JPH0347958B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for cutting an object using a laser beam and an assist gas.

Generally, when cutting, for example, a steel plate using a laser beam, as shown in FIG. Oxygen gas (first gas) is blown onto the workpiece 7 from the coaxial nozzle 4, and the workpiece is melted and cut using the oxidation heat generation effect. As described above, the laser cutting method has many advantages such as non-contact processing, free cutting direction, narrow cutting width, and less thermal influence on the workpiece.

However, this method also has the following disadvantages. That is, the molten oxide 9 produced during the cutting process descends along the cut surface 8, as shown in FIGS. 2a and d.
As shown in FIG. 2, the lower surface of the cut portion 8 of the workpiece 7 is drooped, and as shown in FIGS. 2b and 2e,
After the cut, it may occur that the lower part of the cut is again blocked by the molten oxide 9. When such a phenomenon occurs, cutting accuracy may be reduced, and additional manufacturing steps such as grinding after cutting are required, resulting in increased costs.

Figure 4 shows the cross-sectional shape of the cut surface when 100% oxygen gas is injected from the cutting nozzle when the workpiece is in a high temperature state. The middle diagram shows when the temperature is room temperature.
The figure on the far right shows the case at 400℃, and the figure on the right shows the case at 800℃. In FIG. 4, 7' is the test piece. As is clear from these figures, as the temperature of the workpiece increases to 400℃ and 800℃, the oxidation exothermic reaction due to oxygen gas from the nozzle increases, and the cutting speed becomes faster, but the cutting width also becomes wider. In addition, the cut surface becomes less uniform and more molten oxides are generated.

An object of the present invention is to provide a method for cutting an object using a laser beam, which can cut with high precision and does not require post-processes such as grinding after cutting. By increasing the temperature of the cutting part, the oxygen mixing ratio of the gas injected from the nozzle is lowered, reducing the oxidative exothermic reaction caused by oxygen gas, and suppressing the generation of molten oxide.
The cutting width is narrow and the cutting surface is uniform.

In addition, preheating increases the wavelength absorption of the laser beam on the steel plate surface, making it possible to generate keyholes (holes created by evaporation of the workpiece) using the laser with less energy. It is something. In addition, inert gas is injected into the vicinity of the cut portion from the front and back, respectively, to prevent the generated molten oxide from adhering to the cut portion.

The present invention will be explained below with reference to the drawings.

FIG. 3 is an explanatory diagram showing a vertical cross section of a cutting head and a workpiece in which the present invention is practiced. Reference numeral 1 denotes a laser beam, which is incident on the cutting head 2 from above.

Inside the cutting head 2, a condensing lens 3, an assist gas inlet 6, etc. are provided. The laser beam 1 passes through the cutting head 2 and passes through the condensing lens 3.
The light is focused and irradiated onto the workpiece 7. Oxygen gas etc. from the assist gas inlet 6 is transferred to the cutting head 2.
The laser beam passes through the interior of the cutting head 2, passes through the cutting nozzle 4 provided at the bottom of the cutting head 2, and the main nozzle hole 5 at the tip of the cutting nozzle 4, and is sprayed onto the same portion of the workpiece 7 as the laser beam irradiation position. This position is the cutting position.

10 is the first sub-nozzle, its tip (lower)
A first sub-nozzle hole 11 is formed at , and is oriented at an angle θ ₁ with respect to the surface of the workpiece 7 so that the gas is injected to a position L ₁ behind the laser beam irradiation position. Further, 20 is a second sub-nozzle, which has an angle of θ ₂ with respect to the back surface of the workpiece 7 in order to inject gas onto the back surface of the workpiece 7. The gas is sprayed a distance L ₂ behind the gas spray position. Further, the second sub-nozzle 20 may be formed at an angle with respect to the cutting line. 21 is the second
It is a sub nozzle hole.

In addition, in the explanatory diagram of the present invention shown in FIG.
0 is the preheating source, distance from the laser beam irradiation point P ₀
Preheat the position P ₃ points forward by L ₃ . The figure also shows a TIG torch. 31 is an arc. Note that any heat source can be used as this preheating source, such as a TIG arc, an electric arc, a gas burner, direct energization, high frequency heating, and a laser beam.

