Laser beam cutting of highly alloyed thick section steels.

At present, highly alloyed steels in the thickness range above 8 mm can be cut by laser radiation to only a limited extent: The high portion of alloying constituents is indeed reducing the thermal conductivity and thus the thermal losses during the cutting process. But on the other hand, especially with the most established laser cutting technique - laser oxygen cutting - the alloying elements are leading to detrimental effects even in the lower thickness range (1-4). Chromium oxides with a high melting point do not dissolve in the metallic melt. This condition causes a limitation of the exothermic reaction in the upper part of the cutting front. At the same time, the high viscosity of the oxide layer complicates the melt ejection. Thus, in the lower region of the cutting front, the oxide film is bursted by stagnating melt volume and subsequently an uncontrollable exothermic superreaction occurs. As is well known, this results in deep erosion, selective burning and high dross attachmen t. In order to solve these problems even in the sheet thickness range between 10 and 30 mm, 5 procedural variants of CO2 laser beam cutting have been investigated and optimized.