CN102719593B - Method for smelting ultra-low carbon steel - Google Patents

Method for smelting ultra-low carbon steel Download PDF

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CN102719593B
CN102719593B CN201110077865.4A CN201110077865A CN102719593B CN 102719593 B CN102719593 B CN 102719593B CN 201110077865 A CN201110077865 A CN 201110077865A CN 102719593 B CN102719593 B CN 102719593B
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steel
content
molten iron
carbon
tapping
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CN102719593A (en
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赵成林
李广帮
廖相巍
张维维
王丽娟
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Angang Steel Co Ltd
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Angang Steel Co Ltd
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    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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Abstract

The invention provides a method for melting ultra-low carbon steel. The method adopts a desulfuration of molten iron-converter-RH-continuous casting process, wherein a sulfur content in the molten iron is 0.002%-0.006% after desulphurization; converter smelting controls oxygen blowing time, an oxygen gun flow, a bottom-blowing intensity and a smelting period, adopts slag-stopping tapping, steel tapping with a content of C being 0.06%-0.08% and with a temperature of 1650-1680 DEG C, and an oxygen content in the molten iron is 0.03%-0.05%; an RH adopts forced decarburization with a highest vacuum degree of 67-100 MPa and decarburization time of 15-27 min, and a carbon content in the molten iron is 0.0010%-0.0020% and a dissolved oxygen content in the molten iron is 0.025%-0.040% after the decarburization; the molten iron is recycled for 3-5 min after deoxidation by adding aluminium and recycled for another 3-5 min after adding other alloys; a nitrogen content in the molten iron is 0.0015%-0.0035%, and the temperature is 1590-1640 DEG C; and killed steel treatment is carried out for 10-30 min. The method adopts converter tapping with a high carbon and low oxygen content, can use less or not use slag modified agents during the tapping process, accelerates the production rhythm, makes the molten steel cleaner, and reduces the production cost.

