JP2000317661A - Method and device for cutting by laser beam and method for cutting graphite block in the case of dismantling waste nuclear reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for cutting a material which has flexibility enabled by locating a laser torch far away from a driving source, is light weighted and easy to handle, and generates less amount of secondary products due to cutting. SOLUTION: In a cutting method by laser beam by which a laser torch is used to converge laser beam by a condensing lens and to project light on an object to be cut, and thus formed converged beam is surrounded and subjected to injection of water jet to execute cutting the object to be cut, the distance between the laser torch 1 at the time of executing gouging and the cutting surface of the object to be cut is set so as to be not less than the thickness of the object to be cut, a focus of the condensing lens 4 is made into a longer focus by the surrounding water jet, and then the cutting object 14 is cut after continuous gouging of several times of descending of the laser torch 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cutting a material by a laser beam, an apparatus for implementing the method, and a method for cutting a graphite block taken out of a nuclear reactor decommissioning applying the laser beam cutting method. About.

[0002]

2. Description of the Related Art Rotating EDM (el
ectric discharge machining), roll cutter, plasma cutting, abrasing water jet (AW)
J), CO laser cutting, and a combination of a YAG laser and AWJ are known. The YAG laser cutting method using an operating gas has a feature that the cutting width is narrow and no abrasive is required, so that there is little secondary processing after cutting, but there is a disadvantage that the one-through cutting thickness is small. .

Japanese Patent Application Publication No. Hei 10-500903 discloses a method of cutting a material by a laser beam, in which a solid liquid jet transparent to laser radiation is generated from a nozzle passage before emitting laser radiation. A method is described wherein the laser beam is optically coupled to the jet and directed at the material to be cut.

Japanese Patent Application Laid-Open No. 2-59190 discloses that a thick plate is laser-cut by tandemly disposing a trailing nozzle for injecting only assist gas from behind a preceding coaxial nozzle for simultaneously performing laser irradiation and assist gas injection. In doing so, gouging a part of the thick plate in the thickness direction with the preceding coaxial nozzle, and then injecting a supersonic assist gas from the following nozzle, which is a divergent type, into the inside of the gouging groove. A laser cutting method for a thick plate is described.

[0005]

SUMMARY OF THE INVENTION A method for cutting a material which has flexibility, is lightweight and easy to handle by being able to separate a laser torch from a driving source, and realizes reduction of secondary products by cutting. It is an object of the present invention to provide an apparatus and a method for easily cutting a graphite block to be treated when dismantling a nuclear reactor decommissioning vessel.

[0006]

According to the present invention, a water jet is used to separate a tip of a torch from a base material, to reduce a cutting width, to perform downing by a torch for continuous gouging, and to use a laser beam. A method and an apparatus for cutting a thick plate material in the air while reducing secondary products.

Specifically, the present invention uses a laser torch for converging a laser beam with a converging lens and irradiating the condensed beam with a work, and encircling and jetting the formed condensed beam with a water jet. In a cutting method using a laser beam for cutting a cutting object, a distance between the laser torch and a cutting surface of the cutting object when performing gouging is set depending on a thickness of the cutting object, and particularly, to a thickness equal to or more than the thickness. The present invention provides a cutting method using a laser beam that sets and sets a long focus with a warder jet surrounding the focal point of the condenser lens and performs continuous gouging to lower the laser torch a plurality of times to cut an object to be cut.

The present invention further provides a laser beam cutting method in which the distance is set to 50 to 200 mm.

According to the present invention, the long focal length is set to 100 to 100.
A cutting method using a laser beam of 150 mm is provided.

The present invention further provides a cutting method using a laser beam in which lasers from a plurality of laser beam sources are combined and the jet diameter of a water jet is set to approximately 0.1 to 0.4 mm (a cutting width is reduced). provide.

The present invention uses a laser torch for condensing a laser beam with a condenser lens and irradiating the object with a laser beam, and injecting a formed beam spot with a water beam to cut the object to be cut. In the beam cutting device, the laser torch is provided with a laser beam cutting device including a torch lowering device that lowers the laser torch a plurality of predetermined times and performs continuous gouging at the time of cutting.

The present invention further provides a laser beam cutting apparatus, wherein the laser torch is provided with a water jet nozzle having a diameter of 0.1 to 0.4 mm.

The present invention further comprises a plurality of laser oscillators, an optical fiber cable connected to the laser oscillator, and the laser torch synthesizes a plurality of lasers from the optical fiber cable to form a condenser lens. A cutting device using a laser beam to be introduced is provided.

