JP5707986B2 - Laser cutting apparatus and laser cutting method - Google Patents

Description

  The present invention relates to a laser cutting apparatus and a laser cutting method for cutting a workpiece using a laser beam.

  Conventionally, this type of laser cutting apparatus cuts a workpiece by irradiating and jetting a laser beam, an assist gas, and a shield gas from a cutting head and a cutting nozzle.

  As the assist gas, high-pressure oxygen is generally used, and plays a role of promoting processing by oxidation reaction heat and a role of blowing molten metal from the kerf groove (cut groove). The shield gas forms an air curtain surrounding the assist gas and plays a role of protecting the assist gas. The assist gas also serves to prevent the condenser lens and the protective window from being damaged.

  The condensing lens plays a role of condensing the laser light from the laser generator, and the laser light condensed by the condensing lens is irradiated as a laser beam from the cutting head and the cutting nozzle. The protective window serves to protect the condenser lens, and a glass plate is generally used.

  In such a laser cutting apparatus, Patent Documents 1 to 3 describe that the cutting nozzle has a double nozzle structure. Specifically, the cutting nozzle is composed of an inner nozzle that coaxially ejects the laser beam and the assist gas, and an outer nozzle that ejects the shield gas.

Japanese Patent No. 2810625 Japanese Patent No. 3092021 Japanese Patent No. 3532223

  In the shipbuilding industry and the plank shirring industry, high quality and efficient cutting technology for planks is required. Furthermore, a thick plate underwater cutting technique is required to dismantle the reactor vessel and the like when the nuclear power plant is decommissioned in the future.

  However, the above prior art has a limit on the thickness of the workable material. In other words, when trying to cut a thick plate, it is necessary to increase the assist gas flow rate to blow off more molten metal, but if the assist gas flow rate is increased, oxygen is supplied excessively and an excessive combustion reaction (self-burning) occurs. As a result, the quality of the cut surface is degraded. Further, when the assist gas flow rate is increased, the nozzle pressure increases excessively and exceeds the pressure resistance strength of the protective window, which may damage the protective window.

  For this reason, since there is a limit in increasing the assist gas flow rate in the above prior art, there is a problem that a thick workpiece cannot be cut stably.

  In view of the above points, an object of the present invention is to provide a laser cutting apparatus and a laser cutting method suitable for cutting a thick workpiece.

In order to achieve the above object, the invention according to claim 1 includes a cutting nozzle (20) through which a laser beam passes,
The cutting nozzle (20) has an assist gas nozzle (21, 22 ) for injecting an assist gas for blowing off the melt melted by the laser beam,
The assist gas nozzle (21, 22) has a double nozzle structure consisting of an inner nozzle (21) and an outer nozzle (22),
The inner nozzle (21) passes the laser beam and injects an oxygen-containing gas,
The outer nozzle (22) is arranged coaxially with the inner nozzle (21), and injects a high flow rate gas having a higher flow rate and lower oxygen concentration than the oxygen-containing gas,
An assist gas is formed by the oxygen-containing gas and the high flow rate gas.

  According to this, since the assist gas is formed of an oxygen-containing gas and a high flow gas, increasing the flow rate of the high flow gas is sufficient to blow off the melt even to a thick workpiece (W). The assist gas flow rate can be secured.

  In addition, since the high-flow gas is a gas having a lower oxygen concentration than the oxygen-containing gas, even if the flow rate of the high-flow gas is increased, the supply of oxygen can be appropriately suppressed to prevent the occurrence of self-burning, and in turn a good cut surface. Quality can be obtained.

  Here, the assist gas nozzle for injecting the assist gas has a double nozzle structure composed of an inner nozzle (21) and an outer nozzle (22). The inner nozzle (21) allows the laser beam to pass through and oxygen-containing gas. Spray.

  For this reason, even if the flow rate of the high flow rate gas is increased to ensure a sufficient assist gas flow rate, an increase in nozzle pressure can be suppressed in the inner nozzle (21) through which the laser beam passes.

Furthermore, if the shield gas nozzle (23) for injecting the shield gas for protecting the assist gas is provided , the assist gas is protected by the shield gas injected from the shield gas nozzle (23), so that the atmosphere to the assist gas , And the assist gas flow rate at the kerf portion (the groove portion between the cut surfaces) can be increased.

