JPH069740B2 - Rotating electrode of axo-cutting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a rotary electrode of an oak saw cutting device used for cutting steel material such as a reactor vessel in water in a nuclear power plant, for example. .

(Prior Art) For example, in a nuclear power plant, equipment such as a reactor pressure vessel suppresses the life after long-term use. In that case, it is necessary to completely dismantle and remove the equipment such as the reactor pressure vessel. At that time, it is necessary to cut the structure in water, and there are the following cutting methods for such work. That is, a gas cutting method, a method combining a gas cutting method and a gouging method,
Hot water jet cutting method, plasma cutting method,
And electric discharge machining method. However, such a method has a problem in cutting steel materials such as thick-walled plates and tubes activated in a nuclear reactor in water. For example, in the case of the above-mentioned gas cutting method, cutting becomes impossible when there is an austenitic stainless steel clad.
In addition, the method that combines the gas cutting method and the Gougeung method has not been put to practical use yet, and even if it is put to practical use, the cutting speed is slow and at the same time there are many by-products during cutting. Not suitable for cutting radioactive materials.

Under such circumstances, a cutting method such as arc saw cutting has been considered. A conventional example will be described below with reference to FIGS. 6 to 8. In FIG. 6, reference numeral 1 is a rotary electrode, and the rotary electrode 1 is fixed to a shaft 3 rotatably installed in a casing 2. As shown in FIG. 6, slits 1A are formed on the outer peripheral edge of the rotary electrode 1 at equal intervals in the circumferential direction, and the slits 1A scrape out and remove the melted material (melting slag) generated during cutting. . The shaft 3 is connected to a hydraulic motor installed outside the casing 2, and the rotary electrode 1 is rotated by driving the hydraulic motor. Inside the casing 2, a copper brush 5 is installed on the outer circumference of the shaft 3, and the copper brush 5 has a cable 5 and a cable 6
Is connected to one pole (− pole) of the DC power supply 7 via. On the other hand, an object 9 to be cut is connected to the other pole (+ pole) of the DC power source 7 via a cable 8.

The casing 2 is the piston 1 of the hydraulic cylinder mechanism 10.
Therefore, the casing 2 slides in the direction in which it separates from or comes into contact with the object 9 to be cut by the uride of the piston 11. The hydraulic cylinder mechanism 10 is controlled by a servo system 12. That is, the rotating electrode 1
The cutting current in the case of cutting the object to be cut by bringing it close to the object 9 is detected by the ammeter 13 inserted in the cable 6, and the detection signal is input to the current comparator 14. The current comparator 14 includes a control panel 15 in addition to the above detection signal.
The control signal set in advance is input by. The current comparator 14 compares the detection signal and the control signal and outputs the difference to the servo system 12 as a difference signal. The servo system 12 uses the difference signal as a basis for the hydraulic cylinder mechanism 1
By controlling 0, the cutting current is kept constant. Reference numeral 16 in the drawing denotes an air inlet, through which compressed air as a shield gas is injected into the casing 2 through the air inlet 16 to shield the power supply portion of the rotary electrode 1.

The above configuration has the following problems. That is, when a thick object 9 is to be cut with the conventional structure, the phenomenon in which the arc current becomes unstable occurs despite the constant current control as shown in FIG. There was a problem that the required cutting could not be performed and a short circuit phenomenon occurred during the cutting to make the cutting impossible. In FIG. 8, the horizontal axis represents the rotary electrode feed and the vertical axis represents the current, showing the change in current. Further, when cutting is interrupted midway, an oxide film is formed on the cut surface, and there is a problem that an arc is less likely to occur due to the influence of the oxide film and it becomes impossible to continue cutting thereafter. The cause of the short circuit is that the current flow abnormally increases between the side surface of the cutting groove of the workpiece 9 and the side surface of the rotating electrode 1, and the current at the tip of the rotating electrode 1 required for cutting is insufficient. It has been found to be due to.

In order to solve the above-mentioned problems, a configuration has been considered in which the side surface of the rotary electrode 1 is covered with an insulating material and the cutting current is concentrated on the tip portion. However, such a structure has the following problems. That is, in the above configuration, the lengths of the non-insulating part and the insulating part are not specified. For example, in the case of a short non-insulating part (50 mm or less), the molten metal generated during cutting logically rotates. Although it is supposed to be removed by the centrifugal force of the electrode 1, it actually enters between the insulating material and the side surface of the cutting groove and is cooled and solidified there.
Since the cooled and solidified molten metal does not melt due to the electric current, it becomes a rotational resistance between the side surface of the rotating electrode 1 and
There was a problem that it hindered the operation.

(Problems to be Solved by the Invention) As described above, in the conventional configuration, the lengths of the non-insulating portion and the insulating portion are not specified, and the action and effect thereof are not clear. There is a problem that the molten metal enters the cutting groove and is cooled and solidified to become a resistance of the cutting operation. The present invention has been made on the basis of such a point. In the structure in which the side surface of the is covered with an insulating member, the current is concentrated at the tip of the rotating electrode, and the molten metal enters the cutting groove and is cooled and solidified to become a resistance of the cutting operation. It is an object of the present invention to provide a rotating electrode of an arc saw cutting device capable of effectively eliminating the above problem.

[Structure of the Invention] (Means for Solving Problems) That is, the present invention provides an arc saw cutting device including a metal disk and ring-shaped insulating members provided on both surfaces of the disk. In the rotating electrode, the outer peripheral edge portion of the disk is 100 to 15 radially from the outer peripheral edge portion of the insulating member.
It is characterized in that the surface of the insulating member is provided at a position recessed from the side surface of the disk by at least 0.5 mm while projecting about 0 mm.

