Laser Cutting of Circular Holes in AISI 304 Stainless Steel Sheet: Heating, Diffusion and Stress Analyses
Due to high melting point and low viscosity of molten oxides formed during cutting of stainless steel, laser cutting offers considerable advantages over the conventional cutting methods. In general, high pressure N2 assisting gas is used coaxially with the laser beam during cutting process, which in turn forms nitrides. The use of N2 in the cutting section prevents high temperature exothermic oxidation reactions in laser irradiated kerf surfaces. In the present study, laser gas-assisted cutting of small diameter holes in thin sheets of AISI 304 stainless steel is carried out. Temperature and stress fields and N2 diffusion in the cutting zone are predicted using finite element method (FEM). The simulation conditions are selected in-line with the experimental parameters, with an experiment being carried out to assess the geometric features of the cut surfaces. The morphological and microstructural changes in the cut sections are examined using an optical microscope, a scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The prediction of surface temperature is compared with its counterpart obtained from the thermocouple data. It is found that the predictions of surface temperature are in good agreement with the experimental data. The cut edge features, such as local dross attachment, striation patterns and sideways burning, in the cut section are also examined.
Keywords: CO2 laser, AISI 304 stainless steel, diffusion, residual stress, morphology, finite element method (FEM), nitrogen (N2)