CN102134629B - Smelting method for low-silicon ultralow-sulphur steel - Google Patents
Smelting method for low-silicon ultralow-sulphur steel Download PDFInfo
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Abstract
A smelting method for a low-silicon ultralow-sulphur steel belongs to the metallurgy technical field. The smelting process for producing low-silicon ultralow-sulphur steel comprises: molten iron 'complete-three-removal' pretreatment, decarburization converter smelting, and LF refining process. In order to ensure that silicon increase in molten steel during deep desulphurization is prevented, the sulphur content in molten steel for refining pull-in is firstly decreased by KR molten iron desulphurization pretreatment, and the pressure for LF deep desulphurization is reduced; then the silicon content in molten iron in a decarburization converter is decreased by desilication pretreatment in a dephosphorization converter to ensure the alkalinity of the slag in the decarburization converter is more than 4.0. The advantages are that the problem of the easy increase of silicon during the LF refining desulphurization process in the prior art is solved; the refining time is shortened; and the production efficiency is improved.
Description
Technical field
The invention belongs to metallurgical technology field, the smelting process of particularly a kind of low silicon, ultralow-sulfur steel takes molten iron " complete three take off " pre-treatment-decarburization converter smelting-LF refinery practice production to hang down the smelting technology of silicon, ultralow-sulfur steel.
Background technology
Present domestic and international most steelworks, the desiliconization of molten iron, dephosphorization all carry out with decarburization in conventional converter simultaneously, and this just makes into the molten iron silicon content of converter higher, so the SiO in the slag
2Content is also higher relatively, and in addition, owing to consider excessive splash or the excessive slag of being easy to generate of the quantity of slag, conventional converter slag charge add-on can not be too big, so the slag dual alkalinity is lower, generally is controlled at 3.0-4.0.And the SiO in the refining slag
2The overwhelming majority derives from slag under the converter tapping, therefore causes the SiO in the refining slag
2Content is also higher.LF refining desulfuration process need is taken off the oxidisability in the slag with aluminium, at SiO
2Under the content condition with higher, meeting of part aluminium and SiO
2Reaction, it is comparatively serious to make that molten steel increases silicon.
It also is a kind of more common technology that converter tapping adds the ferro-aluminum deoxidation; But the purpose of deoxidation mainly is the yield in order to guarantee that alloy is stable; Improve the molten steel purity and shorten refining time etc., generally all only need to guarantee the effect of deoxidation, and do not do specific requirement for the aluminium content in the steel; Perhaps aluminium content require relatively lowly, generally all be lower than 0.03%.
The LF refining desulfuration also is more common a kind of dark desulfurizing and refining technology; What but most of steel mill adopted is conventional slag deoxidization technique; Promptly on the top of the slag, add the aluminum shot deoxidation; The deoxidation rapid speed of slag like this, but cause instantaneous or local top of the slag aluminium content higher easily simultaneously, cause the SiO in the slag easily
2By aluminium reducing, thereby cause that molten steel increases silicon.
Summary of the invention
The object of the present invention is to provide the smelting process of a kind of low silicon, ultralow-sulfur steel; Solved that LF refining desulfuration process increases the silicon problem easily in the prior art; The present invention is reasonable in design, can realize more stable production, and reinforced equal time arrangement is reasonable; Can shorten refining time, enhance productivity.
Low silicon according to the invention, ultralow-sulfur steel are according to mass percent [Si]≤0.03%, [S]≤0.003%.
The present invention takes molten iron " complete three take off " pre-treatment-decarburization converter smelting-LF refinery practice production to hang down the smelting technology of silicon, ultralow-sulfur steel.For guaranteeing under the situation of dark desulfurization, to prevent that molten steel from increasing silicon, at first reduce the refining sulphur content in the molten steel that enters the station through the pre-treatment of KR desulfurizing iron, alleviate the pressure of the dark desulfurization of LF; Through the desiliconization pre-treatment of dephosphorization converter, reduce the silicone content of going into decarburization converter molten iron then, thereby guarantee decarburization converter slag basicity＞4.0, the following technical parameter of control in process step:
(1) adopt KR to carry out molten iron pretreatment desulfurizing, processing finishes [S]≤0.003%, molten iron rate＞95% of skimming;
(2) desiliconization, dephosphorization are carried out in the dephosphorization converter, smelt and finish [Si]≤0.01%;
(3) molten iron gets into the decarburization converter, and lime adding amount is a 18-25Kg/ ton steel, and the slag dual alkalinity is at 4.0-5.0;
(4) the decarburization converter tapping adds ferro-aluminum deoxidation operation, makes that acid-soluble aluminum content reaches 0.03～0.05% in the molten steel after the tapping;
(5) LF enters the station the back according to sampling analysis molten steel composition behind the decarburization converter stove, and according to target acid-soluble aluminum content 0.05% adds the operation of ferro-aluminum accent aluminium, and argon bottom-blowing stirs then, takes off the oxygen in the slag with the dissolved aluminum in the steel, realizes that all iron content is less than 0.5% in the slag.
