CN114774615A - Method for producing ultra-low sulfur steel by adopting high-sulfur semi-steel - Google Patents

Method for producing ultra-low sulfur steel by adopting high-sulfur semi-steel Download PDF

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CN114774615A
CN114774615A CN202210450920.8A CN202210450920A CN114774615A CN 114774615 A CN114774615 A CN 114774615A CN 202210450920 A CN202210450920 A CN 202210450920A CN 114774615 A CN114774615 A CN 114774615A
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steel
sulfur
slag
equal
percent
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CN114774615B (en
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胡楚江
王前
王启丞
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Heilongjiang Jianlong Iron and Steel Co Ltd
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Heilongjiang Jianlong Iron and Steel Co Ltd
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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
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28—Manufacture of steel in the converter
    • 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
    • C21C7/0006—Adding metallic additives
    • 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
    • C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
    • 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
    • C21C7/06—Deoxidising, e.g. killing
    • 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
    • C21C7/076—Use of slags or fluxes as treating agents
    • 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
    • C21C7/10—Handling in a vacuum
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Abstract

A method for producing ultra-low sulfur steel by adopting high sulfur semi-steel belongs to the technical field of ferrous metallurgy. The method solves the problems of complex process and high cost of the existing batch production of the ultra-low sulfur steel by adopting high-sulfur semisteel. The method comprises the following steps: firstly, charging steel materials and silicon-carbon alloy into a converter for smelting; secondly, steel ladle deoxidation, alloying and slagging during tapping; thirdly, sampling and analyzing after LF refining; feeding an aluminum wire to adjust Als after the analysis result is qualified, and tapping in an LF (ladle furnace); and V, VD high vacuum treatment, deep deoxidation and calcium treatment, soft blowing and tapping to obtain the ultra-low sulfur steel with the S less than or equal to 0.002 percent. The method adopts the high-sulfur semisteel to produce the ultra-low-sulfur steel, realizes single-slag refining, ensures furnace matching and smooth production, creates a precedent for stably producing the ultra-low-sulfur steel in batches by using high-sulfur raw and auxiliary materials, and has the advantages of simple process, low cost and capability of stably controlling the sulfur content in a finished product to be less than 0.002 percent. The invention is suitable for producing the ultra-low sulfur steel by the high sulfur semi-steel.

Description

Method for producing ultra-low sulfur steel by adopting high-sulfur semi-steel
Technical Field
The invention belongs to the technical field of ferrous metallurgy, and particularly relates to a method for producing ultra-low sulfur steel by adopting high sulfur semi-steel.
Background
Working condition strip along with continuous deep progress of oil exploitationOil fields with good quality and low content of corrosive medium are developed and utilized, the productivity of the high-quality oil fields can not meet the increasing economic development requirement, and in order to meet the increasing petroleum requirement, the oil fields with complex geological structure and corrosive medium H2S、CO2The exploitation of oil gas with high content, high salt and high alkali is imperative. The exploitation of oil gas with complex working conditions and high content of corrosive medium needs to use high-end oil pipes with high strength, high toughness and corrosion resistance, and the high-end oil pipes have the common characteristic that the S content in the pipes is required to be controlled in an ultra-low content range (S is less than or equal to 0.003 percent, and some S is less than or equal to 0.001 percent or even lower), and belong to ultra-low sulfur steel and ultra-low sulfur steel. The Heilongjiang Jianlong Steel Co Ltd has a complete industrial chain production line of a round billet, two rolled tubes and a heat-treated seamless steel tube, and has the tooling conditions for producing high-end oil and gas pipes. Development of batch production process of ultra-low sulfur steel, development of high strength, high toughness and H resistance2S corrodes oil well pipe, which is to meet the industry requirement of oil exploitation.
The raw material conditions of the Heilongjiang Jianlong Steel Limited company are as follows: the sulfur content in the high-vanadium molten iron is high and is between 0.040 and 0.070 percent; firstly, vanadium extraction is carried out on high-vanadium molten iron, in order to ensure the vanadium content in vanadium slag obtained by vanadium extraction, pretreatment desulfurization of the molten iron cannot be carried out, meanwhile, slag materials such as lime and the like cannot be added during vanadium extraction, and the vanadium extraction slag is acid slag and has no desulfurization capability; the blowing temperature needs to be controlled to be between 1340 and 1390 ℃ stably for ensuring the recovery rate of vanadium during vanadium extraction, the thermodynamic condition difference of vanadium extraction for desulfurization is determined, the desulfurization rate is extremely low, and the S content of semisteel obtained after vanadium extraction from molten iron is high and is between 0.04 and 0.07 percent. In order to develop a high-end petroleum pipe of high-strength high-toughness and hydrogen sulfide corrosion-resistant ultra-low-sulfur steel, a technology for stably producing the ultra-low-sulfur steel by using high-sulfur semi-steel is developed, so that the ultra-low-sulfur steel is stably produced in batches by using the high-sulfur semi-steel, and the problems of complex process and high cost exist in the conventional method for producing the ultra-low-sulfur steel in batches by using the high-sulfur semi-steel.
