Production method of nitrogenous low-carbon aluminum killed molten steel

Abstract

The invention relates to a production method of nitrogen-containing low-carbon aluminum killed molten steel. The method comprises the following steps: 1) smelting by adopting a top-bottom combined blown converter; (2) the converter smelting process is controlled; (3) controlling the smelting end point of the converter; (4) controlling molten steel sedation; (5) controlling tapping of the converter; and (6) refining of a molten steel argon blowing station is controlled, the molten steel fed with the aluminum wire is subjected to weak stirring, the argon flow is controlled to be 50-100 L / min, the molten steel is subjected to weak stirring for 6-8 min, finished molten steel is obtained, and the finished molten steel comprises, by weight, 0.02%-0.045% of C, smaller than or equal to 0.034% of Si, 0.2%-0.3% of Mn, smaller than or equal to 0.015% of P, smaller than or equal to 0.012% of S, 0.025%-0.06% of Al, 0.0035%-0.0065% of N, smaller than or equal to 0.0035% of T [O] and the balance Fe and residual elements. According to the method, the problem of accurate nitrogen increasing in converter smelting of the low-carbon aluminum killed molten steel is solved, the cleanliness of the molten steel is improved, the argon blowing direct feeding process of the nitrogen-containing low-carbon aluminum killed molten steel is achieved, and the smelting cost is reduced.

Description

Technical Field

[0001] This invention relates to a method for producing nitrogen-containing steel, and more particularly to a method for producing nitrogen-containing low-carbon aluminum-killed molten steel, belonging to the field of steel smelting and continuous casting technology. Background Technology

[0002] Adding trace amounts of nitrogen to low-carbon aluminum-killed steel allows it to react with aluminum in the steel to form aluminum nitride, thereby improving the surface strengthening and hardening effect of the product. The current conventional process for smelting nitrogen-containing low-carbon aluminum-killed steel in a converter involves first adding nitrogen to the molten steel in the converter, and then using a nitrogen-adding process or an alloy nitrogen-adding process in the refining furnace to achieve stable control of the nitrogen content in the molten steel. If the converter smelting process can achieve stable control of the target nitrogen content of the steel grade, the refining process path can be optimized, changing from LF or RH to direct argon blowing, reducing steelmaking and refining costs; or the use of nitride alloys can be avoided, reducing alloy costs.

[0003] Chinese patent application CN114774621B discloses an extremely low-cost method for producing rebar in a converter. This method involves replacing the oxygen lance gas supply with nitrogen gas at the end of the converter smelting process, with the lance positioned at 2-2.4m and the gas supply intensity at 2.4-2.8 Nm. 3 / (min·t steel), time is 2-3min, and nitrogen is blown from the bottom throughout the smelting process, with an intensity of 0.03-0.06Nm. 3 / (min·t steel), the nitrogen content of the molten steel at the smelting endpoint is 30-50×10 -6 After the argon blowing station finishes processing, the temperature reaches 40-70×10⁻⁶. -6 This provides a good foundation for subsequent microalloying.

[0004] Chinese patent application CN108690898B discloses a precise control method for nitrogen enhancement in a combined blowing converter. This method achieves control over different nitrogen contents by switching between bottom-blown nitrogen and argon. The target nitrogen content is 40-60 × 10⁻⁶. -6 During the penultimate oxygen step, N2 is switched to Ar until the steel tapping is completed; the target nitrogen content is 61-80 × 10⁻⁶. -6 During the TSC test of the blowing process, N2 was switched to Ar until the end of tapping; the target nitrogen content was 81-100×10⁻⁶. -6 At the start of tapping from the converter, N2 is switched to Ar and continues until tapping ends. The supply intensities of nitrogen and argon are 0.06-0.07 and 0.025-0.04 Nm, respectively. 3 / (min﹒t steel).

