A method for refining low-sulfur low-carbon steel under low-oxygen high-carbon condition by pre-blowing argon, VD and LF

Abstract

The application relates to a method for refining low-sulfur low-carbon steel under low-oxygen high-carbon conditions through pre-argon blowing+VD+LF, which comprises the following steps: carrying out converter smelting on molten iron to obtain first molten steel; the converter smelting comprises bottom gas blowing control, end point control and temperature and composition control; carrying out pre-argon blowing on the first molten steel, wherein the pre-argon blowing comprises argon stirring and slag addition, to obtain pretreated molten steel; carrying out VD vacuum degassing on the pretreated molten steel, wherein the VD vacuum degassing comprises vacuum decarburization and vacuum desulfurization, to obtain VD-treated molten steel; carrying out LF refining on the VD-treated molten steel, wherein the LF refining comprises deoxidation, desulfurization and temperature control, to obtain LF-refined molten steel; and sequentially carrying out calcium treatment and soft blowing on the LF-refined molten steel, to obtain low-sulfur low-carbon steel. The method realizes stable and efficient production of low-carbon low-sulfur steel, and achieves the targets of reducing consumption, improving purity and prolonging the service life of equipment through low-oxygen high-carbon tapping and pre-argon blowing+VD+LF collaborative refining and dynamic control.

Description

Technical Field

[0001] This application relates to the field of iron and steel smelting technology, and in particular to a method for refining low-sulfur and low-carbon steel under low-oxygen and high-carbon conditions using argon pre-blowing + VD + LF. Background Technology

[0002] Low-sulfur, low-carbon steel produced by thin slab continuous casting and rolling production lines is a key basic material in fields such as home appliance manufacturing, hardware processing, and automotive structural parts. Low-sulfur, low-carbon steel has stringent requirements for compositional purity, mechanical properties, and surface quality. The production process of low-sulfur, low-carbon steel directly determines the reliability and market competitiveness of the end products.

[0003] However, the stable and efficient production of low-sulfur, low-carbon steel faces significant challenges. First, traditional converter processes employ a low-carbon tapping method, relying on supersaturated dissolved oxygen to control the final carbon content. This easily leads to over-oxidation of the molten steel and severe corrosion of the furnace lining, shortening the converter's lifespan. Simultaneously, frequent fluctuations in the final carbon content can cause quality incidents, and insufficient stirring in the molten pool under high iron consumption ratios results in an imbalance in the gas-slag-metal reaction. Second, existing refining technologies also have limitations: for example, while RH vacuum treatment can control carbon, it lacks deep desulfurization conditions and the precision of final oxygen control is insufficient, making it difficult to meet casting requirements; the refining process carries the risk of carbon increase, and insufficient weak stirring time leads to inadequate inclusion removal, resulting in high deoxidizer consumption and low steel purity. Overall, existing processes have deficiencies in deoxidation efficiency, temperature control, and compositional stability, hindering the stable production of low-sulfur, low-carbon steel. Summary of the Invention

[0004] This application provides a method for refining low-sulfur and low-carbon steel under low-oxygen and high-carbon conditions using argon pre-blowing + VD + LF, in order to solve the following technical problem: how to achieve efficient and stable production of low-sulfur and low-carbon steel under low-oxygen and high-carbon conditions.

[0005] In a first aspect, embodiments of this application provide a method for refining low-sulfur, low-carbon steel under low-oxygen, high-carbon conditions using argon pre-blowing + VD + LF, wherein the low-sulfur, low-carbon steel has a carbon content ≤0.035wt% and a sulfur content ≤0.0020wt%, and the method includes: Molten iron is smelted in a converter to obtain the first molten steel; the converter smelting includes bottom blowing gas control, endpoint control, and temperature and composition control. The first molten steel is pre-blown with argon, the pre-blowing of argon includes argon gas stirring and slag addition, to obtain pre-treated molten steel; The pretreated molten steel is subjected to VD vacuum degassing, which includes vacuum decarburization and vacuum desulfurization, to obtain VD-treated molten steel. The VD-treated molten steel is then subjected to LF refining, which includes deoxidation, desulfurization and temperature control, to obtain LF-refined molten steel. The LF-refined molten steel is then subjected to calcium treatment and soft blowing in sequence to obtain low-sulfur, low-carbon molten steel.

