US3528799A - Process for continuously refining cast iron into steel - Google Patents

Process for continuously refining cast iron into steel Download PDF

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Publication number
US3528799A
US3528799A US3528799DA US3528799A US 3528799 A US3528799 A US 3528799A US 3528799D A US3528799D A US 3528799DA US 3528799 A US3528799 A US 3528799A
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US
United States
Prior art keywords
slag
cast iron
steel
reactor
oxygen
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Expired - Lifetime
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English (en)
Inventor
Aldo Ramacciotti
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Centro Sperimentale Metallurgico SpA
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Centro Sperimentale Metallurgico SpA
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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
    • C21C1/00—Refining of pig-iron; Cast iron
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K3/00—Materials not provided for elsewhere
    • C09K3/14—Anti-slip materials; Abrasives
    • C09K3/1436—Composite particles, e.g. coated particles
    • 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
    • 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
    • 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
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S75/00—Specialized metallurgical processes, compositions for use therein, consolidated metal powder compositions, and loose metal particulate mixtures
    • Y10S75/957—Continuous refining of molten iron

Definitions

  • the slag and gaseous material rise as a thick foam in the vertical shaft in a flow which is countercurrent to the flow of the descending metal.
  • Chemical reactions among the metal, the flux and the gaseous material, which result in the refinement of the cast iron take place during the countercurrent flow of materials; the flux and gaseous materials discharge from the upper part of the reactor and the refined cast iron decants from the emulsion and is withdrawn from the tapping hole provided in the reactor.
  • Non-continuous processes have many disadvantages compared to a continuous process.
  • every transformation from the raw materials to the finished product is in permanent operation, and the material flows constantly through the reactor, coming out thereof in a continuous manner with the characteristics required of the finished product.
  • the advantages generally attributed to continuous processes in comparison with similar non-continuous processes are: a greater uniformity of the product, possibility of using more refined adjustment and control techniques, smaller size of the reactor per unit of product, and finally, the possibility of direct connection of. the process under consideration with processes upstream and downstream which have already been made continuous.
  • the blast furnace as an upstream process can be made continuous without excessive difliculties; while downstream, the known continuous leakage process can utilize directly a permanent flow of liquid steel coming from a continuous refining process.
  • the continuous process for transforming cast iron into steel, according to the invention is carried out by pouring liquid metal, i.e. liquid cast iron, from above onto slag in a reaction zone, so that the liquid metal descends and is scattered through the slag in the form of small drops.
  • An oxygen stream is introduced into the slag-metal emulsion which agitates the entire mixture vigorously and also enters into reaction therewith.
  • the mixture of slag and gaseous material rises in the form of a thick foam moving countercurrent to the descending liquid metal in the reaction zone.
  • the refining of cast iron according to this invention is characterized by the counter-current flow of the liquid metal and the thick foam mixture of slag and gaseous material; during the countercurrent flow, the chemical reactions among the slag, gaseous materials and metal take place.
  • the refined steel decants from the emulsion, and the mixture of slag and gaseous material discharges from the top of the reaction zone.
  • the oxygen stream is introduced into the slag-metal mixture by means of substantially horizontal jets, i.e. at substantially right angles to the countercurrent flows of liquid metal and of slag.
  • the device of the present invention for the execution of the method is consituted by a vertical shaft covered inside with refractory material, and provided with a tapping hole for the refined steel.
  • a feed conduit for the cast iron to be refined In the upper part of the device there is provided a feed conduit for the cast iron to be refined, an overflow conduit for the slag, discharge means for the gases and/ or vapors developed during the refining reaction and at least a load port for introduction of additional compounds which may, when desired take part in the refining process.
  • Nozzles for blowing oxygen into the mass of the slag-metal emulsion, having substantially horizontal axes are positioned in the shaft walls and end inside it above the level of the pool of refined steel which collects once the operation has started.