[0005] Chinese patent application CN103468857B discloses a method for controlling the nitrogen content in molten steel during converter smelting. This method involves bottom-blowing argon gas during the early and late stages of converter smelting, deoxidizing the slag and molten steel at the end of the smelting process, and then using top-blowing and bottom-blowing nitrogen gas from an oxygen lance to control the nitrogen content in the molten steel to 100-260 × 10⁻⁶. -6 The supply intensities of nitrogen and argon are 0.05-0.09 and 0.03-0.05 Nm, respectively. 3 / (min﹒t steel).

[0006] Chinese patent application CN102732665A discloses a method for increasing nitrogen content in molten steel at the end of converter smelting. In this method, a deoxidizing alloy is added to the furnace at the end of the converter smelting process to control the oxygen content of the molten steel to no more than 0.05%. Then, nitrogen gas is simultaneously blown into the molten pool using both top and bottom lances, achieving a nitrogen content of 50-300 × 10⁻⁶ ppm. -6 .

[0007] The literature "Research and Application of Converter Nitrogen Enhancement Technology" (Hu Jingtao, *Henan Metallurgy*, Vol. 28, No. 159, February 2019, pp. 6-8) discloses that when smelting HBR400 and HBR500 in a converter, opening the nitrogen valve at 100% blowing rate with a valve opening of 30% and a blowing time of 120 seconds can achieve a final nitrogen content >80×10⁻⁶. -6 This reduces the cost of alloys.

[0008] The literature "Influence of Converter Bottom Blowing Nitrogen and Argon Switching on Nitrogen Mass Fraction" (Sun Liang et al., *China Metallurgy*, Vol. 29, No. 5, May 2019, pp. 62-65) discloses that when using a full-process nitrogen blowing process for nitrogen-blowing steel grades in converter smelting, the average TSO nitrogen content is 0.0043%. By controlling the bottom blowing flow rate at a high level during the later stages of blowing, when the oxygen ratio is not less than 80%, and during the waiting period before tapping, the nitrogen content can reach 83-125 × 10⁻⁶. -6 .

[0009] The literature "Research on Smelting Process of Nitrogen-Enhanced Steel Q345R" (Huang Zhicheng et al., *Metallic Materials and Metallurgical Engineering*, June 2019, pp. 34-38) discloses a method of increasing nitrogen content in molten steel by increasing the intensity of bottom-blown nitrogen in the converter and using RH circulating nitrogen. The bottom-blown nitrogen intensity in the converter is 0.045 Nm. 3 When the nitrogen content at the converter outlet is 40-53 × 10⁻⁶ (min·t steel), the nitrogen content is 40-53 × 10⁻⁶. -6 The average is 45×10 -6 .

[0010] Existing technologies all approach the problem from different angles, using oxygen lances or bottom lances to blow nitrogen into the molten pool to increase the nitrogen content of the steel. Currently, there is a lack of methods for smelting nitrogen-containing low-carbon aluminum-killed molten steel in converters, solving the problem of precise control of nitrogen content in converter steel, and thus realizing the direct argon blowing process for molten steel. Summary of the Invention

[0011] The purpose of this invention is to provide a method for producing nitrogen-containing low-carbon aluminum-killed molten steel, which mainly solves the problem that existing converters cannot achieve precise nitrogen control technology for molten steel. The method of this invention completely solves the problem of precise nitrogen increase in converter smelting of low-carbon aluminum-killed molten steel, improves the cleanliness of molten steel, realizes the argon blowing process for direct refining of molten steel, and reduces smelting costs.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0013] A method for producing nitrogen-containing low-carbon aluminum-killed molten steel includes the following steps:

[0014] 1) The smelting process uses a top-and-bottom blown converter. The mass percentage of the raw materials fed in is 80-90% molten iron, with the remainder being scrap steel. The bottom-blown gases are argon and nitrogen, with a supply intensity of 0.08-0.15 Nm³. 3 / (min·t steel);

