JP2001047268A - Method for laser piercing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute piercing in a short time without enlarging a diameter of a hole when forming a through hole in the direction of thickness of a material to be cut by jetting a assist gas and secondary gas flow on the material while emitting a laser beam on the material. SOLUTION: A laser beam is emitted on a material C to be cut from a nozzle 1a of a torch 1, and at the same time along this laser beam, a gas selected out of air, a mixture of air and an inert gas, a mixture of oxygen and an inert has, and the inert gases is jetted as assist gases. Along this assist gas flow, from a jet outlet of a secondary gas flow nozzle 7, a gas selected out of oxygen, a mixture of oxygen and an inert gas, air, a mixture of air and an inert gas, and the inert gases is jetted as a secondary gas flow.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser piercing method capable of smoothly performing a piercing operation on a steel sheet and improving the quality of a piercing portion.

[0002]

2. Description of the Related Art At the same time, a base material is melted and evaporated by irradiating a steel sheet with a laser beam from a laser torch, and at the same time, an oxygen gas called an assist gas is injected from the laser torch to burn the base material, 2. Description of the Related Art A steel sheet is cut by moving a laser torch in a desired direction while continuing a process of removing a melt from a base material by injection energy.

When a predetermined figure is cut from the steel sheet by a laser cutting method, when cutting is started from the end of the steel sheet, the steel sheet may be distorted by heat or other factors. For this reason, it is common practice to make a hole called piercing in the inside of a steel plate and execute a target cutting starting from this hole. In addition, when forming a hole in a target figure, it is necessary to perform piercing inside the hole serving as a scrap.

In a laser torch using a secondary airflow, when piercing is performed by irradiating a steel sheet with a laser beam,
Generally, oxygen gas is used for both the assist gas and the secondary airflow. Then, simultaneously with the injection of the assist gas and the secondary airflow, a method of emitting a laser beam at a high output and performing piercing to form a hole at a stretch (first known example) and a pulsed output of the laser beam (A second well-known example).

[0005]

The piercing methods of the above-mentioned known examples all have advantages and disadvantages. For example, in the piercing method of the first known example, the portion of the steel plate irradiated with the laser beam is instantaneously melted, and the melted base material is blown up by the assist gas to form a hole. I can do it. However, since the assist gas and the secondary air flow are oxygen gas, and the combustion of the base material is promoted, the diameter of the formed hole becomes large. It takes time for the laser light to reach the base material,
The problem of not being able to smoothly transition to cutting, and the large diameter of the hole formed in the steel plate, increasing the amount of melt removed from the base metal, and the large amount of melt forming oxygen secondary air. As a result, there is a problem that the reaction time is short and the oxygen cannot be contacted with a sufficient amount of oxygen, so that sufficient oxidation is not performed and the material adheres to the surrounding objects.

In the second known example, since the melting of the base material and the removal of the melt proceed relatively slowly, the diameter of the formed hole is small. However, there is a problem that the time required for the piercing operation is reduced and the operating rate of the cutting device is reduced.

An object of the present invention is to provide a laser piercing method capable of making a hole in a short time without increasing the diameter of a hole formed in a steel plate.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, a laser piercing method according to the present invention irradiates a steel sheet with a laser beam and injects an assist gas along the laser beam to pierce the steel sheet. A laser piercing method to be performed, wherein a gas selected from air, a mixed gas of air and an inert gas, a mixed gas of an oxygen gas and an inert gas, and an inert gas is injected as an assist gas; Along with the selected gas, a gas selected from oxygen gas, a mixed gas of oxygen gas and inert gas, air, a mixed gas of air and inert gas, and a gas selected from inert gas is used as a secondary air flow. It is characterized by injecting.

In the above laser piercing method (hereinafter referred to as “piercing method”), air or a mixed gas of the air and an inert gas or an oxygen gas and an inert gas is used as an assist gas injected along a laser beam. Mixed gas,
In the gas selected from the inert gases, the purity of oxygen is reduced and the oxidation performance is reduced. Therefore, even when the steel sheet is melted by the irradiation of the laser beam, the assist gas only exerts the function of removing the melted base material without burning the melted portion. Therefore, the diameter of the hole is not increased.