Decarburization converter tapping step: when tap 1/5, add granule lime and fluorite, the add-on of granule lime is a 2.5-2.8Kg/ ton steel, and the add-on of fluorite is a 0.5-0.8Kg/ ton steel.
The LF refinement step: according to the slag making effect of LF refining process, an amount of (add-on of granule lime is steel 4.0-8.0Kg per ton, and the add-on of fluorite is steel 1.0-2.0Kg per ton) adds granule lime and fluorite, and the proportioning of granule lime and fluorite is 4: 1.
Two-way argon gas, every road bottom blowing flow 600-800NL/min are adopted in the stage bottom blowing of LF refining desulfuration.
The present invention further specifies as follows:
Dephosphorization converter desiliconization pre-treatment: the dephosphorization converter is in converting process; Silicon in the molten iron, manganese preferential oxidation; Therefore the silicon in the molten iron is almost oxidized fully after the dephosphorization stove is smelted; Silicone content after the smelting is guaranteed to reach below 0.01%, thereby has reduced the silicone content of going into decarburization converter molten iron, guarantees that decarburization stove slag has higher basicity.
The decarburization converter smelting: decarburization converter molten iron silicon content is lower owing to going into, and converter slag basicity can reach more than 4.0, because SiO in the refining slag
2Main source be slag under the converter, therefore, can guarantee SiO lower in the refining slag
2Content is for preventing that refining from increasing silicon prerequisite is provided.
In addition, in dephosphorization converter and decarburization converter steelmaking process,, can occur the sulphur that returns in various degree in therefore smelting, but decarburization converter terminal sulphur content can be controlled in below 0.012% usually owing to contain sulphur in steel scrap, lime and other slag charges.
Through the molten steel after dephosphorization converter and the decarburization converter smelting; Its terminal point silicone content≤0.005%, final sulfur content≤0.012%, the decarburization basicity of slag is at 4.0-5.0; Advance refining station top basicity of slag for nearly step raising, in tapping process, add granule lime and fluorite; In addition, because the purified slagging process is different from common slagging process, the speed of refining slag deoxidation is slower, for shortening refining cycle, in tapping process, improves the ferro-aluminum add-on, guarantees higher aluminium content in the molten steel, and concrete steps and CCP are following:
Tapping process adds granule lime and fluorite: add granule lime and fluorite during converter tapping amount 1/5, the add-on of granule lime is steel 2.5-2.8Kg per ton, and the add-on of fluorite is steel 0.5-0.8Kg per ton; Through adding slag charge, can further improve the basicity of refining slag, guarantee that basicity is at 6.0-8.0;
Tapping adds the ferro-aluminum deoxidation: add the ferro-aluminum deoxidation during converter tapping amount 2/5-1/2, assurance deoxidation of molten steel back dissolved aluminum content is fully transferred the aluminium amount to reduce refining, the shortening refining time at 0.03-0.05%;
The online bottom blowing of tapping process ladle: in tapping process, the two-way argon bottom-blowing of opening ladle stirs, and the bottom blowing flow control of every road is at 200-400NL/min, and is even as early as possible with fusing and the molten steel composition of realizing adding granule lime;
Sampling after tapping is accomplished: after tapping was accomplished, the steel ladle bottom argon blowing gas mixing was got firm water sample after mixing 3min, and sent the laboratory to analyze composition as early as possible, as the reference of refining adjustment composition.
Owing to promptly add slag charge in early days in tapping; And certain dissolved aluminum is arranged in the assurance steel, therefore, just can improve the basicity of top slag and reduce the oxidisability in the slag through the impact of tapping process steel stream and the stirring of argon bottom-blowing; Its basicity can reach 6.0-8.0; The all iron content of top slag is below 1.5%, so ability implementation part sweetening effectiveness in the tapping process, the sulphur content in the molten steel of tapping back can be controlled in below 0.010%.
Through the processing of each operation of front, advance LF purified molten steel sulphur content≤0.010%, top basicity of slag 6.0-8.0; The all iron content of top slag≤1.5%; Thereby alleviated the pressure of the dark desulfurization of LF refining, can realize taking off with the dissolved aluminum of steel grade the purpose of oxygen slag making in the slag, concrete steps are following:
Add ferro-aluminum and transfer aluminium in the steel: according to the aluminium content among the sampling analysis result in the ladle of tapping back; Transfer the aluminium operation according to target aluminium content 0.05%; 2min promptly carries out atm number argon bottom-blowing stirring desulphurization after adding ferro-aluminum, adopts the two-way bottom blowing, and the bottom blowing flow control is at every road 600-800NL/min; The stirring of 5-8min can realize all iron content in the slag≤0.5%, and 10-12min stirs can realize sulphur content in the steel≤0.003%;
The adding of granule lime and fluorite: get slag specimen in the refining process and observe, can add granule lime and fluorite slag making in right amount according to the slag making effect, granule lime and fluorite add according to weight ratio at 4: 1.
