Cutting of 1.2 mm thick austenitic stainless steel sheet using pulsed and CWNd:YAG laser

Stainless steel is an important engineering material that is difficult to be cut by oxy-fuel methods because of the high melting point and low viscosity of the formed oxides. However, it is suitable to be cut by laser. This work aims to evaluate the optimum laser cutting parameters for 1.2 mm austenitic stainless steel sheets by using pulsed and CW Nd:YAG laser beam and nitrogen or oxygen as assistant gases, each one separately. It was shown that the laser cutting quality depends mainly on the laser power, pulse frequency, cutting speed and focus position. The optimum cutting was achieved during pulsed mode at applied power 210 W, frequency 200-250 Hz, speed 1-1.5 m/min, focus position -0.5 to -1 mm, nitrogen pressure 9-11 bar and oxygen pressure 2-4 bar. Increasing the frequency and cutting speed decreased the kerf width and the roughness of cut surface, while increasing the power and gas pressure increased the kerf width and roughness. Comparing with oxygen, nitrogen produced brighter and smoother cut surface with smaller kerf, although it did not prove to be economical. In CW mode, the speed can be increased to more than 8 m/min with equivalent power and gas pressure (limited by the laser system). Pulsed mode was also not economical, especially in limited frequency laser systems, where the pulse overlap should be controlled by both frequency and speed. In CW, the speed can be increased to the maximum system limit. The results should be included in computerized database for the automatic implementation of laser process. (c) 2005 Elsevier B.V. All rights reserved.