# US 5,704,993 A · High conductivity composite metal > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,704,993 A - Document ID: US5704993A - Status: Granted - Kind: A - Application number: 08/565,523 - Filed: 1995-11-30 - Granted: 1998-01-06 - Earliest claimed: 1995-11-30 - Assignees: The Regents of the Univerisity of California, Office of Technology Transfer - Inventors: Ruoyi Zhou; James L. Smith; John David Embury - Web page: https://patentgrep.com/patent/US5704993A ## CPC - H01B 1/02: mainly consisting of metals or alloys - B32B 15/01: all layers being exclusively metallic {(making layered metal workpieces by pressure cladding B23K20/22; making coatings with a metallic material characterised by its composition C23C30/00)} - H01B: CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES (selection for magnetic properties H01F1/00; waveguides H01P {; printed circuits H05K}) - B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM ## Abstract Electrical conductors and methods of producing them, where the conductors possess both high strength and high conductivity. Conductors are comprised of carbon steel and a material chosen from a group consisting of copper, nickel, silver, and gold. Diffusion barriers are placed between these two materials. The components of a conductor are assembled and then the assembly is subjected to heat treating and mechanical deformation steps. ## Claims ### Claim 1 A method for making an electrical conductor comprising: a. providing a core element of carbon steel having an elongated generally cylindrical shape and a carbon content of from about 0.3 to about 0.8 weight percent; b. covering the elongated surface of said core element with a diffusion barrier; c. placing said covered core element inside a hollow cylinder of a highly conductive material to form an assembly, where said material is chosen from a group consisting of copper, nickel, silver, and gold; d. evacuating air from said assembly and sealing the ends of the assembly to maintain its interior in the evacuated condition; e. annealing the assembly; f. mechanically deforming the assembly by reducing its cross-sectional area to form a billet; g. heating said billet to a temperature greater than austenization temperature of said carbon steel and maintaining it at that temperature for a time period effective for austenization to take place; h. rapidly cooling the billet to a temperature of from about 270.degree. C. to about 310.degree. C.; i. heating the billet to a temperature of from about 400.degree. C. to about 500.degree. C. and maintaining its temperature within that range for a time period of from about 5 to about 20 minutes; j. rapidly cooling the billet to a temperature of less than about 200.degree. C.; and k. mechanically deforming the billet by reducing the cross-sectional area of the billet to form a conductor. ### Claim 2 (depends on 1) The method of claim 1 where said diffusion barrier is chosen from a group consisting of niobium, vanadium, and tantalum. ### Claim 3 (depends on 1) The method of claim 1 where said diffusion barrier is effective to separate the highly conductive material from the carbon steel after mechanical deformation is complete. ### Claim 4 (depends on 1) The method of claim 1 where step d comprises placing the assembly in an evacuated electron beam welding chamber and using electron beam welding to attach closures to the ends of the assembly. ### Claim 5 (depends on 1) The method of claim 1 where step d comprises evacuating the assembly to a pressure of at least 10.sup.-5 Torr. ### Claim 6 (depends on 1) The method of claim 1 where step e comprises annealing the assembly at a temperature of from about 600.degree. C. to about 900.degree. C. for a period of from about 3 to about 5 hours. ### Claim 7 (depends on 1) The method of claim 1 where step f comprises mechanically deforming the assembly by extrusion. ### Claim 8 (depends on 1) The method of claim 1 where step f comprises mechanical deforming the assembly at temperatures of from about 600.degree. C. to about 800.degree. C. ### Claim 9 (depends on 1) The method of claim 1 where step k comprises mechanically deforming the billet by swaging and wire-drawing. ### Claim 10 (depends on 1) The method of claim 1 where step k comprises mechanically deforming the billet in a plurality of stages and further comprising an intermediate anneal between each of said stages. ### Claim 11 (depends on 10) The method of claim 10 where said annealing is done at a temperature of about 300.degree. C. for about 1 hour. ### Claim 12 (depends on 1) The method of claim 1 further comprising a step of annealing the conductor after mechanical deformation is complete. ### Claim 13 (depends on 1) The method of claim 1 where step k comprises reducing the cross-sectional area of the billet by 90%. ### Claim 14 (depends on 1) The method of claim 1 where the temperature of step g is about 920.degree. C. ### Claim 15 (depends