CN104846146A - Control method for preventing nitrogen increasing in LF refining treatment - Google Patents
Control method for preventing nitrogen increasing in LF refining treatment Download PDFInfo
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- CN104846146A CN104846146A CN201410050292.XA CN201410050292A CN104846146A CN 104846146 A CN104846146 A CN 104846146A CN 201410050292 A CN201410050292 A CN 201410050292A CN 104846146 A CN104846146 A CN 104846146A
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Abstract
The invention discloses a control method for preventing nitrogen increasing in LF refining treatment. The control method comprises: before refining, performing submerged-arc heating via replenishing slag materials; in an initial stage of refining, producing white slag via ladle bottom high-flow-argon blowing, and adopting a low-current and low-voltage power supply; in an intermediate stage of refining, adopting a high-current and high-voltage power supply, and reducing frequency of heating and frequency of opening a furnace door for temperature measurement and sampling in order to improve the temperature raising efficiency; and in a later stage of refining, adopting ladle bottom small-flow-argon blowing, and the low-current and low-voltage power supply. The control method adopts the ways above for preventing nitrogen increasing, so that nitrogen increasing of an LF during a working process is effectively prevented; the average amount of nitrogen increasing is controlled in a range of 3-5ppm; and the quality of molten steel is further improved.
Description
Technical field
The present invention relates to LF stove refinery practice, more particularly, relate to the control method preventing nitrogen pick-up in a kind of LF stove refining treatment.
Background technology
For most of product made from steel, the nitrogen element in steel is a kind of harmful element.Nitrogen content in steel is high, easily causes timeliness and the blue shortness phenomenon of steel; When nitrogen exceedes certain content, also slab bubble and center porosity can be caused; In addition, nitrogen also reduces the toughness of steel, plasticity and welding property.Due to the essential substance that nitrogen is in air, in steelmaking process, be easy to be sucked by molten steel, and be difficult to remove by ordinary method.So the nitrogen pick-up in each process that how to prevent from making steel is particularly important.
Ladle refining furnace (hereinafter referred to as LF stove) is in the process of process molten steel, adopt Bottom Argon Stirring technique, in current LF stove slag making desulfurization operations process, owing to not controlled the several factors affecting molten steel nitrogen pick-up, particularly submerged arc and furnace pressure control and hold on deoxidation opportunity improper, and there is blindness in the selection of heating gear, thermo-efficiency is not made to maximize, thus extend power-on time, add operation lack of standardization, molten steel is in desulfuration operations process, very easily there is serious nitrogen pick-up in molten steel, and process nitrogen pick-up is unstable, the highest nitrogen pick-up can reach 18ppm, have a strong impact on steel quality.
At present, conventional LF disposition is as follows:
1) slag charge situation: add appropriate lime, appropriate high aluminium deoxidizer, changes slag speed slower.
2) power supply system: when LF stove heats, adopt high-voltage, long arc, noise is larger.
3) in bell, atmosphere is not considered, dust removing valve aperture is random.
4) heating-up time: the heating-up time in early stage is longer, and a heating-up time controls at about 23min, and ladle slag line easily occurs redness phenomenon.
5) ladle bottom blowing flow control: treating processes all adopts large discharge Argon, ensures the fully reaction of slag gold, promotes desulfurization.
6) process of this stove steel LF stove terminates, and the nitrogen pick-up of LF stove reaches 13ppm.
In sum, in prior art LF stove refining process, the major cause of nitrogen pick-up is as follows:
1, molten steel and top slag layer thickness is inadequate, can not carry out effective submerged arc heating.
2, LF stove is in heat-processed, and power supply system is selected unreasonable.
3, ladle bottom blowing flow control is lack of standardization, causes the exposed suction nitrogen of molten steel.
4, molten steel is long for heat-up time, and nitrogen pick-up is more.
5, LF Atmosphere Control is improper, causes molten steel nitrogen pick-up.
Summary of the invention
For the above-mentioned shortcoming existed in prior art, the object of this invention is to provide the control method preventing nitrogen pick-up in a kind of LF stove refining treatment, can effectively prevent the nitrogen pick-up in refining treatment.
For achieving the above object, the present invention adopts following technical scheme:
Prevent a control method for nitrogen pick-up in LF stove refining treatment, comprise the following steps:
A. before refining treatment, by supplementary slag charge to implement submerged arc heating;
B. at the refining treatment initial stage, ladle bottom blowing adopts large discharge Argon to produce white slag, and adopts low-grade current/voltage to power;
C. in refining treatment mid-term, adopt high-grade current/voltage to power, and reduce heating times and open the fire door thermometric sampling frequency to improve intensification efficiency;
D. in the refining treatment later stage, ladle bottom blowing adopts weak current amount Argon, and adopts low-grade current/voltage to power.