Disclosure of Invention
The invention aims to solve the problems of complex process and high cost of the existing batch production of the ultra-low sulfur steel by adopting the high-sulfur semi-steel, and provides a method for producing the ultra-low sulfur steel by adopting the high-sulfur semi-steel.
A method for producing ultra-low sulfur steel by adopting high sulfur semi-steel comprises the following steps:
firstly, loading steel materials and silicon-carbon alloy into a converter for smelting, and controlling the binary alkalinity of the final slag of the converter to be more than or equal to 4.5, the FeO content to be 15-20%, the end point carbon content of the converter to be 0.05-0.08%, the end point temperature to be 1630-1650 ℃ and the desulfurization rate of the converter to be more than or equal to 30%;
the steel material consists of 94 percent of high-sulfur semisteel and 6 percent of low-sulfur steel scrap in percentage by mass, and S in the low-sulfur steel scrap is less than or equal to 0.006 percent; the dosage of the silicon-carbon alloy is 4 percent of the total mass of the steel material; the silicon-carbon alloy comprises the following components in percentage by weight: c is more than or equal to 2 percent, Si is more than or equal to 45 percent, and the balance is Fe;
secondly, carrying out ladle deoxidation, alloying and slagging during converter tapping;
and (3) deoxidizing and alloying the ladle and slagging: when the steel is discharged to 1/5, adding calcium carbide, adding half of the total amount of aluminum ingots, then adding a carburant, when the steel is discharged to 1/3, beginning to add alloy and the rest of aluminum ingots until the steel is discharged to 1/2, then adding slag under the stirring of argon, wherein Als after argon of molten steel is more than or equal to 0.015%, and the top slag of the steel ladle after argon is whitened or grayish;
thirdly, transferring to an LF refining station after the second step is finished, feeding an aluminum wire to adjust Als in the molten steel to 0.020%, starting power transmission under the condition that the argon flow is 3-4 NL/min/t steel, adding part of slag after 1min, adding aluminum particles and calcium carbide for deoxidation and white slag making after the ladle top slag is melted, stopping power when the refined slag is white and the temperature is higher than or equal to 1560 ℃, forcibly stirring for 2min under the condition that the argon flow is 6-8 NL/min/t steel, then taking a refined slag sample for analysis, starting power transmission under the condition that the argon flow is 3-4 NL/min/t steel, adding the rest slag after 1min, adding the aluminum particles and the calcium carbide for deoxidation and white slag making after the ladle top slag is melted, stopping power after the refined slag sample is analyzed and qualified, adjusting the argon flow to 6-8 NL/min/t steel, adding alloy and carburant, adjusting the argon flow to 3-4 NL/min/t steel after 3min, starting power transmission, cutting off the power after 5min, forcibly stirring for 3min under the condition that the argon flow is 6-8 NL/min/t steel, and then sampling and analyzing;
fourthly, after the sampling analysis result is qualified, feeding an aluminum wire to adjust Als in the molten steel to 0.035-0.040% when the temperature reaches 1660-1710 ℃, and tapping in an LF furnace;
and (3) the standard that the sampling analysis result is qualified: comprises the following components in percentage by weight: c: 0.10 to 0.35%, Si: 0.15 to 0.35%, Mn: 0.40-1.60%, Cr: 0.20 to 1.20%, Mo: 0.10 to 1.10%, Nb: 0.020 to 0.050%, V: 0.03-0.12%, P is less than or equal to 0.015%, S is less than or equal to 0.002%, residual impurities and the balance of Fe;
and fifthly, carrying out VD high vacuum treatment after the LF steel is tapped, feeding a silicon-calcium line for deep deoxidation and calcium treatment after VD is broken, then carrying out soft blowing, tapping at 1580-1600 ℃, and obtaining the ultralow-sulfur steel with S less than or equal to 0.002 percent, thus completing the method.
The method adopts the high-sulfur semi-steel to produce the ultra-low-sulfur steel, realizes single-slag refining, ensures furnace matching and smooth production, creates a precedent for stably producing the ultra-low-sulfur steel in batches by using high-sulfur raw and auxiliary materials, and has simple process and low cost. The sulfur content of the semisteel loaded into the converter is 0.04-0.07%, the converter desulfurization rate is not less than 30%, the refining desulfurization rate is not less than 95% under the condition of desulfurization without pretreatment, and the sulfur content of the finished product can be stably controlled below 0.002%.
