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EP1457574A1 - Procede de pretraitement de fer fondu et procede de raffinage - Google Patents

Procede de pretraitement de fer fondu et procede de raffinage Download PDF

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Publication number
EP1457574A1
EP1457574A1 EP02772944A EP02772944A EP1457574A1 EP 1457574 A1 EP1457574 A1 EP 1457574A1 EP 02772944 A EP02772944 A EP 02772944A EP 02772944 A EP02772944 A EP 02772944A EP 1457574 A1 EP1457574 A1 EP 1457574A1
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EP
European Patent Office
Prior art keywords
molten iron
flux
pretreatment
injection
carbon source
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP02772944A
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German (de)
English (en)
Other versions
EP1457574A4 (fr
EP1457574B1 (fr
Inventor
H. C/O Nippon Steel Corp. Muroran Works Hirata
H. C/O Nippon Steel Corp. Muroran Works Ishii
H. C/O Nippon Steel Corp. Muroran Works Hayashi
Y. C/O Nippon Steel Corp. Ogawa
N. C/O Nippon Steel Corp. Sasaki
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Nippon Steel Corp
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Nippon Steel Corp
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Filing date
Publication date
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Publication of EP1457574A1 publication Critical patent/EP1457574A1/fr
Publication of EP1457574A4 publication Critical patent/EP1457574A4/fr
Application granted granted Critical
Publication of EP1457574B1 publication Critical patent/EP1457574B1/fr
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Expired - Lifetime legal-status Critical Current

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    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04Removing impurities by adding a treating agent
    • C21C7/068Decarburising
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C1/00Refining of pig-iron; Cast iron
    • C21C1/02Dephosphorising or desulfurising
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C1/00Refining of pig-iron; Cast iron
    • C21C1/04Removing impurities other than carbon, phosphorus or sulfur
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0025Adding carbon material
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04Removing impurities by adding a treating agent
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21CPROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28Manufacture of steel in the converter
    • C21C5/30Regulating or controlling the blowing
    • C21C5/32Blowing from above

