US3661560A - Manganese control in basic steelmaking process - Google Patents

Manganese control in basic steelmaking process Download PDF

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US3661560A
US3661560A US878448A US3661560DA US3661560A US 3661560 A US3661560 A US 3661560A US 878448 A US878448 A US 878448A US 3661560D A US3661560D A US 3661560DA US 3661560 A US3661560 A US 3661560A
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stage
manganese
oxygen
refining
reversion
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Hugh Willmott Grenfell
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British Steel Corp
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British Steel Corp
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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
    • C21C5/28—Manufacture of steel in the converter
    • C21C5/30—Regulating or controlling the blowing
    • C21C5/32—Blowing from above

Definitions

  • Grenfell [54] MANGANESE CONTROL IN BASIC STEEILMAKING PROCESS [72] Inventor: Hugh Willmott Grenfell, Glamorgan,
  • the invention particularly provides for a method of controlling the manganese content of the melt at turn-down of a steel refining process by at least a two stage process in which the refining is carried out using a gas stream comprising the products of combustion of a fuel and uncombined oxygen by varying the proportions of combustion products to uncombined oxygen in a first stage in which the gas stream is relatively poor in uncombined oxygen and in a subsequent or second stage in which the gas stage is relatively rich in uncombined oxygen and varying the duration of the first stage so that with a relatively long first stage a low manganese reversion is obtained and by providing a relatively short first stage a high manganese reversion to the melt at turn-down is obtained.
  • the present invention relates to an oxygen fuel process for the refining of crude iron to steel.
  • the invention is concerned with the control of the manganese content in the melt at the tum-down" or end of such a process.
  • a process for controlling the manganese reversion of a ferrous metal charge during refining which process comprises subjecting the molten charge to a treatment with a stream of hot refining gases obtained by the combustion of a fuel in an excess of oxygen to provide a gas stream comprising the products of combustion and uncombined oxygen and varying the proportion of combustion products and uncombined oxygen in the refining gas stream in at least two stages to provide a first stage in which the gas stream is relatively poor in uncombined oxygen and a subsequent stage in which the gas stream is relatively rich in uncombined oxygen and varying the duration of said first stage so that by providing a relatively short first stage a high manganese reversion to the melt at tum-down is obtained and by providing a relatively long first stage a low manganese reversion to the melt at tum-down is obtained.
  • the present invention also provides a process for refining a ferrous metal charge to steel in a converter vessel by employing hot refining gases directed downwardly to the charge at high velocity from a nozzle fed by oxygen and fuel to provide a refining gas stream comprising combustion products and uncombined oxygen and varying the proportion of combustion products and uncombined oxygen in the refining gas stream in at least two stages which stages comprise a first slag forming manganese control stage in which the gas stream is relatively rich in combustion products and relatively poor in uncombined oxygen and a second or subsequent decarburizing stage in which the gas stream is relatively poor in combustion products but relatively rich in uncombined oxygen and varying the duration of said first stage so that by providing a relatively short first stage, a high manganese reversion to the melt at turn-down is obtained and by providing a relatively long first stage a low manganese reversion to the melt at tum-down is obtained.
  • a third stage constituting a regulating and terminal refining stage may be provided in which the gas stream is relatively rich in combustion products and relatively poor in uncombined oxygen.
  • Typical fuels which may be employed are hydrocarbon fuels and in particular liquid hydrocarbons. It is preferred that the fuel is fuel oil, residual fuel oils being suitable.
  • the liquid fuel and oxygen may be fed to a burnertype lance having a nozzle which provides a flame surrounded by an oxygen rich envelope.
  • the surrounding envelope substantially prevents uncombusted fuel from contacting the melt or reactive portions of the slag thereby preventing the introduction of fuel contained impurities into the charge.
  • the oil flow can remain constant and the oxygen flow can be varied.
  • FIG. 1 illustrates the variation of the manganese content of a melt during the course of typical blows
  • FIG. 2 is a sectional view of an open top converter type vessel having a lance suitable for use in the process of the present invention
  • FIG. 3 is a section through a preferred lance for use in the practice of the present invention.
  • an open top basic refractory lined converter vessel is charged with molten iron and solid scrap.
  • a burner-type lance and mounting assembly is disposed with respect to the converter so that the lance is capable of being moved vertically into and out of the open top of the vessel as shown in FIG. 2.