(Operation) In other words, in a rotating electrode in which insulating members are concentrically attached to both sides of a metal disc, a non-insulating portion with a width of 100 to 150 mm is secured on the outer peripheral portion of the disc and covered with an insulating member. The recessed insulating portion is recessed from other non-insulating portions to prevent a short circuit phenomenon and an increase in rotation resistance due to solidification of the molten metal.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 5. FIG. 1 is a plan view of a rotary electrode according to this embodiment, and FIG. 2 is a sectional view taken along line II-II of FIG. Reference numeral 1 in the figure
Reference numeral 01 denotes a metal disc, and a plurality of slits 101A are formed on the outer peripheral portion of the disc 1. Also the disk 10
A through hole 101B for fixing the rotating shaft is formed at the center of the No. 1. As shown in FIG. 2, annular recesses 102 are formed on both surfaces of the disc 101, and an annular insulating member 103 is attached to each of these annular recesses 102. The insulating member 103 is fixed to the disc 101 by a plurality of screws 104. The width (indicated by l in FIG. 2) of the outer peripheral portion (hereinafter referred to as the non-insulating portion) of the disc 101 which is not covered by the insulating member 103 is 100 to 150 mm. This is because when the thickness is 100 mm or less, the area of the side surface that blows the arc is reduced and the function of scraping the molten metal is impaired. The reason why it is set to 150 mm or less is that if it is larger than that, the current cannot be concentrated on the tip portion. Further, the portion to which the insulating member 103 is attached is recessed more than the other portions, and the recessed amount (shown by symbol h in FIG. 2) is 0.5 mm or more as shown in FIG. This is to effectively prevent adhesion and singulation of the molten metal by appropriately providing a gap between the insulating portion having no melting function and the object 105 to be cut.

The operation will be described based on the above mechanism. That is, as shown in FIGS. 3 and 4, the rotary electrode melts and cuts the object 105 while flowing a current in the outer peripheral portion. Then, as shown in FIG. 4, the rotary electrode moves in the direction A in the figure, and at this time, the side surface of the non-insulating portion is cut while flowing a current between the side surface of the non-cutting object 105 and the groove side surface. The molten metal is scraped out together with the function of the slit 101A.

According to this embodiment, the following effects can be obtained.

First, since the insulating member 103 is attached, the insulating member 103 effectively prevents a current from leaking between the rotary electrode and the groove side surface of the object 105 to be cut when cutting is continued. Therefore, the arc current can be concentrated on the outer peripheral portion of the disc 101, and a short circuit can be prevented.

Also, an appropriate length (100 to 150 mm) is provided on the outer peripheral portion of the disc 101.
Since the insulated portion is secured, the arc current can be concentrated on the outer peripheral portion, and the area where the arc is blown can be secured on the side surface, and the molten metal is effective in combination with the function of the slit 101A. Can be scraped off.

Also, because the insulating member 103 is recessed (5 mm
Above) It is possible to secure an appropriate gap between the insulating portion and the object 105 to be cut, and effectively prevent the molten metal from adhering and solidifying to the insulating portion, which has been a concern in the past, and an increase in rotation resistance. can do. In particular, in the case of this embodiment, both surfaces of the rotary electrode are so configured, which is extremely effective.

Due to the above effects, problems such as the occurrence of a short circuit phenomenon, which is a problem when cutting a thick plate material, a decrease in the rotation speed due to an increase in the rotation resistance, and the problem that the rotation cannot be performed are effectively solved, and the cutting work is greatly performed. In addition to being prepared, the work time is shortened, and in the case of dismantling work of nuclear equipment, radiation exposure of workers can be effectively eliminated. The change in current in the case of this embodiment is shown in FIG. This fifth
As shown in the figure, it can be seen that there is no large disturbance and a stable cutting operation is performed.

The present invention is not limited to the one embodiment described above, and the recessed amount of the insulating portion may not be 0.5 mm or more, for example. As described above, it is particularly effective when the thickness is 0.5 mm or more, but it is within the scope of the present invention when recessed by an amount less than 0.5 mm. In some cases, only one of the surfaces of the rotary electrode may be recessed. For example, when the rotating electrode rotates in a horizontal state, there is a concern that molten metal may adhere and solidify on the upper surface side, and in that case, at least the upper surface side may be recessed to obtain the effect.

[Effects of the Invention] As described in detail above, the rotating electrode of the arc saw cutting apparatus according to the present invention prevents a short circuit phenomenon during cutting and effectively increases the rotational resistance due to adhesion and solidification of molten metal. It is possible to solve the above problems, and it is possible to provide a smooth cutting operation.

[Brief description of drawings]

1 to 5 are views showing an embodiment of the present invention.
The figure is a plan view of the rotary electrode, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, FIG. 3 is a sectional view showing the action, and FIG. 4 is a sectional view taken along the line IV- of FIG.
IV arrow view, FIG. 5 is a characteristic diagram showing a change in current at the time of cutting, and FIGS. 6 to 8 are diagrams for explaining the conventional example.
FIG. 7 is a diagram showing a schematic configuration of an arc saw cutting device, FIG. 7 is a plan view of a rotary electrode, and FIG. 8 is a characteristic diagram showing a current change at the time of cutting. 101 ... Disc, 102 ... Annular recess, 103 Insulating member.

Claims (1)

[Claims] 1. A rotating electrode of an arc saw cutting device comprising a metal disc and annular insulating members provided on both sides of the disc, wherein the outer peripheral edge of the disc is the insulating member. A rotary electrode for an arc saw cutting device, which is protruded from the outer peripheral edge portion in the radial direction by about 100 to 150 mm and the surface of the insulating member is recessed from the side surface of the disc by at least 0.5 mm or more. .