  • FIG. 1 is a vertical section of a reactor of the present invention.
  • FIG. 2 is a vertical axial section of another reactor of the present invention and FIG. 3 is a view of the reactor of FIG. 2 from above.
  • FIG. 4 illustrates diagrammatically a reactor of this invention provided with regulating means.
  • the reactor used to carry out the transformation of cast iron into steel according to this invention may include checking or regulating means which, as a function of the shaft weight and the material contained therein, adjust the inflow into the shaft of the liquid cast iron, the oxygen and the other elements which take part in the refining reaction, so as to maintain the level of the refined steel inside the shaft substantially constant.
  • the refractory coating inside the shaft extends only to the bottom and the lower part of the walls of the shaft; the refractory coating extends upwards, at least over the level of the refined steel; and the remaining innner walls of shaft of plate, are cooled by means of a water veil or by means of a water circulation jacket.
  • FIG. 1 a shaft reactor 1, of cylindric form is coated in side with refractory material based on magnesia or dolomite, and this reactor substantially constitutes the whole equipment.
  • a bath 2 of refined steel is collected on the bottom of the shaft 1; the spout 3 at the bottom of shaft 1 acts as a tapping hole for the continuous withdrawal of the steel casting.
  • a conduit 4, at the top of shaft 1 is provided for feeding the smelt cast iron which is poured from the skip 5 which contains the liquid cast iron coming from the blast furnace.
  • Nozzles, 6, for blowing 0 into the mixture contained in the shaft are provided in the walls of shaft 1.
  • An opening 7 in the upper part of shaft 1 allows for the insertion of additional materials such as scraps, ferrous minerals, etc.
  • An outflow conduit 8 for the slag is also provided in the upper section of shaft 1.
  • a hood 9 is placed over the upper end of shaft 1 for collecting and conveying the gases developed inside the shaft.
  • FIGS. 2 and 3 illustrate a reactor of this invention which is provided with water cooling means and which is partially lined with refractory material.
  • the reactor is formed by a plate cylinder 11, the lower part of which is lined by a very thick coat of refractory material 12.
  • a conduit 14 feeds cooling Water to an annular collector 15 which surrounds the upper edge of the reactor.
  • Nozzles 16 which extend from the annular collector 15 provide a continuous coat of cooling water 17 which flows on to the external face of the cylinder 11, thus effecting cooling of the reactor.
  • the slag contained in the internal face of the cylinder 11 solidifies forming a coat 18 which behaves as an insulating layer and protects the plate of cylinder 11.
  • FIG. 4 illustrates a continuous automatic reactor of this invention wherein the level of the liquid steel at the bottom of the reactor is maintained automatically at a predetermined level by automatic adjustment of the rate of inflow of liquid steel, oxygen and possible of the materials such as lime and minerals which are used in the refining process, and/ or other fuel.
  • the reactor 1 rests on weighing cell 20 which Weighs the reactor and its contents and transmits this information through line 23 to the weighing cell 22 on which the ship 5 and its contents rest and which regulates the flow of liquid cast iron therefrom through line 24 depending on the information reviewed from the weighing cell 20.
  • Weighing cell 20 also transmits information through lines 25, to the valves 6a of nozzles 6 to control the flow of oxygen and any other material blown through the nozzles into the reactor.
  • the process of the invention takes place in the central part 10 of the reactor 1, shown in any of the figures in the following manner
  • steel bath 2 is collected at the bottom of the reactor.
  • the collected steel bath 2 has the characteristics required of the finished product and discharges continuously through the casting hole, of the spout 3, into a collecting container or it is sent directly to the continuous leakage equipment for the production of slabs or billets.
  • the cast iron to be refined is introduced from a suitable overstanding container 5.
  • the whole central part 10 of the reactor is occupied by a foamy slag which is maintained in agitation by a series of jets of gaseous oxygen, pure in a high degree.
  • the jets of oxygen are blown through water-cooled side piping 6.
  • the oxygen reacts with the slag and the gas maintained in the vesicular state in the foam, and, finally, with the cast iron drops obtained by the crushed blast coming from the feed conduit 4.
  • the cast iron drops react also with the slag so that, when collected in the bath 2, they are wholly refined and transformed into steel with the desired characteristics.
  • lime powders, minerals etc. may be also blown into the reactor, in order to reinstate or modify the slag composition; gaseous, liquid or solids fuels may also be introduced therein.
  • Other additions, such as steel scraps, ferrous minerals, lime, limestone, fiuidizing materials may be effected continuously or not, through the upper opening 7 of the reactor.
