Analysis of cut surface quality of sheet metals obtained by laser machining: thermal effects
Résumé
During laser cutting, the heat caused by cutting has thermal effects on the cutting surface. This results in a hardening zone directly at the cut edge and an adjacent tempering zone. These zones are often associated with undesirable effects such as surface cracking and fatigue resistance. In the present study, high-power CO2 laser cutting of steel sheets is considered and the thermal influence of laser cutting and its main operating parameter, laser power, on the microhardness beneath the cutting section is examined using Vickers microhardness tester. The microstructure changes of the cut edge surface and of the cut surface are investigated using optical and electron scanning microscopes. The results show that laser cutting has a thermal effect on the surface microstructure and on the microhardness beneath the cut section. The microstructure and microhardness of the cut edge are affected by the main input laser cutting parameter, the laser power. Also the microhardness of the affected zone depends on the value of laser power. Microstructure analysis shows that high-power laser cutting leads to the formation of cracks and the average size of grains of the heat affected zone increases with laser power.