JPH1117287A - Excitation medium gas for gas laser beam for cutting steel product and gas laser steel product cutter using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excitation medium gas for gas laser beams for cutting a thick steel product which is more than 20 mm thick in a satisfactory state, and a gas laser steel product cutter using this. SOLUTION: Excitation medium gas E sealed in a discharging tube 2, and allowed to circulate in a blower 3 so as to be cooled through a heat exchanger 4 is excited by impressing and discharging a high voltage with prescribed frequencies to electrodes 6 and 7 by a power source 5 for oscillation, and the optical resonation of excited lights is operated between a total reflecting mirror 8 and a partial transmitting mirror 9 in the discharging tube 2 so that laser beams can be generated. This is derived from the partial transmitting mirror 9, and the beams converged on a lens are used for cutting a steel product. Then, the excitation medium gas is obtained by adding less than 5 capacity % of Xe+Kr to C02, N2, and He, and a composition ratio (capacity) within the range of the value of Kr/Xe=3-7 is provided. Then, it is possible to attain the satisfactory cutting of a thick steel product which is more than 20 mm thick while the roughness of a cut surface is fine, and curve width is thin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excitation medium gas for obtaining a gas laser beam suitable for cutting a steel material, especially a thick steel plate, a steel pipe, an H-shaped steel, a steel column, and the like, and a gas laser steel material using the gas. It relates to a cutting machine.

[0002]

2. Description of the Related Art As a method for cutting steel materials such as carbon steel and stainless steel, for example, steel plates, steel pipes, shaped steels, etc., generally,
Mechanical cutting methods such as cutting using a blade, cutting using abrasive grains, cutting using a press machine, and cutting methods using heat such as gas cutting using a gas flame, cutting using a plasma beam, cutting using a laser beam, etc. There is. Among these, the cutting method using heat is different from the mechanical cutting method in that there is no portion that makes fixed contact with the workpiece, such as a cutting blade for cutting, and the operation is free and easy to control. is there. For this reason, there are few restrictions on the shape to be cut,
Further, there is an advantage that the cutting speed is high, the cutting operation efficiency is high, and the cost is low.

[0003] Among the above-mentioned cutting methods using heat, the cutting method using laser light has a greater dimensional accuracy, squareness, and the like than the cutting method using gas and the cutting method using plasma beam.
It has excellent straightness, low penetration of the upper edge, and small thermal deformation and a small width of the cutting groove. Therefore, it is particularly suitable for precision fine cutting.

FIG. 10 is a schematic structural view showing a side surface of a high-frequency discharge pumped high-speed axial flow type gas laser oscillator.
The high-frequency discharge pumped high-speed axial-flow type gas laser oscillator 1 has a discharge tube 2 made of glass filled with an excitation medium gas E,
In order to cool the excited medium gas E after being excited by the blower 3, the gas is circulated from the front to the rear of the discharge tube 2 via the cooling heat exchanger 4. Then, when a high voltage of a predetermined frequency is applied between the pair of discharge electrodes 6 and 7 provided on the discharge tube 2 from the oscillation power supply 5, discharge occurs in the discharge tube 2. The discharge excites the excitation medium gas E sealed in the discharge tube 2, and as a result, the optical resonator composed of the total reflection mirror 8 and the partial transmission mirror 9 disposed before and after in the longitudinal direction of the discharge tube 2 is used. Laser oscillation occurs between them. A part of the generated oscillation light is extracted as a laser light L via the partial transmission mirror 9. During this time, the excitation medium gas E passes through the discharge tube 2 by the blower 3 at a speed of several tens to several hundreds m / s, is introduced into the heat exchanger 4 and is cooled, and is sent again into the discharge tube 2. Is circulating.

The laser light L extracted from the partial transmission mirror in this manner is converted into several bend mirrors (bend mirrors).
Is guided to a torch at a predetermined position via a torch, and is condensed by a condensing lens provided on the torch, and is projected on a workpiece steel workpiece to cut the steel workpiece into a desired shape.

[0006] However, for cutting the steel material by the above-mentioned laser beam, a laser beam commonly called a carbon dioxide laser beam is used. As the excitation medium gas E of the laser light, a mixed gas of three types of carbon dioxide (CO ₂ ), nitrogen (N ₂ ), and helium (He) has been used. And the volume composition ratio is CO ₂ : N ₂ : He
= 5 to 10:50 to 60:20 or more was considered suitable. However, in the cutting of steel by laser light using a gas having this composition as the excitation medium gas E, when cutting a steel plate having a thickness of 20 mm or more, for example, a steel plate, the output of the laser light fluctuates with time, The intensity distribution of the beam changes, the cut surface becomes rough, and the penetration of the cut surface becomes uneven depending on the cutting direction.