[0006] Optionally, the bottom blowing gas control includes: using nitrogen and argon as the bottom blowing gas, and automatically switching from nitrogen to argon when the blowing time reaches 70% of the total oxygen blowing volume.

[0007] Optionally, the endpoint control includes: the converter final slag basicity is 2.8~3.2, and the oxygen lance position is reduced to 1.5m~1.7m during the endpoint carbon removal stage.

[0008] Optionally, the temperature and composition control includes: an endpoint temperature of 1640℃~1660℃ and an endpoint carbon content of 0.08wt%~0.12wt%.

[0009] Optionally, the argon flow rate of the pre-blown argon is 150 L / min to 200 L / min, and the pressure of the pre-blown argon is 0.35 MPa to 0.40 MPa.

[0010] Optionally, the addition of slag includes: adding 5 kg / t to 6 kg / t of quicklime, and / or adding sintered ore for a processing time of 8 min to 12 min.

[0011] Optionally, the vacuum degree of the VD vacuum degassing is ≤67Pa, and the holding time under the vacuum degree is 5min~12min.

[0012] Optionally, the VD vacuum degassing includes argon blowing and stirring, wherein the argon flow rate of the argon blowing and stirring is 30L / min~100L / min.

[0013] Optionally, the carbon content of the molten steel after VD treatment is 0.005wt%~0.008wt%.

[0014] Optionally, the deoxidizer used in the LF refining process is at least one of aluminum granules, a high-efficiency deoxidizer, and aluminum blocks.

[0015] Optionally, the LF refining time is 35 min to 45 min, and the LF refining temperature is 1570℃ to 1580℃.

[0016] Optionally, the slag from the LF refining process is white slag, and the basicity of the white slag is 8-15.

[0017] Optionally, the sulfur content of the molten steel after LF refining is ≤0.0020wt%.

[0018] Optionally, the feed material for the calcium treatment is pure calcium-aluminum wire, and the feed length is 450m~500m for the first furnace and 300m~350m for subsequent furnaces.

[0019] Optionally, the calcium-aluminum ratio of the calcium-treated slag is 1.6 to 2.2.

[0020] Optionally, the argon blowing time of the soft blowing is ≥10 min, and the argon flow rate of the soft blowing is 30 L / min to 50 L / min.

[0021] Secondly, embodiments of this application provide a low-sulfur, low-carbon steel prepared by the method described in the first aspect, wherein the low-sulfur, low-carbon steel comprises the following chemical composition by mass fraction: C: 0.015wt%~0.035wt%, S: ≤0.0020wt%, O: ≤0.0015wt%, P: ≤0.015wt%, N: ≤0.0040wt%, H: ≤0.0002wt%, The balance consists of Fe and unavoidable impurities.

[0022] Optionally, the inclusion grades of the low-sulfur, low-carbon steel shall meet the following requirements: Class A ≤ 1.5, Class B ≤ 1.5, Class C ≤ 1.0, Class D ≤ 1.5, and Class DS ≤ 1.5.

[0023] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a method for refining low-sulfur, low-carbon steel under low-oxygen, high-carbon conditions using pre-blown argon + VD + LF. The converter smelting process establishes a low-oxygen, high-carbon endpoint control mode by strengthening bottom blowing and low lance position operation. This ensures the endpoint carbon content meets the requirements for high-carbon steel tapping while significantly suppressing steel over-oxidation. This process reduces refractory material erosion in the converter and provides a basis for controllable oxygen content in the molten steel for subsequent refining. The pre-blown argon treatment process follows the converter steel's post-furnace oxygenation and pre-slag washing operations. Argon agitation promotes the flotation of non-metallic inclusions and initially regulates oxygen activity, creating thermodynamic conditions for vacuum treatment. The VD vacuum treatment process performs deep decarburization, degassing, and desulfurization of the molten steel in a low-vacuum environment. Vacuum pressure difference drives the carbon-oxygen reaction and decomposes gaseous inclusions, achieving synergistic removal of carbon and sulfur. The LF refining process uses a white slag process to fine-tune the composition and precisely compensate the temperature of the VD-treated molten steel. High-alkalinity slag adsorption desulfurizes and blocks the carbonization path, ensuring the sulfur content is reduced to an ultra-low level. The calcium treatment process dynamically feeds calcium wire according to the state of the molten steel to modify the morphology of inclusions. Combined with a weak stirring operation, it promotes the aggregation and flotation of inclusions, ultimately obtaining high-purity molten steel.

