EP0714989B1 - Steel manufacturing method using converter dephosphorisation - Google Patents

Steel manufacturing method using converter dephosphorisation Download PDF

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Publication number
EP0714989B1
EP0714989B1 EP94919835A EP94919835A EP0714989B1 EP 0714989 B1 EP0714989 B1 EP 0714989B1 EP 94919835 A EP94919835 A EP 94919835A EP 94919835 A EP94919835 A EP 94919835A EP 0714989 B1 EP0714989 B1 EP 0714989B1
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EP
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Prior art keywords
slag
molten iron
converter
dephosphorization
oxygen
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EP94919835A
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German (de)
English (en)
French (fr)
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EP0714989A1 (en
EP0714989A4 (en
Inventor
Masataka Nippon Steel Corporation Techn. YANO
Yuji Nippon Steel Corporation Techn. OGAWA
Masayuki Nippon Steel Corporation ARAI
Fumio Nippon Steel Corporation KOIZUMI
Noriyuki Nippon Steel Corporation MASUMITSU
Hideaki Nippon Steel Corporation SASAKI
Hiroshi Nippon Steel Corporation HIRATA
Yoshiaki Nippon Steel Corporation KUSANO
Hirobumi Maede
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Nippon Steel Corp
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Nippon Steel Corp
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Priority claimed from JP16256493A external-priority patent/JP2958842B2/ja
Priority claimed from JP32908693A external-priority patent/JP2896838B2/ja
Priority claimed from JP32908893A external-priority patent/JP2958848B2/ja
Priority claimed from JP01102794A external-priority patent/JP3239197B2/ja
Application filed by Nippon Steel Corp filed Critical Nippon Steel Corp
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Publication of EP0714989A4 publication Critical patent/EP0714989A4/en
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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
    • 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
    • C21C5/35—Blowing from above and through the bath
    • 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
    • C21C1/02—Dephosphorising or desulfurising
    • 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
    • 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
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/064—Dephosphorising; Desulfurising
    • 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
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/068—Decarburising
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D19/00—Arrangements of controlling devices
    • F27D2019/0028—Regulation
    • F27D2019/0075—Regulation of the charge quantity
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D19/00—Arrangements of controlling devices
    • F27D2019/0028—Regulation
    • F27D2019/0078—Regulation of the speed of the gas through the charge
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
    • F27D27/00—Stirring devices for molten material
    • F27D2027/002—Gas stirring

