Investigations on the influence of high pressure coolant jet in turning hardened steels under variable machining conditions

Abstract

The energy dissipated in hard machining operation is converted into heat which raises the temperature in the cutting zone. With the increase of cutting temperature; tool wear, surface roughness, dimensional inaccuracy increases significantly. Various researchers worked on various techniques to effectively control the increased cutting temperature as well as tool wear rates, and surface integrity. The cutting temperature, which is the cause of several problems restraining productivity, quality and hence machining economy, can be controlled by the application of high-pressure coolant (HPC) jet. High-pressure coolant (HPC) jet cooling is a promising technology in high speed machining, which economically addresses the current processes, environmental and health concerns. The benefits of reduction in machining temperature are reduction in cutting force, tool wear and surface roughness. This benefit of HPC cooling depends on the process parameters and cutting tool. In this research work turning of AISI 1040 hardened steels (40 HRC, 48 HRC, 56 HRC) with HPC condition has been investigated and its performance is evaluated on the basis of chip morphology, surface finish, flank wear and cutting temperature. An effort is made to investigate the effect of cutting parameters (cutting velocity, feed and depth of cut) and the cutting environment on cutting performance. The cutting oil has been delivered through a specially designed and developed nozzle in such a way so that it can deliver oil jet at critical zones during hard turning. An investigative comparison with dry and HPC under same conditions has been done to evaluate the relative performance of hard turning with HPC jet. A model of tool wear was also developed for specific working condition. The model is developed to estimate the amount of principal flank wear with machining time for any one of the tool-work combinations and cutting environments. The experimental results indicate that the performance of the machining under HPC condition is quite good and more effective compared to machining under dry condition. With the help of the experimental results, model of principal flank wear has been developed to understand the basic phenomenon in metal machining. Finally the model was validated with experimental results to make it an acceptable model.