# US 10,441,982 B2 · Plug for rolling of seamless steel pipe, method for manufacturing the same and method for manufacturing seamless steel pipe using the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,441,982 B2 - Document ID: US10441982B2 - Status: Granted - Kind: B2 - Application number: 14/427,414 - Filed: 2013-09-09 - Published: 2015-08-06 - Granted: 2019-10-15 - Earliest claimed: 2012-09-11 - Assignees: Jfe Steel Corporation - Applicants: Jfe Steel Corporation - Inventors: Takaaki Iguchi; Tatsuro Katsumura; Hideto Kimura - Web page: https://patentgrep.com/patent/US10441982B2 ## CPC - B21B 28/00: Maintaining rolls or rolling equipment in effective condition (lubricating, cooling or heating rolls while in use B21B27/06) - B21B 25/00: Mandrels for metal tube rolling mills, e.g. mandrels of the types used in the methods covered by group B21B17/00; Accessories or auxiliary means therefor {; Construction of, or alloys for, mandrels or plugs} - C23C 8/02: Pretreatment of the material to be coated (C23C8/04 takes precedence) - C23C 8/12: using elemental oxygen or ozone - C25D 5/50: by heat-treatment - C25D 7/00: Electroplating characterised by the article coated - B21B 19/04: Rolling basic material of solid, i.e. non-hollow, structure; Piercing {, e.g. rotary piercing mills} - B21B: ROLLING OF METAL (auxiliary operations used in connection with metal-working operations covered in B21, see B21C; bending by rolling B21D; manufacture of particular objects, e.g. screws, wheels, rings, barrels, balls, by rolling B21H; pressure welding by means of a rolling mill B23K20/04) - C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04) - C25D: PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR ## Abstract A plug for rolling of a seamless steel pipe, the plug having an oxide layer composed of a cobalt-base oxide on a surface of a coating layer formed by coating a surface of a base metal with cobalt or a cobalt-base alloy, a method for manufacturing the plug and a method for manufacturing a seamless steel pipe using the plug. ## Claims ### Claim 1 A plug for rolling of a seamless steel pipe, the plug comprising: a base metal; a coating layer formed on the base metal by coating a surface of the base metal with pure cobalt comprising 99 mass % or more of cobalt and a balance being inevitable impurities or a cobalt-nickel alloy, the cobalt-nickel alloy containing 0.3 mass % or more and 30 mass % or less of Ni; and an oxide layer including a cobalt-base oxide formed on a surface of the coating layer, wherein an average thickness of the oxide layer is in the range of 10 μm to 40 μm. ### Claim 2 (depends on 1) The plug for rolling of a seamless steel pipe according to claim 1, wherein the oxide layer is formed by performing a heat treatment by holding at a high temperature. ### Claim 3 (depends on 2) The plug for rolling of a seamless steel pipe according to claim 2, wherein the oxide layer is also formed using heat applied when rolling of the seamless steel pipe is performed. ### Claim 4 (depends on 1) The plug for rolling of a seamless steel pipe according to claim 1, wherein the oxide layer is formed using heat applied when rolling of the seamless steel pipe is performed. ### Claim 5 (depends on 1) The plug for rolling of a seamless steel pipe according to claim 1, wherein the base metal includes a ferrous material. ### Claim 6 (depends on 1) A method for manufacturing a seamless steel pipe, using the plug according to claim 1 comprising: piercing a billet with the plug; and rolling the billet to form the seamless steel pipe. ### Claim 7 (depends on 1) The plug for rolling of a seamless steel pipe according to claim 1, wherein the coating layer is formed by coating the surface with the cobalt-nickel alloy. ### Claim 8 (depends on 1) The plug for rolling of a seamless steel pipe according to claim 1, wherein the average thickness of the oxide layer is in the range of 28 μm to 40 μm. ### Claim 9 A method for manufacturing a plug for rolling of a seamless steel pipe, the method comprising: coating a surface of a metallic plug with a film including pure cobalt comprising 99 mass % or more of cobalt and a balance being inevitable impurities or a cobalt-nickel alloy having a thickness in the range of 0.1 mm to 2 mm, the cobalt-nickel alloy containing 0.3 mass % or more and 30 mass % or less of Ni; and after the coating step, performing a heat treatment in atmospheric air at a temperature of 300° C. to 1000° C. in order to form an oxide layer including a cobalt-base oxide, the oxide layer having an average thickness in the range of 10 μm to 40 μm. ### Claim 10 (depends on 9) The method for manufacturing a plug according to claim 9, wherein the heat treatment is performed using heat applied when rolling of the seamless steel pipe is performed. ### Claim 11 (depends on 9) The method for manufacturing a plug according to claim 9, wherein the coating of the metallic plug is performed by plating. ### Claim 12 (depends on 9) The method for manufacturing a plug according to claim 9, wherein the oxide layer has an average thickness in the range of 28 μm to 40 μm. ### Claim 13 A plug for rolling of a seamless steel pipe, the plug comprising: a base metal; a coating layer formed on the base metal by coating a surface of the base metal with pure cobalt comprising 99 mass % or more of cobalt and a balance being inevitable impurities; and an oxide layer including a cobalt-base oxide formed on a surface of the coating layer, wherein an average thickness of the oxide layer is in the range of 10 μm to 40 μm. ### Claim 14 (depends on 13) The plug for rolling of a seamless steel pipe according to claim 13, wherein the average thickness of the oxide layer is in the range of 28 μm to 40 μm.