CN118256683A - Smelting method of molten steel with extremely low sulfur content and application thereof - Google Patents
Smelting method of molten steel with extremely low sulfur content and application thereof Download PDFInfo
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- CN118256683A CN118256683A CN202410567756.8A CN202410567756A CN118256683A CN 118256683 A CN118256683 A CN 118256683A CN 202410567756 A CN202410567756 A CN 202410567756A CN 118256683 A CN118256683 A CN 118256683A
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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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- 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
- C21C1/00—Refining of pig-iron; Cast iron
- C21C1/02—Dephosphorising or 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
- 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
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- 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
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Abstract
The application discloses a smelting method of molten steel with extremely low sulfur content and application thereof. The smelting method comprises the following steps: desulfurizing the molten iron to obtain desulfurized molten iron, wherein the sulfur content in the molten iron before desulfurization is less than or equal to 0.050 percent, and the sulfur content in the desulfurized molten iron is less than or equal to 0.0010 percent; carrying out converter smelting treatment on the desulfurized molten iron, adding auxiliary materials into the molten iron during the converter smelting treatment, wherein the sulfur content in the auxiliary materials is less than or equal to 0.015 percent, and adding slag washing lime into the molten steel during tapping to obtain molten steel after converter smelting; refining molten steel smelted by a converter, deoxidizing and alloying the molten steel, and adding a desulfurizing agent after deoxidizing and alloying to perform desulfurization treatment to obtain refined molten steel, wherein the desulfurizing agent comprises CaO-Al 2O3 series desulfurizing agent, and the adding amount of the CaO-Al 2O3 series desulfurizing agent is 0.5-1.0kg/t. The smelting method and the application thereof can further reduce the sulfur content in the molten steel, obtain the molten steel with extremely low sulfur content, and improve the magnetic performance of the non-oriented electrical steel and the quality of products.
Description
Technical Field
The application relates to the technical field of steel smelting, in particular to a smelting method of molten steel with extremely low sulfur content and application thereof.
Background
Sulfur in non-oriented electrical steels is typically a detrimental element. Sulfur forms fine manganese sulfide inclusions with manganese that inhibit grain growth during the annealing process of non-oriented electrical steel. The segregation of sulfur at grain boundaries also hinders grain formation during annealing, and finely dispersed manganese sulfide inclusions during magnetization strongly hinder the movement of magnetic domain walls. Therefore, the lower the sulfur content in the non-oriented electrical steel, the better. In the production process of non-oriented electrical steel, the sulfur content in the non-oriented electrical steel is generally reduced by controlling the smelting process of molten iron, but the current smelting method has limited reduction of the sulfur content in the molten steel, thereby influencing the improvement of the magnetic performance of the non-oriented electrical steel and the improvement of the product quality.
Therefore, it is necessary to develop a method for further reducing the sulfur content in non-oriented electrical steel.
Disclosure of Invention
The embodiment of the application provides a smelting method of molten steel with extremely low sulfur content and application thereof, which can further reduce the sulfur content in the molten steel to obtain the molten steel with extremely low sulfur content, thereby improving the magnetic performance of non-oriented electrical steel and improving the quality of products.
In a first aspect, an embodiment of the present application provides a method for smelting molten steel with extremely low sulfur content, including: desulfurizing the molten iron to obtain desulfurized molten iron, wherein the sulfur content in the molten iron before desulfurization is less than or equal to 0.050 percent, and the sulfur content in the desulfurized molten iron is less than or equal to 0.0010 percent; carrying out converter smelting treatment on the desulfurized molten iron, adding auxiliary materials into the molten iron during the converter smelting treatment, wherein the sulfur content in the auxiliary materials is less than or equal to 0.015 percent, and adding slag-washed lime into the molten steel during tapping of the converter smelting treatment to obtain molten steel after the converter smelting; refining molten steel smelted by a converter, deoxidizing and alloying the molten steel, and adding a desulfurizing agent into the molten steel after deoxidizing and alloying to perform desulfurization treatment to obtain refined molten steel, wherein the desulfurizing agent comprises CaO-Al 2O3 series desulfurizing agent, and the adding amount of the CaO-Al 2O3 series desulfurizing agent is 0.5-1.0kg/t.