  • the lance has a delivery nozzle at one end through which fluid may pass.
  • the nozzle preferably has a plurality of discharge orifices positioned whereby fluids passing therethrough are directed generally downwardly and outwardly.
  • Stage 1 the pattern to be taken with the three stages of the process is established.
  • the three refining stages will hereinafter be referred to for convenience as Stage 1, Stage II and Stage III.
  • the lance is purged with steam and is lowered to its initial operating position.
  • the oxygen flow is started and as oxygen issues from the end of the lance, the steam purge is terminated and the fuel oil supply started. Ignition of the fuel oil is instantaneous and the melt ignition occurs almost immediately afterwards.
  • Slag forming materials may be part of the initial charge but usually are added to the charge 1 or 2 minutes after ignition.
  • the slag-forming materials may be, e.g., lime, limestone, dolomitic lime or mixtures thereof.
  • the first slag of the process is essentially a slag-forming and preliminary refining stage in whichthe control of the manganese reversion in the melt is effected.
  • streams of high purity oxygen and liquid carbonaceous fuel are flowed to the burner lance in proportions to produce a stream of hot gas relatively rich in combustion products and relatively poor in uncombined oxygen.
  • the manganese content of the melt follows the general form of the curves shown in FIG. 1 of the accompanying drawings. It will be noted that during the blow the manganese content of the melt is first reduced to a minimum and manganese is abstracted from the melt and enters the slag. As the flow proceeds, a manganese reversion occurs whereby manganese leaves the slag and re-enters the melt. This reversion rises to a peak towards the end of the blow and then begins to reduce as the manganese is again abstracted from the melt by the slag.
  • the slag forms and becomes hot relative to the melt and manganese is abstracted from the melt and enters the slag quickly so that the minimum manganese content in the melt is reached as quickly as possible.
  • manganese re-enters the melt from the slag and a proportion of manganese in the melt increases to a peak after about two-thirds of the blowing time and thereafter reduces as the temperature of the melt increases towards the turn-down temperature so that at the end of the blow the amount of manganese within the melt is quite low.
  • the slag With a short first stage, the slag is comparatively cool as formed, and the manganese is retained in the melt very much longer so that the minimum quantity of manganese within the bath is reached at a much later time in the blow than in the case where a relatively long first stage blow is employed. Thereafter, the manganese reversion occurs with the manganese re-entering the bath from the slag so that the manganese content of the bath due to reversion reaches a peak just before termination of the blow so that very little manganese is abstracted from the bath by the slag prior to turn-down and teeming of the melt. in consequence, the proportion of manganese within the bath at this stage is very much higher.
  • relatively short first stage a first stage blow having a duration sufiicient to form a cool slag so as to retard the abstraction of manganese from the melt in the early part of the blow thereby delaying the reversion peak until towards the end of the blow thereby resulting in a melt having, at tum-down, a comparatively high manganese content when considered in comparison with a normal blow using pure oxygen.
  • a typical period for a short first stage is 4 to 6 minutes.
  • relatively long first stage a stage having a duration sufficient to form a hot slag to result in the rapid abstraction of manganese from the melt so that the minimum manganese content is reached early in the refining process thereby permitting the reversion to occur as the temperature of the melt rises so that the reversion peak is attained substantially before the end of the blow thereby resulting in a reduced manganese content in the melt at the turndown;
  • a typical period for a long first stage is 8 to 10 minutes.
  • Stage 1 oxygen is flowed to the lance in a quantity in excess of that required forcomplete combustion of the fuel, thereby providing uncombined oxygen in the refining gases employed in that stage.
  • the excess oxygen flowed to the lance in Stage I while small when compared to the excess employed in Stage II, ensures complete combustion of the fuel, minimizes the danger of introduction of fuel-contained impurities into the charge, and provides uncombined oxygen for preliminary refining.
  • the excess is not so great as to initiate a vigorous early carbon boil as in the L.D. process. Rather, the hot refining gases of the process are oxygen-starved relative to L.D.
  • refining gas undiluted, pure oxygen
  • the hot gases typically 4,000 5,000 P. in this stage, aid in fiuxing the slag making materials to provide a reactive fluid slag within the first few minutes of Stage I.
  • a reactive basic slag is formed in the process in advance of excessive acid silica formation, thereby reducing silica attack of the converters basic refractory lining.
  • the foregoing is in contrast to the autogeneous L.D. process wherein slag development is dependent upon heat produced by exothermic refining reactions of cold oxygen with impurities in the crude iron charged to the converter.