When the secondary gas flow is oxygen gas, the oxygen gas is melted by the irradiation of the laser beam without contacting the inside of the hole formed in the steel sheet, and comes into contact with the melt removed from the base material by the injection of the assist gas. The melt can be oxidized and burned. Therefore, when the steel sheet is an iron-based metal such as a mild steel sheet, a welding steel sheet, a low carbon steel sheet, and a high-strength steel sheet, it is possible to prevent re-welding of the melt removed from the base metal to the base metal.

The secondary air stream may be a gas mixture of oxygen gas and inert gas, air or a gas mixture of air and inert gas,
In the case of using an inert gas, the cut surface can be shielded from the atmosphere by an inert secondary airflow, so that when piercing is performed, oxidation of the processed surface can be reduced as much as possible. Further, the melt removed from the base material can be cooled to prevent re-welding to the base material.

Another piercing method is a laser piercing method for irradiating a steel sheet with a laser beam and injecting an assist gas along the laser beam to perform piercing on the steel sheet. A gas selected from among a mixed gas of oxygen and an inert gas, a mixed gas of an oxygen gas and an inert gas, and an inert gas is injected, and an oxygen gas, an oxygen gas and an inert gas are injected along the selected gas. A first step of injecting a gas selected from a mixed gas with an active gas, air, a mixed gas of air and an inert gas, and an inert gas as a secondary airflow; A gas selected from among a mixed gas with an inert gas, an oxygen gas, a mixed gas with an oxygen gas and an inert gas, and an inert gas is injected, and an oxygen gas, Injects a gas selected from among a mixed gas of inert gas and inert gas, air, a mixed gas of air and inert gas, and an inert gas as a secondary airflow, and changes the laser output in a pulsed manner. And a second step.

In the above piercing method, when the thickness of the steel plate is so large that a hole penetrated in the thickness direction of the steel plate cannot be formed in the first piercing operation, air and air are successively used as assist gases. A gas selected from among a mixed gas with an inert gas, an oxygen gas, a mixed gas of an oxygen gas and an inert gas, and an inert gas is injected, and air, a mixture of air and the inert gas is used as a secondary air flow. Injection of gas, oxygen gas, mixed gas of oxygen gas and inert gas, and inert gas, and piercing work of the second stage to change the output of the laser in a pulsed manner, A hole penetrated in the direction can be formed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the piercing method will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a laser cutting device capable of implementing a piercing method according to the present invention, and FIG. 2 is a diagram illustrating a configuration of a laser cutting torch capable of performing cutting while performing the piercing method according to the present invention. It is a schematic diagram.

The laser cutting apparatus A capable of implementing the piercing method of the present invention is, for example, a numerical control (NC).
The steel sheet C is mounted on a cutting machine B such as a cutting machine or a copying cutter having a tracer that imitates a drawing, and is moved along a target cutting line by the cutting machine B so that the steel sheet C can be cut along a movement locus. Is configured.

When the piercing operation is performed at a predetermined position prior to the cutting operation on the steel sheet C, the assist gas is replaced with air, regardless of the composition of the assist gas and the secondary gas flow in the cutting process. It is composed of a gas selected from a mixed gas of air and inert gas, a mixed gas of oxygen gas and inert gas, and a gas selected from inert gas. By injecting a secondary gas stream consisting of a gas selected from the group consisting of gas mixture, air, gas mixture of air and inert gas, and inert gas, the base material is melted by laser light irradiation. When a substance is generated, a small diameter hole can be formed by removing the melt from the base material without burning the base material by the assist gas, and the removed melt is burned. Or allowed to cool is obtained by realizing the prevention of a re-welding for the base material.