Furthermore, in the invention according to claim 1, the distal end of the outer side nozzle (22) is extended to the irradiation direction of the laser beam from the tip of the inner nozzle (21),
A minimum diameter of a portion of the outer nozzle (22) extending from the inner nozzle (21) is narrowed to be smaller than a tip diameter of the inner nozzle (21).

  Thereby, even if the inner nozzle (21) is provided inside the outer nozzle (22), the diameter of the outer nozzle (22) can be reduced to increase the flow velocity of the assist gas, so that the melt can be blown off quickly. As a result, the thick workpiece (W) can be cut better.

Furthermore, in the invention according to claim 1, the outer side nozzle (22) is constituted by a Laval nozzle in which there is a skirt portion (222) ahead of the throat portion (221),
The throat portion (221) and the skirt portion (222) are formed in a portion of the outer nozzle (22) that extends beyond the inner nozzle (21).

According to this, since the flow velocity of the assist gas formed by the oxygen-containing gas and the high flow rate gas can be further increased, the melt can be blown off more rapidly.
According to a second aspect of the present invention, in the laser cutting device according to the first aspect, the laser cutting device includes a condensing lens (31) that condenses the laser light from the laser generator (30), and the condensing lens (31) The condensed laser beam is irradiated as a laser beam, and the focal position of the laser beam coincides with the throat portion (221) of the outer nozzle (22).

According to a third aspect of the present invention, in the laser cutting device according to the first or second aspect , the cross sectional area (a) of the outer nozzle (22) at the tip position of the inner nozzle (21) is equal to that of the outer nozzle (22). Of these, the cross-sectional area (b) of the portion (221) extending from the inner nozzle (21) and having the minimum diameter is larger.

  Thereby, it is possible to sufficiently supply the high flow rate gas to the throat portion (221) side and sufficiently secure the flow velocity and flow rate of the assist gas.

In the invention described in claim 4 , the workpiece (W) is cut by irradiating the workpiece (W) with a laser beam using the laser cutting device according to any one of claims 1 to 3. A laser cutting method,
The workpiece (W) is cut while irradiating a laser beam from the inner nozzle (21) and injecting an oxygen-containing gas and injecting a high flow rate gas from the outer nozzle (22).

The invention relating to the laser cutting method according to claim 4 can be used in a process of processing the workpiece (W) into a desired shape and size. Therefore, it is possible to grasp the invention according to claim 4 as an invention of a manufacturing method.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is a lineblock diagram showing an outline of a laser cutting device in a 1st embodiment of the present invention. It is sectional drawing which shows the nozzle for a cutting | disconnection of FIG. It is a principal part enlarged view of Fig.2 (a). It is sectional drawing which shows the nozzle for cutting in 2nd Embodiment of this invention.

(First embodiment)
A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a configuration diagram showing an outline of the laser cutting apparatus of the present embodiment.

  The laser cutting apparatus according to the present embodiment performs so-called air cutting in which the workpiece W is cut by irradiating a laser beam in the air. As an example of the workpiece W, a thick plate member formed of carbon steel, stainless steel (SUS) or the like to a thickness of about 25 to 150 mm can be given.

  Specifically, the laser cutting device sprays the assist gas, the shield gas, and the pressurized water curtain simultaneously with the irradiation of the laser beam.

  The assist gas is a gas containing oxygen, and plays a role of promoting processing by oxidation reaction heat and a role of blowing off a melt (molten metal).

  The shield gas serves as an air curtain that protects the assist gas. More specifically, by enclosing the assist gas in layers, the entrainment of the atmosphere is blocked and the assist gas flow rate at the kerf portion (the groove portion between the cut surfaces) is increased.

  The pressurized water curtain blocks the assist gas from the atmosphere to maintain the concentration and pressure of the assist gas, and suppresses the excessive temperature rise of the workpiece W to suppress the occurrence of self-burning. It should be noted that the pressurized water curtain is not essential for cutting in the air.

  The laser beam, the assist gas, the shield gas, and the pressurized water curtain are irradiated and ejected through the cutting head 10 and the cutting nozzle 20.

