Investigation of the effect of tempered temperature on machinability at turning of k390 cold work tool steel

In this study, relationship between different tempered temperatures and machinability properties was investigated in turning of BÖHLER K390 cold work tool steel which is preferred one of the powder metallurgical steels for the machine and manufacturing area in recent years. After the quenching process, test materials were tempered in three different temperatures 550°C, 575°C and 600°C. Turning tests were performed in dry condition with coated SNMA 120408 coded CBN inserts. At 0.25 mm depth of cut, four different cutting speed (80-120-160 ve 200m/min) and feed rate (0.05-0.1-0.15-0.2 mm/rev) were used in cutting tests. Depending on the cutting parameters, cutting force, surface roughness and tool wear were measured for the machinability evaluations. Besides, scanning electron microscope (SEM) images were taken for determining of the wear types and wear mechanism. According to the experimental results, optimal results were obtained in 3th specimen tempered in high temperature. In terms of surface quality, the best cutting parameters 0.05 mm/rev and 120-160 m/min were determined.