on 1) The method of claim 1 where the time period of step g is about 30 minutes. ### Claim 16 (depends on 1) The method of claim 1 where the rapid cooling of step h is done by immersing the billet in a liquid at a temperature of from about 270.degree. C. to about 310.degree. C. ### Claim 17 (depends on 1) The method of claim 1 where the heating of step i is accomplished immediately after the rapid cooling of step h. ### Claim 18 (depends on 1) The method of claim 1 where the temperature of step h is about 290.degree. C. ### Claim 19 (depends on 1) The method of claim 1 where the temperature of step i is about 450.degree. C. ### Claim 20 (depends on 1) The method of claim 1 where the time period of step i is about 10 min. ### Claim 21 A method for making an electrical conductor comprising: a. providing a core element of a highly conductive material having an elongated generally cylindrical shape, where said material is chosen from a group consisting of copper, nickel, silver, and gold; b. covering the elongated surface of said core element with a diffusion barrier; c. placing said covered core element inside a hollow cylinder of carbon steel having a carbon content of from about 0.3 to about 0.8 weight percent to form a first assembly; d. covering the elongated surface of said first assembly with a diffusion barrier; e. placing said covered first assembly in a hollow cylinder of a highly conductive material to form a second assembly, where said material is chosen from a group consisting of copper, nickel, silver, and gold; f. evacuating air from said second assembly and sealing the ends of the second assembly to maintain its interior in the evacuated condition; g. annealing the second assembly; h. mechanically deforming the second assembly by reducing its cross-sectional area to form a billet; i. heating said billet to a temperature greater than austenization temperature of said carbon steel and maintaining it at that temperature for a time period effective for austenization to take place; j. rapidly cooling the billet to a temperature of from about 270.degree. C. to about 310.degree. C.; k. heating the billet to a temperature of from about 400.degree. C. to about 500.degree. C. and maintaining its temperature within that range for a time period of from about 5 to about 20 minutes; l. rapidly cooling the billet to a temperature of less than about 200.degree. C.; and m. mechanically deforming the billet by reducing the cross-sectional area of the billet to form a conductor. ### Claim 22 (depends on 21) The method of claim 21 where said diffusion barrier is chosen from a group consisting of niobium, vanadium, and tantalum. ### Claim 23 (depends on 21) The method of claim 21 where said diffusion barrier is effective to separate the highly conductive material from the carbon steel after mechanical deformation is complete. ### Claim 24 (depends on 21) The method of claim 21 where step f comprises placing the second assembly in an evacuated electron beam welding chamber and using electron beam welding to attach closures to the ends of the assembly. ### Claim 25 (depends on 21) The method of claim 21 where step f comprises evacuating the second assembly to a pressure of at least 10.sup.-5 Torr. ### Claim 26 (depends on 21) The method of claim 21 where step q comprises annealing the second assembly at a temperature of from about 600.degree. C. to about 900.degree. C. for a period of from about 3 to about 5 hours. ### Claim 27 (depends on 21) The method of claim 21 where step h comprises mechanically deforming the second assembly by extrusion. ### Claim 28 (depends on 21) The method of claim 21 where step h comprises mechanical deforminq the second assembly at temperatures of from about 600.degree. C. to about 800.degree. C. ### Claim 29 (depends on 21) The method of claim 21 where step m comprises mechanically deforming the billet by swaging and wire-drawing. ### Claim 30 (depends on 21) The method of claim 21 where step m comprises mechanical deforming the billet in a plurality of stages and further comprising an intermediate anneal between each of said stages. ### Claim 31 (depends on 21) The method of claim 21 where said annealing is done at a temperature of about 300.degree. C. for about 1 hour. ### Claim 32 (depends on 21) The method of claim 21 further comprising a step of annealing the conductor after mechanical deformation is complete. ### Claim 33 (depends on 21) The method of claim 21 where step m comprises reducing the cross-sectional area of the billet by 90%. ### Claim 34 (depends on 21) The method of claim 21 where the temperature of step i is about 920.degree. C. ### Claim 35 (depends on 21) The method of claim 21 where the time period of step i is about 30 minutes. ### Claim 36 (depends on 21) The method of claim 21 where the rapid cooling of step j is done by immersing the billet in a liquid at a temperature of from about 270.degree. C. to about 310.degree. C.