Control method for producing low-nitrogen high-strength steel from semi-steel

Abstract

The invention relates to the field of metallurgy, and provides a control method for producing low-nitrogen high-strength steel from semi-steel. The method comprises the steps that vanadium in blast furnace molten iron is extracted through a vanadium extraction converter, and obtained vanadium-extracted molten steel serves as semisteel; a desulfurizing agent is added into the semisteel, and desulfurization pretreatment is conducted through composite injection; the desulfurized semisteel enters an LD converter and an LF furnace in sequence for refining; and the refined semisteel is subjected to vacuum degassing and then cast into the low-nitrogen high-strength steel. The argon and other inert gases are blown into the molten steel to form a large number of bubbles and drive the molten steel to circularly flow, so that the contact area and contact time of the molten steel and a gas phase are increased, escape of nitrogen and other gases is facilitated, the nitrogen content in steel is reduced, the quality of steel is improved, semi-steel becomes low-nitrogen high-strength steel, the yield is increased, and the production cost is reduced. And waste in the production process is reduced.

Description

Technical Field

[0001] The invention relates to the field of metallurgy, and more specifically to a control method for producing low-nitrogen high-strength steel from semi-steel. Background Art

[0002] In the field of steel production, as the requirements for steel performance become increasingly stringent, the research and development of low-nitrogen high-strength steel has become a hot topic. The existing technology uses optimized converter blowing process to accurately control oxygen flow and gun position to promote nitrogen removal; some use vacuum refining equipment to reduce the solubility of nitrogen in molten steel under low pressure to achieve low nitrogen control.

[0003] In similar technical fields, traditional high-strength steel production is mostly based on conventional molten iron, and its process focuses on improving the strength of steel through complex alloying schemes. For example, a large amount of precious alloying elements such as nickel and chromium are added during the refining process, and multiple heat treatment processes are used to control the microstructure of the steel, thereby enhancing its strength and toughness. At the same time, high-power arc heating or oxygen top blowing are generally used in the steelmaking process to maintain the high temperature of the molten steel to ensure that various metallurgical reactions are fully carried out.

[0004] However, when using low-silicon, low-carbon, and low-heat source semi-steel produced from high-vanadium, high-titanium molten iron as raw material, existing technologies face many severe challenges. Compared with conventional molten iron, the low heat source characteristics of this semi-steel make it difficult to spontaneously maintain the ideal reaction temperature during the steelmaking process, making it difficult to effectively carry out conventional denitrification reactions, because the denitrification process often requires higher temperatures to provide sufficient reaction kinetic conditions. At present, the low-nitrogen control and high-strength steel production processes for conventional molten iron cannot be directly applied to this type of semi-steel, resulting in a blank in the production control method of low-nitrogen and high-strength steel for this special semi-steel, which cannot meet the needs of modern high-end steel manufacturing for special raw material steelmaking technology.

[0005] Due to the low heat source characteristics of semi-steel, the traditional denitrification process is difficult to implement effectively during the steelmaking process. For example, the conventional argon blowing and stirring denitrification method may cause poor fluidity of the molten steel due to insufficient temperature, resulting in low denitrification efficiency and the inability to accurately control the nitrogen content within the range required for low-nitrogen high-strength steel (usually required to be lower than a specific content, such as 50ppm). Semi-steel is prone to absorb nitrogen when it comes into contact with the external atmosphere. How to reduce the contact opportunities between semi-steel and nitrogen-containing media such as air and prevent nitrogen increase in the entire steelmaking process (from raw material pretreatment to continuous casting) is a difficulty that needs to be overcome.

