DD156953A1 - PROCESS FOR LASER CUTTING OF REACTIVE METALS - Google Patents

Abstract

The invention relates to the laser cutting of reactive metals, in particular of zirconium and similar materials. The aim is to improve the performance of laser cutting on reactive metals and to expand the field of application. Measures must be proposed which make it possible to produce quality cuts of reactive metals with essentially burr-free cut edges with low laser power and low technical expenditure. According to the invention, the rate of combustion of the reactive metal is adjusted to its rate of vaporization using a cutting gas consisting of 65-75% argon and 25-35% oxygen, the amount of cutting gas corresponding to the condition Q = e high -1 x InN and the cutting speed corresponding to the condition v = K xs high -1 x root can be set from N, where Q = cutting gas quantity in m high 3 / h N = laser power in W, s = cutting thickness in mm, K = material factor with K = 25 ... 120, especially at Zirconium 30 ... 50 mean.

Description

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Method of laser cutting reactive metals

Field of application of the invention

The invention relates to a method for the laser cutting of reactive metals, in particular zirconium and similar materials, using "known gas power laser systems for the production of substantially burr-free cut edges.

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Characteristic of the known technical solutions

It is known that various cutting gases are used for laser cutting. In the laser cutting of metals, oxygen or air is preferably used. In this case, laser cutting is used because the exothermic heat of combustion of the metal oxygen reaction is used to increase the cutting speed. When inert gases, such as argon or nitrogen, are used, it is called laser fusion welding. At the same laser power, the cutting speed is reduced. According to DE-AS 16 90 637 a method and apparatus for machining a workpiece by means of a laser beam directed to this is known, wherein the workpiece and laser beam are moved in the presence of a gas with exothermic reactivity relative to each other. According to the invention, the workpiece is cut from one surface to the other surface by directing the gas with exothermic reactivity in the form of a stream at high speed coaxially with the laser beam on the workpiece, so that the gaseous or molten products are blown away from the cut. To be able to produce smooth cutting edges, the cutting speed would have to be above a minimum speed, which is determined by the strength of the laser beam and the material thickness. - DE-OS 27 43 544 discloses a method for! Separating electric sheets by means of a laser, in particular with a CX ^ - laser, wherein also an oxygen-containing cutting gas is directed at high speed on the workpiece, the focal spot diameter is extremely small and the power density in the focal spot and the cutting speed are adjusted so that the structure in the cutting area remains as unaffected. By own experiments it was found out that the structure in the cutting area was influenced by the influence of the laser beam

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the material is always affected, so that the target in DE-OS 27-43 544 effect does not occur. In summary, it can be stated that, with the solutions disclosed in the patent specifications described above, unalloyed and high-alloy steels with good surface quality can be cut. When laser cutting of reactive metals, however, both proposed solutions fail. Reactive metals are cut according to the current state of the art by means of oxygen, air or other oxygen-containing gases always only with very poor quality cut, since the existing oxygen triggers strong uncontrolled reactions with the reactive metal. The cuts are basically uneven, the kerfs uneven, with the cut edges are always occupied by a large and firmly adhering ridge.

When argon, nitrogen or mixtures thereof are to be used for laser cutting, the laser power must be increased many times to achieve an economical cutting speed. Nevertheless, burr formation at the lower edges is unavoidable.

Object of the invention

The invention improves the performance of laser cutting on reactive metals and extends the field of application.

The essence of the invention

The invention is therefore based on the object, a method

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to develop laser cutting of reactive metals and to propose measures that make it possible to produce quality cuts with substantially burr-free cut edges with low laser power and low technical effort. The object of the invention is achieved by a method in that, according to the invention, the rate of evaporation of the reactive metal is adapted to its rate of evaporation by using a cutting gas consisting of 65-75 # argon and 25 - 35 # oxygen, the cutting gas quantity according to the condition Q = e ~ · InH and the cutting speed according to the condition V = K · s ~. "ffi * is set, where

Q = cutting gas quantity in nr / h. N = laser power in W s = cutting thickness K = material factor

and E = 25 ··· ··· 120, in particular for zirconium K = 30 ... 50.

Executed by spi el

The invention will be explained below with reference to an embodiment "^

For cutting drilling consisting of an alloy with 99 # zirconium, 1 # niobium and trace amounts of about 0.3 # iron, carbon, hafnium, calcium and the like. a. a COp Saslaser is used. The outer diameter of the tubes is 9 minutes with a wall thickness of 0.7 mm. With the (X ^ -aslaser a laser beam of 200 W continuous power is generated, which in a known cutting

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optics is focused. For cutting, the focus is set in a likewise known manner on the outer wall. The cutting gas used is a mixture of 70 # argon and 30 # oxygen, the cutting gas quantity Q being set to 1.95 nr / h. The cutting speed τ is 0.6 m / min corresponding to the existing pipe wall thickness and laser power H ·

Claims (1)

Invention sanction Method for laser cutting reactive metals, in particular zirconium and similar materials, using "known gas power laser systems for producing substantially burr-free cut edges, characterized in that the rate of diffusion of the reactive metal is adapted to its rate of evaporation, using a cutting gas consisting of 65 - $ 75 argon and 25 - 35 # oxygen, the cutting gas quantity according to the condition Q = e ~ ¹ · InN and the cutting speed according to the condition ν = K. s " ¹ .W
be set, where Q = cutting gas quantity in rar / h N = laser power in W
s = cutting thickness in mm
K = material factor with K = 25 ... 120 especially for zirconium 30 ... 50 mean"