CN102876851A - Method for improving calcium yield of RH vacuum furnace - Google Patents
Method for improving calcium yield of RH vacuum furnace Download PDFInfo
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- CN102876851A CN102876851A CN2012103771882A CN201210377188A CN102876851A CN 102876851 A CN102876851 A CN 102876851A CN 2012103771882 A CN2012103771882 A CN 2012103771882A CN 201210377188 A CN201210377188 A CN 201210377188A CN 102876851 A CN102876851 A CN 102876851A
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Abstract
A method for improving the calcium yield of an RH vacuum furnace includes the steps: molten iron treatment; converter smelting; refining in an LF furnace; RH vacuum treatment; and tapping and casting to form a billet. By the method, the calcium yield of the RH vacuum furnace is stably improved from 3-5% to 8-12%, and the number of continuous molten iron casting and rolling furnaces of the RH vacuum furnace is increased from 2.7 to 9, so that consumption of raw materials is reduced, the operating rate of a unit is increased, and production cost is reduced. The method is wide in applicable range, namely, the method can be used for all steel types of continuous casting and rolling RH production for sheet billets.
Description
Technical field
The present invention relates to the smelting process of molten steel, refer to particularly the method for calcium recovery rate in a kind of RH of raising vacuum oven.
Background technology
The relation of the casting properties of continuous casting steel, tissue, characteristic and non-metallic inclusion is very close.Therefore, in steelmaking process, not only to control the chemical ingredients of molten steel well, but also will control the non-metallic inclusion in the steel, with so that guarantee the purity of molten steel.In order to improve steel performance, as using the formation of manganese sulfide inclusion in " calcium processings " minimizing steel, thereby the sulfide inclusion of avoiding forming strip improves the anisotropy of steel; Process by calcium molten steel is carried out " hot-short " etc. that desulfurization reduces steel, usually all use the method that molten steel is carried out " calcium processing " to change slag inclusion thing form in the steel.
Aluminium is widely adopted in steelmaking process as strong reductor, but with in steel, forming a large amount of aluminium sesquioxides behind the aluminium deoxidation.Because it is clean that aluminium sesquioxide is difficult to remove, thereby when casting, be easy to stick to the interruption that mouth of a river wall causes the nozzle clogging casting cycle from steel.In order to address this problem, method commonly used is molten steel to be carried out calcium process, and by to adding certain calcium in the steel, forms low-melting calcium aluminate so that dystectic aluminium sesquioxide is combined with calcium oxide, thereby greatly improves the casting properties of molten steel.
The calcium metallurgical technology has been used very generally in modern steelmaking process in a word, but improper if the calcium processing is controlled, and not only can not reach the metallurgical effect of expection, can worsen on the contrary the casting properties of steel.If the control of calcium treatment technology was not at that time; not only nozzle clogging is brought impact; and also can make a big impact to the covering slag performance of melting in the continuous cast mold and the behavior of solidifying of molten steel; when the CaO pulvis of using such as desulfurization makes moist; if being sprayed into a large amount of CaO, molten steel carries out the desulfurization processing; can cause that [H] content significantly raises in the steel; if add that rhythm of production is nervous; after calcium is processed; later stage stirs and calm deficiency of time; inclusion floating is insufficient, and after continuous casting was opened and watered, the covering slag performance can sharply worsen; can't keep its normally lubricated and heat transmission function; this moment, the serious variation of heat-transfer effect in the crystallizer can not reach the metallurgical effect of expection, produced a series of product quality problems and even bleed-out accident.
Because the density solubleness lower, in steel of calcium is little, the vapour pressure of calcium is large, boiling point is low, high volatile volatile and chemically reactive, so that the calcium amount that adds in the steel is large, yet recovery rate is but very low, and being subjected to factor affecting such as the quantity of slag in deoxidation of molten steel situation, the ladle, the calcium contents difficulty that will stablize in the large production of reality in the control steel is larger.The method that the Xiang Gangzhong that commonly uses in the large production of at present industry adds calcium has two kinds: the one, dust; The 2nd, feed silk.The conditional request of the pulvis preparation of the technology of dusting, conveying, protection against the tide is higher, facility investment is larger, cost is high, and dusting, it is large easily to cause increasing in the steel hydrogen, nitrogen pick-up, temperature drop, not only can reach the effect of dusting and greatly overcome the shortcoming of dusting and feed silk, therefore " calcium processing " hello silk technology has obtained rapid popularization in the eighties.
In continuous casting and rolling technique of sheet bar, because a lot of steel grades are to S, P, O, N, H, the C element requires very low, need to process through the RH vacuum oven, for " slag inclusion thing sex change in the steel " and " desulfurization " reach " castability that solves continuous caster " problem, all need in processing, the RH vacuum oven carry out " calcium processing ", but FeO+MnO is unstable in the RH Zinc Vacuum Furnace Slag, usually cause RH vacuum oven calcium to process recovery rate and only be 3-5% and unstable, the non-constant of calcium treatment effect, make smelting cost high, steel quality is poor, the continuous casting of molten steel that causes RH in the continuous casting and rolling technique of sheet bar to produce connects that to water the stove number often very low, usually only has 2～3 stoves.The major cause that produces this phenomenon is that slag fluidity was bad after the RH vacuum oven was processed, between the slag reaction insufficient, the oxygen in the slag and the oxygen in the molten steel are in nonequilibrium state, FeO+MnO is in utmost point unsteady state in the slag, the time low when high.And the calcium line amount of squeezing in the steel by production engineering specifications in the calcium treating processes is certain, and therefore when FeO+MnO content was high, it is on the low side that calcium is processed recovery rate.When FeO+MnO content was low, it is higher that calcium is processed recovery rate.And the molten aluminium content of the acid in the molten steel is high, in the cast, cotton-shapedly be mixed in the enrichment of mouth of a river place and cause nozzle clogging, because the thinslab casting slab thickness is 50mm thick (it is thick that conventional continuous caster slab thickness is generally 200mm) only, therefore in its continuous casting water-coating port than little many of water-coating port in the conventional continuous casting, purity and castability to molten steel are had relatively high expectations, and require higher to RH vacuum oven calcium treatment effect.Calcium processing recovery rate is on the low side or higher all can not to form low-melting calcium aluminate so that dystectic aluminium sesquioxide is combined with calcium oxide, (annotate: thinslab casting generally is middle water-coating port dross finally to cause in the continuous casting water-coating port or ladle nozzle dross, conventional continuous caster generally is the ladle nozzle dross, generally solve many than conventional continuous caster nozzle clogging problem hard of thinslab casting nozzle clogging, because of in thinslab casting in the water-coating port dross, its ladle nozzle does not have dross), it is unstable that RH vacuum oven calcium is processed recovery rate, and the low restricted link that has become sheet billet continuous casting and rolling production line production RH steel.
Process the low and instability problem of recovery rate for solving calcium, have the special-purpose used device of use that the calcium alloy rod is inserted into ladle bottom, improve the recovery rate of calcium, the deficiency of its existence is that not only cost is too high, and the FeO+MnO problem is very little in the solution slag;
For the stove number waters in the company of improving RH steel continuous caster, some factory has adopted " converter+LF+RH+ calcium is processed " to reach " converter+RH+LF+calcium is processed ", " converter+LF+RH+ LF+ calcium is processed " technique, though the stove number is watered in the company of continuous caster certain effect is arranged, finally all can't resolve RH steel calcium and process oxidisability problem and the low and instability problem of RH steel calcium processing recovery rate in the front slag.
Summary of the invention
The objective of the invention is only to be 3-5% and unstable in order to solve CSP RH vacuum oven calcium processing recovery rate, and improve continuous casting and even water the low problem of stove number, provide a kind of RH vacuum oven calcium to process recovery rate and be at least 8% and stable, connect the method for watering calcium recovery rate in the raising RH vacuum oven that the stove number reaches 9 stoves at least.
Realize the measure of above-mentioned purpose:
A kind of method that improves calcium recovery rate in the RH vacuum oven, its step:
1) carrying out molten iron processes;
2) carry out converter smelting;
3) in the LF stove, carry out refining:
A, carry out Argon, argon blowing time is not less than 1 minute, and adopts the positive pressure operation, and namely pressure is higher than environmental stress and gets final product;
B, change slag, change the slag time to be controlled at 3～10 minutes;
C, change slag and finish after, add lime according to 3.3～5.0 kg/tonnes of steel, add refining slag according to 0.67～2.0 kg/tonne of steel, and according to 6.0～7.0 kg/tonnes of steel control quantity of slag, the oxygen level in the control molten steel is at 350～450PPm;
4) carry out the RH vacuum-treat, and add lime according to 2.0～3.0 kg/tonnes of steel, and according to being routinely added to refining agent or sweetening agent;
5) be sprinkled into aluminum shot according to 0.1～0.5 kg/tonne of steel at the slag surface uniform, again according to 4.0～6.0 meters/ton steel feeding silicon-calcium wires, and the control wire-feeding velocity is not less than 5 meter per seconds; FeO+MnO≤5.5 (wt%) in the control slag; Carry out conventional soft blow;
6) tap and pour into base.
It is characterized in that: when slag produces the crust phenomenon, adopt adding iron calcium line to carry out broken shell, the iron calcium line adds according to 0.70～1.4 meter/ton steel control.
The present invention compared with prior art, RH vacuum oven calcium is processed recovery rate by the stable 8-12% that brings up to of 3-5%, RH vacuum oven continuous casting of molten steel tandem rolling stove number is brought up at least 9 stoves by 2.7 stoves, thereby reduced the usage quantity of this raw material, improve the unit operation rate, reduce production costs, and the present invention is applied widely, namely can be used for all steel grades that CSP RH produces.
Embodiment
The below is described in detail the present invention:
Embodiment 1
A kind of method that improves calcium recovery rate in the RH vacuum oven, its step:
1) carrying out molten iron processes;
2) carry out converter smelting;
3) in the LF stove, carry out refining:
A, carry out Argon, argon blowing time 1.5 minutes, and adopt the positive pressure operation, namely pressure is higher than environmental stress and gets final product;
B, change slag, change the slag time to be controlled at 3 minutes;
C, change slag and finish after, add lime according to 3.3 kg/tonnes of steel, add refining slag according to 0.67 kg/tonne of steel, and according to 6.5 kg/tonnes of steel control quantity of slag, the oxygen level in the control molten steel is at 380PPm;
4) carry out the RH vacuum-treat, and add lime according to 2.0 kg/tonnes of steel, and according to being routinely added to refining agent or sweetening agent;
5) be sprinkled into aluminum shot according to 0.4 kg/tonne of steel at the slag surface uniform, again according to 4.0 meters/ton steel feeding silicon-calcium wires, and the control wire-feeding velocity is at 5 meter per seconds; FeO+MnO is 5.0 (wt%) in the slag; Carry out conventional soft blow;
6) tap and pour into base.
Present embodiment after testing, the calcium recovery rate is 8.3% in the RH vacuum oven, connects that to water the stove number be 9 stoves.
Embodiment 2
A kind of method that improves calcium recovery rate in the RH vacuum oven, its step:
1) carrying out molten iron processes;
2) carry out converter smelting;
3) in the LF stove, carry out refining:
A, carry out Argon, argon blowing time 2 minutes, and adopt the positive pressure operation, namely pressure is higher than environmental stress and gets final product;
B, change slag, change the slag time to be controlled at 4.5 minutes;
C, change slag and finish after, add lime according to 3.8 kg/tonnes of steel, add refining slag according to 0.95 kg/tonne of steel, and according to 6.0 kg/tonnes of steel control quantity of slag, the oxygen level in the control molten steel is at 390PPm;
4) carry out the RH vacuum-treat, and add lime according to 2.3 kg/tonnes of steel, and according to being routinely added to refining agent or sweetening agent;
5) be sprinkled into aluminum shot according to 0.45 kg/tonne of steel at the slag surface uniform, again according to 5.0 meters/ton steel feeding silicon-calcium wires, and the control wire-feeding velocity is at 5.5 meter per seconds; FeO+MnO is 4.5 (wt%) in the slag; Carry out conventional soft blow;
6) tap and pour into base.
Present embodiment after testing, the calcium recovery rate is 8.8% in the RH vacuum oven, connects that to water the stove number be 10 stoves.
Embodiment 3
A kind of method that improves calcium recovery rate in the RH vacuum oven, its step:
1) carrying out molten iron processes;
2) carry out converter smelting;
3) in the LF stove, carry out refining:
A, carry out Argon, argon blowing time 2.5 minutes, and adopt the positive pressure operation, namely pressure is higher than environmental stress and gets final product;
B, change slag, change the slag time to be controlled at 6 minutes;
C, change slag and finish after, add lime according to 4.2 kg/tonnes of steel, add refining slags according to 1.35 kg/tonnes of steel, and according to 7.0 kg/tonnes of steel control quantity of slag, the oxygen level in the control molten steel is at 400PPm;
4) carry out the RH vacuum-treat, and add lime according to 2.6 kg/tonnes of steel, and according to being routinely added to refining agent or sweetening agent;
5) be sprinkled into aluminum shot according to 0.2 kg/tonne of steel at the slag surface uniform, again according to 5.5 meters/ton steel feeding silicon-calcium wires, and the control wire-feeding velocity is at 6.5 meter per seconds; FeO+MnO is 4.8 (wt%) in the slag; Carry out conventional soft blow;
6) tap and pour into base.
Present embodiment after testing, the calcium recovery rate is 9.5% in the RH vacuum oven, connects that to water the stove number be 11 stoves.
Embodiment 4
A kind of method that improves calcium recovery rate in the RH vacuum oven, its step:
1) carrying out molten iron processes;
2) carry out converter smelting;
3) in the LF stove, carry out refining:
A, carry out Argon, argon blowing time 3 minutes, and adopt the positive pressure operation, namely pressure is higher than environmental stress and gets final product;
B, change slag, change the slag time to be controlled at 8 minutes;
C, change slag and finish after, add lime according to 4.6 kg/tonnes of steel, add refining slags according to 1.6 kg/tonnes of steel, and according to 6.6 kg/tonnes of steel control quantity of slag, the oxygen level in the control molten steel is at 420PPm;
4) carry out the RH vacuum-treat, and add lime according to 2.8 kg/tonnes of steel, and according to being routinely added to refining agent or sweetening agent;
5) be sprinkled into aluminum shot according to 0.3 kg/tonne of steel at the slag surface uniform, again according to 6 meters/ton steel feeding silicon-calcium wires, and the control wire-feeding velocity is at 6.8 meter per seconds; FeO+MnO is 4.3 (wt%) in the slag; Carry out conventional soft blow;
6) tap and pour into base.
Present embodiment after testing, the calcium recovery rate is 10% in the RH vacuum oven, connects that to water the stove number be 11 stoves.
Embodiment 5
A kind of method that improves calcium recovery rate in the RH vacuum oven, its step:
1) carrying out molten iron processes;
2) carry out converter smelting;
3) in the LF stove, carry out refining:
A, carry out Argon, argon blowing time 2.5 minutes, and adopt the positive pressure operation, namely pressure is higher than environmental stress and gets final product;
B, change slag, change the slag time to be controlled at 10 minutes;
C, change slag and finish after, add lime according to 5 kg/tonnes of steel, add refining slags according to 2 kg/tonnes of steel, and according to 7 kg/tonnes of steel control quantity of slag, the oxygen level in the control molten steel is at 410PPm;
4) carry out the RH vacuum-treat, and add lime according to 3 kg/tonnes of steel, and according to being routinely added to refining agent or sweetening agent;
5) be sprinkled into aluminum shot according to 0.4 kg/tonne of steel at the slag surface uniform, again according to 5.7 meters/ton steel feeding silicon-calcium wires, and the control wire-feeding velocity is at 6 meter per seconds; FeO+MnO is 4.6 (wt%) in the slag; Carry out conventional soft blow;
6) tap and pour into base.
Present embodiment after testing, the calcium recovery rate is 11.5% in the RH vacuum oven, connects that to water the stove number be 12 stoves.
If when slag produces the crust phenomenon, can add the iron calcium line according to 0.70～1.4 meter/ton steel and carry out broken shell.
Above-described embodiment only exemplifies for the best, and is not to be restriction to embodiments of the present invention.
Claims (2)
1. method that improves calcium recovery rate in the RH vacuum oven, its step:
1) carrying out molten iron processes;
2) carry out converter smelting;
3) in the LF stove, carry out refining:
A, carry out Argon, argon blowing time is not less than 1 minute, and adopts the positive pressure operation, and namely pressure is higher than environmental stress and gets final product;
B, change slag, change the slag time to be controlled at 3～10 minutes;
C, change slag and finish after, add lime according to 3.3～5.0 kg/tonnes of steel, add refining slag according to 0.67～2.0 kg/tonne of steel, and according to 6.0～7.0 kg/tonnes of steel control quantity of slag, the O content in the control molten steel is at 350～450PPm;
4) carry out the RH vacuum-treat, and add lime according to 2.0～3.0 kg/tonnes of steel, and according to being routinely added to refining agent or sweetening agent;
5) be sprinkled into aluminum shot according to 0.1～0.5 kg/tonne of steel at the slag surface uniform, again according to 4.0～6.0 meters/ton steel feeding silicon-calcium wires, and the control wire-feeding velocity is not less than 5 meter per seconds; FeO+MnO≤5.5 (wt%) in the control slag; Carry out conventional soft blow;
6) tap and pour into base.
2. a kind of method that improves calcium recovery rate in the RH vacuum oven as claimed in claim 1 is characterized in that: when slag produces the crust phenomenon, adopt to add the iron calcium line and carry out broken shell, the iron calcium line adds according to 0.70～1.4 meter/ton steel control.
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Cited By (3)
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| CN103695597A (en) * | 2013-12-11 | 2014-04-02 | 首钢总公司 | Molten steel calcium treatment process adopting pure calcium line |
| CN107541580A (en) * | 2017-08-25 | 2018-01-05 | 武汉钢铁有限公司 | The inclusion control method of Hot Rolling Automobile steel is smelted in CSP producing lines |
| CN111575446A (en) * | 2020-06-25 | 2020-08-25 | 江苏省沙钢钢铁研究院有限公司 | RH vacuum calcification furnace process treatment method |
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