US3236637A - Process of continuously converting molten crude iron into steel - Google Patents

Process of continuously converting molten crude iron into steel Download PDF

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Publication number
US3236637A
US3236637A US20476362A US3236637A US 3236637 A US3236637 A US 3236637A US 20476362 A US20476362 A US 20476362A US 3236637 A US3236637 A US 3236637A
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iron
zone
jet
molten
reaction
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English (en)
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Mittermayr Alfred
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Voestalpine AG
Voest AG
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Voestalpine AG
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    • 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
    • C21C5/56—Manufacture of steel by other methods
    • C21C5/567—Manufacture of steel by other methods operating in a continuous way
    • 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
    • C21C5/42—Constructional features of converters
    • C21C5/46—Details or accessories
    • C21C5/4606—Lances or injectors
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • Continuous refining processes are known, in which the reactants crude iron, refining agent and slag-forming substances are continuously introduced into a reaction vessel and the steel produced is continuously Withdrawn.
  • a known proposal of this kind calls for passing the molten crude iron in contact with the refining agent through a horizontal drum-type converter, which is divided by baffles into a plurality of cylindrical sections. It was an object of this proposal to divide the process into stages, in Which different reactions (desiliconizing, decarburizing, dephosphorizing) take place.
  • the refining process is carried out in a plurality of separate reaction zones, including one or more prerefining reaction zones and a decarburizing zone, in which zones different temperatures are maintained and into each of which zones oxygen is blown with lances.
  • the invention provides a continuous process for converting liquid crude iron into steel, in which process the desired high mate of reaction in small reaction chambers is actually achieved.
  • the process according to the invention is carried out in a plurality of separate reaction zones, including at least one prerefining reaction zone and one decanbur-izing reaction zone, in which zones different temperatures are maintained, and is characterized in that the crude iron is atomized at its entrance into at least one of the reaction zones by means of the refining agent.
  • the fact that the reaction is carried out according to the invention in a finely divided, e.g., atomized state, ensures the large contact surface required, which enables a maximum rate of reaction and, consequently, a minimum refining time in each zone, while optimum conditions regarding temperature and oxygen supply are maintained.
  • small react-ion chambers are sufiicient and there is no need for extensive conveying and auxiliary installations.
  • reaction zones are completely separated, i.e., closed reaction chambers are used, which do not communicate with each other.
  • closed reaction chambers are used, which do not communicate with each other.
  • different conditions regarding temperature and pressure can be maintained in the diverse chambers; any mutual influence is avoided, a formation ice of smoke and dust is prevented and combustible Waste gases from one chamber can be rendered utilizatlble.
  • the reaction zones or chambers are suitably arranged one behind the other in cascade so that the crude iron can be transferred by gravity.
  • these relations are taken into account by the maintenance of specific temperatures in the individual zones and/or by the maintenance of the optimum oxygen supply. If the accompanying elements contained in the crude iron besides carboncomprise only manganese and silicon, which can be removed without addition of slag-forming substances, a single prerefining reaction zone is sufficient. When phosphorus is also present, an additional prerefining reaction zone is provided; in this case silicon and/or manganese will be removed in the first reaction zone without addition of slag-forming substances and phosphorus will be removed in the second reaction zone, to which lime, particularly lime dust, is added.
  • the prerefining and the dephosphorizing reaction zones are preferably held at a temperature of 12501350 C.
  • the decarburizing zone is held at a higher temperature, of 1550-1800 C.
  • a refining agent having a relatively small oxygen content such as air or a mixture of oxygen and CO or H O is suitably employed.
  • oxygen-enriched air or technically pure oxygen in the decanburizing zone, best results are obtained with oxygen-enriched air or technically pure oxygen.
  • Solid oxides, particularly oxides of iron, may be added to the gaseous refining agent, as Will be described more fully hereinafter.
  • the individual reaction zones are suitably held at the predetermined temperature by a heating which is independent of the refining process.
  • a preferred embodiment for the conversion of crude iron which contains phosphorus in addition to silicon and manganese comprises the following stages:
  • the crude iron is heated to the temperature of the decarburizing zone.
  • the heat of combustion of silicon, manganese, phosphorus and iron which are highly expensive heating means, is not required for this purpose, the heating being accomplished with an inexpensive heating means, such as gas or electric heat.
  • the oxidation of the crude iron-accompanying elements in the prerefining reaction zones should not result in a substantial temperature rise because this would lower the reaction rate in the prerefining zones.
  • prerefining is preferably effected with a slightly oxidizing gas, such as CO H O or air or mixtures thereof.
  • the refining agent may be selected from the group consisting of air, a mixture of oxygen and CO H 0, and a mixture of oxygen and H 0.
  • a mixture of solid and gaseous reactants may be employed.
  • the most economical operation will be obtained when a mixture of gaseous and solid oxidizers is used for refining because in this case the iron ore (solid oxidizer) is reduced to iron in a direct steelmaking process by the elements silicon, manganese, phosphorus, and carbon.
  • the refining process constitutes a combined smelting and refining process.
  • FIG. 1 is a flow sheet
  • FIG. 2 is a diagrammatic showing of a preferred method of atomizing the metal.
  • FIG. 1, 1 is a blast furnace, which can be operated with a minimum coke requirement (stahleisen).
  • the crude iron passes over a slag separator, which is shown as a forehearth 2, to the desulfurizing unit 3, in which the crude iron is to be desulfurized to a high degree because a special desulfurizing step is not provided for in the succeeding refining process.
  • a mixer 4 precedes the cascade refining plant according to the invention.
  • This mixer serves as a crude iron storage and equalizing container.
  • the mixer is not essential because the crude iron may be supplied directly from the blast furnace if the same supplies crude iron continuously.
  • the cascade refining process comprises the previously listed stages I to VI; the oxidizing and refining stages are carried out in the closed oxidizing chambers 5, 14 and 22 lined with refractory material.
  • Stage I is carried out in reaction chamber 5.
  • Gaseous refining agent is blown through the nozzle 10 onto the crude iron entering in a vertical jet and the crude iron is atomized.
  • CO H O steam, air from storage containers 6, 7, 8 and 8a or mixtures thereof may be used as refining agents, and iron ore from the storage container 7a may be added.
  • the refining agent is conducted through the conduit 9 to the nozzle 10. In the preceding mixing nozzle 10a the gaseous and solid refining agents are mixed.
  • the reaction chamber is heated to the desired temperature of about 1250 C. Electric heating is preferable to gas heating because the former will not produce waste gases which contaminate the reaction product and will not increase the volume of gas in the reaction space. It is sufficient if iron having low silicon and manganese contents is obtained in stage I.
  • the oxidation of silicon and manganese in stage I is about 70% so that about 0.1-0.3% silicon and manganese remain where steelmaking iron is used as a starting material.
  • a complete oxidation in stage I is not desired because the iron should be protected from oxidation in the following stages.
  • stage 1 carbon, phosphorus and sulfur are hardly changed and correspond approximately to the values they have in the crude iron.
  • conduit 13 the metal is conducted into the reaction chamber 14, which is at 1250 C., and in which stage II is carried out.
  • oxygen from container 7 and ore from container 7a are supplied through the mixing nozzle 18a and the conduit 16.
  • the metal flowing in through the conduit 13 is atomized by means of the nozzle 15.
  • lime dust is used, which is supplied through the mixing nozzle 18 in a mixture with the oxygen. The share of ore must be increased if the reaction temperature is too high when pure oxygen is used.
  • the P O -containing slag is separated from the iron as in the first chamber.
  • the iron flowing out of stage II is almost free of manganese, silicon, phosphorus and sulfur.
  • the high-carbon iron is heated from about 1300 C. to 1650 C. (stage III). Heating is effected by an electric or flame heating system. When discharged from the furnace, the iron is at steel melting temperature, which enables also the carbon oxidizing reaction.
  • Carbon is oxidized in chamber 22 (stage IV) of the refining cascade.
  • the metal enters through nozzle 23 and is atomized by the refining agent supplied through nozzle 24.
  • the oxidizing effect may be controlled by mixing O Fe O H O steam, CO and air. This control of the oxygen supply serves to prevent a combustion of iron.
  • the carbon reaction chamber 22 is preheated to 1650 C. to 1800 C.
  • the CO formed during the reaction is conducted through conduit 27 into the manifold 12. Any existing slag is separated from the iron outside chamber 22, as in connection with stages I and II.
  • the iron is caused to fiow through the several stages I to IV of the cascade as a result of the head. If this is prevented by the structural arrangement, i.e., when the required head is not available for all zones, the metal may be raised between zones with an elevator. This possibility is indicated in the diagrammatic showing of FIG. 1 after zone IV. Behind the carbon reaction stage, the iron flows into a pressure chamber 28, which serves to raise the iron to a level which corresponds to the structural arrangement. In this case the iron is raised with the aid of CO this may be effected with a mammoth pump.
