Manufacture of carbides and the like

DETAILED DESCRIPTION One embodiment of an indirect arc furnace involving the practice of this invention is referenced generally as 10 in the drawings.
Furnace 10 has an essentially closed and pressure-sealed exterior metal shell 11 that also serves as a support for charge hopper 12 and for a pair of charge feed screws 13, of which only one is illustrated in the drawings.
Each such feed screw is controllably driven by an electric motor 14 through a coupled intermediate reduction gear box.
Charge hopper 12 normally is made of metal, has bottom openings such as 15 that deliver charge material to feed screw assemblies 13, and should be provided with a charging door (not illustrated) that is pressure sealed in its closed condition since furnace 10 operates without the presence of atmospheric gases within its interior crucible and frequently is advantageously operated with interior pressures either appreciably greater or appreciably less than atmospheric pressure.
Feed screw assemblies 13 deliver a silica and reductant charge material mixture received from hopper 12 into vertically-oriented charge chutes 16 and 17 (FIG.
2).
It is important that such charge chutes be located in shell 11 so that the charge material introduced into crucible interior 18 defined by graphite lining 19 does not fall either onto portions the furnace electrode assemblies 20 projected within interior 18 or into the indirect arc zones established within interior 18 between and during electrical energization of the furnace electrodes.
Furnace system 10 also is provided with a pair of opposed electrode/electrode holder assemblies 20 that are each removably mounted through their respective bearing supports 21 on shell 11.
Supports 21 are water-cooled and also are normally secured to shell 11 by conventional threaded fastener devices.
Additional details regarding preferred electrode elements incorporated into assemblies 20 are provided below in connection with the description of FIG.
3.
An effluent gas outlet 22 (FIG.
2) and a movable graphite crucible bottom 23 are also provided in furnace 10