CN103074468A - Flux for removal of impurities in steel during vacuum refining and preparation method thereof - Google Patents
Flux for removal of impurities in steel during vacuum refining and preparation method thereof Download PDFInfo
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- CN103074468A CN103074468A CN2011103265227A CN201110326522A CN103074468A CN 103074468 A CN103074468 A CN 103074468A CN 2011103265227 A CN2011103265227 A CN 2011103265227A CN 201110326522 A CN201110326522 A CN 201110326522A CN 103074468 A CN103074468 A CN 103074468A
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- steel
- inclusion
- molten steel
- flux
- impurities
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Abstract
The invention provides a flux for removal of impurities in steel during vacuum refining and a preparation method thereof. The flux comprises, by weight, 55.0 to 68.0% of CaO, 10.0 to 18.0% of CaCO3, 7.0 to 15.0% of Ca, 2.0 to 7.0% of Al and 3.0 to 8.0% of Na2CO3, with the balance being impurities. The flux provided by the invention is added into molten steel after vacuum refining deoxidation of the molten steel, and since small bubbles generated during decomposition of the flux at a high temperature carry impurities in steel and calcium to undergo deep deoxidation with the molten steel and to form composite inclusions which has a low melting point and can be easily removed with alumina and the like in steel, the content of impurities in steel is decreased, the size of the impurities is reduced, and the purpose of purifying the molten steel is achieved.
Description
Technical field
The present invention relates to SECONDARY REFINING IN A VACUUM CHAMBER, particularly a kind of vacuum refinement process is removed flux of steel inclusion and preparation method thereof.
Background technology
The deoxidation to molten steel, degassed and the composition of molten steel and the adjustment of temperature are mainly finished in vacuum refinement, remove steel inclusion, thereby the cleanliness factor of raising steel improves the performance of steel.The vacuum refinement process is to the deoxidation of molten steel, so that the reaction of the reductors such as the dissolved oxygen in the molten steel and metallic aluminium forms a large amount of deoxidation productss such as aluminum oxide, these deoxidation productss are main sources of nonmetallic inclusionsin steel.These non-metallic inclusions are carrying with the circulation stirring of molten steel and bubble in the vacuum refinement process and are removing, but still have the part non-metallic inclusion to remain in the molten steel and affect the performance of steel.
The harm that control remains in the Non-metallic Inclusion on Property of Steel in the steel is mainly worked from two aspects, the one, reduce the steel inclusion total amount, the reduction of steel inclusion total amount is so that molten steel is cleaner, to rigidity can harm alleviated; The 2nd, form, composition and the size etc. of control steel inclusion, such as the size of non-metallic inclusion at 10 μ m even below the 5 μ m, its to rigidity can harm greatly alleviate the inclusion in the steel about 1 μ m even can improve some performances of steel; The form of steel inclusion and composition have the different requirement of table to the steel of different service requirementss.To requiring harsh wire rod, strictly control brittle inclusion in the steel, it is good moulding that steel inclusion is had, deformable in the course of processing; And for sheet material, then need steel inclusion to have isotropy, wish to form small nodule.Therefore, the removal of steel inclusion and control are the important tasks of steelmaking process.
Summary of the invention
The object of the invention is to develop a kind of vacuum refinement process and remove flux of steel inclusion and preparation method thereof, after the vacuum refining of liquid steel deoxidation finishes, add in the molten steel, utilize its at high temperature decompose produce micro-bubble carry steel inclusion and calcium and the deoxidation of the molten steel degree of depth and with steel in the low-melting complex inclusion of formation such as aluminum oxide and be easy to the mode such as removal, reduce inclusion content of steel, the size of steel inclusion is reduced, reach the purpose of cleaning molten steel.
For achieving the above object, technical scheme of the present invention is:
A kind of vacuum refinement process is removed the flux of steel inclusion, and its composition weight percent is: CaO 55.0～68.0%, CaCO
310.0～18.0%, Ca 7.0～15.0%, Al 2.0～7.0%, Na
2CO
33.0～8.0%, surplus impurity.
A kind of vacuum refinement process is removed the preparation method of the flux of steel inclusion, with raw materials of Ca O, CaCO
3, Na
2CO
3, calcium metal Ca mixes by following proportioning, its composition weight percent is: CaO 55.0～68.0%, CaCO
310.0～18.0%, Ca 7.0～15.0%, Al 2.0～7.0%, Na
2CO
33.0～8.0%, surplus impurity, wherein CaO, CaCO
3, Na
2CO
3Granularity below 0.1mm;
Behind the abundant mixing of above-mentioned raw materials, dry pressing.
