torch is simplified by combining the forced cooling by the cooling water device and the natural cooling by the external water.

Further, the nozzle used in the conventional general plasma cutting torch is originally developed with the cutting (or welding) work in the air in mind, and the work performed by the operator directly holding the torch is required. Since it was the main item, it was easily considered as a consumable item. Also, the replacement work of the nozzle,
The frequency was high and it was not considered that the burden on the workers would be heavy, even if it took some effort.

It is an object of the present invention, particularly in plasma cutting (or welding) work performed in a nuclear power plant or the like, in order to reduce the burden on the operator such as exposure due to replacement work of consumables such as the nozzle, the length of the nozzle is reduced. It is to realize a longer life or a shorter nozzle replacement time.

Further, copper has been used for a nozzle used in a conventional general plasma cutting torch because of its high conductivity, good thermal conductivity and low cost. But,
When performing underwater plasma cutting in a pool containing nuclear reactor fuel such as a spent fuel pool of a nuclear power plant, the copper component of the nozzle may dissolve into the pool water as copper ions due to plasma heat. It is not preferable to diffuse the copper component into the pool by plasma cutting because copper ions may cause corrosion when attached to the reactor fuel.

An object of the present invention is to realize an underwater plasma cutting operation in a spent fuel pool of a nuclear power plant.

[0009]

In order to achieve the object of simplifying the torch structure among the above objects, the present invention provides a nozzle for generating a plasma arc in a plasma cutting torch constituting a plasma cutting apparatus. At least one of the electrode rod and the electrode rod has a structure of a plasma cutting torch that is in direct contact with external water so that the cutting pool can be cooled by external water such as pool water.

In order to achieve the object of reducing the burden on the operator among the above objects, the present invention provides a plasma cutting torch which constitutes a plasma cutting apparatus,
In order to prolong the life of the nozzle, the consumption of the nozzle was suppressed by using a means such as adding a highly heat-resistant material such as a ceramic member to the tip of the nozzle. Further, as another means, the part of the nozzle tip, which is likely to be worn, is divided from the nozzle body to facilitate the replacement work of consumable parts.

Further, among the above-mentioned objects, aluminum or the like is adopted as the nozzle material in order to achieve the purpose of realizing water or plasma cutting work in the spent fuel pool of the nuclear power plant.

[0012]

When performing underwater plasma cutting using the plasma cutting device, a current flows between the electrode rod inside the plasma cutting torch and the nozzle (or the object to be cut; hereinafter referred to as the nozzle), and the current flows. The working gas (argon gas or the like) is turned into plasma, a plasma arc (or a plasma jet) is generated, the heat is used to melt the object to be cut, and at the same time, the working gas stream is wiped off to realize cutting. At this time, the nozzle of the plasma cutting torch and the electrode rod are heated by the heat of the plasma arc. At this time, in the present invention, at least one of the nozzle and the electrode rod is in contact with external water such as pool water, and the nozzle or electrode rod is cooled by the influence of the flow of external water accompanying the working gas flow or convection of pool water. It does not melt abruptly and satisfies the specified function. Further, the cooling performance is improved by providing a cooling fin or the like so that the contact area of the nozzle or the electrode rod with the external water becomes large.

Further, for example, when plasma cutting is performed using a nozzle having a highly heat-resistant material such as ceramics added to the tip of the nozzle of the present invention, current flows through the electrode rod inside the plasma cutting torch and the nozzle body. , The arc will be narrowed at the tip. Therefore, even if the nozzle body is worn to some extent, the hole diameter at the tip of the nozzle does not change and the arc is narrowed, so that the cutting performance hardly changes and the nozzle life is extended. Further, in a plasma cutting device using a nozzle divided into a nozzle body and a nozzle tip, when the nozzle is worn out and needs to be replaced, only the nozzle tip is removed without removing the torch cap,
Since a new nozzle tip can be attached, nozzle replacement work can be shortened.

Further, when a material other than copper is used as the nozzle material in the underwater plasma cutting, copper ions do not elute into the water, and therefore there is no restriction on use in the spent fuel pool of a nuclear power plant. .

[0015]

【Example】

<Embodiment 1> One embodiment of the present invention will be described below as Embodiment 1 with reference to FIGS. The first embodiment applies the present invention to a plasma cutting torch 20 for an underwater plasma cutting apparatus.