Description

A kind of method of smelting suprelow carbon steel
Technical field
The invention belongs to steelmaking technical field, relate to a kind of method of smelting suprelow carbon steel, especially when smelting suprelow carbon steel, molten steel carbon, oxygen level, liquid steel temperature, Cleanliness of Molten Steel are realized to the stable method of controlling.
Background technology
Ultra low-carbon steel refers in steel that carbon content is at the steel grade below 0.010%.Ultra low-carbon steel is smelted at present two kinds of common process: a kind of is bessemerize-RH vacuum-treat-continuous casting process, the difficult point of this technique maximum is that Cleanliness of Molten Steel is controlled, because molten steel in tapping process of converter dissolved oxygen content is higher, slag oxidation is stronger, and that converter slag enters ladle is inevitable, therefore in RH vacuum-treat process, the top slag with higher oxygen voltinism will continue oxidation to molten steel, cause oxide inclusion in molten steel to increase, simultaneously in casting cycle, this hyperoxia voltinism top slag also can flow in tundish with molten steel, continuation is oxidized molten steel, final oxide inclusion on the one hand can cause molten steel mouth of a river in casting cycle to hold stream, affecting ultra low-carbon steel normally produces, make on the other hand Molten Steel Cleanliness reduce, affect the surface quality of cold-reduced sheet.Another kind is bessemerize-LF refining-RH vacuum-treat-continuous casting process, this technique is carried out deoxidation slag making operation at LF, in RH vacuum-treat, adopts and forces oxygen decarburization to control the carbon content in steel, and this operational path is complicated, production cost is higher, can cause the serious waste of resource simultaneously.
Chinese patent 200710159224.7 discloses a kind of smelting process of ultra low-carbon steel, its smelting technology is: molten iron pretreatment desulfurizing-bessemerizing-LF refining-RH vacuum-treat-continuous casting, especially before RH vacuum decarburization, through LF, molten steel top slag is carried out to modification, make iron oxide content≤2% in the slag of molten steel top.This patent Introduction belong to the second common process, can cause the serious waste of resource.
Chinese patent 200910084426.9 discloses a kind of method of smelting suprelow carbon steel, its smelting technology is: molten iron pretreatment desulfurizing-bessemerizing-ladle furnace processing-RH vacuum-treat-continuous casting, control converter tapping [C]=0.04%-0.05%, tapping temperature 1700-1720 ℃, tapping molten steel oxygen activity 600ppm-900ppm, the not deoxidation of tapping adopts pushing off the slag operation, LF ladle furnace is processed top slag is carried out to upgrading, go out LF liquid steel temperature at 1640-1650 ℃, in RH vacuum-treat process, adopt nature decarburization pattern to control carbon content of molten steel, carbon in steel can be controlled to 0.0014%-0.0025%.By the technique of its introduction, in the slag upgrading process of LF top, molten steel dissolved oxygen content will reduce, and still adopts nature decarburization that carbon in molten steel is taken off to being less than 0.0030% difficulty very big at RH.
What application was more at present is the-kind of common process, and especially the modifying process of hyperoxia voltinism slag receives publicity, and Chinese patent 200810013374.1, Chinese patent 200710158736.1, Chinese patent 200510094825.5 all disclose the technology of this respect.But all technology of this respect all exist a problem at present, will cause the reduction of molten steel dissolved oxygen when reducing slag oxidation, this is unfavorable for follow-up RH vacuum decarburization processing.
Summary of the invention
The object of the invention is to solve the existing defect of above-mentioned prior art, provide a kind of and can improve Molten Steel Cleanliness, reduce production costs, can improve again the method for the smelting suprelow carbon steel of molten steel composition control accuracy.
The operational path that the present invention adopts is: molten iron pretreatment desulfurizing-converter smelting-RH vacuum refinement-sheet billet continuous casting.Process parameter control in each operation is as follows:
(1) molten iron pretreatment desulfurizing: adopt the desulfurization of blowing magnesium powder+lime powder, the operation of skimming after desulfurization, guarantees to skim effect, and the sulphur content in desulfurized molten iron is 0.002%~0.006% (weight percent).
(2) converter smelting: be blended into molten iron after packing steel scrap into converter, converter smelting oxygen blow duration is controlled at 10~17min, and oxygen gun blowing flow control is at 160~240m 3/ ht, bottom blowing intensity control is at 0.01~0.1m 3/ tmin; Slag material be take lime and light dolomite as main, and in lime, sulphur content requires≤0.03% (weight percent); Converter smelting periodic Control, at 30~42min, is carried out decarburization, dephosphorization, intensification and the operation of removal detrimental impurity to molten steel.Converter tapping [C]=0.06%-0.08% (weight percent), tapping temperature T=1650 ℃~1680 ℃, tapping Oxygen Content in Liquid Steel 0.03%~0.05% (weight percent).The not deoxidation of tapping, employing pushing off the slag operation, as the Oxygen Content in Liquid Steel of tapping is greater than 0.04% (weight percent), tapping process adds the agent of 0.5kg~1.0kg slag modification according to molten steel per ton, modification agent composition is: the quality percentage composition of Al is 35%~45%, the quality percentage composition of CaO is 15%~25%, SiO 2quality percentage composition≤10%.
(3) RH vacuum refinement: adopt and force decarburization pattern to be controlled carbon content in molten steel, carry out chemical heating simultaneously.RH maximum vacuum is controlled at 67~100Pa, and lift gas flow is 0.4~0.6m 3/ ht, decarburization time is controlled at 20~27min, after decarburization finishes, the carbon in molten steel is controlled to 0.0010%~0.0020% (weight percent), and dissolved oxygen content is 0.025%~0.040% (weight percent).Adopt aluminium deoxidation, add molten steel circulation 3~5min after aluminium, after this carry out alloying operation, add molten steel circulation 3~5min after alloy, to guarantee that alloy fully dissolves and Al 2o 3the removal of inclusion.It is 0.0015%~0.0035% (weight percent) that RH processing finishes molten steel nitrogen content, and liquid steel temperature is 1590~1610 ℃.Vacuum finishes molten steel is carried out to calmness to process, calm time 10~30min afterwards.