[0006] The low heat source property of semi-steel leads to insufficient heat in the steelmaking process, which cannot provide a suitable temperature environment for various metallurgical reactions (such as dephosphorization, desulfurization, denitrification and alloying reactions). For example, during the refining process, the deep desulfurization reaction that relies on high temperature may not be fully carried out, affecting the purity and quality of the molten steel, so it is necessary to develop effective heat compensation technology, such as using appropriate heating methods or using chemical reaction heat to increase and stabilize the temperature of the molten steel. Temperature control not only solves the problem of insufficient heat, but also avoids other quality problems caused by excessive or uneven heating, such as element burning and steel liquid aspiration caused by local overheating. Summary of the invention

[0007] Based on the above purpose, the present invention proposes a control method for producing low-nitrogen high-strength steel from semi-steel, comprising the following steps: extracting vanadium from molten iron from a blast furnace through a vanadium extraction converter to obtain molten steel after vanadium extraction as semi-steel; Adding a desulfurizing agent into the semi-steel and performing desulfurization pretreatment by composite injection; The desulfurized semi-steel enters the LD converter and LF furnace for refining in turn; The refined semi-steel is vacuum degassed and then cast into low-nitrogen high-strength steel.

[0008] In some embodiments, the composition of the blast furnace iron comprises, by mass percentage: C ≥ 4.00%, P ≤ 0.100%, S ≤ 0.100%, and the rest is iron.

[0009] In some embodiments, the weight of molten iron in the blast furnace entering the vanadium-extracting converter is in the range of 210-240 t, and the loading amount of the vanadium-extracting converter is in the range of 225±10 t; The temperature range of the vanadium extraction converter is ≥1280℃.

[0010] In some embodiments, in terms of mass percentage, the C of the semi-steel is in the range of 3.50±0.30%, the temperature is 1350±20°C, the clearance range of the semi-steel tank is 300~500mm, and the semi-steel amount is 225±15t.

[0011] In some embodiments, the S content of the desulfurized semi-steel is in the range of ≤0.004%.

[0012] In some embodiments, argon is blown from the bottom of the LD converter during blowing. In some embodiments, the process further includes, after the LD converter refining is completed, performing a refining process on a small refining platform and taking samples to analyze the nitrogen content.

[0013] In some embodiments, during the refining process of the LF furnace, the argon blowing intensity during the heating process is less than 80Nm 3 / min, the dust removal valve opening is adjusted to 50% during the non-heating process.

[0014] In some embodiments, the carbon content of the steel tapped from the LD converter is ≤0.04%, the tapping temperature is 1620-1650°C, the tapping slag thickness is ≤80mm, and the clearance range is 300-600mm.

[0015] In some embodiments, 1000±100 Kg of active lime is added into the LD converter during the steel tapping process.

[0016] The present invention has at least the following beneficial technical effects: The present invention proposes a control method for producing low-nitrogen high-strength steel from semi-steel, the method comprising: extracting vanadium from molten iron in a blast furnace through a vanadium extraction converter to obtain molten steel after vanadium extraction as semi-steel; adding a desulfurizer to the semi-steel and performing desulfurization pretreatment through composite injection; the desulfurized semi-steel sequentially enters an LD converter and an LF furnace for refining; and vacuum degassing the refined semi-steel and then casting it into low-nitrogen high-strength steel.

[0017] The present invention blows inert gases such as argon into molten steel to form a large number of bubbles and drive the molten steel to circulate, thereby increasing the contact area and contact time between the molten steel and the gas phase, which is beneficial to the escape of gases such as nitrogen, reduces the nitrogen content in the steel, improves the quality of the steel, makes semi-steel become low-nitrogen high-strength steel, improves the yield rate, and reduces waste in the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings: Figure 1 A flow chart of a control method for producing low-nitrogen high-strength steel from semi-steel according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0019] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0020] In addition, reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0021] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of those skilled in the art to which this application belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless specifically defined as in the embodiments of this application.

[0022] The present invention proposes a control method for producing low nitrogen high strength steel from semi-steel. Figure 1 The method comprises the following steps: extracting vanadium from molten iron from a blast furnace through a vanadium extraction converter to obtain molten steel after vanadium extraction as semi-steel; Adding a desulfurizing agent into the semi-steel and performing desulfurization pretreatment by composite injection; The desulfurized semi-steel enters the LD converter and LF furnace for refining in turn; The refined semi-steel is vacuum degassed and then cast into low-nitrogen high-strength steel.

