JP2002273588A - Laser cutting processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cut a thick plate workpiece accurately and at high speed by eliminating cutting defects in the deep part of the thick plate workpiece which is a problem in a conventional laser cutting method. SOLUTION: In this laser cutting processing method by which the irradiation position of a laser beam is moved in a cutting direction P to cut the workpiece while carrying out irradiation of the laser beam and the feed of an assist gas towards the workpiece 4 of a thick plate metallic material from a processing head 1 provided with a condensing lens 3 and an assist gas lead-in opening 2b, an auxiliary torch 5 provided with a condensing lens 6 is additionally equipped behind the processing head 1, and the laser beam is used as a main laser beam, and the auxiliary torch is directed to the deeper part of a workpiece cutting plane 4a to be irradiated with an auxiliary laser beam. Power attenuation associated with the reflection of the main laser beam is compensated by the auxiliary laser beam. Thereby, a cutting delay in the workpiece rear side and a cutting failure which are the problems in the conventional laser cutting processing method are prevented to enable the high-speed cutting of the thick plate workpiece.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser cutting method for cutting a work of a thick metal material (structure) by irradiating a laser beam.

[0002]

2. Description of the Related Art The laser cutting method described above focuses a laser beam emitted from a laser oscillator using a mirror and a condensing lens, and irradiates the beam spot onto the surface of a workpiece while irradiating the laser beam. This is a processing method in which the irradiation position is moved step by step in the cutting direction, and the work material is melted and evaporated at the irradiation position to cut it. The laser beam is focused on a minute spot and the irradiation energy per unit area is extremely high. It has been widely used in various fields at present because of its excellent operability.

Further, in order to improve the processing performance of laser cutting, it is common practice to supply an assist gas simultaneously with the irradiation of a laser beam. As is well known, this assist gas serves to quickly remove molten dross and evaporated matter generated by laser cutting from a processing portion, and when the work is a steel material such as stainless steel or carbon steel, the assist gas is used as an assist gas. By using oxygen gas, iron as the main component and the assist gas oxidize and generate heat, thereby increasing the cutting speed of the workpiece. Note that there is also a method of using an inert gas such as nitrogen as an assist gas to prevent unnecessary oxidation of a cut surface while sacrificing a cutting speed of a work.

[0004] Next, a conventional coaxial processing head and a cutting method used for the laser cutting processing will be described with reference to FIG. That is, the laser processing head 1 has a structure in which the condenser lens 3 is built in the torch 2 having the nozzle 2a formed at the tip, and the assist gas introduction port 2b communicating with the nozzle 2a is opened on the side surface of the torch 2. When cutting the work (steel structure or the like) 4, the torch nozzle 2a of the processing head 1 is set to face the upper surface of the work 4 as shown in the figure, and a laser oscillator (not shown) is set in this state. While irradiating and supplying the laser beam and the assist gas emitted from the processing head 1 to the plate surface of the work 4, the laser beam is moved in the cutting direction P with respect to the work 4 (moving the processing head 2 in the cutting direction P, Alternatively, the work 4 is moved in the direction opposite to the cutting direction P while the processing head is fixed.

[0005] Thereby, the laser beam incident on the processing head 1 from above is focused by the condenser lens 3 into a beam spot having a small diameter, and is irradiated on the upper surface of the work 4 through the nozzle 2 a of the torch 2. The focus position of the condenser lens 3 is usually set in accordance with the surface of the work 4 in many cases. However, in some cases, the focus position is set such that the focus position is defocused inside the work 4 surface. At the same time as the irradiation of the laser beam, the assist gas supplied to the torch 2 from the assist gas inlet 2b flows coaxially with the laser beam, becomes a gas jet, and becomes a gas jet from the nozzle 2b.
Blow out towards. Thereby, the work 4 is cut according to the processing principle described above.

[0006]

By the way, in the above-mentioned conventional laser cutting method, the focal position and the converging angle of the laser beam, and the type and flow rate of the assist gas,
Even if the conditions such as pressure and blowing direction are variously changed,
The thickness of the work that can be cut is determined by the output of the laser oscillator. For example, when a pulsed YAG laser having an average output of about 2 kW is used, the thickness of the work that can be cut is 1 at most.
In the case of a work having a plate thickness of about 0 mm or more, the cutting speed may be extremely slow, or the laser beam may not be able to be cut without penetrating to the back side of the work.