[0015] 2) Control of the converter smelting process: The oxygen supply in the early stage of converter smelting is 25-30% of the total oxygen supply for the smelting furnace, and the oxygen supply intensity is controlled at 3.3-3.8 Nm³. 3 / (min·t steel), the bottom-blown gas is argon, and the gas supply intensity is 0.1-0.13 Nm. 3 / (min·t steel); The oxygen supply during the middle stage of converter smelting is 40-50% of the total oxygen supply for the smelting batch, and the oxygen supply intensity is controlled at 2.8-3.3 Nm. 3 / (min·t steel), the bottom-blown gas is argon, and the gas supply intensity is 0.08-0.10 Nm. 3 / (min·t steel); The oxygen supply in the later stage of converter smelting is 25-30% of the total oxygen supply for the smelting furnace, and the oxygen supply intensity is controlled at 3.0-3.5 Nm. 3 / (min·t steel), the bottom-blown gas is nitrogen, and the gas supply intensity is 0.12-0.15 Nm. 3 / (min·t steel), when the oxygen supply reaches 85-90% of the total oxygen supply, adjust the oxygen lance position to low lance position for blowing until the blowing ends;

[0016] 3) Control of the endpoint of converter smelting: Sampling and testing of w[O] and temperature of molten steel at the endpoint of converter blowing. When w[O] in molten steel at the endpoint of converter blowing is detected to be 0.045-0.065% and the temperature of molten steel at the endpoint of converter blowing is 1640-1660℃, converter blowing ends.

[0017] 4) Control of molten steel calming: After converter blowing, the molten steel is calmed for 2-3 minutes. The bottom blowing gas is nitrogen, with a supply intensity of 0.12-0.15 Nm. 3 / (min·t steel), then tap the steel;

[0018] 5) Control of converter tapping: Argon is used as the bottom blowing gas in the converter, with a supply intensity of 0.08-0.10 Nm³. 3 / (min·t steel); the bottom blowing gas in the ladle is argon, with a gas supply flow rate of 800-1000L / min. When the amount of molten steel tapped from the converter reaches 10-20% of the total molten steel, quicklime is added to the ladle; when the amount of molten steel tapped from the converter reaches 45-55% of the total molten steel, ferroaluminum, ferromanganese, and carbon powder are added to the ladle, and the argon flow rate is adjusted to 200-400L / min; after the converter tapping is completed, medium-aluminum slag deoxidizer is added to the ladle; the calcium-aluminum ratio (w(CaO) / w(Al2O3)) of the ladle slag is controlled to be 1.0-1.3, and the total iron weight percentage is 1.5-5.0%;

[0019] 6) Control of argon blowing station refining: Molten steel from the ladle is transported to the argon blowing station for processing. The argon flow rate is adjusted to 400-600 L / min, and the molten steel is stirred for 2-3 minutes. Then, the argon flow is stopped, and the oxygen content and temperature of the molten steel are measured. Argon is then introduced into the molten steel again, controlling the argon flow rate at 100-200 L / min and adjusting the molten steel temperature to 1590-1605℃. Aluminum wire is then fed into the molten steel. After the aluminum wire is fed, the molten steel is weakly stirred, and the temperature is controlled... Argon gas flow rate is 50-100 L / min. The molten steel is gently stirred for 6-8 minutes to obtain the finished molten steel. The chemical composition of the finished molten steel by weight percentage is: C: 0.02-0.045%, Si≤0.034%, Mn: 0.2-0.3%, P≤0.015%, S≤0.012%, Al: 0.025-0.06%, N: 0.0035-0.0065%, T[O]≤0.0035%, with the balance being Fe and residual elements.

[0020] In step 1) of this invention, the number of bottom lances in the top and bottom combined blowing converter is 8-12, and the carbon-oxygen product value at the end of the converter blowing is 0.0015-0.0025, preferably 0.0015-0.0020.

[0021] In step 2) of this invention, the low gun position is H0 + H0 * (0 - 0.05), where H0 is the height of the molten steel level in the converter.

