US3807988A - Refining hematite pig iron in a converter - Google Patents

Refining hematite pig iron in a converter Download PDF

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Publication number
US3807988A
US3807988A US00224746A US22474672A US3807988A US 3807988 A US3807988 A US 3807988A US 00224746 A US00224746 A US 00224746A US 22474672 A US22474672 A US 22474672A US 3807988 A US3807988 A US 3807988A
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United States
Prior art keywords
lime
converter
granulometry
pig iron
fine
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Expired - Lifetime
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US00224746A
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English (en)
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P Nilles
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Centre de Recherches Metallurgiques CRM ASBL
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Metallureiques Ct Voor Res In
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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
    • C21C5/34—Blowing through the bath

Definitions

  • C2lc 7/00, 0210 5/34 q y of lime is introduced through the month of 58 Field of Search 75/52-60 the eenvener-
  • the quantity is lower than 12 g Si in the pig iron.
  • the total surface of the lime is at least 5 References Cited 45 m /t pig iron, and a part of the lime has a specific surface higher than 2.5 m /kg.
  • the present invention concerns improvements in methods for refining hematite pig iron in a converter by means of an oxygen-containing gas blown in through the bottom or through the lateral wall of the converter through at least one tuyere situated under the surface of the bath of metal to be refined.
  • the present invention provides a method of refining hematite pig iron in a converter comprising the refining operation of blowing in a gas consisting mainly of commercially pure oxygen through at least one tuyere opening out under the surface of the molten metal, the method including introducing through the mouth of the converter at the beginning of the refining operation a quantity of lime lower than 12 kg per kilogram of silicon initially contained in the pig iron, the granulometry of the quantity of lime being such that itstotal surface is at least 45 m per metric ton of pig iron, and a part of the quantity of lime being fine lime having a specific surface higher than 2.5m kg.
  • Specific surface means the sum of the external surfaces of all the pieces contained in a kilogram of lime, all the pieces being assumed to be spherical.
  • the lime used is assumed to be constituted of small spheres of a diameter equal to the mean granulometry excluding abrasion fines.
  • the specific surface can be determined for instance from the graph shown in the FIGURE, in which y is the specific surface (m /kg) and x is the average granulometry of the lime (mm).
  • the graph plotted is a hyperbola whose equation is approximately xy 6.
  • the total surface per metric ton of pig iron is equal to the sum, over all the categories of lime used, of the specific surface multiplied by the corresponding amount of lime per metric ton of pig iron for each category of lime.
  • the lime supplied is customary for the lime supplied to be of granulometry 20/40mm, which corresponds to a specific surface of approximately 0.2m /kg; if one introduces 60 kg of lime per metric ton of pig, iron, the total surface is equal to 0.2 X 60 l2m /t pig iron.
  • the basic Bessemer or Thomas process the customary lime granulometry is /60 which corresponds to a specific surface of 0.l7m /kg.
  • the lime which constitutes the fine fraction has an average granulometry not exceeding lmm, the remainder being constituted of pieces of granulometry larger than that of the lime added at the beginning, and preferably of a granulometry of at least mm.
  • This variation has the advantage of using a considerable part of the lime in an economical form.
  • one uses rich lime, that is lime having a granulometry the major part of which does not exceed 0.02mm. With this variation it is possible to use a minimum quantity of lime with high specific surface.
  • Another advantageous variation consists in effecting the deposition of the lime in powder form on the pig iron by pneumatic means.
  • This variation is also very suitable for adding, at the beginning of oxygen blowing, lime with a granulometry which is for instance lower than lmm.
  • the powdered lime may be fluidized with air and conducted into the mouth of the converter.
  • the quantity of lime of high specific surface that is lime whose specific surface is greater than 2.5m /kg, (which quantity is preferably between 0.5 and 5 kg per kg of silicon initially contained in the pig iron) to be linked to the specific volume, V, of the converter.
  • V volume, there should be understood the ratio between the internal volume of the converter (immediately after construction or re-lining) and the average of steel tapped into the ladle from the converter per cast (blow).
  • the ratio P of the quantity Q of lime with high specific surface (fine lime) to the total quantity of lime introduced into the furnace is accordingly a function of the same factors i, V. In general, P 2 V 10 i.
  • a particularly interesting example of the method of the invention is one in which: a. refining is effected by means of a gas consisting mainly of commercial oxygen, blown into the converter under the surface of the bath (for instance through the walls or the bottom) by means of at least one tuyere with two coaxial tubes, the internal tube being for the injection of the refining gas, while the peripheral tube is intended for blowing a gaseous or liquid protective fluid, i.e., a fluid with endothermic dissociation, for instance a hydrocarbon; b.
  • a gaseous or liquid protective fluid i.e., a fluid with endothermic dissociation, for instance a hydrocarbon
  • the converter at the very beginning of the refining operation, and preferably before its commencement, one introduces through the mouth of the converter a quantity of lime less than 12 kg per kg of silicon initially contained in the pig iron; the granulometry of this lime is such that the total surface (assuming the pieces to be spherical) is higher than 45m per metric ton of pig iron, and a portion of this lime (between 0.5 and 5 kg per kg of silicon initially contained in the pig iron) has a specific surface higher than 2.5m /kg of lime; c.
  • the total quantity of pig iron, scrap, and possibly ores, charged into the converter before the beginning or during the course of the refining operation is such that the specific volume is between 0.40 and 0.90 m metric ton of steel produced; and d. the ratio P between the quantity of lime with specific surface higher than 2.5m /kg of lime and the total quantity of lime increases (for a given silicon content of the pig iron) as the specific volume of the ladle decreases.
  • condition ((1) can be expressed by the relationship where V is expressed in m /t of steel obtained in i represents the silicon content of the pig iron in weight percent.
  • the method does not involve the injection of lime directly into or onto the bath of molten metal.
  • the addition of lime to the converter in the form of pieces can be effected in the conventional manner, for instance by means of a hopper, the addition of lime of granulometry below 2 mm preferably taking place either in sacks or by pneumatic means, excluding any injection of lime onto or into the metal.
  • the lime introduced before the blowing operation or at the beginning of the blowing operation can be mixed with constituents such as fluidizers (spath fluor, alumina), cooling agents (ores, soda, scale), and so on, these constituents preferably having a granulometry similar to that of the lime.
  • constituents such as fluidizers (spath fluor, alumina), cooling agents (ores, soda, scale), and so on, these constituents preferably having a granulometry similar to that of the lime.
  • a converter of 11.3 in useful volume was charged with 14.6 t (metric ton) of pig iron containing 0.55% Si, 3.2 t scrap, and 800 kg lime made up as follows:
  • the yield was 16.4 t good quality steel, with no losses or spattering.
  • the quantity of lime introduced before the start or at the start of the blowing operation represents 504 kg 296 kg/l4.6 X 5.5 kg lime per kg silicon initially contained in the pig iron; the first condition is satisfied 12 kg).
  • the total surface of the lime is 0.2 m X 296 6 m X 504/ 14.6 or 211 m /t pig iron, satisfying the second condition 45 m P 130 150 V 10 i is also satisfied:
  • Example B The same converter was charged with 18.5 t hematite pig iron with 0.80 percent silicon, 4.9 t scrap, and 1,400 kg lime: 700 kg in pieces (20/40 mm) and 700 kg in powder of average granulometry 2 mm (specific surface: 3 m /kg). The yield was 21.5 metric tons of steel but there 'was some spattering.
  • the specific surface of the fine lime is 3 m lkg (i.e., 2.5), the quantity of lime of this category being 4.7 kg/kg Si (i.e., within the preferred range);
  • P is the proportion of fine lime in the said quantity of lime, in percent by weight
  • V is the specific volume of the converter in m lmetric ton of steel produced
  • i is the silicon content of the pig iron charged into the converter, in percent by weight.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Carbon Steel Or Casting Steel Manufacturing (AREA)
US00224746A 1971-02-10 1972-02-09 Refining hematite pig iron in a converter Expired - Lifetime US3807988A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
LU62570 1971-02-10
LU62944 1971-04-07

