Visualization and modeling of combustion effects at laser cutting of mild steel with oxygen

The iron-oxygen combustion front dynamics has a great influence on the surface quality of mild steel samples cut with laser. At the present work different modes of the combustion front propagation, such as: stationary attached to the laser beam, cyclic non-self-sustained, self-sustained, are explored both theoretically and experimentally. Theoretical model is based on the numerical solution of heat balance on the cut front. It allows to obtain 3D evolution of the cutting kerf. Numerical results are in a good agreement with the accompanying experiments. The experimental setup with one wall of the kerf being replaced with the glass is developed to register the process. High speed recordings with the frame rates up to 10 000 f/s are done for 4mm and 12mm thick mild steel plates cut with 2 KW fiber laser. Such phenomena as cyclical burn propagation and transition from cyclical reaction to side burn (self-sustained) mode are captured.