  • Iron passes through conduit 29 and nozzle 30 into the reaction chamber 32, in which the deoxidizing stage V is carried out.
  • the deoxidation is carried out in accordance with the same principle as the oxidizing processes described, i.e., with the metal in atomized condition so that a maximum reaction surface is obtained and the residence time in the deoxidizing chamber corresponds to the residence time in the oxidizing chambers.
  • the oxygen content of the iron should be reduced and the resulting deoxidation product should be completed separated from the iron.
  • a complete separation can be effected mostly reliably when the deoxidation product is gaseous.
  • a gaseous deoxidation product will be obtained Where carbon is used as a deoxidizer.
  • This deoxidizer can be applied only in rare cases (only with high-carbon steels). In most cases, other deoxidizers must be used, such as magnesium, aluminium etc. These agents are blown in powdered form together with the atomizing gas.
  • the atomizing gas is a non-oxidizing gas, such as CO.
  • CO is removed through conduit 35 from the CO conduit 12 and is cooled in cooler 36 to purifying temperature, purified in the washer 37 and fed by the pump 38 through the conduit 34.
  • a mixing nozzle 39 the atomizing gas is mixed with the solid deoxidizer.
  • the metal is atomized with the aid of nozzles 30 and 31.
  • the deoxidizing stage is heated to 1650 C.
  • the steel and the deoxidation slag flow together out of chamber 32 and are separated outside.
  • the resulting waste gas is discharged through the pipe 33.
  • Alloying stage V1 is carried out in chamber 41, into which alloying elements are introduced in solid or liquid condition. Chambers 41 should be heatable for the production of high-alloy steels.
  • scrap cannot be melted in the various stages.
  • Scrap can be melted, however, with the aid of the CO from stages I and IV so that the process according to the invention is not inferior to other methods also in this respect.
  • the shaft furnace 42 is provided for melting the scrap.
  • the cascade refining process according to the invention is carried out in gastight chambers, there are no or only small gas losses. For this reason the waste gases which contain combustible components may be collected and used for heating purposes so that heat is available for melting the scrap.
  • the shaft furnace is a combined gas and solid fuel furnace.
  • the CO from stages I and IV is blown in unpurified condition into conduit 12.
  • the bottom nozzle 43 of the shaft furnace 42 consists of a burner, in which the unpurified CO is burned.
  • the coke layer in the shaft furnace reduces any Fe O -containing dust which may be blown in with the CO so that a separate cleaning of the gas is not required.
  • the process of the shaft furnace is not a pure melting process but lies between that of a blast furnace and that of a foundry shaft furnace.
  • the iron from the shaft furnace passes over the forehearth 43a and the soda desulfurizer 44 to the hot metal mixer 4 and from there into the cascade refining plant.
  • the waste gas from the cupola is either passed into the hot blast stove 45 or supplied to a different use.
  • FIG. 2 A preferred structure of an atomizing nozzle is diagrammatically shown in FIG. 2.
  • the atomizing nozzle has an outlet piece a for forming a dropping metal jet and blowing nozzles b which extend at right angles or at an oblique angle thereto and have an orifice member d.
  • the pressurized gaseous refining agent is blown in through the blowing nozzles.
  • c is the turbulence-producing edge.
  • the relative position of a and d influences the atomizing effect.
  • Example Crude iron was refined in a cascade refining plant according to the invention.
  • a prerefining reaction zone and a decarburizing reaction zone with an intervening heating-up zone were provided in separate chambers.
  • the prerefining chamber was held at a temperature of 1250 C. Air under a pressure of 8 kg./sq.cm. gauge was used as a refining agent in the prerefining zone.
  • the atomizing nozzle was 12 mm. in diameter.
  • the outlet member for forming the dropping crude iron jet was 14 mm. in diameter. Complete atomization was achieved under these conditions.
  • the decarburizing chamber was held at a temperature of 1550 C. Pure oxygen was used as a refining agent.
  • the atomizing conditions were the same as in the prerefining zone (nozzle diameter 12 mm., diameter of iron jet 14 mm., pressure 8 kg./sq.cm. gauge).
  • Second Oxidizing Stage (0 Sampling after O, Si, Mn, 0, Si, Mn, 0, Si, Mn, 0, Si, Mn,
  • a process of continuously converting molten crude iron containing more than 0.1% silicon and more than 0.3% manganese and also containing phosphorus, sulfur, and carbon into steel comprising the steps of placing the iron in a first zone, maintaining the iron in the first zone at a temperature of about 1250" C.
  • a process of continuously converting crude iron into steel comprising the steps of (a) heating said crude iron to bring it to a molten state,

