Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
  • C21C5/28—Manufacture of steel in the converter
  • C21C5/30—Regulating or controlling the blowing
  • C21C5/32—Blowing from above
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
  • C21C5/28—Manufacture of steel in the converter
  • C21C5/30—Regulating or controlling the blowing
  • C21C5/34—Blowing through the bath

Definitions

• a method for refining molten metal containing minor amounts of oxiclizable elements in a metallurgical vessel comprising the steps of introducing at least one stream of oxygen through at least one injector into the body of molten metal to form at least one reaction zone, introducing at least one oxide of the oxidizable elements present in the molten metal to at least one of the reaction zones in amounts sufficient to provide high concentration of the oxide or oxides to inhibit or eliminate oxidation of the elements in the molten metal bath that correspond to said oxide or oxides, and continuing to introduce oxygen and oxides until oxidation of the element in the molten metal of the oxide introduced is reduced or prevented by the law of mass action.
• the advantage of the method of this invention is that it not only accelerates the process of refining the molten metal, but, in addition, such elements as silicon, manganese, and chromium are conserved and are retained in the resulting refined metal. Ferroalloy addi tions may be omitted in most cases. As a result the cost of producing steel is lowered significantly.
• the process for refining molten metal of this invention is applicable to the refining of any metal that is ordinarily refined by oxygen.
• the process is particularly adaptable to the refining of steei either from pig iron or from some intermediate stage of refinement to the ultimate desired steel analysis.
• Fig iron contains small amounts of various elements depending upon varying factors such as the composition of the original ore and such elements usually include from about 3 to about 4.5% carbon, from about U.l5 to about 2.5% manganese, from about 0.5 to about 4.0% silicon, from about 0.8 to about 2.0% phosphorus, and from about 0.4 to about l.()% sulfur.
• Other elements may also be included such as chromium, titanium, molybdenum, nickel, etc.
• the method of this invention is particularly applicable to those processes where oxygen is introduced into a body or on the surface of the molten-iron-base metal, such as in various forms of the so-called basic oxygen process (BOP), the method may also be used for refining steel in an electric furnace, or open hearth furnace, by the injection of oxides through roof lances or submerged tuyeres.
• BOP basic oxygen process
• the method of this invention is preferably employed for the refining of pig iron into various types of steel, such as steels containing various amounts of carbon, manganese, silicon, phosphorus, sulfur, chromium, titanium, molybdenum, nickel, vanadium, boron, columbium, copper, and mixtures thereof.
• An example of the method of this invention involves pouring of a desired amount of molten steel into a basic oxygen converter, commencing to blow at least one stream of oxygen into the body of the molten metal, introducing the necessary amounts of slag-forming materials, such as burnt lime, fluorspar (CaF j or other stag conditioners, introducing with the steam oxygen particles of the oxide of one or more oxidizable elements present in the molten steel in amounts sufficient to reduce or eliminate oxidation of the element corresponding to the oxide being reduced, whereby the oxygen input then preferentially oxidizes the other elements in the metal such as phosphorus, sulfur, and carbon.
• slag-forming materials such as burnt lime, fluorspar (CaF j or other stag conditioners
• All forms of oxides of the oxidizable elements present in the molten metal are suitable for the purposes of this invention.
• the oxides When the oxides are transported by the oxygen stream, the oxides are physically sized to conform to the physical factors required for such transport.
• iron oxide is preferably introduced with the oxygen stream in order to minimize oxidation of iron during the refining process.
• the source of iron oxide to be used is dust of precipitators and collectors of dust resuiting from the refining of steel in such furnaces as the open hearth, and the basic oxygen converter either top blown or bottom blown. Dusts of iron oxide and man ganese oxide from collection systems are essential materials for introduction with oxygen in accordance with this invention.
• these dusts have a particle size of about one micron. Sized iron ore or roll scale are further sources of iron oxide. This invention affords the metal industry the opportunity to utilize useless waste products of their refining processes to conserve vital raw materials, such as iron, manganese, chromium. nickel, by lowering the total amount oxidized from the materials charged and further drastically reduces the production of these waste products.
• an oxygen stream containing particles of iron oxide and manganese oxide forms a reaction zone in a molten pig iron bath
• the presence of said particles in the reaction zone absorbs heat in their conversion to the molten state and provides high concentrations of molten oxides of iron and manganese in the reaction zone. This diverts the oxidation reaction between the oxygen stream and the molten pig iron to elements other than iron and manganese. lf particles of silicon oxide and manganese oxide were used, the oxidation of silicon and manganese would be reduced or preeluded.
• the introduction of the oxide of manganese is delayed until the excess quantity of manganese in the molten bath has been oxidized and given up to the slag.
• Metallic oxides have high heat capacities and absorb heat from reaction zones in their conversion to the mol ten state.
• the effective temperature in the reaction zone is lowered below the vaporization temperatures of iron and manganese. Consequently, the emission of vaporized iron and manganese from the bath is reduced or eliminated by controlling the amounts of particulate oxide introduced with the oxygen stream.
• oxides of such elements may be introduced into the oxygen stream either with or without iron oxide.