Definitions

  • the present invention relates to a refining process, using a converter having a bottom-blowing function, in steel production.
  • the present invention relates, in more detail, to a converter refining process wherein molten iron is refined by desiliconization and dephosphorization in the same converter, intermediate slag discharge is conducted, and the molten iron is successively refined by decarbonization, and to the operation conditions of the dephosphorization refining.
  • molten iron pretreatment installations or secondary refining installations have been enlarged and arranged in a steel production process. Since dephosphorization is particularly efficient in the molten iron stage where the temperature level is low, precedent dephosphorization is generally carried out in the molten iron pretreatment step. In precedent dephosphorization, there are refining vessel systems such as a torpedo car system, a ladle system and a two converter system where decarbonization is conducted in a separate furnace.
  • any of the systems can be carried out by charging flux such as CaO and iron oxide either through top addition or injection, and agitating through nitrogen bubbling or nitrogen bubbling and oxygen top blowing in combination.
  • flux such as CaO and iron oxide
  • Japanese Patent Publication Kokai No. 58-16007 discloses a Process for Dephosphorizing and Desulfurizing Molten Iron wherein a CaO flux is blown into a molten iron, together with a carrier gas, while oxygen is being top blown, the molten iron is subsequently dephosphorized so that the slag basicity and the iron oxide content subsequent to the treatment become at least 2.0 and up to 15%, respectively, top blowing oxygen is then stopped, and the molten iron is desulfurized by blowing a desulfurizing agent without forcibly removing the slag.
  • Japanese Patent Publication Kokai No. 62-109908 discloses a Process for Desiliconizing, Dephosphorizing and Desulfurizing Moten Iron wherein a dephosphorizing flux containing CaO as its main component is added to a molten iron surface from the initial stage of pretreating the molten iron, oxygen or an oxygen source in a solid state is added to the molten iron surface while iron oxide flux powder is being blown into the molten iron with a carrier gas, and the flux is changed to an alkali type flux after the desiliconization stage to conduct dephosphorization and desulfurization simultaneously.
  • 63-195209 discloses a Process for Producing Steel wherein two converters, a top-blowing converter and a bottom-blowing converter, are used, one is employed as a dephosphorizing furnace and the other is employed as a decarbonizing furnace, the converter slag produced in the decarbonizing furnace is recycled to the dephosphorizing furnace, and the dephosphorized molten iron obtained by dephosphorization is charged into the decarbonizing furnace.
  • the step has the following drawbacks: the treating time is long and the heat loss at the time of treating is large; it takes much time to supply the molten iron to a converter; and, even when two converters are utilized, a decrease in the molten iron temperature is unavoidable due to the discharge of the molten iron subsequent to the treatment from a first converter and the recharge thereof into the other converter. Accordingly, the process is by no means a satisfactory one in view of a heat margin. Moreover, dephosphorization of the total amount of the molten iron in recent years has further lowered the heat margin in the converter process. As a result, freedom to select the raw materials to be used is lost, and there will arise a serious problem, from the standpoint of positively recycling scrap in converters, in the future.
  • the cost of the process is high and refractory materials consumed therein is large as described below: (1) since refining by soft blowing (the agitation force of the molten iron within the converter is lowered, and the material transfer of [C] in the molten iron is made in a rate-determining state) is intentionally conducted and the (% T.Fe) concentration in the slag is maintained at least at about 15% to make the slag liable to foam, the iron loss increases, (2) in order to maintain the flowability of the slag, the refining temperature is increased so that the blowing-off temperature during dephosphorization refining becomes at least 1,400°C, and consequently the wear and melt loss of refractory materials at converter-inclined portions increase, and (3) since the dephosphorization efficiency is lowered due to a high blowing-out temperature, the slag basicity, CaO/SiO 2 , is maintained at least at 3.0, and the flux cost increases. Accordingly, the technique
  • the present invention has been achieved under such circumstances. Although separate refining is directed in order to desiliconizing and dephosphorizing a molten iron in the conventional process, the present invention makes it possible to combine the pretreatment steps in a converter process.
  • An object of the present invention is to provide a refining process effective in greatly improving a heat margin and greatly reducing steel refining costs.
  • the present invention has been achieved by combine the desiliconization step and the dephosphorization step for a molten iron in a converter process.
  • rapid and complete discharge of dephosphorization refining slag becomes an essential condition.
  • discharging slag subsequently to the molten iron treating steps causes problems such as described below: (1) a molten metal flows out during slag discharge, and as a result the yield lowers; (2) the productivity lowers due to the increase in the discharge time; and (3) ensuring a high slag discharge ratio is extremely difficult, and a rephosphorization phenomenon takes place when there remains dephosphorizing slag containing P 2 O 5 at a high concentration.
  • the present inventors have done research and development to improve the discharge efficiency of slag after desiliconizing and dephosphorizing a molten iron by utilizing a converter, combine pretreatment steps of the molten iron in a converter process, greatly improve a heat margin, and reduce flux costs.