Compared with the existing steel-making enterprises which adopt the processes of molten iron pre-desulfurization, converter smelting, refining and continuous casting to produce ultra-low sulfur and ultra-low sulfur steel, the sulfur content in the molten iron which is loaded into the converter after pre-desulfurization is less than or equal to 0.006 percent; the S content of the semisteel loaded into the converter is 0.04-0.07%.
Compared with the method for increasing the scrap steel ratio and reducing the iron ratio of a conventional converter (the adding proportion of common scrap steel exceeds 20 percent), the steel material consists of 94 percent of high-sulfur semisteel and 6 percent of low-sulfur scrap steel, and S in the low-sulfur scrap steel is less than or equal to 0.006 percent; adding silicon-carbon alloy accounting for 4 percent of the total weight of the steel materials into each furnace; so as to ensure that the end temperature of the converter is more than or equal to 1630 ℃, and create temperature conditions for the desulfurization of the converter.
Compared with a conventional converter, the method focuses on the desulfurization rate of the converter process, and controls the binary alkalinity of the converter final slag to be more than or equal to 4.5, the FeO content to be 15-20%, the end point carbon content of the converter to be 0.05-0.08%, the end point temperature to be 1630-1650 ℃ and the desulfurization rate of the converter to be more than or equal to 30%.
Compared with the conventional steel ladle deoxidation alloying, the invention emphasizes the full deoxidation of the steel ladle in the converter tapping process and the advanced white slag making, and creates good conditions for the LF desulfurization.
Compared with the conventional refining, the invention adopts the specific CaO-MgO-Al2O3-SiO2BaO-CaO-Al with stronger desulfurization capability2O3-MgO-SiO2And the content ranges of all components are strictly controlled, so that the desulfurization capacity of the top slag of the refining ladle is lower, and the sulfur in the steel is removed to be lower.
Compared with the conventional refining slag components, the steel ladle top slag provided by the invention has the advantages that the BaO component is added into the steel ladle top slag, the content of each component is strictly controlled, the distribution coefficient of sulfur among slag steel is improved, the desulfurization capability of the steel ladle top slag is improved, meanwhile, the large slag amount is realized, the desulfurization capability of the steel ladle top slag is improved, and the sulfur content in steel is controlled to be lower.
The invention is suitable for producing the ultra-low sulfur steel by the high sulfur semi-steel.
Detailed Description
The technical solution of the present invention is not limited to the embodiments listed below, and includes any combination of the embodiments.
The first embodiment is as follows: the method for producing the ultra-low sulfur steel by adopting the high sulfur semi-steel comprises the following steps:
firstly, steel materials and silicon-carbon alloy are loaded into a converter for smelting, the binary alkalinity of the converter final slag is controlled to be more than or equal to 4.5, the FeO content is controlled to be 15-20%, the end point carbon content of the converter is controlled to be 0.05-0.08%, the end point temperature is 1630-1650 ℃, and the desulfurization rate of the converter is controlled to be more than or equal to 30%;
the steel material consists of 94 percent of high-sulfur semisteel and 6 percent of low-sulfur steel scrap in percentage by mass, and S in the low-sulfur steel scrap is less than or equal to 0.006 percent; the dosage of the silicon-carbon alloy is 4 percent of the total mass of the steel material; the silicon-carbon alloy comprises the following components in percentage by weight: c is more than or equal to 2 percent, Si is more than or equal to 45 percent, and the balance is Fe;
secondly, carrying out ladle deoxidation, alloying and slagging during converter tapping;
and (3) deoxidizing and alloying the ladle and slagging: when the steel is discharged to 1/5, adding calcium carbide, adding half of the total amount of aluminum ingots, then adding a carburant, when the steel is discharged to 1/3, beginning to add alloy and the rest of aluminum ingots until the steel is discharged to 1/2, then adding slag under the stirring of argon, wherein Als after argon of molten steel is more than or equal to 0.015%, and the top slag of the steel ladle after argon is whitened or grayish;
thirdly, transferring to an LF refining station after the second step is finished, feeding an aluminum wire to adjust Als in the molten steel to 0.020%, starting power transmission under the condition that the argon flow is 3-4 NL/min/t steel, adding part of slag after 1min, adding aluminum particles and calcium carbide for deoxidation and white slag formation after the top slag of the steel ladle is melted, stopping power when the refined slag is white and the temperature is not lower than 1560 ℃, forcibly stirring for 2min under the condition that the argon flow is 6-8 NL/min/t steel, then taking a refined slag sample for analysis, starting power transmission under the condition that the argon flow is 3-4 NL/min/t steel, adding the residual slag after 1min, adding the aluminum particles and the calcium carbide for deoxidation and white slag formation after the top slag of the steel ladle is melted, stopping power after the refined slag sample is analyzed and qualified, adjusting the argon flow to 6-8 NL/min/t steel, supplementing alloy and carburant, adjusting the argon flow to 3-4 NL/min/t steel after 3min, starting power transmission, powering off after 5min, forcibly stirring for 3min under the condition that the argon flow is 6-8 NL/min/t steel, and then sampling and analyzing;
fourthly, after the sampling analysis result is qualified, feeding an aluminum wire to adjust Als in the molten steel to 0.035-0.040% when the temperature reaches 1660-1710 ℃, and tapping in an LF furnace;
and (3) the sampling analysis result is qualified: comprises the following components in percentage by weight: c: 0.10 to 0.35%, Si: 0.15 to 0.35%, Mn: 0.40-1.60%, Cr: 0.20 to 1.20%, Mo: 0.10 to 1.10%, Nb: 0.020-0.050%, V: 0.03-0.12%, P is less than or equal to 0.015%, S is less than or equal to 0.002%, residual impurities and the balance of Fe;
and fifthly, carrying out VD high vacuum treatment after the LF furnace steel is tapped, feeding a silicon-calcium line for deep deoxidation and calcium treatment after VD is broken, then carrying out soft blowing, and tapping at 1580-1600 ℃ to obtain the ultralow-sulfur steel with S being less than or equal to 0.002%, thus completing the method.
