JPS63264270A - Rotary electrode for arc saw cutting device - Google Patents

Abstract

PURPOSE:To prevent the short circuit phenomenon, the solidification of a molten metal and the increase in the rotation resistance thereby by securing a non- insulating part in specific width on the outer periphery of a metal made disk and hollowing the insulating part covered by an insulating material more than the other non-insulating part as well. CONSTITUTION:An annular recessed part 102 is respectively formed on both faces of a metal made disk 101 and an annular insulating member 103 is fitted to these recessed parts 102. The width l of the outer peripheral part (non- insulating part) not covered by the insulating member 103 of the disk 101 is 100-150mm. The part to which the insulating member 103 is fitted is hollowed more than the other parts and its recessed amt. is >=0.5mm. The current leaking in cutting is prevented by the insulating member 103 to hollow the part of the insulating member 103, hence the sticking and solidification of a molten metal are thus prevented.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention can be applied, for example, to a nuclear power plant.

The present invention relates to a rotating electrode of an arc saw cutting device used when cutting steel materials such as nuclear reactor vessels underwater.

(Prior Art) For example, in a nuclear power plant, a vessel such as a reactor pressure vessel reaches the end of its life after long-term use.

In that case, it is necessary to completely dismantle and remove equipment such as the reactor pressure vessel. At this time, it is necessary to cut the structure underwater, and the following cutting methods are available for such work.

In other words, gas cutting method, □method combining gas cutting method and gouging method, "water jet cutting method using electrode,"
These include plasma cutting methods and electrical discharge machining methods. However, with this method, there is a problem in cutting underwater steel materials such as thick plates and pipes that have been activated in a nuclear reactor. For example, in the case of the gas cutting method described above, if there is a cladding of austenitic stainless steel, cutting becomes impossible. Furthermore, a method that combines the gas cutting method and gouging method has not yet been put to practical use, and even if it were to be put into practical use, the cutting speed would be slow and there would be a lot of by-products during cutting. Not suitable for cutting radioactive materials.

Under these circumstances, a cutting method called arc saw cutting has been considered. A conventional example will be explained below with reference to FIGS. 6 to 8. Reference numeral 1 in FIG. 6 is a rotating electrode, and this rotating electrode 1 is fixed to a shaft 3 rotatably installed in a casing 2. As shown in FIG. 6, slits 1A are formed at equal intervals in the circumferential direction on the outer peripheral edge of the rotating electrode 1, and the slits 1A scrape out and eliminate the molten material (molten slag) generated during cutting. . This shaft 3 is connected to a hydraulic motor installed outside the casing 2, and by driving this hydraulic motor, the rotating electrode 1 is rotated. Inside the casing 2, a copper brush 5 is installed on the outer periphery of the shaft 3, and this copper brush 5 is connected to one pole (-pole) of a DC power source 7 via a cable 6. On the other hand, the object to be cut 9 is connected to the other ffi (+lU) of the DC power supply 8!7 via a cable 8.

The casing 2 is a piston 1 of a hydraulic cylinder mechanism 10.
1, and the sliding of this piston 11 causes the casing 2 to slide toward and away from the object 9 to be cut. The hydraulic cylinder mechanism 10 is controlled by a servo system 12. That is, when cutting is performed by bringing the rotating electrode 1 close to the object 9 to be cut, the cutting current is detected by the ammeter 13 inserted in the cable 6, and the detection signal is input to the current comparator 14.

This current comparator 14 includes a control 2D signal in addition to the above detection signal.
A preset control signal is input by W15. The current comparator 14 compares these detection signals and the υItll signal, and outputs the difference as a difference signal to the servo system 12. The servo system 12 operates the hydraulic cylinder mechanism 10 21'drJ based on this difference signal to maintain the cutting current constant.

In addition, the reference numeral 16 in the figure indicates an air inlet, and this air inlet 1
Compressed air as a shielding gas is injected into the casing 2 through the casing 6 to shield the power supply section of the rotating electrode 1.

According to the above configuration, there were the following problems.