According to one aspect of the embodiment of the present application, in the step of refining molten steel after converter smelting, the CaO-Al 2O3 -based desulfurizing agent comprises, based on 100% by weight of the total CaO-Al 2O3 -based desulfurizing agent ：CaO：52.75％-53.75％;SiO2：6％-6.86％;Al2O3：31.56％-32.56％;F：3.7％-3.9％;C：0.032％-0.038％;S：0.05％-0.07％;TiO2：0.033％-0.053％;MgO：4.6％-5.44％.
According to one aspect of the embodiment of the application, the step of desulfurizing the molten iron further comprises adding CaO-CaF 2 series desulfurizing agents into the molten iron, wherein the adding amount of the CaO-CaF 2 series desulfurizing agents is 4.5-5.5kg/t.
According to one aspect of the embodiment of the application, the CaO-CaF 2 series desulfurizing agent comprises the following components, calculated by taking the total mass of the CaO-CaF 2 series desulfurizing agent as 100 percent: siO 2：≤5.0％,CaF2：7.0％-12.0％,CaO≥76.0％;S：≤0.045％;H2 O: less than or equal to 0.5 percent.
According to one aspect of the embodiment of the present application, the step of desulfurizing the molten iron includes a stirring speed of 100-120r/min for the desulfurizing.
According to one aspect of the embodiment of the application, the step of carrying out converter smelting treatment on the desulfurized molten iron comprises the steps of charging the molten iron into the furnace at a temperature of 1280-1320 ℃ and carrying out converter smelting at an end point temperature of 1630-1670 ℃.
According to one aspect of the embodiment of the application, the slag-washed lime is added in an amount of 4-5kg/t.
According to one aspect of the embodiment of the application, in the step of carrying out converter smelting treatment on the desulfurized molten iron, the auxiliary materials comprise one or more of scrap steel, lime and light burned magnesium balls.
According to one aspect of the embodiment of the application, the particle size of the light burned magnesium balls is 10-50mm.
According to one aspect of the embodiment of the application, the step of refining the molten steel after converter smelting further comprises the steps of starting the refining at 1570-1610 ℃, performing the refining at 65-75Pa, finishing at 1560-1600 ℃ and performing the refining for 40-50min.
In a second aspect, the application provides the use of the smelting process of the first aspect in the manufacture of non-oriented electrical steel.
According to the embodiment of the application, the sulfur content in the molten iron before desulfurization treatment is controlled to be less than or equal to 0.050 percent, and the sulfur content in the molten iron after desulfurization treatment is controlled to be less than or equal to 0.0010 percent, so that high-quality molten steel is provided for converter smelting treatment. The sulfur content in the auxiliary materials added in the converter smelting treatment is controlled to be less than or equal to 0.015%, the addition amount of sulfur in the converter smelting process is further controlled, slag washing lime is added in the converter smelting process, impurities in molten steel can be adsorbed, and the sulfur content in the molten steel is further reduced in the converter smelting treatment. The CaO-Al 2O3 desulfurizing agent is added into the molten steel in the refining treatment, so that the sulfur content in the molten steel can be further reduced, and the molten steel with extremely low sulfur content can be obtained, thereby improving the magnetic performance of the non-oriented electrical steel and improving the quality of products.
Drawings
Features, advantages, and technical effects of exemplary embodiments of the present application will be described below with reference to the accompanying drawings.
FIG. 1 is a schematic flow chart of a smelting method of molten steel with extremely low sulfur content, which is provided by the embodiment of the application.
Detailed Description
Features and exemplary embodiments of various aspects of the present application will be described in detail below, and in order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be described in further detail below with reference to the accompanying drawings and the detailed embodiments. It should be understood that the particular embodiments described herein are meant to be illustrative of the application only and not limiting. It will be apparent to one skilled in the art that the present application may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the application by showing examples of the application.
