CN104988281A - Method for preventing nitrogen increment of LF refined low-nitrogen steel - Google Patents
Method for preventing nitrogen increment of LF refined low-nitrogen steel Download PDFInfo
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- CN104988281A CN104988281A CN201510462321.8A CN201510462321A CN104988281A CN 104988281 A CN104988281 A CN 104988281A CN 201510462321 A CN201510462321 A CN 201510462321A CN 104988281 A CN104988281 A CN 104988281A
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Abstract
The invention discloses a method for preventing nitrogen increment of LF refined low-nitrogen steel. The method comprises the following steps: allowing molten steel tapped from a converter to enter a station, and carrying out argon stirring under an argon flow of 30-60Nm/l; sequentially adding fluorite, submerged arc slag, small-grain ash, calcium carbide and a deoxidizer in the LF refining process; and selecting a high-grade heavy-current heating mode of the above LF furnace. The method avoids exposure of the molten steel through controlling the argon flow amount without changing present devices or refractory, shortens the existence time of high temperature slag through controlling the heating grade and the current value, avoids slag agglomeration induced long-time heating and stirring through controlling the charging sequence, and reduces the nitrogen absorption of the molten steel in a low oxygen state through controlling the deoxidation moment in order to reduce the nitrogen increment of the molten steel in the refining process. The method has the characteristics of production of low-carbon steel through fully utilizing present conditions of refining without vacuum treatment, easy realization and low production cost.
Description
Technical field
The present invention relates to a kind of smelting process of low nitrogen steel, especially a kind of LF stove smelting low-nitrogen steel prevents the method for nitrogen pick-up.
Background technology
Because nitrogen belongs to harmful element in the production of part steel grade, he can be combined with TI or AL of steel grade and generate (TiN) or (AlN), weaken grain-boundary strength, reduce toughness, welding property, the thermal stresses district toughness of steel, particularly in the production of hard wire steel, easily cause quality fluctuation.And in refining furnace operating process, heating and line feeding are processes of seriously inhaling nitrogen, and to enter the station condition difference due to the difference of operator and molten steel, cause nitrogen content and instability thereof in molten steel, the nitrogen content of indivedual heat can exceed finished product requirement, causes degradation to change the original sentence to.
Application number is the Chinese patent application of 201410237276.1, provide a kind of method of LF stove smelting low-nitrogen steel, which employs a kind of hollow graphite electrode, require in refining process, centre hole through Graphite Electrodes is blown into argon gas to whole process in ladle, coordinate argon bottom-blowing to stir molten steel simultaneously, molten steel face forms argon gas atmosphere, and then the molten steel nitrogen pick-up avoided molten steel to occur to inhale nitrogen phenomenon and cause.The method needs to transform electrode, and argon gas cost is higher, has the weak point that enforcement is more difficult, cost is high.
Summary of the invention
The LF stove smelting low-nitrogen steel that the technical problem to be solved in the present invention is to provide a kind of existing installation and resistance to material prevents the method for nitrogen pick-up.
For solving the problems of the technologies described above, the technical solution used in the present invention is: after the molten steel of converter tapping enters the station, and adopt argon gas to stir, argon flow amount controls at 30 ~ 60Nm/l; During the refining of LF stove, the order of addition(of ingredients) of slag charge is followed successively by: fluorite, submerged arc slag, granule ash, calcium carbide and reductor; The heating mode of high tap position big current selected by LF stove.
During LF stove refining of the present invention, fluorite add-on is 1.2 ~ 1.6kg/ ton, and submerged arc slag add-on is 1.6 ~ 1.8kg/ ton, and granule ash add-on is 3.2kg/ ton, and calcium carbide add-on is 0.25 ~ 0.5kg/ ton, and reductor add-on is 0.7 ~ 0.8kg/ ton.
In converter tapping of the present invention and LF stove refining process, granule ash adds that total amount is 6.4 ~ 7.2kg/ ton, to add total amount be 1.6 ~ 1.8kg/ ton to submerged arc slag.
LF stove of the present invention refining terminates rear feeding silicon-calcium wire.
