Techno-economic analysis of blanking punch life improvement by environment friendly cryogenic treatment

Abstract

Cryogenic treatment is an environment friendly supplementary process to conventional heat treatment used to improve wear resistance of tool and die steels. The potential of cryogenic treatment on AISI D2 die steel under laboratory conditions is well researched and documented. However to ensure the sustainable use of this technology in real life manufacturing, techno-economical analysis is required to be undertaken. Hence, a small scale production unit manufacturing medical instruments was identified and impact of cryogenic treatment on AISI D2 steel blanking punch was evaluated in terms of tool life, part quality and pecuniary gain. The cryogenically treated punches were inserted into the die and subjected to blanking of medical grade stainless steel sheets under real life manufacturing conditions. The improved wear resistance of cryogenically treated punch resulted in approximately 60% production rise and savings of 3.5% of annual turnover. Punch life was studied and correlated to part quality in term of burr size to divulge wear behavior of blanking punch. The AISI D2 steel samples were also prepared and subjected to laboratory tests comprising of metallographic observations and hardness. It was found that laboratory tests were not reliable enough to predict improvements in mechanical properties. The mechanism responsible for augmented wear resistance by cryogenic treatment was identified to be conversion of retained austenite in to martensite and precipitation of fine secondary carbides.