  • the present inventors conducted experiments wherein a 300-ton converter having a bottom-blowing function in a practical installation scale was used, about 290 ton of a molten iron was charged thereinto, burnt lime for dephosphorization and iron ore were added, top-blown oxygen was supplied while bottom-blowing agitation was being conducted to effect desiliconization and dephosphorization, intermediate slag discharge was practiced by once interrupting blowing after dephosphorization and tilting the converter, and decarbonization blowing was continuously conducted.
  • the molten iron had contained 0.40% of Si and 0.100% of P on the average before the treatment, and a desired temperature of the molten iron subsequent to dephosphorization had been determined to be 1,350°C on the basis of a conventional knowledge for the purpose of achieving efficient dephosphorization reaction. Consequently, the present inventors have paid attention to the fact that the agitation force of bottom-blown gas and the slag composition subsequent to dephosphorization greatly influence a dephosphorization ratio and a slag discharge efficiency, and have found that there is an optimum composition of the slag satisfying both factors.
  • the slag discharge ratio is influenced by the agitation force of bottom-blown gas, and that the slag discharge ratio is sharply improved at an agitation energy of bottom-blown gas of at least 0.5 kW/ton even when the slag composition is the same.
  • the slag discharge efficiency is improved because the bottom-blown gas enhances the slag-foaming level and slag discharge is conducted at a stage much earlier than that of intermediate slag discharge.
  • dephosphorization experiments were conducted using an 8-ton test converter.
  • About 6 tons of a molten iron which had an initial temperature of 1,180 to 1,300°C and contained from 4 to 4.8% of C, from 0.1 to 0.15% of P and about 0.3% of Si was refined for 8 to 10 minutes.
  • the molten iron was refined, with a predetermined amount of CaO charged as a flux, under the following conditions: a top-blown oxygen feed rate of 1.1 to 3.6 Nm 3 /min/ton, and a bottom-blown N 2 gas feed rate of 3 to 350 Nm 3 /h (0.03 to 3.7 kW/ton).
  • the CaO/SiO 2 ratio in the slag was from 0.6 to 2.5, and the molten iron temperature was from 1,250 to 1,400°C after the treatment.
  • Fig. 3 shows the relationship between the bottom-blowing agitation power and an equilibrium accomplishment degree (ratio of a record (P)/[P] ratio to a (P)/[P] ratio obtained from the formula (2)).
  • the dephosphorization reaction substantially proceeds to an equilibrium when the bottom-blowing agitation energy of at least 1 kW/ton is ensured.
  • the bottom-blowing agitation power increases with the flow rate of bottom-blown gas, the gas is blown through the molten iron and spitting greatly increases when the gas flow rate becomes excessively large.
  • the upper limit of the agitation energy is, therefore, determined in accordance with the bath depth of the molten iron and the diameter of a bottom-blowing tuyere, and that the blown gas has such an agitation energy that it is not blown through the molten iron.
  • Fig. 4 shows the relationship between burnt lime consumption and a dephosphorization amount in dephosphorization refining when a bottom-blowing agitation power of at least 1.0 kW/ton is practically applied.
  • the present inventors variously investigated the relationship (for achieving a dephosphorization ratio of 80%) between a molten steel-treating temperature and a CaO/SiO 2 ratio in slag subsequent to treatment while the flow rate of bottom-blown gas was adjusted so that the agitation energy became at least 0.5 kW/ton.
  • the results thus obtained are shown in Fig. 5.
  • the present inventors carried out an intermediate slag discharge test by changing the temperature and the CaO/SiO 2 ratio in slag subsequent to the treatment, and investigated variously the relationship between the CaO/SiO 2 ratio and the slag discharge ratio. The results thus obtained are shown in Fig. 6.
  • the total amount of the burnt lime used in the dephosphorization stage and in the decarbonization stage may be made to amount to up to 10 kg/ton by recycling the decarbonizing slag.
  • the decarbonizing slag when the decarbonizing slag is not recycled, the sum of a consumption unit in the dephosphorization stage and in the decarbonization stage is about 15 kg/ton. Accordingly, recycling the decarbonizing slag may reduce a burnt lime consumption by about at least 5 kg/ton.
  • the slag discharge ratio when the temperature subsequent to the treating is less than 1,200°C, the slag discharge ratio does not reach 60% at any CaO/SiO 2 ratio subsequent to the treatment, and that when the temperature subsequent to the treatment exceeds 1,450°C, the slag discharge ratio also does not reach 60% at a CaO/SiO 2 ratio of at least the necessary one obtained from Fig. 5. Accordingly, in order to obtain a high dephosphorization efficiency and a high slag discharge efficiency, dephosphorization is required to be carried out so that the molten iron temperature subsequent to the treatment becomes at least 1,200°C and up to 1,450°C and the CaO/SiO 2 ratio in the slag subsequent thereto becomes at least 0.7 and up to 2.5.
  • the CaO/SiO 2 ratio in the slag subsequent to the treatment herein can be freely controlled by the amount of flux charged during dephosphorization refining, and the molten steel temperature subsequent to the treatment can also be freely controlled by coolants (scrap and iron ore) charged during dephosphorization refining.
  • the desired slag discharge ratio of 60% as well as the desired dephosphorization amount can be sufficiently achieved at a CaO/SiO 2 ratio in the slag subsequent to the treatment of 0.7 to 2.5 in accordance with the molten iron temperature subsequent to the treatment which is from 1,200 to 1,450°C, under the condition of a bottom-blowing agitation power of at least 0.5 kW/ton.