It should be noted that, in the present application, the term "comprises," "comprising," or any other variation thereof is intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
Unless otherwise indicated, the numerical values of the parameters set forth in the present application may be measured by various measurement methods commonly used in the art (e.g., may be tested according to the methods set forth in the examples of the present application). The test temperature for each of the parameters mentioned in the present application was 25℃and the test pressure was the standard atmospheric pressure, unless otherwise specified.
The term "one or more of" a list of connected items may mean any combination of the listed items. The term "plurality" means two or more.
It should be noted that, there are many harmful elements in the electrical steel, for example, C, S, N, ti, the content of the S element in the electrical steel is only controlled, and the content of other harmful elements is within a reasonable range.
The steel smelting process involves decarbonization, dephosphorization, deoxidation, desulfurization, removal of harmful gases and nonmetallic inclusions, temperature increase, component adjustment and other operations. As described in the background section, the smelting method of the embodiment of the application mainly relates to the control of sulfur content in molten steel used for non-oriented electrical steel.
FIG. 1 is a schematic flow chart of a smelting method of molten steel with extremely low sulfur content provided by the embodiment of the application. As shown in fig. 1, the embodiment of the application provides a smelting method of molten steel with extremely low sulfur content, which comprises the following steps:
S10: desulfurizing the molten iron to obtain desulfurized molten iron, wherein the sulfur content in the molten iron before desulfurization is less than or equal to 0.050 percent, and the sulfur content in the desulfurized molten iron is less than or equal to 0.0010 percent;
S20: carrying out converter smelting treatment on the desulfurized molten iron, adding auxiliary materials into the molten iron during the converter smelting treatment, wherein the sulfur content in the auxiliary materials is less than or equal to 0.015 percent, and adding slag-washed lime into the molten steel during tapping of the converter smelting treatment to obtain molten steel after the converter smelting;
S30: refining molten steel smelted by a converter, deoxidizing and alloying the molten steel, and adding a desulfurizing agent into the molten steel after deoxidizing and alloying to perform desulfurization treatment to obtain refined molten steel, wherein the desulfurizing agent comprises CaO-Al 2O3 series desulfurizing agent, and the adding amount of the CaO-Al 2O3 series desulfurizing agent is 0.5-1.0kg/t.
According to the embodiment of the application, the sulfur content in the molten iron before desulfurization treatment is controlled to be less than or equal to 0.050 percent, and the sulfur content in the molten iron after desulfurization treatment is controlled to be less than or equal to 0.0010 percent, so that high-quality molten steel is provided for converter smelting treatment. The sulfur content in the auxiliary materials added in the converter smelting treatment is controlled to be less than or equal to 0.015%, the addition amount of sulfur in the converter smelting process is further controlled, slag washing lime is added in the converter smelting process, impurities in molten steel can be adsorbed, and the sulfur content in the molten steel is further reduced in the converter smelting treatment. The CaO-Al 2O3 desulfurizing agent is added into the molten steel in the refining treatment, so that the sulfur content in the molten steel can be further reduced, and the molten steel with extremely low sulfur content can be obtained, thereby improving the magnetic performance of the non-oriented electrical steel and improving the quality of products.
If the deoxidation is not performed in the molten steel, the molten steel cannot be desulfurized in the oxidizing atmosphere, and therefore, after the deoxidation alloying treatment, that is, after the removal of oxygen in the molten steel, the molten steel is made into a reducing environment, and a desulfurizing agent can be added to the molten steel to perform the desulfurization treatment.
The deoxidizing alloying treatment may include adding an aluminum-iron alloy, a silicon-iron alloy, a manganese-iron alloy, or the like to the molten steel.
The addition of the desulfurizing agent in the embodiment of the application is calculated by taking the total mass of molten iron or molten steel as a reference, and the addition of the desulfurizing agent is the addition of the desulfurizing agent in each ton of molten iron or molten steel.
The addition amount of the CaO-Al 2O3 series desulfurizing agent is controlled within the range, so that the requirement of molten steel desulfurization in refining treatment can be better met, the excessive addition amount of the CaO-Al 2O3 series desulfurizing agent can cause waste of the desulfurizing agent, the cost is increased, and the effect of desulfurization cannot be achieved when the addition amount of the CaO-Al 2O3 series desulfurizing agent is too small.