In view of the above, Japanese Patent Application Laid-Open No. 60-18018 discloses a method for increasing the output of laser light and improving the pumping efficiency.
A technique as disclosed in Japanese Patent Application Publication No. 5 (1994) has been proposed. The technique disclosed in this publication is based on the use of carbon dioxide, nitrogen, and helium as the excitation medium gas E of the carbon dioxide laser light.
Xenon (X) having a mole fraction of 5% or less
e) is added. By adding xenon, a stable high-power laser beam can be output, and the effect of uniformly dispersing the discharge in the discharge tube is produced. As a result, the current density can be suppressed low. Therefore, it is possible to increase the pumping efficiency of the laser light and to stably extract the output laser light. From this, when this laser light is used for a cutting machine, it is possible to obtain a laser light intensity more stable than before by condensing the output laser light.

[0008]

However, in the above-described carbon dioxide laser light to which xenon is added, when the derived laser light is condensed by a condenser lens, the energy distribution in the thickness direction is concentrated at one point. Only the point heat source with high beam intensity is used. Therefore, when cutting a steel material having a large wall thickness, especially a steel material having a thickness of 20 mm or more, it is possible to cut a portion located at the light condensing point, but the cutting property is deteriorated at a portion deviated from the light condensing point. Therefore, in order to cut such a thick steel material, it is desirable that the condensed energy distribution by condensing is a so-called linear heat source having a width in the thickness direction of the thick steel material to be cut. We paid attention to. The present invention solves the above problems, and provides a laser beam excitation medium gas for obtaining a laser beam intensity so as to form a linear heat source suitable for cutting a thick steel material satisfactorily, and a gas laser steel material cutting machine using the gas. The purpose is to provide.

[0009]

[MEANS FOR SOLVING THE PROBLEMS] To solve the above-mentioned problems,
In order to achieve the object, in claim 1 of the present invention, the composition component comprises a mixed gas of five kinds of gases of carbon dioxide, nitrogen, helium, xenon, and krypton. The medium gas for exciting a laser beam for cutting steel material according to claim 1, wherein the content of xenon + krypton in the mixed gas of the five types of gases is 5% by volume or less. 3. The method according to claim 1, wherein the volume ratio of xenon: krypton in the mixed gas of the five types of gases is 1: 3 to 7. It is an excitation medium gas of a steel material cutting gas laser beam. According to a fourth aspect of the present invention, there is provided a gas laser steel cutting apparatus using the excitation medium gas of the gas laser light for cutting a steel material according to any one of the first to third aspects.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a steel material having a thickness of 20 m.
In order to generate a gas laser beam suitable for cutting a steel material having a thickness of m or more, an excitation medium gas which is enclosed in a discharge tube 2 of a high-frequency discharge-excited high-speed axial flow gas laser oscillator 1 shown in FIG. As E, a gas obtained by mixing five kinds of gases of carbon dioxide, nitrogen, helium, xenon, and krypton is used. Preferably, the ratio of the constituent components of this gas is CO ₂ : N ₂ : He = 5 to 10:50 to 60:
Xe + Kr is added to a mixed gas of 20 or more.

In order to obtain a laser beam intensity distribution particularly preferable for cutting a thick steel material with the five kinds of mixed gases, the content of xenon + krypton in the five kinds of mixed gases is set to 5% by volume or less. Things. Further, by setting the krypton / xenon content in the mixed gas of 5 to 3 to 7 in a state where the diameter of the derived laser beam is stable with time, the output intensity is reduced in the axially symmetric low-order mode. And a stable beam with a high

In a gas laser steel cutting machine using a gas laser oscillator in which an excitation medium gas having the above-mentioned composition ratio is enclosed in a discharge tube 2, an output beam is stable, an axially symmetric lower-order mode energy distribution is obtained, and The spot radius of the focused beam has an energy spread in the thickness direction,
The cut surface of a thick steel material is made uniform to enable fine cutting with a narrow kerf width.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Various confirmation experiments performed on the gas composition components specified as examples will be described below by way of example. As the exciting medium gas to be excited, the exciting medium gas used for the carbon dioxide laser beam conventionally used for cutting steel materials and its composition ratio (volume) CO ₂ : N ₂ : He = 5 to 10: 5
Based on 0 to 60:20 or more, Xe + Kr was added thereto, and various characteristics were confirmed by experiments. The gas laser light used was a high-frequency discharge-excited high-speed axial flow type (refer to FIG. 10), which is generally called a carbon dioxide laser light, and used an oscillator having an output of 6 KW, a frequency of 500 Hz, and a duty cycle of 70%. . Further, a carbon steel plate having a thickness of 25 mm was used as the thick steel material used for cutting.

