Study on striation generation process during laser cutting of steel

Abstract

Recent experimental observations of melt flow dynamics during laser cutting have brought us new insights into striation generation process, which is not fully understood. The object of this paper is to discuss theoretical aspects of the different cut surface quality observed between the laser wavelengths of 1 µm and 10 µm for thick section cutting of steel, based on a 3D structure of melt flow on kerf front revealed by our experimental observations. Concerning the reasons of the different quality between the two wavelengths, two fundamental processes are proposed: downward displacement of discrete melt accumulations along the kerf side and destabilization of melt flow in the central part of the kerf front. We analyze each of the processes using simplified analytical models. The results show that for the both processes, different angular dependence of the absorptivity can lead to the different quality. Finally we propose utilization of radial polarization as a possible solution to improve the quality for the 1 µm wavelength.Recent experimental observations of melt flow dynamics during laser cutting have brought us new insights into striation generation process, which is not fully understood. The object of this paper is to discuss theoretical aspects of the different cut surface quality observed between the laser wavelengths of 1 µm and 10 µm for thick section cutting of steel, based on a 3D structure of melt flow on kerf front revealed by our experimental observations. Concerning the reasons of the different quality between the two wavelengths, two fundamental processes are proposed: downward displacement of discrete melt accumulations along the kerf side and destabilization of melt flow in the central part of the kerf front. We analyze each of the processes using simplified analytical models. The results show that for the both processes, different angular dependence of the absorptivity can lead to the different quality. Finally we propose utilization of radial polarization as a possible solution to improve the quality for t...