JP2010234373A - Laser machining nozzle, and laser machining apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser machining nozzle and a laser machining apparatus which are capable of discharging and blowing a molten metal from the inside of a cutting groove in an oxygen-free cutting operation using the laser beam, thereby preventing the deposition of dross on a back side of a workpiece. <P>SOLUTION: A double nozzle comprises a main assist gas injection port for injecting laser beam and main assist gas, and an auxiliary assist gas injection port disposed concentrically and annularly around the main assist gas injection port for injecting auxiliary assist gas. The auxiliary assist gas injection port has its face formed downstream of the main assist gas injection port face in the assist gas flow, and the injection angle of the auxiliary assist gas at the position of intersection between a gas flow axis of the main assist gas and a gas flow axis of the auxiliary assist gas is set within a range of 0 to 80° with respect to the injection axis of the main assist gas. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a laser processing nozzle (hereinafter also simply referred to as a processing nozzle) for supplying an assist gas to the surface of a workpiece when performing laser processing, and a laser processing apparatus including the processing nozzle. . In this specification, laser cutting will be described as an example of laser processing.

  Laser processing is thermal processing in which a laser beam output from a laser oscillator is focused on a processing surface by an optical part such as a lens, and cutting or welding is performed using high-density energy at this time. Therefore, since the laser beam has high-density energy, the time required for melting and solidifying the workpiece is short and the processing speed is 5 to 10 times or more compared with arc welding which is a conventional method.

  In general, the cutting performance in laser processing depends on processing condition parameters such as the output of the laser beam, the focal position of the laser beam with respect to the surface of the workpiece, the assist gas pressure, the distance between the workpiece and the tip of the processing nozzle, and the like. It also depends on material conditions such as material type, surface condition, quality, composition and thickness. The laser processing apparatus is required to have a wide tolerance for such processing condition parameters and material conditions and to obtain stable processing quality. In particular, in non-oxidative cutting that cuts stainless steel, aluminum, etc. using high-pressure nitrogen gas as the assist gas, the metal melted by the laser beam is pushed down to the lower part of the cutting groove and discharged by the assist gas jet, and dross is formed on the back of the workpiece. It is required not to adhere as.

  In particular, as the thickness of the plate to be processed increases, the lower surface of the plate thickness is separated from the injection port of the processing nozzle, so that the assist gas pressure decreases, and it becomes difficult to discharge the molten metal from the cutting groove, and dross occurs. For discharging molten metal from the cutting groove, it is effective to increase the assist gas pressure by using a large-diameter nozzle. However, the consumption of the assist gas increases, which increases the processing cost and is not practical. .

  On the other hand, inventions of machining nozzles for improving machining quality have been conventionally made, all of which relate to preventing impure fluid from being caught in a machining portion. There has been no invention that efficiently discharges molten metal from the inside of the cutting groove and prevents it from adhering to the back surface of the workpiece as dross.

  In the conventional processing torch, in the process of cutting a thick steel plate using oxygen as an assist gas with oxygen, the inclination angle from the horizontal plane of at least one assist gas channel except the innermost side is 60 degrees or more, and the channel There is provided a nozzle whose intersection between the center line and the nozzle axis is 10 to 15 mm from the tip of the nozzle (see, for example, Patent Document 1). Another feature is that the outlet of the outer nozzle body is oriented in a direction crossing the outlet of the inner nozzle body (see, for example, Patent Document 2).

JP-A-9-136183 (FIG. 7) JP-A-11-123578 (FIG. 1)

  Conventionally, in laser cutting, a processing method in which oxygen gas is used as an assist gas for mild steel cutting or stainless steel cutting and an oxidation combustion reaction is generated is generally used. In cutting using oxygen as an assist gas, active research has been conducted on nozzles to improve machining quality and cutting speed, but most of them are designed to prevent air around the machined part from being entrained. It was. As a result of the research, cutting quality and ability using oxygen gas have improved dramatically, and its spread has progressed at a stretch. However, since the cut surface is oxidized, an oxide film generated on the cut surface becomes an obstacle when the parts are welded or painted after laser cutting. Therefore, it was necessary to remove the oxide film by cutting or chemical treatment as a post-processing after cutting.