[Experiment 1] First, it was confirmed by an experiment that a temporal change of a radius of a non-condensed beam of a laser beam derived from a discharge tube due to a difference in a composition component of an excitation medium gas was confirmed. The following three types of excitation medium gases were used. Exciting medium gas composition component ratio (volume) of the present invention CO ₂ : N ₂ : He: (Xe + Kr) = 5: 54: 40:
1 Kr / Xe = 5 Composition ratio (volume) of Xe added only to a conventional excitation medium gas of carbon dioxide laser light CO ₂ : N ₂ : He: (Xe + Kr) = 5: 54: 40:
1 And Kr / Xe = 0/1 (only Xe is added) The composition ratio (volume) of the excitation medium gas of the conventional carbon dioxide laser light CO ₂ : N ₂ : He = 5: 55: 40 These three types of excitation medium gas FIG. 1 is a graph showing a change with time of the radius of the non-condensed beam of the laser beam due to the above.

As is apparent from FIG. 1, in a conventional excitation medium gas using a carbon dioxide laser beam, the radius of the non-condensed beam of the laser beam changes with time and is very unstable as a laser beam. . On the other hand, the variation with time of the radius of the non-condensed beam of the laser beam due to the excitation medium gas of the present invention is very stable, with almost no Xe alone and the excitation medium gas added to the conventional excitation gas of carbon dioxide laser light. You can see that it is. This is convenient as a laser beam for cutting.

[Experiment 2] Next, an experiment was performed to confirm the intensity distribution of the non-condensed beam of laser light. The excitation medium gas used was the excitation medium gas having the above-mentioned composition ratio (volume) used in Experiment 1, CO ₂ : N ₂ : He: (Xe + Kr) = 5: 54: 40:
1 Then, Kr / Xe = 5, and as a comparative example, the composition ratio (volume) of the conventional carbon dioxide laser beam excitation medium gas of Experiment 1 was CO ₂ : N ₂ : He = 5: 55: 40. Was performed using the following gas. FIG. 2 shows the results of the excitation medium gas of the present invention, and FIG. 3 shows the intensity distribution of a conventional carbon dioxide laser beam excitation medium gas as a comparative example. In the distribution, the horizontal axis represents the distance (r), ie, r / w, of the non-condensed beam in the radial direction with respect to the radius (w) containing 86% of the intensity, and the vertical axis represents the relative intensity of the beam.

As shown in FIG. 2, the intensity distribution of the non-condensed beam of the laser beam by the excitation medium gas comprising the composition component of the present invention showed a very stable axis-symmetric low-order mode. That is, the variance of the peaks of the intensity distribution is only dispersed in two less modes (referred to as a lower-order mode), and the higher-order mode (also referred to as a multimode or a multimode) is dispersed in many peaks. It is concentrated without dispersion of strength as in Moreover, they are distributed symmetrically about the axis. On the other hand, as shown in FIG. 3, the intensity distribution of the non-condensed beam of the laser beam in the excitation medium gas used for the conventional carbon dioxide laser beam shows a low-order mode but is asymmetric with the axis. It was recognized that.

As a result, in the conventional carbon dioxide laser light, since the beam intensity distribution is a low-order mode in which the beam intensity distribution is asymmetric about the axis,
In the cutting, cutting in the direction in which the asymmetric lower-order mode proceeds along the same line is possible, but cutting in the direction in which the lower-order mode asymmetrical to the axis proceeds in parallel is not preferable because uneven cutting occurs. That is, in the cutting by the laser beam using the excitation medium gas, the direction in which cutting can be performed in a preferable state is limited to a specific direction. On the other hand, the intensity distribution of the laser beam by the excitation medium gas according to the present invention is formed symmetrically with respect to the axis, and there is no restriction on the directionality of the cutting, and it is extremely stable.