In the second step of the present embodiment, the aluminum ingot and calcium carbide are used as a deoxidizer.
In the second step of the embodiment, the slag on the top of the steel ladle is whitened or grayish white after argon, so that the good melting of the alloy, the uniform components and the good melting of the slag on the top of the steel ladle are ensured, and the purpose of advanced slagging is achieved.
In the practical production in the third step of the embodiment, under the abnormal states of the argon system, such as abnormal ventilation of the air brick, air leakage of the pipeline and the interface valve, etc., the argon is adjusted according to the practical stirring effect, so that the good stirring effect is ensured.
In the third step of the embodiment, the adding amount of various slag materials is calculated and controlled according to the total slag amount of the steel ladle top slag and the percentage content of each component of the steel ladle top slag.
In the fifth step of the embodiment, a calcium-silicon wire is added after the VD is broken to perform deep deoxidation and calcium treatment, so that resulfurization is avoided, and the sulfur content in the steel is controlled within the range required by the ultra-low sulfur steel.
The second embodiment is as follows: the embodiment is different from the first embodiment in that the high-sulfur semisteel in the first step is prepared by extracting vanadium from high-vanadium molten iron, the sulfur content in the semisteel is 0.04-0.07%, the C content in the semisteel is 3.3-3.6%, the P content is 0.08-0.12%, the residual amounts of Si and Mn are Si and Mn, and the balance is Fe. Other steps and parameters are the same as those in the first embodiment.
The third concrete implementation mode: the difference between the first embodiment and the second embodiment is that, in the first step, the method for controlling the converter final slag binary alkalinity comprises the following steps: the binary alkalinity of the converter final slag is controlled to be more than or equal to 4.5 through the addition amount of lime, and the addition amount of the lime is calculated according to the following formula: 3.5 × (1000 × W1 × N1+1000 × W2 × N2+ W3 × N3) × 60 ÷ 28 ÷ (M1-3.5 × N4), where W1 represents the amount of half-steel added in tons; n1 represents the Si content in the semi-steel by mass percent; w2 represents the amount of scrap added in tons; n2 represents the Si content in the scrap by mass percent; w3 represents the addition of silicon-carbon alloy, and the unit is kilogram; n3 represents the mass percent content of Si in the silicon-carbon alloy; m1 represents the CaO content in the lime by mass percent; n4 denotes SiO in lime2The mass percentage content. Other steps andthe parameters are the same as in the third embodiment.
The fourth concrete implementation mode: the difference between the first embodiment and the second embodiment is that the dosage of the calcium carbide in the second step is as follows: each furnace was 40 kg. Other steps and parameters are the same as those in the first embodiment.
The fifth concrete implementation mode: in this embodiment and the specific embodiment, the amount of the aluminum ingot used in the second step is: the end point carbon content is less than or equal to 0.05 percent, and the consumption of the aluminum ingot is 1.7kg/t steel; the end point carbon content is less than or equal to 0.06 percent, and the consumption of the aluminum ingot is 1.4kg/t steel; the end point carbon content is less than or equal to 0.07 percent, and the consumption of the aluminum ingot is 1.2kg/t steel; the end point carbon content is more than or equal to 0.08 percent, and the consumption of the aluminum ingot is 1.0kg/t steel. Other steps and parameters are the same as those in the first embodiment.
