When steel (and similar material) is cut by laser beam oxygen is mainly carried coaxial to the focussed beam as assistance gas. This results in an accelaration of the exothermal reaction. Principally, to form a gas beam simple orifice nozzles are used which are in no way aerodynamically optimized. However, the shape of the gas beam has a great influence on the operation result. The profile of the nozzles which are roughly determined by the focussed laser beam impedes the forming of the gas beam. Within these limits Laval nozzles with a gas flow coaxi to the beam were produced for a laser cutter type Belcut 1250 of the C. Behrens AG, Alfeld, West Germany. For such a jet forming one can expect above all higher cutting speeds. The reasons are:
An increase in the mass current of the gas jet entering the cutting joint causes a greater quantity of heat which is released during the exothermal reaction between oxygen and iron.
An increase in the flow rate of the gas jet as a result of the application of Laval nozzles for a constant mass current leads to the complete removal of scoria of the cutting joint.
These effects were comprehended in the following commented series of experiments.