  On the other hand, in order to reduce the post-processing process, there is a method of cutting by using nitrogen gas as an assist gas, so-called non-oxidation cutting, but the molten metal is completely discharged from the cutting groove having a width of about 0.5 mm. In addition, it is not easy to blow away, and it may adhere as dross to the back surface of the workpiece.

  In the prior art disclosed in Patent Document 1, a triple nozzle including an innermost nozzle (3c in FIG. 7), a second circumferential nozzle (3d in FIG. 7), and a third circumferential nozzle (3e in FIG. 7). Is disclosed. This nozzle is provided so that there is an intersection between the flow path center line and the nozzle axis at a position 10 mm from the tip of the outer nozzle. In this structure, the third week nozzle does not contribute to restrict the gas flow at the outlet from the innermost nozzle. In non-oxidative cutting in which molten metal is blown away by high-pressure gas, it is necessary to efficiently pour the assist gas into a cutting groove having a width of about 0.5 mm. Therefore, the distance between the workpiece and the nozzle should be set to about 1 mm or less. It is common. However, in Patent Document 1, since the flow path center line and the nozzle axis intersect at a position of 10 mm from the tip of the outer nozzle with a triple nozzle, only a part of the gas from the outer peripheral nozzle is guided into the cutting groove. I can't. This method is effective in using oxygen gas as an assist gas for mild steel cutting and shielding the machined part with oxygen gas. However, in non-oxidation cutting, the momentum of the gas flow from the central nozzle is increased to increase the molten metal. It is not effective for discharging.

  Moreover, in the prior art disclosed in Patent Document 2, the outlet of the outer nozzle body is arranged such that a blocking curtain is formed by the gas injected from the outlet of the inner nozzle body. This application is effective when the assist gas pressure is low, such as laser welding, but the gas flow is less disturbed and effective, but in non-oxidation cutting using a high pressure gas, the gas flow from the central nozzle is disturbed, resulting in machining performance. Is significantly reduced.

  As a countermeasure to the problem in non-oxidation cutting, for a thick plate cutting with a thickness of 12 mm or more, examination of a processing method for setting the assist gas condition to a high pressure of 2 MPa or more and discharging molten metal from the cutting groove has started. Due to the characteristics of the free jet of fluid, turbulent flow is generated when the fluid is ejected from the nozzle, and the gas pressure of the assist gas decreases with increasing distance from the nozzle outlet. A state in which a high pressure in the nozzle is maintained after spraying from the nozzle is called a potential core. However, as the plate thickness of the workpiece increases, the potential core needs to be lengthened. Since the length of the potential core is proportional to the diameter of the nozzle for injecting the assist gas, it is necessary to increase the nozzle diameter as the plate thickness increases. However, if the gas pressure is set high and the nozzle diameter is increased, the consumption amount of the assist gas increases rapidly, resulting in a problem that the laser processing cost increases.

  Further, when the molten metal melted by the laser beam is pushed down from the upper part to the lower part in a narrow cutting groove having a width of about 0.5 mm, the molten metal flow is disturbed when the pressure of the assist gas is lowered. Getting worse. When the roughness of the cut surface is deteriorated, a step of polishing or grinding the cut surface after laser cutting is required. Moreover, if the flow of the molten metal is disturbed, the residence time of the molten metal in the cutting groove becomes longer, leading to an increase in the temperature of the laser workpiece. Thus, when the temperature of the laser workpiece increases, thermal distortion occurs, and the machining accuracy deteriorates. A processed product whose processing accuracy has deteriorated requires strain removal and grinding as post-processing.

  The present invention has been made to solve such a problem, and it is possible to reduce the consumption of the assist gas, improve the roughness of the cut surface, and reduce the thermal strain. The purpose is to obtain a machining nozzle that can supply a gas flow with less turbulence and stably perform high-speed and high-quality machining. Using this machining nozzle, a laser machining apparatus capable of machining stably and accurately is obtained. It is aimed at that.