[Experiment 3] Next, the change of the intensity of the output beam of the oscillated laser light with time was confirmed by an experiment.
The experiment was performed using three types of excitation medium gas as in the case of Experiment 1 as the excitation medium gas, and these were compared. That is, the composition ratio (volume) of the excitation medium gas composition of the present invention: CO ₂ : N ₂ : He: (Xe + Kr) = 5: 54: 40:
1 Kr / Xe = 5 Composition ratio (volume) of Xe added only to a conventional excitation medium gas of carbon dioxide laser light CO ₂ : N ₂ : He: (Xe + Kr) = 5: 54: 40:
1 And Kr / Xe = 0/1 (only Xe is added) The composition ratio (volume) of the excitation medium gas of the conventional carbon dioxide laser light CO ₂ : N ₂ : He = 5: 55: 40 The graph of this result is shown in FIG. Illustrated in FIG. The output beam intensity was evaluated with respect to an output peak having a relative intensity of 90% or more and 100%.

As is apparent from the graph of FIG. 4, the output beam intensity of the laser beam using the conventional carbon dioxide laser beam excitation medium gas may show a high value, while it may show a low value. The variation is extremely large with time, which indicates that it is very unstable. On the other hand, the intensity of the output beam of the laser beam by the excitation medium gas to which Xe + Kr is added according to the present invention is the output beam of the laser beam by the excitation medium gas to which only Xe is added to the excitation medium gas of the conventional carbon dioxide laser beam. Like the strength of
A beam with a high output intensity such as a laser beam generated by the excitation medium gas in the carbon dioxide gas laser beam does not appear, and the beam does not become a low output intensity beam.It is very stable, and the fluctuation with time is extremely small. Is shown. This makes it possible to cut the steel material evenly and to keep the yield of the processed product high.

According to the above three experiments, the conventional carbon dioxide laser light of the present invention shows that the laser light using the excitation medium gas obtained by adding Xe + Kr to the excitation medium gas has a non-condensed beam radius and output beam intensity with time. It has been found that the material has little fluctuation, is extremely stable, has a uniform workability of cutting the steel material, and has good workability. In addition, since a stable axially symmetric low-order mode beam intensity distribution is formed, it has been found that there is no directivity depending on the beam cutting direction, and that it has a characteristic that it can be used well in all directions.

Next, Xe + Kr to be added as the excitation medium gas of the present invention to the mixed gas of CO ₂ , N ₂ , and He, which is the excitation medium gas used in the conventional carbon dioxide laser light, That is, it was confirmed what value of the Kr / Xe composition ratio (volume) was an appropriate value.

[Experiment 4] Laser light generated by changing the composition ratio (volume) of Xe and Kr in the excitation medium gas of the present invention in which Xe + Kr is added to the conventional excitation medium gas used for carbon dioxide laser light. Using a lens having a focal length of 254 mm, the change in the radius of the focused spot was confirmed. The resulting graph is shown in FIG. In the graph of FIG. 5, the horizontal axis represents Kr / (Xe + Kr), and the Kr / Xe ratio (volume) corresponding thereto is shown below for easy understanding below the graph. The vertical axis indicates the spot radius (μm).

As is clear from FIG. 5, Kr / (Xe
+ Kr) = 0, that is, when only Xe is added without containing Kr, the spot radius becomes about 225 μm, which is the smallest spot radius as compared with the spot radius of the excitation medium gas of the composition containing Kr. When Kr is contained and its amount is increased, the spot radius gradually increases gradually, and in particular, Kr / (Xe + Kr) =
The increase of the spot radius at 0.75 or more (Kr / Xe = 3/1 or more) is remarkable. Further, when only Kr of Kr / (Xe + Kr) = 1 is added, the spot radius becomes about 238.
μm, and when Kr / (Xe + Kr) = 0 (Xe
It was confirmed that the spot radius increased by about 6% from the spot radius of (only added).

Referring to the above Experiment 4, Xe + Kr to be added is Kr / (Xe + Kr) as an excitation medium gas of the present invention for forming a preferable spot radius for cutting a thick steel material.
= 0.75 or more (Kr / Xe = 3/1 or more). Based on this, it was confirmed in Experiment 5 below how the spot radius acts in the thickness direction of the steel material to be cut.