According to the present invention, in a method of cutting a graphite block when dismantling a nuclear reactor decommissioning vessel, a laser beam is condensed on the graphite block taken out upon dismantling of the nuclear reactor decommissioning by a laser torch for condensing the laser beam. Irradiate, around this irradiated beam, inject a warder jet into the graphite evaporator of the graphite block, and when dismantling the reactor decommissioning furnace that cuts the laser torch by performing continuous gouging on the graphite block. And a method for cutting a graphite block.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows an apparatus according to an embodiment of the present invention when the environment is air. In the figure, a laser torch 1 has two condenser lenses 3, 4 inside a main body 2 thereof.
A protective glass 11 is provided behind the two mirrors 5 and 6 and the condenser lens 4. The laser torch 1 is provided with a water jet nozzle 10 composed of a pressurized water chamber 9 and quartz at the outlet, to which two optical fiber cables 7, 8 are connected at the inlet. Furthermore, the laser torch 1 is provided with its lowering device 12, to which a position controller 13 for its movement is connected. Reference numeral 14 denotes an object to be cut, for example, a graphite block.

The beams flowing through the two optical fiber cables 7 and 8 are laser-combined and introduced into the laser torch 1. The laser beam 15 is converted into a parallel laser beam 16 by a condenser lens, reflected by mirrors 5 and 6, converged by the condenser lens 4, passes through the protective glass 11, and forms a beam spot 17. On the other hand, pressurized water 18
(In this case, 50 MPa) is introduced, and is injected from the water jet nozzle 10 toward the workpiece while surrounding the laser beam, that is, the beam spot 17. The diameter of the water jet nozzle 10 is as narrow as 0.1 to 0.4 mm. As a result, the cutting width is reduced and the workpiece 1
4 can be cut, and secondary generation is reduced.

The distance between the laser torch 1 and the workpiece 14 at the time of the first gouging is determined by the thickness of the workpiece 4. The thickness is set to 70 to 80 mm for a thickness of 50 mm, and to 140 to 150 mm for a thickness of 100 mm.
In the figure, it is about 100 mm. The focal length of the condensing lens 4 is determined so that the laser beam condensed by the condensing lens 4 forms a beam spot 17, but the laser beam 21 having formed the beam spot 17 is It is confined and reaches the workpiece 14 without leaking to the outside. That is, the focal length of the condenser lens 4 is apparently subjected to the effect of increasing the focal length by the water jet 22 as in the workpiece 14. It is easy to control the width of the water jet 22 to be constant, and the water jet nozzle diameter is 0.1 to 0.1.
A diameter of 0.4 mm will be maintained. That is, 0.1 to
The laser beam 22 and the water jet 21 impinge on the workpiece 14 with a narrow body width of 0.4 mm.
A strong cutting force is applied to the workpiece 14 while the tip of the laser torch 1 is kept away from the workpiece 14 to cut the workpiece. When a certain distance is cut, the lowering device 12 is operated to lower the laser torch 1 (down).
I do. FIG. 2 shows a state in which the laser torch is lowered. In the case shown in the figure, four successive descents are performed. That is,
Continuous gouging is implemented.

In FIG. 2, the workpiece 14 is cut by continuous gouging while lowering the laser torch. By lowering the laser torch 1 a plurality of times and performing gouging continuously, a thick plate (material) can be cut.

Next, a method for cutting a graphite block taken out when dismantling a nuclear reactor decommissioning using the method and apparatus of the present invention will be described. Usually, the graphite block has a hexagonal shape and counts tens of thousands, and it is an essential condition that its cutting is quick and the amount of secondary products is reduced.

FIG. 3 shows a known method for removing a graphite block. The graphite block 33 is taken out of the nuclear reactor 31 by the take-out device 32, passed to the receiving device 34, passed to the next secondary receiving device 35, placed in the transport container 36, and transported by the transport vehicle 37.
Is carried out by The steps are shown as A → B → C → D, but they are well known and need no further explanation.

In FIG. 4, since high energy is desirable for cutting and cutting while rotating the graphite block 41, two laser oscillators 42 and 43 are used. Accordingly, two cooling devices 44 and 45 are used, and two control personal computers 46 and 47 are used.

The lasers oscillated from the two laser oscillators 42 and 43 are guided to the laser torch 1 via two optical fiber cables 7 and 8. Pressurized water from the water jet pump device 48 is applied to the laser torch 1.
Will be introduced.

