Laser-cut mild steel — factors affecting edge quality

Laser cutting of mild steel, although a continuous process, is an intrinsically cyclic laser—material interaction. This causes the cut edge to exhibit regularly spaced striations. These striations are the primary factor which limits the quality of the cut edge. The topography of the edge produced by continuous-wave CO 2 laser-O 2 cutting of mild steel 1.25 mm thick is examined in this paper. The characteristic cut surface is quantified using stylus profile measurements and scanning electron microscopy. The periodicity of the cutting event is of particular interest and experiments are described which show the effects of altering the laser-material interaction by modulating the incident laser power at frequencies derived from the “natural” striation frequency previously observed under continuous-wave laser cutting. It is shown that by careful selection of process parameters, and in particular the modulating frequency for the laser, the surface finish can be greatly improved. R a values have been reduced by a factor of 3 or more and beneficial effects on other profile parameters can be observed.