CN103215410B - A kind of method improved containing Nb, Ti steel cleanness - Google Patents
A kind of method improved containing Nb, Ti steel cleanness Download PDFInfo
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- CN103215410B CN103215410B CN201310136225.5A CN201310136225A CN103215410B CN 103215410 B CN103215410 B CN 103215410B CN 201310136225 A CN201310136225 A CN 201310136225A CN 103215410 B CN103215410 B CN 103215410B
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Abstract
The invention provides a kind of method improved containing Nb, Ti steel cleanness, comprise the following steps: top and bottom combined blown converter smelting, omnidistance argon bottom-blowing, add granule lime and fluorite in tapping process, after tapping, the top of the slag adds slow release deoxidizing agent; Molten steel carries out secondary refining; Continuous casting is sent to carry out full guard casting on the molten steel after refining.The present invention takes omnidistance argon bottom-blowing pattern can obtain low nitrogen steel water by converter smelting, carries out Calcium treatment and soft blow, then carry out Nb-Ti alloying after LF stove refining desulfuration and intensification complete, and soft blow promotes alloy melting again.Oxide-based being mingled with is reduced by first Calcium treatment and soft blow technique, soft blow promotes Nb-Ti alloy melting, degassed the going of RH vacuum refinement is mingled with, the further removal of inclusions of soft blow after vacuum breaker, the casting of continuous casting low overheat can weaken strand segregation, thus reaches and control oxide-based in steel being mingled with and the nitride-based object be mingled with.
Description
Technical field
The present invention relates to steel-making refining controlling field, particularly relate to a kind of method reduced containing Nb, Ti nonmetallic inclusionsin steel.
Background technology
The technique of LF refining+RH vacuum refinement taked mostly by current domestic production high-grade pipe line steel and high-strength steel, and LF stove mainly realizes heating up and dark desulfurization, and RH realizes degassed going and is mingled with, then in conjunction with the pipe line steel of full guard casting process production high-quality and high-strength steel.High-strength steel and high-grade pipe line steel substantially take Nb, Ti strengthen improve performance, Nb and Ti is easy segregation element, and can be combined with N in pyroprocess generate NbN and TiN, NbN and TiN with independence or accompany form to exist with oxide inclusion.Superheating temperature is higher, N content is higher, the oxide-based inclusion that can occur a large amount of oxide compound and nitride compound when being mingled with more at strand core, and it is higher that hot-rolled sheet shows as the grading of D class non-metallic inclusion.
Usually by technology controlling and process nonmetallic inclusionsin steels such as hypoxemia, low-sulfur, slag refining, vacuum refinement, Calcium treatment, soft blow and full guard casting in steel-making and refining process.Steel grade Nb and Ti for Nb, Ti strengthening at high temperature can be combined with N and form TiN and NbN, and usual nitride inclusion is less, but the core that oxide inclusion can be formed as nitride, therefore in steel oxide inclusion more in nitride can appearance in a large number.
Current smelting technology Nb adds in the refining of LF stove early stage, adds Ti after completing slag making desulfurization and temperature adjustment.The membership that adds of Nb and Ti inevitably generates NbN and TiN, in LF stove treating processes and when just terminating, in steel, oxide inclusion is more, NbN and TiN generated in this process can be that core combines formation complex inclusion with oxide inclusion, complex inclusion forms rear being difficult to and removes from molten steel, can remain in strand always and finally cause the grading of hot-rolled sheet D type impurity higher.This patent be reduce oxide-basedly to be mingled with, reduces nitride inclusion while optimize the object that Nb and Ti alloying technology realizes oxide compound and nitride inclusion in reduction steel.
Summary of the invention
The present invention is existing containing Nb, Ti production technique above shortcomings for solving, and provides a kind of technique improved containing 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 method improved containing Nb, Ti steel cleanness, comprises the following steps:
Step a: molten iron is blended into top and bottom combined blown converter blowing, omnidistance argon bottom-blowing, has smelted rear tapping, and tapping process adds granule lime and fluorite, and after tapping, the top of the slag adds slow release deoxidizing agent;
Step b: molten steel is carried out LF stove slag refining, completes slag making desulfurization, Calcium treatment, Nb-Ti alloying, soft blow;
After refining, control ladle is determined 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: the molten steel after refining is carried out RH vacuum refinement and secondary Calcium treatment again, finally guarantees that 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, in described step a, granule lime and fluorite add-on are 8kg/ ton steel and 2kg/ ton steel, and slow release deoxidizing agent metal aluminum content is 50%, and its add-on is 1kg/ ton steel.
Further, Ca content 15-30ppm, soft blow argon flow amount 100-200NL/min, soft blow time 5-10min in molten steel after Calcium treatment in described step b.
Further, soft blow argon flow amount 100-200NL/min in described step b, soft blow time 5-10min.
Further, secondary soft blow argon flow amount 100-160NL/min, soft blow time 10-15min in described step c.
Further, in described step c, low overheat is 15-25 DEG C of tundish superheating temperature.
The present invention completes desulfurization in the refining of LF stove and carries out Calcium treatment and soft blow after heating up; then Nb and Ti alloy is added; then soft blow promotes alloy melting; carry out RH vacuum refinement and secondary soft blow subsequently; last continuous casting low overheat full guard casting, can realize oxide-based and stability contorting etc. that is nitride inclusion thing.
Embodiment
Be described principle of the present invention and feature below, example, only for explaining the present invention, is not intended to limit scope of the present invention.
The operational path that the present invention takes is: ' converter smelting → LF slag refining → RH vacuum refinement → full guard casting '.
Know-why of the present invention is: the present invention controls Sulfide inclusion by low-sulfur, hypoxemia and Calcium treatment, the control oxide type impurity such as hypoxemia, slag refining, Calcium treatment, soft blow, hypoxemia, low nitrogen, rear Nb-Ti alloying, low overheat etc. control nitride inclusion thing.The aluminate that converter tapping aluminium deoxidation produces, is tinyly distributed in molten steel in tufted, changes gradually, effectively can reduce the total amount of oxide-based inclusion after soft blow under the effect of high alkalinity top slag and Calcium treatment to the calcium-aluminate type impurity of low melting point.After oxide inclusion reduces, carry out Nb-Ti alloying can reduce nitride formation.RH vacuum refinement can further degassed removal of inclusions, and less inclusion also can agglomeration, and secondary soft blow subsequently can remove this part inclusion of growing up, and improves cleanliness factor further.The casting of continuous casting low overheat can weaken the segregation of easy Nb and Ti, reduces the trend that 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 terminates the top of the slag and adds slow release deoxidizing agent.
(2), after the refining of LF stove, top slag composition is controlled: 55 ~ 60%CaO, 25 ~ 30%Al
2o
3, 6 ~ 9%MgO, 5 ~ 10%SiO
2, TFe+MnO≤1.0%; Desulfurization and the rear Calcium treatment that heats up, molten steel Ca content 15-30ppm; Soft blow, soft blow argon flow amount 100-200NL/min, soft blow time 5-10min; Nb-Ti alloying, soft blow, soft blow argon flow amount 100-200NL/min, soft blow time 5-10min.
(3) RH vacuum cycle, soft blow after vacuum breaker, soft blow argon flow amount 100 ~ 160NL/min, 10 ~ 15min is carried out in soft blow; Continuous casting low overheat full guard is finally sent to cast, tundish superheating temperature 15-25 DEG C.
Embodiment:
Singly water time production 8 stoves containing Nb and Ti hot rolling steel grade, adopt ' converter-LF refining-RH refining-continuous casting ' operational path to produce.
300 tons of top and bottom combined blown converter steelmakings, tapping process adds granule lime 8kg/ ton steel and fluorite 2kg/ ton steel, and after tapping, the top of the slag adds slow release deoxidizing agent 1kg/ ton steel, and after tapping, nitrogen content in liquid steel is in table 1.LF stove completes desulfurization and carries out Calcium treatment after heating up, and Si-Ca line 600m fed by every stove, and soft blow, Nb-Ti alloying, soft blow, process parameter is in table 3, and the refining of LF stove terminates Ca content in table 1, and ladle final slag composition is in table 2.Then carry out RH vacuum refinement process, soft blow after vacuum breaker, soft blow parameter, in table 3, carries out full guard casting after soft blow completes, and tundish superheating temperature is in table 1.
Table 1 process molten steel component
Table 2 ladle top slag composition
Table 3 soft blow process control parameters
Hot rolling after ray examination cleaning under 8 heat strands, on every stove heat bundle coiled sheet, all non-metallic inclusion grading inspection is done in sampling, and hot-rolled sheet coil non-metallic inclusion rating result is in table 4, and the grading of category-B inclusion is all below 1.5 grades.It is desirable that inclusion grading situation shows that the inventive method controls non-metallic inclusion, and this processing method can meet the requirement to non-metallic inclusion such as hot rolling pipe line steel, cylinder steel and high-strength steel.
Table 4 hot-rolled sheet coil non-metallic inclusion is graded
Raising provided by the invention obtains following technique effect containing the method for Nb, Ti steel cleanness, is specially:
(1) compared with existing patented technology, this invention exploits the technique of LF stove slag refining, Calcium treatment, Nb and Ti alloying, soft blow.
(2) control of sulphur and oxide-based inclusion is realized by controlling refining top slag ingredient, Calcium treatment technique reduces oxidation class and is mingled with rear Nb and Ti alloying, improve yield of alloy, reduce the nitride-based formation be mingled with, the requirement of finished product hot-rolled sheet coil to inclusion can be met.
(3) omnidistance argon bottom-blowing in converter steelmaking process, stably manufactured N content can be less than the molten steel of 25ppm.
(4) after RH vacuum refinement soft blow can promote to grow up in vacuum cycle process, do not have enough time to float little inclusion float further and enter in slag.
(5) the present invention can be applicable to high-strength steel or the pipe line steel of Nb or Ti strengthening, not only can stability contorting oxide compound non-metallic inclusion, and can the nitride-based non-metallic inclusion of stability contorting, realize hot-rolled sheet non-metallic inclusion grading qualification rate improve and performance uniform and stable.
It should be noted last that, above embodiment is only in order to illustrate technical scheme of the present invention and unrestricted, although with reference to example to invention has been detailed description, those of ordinary skill in the art is to be understood that, can modify to technical scheme of the present invention or equivalent replacement, and not departing from the spirit and scope of technical solution of the present invention, it all should be encompassed in the middle of right of the present invention.
Claims (1)
1. improve the method containing Nb, Ti steel cleanness, it is characterized in that: comprise the following steps:
Step a: molten iron is blended into top and bottom combined blown converter blowing, omnidistance argon bottom-blowing, has smelted rear tapping, and tapping process adds granule lime and fluorite, and after tapping, the top of the slag adds slow release deoxidizing agent; In described step a, granule lime and fluorite add-on are 8kg/ ton steel and 2kg/ ton steel, metal aluminum content be 50% slow release deoxidizing agent add-on be 1kg/ ton steel;
Step b: molten steel is carried out LF stove slag refining, completes slag making desulfurization, intensification, Calcium treatment, Nb-Ti alloying, soft blow;
After the refining of LF stove, ladle top slag composition comprises 50 ~ 55%CaO, 24 ~ 28%Al
2o
3, 6 ~ 9%MgO, 4 ~ 8%SiO
2, TFe+MnO≤1.0%; Ca content 15-30ppm in molten steel after Calcium treatment in described step b, soft blow gas is argon gas, the flow 100-200NL/min of soft blow, soft blow 5-10min;
Step c: the molten steel after refining is carried out RH vacuum refinement and secondary Calcium treatment again, carries out soft blow after vacuum breaker, finally guarantees that continuous casting carries out the casting of low overheat full guard; Described step c soft blow gas is argon gas, the flow 100-160NL/min of soft blow, soft blow time 10-15min;
In described step c, low overheat is 15-25 DEG C of tundish superheating temperature.
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Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| 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 |
| CN111020096B (en) * | 2019-11-22 | 2021-05-28 | 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 |
| 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 |
| 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 |
| 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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| CN102851432A (en) * | 2012-09-12 | 2013-01-02 | 首钢总公司 | Method for removing non-metal foreign substances from pipeline steel |
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| JP3918568B2 (en) * | 2001-03-16 | 2007-05-23 | Ｊｆｅスチール株式会社 | Method for producing ultra-low sulfur steel |
| JP3922181B2 (en) * | 2002-12-27 | 2007-05-30 | Ｊｆｅスチール株式会社 | Melting method of high clean steel |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1600885A (en) * | 2003-09-27 | 2005-03-30 | 首钢总公司 | Method for manufacturing continuous casting low carbon steel containing boron in small square billets |
| CN102337378A (en) * | 2011-10-31 | 2012-02-01 | 首钢总公司 | Process for removing non-metallic inclusions in molten steel |
| CN102719612A (en) * | 2012-06-18 | 2012-10-10 | 首钢总公司 | Method for producing hydrogen-induced cracking (HIC)-resistant pipeline steel |
| CN102851432A (en) * | 2012-09-12 | 2013-01-02 | 首钢总公司 | Method for removing non-metal foreign substances from pipeline steel |
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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 |
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