FIG. 5 shows the function and principle of cutting when a laser shet composed of a laser beam and a water jet 50 is jetted from the laser torch 1. Graphite evaporation section 5
1 is blown off by the water jet nozzle 10 to perform continuous gouging cutting while preventing burning of graphite.
The automatic position adjustment of the laser torch 1 for focusing on the gouging position is performed.

The focus of the condenser lens 4 can be made longer by narrowing the laser beam by the water jet and increasing the energy density. Further, by setting the width of the warder jet to a small value of 0.1 to 0.4 mm, the cutting width can be minimized and the cutting thickness can be increased. still,
The pressure of the water jet is 50 to 200 MPa Can be set to

FIG. 6 shows the function of laser cutting in ambient air when the working medium is a water jet. It is possible to obtain a thin plate high-precision cutting and cleaning effect, and a thick plate cutting and cleaning effect. In the drawing, WT represents a ward jet.

[0027]

As described above, according to the present invention, the following effects can be achieved.

The distance between the tip of the laser torch and the workpiece can be separated by the water jet. ・ The cutting width is narrow. ・ The torch can be lowered to cut the thick plate continuously by gouging. ・ Secondary generation because no gas is used. The material is small and easy to recover. ・ A thick plate can be cut in the air. The present invention can be desirably used for cutting a pressure vessel, a steam generator or a heat exchanger other than the graphite block.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a continuous gouging method.

FIG. 3 is a view showing removal of a graphite block.

FIG. 4 is a diagram showing a YAG laser jet cutting method.

FIG. 5 is a diagram showing the principle of a laser jet.

FIG. 6 is a diagram showing influencing factors of YAG laser cutting.

[Explanation of symbols]

1: laser torch, 2: body, 3, 4: condensing lens,
5,6 ... mirror, 7,8 ... optical fiber cable, 9 ...
Pressurized water chamber, 10: water jet nozzle, 11: protective glass, 12: descending device, 13: position control device, 14 ...
Workpiece.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenichi Maeda 3-2-2, Sachimachi, Hitachi-shi, Ibaraki F-term in Hitachi Engineering Services Co., Ltd. (Reference) 2E176 AA17 DD53 4E068 AE01 CA11 CA12 CB05 CD02 CE08 CH08 CJ07 DA00 DB00

Claims (8)

[Claims] 1. A laser for cutting a workpiece by using a laser torch for condensing a laser beam with a condenser lens and irradiating the workpiece with a laser torch. In the cutting method using a beam, when performing gouging, the laser beam is surrounded by a water jet, and the distance between the laser torch and the cut surface of the workpiece when performing the first gouging is set to be equal to or greater than the thickness of the workpiece. And cutting the workpiece by performing continuous gouging by lowering the laser torch a plurality of times. 2. The cutting method according to claim 1, wherein the distance is set to 50 to 200 mm. 3. The cutting method according to claim 1, wherein the distance is set to 100 to 150 mm. 4. The method according to claim 1, wherein lasers from a plurality of laser beam sources are combined, and the diameter of the jet circle of the water jet is set to approximately 0.1 to 0.4 mm (a reduction in cutting width). Cutting method using a laser beam. 5. A laser torch for condensing a laser beam with a condenser lens and irradiating the object with a laser beam, and injecting a water beam onto a formed beam spot to cut the object to be cut. A cutting device using a laser beam, wherein the laser torch is provided with a torch lowering device that lowers the laser torch a plurality of predetermined times and performs continuous gouging during cutting. 6. The cutting apparatus according to claim 5, wherein the laser torch includes a water jet nozzle having a diameter of 0.1 to 0.4 mm. 7. The laser torch according to claim 6, further comprising a plurality of laser oscillators, an optical fiber cable connected to the laser oscillator, and the laser torch combining and condensing a plurality of lasers from the optical fiber cable. A cutting device using a laser beam, which is introduced into a lens. 8. A method of cutting a graphite block when dismantling a nuclear reactor decommissioning, comprising: irradiating the graphite block taken out with the dismantling of the nuclear reactor decommissioning with a laser beam by a laser torch for condensing the laser beam. Around the radiated beam, a nuclear reactor decommissioning furnace characterized by injecting a water jet into a graphite evaporating portion of a graphite block, and cutting the laser torch by performing continuous gouging on the graphite block. How to cut graphite block when dismantling.