USRE37897E1 - Method for making steel in a liquid melt-fed electric furnace - Google Patents

Method for making steel in a liquid melt-fed electric furnace Download PDF

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Publication number
USRE37897E1
USRE37897E1 US09/968,830 US96883001A USRE37897E US RE37897 E1 USRE37897 E1 US RE37897E1 US 96883001 A US96883001 A US 96883001A US RE37897 E USRE37897 E US RE37897E
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US
United States
Prior art keywords
furnace
charging
rate
pig iron
metal bath
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.)
Expired - Fee Related
Application number
US09/968,830
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English (en)
Inventor
André Kremer
Guy Denier
Jean-Luc Roth
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Paul Wurth SA
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Paul Wurth SA
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Priority to US09/968,830 priority Critical patent/USRE37897E1/en
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Publication of USRE37897E1 publication Critical patent/USRE37897E1/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
    • C21C5/52—Manufacture of steel in electric furnaces
    • C21C5/527—Charging of the electric furnace
    • 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
    • C21C5/52—Manufacture of steel in electric furnaces
    • 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
    • C21C5/52—Manufacture of steel in electric furnaces
    • C21C5/5211—Manufacture of steel in electric furnaces in an alternating current [AC] electric arc furnace
    • C21C5/5217—Manufacture of steel in electric furnaces in an alternating current [AC] electric arc furnace equipped with burners or devices for injecting gas, i.e. oxygen, or pulverulent materials into the furnace
    • 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
    • C21C5/52—Manufacture of steel in electric furnaces
    • C21C5/5252—Manufacture of steel in electric furnaces in an electrically heated multi-chamber furnace, a combination of electric furnaces or an electric furnace arranged for associated working with a non electric furnace
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • the present invention relates to a method of producing steel in an electric furnace by charging with molten pig iron.
  • a high proportion of steel scrap is recycled using electric furnaces such as arc furnaces. These furnaces make it possible to melt and re-use the steel scrap treated in this way in order to produce new steel products.
  • One way of reducing the concentration of residual elements in the steel obtained from steel scrap and of simultaneously improving the energy efficiency of the electric furnace consists in adding molten pig iron to the electric furnace.
  • molten pig iron typically 4.5% C and 0.6% Si
  • charging with molten pig iron leads to a considerable increase in the concentration of these elements in the metal bath.
  • the result of this is a longer refining stage in the metal bath in order to reduce the carbon and silicon concentrations in the metal bath to target values, which are generally very low, e.g. for the carbon concentration the target value is between 0.05% and 0.1%.
  • the document EP-A-0 630 977 describes a process for the treatment of molten pig iron in a converter equipped with at least one electrode. It relates to a process in which the total amount of pig iron is charged into the converter before the electric arc is activated.
  • the object of the present invention is to propose a method of producing steel in an electric furnace by charging with molten pig iron which enables the duration of a melting cycle to be reduced.
  • this objective is achieved by a method for producing steel in an electric furnace, in which a quantiity quantity of scrap is charged into the electric furnace and molten by use of an electric arc a predetermined quantity of molten pig iron is charged into the electric furnace, after a part of the scrap is molten, and a refining gas is injected into the furnace after the planned quantity of pig iron is charged until a target value of the concentration of carbon and/or silicon in the metal bath is reached.
  • the quantity of molten pig iron is charged continuously and at a controlled rate without interruption of the heating by the electric arc, and injection of the refining gas into the furnace starts during the continuous charging before the concentration of carbon and/or of silicon in the metal bath has reached a predetermined limiting value, the injection taking place continuously until the end of the charging, and the target value of the concentration of carbon and/or silicon in the metal bath is reached.
  • This method has the advantage, firstly, that the charging is carried out without switching off the power supply, i.e. without interruption of the heating by the electric arc. Consequently, the melting of the steel scrap is not interrupted and is carried out more rapidly than in traditional methods of charging with molten pig iron. Secondly, the refining by injection of a gas begins before the end of the charging, i.e. at a time which is earlier than in traditional charging methods. As a result of this, the duration of a melting cycle is reduced, even though the rate of injection of the gas is not increased.
  • this method also make it possible to reduce the maximum carbon and/or silicon concentration in the metal bath during a melting cycle by an adjustment of the rates of charging and of gas injection.
  • the concentration, for example of carbon, in the metal bath is in fact significantly lower than that obtained in traditional methods in which the refining begins only after charging with the total quantity of molten pig iron (it is the same for the silicon concentration).
  • at least a part of the carbon in the bath is oxidised as it is supplied, so that the increase in the carbon concentration in the metal bath as charging proceeds is substantially reduced and so that its concentration does not exceed a predetermined limiting value, which for the carbon concentration for example is less than 2%, and preferably less than 1.5%.
  • the silicon concentration behaves in the same way but on a reduced scale.
  • the predetermined limiting value for the silicon concentration is less than 0.3% for example, preferably less than 0.2%.
  • the charging with pig iron is achieved without stoppage of the heating by the electric arc and that the roof of the furnace remains closed for the whole duration of the charging.
  • the latter is carried out preferably through a lateral opening in the furnace. Since the roof is closed during the whole melting cycle, inputs of air into the furnace chamber are avoided and the nitrogen input is considerably reduced.