To cut a workpiece (hereinafter referred to as a steel plate) 7 according to the present invention, the cutting portion of the steel plate 7 is set in the apparatus of the present invention as shown in FIG. Preheat ₃ points. After that, when the steel plate 7 is moved and the preheating point reaches the position below the cutting nozzle 4, the laser beam 1 and the center gas _G1 are emitted from the main nozzle hole 5 of the cutting nozzle 4.
As a result, the steel plate 7 is cut.

Since this operation is performed continuously as the steel plate moves, long steel plates can be cut. At this time, if the composition of the center gas G ₁ is a synthetic gas of oxygen and an inert gas such as nitrogen, the cutting efficiency will not be reduced, and there will be less generation of molten oxide due to the oxidation exothermic action of oxygen, resulting in an efficient Cutting can be done.

Further, the present invention is more effective when the inert gases G ₂ and G ₃ are injected into the non-solidified region near the cut portion from the sub-nozzle during the above-mentioned cutting.

That is, as shown in FIG. 3, a first sub-nozzle 10 is obliquely attached to the cutting nozzle 4, and a second sub-nozzle 20 is provided below the first sub-nozzle 10. The inert gas G ₂ injected from the nozzle 10 is sprayed at _one point P in FIG.
G ₃ is also configured to be sprayed at _two points P.

Therefore, the inert gas G ₂ from the first sub-nozzle 10 is blown into the cutting groove of the steel plate 7 which has been preheated by the preheating source 30 and further cut by the laser beam 1. The molten oxide before solidification is removed outside the groove. On the other hand, since the inert gas G ₃ injected from the second sub-nozzle 20 is sprayed at the point P ₂ on the back surface of the steel plate 7, the gas G ₂ from the first sub-nozzle 10 is applied to the outside of the cutting groove. The molten oxide discharged to the inert gas _G3 is scattered by the inert gas G3 and does not adhere to the back surface of the steel plate. Therefore, the cut portion becomes as shown in FIGS. 2c and 2f, and maintenance such as grinding is therefore unnecessary.

Here, conditions suitable for carrying out the present invention are as follows.

Sample: Electrical steel plate (Si3%), thickness 2mm; Distance between TIG arc and laser irradiation position (L ₃ ): 10
~20mm TIG arc: 10V, 100~300A Laser output: 2Kw, 50~150mm/S Mixed gas component ratio of gas from the cutting nozzle: Oxygen gas 60~80%, Nitrogen gas 20~40% Angle of 1st sub nozzle (θ ₁ ): 30 to 60° Gas flow rate from the first sub-nozzle (Q ₁ ): 60 to 120
/min Gas spraying position of the first sub-nozzle (distance from the cutting point) L ₁ : 2 to 7 mm Angle of the second sub-nozzle (θ ₂ ): 5 to 20° Gas flow rate from the second sub-nozzle (Q ₂ ):80~140
/min Gas spraying position of the second sub-nozzle (distance from the gas spraying position of the first sub-nozzle) _L2 : 3 to 10 mm The above conditions are fully applicable even when the workpiece is other than an electromagnetic steel plate.

Next, examples of the present invention will be shown.

Example 1 A CO ₂ laser device with an output of 2.0 Kw was used as a laser beam source to cut 3% Si steel with a thickness of 2.0 mm at a speed of 80 mm/sec. A TIG arc was used as a preliminary heating source, set at 10 V and 150 A, and a mixed gas of 70% oxygen gas and 30% nitrogen gas was injected from the main nozzle 4. As a result, it was possible to cut the cut surface sharply. On the other hand, when other conditions were the same without preheating, cutting could not be performed.

In addition, when 100% oxygen gas was injected from the main nozzle, cutting was possible, but there was more molten oxide than in the case of preheating with a TIG arc, and the cut surface was not sharp, requiring maintenance as a post-process.