Further, mix front described calcium metal and do Passivation Treatment.
In the vacuum refinement process of molten steel, mainly adopt Al as reductor molten steel to be carried out deoxidation treatment, [O] in the molten steel with the reaction of metal A l is:
2Al+3[O]＝Al
2O
3(s) (1)
Deoxidation products is Al
2O
3 (s), the removal of floating of the density difference by itself and molten steel, according to Stokes'theorem:
In the formula, u
sBe the ascent rate of inclusion content in melting steel particle, d is the diameter of inclusion particle, μ
lBe the viscosity of molten steel, ρ
lAnd ρ
sBe respectively the density of molten steel and inclusion particle, g is universal gravity constant.By Stokes'theorem as can be known, the inclusion particle size is larger, and inclusion is easier come-up in molten steel.Therefore, the large-sized inclusion particle in the molten steel (＞50 μ m) is easy in liquid steel refining process gathering come-up and removes.And the small inclusion particle in the molten steel (particle of＜50 μ m is the particle of μ m particularly＜10) ascent rate is very slow, and mostly is to remove by entering in ladle slag, the ladle lining under the carrying that reaches molten steel bubble in the mobile and molten steel that the Argon stirring causes.
The deoxygenation of molten steel comprises that also silicon and MgO are generated the reaction of oxygen in [Mg] that be dissolved in the molten steel etc. and the steel by reductor Al reduction, form SiO
2, MgO, MgOAl
2O
3, 2MgOSiO
2, 3Al
2O
32SiO
2Deng deoxidation products, these deoxidation productss are main sources of steel inclusion.Its pattern, size, composition etc. can exert an influence to the quality and performance of steel.Particularly larger-size inclusion is more remarkable on the impact of steel quality.
Under the steel-making temperature, calcium (Ca) not only has fabulous avidity with oxygen and sulphur, but also has the very strong controllability to inclusion morphology and size.For Al deoxidization steel, adopt calcium to process and further reducing in the steel in the dissolved oxygen and sulphur content (deoxidizing capacity of calcium is stronger than aluminium), can be with the Al in the steel
2O
3Be mingled with and become compound mCaOnSiO
2, mCaOnAl
2O
3And dystectic MgOAl
2O
3Deng inclusion, reduce the polymerization of solid inclusions and grow up, so that being easy to come-up, low-melting liquid inclusions removes.The reaction of oxygen and sulphur is as follows in calcium and aluminium, silicon and the steel:
m[Ca]+n[Si]+(m+2n)[O]＝(mCaO·nSiO
2) (3)
m[Ca]+2n[Al]+(m+3n)[O]＝(mCaO·nAl
2O
3) (4)
[Ca]+[S]＝(CaS) (5)
Therefore, by calcium metal or calcium alloy molten steel is carried out degree of depth deoxidation and inclusion modification processing, the total amount of the oxide inclusion that forms in the steel is reduced, steel inclusion forms complex inclusion, and size is tiny and disperse is distributed in the steel, reaches the purpose that improves steel quality and improve the rigidity energy.
In addition, carbonate is (such as CaCO
3, Na
2CO
3Deng) thereby decomposition reaction can occur under the high temperature below 1000 ℃ produces CO
2Gas, these gases form the micro-bubble disperse and are distributed in the molten steel, and with flowing of molten steel, the bubble that these disperses distribute and the collision of the inclusion particle in the molten steel so that short grained inclusion is attached to bubble surface, enters slag blanket with bubble floating and remove.Carbonate is (such as CaCO
3, Na
2CO
3Deng) at high temperature decomposition reaction is:
Na
2CO
3＝Na
2O+CO
2 (6)
CaCO
3＝CaO+CO
2 (7)
The course of processing that the vacuum refinement process is removed the flux of steel inclusion needs each granularity that forms of strict control, is that each component can fully be reacted with molten steel for it enters the bubble that forms small and dispersed behind the molten steel.CaO wherein, CaCO
3, Na
2CO
3Granularity requirements below 0.1mm, calcium metal require to adopt Passivation Treatment, keeps the stable of its character.Behind the abundant mixing of these raw materials that meet the demands, dry pressing.
Molten steel is after vacuum refinement process aluminum deoxidation finishes, in molten steel, add the flux that the vacuum refinement process is removed steel inclusion, molten steel is carried out deep deoxidation and inclusion modification processing, the micro-bubble that utilizes simultaneously the carbonate high-temperature decomposition reaction in the flux to produce, disperse is distributed in the molten steel, in the Circulating Flow of Molten Steel process, micro-bubble carries the inclusion particle come-up in the molten steel, reaches the purpose of removing steel inclusion, cleaning molten steel.Its add-on is 0.3kg/t～0.8kg/t, adds in the molten steel after the vacuum refinement process removes the flux of steel inclusion, continues to keep the 3min～5min that circulates of molten steel, can reach good inclusion removal effect.