  • Fig. 8 shows the relationship between the sum of a T.Fe concentration and a MnO concentration and a (%P)/[%P] ratio at a molten iron temperature of 1,350°C subsequent to the treatment, with the CaO/SiO 2 ratio in the slag subsequent to the treatment being 1.0, 1.5 or 2.0. It is seen from Fig.
  • the sum of the T.Fe concentration and the MnO concentration subsequent to the treatment is desirably maintained at least at 10% and up to 35% as a better control parameter by operating the converter while adjusting a top-blown oxygen feed rate, a bottom-blown gas flow rate or the height of a top-blowing lance.
  • L/L o ⁇ L h ⁇ 10 -3 ⁇ exp(-0.78h/L h ) ⁇ /L o
  • L o is a bath depth (m)
  • h is the height of a top-blowing lance for oxygen
  • L is the depth of a molten steel recess and is represented by the formula L h ⁇ 10 -3 ⁇ exp(-0.78h/L h )
  • L h is represented by the formula 63.0 x ⁇ kQ 02 /(nd) ⁇ 2/3 (wherein Q 02 is the flow rate of oxygen Nm 3 /h), n is a number of nozzles, d is the diameter of each of the nozzles (mm), and k is a constant determined by the ejecting angle of the nozzles).
  • the lance height is required to be elevated.
  • the secondary combustion ratio within the furnace is increased, and the recovery amount of LDG is lowered or heat damage to the bricks in the inclined portions of the converter increases. Accordingly, the increase in the lance height is restricted.
  • the minimum L/L o ratio is restricted to at least 0.1.
  • the L/L o ratio increases, the (%T.Fe) in the slag is decreased, and the dephosphorization capacity is lowered. Accordingly, in order to ensure (the sum of the T.Fe concentration and the MnO concentration) of at least 10% in the slag during dephosphorization refining so that efficient dephosphorization refining can be practiced, the L/L o ratio is required to be restricted to up to 0.3.
  • the dephosphorization time can be decreased with an increase in an oxygen feed rate.
  • Fig. 9 shows a change of the [P] concentration in the molten iron with time at different oxygen-blowing rates under the condition that the slag composition and the slag temperature subsequent to the treatment are each approximately constant.
  • the treating time can be decreased by about 4 minutes compared with the operation wherein oxygen is fed at a rate of 1.1 Nm 3 /min/ton.
  • Fig. 10 shows the relationship between an oxygen feed rate and a primary dephosphorization rate constant (Kp').
  • Fig. 10 also shows the relationship in conventional processes (1), (2) and (3) in actual installations. Even when the CaO/SiO 2 ratio is lowered to 0.6 to 1.1 subsequent to the refining to decrease burnt lime consumption, a dephosphorization rate constant equivalent to that of the conventional process (1) using a torpedo car or that of the conventional process (2) using a ladle can be obtained by increasing the oxygen feed rate. When the CaO/SiO 2 ratio is at least 1.1 and up to 2.5, it is confirmed that a dephosphorization rate constant about twice as much as that of the conventional process (3) using the same converter can be obtained.
  • the converter is tilted, and the slag is discharged.
  • steps subsequent to the slag discharge the converter is immediately made to stand vertically, and flux such as burnt lime and light burned dolomite in the necessary and lowest amounts in accordance with a slag discharge ratio, a state of the melt loss of the furnace, a desired [P] concentration, etc. is charged in addition, followed by decarbonizing the molten iron by blowing oxygen until the molten iron has a desired end point [C].
  • Scrap, iron ore, Mn ore corresponding to a desired [Mn] concentration, and the like may optionally be charged.
  • the burnt lime consumption may greatly be cut as shown in Fig. 7.
  • C in the molten iron drastically reacts with oxygen sources in the converter decarbonizing slag, namely FeO, Fe 2 O 3 and MnO according to the reaction formulas (4), (5) and (6): FeO + C ⁇ Fe + CO Fe 2 O 3 + 3C ⁇ 2Fe + 3CO MnO + C ⁇ Mn + CO to form a large amount of a CO gas.
  • the CO gas makes the slag and charged molten iron jump out from the converter and produces slag foaming so that the slag flows out of the converter.
  • the CO gas generation in a large amount results not only in that the yield of iron is lowered but also that the operation may be obliged to be interrupted.
  • the amount of a CO gas produced by the reaction of the formulas (4) to (6) increases with a FeO, a Fe 2 O 3 or MnO concentration in the slag. Moreover, the rates of these reactions increase with a temperature of the slag or molten iron. That is, the reaction becomes more drastic when the temperature is higher. However, even when the concentration of FeO, Fe 2 O 3 or MnO in the slag is high, the reaction rates become slow at a low slag temperature or a low molten iron temperature. As a result, bumping or slag foaming may not take place sometimes.
  • the formula (1) signifies that when the relationship of T.Fe (sum of the concentrations of iron in FeO and Fe 2 O 3 ), a MnO concentration, a slag and a molten iron on the left side is up to 0.1, bumping and slag foaming do not take place.
  • the slag temperature or molten iron temperature is selected so that they match the concentrations of FeO, Fe 2 O 3 and MnO in the slag, and as a result the value of the left side of the formula (1) becomes up to 0.1.
  • the molten iron is then charged, bumping and slag foaming may be prevented.
  • bumping and slag foaming may also be prevented by adjusting the concentrations of T.Fe and MnO in the slag on the basis of the slag temperature and the molten iron temperature so that the relationship of the formula (1) is satisfied, and by charging the molten iron.
  • CaCO 3 when CaCO 3 is used as the coolant, CaCO 3 is decomposed into CaO and CO 2 . Since the decomposition reaction is endothermic, the decarbonizing slag temperature is lowered, and the conditions of the formula (1) can be satisfied in a short period of time. Moreover, since CaO produced by decomposition acts as a flux in dephosphorization reaction, flux for dephosphorization in the dephosphorization stage can be advantageously reduced.