  In the processing nozzle of the laser processing apparatus according to the present invention, a main assist gas outlet for injecting a laser beam and main assist gas, and an auxiliary assist gas concentrically provided around the main assist gas outlet. And the auxiliary assist gas outlet surface is provided downstream of the assist gas flow with respect to the main assist gas outlet surface, and the gas flow axis of the main assist gas and the auxiliary assist gas are provided. The auxiliary assist gas injection angle at the position where the gas flow axes intersect is set to a range of 0 to 80 degrees with respect to the main assist gas injection axis.

  The processing nozzle of the laser processing apparatus of the present invention includes a main assist gas ejection port for injecting a laser beam and a main assist gas, and an auxiliary assist gas concentrically provided around the main assist gas ejection port. An auxiliary assist gas ejection port for injecting, the auxiliary assist gas ejection port surface provided downstream of the assist gas flow from the main assist gas ejection surface, and a gas flow axis of the main assist gas and the auxiliary assist gas Since the nozzle in which the injection angle of the auxiliary assist gas at the position where the gas flow axes intersect is set in the range of 0 to 80 degrees with respect to the injection axis of the main assist gas is provided, the assist gas injected from the nozzle is disturbed. The phenomenon of pressure drop due to flow is improved and the area under the nozzle where high pressure continues is lengthened. Thereby, it is possible to supply the assist gas pressure necessary for discharging the molten metal from the cutting groove and preventing the dross adhesion. In addition, the assist gas from the annular outer nozzle acts to reduce the diameter of the gas flow ejected from the center nozzle, and by supplying a sufficient assist gas flow rate in the narrow cutting groove, cutting of the molten metal The discharge from the groove can be effectively performed.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a laser machining apparatus and a longitudinal sectional view of a machining nozzle in a first embodiment for carrying out the present invention. Reference numerals 2 and 3 denote an inner main assist gas nozzle (hereinafter also referred to as an inner nozzle) and an outer auxiliary assist gas nozzle (hereinafter also referred to as an outer nozzle), which constitute the double nozzle 1. Reference numeral 4 denotes a main assist gas ejection port provided at the tip of the main assist gas nozzle 2, which injects a laser beam 6 emitted from the laser oscillator 5 and the main assist gas. Then, the laser beam is irradiated by irradiating the workpiece 7 disposed below the double nozzle 1 with the injected laser beam. Reference numeral 8 denotes an auxiliary assist gas ejection port provided at the tip of the outer nozzle 3, which is set downward from the main assist gas ejection port 4. Reference numeral 9 denotes a main assist gas supply passage provided at the center of the main assist gas nozzle 2, and 10 denotes an annular auxiliary assist gas supply passage formed between the main assist gas nozzle 2 and the auxiliary assist gas nozzle 3. 11 is a main assist gas supply source that supplies main assist gas to the main assist gas supply path 9 of the inner nozzle 2, and 12 is an auxiliary assist gas supply source that supplies auxiliary assist gas to the auxiliary assist gas supply path 10. The gas supply sources 11 and 12 are provided separately.

  FIG. 2 is an enlarged vertical cross-sectional view of the nozzle tip in the processing nozzle vertical cross-sectional view of FIG. 1. Reference numeral 21 denotes a gas flow axis of the main assist gas ejected from the main assist gas nozzle 2, and reference numeral 22 denotes a gas flow axis of the auxiliary assist gas ejected from the auxiliary assist gas nozzle 3. As shown in FIG. 2, the flow axis of the auxiliary assist gas is set to be inclined by an angle Θ with respect to the flow axis of the main assist gas.

