US20110167960A1 - Flux for refining steel of low nitrogen, low oxygen and low sulfur - Google Patents

Flux for refining steel of low nitrogen, low oxygen and low sulfur Download PDF

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Publication number
US20110167960A1
US20110167960A1 US12/311,330 US31133007A US2011167960A1 US 20110167960 A1 US20110167960 A1 US 20110167960A1 US 31133007 A US31133007 A US 31133007A US 2011167960 A1 US2011167960 A1 US 2011167960A1
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US
United States
Prior art keywords
flux
mgo
cao
steel
refining
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Abandoned
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US12/311,330
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English (en)
Inventor
Shiro Ban-Ya
Yoko Ban-Ya
Mitsutaka Hind
Hiroyasu Ito
Syuhei Takeda
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Yohizawa Lime Ind Co Ltd
Yoshizawa Lime Industry Co Ltd
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Yohizawa Lime Ind Co Ltd
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Filing date
Publication date
Priority claimed from JP2006346771A external-priority patent/JP4079190B2/ja
Application filed by Yohizawa Lime Ind Co Ltd filed Critical Yohizawa Lime Ind Co Ltd
Assigned to YOSHIZAWA LIME INDUSTRY CO., LTD. reassignment YOSHIZAWA LIME INDUSTRY CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BAN-YA, SHIRO, HINO, MITSUTAKA, TAKEDA, SHUHEI, ITO, HIROYASU
Publication of US20110167960A1 publication Critical patent/US20110167960A1/en
Abandoned legal-status Critical Current

