Selecting Laser Cutting Modes for Engineering Steel Sheets Aiming at Provision of the Required Properties of Surface Quality

The roughness RZ, the duration of the area of laser thermal impact (ALTI) (L), and the inclination of cut wall (α) after various modes of laser cutting of steel sheets of different thickness of grades 40Kh, 20Kh13, 65G, 09G2S, 60S2KhA, and 30KhGSA have been determined. It has been established that, despite different chemical compositions of the steels, the microstructure of ALTI in surface areas after laser cutting (LC) is similar: a white layer with higher hardness, a layer with martensite structure and residual austenite, and a transient area between ALTI and initial structure not affected by LC. Mathematical models have been developed describing the influence of chemical composition, LC parameters, and sheet thickness on RZ, L, and α. The procedure of selection of a rational LC mode is proposed and exemplified by multiparametric optimization making it possible to determine LC modes to provide the best quality of cut surface in the sheets of different thickness and chemical composition.