  • the sum of the concentrations of iron oxide and manganese oxide in the decarbonizing slag is determined either by sampling a slag sample and rapidly analyzing it or by obtaining in advance the relationship between a carbon concentration in the molten steel and the sum of an iron oxide concentration and a manganese oxide concentration in the decarbonizing slag and calculating the sum from the analytical results of the carbon concentration in the molten steel of the previous charge after decarbonization.
  • the decarbonizing slag temperature is measured by a radiation thermometer, etc.
  • Fig. 1 shows the outline of the entire process.
  • the present invention has been illustrated above on the basis of the cases where a molten iron having been predesulfurized outside a converter is used.
  • the molten iron can be desulfurized within a converter before dephosphorization as described above. That is, desulfurizing flux which is one or at least two substances selected from CaO, Na 2 CO 3 and Mg is charged by top charging or bottom-blowing injection, and then desulfurization is conducted in a short period of time of 2 to 5 minutes. Dephosphorization as mentioned above is subsequently conducted. Since from 40 to 60% of S in the slag is then vaporized and desulfurized, desulfurization of from 30 to 50% of [S] in the molten iron at the initial stage in combination with dephosphorization becomes possible by adjusting the flux amount.
  • desulfurizing flux which is one or at least two substances selected from CaO, Na 2 CO 3 and Mg is charged by top charging or bottom-blowing injection, and then desulfurization is conducted in a short period of time of 2 to 5 minutes
  • the converter when slag is discharged by tilting the converter, the converter is desirably turned in a short period of time such as within 1 minute (as short as possible) while the slag is being prevented from scattering with a slag-preventive plate in front of the converter as shown in Fig. 11.
  • Table 1 shows concrete conditions, chemical compositions of molten steels, and temperature changes of the steels.
  • the molten iron subsequent to dephosphorization had [P] of 0.025%, and the resulting molten steel subsequent to decarbonization had [P] of 0.019%.
  • the total amount of burnt lime added in both the predesulfurization stage and dephosphorization and decarbonization stage in the converter was about 20 kg/ton. The consumption could thus be significantly cut compared with the average total burnt lime consumption of 34 kg/ton in a conventional process (desulfurization and dephosphorization of the molten iron + decarbonization in the converter) for obtaining refining effects equivalent to those in the present invention.
  • Table 2 shows conditions such as the chemical composition, the temperature, etc. of each of the charges.
  • scrap in a large amount of about 17% could be charged according to the process of the present invention having a high heat margin, whereas scrap only in an amount of about 7% could be charged in the conventional process where dephosphorization and decarbonization were conducted in a torpedo car and in a converter, respectively.
  • the molten iron may be dephosphorized at a lower basicity due to an increase in the amount of slag formed in the dephosphorization stage, and that as a result the burnt lime consumption unit does not increase much.
  • the operation is stabilized without drastic slopping due to an operation with a low basicity and at low temperatures.
  • the operation may be conducted with a scrap ratio of 25% using a molten iron having an [Si] content of 1%.
  • Table 3 shows concrete conditions, chemical compositions of molten steels, and temperature changes of the steels.
  • Table 4 shows each of the examples wherein a molten iron was charged into a 300-ton top- and bottom-blowing converter equipped with a bottom-blowing tuyere at the bottom in an amount of 290 to 300 ton, CO 2 and O 2 were blown thereinto from the bottom-blowing tuyere and the top-blowing lance, respectively.
  • Comparative Examples 1 to 3 are instances wherein the slag basicity subsequent to dephosphorization was at least 2.0, or a molten iron was refined with a decreased agitation force.
  • Examples 4 to 7 were carried out according to the present invention.
  • the basicity of a molten iron could be easily adjusted by charging burnt lime in an amount in accordance with an amount of SiO 2 to be formed from Si in the molten iron before the treatment, and an amount of SiO 2 remaining in the slag in the furnace, etc.
  • the molten iron in an amount of 300 ton having a temperature of 1) 1,290 to 1,310°C, 2) 1,340 to 1,360°C or 3) 1,390 to 1,410°C was charged thereinto.
  • the chemical composition of the molten iron was as follows: a [C] concentration of 4.5 to 4.8%, a [Si] concentration of 0.39 to 0.41%, and a [P] concentration of 0.099 to 0.103%.
  • the amount of the decarbonizing slag which had been left in the converter was about 30 kg/ton.
  • even a molten iron which did not satisfy conditions of the formula (1) was also charged for comparison. Whether bumping or rapid foaming took place or not after the charging is shown in Fig. 11 to Fig. 13 at respective molten iron temperatures.
  • Each of the slant line portions in Fig. 11 to Fig. 13 is a region where the conditions of the formula (1) are satisfied.
  • the mark o designates the case where bumping and slag foaming did not take place when the molten iron was charged.
  • the mark X designates the case where bumping and slag foaming took place when the molten iron was charged.
  • Dephosphorization was subsequently practiced, and the results were as follows: the reutilized decarbonizing slag acted as dephosphorizing flux; the CaO component in the decarbonizing slag was effectively used for dephosphorization; and the consumption unit of CaO to be charged in the dephosphorization stage could be reduced compared with the case where the decarbonizing slag was not reused.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Carbon Steel Or Casting Steel Manufacturing (AREA)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
EP94919835A 1993-06-30 1994-06-30 Steel manufacturing method using converter dephosphorisation Revoked EP0714989B1 (en)