  • the earlier and continuous refining leads to a continual washing of the metal bath by the reaction gases like CO. Through this washing by CO, the nitrogen dissolved in the metal bath is dissolved in the CO bubbles, which take it out of the metal bath. The nitrogen is then removed from the vessel together with the reaction gas by the furnace exhaust system. Such continuous washing thus leads to very low nitrogen concentrations in the steel produced.
  • the method according to the invention is perfectly adapted to the production of quality steels, particularly to that of very ductile steels, for which very low nitrogen concentrations are required.
  • the rate of supply of the refining gas and the rate of charging with pig iron are preferably adjusted so that the carbon and/or silicon concentration in the metal bath no longer increases after the refining has started. It is possible, for example, to adapt the rate of charging with pig iron to the maximum rate of oxygen supply so as to oxidise all the carbon in the bath as it is supplied. In this way, the carbon and silicon concentrations in the metal bath may be very precisely controlled during a melting cycle and it is possible to limit the maximum concentration to very low values, e.g. for the carbon, to a concentration of 0.5%
  • the refining gas is injected into one of the two quadrants of the furnace, which are opposite the feed opening relating to an electrode of the electric furnace.
  • the direction of the gas injection is adjusted so that a first vertical plane containing the direction of charging and a second vertical plane containing the direction of injection intersect each other substantially in the region of the furnace electrode.
  • reaction gases such as CO for example, which are released continuously during the refining, are more abundant in the region where the fluxes of gas and pig iron meet each other than in the neighbouring regions.
  • these gases displace the nitrogen in the vessel and create above the surface of the metal bath a protective atmosphere against the input of nitrogen into the bath.
  • the charging with molten pig iron can be carried out with an amount lying between 20% and 60% of the total furnace charge and that the rate of charging with pig iron is preferably less than 4% of the capacity of the furnace per minute.
  • the rate at which oxygen is injected per tonne of furnace capacity lies with advantage between 0.5 and 1 m 3 O 2 per minute.
  • FIGS. 1 and 2 show:
  • FIG. 1 the variations with time of the electric power, of the quantity of molten metal and of the carbon concentration for a traditional charging method
  • FIG. 2 the variations with time of the electric power, of the quantity of molten metal and of the carbon concentration for a charging method according to the invention.
  • FIG. 3 the injection of the refining gas in the furnace.
  • the silicon concentration shows a behaviour essentially the same as that of the carbon concentration, except that the silicon oxidises before the carbon. As a result, after having reached the target value of the carbon concentration, the silicon is almost eliminated from the metal bath.
  • a start is first made with the same maximum rate of oxygen supply for both methods, a rate which is of the order of 4000 m 3 /h and which corresponds to a decarburising rate of 60 kg carbon/min.
  • the electric furnace is first run at maximum power to melt a certain quantity of steel scrap. After ten minutes, the electric arc is once again switched off, the furnace cover is removed and the charging with molten pig iron is carried out for 5 minutes. After the charging, the furnace cover is replaced and the arc is switched on again. It should be noted that, because of the time required to open and close the furnace cover, a 5 minute charge means that the furnace is shut down for approximately 10 minutes.
  • the mass of molten metal and the carbon concentration in the metal bath increase linearly because of the charging rate, and at the end of the charging, the carbon concentration reaches a value of 3% (the silicon concentration amounts of 0.4%). It is mainly because of these very high silicon and carbon concentrations that the rate of oxygen supply must be limited during the refining to one of 4000 m 3 /h. During this refining, which begins after the cover has been closed, the carbon concentration is reduced at a substantially linear rate to end up at a value of less than 0.1%.
  • the decarburisation lasts for 38 minutes in all. Because it begins only 20 minutes after the beginning of the melting cycle, the whole melting cycle lasts for 58 minutes.
  • the charging begins after 10 minutes and continues at a rate of 3 t/min, i.e. taking about 15 minutes.
  • the furnace remains powered so that the quantity of molten metal in the furnace increases not only because of the charging but also because of the simultaneous melting of the steel scrap. Consequently, the melting of the steel scrap ceases 10 minutes sooner than in the method of FIG. 1 .
  • the decarburisation which requires 38 minutes for the same rate of 4000 m 3 /h, begins a little after the beginning of charging before the carbon concentration in the metal bath exceeds a value of 1.5%. Beginning the charging in this way, earlier than in the method of FIG. 1, already enables the duration of the melting cycle to be reduced by more than 10%. If the maximum oxygen supply rate is now increased, which is possible without the risk of splashes because of the low carbon concentration in the metal bath, the decarburisation rate increases and the duration of a melting cycle is reduced still further. As a result, the method according to the invention enables the productivity of an electric furnace to be improved by at least 10%.
  • q pig iron ( t/min ) qO 2 ( m 3 /min )/43.
  • Such a method with early and optimised charging is represented by a broken line in FIG. 2 for a maximum oxygen supply rate of 5200 m 3 /h.
  • the charging in this case occurs at a rate of 2 t/min. It can be seen that the charging begins as soon as the cycle begins and that consequently the mass of molten metal increases linearly from the start.
  • the carbon concentration on the other hand, remains substantially constant during the whole charging and is less than 0.5%. This method makes it possible to increase productivity by 20% in comparison with traditional charging methods.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (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)
  • Vertical, Hearth, Or Arc Furnaces (AREA)
  • Carbon Steel Or Casting Steel Manufacturing (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
  • Silicon Compounds (AREA)
US09/968,830 1996-07-03 1997-06-10 Method for making steel in a liquid melt-fed electric furnace Expired - Fee Related USRE37897E1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US09/968,830 USRE37897E1 (en) 1996-07-03 1997-06-10 Method for making steel in a liquid melt-fed electric furnace

