JP2017121660A - Laser machining device and laser machining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce dispersion of secondary products containing molten materials generated by laser machining to external environment.SOLUTION: A laser machining device 10 which melts a material to be machined 1 with a laser beam 2 to machine the material includes: an irradiation head 11 which is provided with an optical system 20, condenses the laser beam transmitted from a laser oscillator 12 by the optical system and irradiates a machining point 4 of the material to be machined with the laser beam; and a nozzle 13 which jets water 3 for discharging secondary products 5 containing molten materials and/or fumes generated by melting of the machining point, to the machining point molten by irradiation of the laser beam from the irradiation head.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a laser processing apparatus and method for processing a workpiece by laser light irradiation.

  Since materials used in nuclear power plants deteriorate due to radiation and environmental effects received from fuel during power generation operation, they are replaced after a certain period of operation. For example, control rods and fuel channel boxes are once stored in water as a highly radioactive solid waste after passing a predetermined operating period. In addition, since decommissioning is expected for a plant that exceeds 40 years after operation in the future, it becomes necessary to cut and store all the constituent materials. Highly radioactive solid waste in a nuclear power plant is made of, for example, stainless steel or a nickel-based alloy, and the cut pieces generated during cutting are also radioactive materials, and are therefore very difficult to handle.

  For the underwater cutting device for highly radioactive solid waste, for example, a used fuel channel box having a rectangular cross section and a used control rod having a cross-shaped cross section can be cut in the direction along the axis, with the object being cut. There is. An underwater cutting device using laser light as a heat source is also known. In these cases, the method of removing the material by heating and melting is adopted as a cutting method, and cutting can be performed without significantly changing the blade and cutting conditions depending on the material, such as mechanical cutting such as a band saw. There are benefits.

  On the other hand, as a method for processing a metal material, a gouging method is known in which the surface is melted using plasma or laser light as a heat source, and the molten metal is removed with air or oxygen gas. In factories and on-site where there are no ignited materials, air and oxygen gas are widely used as a method for removing molten metal because they have high processing efficiency and are easily available. However, in this method, the temperature rise of the metal material due to the heat source becomes significant, so that the generated fumes (metal vapor and metal fine powder obtained by solidifying the metal vapor) are scattered over a wide range, and the work environment deteriorates. is there.

  In view of this, a construction method combining laser light and a water jet has been developed as a construction method for reducing the amount of fumes generated from the material melted by a heat source and the amount of scattering. For example, the laser beam is condensed on the surface of the material, and a water jet is blown from the water jet nozzle to the laser beam condensing position, or the water jet is ejected coaxially with the laser beam, and cut by the laser beam and the water jet. Some water jets reduce the generation of secondary products.

JP-A-8-285996 JP 2003-156593 A JP 2000-317659 A JP 2000-317661 A

  When radioactive materials are cut by thermal means such as plasma or laser light, the fumes generated when the radioactive materials are melted are also radioactive materials, so these fumes are scattered in the atmosphere and the radiation dose in the external environment increases. As a result, exposure of workers and activation of equipment become a problem. The above-mentioned underwater cutting device is equipped with a recovery device that recovers cutting powder and gaseous radioactive material, but there is a problem that the filter must be frequently replaced, and it is possible to perform cutting work in an air environment. Can not.

  Further, in the cutting process combining laser light and water jet, the laser light is condensed and cut by spraying the water jet, so that cutting waste is likely to be scattered in various directions by the water jet and is difficult to collect. . It is only necessary to cover this cutting device completely like a machine tool used in a factory and collect cutting waste downstream of the device, but it is difficult to cover the entire scattering range when cutting by remote control. It is.

  An object of an embodiment of the present invention is made in consideration of the above-described circumstances, and a laser processing apparatus capable of reducing scattering of a secondary product including a melt and a fume generated by laser processing to an external environment, and It is to provide a method.

  A laser processing apparatus according to an embodiment of the present invention includes an optical system in a laser processing apparatus that melts and processes a workpiece with laser light, and condenses laser light transmitted from a laser oscillator by the optical system. Irradiation head for irradiating a processing point of the workpiece, and a nozzle for ejecting a fluid for discharging a secondary product generated by irradiation of the laser beam to the processing point in a predetermined direction toward the processing point It is characterized by having.

  A laser processing method according to an embodiment of the present invention is a laser processing method in which a workpiece is melted and processed by a laser beam, and the laser beam transmitted from a laser oscillator is condensed by an optical system of an irradiation head. Irradiating a processing point of an object, ejecting a fluid from a nozzle toward the processing point, and discharging a secondary product generated by irradiation of the laser beam to the processing point in a predetermined direction. Is.

