Evaluation of machinability in turning of microalloyed and quenched-tempered steels: Tool wear, statistical analysis, chip morphology

The machinability of microalloyed steel (30MnVS6) and quenched-tempered (QT) steels (AISI 1045 and AISI 5140), at different cutting condition, is presented in the paper. An experimental investigation was conducted to determine the effects of cutting speed, feed rate, hardness, and workpiece material on the flank wear land and tool life of coated cemented carbide inserts in the hard turning process. It was tried that for any test condition the hardness of these steels became almost identical by using appropriate heat-treatment processes. The statistical analysis was used for evaluation of different factors on cutting forces. Chips characteristics and chip/tool contact length were also investigated. The different sections (shear plane, microcrack, thickness and edge) of the chip were examined by scanning electron microscope (SEM). Shear planes and microcracks of the chips in microalloyed steel show that the chips of microalloyed steel are regular and discontinuous. Crater wear of the tools was studied by using video microscope in turning process. The results showed that the tool life and machinability of the microalloyed steel is better than the QT steels at identical cutting condition.