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
LU88785 1996-07-03
LU88785A LU88785A1 (fr) 1996-07-03 1996-07-03 Procédé de fabrication d'acier dans un four électrique avec enfournement de fonte liquide
US09/968,830 USRE37897E1 (en) 1996-07-03 1997-06-10 Method for making steel in a liquid melt-fed electric furnace
PCT/EP1997/003005 WO1998001588A1 (fr) 1996-07-03 1997-06-10 Procede de fabrication d'acier dans un four electrique avec enfournement de fonte liquide
US09/202,756 US6238452B1 (en) 1996-07-03 1997-06-10 Method for making steel in a liquid melt-fed electric furnace

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
US09/202,756 Reissue US6238452B1 (en) 1996-07-03 1997-06-10 Method for making steel in a liquid melt-fed electric furnace

Publications (1)

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USRE37897E1 true USRE37897E1 (en) 2002-11-05

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US09/968,830 Expired - Fee Related USRE37897E1 (en) 1996-07-03 1997-06-10 Method for making steel in a liquid melt-fed electric furnace
US09/202,756 Ceased US6238452B1 (en) 1996-07-03 1997-06-10 Method for making steel in a liquid melt-fed electric furnace

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Country Status (27)

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US (2) USRE37897E1 (es)
EP (1) EP0909334B1 (es)
JP (1) JP2001516397A (es)
CN (1) CN1069700C (es)
AR (1) AR013587A1 (es)
AT (1) ATE193332T1 (es)
AU (1) AU713175B2 (es)
BR (1) BR9710996A (es)
CA (1) CA2259522A1 (es)
CZ (1) CZ288467B6 (es)
DE (1) DE69702134T2 (es)
EA (1) EA001340B1 (es)
ES (1) ES2146472T3 (es)
GE (1) GEP20022842B (es)
GR (1) GR3033674T3 (es)
ID (1) ID17569A (es)
LU (1) LU88785A1 (es)
MY (1) MY126318A (es)
NO (1) NO990027L (es)
NZ (1) NZ333307A (es)
PL (1) PL185211B1 (es)
PT (1) PT909334E (es)
TR (1) TR199802334T2 (es)
TW (1) TW345596B (es)
UA (1) UA47487C2 (es)
WO (1) WO1998001588A1 (es)
ZA (1) ZA975512B (es)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20140318314A1 (en) * 2012-01-03 2014-10-30 Rebei Bel Fdhila Method For Melting Steel

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT410333B (de) * 2000-10-10 2003-03-25 Josef Martin Gmbh & Co Kg Anordnung zum auswechselbaren befestigen eines anbauteiles, z.b. einer baggerschaufel, an einem baggerausleger oder einem fahrzeug
US6693947B1 (en) 2002-09-25 2004-02-17 D. L. Schroeder & Associates Method to protect the anode bottoms in batch DC electric arc furnace steel production
DE102004040494C5 (de) * 2004-08-20 2012-10-11 Siemens Ag Verfahren und Vorrichtung zum Betrieb eines Elektrolichtbogenofens
CN104328243B (zh) * 2014-11-07 2016-02-17 达力普石油专用管有限公司 适量配碳大用电量控制用氧电弧炉炼钢法
CN112410505B (zh) * 2020-09-30 2022-06-14 盐城市联鑫钢铁有限公司 一种电炉高效低成本冶炼工艺