Definitions

  • the present invention relates: to a molten iron pretreatment method wherein molten iron is desiliconized and dephosphorized in a refining vessel capable of top and bottom blowing; and to a molten iron refining method wherein molten iron is decarburized after said molten iron pretreatment.
  • a molten iron pretreatment method wherein molten iron is desiliconized and dephosphorized in another vessel different from a vessel in which the molten iron is subsequently decarburized has been employed in place of a converter steelmaking method wherein molten iron is simultaneously desiliconized, dephosphorized and decarburized in a converter.
  • molten iron pretreatment at an early stage it has been the common method to refine molten iron by adding a solid oxygen source including iron oxide and desiliconizing the molten iron and subsequently adding a flux for dephosphorization and dephosphorizing the molten iron.
  • molten iron has been dephosphorized by adding a lime source as a flux, thus forming dephosphorizing slag having a high basicity, and further adding a solid oxygen source including iron oxide as another flux.
  • a vessel for preliminary dephosphorization refining a torpedo car or a ladle has been used and a method wherein molten iron is dephosphorized preliminarily by injecting a flux for dephosphorization into the molten iron in the vessel has been employed.
  • solid oxygen means oxygen contained in iron oxide (FeO, Fe 2 O 3 ) and a solid oxygen source means a substance containing iron oxide such as iron ore, dust and mill scale, these being used as a flux or a coolant.
  • a molten iron pretreatment method wherein a converter-type refining vessel capable of top and bottom blowing is employed as a molten iron pretreatment vessel and molten iron is desiliconized and dephosphorized simultaneously has been adopted.
  • this method as the dephosphorization can be accelerated by the strong stirring caused by the top and bottom blowing even when slag having a low basicity is used, it is possible to simultaneously desiliconize and dephosphorize molten iron.
  • a molten iron temperature after pretreatment can be maintained at a high temperature in comparison with a conventional method wherein only solid oxygen is used or, even when oxygen gas is used, a very small amount of that is used, and moreover, since the treatment time can be shortened, in comparison with a pretreatment wherein a torpedo car is used, the heat loss during the pretreatment is small and a heat margin in all the refining processes including a decarburization treatment process can be secured.
  • a method of adding a flux for pretreatment refining to molten iron a method wherein a flux is added to molten iron in a refining vessel from above or an injection method wherein a flux is added to molten iron by injecting bottom-blown gas into the molten iron as the carrier gas of the flux can be adopted.
  • the flux injection method it is possible to improve the dephosphorization efficiency in pretreatment.
  • the dephosphorizing capability increases as a molten iron temperature, at the end of pretreatment, lowers. Therefore, despite the fact that a heat margin can be increased by using gas oxygen in pretreatment, an excessive rise of a molten iron temperature after pretreatment makes it impossible to sufficiently exploit the dephosphorizing capability in a pretreatment.
  • a carbon source is added to molten iron during molten iron pretreatment or decarburization refining
  • the carbon source is used as a heat source during decarburization treatment and resultantly the heat margin in refining can be increased.
  • a method of adding a carbon source during decarburization treatment a method wherein lump anthracite is added from above may be adopted.
  • the problem of the method is that the dispersion loss of carbon caused by the upward flow of gas generated by oxygen top blowing is large.
  • SiO 2 included in carbonaceous materials is added to molten iron, an increase in the burnt lime is undesirably required for securing the basicity of slag during decarburization treatment.
  • Japanese Unexamined Patent Publication No. S62-170409 discloses a method comprising the processes of: adding from above a flux produced by combining main component SiO 2 with a slag formation improvement material (Mn ore, calcium fluoride (fluorite), etc.) at the first stage of molten iron pretreatment; injecting a flux for desiliconization (iron oxide) into the molten iron; supplying a gas/solid oxygen source to the surface of the molten iron; simultaneously injecting a carbon source with a carrier gas into the molten iron together with the injection of the flux for desiliconization or after the completion of desiliconizing reaction; and resultantly increasing the concentration of carbon in the molten iron.
  • a flux for desiliconization iron oxide
  • supplying a gas/solid oxygen source to the surface of the molten iron
  • simultaneously injecting a carbon source with a carrier gas into the molten iron together with the injection of the flux for desiliconization or after the completion of desiliconizing reaction and resultant
  • molten iron refining processes comprising the steps of applying molten iron pretreatment wherein molten iron is desiliconized and dephosphorized in single vessel without intermediate slag discharging and subsequently applying decarburization refining
  • a conventional molten iron pretreatment has difficulty in sufficiently dephosphorizing molten iron after the pretreatment and therefore it has been required to form slag and dephosphorize molten iron even in decarburization treatment.
  • the formation of slag for dephosphorization in a decarburization process causes the cost to increase and further makes it necessary to use fluorite for the formation of slag for dephosphorization in a decarburization process and therefore the method goes against the aforementioned trend of not using fluorite.
