DE102009017441A1 - Laser beam machining method for machining a metallic workpiece, comprises coaxially directing a cutting gas at a processing location of a laser beam together with the laser beam to or into the metallic workpiece - Google Patents

Abstract

The laser beam machining method comprises coaxially directing a cutting gas (5) at a processing location of a laser beam (4) together with the laser beam to or into a metallic workpiece, where the cutting gas is used at a temperature of 0[deg] C to -40[deg] C and a pressure of 5-20 bar at an outlet of a nozzle with a throughput of 1-200 Nm 3>/h. The throughput of the gas without oxygen is 30-60 Nm 3>/h, and the throughput of the gas with oxygen is 10-20 Nm 3>/h in the case of nitrogen/oxygen mixture and is 1-4 Nm 3>/h in the case of oxygen alone. The laser beam machining method comprises coaxially directing a cutting gas (5) at a processing location of a laser beam (4) together with the laser beam to or into a metallic workpiece, where the cutting gas is used at a temperature of 0[deg] C to -40[deg] C and a pressure of 5-20 bar at an outlet of a nozzle with a throughput of 1-200 Nm 3>/h. The throughput of the gas without oxygen is 30-60 Nm 3>/h, and the throughput of the gas with oxygen is 10-20 Nm 3>/h in the case of nitrogen/oxygen mixture and is 1-4 Nm 3>/h in the case of oxygen alone. A less quantity of rinsing gas is used for rinsing-out or post-rinsing the lens of a focusing device, where the rinsing gas is selected hotter than the cutting gas.

Description

Technical area

The The invention relates to a method for laser beam cutting according to the The preamble of claim 1 and the use of a gas thereby.

State of the art

laser cutting is a form of thermal cutting, when used as a cutting tool a laser beam is used. For this purpose, the laser beam on the The desired body is directed, for which he usually with a lens in the cutting head on the surface of the to be cut workpiece or in the interior of the workpiece is focused. The high energy density leads to a rapid heating of the material to be cut.

At the Laser beam melting cuts the material to melting temperature heated, in laser sublimation cutting to evaporation temperature. When laser beam cutting is to the point to be cut Passed oxygen, so as necessary for flame cutting through the combustion of oxygen with the material adds energy is introduced. The laser beam heats the workpiece at the processing station continuously on the ignition temperature, so that the combustion of the material material with the cutting oxygen can take place.

The Molten material is produced by laser cutting with the cutting gas expelled from the kerf, with the laser beam cutting the cutting oxygen jet next to the molten material too expels the resulting slag. As a cutting gas is laser beam cutting Oxygen used, otherwise is usually used as cutting gas nitrogen, Argon, carbon dioxide (also mixed with nitrogen) and / or helium used. Also compressed air is used. The laser beam is on ideal tool for metallic and non-metallic materials to cut small thicknesses. As the material thickness increases However, the cutting speed of the laser beam from strong. So For example, laser cutting can be used in laser cutting with a thickness of about two millimeters six times faster than Cut sheets with a thickness of about fifteen millimeters become.

The prior art proposes to increase the cutting speed to supply the cutting gas in a turbulent flow. For example, from the publication DE 43 36 010 A1 a laser cutting apparatus is known in which by means of a processing head, a main auxiliary gas and a secondary auxiliary gas are supplied such that the gas flow is in total in a turbulent flow state. Furthermore, from the DE 10 2004 052 323 A1 It is known that the cutting speed or the sheet thickness to be cut can be increased by a modulated movement of the cutting head. This can also be achieved by a modulation of laser power and gas pressure which is not detailed.

The use of gases at low temperatures for cutting is known. In the FR 2 810 913 A1 In laser beam cutting in addition to oxygen, a cryogenic gas, in particular carbon dioxide, nitrogen or helium, at a pressure of 0.5 to 50 bar and a throughput of 0.5 to 20 m ³ / h directed to the kerf. The task of the cryogenic gas is to avoid unwanted oxidation at the edge or at the surfaces of the kerf. As a rule, the cryogenic gas is directed coaxially with the oxygen and at an angle <90 ° to the workpiece.

Further, the use of gases at low temperatures for cutting, for abrasive treatment, for polishing or other modification of the surface also from the document WO 99/51393 A1 known. There may be, inter alia, a cryogenic material, such as liquid nitrogen or carbon dioxide suspended in liquid nitrogen, at a temperature of below 100 ° F (-37 ° C) at a speed of 3400 ft / sec (1020 m / s) along a common Axis to be directed to a workpiece. In the specific embodiments mentioned above, another material, such as diamond or graphite, is directed onto the surface in order to roughen or smooth it. Cutting is not specifically mentioned.

In the process of EP 484 392 B1 For machining a metallic workpiece, in addition to the laser beam focused on the workpiece, a gas jet at a temperature of 0 ° C to -100 ° C is directed to the focal spot of the laser to control the plasma formation. Nothing is stated about the gas pressure. As special processing only laser welding is mentioned. The EP 0 458 181 B1 mentions the possibility that cold gas is pumped through a nozzle for laser welding or laser beam cutting.