  In the double nozzle 1 configured as described above, the auxiliary assist gas from the outer auxiliary assist gas nozzle 3 is ejected from the main assist gas nozzle 2 at a certain angle Θ, thereby ejecting the main assist gas from the main assist gas nozzle 2. It has the effect of preventing diffusion due to turbulent flow. FIG. 3 shows the experimental results of visualizing the flow of the main assist gas in the double nozzle in which the auxiliary assist gas is provided around the main assist gas. FIG. 3A shows the flow of the main assist gas when there is no auxiliary assist gas due to the single nozzle, and FIG. 3B shows the angle of the auxiliary assist gas due to the double nozzle Θ = 0. The main assist gas flow is shown in a state of being ejected at a degree. When there is no auxiliary assist gas, as shown in FIG. 3A, the main assist gas ejected from the nozzle outlet turbulently flows with the surrounding air and spreads rapidly. Causes pressure drop of main assist gas. FIG. 4 shows the relationship between the distance from the nozzle tip and the pressure of the main assist gas in the case of a single nozzle. The pressure of the main assist gas is within the nozzle at a position 5 mm away from the nozzle tip. The gas pressure was reduced by 50%. On the other hand, when the auxiliary assist gas is present, as shown in FIG. 3B, the main assist gas ejected from the nozzle outlet does not cause turbulent flow with the surrounding air, and the gas flow does not spread. . This turbulent assist gas flow did not cause a pressure drop, and the gas pressure in the nozzle was only reduced by 5% at a position 5 mm away from the double nozzle 1.

  If the pressure of the assist gas does not decrease depending on the distance from the nozzle and a high pressure is maintained, the molten metal discharged from the narrow cutting groove can be removed without adhesion of dross or the like. FIG. 5 shows the result of measuring the assist gas pressure when the main assist gas pressure is ejected at 2 MPa at a position 5 mm away from the tip of the double nozzle 1. Here, the double nozzle used in the measurement has an inner nozzle inner diameter of φ1.5 mm, an outer diameter of φ2.5 mm, an outer nozzle inner diameter of φ5 mm, and the height difference between the inner nozzle and the outer nozzle is 4 mm. Yes, the measurement was performed with the gas pressure of the auxiliary assist gas set to 0.3 MPa.

  When the injection angle Θ of the auxiliary assist gas was changed from 0 degree to 90 degrees, as shown in FIG. 5, the pressure of the main assist gas gradually decreased and extremely decreased from the angle of 80 degrees. If the angle exceeds 80, the flow of the main assist gas is considered to have occurred because the flow of the auxiliary assist gas changes to an action that disturbs the flow of the auxiliary assist gas. In order to cut stainless steel with a plate thickness of 16 mm with high quality, a pressure of 1.5 MPa is required at a distance of 5 mm from the nozzle tip, and the angle Θ of the auxiliary assist gas is from 0 to 80 degrees. It is an appropriate range. In order to further improve the processing quality, it is more desirable to set the angle Θ to 10 to 30 degrees.

  Next, the operation of the machining nozzle and the laser machining apparatus configured as described above will be described. First, the main assist gas is introduced from the main assist gas supply source 11 into the main assist gas supply passage 9 of the inner nozzle 2. On the other hand, the auxiliary assist gas is introduced into the auxiliary assist gas supply passage 10 from the auxiliary assist gas supply source 12. At this time, the laser beam 6 is irradiated onto the workpiece through the main assist gas supply passage 9, the main assist gas injection port 4, and the auxiliary assist gas injection port 8 of the inner nozzle 2 together with the main assist gas. On the other hand, the auxiliary assist gas is supplied from the auxiliary assist gas supply source 12 through the auxiliary assist gas supply path 10 to the auxiliary assist gas ejection port 8 to correct the flow of the main assist gas. At this time, a difference is provided in the position of the ejection port so that the ejection port of the inner nozzle 2 is above the ejection port of the outer nozzle 3, and the angle Θ of the gas flow axis of the auxiliary assist gas is 0 to 80 degrees. Therefore, the phenomenon that the pressure of the assist gas injected from the nozzle drops due to the turbulent flow is improved, and the flow rate of the main assist gas from the inner nozzle 2 is not easily attenuated.

  Thereby, since the range under the nozzle where the high pressure of the main assist gas continues is extended, the assist gas pressure necessary for discharging the molten metal from the cutting groove and preventing the dross adhesion can be supplied. In addition, the assist gas from the annular outer nozzle acts to reduce the diameter of the gas flow ejected from the center nozzle, and by supplying a sufficient assist gas flow rate in the narrow cutting groove, cutting of the molten metal The discharge from the groove can be effectively performed. As a result, the laser beam 6 can be cut with high quality by utilizing the momentum of the main assist gas in contrast to the oxidation-free cutting of thick stainless steel.