On the other hand, there is a demand for cutting a steel plate of several tens of mm in practical use. The inventors of the present invention have investigated the problems in the conventional cutting method in order to expand the limit of laser cutting, and found that the cause is as follows. Next, this will be described with reference to FIGS. That is,
Using the laser processing head 1 shown in FIG.
When a laser beam is irradiated from above by adjusting the focal position of the work 4 to the surface (upper surface) of the work 4 and the laser beam propagates a distance corresponding to the plate thickness t of the work 4, as shown in FIG. It becomes a spreading pattern. For this reason, particularly when the work 4 is a thick plate, the power density of the laser is reduced in a region near the back surface (lower surface) side of the work, and the cutting progress is reduced. 4, the cutting delay (the cut surface 4a)
Are not vertical but arc backwards).

In actual laser cutting, FIG.
The cutting groove 4b generated along the cutting direction as shown in FIG.
Calf width d does not spread to the left. This is because the laser beam propagates to the back surface of the work while being repeatedly reflected on the inner wall surface of the cutting groove 4b. In this process, the laser power is absorbed by the wall surface of the work, and the heat of the work material is melted by the heat generated.
It is considered that the cutting progresses from the surface of the work 4 to the deep part due to evaporation, but the laser power is attenuated toward the deep part of the cutting groove 4b, so that the cutting delay of the work and the inability to cut as described above occur. Become like

Furthermore, there is a problem in the method of supplying the assist gas. That is, the gas jet of the assist gas blown from the processing head 1 toward the work 4 in FIG.
As shown in (c), it spreads as it flows down in the cutting groove 4b of the work 4, and in a region near the back surface side of the work, it moves away from the cut surface 4a irradiated with the laser beam. That is, the assist gas is separated from the cut surface 4b, and in this portion, the function of the assist gas is not sufficiently performed, and the oxidative heat generation reaction with the work 4 is reduced. For this, work 4
On the back side, the cutting progresses more slowly than on the front side, which is considered to be the cause of limiting the maximum thickness that can be cut.

An object of the present invention is to solve the above-mentioned problems of the conventional cutting method and to compensate for a decrease in the power of the irradiation laser and a decrease in the function of the assist gas in the deep part of the workpiece cut surface. An object of the present invention is to provide an improved laser cutting method capable of cutting a metal work at high speed and with high accuracy.

[0011]

According to the present invention, in order to achieve the above-mentioned object, according to the present invention, a laser beam is irradiated from a processing head to a work of a thick metal material and an assist gas is supplied to the work. In the laser cutting method performed by moving the irradiation position in the cutting direction, (1) using the laser beam as a main laser beam, from the rear in the cutting direction toward the deep portion of the work cutting surface corresponding to the irradiation position, An auxiliary laser beam is radiated to compensate for a reduction in power of the main laser beam to assist cutting at a deep portion in the groove.

(2) Using the assist gas as a main assist gas, the auxiliary assist gas is supplied from the rear in the cutting direction toward a deep portion in the work cutting groove corresponding to the irradiation position of the laser beam, and the cut surface by the laser irradiation. The function of the assist gas is recovered by suppressing the separation of the assist gas acting on the gas. (3) Using the laser beam and the assist gas as a main laser beam and a main assist gas, respectively, irradiating the auxiliary laser beam from the rear in the cutting direction toward the deep part of the workpiece cutting surface corresponding to the irradiation position of the main laser beam, The functions (1) and (2) are simultaneously operated by using the assist gas blow (claim 3).

(4) In the above items (2) and (3), for a steel workpiece, the main assist gas is an oxygen gas and the auxiliary assist gas is an inert gas such as nitrogen, and the oxygen gas as the main assist gas is cut off. Auxiliary assist gas suppresses the flow of the main assist gas from around so as to prevent peeling from the surface, and at the same time, prevents the oxygen gas from acting on the wall surface inside the cut groove except for the cut surface, increasing the cut groove width (Claim 4).