• oxides of such elements as silicon, phosphorus, sulfur may be added in particulate form, whereby the elements are retained through the refining process and in the resulting refined steel.
• the reaction zone of the molten metal receive particulates of the oxides of the elements that are to be retained in the refined metal and the oxygen in the oxygen stream oxidizes the other elements.
• the particulate of the oxides are introduced into the reaction zone or zones in quantities ranging from concentrations sufficient to inhibit oxida tion of the elements desired to be retained in some cases in quantities sufficient to create saturation or supersaturation of said zone(s).
• Those elements to be retained or eliminated comprise any and all of those oxidizable elements ordinarily contained in molten pig iron and any other intermediate grade of refined steel.
• the oxides introduced may consist of at least one of the elements including iron, carbon, manganese, silicon,
• chromium oxide is introduced into the oxygen stream to prevent oxidation of the chromium in the molten metal.
• EXAMPLE A charge of metal consisting of 79 tons of plain carbon steel scrap and of [84 tons of hot metal is charged into a basic oxygen furnace.
• the hot metal has a typical composition of 3.4% carbon, l.0% manganese, 0.8% silicon, 1.2% phosphorus, 0.55% sulfur, and the balance is iron.
• a lance is introduced into the top of the converter and an oxygen stream at about 180 psi. is directed into the top of the molten charge.
• Oxide particles of silicon and manganese having a size of from /2 to 30 microns (preferably 1 micron) are included with the oxygen stream. it is desired to retain about 0.35% silicon and about 0.40% manganese in the refined metal.
• the cited example indicates a conservation of one ton of manganese and of 0.9 ton of silicon. That is, it was unnecessary to replace silicon or manganese that would otherwise have been removed from the bath by oxidation in conventional basic oxygen converter prac tice. Moreover, the emission of fine particulate matter from the converter is reduced by 38%, because the re action zone temperature is lowered by the oxide introduction.
• iron oxide which would commence after the tenth minute of the blow.
• a useful range of input is from 10 to 2,000 lbs. per minute of iron oxide (or 0.06 to 1] lbs./minute/ton of pig iron charged) with a preferred range of from about to about 300 lbs. per minute (or 0.9 to 1.63 lbs/minutelton).
• the broad ranges cited reflect the cumulative effect of more than one specific oxide being introduced both from a chemical and temperature standpoint.
• iron oxide may be introduced at earlier stages of the oxygen blow either with or without oxides to achieve desired final analysis.
• the useful range of from about 10 to about 600 lbs/minute (0.06 to 3.26 lbs./minute/ton of pig iron charged) and a preferred range of from about to about 500 lbs/minute of silicon dioxide (0.6 to 2.72 lbs./minute/ton) may be added.
• the useful range of manganese oxide is from about 20 to about i000 lbs/minute (or 0.l l to 5.4 lbs./minute/ton) with a preferred range of from about to about 800 lbs/minute (0.95 to 4.35
• the original charge includl0 ing scrap would contain higher precentages of nickel and chromium. Thereafter, during the oxygen blow, oxides of chromium, nickel, and/or other elements are added in particulate form with the oxygen stream.
• the preferred procedure for introducing oxides of the elements set forth above is to introduce those oxides as particulates or powders through a lance with the oxygen stream
• the oxides may be introduced into the reaction zone between the oxygen stream and the molten bath separately through other conduits or methods.
• the oxygen may be introduced axially or centrally of the oxides with the oxides peripherally of the oxygen.
• the oxides may be centrally or axially disposed with respect to the oxygen.
• the transport of particulate oxides to the reaction zone may be accomplished in diverse methods.
• Use of relatively inert gases such as steam, carbon dioxide, compressed air, argon, for transport of the oxide particulate and relatively inert gases plus controlled amounts of oxygen in a peripheral disposition in relation to a central oxygen stream represent the optimum concept for said introduction, but provision of the desired oxide particulate in the reaction zone can be achieved in a variety of ways or combinations.
• the oxides may be introduced in a carrier stream of oxygen with or without inert gases.
• the oxygen stream may be introduced by impinging on the molten bath from the top of the vertical axis, from the side of the vertical axis, or from the bottom of the vertical axis (submerged).
• the method for refining molten metal and preferably steel of this invention provides for the elimination of extraneous sources of hydrogen into the molten metal, avoid unintentional introduction of sulfur and prevents the pollution of the atmosphere with 50;, where iron oxide and/or manganese oxide is introduced, increases the yield of iron from pig iron from 1.0 to 1.5% by saturating the reaction zone with oxide particles, increases the yield of metallic manganese, avoids the use of critical energy producing hydrocarbons, and reduces oxygen consumption because excessive oxidation of iron is prevented and desirable elements are oxidized only to a desired degree.
• a method of refining molten metal containing oxidizable elements in a metallurgical vessel comprising:
• the oxide introduced is selected from the group consisting of at least one of the elements including iron, carbon, manganese, silicon, phosphorus, sulfur, chromium, titanium, molybdenum, nickel, vanadium, boron, columbium, copper, and mixtures thereof.
• the molten metal body consists essentially of pig iron into which silicon dioxide particles are introduced at a rate of from about 0.06 to about 3.26 lbs/minute/ton of pig iron charged.
• iron oxide is introduced at a rate of from about 0.06 to about ll lbs./minute/ton 25.
• the method of claim 24 wherein iron oxide is introduced at a rate of from about 0.90 to about 1.63 lbsjminute/ton 26.
• the method of claim 20 wherein iron oxide is introduced at a rate of from 0.06 to about l l lbs./minute/ton about eight minutes after the start of the oxygen blow.
• a method of refining molten metal containing oxidizable elements in a metallurgical vessel comprising:

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Treatment Of Steel In Its Molten State (AREA)
• Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)

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Citations (3)

• 1973
  • 1973-11-05 US US412563A patent/US3904399A/en not_active Expired - Lifetime
• 1974
  • 1974-10-05 SE SE7413887A patent/SE7413887L/xx unknown
  • 1974-10-08 ZA ZA00746415A patent/ZA746415B/xx unknown
  • 1974-10-11 CA CA211,319A patent/CA1042215A/en not_active Expired
  • 1974-10-17 IN IN2304/CAL/1974A patent/IN140315B/en unknown
  • 1974-10-18 GB GB45235/74A patent/GB1495723A/en not_active Expired
  • 1974-10-18 BE BE149700A patent/BE821264A/xx unknown
  • 1974-10-21 BR BR8753/74A patent/BR7408753A/pt unknown
  • 1974-10-22 NL NL7413799A patent/NL7413799A/xx not_active Application Discontinuation
  • 1974-10-30 IT IT28979/74A patent/IT1025337B/it active
  • 1974-10-31 AR AR256356A patent/AR203661A1/es active
  • 1974-11-02 DE DE19742452158 patent/DE2452158A1/de active Pending
  • 1974-11-04 NO NO743951A patent/NO743951L/no unknown
  • 1974-11-05 FR FR7436680A patent/FR2249956B1/fr not_active Expired
  • 1974-11-05 LU LU71234A patent/LU71234A1/xx unknown
  • 1974-11-05 RO RO7480428A patent/RO68039A/ro unknown
  • 1974-11-05 ES ES431671A patent/ES431671A1/es not_active Expired
  • 1974-11-05 JP JP49126655A patent/JPS5075515A/ja active Pending

Patent Citations (3)

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