The beneficial effect adopting technique scheme to produce is: the present invention is on the basis not changing existing installation and resistance to material, avoid molten steel exposed by controlling argon flow amount size, control heating gear and size of current shorten high temperature sludge lifetime, the long-time heating that control order of addition(of ingredients) is avoided slag charge to lump and caused and stirring, reach the suction nitrogen of reduction molten steel under hypoxia by controlling deoxidation opportunity; Thus reach the effect reducing molten steel nitrogen increased amount in refining process.
The present invention's invention solves the serious phenomenon of nitrogen pick-up in refining process, and changes the idea only having vacuum-treat could smelt low nitrogen steel; Present method is inhaled nitrogen condition and is started with from refining process, is reached reduce molten steel nitrogen pick-up by standard operation, and effect stability, without the need to the input of cost.The present invention can make full use of refining existence conditions, require no vacuum-treat produces low nitrogen steel, has easy realization, feature that production cost is low.
Embodiment
Below in conjunction with specific embodiment, the present invention is further detailed explanation.
This LF stove smelting low-nitrogen steel prevents the method for nitrogen pick-up from adopting following processing step:
(1) converter tapping: converter tapping process needs omnidistance on-line argon-blow; Need in alloying process to add a certain amount of granule ash, to ensure certain thickness of slag layer; A certain amount of dissolving agent is added while adding granule ash; After converter has gone out steel, molten steel face is forbidden to be crusted.
(2) after molten steel enters the station, do not allow large argon gas to stir, avoid causing suction nitrogen because molten steel is exposed, argon flow amount controls at 30 ~ 60Nm/l.
(3) during the refining of LF stove, order of addition(of ingredients) order: fluorite 1.2 ~ 1.6kg/ ton steel-submerged arc slag 1.6 ~ 1.8kg/ ton steel-granule ash 3.2kg/ ton steel-calcium carbide (carbide of calcium) 0.25 ~ 0.5kg/ ton-reductor 0.7 ~ 0.8kg/ ton; Adopt conventional fluorite, submerged arc slag, granule ash, calcium carbide and reductor; Such order of addition(of ingredients) advantage:
A, first add contributing to of fluorite slag, avoid sticking together phenomenon because slag material concentrated adds knot;
Adjustment basicity is played in adding of B, submerged arc slag, improves slag system;
C, add the working method of granule ash killing again, be ensure there is being the deoxidation on basis of certain slag blanket, avoid because of under the state of hypoxemia, stirring slag and the molten steel that causes seriously inhales nitrogen.
(4) the strict total add-on controlling slag charge; in converter tapping process and LF refining process; granule ash adds total amount 6.4 ~ 7.2kg/ ton steel, submerged arc slag adds total amount 1.6 ~ 1.8kg/ ton steel, thus reaches by controlling basicity of slag the object that sulphur in steel controls between 0.005% ~ 0.010%.Theoretical display is when molten steel dissolved oxygen is lower (≤5*10-6), and sulphur content is lower, and the mass transfer coefficient inhaling nitrogen is larger.
(5) heating mode of high tap position big current is selected: the heating mode selecting 4 gear 36000 electric currents; Slag temperature height can produce certain impact to absorption of nitrogen by steel, and slag temperature is higher, more easily inhales nitrogen; And Heating Zone Temperature reaches degree more than 2100 during heated by electrodes, molten steel very easily inhales nitrogen, so new methodology regulation, high-power power supply is adopted during heating, molten steel rapid temperature increases is made in short period of time, reduce electric arc ionization nitrogen pick-up chance, decrease high temperature sludge lifetime simultaneously, be conducive to preventing nitrogen from entering molten steel by slag.
(6) refining of LF stove terminates rear feeding silicon-calcium wire, and the theoretical basis selecting silicon-calcium wire to substitute calcium iron wire is: when feeding calcium iron wire, and reaction is comparatively strong, and molten steel is very easily exposed; Silicon-calcium wire then reduces response intensity, reduces molten steel amount of nitrogen sucking.
Embodiment 1: this LF stove smelting low-nitrogen steel prevents the method for nitrogen pick-up from adopting following concrete technology.