  The laser beam is formed by the laser generated by the laser generator 30 being guided to the cutting head 10 via the condenser lens 31 (optical component). The laser guided to the cutting head 10 is guided to the cutting nozzle 20 through the laser passage hole 101 of the cutting head 10.

  A protective window 32 (optical system protection component) that protects the condenser lens 31 is disposed in the laser passage hole 101. As the protective window 32, a glass plate or the like can be used. Further, the cutting head 10 is provided with a nozzle alignment mechanism (not shown) for allowing the laser beam to pass through the center of the cutting nozzle 20.

The assist gas is formed by an oxygen-containing gas containing oxygen (O ₂ ) and a high flow gas having a higher flow rate (pressure) than the oxygen-containing gas. High purity oxygen is used as the oxygen-containing gas. As the high flow rate gas, a gas having a lower oxygen concentration than the oxygen-containing gas, for example, air (Air) or an inert gas (nitrogen or the like) is used.

  The supply of the oxygen-containing gas is performed by an oxygen-containing gas cylinder 40, a pressure adjustment valve 41, and a flow rate adjustment valve. The oxygen-containing gas cylinder 40, the pressure adjustment valve 41, and the flow rate adjustment valve 42 constitute oxygen-containing gas supply means.

  The pressure adjustment valve 41 and the flow rate adjustment valve 42 are arranged in series in a gas pipe (oxygen-containing gas supply path) extending from the oxygen-containing gas cylinder 40 to the cutting head 10. A pressure gauge 43 and a flow meter 44 are also arranged in the gas piping from the oxygen-containing gas cylinder 40 to the cutting head 10.

  The supply of the high flow rate gas is performed by the high flow rate gas cylinder 45, the pressure adjustment valve 46 and the flow rate adjustment valve 47. The high flow gas cylinder 45, the pressure adjustment valve 46, and the flow adjustment valve 47 constitute high flow gas supply means.

  The pressure adjustment valve 46 and the flow rate adjustment valve 47 are arranged in series in a gas pipe (oxygen-containing gas supply path) extending from the high flow rate gas cylinder 45 to the cutting head 10. A pressure gauge 48 and a flow meter 49 are also arranged in the gas piping from the high flow gas cylinder 45 to the cutting head 10.

  The pressure and flow rate of the oxygen-containing gas and the pressure and flow rate of the high flow rate gas are set according to the material and thickness of the workpiece W. In this example, the flow rate of the oxygen-containing gas is set to 30 to 50 liters / minute, and the flow rate of the high flow rate gas is set to 300 to 350 liters / minute.

  When manual valves are used as the pressure regulating valves 41 and 46 and the flow regulating valves 42 and 47, the pressure and flow rate of the oxygen-containing gas and the pressure and flow rate of the high flow rate gas are manually set. In addition, when electromagnetic valves are used as the pressure regulating valves 41 and 46 and the flow regulating valves 42 and 47, the pressure / flow rate of the oxygen-containing gas and the pressure / flow rate of the high flow gas are controlled by a control device (control means). Can do.

  The cutting head 10 is formed with an oxygen-containing gas passage 102 into which oxygen-containing gas flows. The oxygen-containing gas passage 102 communicates with the laser passage hole 101 in the cutting head 10.

  Therefore, the oxygen-containing gas supplied to the cutting head 10 is supplied to the cutting nozzle 20 through the oxygen-containing gas passage 102 and the laser passage hole 101 of the cutting head 10. The high flow gas supplied to the cutting head 10 is supplied to the cutting nozzle 20 through the high flow gas passage 103 of the cutting head 10.

  As the shielding gas, air (Air) supplied by the compressor 50 is used. The shield gas supplied to the cutting head 10 is supplied to the cutting nozzle 20 through the shield gas passage 104 of the cutting head 10.

  Water (Water) forming the pressurized water curtain is supplied from the water tank 60 by the water pump 61. The water supplied to the cutting head 10 is supplied to the cutting nozzle 20 through the water passage 105 of the cutting head 10.

  FIG. 2 is a cross-sectional view showing the cutting nozzle 20. The cutting nozzle 20 has a quadruple nozzle structure.