The sixth specific implementation mode is as follows: in this embodiment, the alloy in the second step: determining the corresponding alloy types and the addition amount according to the content requirements of various alloy components in the steel. Other steps and parameters are the same as those in the first embodiment.
The seventh embodiment: the second embodiment is the same as the first embodiment in that the composition of the slag in the second step is as follows: lime 2.5kg/t steel, BaCO34kg/t steel and 2.5kg/t pre-melted slag steel; the blanking speed of the slag is 60 kg/s. Other steps and parameters are the same as those in the first embodiment.
The specific implementation mode eight: in this embodiment, together with the specific embodiment, the alloy supplement and the carburant in step three are as follows: determining the carburant, the corresponding alloy types and the addition amount thereof according to the carbon content of the steel, the content requirement of each alloy component and the sampling analysis result; and adding the additional alloy and the recarburizer to the steel liquid level exposed above the argon port. Other steps and parameters are the same as those in the first embodiment.
The specific implementation method nine: in the present embodiment and the specific embodiment, the qualification standard of the analysis result of the refining slag sample in the third step is: the composition comprises BaO in percentage by weight: 31-37%, CaO: 25-30%, MgO: 5 to 8% of Al2O3：21～25％、SiO2: 6-10% of FeO, less than 0.5% of FeO, and the balance of MnO and TiO2. Other steps and parameters are the same as those in the first embodiment.
The specific implementation mode is ten: the embodiment is the same as the specific embodiment in that the total amount of the slag charge in the third step is 25kg/t steel, 65% of the total amount is added for the first time, and the rest amount is added for the second time. Other steps and parameters are the same as those in the first embodiment.
The concrete implementation mode eleven: the embodiment and the concrete embodiment are that, the composition of the slag charge in the third step is as follows: lime 2.5kg/t steel, BaCO34kg/t steel and 2.5kg/t pre-melted slag. Other steps and parameters are the same as those in the first embodiment.
The detailed implementation mode is twelve: in this embodiment, the VD high vacuum processing in the fifth step is: the vacuum degree is less than or equal to 67Pa, and the degassing time is more than or equal to 15 min. Other steps and parameters are the same as those in the first embodiment.
The specific implementation mode is thirteen: this embodiment is the same as the embodiment in that the deep deoxidation and calcium treatment in the fifth step: the feeding amount of the silicon-calcium wire is 2m/t steel, the diameter of the silicon-calcium wire is 13mm, the weight of core powder of the silicon-calcium wire is 220g/m, the mass percentage of Si in the core powder is 55-65%, the mass percentage of Ca in the core powder is 30-33%, and the balance is iron. Other steps and parameters are the same as those in the first embodiment.
The specific implementation mode is fourteen: in this embodiment, the soft blowing in step five is: and blowing argon gas for treatment, wherein the flow is 20-40 NL/min/t steel, and the time is more than or equal to 15 min. Other steps and parameters are the same as those in the first embodiment.
The beneficial effects of the present invention are demonstrated by the following examples:
the embodiment is as follows:
a method for producing ultra-low sulfur steel by adopting high sulfur semi-steel comprises the following steps:
firstly, steel materials and silicon-carbon alloy are loaded into a converter for smelting, the binary alkalinity of the converter final slag is controlled to be more than or equal to 4.5, the FeO content is controlled to be 15-20%, the end point carbon content of the converter is controlled to be 0.05-0.08%, the end point temperature is 1630-1650 ℃, and the desulfurization rate of the converter is controlled to be more than or equal to 30%;
the steel material consists of 94 percent of high-sulfur semisteel and 6 percent of low-sulfur steel scrap in percentage by mass, and S in the low-sulfur steel scrap is less than or equal to 0.006 percent; the dosage of the silicon-carbon alloy is 4 percent of the total mass of the steel material; the silicon-carbon alloy comprises the following components in percentage by weight: c is more than or equal to 2 percent, Si is more than or equal to 45 percent, and the balance is Fe;
secondly, carrying out ladle deoxidation, alloying and slagging during converter tapping;
and (3) deoxidizing and alloying the ladle and slagging: when the steel is discharged to 1/5, adding calcium carbide, adding half of the total amount of aluminum ingots, then adding a carburant, when the steel is discharged to 1/3, beginning to add alloy and the rest of aluminum ingots until the steel is discharged to 1/2, then adding slag under the stirring of argon, wherein Als after argon of molten steel is more than or equal to 0.015%, and the top slag of the steel ladle after argon is whitened or grayish;