  According to the embodiment of the present invention, it is possible to reduce scattering of secondary products including melts and fumes generated by laser processing to the external environment.

The block diagram which shows the condition of the cutting process by the laser processing apparatus which concerns on one Embodiment. The block diagram which shows the condition of the gouging process by the laser processing apparatus of FIG. The top view which shows the relationship between the penetration process and cutting process, and the spot diameter of a laser beam, (A) shows a spot diameter, (B) is a schematic sectional drawing which shows the processing state of a penetration process and a cutting process. The relationship between a gouging process and the spot diameter of a laser beam is shown, (A) is a top view which shows a spot diameter, (B) is a schematic sectional drawing which shows the process state of a gouging process.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram showing a state of cutting processing by a laser processing apparatus according to an embodiment. A laser processing apparatus 10 shown in FIG. 1 melts and processes a workpiece (for example, a radioactive substance such as a highly radioactive solid waste generated in a nuclear power plant) with a laser beam 2. The laser oscillator 12, the nozzle 13, the fluid supply source 14, the angle changing mechanism 15, the monitoring device 16, the control device 17, and the recovery device 18 are configured.

  The irradiation head 11 includes an optical system 20, and the optical system 20 is connected to the laser oscillator 12 via an optical fiber 19 as a transmission unit. Accordingly, the laser beam 2 emitted from the laser oscillator 12 is transmitted through the optical fiber 19 and introduced into the optical system 20 of the irradiation head 11. The optical system 20 includes condensing lenses 21A and 21B. The laser light 2 introduced into the optical system 20 is enlarged or reduced to a predetermined beam diameter by the condensing lens 21A, and then is condensed by the condensing lens 21B. The light is condensed and irradiated to the processing point 4 of the workpiece 1.

  When the laser beam 2 is focused on the processing point 4 of the workpiece 1 and energy of a certain power density or more is introduced, the processing point 4 is locally melted. For example, if the laser output from the laser oscillator 12 is 5 kW, and the spot diameter S (FIG. 3; described later) of the laser beam 2 at the processing point 4 of the workpiece 1 is 1 mm, it penetrates 16 mm thick stainless steel. And can be melted. Here, the code | symbol 6 in FIGS. 1-3 shows a fusion | melting part. The laser beam 2 used in the present embodiment is preferably a fiber laser beam (wavelength: 1070 nm) that can be transmitted through the optical fiber 19 by melting metal with a high output, but a YAG laser beam (wavelength: 1064 nm). ) Or direct diode laser light (wavelength: 800 to 900 nm).

  The nozzle 13 is connected to a fluid supply source 14 such as a pump via a pipe or a hose 22 as supply means. Accordingly, for example, water as a fluid is supplied from the fluid supply source 14 to the nozzle 13 via the hose 22 and the like, and the nozzle 13 ejects the water 3 toward the processing point 4 of the workpiece 1. At this time, since the diameter of the water 3 ejection port in the nozzle 13 is set to 5 mm to 10 mm, the ejection diameter (diameter) D of the water 3 ejected from the ejection port of the nozzle 13 is also set to 5 mm to 10 mm. .

  By ejecting water 3 from the nozzle 13 toward the processing point 4 melted by the irradiation of the laser beam 2 from the irradiation head 11, the secondary product 5 generated by the irradiation of the laser beam 2 to the processing point 4. Is taken into the jetted water 3 and discharged in a predetermined direction A together with the water 3. Here, the secondary product 5 is a melt (molten metal) or fume in the melted portion 6 generated by melting a material such as a metal in the vicinity of the processing point 4 of the workpiece 1 by irradiation with the laser beam 2. (Metal vapor and metal fine powder obtained by solidifying the metal vapor), and takes the form of gas, liquid, colloid or aerosol.

  In the predetermined direction A in which the secondary product 5 is discharged together with the water 3, for example, the irradiation head 11 irradiates the laser beam 2, and the nozzle 13 irradiates the water 3 both at an angle close to perpendicular to the workpiece 1. In the case of jetting, it is the flow direction of the water 3 along the thickness direction of the workpiece 1. When the irradiation head 11 irradiates the laser beam 2 and the nozzle 13 irradiates and ejects water 3 at an angle inclined with respect to the workpiece 1 (in the case of FIG. 2), the water 3 is processed. This is a direction that reflects and flows on the surface of the object 1.