[Experiment 5] Based on the result obtained in Experiment 4, it was confirmed how the spot radius of the condensed beam at the focal position changes with the cutting depth (in the thickness direction).
The derived laser beam is 2 mm in front of the steel workpiece to be cut (lens side) using a lens with a focal length of 254 mm.
Is focused at the position, and the spot radius of the condensed beam at the focal position, the condensed beam at each position from the focal position to the position of the work (position of scale 0) and the thickness direction (depth) of the work The spot radius of each spot was measured, and the fluctuation trend of the spot radius at each position was confirmed. The excitation medium gas used was the following a. b. c. There are three types. a. Exciting medium gas composition component ratio (volume) of the present invention CO ₂ : N ₂ : He: (Xe + Kr) = 5: 54: 40:
1 Then, Kr / Xe = 3, [Kr / (Xe + Kr) =
0.75] b. Exciting medium gas composition component ratio (volume) of the present invention CO ₂ : N ₂ : He: (Xe + Kr) = 5: 54: 40:
1 Then, Kr / Xe = 7, [Kr / (Xe + Kr) =
0.88] c. Composition ratio (volume) of Xe added only to the excitation medium gas of the conventional carbon dioxide laser light CO ₂ : N ₂ : He: (Xe + Kr) = 5: 54: 40:
1 And Kr / Xe = 0/1 (only Xe was added) A graph of this result is shown in FIG. With the position of the steel workpiece to be cut as the reference 0 on the horizontal axis, the negative (-) side is the lens side,
The positive (+) side is the unit (m) in the thickness direction (depth) of the steel workpiece.
m). The vertical axis shows the radius of the spot (μm)
Is shown.

As is apparent from FIG. 6, when the excitation medium gas a to be used in the present invention is used, the spot radius of the focused beam at the position of −2 mm is about 237 μm, and at this time, the spot radius of −2 mm is used. + 8m on the work side 10mm from the position
At the position of m, the radius of the spot is about 276 μm, and the radius of the spot of about 39 μm is expanding. Similarly, when the excitation medium gas b, which is the object of the present invention, is used,
The radius of the focused beam spot at position m is about 239 μm
At this time, the radius of the spot at a position of +8 mm on the work side 10 mm from this is about 277 μm, and the radius of the spot of about 38 μm is widened. On the other hand, in the case of the laser beam using the excitation medium gas c which is out of the scope of the present invention, the radius of the spot of the focused beam at the position of −2 mm was about 225 μm. The spot radius of this beam at a position +8 mm on the work side 10 mm from this position was about 270 μm, and the spread of the spot radius of about 45 μm was observed during this time.

From the results of Experiment 5 described above, in the case of laser light using the excitation medium gases a and b, which are the objects of the present invention, the spot radius of the condensed beam is 10 m from the focal position.
At the position of +8 mm on the thickness direction side of the workpiece m, the diameter of the work is expanded by about 39 and 38 μm, respectively. It was found that the spread increased by about 45 μm at a position of +8 mm on the thickness direction side of the workpiece 10 mm ahead, and the spread was larger than that of the laser light by the excitation medium gases a and b of the present invention. This means that the excitation medium gas c has a spot radius spread at a position of +8 mm, the energy distribution in the thickness direction (depth) is reduced, and the excitation medium gas c is in a state close to a point heat source. On the other hand, the excitation medium gases a and b, which are the objects of the present invention, in which the spread of the spot radius is small, have an energy distribution in the thickness direction (depth) and are determined to be in a state close to the linear heat source. This is considered to be suitable for cutting a thick steel material.

Furthermore, in order to more clearly confirm the Kr / Xe ratio (volume) of Xe + Kr of the present invention added to the excitation medium gas used in the conventional carbon dioxide laser light, a thick steel material, for example, Cutting thick steel plate,
The roughness of the cut surface and the calf width were checked. [Experiment 6] Xe + added as excitation medium gas of the present invention
In order to clarify the Kr / Xe ratio (volume) of Kr, the ratio was changed, and the laser light generated by the excitation medium gas of each ratio was condensed using a lens having a focal length of 254 mm. SS400 (mild steel), thickness 25m
m thick steel plate was cut as a sample. And
After cutting, (a) cutting upper surface (1 mm from the surface), (b) deep center of cutting (12.5 mm from the surface), (c) cutting lower surface (1 mm from the lower surface)
The roughness was measured at each location. The laser oscillator used was a high-frequency discharge pumped high-speed axial flow gas laser oscillator with an output of 6 kW shown in FIG. The resulting graph is shown in FIG. In the figure, the horizontal axis shows the change in the Kr / Xe ratio (volume) by the value of Kr / (Xe + Kr), and the vertical axis shows the roughness (μm) of the cut surface.

