Study of machinability in boring operation of microalloyed and heat-treated alloy steels

The machinability of microalloyed steel (38MnVS5) and heat-treated alloy steels (AISI 1045 and AISI 5140) with the same hardness are presented in the paper. In this investigation, the effects of cutting speed, cutting force and feed rate on flank wear land and tool life of TiN coated carbide inserts in boring operations were studied. The criteria of flank wear (VBB max = 0.3 mm) used, when boring of these steels at different cutting speeds, to determine the tool life of inserts. SEM micrographs of flank wear and chips of the steels obtained in boring operations were analyzed. Chip characteristics in machining of these three steels interested. Shear planes and microcracks of the chips in microalloyed steel showed that the chips of microalloyed steel are regular and discontinuous. The results showed that the machinability of microalloyed steel is better than the heat-treated alloy steels at the identical conditions.