In FIG. 1, a plasma cutting torch 20 according to the first embodiment is mainly composed of an electrode rod 1 which serves as one electrode (in this example, a negative electrode) when an arc is generated, and a polarity opposite to that of the electrode rod 1 ( Nozzle 2 that can be a positive pole in this example)
An insulating collar 3 and an insulating body 4 for insulating the electrode rod 1 and the nozzle 2, a cap 5 for fixing the nozzle 2, an operating gas hose 7, a minus side power cable 8, and a plus side power cable 9. It is composed of a protection cylinder 6 for protection. Further, the nozzle 2 includes a nozzle body 2a and a nozzle tip 2 having a nozzle hole 2c at the tip.
b, and is electrically connected to the plus side power cable 9 via the holder 10 and the conducting conductor 11,
The electrode rod 1 is electrically connected to the negative power cable 8.

The electrode rod 1 and the insulating body 4 include an electrode rod 1
Cooling holes 1a and 4a for cooling water with external water are opened, and the inner surface of the electrode rod 1 and external water are in contact with each other. Further, the nozzle 2 has a structure in which the outer surface is in direct contact with external water.

In the underwater plasma cutting in the first embodiment, the working gas is supplied from the working gas cylinder 24 through the working gas hose 7 into the torch through the working gas hole 4b provided in the insulating body 4, and the arrow 12a in FIG. , 12
b, 12c and 12d, 12e in this order. In this state, the voltage obtained from the power source 23 by the plasma power source 22 is applied as a no-load voltage between the electrode rod 1 and the nozzle 2 of the plasma cutting torch 20, and is ignited by the high frequency generator 21 to generate the plasma current 13 Flowing between the electrode rod 1 and the nozzle 2, the working gas is turned into plasma, and is narrowed down by the nozzle hole 2c to generate a plasma arc 14. This plasma arc 14
The object to be cut 15 is melted by the heat of and is blown off by the working gas flow 12e to realize cutting. At this time, the electrode rod 1 and the nozzle 2 are heated by the heat of the plasma arc 14, but as described above, both are in contact with the external water and are cooled. However, since the nozzle tip 2b of the nozzle 2 has the highest temperature, the nozzle tip 2b and the nozzle body 2a have a large surface area in order to have a cooling effect, for example, as shown in FIGS. In the example of FIG. 3, the cooling fins 30 are provided in the axial direction of the nozzle 2. In the example of FIG. 4, the cooling fins 40 are provided in the direction perpendicular to the axis of the nozzle 2. Further, in the example of FIG. 5, the surface of the nozzle 2 is increased by making scratches 50 on the surface of the nozzle 2 by knurling.

Further, the nozzle 2 by the plasma arc 14
The consumable part is on the nozzle hole 2c side of the nozzle tip 2b. The nozzle tip 2b is screwed into the nozzle body 2a (not shown) so that only the nozzle tip 2b can be removed without removing the cap 5 when the nozzle is consumed. Installed.

<Second Embodiment> An embodiment of the present invention different from the first embodiment will now be described as a second embodiment with reference to FIGS. 6 and 7. In the second embodiment, the present invention is applied to the nozzle 2 ″ of the plasma cutting torch 20.

FIG. 6 shows the progress of consumption of the conventional nozzle 2 and the diffusion of the arc. As shown in FIG. 6, in the conventional nozzle 2 ', since the entire nozzle 2'is made of a conductor (copper), the consumable portion is concentrated in the vicinity of the nozzle hole 2c' which is a current-carrying portion of the nozzle 2 '. Therefore, as the nozzle 2'is consumed, the diameter of the nozzle hole 2c 'increases, so that the plasma arc flow 14' is gradually stopped. for that reason,
The temperature of the plasma arc stream 14 'decreased, leading to a decrease in cutting ability.

In the second embodiment of the present invention, the nozzle 2 ″ is a nozzle body (a nozzle tip in some cases) 2 which is a conductor.
It is composed of an arc baffle plate 2d ″ made of a material having a high heat resistance (heat resistant ceramic in this example), which is non-conductive with a ″. In this case, as shown in FIG. 7, the nozzle body 2 which is a current-carrying portion due to generation of plasma arc
Even if a ″ is consumed, the arc baffle plate 2d ″ at the tip is hardly consumed, and the plasma arc flow 14 ″ is throttled as in the initial stage, so that the cutting ability does not decrease as the nozzle body 2a ″ is consumed. . Therefore, the life of the nozzle 2 ″ is longer than that of the conventional nozzle 2 ′.