FIG. 7 shows that the roughness of the cut surface is the upper surface (a) <
It was confirmed that the roughness increased in the order of the deep part in the center (b) <the lower surface (c), and the following was confirmed. (A) The roughness of the cut surface of the cut upper surface (a) is Kr / (Xe
+ Kr) = 0, that is, when Kr = 0, Xe = 1, and when only xenon is added, the roughness is about 53 μm;
(Xe + Kr) = 1, that is, when Xe = 0 and Kr = 1,
The roughness when only krypton is added is about 54 μm, and the roughness when the ratio of Kr / (Xe + Kr) = 0.83, ie Kr / Xe = 5, is about 52.5 μm, respectively. No significant change was observed in the roughness due to the change in the Kr / Xe ratio. That is, the cutting upper surface (a)
Regarding the roughness, no significant effect was observed by the excitation medium gas to which xenon and krypton were added.

(B) Next, the roughness of the cut surface at the center of the cut (b) is Kr / (Xe + Kr) = 0, that is, Kr = 0, X
The roughness when only xenon is added at e = 1 is about 73 μm
And Kr / (Xe + Kr) = 1, that is, Xe =
0, Kr = 1, the roughness when only krypton is added is about 73 μm, and further Kr / (Xe + Kr) =
The roughness at the ratio of 0.83, that is, Kr / Xe = 5, is as small as about 71 μm. The surface roughness of about 71 μm is 0.75 ≦ Kr / (Xe + Kr) ≦ 0.9
, That is, 3 ≦ Kr / Xe ≦ 9. Therefore, the effect of adding xenon and krypton in this range was recognized.

(C) The roughness of the cut surface of the cut lower surface (c) is Kr / (Xe + Kr) = 0, that is, Kr = 0, Xe
= 1 and the roughness when only xenon is added is about 93 µm, and Kr / (Xe + Kr) = 1, ie Xe = 0,
When Kr = 1 and only krypton is added, the roughness is about 95.
μm, and further Kr / (Xe + Kr) = 0.8
3, that is, the roughness at the ratio of Kr / Xe = 5 is about 90 μm.
m, which is the minimum value at the cut lower surface. The surface roughness having a value close to about 90 μm is 0.75 ≦ K
r / (Xe + Kr) ≦ 0.88, that is, 3 ≦ Kr /
Xe was maintained in the range of 7 or less. Therefore, the effect of adding xenon and krypton was recognized in this range.

(D) From the above, based on the roughness of the cut surface, it was judged whether the composition ratio (volume) of Kr / Xe of Xe + Kr to be added to the excitation medium gas was appropriate or not. Whether or not, as the roughness of the cut surface of the cut lower surface of the steel plate to be cut is smaller, the energy of the focused beam of the laser beam is applied over the entire thickness in the thickness direction of the steel plate material to be cut and is suitable. Therefore, according to Experiment 6, Xe + Kr was set to 3 ≦ Kr / Xe ≦ 7 as the excitation medium gas used for cutting steel having a thickness of 20 mm or more.
It has been confirmed that it is preferable to add at a composition ratio (volume) within the range described above.

[Experiment 7] Confirmation of the roughness of the cut surface in Experiment 6
Cutting kerf width (m) on the front surface (x) and the back surface (y) of the steel sheet workpiece to be cut with a change in the composition ratio (volume) of r / Xe
m) was measured. The conditions of the experiment, the cut sample steel material, and the like are the same as those in Experiment 6. FIG. 8 shows a graph of the experimental results.
Illustrated in FIG. The horizontal axis in the figure indicates the change in the composition ratio Kr / Xe as K
Displayed as r / (Xe + Kr), the vertical axis represents the calf width (mm)
Was displayed.

As is apparent from the graph of FIG. 8, the kerf width of the surface (x) hardly changes even when the value of Kr / (Xe + Kr) changes, and the value is maintained at about 0.75 mm. There is no influence from the change of the composition ratio Kr / Xe of Xe + Kr to be added. However, the kerf width on the back surface (y) is Kr / (Xe + Kr) = 0, that is, Xe = Kr = 0
At the time of 1, there is a kerf width of about 2 mm, and Kr / (Xe + K
As the value of r) increases, the kerf width decreases, and K
r / (Xe + Kr) = 0.75, that is, Xe + K to be added
When the composition ratio of Kr / Xe = 3/1, the kerf width is about 1.
7 mm. When the value of Kr / (Xe + Kr) is 0.75 or more and 0.88, a substantially constant kerf width of about 1.7 mm is maintained. That is, the excitation medium gas of the laser beam that enables a thick plate having a plate thickness of 20 mm or more to be cut with a thinner and sharper kerf width to the back surface (y) is added with Xe + Kr, and this composition ratio (volume) Kr / Xe It was confirmed that it was preferable to set the range of 3 to 7.

