Influence of laser cutting parameters on the cut surface roughness of high-speed steel

The article presents a study of laser-nitrogen cutting of high-speed steel sheets using a gas-discharge CO2 laser. Experimental cuts of R6M5 steel blanks with a thickness h from 3.5 to 9.5 mm were obtained in various modes. The laser radiation power varied from 3.0 to 4.4 kW, the cutting speed from 0.2 to 3.0 m/min, the auxiliary nitrogen gas pressure from 0.8 to 1.4 MPa. The influence of laser cutting parameters on the surface roughness of high-speed steel cuts was studied. Multifactorial mathematical models of laser cutting processes for different steel grades are presented (literature review). The roughness parameter Ra (the arithmetic mean deviation of the profile) was chosen as the quality criterion for the studied samples; it is statistically the most stable surface roughness parameter. As a characteristic of the laser cutting process, complex parameters are proposed: the energy parameter containing the power per unit of sheet thickness and cutting speed, and a dimensionless parameter that includes, in addition to the energy parameter, the pressure of the auxiliary gas. For an analytical description of the dependence of the cut surface roughness characteristic on the technological parameters of laser cutting, numerical models are used, constructed on the basis of statistical processing of experimental data (correlation and regression analysis). Empirical formulas are given that relate the optimal values of the dimensionless roughness Ra/h of the cut surface and complex parameters. The results of comparing the experimental and calculated values of the roughness parameter confirm the adequacy of the proposed mathematical models. The correlation coefficient of the calculated and experimental Ra/h values is not less than 0.7 and corresponds to a high correlation degree.