In some alternative embodiments, in the step of refining molten steel after converter smelting, the CaO-Al 2O3 series desulfurizing agent may include, based on 100% of the total mass of the CaO-Al 2O3 series desulfurizing agent ：CaO：52.75％-53.75％;SiO2：6％-6.86％;Al2O3：31.56％-32.56％;F：3.7％-3.9％;C：0.032％-0.038％;S：0.05％-0.07％;TiO2：0.033％-0.053％;MgO：4.6％-5.44％.
The CaO-Al 2O3 desulfurizing agent mainly controls the content of CaO and Al 2O3.
CaO can react with sulfur in molten steel after converter smelting, the desulfurization efficiency can be improved by controlling the mass fraction of CaO within the range of 52.75% -53.75%, the viscosity is too high due to the excessive mass content of CaO, the desulfurization efficiency is reduced, and the desulfurization efficiency is also reduced due to the too small mass fraction of CaO.
Al 2O3 can form aluminate phases with relatively low melting points on the outer surfaces of the lime phase and the silicate phase, and the aluminum phases have a much higher sulfur dissolving capacity than the silicate phase, so that the slag desulfurization effect can be improved to a certain extent. The mass fraction of Al 2O3 is controlled within the range of 31.56-32.56%, and a certain amount of aluminate phase can be formed, so that the desulfurization efficiency of molten steel is improved.
According to the embodiment of the application, the sulfur content in molten steel can be further reduced by controlling the components of the CaO-Al 2O3 series desulfurizing agent in the range, so that the molten steel with extremely low sulfur content is obtained.
The conventional desulfurizing agent used in conventional refining treatment contains fluoride, for example, caF 2, and the fluoride has serious corrosion to materials, and if the conventional desulfurizing agent is used for desulfurizing treatment, the service life of a refining furnace is reduced, and the treatment efficiency of the refining treatment is also reduced.
The desulfurizing agent added in the refining treatment process of the embodiment of the application does not contain fluoride, and the CaO-Al 2O3 series desulfurizing agent contains a small amount of F element, so that the vacuum tank and the dipping pipe can not be disconnected due to corrosion on the premise of removing the sulfur element in molten steel, and the service life of the refining furnace can be prolonged.
In some alternative embodiments, the refining process may be an RH refining process.
The CaO-Al 2O3 series desulfurizing agent is added in the RH refining treatment process, so that sulfur elements in molten steel can be removed, the RH vacuum tank and the dip pipe cannot be caused to be disconnected due to corrosion, the service times of an RH furnace can be prolonged, and the service life of the RH furnace can be prolonged.
In some alternative embodiments, the step of desulfurizing the molten iron may further include adding a CaO-CaF 2 series desulfurizing agent to the molten iron, wherein the CaO-CaF 2 series desulfurizing agent is added in an amount of 4.5 to 5.5kg/t.
In some alternative embodiments, the CaO-CaF 2 system desulfurizing agent may include the following components, calculated as 100% of the total mass of the CaO-CaF 2 system desulfurizing agent: siO 2：≤5.0％,CaF2：7.0％-12.0％,CaO≥76.0％;S：≤0.045％;H2 O: less than or equal to 0.5 percent.
CaF 2 in the CaO-CaF 2 desulfurizing agent can reduce the melting point of CaO, quicken the desulfurizing reaction of molten iron, and control the mass content of CaF 2 within the range of 7.0-12.0 percent, so that the corrosion degree of the CaO-CaF 2 desulfurizing agent on equipment and refractory materials is lower.
In some alternative embodiments, the CaO-CaF 2 system desulfurizing agent has an activity of greater than or equal to 300mL.
In some alternative embodiments, the step of desulfurizing the molten iron may include a stirring speed of 100-120r/min for the desulfurizing.
The desulfurization treatment in the embodiment of the application can be KR desulfurization treatment, and the stirring depth of the stirring head for KR desulfurization treatment can be 780-820mm. The sulfur content can be reduced during KR desulfurization treatment, while the content of other elements is not changed basically.
In some alternative embodiments, the step of performing the converter smelting treatment on the desulphurized molten iron may include a charging temperature of the molten iron of 1280-1320 ℃, and a finishing temperature of the converter smelting of 1630-1670 ℃.