The publication EP 484 392 B1 discloses a method in which, in a laser beam cutting method, an inert shielding gas (mentioned argon) is directed to a metallic workpiece together with liquid nitrogen. The protective gas is cooled to -170 to -200 ° C. The nitrogen serves as a material that forms an alloy with the metallic material.

Summary of the invention

To solve the above-mentioned problem, this invention proposes a laser beam cutting method in which, together with the laser beam, a cutting gas is directed onto the processing point of the laser beam on or in a metallic workpiece, characterized in that the gas is at a temperature of 0 ° C to -. 100 ° C and a pressure of 1 to 80 bar at the outlet of a nozzle with a throughput of 1 to 200 Nm ³ / h is used.

Another embodiment of the invention relates to the use of a cutting gas at a temperature of 0 ° C to -100 ° C and a pressure of 1 to 80 bar at the outlet of a nozzle with a throughput of 3 to 200 Nm ³ / h for laser beam cutting of a metallic workpiece ,

Short description of the drawing

1 shows an arrangement of laser beam, cutting gas and workpiece in a laser beam cutting method.

2 represents a device for obtaining the gas used.

Description of the embodiments

In the method of the invention, in a laser beam cutting method together with the laser beam, a cutting gas before a method in which in a laser beam cutting process together with the laser beam, a cutting gas at a temperature of 0 ° C to -100 ° C and a pressure of 1 to 80 bar Outlet of a nozzle with a throughput of 1 to 200 Nm ³ / h on the processing point of the laser beam on or in a metallic workpiece (ie in the kerf) is directed.

The The invention also relates to the use of such a cutting gas for laser beam cutting of a metallic workpiece.

Except The cooled cutting gas can in small amounts, usually <10 vol .-%, in particular <5 vol .-%, a warmer (eg 10-25 ° C) purge gas for the rinsing or rinsing the lens of the focusing device can be used, which is selected from nitrogen, argon and / or helium is. Since purge gas is said to condensation of moisture prevent on the lens.

The Cutting gas is preferably oxygen, nitrogen, argon, carbon dioxide (also in mixture with nitrogen), compressed air and helium and their Mixtures and mixtures of hydrogen with nitrogen, argon and helium and the mixtures selected.

At the Laser beam cutting is preferably used alone oxygen.

In Preferred embodiments is the cutting gas temperature 0 ° C to -40 ° C. The pressure of the cutting gas at the outlet of the nozzle is preferably 1 to 50 bar, z. B. 1 to 40 bar, more preferably 5 to 40 bar and in particular 5 to 20 bar.

The throughput for gas containing no oxygen is preferably 10 to 100 Nm ³ / h, for example 20 to 80 Nm ³ / h, particularly preferably 30 to 60 Nm ³ / h. For oxygen-containing gas, the preferred range is 1 at 40 Nm ³ / h, z. B. at 10 to 20 Nm ³ / h in the case of N ₂ / O ₂ mixtures (ie also of compressed air) and at 1-4 Nm ³ / h in the case of oxygen alone.

At the Laser cutting is the kerf very narrow. This will the gas movement is inhibited, and the more so, the deeper the kerf is. The gas movement is for the expulsion of the kerf material to be removed of great importance. For laser fusion cutting this material is melted. In addition to molten material need in the laser sublimation process also present in the gas phase Materials are removed from the kerf, when Lasserstrahlbrennschneiden also the oxidation products of the material ("slag"), otherwise a "beard formation" (deposition of slag) takes place at the edge of the kerf.

happens this exhalation not fast enough, the process is slowed down, if you do not lose optical and other quality wants to accept. This is especially true when cutting of workpieces with a thickness of more than 3 mm, for Example of very thick sheets with a thickness of more than 10 mm, noticeable, because with increasing material thickness not only the expulsion process is increasingly inhibited, but also the amount of expelled Material increases.

• a) beim Laserstrahlschmelzschneiden oder Lasersublimierschneiden mit einem Schneidgas (z. B. Stickstoff, Argon, Kohlendioxid, Druckluft und/oder Helium) das schmelzflüssige und/oder sublimierte Material aus dem metallischen Werkstück besser ausgetragen;
• b) beim Laserstrahlbrennschneiden mit Sauerstoff neben der Verbesserung des Austragens von geschmolzenem Material und Schlacke auch die Reaktionsgeschwindigkeit zwischen Metall und Sauerstoff erhöht, wodurch sich mehr Sauerstoff in der Schnittfuge befindet und somit das Gleichgewicht Richtung Oxid verschoben wird.

A temperature reduction and pressure increase of the cutting gas at a relatively high throughput causes both more gas enters the kerf and the gas movement is turbulent due to the sudden expansion in the joint heated by the laser beam. Is advantageous by

• a) in laser beam fusion cutting or laser sublimation cutting with a cutting gas (eg., Nitrogen, argon, carbon dioxide, compressed air and / or helium) the molten and / or sublimated material from the metal workpiece better discharged;
• b) in the laser cutting with oxygen, in addition to improving the discharge of molten material and slag and the Re action rate between metal and oxygen increased, which is more oxygen in the kerf and thus the balance is shifted towards oxide.

consequently can with a constant cutting quality a higher Cutting speed achieved. The invention Method therefore enables efficient cutting also for workpieces with a thickness of more than 5 mm, z. B. 10-30 mm.