First, the configuration of the cutting machine B will be briefly described. As described above, as the cutting machine B, it is possible to selectively use a cutting machine such as an NC cutting machine or a copying machine using a tracer, or a cutting machine that simply travels in a linear direction. In the present embodiment, an NC cutting machine selected from the above cutting machines is used as the cutting machine B.

The cutting machine B composed of an NC cutting machine is configured to be mounted on a pair of rails laid in parallel and run. Further, the cutting machine B has a frame in which two garters are arranged in a direction orthogonal to the rails. A drive motor is mounted at a predetermined position corresponding to the rails of the frame, and a cuttable plate thickness is provided on the upper surface. A laser oscillator 2 having an output corresponding to the above is mounted.

The driving motor drives the cutting machine B along the rail, and controls the rotation of the driving motor to move the cutting machine B along the rail at a desired speed in a desired direction. Is possible.

The torch 1 constituting the laser cutting device A
Is mounted on a carriage provided so as to be able to traverse along the frame of the cutting machine B, and by controlling the rotation of a transverse drive motor provided on the carriage, a desired direction is provided in a direction perpendicular to the rail along the garter. At a desired speed.

A laser beam path 3 is formed by connecting the torch 1 and the laser oscillator 2. This laser beam path 3 is also formed using a garter of the frame. That is, the laser beam path 3 returns from the exit of the laser oscillator 2 along the garter in the opposite direction to the laser oscillator 2, is inverted by the inverting mirror, and changes direction again along the garter in the direction of the exit of the laser oscillator 2. The torch 1 is formed so that it can enter the torch 1.

Therefore, the drive motor is driven to move the frame along the rail in the direction and speed necessary to cut the desired shape, and at the same time, the lateral drive motor is driven to move the carriage along the frame. The torch 1 can be moved along the target shape by traversing in the direction and speed necessary to cut the shape of the torch. By driving the torch 1 in this moving process while moving the torch 1 as described above, the steel sheet C can be cut into a desired shape.

The steel sheet C is a steel sheet made of an iron-based metal, and is intended for a mild steel sheet, a welding steel sheet, a low carbon steel sheet, a high tensile steel sheet and the like.

Next, the configuration of the laser cutting device A will be described. The laser cutting device A is connected to the laser oscillator 2 and irradiates a laser beam from a nozzle 1a formed at the center toward the steel plate C, and irradiates air, a mixed gas of air and an inert gas, oxygen gas and an inert gas. A torch 1 for injecting an assist gas consisting of a gas selected from the group consisting of a mixed gas and an inert gas, an assist gas supply device 4 for supplying an assist gas to the torch 1, an oxygen gas for the torch 1,
A secondary airflow supply device 5 for supplying a secondary airflow of a gas selected from a mixed gas of oxygen gas and inert gas, air, a mixed gas of air and inert gas, and an inert gas; It is configured.

The assist gas supply device 4 includes an air supply section 4a for supplying air, an oxygen gas supply section 4b for supplying oxygen gas, and an inert gas supply section 4c for supplying inert gas.
And a plurality of gas supply units 4a to 4c from among the gas supply units 4a to 4c.
And a gas mixing unit 4e that forms an assist gas by mixing these gases when there are a plurality of selected gases.

The secondary air flow supply device 5 includes an air supply unit 5a for supplying air and an oxygen gas supply unit 5 for supplying oxygen gas.
b. and a plurality of gas supply units 5c each of which supplies an inert gas.
Selecting unit 5d for selecting one or a plurality of gas supply units 5a to 5c from to 5c, when there are a plurality of selected gases,
And a gas mixing section 5e that forms a secondary airflow in which these gases are mixed.

The torch 1 is, as schematically shown in FIG.
A laser beam path 3 is formed at the center, and a lens 6 is provided across the laser beam path 3. The lens 6 focuses the incident laser light on a desired position in the thickness direction of the steel sheet C according to the thickness and the material of the steel sheet C.

