CN103215410A - Method for improving cleanness of Nb-Ti containing steel - Google Patents
Method for improving cleanness of Nb-Ti containing steel Download PDFInfo
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- CN103215410A CN103215410A CN2013101362255A CN201310136225A CN103215410A CN 103215410 A CN103215410 A CN 103215410A CN 2013101362255 A CN2013101362255 A CN 2013101362255A CN 201310136225 A CN201310136225 A CN 201310136225A CN 103215410 A CN103215410 A CN 103215410A
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Abstract
The invention provides a method for improving cleanness of Nb-Ti containing steel. The method comprises the following steps of: smelting in a top-bottom combined blowing converter under the condition of argon gas bottom-blowing in the whole process; adding small-grain limes and fluorite in a steel tapping process; adding slow-release deoxidizing agent to the top of the slag after the steel tapping; carrying out secondary refining onto molten steel; feeding the refined molten steel to a continuous casting process for carrying out full-protection casting. According to the invention, low-nitrogen molten steel is obtained by adopting an argon gas bottom-blowing mode in the whole converter smelting process, calcium treatment and soft blowing are performed after LF (Low Frequency) furnace refining desulfuration and heating up, Nb-Ti alloying is carried out and the alloy melting is promoted by carrying out soft blowing again. Moreover, oxide impurities can be reduced by calcium pre-treatment and a soft-blowing process, the Nb-Ti alloy is promoted to melt by the soft blowing, impurities are removed by RH (Ruhrstahl Heraeus) vacuum refining and degassing, impurities are further removed by carrying out soft blowing after breaking the vacuum, and casting blank segregation can be weakened by continuous casting and low-superheat-degree casting, so that the purpose of controlling the oxide impurities and the nitride impurities in the steel is achieved.
Description
Technical field
The present invention relates to make steel the refining controlling field, relate in particular to the method that a kind of minimizing contains Nb, Ti nonmetallic inclusionsin steel.
Background technology
Domestic production high-grade pipe line steel and high-strength steel are taked the technology of LF refining+RH vacuum refinement mostly at present, and the LF stove is mainly realized heating up and dark desulfurization, and the RH realization degassing goes to be mingled with, and produces high-quality pipe line steel and high-strength steel in conjunction with the full guard casting process again.High-strength steel and high-grade pipe line steel take Nb, Ti to strengthen the raising performance substantially, and Nb and Ti are easy segregation element, and can combine generation NbN and TiN in pyroprocess with N, and NbN and TiN are independently or with oxide inclusion companion form to exist.Superheating temperature is higher, higher, oxide-based being mingled with of N content can a large amount of oxide compounds and nitride compound inclusion occur at the strand core more the time, and it is higher that hot-rolled sheet shows as the grading of D class non-metallic inclusion.
In steel-making and refining process, pass through technology controlling and process nonmetallic inclusionsin steels such as hypoxemia, low-sulfur, slag making refining, vacuum refinement, calcium processing, soft blow and full guard casting usually.Steel grade Nb that strengthens for Nb, Ti and Ti at high temperature can combine with N and form TiN and NbN, and nitride inclusion is less usually, but oxide inclusion can be used as the core that nitride forms, therefore in steel oxide inclusion more in nitride can occur in a large number.
Present smelting technology Nb adds in earlier stage in the refining of LF stove, adds Ti after finishing slag making desulfurization and temperature adjustment.The affiliation that adds of Nb and Ti inevitably generates NbN and TiN, in LF stove treating processes and when just having finished in the steel oxide inclusion more, NbN that generates in this process and TiN can be that core is in conjunction with forming complex inclusion with the oxide inclusion, complex inclusion forms the back and is difficult to remove from molten steel, can remain into finally to cause the grading of hot-rolled sheet D type impurity higher in the strand always.This patent is oxide-basedly to be mingled with, to optimize when reducing nitride inclusion the purpose that Nb and Ti alloying technology realize oxide compound and nitride inclusion in the reduction steel reducing.
Summary of the invention
The present invention contains Nb, Ti production technique above shortcomings for solving to have now, provides a kind of raising to contain the technology of Nb, Ti steel cleanness.
The technical scheme that the present invention solves the problems of the technologies described above is as follows: a kind of raising contains the method for Nb, Ti steel cleanness, may further comprise the steps:
Step a: molten iron is blended into the top and bottom combined blown converter blowing, omnidistance argon bottom-blowing, tapping after smelting is finished, tapping process adds granule lime and fluorite, and the tapping back top of the slag adds the slowly-releasing reductor;
Step b: molten steel is carried out LF stove slag making refining, finish slag making desulfurization, calcium processing, Nb-Ti alloying, soft blow;
After the refining, the control ladle is decided slag ingredient and is comprised 50～55%CaO, 24～28%Al
2O
3, 6～9%MgO, 4～8%SiO
2, TFe+MnO≤1.0%;
Step c: molten steel after refining is carried out RH vacuum refinement and the processing of secondary calcium once more, guarantee that at last continuous casting carries out the casting of low overheat full guard.
On the basis of technique scheme, the present invention can also do following improvement.
Further, granule lime and fluorite add-on are 8kg/ ton steel and 2kg/ ton steel among the described step a, and slowly-releasing reductor metallic aluminium content is 50%, and its add-on is a 1kg/ ton steel.
Further, calcium is handled Ca content 15-30ppm in the molten steel of back, soft blow argon flow amount 100-200NL/min, soft blow time 5-10min among the described step b.
Further, soft blow argon flow amount 100-200NL/min among the described step b, soft blow time 5-10min.
Further, secondary soft blow argon flow amount 100-160NL/min among the described step c, soft blow time 10-15min.
Further, low overheat is a 15-25 ℃ of tundish superheating temperature among the described step c.
The present invention carries out calcium and handles and soft blow after the refining of LF stove is finished desulfurization and heated up; add Nb and Ti alloy then; soft blow promotes alloy melting then; carry out RH vacuum refinement and secondary soft blow subsequently; last continuous casting low overheat full guard casting can realize the stable control of oxide-based and nitride inclusion thing etc.
Embodiment
Below principle of the present invention and feature are described, institute gives an actual example and only is used to explain the present invention, is not to be used to limit scope of the present invention.
The operational path that the present invention taked is: ' converter smelting → LF slag making refining → RH vacuum refinement → full guard casting '.
Know-why of the present invention is: the present invention is by low-sulfur, hypoxemia and calcium processing controls sulfide inclusion thing, controlled oxidation thing type impurities such as hypoxemia, slag making refining, calcium processing, soft blow, control nitride inclusion things such as hypoxemia, low nitrogen, back Nb-Ti alloying, low overheat.The aluminate that the converter tapping aluminium deoxidation produces, the tiny bunch shape that is is distributed in the molten steel, changes to low-melting calcium-aluminate type impurity gradually under the effect of high basicity top slag and calcium processing, can effectively reduce the total amount of oxide-based inclusion after the soft blow.After oxide inclusion reduces, carry out the Nb-Ti alloying and can reduce nitride formation.The RH vacuum refinement removal inclusion that can further outgas, less inclusion also can be assembled and grow up, and secondary soft blow subsequently can be removed the inclusion that this part is grown up, and further improves cleanliness factor.The segregation of the casting can weakening of continuous casting low overheat easy Nb and Ti reduces the trend that the process of setting inclusion is grown up.
(1) 300 ton of top and bottom combined blown converter smelting, omnidistance argon bottom-blowing adds granule lime and fluorite in tapping process, and tapping finishes the top of the slag and adds the slowly-releasing reductor.
(2) after the refining of LF stove, control top slag composition: 55～60%CaO, 25～30%Al
2O
3, 6～9%MgO, 5～10%SiO
2, TFe+MnO≤1.0%; The desulfurization and the back calcium that heats up are handled molten steel Ca content 15-30ppm; Soft blow, soft blow argon flow amount 100-200NL/min, soft blow time 5-10min; The Nb-Ti alloying, soft blow, soft blow argon flow amount 100-200NL/min, soft blow time 5-10min.
(3) RH vacuum cycle, soft blow behind the vacuum breaker, soft blow argon flow amount 100～160NL/min, 10～15min is carried out in soft blow; Send the casting of continuous casting low overheat full guard at last, 15-25 ℃ of tundish superheating temperature.
Embodiment:
Singly water time production 8 stoves and contain Nb and Ti hot rolling steel grade, adopt ' converter-LF refining-RH refining-continuous casting ' operational path production.
300 tons of top and bottom combined blown converter steelmakings, tapping process adds granule lime 8kg/ ton steel and fluorite 2kg/ ton steel, and the tapping back top of the slag adds slowly-releasing reductor 1kg/ ton steel, and tapping back molten steel nitrogen content sees Table 1.The LF stove carries out the calcium processing after finishing desulfurization and intensification, and every stove is fed Si-Ca line 600m, soft blow, Nb-Ti alloying, soft blow, and process parameter sees Table 3, and the refining of LF stove finishes Ca content and sees Table 1, and the ladle final slag composition sees Table 2.Carry out the RH vacuum refinement then and handle, soft blow behind the vacuum breaker, the soft blow parameter sees Table 3, carries out the full guard casting after soft blow is finished, and the tundish superheating temperature sees Table 1.
Table 1 process molten steel component
Table 2 ladle top slag composition
Table 3 soft blow process control parameters
Ray examination cleaning back hot rolling under 8 heat strands, all non-metallic inclusion grading check is done in sampling on every stove heat bundle coiled sheet, and hot-rolled sheet coil non-metallic inclusion rating result sees Table 4, and the category-B inclusion is graded all below 1.5 grades.Inclusion grading situation shows that the inventive method is desirable to non-metallic inclusion control, and this processing method can satisfy the requirement to non-metallic inclusion such as hot rolling pipe line steel, weldering bottle steel and high-strength steel.
The grading of table 4 hot-rolled sheet coil non-metallic inclusion
The method that raising provided by the invention contains Nb, Ti steel cleanness obtains following technique effect, is specially:
(1) compare with existing patented technology, the present invention has developed the technology of LF stove slag making refining, calcium processing, Nb and Ti alloying, soft blow.
(2) realize the control of sulphur and oxide-based inclusion by controlling refining top slag ingredient, the calcium treatment process reduces the oxidation class and is mingled with back Nb and Ti alloying, improved yield of alloy, reduced the nitride-based formation that is mingled with, can satisfy of the requirement of finished product hot-rolled sheet coil inclusion.
(3) omnidistance argon bottom-blowing in the converter steelmaking process, can stably manufactured N content less than the molten steel of 25ppm.
(4) soft blow can promote to grow up in the vacuum cycle process after the RH vacuum refinement, do not have enough time to float little inclusion further come-up enter in the slag.
(5) the present invention can be applicable to the high-strength steel or the pipe line steel of Nb or Ti reinforcement, not only can stablize controlled oxidation thing non-metallic inclusion, and can stablize the nitride-based non-metallic inclusion of control, realize that hot-rolled sheet non-metallic inclusion grading qualification rate improves and performance is uniform and stable.
It should be noted last that, above embodiment is only unrestricted in order to technical scheme of the present invention to be described, although the present invention is had been described in detail with reference to example, those of ordinary skill in the art is to be understood that, can make amendment or be equal to replacement technical scheme of the present invention, and not breaking away from the spirit and scope of technical solution of the present invention, it all should be encompassed in the middle of the claim scope of the present invention.
Claims (6)
1. a raising contains the method for Nb, Ti steel cleanness, it is characterized in that: may further comprise the steps:
Step a: molten iron is blended into the top and bottom combined blown converter blowing, omnidistance argon bottom-blowing, tapping after smelting is finished, tapping process adds granule lime and fluorite, and the tapping back top of the slag adds the slowly-releasing reductor;
Step b: molten steel is carried out LF stove slag making refining, finish slag making desulfurization, intensification, calcium processing, Nb-Ti alloying, soft blow;
After the refining of LF stove, the ladle top slag composition comprises 50～55%CaO, 24～28%Al
2O
3, 6～9%MgO, 4～8%SiO
2, TFe+MnO≤1.0%;
Step c: molten steel after refining is carried out the RH vacuum refinement once more, carry out soft blow behind the vacuum breaker, guarantee that at last continuous casting carries out the casting of low overheat full guard.
2. raising according to claim 1 contains the method for Nb, Ti steel cleanness, it is characterized in that, granule lime and fluorite add-on are 8kg/ ton steel and 2kg/ ton steel among the described step a, and metallic aluminium content is that 50% slowly-releasing reductor add-on is a 1kg/ ton steel.
3. raising according to claim 1 contains the method for Nb, Ti steel cleanness, it is characterized in that, calcium is handled Ca content 15-30ppm in the molten steel of back among the described step b, and soft blow gas is argon gas, the flow 100-200NL/min of soft blow, soft blow 5-10min.
4. raising according to claim 1 contains the method for Nb, Ti steel cleanness, it is characterized in that, soft blow gas is argon gas among the described step b, the flow 100-200NL/min of soft blow, soft blow time 5-10min.
5. raising according to claim 1 contains the method for Nb, Ti steel cleanness, it is characterized in that, described step c soft blow gas is argon gas, the flow 100-160NL/min of soft blow, soft blow time 10-15min.
6. raising according to claim 1 contains the method for Nb, Ti steel cleanness, it is characterized in that, low overheat is a 15-25 ℃ of tundish superheating temperature among the described step c.
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Cited By (7)
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| CN107012291A (en) * | 2016-01-27 | 2017-08-04 | 鞍钢股份有限公司 | A kind of method for reducing the RH ferro-niobium additions of steel containing niobium |
| CN109082493A (en) * | 2018-07-20 | 2018-12-25 | 邯郸钢铁集团有限责任公司 | Reduce the smelting process that TiN in high titanium microalloying high-strength steel is mingled with content |
| CN111020096A (en) * | 2019-11-22 | 2020-04-17 | 辽宁科技大学 | Single LF (low frequency) process low-nitrogen control method for dual-phase automobile steel DP590 |
| CN113512618A (en) * | 2021-04-02 | 2021-10-19 | 首钢京唐钢铁联合有限责任公司 | Refining duplex method for effectively controlling inclusions |
| CN114836594A (en) * | 2022-05-13 | 2022-08-02 | 福建三钢闽光股份有限公司 | Method for controlling content of Ti in high-strength steel based on LF (ladle furnace) |
| CN115287406A (en) * | 2022-07-18 | 2022-11-04 | 首钢集团有限公司 | Smelting method for removing impurities in steel |
| CN115323116A (en) * | 2022-07-13 | 2022-11-11 | 首钢京唐钢铁联合有限责任公司 | Sulfur control method for treating steel grade based on low sulfur and calcium |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113512618A (en) * | 2021-04-02 | 2021-10-19 | 首钢京唐钢铁联合有限责任公司 | Refining duplex method for effectively controlling inclusions |
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| CN114836594B (en) * | 2022-05-13 | 2024-02-09 | 福建三钢闽光股份有限公司 | Method for controlling Ti content in high-strength steel based on LF furnace |
| CN115323116A (en) * | 2022-07-13 | 2022-11-11 | 首钢京唐钢铁联合有限责任公司 | Sulfur control method for treating steel grade based on low sulfur and calcium |
| CN115323116B (en) * | 2022-07-13 | 2024-03-19 | 首钢京唐钢铁联合有限责任公司 | Sulfur control method for treating steel grades based on low sulfur calcium |
| CN115287406A (en) * | 2022-07-18 | 2022-11-04 | 首钢集团有限公司 | Smelting method for removing impurities in steel |
| CN115287406B (en) * | 2022-07-18 | 2023-07-11 | 首钢集团有限公司 | Smelting method for removing inclusions in steel |
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| CN103215410B (en) | 2016-03-30 |
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Address after: 100041 Shijingshan Road, Beijing, No. 68, No. Patentee after: Shougang Group Co. Ltd. Address before: 100041 Shijingshan Road, Beijing, No. 68, No. Patentee before: Capital Iron & Steel General Company |