[0023] In the steel production process, denitrification usually occurs in the refining stage of molten steel, especially in the LF (ladle refining furnace) and RH / VD (vacuum degassing) processes.

[0024] In the LF refining furnace, although the main purpose is to carry out deoxidation, desulfurization, alloying and other operations, some reducing agents (such as aluminum, silicon, calcium, etc.) added during the refining process may also react with nitrogen in molten steel, thereby reducing its content. However, the contribution of the LF furnace to denitrification is relatively limited, because the solubility of nitrogen in molten steel is affected by many factors such as temperature and pressure, and its reaction kinetics conditions are relatively harsh.

[0025] In contrast, the RH / VD process is more effective in removing nitrogen. The RH method (circulation degassing method) forms a large number of bubbles and drives the circulation of molten steel by blowing inert gases such as argon into the molten steel, thereby increasing the contact area and contact time between the molten steel and the gas phase, which is conducive to the escape of gases such as nitrogen. At the same time, the RH furnace also has a vacuum pumping function, which can further reduce the pressure around the molten steel, reduce the solubility of nitrogen and accelerate its escape process. Although the VD method (vacuum degassing method) is different from the RH method in operation, it also promotes the removal of nitrogen by reducing the pressure and increasing the contact between the molten steel and the gas phase.

[0026] Nitrogen is generally regarded as a harmful element in steel. It may cause aging hardening, blue brittleness and other phenomena in steel, and reduce the plasticity and toughness of steel. By blowing inert gases such as argon into molten steel, the escape of gases such as nitrogen can be effectively promoted, thereby reducing the nitrogen content in steel and improving the quality of steel. The blowing of argon can also improve the morphology and distribution of inclusions in steel and reduce the adverse effects of inclusions on steel properties. The morphology and distribution of inclusions have an important influence on the fatigue performance and fracture toughness of steel. By optimizing the morphology of inclusions, the comprehensive performance of steel can be further improved.

[0027] Low nitrogen high strength steel achieves high strength by precisely controlling the nitrogen content and other alloying elements. This allows the steel to have a thinner section when bearing the same load, thereby reducing the weight of the structure and improving design flexibility. While ensuring high strength, low nitrogen high strength steel also has good toughness, which can maintain the integrity of the structure under various stress conditions and reduce the risk of brittle fracture.

[0028] In some embodiments, see Figure 1 , in terms of mass percentage, the composition of blast furnace molten iron includes: C ≥ 4.00%, P ≤ 0.100%, S ≤ 0.100%, and the rest is iron.

[0029] The vanadium extraction from molten iron in blast furnace is a key step in extracting vanadium from vanadium-containing molten iron. The vanadium-containing molten iron produced by the blast furnace is treated in the converter, and the vanadium enters the slag through selective oxidation to form vanadium slag, and then the vanadium slag is used for vanadium extraction. The vanadium extraction methods include shaking bag vanadium extraction, atomization vanadium extraction, sodium vanadium slag method, converter vanadium extraction, etc. By optimizing the converter vanadium extraction process, such as using double blowing technology and controlling the temperature of the molten pool, the vanadium content in the vanadium slag can be further increased, thereby improving the grade and value of the vanadium slag.

[0030] Appropriate molten iron composition can ensure the full oxidation and enrichment of vanadium during the vanadium extraction process, thereby improving the recovery rate of vanadium.

[0031] In some embodiments, see Figure 1 The weight of molten iron entering the vanadium-extracting converter is in the range of 210-240t, and the loading amount of the vanadium-extracting converter is in the range of 225±10t; The temperature range of the vanadium extraction converter is ≥1280℃.

[0032] A reasonable molten iron temperature range helps control the molten pool temperature during vanadium extraction, avoiding excessively high temperatures that inhibit vanadium oxidation, or excessively low temperatures that affect vanadium extraction efficiency. By precisely controlling the conditions of molten iron entering the furnace, energy consumption and raw material waste in the vanadium extraction process can be reduced, thereby reducing production costs. High-quality vanadium slag and semi-steel products can improve the efficiency and quality of subsequent smelting processes, further reducing overall production costs.