In flux of the present invention,
Calcium metal Ca, the main purpose that rises molten steel deep deoxidation and inclusion modification further reduces the free oxygen in the molten steel, forms calcium aluminate class low melting point complex inclusion, and its content is controlled at 7%～15%.Too high calcium contents can reduce the result of use of calcium, the effusion molten steel because calcium at high temperature forms easily the calcium steam, and excessively low calcium contents then is difficult to reach the purpose to the deoxidation of the molten steel degree of depth and inclusion modification.
CaO, mainly be with molten steel in Al
2O
3Inclusion forms low-melting complex inclusion calcium aluminate, shown in reaction (4).Its content is controlled at 55%-68%.Too high CaO content can make CaO rest on the new inclusion of formation in the molten steel, is unfavorable for the purification of molten steel, excessively low CaO content then make with molten steel in Al
2O
3The CaO quantity not sufficient of inclusion combination can't reach better Control and Inclusion Removal requirement.
CaCO
3, mainly be to utilize to decompose under its high temperature to produce CO
2Micro-bubble, shown in reaction (7), these micro-bubbles can carry inclusion particle in the molten steel and the removal of floating.Its content is controlled at 10%～18%.Too high CaCO
3Content can make its high-temperature decomposition reaction heat absorption too many, causes liquid steel temperature control difficulty to strengthen, and the CO that produces
2Gas so that molten steel recarburization affects the accurate control of molten steel composition, especially for ultra low-carbon steel, can make molten steel recarburization 3-8 * 10 under reductive condition
-6, affect the performance of such steel grade; Cross low CaCO
3Content then makes the bubble generation quantity not sufficient, affects the removal effect of steel inclusion.
Na
2CO
3, its effect and CaCO
3Similar, but Na
2CO
3Reduce in addition the purpose of flux fusing point, form liquid inclusions better and remove.Its content is controlled at 3%-8%.Too high Na
2CO
3Content also can make its high-temperature decomposition reaction heat absorption too much and cause molten steel recarburization, and the erosion of refractory materials is aggravated; Cross low Na
2CO
3Content then makes the bubble generation quantity not sufficient, and is not enough to the reduction of flux fusing point, affects the removal effect of steel inclusion.
Metallic aluminium Al, the main purpose that rises deoxidation of molten steel further reduces free oxygen in the molten steel with calcium metal, and its content is controlled at 2%～7%.Too high aluminium content can affect the accurate control of molten steel aluminium component, and excessively low aluminium amount then affects the deoxidation effect of molten steel.
Beneficial effect of the present invention
Compared with prior art, remove the flux of steel inclusion by vacuum refinement process of the present invention, can reduce inclusion content of steel, make T[O in the steel] content reaches 10 * 10
-6Below; The size of steel inclusion is reduced, and its mean diameter reaches below the 1.5 μ m, thereby cleaning molten steel improves the performance of steel.The present invention has no adverse effects to environment.
Embodiment
The present invention will be further described below in conjunction with embodiment.
Table 1 is the embodiment of the invention, and table 2 is result of use of the present invention.
With raw materials of Ca O, CaCO
3, Na
2CO
3, calcium metal Ca is by behind the abundant mixing of ratio requirement, dry pressing.Wherein, CaO, CaCO
3, Na
2CO
3Granularity requirements below 0.1mm, calcium metal Ca does Passivation Treatment.