  • the object of the present invention is to provide a pretreatment method and a refining method for molten iron, the methods allowing the refining to not use fluorite in both the processes of molten iron pretreatment and decarburization, to minimize the formation of slag for dephosphorization in the decarburization process, and to increase a heat margin by adding a carbon source to the molten iron with great efficiency.
  • the amount of a flux injected into molten iron during a desiliconizing reaction period can considerably be reduced. Therefore, if a carbon source is injected into molten iron as a heat source together with a carrier gas at a desiliconizing reaction period, it becomes possible to add only a carbon source to molten iron before the commencement of flux injection. In this case, the carbon source and a flux containing lime-based components for dephosphorization are not injected at the same time and therefore the hindrance of dephosphorization by the injection of a carbon source is avoided. Further, by eliminating the simultaneous injection of a carbon source and an iron oxide-contained flux, the effect of avoiding the risk of reaction between the carbon source and the iron oxide, and the resultant ignition, can be achieved.
  • Figure 1 is a schematic illustration showing a molten iron pretreatment furnace used in the present invention.
  • a refining vessel 1 capable of top and bottom blowing is used as shown in Figure 1.
  • top blowing mainly oxygen gas 8 is blown from the tip of a top-blowing lance 3 onto the surface of molten iron.
  • a top-blown oxygen gas used during a desiliconizing reaction period may be used as an oxygen source for desiliconization.
  • the top blowing is used not only for preventing the restoration of phosphorus by raising the oxygen potential of slag but also for controlling a molten iron temperature to a prescribed temperature by making up for heat dissipation.
  • bottom-blowing nozzles 2 disposed at the bottom of the refining vessel 1 are used.
  • the bottom blowing has the functions of: stirring molten iron by injecting a gas containing oxygen gas or an inert gas through the nozzles; and injecting fluxes 9 together with a carrier gas 7 into the molten iron through the bottom-blowing nozzles 2.
  • top- and bottom-blown converters By using two top- and bottom-blown converters, it is possible to use one of them for molten iron pretreatment and the other for decarburization treatment.
  • Molten iron is subjected to pretreatment in a converter for molten iron pretreatment, subsequently transferred to the other converter for decarburization treatment, and subjected to decarburization treatment.
  • a flux injected together with a carrier gas into molten iron is mainly composed of a component consisting of one or more of burnt lime, limestone and iron oxide, the component containing at least iron oxide.
  • a flux used for dephosphorization contains iron oxide and a CaO source such as burnt lime and limestone.
  • a flux mainly composed of iron oxide may be injected as a desiliconization aid prior to the commencement of the injection of a flux for dephosphorization. Iron ore, mill scale, sinter dust and other various sources may be adopted as iron oxide used as a flux component.
  • a top-blown gas oxygen is mainly used as an oxygen source.
  • a flux containing iron oxide may be injected into molten iron together with a carrier gas during desiliconizing reaction and used as an oxygen source aid for desiliconization.
  • the gas oxygen should be used as the oxygen source for desiliconization and a flux for desiliconization should not be injected.
  • a carbon source is injected together with a carrier gas through bottom-blowing nozzles into molten iron during desiliconizing reaction in molten iron pretreatment.
  • Anthracite powder, coke powder and others may be used as a carbon source.
  • Carbon source injection is started prior to the commencement of the aforementioned flux injection. Therefore, there is always a time period during which the aforementioned flux injection is not applied but the carbon source injection is applied.
  • As a carbon source alone is injected, such a problem of hindering dephosphorization as seen in the case of simultaneously injecting a carbon source and a flux for dephosphorization is avoided.
  • the term “during desiliconizing reaction” means the time period during which an [Si] concentration is being lowered with the lapse of time by the oxidation of [Si] in molten iron.
  • an [Si] concentration in molten iron lowers to 0.03 mass %, an oxidizing velocity of [Si] decreases considerably and, therefore, a desiliconizing reaction is regarded as completed.
  • the flux injection may be started at any time during desiliconizing reaction. Unless flux injection is started at least at the end of desiliconizing reaction, a dephosphorizing reaction succeeding the desiliconizing reaction cannot be processed smoothly. In the meantime, as shown in the aforementioned item (2) of the present invention, it is preferable to start flux injection after an [Si] concentration is lowered to 0.15 mass %. After an [Si] concentration is lowered to 0.15 mass %, if dephosphorizing slag (flux) exists, dephosphorizing reaction advances together with desiliconizing reaction.
  • a desirable means for determining an [Si] concentration during desiliconization is to estimate a desiliconized amount from an oxygen supply amount and a desiliconizing reaction efficiency on the basis of an initial value of [Si] in molten iron.
  • the effect of the present invention can be achieved even though a time period at which a carbon source and a flux are injected simultaneously exists.
  • the present invention favors dephosphorization in molten iron pretreatment in this way, it becomes possible to advance a prescribed dephosphorizing reaction without the use of fluorite in a molten iron pretreatment as described in the aforementioned item (4) of the present invention.
  • High-carbon low-phosphorus steels were melted and refined by using two 280-ton top- and bottom-blown converters; one as a refining vessel 1 for molten iron pretreatment as shown in Figure 1 and the other as a refining vessel for decarburization treatment.