The charging temperature of the molten iron in the embodiment of the application is the starting temperature of the smelting treatment of the converter. The type of the converter is not limited in the embodiment of the present application, and the converter may be a bottom blowing converter, a top blowing converter, or a top and bottom combined blowing converter, for example.
In some alternative embodiments, the slag-washed lime may be added in an amount of 4-5kg/t.
The main component of the slag washing lime in the embodiment of the application is CaO.
In some alternative embodiments, slag wash lime may be added at 1/4-1/2 of converter tapping. For example, slag-washed lime may be added 1/3 of the time of tapping from the converter.
According to the embodiment of the application, slag washing lime with the mass is added in the converter smelting process, so that the sulfur content in molten steel can be reduced in the converter smelting process and in the later stage of converter smelting while the inclusion in the molten steel is adsorbed.
The adding amount of auxiliary materials is not limited in the embodiment of the application, so long as the control of components in the final molten steel and the stable operation of converter smelting are satisfied.
In some alternative embodiments, in the step of performing the converter smelting treatment on the desulphurized molten iron, the auxiliary materials may include one or more of scrap steel, lime and light burned magnesium balls.
Illustratively, the scrap is a low sulfur clean scrap, the S content of which is less than or equal to 0.015%.
According to the embodiment of the application, the sulfur content in the low-sulfur clean scrap steel is controlled within the range, and the sulfur content in the molten steel can be reduced by controlling the source of sulfur in the converter.
The low-sulfur clean scrap steel can be obtained through outsourcing or internal recovery, and can be quickly dissolved in a converter, so that the air suction amount in the converter is reduced, and the control of nitrogen elements in the converter smelting process is not influenced.
In some alternative embodiments, the S content of the lime is less than or equal to 0.015%.
When the converter is used for smelting, lime is added into molten iron to make sulfur element and phosphorus element react with CaO, so as to attain the goal of slagging, desulfurizing and dephosphorizing.
In some alternative embodiments, the S content in the light burned magnesium balls is less than or equal to 0.015%.
By controlling the sulfur content in the lime and the light burned magnesium pellets within the above-mentioned ranges, the sulfur content in the converter can be further reduced.
In some alternative embodiments, the major component of the light burned magnesium spheres is MgO.
In some alternative embodiments, the particle size of the light burned magnesium spheres may be 10-50mm.
In some alternative embodiments, the S content in the molten steel at the outlet of the converter smelting process is less than or equal to 0.003%.
In some alternative embodiments, the step of refining the molten steel after converter smelting may further include a refining process having an initial temperature of 1570-1610 deg.c, a refining process vacuum of 65-75Pa, a refining process end temperature of 1560-1600 deg.c, and a refining process time of 40-50min.
In some alternative embodiments, the sulfur content of the refined molten steel may be 3ppm to 15ppm.
In some alternative embodiments, the sulfur content of the refined molten steel may be 3ppm to 8ppm.
The smelting method can obviously reduce the sulfur content in the molten steel after refining treatment.
In some alternative embodiments, the smelting process may further include subjecting the refined molten steel to a continuous casting process.
The preparation method provided by the embodiment of the application can reduce the sulfur content in the molten steel in the continuous casting tundish.
The smelting method provided by the embodiment of the application can reduce the average value of the sulfur content in the continuous casting treatment tundish from 36ppm to 8ppm on the premise of not increasing equipment investment.
After the refined molten steel enters the tundish, some elements which are easy to oxidize, such as Al, ti and the like, in the molten steel are oxidized, so that the content of the refined molten steel component is different from that of the tundish, and in general, the content of the elements which are easy to oxidize in the tundish is lower than that in the molten steel at the outlet, namely the aluminum loss and the titanium loss. However, the tundish component is the most representative steel grade determination sample, that is, the content of refined molten steel component, and the component of the continuous casting tundish is taken as the steel grade determination sample worldwide.
The application provides application of the smelting method in preparing non-oriented electrical steel.
The smelting method provided by the embodiment of the application can be used for obtaining refined molten steel with extremely low sulfur content, so that the smelting method can be used for improving the magnetic performance of non-oriented electrical steel and improving the quality of products.