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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
    • 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
    • C21C7/076—Use of slags or fluxes as treating agents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
    • 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
    • C21C7/06—Deoxidising, e.g. killing
    • 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
    • C21C7/064—Dephosphorising; Desulfurising
    • C21C7/0645—Agents used for 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
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/10—Handling in a vacuum
    • 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
    • C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
    • C21C2007/0062—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires with introduction of alloying or treating agents under a compacted form different from a wire, e.g. briquette, pellet
    • 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 concerns a novel flux for refining steel of low nitrogen, low oxygen and low sulfur, and a process for making the high purity steel by using this flux.
  • the flux consists of the main components, CaO: 40-70% (weight percent), Al 2 O 3 : 10-30% and CaF 2 : 10-30%, and additional components, MgO: 0.5-5%, SiO 2 : 0.5-5% and CaF 2 : 1-5%, and the mixture is sintered before use (Japanese Patent Disclosure No. 60-36610).
  • CaF 2 one of the flux components, is added of course for lowering the melting point. Due to consideration on the effect to the environment, it is current tendency to avoid use of CaF 2 , if possible, and another flux of CaO—Al 2 O 3 base containing no CaF 2 is known as a low-melting point desulfurization flux.
  • fluxes of the compositions containing MgO of 5-20% have been used to prevent damaging of the refractory caused by erosion or dissolution of MgO-component out of MgO-based refractory such as magnesia-carbon bricks so that the resulting progress in damaging of the refractory may be avoided.
  • the flux for denitrification there has been proposed to use a flux consisting of CaO: 30-70%, Al 2 O 3 : 70-30% and CaC 2 : 1-25% (Japanese Patent Disclosure No. 9-165615).
  • CaC 2 takes the role of a deoxidizing agent.
  • This flux is used in such the manner that, after covering the surface of the molten steel with slag, the flux is charged into the refining vessel at the same time of blowing oxidizing gas to the surface of the covering slag.
  • Al of 2-20% is added to the denitrification flux to enhance the deoxidizing effect.
  • the object of the present invention is to provide a steelmaking flux which enables, by choosing suitable components of the flux for refining, production of extremely pure steel containing very little amounts of oxygen, nitrogen and sulfur without using CaF 2 .
  • To provide the process for producing the extremely pure steel is also the object of the invention.
  • the flux according to the present invention is the flux for producing low-nitrogen, low-oxygen and low-sulfur steel consisting of, by weight, CaO: 30-57%, Al 2 O 3 : 35-64% and MgO: 5-17%, and having a composition in the region defined by the points A to E of Table 1 below in the MgO—CaO—Al 2 O 3 diagram of FIG. 1 , in which the activity of alumina is 10 ⁇ 2 or less.
  • FIG. 1 is a MgO—CaO—Al 2 O 3 diagram showing the range of the composition of the flux for refining according to the present invention
  • FIG. 2 is a MgO—CaO—Al 2 O 3 diagram showing the range of the preferable composition of the flux for refining according to the present invention
  • FIG. 3 is a graph made by inserting iso-activity lines of alumina (1873K) into the MgO—CaO—Al 2 O 3 diagram;
  • FIG. 4 is a graph made by inserting iso ⁇ Cs (sulfide capacity) lines (1873K) into the MgO—CaO—Al 2 O 3 diagram;
  • FIG. 5 is a graph made by inserting iso ⁇ Ls (sulfur distribution ratio) lines (1873K) into the MgO—CaO—Al 2 O 3 diagram;
  • FIG. 6 is a graph showing the results of denitrification according to the conventional technology.
  • alumina activity is 10 ⁇ 2 or less in the area which is left-above of the line starting from point A extending to the left-lower part of the Figure.
  • a refining flux should have a melting point lower than the refining temperature, approximately 1600° C.
  • the preferable flux composition will be in the area of the pentangle formed by the lines connecting points A to E, compositions in which are defined in Table 1 above.
  • the concentrations at the points A to E in mass basis corresponding to the molar basis concentrations shown in Table 1 are as shown in Table 1.2 below.
  • FIG. 2 illustrates the alumina activities in the MgO—CaO—Al 2 O 3 system shown in FIG. 1 with iso-activity lines.
  • alumina activity is 10 ⁇ 5 at the line connecting point B and point C′, and the area left-over to the line has flux compositions preferable for the object of the present invention.
  • the synthetic flux having the compositions in the area shown by hatching in FIG. 2 and defined by the points B, C and D′ as in Table 2, in which the alumina activity is 10 ⁇ 5 or less, is preferable.
  • the composition around the point C is the most preferable.
  • compositions at the points in mass basis are shown in Table 2.2 below:
  • FIG. 3 shows the results of determining the activity of alumina, aAl 2 O 3 , in MgO—CaO—Al 2 O 3 system carried out by Ban'ya et al. (S. Ban'ya, UHPM-94, p. 390).
  • the graph illustrates the iso-activity lines of alumina in the molten slag zone at 1873K.
  • aAl 2 O becomes the minimum value around the MgO—CaO saturation zone.
  • Even in the zone where the alumina activity is less than 10 ⁇ 2 around the MgO—Al 2 O 2 saturation zone it is possible that spinel type non-metallic inclusion (MgO.Al 2 O 3 ) is formed. Therefore, it is preferable to choose a flux composition around the MgO—CaO saturation zone.
  • Sulfide capacity [Cs] which is a measure of desulfurizability of the molten steel is defined as formula (6) based on formula (5). If this value is large, then the desulfurization ability of the flux will be high.
  • FIG. 4 illustrates iso-Cs lines of MgO—CaO—Al 2 O 3 system at 1873K. According to this, like the deoxidation equilibrium mentioned above, the value of Cs will be maximum around the MgO—CaO saturation zone.
  • V volume of the molten steel (cm 3 )
  • FIG. 6 compares the nitrogen contents in the molten steel before and after the vacuum degassing, which have been realized in the conventional technology (Japan Iron and Steel Association ed. “ Handbook of Iron and Steel II, Production of Pig Iron/Steel” , p. 675, 1981). According to the graph the rate of denitrification achievable by vacuum degassing such as DH-degassing and RH-degassing is 25% at highest, and the content of nitrogen after the degassing is limited to 20 ppm at lowest. The present invention broke through this limitation.
  • the flux for refining according to the invention may be conveniently used if it is prepared in certain compositions and processed into pellets or briquettes of sizes of 5-20 mm.
  • the refining is carried out with consideration of such initial formulation of the flux materials may give desired composition of the flux at the later period of refining taking into account anticipated increase of Al 2 O 3 resulting from oxidation of Al in the refining flux.
  • the refining of steel using the flux according to the invention can be practiced both in converters and electric furnaces including ladle furnaces (LF).
  • the latter period of the refining may be carried out under reducing conditions with blowing of Ar gas from the bottom of the vessel.
  • the refining can be combined with VOD-process for production of stainless steel. Needless to say, the refining can be applied to top-blowing converter operation.
  • LVD-process and REDA-process may be combined with the present refining.
  • These degassing processes need treatment for a long period of time, and therefore, temperature of the molted steel may decrease during the refining.
  • ASEA-SKF process VAD-process or refining in LF under vacuum or Ar-bubbling are recommended.
  • the refining of steel using the present flux makes it possible to produce steel containing impurities in the amounts remarkably smaller than the limits achieved in the conventional steelmaking technologies.
  • the limits in the conventional technologies were 10-15 ppm as to oxygen and 100 ppm as to sulfur, which are broken through by the present invention. More specifically, it is possible to realize such low contents of oxygen of 5 ppm or less and sulfur of 60 ppm or less.
  • Nitrogen content is usually 60-80 ppm, which may be further reduced by combination with vacuum degassing to 40 ppm or less, and under preferable operating conditions, 20 ppm or less.
  • the present flux due to MgO component therein, contributes to prevention of damage of MgO-based refractory. Since no fluoride such as CaF 2 is contained, at disposal or reuse of the used flux, different from the conventional flux containing a fluoride, it is not necessary to take a measure to leaching out of fluorine compound and the used flux can be directly used as a roadbed material or a soil-improving agent.
  • Scrap iron was melted in an electric furnace of capacity 130 tons.
  • the molten iron was poured into an LF (ladle furnace) and refined at a temperature of 1600° C. or higher for 40-60 minutes to give composition of a steel for machine structural use.
  • the molten steel was degassed in an RH-degassing equipment over 30 minutes.
  • Fluxes of various compositions according to the present invention were prepared by formulating [quick lime+dolomite+aluminum ash briquettes (almond ⁇ shaped)] and used for the LF refining. Addition amount of the fluxes was 1.6 ton per 130 ton of the molten steel.
  • the Sulfur Distribution Ratios, (S)/[S] are stably of a value near 400. Even in the cases of using the conventional flux, approximately the same values were obtained. This is, however, because the fluxes used contained fluorite as a component. It was experienced that, if a flux containing no fluorite was used, it was difficult to achieve such stable values.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
US12/311,330 2006-12-22 2007-12-21 Flux for refining steel of low nitrogen, low oxygen and low sulfur Abandoned US20110167960A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2006346771A JP4079190B2 (ja) 2005-12-27 2006-12-22 低窒素、低酸素および低イオウの鋼を製錬するためのフラックス
JP2006-346771 2006-12-22
PCT/JP2007/074762 WO2008081763A1 (ja) 2006-12-22 2007-12-21 低窒素、低酸素および低イオウの鋼を製錬するためのフラックス