  The innermost first nozzle 21 (circular nozzle) passes the laser beam from the laser passage hole 101 of the cutting head 10 and from the oxygen-containing gas passage 102 and the laser passage hole 101 of the cutting head 10. Inject oxygen-containing gas. Therefore, the first nozzle 21 is hereinafter referred to as an oxygen-containing gas nozzle.

  A double nozzle 22 (annular nozzle) located outside the oxygen-containing gas nozzle 21 injects a high flow rate gas from the high flow rate gas passage 103 of the cutting head 10. Therefore, the double nozzle 22 is hereinafter referred to as a high flow gas nozzle.

  The high flow gas nozzle 22 is disposed coaxially with the oxygen-containing gas nozzle 21. The tip of the high flow rate gas nozzle 22 extends in the laser beam irradiation direction from the tip of the oxygen-containing gas nozzle 21 and has a circular shape. In other words, the tip of the oxygen-containing gas nozzle 21 is disposed at a position deeper than the tip of the high flow gas nozzle 22.

  The minimum diameter (inner diameter) of the portion of the high flow rate gas nozzle 22 extending from the oxygen-containing gas nozzle 21 is narrower than the tip diameter (inner diameter) of the oxygen-containing gas nozzle 21.

  Thereby, oxygen-containing gas and high flow gas are injected from the tip of high flow gas nozzle 22. The assist gas is formed by the oxygen-containing gas and the high flow gas injected from the tip of the high flow gas nozzle 22.

  That is, the double nozzle composed of the oxygen-containing gas nozzle 21 and the high flow gas nozzle 22 constitutes an assist gas nozzle that injects assist gas. In other words, the oxygen-containing gas nozzle 21 constitutes an inner nozzle part of the assist gas nozzle having a double nozzle structure, and the high flow gas nozzle 22 constitutes an outer nozzle part of the assist gas nozzle having a double nozzle structure. doing.

  The high flow rate gas nozzle 22 is configured by a Laval nozzle having a skirt portion (expanded tube portion) 222 at the tip of the throat portion (narrowest narrow portion) 221. The throat portion 221 is a minimum diameter portion of the high flow rate gas nozzle 22. More specifically, the throat portion 221 and the skirt portion 222 are formed in a portion of the high flow rate gas nozzle 22 that extends beyond the tip of the oxygen-containing gas nozzle 21.

  3 is an enlarged cross-sectional view of the oxygen-containing gas nozzle 21 and the high-flow gas nozzle 22 shown in FIG. 2A. The cross-sectional area a of the high-flow gas nozzle 22 at the tip position of the oxygen-containing gas nozzle 21 and the cross-sectional area of the throat portion 221 are shown. b is shown.

  The cross-sectional area a of the high-flow gas nozzle 22 at the tip position of the oxygen-containing gas nozzle 21 is a cross-sectional area of the portion where the oxygen-containing gas nozzle 21 transitions from the annular flow path to the circular flow path, and is a cross-section having a truncated cone shape. Area.

  In this example, the cross-sectional area a of the high flow rate gas nozzle 22 at the tip position of the oxygen-containing gas nozzle 21 is larger than the cross-sectional area b of the throat portion 221 (a> b). That is, the cross-sectional area a of the high flow gas nozzle 22 at the tip position of the oxygen-containing gas nozzle 21 is larger than the cross-sectional area b of the outer nozzle 22 that extends beyond the inner nozzle 21 and has a minimum diameter (a > B).

  In this example, it is designed so that the focal position of the long-focus laser beam coincides with the throat portion 221 of the high flow rate gas nozzle 22.

  A triple nozzle 23 (annular nozzle) located outside the high flow rate gas nozzle 22 injects a shield gas from the shield gas passage 104 of the cutting head 10. Therefore, the triple nozzle 23 is hereinafter referred to as a shield gas nozzle.

  The shield gas nozzle 23 is disposed coaxially with the oxygen-containing gas nozzle 21 and the high flow rate gas nozzle 22. The tip of the shield gas nozzle 23 is arranged in alignment with the tip of the high flow gas nozzle 22.

  The outermost quadruple nozzle 24 (annular nozzle) injects water from the water passage 105 of the cutting head 10 to form a pressurized water curtain. Therefore, the quadruple nozzle 24 is hereinafter referred to as a pressurized water curtain nozzle.