(4) sheet billet continuous casting: adopt carbon-free covering agent, carbon-less protecting slag in casting cycle, prevent casting cycle carburetting, casting process adopts full guard casting, reduces molten steel nitrogen pick-up; Casting cycle is rationally controlled pulling rate according to slab section.
The present invention adopts converter high-carbon, hypoxemia tapping, and carbon content is 0.06%~0.08%, and tapping oxygen level is 0.03%~0.05%.With common process tapping [C]=0.03%-0.05%, tapping oxygen level is 0.06%~0.10% to compare, and carbon content of molten steel increases, and oxygen level reduces, and can produce following beneficial effect thus:
(1) tapping temperature reduces.Reduce tapping temperature and be conducive to reduce the erosion to resistance to material, be conducive to faster production rhythm, reduce production costs.
(2) converter finishing slag oxidisability reduces.The present invention is transferred to RH by the decarburization task in molten steel low-carbon (LC) region by converter, when carbon content of molten steel is less than 0.1%, if continue decarburization in converter, will cause slag to be oxidized in a large number, and also will carry out modifying process to hyperoxia voltinism slag in tapping process, upgrading process molten steel also will be by part deoxidation, for molten steel and slag, the contradiction that all has initial oxidation-rear reduction, had both increased production cost, can bring impact to Cleanliness of Molten Steel again.Therefore, converter tapping process of the present invention can use less or without slag modification agent, meanwhile, the carbon rejection process in RH can not be oxidized top slag, though therefore slightly increased the decarburization task of RH, reduced generally production cost, and molten steel is cleaner.
Embodiment
The present invention is further described by the following embodiment.
Embodiment 1:
Smelting ultralow-carbon IF steel, the operational path of employing is: bessemerize-RH of molten iron pretreatment desulfurizing-260t vacuum refinement-sheet billet continuous casting.
Molten iron pretreatment desulfurizing: adopt the desulfurization of blowing magnesium powder+lime powder, the operation of skimming after desulfurization, guarantees to skim effect, and the sulphur content in desulfurized molten iron is 0.0030%.
Converter smelting: be blended into molten iron after packing steel scrap into converter, converter smelting oxygen blow duration is controlled at 13min, and oxygen gun blowing flow control is at 40000~59000m 3/ h, front 1~9min bottom blowing intensity control is at 7~8m 3/ min, blowing 9min after to blow end point bottom blowing intensity control at 8~12m 3/ min; Control converter and enter the slag making materials quality such as hearthstone ash, light dolomite, activity of lime>=300ml, quality percentage composition≤0.015% of sulphur in lime, meets rapid slagging and dephosphorization requirement.Converter tapping [C]=0.08%, tapping temperature T=1660 ℃, tapping Oxygen Content in Liquid Steel 0.035%.The not deoxidation of tapping, adopts pushing off the slag operation, and finishing slag FeO content is 12.3%.The converter smelting cycle is 39min.
RH vacuum refinement: vacuum refinement adopts forces decarburization pattern to be controlled carbon content in molten steel, and in decarburization endpoint molten steel, carbon content is 0.0018%, decarburization time 25min, RH maximum vacuum 67Pa, lift gas flow is 100~150m 3/ h, decarburization endpoint molten steel oxygen level is 0.0310%.After decarburization finishes, add aluminium deoxidation, add other alloy recirculation 3min after adding aluminium circulation 4min, it is 1603 ℃ that processing finishes rear liquid steel temperature, and RH treatment cycle is 35min.Vacuum finishes rear molten steel to be carried out to calmness, calm time 15min.
Sheet billet continuous casting: adopt carbon-free covering agent, carbon-less protecting slag in casting cycle, prevent casting cycle carburetting, carbon increasing amount is 0.0002%, casting process adopts full guard casting, reduces molten steel nitrogen pick-up, and nitrogen increased amount is 0.0001%.
As follows through this technique finished product principal element Composition Control: (by weight percentage: %)
??C ??P ??S ??N ??T[O]
??0.0020 ??0.008 ??0.007 ??0.0032 ??0.0017
Embodiment 2:
Smelting ultralow-carbon IF steel, the operational path of employing is: bessemerize-RH of molten iron pretreatment desulfurizing-260t vacuum refinement-sheet billet continuous casting.
Molten iron pretreatment desulfurizing: adopt the desulfurization of blowing magnesium powder+lime powder, the operation of skimming after desulfurization, the sulphur content in desulfurized molten iron is 0.0026%.
Converter smelting: be blended into molten iron after packing steel scrap into converter, converter smelting oxygen blow duration is controlled at 13min, and oxygen gun blowing flow control is at 40000~59000m 3/ h, front 1-9min bottom blowing intensity control is at 7~8m 3/ min, blowing 9min after to blow end point bottom blowing intensity control at 8~12m 3/ min; Control converter and enter the slag making materials quality such as hearthstone ash, light dolomite, activity of lime>=300ml, quality percentage composition≤0.015% of sulphur in lime, meets rapid slagging and dephosphorization requirement.Converter tapping [C]=0.06%, tapping temperature T=1678 ℃, tapping Oxygen Content in Liquid Steel 0.047%.Tapping adopts pushing off the slag operation, adds 150kg modification agent to carry out modifying process to slag after tapping, and modification agent composition is: the quality percentage composition that the quality percentage composition of Al is 35%~45%, CaO is 15%~25%, SiO 2quality percentage composition≤10%.After upgrading, finishing slag FeO content is 10.5%.The converter smelting cycle is 40min.
RH vacuum refinement: vacuum refinement adopts forces decarburization pattern to be controlled carbon content in molten steel, and in decarburization endpoint molten steel, carbon content is 0.0015%, decarburization time 21min, RH maximum vacuum 67Pa, lift gas flow is 100~150m 3/ h, decarburization endpoint molten steel oxygen level is 0.0290%.After decarburization finishes, add aluminium deoxidation, add other alloy recirculation 3min after adding aluminium circulation 4min, it is 1605 ℃ that processing finishes rear liquid steel temperature, and RH treatment cycle is 31min.Vacuum finishes rear molten steel to be carried out to calmness, calm time 15min.
Sheet billet continuous casting: adopt carbon-free covering agent, carbon-less protecting slag in casting cycle, prevent casting cycle carburetting, carbon increasing amount is 0.0003%, casting process adopts full guard casting, reduces molten steel nitrogen pick-up, and nitrogen increased amount is 0.0001%.
As follows through this technique finished product principal element Composition Control: (by weight percentage: %)
????C ????P ????S ????N ????T[O]
????0.0018 ????0.008 ????0.007 ????0.0030 ????0.0019