[0024] In summary, by reducing oxidation damage at the source through converter smelting, achieving deep and synergistic removal of carbon and sulfur using a three-stage refining system of pre-blown argon + VD + LF, and preventing secondary oxidation risks through dynamic calcium treatment, and by implementing precise control of each process based on changes in the molten steel state, the process overcomes the technical barrier of the traditional incompatibility between high-carbon steel and low-carbon, low-sulfur finished products while ensuring converter life and metal yield. Ultimately, this leads to the establishment of a highly efficient and stable end-to-end production process for low-sulfur, low-carbon steel. Attached Figure Description

[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0027] Figure 1 The flowchart illustrates a method for refining low-sulfur, low-carbon steel under low-oxygen, high-carbon conditions using argon pre-blowing + VD + LF. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0029] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges between 1 and 6 (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6). Unless otherwise specified, the terms "including" and "contains" used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship. "And / or" indicates that multiple situations can exist individually or simultaneously. Expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0030] Figure 1 The flowchart illustrates a method for refining low-sulfur, low-carbon steel under low-oxygen, high-carbon conditions using argon pre-blowing + VD + LF.

[0031] Please see Figure 1 In a first aspect, embodiments of this application provide a method for refining low-sulfur, low-carbon steel under low-oxygen, high-carbon conditions using argon pre-blowing + VD + LF, wherein the low-sulfur, low-carbon steel has a carbon content ≤0.035wt% and a sulfur content ≤0.0020wt%, and the method includes: S1. Molten iron is smelted in a converter to obtain the first molten steel; the converter smelting includes bottom blowing gas control, endpoint control, and temperature and composition control. S2. Pre-blowing argon into the first molten steel, the pre-blowing argon including argon gas stirring and slag addition, to obtain pre-treated molten steel; S3. The pretreated molten steel is subjected to VD vacuum degassing, which includes vacuum decarburization and vacuum desulfurization, to obtain VD-treated molten steel. S4. The VD-treated molten steel is subjected to LF refining, which includes deoxidation, desulfurization and temperature control, to obtain LF-refined molten steel. S5. The molten steel after LF refining is subjected to calcium treatment and soft blowing in sequence to obtain low sulfur and low carbon steel.

[0032] VD Vacuum Degassing: A refining process that removes gases from molten steel through vacuum treatment. LF Refining: Ladle refining furnace, a refining device used for heating molten steel, precise control of composition, and removal of inclusions. Low-sulfur, low-carbon steel: C content ≤0.035wt%, S content ≤0.0020wt%, continuously cast and rolled steel produced by VD furnace vacuum deep decarburization and LF furnace carbon control processes.

[0033] In the above technical solution, a low-oxygen, high-carbon endpoint control mode is established through the converter smelting process to inhibit steel over-oxidation and reduce refractory material corrosion from the source; the pre-blowing argon treatment process implements preliminary deoxidation and inclusion removal of molten steel, creating thermodynamic conditions for vacuum degassing; the VD vacuum treatment process utilizes a low-pressure environment to drive deep decarburization, desulfurization, and gas removal, achieving synergistic purification of carbon and sulfur; the LF refining process uses white slag technology to precisely control composition and temperature, blocking the carbon increase path and achieving ultra-low sulfur control; the calcium treatment and soft blowing processes synergistically modify the morphology of inclusions and promote flotation, ultimately obtaining high-purity, low-carbon, and low-sulfur molten steel.

[0034] In some embodiments, the bottom blowing gas control includes: using nitrogen and argon as the bottom blowing gas, and automatically switching from nitrogen to argon when the blowing time reaches 70% of the total oxygen blowing volume.

[0035] Bottom-blown gas control blocks the path of nitrogen increase in molten steel by switching the composition of bottom-blown gas in the later stage of blowing, thus maintaining the purity of molten steel while ensuring sufficient stirring of the molten pool.

[0036] In some embodiments, the endpoint control includes: the converter final slag basicity is 2.8~3.2, and the oxygen lance position is reduced to 1.5m~1.7m during the endpoint carbon removal stage.

[0037] Endpoint control optimizes molten pool kinetics through specific lance position operation and, in conjunction with slag system regulation, optimizes metallurgical reaction balance to achieve precise and stable carbon-oxygen balance at the endpoint. For example, the converter final slag basicity can be 2.8, 2.9, 3.0, 3.1, 3.2, etc.; during the carbon removal stage at the endpoint, the oxygen lance position can be reduced to 1.5m, 1.6m, 1.7m, etc.