That is, when trying to cut a thick object 9 with the conventional configuration, a constant current R+II 0 is applied as shown in FIG.
0, the arc current becomes unstable, and the required cutting cannot be performed, and a short circuit occurs during cutting, making it impossible to cut. . In addition, FIG. 8 shows the current change, with the horizontal axis representing the rotary electric current tea feed and the vertical axis representing the current. Further, when cutting is interrupted midway, an oxide film is formed on the cut surface, and due to the influence of the oxide film, arcing becomes difficult to occur, making it impossible to continue cutting thereafter. The cause of the short circuit mentioned above is the cutting of the workpiece 9.
It has been found that this is caused by an abnormal increase in the current flow between the side surface of fA and the side surface of the rotating electrode 1, resulting in insufficient current at the tip of the rotating electrode 1 required for cutting.

In order to solve the above problems, a configuration has been considered in which the side surface of the rotating electrode 1 is covered with an insulating material and the cutting current is concentrated at the tip. However, this configuration has the following problems. In other words, in the structure described above, the lengths of the non-insulated part and the insulated part are not specified, and for example, the length of the non-insulated part is not specified.
8 In the case of short edges (50#ll11 or less), the molten metal generated during cutting is theoretically supposed to be removed by the centrifugal force of the rotating electrode 1, but in reality, the molten metal is removed by the insulating material. It enters between the side surface of the cutting groove and is cooled and solidified there. Since this cooled and solidified molten metal is not melted by electric current, there is a problem in that it creates rotational resistance with the side surface of the rotating electrode 1, impeding its operation.

(Problems to be Solved by the Invention) As described above, in the conventional configuration, the lengths of the non-insulated part and the insulated part are not specified, and the effects and effects thereof are not clear. There is a problem in that molten metal enters the cutting groove and is cooled and opened up, creating resistance to the cutting operation.The present invention was made based on this point, and its purpose is to The side surface of the rotary electrode is covered with an insulating material, and the current is concentrated at the tip of the rotating electrode, and the molten metal enters the cutting groove where it is cooled and solidified, providing resistance to photopic operation. An object of the present invention is to provide a rotary snow shovel for an arc saw cutting device that can effectively solve such problems.

[Structure of the Invention] (Means for Solving the Problems) That is, the rotating electrode of the arc saw cutting 11B device according to the present invention is a rotating electrode formed by attaching insulating members to both sides of a metal disk concentrically with the disk. In the above, the outer peripheral part of the disk is a non-insulated part, and the width of this insulated part is 100 to 1
50 m, and the insulating part covered with the insulating member is recessed relative to the non-insulating part.

(Function) In other words, it is a rotating electrode in which insulating members are attached concentrically to both sides of a disc made of gold B, and 100 to 150
By ensuring a non-insulated part with a width of m, and by recessing the insulated part covered by the insulating member from other non-insulated parts, short circuit phenomena can be prevented and rotational resistance increased due to thinning of the molten metal. It is intended to prevent

(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 the rotating electrode according to this embodiment, and FIG. 2 is a sectional view taken along line 11-4 in FIG. Reference numeral 101 in the figure is a metal disc, and a plurality of slits 101A are formed in the outer circumference of this disc 1. Also disk 1
There is a through hole 101B in the center of 01 for fixing the rotating shaft.
is formed. As shown in FIG. 2, four annular portions 102 are formed on both sides of the disk 101, and these core annular recesses 102 have annular! Eight edge members 103 are attached. the above! 8 edge material '103 is fixed to the disc 101 with PJ number of screws 104. The width (indicated by λ in the second factor) of the outer peripheral portion of the disk 101 that is not covered by the insulating member 103 (hereinafter referred to as non-insulating portion) is 100 to 150M. This is because if the arc is less than 100 μm, the area of the side surface where the arc is blown is reduced and the molten metal scraping function is impaired. Also 150 mtt
The reason why it is set to be less than r is because if it becomes larger than that, it becomes impossible to concentrate the current at the tip. Further, the part where the insulating member 103 is attached is more depressed than the other parts, and as shown in FIG. 2, the depression base (indicated by the reference numeral in FIG. 2) is 0.5 rNR or more. This is to effectively prevent adhesion and thinning of molten metal by providing an appropriate gap between the insulating portion, which does not have a melting function, and the object 105 to be cut.