The inside of the torch 1 is hollow, and a supply path of the assist gas supply device 4 is connected to a chamber 1b formed from the lens 6 to the nozzle 1a. Therefore,
When the assist gas is supplied from the assist gas supply device 4 to the torch 1 while irradiating the laser beam from the nozzle 1a toward the steel plate C by operating the laser oscillator 2, the supplied assist gas flows along the assist gas from the nozzle 1b. To the steel sheet C.

A secondary air flow nozzle 7 is provided at the tip of the torch 1.
Is attached. The secondary airflow nozzle 7 injects a secondary airflow along the assist gas injected from the nozzle 1a, and is connected to the secondary airflow supply device 5. When the gas supplied from the secondary airflow supply device 5 is supplied to the secondary airflow nozzle 7, this gas can be injected as a secondary airflow along the assist gas.

The air supply sections 4a and 5a have a function of supplying dry air, and are constituted by an air compressor, a dehumidifier, a pressure regulator and the like.

The oxygen gas supply units 4b and 5b have a function of supplying oxygen gas having high purity, and include a cylinder containing oxygen gas, a pressure regulator, and / or a flow regulator. It is configured.

The inert gas supply units 4c and 5c have a function of supplying an inert gas typified by nitrogen gas or argon gas, and include a cylinder containing an inert gas, a pressure regulator, and / or a flow rate control unit. It has an adjuster and the like.

The selectors 4d and 5d are connected to the respective gas supply units 4
a to 4c, 5a to 5c, and has a function of selecting a gas corresponding to the material of the steel sheet C and supplying the selected gas to the mixing units 4e, 5e. For example, the gas supply units 4a to 4c,
It is configured to have an electromagnetic valve, a gas mixing valve, and the like provided for each of 5a to 5c.

The gas mixing units 4e and 5e are connected to the selection units 4d and 5
In the case where a plurality of gases are selected from the gas supply units 4a to 4c and 5a to 5c in d, the selection units 4d and 5d
Has a function of mixing a plurality of gases supplied from the torch 1 and supplying the mixed gas to the secondary airflow nozzle 7 of the torch 1, and is constituted by a gas mixing valve.

The secondary air flow nozzle 7 is for injecting air, oxygen gas, and inert gas alone or a mixed gas obtained by mixing a plurality of gases along the assist gas. Are formed around the periphery of the nozzle. The injection port 7a may be formed in a ring shape centering on the nozzle 1a, or may be formed by forming a plurality of holes on a circumference centering on the nozzle 1a. Further, a single hole may be provided on the upstream side, the downstream side, or the side surface of the nozzle 1a in the traveling direction to form the injection port 7a.

Laser cutting apparatus A constructed as described above
With reference to FIG. 2, a procedure for piercing a steel sheet C will be described.

First, the control section of the cutting machine B stores the information of the target graphic and sets the moving path of the torch 1. Next, the cutting machine B is driven to move the torch 1 to the piercing position set near the target figure, and is stopped at the piercing position.

According to the material of the steel sheet C, each of the selecting sections 4d, 5d
Is operated, one type of gas except oxygen gas or two types of gas is selected from the gas supply units 4a to 4c constituting the assist gas supply device 4, and the gas mixing unit 4e is selected.
The assist gas is supplied to the torch 1 as an assist gas through the nozzle 1, and the assist gas 8 is injected from the nozzle 1a. At the same time, one of the gas supply units 5a to 5c constituting the secondary airflow supply device 5 is
Gas mixing section 5
e, and is supplied to the secondary airflow nozzle 7 to inject the secondary airflow 9 from the injection port 7a.

The laser oscillator 2 is operated to emit laser light at the same time as or before and after the assist gas 8 and the secondary air flow 9 are injected, and the lens 6 provided on the torch 1 is used to emit laser light in the thickness direction of the steel sheet C. Light is condensed to a predetermined depth.
Thereby, the energy of the laser beam is applied to the steel sheet C, and a part of the base material is melted.