  • the excess may be within the range 25 to 300 percent in excess of the quantity of oxygen theoretically required for complete combustion of the fuel. It is preferred that an oxygen excess of 50 to 150 percent is employed and typically an oxygen excess of 60 to 70 percent is employed.
  • An excess of uncombined oxygen in Stage I greater than about 300 percent results in relatively poor slag-making and bath-conditioning since a cooler flame is obtained in the higher excess range and also since higher excesses cause excessive refining reactions, especially silicon reactions, at a point too early in the process.
  • An excess of less than 25 percent results in unnecessary lengthening of refining time, resulting in poor heat transfer efficiency of the oilburnt.
  • the low excess can cause a high percentage of iron oxide to remain in the slag, thereby decreasing the yield due to a soft" blow.
  • the preferred excesses may vary in the case that there is employed in the process a fuel of substantially different heating value and/or an oxygen supply rate substantially different from those as discussed in the examples.
  • the hot gases issuing from the flame at the lower end of the lance, typically at a temperature of 4,000 to 5,000 F., in Stage I are usually themselves sufficient to flux the slag making material without the use of conventional fiuxing agents.
  • Conventional fiuxing agents, such as fiuorspar or millscale may however be added to further accelerate formation of the fluid slag and to assist in the early phosphorus removal in the process as explained hereafter.
  • Stage I of the process the FeO content of the slag is still quite high since the bath is relatively cool and this condition lends itself to the early removal of phosphorus andsulphur from the bath.
  • Some car bon and silicon is also refined in Stage 1 although major car bon refining is delayed until a later stage in the process.
  • Stage II of the process is the stage in which the major decarburisation of the melt takes place.
  • the refining occurs using a high excess of uncombined oxygen over that required to effect complete combustion of the fuel and typically the excess is within the range of 1,000 to 1,300 percent.
  • the fuel is a liquid carbonaceous fuel such as fuel oil
  • the great excess of oxygen in Stage ll initiates a vigorous carbon boil in the melt and the major portion of the carbon refining in the process occurs during this stage.
  • the hot refining gas stream issuing from the burner type lance atthis stage of the process comprises to percent by weight of hot uncombined oxygen directed by means of discharge orifices or nozzles of the lance towards the charge at high velocity.
  • the hot gases typically at a temperature of the order of 2,500 to 3 ,000 F. issue from the nozzles in the lance and assist in maintaining the slag fluid by preventing slag cooling or chilling, which can occur in the L.D. process where cold oxygen alone at a temperature of 1 50 F. is blown onto the charge.
  • the duration of Stage II is generally within the range 8 to 15 minutes, more or less, depending for example upon the desired carbon and temperature end points. Also, the Stage II duration is dependent on the proportion of scrap included in the charge. In general the higher the proportion of scrap in the charge, the shorter the duration of Stage ll.
  • the stage III is a terminal refining and regulating stage which serves to control as far as possible the end point temperature and the carbon content. This control is effected by increasing the proportion of'combustion products in the refining gas stream so that the excess of uncombined oxygen over that required to effect complete combustion of the fuel is generally 25 to 200 percent.
  • the duration of Stage III is controlled principally by the need to ensure that the required total amount of fuel is employed during the process. In a typical operation, the desired turn-down temperature is of the order of l,600 C. This temperature may be controlled by the amount of scrap incorporated in the charge and by the total amount of oil needed to be supplied to the refining vessel during the blow to effect heating of the charge.
  • the duration of the final stage when employed is typically 5 to 16 minutes.
  • the total refining time of the process of the present invention is generally 20 to 30 minutes, but this can be varied as necessary or desirable and depends to a degree on available oxygen capacity of converter vessel, fuel characteristic and lance characteristics. Generally, the greater the oxygen availability, the shorter will be the overall refining time.
  • streams of hydrocarbon fuel preferably a liquid carbonaceous fuel, and substantially pure oxygen are, in proportions defined above, flowed to the burner-type lance and contacted therein to form a fuel-oxygen stream.
  • the fuel-oxygen stream is ejected from the lance, preferably at supersonic velocity to eliminate or reduce turbulance in the stream. Turbulence in the streams is generally to be avoided since a non-turbulant stream is important for effectively delivering the hot refining gases to the charge being refined.
  • the radiant heat from the vessel walls and charge is sufficient to cause ignition to produce a flame (of. FIG. 2) extending from the discharge orifices of the lance.
  • the hot refining gases emitting from the flame comprise combustion products and uncombined oxygen and are directed generally downwardly and outwardly from the lance toward the charge at a high velocity.
