Abstract: The heating element is made of a plurality of silicon carbide rods, at least four rods being employed in the heating element. The hot ends of all the rods are connected together by a single silicon carbide bridge member. The other (cold) ends of the rods are arranged so that at the current input side two rods are in parallel and on the output side the other two rods are also in parallel and the two pairs of electrically parallel rods are connected in series electrically at the silicon carbide bridge member. The rods are preferably arranged in a square configuration and preferably extend perpendicular to the bridge member. Accordingly the rods can be inserted in a silicon carbide tube closed at the hot end. The interior heating rods are electrically insulated from the silicon carbide tube.

Abstract: A new form of reaction bonded silicon nitride is described along with the process of making this new product. The product is characterized by isotropic structure, extremely fine pore and grain size, high strength and a high ratio of alpha silicon nitride to beta silicon nitride. The product has a density of at least 2.45 grams/cc and is essentially free of pores greater than 15 microns.

Abstract: A castable slip of a bimodal distribution of silicon carbide particles is prepared, the slip preferably containing a water miscible curable resin. A shaped body is cast in a plaster of paris mold which also preferably contains a small amount of a water soluble polymer. The casting and mold are then heat treated to increase the strength of the green casting. In a preferred embodiment of the invention the resin in the slip is cured by the heat treating step. The mold is then removed by decomposing the mold material, preferably by dipping the mold in acid to attack the mold material (e.g. the water soluble polymer or the plaster of paris itself). The cured resin in the casting is sufficiently resistant to attack by the acid to survive the mold removal. In an alternative embodiment the silicon carbide body is heated to a sufficiently high temperature (e.g. 650.degree.-750.degree. C) to slightly oxidize the SiC and to strengthen the green casting.

Abstract: A lightweight insulating refractory shape is made of Si.sub.2 ON.sub.2 having a density of less than 50% of theoretical, a relatively high compressive strength, a low thermal conductivity and high resistance to attack by chlorine, fused chlorides and molten aluminum.

Abstract: A resilient, controlled-density, porous, abrasive material is manufactured having a backing member which in the preferred embodiment is a foam layer of a plurality of discrete resilient particles of varying degrees of compressibility. The backing member is provided from a larger body of foam material reconstituted from particulate foam. The surface of the backing member, on which is coated an abrasive grain - binder adhesive slurry, is subjected, prior to the coating of the slurry on the particulate foam layer, to the action of a plurality of rapidly moving small abrasive particles whereby a relatively non-compressive shearing of the foam surface is effected to condition it for reception of abrasive grains and associated binder adhesive and to produce a uniform thickness of the porous abrasive grain support.

Abstract: The strength of a reaction sintered silicon nitride body is substantially increased by impregnating the surface of the body with finely divided alumina and then firing the body in a nitrogen atmosphere to a temperature in excess of 1200.degree. C, the reaction being carried out under an appreciable partial pressure of SiO.

Abstract: An endless coated abrasive article is formed by helically winding a strip of abrasive material into a spiral of coils, the edges of which are in abutting engagement thus forming a spiral butt joint and coating the inner periphery of the helically wound strip of abrasive material with a continuous layer of resinous composition whereby an abrasive article is formed of greater width than the strip of abrasive material.

Abstract: Coated abrasive material is provided having a supersize layer thereon which improves grinding. This layer comprises an elastomeric material having substantial residual unsaturation and an active solid, particulate grinding aid.

Abstract: An automatic progressively or continuously operative mold assembly for chilling a material which melts in excess of 1700.degree. C and forming quickly a fine crystalline solid material therefrom by depositing said material in a molten state in the relatively thin spaces between a plurality of relatively thick heat sink plates maintained tightly contiguous as they are moved sequentially through and beyond a first mold filling or discharging station, and then moved very rapidly sequentially through a second mold emptying or discharging station in which the relatively thick heat sink plates are maintained spaced apart to discharge therefrom the fine crystalline solid material adhered thereto.

Abstract: A composition for filling a mold with abrasive grits and bond making use of resin bond particles and abrasive grains of approximately the same size intimately mixed together for use in a blow molding procedure.

Abstract: A grinding wheel is made by locating a grindstone element in a molding tool and injection-molding a supporting part so that a portion of the grindstone element is embedded in the supporting part and securely bonded thereto by the molding operation. Recesses in the embedded portion of the grindstone element ensure good torque transmission between the molded supporting part and the grindstone element.

Abstract: A composition for filling a mold with abrasive grits and bond making use of resin bond particles and abrasive grains of approximately the same size intimately mixed together for use in a blow molding procedure.