Abstract: An environment-friendly dielectric fluid which can be an alternative to kerosene oil in electro-discharge machining (EDM) application is developed. It is water-in-oil emulsion. The effects of the change of water volume fraction and temperature on the microstructure and rheological property of the emulsion are experimentally studied by means of microscopy and rheological measurement. The results show that the viscosity of the emulsion increases exponentially with the increase of water volume fraction, and the emulsion turns from Newtonian fluid to non-Newtonian fluid gradually. However, with rising temperature the viscosity of the emulsion reduces enormously and when the temperature exceeds about 40℃, the emulsion will turn from non-Newtonian to Newtonian fluid. The character of low viscosity at high temperature is very suitable for the flushing requirement in die-sinking EDM. The experiment shows that the material removal rate with the use of the water-in-oil emulsion is as high as that of kerosene-based dielectric fluid, while the working environment is improved significantly in comparison to that of kerosene-based dielectric fluid. The research lays a theoretical and technological foundation for the EDM to realize green manufacturing.

Key words: Dielectric fluid, Electro-discharge machining, Emulsion, Green manufacturing, Rheology, Water-in-oil