Arc furnace for the production of small investment castings of reactive or refractory metals such as titanium

An improved arc furnace and investment casting apparatus comprising, in combination:

• (a) an arc furnace, vacuum sealed melting chamber for maintaining a vacuum or inert gas including a cooled inert material bottom enclosure wall as an anode, a metal crucible formed in the cooled inert bottom wall, the crucible positioned substantially at the middle of the bottom wall;
• (b) a non-consumable cathode projecting into the melting chamber over the inert crucible;
• (c) means for providing power to the cathode and the anode to melt the crucible contents;
• (d) a passage through the bottom wall from the inert crucible, the passage including a meltable foil valve;
• (e) a first vacuum sealed casting chamber suspended from the bottom wall beneath the crucible passage, the casting chamber including a removable bottom cover for access to the interior of the casting chamber;
• (f) a second vacuum sealed casting chamber suspended from the bottom wall beneath the crucible passage, the second casting chamber being located within the first casting chamber and including a removable bottom cover for access to the interior of the casting chamber;
• (g) a removable hot mold assembly within the second casting chamber including a sprue in communication with the crucible passage;
• (h) means for evacuating each chamber;
• and
• (i) means for purging the melting chamber and the first casting chamber with inert gas.