[0038] In some embodiments, the temperature and composition control includes: an endpoint temperature of 1640°C to 1660°C and an endpoint carbon content of 0.08 wt% to 0.12 wt%.

[0039] Temperature and composition control ensure that the carbon content of the molten steel is controlled within the high-temperature range, providing a foundation for subsequent refining processes with molten steel that meets compositional standards and is in a suitable thermal state. For example, the endpoint temperature can be 1640℃, 1650℃, 1660℃, etc.; the endpoint carbon content can be 0.08wt%, 0.09wt%, 0.10wt%, 0.11wt%, 0.12wt%, etc.

[0040] In some embodiments, the argon flow rate of the pre-blown argon is 150 L / min to 200 L / min, and the pressure of the pre-blown argon is 0.35 MPa to 0.40 MPa.

[0041] The argon flow rate during pre-blowing is between 150 L / min and 200 L / min. This specific flow rate range promotes efficient flotation and separation of non-metallic inclusions in the molten steel, achieving preliminary purification and optimizing the kinetics of subsequent deoxidation reactions. For example, the argon flow rate during pre-blowing can be 150 L / min, 160 L / min, 170 L / min, 180 L / min, 190 L / min, or 200 L / min. The pressure during pre-blowing is between 0.35 MPa and 0.40 MPa. This pressure range creates a stable and dispersed argon bubble flow, ensuring uniform mixing of the molten pool while preventing steel splashing, thus creating a low-oxygen environment for the vacuum treatment process. For example, the pressure during pre-blowing can be 0.35 MPa, 0.36 MPa, 0.37 MPa, 0.38 MPa, 0.39 MPa, or 0.40 MPa.

[0042] In some embodiments, the addition of slag includes: adding 5 kg / t to 6 kg / t of quicklime, and / or adding sintered ore for a processing time of 8 min to 12 min.

[0043] During the pre-argon blowing process, the amount of quicklime added is 5 kg / t to 6 kg / t. Controlling the quicklime dosage allows for the construction of a highly reactive slag layer through a specific proportion of calcium-based slag material. This effectively adsorbs phosphorus and sulfur impurities in the molten steel and optimizes the slag-metal interfacial tension. For example, the amount of quicklime added can be 5 kg / t, 6 kg / t, etc. The processing time for adding sintered ore is 8 min to 12 min. This processing time ensures the ore is fully melted and diffused in the molten steel, achieving slag composition modification and precise control of oxygen activity, creating a stable low-oxygen environment for subsequent vacuum treatment. For example, the processing time for adding sintered ore can be 8 min, 9 min, 10 min, 11 min, 12 min, etc.

[0044] In some embodiments, the vacuum degree of the VD vacuum degassing is ≤67Pa, and the time at the vacuum degree is 5min~12min.

[0045] Vacuum degassing (VD) operates at a vacuum level ≤67 Pa. This high-vacuum environment drives a vigorous carbon-oxygen reaction in the molten steel, achieving deep carbon removal and efficient decomposition of gas inclusions. The vacuum is maintained for 5-12 minutes to ensure the decarburization reaction approaches equilibrium, simultaneously promoting the flotation and separation of sulfide inclusions, ultimately yielding pure molten steel with ultra-low gas content. For example, the vacuum level for VD degassing can be 61 Pa, 63 Pa, 65 Pa, or 67 Pa; the holding time can be 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, 11 minutes, or 12 minutes.

[0046] In some embodiments, the VD vacuum degassing includes argon blowing and stirring, wherein the argon flow rate of the argon blowing and stirring is 30 L / min to 100 L / min. Vacuum degassing (VD) includes argon blowing and stirring, with the argon flow rate between 30 L / min and 100 L / min. This gas stirring at a specific intensity accelerates the renewal of the carbon-oxygen reaction interface in the molten steel, significantly improving decarburization kinetic efficiency and promoting the polymerization and flotation of non-metallic inclusions. For example, the argon flow rate for argon blowing and stirring can be 40 L / min, 60 L / min, 80 L / min, 100 L / min, etc.

[0047] In some embodiments, the carbon content of the molten steel after VD treatment is 0.005wt% to 0.008wt%.