  • the slag in excess is discharged automatically through the outflow conduit 8 into a suitable container.
  • the gases originated from the reactions and coming from the foamy slag are conveyed by means of an overstanding hood 9, cooled and purified by the usual means and discharged into the atmosphere or utilized as combustible gases.
  • the weight P of the reactor is given by:
  • the heights lz of the steel column and hslag of the slag column are bound from the following ratio:
  • the delivery of the cast iron introduced is obtained by deriving, with respect to the time, the weight of the container.
  • the process is started in the following way: after preheating the reactor at a temperature of 900-1000 C. by means of auxiliary burners not shown in the figure, but usually employed in pre-heating of steel works, a suitable quantity of slag casting at a low temperature is introduced on the reactor bottom, said slag being preferably formed by calcium ferrite added to 3-4% of fluorine.
  • the tapping hole must be closed with a combustible cap or refractory mass easily removable mechanically or by use of oxygen; then the liquid cast iron is poured in, which, in this first phase, is preferably at high temperature.
  • the liquid cast iron is introduced into the reaction vessel at a temperature of about 1250 to 1450 C.
  • reaction 8 The slag, in contact with the cast iron, smelts and begins to swell owing to the reactions of carbon oxidation (reaction 8).
  • reaction 8 When the slag level reaches the oxygen blowing nozzles, the oxygen blowing is started together with the introduction of liquid cast iron.
  • the tapping hole When the metal on the reactor bottom has reached the established level, defined as indicated above, which for safety reasons must be a little under the first set of nozzles, the tapping hole is opened and the metal is permitted to flow out. From this moment on, an automatic or manual system of regulation maintains the metal on the reactor bottom of a constant level, by reducing or increasing the cast iron feeding.
  • Temperature regulation of the reactor is obtained by introducing more or less iron scraps from above, more or less mineral from above or through the piping in the sides or by modifying the amount of the fuel which may be charged through the piping if desired.
  • the amounts of oxygen, lime, iron, ore and steel scrap used in the present process, per ton of cast iron treated are in the following ranges; 50410 Nm. of oxygen, 50-100 kg. of lime, 0-100 kg. of iron ore and 200 to 400 kg. of steel scrap.
  • the slag discharge occurs spontaneously through the conduit 8 in the upper section of the reactor but it is also possible to activate the removal of the slag by blowing suitable lime through the pipings or by adding tensioactive additives from above.
  • the blast of liquid steel may be deviated by means of an Y conduit or other known means into an empty ladle which is provided for the purpose. Then the discharge is completed, the feeder of the liquid cast iron is replaced by a full one, by similar means. In such a way the process may continue indefinitely, and it is necessary to stop the operation only for the periodic restoration of the refractory coating.
  • the refractory coating in this zone may also be completely removed by simply introducing water veil cooling outside the clamping sheet.
  • a coating of solidified slag will quickly and automatically form on the inner surface of the sheet, with excellent characteristics of thermal non-conducting material, as a consequence of its high porosity.
  • the refractory coating of course, must be maintained in the lower zone occupied by the steel.
  • the process described has all the advantages, previously pointed out, of continuous processes, particularly, decreased size of the apparatus with equal capacity, simpler equipment for the smoke treatment, greater regularity in the development of said smokes, possibility of controlling the process in phase, etc.
  • EXAMPLE 1 A cylindrical reactor of the type described with reference to FIGS. 2 and 3 is used, having the following dimensions:
  • a process for continuously transforming iron into steel which comprises pouring liquid cast iron over slag in a reaction Zone so that said liquid cast iron descends through said slag in the form of small drops, and introducing an oxygen stream into said slag which agitates the mixture of said slag and iron whereby the slag and gaseous material rise in the form of a thick foam moving countercurrent to the flow of said liquid iron, and the chemical reactions among said slag, said oxygen and said cast iron which transform said cast iron into steel take place in said reaction zone between the materials in countercurrent flow, and whereby the slag and gaseous material discharge near the top of the reaction zone and the thus-refined steel decants from the mixture.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Metallurgy (AREA)
  • Manufacturing & Machinery (AREA)
  • Composite Materials (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)
US3528799D 1967-03-18 1969-03-19 Process for continuously refining cast iron into steel Expired - Lifetime US3528799A (en)