  The pressurized water curtain nozzle 24 is arranged coaxially with the oxygen-containing gas nozzle 21, the high flow gas nozzle 22 and the shield gas nozzle 23. The tip of the pressurized water curtain nozzle 24 is arranged in alignment with the tips of the high flow gas nozzle 22 and the shield gas nozzle 23.

  In the example of FIGS. 1 and 2, the pressurized water injection port of the pressurized water curtain nozzle 24 is not parallel to the axial direction but slightly outward, so that the pressurized water spreads outward and is injected. In the middle cutting, the direction of the pressurized water injection port of the pressurized water curtain nozzle 24 may be parallel to the axial direction.

  Next, the operation in the above configuration will be described. The laser cutting device irradiates the workpiece W with a laser beam from the center of the oxygen-containing gas nozzle 21 and simultaneously injects assist gas (oxygen-containing gas and high-flow gas) from the oxygen-containing gas nozzle 21 and the high flow gas nozzle 22. To do. Further, the laser cutting device ejects the shield gas from the shield gas nozzle 23 and the pressurized water curtain from the pressurized water curtain nozzle 24.

  Since the assist gas is formed of an oxygen-containing gas and a high flow rate gas, by increasing the flow rate of the high flow rate gas, a sufficient assist gas flow rate is ensured to blow away the molten metal even to the thick workpiece W. be able to.

  Moreover, since the oxygen-containing gas is high-purity oxygen and the high-flow gas is a gas having a lower oxygen concentration than the oxygen-containing gas, even if the flow rate of the high-flow gas is increased, the oxygen supply is moderately suppressed and self-burning is performed. Occurrence can be prevented. For this reason, favorable cut surface quality can be obtained.

  Here, in the present embodiment, the assist gas nozzle for injecting the assist gas has a double nozzle structure including the oxygen-containing gas nozzle 21 and the high flow gas nozzle 22, and the low flow (low pressure) oxygen of both nozzles. A laser beam is passed through the contained gas nozzle 21.

  For this reason, even if the assist gas flow rate sufficient to blow off the molten metal is ensured even for the thick workpiece W, it is possible to prevent the pressure resistance of the protective window 32 from being exceeded, and consequently to prevent the protective window 32 from being damaged. .

  By combining the above effects, a thick workpiece W having a thickness of about 25 to 150 mm can be cut well.

  Further, as described above, the shielding gas serves as an air curtain that protects the assist gas. More specifically, by enclosing the assist gas in layers, the entrainment of the atmosphere is blocked and the assist gas flow rate at the kerf portion (the groove portion between the cut surfaces) is increased. For this reason, the thick workpiece W can be cut more satisfactorily.

  In the present embodiment, the tip of the high flow gas nozzle 22 extends in the laser beam irradiation direction from the tip of the oxygen containing gas nozzle 21, so the oxygen containing gas nozzle 21 is provided inside the high flow gas nozzle 22. Even in this case, the tip diameter (inner diameter) of the high flow gas nozzle 22 can be reduced. For this reason, since the flow velocity of the assist gas can be effectively increased, the molten metal can be quickly discharged from the kerf groove (cutting groove), and as a result, the thick workpiece W can be cut even better. .

  Further, since the high flow rate gas nozzle 22 is composed of a Laval nozzle, the flow rate of the assist gas can be increased to a supersonic speed, and the molten metal can be discharged more quickly from the kerf groove (cutting groove), and consequently the thick workpiece W Can be cut more satisfactorily.

  If the cross-sectional area a (FIG. 3) of the high-flow gas nozzle 22 at the tip position of the oxygen-containing gas nozzle 21 is too small, the high-flow gas is excessively squeezed at that portion and the high-flow gas is sufficiently supplied to the throat portion 221 side. As a result, it becomes impossible to sufficiently secure the flow velocity and flow rate of the assist gas.

  Therefore, in order to sufficiently supply the high flow rate gas to the throat portion 221 side and sufficiently secure the flow velocity and flow rate of the assist gas, the cross-sectional area a of the high flow rate gas nozzle 22 at the tip position of the oxygen-containing gas nozzle 21 is sufficiently large. It needs to be bigger.