thirdly, transferring to an LF refining station after the second step is finished, feeding an aluminum wire to adjust Als in the molten steel to 0.020%, starting power transmission under the condition that the argon flow is 3-4 NL/min/t steel, adding part of slag after 1min, adding aluminum particles and calcium carbide for deoxidation and white slag formation after the top slag of the steel ladle is melted, stopping power when the refined slag is white and the temperature is not lower than 1560 ℃, forcibly stirring for 2min under the condition that the argon flow is 6-8 NL/min/t steel, then taking a refined slag sample for analysis, starting power transmission under the condition that the argon flow is 3-4 NL/min/t steel, adding the residual slag after 1min, adding the aluminum particles and the calcium carbide for deoxidation and white slag formation after the top slag of the steel ladle is melted, stopping power after the refined slag sample is analyzed and qualified, adjusting the argon flow to 6-8 NL/min/t steel, supplementing alloy and carburant, adjusting the argon flow to 3-4 NL/min/t steel after 3min, starting power transmission, powering off after 5min, forcibly stirring for 3min under the condition that the argon flow is 6-8 NL/min/t steel, and then sampling and analyzing;
fourthly, after the sampling analysis result is qualified, feeding an aluminum wire to adjust Als in the molten steel to 0.035-0.040% when the temperature reaches 1660-1710 ℃, and tapping in an LF furnace;
and (3) the standard that the sampling analysis result is qualified: comprises the following components in percentage by weight: c: 0.10 to 0.35%, Si: 0.15 to 0.35%, Mn: 0.40 to 1.60%, Cr: 0.20 to 1.20%, Mo: 0.10 to 1.10%, Nb: 0.020-0.050%, V: 0.03-0.12%, P is less than or equal to 0.015%, S is less than or equal to 0.002%, residual impurities and the balance of Fe;
and fifthly, carrying out VD high vacuum treatment after the LF steel is tapped, feeding a silicon-calcium line for deep deoxidation and calcium treatment after VD is broken, then carrying out soft blowing, tapping at 1580-1600 ℃, and obtaining the ultralow-sulfur steel with S less than or equal to 0.002 percent, thus completing the method.
In the second step of this embodiment, the aluminum ingot and the calcium carbide are used as a deoxidizer.
In the second step of the embodiment, the slag on the top of the ladle becomes white or offwhite after argon, so that the good melting of the alloy, uniform components and good melting of the slag on the top of the ladle are ensured, and the purpose of advanced slagging is achieved.
In the third step of the present embodiment, in the actual production, under the abnormal conditions of the argon gas system, such as the abnormal ventilation of the air brick, the leakage of the pipeline and the interface valve, etc., the argon gas is adjusted according to the actual stirring effect, so as to ensure the good stirring effect.
In the third step of this embodiment, the addition amount of each slag charge is calculated and controlled according to the total slag amount of the ladle top slag and the percentage content of each component of the ladle top slag.
In the fifth step of the embodiment, a calcium-silicon wire is added after the VD is broken to perform deep deoxidation and calcium treatment, so that resulfurization is avoided, and the sulfur content in the steel is controlled within the range required by the ultra-low sulfur steel.
In the first step of this embodiment, the high-sulfur semisteel is prepared by extracting vanadium from high-vanadium molten iron, the sulfur content in the semisteel is 0.04-0.07%, the C content in the semisteel is 3.3-3.6%, the P content is 0.08-0.12%, Si and Mn are residual amounts, and the balance is Fe.
The method for controlling the converter final slag binary alkalinity in the first step of this embodiment comprises the following steps: the binary alkalinity of the converter final slag is controlled to be more than or equal to 4.5 by the addition amount of lime, and the addition amount of the lime is calculated according to the following formula: 3.5 × (1000 × W1 × N1+1000 × W2 × N2+ W3 × N3) × 60 ÷ 28 ÷ (M1-3.5 × N4), where W1 represents the half-steel charge in tons; n1 represents the Si content in the semi-steel by mass percent; w2 represents the amount of scrap added in tons; n2 represents the Si content in the scrap by mass percent; w3 represents the addition of silicon-carbon alloy, and the unit is kilogram; n3 represents silicon carbideThe mass percentage content of Si in gold; m1 represents the CaO content in the lime by mass percentage; n4 denotes SiO in lime2The mass percentage content.
In the second step of this embodiment, the dosage of calcium carbide: each furnace was 40 kg.
The amount of the aluminum ingot in step two of this embodiment: the end point carbon content is less than or equal to 0.05 percent, and the consumption of the aluminum ingot is 1.7kg/t steel; the end point carbon content is less than or equal to 0.06 percent, and the consumption of the aluminum ingot is 1.4kg/t steel; the end point carbon content is less than or equal to 0.07 percent, and the consumption of the aluminum ingot is 1.2kg/t steel; the end point carbon content is more than or equal to 0.08 percent, and the consumption of the aluminum ingot is 1.0kg/t steel.
The alloy in step two of this example: determining the corresponding alloy types and the addition amount according to the content requirements of various alloy components in the steel.