[0022] In step 5) of this invention, the chemical composition of quicklime by weight percentage is: CaO≥92%, SiO2≤3%, loss on ignition≤5%, and the amount of quicklime added is 1.5-2.5 kg / t steel; the chemical composition of aluminum and iron by weight percentage is: aluminum: 46-50%, calcium: 3-7%, Fe: 43-47%, others≤3%, and the amount of aluminum and iron added is 1.6-2.6 kg / t steel, controlling w[O] in molten steel to be 0.001-0.003%; the chemical composition of the medium-aluminum slag deoxidizer by weight percentage is: Al: 20-25%, Al2O3: 20-30%, CaO: 40-50%, SiO2≤5%, H2O≤1%, and the amount of medium-aluminum slag deoxidizer added is 0.4-0.6 kg / t steel.

[0023] The reasons for determining the process control parameters in this invention are as follows:

[0024] In existing converter smelting processes for nitrogen-containing low-carbon aluminum killed steel, the nitrogen content control accuracy of the molten steel at the converter endpoint is poor, requiring adjustments to the nitrogen content in the refining furnace. Compared to the direct argon blowing process, the refining furnace treatment of molten steel allows for more complete flotation of inclusions, which is beneficial for controlling the cleanliness of the molten steel. Therefore, simplifying the nitrogen-containing low-carbon aluminum killed steel smelting process from a refining furnace to direct argon blowing requires first solving the problem of stable nitrogen content control in converter smelting, and secondly, ensuring that the cleanliness of the argon-blown molten steel meets product quality requirements.

[0025] Regarding the stable control of nitrogen content in molten steel produced in converter smelting, according to Sievt's Law, the nitrogen content in molten steel is directly proportional to the square root of the nitrogen partial pressure; that is, the higher the nitrogen partial pressure, the higher the nitrogen content. During converter smelting, carbon-oxygen reactions of varying intensities occur. Vigorous carbon-oxygen reactions result in low nitrogen partial pressure, leading to denitrification; weak carbon-oxygen reactions result in high nitrogen partial pressure, leading to nitrogen enrichment. Therefore, increasing nitrogen content in molten steel using nitrogen in converter smelting requires a clear understanding of the carbon-oxygen reaction rate to achieve precise nitrogen content control. The applicant's research revealed that in the middle stage of converter smelting, the carbon-oxygen reaction is intense, making nitrogen enrichment via bottom-blown nitrogen difficult and highly unstable. In the later stage of converter smelting, the carbon-oxygen reaction weakens, making nitrogen enrichment via bottom-blown nitrogen feasible and relatively stable. At the end of converter smelting, with oxygen content controlled within a certain range, the carbon-oxygen reaction further weakens, making nitrogen enrichment via bottom-blown nitrogen even more efficient and stable.

[0026] Regarding the control of molten steel cleanliness in argon-blown direct-flow steelmaking: Ladle slag plays a crucial role in adsorbing inclusions in molten steel. Suitable ladle slag properties facilitate the removal of inclusions, thereby improving the castability and product quality of the molten steel. In argon-blown direct-flow steelmaking, ladle slag adjustment is completed during the converter tapping process. The slag formation time is short, making it difficult to control suitable ladle slag properties. The applicant's research has found that designing ladle slag with a lower liquidus temperature, giving it good fluidity, enables rapid slag formation during converter tapping. Furthermore, by controlling the appropriate calcium-aluminum ratio and total iron content of the ladle slag, efficient adsorption of alumina inclusions in the molten steel can be achieved, while reducing secondary oxidation pollution of the molten steel by the ladle slag. This meets the requirements for controlling inclusions and cleanliness in molten steel using the argon-blown direct-flow process.

[0027] Based on the applicant's research findings, this invention improves the accuracy of nitrogen content control and steel cleanliness in converter smelting by increasing nitrogen content in molten steel and controlling the physical property parameters of ladle slag, thereby enabling direct argon blowing into nitrogen-containing, low-carbon aluminum-killed molten steel.