Examples
The present disclosure is more particularly described in the following examples that are intended as illustrations only, since various modifications and changes within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages and ratios reported in the examples below are on a mass basis, and all reagents used in the examples are commercially available or were obtained synthetically according to conventional methods and can be used directly without further treatment, as well as the instruments used in the examples.
Example 1
(1) Carrying out KR desulfurization treatment on molten iron, wherein the stirring depth of a stirring head for the KR desulfurization treatment is 780-820mm, the stirring speed is 110r/min, a CaO-CaF 2 series desulfurizing agent is added, and the CaO-CaF 2 series desulfurizing agent comprises the following components by taking the total mass of the CaO-CaF 2 series desulfurizing agent as 100 percent: siO 2：≤5.0％,CaF2：7.0％-12.0％,CaO≥76.0％;S：≤0.045％;H2 O: less than or equal to 0.5 percent. The sulfur content in the molten iron before the desulfurization treatment is 0.045%, and the sulfur content in the molten iron after the desulfurization treatment is 0.0009%.
(2) The method comprises the steps of carrying out converter smelting treatment on desulfurized molten iron, wherein the charging temperature of the molten iron is 1280-1320 ℃, the finishing temperature of converter smelting is 1630-1670 ℃, low-sulfur clean scrap steel, lime and light burned magnesium balls are added into the molten iron during the converter smelting treatment, the sulfur content in the low-sulfur clean scrap steel is 0.012%, the sulfur content in the lime and the light burned magnesium balls are both 0.013%, slag-washing lime is added into the molten steel during tapping of the converter smelting treatment, and the S content in the molten steel in an argon station is 0.0021%.
(3) RH refining treatment is carried out on molten steel smelted by a converter, deoxidization alloying treatment is carried out on the molten steel, the initial temperature of the RH refining treatment is 1590 ℃, the vacuum degree of the RH refining treatment is 65-75Pa, the end temperature of the RH refining treatment is 1580 ℃, and the refining treatment time is 40-50min. After deoxidizing alloying treatment, 0.5-1.0kg/t of CaO-Al 2O3 series desulfurizing agent is added into the molten steel for desulfurizing treatment, and the CaO-Al 2O3 series desulfurizing agent comprises the following components ：CaO：53.25％;SiO2：6.055％;Al2O3：32.06％;F：3.8％;C：0.035％;S：0.06％;TiO2：0.043％;MgO：4.697％,, calculated by 100 percent of the total mass of the CaO-Al 2O3 series desulfurizing agent, to obtain refined molten steel. The sulfur content in the molten steel was measured to be 0.0008%.
Example 2
The procedure of example 1 was repeated except that the composition of CaO-Al 2O3 -based desulfurizing agent was changed in the RH refining treatment.
Based on 100 percent of the total mass of the CaO-Al 2O3 series desulfurizing agent, the CaO-Al 2O3 series desulfurizing agent comprises the following components ：CaO：71.02％;SiO2：6.055％;Al2O3：14.29％;F：3.8％;C：0.035％;S：0.06％;TiO2：0.043％;MgO：4.697％.
The sulfur content in the molten steel after RH refining was 0.0018%.
Example 3
The procedure of example 1 was repeated except that the composition of CaO-Al 2O3 -based desulfurizing agent was changed in the RH refining treatment.
Based on 100 percent of the total mass of the CaO-Al 2O3 series desulfurizing agent, the CaO-Al 2O3 series desulfurizing agent comprises the following components ：CaO：30.18％;SiO2：6.055％;Al2O3：55.13％;F：3.8％;C：0.035％;S：0.06％;TiO2：0.043％;MgO：4.697％.
The sulfur content in the molten steel after RH refining was 0.0019%.
Comparative example
The preparation process was the same as in example 1 except that the kind of desulfurizing agent was different in the RH refining treatment.