Claims (4)

1. a method for smelting suprelow carbon steel, adopts molten iron pretreatment desulfurizing-converter smelting-RH vacuum refinement-sheet billet continuous casting technique, it is characterized in that in desulfurized molten iron, sulphur content is 0.002%~0.006%; Described converter smelting oxygen blow duration is 10~17min, and oxygen gun blowing flow is 160~240m 3/ ht, bottom blowing intensity is 0.01~0.1m 3/ tmin, smelting cycle 30~42min, tapping [C]=0.06%~0.08%, temperature T=1650~1680 ℃, Oxygen Content in Liquid Steel is 0.03%~0.05%, adopts pushing off the slag tapping; Described RH vacuum refinement adopts forces decarburization, and maximum vacuum is 67~100Pa, and lift gas flow is 0.4~0.6m 3/ ht, decarburization time is 15~27min, and decarburization finishes that in molten steel, carbon content control is 0.0010%~0.0020%, and dissolved oxygen content is 0.025%~0.040%; Adopt aluminium deoxidation, add molten steel circulation 3~5min after aluminium, alloying then, adds molten steel circulation 3~5min after alloy, and after RH processes, molten steel nitrogen content is 0.0015%~0.0035%, and temperature is 1590~1610 ℃, the calmer 10~30min that processes; Above per-cent is all weight percentage; Described sheet billet continuous casting process adopts carbon-free covering agent, carbon-less protecting slag and whole process protection casting.
2. the method for smelting suprelow carbon steel according to claim 1, is characterized in that described molten iron pretreatment desulfurizing adopts blowing magnesium powder+lime powder, the operation of skimming after desulfurization.
3. the method for smelting suprelow carbon steel according to claim 1, is characterized in that described converter smelting slag material take lime and light dolomite as main, sulphur weight percent content≤0.03% in lime; Converter tapping process adds slag modification agent depending on Oxygen Content in Liquid Steel.
4. the method for smelting suprelow carbon steel according to claim 1, carries out chemical heating while it is characterized in that described RH vacuum refinement.
CN201110077865.4A 2011-03-29 2011-03-29 Method for smelting ultra-low carbon steel Active CN102719593B (en)

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