The evaluation of machinability of microalloyed steels from the point of view of tool life and surface roughness criteria

viTHE EVALUATION OF MACHINABILITY OF MICROALLOYED STEELSFROM THE POINT OF VIEW OF TOOL LIFE AND SURFACEROUGHNESS CRITERIA(M.Sc. Thesis)Sadi ŞANGAZİ UNIVERSITYINSTITUTE OF SCIENCE AND TECHNOLOGYFebruary 2007ABSTRACTIn this study the properties of machinability of (38MnVS5) medium carbonvanadium microalloyed steel have been evaluated from the view of tool wearand surface roughness criteria. P20 grade uncoated UTi20T, VP15TF, (Al,Ti)Ncoated with PVD method, UC6010, TiCN/Al2O3/TiN coated with CVD methodas cutting inserts of Mitsubishi SNMG-MS 120408 have been used. The cuttingparameters used in the experiments are the cutting speeds of 150-200-250-300-400 m/min, feed rates of 0,15-0,25-,035 mm/rev and 2,5 mm cutting depth.According to the results tool life increased by decreasing the cutting speed forall the cutting inserts. The cutting inserts VP15TF (Al,Ti)N coated with PVDmethod had longer tool life than the other cutting inserts in the value of 150m/min cutting speed used for all cutting tools. The crater wear was not formedin VP15TF and UC6010 cutting inserts, but a regular wear was formed at theflank fase until reaching the wear criteria. The wears occured on the nose of theinsert and on the areas near the second cutting edge. In addition, plasticdeformation took place in the UC6010 cutting inserts with the feed rate of 0,35mm/rev and high cutting speed. The best surface roughness (as 0,73µm) wasobtained with the inserts VP15TF (Al,Ti)N coated with PVD method amongthe cutting inserts used with the cutting speed of 250 m/min. It was concludedviithat the effect of the feed rate on the surface roughness is more important thanthe cutting speed. There is a proportional relation between feed rate and surfaceroughness. The surface roughness increased with the increasing of the feed rate.The relation between cutting speed and surface roughness was inverslyproportional until 250 m/min, but after this cutting speed it was proportional.Science Code :708.3.028Key Words :Microalloyed steel, machinability, tool wear, surfaceroughnessPage Number :133Adviser :Prof. Dr. Mahmut GÜLESİN