Table 1 unit: weight percent
| Embodiment | CaO | CaCO 3 | Ca | Al | Na 2CO 3 | Impurity |
| 1 | 55.0 | 18.0 | 15.0 | 3.5 | 7.0 | Surplus |
| 2 | 61.5 | 13.0 | 14.0 | 5.5 | 3.0 | Surplus |
| 3 | 64.0 | 15.0 | 12.0 | 2.0 | 5.0 | Surplus |
| 4 | 68.0 | 10.0 | 7.0 | 7.0 | 6.0 | Surplus |
| 5 | 66 | 13.5 | 7.5 | 6.5 | 5.5 | Surplus |
| 6 | 66.8 | 12.9 | 8.1 | 6.8 | 4.8 | Surplus |
| 7 | 56.7 | 16.1 | 14.6 | 5.2 | 6.6 | Surplus |
Table 2
| Embodiment | Add-on, kg/t.s | The steel inclusion total amount, % | Steel inclusion mean diameter (μ m) |
| 1 | 0.80 | 0.0006 | 1.13 |
| 2 | 0.65 | 0.0008 | 1.22 |
| 3 | 0.55 | 0.0009 | 1.30 |
| 4 | 0.30 | 0.0010 | 1.28 |
| 5 | 0.35 | 0.0010 | 1.48 |
| 6 | 0.41 | 0.0009 | 1.37 |
| 7 | 0.75 | 0.0007 | 1.19 |
By as seen from Table 2, the flux that adopts the vacuum refinement process to remove steel inclusion is processed molten steel, can reduce inclusion content of steel, makes T[O in the steel] content reaches 10 * 10
-6Below; The size of steel inclusion is reduced, and its mean diameter reaches below the 1.5 μ m, oarse-grained Al in the steel
2O
3Etc. the inclusion of fragility seldom, reach cleaning molten steel, improved the purpose of the performance of steel.
The flux of a kind of containing metal calcium of the present invention, carbonate, calcium aluminate etc., after the vacuum refining of liquid steel deoxidation finishes, add in the molten steel, utilize its at high temperature decompose produce micro-bubble carry steel inclusion and calcium and the deoxidation of the molten steel degree of depth and with steel in the low-melting complex inclusion of formation such as aluminum oxide and be easy to the mode such as removal, can carry out deoxidation and inclusion modification processing to molten steel, can obviously reduce the inclusion total amount in the steel, its mean diameter obviously reduces, and reaches the purpose of cleaning molten steel.Highly beneficial to improving steel quality and improving the performance of steel, be particularly suitable for the Control and Inclusion Removal of low-carbon (LC) class steel grade.The present invention has no adverse effects to environment, and STEELMAKING PRODUCTION is had application value.
Claims (3)
1. a vacuum refinement process is removed the flux of steel inclusion, and its composition weight percent is: CaO 55.0～68.0%, CaCO
310.0～18.0%, Ca 7.0～15.0%, Al 2.0～7.0%, Na
2CO
33.0～8.0%, surplus impurity.
2. a vacuum refinement process is removed the preparation method of the flux of steel inclusion, with raw materials of Ca O, CaCO
3, Na
2CO
3, calcium metal Ca mixes by following proportioning, its composition weight percent is: CaO 55.0～68.0%, CaCO
310.0～18.0%, Ca 7.0～15.0%, Al 2.0～7.0%, Na
2CO
33.0～8.0%, surplus impurity, wherein CaO, CaCO
3, Na
2CO
3Granularity below 0.1mm; Behind the abundant mixing of above-mentioned raw materials, dry pressing.
3. vacuum refinement process as claimed in claim 2 is removed the preparation method of the flux of steel inclusion, it is characterized in that, described calcium metal is done Passivation Treatment before mixing.
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|---|---|---|---|
| CN201110326522.7A CN103074468B (en) | 2011-10-25 | 2011-10-25 | Flux for removal of impurities in steel during vacuum refining and preparation method thereof |
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|---|---|---|---|
| CN201110326522.7A CN103074468B (en) | 2011-10-25 | 2011-10-25 | Flux for removal of impurities in steel during vacuum refining and preparation method thereof |
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| CN103074468B CN103074468B (en) | 2014-10-29 |
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Cited By (3)
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| CN108504822A (en) * | 2018-05-15 | 2018-09-07 | 首钢集团有限公司 | A kind of method of small particle aluminate pattern in control ultra-low-carbon steel |
| CN109957688A (en) * | 2019-03-22 | 2019-07-02 | 广西南南铝加工有限公司 | A kind of preparation method of the big specification rectangle ingot of Al-Zn-Mg |
| CN112011671A (en) * | 2020-09-11 | 2020-12-01 | 山东钢铁集团日照有限公司 | Method for removing impurities in RH single-link molten steel under vacuum |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109957688A (en) * | 2019-03-22 | 2019-07-02 | 广西南南铝加工有限公司 | A kind of preparation method of the big specification rectangle ingot of Al-Zn-Mg |
| CN109957688B (en) * | 2019-03-22 | 2021-02-12 | 广西南南铝加工有限公司 | Preparation method of Al-Zn-Mg large-size flat ingot |
| CN112011671A (en) * | 2020-09-11 | 2020-12-01 | 山东钢铁集团日照有限公司 | Method for removing impurities in RH single-link molten steel under vacuum |
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| CN103074468B (en) | 2014-10-29 |
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