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An investigation of arc zone pressures during CEVAR (consumable-electrode vacuum-arc remelting) experiments has shown that pressure differences and gradients within furnaces are functions of pressure itself, electrode composition, and the degree of arc-zone confinement. There is evidence also that some previously puzzling contrasts in arc-furnace behavior may be explainable on the basis that two pressure dependent forms of electrical discharge operate with distinct potentials. The lower voltage form tends to become unstable at pressures <0.5 Torr and behaves best at pressures >1 Torr. The higher voltage form seems to be most stable at pressures <0.1 Torr. For continuous operation and maximum versatility, a CEVAR furnace should be able to accommodate both discharge forms by providing for variability of vacuum conditions.

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