  By the way, the laser oscillator 12 is configured so that the laser beam 2 irradiated from the irradiation head 11 is a continuous wave or a pulse wave. That is, the laser oscillator 12 uses the laser beam 2 as a continuous wave when cutting the workpiece 1 or performing a gouging process, which will be described later. For example, when performing the cutting process, if the end of the workpiece 1 is irradiated with the laser beam 2, the energy of the laser beam 2 is concentrated on the end, so that the end of the workpiece 1 has a thickness. The workpiece 1 can be cut by melting in the direction and moving the irradiation head 11 and the nozzle 13 in the processing direction B from this end.

  On the other hand, when cutting is started from, for example, the central portion other than the end portion of the workpiece 1, if the central portion is irradiated with the continuous wave laser light 2, the energy of the laser light 2 is diffused to the surroundings. . Therefore, when a through-hole is formed in the central portion in order to start cutting from, for example, the central portion of the workpiece 1, the laser oscillator 12 uses the emitted laser light 2 as a pulse wave, and from the irradiation head 11. The processing point 4 in the center of the workpiece 1 is irradiated with a pulsed laser beam 2, and the workpiece 1 is melted stepwise in the thickness direction and excavated for piercing. The laser oscillator 12 irradiates the continuous laser beam 2 from the irradiation head 11 with the laser beam 2 to be emitted as a continuous wave after the through-hole is formed in, for example, the central portion of the workpiece 1. In this state, the workpiece 1 can be cut by moving the irradiation head 11 and the nozzle 13 in the processing direction B at a speed of, for example, 0.1 to 0.5 m / min.

  The fluid supply source 14 continuously ejects water 3 as a fluid from the nozzle 13 when the continuous wave laser beam 2 is irradiated from the irradiation head 11. Further, when the pulsed laser beam 2 is irradiated from the irradiation head 11, the fluid supply source 14 ejects water 3 as a fluid from the nozzle 13 continuously or in a pulsed manner. When jetting the water 3 from the nozzle 13 in a pulsed manner, the fluid supply source 14 synchronizes the jetting timing of the water 3 with the irradiation timing (irradiation frequency) of the laser beam 2 of the pulse wave, and the workpiece Control is performed so that the water 3 reaches the vicinity of the processing point 4 when a melt is generated at one processing point 4.

  The angle changing mechanism 15 can change the angle θ of the irradiation head 11 and the nozzle 13 with respect to the surface of the workpiece 1. The angle changing mechanism 15 may change the angle θ of the irradiation head 11 and the nozzle 13 at the same time, or may change them independently independently. The angle changing mechanism 15 sets the angle θ of the irradiation head 11 and the nozzle 13 to be substantially perpendicular (θ≈90 °) with respect to the surface of the workpiece 1, thereby penetrating and cutting as shown in FIG. Processing is performed. Further, the angle θ of the irradiation head 11 and the nozzle 13 is arranged to be inclined (θ = 20 to 60 °) with respect to the surface of the workpiece 1 by the angle changing mechanism 15 as shown in FIG. A gouging process is performed in which a depth range of 1 to 5 mm from the surface of the workpiece 1 is melted by the laser beam 2 and the secondary product 5 is discharged by the water 3 and scraped off.

  The optical system 20 of the irradiation head 11 includes a variable focal length mechanism (zoom mechanism), and the spot of the laser beam 2 that irradiates the workpiece 1 depending on the type of processing such as penetration processing, cutting processing, and gouging processing. The diameter S (that is, the diameter of the laser beam 2 when irradiated on the processing point 4 of the workpiece 1 as shown in FIGS. 3 and 4) can be changed. That is, as shown in FIGS. 3A and 3B, when the spot diameter S of the laser beam 2 is small, the energy density of the laser beam 2 introduced into the workpiece 1 is increased. Although the surface area melted by 2 becomes narrow, it melts | dissolves to a deep area | region and the fusion | melting part 6 is formed. Therefore, in the case of performing penetration processing or cutting processing, the spot diameter S of the laser beam 2 is set to be as small as about 1 mm by the optical system 20.

  When the spot diameter S of the laser beam 2 is large, as shown in FIGS. 4A and 4B, the surface area melted by the laser beam 2 is widened, but is melted in a shallow region and melted. 6 is formed. Therefore, when the gouging process for scraping the surface of the workpiece 1 is performed, the spot diameter S of the laser beam 2 is set larger than in the case of the penetration process or the cutting process.