  • the lance comprises an elongate body member 11 which is provided with a combined delivery and burner nozzle 12 at the lower end thereof.
  • the interior of the body member 11 of the lance is built up with a number of annular passageways and conduits by which oxygen and liquid fuel are supplied to a plurality of discharge orifices 13 formed in the combined delivery and burner nozzle 12.
  • the number of nozzles is determined to some extent by the size of the refining vessel.
  • a fuel oil supply conduit comprising a pipe 14 is preferably located centrally of the body member 11 of the lance 10.
  • a plurality of pipes 16 are welded at 15 to the lower end of the pipe 14 and extend downwardly therefrom the pipes 16 corresponding in number to the number of discharge orifices 13, and the plurality of oxygen supply pipes 21 disposed at an angle to the longitudinal axis of the lance and incorporate means such as venturi 33 for accelerating the oxygen.
  • the fuel supply conduit is preferably provided with an annular jacket disposed between the oil conduit and the oxygen supply conduit to insulate preheated fuel in the fuel supply conduit. This is necessary since when using heavy grades of fuel oil, the low temperature of the oxygen passing down the oxygen supply conduit 18 chills the oil and may prevent oil flow.
  • Fuel supply conduit 14 is provided at its outlet end with a plurality of fuel supply pipes 23 extending therefrom and each having its end portion secured in the corresponding oxygen supply pipe 21 so that oxygen flowing through said supply pipes to the discharge orifices will flow in an annulus around the end of the corresponding fuel supply pipes whereby fuel will be entrained in the oxygen supplies when discharged from the discharge orifices.
  • the lance nozzle arrangement provides for the entrainment of fuel in a substantially pure stream of oxygen and when ejected from the lance nozzle will ignite to provide a short flame surrounded by a sheath-like envelope rich in uncombined oxygen. This arrangement ensures that during the refining process the products of combustion but not the flame itself is in contact with the melt and with the slag thereby preventing contamination of the melt with fuel-contained impurities such as sulfur. The avoidance of charge-contamination with such impurities is generally important in the process of the invention.
  • EXAMPLE 1 This is an example of pure oxygen blow and is not in accordance with the invention.
  • a charge comprising lbs. of scrap, 1,000 lbs. of hot metal and 40 lbs. of lime were added to a top blown converter.
  • a single orifice lance having a nozzle construction as described above was introduced into the mouth of the vessel and pure oxygen was supplied to the lance for a period of 24 minutes at a rate of 3,200 cubic ft. of oxygen.
  • the hot metal temperature at the start of the blow was l,350 C. and the finishing temperature was l,600 C.
  • the quantity of FeO in the slag was 20.5 percent.
  • Table 1 illustrates the comparison of hot metal and finishing steel analyses.
  • This example is an example in accordance with the present invention to obtain a low manganese figure in the finishing steel analysis.
  • An open top converter vessel was charged with 200 lbs. of scrap, 1,000 lbs. of hot metal and 40 lbs. of lime.
  • the hot metal temperature was l,350 C.
  • the charge was blown with fuel oil and oxygen using a single orifice lance as described above.
  • the fuel oil was a gas oil and the blowing practice was a first stage of 10 minutes at a fuel oil flow of 12 gallons per hour and an oxygen flow of 5,600 cubic ft. per hour, a second stage of 8 minutes at a fuel oil flow of 2 gallons per hour and an oxygen flow of 5,600 cubic ft. per hour and a final stage of 6 minutes at a fuel oil flow of 12 gallons per hour and an oxygen flow of 5,600 cubic ft. per hour.
  • the total blowing time was, therefore, 24 minutes.
  • the finishing temperature was l,610 C. and the quantity of FeO in the slag was 23 percent.
  • Table 1 sets out a comparison of the hot'metal analysis and finishing steel analyses.
  • EXAMPLE 3 This example is a repeat of Example 2 to illustrate the practice to obtain a high manganese yield in the finishing steel analysis.
  • Example 2 The converter used in Example 2 was charged with 200 lbs. of scrap, 1,000 lbs. of hot metal and 40 lbs. of lime. The hot metal temperature was 1,370 C. The charge was blown for a period of 24 minutes using fuel oil and oxygen by the process comprising a first stage of 5 minutes at a fuel oil flow of 12 gallons per hour and an oxygen flow of 5,600 cubic ft. per hour, a
  • FIG. 1 illustrates the manganese content during the course of the blow.
  • Curve B is the variation of the manganese content of the melt with time during the course of the blow using pure oxygen as in Example 1 above.
  • Curve A illustrates the variation of the manganese with time during the blow in which a long first stage is employed as in Example 2 and
  • Curve C is a similar curve in which a short first stage is employed as in Example 3. It will be noted that the final peak of Curve C is very much later than that of either of Curves A and B and that as a result the proportion of manganese in the melt at the termination of the blow is very much greater. It will be appreciated that by selecting a suitable duration for the first stage, the proportion of manganese within the melt at turn-down can be controlled quite accurately.