In step, specifically comprise the following steps:
A1. in LF stove, add lime, high aluminium deoxidizer, make molten steel top slag thickness reach submerged arc demand;
A2. simultaneously with addition of pre-melted slag, inhale nitrogen probability to reduce molten steel and improve LF thermo-efficiency;
A3. the pre-melted slag of lime, high aluminium deoxidizer and desulfurization is again added.
In steps A 1, described molten steel top slag thickness is more than 70mm.
In steps A 2, described adds at interval in two batches with addition of pre-melted slag.
In step C, described heat-up time is once no longer than 15min.
In stepb, by controlling dust removing valve aperture, bell micro-pressure-difference is controlled at-0.5 ~ 1Pa;
In step C, by controlling dust removing valve aperture, bell micro-pressure-difference is controlled at 2 ~ 4Pa.
In stepb, it is between 15% ~ 18% that described dust removing valve aperture controls;
In step C, it is between 10% ~ 15% that described dust removing valve aperture controls.
In technique scheme, in LF stove refining treatment of the present invention, prevent the control method of nitrogen pick-up, before refining, by supplementary slag charge to implement submerged arc heating; At the refining treatment initial stage, adopt large discharge Argon to produce white slag by ladle bottom blowing, and adopt low-grade current/voltage to power; In refining treatment mid-term, adopt high-grade current/voltage to power, and reduce heating times and open the fire door thermometric sampling frequency to improve intensification efficiency; In the refining treatment later stage, adopt weak current amount Argon by ladle bottom blowing, and adopt low-grade current/voltage to power.Adopt the means preventing nitrogen pick-up of above-mentioned many aspects, effectively can prevent the nitrogen pick-up in operation process of LF stove, make its average nitrogen pick-up control at 3 ~ 5ppm, to improve the quality of molten steel further.
Accompanying drawing explanation
Fig. 1 is the main flow block diagram of control method of the present invention;
Fig. 2 is the FB(flow block) of supplementary slag charge of the present invention.
Embodiment
Technical scheme of the present invention is further illustrated below in conjunction with drawings and Examples.
Refer to shown in Fig. 1, prevent the control method of nitrogen pick-up in LF stove refining treatment of the present invention, mainly comprise the following steps:
A. before refining treatment, by supplementary slag charge to implement submerged arc heating.Namely molten steel is in non-energising situation, first needs to add a collection of slag charge in molten steel and covers.
This is because in converter tapping process, carry out pushing off the slag operation, under converter, the quantity of slag controls at below 50mm, because molten steel does not contact with air, the thermodynamics and kinetics condition of absorption of nitrogen by steel is not enough, and slag can play the effect preventing absorption of nitrogen by steel, if molten steel enters LF stove do not supplement slag charge, do not realize arc-covering slag operation, LF stove heats by high arc temperature, electric arc is a kind of high temperature, gas-jet at a high speed, can be formed recessed anti-at shock point place, the recessed anti-mean depth 3mm/kA of electric arc, in heat-processed, arc light is excessive, thermo-efficiency reduces, and molten steel nitrogen pick-up can be caused because of electric arc ionized air.If high-temperature electric arc is buried by LF refining process, then greatly reduce molten steel and inhale the generation of nitrogen phenomenon.
Shown in Fig. 2, therefore for not desulfurization steel grade, LF stove every stove that enters the station adds 800kg lime, 100 ~ 150kg height aluminium deoxidizer (being conducive to slag, deoxidation), can ensure that molten steel top slag thickness reaches 70mm, substantially can submerged arc, every stove is with addition of 100kg pre-melted slag simultaneously, divide two batches to add, interval 5min, inhales nitrogen probability to reduce molten steel, can improve LF thermo-efficiency 20 ~ 30% simultaneously.After this batch of material adds 2min, then add appropriate lime, the pre-melted slag of appropriate high aluminium deoxidizer and desulfurization.
