Abstract: A porous plug assembly for use in a vessel containing molten metal, such as a melting furnace or a holding furnace, for introducing fluxing or other gases into the molten metal. The porous plug assembly includes a frustoconical porous refractory core member that is enclosed around its side and bottom by a non-porous refractory lining. Positioned about the outer surface of the non-porous refractory lining is a metallic outer liner, preferably made from inconel, which includes a ceramic anti-corrosion coating. A gas distribution pipe, which also can be made from inconel, extends upwardly through the bottom of the metallic outer liner, through the non-porous refractory lining, and into the interior of the core member for introducing a fluxing gas therein. Surrounding the intermediate, non-porous refractory lining and the metallic outer liner is a refractory nest block. The fluxing gas passes through the porous core member and exits at the top thereof to enter the molten metal melt.

Abstract: The density of various refractory hard metal articles are controlled so that articles made from the refractory hard metals are able to float on the surface of molten aluminum. Floating such articles on aluminum has been found to both stabilize and protect the surface of molten aluminum. Floating cathodes for use in aluminum reduction cells is a particular application for the floating refractory hard metals.

Abstract: An improved alumina reduction cell is described in which the carbonaceous cathode includes refractory hard metal shapes forming the true cathode surface and inert refractory protective sleeves for the refractory hard metal shapes. Reduced amounts of refractory hard metal material are employed through an improved refractory hard metal support system.

Abstract: An improved alumina reduction cell is described in which the carbonaceous cathode includes refractory hard metal shapes projecting upwardly from the cell surface thereof, forming the true cathode surface, and permanently mounted and replaceable protective sleeves formed of inert refractory material surrounding the refractory hard metal shapes and protecting these shapes from accidental contact by the anode.

Abstract: A protective barrier for alumina reduction cell cathodes is disclosed. This barrier layer comprises a layer of borosilicate glass which may optionally be surrounded by layers of alumina silicate glass. The barrier prevents cryolitic salts from attacking the reduction cell insulation, preventing degradation of the insulation and improving cell efficiency.

Abstract: An improved alumina reduction cell is disclosed. Vapor barriers, formed from a castable refractory and a silicon carbide mortar protect the bottom and sidewall insulation material of the cell from attack by the corrosive materials contained within the cell.