Cutting of Al-alloys using high pressure coaxial nozzle

Abstract

In aerospace industry Al-alloys are used for constructive parts because of their high strength and low weight. Unfortunately these alloys are difficult to cut by laser processing. At first their affinity to atmospheric gases, secondly the formation of high melting point reaction products and more over the difference between solidus and liquidus temperature, which will lead to the formation of a muchy zone, has to be considered. The present paper outlines the possibility of cutting such Al-alloys with CO2-lasers by optimizing the cutting parameters. Pressure and flow rate of the assist gas were varied and three different types of nozzles were applied (standard coaxial nozzle, ring nozzle, high pressure coaxial nozzle). The gas flow field of the high pressure nozzle was examined for different gas pressures. Furthermore the micro- and macrogeometrical aspects are investigated using a test piece that allows to derive the technical interesting cutting accuracy. Mechanical and corrosion tests of laser cut samples demonstrate that the cut quality is only sufficient for aerospace application if a post heat treatment is applied to avoid pitting corrosion in the heat affected zone (HAZ).In aerospace industry Al-alloys are used for constructive parts because of their high strength and low weight. Unfortunately these alloys are difficult to cut by laser processing. At first their affinity to atmospheric gases, secondly the formation of high melting point reaction products and more over the difference between solidus and liquidus temperature, which will lead to the formation of a muchy zone, has to be considered. The present paper outlines the possibility of cutting such Al-alloys with CO2-lasers by optimizing the cutting parameters. Pressure and flow rate of the assist gas were varied and three different types of nozzles were applied (standard coaxial nozzle, ring nozzle, high pressure coaxial nozzle). The gas flow field of the high pressure nozzle was examined for different gas pressures. Furthermore the micro- and macrogeometrical aspects are investigated using a test piece that allows to derive the technical interesting cutting accuracy. Mechanical and corrosion tests of laser cut sampl...