  In addition, since each assist gas supply source 11 and 12 is attached separately, the kind of gas or gas pressure can be changed according to the purpose, and the material and plate thickness of the workpiece can be changed. It can be set optimally accordingly. Thereby, processing with a higher degree of freedom is possible.

Embodiment 2. FIG.
FIG. 6 is a configuration diagram of a laser machining apparatus and a longitudinal sectional view of a machining nozzle according to the second embodiment of the present invention. Reference numeral 31 denotes an annular branch assist gas supply path branched from the main assist gas supply path 9 and is formed between the inner nozzle 2 and the outer nozzle 3. A communication port 32 communicates the main assist gas supply passage 9 and the branch assist gas supply passage 31. The flow rate of the assist gas is determined by the opening area of the communication port 32. An assist gas supply source 33 supplies the assist gas to the main assist gas supply path 9 and the branch assist gas supply path 31. Other configurations are the same as those in the first embodiment.

  The operation of the machining nozzle and the laser machining apparatus configured as described above will be described. The assist gas is led from the single assist gas supply source 33 into the main assist gas supply path 9 of the inner nozzle 2 to become the main assist gas, and part of the assist gas passes from the communication port 32 through the branch assist gas supply path 31. Auxiliary assist gas. At this time, the laser beam 6 emitted from the laser oscillator passes through the main assist gas supply path 9 of the inner nozzle 2, the main assist gas outlet 4, and the outlet 8 of the outer nozzle 3 together with the main assist gas to the workpiece 7. Irradiated. On the other hand, the auxiliary assist gas passes through the branch assist gas supply passage 31 and reaches the outlet 8 of the outer nozzle 3 and is supplied as a gas for correcting the flow of the main assist gas. At this time, as in the first embodiment, the positions of the ejection ports 4 and the ejection ports 8 of the inner nozzle 2 and the outer nozzle 3 are shifted, and the auxiliary assist gas flow is changed with respect to the axis of the main assist gas flow. Since the shaft angle Θ is set from 0 to 80 degrees, the main assist gas flow velocity and pressure attenuation by the inner nozzle 2 are reduced, and the cutting quality is improved.

  Furthermore, since the gas to the main nozzle and the auxiliary nozzle is supplied from the same supply source, the respective gas supply amounts cannot be arbitrarily changed according to the processing situation, but the structure of the apparatus can be simplified. The manufacturing cost of the apparatus can be greatly reduced.

Embodiment 3 FIG.
FIG. 7 is an enlarged longitudinal sectional view of the tip end portion of the machining nozzle according to the third embodiment of the present invention and a bottom view seen from the workpiece side. Here, as shown in FIG. 7, the inner diameter of the inner nozzle 2 is D1, and the outer diameter is D2. In the present embodiment, the diameter difference between D1 and D2 is formed within 16 mm. Other configurations are the same as those in the first embodiment or the second embodiment.

  FIG. 8 shows the inner nozzle 2 by cutting the stainless steel plate with a plate thickness of 16 mm by jetting the main assist gas pressure at 2 MPa at a position where the diameter difference between D1 and D2 and the distance from the double nozzle 1 is 5 mm apart. This is a result of measuring the generation height of dross using the difference between the inner diameter D1 of the inner nozzle 2 and the outer diameter D2 of the inner nozzle 2 as a parameter. Here, the double nozzle used for the measurement has an inner nozzle diameter of φ1.5 mm, the height difference between the inner nozzle and the outer nozzle tip is 4 mm, and the auxiliary assist gas pressure is set to 0.3 MPa. And measured.

  FIG. 8 shows the case where the crossing angle between the flow axis of the auxiliary assist gas and the flow axis of the main assist gas is 0 degrees and 80 degrees. Empirically, the dross height, which is acceptable within the quality of stainless steel, is 0.8 mm or less, and the dross height H is 0.8 mm or less, as shown in FIG. This is a case where the difference in the outer diameter D2 of the nozzle 2 is 16 mm or less. When the difference between the diameter D1 of the inner nozzle 2 and the outer diameter D2 of the inner nozzle 2 is increased, the effect of the assist gas ejected from the outer nozzle 3 suppressing the turbulent flow of the main assist gas ejected from the inner nozzle 2 is reduced. Dross is considered to occur.