Applications Claiming Priority (16)

Application Number Priority Date Filing Date Title
JP16256493 1993-06-30
JP162564/93 1993-06-30
JP16256493A JP2958842B2 (ja) 1993-06-30 1993-06-30 転炉精錬方法
JP16579093 1993-07-05
JP16579093 1993-07-05
JP165790/93 1993-07-05
JP32908693A JP2896838B2 (ja) 1993-12-24 1993-12-24 溶鋼製造法
JP329086/93 1993-12-24
JP32908693 1993-12-24
JP32908893 1993-12-24
JP32908893A JP2958848B2 (ja) 1993-12-24 1993-12-24 溶銑の脱りん方法
JP329088/93 1993-12-24
JP11027/94 1994-02-02
JP1102794 1994-02-02
JP01102794A JP3239197B2 (ja) 1993-07-05 1994-02-02 転炉製鋼法
PCT/JP1994/001070 WO1995001458A1 (fr) 1993-06-30 1994-06-30 Procede de production et d'acier au moyen d'un convertisseur

Publications (3)

Publication Number Publication Date
EP0714989A1 EP0714989A1 (en) 1996-06-05
EP0714989A4 EP0714989A4 (en) 1997-06-25
EP0714989B1 true EP0714989B1 (en) 2000-03-22

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EP94919835A Revoked EP0714989B1 (en) 1993-06-30 1994-06-30 Steel manufacturing method using converter dephosphorisation

