THE EFFECT OF THE CUTTING SPEED ON THE CUTTING FORCES AND SURFACE FINISH WHEN MILLING CHROMIUM 210 Cr12 STEEL HARDFACINGS WITH UNCOATED CUTTING TOOLS

The experimental study presented in this paper aims to select the most suitable cutting and offset parameter combination for a milling process in order to obtain the desired surface roughness value for a machined workpiece of chromium 210 Cr12 steel, in terms of cutting speed, feed rate and depth of cut for the milling process. A series of experiments was performed on chromium material with a cutting width of 50 mm using a round, uncoated, cemented-carbide insert on a engine power 5.5 kW Jhonford VMC550 CNC vertical machining center without any cutting fluid. The experiments were carried out using four different cutting speeds ((70, 90, 110, 130) m/min) at a constant depth of cut (1 mm) and feed rate (0.3 mm/r) and the effects of the cutting speeds on the primary cutting force and the surface roughness were investigated. The cutting force (F-c) and the surface roughness (R-a) decreased with the workpiece material's easy machinability. From the experiments, the highest average primary cutting force was obtained as 658.17 N at a cutting speed of 70 m/min. The lowest average surface roughness was 0.36 mu m, which was obtained at a cutting speed of 70 m/min. The experimental results indicated that the obtained chip form is narrow and short stepped.