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IT789191 1967-03-18

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US (1) US3528799A (enrdf_load_stackoverflow)
DE (1) DE1608309B2 (enrdf_load_stackoverflow)
GB (1) GB1187942A (enrdf_load_stackoverflow)
LU (1) LU55578A1 (enrdf_load_stackoverflow)
NL (1) NL6803844A (enrdf_load_stackoverflow)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4174965A (en) * 1977-06-02 1979-11-20 Swiss Aluminium Ltd. Process for the production of metal alloys
US4203580A (en) * 1977-06-02 1980-05-20 Swiss Aluminium Ltd. Static mixer for the production of metal alloys
US4205980A (en) * 1977-04-27 1980-06-03 Stora Kopparbergs Bergslags Aktiebolag Process for removing sulphur from crude iron
US4310352A (en) * 1979-06-20 1982-01-12 Centro Ricerche Fiat S.P.A. Process for the preparation of a mixture comprising a solid phase and a liquid phase of a metal alloy, and device for its performance
US4667939A (en) * 1986-03-26 1987-05-26 Foseco International Limited Purifying steel
US4725310A (en) * 1986-03-26 1988-02-16 Foseco International Limited Method of purifying steel

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ATE193562T1 (de) * 1993-12-30 2000-06-15 Aktsionernoe Obschestvo Otkryt Verfahren und vorrichtung zur kontinuierlichen metallraffination

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2572489A (en) * 1949-02-01 1951-10-23 Jordan James Fernando Refining tower
US2819160A (en) * 1955-06-02 1958-01-07 British Oxygen Co Ltd Process for reducing the metalloid content of iron
US2969282A (en) * 1959-05-06 1961-01-24 British Oxygen Co Ltd Treatment of ferrous metal
US3356490A (en) * 1964-05-04 1967-12-05 Centre Nat Rech Metall Refining pig iron

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2572489A (en) * 1949-02-01 1951-10-23 Jordan James Fernando Refining tower
US2819160A (en) * 1955-06-02 1958-01-07 British Oxygen Co Ltd Process for reducing the metalloid content of iron
US2969282A (en) * 1959-05-06 1961-01-24 British Oxygen Co Ltd Treatment of ferrous metal
US3356490A (en) * 1964-05-04 1967-12-05 Centre Nat Rech Metall Refining pig iron

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4205980A (en) * 1977-04-27 1980-06-03 Stora Kopparbergs Bergslags Aktiebolag Process for removing sulphur from crude iron
US4174965A (en) * 1977-06-02 1979-11-20 Swiss Aluminium Ltd. Process for the production of metal alloys
US4203580A (en) * 1977-06-02 1980-05-20 Swiss Aluminium Ltd. Static mixer for the production of metal alloys
US4310352A (en) * 1979-06-20 1982-01-12 Centro Ricerche Fiat S.P.A. Process for the preparation of a mixture comprising a solid phase and a liquid phase of a metal alloy, and device for its performance
US4667939A (en) * 1986-03-26 1987-05-26 Foseco International Limited Purifying steel
US4725310A (en) * 1986-03-26 1988-02-16 Foseco International Limited Method of purifying steel

Also Published As

Publication number Publication date
DE1608309A1 (de) 1971-01-07
NL6803844A (enrdf_load_stackoverflow) 1968-09-19
GB1187942A (en) 1970-04-15
LU55578A1 (enrdf_load_stackoverflow) 1968-05-06
DE1608309B2 (de) 1973-06-14

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