Investigation on Normal Hard Turning of AISI 4340 Steel

The turning of hardened steel is the current problem with required minimum machining force and surface roughness. In this investigation on normal defect hard turning AISI 4340 steel has been used, because of it is medium carbon (0.4% C) high strength martensitic steel. This material is more important in the critical applications like aerospace and automotive transmissions. To machine a ferrous alloy which is over 45 HRC, the hard turning process has been used to remove the material which has single-point cutting tool at high speeds. For processing hard steel, it involves a traditional approach, and those operations were consumed significant amount of cost and time. When it is compared with hard turning (HT), it reduces the annealing and grinding requirements. Still researchers are finding the best combination of inserts in HT where tool life plays significant role due to its cost and obtaining better surface finish. To discover the best ideal parameters for normal hard turning process by considering the cutting speed, feed rate, and depth of cut as input parameters using L9 orthogonal array in Taguchi method and Grey relational analysis for ANOVA. Normal HT was performed on hardened AISI 4340 steel and obtained the results. The optimal setting for this normal HT with consideration of machining force & surface roughness to the level of factors applying Grey relation grade is speed—900 rpm, feed—0.05 mm/rev, and depth of cut—0.5 mm.