Circuit breaker contact containing silver and graphite fibers

Claim 1

A method of producing an electrical contact material of silver and graphite fiber which comprises the steps of mixing quantities of silver powder, graphite fiber particles, wetting agent powder, a solution of a lubricant and a solvent to provide a homogeneous mixture of ingredients and including from about 0.5 to about 10 weight percent of graphite fiber particles, from about 0.1 to about 3 weight percent of powdered wetting agent selected from the group consisting of Ni, Fe, Co, Cu, Au, and mixtures thereof, the solution being a slurry of a volatile hydrocarbon solvent and of a lubricant selected from the group consisting of polyethylene glycol, paraffin, and stearic acid, and the residual part consisting of silver powder; drying the mixture of ingredients to eliminate the volatile solvent and to produce a dried mixture; screening the dried mixture to agglomerate the ingredients into clusters; pressing the dried mixture under a pressure of from about 7.5 to about 10 tons per square inch to form a solid briquet; heating the solid briquet from about 250° F. to about 450° F. for about one hour at each temperature of 250° F., 350° F., and 450° F., in air to bake out the lubricant; sintering the solid briquet at temperature range of from about 1500° F. to 1700° F. in a reducing atmosphere to shrink the briquet to a higher density; repressing the solid briquet under a pressure of about 50 tons per square inch to increase the density; resintering the solid briquet at a temperature of from about 1500° F. to about 1700° F. in a reducing atmosphere to anneal stress from repressing; and re-repressing the solid briquet under a pressure of from about 50 to 60 tons per square inch.

Claim 2

A method of producing an electrical contact material of silver and graphite fiber which comprises the steps of mixing quantities of silver powder, graphite fiber particles, wetting agent powder, a solution of a lubricant and a solvent to provide a homogeneous mixture of ingredients and including from about 0.5 to about 10 weight percent of graphite fiber particles, from about 0.1 to about 3 weight percent of powdered wetting agent selected from the group consisting of Ni, Fe, Co, Cu, Au, and mixtures thereof, the solution being a slurry of a volatile hydrocarbon solvent and of a lubricant selected from the group consisting of polyethylene glycol, paraffin, and stearic acid, and the residual part consisting of silver powder; drying the mixture of ingredients to eliminate the volatile solvent and to produce a dried mixture; screening the dried mixture to agglomerate the ingredients into clusters; pressing the dried mixture under a pressure of from about 7.5 to about 10 tons per square inch to form a solid briquet; heating the solid briquet from about 250° F. to about 450° F. for about one hour at each temperature of 250° F., 350° F., and 450° F., in air to bake out the lubricant; sintering the solid briquet at temperature range of from about 1500° F. to 1700° F. in a reducing atmosphere to shrink the briquet to a higher density; repressing the solid briquet under a pressure of about 50 tons per square inch to increase the density; resintering the solid briquet at a temperature of from about 1500° F. to about 1700° F. in a reducing atmosphere to anneal stress from repressing; and re-repressing the solid briquet under a pressure of from about 50 to 60 tons per square inch.