For example, when air is selected as the assist gas and oxygen gas is selected as the secondary air flow, the melt of the base material is blown up to the upper surface side of the steel sheet C by the assist gas injected along the laser beam. The dross 10 is removed from the base material, and with the removal of the dross 10, a hole 11 is formed in the steel sheet C. Since only the assist gas enters into the hole 11 formed in the steel plate C, the base material is heated but not burned, and the hole 11 maintains a small diameter. Therefore, the amount of dross 10 removed from the steel sheet C is small.

The dross 10 blown up to the upper surface of the steel sheet C comes into contact with oxygen gas constituting the secondary air flow 9. At this time, since the amount of the dross 10 is small and the temperature is high, the dross 10 reacts with oxygen and oxidizes or burns to form an oxide. This oxide does not adhere to the torch 1 or the secondary airflow nozzle 7 or re-weld to the steel sheet C. Even if it adheres to these, it is easily peeled off by rubbing with a brush or the like.

Melting of a part of the steel sheet C, elimination of the melt, and oxidation of the eliminated dross 10 are continuously performed as described above. In this process, holes 10 grow and penetrate the steel sheet C in the thickness direction. To complete the piercing.

When the hole 10 penetrates the steel sheet C, no energy is applied to the steel sheet C regardless of the irradiation of the laser beam, the assist gas 8 and the injection of the secondary air flow 9. Therefore, no melt is generated, and no reaction to the steel sheet C is performed.

When the mixed gas of oxygen gas and inert gas, air, the mixed gas of air and inert gas, and the inert gas are selected as the secondary air flow 9, the dross 10 removed from the base material is extremely small. The secondary air stream 9 having low oxygen purity is rapidly cooled without being oxidized by touching. Therefore, the cooled dross 10 does not weld to the torch 1 or the secondary airflow nozzle 7 and does not re-weld to the steel sheet C.

The piercing method described above is applied when the steel sheet C is relatively thin. However, when the thickness of the steel sheet C increases, it may be difficult to form the hole 11 in a short time only by performing the piercing method.

For example, when the thickness of the steel sheet C is about 12 mm or less, the hole can be easily formed by performing the piercing method.
It is possible to form 11. However, when the plate thickness is about 13 mm or more, it is difficult to form the hole 11 in a short time only by performing the piercing method.

When the thickness of the steel sheet C is increased as described above, the above-described piercing method is performed as a first step,
Thereafter, the assist gas 8 is selected from air, a mixed gas of air and an inert gas, oxygen gas, a mixed gas of an oxygen gas and an inert gas, and an inert gas. Mixed gas of oxygen gas and inert gas, air,
By selecting from a mixed gas of air and an inert gas or an inert gas, and further proceeding to a second stage in which the output of the laser oscillator 3 is changed into a pulse shape, the holes formed in the steel sheet C are formed.
11 can be grown in the thickness direction and penetrated.

That is, in the second stage, a pulse-like energy can be applied to the hole 11 formed by the piercing operation in the first stage by irradiating a laser beam whose output is controlled in a pulse shape. It is. When oxygen gas is selected as the assist gas 8 and the secondary gas flow 9, a part of the molten base material is oxidized and removed from the hole 11 while being oxidized by the energy applied in a pulsed manner. It is possible to promote the oxidation by further contacting the formed oxide with the secondary airflow 9 to prevent the oxide from being welded to the torch 1 and the secondary airflow nozzle 7, and to prevent re-welding to the steel sheet C.

When a gas other than the oxygen gas is selected as the assist gas 8, the base material is not burned while the holes 11 formed in the steel sheet C are grown. Therefore, the hole
The growth direction of the hole 11 can be limited to the thickness direction without increasing the diameter of the hole 11. When a gas other than oxygen gas is selected as the secondary air flow 9, the dross 10 removed from the hole 11 is rapidly cooled and does not re-deposit.

By irradiating the steel sheet C with a pulsed laser beam while selectively jetting the assist gas 8 and the secondary gas flow 9 as described above, the energy is imparted to the steel sheet C and the molten base material is melted. The material is alternately removed, so that the hole 11 can be smoothly grown and penetrated in the thickness direction.