[0033] In some embodiments, in terms of mass percentage, the C of the semi-steel is in the range of 3.50±0.30%, the temperature is 1350±20°C, the semi-steel tank clearance (i.e., the vertical distance from the liquid level in the tank to the top of the tank mouth) is in the range of 300~500mm, and the semi-steel amount is 225±15t.

[0034] The carbon content of the semi-steel after vanadium extraction is adjusted to be closer to the composition range required for subsequent steelmaking. This reduces the need to adjust these elements during the steelmaking process, thereby shortening the smelting cycle and improving smelting efficiency. The vanadium extraction process removes some impurities in the molten iron, such as sulfur and phosphorus, which improves the purity of the semi-steel, obtains higher quality molten steel during the steelmaking process, and reduces the generation of inclusions and defects. The composition of the semi-steel is precisely controlled with a small fluctuation range to maintain the stability and consistency of the molten steel composition during the steelmaking process. Stable composition can improve the performance and quality stability of the product.

[0035] In some embodiments, the S content of the desulfurized semi-steel is in the range of ≤0.004%.

[0036] Sulfur is one of the harmful elements in steel. It will cause hot brittleness of steel during hot working and reduce the plasticity and toughness of steel. By reducing the sulfur content in molten iron to the specified range through desulfurization treatment, the mechanical properties and processing properties of steel can be significantly improved.

[0037] Hot metal desulfurization is an important pretreatment step before hot metal enters the converter or electric furnace for smelting. By adding desulfurizers (such as lime, magnesium powder, etc.) to the hot metal and using methods such as composite injection to remove sulfur from the hot metal, the quality of steel can be improved.

[0038] The desulfurization efficiency is affected by many factors, such as the amount of desulfurizer, initial temperature, and the method of adding the desulfurizer. Efficient desulfurization is essential for the production of high-quality steel.

[0039] The low sulfur content in hot metal after desulfurization can reduce the desulfurization burden in the subsequent steelmaking process, making the steelmaking process smoother and more efficient. The reduction in sulfur content can reduce the amount of additional alloying elements added to compensate for the adverse effects of sulfur on steel properties, thereby reducing alloying costs.

[0040] In some embodiments, argon is blown from the bottom of the LD converter during blowing.

[0041] During the whole process of converter blowing, argon was blown from the bottom of the furnace. The whole process argon blowing mode was not selected to track the nitrogen content of molten steel in the later process. Bottom argon blowing can promote the floating and removal of inclusions in molten steel, thereby optimizing the morphology and distribution of inclusions. This helps to improve the mechanical properties and processing properties of steel.

[0042] The full argon blowing mode may cause excessive nitrogen absorption by molten steel at certain smelting stages, because although argon itself does not react with molten steel, the contact between molten steel and air during the argon blowing process may increase the risk of nitrogen absorption. By flexibly adjusting the bottom blowing gas, it is possible to switch to other gases (such as nitrogen or carbon dioxide) when necessary to optimize the stirring effect and reduce nitrogen absorption. According to the different stages of the smelting process, such as the early, middle and late stages of decarburization, as well as the steelmaking process, flexible adjustment of the bottom blowing gas and flow rate can more specifically control the nitrogen content of the molten steel.

[0043] By precisely controlling the bottom blowing gas, the stirring and reaction conditions of the molten pool during the smelting process can be optimized, and the smelting efficiency can be improved. Increasing stirring during the decarburization stage can promote the carbon-oxygen reaction, while reducing stirring during the steelmaking stage can reduce the risk of nitrogen absorption.

[0044] In some embodiments, the method further comprises, after the LD converter refining is completed, performing refining treatment on a refining platform and taking samples to analyze the nitrogen content.

[0045] Sampling and analysis on the refining platform can obtain real-time information on the nitrogen content in molten steel. According to the analysis results, smelting personnel can adjust smelting parameters in time, such as adjusting the type and flow of bottom blowing gas, controlling the refining time, etc., to accurately control the nitrogen content in molten steel. Different steel grades have different requirements for nitrogen content. Sampling and analysis on the refining platform can ensure that the nitrogen content in molten steel meets the production requirements of specific steel grades, thereby improving the quality and performance of steel.

