# US 5,348,694 A · Method for electroconsolidation of a preformed particulate workpiece > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,348,694 A - Document ID: US5348694A - Status: Granted - Kind: A - Application number: 08/032,628 - Filed: 1993-03-17 - Granted: 1994-09-20 - Earliest claimed: 1988-12-20 - Assignees: Superior Graphite Co. - Inventors: William M. Goldberger - Web page: https://patentgrep.com/patent/US5348694A ## CPC - C04B 35/52: based on carbon, e.g. graphite - C04B 35/563: based on boron carbide - C04B 35/575: obtained by pressure sintering - C04B 35/645: Pressure sintering - C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE ## Abstract A method of consolidating particulate materials or combinations of such materials into shaped products of very low porosity. High compaction pressures are applied at temperatures in the range of sintering temperature of the materials being consolidated to achieve essentially complete densification at extremely rapid processing rates. Electrothermal heating is utilized to accomplish these results. Difficult materials such as silicon carbide, boron carbide and other very high melting point materials may be densified by these techniques. ## Claims ### Claim 1 An improved method of consolidating a workpiece preformed from particulate, powdered, sintered, fibrous, spongiose, or other solid containing material capable of consolidation, said method including the steps of: providing at a temperature insufficient to effectuate any substantial consolidation of the workpiece a bed comprising a bed material of electrically conductive, flowable particles within a contained zone; positioning the preformed workpiece in the bed; applying a first pressure to the bed material for sufficient compaction to the bed material to provide suitable electrical contact of such bed material; thereafter applying electrical energy to said electrically conductive, flowable particles within the bed while the bed contains the workpiece, and in sufficient amount to heat the bed to the consolidation temperature for the workpiece, substantially all of the heat for consolidation provided to the bed while the preformed workpiece is positioned therein; applying a second pressure to such bed of electrically conductive, flowable particles to transmit a compressive force to the workpiece sufficient effectuate substantial consolidation of the workpiece; and purging the bed with an inert gas at least during the application of electrical energy to such bed. ### Claim 2 (depends on 1) The improve method of claim 1 wherein the electrically conductive, flowable particles of the bed comprise carbonaceous particles. ### Claim 3 (depends on 1) The improved method of claim 1 wherein the electrically conductive, flowable particles of the bed primarily consist of flowable and a resiliently compressible substantially carbonaceous particles in the form of beads at least some of which have outwardly projecting nodules thereon, and at least some beads having surface fissures thereinto. ### Claim 4 (depends on 1) The improved method of claim 1 wherein said preformed workpiece comprises silicon carbide. ### Claim 5 (depends on 4) The improved method of claim 4 wherein sufficient electrical energy is applied to the bed of electrical conductive flowable particles to raise its temperature to in excess of approximately 2200.degree. C. ### Claim 6 (depends on 5) The improved method of claim 5 wherein electrical energy is supplied in an amount sufficient to raise the bed temperature to in excess of approximately 2200.degree. C. in less than approximately 60 seconds. ### Claim 7 (depends on 1) The improved method of claim 1 wherein the electrically conductive bed is substantially electrically isolated. ### Claim 8 (depends on 1) The improved method of claim 1 wherein the step of purging the bed includes inputting and maintaining a supply of an inert gas within the bed prior to and during the application of electrical energy to the bed. ### Claim 9 (depends on 1) The improved method of claim 1 wherein the electrically conductive, flowable particles of the bed are selected from the group consisting of spherical graphite, and carbided graphitic material. ### Claim 10 (depends on 9) The improved method of claim 9 wherein the particles comprise substantially spherical graphite particles having a diameter of approximately 0.1 mm to 0.8 mm. ### Claim 11 (depends on 10) The improved method of claim 10 wherein said particles comprise approximately 50% silicon carbide, with substantially the balance thereof comprising free carbon. ### Claim 12 (depends on 1) The improved method of claim 1 wherein the electrically conductive, flowable particles have a resiliency of approximately at least 50%. ### Claim 13 (depends on 1) The improved method of claim 1 wherein the preformed workpiece comprises B.sub.4 C. ### Claim 14 (depends on 1) The improved method of claim 1 wherein the preformed workpiece includes phenolic resin binder in an amount equal to provide approximately 2% free carbon after pyrolysis. ### Claim 15 (depends on 1) The improved method of claim 1 wherein the pressure applied to the electrically conductive, flowable particles is a compaction pressure in the range of approximately 3,000-5,000 psi. ### Claim 16 (depends on 8) The improved method of claim 8 wherein the inert gas is selected from the group consisting of nitrogen, argon and the noble gases. ### Claim 17 (depends on 1) The improved method of claim 1 wherein the preformed workpiece is consolidated to approximately at least 80% theoretical density. ### Claim 18 (depends on 1) The improved method of claim 1 wherein the preformed workpiece is consolidated to approximately 60% theoretical density prior to the application of electrical energy and pressure thereto. ### Claim 19 (depends on 1) The improved method of claim 1 wherein the density of the preformed workpiece is increased from approximately 2.01 g/cc to approximately 2.80 g/cc. ### Claim 20 (depends on 9) The improved method of claim 9 wherein the electrically conductive flowable particles of the bed comprise boron incorporated into the structure of the particles. ### Claim 21 (depends on 19) The improved method of claim 19 wherein the incorporated boron comprises approximately 1.75% by weight of the electrically conductive, flowable particles. ### Claim 22 (depends on 1) The improved method of claim 1 wherein the preformed workpiece is formed by cold compaction. ### Claim 23 (depends on 22) The improved method of claim 22 wherein the cold compaction is uniaxially applied. ### Claim 24 (depends on 1) The improved method of claim 1 wherein at least approximately 20 KW of electrical energy is supplied to the electrically conductive, flowable particles during consolidation of the workpiece. ### Claim 25 (depends on 1) The improved method of claim 1 wherein the preformed workpiece is substantially non-conductive. ### Claim 26 (depends on 1) The improved method of claim 1 wherein such application of pressure to the bed is uniaxially applied. ### Claim 27 (depends on 1) The improved method of claim 1 wherein the electrically conductive, flowable particles have an electrical resistivity of approximately 3.8-4.6 ohm-cm.times.10.sup.2.