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  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Carbon Steel Or Casting Steel Manufacturing (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
US878448A 1969-03-21 1969-11-20 Manganese control in basic steelmaking process Expired - Lifetime US3661560A (en)

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GB4990769A GB1244939A (en) 1969-03-21 1969-03-21 Manganese control in oxygen fuel refining processes
GB1497769 1969-03-21

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JP (1) JPS4931171B1 (xx)
BE (1) BE742108A (xx)
CA (1) CA924907A (xx)
CH (1) CH549096A (xx)
DE (1) DE1959701A1 (xx)
ES (1) ES374390A1 (xx)
FR (1) FR2035136B1 (xx)
LU (1) LU59881A1 (xx)
NL (1) NL6917948A (xx)
NO (1) NO128072B (xx)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4190238A (en) * 1978-05-11 1980-02-26 Stahlwerke Peine-Salzgitter Ag Lance head for a fining lance
US4293123A (en) * 1978-12-22 1981-10-06 Klockner-Humboldt-Deutz Ag Blow lance
US4366953A (en) * 1980-10-13 1983-01-04 Arbed S.A. Oxygen lance
US4402739A (en) * 1982-07-13 1983-09-06 Kawasaki Steel Corporation Method of operation of a top-and-bottom blown converter
US20130195712A1 (en) * 2010-01-28 2013-08-01 Kimura Chuzosho Co., Ltd. Method for removing impurities in molten cast iron, and cast iron raw material

