# US 7,608,130 B2 · Method for producing high cleanliness steel excellent in fatigue strength or cold workability > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,608,130 B2 - Document ID: US7608130B2 - Status: Granted - Kind: B2 - Application number: 10/564,061 - Filed: 2004-12-17 - Published: 2006-07-20 - Granted: 2009-10-27 - Earliest claimed: 2004-01-22 - Assignees: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) - Inventors: Koichi Sakamoto; Tomoko Sugimura; Atsuhiko Yoshida; Yoshio Fukuzaki; Sumie Suda - Web page: https://patentgrep.com/patent/US7608130B2 ## CPC - C22C 38/46: with vanadium - C01B 33/06: Metal silicides (alloys C22) - C21C 7/0006: {Adding metallic additives} - C21C 7/04: Removing impurities by adding a treating agent - C21C 7/076: Use of slags or fluxes as treating agents (C21C7/06, C21C7/064, C21C7/068 take precedence) - C21D 8/06: during manufacturing of rods or wires - C22C 38/002: {containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60} - C22C 38/02: containing silicon - C22C 38/04: containing manganese - C22C 38/18: containing chromium - C22C 38/24: with vanadium - C22C 38/40: with nickel - Y02P 10/20: Recycling - C22C: ALLOYS (treatment of alloys C21D, C22F) - C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C} - C21C: PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS - C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B) - Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS ## Abstract The present invention relates to a high-cleanliness steel having a high fatigue strength and high cold workability, and a method of making the high-cleanliness steel. The method adds a Li—Si alloy having a Li content between 20 and 40% and/or Li2CO3 as a Li-containing substance to a molten steel. The Li-containing substance is added to the molten steel after the completion of a series of steps of a ladle refining process including composition adjustment, temperature adjustment and slag refining. The high-cleanliness steel has a total-Li content between 0.020 and 20 ppm by mass and contains 1.0 or below oxide inclusion particle having a major diameter of 20 μm or above at a maximum in 50 g of the steel wire. The steel contains an oxide inclusion that has a CaO content between 15 and 55%, SiO2 content between 20 and 70%, an Al2O3 content of 35% or below, a MgO content of 20% or below and a Li2O content between 0.5 and 20%. The high-cleanliness steel has improved fatigue characteristics and improved cold workability. ## Claims ### Claim 1 A high-cleanliness steel having a total-Li content between 0.020 and 9 ppm by mass and containing 1.0 or below of oxide inclusion particles having a major diameter of 20 μm or above in 50 g of the steel. ### Claim 2 (depends on 1) The high-cleanliness steel according to claim 1, wherein the total-Li/Si mass ratio representing the ratio in mass of the total amount of Li contained in the steel to the amount of Si contained in the steel is between 1×10−6 and 1000×10−6. ### Claim 3 (depends on 1) The high-cleanliness steel according to claim 1, wherein each of the oxide inclusion particles has a CaO content between 15 and 55% by mass, a SiO2 content between 20 and 70% by mass, an Al2O3 content of 35% by mass or below, a MgO content of 20% by mass or below and a Li2O content between 0.5 and 20% by mass. ### Claim 4 (depends on 3) The high-cleanliness steel according to claim 3, wherein each of the oxide inclusion particles has a Li2O/SiO2 mass ratio between 0.01 and 0.5. ### Claim 5 (depends on 3) The high-cleanliness steel according to claim 3, wherein each of the oxide inclusion particles has a SiO2 content of 30% by mass or above and below 45% by mass. ### Claim 6 (depends on 3) The high-cleanliness steel according to claim 3, wherein each of the oxide inclusion particles contains Na2O and/or K2O and the sum of Li2O content, Na2O content and K2O content is between 0.5 and 20% by mass. ### Claim 7 (depends on 1) The high-cleanliness steel according to claim 1, wherein the steel has a C content of 1.2% by mass or below, a Si content between 0.1 and 4% by mass, a Mn content between 0.1 and 2.0% by mass, and an Al content of 0.01% by mass or below. ### Claim 8 (depends on 7) The high-cleanliness steel according to claim 7, wherein the steel has an O content of 0.005% by mass or below, a total-Mg content between 0.1 and 15 ppm by mass and a total-Ca content between 0.1 and 40 ppm by mass. ### Claim 9 (depends on 7) The high-cleanliness steel according to claim 7, wherein the steel contains at least one of Cr, Ni, V, Nb, W, Cu and Ti. ### Claim 10 (depends on 7) The high-cleanliness steel according to claim 7, wherein the other elements of the steel are Fe and unavoidable impurities. ### Claim 11 (depends on 8) The high-cleanliness steel according to claim 8, wherein the steel contains at least one of Cr, Ni, V, Nb, W, Cu and Ti. ### Claim 12 (depends on 8) The high-cleanliness steel according to claim 8, wherein the other elements of the steel are Fe and unavoidable impurities. ### Claim 13 (depends on 9) The high-cleanliness steel according to claim 9, wherein the other elements of the steel are Fe and unavoidable impurities. ### Claim 14 (depends on 1) The high-cleanliness steel according to claim 1, wherein the steel has a total-Li content between 0.020 and 6 ppm by mass. ### Claim 15 (depends on 1) A method of making a high-cleanliness steel excellent in cold workability and fatigue characteristic, said method comprising adding a Li-containing substance selected from the group consisting of a Li—Si alloy, Li2CO3, and a combination thereof, having a Li content between 20 and 40 % by mass, to a molten steel; and producing the steel of claim 1. ### Claim 16 (depends on 15) The method of making a high-cleanliness steel according to claim 15, characterized by adding a substance containing at least one of Ca, Mg, Na and K to the molten steel in addition to the Li-containing substance. ### Claim 17 (depends on 15) The method of making a high-cleanliness steel according to claim 15, characterized by adding the Li-containing substance to the molten steel after the completion of a series of operations of a ladle refining process including composition adjustment, temperature adjustment and slag refining to control the composition of the molten steel such that the steel has a total-Li content between 0.020 and 9 ppm by mass and contains 1.0 or below of oxide inclusion particles having a major diameter of 20 μm or above in 50 g of the steel. ### Claim 18 (depends on 15) The method of making a high-cleanliness steel according to claim 15, characterized by adding the Li-containing substance at a final stage of a series of operations of a ladle refining process including composition adjustment, temperature adjustment and slag refining such that an oxide inclusion contained in the steel has a CaO content between 15 and 55% by mass, a SiO2 content between 20 and 70% by mass, an A12O3 content of 35% by mass or below, a MgO content of 20% by mass of below and a Li2O content between 0.5 and 20% by mass. ### Claim 19 (depends on 15) The method of making a high-cleanliness steel according to claim 15, characterized by adding the Li-containing substance to the molten steel contained in at least one of a ladle, a tundish for continuous casting, and a mold for continuous casting. ### Claim 20 (depends on 15) The method of making a high-cleanliness steel according to claim 15, characterized by adding the Li-containing substance to the molten steel by stirring the molten steel with iron tubular wires containing the Li-containing substance. ### Claim 21 (depends on 15) The method of making a high-cleanliness steel according to claim 15, characterized by adding the Li-containing substance to the molten steel by blowing an inert gas carrying the Li-containing substance into the molten steel.