It is the block diagram of the laser processing apparatus which shows Embodiment 1 of this invention, and the longitudinal cross-sectional view of a process nozzle. It is a longitudinal cross-sectional view of the nozzle front-end | tip part of the process nozzle of the laser processing apparatus which shows Embodiment 1 of this invention. It is a figure which shows the effect of diffusion prevention of the main assist gas by the process nozzle of the laser processing apparatus which shows Embodiment 1 of this invention. It is the graph which showed the relationship between the distance from the nozzle tip in the case of the single nozzle which is a prior art, and the pressure of main assist gas. It is a graph which shows the result of having measured the relationship between the angle which the main assist gas flow axis and the auxiliary assist gas flow axis make, and the main assist gas pressure in the position 5 mm away from the front-end | tip of a double nozzle. It is the block diagram of the laser processing apparatus which shows Embodiment 2 of this invention, and the longitudinal cross-sectional view of a process nozzle. It is a longitudinal cross-sectional view of the process nozzle which shows Embodiment 3 of this invention. It is a graph which shows the result of having measured the relationship between the internal diameter of an inner nozzle, the difference of an external shape, and dross height.

Explanation of symbols

1 Double nozzle,
2 Main assist gas nozzle,
3 Auxiliary assist gas nozzle,
4 Main assist gas outlet,
5 Laser oscillator,
6 Laser beam,
7 Workpiece,
8 Auxiliary assist gas outlet
9 Main assist gas supply path,
10 Auxiliary assist gas supply path,
11 Main assist gas supply source,
12 Auxiliary assist gas supply source,
21 Gas flow axis of the main assist gas,
22 Gas flow axis of auxiliary assist gas,
31 Branch assist gas supply path,
32 communication port,
33 Assist gas supply source

Claims (7)

A main assist gas outlet for injecting the main assist gas together with the laser beam;
An auxiliary assist gas outlet that is concentrically provided around the main assist gas outlet and injects an auxiliary assist gas;
The auxiliary assist gas outlet face is provided downstream of the assist gas flow from the main assist gas outlet face.
At a position where the axis of gas flow of the main assist gas and the axis of gas flow of the auxiliary assist gas intersect, the injection angle of the auxiliary assist gas is in the range of 0 to 80 degrees with respect to the injection axis of the main assist gas. Laser processing nozzle characterized by setting. A main assist gas outlet for emitting a laser beam and injecting a main assist gas;
An auxiliary assist gas outlet that is concentrically provided around the main assist gas outlet and injects an auxiliary assist gas;
The auxiliary assist gas outlet face is provided downstream of the assist gas flow from the main assist gas outlet face.
A laser processing nozzle, wherein a difference between an inner diameter and an outer diameter of the main assist gas outlet is set to be 16 mm or less. The nozzle for laser processing according to claim 1,
A laser processing nozzle, wherein a difference between an inner diameter and an outer diameter of the main assist gas outlet is set to be 16 mm or less. A laser processing nozzle according to any one of claims 1 to 3,
A main assist gas supply source for supplying main assist gas to the nozzle and ejecting the main assist gas from the main assist gas outlet;
An auxiliary assist gas is supplied to the nozzle, and an auxiliary assist gas is supplied from the auxiliary assist gas ejection port;
A laser oscillator that outputs laser light emitted from the nozzle;
A laser processing apparatus comprising:   The said main assist gas supply source and the said auxiliary assist gas supply source consist of the same assist gas supply source, and supply the same assist gas to the main assist gas and the auxiliary assist gas of Claim 4 characterized by the above-mentioned. Laser processing equipment.   The laser processing apparatus according to claim 4, wherein the assist gas does not contain oxygen.   The laser processing apparatus according to claim 6, wherein the assist gas is nitrogen.

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