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS58189084A (ja) * 1983-04-04 1983-11-04 本田　肇 水流式洗浄機

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB838503A (en) * 1955-11-22 1960-06-22 Hoerder Huettenunion Ag Process for refining steel
CA624886A (en) * 1961-08-01 L. Spencer Philip Refining treatment for molten ferrous metal
US3112194A (en) * 1960-10-19 1963-11-26 Union Carbide Corp Molten bath treating method and apparatus
GB985586A (en) * 1962-07-25 1965-03-10 British Oxygen Co Ltd Improvements in or relating to the treatment of molten steel
US3232748A (en) * 1959-05-19 1966-02-01 Bot Brassert Oxygen Technik Ag Process for the production of steel
US3234011A (en) * 1962-04-07 1966-02-08 Bot Brassert Oxygen Technik Ag Process for the production of steel
FR1453442A (fr) * 1965-08-10 1966-06-03 Air Liquide Perfectionnements à des procédés d'affinage de la fonte
FR1511820A (fr) * 1966-02-16 1968-02-02 Steel Co Of Wales Ltd Perfectionnements aux procédés pour l'affinage de métaux

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA624886A (en) * 1961-08-01 L. Spencer Philip Refining treatment for molten ferrous metal
GB838503A (en) * 1955-11-22 1960-06-22 Hoerder Huettenunion Ag Process for refining steel
US3232748A (en) * 1959-05-19 1966-02-01 Bot Brassert Oxygen Technik Ag Process for the production of steel
US3112194A (en) * 1960-10-19 1963-11-26 Union Carbide Corp Molten bath treating method and apparatus
US3234011A (en) * 1962-04-07 1966-02-08 Bot Brassert Oxygen Technik Ag Process for the production of steel
GB985586A (en) * 1962-07-25 1965-03-10 British Oxygen Co Ltd Improvements in or relating to the treatment of molten steel
FR1453442A (fr) * 1965-08-10 1966-06-03 Air Liquide Perfectionnements à des procédés d'affinage de la fonte
FR1511820A (fr) * 1966-02-16 1968-02-02 Steel Co Of Wales Ltd Perfectionnements aux procédés pour l'affinage de métaux

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4190238A (en) * 1978-05-11 1980-02-26 Stahlwerke Peine-Salzgitter Ag Lance head for a fining lance
US4293123A (en) * 1978-12-22 1981-10-06 Klockner-Humboldt-Deutz Ag Blow lance
US4366953A (en) * 1980-10-13 1983-01-04 Arbed S.A. Oxygen lance
US4402739A (en) * 1982-07-13 1983-09-06 Kawasaki Steel Corporation Method of operation of a top-and-bottom blown converter
US20130195712A1 (en) * 2010-01-28 2013-08-01 Kimura Chuzosho Co., Ltd. Method for removing impurities in molten cast iron, and cast iron raw material

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BE742108A (xx) 1970-05-04
ES374390A1 (es) 1972-03-01
LU59881A1 (xx) 1970-01-26
FR2035136B1 (xx) 1974-03-01
CH549096A (fr) 1974-05-15
CA924907A (en) 1973-04-24
FR2035136A1 (xx) 1970-12-18
NO128072B (xx) 1973-09-24
NL6917948A (xx) 1970-09-23
JPS4931171B1 (xx) 1974-08-20
DE1959701A1 (de) 1970-10-08

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