  The monitoring device 16 monitors the processing status of the processing point 4 of the workpiece 1 and is installed, for example, in the vicinity of the optical system 20 of the irradiation head 11 or in the optical system 20. In any case of the penetration processing, the cutting processing, and the gouging processing, the workpiece 1 is melted in the depth direction from the surface by the laser beam 2, and the secondary product 5 such as the melt is discharged by the water 3. The monitoring device 16 that monitors the processing status of the workpiece 1 is preferably a distance meter that measures the distance from the optical system 20 to the workpiece 1. Specifically, the monitoring device 16 is preferably a distance meter using ultrasonic waves or laser light.

  The monitoring result of the processing status by the monitoring device 16 is transmitted to the control device 17, and the control device 17 controls the operations of the laser oscillator 12 and the fluid supply source 14 based on the monitoring result. Further, the control device 17 controls the angle changing mechanism 15 according to the type of processing such as penetration processing and gouging processing, and changes the angle θ of the irradiation head 11 and the nozzle 13 with respect to the surface of the workpiece 1, Furthermore, the optical system 20 of the irradiation head 11 is controlled to adjust the spot diameter S of the laser light 2. Further, the control device 17 controls the laser oscillator 12 when performing the penetrating process, and causes the laser oscillator 12 to emit a pulsed laser beam to perform the piercing process. Further, the control device 17 controls the laser oscillator 12 to cause the laser oscillator 12 to emit a continuous wave laser beam 2 when performing a cutting process or a gouging process.

  The structure of the irradiation head 11 including the optical fiber 19 and the connection portion between the optical fiber 19 is a liquid-tight structure (for example, a water-tight structure). The laser processing apparatus 10 has a watertight structure from the optical fiber 19 to the condensing lens 21B at the tip of the optical system 20 in the irradiation head 11, and further, the ejection diameter of the water 3 ejected from the nozzle 13 is set to 5 mm to 10 mm. As a result, the ejection energy of the water 3 from the nozzle 13 is increased, so that the workpiece 1 can be laser processed in air or water.

  In the case of underwater processing, the area between the condenser lens 21B of the optical system 20 in the irradiation head 11 and the processing point 4 of the workpiece 1 is an underwater environment. For this reason, for example, when the laser beam 2 has a wavelength of 1064 nm to 1070 nm, such as a fiber laser beam or a YAG laser beam, the laser beam 2 is absorbed and attenuated by water, and the laser oscillator is used in underwater processing. If the laser output of 12 is the same as in the air, the laser energy at the processing point 4 of the workpiece 1 will be insufficient.

  Therefore, in the case of underwater processing, the laser beam 2 is attenuated in consideration of the attenuation of the laser beam 2 due to water according to the distance from the condenser lens 21B of the optical system 20 of the irradiation head 11 to the processing point 4 of the workpiece 1. By adjusting the laser output of the laser beam 2 emitted from the oscillator 12, laser processing can be performed in water as in the air. For example, when the distance from the condenser lens 21B of the optical system 20 of the irradiation head 11 to the processing point 4 of the workpiece 1 is 100 mm, the laser output of the laser oscillator 12 is 5 kW in laser processing in the air. When the attenuation rate of the laser beam 2 by water is 50%, in laser processing in water, the laser output of the laser oscillator 12 is doubled to 100 kW, so that laser processing equivalent to that in air can be performed in water. become.

  The recovery mechanism 18 recovers the secondary product 5 (melt and fume) generated by melting the processing point 4 by laser processing, and the discharge direction of the secondary product 5 discharged together with the water 3 (predetermined) Installed in direction A). In the case of penetration processing and cutting processing, the discharge direction (predetermined direction A) of the secondary product 5 is the flow direction of the water 3 along the thickness direction of the workpiece 1, so the workpiece in this flow direction A collection device 18 is installed on the back surface side of 1.

  In the case of gouging, the discharge direction (predetermined direction A) of the secondary product 5 is the direction in which the water 3 from the nozzle 13 is reflected by the surface of the workpiece 1 and flows in this direction. A recovery device 18 is installed on the processing direction B side of the head 11 and the nozzle 13. The secondary product 5 recovered together with the water 3 by the recovery device 18 is separated and recovered from the water 3 by a separation means such as centrifugal separation.

With the configuration as described above, according to the present embodiment, the following effects (1) to (5) are obtained.
(1) Water 3 is ejected from the nozzle 13 toward the processing point 4 of the workpiece 1 melted by the laser beam 2 irradiated from the irradiation head 11. Since the ejection diameter of the water 3 is as large as 5 to 10 mm, the secondary product 5 containing the melt and fume generated at the processing point 4 of the workpiece 1 is solidified by the water 3 and the water. 3 and is discharged in the predetermined direction A together with the water 3. As a result, it is possible to reduce inadvertent scattering of the secondary product 5 including the melt and fume generated by laser processing to the external environment.

