Electric heating – Metal heating – By arc
Reexamination Certificate
1999-05-05
2001-08-28
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
By arc
Reexamination Certificate
active
06281472
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method and to a process gas for the laser welding of metal workpieces. In the method, the weld point is flushed with a process gas.
BACKGROUND
Laser welding is known from prior public use. In this technique, a laser beam is focused onto the workpiece which is to be welded. Often, a process gas which has to meet a number of demands is fed to the weld point at the same time. The intention is, on the one hand, to protect the laser optics used from spatter and contamination and, on the other hand, to prevent or limit undesirable reactions between the environmental atmosphere and the weld area. Generally, the process gas is directed through a nozzle which is coaxial with respect to the laser beam, although under certain circumstances a second nozzle which is directed transversely with respect to the laser beam may be used instead or in addition.
In the prior art, inert gases are generally used as the process gas. Nitrogen and argon are gases which are available at low cost, but they do have the drawback that the laser beam interacts with the nitrogen molecules or the argon atoms so as to form a process gas plasma which is undesirable for many applications, since it reduces the welding efficiency. Therefore, process gases which contain approximately ≧30% helium in argon are often employed. Helium suppresses plasma formation in the process gas.
SUMMARY OF THE INVENTION
The invention is based on the object of providing a method for laser welding of the type mentioned at the outset which allows efficient welding to be combined with a good quality of weld seam.
The invention achieves this object by using a mixture of at least one inert gas and at least 0.5% by volume of nitrogen as the process gas.
REFERENCES:
patent: 3066215 (1962-11-01), Espy
patent: 5488216 (1996-01-01), Farwer
patent: 43 15 849 C1 (1994-06-01), None
patent: 0 640 431 A1 (1994-07-01), None
patent: 58-093592 (1983-06-01), None
patent: 58-173094 (1983-10-01), None
patent: 61-232087 (1986-10-01), None
patent: 9-220682 (1997-08-01), None
AGA Aktiebolag
Evans Geoffrey S.
Morrison & Foerster / LLP
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