[0028] 1. Setting of nitrogen increase control parameters for converter steelmaking

[0029] 1) Setting control parameters for the early and middle stages of converter smelting

[0030] When the carbon-oxygen product in a top-and-bottom blown converter is between 0.0015 and 0.0025, the bottom blowing effect is good, which is conducive to a stable smelting process. Argon is used throughout the bottom blowing process in the early and middle stages of converter smelting. In the early stage, the molten pool temperature is low and the carbon-oxygen reaction is weak, so the oxygen supply intensity and bottom blowing gas supply intensity are increased, and the molten pool stirring is strengthened. In the middle stage, the carbon-oxygen reaction is intense, so the oxygen supply intensity and bottom blowing gas supply intensity are reduced to avoid slag drying, thus stabilizing the smelting process and preventing abnormal nitrogen increase in molten steel. The nitrogen content of the molten steel is stably controlled at 0.0011-0.0014%.

[0031] 2) Setting of control parameters for the later stage of converter smelting and molten steel killing

[0032] During the later stages of converter smelting and the steel calming process, nitrogen is used for bottom blowing throughout the entire process, with a gas supply intensity of 0.12-0.15 Nm. 3 / (min·t steel). As the carbon content in the molten pool decreases, the intensity of the carbon-oxygen reaction further decreases. Therefore, it is necessary to increase the oxygen supply intensity and bottom blowing gas supply intensity, lower the oxygen lance position, and strengthen the stirring of the molten pool. The oxygen weight percentage of the molten steel at the converter's final stage should be controlled at 0.045-0.06%. This is to avoid both low oxygen content and high carbon content, which would affect the stability of nitrogen addition due to the carbon-oxygen reaction; and high oxygen content and low carbon content, which could lead to overblowing and abnormal nitrogen addition in the molten steel. The blowing time in the later stage of converter smelting is 3-4 minutes, with an average nitrogen addition rate of 0.0005% / min; the steel calming time is 2-3 minutes, with an average nitrogen addition rate of 0.0008% / min. At the time of tapping from the converter, the nitrogen content of the molten steel is stably controlled at 0.0032-0.0058%.

[0033] 3) Setting of converter tapping control parameters

[0034] Argon is used throughout the converter bottom blowing and ladle bottom blowing processes. By controlling the amount of aluminum and iron added, the oxygen weight percentage of the molten steel can be controlled to be 0.001-0.003%, and the nitrogen increase in the molten steel during the tapping process can be controlled to be 0.0003-0.0007%.

[0035] 2. Setting of control parameters for ladle slag

[0036] When quicklime is added in the early stage of converter tapping, a strong stirring process is used in the bottom blowing of the ladle to promote the rapid dissolution of the lime. When alloy is added in the middle stage of tapping, a medium-intensity stirring process is used in the bottom blowing of the ladle to avoid secondary oxidation of the alloy and promote the flotation of deoxidation products, which are then fully mixed with the lime dissolved in the top slag of the ladle to form initial slag. After the converter tapping is completed, a medium-alumina slag deoxidizer is added to the ladle to deoxidize the ladle slag and obtain the target slag. The dosage of quicklime and medium-alumina slag deoxidizer per ton of steel is 1.5-2.5 kg and 0.4-0.6 kg, respectively. The relatively small dosage is conducive to rapid slag formation. The calcium-aluminum ratio of the target slag is 1.0-1.3, and the total iron weight percentage is 1.5-5.0%. The low melting temperature of the ladle slag further promotes rapid slag formation. The controlled calcium-aluminum ratio is conducive to the adsorption of alumina inclusions in the molten steel. The controlled total iron content helps to reduce the loss of aluminum in the molten steel and avoid pollution caused by secondary oxidation. This enhances the ladle slag's ability to adsorb inclusions, meeting the process requirements of direct argon blowing into nitrogen-containing, low-carbon, aluminum-killed molten steel.

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] 1. This invention controls the nitrogen content in molten steel during converter smelting and tapping processes, achieving a stable nitrogen content of 0.0035-0.0065%.