[0048] After VD treatment, the carbon content of the molten steel is between 0.005 wt% and 0.008 wt%, ensuring that the steel reaches an ultra-low carbon content level. This provides a foundation for molten steel with compliant composition for subsequent refining processes, while simultaneously blocking sources of carbon increase risk. For example, the carbon content of the molten steel after VD treatment can be 0.005 wt%, 0.006 wt%, 0.007 wt%, 0.008 wt%, etc.

[0049] In some embodiments, the deoxidizer used in the LF refining is at least one of aluminum granules, a high-efficiency deoxidizer, and aluminum blocks.

[0050] LF Refining uses at least one of aluminum granules, high-efficiency deoxidizers, and aluminum blocks as its deoxidizers. By precisely matching the oxygen activity state of molten steel through a specific combination of deoxidizing media, it achieves synergistic optimization of efficient deoxidation and inclusion morphology control.

[0051] In some embodiments, the LF refining time is 35 min to 45 min, and the LF refining temperature is 1570℃ to 1580℃.

[0052] The LF refining time is between 35 and 45 minutes to ensure the slag-gold reaction reaches full thermodynamic equilibrium, guaranteeing deep removal of sulfides and homogenization of composition. For example, the LF refining time can be 35 minutes, 40 minutes, or 45 minutes. The LF refining temperature is between 1570℃ and 1580℃ to maintain a specific thermal state range, maximizing slag adsorption efficiency while mitigating the risk of carbon enrichment. For example, the LF refining temperature can be 1570℃, 1575℃, or 1580℃.

[0053] In some embodiments, the slag from the LF refining process is white slag, and the basicity of the white slag is 8-15.

[0054] The slag produced by LF refining is white slag with a basicity between 8 and 15. A highly reactive slag system creates a strongly adsorbent metallurgical environment, significantly enhancing the slag's ability to capture sulfides and inclusions. For example, the basicity of the white slag can be 8, 10, 12, or 14.

[0055] In some embodiments, the sulfur content of the molten steel after LF refining is ≤0.0020wt%.

[0056] After LF refining, the sulfur content of the molten steel is ≤0.0020wt%, ensuring the achievement of the goal of deep purification of molten steel and providing excellent corrosion resistance and mechanical stability for low-sulfur and low-carbon steel. For example, the sulfur content of the molten steel after LF refining can be 0.0010wt%, 0.0015wt%, 0.0020wt%, etc.

[0057] In some embodiments, the feed material for the calcium treatment is pure calcium-aluminum wire, and the feed length is 450m~500m for the first furnace and 300m~350m for subsequent furnaces.

[0058] The wire feed material for calcium treatment is pure calcium-aluminum wire. The composite coating structure significantly improves the effective utilization rate of calcium vapor, achieving efficient spheroidization modification of inclusions and inhibition of secondary oxidation of molten steel. The differentiated control of the wire feed length for calcium treatment dynamically adjusts the calcium treatment intensity based on the thermal state of each heat, ensuring stable calcium yield under different operating conditions, ultimately establishing a precise and reliable steel purity control mechanism. For example, the first heat after commissioning can be 450m, 460m, 470m, 480m, 490m, 500m, etc.; subsequent heats can be 300m, 310m, 320m, 330m, 340m, 350m, etc.

[0059] In some embodiments, the calcium-to-aluminum ratio of the calcium-treated slag is 1.6 to 2.2.

[0060] Calcium-aluminum ratio: The mass ratio of calcium oxide to aluminum oxide in refining slag, used to control desulfurization and inclusion morphology. The calcium-aluminum ratio of calcium-treated slag is between 1.6 and 2.2. By optimizing the slag phase composition through a specific ratio, inclusions in the steel can be effectively maintained in a low-melting-point liquid state, and these inclusions can be promoted to float and separate. For example, the calcium-aluminum ratio of calcium-treated slag can be 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, etc.

[0061] In some embodiments, the argon blowing time of the soft blowing is ≥10 min, and the argon flow rate of the soft blowing is 30 L / min to 50 L / min.

[0062] The argon blowing time for soft blowing is ≥10 min to provide sufficient gas stirring duration, ensuring the polymerization and removal of modified inclusions. For example, the argon blowing time for soft blowing can be 10 min, 12 min, 14 min, etc. The argon flow rate for soft blowing is between 30 L / min and 50 L / min to form a mild and stable molten pool flow field, achieving efficient separation of inclusions while avoiding secondary oxidation of the molten steel. For example, the argon flow rate for soft blowing can be 30 L / min, 40 L / min, 50 L / min, etc.

