Utilização de fluidos dielétricos à base de óleos vegetais na usinagem por descargas elétricas por penetração

Abstract

Dielectric fluids usually used in electrical discharge machining (EDM) are generally expensive, toxic and demand special storage and disposal procedures. Oil-based dielectric fluids pollute the environment and are subject to the price variations of the international market. Moreover, they are used in large quantities and discarded after short periods of time, thus increasing the production cost. Furthermore, the tendency toward exhausting world oil reserves should not be disconsidered. This paper presents a performance comparison of five vegetal-based dielectric fluids with kerosene and a specific synthetic oil. High speed steel with pre-established fine finishing and wear parameters was utilized, employing both copper and graphite electrodes. The material removal rate (MRR) and wear of the tool electrode were measured. An evaluation of the superficial modifications of the machined material was made including roughness, the morphology, number and lenght of microcracks, the thickness of the recast layer and the heat-affected zone. The modifications of the mechanical properties were evaluated by Vickers micro-hardness testing. In comparison to traditional fluids, using both copper and graphite electrodes, the results show the competitiveness of the vegetal-based fluids, especially in terms of rough regimen.