B. at the refining treatment initial stage, ladle bottom blowing adopts large discharge Argon to produce white slag, and adopts low-grade current/voltage to power.Specific as follows:
Ladle bottom blowing flow control, early stage is guaranteeization slag, can adopt large discharge Argon, produce white slag.And the heating of LF stove adopts high-power power supply, in short period of time, molten steel rapid temperature increases, can reduce electric arc ionization nitrogen pick-up chance, simultaneously, reduce high temperature sludge lifetime, the easier nitrogen pick-up of slag Wen Yuegao, if high-power power-on time and bubble wash one's hair the slag time length quite, bubble is washed one's hair slag and is surrounded arc light, effectively can improve utilization rate of electrical, prevent electric arc from ionizing nitrogen pick-up.So when LF heats, adopt low voltage, large discharge short arc power supply system or long arc add bubble and wash one's hair slag power supply system.Therefore, start in 5min in refining, because slag charge does not melt completely, adopt low-grade current/voltage to power.
For ensureing the formation of reducing atmosphere in bell, when LF stove heats in the early stage, because furnace reduction atmosphere is not formed, produce more flue dust, consider environmental factors, dust removing valve aperture controls between 15% ~ 18%, and bell micro-pressure-difference is controlled at-0.5 ~ 1Pa.
C. in refining treatment mid-term, adopt high-grade current/voltage to power, and reduce heating times and open the fire door thermometric sampling frequency to improve intensification efficiency.Specific as follows:
Reach certain thickness (slag is thick is at least no less than arc length) when slag melting, now adopt high-grade current/voltage to power, to obtain maximum temperature rise rate, according to liquid steel temperature, rhythm of production, calculates increasing extent of temperature before heating, reduce heating times as far as possible, reduce and open the fire door thermometric sampling frequency, improve intensification efficiency, reduce electrode and steel contacts time, but heat a time no longer than 15min, prevent ladle surface overheated, slag line corrodes serious, and heat-up time is directly proportional to molten steel nitrogen increased amount.
Ladle bottom blowing flow control, at middle flow, ensures that molten steel fully contacts with slag, promotes that desulphurization reaction and the reaction of other slag interface are carried out.
In addition, Atmosphere Control, after change slag, want timely manual setting valve position, dedusting valve seat opening controls 10% ~ 15%, and bell micro-pressure-difference, at 2 ~ 4Pa, is slightly smoldered during to heat and is advisable, can ensure furnace reduction atmosphere like this.Reduce molten steel to contact with air, prevent nitrogen pick-up.
D. in the refining treatment later stage, ladle bottom blowing adopts weak current amount Argon, and adopts low-grade current/voltage to power.Specific as follows:
LF process later stage main purpose is composition adjustment and insulation, now adopts low-grade current/voltage to power, and the later stage that is energized adopts comparatively soft argon blowing flow, prevents molten steel to be again oxidized, and is conducive to steel grade inclusion simultaneously and floats in time; When carrying out Calcium treatment, exposed for reducing molten steel, argon blowing rate is then as the criterion so that the top of the slag is not exposed.
To produce certain steel grade, each component requirements [C] 0.14%, [Si] 0.075%, [Mn] 1.3%, [N] 0.003%, the dual refining treatment steel of LF+RH, S composition in molten steel takes off to below 20ppm by 83ppm by LF stove process main purpose, and control nitrogen content within 40ppm, converter tapping nitrogen content is at about 25ppm, do not adopt of the present invention prevent the control method of nitrogen pick-up time, after the process of this stove steel LF stove terminates, the nitrogen pick-up of LF stove reaches 13ppm, and employing of the present invention prevent the control method of nitrogen pick-up after, after the process of this stove steel LF stove terminates, the nitrogen pick-up of LF stove is only 5ppm, effect is fairly obvious.
In sum, adopt the control method preventing nitrogen pick-up in LF stove refining treatment of the present invention, prevent nitrogen pick-up measure by multinomial, effectively can prevent the nitrogen pick-up in operation process of LF stove, make its average nitrogen pick-up control at 3 ~ 5ppm, to improve the quality of molten steel further.
Those of ordinary skill in the art will be appreciated that, above embodiment is only used to the present invention is described, and be not used as limitation of the invention, as long as in spirit of the present invention, all will drop in Claims scope of the present invention the change of the above embodiment, modification.
Claims (7)
1. prevent a control method for nitrogen pick-up in LF stove refining treatment, it is characterized in that,
Comprise the following steps:
A. before refining treatment, by supplementary slag charge to implement submerged arc heating;
B. at the refining treatment initial stage, ladle bottom blowing adopts large discharge Argon to produce white slag, and adopts low-grade current/voltage to power;
C. in refining treatment mid-term, adopt high-grade current/voltage to power, and reduce heating times and open the fire door thermometric sampling frequency to improve intensification efficiency;
D. in the refining treatment later stage, ladle bottom blowing adopts weak current amount Argon, and adopts low-grade current/voltage to power.