The composition of the slag in step two of this example is as follows: lime 2.5kg/t steel, BaCO34kg/t steel and 2.5kg/t pre-melted slag steel; the blanking speed of the slag is 60 kg/s.
The alloy and carburant are added in the third step of this example: determining the carburant, the corresponding alloy types and the addition amount thereof according to the carbon content of the steel, the content requirements of each alloy component and the sampling analysis result; and adding the additional alloy and the recarburizer to the steel liquid level exposed above the argon port.
The qualification standard of the analysis result of the refining slag sample in the third step of this embodiment is as follows: the composition comprises BaO in percentage by weight: 31-37%, CaO: 25-30%, MgO: 5 to 8% of Al2O3：21～25％、SiO2: 6-10% of FeO, less than 0.5% of FeO, and the balance of MnO and TiO2。
In the third step of this embodiment, the total amount of the slag is 25kg/t steel, 65% of the total amount is added for the first time, and the remaining amount is added for the second time.
The composition of the slag in the third step of this example is as follows: lime 2.5kg/t steel, BaCO34kg/t steel and 2.5kg/t pre-melted slag.
In the fifth step of this embodiment, the VD high vacuum process: the vacuum degree is less than or equal to 67Pa, and the degassing time is more than or equal to 15 min.
Deep deoxygenation and calcium treatment as described in step five of this example: the feeding amount of the silicon-calcium wire is 2m/t steel, the diameter of the silicon-calcium wire is 13mm, the weight of core powder of the silicon-calcium wire is 220g/m, the mass percentage of Si in the core powder is 55-65%, the mass percentage of Ca in the core powder is 30-33%, and the balance is iron.
In the fifth step of this embodiment, the soft blowing: and blowing argon gas for treatment, wherein the flow is 20-40 NL/min/t steel, and the time is more than or equal to 15 min.
In the embodiment, the content of sulfur in the finished product of the ultralow-sulfur steel produced by the high-sulfur semi-steel can be stably controlled to be below 0.002 percent through detection.

Claims (10)

1. A method for producing ultra-low sulfur steel by adopting high-sulfur semi-steel is characterized by comprising the following steps:
firstly, loading steel materials and silicon-carbon alloy into a converter for smelting, and controlling the binary alkalinity of the final slag of the converter to be more than or equal to 4.5, the FeO content to be 15-20%, the end point carbon content of the converter to be 0.05-0.08%, the end point temperature to be 1630-1650 ℃ and the desulfurization rate of the converter to be more than or equal to 30%;
the steel material consists of 94 percent of high-sulfur semisteel and 6 percent of low-sulfur steel scrap in percentage by mass, and S in the low-sulfur steel scrap is less than or equal to 0.006 percent; the dosage of the silicon-carbon alloy is 4 percent of the total mass of the steel material; the silicon-carbon alloy comprises the following components in percentage by weight: c is more than or equal to 2 percent, Si is more than or equal to 45 percent, and the balance is Fe;
secondly, carrying out ladle deoxidation, alloying and slagging during converter tapping;
and (3) deoxidizing and alloying the ladle and slagging: when the steel is discharged to 1/5, adding calcium carbide, adding half of the total amount of aluminum ingots, then adding a carburant, when the steel is discharged to 1/3, beginning to add alloy and the rest of aluminum ingots until the steel is discharged to 1/2, then adding slag under the stirring of argon, wherein Als after argon of molten steel is more than or equal to 0.015%, and the top slag of the steel ladle after argon is whitened or grayish;
thirdly, transferring to an LF refining station after the second step is finished, feeding an aluminum wire to adjust Als in the molten steel to 0.020%, starting power transmission under the condition that the argon flow is 3-4 NL/min/t steel, adding part of slag after 1min, adding aluminum particles and calcium carbide for deoxidation and white slag formation after the top slag of the steel ladle is melted, stopping power when the refined slag is white and the temperature is not lower than 1560 ℃, forcibly stirring for 2min under the condition that the argon flow is 6-8 NL/min/t steel, then taking a refined slag sample for analysis, starting power transmission under the condition that the argon flow is 3-4 NL/min/t steel, adding the residual slag after 1min, adding the aluminum particles and the calcium carbide for deoxidation and white slag formation after the top slag of the steel ladle is melted, stopping power after the refined slag sample is analyzed and qualified, adjusting the argon flow to 6-8 NL/min/t steel, supplementing alloy and carburant, adjusting the argon flow to 3-4 NL/min/t steel after 3min, starting power transmission, powering off after 5min, forcibly stirring for 3min under the condition that the argon flow is 6-8 NL/min/t steel, and then sampling and analyzing;
fourthly, after the sampling analysis result is qualified, feeding an aluminum wire to adjust Als in the molten steel to 0.035-0.040% when the temperature reaches 1660-1710 ℃, and tapping in an LF furnace;
and (3) the standard that the sampling analysis result is qualified: comprises the following components in percentage by weight: c: 0.10 to 0.35%, Si: 0.15 to 0.35%, Mn: 0.40-1.60%, Cr: 0.20 to 1.20%, Mo: 0.10 to 1.10%, Nb: 0.020 to 0.050%, V: 0.03-0.12%, P is less than or equal to 0.015%, S is less than or equal to 0.003%, residual impurities and the balance of Fe;
and fifthly, carrying out VD high vacuum treatment after the LF furnace steel is tapped, feeding a silicon-calcium line for deep deoxidation and calcium treatment after VD is broken, then carrying out soft blowing, and tapping at 1580-1600 ℃ to obtain the ultralow-sulfur steel with S being less than or equal to 0.002%, thus completing the method.