  In particular, when the workpiece 1 is a radioactive substance, the secondary product 5 generated by the laser processing also becomes a radioactive substance. The secondary product 5 is solidified by the water 3 and is contained in the water 3. Inadvertent scattering to the external environment by being taken into the environment is reduced, so that an increase in radiation dose in the external environment can be suppressed.

  (2) The irradiation head 11 and the nozzle 13 are configured such that the angle θ with respect to the workpiece 1 can be changed by the angle changing mechanism 15. For this reason, even if the laser processing apparatus 10 has the same configuration, the angle changing mechanism 15 changes the angle θ of the irradiation head 11 and the nozzle 13 with respect to the workpiece 1 to perform cutting or penetrating processing. And the case where gouging is performed.

  (3) Since the monitoring device 16 for monitoring the processing state at the processing point 4 of the workpiece 1 is installed in the irradiation head 11, the workpiece 1 is a mixture of various substances such as fuel debris. Even when the absorptance of the laser beam 2 differs depending on each of these substances, the laser processing can be performed reliably by performing the laser processing while confirming the processing state by the laser beam 2.

  (4) Since the secondary product 5 generated by melting the processing point 4 of the workpiece 1 by the laser beam 2 from the irradiation head 11 is recovered by the recovery device 18, the processing of the secondary product 5 is speeded up. it can. In particular, when the secondary product 5 is a radioactive substance, the secondary product 5 is recovered by the recovery device 18, so that an increase in the radiation dose in the external environment can be reliably suppressed.

  (5) When the laser beam 2 irradiated from the irradiation head 11 is a pulse wave, the ejection timing of the water 3 ejected from the nozzle 13 is controlled in a pulse shape in synchronization with the pulse wave of the laser beam 2. For this reason, the ejection amount of the water 3 can be reduced compared with the case where the water 3 is continuously ejected. As a result, the amount of the water 3 recovered together with the secondary product 5 by the recovery device 18 is reduced, so that centrifugation or the like for separating the secondary product 5 from the water 3 can be easily performed.

  As mentioned above, although embodiment of this invention was described, this embodiment is shown as an example and is not intending limiting the range of invention. This embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. It is included in the scope and gist of the invention, and is included in the invention described in the claims and the equivalent scope thereof.

  DESCRIPTION OF SYMBOLS 1 ... Workpiece, 2 ... Laser beam, 3 ... Water (fluid), 4 ... Processing point, 5 ... Secondary product, 10 ... Laser processing apparatus, 11 ... Irradiation head, 12 ... Laser oscillator, 13 ... Nozzle, DESCRIPTION OF SYMBOLS 14 ... Fluid supply source, 15 ... Angle change mechanism, 16 ... Monitoring apparatus (monitoring means) 18 ... Recovery apparatus, 20 ... Optical system, A ... Predetermined direction, D ... Jet diameter, (theta) ... Angle.

Claims (6)

In a laser processing apparatus that melts and processes a workpiece by laser light,
An irradiation head comprising an optical system, condensing the laser beam transmitted from the laser oscillator by the optical system and irradiating the processing point of the workpiece;
A laser processing apparatus, comprising: a nozzle that ejects a fluid for discharging a secondary product generated by irradiation of the laser beam to the processing point in a predetermined direction toward the processing point. The laser processing apparatus according to claim 1, wherein an ejection diameter of fluid ejected from the nozzle is set to 5 mm to 10 mm. 3. The laser processing apparatus according to claim 1, further comprising a recovery device that is installed in a discharge direction of the secondary product and recovers the secondary product. 4. The laser processing apparatus according to claim 1, wherein the irradiation head and the nozzle are configured to be capable of changing an angle with respect to a workpiece. The laser processing according to any one of claims 1 to 4, wherein the laser beam emitted from the irradiation head is a pulse wave, and the ejection timing of the fluid ejected from the nozzle is controllable. apparatus. In a laser processing method for melting and processing a workpiece by laser light,
The laser beam transmitted from the laser oscillator is condensed by the optical system of the irradiation head and irradiated to the processing point of the workpiece,
A laser processing method, wherein a fluid is ejected from a nozzle toward the processing point, and a secondary product generated by irradiation of the laser beam onto the processing point is discharged in a predetermined direction.

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