2. prevent the control method of nitrogen pick-up in LF stove refining treatment as claimed in claim 1, it is characterized in that:
In step, specifically comprise the following steps:
A1. in LF stove, add lime, high aluminium deoxidizer, make molten steel top slag thickness reach submerged arc demand;
A2. simultaneously with addition of pre-melted slag, inhale nitrogen probability to reduce molten steel and improve LF thermo-efficiency;
A3. the pre-melted slag of lime, high aluminium deoxidizer and desulfurization is again added.
3. prevent the control method of nitrogen pick-up in LF stove refining treatment as claimed in claim 2, it is characterized in that:
In steps A 1, described molten steel top slag thickness is more than 70mm.
4. prevent the control method of nitrogen pick-up in LF stove refining treatment as claimed in claim 2, it is characterized in that:
In steps A 2, described adds at interval in two batches with addition of pre-melted slag.
5. prevent the control method of nitrogen pick-up in LF stove refining treatment as claimed in claim 1, it is characterized in that:
In step C, described heat-up time is once no longer than 15min.
6. prevent the control method of nitrogen pick-up in LF stove refining treatment as claimed in claim 1, it is characterized in that:
In stepb, by controlling dust removing valve aperture, bell micro-pressure-difference is controlled at-0.5 ~ 1Pa;
In step C, by controlling dust removing valve aperture, bell micro-pressure-difference is controlled at 2 ~ 4Pa.
7. prevent the control method of nitrogen pick-up in LF stove refining treatment as claimed in claim 6, it is characterized in that:
In stepb, it is between 15% ~ 18% that described dust removing valve aperture controls;
In step C, it is between 10% ~ 15% that described dust removing valve aperture controls.
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107012297A (en) * | 2016-01-27 | 2017-08-04 | 鞍钢股份有限公司 | Method for improving temperature rising efficiency of LF (ladle furnace) |
| CN109338032A (en) * | 2018-11-06 | 2019-02-15 | 芜湖新兴铸管有限责任公司 | LF furnace control nitrogen method of refining |
| CN111313487A (en) * | 2020-03-24 | 2020-06-19 | 芜湖新兴铸管有限责任公司 | Power transmission method for ladle refining furnace |
| CN112126742A (en) * | 2020-09-22 | 2020-12-25 | 承德建龙特殊钢有限公司 | LF refining method for controlling nitrogen content in gear steel |
| CN113817950A (en) * | 2021-07-15 | 2021-12-21 | 新疆八一钢铁股份有限公司 | Method for stably controlling nitrogen in LF furnace by using nitrogen |
| CN113832296A (en) * | 2021-09-30 | 2021-12-24 | 广东韶钢松山股份有限公司 | Rapid desulfurization method of slab steel in LF refining furnace |
| CN116121488A (en) * | 2023-02-24 | 2023-05-16 | 成都先进金属材料产业技术研究院股份有限公司 | Low-energy-consumption LF furnace smelting method |
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| 吴雄 等: ""浅析宝钢厚板成品氮的控制"", 《第十六届全国炼钢学术会议论文集》 * |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107012297A (en) * | 2016-01-27 | 2017-08-04 | 鞍钢股份有限公司 | Method for improving temperature rising efficiency of LF (ladle furnace) |
| CN109338032A (en) * | 2018-11-06 | 2019-02-15 | 芜湖新兴铸管有限责任公司 | LF furnace control nitrogen method of refining |
| CN111313487A (en) * | 2020-03-24 | 2020-06-19 | 芜湖新兴铸管有限责任公司 | Power transmission method for ladle refining furnace |
| CN112126742A (en) * | 2020-09-22 | 2020-12-25 | 承德建龙特殊钢有限公司 | LF refining method for controlling nitrogen content in gear steel |
| CN113817950A (en) * | 2021-07-15 | 2021-12-21 | 新疆八一钢铁股份有限公司 | Method for stably controlling nitrogen in LF furnace by using nitrogen |
| CN113832296A (en) * | 2021-09-30 | 2021-12-24 | 广东韶钢松山股份有限公司 | Rapid desulfurization method of slab steel in LF refining furnace |
| CN116121488A (en) * | 2023-02-24 | 2023-05-16 | 成都先进金属材料产业技术研究院股份有限公司 | Low-energy-consumption LF furnace smelting method |
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