And adding a common RH desulfurizing agent in the step of carrying out RH refining treatment on molten steel smelted by the converter. Based on the total mass of the common RH desulfurizing agent being 100%, the common RH desulfurizing agent comprises the following components: the desulfurizing agent is CaO:67.4%, caF 2: 20.23%, total% of C: 0.133%, S:0.016%, tiO 2: 0.011%, the remaining unavoidable impurities: 12.21%.
The sulfur content in the molten steel after the RH refining treatment was 0.0025%.
From examples 1 to 3 and comparative examples, it is understood that the sulfur content in molten steel can be reduced by the smelting method of the present application in examples to obtain molten steel having an extremely low sulfur content. The sulfur content in the molten steel can be further reduced by controlling the content of CaO and Al 2O3 in the CaO-Al 2O3 series desulfurizing agent.
While the application has been described with reference to a preferred embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the application. In particular, the technical features mentioned in the respective embodiments may be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions falling within the scope of the claims.
Claims (10)
1. A method for smelting molten steel with extremely low sulfur content, which is characterized by comprising the following steps:
Desulfurizing the molten iron to obtain desulfurized molten iron, wherein the sulfur content in the molten iron before desulfurization is less than or equal to 0.050 percent, and the sulfur content in the molten iron after desulfurization is less than or equal to 0.0010 percent;
Carrying out converter smelting treatment on desulfurized molten iron, adding auxiliary materials into the molten iron during the converter smelting treatment, wherein the sulfur content in the auxiliary materials is less than or equal to 0.015 percent, and adding slag-washed lime into the molten steel during tapping of the converter smelting treatment to obtain molten steel after converter smelting;
Refining molten steel smelted by a converter, deoxidizing and alloying the molten steel, and adding a desulfurizing agent into the molten steel after the deoxidizing and alloying treatment to perform desulfurization treatment to obtain refined molten steel, wherein the desulfurizing agent comprises CaO-Al 2O3 series desulfurizing agent, and the adding amount of the CaO-Al 2O3 series desulfurizing agent is 0.5-1.0kg/t.
2. The method according to claim 1, wherein in the step of refining molten steel after converter smelting, the CaO-Al 2O3 -based desulfurizing agent comprises, based on 100% by weight of the total amount of the CaO-Al 2O3 -based desulfurizing agent ：CaO：52.75％-53.75％;SiO2：6％-6.86％;Al2O3：31.56％-32.56％;F：3.7％-3.9％;C：0.032％-0.038％;S：0.05％-0.07％;TiO2：0.033％-0.053％;MgO：4.6％-5.44％.
3. The method according to claim 1, wherein the step of desulfurizing the molten iron further comprises adding a CaO-CaF 2 -series desulfurizing agent to the molten iron, wherein the addition amount of the CaO-CaF 2 -series desulfurizing agent is 4.5 to 5.5kg/t.
4. A smelting process according to claim 3, wherein the CaO-CaF 2 -based desulfurizing agent comprises, based on 100% of the total mass of the CaO-CaF 2 -based desulfurizing agent: siO 2：≤5.0％,CaF2：7.0％-12.0％,CaO≥76.0％;S：≤0.045％;H2 O: less than or equal to 0.5 percent.
5. The method according to claim 1, wherein the step of desulfurizing the molten iron comprises stirring at a speed of 100 to 120r/min.
6. The method according to claim 1, wherein the step of performing the converter smelting treatment on the desulfurized molten iron comprises the step of charging the molten iron to a furnace temperature of 1280-1320 ℃, and the step of performing the converter smelting at a terminal temperature of 1630-1670 ℃; and/or the number of the groups of groups,
The adding amount of the slag washing lime is 4-5kg/t.
7. The method according to claim 1, wherein in the step of performing the converter smelting treatment on the desulfurized molten iron, the auxiliary material includes one or more of scrap steel, lime and light burned magnesium balls.
8. The smelting method according to claim 7, wherein the particle size of the light burned magnesium balls is 10-50mm.
9. The method according to claim 1, wherein the step of refining molten steel after converter smelting further comprises the steps of initial temperature of 1570-1610 ℃, vacuum degree of 65-75Pa, final temperature of 1560-1600 ℃ and time of 40-50min.
10. Use of the smelting process according to any one of claims 1 to 9 for the preparation of non-oriented electrical steel.
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