[0051]

As described in detail above, in the piercing method according to the present invention, air, a mixed gas of air and an inert gas, a mixed gas of an oxygen gas and an inert gas, an inert gas, A gas selected from the gases is injected as an assist gas, and further along the assist gas, an oxygen gas, a mixed gas of an oxygen gas and an inert gas, air, a mixed gas of an air and an inert gas, and an inert gas. By injecting a gas selected from the active gas as a secondary air flow, the melt of the base material is eliminated without increasing the diameter of the hole formed in the steel sheet, and the eliminated melt is oxidized, Alternatively, it can be cooled to prevent the melt from adhering to the surroundings.

In particular, since the assist gas is formed of a gas having a very low oxygen purity, it does not oxidize even if it touches the molten base material by the energy of the laser beam applied to the steel sheet. Therefore, when entering the hole formed after removing the melt, the surrounding base material is not burned, and the diameter of the hole is not increased.

After the piercing method is performed as the first step, the output of the laser is controlled in a pulsed manner, and the assist gas is air, a mixed gas of air and inert gas, oxygen gas, oxygen gas and inert gas. Secondary gas is selected from oxygen gas, mixed gas of oxygen gas and inert gas, air, mixed gas of air and inert gas, and inert gas. In the case of selecting from, the piercing of a relatively thick steel plate can be performed in a short time, and the diameter of the hole is not increased.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a laser cutting device capable of implementing a piercing method according to the present invention.

FIG. 2 is a schematic view illustrating a configuration of a laser cutting torch capable of performing the piercing method according to the present invention and cutting the laser.

[Explanation of symbols]

 Reference Signs List A laser cutting device B cutting machine C steel plate 1 torch 1a nozzle 2 laser oscillator 3 laser beam path 4 assist gas supply device 4a, 5a air supply unit 4b, 5b oxygen gas supply unit 4c, 5c inert gas supply unit 4d, 5d selection unit 4e, 5e Gas mixing section 5 Secondary air flow supply device 6 Lens 7 Secondary air flow nozzle 7a Injection port 8 Assist gas 9 Secondary air flow 10 Dross 11 hole

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4E001 AA01 BB06 CA01 DD01 DD05 DD09 LA05 LD01 LD20 4E068 AF01 CA02 CA03 CJ01 CJ04 CJ05 DB01

Claims (2)

[Claims] 1. A laser piercing method for irradiating a steel sheet with a laser beam and injecting an assist gas along the laser beam to pierce the steel sheet, wherein air, air and an inert gas are used as the assist gas. A gas selected from among a mixed gas of oxygen gas, a mixed gas of oxygen gas and an inert gas, and an inert gas is injected, and an oxygen gas, a mixed gas of an oxygen gas and an inert gas is injected along the selected gas. A laser piercing method characterized by injecting a gas selected from a mixed gas, air, a mixed gas of air and an inert gas, and an inert gas as a secondary air flow. 2. A laser piercing method for irradiating a steel sheet with a laser beam and injecting an assist gas along the laser beam to pierce the steel sheet, wherein air, air and an inert gas are used as the assist gas. A gas selected from among a mixed gas of oxygen gas, a mixed gas of oxygen gas and an inert gas, and an inert gas is injected, and an oxygen gas, a mixed gas of an oxygen gas and an inert gas is injected along the selected gas. A first stage in which a gas selected from a mixed gas, air, a mixed gas of air and an inert gas, and an inert gas is injected as a secondary airflow, and air, air and an inert gas as an assist gas. A gas selected from among a mixed gas, an oxygen gas, a mixed gas of an oxygen gas and an inert gas, and an inert gas is injected, and an oxygen gas, an oxygen gas and an inert gas are injected along the selected gas. When A second step of injecting a gas selected from among a mixed gas, air, a mixed gas of air and an inert gas, and an inert gas as a secondary airflow and changing the output of the laser in a pulsed manner. A laser piercing method comprising: