CN112458236B - Method for refining and deep desulfurization of molten steel, device for refining molten steel and application - Google Patents
Method for refining and deep desulfurization of molten steel, device for refining molten steel and application Download PDFInfo
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- CN112458236B CN112458236B CN202110121970.7A CN202110121970A CN112458236B CN 112458236 B CN112458236 B CN 112458236B CN 202110121970 A CN202110121970 A CN 202110121970A CN 112458236 B CN112458236 B CN 112458236B
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/064—Dephosphorising; Desulfurising
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0025—Adding carbon material
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/064—Dephosphorising; Desulfurising
- C21C7/0645—Agents used for dephosphorising or desulfurising
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Abstract
The invention relates to a method for refining and deep desulfurization of molten steel, a device for refining the molten steel and application of the device. The method comprises the following steps: s1, tapping the molten steel to be refined into a steel ladle, and adding smelting materials into the steel ladle filled with the molten steel to be refined to obtain a steel material to be refined; s2 according to the initial sulfur content of the molten steel to be refined during tapping]IntoAnd a target sulfur content [ S ]]Eyes of a userDetermining technological parameters of lime powder injection, carbon powder injection and top-blown argon injection when molten steel refining is carried out on a steel material to be refined; s3, carrying out molten steel refining on the steel material to be refined; during molten steel refining, lime powder-carbon powder-argon mixed powder airflow is blown into the steel material to be refined through the hollow electrode so as to enable the molten steel to be desulfurized deeply. According to the invention, the lime powder and the carbon powder are dynamically injected by the hollow electrode to carry out deep desulfurization, so that reasonable decarburization and desulfurization of the molten steel can be ensured, the desulfurization dynamic condition is improved, the desulfurization efficiency is improved, the smelting time is shortened, the power consumption and the electrode loss can be reduced, and the production cost is reduced.
Description
Technical Field
The invention belongs to the technical field of secondary refining, and particularly relates to a method for refining and deep desulfurization of molten steel, a device for refining the molten steel and application of the device.
Background
Generally, sulfur is a harmful element for most steel grades. The sulfur exists in the form of sulfide on the grain boundary or heterogeneous interface of the steel, and has great influence on the processing performance, mechanical property, corrosion, welding performance and the like of the steel. Such as: the sulfide inclusions formed reduce the ductility and toughness of the steel; the generated FeS with low melting point can cause the steel to be hot-brittle in hot rolling and welding; when the sulfur content in the steel is high, the hydrogen-induced crack corrosion resistance of the steel is obviously reduced. Therefore, it is important to improve the quality and performance of steel, reduce the generation of defects, and reduce the sulfur content in steel. The LF refining furnace (ladle refining furnace) is used as an effective buffer link for steel making and continuous casting, and plays an important role in molten steel desulfurization. When deep desulfurization is carried out in a traditional LF refining furnace, desulfurizing agents such as lime and the like are usually added for slagging, the electrode is utilized for heating and slagging, and after better desulfurized slag is formed, argon is blown from the bottom to carry out stirring desulfurization; the early slagging time of the traditional deep desulfurization method is generally 3-5 min, the average power consumption of each ton of molten steel to be refined after the molten steel is refined and deeply desulfurized is about 28 kW.h, the electrode consumption of each ton of molten steel to be refined after the molten steel is refined and deeply desulfurized is about 0.25 kg-0.55 kg, and the desulfurization rate is generally 70-80%. Therefore, the deep desulfurization method requires a long molten steel refining time, which results in high power consumption, high electrode loss, high production cost and long production time.
The Chinese patent application CN201410723336.0 discloses a method for improving the desulfurization rate at low cost by pre-treating refined molten steel in an LF furnace, which is characterized in that lime for manufacturing top slag in the LF furnace is added in the tapping process of a converter, and an aluminum-containing deoxidizer is added on the slag surface after the tapping is finished so as to improve the desulfurization rate of molten steel, the total desulfurization rate can reach more than 85 percent, and the sulfur content in steel can be controlled between 0.001 percent and 0.004 percent. However, the method involved in the patent application is to add all the refining slag in the tapping process, and although a certain desulfurization effect can be achieved, the temperature of the molten steel is greatly reduced, the fluidity of the steel slag is deteriorated, and the temperature rise and slagging time of the LF furnace is prolonged. Chinese patent application CN110982988A discloses a desulfurization method for promoting the contact of steel slag in an LF refining furnace and a steelmaking method, wherein the method comprises the steps of blowing argon from one side of a furnace cover of the LF refining furnace to the liquid level of a steel ladle, and simultaneously combining with bottom blowing argon to ensure that the steel slag and molten steel simultaneously carry out circulating flow desulfurization; but the stirring effect of the argon enhanced molten pool which can be realized by adopting the method is relatively low, and the desulfurization kinetic condition of the argon enhanced molten pool is required to be further improved.
Therefore, it is very desirable to provide a method for rapid deep desulfurization in molten steel refining, so as to improve the thermodynamic and kinetic conditions of desulfurization, improve the desulfurization efficiency, and reduce the production cost, so as to meet the requirements of the steel industry.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a method for refining and deep desulfurization of molten steel, a device for refining the molten steel and application. The method adopts argon as carrier gas, and dynamically sprays lime powder and carbon powder through the central channel of the hollow electrode to carry out deep desulfurization, thereby not only ensuring reasonable decarburization and desulfurization of molten steel, improving thermodynamic and kinetic conditions of desulfurization, improving desulfurization efficiency, shortening smelting time, but also reducing power consumption and electrode loss and reducing production cost.
The invention provides a method for refining and deep desulfurization of molten steel in a first aspect, which comprises the following steps:
s1, tapping the molten steel to be refined into a steel ladle, and adding smelting materials into the steel ladle filled with the molten steel to be refined to obtain a steel material to be refined;
s2 according to the initial sulfur content of the molten steel to be refined during tapping]IntoAnd a target sulfur content [ S ]]Eyes of a userDetermining technological parameters of lime powder injection, carbon powder injection and top-blown argon injection when molten steel refining is carried out on a steel material to be refined;
s3, carrying out molten steel refining on the steel material to be refined; during molten steel refining, lime powder-carbon powder-argon mixed powder airflow is blown into the steel material to be refined through the hollow electrode so as to enable the molten steel to be desulfurized deeply.
Preferably, in step S2, the initial sulfur content [ S ] is determined according to the molten steel to be refined]IntoAnd a target sulfur content [ S ]]Eyes of a userDetermining the technological parameters of lime powder, carbon powder and argon injection as follows:
when [ S ]]Into≥40ppm，5ppm≤[S]Eyes of a userWhen the content is less than 10ppm, the blowing rate of the lime powder is 0.6-0.95 kg/(min.t), the blowing rate of the carbon powder is 0.13-0.18 kg/(min.t), the flow rate of top-blown argon is 3-8 NL/(min.t), and the blowing time is 10-15 min;
when [ S ]]Into≥40ppm，[S]Eyes of a userWhen the content is less than 5ppm, the blowing rate of the lime powder is 0.4-0.6 kg/(min.t), the blowing rate of the carbon powder is 0.08-0.13 kg/(min.t), the flow rate of top-blown argon is 5-10 NL/(min.t), and the blowing time is 15-20 min;
when [ S ]]Into＜40ppm，5ppm≤[S]Eyes of a userWhen the content is less than 10ppm, the blowing rate of the lime powder is 0.5-0.75 kg/(min.t), the blowing rate of the carbon powder is 0.11-0.15 kg/(min.t), and the flow rate of top-blown argon is 1-6 NL/(min.t)) The blowing time is 5-10 min;
when [ S ]]Into＜40ppm，[S]Eyes of a userWhen the content is less than 5ppm, the blowing rate of the lime powder is 0.2-0.55 kg/(min.t), the blowing rate of the carbon powder is 0.03-0.11 kg/(min.t), the flow rate of top-blown argon is 2-7 NL/(min.t), and the blowing time is 10-15 min.
Preferably, the smelting material comprises lime and aluminum slag, and the step S1 includes the following substeps:
s11, in the process of tapping molten steel to be refined to the ladle, bottom blowing argon after the ladle flows, wherein the flow rate of the bottom blowing argon is 0.5-2 NL/(min.t); tapping 1/3-1/4 of the total mass of the molten steel to be refined into a ladle, and adding lime, wherein the adding amount of the lime is 3-4 kg/t;
s12, after all the molten steel to be refined is tapped into a ladle, conveying the ladle filled with the molten steel to be refined to a refining station, and adjusting the flow of bottom-blown argon to be 3-8 NL/(min.t);
s13, top-blowing argon into the steel ladle, wherein the flow rate of the top-blown argon is 1-10 NL/(min.t), then utilizing argon plasma slag formed by the top-blown argon for 2-5 min, then adjusting the flow rate of the top-blown argon to be 0.5-5 NL/(min.t), and adding aluminum slag into the steel ladle to obtain a steel material to be refined; the adding amount of the aluminum slag is 1-3 kg/t.
Preferably, the flow rate of the bottom-blown argon gas is adjusted to 2 to 10 NL/(min · t) in the molten steel refining.
Preferably, after the step S3 is performed to obtain the molten desulfurized steel, the method further includes the step S4: and stopping blowing the carbon powder and the lime powder in sequence, adjusting the flow rate of top-blown argon to be 5-10 NL/(min.t), adjusting the flow rate of bottom-blown argon to be 2-6 NL/(min.t), stirring the desulfurized molten steel for 5-10 min by using argon plasma formed by top-blown argon and in a bottom-blown argon mode, and then closing the top-blown argon.
Preferably, after the step S4 is performed to obtain the refined molten steel, the method further includes the step S5: adjusting the flow rate of bottom-blown argon to be 0.5-5 NL/(min.t), and stirring the refined molten steel in a bottom-blown argon mode for 3-5 min.
Preferably, the capacity of the ladle is 50-300 t; the lime powder is passivated lime powder, and the granularity of the lime powder is 100-300 meshes; and/or the carbon powder is coke powder and/or graphite powder, the granularity of the carbon powder is 100-300 meshes, and the sulfur content of the carbon powder is not more than 0.2 wt%.
The present invention provides in a second aspect an apparatus for the refining of molten steel, the apparatus comprising: a ladle refining furnace: the ladle refining furnace comprises a ladle, a furnace cover for sealing a ladle opening and an electric arc heating system; the electric arc heating system comprises a hollow electrode and an electrode holder for holding the hollow electrode, and a conveying pipeline is communicated with the hollow electrode; the furnace cover is provided with a temperature measuring port, a feeding device and a furnace cover hole for inserting the hollow electrode; the bottom of the ladle is provided with an air brick; a bottom-blown argon gas source communicated with the steel ladle through the air brick; a top-blown argon gas source communicated with the hollow electrode through the delivery pipe; a lime powder injection system for injecting lime powder and a carbon powder injection system for injecting carbon powder, which are sequentially arranged on the conveying pipeline; and the control system is used for regulating and controlling the technological parameters of lime powder injection, carbon powder injection, top-blown argon injection and bottom-blown argon injection.
Preferably, the ladle refining furnace further comprises a ladle car, and the ladle is arranged on the ladle car; and/or a ladle sliding plate is arranged at the bottom of the ladle.
In a third aspect, the invention provides use of the apparatus of the second aspect of the invention in deep desulphurisation in refining of molten steel.
Compared with the prior art, the invention at least has the following beneficial effects:
(1) the invention uses the hollow electrode to dynamically spray lime powder and carbon powder, and uses the lime powder and the carbon powder to generate Ca (g) or CaC by the carbothermic reduction reaction under the action of electrode arc2(s) or Ca (g) with CaC2(s) mixture of(s) wherein CaC2(s) Ca (g) produced by decomposition at high temperature and Ca (g) produced by carbothermic reduction reaction can cause strong reduction and alkaline oxide atmosphere, and Ca (g) and CaC produced2(s) has a strong desulfurization ability,the sulfur in the molten steel can be captured quickly, the low-cost and high-efficiency removal of the sulfur in the molten steel is realized, and the rapid deep desulfurization can be carried out; meanwhile, Ca atoms can react with O atoms in the molten steel and absorb other impurities in the molten steel to form larger particle impurities which float upwards along with CO bubbles to be removed, so that the cleanliness of the molten steel is improved; in the invention, after CO gas generated by carbothermic reduction reaction escapes into slag, slag foaming can be promoted to form good foamed slag, so that the reaction activity between slag and steel is enhanced, and the desulfurization efficiency in the refining process is further improved.
(2) The hollow electrode (hollow graphite electrode) adopted by the invention has lower carburetion amount, average carburetion rate and electrode consumption rate than a solid electrode, thereby reducing the production cost; in addition, the invention uses argon as carrier gas to spray lime powder and carbon powder, which not only increases the contact area between the powder and the molten steel, but also utilizes argon plasma formed by top-blown argon to stir the molten steel, thereby improving the heating efficiency of the molten steel, improving the thermodynamic and kinetic conditions of desulfurization, effectively improving the desulfurization efficiency, shortening the smelting time, reducing the power consumption and the electrode loss, and also reducing the production cost.
(3) According to the invention, argon is injected in the molten steel refining and smelting process to form argon plasma, so that the heat efficiency can be improved, the early stage heating and slagging time, the middle stage desulphurization time and the later stage soft blowing and stirring time in the smelting process are shortened, the overall refining time (smelting time) is shortened, and the refining period is shortened by 5-15 min; according to the invention, the hollow electrode is used for blowing argon, so that the stability of electric arc can be improved, the service life of refractory materials in the furnace can be prolonged, meanwhile, the hollow electrode is used for blowing argon, the arc heating efficiency of argon plasma is far higher than that of the traditional solid electrode, and the required heating time is shortened; compared with a solid electrode, the recarburization amount, the recarburization rate and the electrode consumption rate of the electrode are obviously reduced, compared with the traditional molten steel refining deep desulfurization method, the power consumption of each ton of molten steel to be refined after molten steel refining deep desulfurization is reduced by about 4-10 (kW.h), the electrode consumption rate can be reduced by about 30%, and the whole production cost is reduced.
Drawings
FIG. 1 is a schematic view showing the construction of an apparatus for molten steel refining according to some embodiments of the present invention.
In the figure: 1: a control system; 2: argon source; 3: a lime powder-carbon powder mixing and blowing system; 3-1: a lime powder injection system; 3-2: a carbon powder injection system; 4: a delivery conduit; 5: a temperature measuring port; 6: a hollow electrode; 7: an electrode holder; 8: a feeding device; 9: a ladle; 10: carrying out buggy ladle; 11. air permeable bricks; 12. a steel ladle sliding plate; 13: a furnace cover.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
The invention provides a method for refining and deep desulfurization of molten steel in a first aspect, which comprises the following steps:
s1, tapping the molten steel to be refined into a steel ladle, and adding smelting materials into the steel ladle filled with the molten steel to be refined to obtain a steel material to be refined;
s2 according to the initial sulfur content of the molten steel to be refined during tapping]IntoAnd a target sulfur content [ S ]]Eyes of a userDetermining technological parameters of lime powder injection, carbon powder injection and top-blown argon injection when molten steel refining is carried out on a steel material to be refined; in the present invention, the initial sulfur content of the molten steel to be refined is defined as [ S ]]IntoExpressed as [ S ] for the target sulfur content]Eyes of a userIndicating that the target sulfur content is the sulfur content of the target molten steel of molten steel refining;
s3, carrying out molten steel refining on the steel material to be refined; during molten steel refining, blowing a lime powder-carbon powder-argon mixed powder airflow into the steel material to be refined through a hollow electrode so as to deeply desulfurize the molten steel; in the invention, the lime powder and the carbon powder are sprayed into the steel material to be refined through the hollow electrode, so that the lime powder and the carbon powder can generate electric arc action in the hollow electrodeGeneration of Ca and/or CaC2Thereby enabling the molten steel to be deeply desulfurized; in the present invention, the hollow electrode refers to an electrode with a central channel, wherein the inside of the electrode is hollow; in the present invention, the hollow electrode is a hollow graphite electrode; in the present invention, the arc action generated by the hollow electrode means an arc heating action generated between the hollow electrode and the molten steel.
As is known, in the refining of molten steel, the consumption of the end part of an electrode is the most important aspect of the consumption of the electrode, the graphite electrode at the front end part is sublimated due to the high temperature of an electric arc, the graphite electrode is cracked due to thermal stress, namely is thermally stripped, meanwhile, the electrode at the end part of the electrode is directly scoured by slag and molten steel caused by the action of bottom blowing argon, the graphite is dissolved or a chemical reaction is generated, the dissolution loss of the electrode is caused, and therefore, the recarburization is caused; the hollow graphite electrode is adopted, the contact area of the hollow graphite electrode and furnace slag or molten steel is smaller, after the hollow electrode is adopted to blow gas, the temperature of a plasma arc is usually 5000-20000K higher than that of the traditional arc, the heating efficiency is far higher than that of the traditional solid electrode, the heating efficiency in the refining process can be improved, the required heating time is shortened, and the smelting time is shortened; in addition, because the hollow electrode sprays argon, the stability of the electric arc is improved, and the service life of the refractory material in the furnace can be effectively prolonged.
In the invention, argon is used as carrier gas, lime powder and carbon powder are dynamically sprayed through a central channel of the hollow electrode, and Ca (g) or CaC is triggered by high-temperature electric arc of the hollow electrode2(s) the generation reaction realizes the rapid deep desulfurization of the molten steel in the molten steel refining process; CaO(s) + C(s) = Ca (g)/CaC occurs to the lime powder and the carbon powder in an arc high-temperature region of the hollow electrode2(s) + CO (g) reaction to form Ca, CaC2Or Ca and CaC2Mixture of (2), CaC2Ca generated by decomposition at high temperature and Ca generated by carbothermic reduction can cause strong reduction and alkaline oxide atmosphere, and the generated Ca and CaC2The method has strong desulfurization capability, can quickly capture sulfur in the molten steel, realizes low-cost and high-efficiency removal of the sulfur in the molten steel, and is a method for quickly and deeply desulfurizing the molten steel in a refining way. The removal of impurities by bubble adhesion and the removal of impurities by bubble wake flow are two important functions of cleaning molten steel when bubbles in the molten steel float upwards; in the invention, Ca atoms can react with O atoms in the molten steel and absorb other impurities in the molten steel to form larger particle impurities which float upwards along with CO bubbles to be removed, so that the cleanliness of the molten steel can be improved to a certain extent; in the invention, after CO gas generated by carbothermic reduction reaction escapes into slag, slag foaming can be promoted to form good foamed slag, so that the reaction activity between slag and steel is enhanced, and the desulfurization efficiency in the refining process is further improved; in addition, the invention uses argon as carrier gas to blow the powder, which not only can increase the contact area between the powder and the molten steel, but also can utilize argon plasma formed by top-blown argon to stir the molten steel, thereby improving the heating efficiency of the molten steel, strengthening the stirring of a molten pool, improving the thermodynamic and kinetic conditions of desulfurization, effectively improving the desulfurization efficiency, shortening the smelting time, reducing the power consumption and the loss of electrodes, and also reducing the production cost.
According to some preferred embodiments, the method for refining and deep desulfurization of molten steel is carried out by an apparatus for refining molten steel, for example, as shown in fig. 1; the device comprises: a ladle refining furnace: the ladle refining furnace comprises a ladle 9, a furnace cover 13 for sealing a ladle opening and an electric arc heating system; the electric arc heating system comprises a hollow electrode 6 and an electrode holder 7 for holding the hollow electrode 6, wherein the hollow electrode 6 is communicated with a conveying pipeline 4; the furnace cover 13 is provided with a temperature measuring port 5, a feeding device 8 and a furnace cover hole for inserting the hollow electrode 6; the bottom of the ladle 9 is provided with an air brick 11; a bottom-blown argon gas source communicated with the ladle 9 through the gas permeable brick 11; a top-blown argon gas source communicated with the hollow electrode 6 through the conveying pipeline 4; a lime powder injection system 3-1 for injecting lime powder and a carbon powder injection system 3-2 for injecting carbon powder, which are sequentially arranged on the conveying pipeline 4; and a control system 1 for regulating and controlling technological parameters of lime powder injection, carbon powder injection, top-blown argon injection and bottom-blown argon injection; in the invention, the bottom-blown argon gas source and the top-blown argon gas source are collectively called as an argon gas source 2; the lime powder injection system 3-1 and the carbon powder injection system 3-2 form a lime powder-carbon powder mixing injection system 3; in the present invention, the charging device 8, as shown in fig. 1 for example, may be composed of a charging hopper and a charging tube, the charging tube being in communication with the ladle opening, the charging hopper being provided on the charging tube and being in communication with the charging tube; in the invention, the top-blown argon gas source provides argon gas as a carrier gas source of the lime powder-carbon powder mixed injection system 3, so that the hollow electrode 6 can inject and blow out lime powder-carbon powder-argon mixed powder gas flow; in the invention, when the device for molten steel refining is used for molten steel refining deep desulfurization, according to the initial sulfur content of molten steel to be refined and the sulfur content of molten steel refined target molten steel during tapping, the control system 1 is used for determining the blowing process parameters of lime powder, carbon powder and argon gas during molten steel refining of a steel material to be refined on line, in the invention, the lime powder and the carbon powder are calculated according to the molar ratio according to the chemical reaction, and the actual blowing amount can be slightly higher than the theoretical molar ratio of 1:1, for example, so that the molar ratio of the lime powder to the carbon powder is (1-1.2): 1; and the lime powder-carbon powder-argon mixed powder airflow is injected into the steel material to be refined through the lime powder-carbon powder mixed injection system 3, the conveying pipeline 4 and the hollow electrode 6, so that the molten steel refining desulfurization efficiency is effectively improved, and the molten steel refining rapid deep desulfurization is realized.
According to some preferred embodiments, the ladle refining furnace further comprises a buggy ladle 10, the ladle 9 being disposed on the buggy ladle 10; and/or the bottom of the ladle 9 is provided with a ladle slide plate 12.
According to some preferred embodiments, in step S2, the initial sulfur content [ S ] of the molten steel to be refined is determined according to]IntoAnd a target sulfur content [ S ]]Eyes of a userDetermining the technological parameters of lime powder, carbon powder and argon injection as follows:
when [ S ]]Into≥40ppm，5ppm≤[S]Eyes of a userWhen the content is less than 10ppm, the blowing rate of the lime powder is 0.6-0.95 kg/(min · t) (e.g., 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, or 0.95 kg/(min · t)), the blowing rate of the carbon powder is 0.13 to 0.18 kg/(min · t) (e.g., 0.13, 0.135, 0.14, 0.145, 0.15, 0.155, 0.16, 0.165, 0.17, 0.175, or 0.18 kg/(min · t)), the flow rate of the top-blown argon gas is 3 to 8 NL/(min · t) (e.g., 3, 4, 5, 6, 7, or 8 NL/(min · t)), and the blowing time is 10 to 15min (e.g., 10, 11, 12, 13, 14, or 15 min);
when [ S ]]Into≥40ppm，[S]Eyes of a userIf < 5ppm, the blowing rate of lime powder is 0.4 to 0.6 kg/(min · t) (e.g., 0.4, 0.45, 0.5, 0.55, or 0.6 kg/(min · t)), the blowing rate of carbon powder is 0.08 to 0.13 kg/(min · t) (e.g., 0.08, 0.085, 0.09, 0.095, 0.1, 0.105, 0.11, 0.115, 0.12, 0.125, or 0.13 kg/(min · t)), the flow rate of top-blown argon gas is 5 to 10/(min · t) (e.g., 5, 6, 7, 8, NL 9, or 10 NL/(min · t)), and the blowing time is 15 to 20min (e.g., 15, 16, 17, 18, 19, or 20 min);
when [ S ]]Into＜40ppm，5ppm≤[S]Eyes of a userIf less than 10ppm, the blowing rate of the lime powder is 0.5 to 0.75 kg/(min · t) (e.g., 0.5, 0.55, 0.6, 0.65, 0.7, or 0.75 kg/(min · t)), the blowing rate of the carbon powder is 0.11 to 0.15 kg/(min · t) (e.g., 0.11, 0.115, 0.12, 0.125, 0.13, 0.135, 0.14, 0.145, or 0.15 kg/(min · t)), the flow rate of the top-blown argon gas is 1 to 6 NL/(min · t) (e.g., 1, 2, 3, 4, 5, or 6 NL/(min · t)), and the blowing time is 5 to 10min (e.g., 5, 6, 7, 8, 9, or 10 min);
when [ S ]]Into＜40ppm，[S]Eyes of a userIf the amount of the carbon powder is less than 5ppm, the lime powder is blown at a rate of 0.2 to 0.55 kg/(min · t) (e.g., 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, or 0.55 kg/(min · t)), the carbon powder is blown at a rate of 0.03 to 0.11 kg/(min · t) (e.g., 0.03, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.065, 0.07, 0.075, 0.08, 0.085, 0.09, 0.095, 0.10, 0.105, or 0.11 kg/(min · t)), the top-blown argon gas has a flow rate of 2 to 7 NL/(min · t) (e.g., 2, 3, 4, 5, 6, or 7 NL/(min · t)), and the time is 10 to 15min (e.g., 10, 11, 12, 13, 14, or 15 min/(min · t)).
In the invention, the lime powder and the carbon powder are calculated according to the molar ratio according to the chemical reaction, and the actual injection amount can be slightly higher than the theoretical molar ratio of 1:1, for example, the molar ratio of the lime powder to the carbon powder is (1-1.2): 1, and the molar amount of the lime powder is preferably slightly higher; the key of the method for determining the blowing process parameters of the lime powder, the carbon powder and the argon gas lies in the total amount of the lime powder and the carbon powder, the total amount of the powder is determined by the blowing rate and the blowing time, the period of the whole refining process is influenced, and the powder blowing rate needs to be properly adjusted according to the bearing capacity of the argon gas; through a large number of creative tests, the invention obtains different initial sulfur contents [ S ] of molten steel to be refined]IntoAnd a target sulfur content [ S ]]Eyes of a userUnder the condition, the optimal technological parameters of lime powder, carbon powder and argon gas injection are adopted when molten steel refining is carried out on the steel material to be refined.
In particular, in the invention, the unit kg/(min.t) of the injection rate represents the injection amount of lime powder or carbon powder per minute per ton of molten steel to be refined; the flow unit NL/(min.t) of the argon is the flow unit under the standard condition, namely standard liters per minute per ton, and the flow unit NL/(min.t) of the argon represents the argon dosage per minute per ton of molten steel to be refined.
According to some preferred embodiments, the smelting material comprises lime and aluminium dross, and the step S1 includes the following substeps:
s11, in the process of tapping molten steel to be refined to the ladle, bottom blowing argon after the ladle flows, wherein the flow rate of the bottom blowing argon is 0.5-2 NL/(min t) (such as 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.4, 1.6, 1.8 or 2.0 NL/(min t)); in the invention, the molten steel to be refined is tapped into a ladle, namely the molten steel to be refined is poured into the ladle; in the invention, the argon gas is bottom blown after the steel ladle flows, which means that the argon gas is bottom blown when the molten steel to be refined which is poured in begins to appear in the steel ladle in the process of tapping the molten steel to be refined to the steel ladle; tapping 1/3-1/4 of the total mass of the molten steel to be refined into a ladle, and adding lime, wherein the adding amount of lime is 3-4 kg/t (for example, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9 or 4 kg/t); the adding amount of the lime is 3-4 kg/t, namely 3-4 kg of lime needs to be added into each ton of molten steel to be refined; particularly, the lime contained in the smelting material is active lime, which is beneficial to rapid slagging; the active lime in the invention can be commercially available active lime.
S12, after all the molten steel to be refined is tapped into a steel ladle, conveying the steel ladle filled with the molten steel to be refined to a refining station (LF station), and adjusting the flow of bottom blowing argon to be 3-8 NL/(min.t); (e.g., 3, 4, 5, 6, 7, or 8 NL/(min. t)); in the invention, preferably, after entering the LF station, the flow of bottom-blown argon needs to be properly increased, the bottom-blown argon can be used for homogenizing the components and the temperature of molten steel, promoting the reaction of steel slag to carry out desulfurization and simultaneously removing impurities.
S13, top-blowing argon into the steel ladle, wherein the flow rate of the top-blown argon is 1-10 NL/(min t) (such as 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 NL/(min t)), then utilizing the argon plasma formed by the top-blown argon to form slag for 2-5 min (such as 2, 2.5, 3, 3.5, 4, 4.5 or 5min NL/(min t)), then adjusting the flow rate of the top-blown argon to be 0.5-5 NL/(min t) (such as 0.5, 1, 2, 3, 4 or 5/(min t)), and adding aluminum slag into the steel ladle to obtain the steel material to be refined, wherein the adding amount of the aluminum slag is 1-3 kg/t (such as 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8 or 3 kg/t); the adding amount of the aluminum slag is 1-3 kg/t, namely 1-3 kg of aluminum slag is required to be added into each ton of molten steel to be refined; in the invention, when the aluminum slag is added, the flow rate of top-blown argon is not required to be too large, and more preferably, the flow rate of the top-blown argon is reduced to 0.5-5 NL/(min t) after 2-5 min of slag melting; the aluminum slag comprises the following components in percentage by mass: 30-45% of Al; al (Al)2O3，10~25%；SiO22-12%; 15-30% of CaO; 0-4% of MgO; s, 0-0.5%; 0-0.5% of P; the present invention does not particularly require specific contents of the components contained in the aluminum dross, as long as the components contained in the aluminum dross are within the above-mentioned ranges.
According to some preferred embodiments, the flow rate of the argon bottom-blown gas is adjusted to 2 to 10 NL/(min. t) (e.g., 2, 3, 4, 5, 6, 7, 8, 9, or 10 NL/(min. t)) during molten steel refining.
According to some preferred embodiments, after the step S3 is performed to obtain the molten desulfurized steel, the method further includes the step S4: stopping blowing the carbon powder and the lime powder in sequence, for example, stopping blowing the carbon powder and the lime powder by closing a carbon powder blowing system and a lime powder blowing system in sequence, adjusting the flow rate of top-blown argon to be 5-10 NL/(min · t) (for example, 5, 6, 7, 8, 9 or 10 NL/(min · t)), and the flow rate of bottom-blown argon to be 2-6 NL/(min · t) (for example, 2, 3, 4, 5 or 6 NL/(min · t)), stirring the desulfurized molten steel for 5-10 min (for example, 5, 6, 7, 8, 9 or 10 min) by using argon plasma formed by top-blown argon and by bottom-blown argon, and then closing the top-blown argon; in the present invention, the stirring of the desulfurized molten steel by bottom-blowing argon gas using the argon plasma formed by top-blowing argon gas means that the desulfurized molten steel is stirred by bottom-blowing argon gas while being stirred by top-blowing argon gas using the argon plasma formed by top-blowing argon gas.
According to some preferred embodiments, after the step S4 is performed to obtain refined molten steel, the method further includes the step S5:
the flow rate of bottom-blown argon gas is adjusted to 0.5 to 5 NL/(min.t) (e.g., 0.5, 1, 2, 3, 4 or 5 NL/(min.t)), and the refined molten steel is stirred for 3 to 5min (e.g., 3, 4 or 5 min) by bottom-blown argon gas.
According to some specific embodiments, the method for refining and deep desulfurization of molten steel comprises the following steps:
s1, tapping the molten steel to be refined into a steel ladle, and adding smelting materials into the steel ladle filled with the molten steel to be refined to obtain a steel material to be refined; the smelting material comprises lime and aluminum slag, and the step S1 comprises the following substeps:
s11, tapping steel in a converter or an electric furnace, and after the steel ladle flows, beginning bottom blowing argon, wherein the flow rate of the bottom blowing argon is 0.5-2 NL/(min.t); in the process of tapping molten steel to be refined into a steel ladle, after the molten steel is tapped at 1/4, adding lime into the steel ladle after 1/4 of the total mass of the molten steel to be refined is tapped, wherein the adding amount of the lime is 3-4 kg/t;
s12, after all the molten steel to be refined is tapped into a steel ladle, conveying the steel ladle filled with the molten steel to be refined to a refining station, and after the molten steel enters the refining station, adjusting the flow of bottom-blown argon to be 3-8 NL/(min.t);
s13, early stage slagging stage: opening a top-blown argon valve, top-blowing argon into the steel ladle, wherein the flow of the top-blown argon is 1-10 NL/(min.t), then lowering an electrode, electrifying and arcing, forming slag by using argon plasma formed by the top-blown argon for 2-5 min, then adjusting the flow of the top-blown argon to be 0.5-5 NL/(min.t), and adding aluminum slag into the steel ladle to obtain a steel material to be refined, wherein the addition amount of the aluminum slag is 1-3 kg/t.
S2 according to the initial sulfur content of the molten steel to be refined during tapping]IntoAnd a target sulfur content [ S ]]Eyes of a userDetermining technological parameters of lime powder injection, carbon powder injection and top-blown argon injection when molten steel refining is carried out on a steel material to be refined; the regulation and control scheme of the technological parameters of lime powder injection, carbon powder injection and top-blown argon injection in the middle-stage desulfurization stage is as follows:
according to the initial sulphur content [ S ] of the molten steel to be refined]IntoAnd a target sulfur content [ S ]]Eyes of a userDetermining technological parameters of lime powder, carbon powder and argon injection;
when [ S ]]Into≥40ppm，5ppm≤[S]Eyes of a userWhen the content is less than 10ppm, the blowing rate of the lime powder is 0.6-0.95 kg/(min.t), the blowing rate of the carbon powder is 0.13-0.18 kg/(min.t), the flow rate of top-blown argon is 3-8 NL/(min.t), and the blowing time is 10-15 min;
when [ S ]]Into≥40ppm，[S]Eyes of a userWhen the content is less than 5ppm, the blowing rate of the lime powder is 0.4-0.6 kg/(min.t), the blowing rate of the carbon powder is 0.08-0.13 kg/(min.t), the flow rate of top-blown argon is 5-10 NL/(min.t), and the blowing time is 15-20 min;
when [ S ]]Into＜40ppm，5ppm≤[S]Eyes of a userWhen the content is less than 10ppm, the blowing rate of the lime powder is 0.5 to 0.75 kg/(min. t), and the blowing rate of the carbon powder is 0.11 to 0.15 kg/(min. t)min · t), the flow rate of top-blown argon is 1-6 NL/(min · t), and the blowing time is 5-10 min;
when [ S ]]Into＜40ppm，[S]Eyes of a userWhen the content is less than 5ppm, the blowing rate of the lime powder is 0.2-0.55 kg/(min.t), the blowing rate of the carbon powder is 0.03-0.11 kg/(min.t), the flow rate of top-blown argon is 2-7 NL/(min.t), and the blowing time is 10-15 min.
S3, middle-stage desulfurization: during molten steel refining, the flow of bottom blowing argon is adjusted to be 2-10 NL/(min.t), lime powder-carbon powder-argon mixed powder airflow is blown into the steel material to be refined through a hollow electrode, and Ca and/or CaC are generated by the lime powder and the carbon powder under the action of electric arc generated by the hollow electrode2So as to deeply desulfurize the molten steel and obtain the desulfurized molten steel.
S4, later soft blowing stage: and after powder injection is finished, firstly closing the carbon powder injection system, then closing the lime powder injection system, adjusting the flow of top-blown argon gas to be 5-10 NL/(min.t), adjusting the flow of bottom-blown argon gas to be 2-6 NL/(min.t), stirring the desulfurized molten steel by using argon plasma formed by top-blown argon gas in a bottom-blown argon gas mode for 5-10 min, then closing a top-blown argon gas valve, lifting an electrode, and finishing molten steel refining to obtain refined molten steel.
S5, static stirring stage: and after the molten steel refining is finished, adjusting the flow of bottom-blown argon to be 0.5-5 NL/(min.t), stirring the refined molten steel for 3-5 min in a bottom-blown argon mode, closing an argon blowing device, finishing the treatment, hanging the ladle away from the ladle refining furnace, and conveying the ladle to the next station.
In the invention, the smelting time not only comprises the early stage slagging stage time, but also comprises the middle stage desulphurization stage time and the later stage soft blowing stage time (the later stage soft blowing stirring time).
According to some preferred embodiments, the ladle has a capacity of 50 to 300 t.
According to some preferred embodiments, the lime powder is passivated lime powder, and the particle size of the lime powder is 100-300 meshes; and/or the carbon powder is coke powder and/or graphite powder, the granularity of the carbon powder is 100-300 meshes, and the sulfur content of the carbon powder is not more than 0.2 wt%; in the invention, the lime powder is preferably passivated lime powder, and the passivated lime powder is prepared by adding a certain proportion of passivators such as silicone oil and the like into active lime powder and carrying out the conventional passivation treatment process; the passivated lime powder can form a passive film on the surface of lime powder particles after passivation treatment, so that moisture absorption of lime is reduced, the storage life of the lime is prolonged, fluidization performance of the lime powder is improved, and the lime is prevented from being blocked in a blowing pipeline; the passivated lime powder adopted in the embodiment of the invention is prepared by adding a certain amount of silicone oil passivator into active lime powder and then performing the existing passivation treatment process, wherein in the passivated lime powder, the mass ratio of the active lime powder to the silicone oil is 99.95: 0.05; in the invention, the active lime powder is also called high reaction lime or soft burnt lime, and has the characteristics of small volume density, high porosity and large specific surface area; the active lime powder in the invention is prepared from commercially available active lime powder.
The present invention provides, in a second aspect, an apparatus for molten steel refining, for example, as shown in fig. 1, the apparatus comprising: a ladle refining furnace: the ladle refining furnace comprises a ladle 9, a furnace cover 13 for sealing a ladle opening and an electric arc heating system; the electric arc heating system comprises a hollow electrode 6 and an electrode holder 7 for holding the hollow electrode 6, wherein the hollow electrode 6 is communicated with a conveying pipeline 4; the furnace cover 13 is provided with a temperature measuring port 5, a feeding device 8 and a furnace cover hole for inserting the hollow electrode 6; the bottom of the ladle 9 is provided with an air brick 11; a bottom-blown argon gas source communicated with the ladle 9 through the gas permeable brick 11; a top-blown argon gas source communicated with the hollow electrode 6 through the conveying pipeline 4; a lime powder injection system 3-1 for injecting lime powder and a carbon powder injection system 3-2 for injecting carbon powder, which are sequentially arranged on the conveying pipeline 4; and a control system 1 for regulating and controlling technological parameters of lime powder injection, carbon powder injection, top-blown argon injection and bottom-blown argon injection; in the present invention, the charging device 8, as shown in fig. 1 for example, may be composed of a charging hopper and a charging tube, the charging tube being in communication with the ladle opening, the charging hopper being provided on the charging tube and being in communication with the charging tube; in the invention, the bottom-blown argon gas source and the top-blown argon gas source are collectively called as an argon gas source 2; the lime powder injection system 3-1 and the carbon powder injection system 3-2 form a lime powder-carbon powder mixing injection system 3; in the invention, the top-blown argon gas source provides argon gas as a carrier gas source of the lime powder-carbon powder mixed injection system 3, so that the hollow electrode 6 can inject and blow out lime powder-carbon powder-argon mixed powder gas flow.
According to some preferred embodiments, the ladle refining furnace further comprises a buggy ladle 10, the ladle 9 being disposed on the buggy ladle 10; and/or the bottom of the ladle 9 is provided with a ladle slide plate 12.
In a third aspect, the invention provides use of the apparatus of the second aspect of the invention in deep desulphurisation in refining of molten steel.
The invention will be further illustrated by way of example, but the scope of protection is not limited to these examples.
Example 1
The molten steel refining deep desulphurization process in the embodiment is carried out by adopting the device for molten steel refining shown in figure 1, and the specific process is as follows:
firstly, tapping steel from a converter, and in the process of tapping the molten steel to be refined to a steel ladle, after the steel ladle flows, bottom blowing argon with the flow rate of 1.2 NL/(min.t); and adding active lime after 1/4 steel of the total mass of the molten steel to be refined is tapped into a ladle, wherein the adding amount of the active lime is 3.2 kg/t.
② sulfur content (initial sulfur content) of molten steel to be refined [ S ] when LF arrives at station]IntoIs 50 ppm; after all the molten steel to be refined is tapped into the steel ladle, the steel ladle filled with the molten steel to be refined is conveyed to an LF (refining station), and after the molten steel enters the LF station, the flow of bottom-blown argon is adjusted to be 4 NL/(min.t).
③ the earlier stage of slagging: opening a top-blown argon valve, top-blowing argon into the steel ladle at a flow rate of 5 NL/(min.t), then lowering an electrode, electrifying for arc striking, and forming by using the top-blown argonThe argon plasma slag is turned for 2min, then the flow of top-blown argon is adjusted to be 2 NL/(min.t), and aluminum slag is added into the steel ladle to obtain a steel material to be refined; the adding amount of the aluminum slag is 1.8 kg/t; the aluminum slag comprises the following components in percentage by mass: 40% of Al; al (Al)2O3，25%；SiO2， 10%；CaO，20%；MgO，4%；S，0.5%；P，0.5%。
Fourthly, middle-period desulfurization: during molten steel refining, the flow rate of bottom-blown argon is adjusted to 7 NL/(min.t); the control system is used for controlling the initial sulfur content [ S ] of the molten steel to be refined during tapping]IntoAnd a target sulfur content [ S ]]Eyes of a userSetting blowing process parameters of lime powder, carbon powder and argon; blowing lime powder and carbon powder into the steel ladle through a central channel of the hollow graphite electrode by taking argon as carrier gas, so that the lime powder and the carbon powder generate Ca and/or CaC under the action of electric arc generated by the hollow graphite electrode2So as to realize deep desulfurization of the molten steel; the blowing rate of lime powder (passivated lime powder) is 0.75 kg/(min.t), the blowing rate of carbon powder (graphite powder) is 0.16 kg/(min.t), the flow of top-blown argon is adjusted to be 5 NL/(min.t), and the blowing time is 10min, so that the desulfurized molten steel is obtained.
Later stage soft blowing stage: and after powder injection is finished, firstly closing the carbon powder injection system, then closing the lime powder injection system, adjusting the flow of top-blown argon to be 8 NL/(min.t), adjusting the flow of bottom-blown argon to be 5 NL/(min.t), stirring the desulfurized molten steel in a bottom-blown argon mode by using argon plasma formed by the top-blown argon for 6min, then closing a top-blown argon valve, lifting an electrode, and finishing molten steel refining to obtain refined molten steel.
Sixthly, a static stirring stage: after LF (molten steel refining) is finished, adjusting the flow of bottom-blown argon to be 2 NL/(min.t), stirring the refined molten steel for 3min in a bottom-blown argon mode, closing an argon blowing device, and finishing treatment; sulfur content in target molten steel obtained after completion (target sulfur content) [ S ]]Eyes of a user8ppm (0.0008%).
Compared with the traditional molten steel refining deep desulfurization method, the time of the middle-period desulfurization stage is shortened by about 11min, and the power consumption of each ton of molten steel to be refined after the molten steel refining deep desulfurization is reduced by about 7 kW.h.
Example 2
The molten steel refining deep desulphurization process in the embodiment is carried out by adopting the device for molten steel refining shown in figure 1, and the specific process is as follows:
firstly, tapping steel from a converter, and in the process of tapping the molten steel to be refined to a steel ladle, beginning bottom blowing argon after the steel ladle flows, wherein the flow rate of the bottom blowing argon is 2 NL/(min.t); and adding active lime after 1/4 steel of the total mass of the molten steel to be refined is tapped into a ladle, wherein the adding amount of the active lime is 3.8 kg/t.
② sulfur content (initial sulfur content) of molten steel to be refined [ S ] when LF arrives at station]Into36 ppm; and after all the molten steel to be refined is tapped into the steel ladle, conveying the steel ladle filled with the molten steel to be refined to an LF (ladle furnace) station, and after the molten steel enters the LF station, adjusting the flow of bottom-blown argon to be 6 NL/(min.t).
③ the earlier stage of slagging: opening a top-blown argon valve, top-blowing argon into the steel ladle, wherein the flow rate of the top-blown argon is 6 NL/(min.t), then lowering an electrode, electrifying for arcing, utilizing argon plasma formed by the top-blown argon to form slag for 2min, then adjusting the flow rate of the top-blown argon to be 2 NL/(min.t), and adding aluminum slag into the steel ladle to obtain a steel material to be refined; the adding amount of the aluminum slag is 2 kg/t; the aluminum slag comprises the following components in percentage by mass: 40% of Al; al (Al)2O3，25%；SiO2， 10%；CaO，20%；MgO，4%；S，0.5%；P，0.5%。
Fourthly, middle-period desulfurization: during molten steel refining, the flow rate of bottom-blown argon is adjusted to 8 NL/(min.t); the control system is used for controlling the initial sulfur content [ S ] of the molten steel to be refined during tapping]IntoAnd a target sulfur content [ S ]]Eyes of a userSetting blowing process parameters of lime powder, carbon powder and argon; blowing lime powder and carbon powder into the steel ladle through a central channel of the hollow graphite electrode by taking argon as carrier gas, and enabling the lime powder and the carbon powder to generate Ca and/or CaC under the action of electric arc generated by the hollow graphite electrode2So as to realize deep desulfurization of the molten steel; lime powder (passivated stone)Ash powder) is 0.49 kg/(min.t), the blowing rate of carbon powder (graphite powder) is 0.1 kg/(min.t), the flow rate of top-blown argon is adjusted to 6 NL/(min.t), and the blowing time is 12min, so as to obtain the desulfurized molten steel.
Later stage soft blowing stage: and after powder injection is finished, firstly closing the carbon powder injection system, then closing the lime powder injection system, adjusting the flow of top-blown argon to be 9 NL/(min.t), adjusting the flow of bottom-blown argon to be 6 NL/(min.t), stirring the desulfurized molten steel in a bottom-blown argon mode by using argon plasma formed by the top-blown argon for 8min, then closing a top-blown argon valve, lifting an electrode, and finishing molten steel refining to obtain refined molten steel.
Sixthly, a static stirring stage: after LF (molten steel refining) is finished, adjusting the flow of bottom-blown argon to be 2 NL/(min.t), stirring the refined molten steel for 4min in a bottom-blown argon mode, closing an argon blowing device, and finishing treatment; sulfur content in target molten steel obtained after completion (target sulfur content) [ S ]]Eyes of a userWas 4ppm (0.0004%).
Compared with the traditional molten steel refining deep desulfurization method, the time of the middle-period desulfurization stage is shortened by about 7min, and the power consumption of each ton of molten steel to be refined after the molten steel refining deep desulfurization is reduced by about 5 kW.h.
Example 3
Firstly, tapping steel from a converter, and in the process of tapping the molten steel to be refined to a steel ladle, beginning bottom blowing argon after the steel ladle flows, wherein the flow rate of the bottom blowing argon is 2 NL/(min.t); and adding active lime after 1/4 steel of the total mass of the molten steel to be refined is tapped into a ladle, wherein the adding amount of the active lime is 4.0 kg/t.
② sulfur content (initial sulfur content) of molten steel to be refined [ S ] when LF arrives at station]Into42 ppm; and after all the molten steel to be refined is tapped into the steel ladle, conveying the steel ladle filled with the molten steel to be refined to an LF (ladle furnace) station, and after the molten steel enters the LF station, adjusting the flow of bottom-blown argon to be 7 NL/(min.t).
③ the earlier stage of slagging: opening a top-blown argon valve, top-blowing argon into the steel ladle, wherein the flow of the top-blown argon is 7 NL/(min)T), then lowering an electrode, electrifying for arc striking, utilizing argon plasma formed by top-blown argon to turn slag into 3min, then adjusting the flow of the top-blown argon to be 2 NL/(min t), and adding aluminum slag into the steel ladle to obtain a steel material to be refined; the adding amount of the aluminum slag is 2.5 kg/t; the aluminum slag comprises the following components in percentage by mass: 40% of Al; al (Al)2O3，25%；SiO2， 10%；CaO，20%；MgO，4%；S，0.5%；P，0.5%。
Fourthly, middle-period desulfurization: during molten steel refining, the flow rate of bottom-blown argon is adjusted to 7 NL/(min.t); the control system is used for controlling the initial sulfur content [ S ] of the molten steel to be refined during tapping]IntoAnd a target sulfur content [ S ]]Eyes of a userSetting blowing process parameters of lime powder, carbon powder and argon; blowing lime powder and carbon powder into the steel ladle through a central channel of the hollow graphite electrode by taking argon as carrier gas, so that the lime powder and the carbon powder generate Ca and/or CaC under the action of electric arc generated by the hollow graphite electrode2So as to realize deep desulfurization of the molten steel; the blowing rate of lime powder (passivated lime powder) is 0.56 kg/(min.t), the blowing rate of carbon powder (graphite powder) is 0.11 kg/(min.t), the flow of top-blown argon is adjusted to be 8 NL/(min.t), and the blowing time is 16min, so that the molten desulfurization liquid is obtained.
Later stage soft blowing stage: and after powder injection is finished, firstly closing the carbon powder injection system, then closing the lime powder injection system, adjusting the flow of top-blown argon to be 10 NL/(min.t), adjusting the flow of bottom-blown argon to be 6 NL/(min.t), stirring the desulfurized molten steel in a bottom-blown argon mode by using argon plasma formed by the top-blown argon for 9min, then closing a top-blown argon valve, lifting an electrode, and finishing molten steel refining to obtain refined molten steel.
Sixthly, a static stirring stage: after LF (molten steel refining) is finished, adjusting the flow of bottom-blown argon to be 3 NL/(min.t), stirring the refined molten steel for 5min in a bottom-blown argon mode, closing an argon blowing device, and finishing treatment; sulfur content in target molten steel obtained after completion (target sulfur content) [ S ]]Eyes of a userWas 3ppm (0.0003%).
Compared with the traditional molten steel refining deep desulfurization method, the time of the middle-period desulfurization stage is shortened by about 5min, and the power consumption of each ton of molten steel to be refined after the molten steel refining deep desulfurization is reduced by about 4 kW.h.
Comparative example 1
Comparative example 1 is substantially the same as example 1 except that:
when LF arrives at the station, the sulfur content (initial sulfur content) of the molten steel to be refined [ S ]]IntoWas 50 ppm.
In the middle-period desulfurization stage, the blowing rate of lime powder (passivated lime powder) is 0.48 kg/(min.t), the blowing rate of carbon powder (graphite powder) is 0.09 kg/(min.t), the flow rate of top-blown argon is adjusted to 11 NL/(min.t), and the blowing time is 16 min.
The sulfur content in the target molten steel obtained after the treatment in the static stirring stage was 12ppm (0.0012%).
Compared with the traditional method for refining and deep desulfurization of molten steel, the time of the middle-period desulfurization stage is shortened by about 5min, and the power consumption of each ton of molten steel to be refined after the molten steel is refined and deep desulfurized is reduced by about 4 kW.h.
Comparative example 2
Comparative example 2 is substantially the same as example 2 except that:
when LF arrives at the station, the sulfur content (initial sulfur content) of the molten steel to be refined [ S ]]IntoWas 36 ppm.
In the middle-period desulfurization stage, the blowing rate of lime powder (passivated lime powder) is 0.65 kg/(min.t), the blowing rate of carbon powder (graphite powder) is 0.12 kg/(min.t), the flow rate of top-blown argon is adjusted to 9 NL/(min.t), and the blowing time is 9 min.
The sulfur content in the target molten steel obtained after the completion of the static stirring stage treatment was 9ppm (0.0009%).
Compared with the traditional method for refining and deep desulfurization of molten steel, the time of the middle-period desulfurization stage is shortened by about 5min, and the power consumption of each ton of molten steel to be refined after the molten steel is refined and deep desulfurized is reduced by about 4 kW.h.
The performance indexes of examples 1 to 3 and comparative examples 1 to 2 measured by the present invention are shown in Table 1. In the present invention, [ S ]]IntoAnd [ S ]]Eyes of a userAll meanIs prepared from the components with the mass percentage of desulfurization rate of S]IntoAnd [ S ]]Eyes of a userDifference of (a) and [ S]IntoThe ratio of (a) to (b).
Table 1: the performance indexes of examples 1 to 3 and comparative examples 1 to 2.
The invention has not been described in detail and is in part known to those of skill in the art.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (6)
1. A method for refining and deep desulfurization of molten steel is characterized by comprising the following steps:
s1, tapping the molten steel to be refined into a steel ladle, and adding smelting materials into the steel ladle filled with the molten steel to be refined to obtain a steel material to be refined;
s2 according to the initial sulfur content of the molten steel to be refined during tapping]IntoAnd a target sulfur content [ S ]]Eyes of a userDetermining technological parameters of lime powder injection, carbon powder injection and top-blown argon injection when molten steel refining is carried out on a steel material to be refined;
s3, carrying out molten steel refining on the steel material to be refined; during molten steel refining, blowing a lime powder-carbon powder-argon mixed powder airflow into the steel material to be refined through a hollow electrode so as to deeply desulfurize the molten steel; the lime powder and the carbon powder generate Ca and/or CaC under the action of electric arc generated by the hollow electrode2Thereby deeply desulfurizing the molten steel;
in step S2, the initial sulfur content [ S ] is determined in accordance with the molten steel to be refinedS]IntoAnd a target sulfur content [ S ]]Eyes of a userDetermining the technological parameters of lime powder, carbon powder and argon injection as follows:
when [ S ]]Into≥40ppm，5ppm≤[S]Eyes of a userWhen the content is less than 10ppm, the blowing rate of the lime powder is 0.6-0.95 kg/(min.t), the blowing rate of the carbon powder is 0.13-0.18 kg/(min.t), the flow rate of top-blown argon is 3-8 NL/(min.t), and the blowing time is 10-15 min;
when [ S ]]Into≥40ppm，[S]Eyes of a userWhen the content is less than 5ppm, the blowing rate of the lime powder is 0.4-0.6 kg/(min.t), the blowing rate of the carbon powder is 0.08-0.13 kg/(min.t), the flow rate of top-blown argon is 5-10 NL/(min.t), and the blowing time is 15-20 min;
when [ S ]]Into＜40ppm，5ppm≤[S]Eyes of a userWhen the content is less than 10ppm, the blowing rate of the lime powder is 0.5-0.75 kg/(min.t), the blowing rate of the carbon powder is 0.11-0.15 kg/(min.t), the flow rate of top-blown argon is 1-6 NL/(min.t), and the blowing time is 5-10 min;
when [ S ]]Into＜40ppm，[S]Eyes of a userWhen the content is less than 5ppm, the blowing rate of the lime powder is 0.2-0.55 kg/(min.t), the blowing rate of the carbon powder is 0.03-0.11 kg/(min.t), the flow rate of top-blown argon is 2-7 NL/(min.t), and the blowing time is 10-15 min.
2. The method according to claim 1, wherein the smelting material comprises lime and aluminum slag, and the step S1 includes the sub-steps of:
s11, in the process of tapping molten steel to be refined to the ladle, bottom blowing argon after the ladle flows, wherein the flow rate of the bottom blowing argon is 0.5-2 NL/(min.t); tapping 1/3-1/4 of the total mass of the molten steel to be refined into a ladle, and adding lime, wherein the adding amount of the lime is 3-4 kg/t;
s12, after all the molten steel to be refined is tapped into a ladle, conveying the ladle filled with the molten steel to be refined to a refining station, and adjusting the flow of bottom-blown argon to be 3-8 NL/(min.t);
s13, top-blowing argon into the steel ladle, wherein the flow rate of the top-blown argon is 1-10 NL/(min.t), then utilizing argon plasma slag formed by the top-blown argon for 2-5 min, then adjusting the flow rate of the top-blown argon to be 0.5-5 NL/(min.t), and adding aluminum slag into the steel ladle to obtain a steel material to be refined; the adding amount of the aluminum slag is 1-3 kg/t.
3. The method of claim 2, wherein:
during molten steel refining, the flow rate of bottom-blown argon is adjusted to 2-10 NL/(min.t).
4. The method of claim 2, wherein after the step S3 is performed to obtain the molten desulfurized steel, the method further comprises the step S4:
and stopping blowing the carbon powder and the lime powder in sequence, adjusting the flow rate of top-blown argon to be 5-10 NL/(min.t), adjusting the flow rate of bottom-blown argon to be 2-6 NL/(min.t), stirring the desulfurized molten steel for 5-10 min by using argon plasma formed by top-blown argon and in a bottom-blown argon mode, and then closing the top-blown argon.
5. The method of claim 4, further comprising, after the step S4 is performed to obtain refined molten steel, the step S5:
adjusting the flow rate of bottom-blown argon to be 0.5-5 NL/(min.t), and stirring the refined molten steel in a bottom-blown argon mode for 3-5 min.
6. The method of claim 1, wherein:
the capacity of the steel ladle is 50-300 t;
the lime powder is passivated lime powder, and the granularity of the lime powder is 100-300 meshes; and/or
The carbon powder is coke powder and/or graphite powder, the granularity of the carbon powder is 100-300 meshes, and the sulfur content of the carbon powder is not more than 0.2 wt%.
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