[0039] 2. This invention improves the adsorption capacity of ladle slag for inclusions by designing the ladle slag composition, thus meeting the requirements for controlling inclusions in nitrogen-containing low-carbon aluminum killed steel directly after argon blowing. Detailed Implementation

[0040] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0041] This invention takes the smelting of MRT2 tinplate steel in a 150-ton top-and-bottom combined blowing converter as an example; the production method includes: converter smelting and argon blowing station steel treatment. The control parameters for steel production in this invention are shown in Tables 1 to 7.

[0042] Table 1 Parameters of metal materials for converter smelting in embodiments of the present invention

[0043]

[0044]

[0045] Table 2 Control parameters for converter smelting process

[0046]

[0047] Table 3. Composition and Temperature of Molten Steel at the End of Converter Process

[0048]

[0049] Table 4. Charging process during converter tapping, unit: kg / t steel

[0050] Furnace quicklime Aluminum Iron Ferromanganese toner Deoxidizer of aluminum slag Example 1 2.22 2.19 0.26 0 0.44 Example 2 2.07 2.05 0.26 0.021 0.41 Example 3 2.23 2.21 0.24 0.033 0.45 Example 4 1.79 2.06 0.27 0.036 0.48 Example 5 2.25 2.29 0.27 0.042 0.46

[0051] Table 5 Composition and temperature of molten steel entering the argon blowing station

[0052]

[0053] Table 6. Processing parameters of the argon blowing station

[0054]

[0055]

[0056] Table 7 Composition and Temperature of Molten Steel Leaving the Argon Blowing Station

[0057]

[0058] This invention achieves stable control of nitrogen content in molten steel through control of the converter smelting process, the converter smelting endpoint, steel killing, converter tapping, and argon blowing station steel refining, solving the problem of direct argon blowing of nitrogen-containing low-carbon aluminum-killed molten steel. As shown in Examples 1-5 of this invention, compared with existing conventional processes, the method of this invention improves the control stability of nitrogen content in molten steel at the converter endpoint to 0.0037-0.0046%; furthermore, it improves the control stability of nitrogen content in molten steel exiting the argon blowing station to 0.0042-0.0052%; and through ladle top slag optimization, it improves the control level of molten steel cleanliness, controlling the total oxygen content in molten steel exiting the argon blowing station to 0.0016-0.0022%, achieving direct argon blowing of tinplate MRT2 molten steel and reducing smelting costs.

[0059] The technical means disclosed in this invention are not limited to those described above, but also include technical solutions composed of any combination of the above technical features.