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2325597A1 (de) * 1973-05-19 1974-12-05 Rheinstahl Ag Verfahren zur erzeugung von fluessigem stahl aus einem sonderroheisen
US4090869A (en) * 1976-04-07 1978-05-23 Lucien Antoine Process of manufacturing alloy steels in a continuously charged arc furnace
EP0240485A1 (de) * 1986-03-17 1987-10-07 VOEST-ALPINE Industrieanlagenbau GmbH Anlage zur Herstellung von Stahl aus Schrott
EP0630977A1 (de) * 1993-06-21 1994-12-28 Voest-Alpine Industrieanlagenbau Gmbh Konverter zur Herstellung von Stahl
DE4434369A1 (de) * 1994-09-15 1996-03-21 Mannesmann Ag Verfahren und Vorrichtung zur Durchführung von metallurgischen Arbeiten von Eisenmetall
WO1996032505A1 (de) * 1995-04-10 1996-10-17 Voest-Alpine Industrieanlagenbau Gmbh Anlage und verfahren zum herstellen von eisenschmelzen nach dem mehrzonenschmelzverfahren

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2325597A1 (de) * 1973-05-19 1974-12-05 Rheinstahl Ag Verfahren zur erzeugung von fluessigem stahl aus einem sonderroheisen
US4090869A (en) * 1976-04-07 1978-05-23 Lucien Antoine Process of manufacturing alloy steels in a continuously charged arc furnace
EP0240485A1 (de) * 1986-03-17 1987-10-07 VOEST-ALPINE Industrieanlagenbau GmbH Anlage zur Herstellung von Stahl aus Schrott
EP0630977A1 (de) * 1993-06-21 1994-12-28 Voest-Alpine Industrieanlagenbau Gmbh Konverter zur Herstellung von Stahl
DE4434369A1 (de) * 1994-09-15 1996-03-21 Mannesmann Ag Verfahren und Vorrichtung zur Durchführung von metallurgischen Arbeiten von Eisenmetall
WO1996032505A1 (de) * 1995-04-10 1996-10-17 Voest-Alpine Industrieanlagenbau Gmbh Anlage und verfahren zum herstellen von eisenschmelzen nach dem mehrzonenschmelzverfahren

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
The Making, Shaping and Treating of Steel. United States Steel Corporation. 1964. p. 1112 (no month). *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20140318314A1 (en) * 2012-01-03 2014-10-30 Rebei Bel Fdhila Method For Melting Steel
US9045810B2 (en) * 2012-01-03 2015-06-02 Abb Research Ltd. Method for melting steel

Also Published As

Publication number Publication date
PL185211B1 (pl) 2003-04-30
EA199900064A1 (ru) 1999-06-24
ZA975512B (en) 1998-01-30
UA47487C2 (uk) 2002-07-15
JP2001516397A (ja) 2001-09-25
CZ288467B6 (en) 2001-06-13
TR199802334T2 (xx) 1999-02-22
GR3033674T3 (en) 2000-10-31
DE69702134D1 (de) 2000-06-29
LU88785A1 (fr) 1998-01-03
NO990027D0 (no) 1999-01-04
NZ333307A (en) 1999-11-29
TW345596B (en) 1998-11-21
US6238452B1 (en) 2001-05-29
CN1223694A (zh) 1999-07-21
EP0909334A1 (fr) 1999-04-21
CA2259522A1 (fr) 1998-01-15
CN1069700C (zh) 2001-08-15
AU3174697A (en) 1998-02-02
AR013587A1 (es) 2001-01-10
ATE193332T1 (de) 2000-06-15
BR9710996A (pt) 2000-03-14
GEP20022842B (en) 2002-11-25
MY126318A (en) 2006-09-29
PT909334E (pt) 2000-10-31
ES2146472T3 (es) 2000-08-01
EA001340B1 (ru) 2001-02-26
WO1998001588A1 (fr) 1998-01-15
PL330956A1 (en) 1999-06-21
DE69702134T2 (de) 2000-11-09
EP0909334B1 (fr) 2000-05-24
ID17569A (id) 1998-01-08
NO990027L (no) 1999-01-04
AU713175B2 (en) 1999-11-25
CZ435998A3 (cs) 1999-09-15

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