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
US20476362 1961-06-26 1962-06-25 Process of continuously converting molten crude iron into steel Expired - Lifetime US3236637A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
AT491161A AT226754B (de) 1961-06-26 1961-06-26 Verfahren und Anlage zur kontinuierlichen Umwandlung von schmelzflüssigem Roheisen in Stahl durch Frischen mit einem gasförmigen Frischmittel

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US (1) US3236637A (xx)
AT (1) AT226754B (xx)
BE (1) BE619320A (xx)
DE (1) DE1433658A1 (xx)
GB (1) GB1003161A (xx)
LU (1) LU41904A1 (xx)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3650518A (en) * 1968-02-02 1972-03-21 Koppers Co Inc Spray steelmaking apparatus and method
US3839018A (en) * 1968-06-03 1974-10-01 British Iron Steel Research Production of low carbon ferroalloys

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US949474A (en) * 1906-05-21 1910-02-15 Globe Steel Filtration Process Company Process of refining iron.
US2662819A (en) * 1949-02-28 1953-12-15 Hofges Heinz Production of transformer and dynamo steels
US2668759A (en) * 1952-05-22 1954-02-09 Inland Steel Co Steelmaking process
US2733141A (en) * 1956-01-31 Pneumatic process for the refining of basic pig iron
GB785337A (en) * 1955-02-11 1957-10-23 Rochlingsche Eisen Und Stahlwe Method of and apparatus for the continuous production of steel
US2819160A (en) * 1955-06-02 1958-01-07 British Oxygen Co Ltd Process for reducing the metalloid content of iron

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2733141A (en) * 1956-01-31 Pneumatic process for the refining of basic pig iron
US949474A (en) * 1906-05-21 1910-02-15 Globe Steel Filtration Process Company Process of refining iron.
US2662819A (en) * 1949-02-28 1953-12-15 Hofges Heinz Production of transformer and dynamo steels
US2668759A (en) * 1952-05-22 1954-02-09 Inland Steel Co Steelmaking process
GB785337A (en) * 1955-02-11 1957-10-23 Rochlingsche Eisen Und Stahlwe Method of and apparatus for the continuous production of steel
US2819160A (en) * 1955-06-02 1958-01-07 British Oxygen Co Ltd Process for reducing the metalloid content of iron

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3650518A (en) * 1968-02-02 1972-03-21 Koppers Co Inc Spray steelmaking apparatus and method
US3839018A (en) * 1968-06-03 1974-10-01 British Iron Steel Research Production of low carbon ferroalloys

Also Published As

Publication number Publication date
AT226754B (de) 1963-04-10
DE1433658A1 (de) 1968-11-28
GB1003161A (en) 1965-09-02
LU41904A1 (xx) 1962-08-18
BE619320A (fr) 1962-10-15

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