Material removal from molten metal was observed in order to investigate the material removal mechanism in the electrical discharge machining (EDM) process. Since material removal occurs intermittently not only during the discharge duration but also just after the discharge duration, we hypothesize for the latter case that degassing of the solution gas in the molten metal, which will occur when the molten metal resolidifies, is one of the possible mechanisms of material removal. A thin steel plate was melted by its own Joule heating and material removal occurring during the cooling process was observed using a color high-speed video camera. The temperature distribution on the plate surface was measured from the ratio of the intensities of RGB signals of the video image. It was found that material removal occurred in atmospheric pressure air, whereas it did not occur in vacuum. It was also found that the material removal occurred at a location when the local temperature fell below the melting point of the material. Therefore, the mechanism of the observed material removal was considered to be degassing of the solution gas in the molten metal.
Hayakawa, S., Minoura, K., Itoigawa, F., & Nakamura, T. (2018). Study on Material Removal Mechanism in EDM Process through Observation of Resolidification of Molten Metal. In Procedia CIRP (Vol. 68, pp. 266–271). Elsevier B.V. https://doi.org/10.1016/j.procir.2017.12.060