[0046] In some embodiments, during the refining process of the LF furnace, the argon blowing intensity during the heating process is less than 80Nm 3 / min, the dust removal valve opening is adjusted to 50% during the non-heating process.

[0047] Argon blowing and stirring can accelerate the material transfer between molten steel and slag, making the composition and temperature of the molten steel more uniform. This helps to reduce component segregation and temperature gradient in the molten steel and improve the quality of the molten steel.

[0048] Adjusting the dust removal valve opening can control the air extraction volume of the dust removal system, thereby improving the dust removal effect. The appropriate dust removal valve opening can ensure that the dust removal system can effectively absorb the smoke generated during the refining process and reduce the impact of smoke on the environment and operators. In the non-heating process, the dust removal valve opening can be adjusted to maintain a slightly positive pressure atmosphere in the furnace. Prevent air from entering the furnace, avoid secondary oxidation and nitrogen absorption of molten steel, and maintain the purity and stable performance of the molten steel.

[0049] In some embodiments, the carbon content of the steel tapped from the LD converter is ≤0.04%, the tapping temperature is 1620-1650°C, the tapping slag thickness is ≤80mm, and the clearance range is 300-600mm.

[0050] The target requirements for tapping molten steel at the end of converter blowing include controlling the content of various elements in the molten steel (such as carbon, silicon, manganese, phosphorus, sulfur, etc.) within the specified range. This helps ensure that the composition of the molten steel is accurate and meets the needs of subsequent smelting or processing.

[0051] Precise composition control can also improve the purity of steel and reduce the adverse effects of impurities on steel performance. The tapping temperature is one of the important control parameters at the end of converter blowing. The appropriate tapping temperature helps maintain the fluidity of the molten steel, which is convenient for subsequent casting and processing. At the same time, the appropriate tapping temperature can also reduce the temperature drop of the molten steel during the transmission and casting process, avoiding defects such as solidification or cracks in the molten steel.

[0052] In some embodiments, 1000±100 Kg of active lime is added into the LD converter during the steel tapping process.

[0053] Active lime can be added to adjust the basicity and fluidity of the slag, so that it can better cover the surface of the molten steel and reduce the secondary oxidation and nitrogen absorption of the molten steel. At the same time, good slag performance can also help improve the desulfurization and dephosphorization effects, and further improve the quality of molten steel. By improving the purity of molten steel and smelting efficiency, the addition of active lime can reduce production costs. In addition, since active lime can reduce the occurrence of lining erosion and splashing, it can also reduce the cost of equipment maintenance and repair.

[0054] In some embodiments, the specific implementation process of the control method for producing low-nitrogen high-strength steel by semi-steel is as follows: using "semi-steel" (molten steel after vanadium is extracted from molten iron in blast furnace of vanadium-titanium magnetite ore in Panzhihua area through vanadium extraction converter), process path: vanadium extraction from molten iron in blast furnace converter - molten iron pretreatment (desulfurization) - LD - small platform - LF - RH / VD - CC process path.

[0055] Technical requirements for the preparation of vanadium-extracting converter and desulfurization process, and requirements for the conditions of molten iron entering the furnace: [C]: ≥4.00%, [P]: ≤0.100%, [S]: ≤0.100%, T: ≥1280℃, molten iron volume: 210~240t, charging volume: 225±10t.

[0056] The target requirements for "semi-steel" after vanadium extraction are: [C]: 3.50±0.30%, T: 1350±20℃, semi-steel tank clearance: 300~500mm, semi-steel quantity: 225±15t.

[0057] Sulfur requirements after desulfurization (hot iron pretreatment): [S] requirement: ≤0.004%.

[0058] LD process preparation technical requirements: “Semi-steel” [C] entering the furnace: 3.50±0.30%, total charge: 225±10t.

[0059] Argon was blown from the bottom of the converter throughout the entire process of blowing. The full-time argon blowing mode was not selected, and the nitrogen content of the molten steel in the subsequent process was tracked.