[0060] It should be noted that the above embodiments are not intended to limit the scope of protection of the present invention. Equivalent transformations or substitutions made based on the above technical solutions all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for producing nitrogen-containing, low-carbon, aluminum-killed molten steel, characterized in that, The method includes the following steps: 1) The smelting process uses a top-and-bottom blown converter. The mass percentage of the raw materials fed in is 80-90% molten iron, with the remainder being scrap steel. The bottom-blown gases are argon and nitrogen, with a supply intensity of 0.08-0.15 Nm³. 3 / (min·t steel); 2) Control of the converter smelting process: The oxygen supply in the early stage of converter smelting is 25-30% of the total oxygen supply for the smelting furnace, and the oxygen supply intensity is controlled at 3.3-3.8 Nm³. 3 / (min·t steel), the bottom-blown gas is argon, and the gas supply intensity is 0.1-0.13 Nm. 3 / (min·t steel); The oxygen supply during the middle stage of converter smelting is 40-50% of the total oxygen supply for the smelting batch, and the oxygen supply intensity is controlled at 2.8-3.3 Nm. 3 / (min·t steel), the bottom-blown gas is argon, and the gas supply intensity is 0.08-0.10 Nm. 3 / (min·t steel); The oxygen supply in the later stage of converter smelting is 25-30% of the total oxygen supply for the smelting furnace, and the oxygen supply intensity is controlled at 3.0-3.5 Nm. 3 / (min·t steel), the bottom-blown gas is nitrogen, and the gas supply intensity is 0.12-0.15 Nm. 3 / (min·t steel), when the oxygen supply reaches 85-90% of the total oxygen supply, adjust the oxygen lance position to low lance position for blowing until the blowing ends; 3) Control of the endpoint of converter smelting: Sampling and testing of w[O] and temperature of molten steel at the endpoint of converter blowing. When w[O] in molten steel at the endpoint of converter blowing is detected to be 0.045-0.065% and the temperature of molten steel at the endpoint of converter blowing is 1640-1660℃, converter blowing ends. 4) Control of molten steel calming: After converter blowing, the molten steel is calmed for 2-3 minutes. The bottom blowing gas is nitrogen, with a supply intensity of 0.12-0.15 Nm. 3 / (min·t steel), then tap the steel; 5) Control of converter tapping: Argon is used as the bottom blowing gas in the converter, with a supply intensity of 0.08-0.10 Nm³. 3 / (min·t steel); the bottom blowing gas in the ladle is argon, with a gas supply flow rate of 800-1000L / min. When the amount of molten steel tapped from the converter reaches 10-20% of the total molten steel, quicklime is added to the ladle; when the amount of molten steel tapped from the converter reaches 45-55% of the total molten steel, ferroaluminum, ferromanganese, and carbon powder are added to the ladle, and the argon flow rate is adjusted to 200-400L / min; after the converter tapping is completed, medium-aluminum slag deoxidizer is added to the ladle; the calcium-aluminum ratio (w(CaO) / w(Al2O3)) of the ladle slag is controlled to be 1.0-1.3, and the total iron weight percentage is 1.5-5.0%; 6) Control of argon blowing station refining: Molten steel from the ladle is transported to the argon blowing station for processing. The argon flow rate is adjusted to 400-600 L / min, and the molten steel is stirred for 2-3 minutes. Then, the argon flow is stopped, and the oxygen content and temperature of the molten steel are measured. Argon is then introduced into the molten steel again, controlling the argon flow rate at 100-200 L / min and adjusting the molten steel temperature to 1590-1605℃. Aluminum wire is then fed into the molten steel. After the aluminum wire is fed, the molten steel is weakly stirred, and the temperature is controlled... Argon gas flow rate is 50-100 L / min. The molten steel is gently stirred for 6-8 minutes to obtain the finished molten steel. The chemical composition of the finished molten steel by weight percentage is: C: 0.02-0.045%, Si≤0.034%, Mn: 0.2-0.3%, P≤0.015%, S≤0.012%, Al: 0.025-0.06%, N: 0.0035-0.0065%, T[O]≤0.0035%, with the balance being Fe and residual elements.

2. The method for producing nitrogen-containing low-carbon aluminum-killed molten steel according to claim 1, characterized in that, In step 1), the number of bottom lances in the top and bottom combined blowing converter is 8-12, and the carbon-oxygen product value at the end of the converter blowing is 0.0015-0.0025, preferably 0.0015-0.0020.

3. The method for producing nitrogen-containing low-carbon aluminum-killed molten steel according to claim 1, characterized in that, In step 2), the low gun position is H0 + H0 * (0 - 0.05), where H0 is the height of the molten steel level in the converter.

4. The method for producing nitrogen-containing low-carbon aluminum-killed molten steel according to claim 1, characterized in that, Step 5) In the steel, the chemical composition of quicklime by weight percentage is: CaO≥92%, SiO2≤3%, loss on ignition≤5%, and the amount of quicklime added is 1.5-2.5 kg / t steel; the chemical composition of aluminum and iron by weight percentage is: aluminum: 46-50%, calcium: 3-7%, Fe: 43-47%, others≤3%, and the amount of aluminum and iron added is 1.6-2.6 kg / t steel, controlling w[O] in molten steel to be 0.001-0.003%; the chemical composition of aluminum slag deoxidizer by weight percentage is: Al: 20-25%, Al2O3: 20-30%, CaO: 40-50%, SiO2≤5%, H2O≤1%, and the amount of aluminum slag deoxidizer added is 0.4-0.6 kg / t steel.

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