  Specifically, as in this example, it is preferable that the cross sectional area a of the high flow rate gas nozzle 22 at the tip position of the oxygen-containing gas nozzle 21 is larger than the cross sectional area b of the throat portion 221 (a> b).

  In the present embodiment, the pressure / flow rate of the oxygen-containing gas and the pressure / flow rate of the high flow rate gas can be adjusted independently by the pressure adjustment valves 41, 46 and the flow rate adjustment valves 42, 47. It is possible to achieve both the proper adjustment of the flow rate of the gas and the appropriate adjustment of the oxygen concentration of the assist gas, and thus the thick workpiece W can be cut even better.

  Further, by appropriately adjusting the pressure / flow rate of the oxygen-containing gas and the pressure / flow rate of the high-flow gas, the oxygen-containing gas can be prevented from flowing back in the oxygen-containing gas nozzle 21. For example, the oxygen-containing gas can be prevented from flowing backward in the oxygen-containing gas nozzle 21 by making the pressure of the oxygen-containing gas and the pressure of the high flow rate gas substantially equal.

  Incidentally, the flow rate of the oxygen-containing gas and the flow rate of the high flow rate gas are set according to the plate thickness of the workpiece W. Therefore, when the plate thickness of the workpiece W is constant, the flow rate of the oxygen-containing gas and the flow rate of the high flow rate gas are adjusted in advance before cutting, and when the plate thickness of the workpiece W is not constant, The flow rate of the oxygen-containing gas and the flow rate of the high flow rate gas are preferably adjusted according to the plate thickness of the cut portion of the workpiece W during the cutting process.

  In the present embodiment, as described above, the pressurized water curtain completely blocks the assist gas from the atmosphere to maintain the concentration and high pressure, and suppresses the excessive temperature rise of the workpiece W and suppresses the occurrence of self-burning. To do. For this reason, the thick workpiece W can be cut more satisfactorily.

(Second Embodiment)
In the first embodiment, only the high flow gas is injected from the high flow gas nozzle 22, but in the second embodiment, as shown in FIG. Spray.

  The powder is supplied from a powder supply device (not shown) to the high flow rate gas nozzle 22. The powder material (main material) is preferably iron (Fe). Further, tin (Sn), phosphorus (P), or the like may be used as a powder material (main material).

  According to the present embodiment, the ability to discharge the molten metal from the kerf groove by the assist gas can be improved by mixing the powder into the high flow rate gas nozzle 22 (that is, the assist gas).

  That is, by injecting powder onto the molten metal, the component ratio of the molten metal can be changed and the viscosity of the molten metal can be lowered, so that the discharge of the molten metal from the kerf groove can be facilitated.

  In particular, it is important to promote the production of iron oxide (FeO) when cutting alloy steel having a high viscosity in a molten state, such as stainless steel (SUS). Therefore, it is important to mix iron (Fe) as powder. preferable.

  In other words, since the viscosity coefficient of iron oxide (FeO) becomes low in a high temperature environment exceeding the melting point, it promotes the production of iron oxide (FeO) and increases the concentration of iron oxide (FeO), thereby melting from the kerf groove. Metal discharge can be facilitated.

  Further, tin (Sn), phosphorus (P), or the like, which is a component that enhances the fluidity of molten iron (Fe), may be mixed as powder.

(Third embodiment)
The laser cutting device of the first embodiment performs cutting in the air. The laser cutting device of the third embodiment cuts the workpiece W by irradiating a laser beam in water. Underwater cutting. Since the cutting nozzle 20 in the present embodiment has the same configuration as that of the first embodiment, the illustration is omitted.

  In underwater cutting, it is necessary to form a dry gas space adjacent to the surface on which the laser beam is incident on the workpiece. In this respect, in the present embodiment, the pressurized water curtain is jetted in a ring shape on the outer periphery of the cutting nozzle 20, so that an air curtain (dry gas space) can be favorably formed inside the pressurized water curtain.

  In the underwater cutting, the pressurized water curtain is formed on the outer periphery of the cutting nozzle 20 if the pressurized water spray port of the pressurized water curtain nozzle 24 is not parallel to the axial direction but slightly outward so that the pressurized water spreads outward. Can be formed satisfactorily.