From the results of the above Experiments 1 to 7, it was confirmed that the following composition components can be suitably used as the excitation medium gas of the gas laser beam for cutting the steel material of the present invention, especially the thick steel material. . (1) Xenon (Xe) + Krypton (Kr) is added to a conventional excitation medium gas for carbon dioxide laser light. That is, CO ₂ : N ₂ : He: (Xe + Kr) = 5 to 10:50
60 to 20 or more: a gas having a composition ratio (volume) of 1 to 5; (2) The composition ratio of Xe + Kr to be added is Xe: Kr
= 1: 3-7. When Xe is set to 1 and Kr is set to 3 or less, the spot radius of the focused beam is small,
The energy distribution in the thickness direction (depth) is small, so that the roughness of the cut lower surface is large, and the cut kerf width of the rear surface is wide, which is not suitable for cutting a thick steel material. Also, Xe
If Kr is set to 7 or more with respect to 1, the peak value of the intensity of the output beam of the laser light fluctuates and becomes unstable, and the cut surface becomes rough and non-uniform, which is not preferable. (3) Xe + Kr composition ratio Xe: Kr =
At 1: 5, the spot radius of the focused beam maintains the energy distribution in the plate thickness direction (depth direction), the kerf width of the back surface by cutting is small, and the roughness of the cut surface is small even at the cut lower surface. It was cut uniformly, and showed a particularly excellent effect as an exciting medium gas of a laser beam for cutting a steel material having a thickness of 20 mm or more.

In each of the experiments described above, the composition of the pumping medium gas of the laser beam was CO ₂ :
N ₂ : He: (Xe + Kr) = 5: 54: 40: 1, that is, a gas in which Xe + Kr is 1% by volume has been described as an example. Next, as Experiment 8, Xe + added to the excitation medium gas
The amount of the mixed gas of Kr was changed, and the effect of this on the laser output was tested.

[Experiment 8] In this experiment, as the excitation medium gas for changing the content of the mixed gas of Xe + Kr, CO ₂ : N ₂ : He: (Xe + Kr) = 5: (〜5)
5): 40: (0) gas was used. That is, Xe + K
With the addition of r, the content of N ₂ gas was adjusted.
The mixing ratio of Xe + Kr was adjusted to have a ratio of Kr / Xe = 5/1 (volume ratio). In this way,
Laser output (K) with change in volume content of Xe + Kr
The change in w) was measured. The results are shown in FIG. 9 with the horizontal axis indicating the volume content of Xe + Kr (%) and the vertical axis indicating the laser output (Kw).

As apparent from FIG. 9, when Xe + Kr was not contained, an output of 6 Kw was obtained. Then, as the content of Xe + Kr increases, the laser output also increases, and when the volume content reaches 2.0%, the output becomes about 6.
The value was 6 Kw, and the peak value was obtained. 2.0% content
Above that, the laser output gradually decreases and Xe
When the content of + Kr becomes 5%, the output becomes 6Kw, and X
The state returned to the same value as the output when e + Kr was not contained. Then, the content of Xe + Kr is further reduced to 5%.
The laser output did not increase even if it increased above.

From the result of Experiment 8, the volume ratio was C
O ₂ : N ₂ : He: (Xe + Kr) = 5: 50: 40:
5, that is, a composition gas containing 5% by volume of Xe + Kr
A laser beam with a peak output of 6 KW, a frequency of 500 Hz and a duty cycle of 70% was obtained using a high-frequency discharge pumped high-speed axial-flow gas laser oscillator shown in FIG.
The same experiment as in No. 7 was performed. As a result, even if the total composition ratio (volume) of Xe + Kr to be added is 5%, the Kr / Xe has a composition ratio (volume) of 0.75 ≦ Kr / (Xe + Kr) ≦ 0. In the range of 88, that is, in the range of 3 ≦ Kr / Xe ≦ 7, the above-mentioned remarkable effect of adding xenon and krypton is exhibited, and it is possible to cut a steel plate having a thickness of 20 mm or more satisfactorily. confirmed. However, in the case of the excitation medium gas to which Xe + Kr is added to 5% by volume or more, the intensity of the output beam of the laser beam is reduced, and it becomes difficult to cut the steel sheet in a good state. Cutting turned out to be difficult.