Through method disclosed by the invention; Can under the situation that does not increase refining cycle, realize the purpose of dark desulfurization, refining finishes sulphur content and can reach≤and 0.003%; Compare to reduce with common process and increase the silicon amount, refining finishes silicone content and can be controlled in below 0.03%.
Embodiment
Following instance is used to set forth the present invention, but protection scope of the present invention is not limited in following examples.Following instance adopts the converter of 300 tons of top and bottom complex blowing dephosphorizations, decarburization converter and LF refining furnace to smelt.
Embodiment 1
1) sulphur content 0.002% after the KR hot metal pretreatment, the rate of skimming＞95%;
2) molten iron silicon content 0.003% behind the dephosphorization converter smelting;
3) decarburization converter smelting endpoint molten steel sulphur content 0.011%, basicity of slag 4.6;
4) add granule lime 810Kg, fluorite 202Kg during tap 1/5;
5) add 1.2 tons of ferro-aluminums during tap 2/5;
6) tapping back sampling analysis sulphur content 0.0096%, acid-soluble aluminum content 0.046%;
7) aluminium operation, the basicity of slag 6.2 that enters the station, all iron content 1.02% are transferred in the LF refining;
8) the LF refining process adds granule lime 2000Kg, fluorite 500Kg, refining slag basicity 8.6, all iron content 0.3%;
9) the LF refining treatment finishes silicone content 0.023%, sulphur content 0.0026%.
Embodiment 2
1) sulphur content 0.001% after the KR hot metal pretreatment, the rate of skimming＞95%;
2) molten iron silicon content 0.002% behind the dephosphorization converter smelting;
3) decarburization converter smelting endpoint molten steel sulphur content 0.011%, basicity of slag 4.4;
4) add granule lime 789Kg, fluorite 205Kg during tap 1/5;
5) add 1.3 tons of ferro-aluminums during tap 2/5;
6) tapping back sampling analysis sulphur content 0.0078%, acid-soluble aluminum content 0.048%;
7) aluminium operation, the basicity of slag 6.5 that enters the station, all iron content 0.94% are transferred in the LF refining;
8) the LF refining process adds granule lime 1500Kg, fluorite 250Kg, refining slag basicity 6.9, all iron content 0.2%;
9) the LF refining treatment finishes silicone content 0.021%, sulphur content 0.0019%.
Claims (2)
1. the smelting process of a low silicon, ultralow-sulfur steel adopts the dark desulfurization of hot metal pretreatment-dephosphorization converter dephosphorization desiliconization-decarburization converter smelting-tapping-LF refinery practice, it is characterized in that, in process step, controls following technical parameter:
(1) adopt KR to carry out molten iron pretreatment desulfurizing, processing finishes [S]≤0.003%, molten iron rate＞95% of skimming;
(2) desiliconization, dephosphorization are carried out in the dephosphorization converter, smelt and finish [Si]≤0.01%;
(3) molten iron gets into the decarburization converter, and lime adding amount is a 18-25Kg/ ton steel, and the slag dual alkalinity is at 4.0-5.0;
(4) the decarburization converter tapping adds ferro-aluminum deoxidation operation, makes that acid-soluble aluminum content reaches 0.03～0.05% in the molten steel after the tapping;
(5) LF enters the station the back according to sampling analysis molten steel composition behind the decarburization converter stove, and according to target acid-soluble aluminum content 0.05% adds the operation of ferro-aluminum accent aluminium, and argon bottom-blowing stirs then, takes off the oxygen in the slag with the dissolved aluminum in the steel, realizes that all iron content is less than 0.5% in the slag;
Said low silicon, ultralow-sulfur steel are according to mass percent [Si]≤0.03%, [S]≤0.003%.
2. method according to claim 1 is characterized in that, two-way argon gas, every road bottom blowing flow 600-800NL/min are adopted in the stage bottom blowing of LF refining desulfuration.
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| CN100372948C (en) * | 2005-04-22 | 2008-03-05 | 涟源钢铁集团有限公司 | Low-silicon low-carbon aluminium full killed steel refining method |
| CN101343677B (en) * | 2008-09-01 | 2010-09-08 | 湖南华菱涟源钢铁有限公司 | Production method of low-silicon low-carbon deep drawing steel |
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Address after: 100041 Shijingshan Road, Shijingshan District, Shijingshan District, Beijing Patentee after: Shougang Group Co. Ltd. Address before: 100041 Shijingshan Road, Shijingshan District, Shijingshan District, Beijing Patentee before: Capital Iron & Steel General Company |