The operation will be explained based on the above configuration. That is, as shown in FIGS. 3 and 4, the rotating electrode melts and cuts the object 105 while passing a current through its outer circumference. Then, as shown in FIG. 4, the rotating electrode moves in the direction shown in the figure, and at this time, it cuts while passing current between the side surface of the non-insulated part and the side surface of the groove of the object to be cut 105. Combined with the function of the slit 101A, one molten metal is ejected.

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

■First, since the insulating member 103 is attached, when continuing cutting, the current leaking between the cut groove side surface of the cut object 105 and the rotating electrode is effectively prevented by the insulating member 103. . Therefore, the arc current can be concentrated on the outer circumference of the disk 101, and short circuits can be prevented.

■Also, add an appropriate length to the outer periphery of the disc 101.
50m> Supply 1) Since the alt is secured, in addition to the above-mentioned effect of concentrating the arc current on the outer periphery, it is also possible to secure an area for blowing the arc on the side, which is combined with the function of the slit 101A. Molten metal can be scraped out effectively.

■Also, since the insulating member 103 is recessed (5#
Above) An appropriate gap can be secured between the insulating part and the object to be cut 105, effectively preventing molten metal from adhering and solidifying to the insulating part and increasing rotational resistance, which was a concern in the past. can do. Particularly, in the case of the 39th case of this embodiment, both surfaces of the rotating electrode have such a structure, which is extremely effective.

■As a result of the above effects, the problems that occurred when cutting thick plates, such as the occurrence of short circuits, decreases in rotational speed due to increased rotational resistance, and even the inability to rotate, have been effectively resolved, making cutting work easier. This greatly facilitates the work, reduces work time, and effectively eliminates radiation exposure of workers when dismantling nuclear power facilities. Incidentally, FIG. 5 shows the change in current in the case of this embodiment. This fifth
As shown in the figure, there were no major disturbances, indicating that a stable cutting operation was being performed.

It should be noted that the present invention is not limited to the above-mentioned embodiment; for example, the maximum recess of the insulating portion may not be 0.5 rmx or more. As mentioned above, it is particularly effective when the amount is 0.5 M or more, but the scope of the present invention also falls under the scope of the present invention when the amount is less than 0.5 M. 'In some cases, only one surface of the rotating electrode may be recessed. For example, when a rotating electrode rotates horizontally, molten metal may adhere to the top surface.
There is a concern that solidification may occur, and in that case, simply recessing the upper surface may be effective.

[Effects of the Invention] As detailed above, the rotating electrode of the arc saw cutting device according to the present invention prevents short-circuiting during cutting, and effectively solves problems such as increased rotational resistance caused by adhesion and solidification of molten metal. Its effects are great, such as being able to solve problems and provide smooth cutting operations.

[Brief explanation of drawings]

Figures 1 to 5 are diagrams showing one embodiment of the present invention.
The figure is a plan view of the rotating electrode, FIG. 2 is a sectional view taken along the line MM in FIG. 1, FIG. 3 is a sectional view showing the action, and FIG.
IV arrow view, Figure 5 is a characteristic diagram showing the current change during cutting,
Figures 6 to 8 are diagrams used to explain conventional examples. Figure 6 is a diagram showing a schematic configuration of an arc saw cutting device, Figure 7 is a plan view of a rotating electrode, and Figure 8 is a current flow during cutting. FIG. 3 is a characteristic diagram showing changes. 101... Disk, 102... Annular recess, 103 Insulating member. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 τ Figure 6 Figure 7

Claims (3)

[Claims] (1) In a rotating electrode consisting of a metal disc with insulating members attached concentrically to both sides of the disc, the outer periphery of the disc is a non-insulated part, and the width of this non-insulated part is 100 mm. ~1
50 mm, and the insulating part covered with the insulating member is recessed relative to the non-insulating part. (2) The rotating electrode for an arc saw cutting device according to claim 1, wherein the insulating part covered with the insulating member is recessed by 0.5 mm or more with respect to the non-insulating part. (3) The rotating electrode for an arc saw cutting device according to claim 1, wherein the insulating portion covered with the insulating member is recessed relative to the non-insulating portion on both surfaces.