Design optimization of cutting parameters when turning hardened AISI H11 steel (50 HRC) with CBN7020 tools

The surface finish of machined parts is known to have considerable effect on some properties such as wear resistance and fatigue strength. Thus, the quality of the surface has a significant importance for evaluating the productivity of machine tools, and mechanical parts. In this paper, the effects of cutting speed, feed rate, depth of cut and workpiece hardness on surface roughness, cutting pressure, and cutting power in the hard turning of hardened AISI H11 (X38CrMoV5-1) using CBN7020 tools were experimentally investigated. The response surface methodology (RSM) and analysis of variance (ANOVA) were used to check the validity of quadratic regression model and to determine the significant parameter affecting the output responses. The mathematical models for output parameters have been developed using Box-Behnken design with 29 runs. The results indicated that the surface roughness parameters are influenced principally by the feed rate and workpiece hardness while the depth of cut has no significant influence. In addition, cutting speed is the main influencing factor on the cutting power. Also, the results show that the tool life is influenced principally by the cutting speed and in the second level by the feed rate.