2. The method for producing ultralow-sulfur steel by using high-sulfur semi-steel according to claim 1, wherein in the step one, the high-sulfur semi-steel is prepared by extracting vanadium from high-vanadium molten iron, the sulfur content in the semi-steel is 0.04-0.07%, the C content in the semi-steel is 3.3-3.6%, the P content is 0.08-0.12%, the residual contents of Si and Mn and the balance of Fe.
3. The method for producing ultra-low sulfur steel from high sulfur semi-steel according to claim 1, wherein the method for controlling the binary basicity of the converter final slag in the first step comprises: the binary alkalinity of the converter final slag is controlled to be more than or equal to 4.5 by the addition amount of lime, and the addition amount of the lime is calculated according to the following formula: 3.5 × (1000 × W1 × N1+1000 × W2 × N2+ W3 × N3) X 60 ÷ 28 ÷ (M1-3.5 xn 4) where W1 represents the half-steel addition in tons; n1 represents the Si content in the semisteel by mass percent; w2 represents the amount of scrap added in tons; n2 represents the Si content in the scrap by mass percent; w3 represents the addition of silicon-carbon alloy, and the unit is kilogram; n3 represents the mass percent content of Si in the silicon-carbon alloy; m1 represents the CaO content in the lime by mass percent; n4 denotes SiO in lime2The mass percentage content.
4. The method for producing ultra-low sulfur steel using high sulfur semi-steel according to claim 1, wherein the amount of the aluminum ingot in the second step is: the end point carbon content is less than or equal to 0.05 percent, and the consumption of the aluminum ingot is 1.7kg/t steel; the end point carbon content is less than or equal to 0.06 percent, and the consumption of the aluminum ingot is 1.4kg/t steel; the end point carbon content is less than or equal to 0.07 percent, and the consumption of the aluminum ingot is 1.2kg/t steel; the end point carbon content is more than or equal to 0.08 percent, and the consumption of the aluminum ingot is 1.0kg/t steel.
5. The method for producing the ultra-low sulfur steel by using the high sulfur semi-steel according to the claim 1, characterized in that the composition of the slag in the second step is as follows: lime 2.5kg/t steel, BaCO34kg/t steel and 2.5kg/t pre-melted slag steel; the blanking speed of the slag is 60 kg/s.
6. The method for producing ultra-low sulfur steel using high sulfur semi-steel as claimed in claim 1, wherein the quality standard of the analysis result of the refining slag sample in step three is: the composition comprises BaO in percentage by weight: 31-37%, CaO: 25-30%, MgO: 5 to 8% of Al2O3：21～25％、SiO2: 6-10% of FeO, less than 0.5% of FeO, and the balance of MnO and TiO2。
7. The method for producing ultra-low sulfur steel from high sulfur semi-steel according to claim 1, wherein the total amount of the slag in step three is 25kg/t steel, 65% of the total amount is added in the first time, and the rest is added in the second time.
8. The method for producing ultra-low sulfur steel using high sulfur semi-steel according to claim 1, characterized in that the VD high vacuum treatment in step five: the vacuum degree is less than or equal to 67Pa, and the degassing time is more than or equal to 15 min.
9. The method for producing ultra-low sulfur steel using high sulfur semi-steel according to claim 1, wherein the deep deoxidation and calcium treatment in step five: the feeding amount of the silicon-calcium wire is 2m/t steel, the diameter of the silicon-calcium wire is 13mm, the weight of core powder of the silicon-calcium wire is 220g/m, the mass percentage of Si in the core powder is 55-65%, the mass percentage of Ca in the core powder is 30-33%, and the balance is iron.
10. The method for producing ultra-low sulfur steel from high sulfur semi-steel according to claim 1, characterized in that the soft blowing in the fifth step: and blowing argon gas for treatment, wherein the flow is 20-40 NL/min/t steel, and the time is more than or equal to 15 min.
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