[0060] Target requirements for tapping molten steel at the end of converter blowing: [C]: ≤0.04%, T: 1620~1650℃. Converter tapping: Slag thickness: Use slide plate to block slag, slag thickness ≤80mm; Clearance: 300~600mm; Slag washing during tapping: Add 1000±100Kg of active lime.

[0061] Refining treatment on the small refining platform after the converter. Temperature measurement and sampling are carried out after entering the station and blowing argon for ≥2 minutes. Nitrogen analysis samples are taken and sent on the small refining platform after the furnace for reference in the subsequent process. When leaving the station, the ladle is put into use and covered until the subsequent process enters the station.

[0062] During the heating process of LF refining, the argon blowing intensity is strictly controlled at 80Nm 3 / min or less, it is not allowed to open the ladle bypass to blow argon, and the dust removal valve opening should be adjusted to 50% during non-heating time.

[0063] A steel mill produced a low-nitrogen high-strength steel grade using the method according to the present invention. For example, in a certain batch of production, 9 furnaces of the same steel grade were continuously produced, and both the molten iron and semi-steel met the target requirements in the claims, the nitrogen content of the finished product was controlled to 29ppm (28-38ppm), the process control was stable, and the nitrogen content of the finished product was stable.

[0064] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0065] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0066] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A control method for producing low-nitrogen high-strength steel from semi-steel, characterized in that: The following steps are involved: The molten iron from the blast furnace is passed through a vanadium extraction converter to extract vanadium from the molten iron, and the molten steel after vanadium extraction is obtained as semi-steel; Adding a desulfurizing agent into the semi-steel and performing desulfurization pretreatment by composite injection; The desulfurized semi-steel enters the LD converter and LF furnace for refining in turn; The refined semi-steel is vacuum degassed and then cast into low-nitrogen high-strength steel.

2. The control method for producing low-nitrogen high-strength steel from semi-steel according to claim 1, characterized in that: In terms of mass percentage, the composition of blast furnace iron includes: C ≥ 4.00%, P ≤ 0.100%, S ≤ 0.100%, and the rest is iron.

3. The control method for producing low-nitrogen high-strength steel from semi-steel according to claim 1, characterized in that: The weight range of blast furnace molten iron entering the vanadium-extracting converter is 210-240t, and the loading range of the vanadium-extracting converter is 225±10t; The temperature range of the vanadium extraction converter is ≥1280℃.

4. The control method for producing low-nitrogen high-strength steel from semi-steel according to claim 1, characterized in that: In terms of mass percentage, the C range of the semi-steel is 3.50±0.30%, the temperature is 1350±20°C, the clearance range of the semi-steel tank is 300~500mm, and the semi-steel amount is 225±15t.

5. The control method for producing low-nitrogen high-strength steel from semi-steel according to claim 1, characterized in that: The range of S in the desulfurized semi-steel is ≤0.004%.

6. The control method for producing low-nitrogen high-strength steel from semi-steel according to claim 1, characterized in that: When the LD converter is blowing, argon is blown from the bottom of the furnace.

7. The control method for producing low-nitrogen high-strength steel from semi-steel according to claim 1, characterized in that: It also includes, after the LD converter refining is completed, refining treatment is carried out on a small refining platform, and sampling and analysis of nitrogen content are carried out.

8. The control method for producing low-nitrogen high-strength steel from semi-steel according to claim 1, characterized in that: During the refining process of the LF furnace, the argon blowing intensity during the heating process is less than 80Nm 3 / min, the dust removal valve opening is adjusted to 50% during the non-heating process.

9. The control method for producing low-nitrogen high-strength steel from semi-steel according to claim 1, characterized in that: The carbon content of the steel tapped from the LD converter is ≤0.04%, the tapping temperature is 1620-1650°C, the tapping slag thickness is ≤80mm, and the clearance range is 300-600mm.

10. The control method for producing low-nitrogen high-strength steel from semi-steel according to claim 1, characterized in that: 1000±100Kg of active lime is added to the LD converter during the steel-making process.

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