In addition, in the second embodiment shown in FIG. 7, the arc focusing plate 2d ″ is separately provided in addition to the nozzle body 2a ″, but the nozzle body 2a ″ is provided with a method such as ion implantation. It is also possible to make the surface ceramic.

[0024]

According to the present invention, since a plasma cutting device for underwater plasma cutting can be constructed without providing a cooling water device, the device can be simplified.

Further, the use of the natural cooling type nozzle with external water according to the present invention simplifies the nozzle structure and facilitates its manufacture.

Further, according to the present invention, since the life of the nozzle of the plasma cutting torch can be extended or the replacement work time can be shortened, it is possible to reduce the burden on the worker such as the exposure reduction in the waste treatment at the nuclear power plant and the like. You can

Further, by using a nozzle other than copper as the nozzle material, it is possible to realize a plasma cutting operation in a pool containing nuclear reactor fuel such as a spent fuel pool of a nuclear power plant.

[Brief description of drawings]

FIG. 1 is a sectional view of a plasma cutting torch according to an embodiment of the present invention.

FIG. 2 is a system diagram of a plasma cutting device using the plasma cutting torch shown in FIG.

FIG. 3 is a perspective view of a nozzle having cooling fins according to a second embodiment of the present invention.

FIG. 4 is a sectional view of a nozzle having cooling fins according to a second embodiment of the present invention.

FIG. 5 is a side view showing an example of a nozzle having a surface provided with a flaw by cooling knurls according to a second embodiment of the present invention.

FIG. 6 is a cross-sectional view showing the degree of progress of conventional nozzle wear and the accompanying spread of the plasma arc.

FIG. 7 is a cross-sectional view according to the third embodiment of the present invention, which shows that the plasma arc hardly changes even when the nozzle according to the present invention is used as compared with the conventional nozzle even when the nozzle is consumed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electrode rod, 2 ... Nozzle, 2a ... Nozzle body, 2b ... Nozzle tip, 2c ... Nozzle hole, 3 ... Insulating collar, 4 ... Insulating body, 5 ... Cap, 6 ... Protective cylinder, 7 ... Working gas hose, 8 ... Minus power cable, 9 ... Power cable, 10 Holder, 11 Conductor, 12a-12
e ... Working gas flow, 13 ... Plasma current, 14 ... Plasma arc, 15 ... Object to be cut, 20 ... Plasma cutting torch.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tomiji Yoshida             3-1-1 Sachimachi, Hitachi City, Ibaraki Prefecture Stock Association             Hitachi, Ltd.Hitachi factory

Claims (8)

[Claims] 1. A plasma cutting power source for supplying a current to a plasma torch, an ignition device such as a high frequency generator for performing arc ignition, and an operating gas supply device such as a gas cylinder for supplying an operating gas. In a plasma cutting device consisting of a plasma torch for cutting or welding using a plasma arc, a plasma torch that can cool the torch during underwater cutting with external water such as pool water of the cutting pool is provided. A plasma cutting device characterized in that a cooling water device for supplying cooling water other than water is not provided. 2. The plasma cutting device according to claim 1, wherein one of the nozzle of the torch and the electrode rod is cooled by a cooling water device such as a cutting pool that supplies cooling water other than external water. 3. The plasma cutting apparatus according to claim 1 or 2, wherein a nozzle or an electrode rod has a large surface area in order to utilize a cooling effect of external water such as a cutting pool. A plasma cutting torch with an electrode rod. 4. A plasma cutting torch provided with a nozzle at the tip of the nozzle, characterized in that a material having high heat resistance such as ceramics is added to the nozzle body separately from the nozzle body. 5. A plasma cutting torch having a nozzle according to claim 4, wherein the nozzle tip surface is made non-conductive such as ceramic by ion implantation or the like at the tip of the nozzle body. 6. A plasma cutting torch, characterized in that the nozzle is divided into a nozzle body and a nozzle tip so that only the nozzle wear portion can be replaced without removing the cap that holds the nozzle at the tip of the torch. torch. 7. The plasma cutting apparatus according to claim 1 or 2, wherein a nozzle made of a material other than copper is used as the nozzle material. 8. The nozzle for use in a plasma cutting torch according to claim 3, wherein the nozzle is integrated.