  • Top blowing was carried out by using a top-blowing lance 3 and blowing oxygen gas 8 onto molten iron 5.
  • Bottom blowing was carried out by using six dual-tube bottom-blowing nozzles 2 and injecting oxygen gas or an inert gas into molten iron through the inner tubes.
  • a hydrocarbon gas was injected as a cooling gas during the oxygen gas injection through the inner tubes and an inert gas such as a nitrogen gas was injected during the inert gas injection through the inner tubes.
  • fluxes 9 stored in flux hoppers 4 could be injected together with a carrier gas 7 through bottom-blowing tuyeres 2.
  • a carbon source 9c, burnt lime 9a and sinter dust 9b were used as the fluxes 9.
  • an inert gas was used as the carrier gas 7.
  • the flow rate of top blowing during a dephosphorizing reaction period was determined so as to not only prevent the restoration of phosphorus by increasing the oxygen potential of slag 6 but also control a molten iron temperature to a prescribed temperature by making up for heat dissipation.
  • Table 1 shows mainly the carbon source in pretreatment and the flux injection state of each example.
  • Figure 2 shows the detailed results of the unit consumptions, the components and the temperatures of each example.
  • the invention examples 1 and 2 are the cases where the present invention is applied and the comparative examples 1 to 4 are the cases where prior arts are applied.
  • All the pretreatment end temperatures were aimed at 1,340°C except that of the comparative example 4 which was aimed at 1,370°C, 30°C higher than the others.
  • Each of the pretreatment end temperatures was adjusted by controlling the charge amount per unit of iron ore injected from above during the pretreatment. Note that, if iron ore is charged before or immediately after the commencement of dephosphorizing reaction, the formation of dephosphorizing slag deteriorates due to the lowering of a molten iron temperature and therefore it is preferable to charge iron ore as late as possible in the dephosphorizing reaction period. In the decarburization treatment, when a heat margin existed, an Mn ferroalloy unit consumption was trimmed by adding Mn ore.
  • the invention example 1 and the comparative examples 1 and 2 are compared with each other.
  • oxygen gas top blowing and sinter dust injection were applied at the desiliconizing reaction period.
  • the iron oxide in the injected sinter dust oxidized [Si] in molten iron and also partially oxidized [C] in molten iron and CO gas was generated. Any of the reactions with iron oxide was endothermic reaction and caused the molten iron temperature to lower at the end of the desiliconizing reaction. Further, the [C] concentration in the molten iron also lowered.
  • the amount of the top-blown oxygen gas was larger than that in the case of the comparative example 1, the amount of FeO formed by the top-blown oxygen gas was large and the slag could be maintained in the state of FeO-SiO 2 slag having a low melting point.
  • the invention example 1 it was possible to make slag have a good slag formation property and to advance the succeeding dephosphorizing reaction advantageously.
  • the carbon source injection was completed by the time the [Si] concentration lowered to 0.15 mass % and the injection of the dephosphorizing flux was started. Therefore, it was made possible to advance the dephosphorizing reaction even at the last half of the desiliconizing reaction and to accelerate the dephosphorizing reaction over the whole pretreatment. As a result, the [P] concentration after the pretreatment could be lowered to 0.010 mass %. In the meantime, since the carbon source injection time was short, the injected carbon source amount per unit was as low as a half of the invention example 1.
  • the [P] concentration after the pretreatment was 0.016 mass %, somewhat preferable to the case of the comparative example 1. This was because the oxygen potential could be raised because carbon source injection was not applied.
  • SiO 2 was introduced from anthracite charged at the decarburization treatment, it was necessary to increase the slag amount to 35 kg/t to secure the basicity of the slag.
  • the [P] concentration after the pretreatment was 0.025 mass %, the highest of all. Therefore, additional dephosphorizing treatment was applied with the slag amount at the decarburization treatment controlled to 40 kg/t and further fluorite of 5 kg/t added.
  • the present invention in a molten iron refining method wherein molten iron is subjected to decarburization treatment after being subjected to molten iron pretreatment wherein the molten iron is desiliconized and dephosphorized by using a refining vessel capable of top and bottom blowing, makes it possible to increase the heat margin at the refining by adding carbon to the molten iron at a high yield and, further, to obtain a high dephosphorizing capability at the pretreatment as the molten iron is desiliconized by using top-blown gas oxygen, a carbon source is injected into the molten iron during the desiliconizing reaction and, thereafter, a dephosphorizing flux is injected.
  • the present invention by starting the injection of a dephosphorizing flux after carbon source injection, it is made possible to increase the heat margin at refining by adding carbon to molten iron at a high yield without the deterioration of the dephosphorizing capability and to avoid the risk of ignition.
  • the present invention makes it possible to reduce a refractory erosion amount and, thus, the refractory cost.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
EP02772944.1A 2001-09-27 2002-09-27 Procede de pretraitement de fer fondu et procede de raffinage Expired - Lifetime EP1457574B1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2001295874 2001-09-27
JP2001295874A JP3854482B2 (ja) 2001-09-27 2001-09-27 溶銑の予備処理方法及び精錬方法
PCT/JP2002/010108 WO2003029498A1 (fr) 2001-09-27 2002-09-27 Procede de pretraitement de fer fondu et procede de raffinage