  That is, according to the present embodiment, the pressurized water curtain prevents external water from entering the laser beam irradiation unit. Water inside the pressurized water curtain is removed to the outside by the air curtain, and a gas space is formed and maintained in the laser beam irradiation portion on the surface of the workpiece W. Further, the intrusion of water into the kerf groove can be prevented by the assist gas ejected from the cutting nozzle 20.

  For this reason, since a laser beam can be reliably delivered to the bottom part of the workpiece W, even if it is the thick workpiece W, underwater cutting can be performed favorably.

(Other embodiments)
In each of the above embodiments, a thick plate member having a thickness of about 25 to 150 mm is used as the workpiece W. However, the present invention is not limited to this. For example, the workpiece W is less than 25 mm. You may use the member of thickness.

  Moreover, in the said 1st, 2nd embodiment, although air is used as the shielding gas injected from the shielding gas nozzle 23, you may inject in a mist form using water and air as shielding gas. In this case, since the excessive temperature rise of the workpiece W can be suppressed by the water contained in the shield gas, the occurrence of self-burning can be further suppressed.

  Moreover, in the said 1st, 2nd embodiment, although air is used as the shielding gas injected from the shielding gas nozzle 23, you may inject in a mist form using water and air as shielding gas. In this case, since the excessive temperature rise of the workpiece W can be suppressed by the water contained in the shield gas, the occurrence of self-burning can be further suppressed.

  In the first and second embodiments, the high flow gas nozzle 22 is configured by a Laval nozzle. However, the workpiece W can be cut even if the high flow gas nozzle 22 is configured by a nozzle other than the Laval nozzle. It is.

  Further, in the first and second embodiments, the cutting gas 20 is provided with the shield gas nozzle 23. However, the workpiece W can be cut even if the cutting nozzle 20 is not provided with the shield gas nozzle 23. Is possible.

20 Cutting nozzle 21 Oxygen-containing gas nozzle (inner nozzle, assist gas nozzle)
22 High flow gas nozzle (outside nozzle, assist gas nozzle)
23 Shield gas nozzle 221 Throat part 222 Skirt part W Workpiece

Claims (4)

A cutting nozzle (20) for passing a laser beam;
The cutting nozzle (20) has an assist gas nozzle (21, 22) for injecting an assist gas for blowing off the melt melted by the laser beam,
The assist gas nozzle (21, 22) has a double nozzle structure comprising an inner nozzle (21) and an outer nozzle (22),
The inner nozzle (21) passes the laser beam and injects an oxygen-containing gas;
The outer nozzle (22) is arranged coaxially with the inner nozzle (21), and injects a high flow rate gas having a higher flow rate and lower oxygen concentration than the oxygen-containing gas,
The assist gas is formed by the oxygen-containing gas and the high flow rate gas,
The tip of the outer nozzle (22) extends in the laser beam irradiation direction from the tip of the inner nozzle (21),
A laser cutting device in which a minimum diameter of a portion extending from the inner nozzle (21) of the outer nozzle (22) is narrower than a tip diameter of the inner nozzle (21) ,
The outer nozzle (22) is a Laval nozzle having a skirt portion (222) at the tip of a throat portion (221),
The laser cutting apparatus according to claim 1, wherein the throat portion (221) and the skirt portion (222) are formed in a portion of the outer nozzle (22) that extends beyond the inner nozzle (21) . A condensing lens (31) for condensing the laser light from the laser generator (30) is provided, and the laser light condensed by the condensing lens (31) is irradiated as the laser beam. ,
The laser cutting device according to claim 1, wherein a focal position of the laser beam coincides with the throat portion (221) of the outer nozzle (22). The cross-sectional area (a) of the outer nozzle (22) at the tip position of the inner nozzle (21) is a portion (221) that extends from the inner nozzle (21) and has a minimum diameter in the outer nozzle (22). ) laser cutting device according to claim 1 or 2, characterized in that it is larger than the cross-sectional area (b) of the. A laser cutting method using the laser cutting device according to any one of claims 1 to 3 , wherein the workpiece (W) is irradiated with a laser beam to cut the workpiece (W).
Cutting the workpiece (W) while irradiating the laser beam from the inner nozzle (21) and injecting the oxygen-containing gas and injecting the high flow rate gas from the outer nozzle (22). A laser cutting method characterized by the above.

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