Abstract: A metal processing furnace of the indirect arc type having opposed electrodes projected into and establishing an ionized atmosphere in the furnace crucible is provided with apparatus that introduces a finely divided charge mixture consisting essentially of silica and coke into the system for free-fall into and through the ionized atmosphere. Following reaction of the mixture's ingredients in the ionized atmosphere, silicon carbide crystals are deposited at the bottom of the furnace interior below the ionized atmosphere for subsequent collection and removal from within the furnace system. By control of charge composition and process parameters, silicon carbide crystals having predominantly either alpha or beta crystalline structures and with crystal sizes predominantly in the range of 250 to 3,000 microns are produced.

Abstract: A metal processing furnace of the indirect arc type employing opposed electrodes projected into an ionizable atmosphere is provided with novel filter-like, vapor nucleation means which enables the furnace to be utilized for numerous different metal melting/smelting operations in a manner which precludes the presence of metals and metal oxides in their vapor or particle forms in process effluent gases delivered from the furnace. The furance achieves substantial operating advantages in the manufacture of ferroalloys, silicon and beryllium-copper metals, and comparable products including carbides such as silicon carbide.

Abstract: A metal processing furnace of the indirect arc type employing opposed electrodes projected into an ionizable atmosphere is provided with novel filter-like, vapor nucleation means which enables the furnace to be utilized for numerous different metal melting/smelting operations in a manner which precludes the presence of metals and metal oxides in their vapor or particle forms in process effluent gases delivered from the furnace. The furnace achieves substantial operating advantages in the manufacture of ferroalloys, silicon and beryllium-copper metals, and comparable products including carbides such as silicon carbide.

Abstract: A metal processing furnace of the indirect arc type having opposed electrodes projected into and establishing an ionized atmosphere in the furnace crucible is provided with apparatus that introduces a finely divided charge mixture consisting essentially of silica and coke into the system for free-fall into and through the ionized atmosphere. Following reaction of the mixture's ingredients in the ionized atmosphere, silicon carbide crystals are deposited at the bottom of the furnace interior below the ionized atmosphere for subsequent collection and removal from within the furnace system. By control of charge composition and process parameters, silicon carbide crystals having predominantly either alpha or beta crystalline structures and with crystal sizes predominantly in the range of 250 to 3,000 microns are produced.

Abstract: Compacted refractory shapes having sufficient densities for lining metal melting furnaces and use at service temperatures of 3,400.degree. to 3,900.degree. F to retain molten metal are formed in place by bonding refractory particles of alumina, for instance, with aluminum hydroxide generated by the reaction of aluminum with water in the presence of a corrosion accelerator, and either with or without a reaction control agent satisfactory for eliminating or significantly suppressing the evolution of hydrogen, nitrogen dioxide, hydrogen chloride, or the like from the reacting mass or for reducing the rate of reaction corrosion.

Abstract: Porous refractory shapes having sufficient strength for use as thermal insulation in metal melting furnaces at insulation service temperatures of 3,400.degree. to 3,900.degree. F are formed in place by bonding refractory particles of alumina, for instance, with aluminum hydroxide generated by the reaction of aluminum with water in the presence of a corrosion accelerator, and either with or without a reaction control agent satisfactory for eliminating or significantly suppressing the evolution of hydrogen, nitrogen dioxide, hydrogen chloride, or the like from the reacting mass or for reducing the rate of reaction corrosion.

Abstract: An indirect arc metal melting furnace of the type having an insulated and essentially sealed or closed exterior shell is operated in a novel manner which thereby improves the electrical operating characteristics of the furnace.