Publications (3)

Publication Number Publication Date
EP1457574A1 true EP1457574A1 (fr) 2004-09-15
EP1457574A4 EP1457574A4 (fr) 2006-02-15
EP1457574B1 EP1457574B1 (fr) 2018-05-30

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EP02772944.1A Expired - Lifetime EP1457574B1 (fr) 2001-09-27 2002-09-27 Procede de pretraitement de fer fondu et procede de raffinage

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EP (1) EP1457574B1 (fr)
JP (1) JP3854482B2 (fr)
KR (1) KR100658807B1 (fr)
WO (1) WO2003029498A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2796569A4 (fr) * 2011-12-20 2015-03-18 Jfe Steel Corp Procédé de fabrication d'acier par convertisseur

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100909691B1 (ko) * 2002-12-18 2009-07-29 주식회사 포스코 진공탈가스설비에서 고순도 산화철을 이용한 용강탈린방법
JP4735169B2 (ja) * 2005-09-30 2011-07-27 Jfeスチール株式会社 溶銑の脱燐処理方法
JP5689024B2 (ja) * 2010-06-07 2015-03-25 株式会社神戸製鋼所 ダストを使用した溶銑の脱りん方法
JP5979017B2 (ja) * 2012-01-19 2016-08-24 Jfeスチール株式会社 溶銑の精錬方法
CN115574554A (zh) * 2022-09-27 2023-01-06 首钢集团有限公司 一种石灰粉干燥装置、转炉及石灰粉喷吹方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62170409A (ja) * 1986-01-21 1987-07-27 Kobe Steel Ltd 溶銑の予備処理方法
EP0714989A1 (fr) * 1993-06-30 1996-06-05 Nippon Steel Corporation Procede de production et d'acier au moyen d'un convertisseur
JPH0920914A (ja) * 1995-06-30 1997-01-21 Nippon Steel Corp 溶銑の予備処理方法

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60221511A (ja) * 1984-04-17 1985-11-06 Nippon Steel Corp 溶鉄加炭溶解精錬法
JPH02228412A (ja) * 1989-02-28 1990-09-11 Kobe Steel Ltd 溶銑予備処理方法
JPH07278636A (ja) * 1994-04-13 1995-10-24 Nippon Steel Corp 溶銑の脱珪方法

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62170409A (ja) * 1986-01-21 1987-07-27 Kobe Steel Ltd 溶銑の予備処理方法
EP0714989A1 (fr) * 1993-06-30 1996-06-05 Nippon Steel Corporation Procede de production et d'acier au moyen d'un convertisseur
JPH0920914A (ja) * 1995-06-30 1997-01-21 Nippon Steel Corp 溶銑の予備処理方法

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
KISHIDA T ET AL: "CONSTRUCTION AND OPERATION OF HOT METAL DEPHOSPHORIZATION PLANT AT THE WAKAYAMA STEEL WORKS" SUMITOMO SEARCH, SUMITOMO METAL INDUSTRIES, TOKYO, JP, vol. 33, November 1986 (1986-11), pages 9-15, XP009010700 ISSN: 0585-9131 *
PATENT ABSTRACTS OF JAPAN vol. 012, no. 015 (C-469), 16 January 1988 (1988-01-16) & JP 62 170409 A (KOBE STEEL LTD), 27 July 1987 (1987-07-27) *
PATENT ABSTRACTS OF JAPAN vol. 1997, no. 05, 30 May 1997 (1997-05-30) -& JP 09 020914 A (NIPPON STEEL CORP), 21 January 1997 (1997-01-21) *
See also references of WO03029498A1 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2796569A4 (fr) * 2011-12-20 2015-03-18 Jfe Steel Corp Procédé de fabrication d'acier par convertisseur
US9493854B2 (en) 2011-12-20 2016-11-15 Jfe Steel Corporation Converter steelmaking method

Also Published As

Publication number Publication date
KR20040033326A (ko) 2004-04-21
JP2003105418A (ja) 2003-04-09
EP1457574A4 (fr) 2006-02-15
EP1457574B1 (fr) 2018-05-30
KR100658807B1 (ko) 2006-12-19
JP3854482B2 (ja) 2006-12-06
WO2003029498A1 (fr) 2003-04-10

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