Example 2 Using a CO ₂ laser device with an output of 2.0 Kw as a laser beam source, a steel plate containing 3.0% Si with a thickness of 2.5 mm was
Cuts at a speed of seconds. Using a TIG arc as a preheating source, set the voltage to 10V and 150A, inject a mixed gas of 70% oxygen gas and 30% nitrogen gas from the main nozzle, and inject nitrogen gas at a flow rate of 80g/min from the first sub-nozzle. Further, nitrogen gas was injected from the second sub-nozzle at a flow rate of 120/min. Also, at this time, the inclination θ ₁ of the first sub-nozzle is 45°, the inclination θ ₂ of the second sub-nozzle is 10°,
Furthermore, the distance L ₁ between the cutting position P 0 and the gas injection position P ₁ from the first sub-nozzle is 5 mm, and the distance L ₂ between the position P ₁ and the gas injection position P ₂ from the second sub-nozzle is ₃ mm.
It was adjusted to Also, the distance L ₃ between the cutting position P ₀ and the tip position of the preheating TIG arm (preheating position) P ₃ is 10 mm.
And so. Note that the diameter of the first sub-nozzle hole 11 is 2.
mm, and the hole diameter of the second sub-nozzle hole 21 was set to 3 mm.

As a result, the cut surface was not blocked by molten oxide, and the steel plate could be completely cut. Furthermore, the cut surface was sharper than when 100% oxygen gas was injected from the main nozzle. Furthermore, when cutting was performed under the same conditions as above with the supply of nitrogen gas stopped from the first sub-nozzle and the second sub-nozzle, molten oxide adhered to the cut surface, although it was less than when using 100% oxygen gas. was seen. Also the second
When only the supply of nitrogen gas from the sub nozzle was stopped, the cut surface was not blocked, but molten oxide was observed to adhere to the cut surface and the lower edge of the cut portion.

In addition, in the above explanation, the preheating source is
Although we have explained an example using a TIG arc, as explained earlier, the preheating source can be any other preheating source as well as the TIG arc, such as an arc, gas burner, direct current, high frequency heating, laser beam, etc. can be used.

[Brief explanation of drawings]

Figure 1 is a schematic cross-sectional view of a device conventionally used to cut objects with a laser beam.
FIGS. 2a and 2d are a front view and a side view of the cut part showing a workpiece cut by the conventional method,
Figures 2b and f are a front view and a side view of the cutting part of a workpiece cut according to the present invention, and Figure 3 is a longitudinal cross-section showing the cutting head, sub-nozzle, and workpiece according to the present invention. It is a diagram. FIG. 4 is a diagram showing the state of cutting when the steel plate reaches a high temperature state.
FIG. 5 is an explanatory diagram showing the configuration of the present invention. 1: Laser beam, 2: Cutting head, 3: Condensing lens, 4: Cutting nozzle, 5: Main nozzle hole, 6:
Assist gas supply port, 7: Workpiece, 7': Test piece, 8: Cut surface, 9: Molten oxide, 10: First sub nozzle, 11: First sub nozzle hole, 20: Second sub nozzle, 21: second sub-nozzle hole, 30: preliminary heating source, _G1 : main nozzle gas, _G2 : first sub-nozzle gas,
G ₃ : Second sub nozzle gas, P ₀ : Laser beam irradiation position, P ₁ : First sub nozzle gas injection position, P ₂ : Second sub nozzle gas injection position, P ₃ : Preheating position,
L ₁ : Distance between P ₀ and P ₁ , L ₂ : Distance between P ₁ and P ₂ , L ₃ : P ₀
and P ₃ interval.

Claims (1)

[Claims] 1. A method of cutting a steel plate by irradiating the steel plate with a laser beam and injecting a first gas consisting of oxygen and an inert gas in substantially the same direction as the laser beam, After preheating the part with another heat source, a laser beam is irradiated, and a second gas consisting of an inert gas is applied to the surface of the steel plate, which is different from the laser beam incident position, near the cutting position, and a second gas consisting of an inert gas is applied to the back side. A method for cutting a steel plate using a laser beam, the method comprising injecting a third gas having the following properties. 2. A means for projecting a laser beam onto a steel plate, a means for preheating the steel plate prior to laser beam projection, and a cutting method for injecting a first gas consisting of oxygen and an inert gas in substantially the same direction with respect to the laser beam. a nozzle; a sub-nozzle arranged at an angle with respect to the cutting nozzle for injecting a second gas made of an inert gas to the vicinity of the cut portion on the surface of the steel plate; and a third gas made of the inert gas applied to the steel plate. A device for cutting a steel plate using a laser beam, comprising: a nozzle for spraying a spray near the cutting part on the back surface.