One Another advantage is that the cooled gas and the Lens of Laserfokussiereinrichtung cools what the optical Properties of the lens maintains. A possible focus shift by heating is eliminated.

Now reference is made to the figures.

In 1 is an arrangement 1 for cutting a thick-walled steel sheet 2 with a kerf 3 shown on a laser beam 4 and a cutting gas 5 with a temperature of 0 to -40 ° C and a pressure of 20 to 40 bar at a throughput of 10 to 50 Nm ³ / h is directed.

2 shows a possible device 10 to obtain the cutting gas used. Gas from a gas bottle with pressure reducer 12 and / or a bottle bundle with pressure reducer 14 and / or a cryogenic tank (tank with liquid cutting gas) 16 with evaporator 18 is via a pipeline network 20 at a pressure of, for example, 6 bar, optionally via a device for mixing gases 21 to a pressure increasing device 22 directed. From there, the gas passes through an indirect heat exchanger 24 for cryogenic or conventional cooling to, for example, -40 ° C via a mass flow control with regulating valve 26 and / or a pressure regulating or pressure limiting device 28 to the consumer (not shown). Depending on the requirements, individual parts of the supply device can be omitted if the laser cutting process can be carried out in the desired quality.

The Advantages of the invention are evident both in laser beam fusion cutting as well as laser beam sublimation cutting and laser beam cutting for all metals to be cut and all cutting gases used.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 4336010 A1 [0005]
• - DE 102004052323 A1 [0005]
• FR 2810913 A1 [0006]
• WO 99/51393 A1 [0007]
• - EP 484392 B1 [0008, 0009]
• EP 0458181 B1 [0008]

Claims (14)

Laser beam cutting method in which, together with the laser beam, a cutting gas is directed to the processing point of the laser beam on or in a metallic workpiece, characterized in that the cutting gas at a temperature of 0 ° C to -100 ° C and a pressure of 1 to 80 bar at the outlet of a nozzle with a throughput of 1 to 200 Nm ³ / h is used. Method according to claim 1, characterized in that that the cutting gas of oxygen, nitrogen, argon, carbon dioxide, Compressed air and helium and their mixtures and mixtures of Hydrogen with nitrogen, argon and helium and their mixtures is selected. Method according to claim 1 or 2, characterized that the temperature of the gas is 0 ° C to -40 ° C is. Method according to one of claims 1 to 3, characterized in that the pressure is 1 to 50 bar, more preferably 5 to 40 bar and more preferably 5 to 20 bar. Method according to one of claims 1 to 4, characterized in that the throughput of gas containing no oxygen, 10-100 Nm ³ / h, preferably 20-80 Nm ³ / h, particularly preferably 30-60 Nm ³ / h, and at oxygen-containing gas 1-40 Nm ³ / h, z. B. 10-20 Nm ³ / h in the case of N ₂ / O ₂ mixtures and 1-4 Nm ³ / h in the case of oxygen alone. Method according to one of claims 1 to 5, characterized in that further in a small amount of a purge gas, which is warmer than the separating gas and made of nitrogen, argon and / or helium is selected for flushing or rinsing the lens of the focusing device used becomes. Method according to one of claims 1 to 6, characterized in that the cutting gas coaxially together is directed onto the workpiece with the laser beam. Use of a cutting gas at a temperature of 0 ° C to -100 ° C and at a pressure of 1 to 80 bar at the outlet of a nozzle with a throughput of 1 to 200 Nm ³ / h for laser beam cutting of a metallic workpiece. Use according to claim 8, characterized that the cutting gas of oxygen, nitrogen, argon, carbon dioxide, Compressed air and helium and their mixtures and mixtures of hydrogen selected with nitrogen, argon and helium and mixtures thereof is. Use according to claim 8 or 9, characterized that the temperature of the gas is 0 ° C to -40 ° C is. Use according to one of claims 8 to 10, characterized in that the pressure is 1 to 50 bar, more preferably 5 to 40 bar and more preferably 5 to 20 bar. Use according to one of claims 8 to 11, characterized in that the throughput for gas containing no oxygen, 10-100 Nm ³ / h, preferably 20-80 Nm ³ / h, particularly preferably 30-60 Nm ³ / h, and at oxygen-containing gas 1 at 40 Nm ³ / h, z. B. 10 to 20 Nm ³ / h in the case of N ₂ / O ₂ mixtures and 1-4 Nm ³ / h in the case of oxygen alone. Use according to any one of claims 8 to 12, characterized in that further in a small amount of a purge gas, which is warmer than the separating gas and made of nitrogen, argon and / or helium is selected for flushing or rinsing the lens of the focusing device used becomes. Use according to one of claims 8 to 13, characterized in that the cutting gas is coaxial with the laser beam is directed to the workpiece.