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US (1) US20110167960A1 (zh)
EP (1) EP2045338A4 (zh)
KR (1) KR20090101407A (zh)
CN (1) CN101365811A (zh)
BR (1) BRPI0717139A2 (zh)
RU (1) RU2008126116A (zh)
TW (1) TW200927946A (zh)
WO (1) WO2008081763A1 (zh)

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CN103443298B (zh) * 2011-03-31 2015-09-09 新日铁住金株式会社 环保钢水脱硫熔剂
TWI510635B (zh) * 2012-11-07 2015-12-01 China Steel Corp 低氮鋼液之製造方法

Citations (1)

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Publication number Priority date Publication date Assignee Title
JPH01210196A (ja) * 1988-02-16 1989-08-23 Nippon Steel Corp サブマージアーク溶接用溶融型フラックスの製造方法

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DE2000735A1 (de) * 1970-01-08 1971-07-22 Continentale Erz Gmbh Durch Sintern hergestellte,vorgebildete Schlacken fuer die Stahlerzeugung
US4417924A (en) * 1982-09-30 1983-11-29 Schwer John W Steelmaking additive composition
JPS6036610A (ja) 1983-08-05 1985-02-25 Ube Ind Ltd 溶鉄精錬用フラツクスの製造方法
JPS60133956A (ja) * 1983-12-23 1985-07-17 Toshin Seikou Kk アルミニウムキルド鋼の鋳造方法
US4795491A (en) * 1987-04-13 1989-01-03 Quigley Joseph R Premelted synthetic slag for ladle desulfurizing molten steel
US5106412A (en) * 1991-05-02 1992-04-21 Usx Corporation Method for providing steel with lowered hydrogen level after ladle treatment
JPH08143940A (ja) * 1994-11-17 1996-06-04 Sumitomo Metal Ind Ltd 鋼中介在物形態の制御方法
JPH09165615A (ja) 1995-12-14 1997-06-24 Kawasaki Steel Corp 溶融金属の脱窒方法
JP3896709B2 (ja) * 1998-10-30 2007-03-22 Ｊｆｅスチール株式会社 高清浄度鋼の溶製方法
JP3978355B2 (ja) 2002-03-13 2007-09-19 Ｊｆｅスチール株式会社 溶銑の脱硫剤および脱硫方法
JP2004204307A (ja) * 2002-12-25 2004-07-22 Nippon Steel Corp 溶鋼の脱硫剤
JP2005179762A (ja) * 2003-12-22 2005-07-07 Kobe Steel Ltd 極低硫鋼の製造方法
JP4079190B2 (ja) * 2005-12-27 2008-04-23 吉澤石灰工業株式会社 低窒素、低酸素および低イオウの鋼を製錬するためのフラックス

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01210196A (ja) * 1988-02-16 1989-08-23 Nippon Steel Corp サブマージアーク溶接用溶融型フラックスの製造方法

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Title
Machine translation of JP 2000129336, 2000. *

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CN101365811A (zh) 2009-02-11
EP2045338A4 (en) 2010-07-21
TW200927946A (en) 2009-07-01
KR20090101407A (ko) 2009-09-28
RU2008126116A (ru) 2010-01-10
BRPI0717139A2 (pt) 2013-11-12
WO2008081763A1 (ja) 2008-07-10
EP2045338A1 (en) 2009-04-08

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