125 tons, the molten steel of converter tapping enters the station without crust, inlet temperature 1493 degree, steel grade XY77B, N content 13ppm before refining; Stokehold requires to add granule ash 400kg, fluorite 200kg in tapping process according to main points.Refining is entered the station and is not allowed large argon gas to stir, argon gas control 50Nm/l, and the order of addition(of ingredients) that enters the station is: fluorite 157kg, submerged arc slag 200kg, granule ash 400kg, calcium carbide 40kg, reductor 100kg; In heat-processed, argon gas (actual flow) controls at 86Nm/l, mends Composition Control argon flow amount control 157Nm/l, and is promoted the dissolving of carbon dust by the mode of heated by electrodes.Soft blow controls argon flow amount and controls at 36Nm/l, and process heating employing 4 grades, 36000 heating modes, feed silicon-calcium wire 300m after process terminates.After testing, refining lifting N content 22ppm, nitrogen pick-up 9ppm, meet steel grade requirement.
Embodiment 2: this LF stove smelting low-nitrogen steel prevents the method for nitrogen pick-up from adopting following concrete technology.
Adopt 125 tons of LF refining furnaces.The molten steel of converter tapping enters the station without crust, inlet temperature 1482 degree, steel grade XY77B, N content 20ppm before refining; Stokehold requires to add granule ash 450kg, fluorite 200kg in tapping process according to main points.Refining is entered the station and is not allowed large argon gas to stir, argon gas control 40Nm/l, and the order of addition(of ingredients) that enters the station is: fluorite 160kg, submerged arc slag 225kg, granule ash 425kg, calcium carbide 62.5kg, reductor 87.5kg; In heat-processed, argon gas (actual flow) controls at 90Nm/l, mends Composition Control argon flow amount control 146Nm/l, and is promoted the dissolving of carbon dust by the mode of heated by electrodes.Soft blow controls argon flow amount and controls at 36Nm/l, and process heating employing 4 grades, 36000 heating modes, feed silicon-calcium wire 300m after process terminates.After testing, refining lifting N content 24ppm, nitrogen pick-up 4ppm, meet steel grade requirement.
Embodiment 3: this LF stove smelting low-nitrogen steel prevents the method for nitrogen pick-up from adopting following concrete technology.
Adopt 125 tons of LF refining furnaces.The molten steel of converter tapping enters the station without crust, inlet temperature 1490 degree, steel grade XY77B, N content 15ppm before refining; Stokehold requires to add granule ash 500kg, fluorite 200kg in tapping process according to main points.Refining is entered the station and is not allowed large argon gas to stir, argon gas control 60Nm/l, and the order of addition(of ingredients) that enters the station is: fluorite 200kg, submerged arc slag 210kg, granule ash 398kg, calcium carbide 31.25kg, reductor 96kg; In heat-processed, argon gas (actual flow) controls at 88Nm/l, mends Composition Control argon flow amount control 150Nm/l, and is promoted the dissolving of carbon dust by the mode of heated by electrodes.Soft blow controls argon flow amount and controls at 36Nm/l, and process heating employing 4 grades, 36000 heating modes, feed silicon-calcium wire 300m after process terminates.After testing, refining lifting N content 22ppm, nitrogen pick-up 7ppm, meet steel grade requirement.
Embodiment 4: this LF stove smelting low-nitrogen steel prevents the method for nitrogen pick-up from adopting following concrete technology.
Adopt 125 tons of LF refining furnaces.The molten steel of converter tapping enters the station without crust, inlet temperature 1487 degree, steel grade XY77B, N content 17ppm before refining; Stokehold requires to add granule ash 470kg, fluorite 200kg in tapping process according to main points.Refining is entered the station and is not allowed large argon gas to stir, argon gas control 30Nm/l, and the order of addition(of ingredients) that enters the station is: fluorite 150kg, submerged arc slag 215kg, granule ash 400kg, calcium carbide 50kg, reductor 92kg; In heat-processed, argon gas (actual flow) controls at 87Nm/l, mends Composition Control argon flow amount control 153Nm/l, and is promoted the dissolving of carbon dust by the mode of heated by electrodes.Soft blow controls argon flow amount and controls at 36Nm/l, and process heating employing 4 grades, 36000 heating modes, feed silicon-calcium wire 300m after process terminates.After testing, refining lifting N content 23ppm, nitrogen pick-up 6ppm, meet steel grade requirement.