The applicable range of the thickness of the thick steel material to be cut is as follows. The laser beam obtained with the excitation medium gas of the present invention used in each of the above-described experiments cuts a 32 mm thick carbon steel in a good condition. Although it has been confirmed that it can be performed, it is a matter of course that a steel material having a larger thickness can be cut well. In addition, although the example of each of the above experiments was conducted using a steel plate having a thickness of 25 mm as the thick steel material, the present invention is not limited to the steel plate, and a steel pipe having the same thickness is used. It can be used as an exciting medium gas of a gas laser for cutting steel columns, steel bars, wires, and the like. Further, it goes without saying that the gas laser cutting machine of the present invention can be widely applied to the processing of steel materials such as drilling of steel materials having the same thickness and welding of steel materials.

[0042]

As described above, the excitation medium gas of the gas laser beam for cutting steel material according to the present invention is a component gas of the conventional excitation medium gas of the carbon dioxide laser beam, the carbon dioxide gas (CO 2 gas).
₂ ), nitrogen (N ₂ ), helium (He) and xenon (X
e) + krypton (Kr) is added to mix five types of gases, and the content of Xe + Kr in the total gas is set to 5% by volume or less, and the volume ratio of Kr to Xe is 3 to 7%. It is what it was. As a result, a gas laser beam using this excitation medium gas can obtain a stable laser beam having a low-order mode beam intensity distribution in an axially symmetric state, the beam intensity is high, and the focal point is thick (depth). ) It is possible to cut a thick steel material of 20 mm or more, which has been considered difficult to cut, with a very good cut surface, kerf width, etc. by forming it in a state close to a linear heat source that advances in the direction. A gas laser steel cutting machine may be provided.

[Brief description of the drawings]

FIG. 1 is a graph showing a temporal change of a non-focused beam radius between a conventional carbon dioxide laser beam and a laser beam using the excitation medium gas of the present invention.

FIG. 2 is a graph showing an intensity distribution of a non-condensed beam of laser light by an excitation medium gas of the present invention.

FIG. 3 is a graph showing the intensity distribution of a conventional non-focused beam of carbon dioxide laser light.

FIG. 4 is a graph showing the change over time of the intensity of laser light in an excitation medium gas depending on whether Xe or Kr is added.

FIG. 5 shows Xe and K of Xe + Kr gas added in the present invention.
6 is a graph showing a change in a spot radius of a focused beam due to a change in a composition ratio (volume) of r.

FIG. 6 shows Xe and K of Xe + Kr gas added in the present invention.
6 is a graph showing a change in a focused beam radius at a workpiece depth position due to a difference in a composition ratio (volume) of r.

FIG. 7 shows Xe and Kr of Xe + Kr gas added in the present invention.
6 is a graph showing a change in roughness of a cut surface cut by a laser beam in which the composition ratio (volume) of r is changed.

FIG. 8 shows Xe and K of Xe + Kr gas added in the present invention.
It is a graph which shows the change of the cutting kerf width cut | disconnected by the laser beam which changed the composition ratio (volume) of r.

FIG. 9 is a graph showing a change in laser output according to a change in the volume content of the Xe + Kr gas.

FIG. 10 is a schematic structural view illustrating a high-frequency discharge pumped high-speed axial flow gas laser oscillator.

[Description of Signs] 1 High-frequency discharge pumped high-speed axial flow gas laser oscillator 2 Discharge tube, 3 Blower, 4 Heat exchanger, 5
Oscillation power supply, 6, 7 discharge electrode, 8 total reflection mirror, 9
Partial transmission mirror, L laser beam, E excitation medium gas

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masayuki Nagahori 11th Takemazawa, Miyoshi-cho, Iruma-gun, Saitama, Japan Tanaka Corporation

Claims (4)

[Claims] An excitation medium gas for a steel material cutting gas laser beam, characterized in that the composition component is a mixed gas of five kinds of gases of carbon dioxide, nitrogen, helium, xenon and krypton. 2. The exciting medium gas for gas laser light for cutting steel material according to claim 1, wherein the content of xenon + krypton in the mixed gas of the five types of gases is 5% by volume or less. 3. The steel material cutting device according to claim 1, wherein a volume ratio of xenon: krypton in the mixed gas of the five types of gases is 1: 3 to 7. Excitation medium gas for gas laser light. 4. A gas laser steel material cutting apparatus using the excitation medium gas of the gas laser light for steel material cutting according to any one of claims 1 to 3.