As described above, when cutting a work made of a thick metal material, a reduction in the laser power density which appears when the processing point advances from the surface side of the work to the deep part of the cut surface, and assist gas By irradiating an auxiliary laser beam and blowing auxiliary assist gas from behind the cutting to the deep part of the cutting groove to compensate for the decrease in cutting progress due to separation from the cutting surface due to diffusion of High-speed cutting of a thick work can be performed without causing a cutting delay or inability to cut on the back side of the work.

[0015]

FIG. 1 is a block diagram showing an embodiment of the present invention.
3 to 3 will be described. In the drawings of each embodiment, members corresponding to those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted. [Embodiment 1] FIG. 1 shows an embodiment corresponding to claim 1 of the present invention. In this embodiment, in addition to the processing head 1 described with reference to FIG. 4, an auxiliary torch 5 is additionally provided in an inclined posture on the rear side in the cutting direction P. 4 is irradiated with an auxiliary laser beam toward a deep portion of the cut surface 4a. Here, the auxiliary laser beam emitted from the auxiliary torch 5 is applied to the cut surface 4a for irradiating the main laser beam.
On the other hand, the focal point is set in accordance with the point Q in the drawing so as to pass obliquely through the cutting groove 4b from behind and irradiate the deep portion of the cutting surface 4a. Uses a lens having a longer focal length than the focusing lens 3 for focusing the main laser.

The auxiliary torch 5 allows the relative angle with respect to the processing head 1 to be finely adjusted in accordance with the thickness of the work 4 so that the processing head 1 is moved in the cutting direction P when the work 4 is cut. Is assembled such that the auxiliary torch 5 moves together with the processing head. This allows
As described with reference to FIG. 5B, when the work 4 is cut, the main laser beam propagates toward the back surface of the work 4 while being repeatedly reflected on the side wall surface of the cut groove 4b, and is absorbed by the work wall. The attenuation of the laser power, which decreases due to this, can be compensated for by the irradiation of the auxiliary laser beam. This makes it possible to irradiate the laser beam while maintaining a strong laser power over the entire area from the work surface side to the deep part of the work cutting surface 4a. As a result, there is a problem with the conventional laser cutting method. Thus, high-speed cutting of a thick work 4 can be performed without delay and inability to cut on the back side of the work.

[Embodiment 2] FIG. 2 shows an embodiment corresponding to claim 2 of the present invention. In this embodiment, an auxiliary assist gas supplied from the outside through an auxiliary torch 5 similar to the auxiliary torch described in the first embodiment is blown toward the deep portion of the cut surface 4a of the work 4.

According to this embodiment, the auxiliary assist gas blown out toward the deep portion of the cutting groove 4b of the work 4 through the auxiliary torch 5 suppresses the flow of the main assist gas blown right below the processing head 1 from obliquely rearward. Prevent the main assist gas from diffusing. As a result, the main assist gas is prevented from being separated from the cut surface 4a of the work 4 as described with reference to FIG. 5B, and the function of the assist gas can be sufficiently exerted even in the deep portion of the cut surface 4a. . In particular, when oxygen gas is used as the main assist gas for the steel workpiece 4 and the heat of oxidation reaction with the workpiece is used to promote the cutting of the workpiece, the effect is great. Cutting becomes possible.

In this case, the following effects can be obtained by using an inert gas such as nitrogen as the auxiliary assist gas. That is, when the work 4 is made of a material having a high iron component ratio and a good thermal conductivity, such as carbon steel, and using oxygen gas as the main assist gas supplied through the processing head 1, High-speed cutting is possible, but the heat generated at the laser irradiation point is transferred to the periphery due to the high thermal conductivity of the work 4, causing unnecessary molten dross to adhere to the periphery of the cut surface and the cutting groove width Causes a problem that the cutting accuracy is reduced and the cutting accuracy is reduced.