Claims (4)
1. LF stove smelting low-nitrogen steel prevents a method for nitrogen pick-up, it is characterized in that, its method adopts following technique: after the molten steel of converter tapping enters the station, and adopt argon gas to stir, argon flow amount controls at 30 ~ 60Nm/l; During the refining of LF stove, the order of addition(of ingredients) of slag charge is followed successively by: fluorite, submerged arc slag, granule ash, calcium carbide and reductor; The heating mode of high tap position big current selected by LF stove.
2. LF stove smelting low-nitrogen steel according to claim 1 prevents the method for nitrogen pick-up; it is characterized in that: during described LF stove refining; fluorite add-on is 1.2 ~ 1.6kg/ ton; submerged arc slag add-on is 1.6 ~ 1.8kg/ ton; granule ash add-on is 3.2kg/ ton; calcium carbide add-on is 0.25 ~ 0.5kg/ ton, and reductor add-on is 0.7 ~ 0.8kg/ ton.
3. LF stove smelting low-nitrogen steel according to claim 1 prevents the method for nitrogen pick-up, it is characterized in that: in described converter tapping and LF stove refining process, and granule ash adds that total amount is 6.4 ~ 7.2kg/ ton, to add total amount be 1.6 ~ 1.8kg/ ton to submerged arc slag.
4. the LF stove smelting low-nitrogen steel according to claim 1,2 or 3 prevents the method for nitrogen pick-up, it is characterized in that: the refining of described LF stove terminates rear feeding silicon-calcium wire.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108690897A (en) * | 2018-05-25 | 2018-10-23 | 本钢板材股份有限公司 | A kind of control nitrogen technique of ER50-6 steel series |
| CN108728607A (en) * | 2018-06-04 | 2018-11-02 | 北京科技大学 | A kind of LF stoves dynamic bottom blowing CO2- Ar method of refining and device |
| CN115717180A (en) * | 2022-11-01 | 2023-02-28 | 山东钢铁股份有限公司 | Method for reducing nitrogen increase of molten steel in LF refining process |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JPH01208413A (en) * | 1988-02-16 | 1989-08-22 | Kobe Steel Ltd | Production of low nitrogen steel |
| CN103627841A (en) * | 2013-11-01 | 2014-03-12 | 南京钢铁股份有限公司 | Control method for nitrogen content of molten steel of wear-resistant steel |
| CN103993132A (en) * | 2014-05-30 | 2014-08-20 | 河北钢铁股份有限公司 | Method for refining low-nitrogen steel by ladle refining furnace (LF) |
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2015
- 2015-07-31 CN CN201510462321.8A patent/CN104988281A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01208413A (en) * | 1988-02-16 | 1989-08-22 | Kobe Steel Ltd | Production of low nitrogen steel |
| CN103627841A (en) * | 2013-11-01 | 2014-03-12 | 南京钢铁股份有限公司 | Control method for nitrogen content of molten steel of wear-resistant steel |
| CN103993132A (en) * | 2014-05-30 | 2014-08-20 | 河北钢铁股份有限公司 | Method for refining low-nitrogen steel by ladle refining furnace (LF) |
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| 张俊同等: "高碳钢72A控氮工艺及生产实践", 《甘肃冶金》 * |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108690897A (en) * | 2018-05-25 | 2018-10-23 | 本钢板材股份有限公司 | A kind of control nitrogen technique of ER50-6 steel series |
| CN108728607A (en) * | 2018-06-04 | 2018-11-02 | 北京科技大学 | A kind of LF stoves dynamic bottom blowing CO2- Ar method of refining and device |
| CN108728607B (en) * | 2018-06-04 | 2019-04-12 | 北京科技大学 | A kind of LF furnace dynamic bottom blowing CO2- Ar method of refining and device |
| CN115717180A (en) * | 2022-11-01 | 2023-02-28 | 山东钢铁股份有限公司 | Method for reducing nitrogen increase of molten steel in LF refining process |
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