Investigations on surface milling of hardened steel with rotary liquid nitrogen applicator

Abstract

Conventional cutting fluid, typically comprising one or more natural or synthetic oils, is used to improve the performance of the cutting tool by cooling the tool and the workpiece, lubricating the cutting surface of the tool and flushing waste particles away from the work area. However, the use and disposal of such cutting fluids raises serious environmental and health related concerns. In the present decade, with increased environmental awareness, the researchers are striving to develop environment friendly machining technology. Cryogenic cooling is a promising new technology in high production machining which economically addressed the current process environmental and health concern. The benefits of reduction in machining temperature are reduction in cutting force, tool wear and surface roughness. This benefit of cryogenic cooling depends on the process parameters and cutting tool. In this research work surface milling of EN24 hardened steel (45 HRC) with cryogenic cooling condition has been investigated and its performance is evaluated on the basis of surface finish, flank wear and cutting force. 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 liquid nitrogen was delivered through a specially designed and developed rotary liquid nitrogen applicator designed based on full factorial analysis (design of experiment) in such a way so that it can deliver liquid nitrogen at critical zones during surface milling. An investigative comparison with dry and conventional wet milling under same conditions has been done to evaluate the relative performance of hard milling with liquid nitrogen application. It was observed that the rotary liquid nitrogen delivery system developed for surface milling on hardened steel can bring forth better performance when compared to dry and conventional wet milling.