Publications (1)

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US3807988A true US3807988A (en) 1974-04-30

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US (1) US3807988A (enrdf_load_stackoverflow)
BE (1) BE778603A (enrdf_load_stackoverflow)
CA (1) CA958896A (enrdf_load_stackoverflow)
DE (1) DE2206081C3 (enrdf_load_stackoverflow)
FR (1) FR2124428B1 (enrdf_load_stackoverflow)
IT (1) IT948907B (enrdf_load_stackoverflow)
NL (1) NL7201589A (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4065297A (en) * 1976-09-28 1977-12-27 Sumitomo Metal Industries Limited Process for dephosphorizing molten pig iron

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
LU62943A1 (enrdf_load_stackoverflow) * 1971-04-07 1973-05-16

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1145506A (en) * 1912-11-20 1915-07-06 Amand Francois Pasquier Process for dephosphorizing pig-iron.
US2855293A (en) * 1955-03-21 1958-10-07 Air Liquide Method and apparatus for treating molten metal with oxygen
US2864689A (en) * 1956-07-24 1958-12-16 Electro Chimie Metal Process of successively desulphurizing and desiliconizing a bath of pig iron
US2918365A (en) * 1953-08-10 1959-12-22 Yawata Seitetsu K K Method for controlling compositions of molten pig iron and slag in a blast furnace
US2950186A (en) * 1957-03-02 1960-08-23 Siderurgie Fse Inst Rech Method for top blowing pulverulent burnt lime and oxygen into cast iron for refining same
US2962277A (en) * 1958-05-15 1960-11-29 Gen Electric Apparatus for continuous process of steel making

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1145506A (en) * 1912-11-20 1915-07-06 Amand Francois Pasquier Process for dephosphorizing pig-iron.
US2918365A (en) * 1953-08-10 1959-12-22 Yawata Seitetsu K K Method for controlling compositions of molten pig iron and slag in a blast furnace
US2855293A (en) * 1955-03-21 1958-10-07 Air Liquide Method and apparatus for treating molten metal with oxygen
US2864689A (en) * 1956-07-24 1958-12-16 Electro Chimie Metal Process of successively desulphurizing and desiliconizing a bath of pig iron
US2950186A (en) * 1957-03-02 1960-08-23 Siderurgie Fse Inst Rech Method for top blowing pulverulent burnt lime and oxygen into cast iron for refining same
US2962277A (en) * 1958-05-15 1960-11-29 Gen Electric Apparatus for continuous process of steel making

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4065297A (en) * 1976-09-28 1977-12-27 Sumitomo Metal Industries Limited Process for dephosphorizing molten pig iron

Also Published As

Publication number Publication date
BE778603A (enrdf_load_stackoverflow) 1972-05-16
DE2206081A1 (de) 1972-08-17
DE2206081C3 (de) 1981-09-17
FR2124428B1 (enrdf_load_stackoverflow) 1974-06-28
IT948907B (it) 1973-06-11
NL7201589A (enrdf_load_stackoverflow) 1972-08-14
FR2124428A1 (enrdf_load_stackoverflow) 1972-09-22
DE2206081B2 (de) 1980-12-04
CA958896A (en) 1974-12-10

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