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KR (1) KR0159180B1 (zh)
CN (1) CN1041843C (zh)
AU (1) AU680268B2 (zh)
BR (1) BR9406985A (zh)
CA (1) CA2166097C (zh)
DE (1) DE69423630T2 (zh)
ES (1) ES2143547T3 (zh)
WO (1) WO1995001458A1 (zh)

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JP3854482B2 (ja) * 2001-09-27 2006-12-06 新日本製鐵株式会社 溶銑の予備処理方法及び精錬方法
JP3940280B2 (ja) * 2001-09-27 2007-07-04 新日本製鐵株式会社 溶銑の脱りん方法
DE10215839A1 (de) * 2002-04-10 2003-11-06 Sms Demag Ag Verfahren und Einrichtung zum Erzeugen von C-Stählen oder nichtrostenden Stählen durch Frischen von phosphorreichem Roheisen im Elektrolichtbogen-Ofen oder im Konverter-Gefäß
DE10215828B4 (de) * 2002-04-10 2007-08-02 Sms Demag Ag Verfahren und Einrichtung zum Erzeugen von nichtrostendem Stahl, insbesondere von chrom- oder chromnickelhaltigem Edelstahl
EP1608652A1 (en) * 2003-03-31 2005-12-28 Vernalis (Cambridge) Limited Pyrazolopyrimidine compounds and their use in medicine
EP1524322A3 (en) * 2003-10-15 2006-08-02 Milan Adelt Method of liquid steel production with slag recycling in a converter, equipment to employ the method
KR100749023B1 (ko) * 2006-05-26 2007-08-14 주식회사 포스코 극저린강의 전로 정련 방법
CN101864508B (zh) * 2010-07-02 2012-10-24 张觉灵 小渣量转炉炼钢方法
CN102071277B (zh) * 2010-12-23 2012-10-24 攀钢集团钢铁钒钛股份有限公司 一种转炉脱磷炼钢方法
CN102168160B (zh) * 2011-03-08 2013-04-17 武汉钢铁(集团)公司 使锰矿直接还原合金化的转炉炼钢工艺
JP5979017B2 (ja) * 2012-01-19 2016-08-24 Ｊｆｅスチール株式会社 溶銑の精錬方法
WO2014112521A1 (ja) * 2013-01-18 2014-07-24 Ｊｆｅスチール株式会社 溶銑の予備処理方法
CN104451022B (zh) * 2014-12-19 2016-03-16 山东钢铁股份有限公司 一种降低脱磷炉终渣全铁含量的方法
KR101660774B1 (ko) 2015-07-09 2016-09-28 주식회사 포스코 전로 조업 방법
JP6589998B2 (ja) * 2016-01-28 2019-10-16 日本製鉄株式会社 排滓方法、スラグの製造方法及び流下スラグのエネルギー減衰構造
WO2018012257A1 (ja) * 2016-07-14 2018-01-18 新日鐵住金株式会社 溶鋼中りん濃度推定方法及び転炉吹錬制御装置
CN106282487B (zh) * 2016-09-13 2019-03-29 北京北科中钢工程技术有限公司 一种铁水预脱磷方法
EP3633051B1 (en) * 2017-05-25 2021-11-17 JFE Steel Corporation Method for manufacturing high manganese steel ingot
CN109097523B (zh) * 2018-08-31 2019-12-24 钢铁研究总院 一种双渣法冶炼工艺
CN114438276B (zh) * 2022-02-11 2022-08-09 山东钢铁集团永锋临港有限公司 一种缩短转炉冶炼周期的方法

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JP2607329B2 (ja) * 1992-03-04 1997-05-07 新日本製鐵株式会社 溶銑の脱りん方法

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WO1995001458A1 (fr) 1995-01-12
EP0714989A1 (en) 1996-06-05
CN1041843C (zh) 1999-01-27
DE69423630T2 (de) 2000-11-09
CA2166097A1 (en) 1995-01-12
CN1128050A (zh) 1996-07-31
EP0714989A4 (en) 1997-06-25
AU7083194A (en) 1995-01-24
DE69423630D1 (de) 2000-04-27
KR960703440A (ko) 1996-08-17
KR0159180B1 (ko) 1999-01-15
AU680268B2 (en) 1997-07-24
CA2166097C (en) 2002-01-15
BR9406985A (pt) 1996-03-05
ES2143547T3 (es) 2000-05-16

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