In this respect, an oxygen gas is used as the main assist gas and an inert gas such as nitrogen is used as the auxiliary assist gas so as to prevent the main assist gas from being separated from the cut surface and diffused to the periphery as described above. This prevents the oxidation reaction between the oxygen assist gas and the work from spreading to the vicinity of the cut surface 4a, thereby improving cutting accuracy. [Embodiment 3] FIG. 3 shows an embodiment corresponding to claim 3 of the present invention. In this embodiment, the configuration of the first embodiment and the second embodiment described above are used in combination. The auxiliary torch 5 which is combined with the processing head 1 and disposed at the rear thereof has a condensing lens 6 and an assist gas inlet. 7 is provided. Then, the auxiliary laser beam is applied to the work 4 by adjusting the focal position of the condenser lens 6 to the deep portion (point Q) of the cut surface 4a of the work 4, and the auxiliary assist gas is used to cut the work 4 coaxially with the auxiliary laser beam. It sprays toward the deep part of the cut surface 4a through the groove 4b.

According to this embodiment, the function of the first embodiment and the function of the second embodiment can be simultaneously exhibited, and the work 4 having a larger thickness can be cut at high speed and with high accuracy by the synergistic effect. You can do it. In the illustrated embodiment, the auxiliary torch 5 is provided at one position, and the auxiliary assist gas is supplied to the deep portion of the cut surface of the work through the auxiliary torch. However, as an application example, the auxiliary torch is provided at a plurality of positions. It is also possible to select the type of auxiliary assist gas in accordance with the material and the thickness of the work, or to simultaneously supply the auxiliary assist gas from a plurality of locations to different deep positions of the cut surface.

[0022]

As described above, according to the laser cutting method of the present invention, the main laser beam and the main assist gas irradiated and supplied from the front surface side of the work through the processing head from behind the cutting direction. Auxiliary laser beam or auxiliary assist gas is irradiated toward the deep part of the workpiece cut surface,
By supplying the material, the problem of poor cutting at the deep part of the thick work, which has been a problem with the conventional laser cutting method, can be solved and the thick work can be cut at high speed and with high accuracy. A laser cutting method capable of sufficiently responding to a request for cutting a thick metal material required for cutting can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an apparatus applied to a laser cutting method according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an apparatus applied to a laser cutting method according to a second embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of an apparatus applied to a laser cutting method according to a third embodiment of the present invention.

FIG. 4 is a schematic structural view of a coaxial processing head used in a conventional laser cutting method.

5A and 5B are explanatory diagrams of the operation of laser cutting by the processing head of FIG. 4; FIG. 5A is a diagram showing the relationship between the thickness of a work and the spread due to the propagation of a laser beam; Diagram showing the path when the laser beam propagates through the cut groove, and (c) shows the flow state of the assist gas flowing near the cut surface of the work

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Processing head 2 Torch 2a Nozzle 2b Assist gas introduction port 3 Condensing lens 4 Work 4a Cutting surface 4b Cutting groove 5 Auxiliary torch 6 Condensing lens of auxiliary laser beam 7 Auxiliary assist gas introduction port

Claims (4)

[Claims] 1. A laser cutting method for cutting a work by moving a laser beam irradiation position in a cutting direction while irradiating a laser beam and supplying an assist gas from a processing head to a work of a thick metal material. , Wherein the laser beam is used as a main laser beam, and an auxiliary laser beam is irradiated from behind the cutting direction toward a deep portion of a workpiece cutting surface corresponding to the irradiation position. 2. A laser cutting method for cutting a work by moving a laser beam irradiation position in a cutting direction while irradiating a laser beam and supplying an assist gas from a processing head to a work of a thick metal material. In the laser cutting, the assist gas is used as a main assist gas, and an auxiliary assist gas is blown from the rear in a cutting direction toward a deep portion in a work cutting groove corresponding to a laser beam irradiation position. Processing method. 3. A laser cutting method for cutting a work by moving a laser beam irradiation position in a cutting direction while irradiating a laser beam and supplying an assist gas from a processing head to a work of a thick metal material. In the method, the laser beam and the assist gas are respectively used as a main laser beam,
As the main assist gas, the auxiliary laser beam is radiated from behind the cutting direction and the auxiliary assist gas is blown and supplied toward the deep part of the workpiece cutting surface corresponding to the irradiation position of the main laser beam. Laser cutting processing method. 4. A laser cutting method according to claim 2, wherein the main assist gas is an oxygen gas and the auxiliary assist gas is an inert gas for a steel workpiece. Cutting processing method.