[0063] Secondly, embodiments of this application provide a low-sulfur, low-carbon steel prepared by the method described in the first aspect, wherein the low-sulfur, low-carbon steel comprises the following chemical composition by mass fraction: C: 0.015wt%~0.035wt%, S: ≤0.0020wt%, O: ≤0.0015wt%, P: ≤0.015wt%, N: ≤0.0040wt%, H: ≤0.0002wt%, The balance consists of Fe and unavoidable impurities.

[0064] Strictly controlling the carbon content to an extremely low range, and coordinating it with extremely low sulfur content, signifies the achievement of the core goals of low carbon and low sulfur. Simultaneously, suppressing the content of gaseous elements such as oxygen, nitrogen, and hydrogen to ultra-low levels directly reflects the high purity of the molten steel, effectively suppressing defects caused by inclusions and harmful gases. Furthermore, phosphorus content is strictly controlled. The combined effect of these component indicators ultimately ensures that low-sulfur, low-carbon steel possesses high purity and excellent overall performance. For example, the mass fraction of C can be 0.015%, 0.020%, 0.025%, 0.030%, 0.035%, etc.; the mass fraction of S can be 0.0010%, 0.0020%, etc.; the mass fraction of O can be 0.0005%, 0.0010%, 0.0015%, etc.; the mass fraction of P can be 0.005%, 0.010%, 0.015%, etc.; the mass fraction of N can be 0.0010%, 0.0020%, 0.0030%, 0.0040%, etc.; and the mass fraction of H can be 0.0001%, 0.0002%, etc.

[0065] In some embodiments, the inclusion grades of the low-sulfur, low-carbon steel meet the following requirements: Class A ≤ 1.5, Class B ≤ 1.5, Class C ≤ 1.0, Class D ≤ 1.5, and Class DS ≤ 1.5.

[0066] The inclusion levels of this low-sulfur, low-carbon steel are all controlled at extremely low levels, indicating that the internal cleanliness of the steel has reached a high standard, providing a fundamental guarantee for the excellent comprehensive performance and reliability of the low-sulfur, low-carbon steel.

[0067] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards / industry standards / the disclosure herein; if there are no corresponding national standards / industry standards / the disclosure herein, they are performed according to generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer.

[0068] Example 1 Molten iron is smelted in a converter to obtain the first molten steel. Converter smelting includes bottom-blowing gas control, endpoint control, and temperature and composition control. The bottom-blowing gas uses nitrogen and argon; when the blowing time reaches 70% of the total oxygen blowing volume, the nitrogen is automatically switched to argon. In endpoint control, the final slag basicity is 3.1. During the final carbon removal stage, the oxygen lance position is lowered to 1.7m. In temperature and composition control, the endpoint temperature is 1645℃, and the endpoint carbon content is 0.089 wt%. The first molten steel is pre-blown with argon, which includes argon gas stirring and slag addition to obtain pre-treated molten steel; wherein, the argon gas flow rate of the pre-blown argon is 180L / min, the pre-blown argon pressure is 0.4MPa; the amount of quicklime added in the slag addition is 5.6kg / t, and the treatment time for adding sintered ore is 8.6min. The pretreated molten steel was subjected to vacuum degassing (VD), which included vacuum decarburization and vacuum desulfurization, to obtain VD-treated molten steel. The vacuum degree of VD degassing was 20 Pa, and the holding time was 8 min. VD degassing also included argon blowing and stirring at an argon flow rate of 100 L / min. The carbon content of the VD-treated molten steel was 0.057 wt%. The VD-treated molten steel was then subjected to LF refining, which included deoxidation, desulfurization, and temperature control to obtain LF-refined molten steel. The deoxidizers used in LF refining were aluminum granules, a high-efficiency deoxidizer, and aluminum blocks. The LF refining time was 44 minutes, the LF refining temperature was 1576℃, the LF refining slag was white slag with a basicity of 9.7, and the sulfur content of the LF-refined molten steel was 0.002 wt%. After LF refining, the molten steel is subjected to calcium treatment. The wire feeding material for calcium treatment is pure calcium-aluminum wire, and the wire feeding length is 450m for the first heat after start-up and 350m for subsequent heats. The calcium-aluminum ratio of the slag after calcium treatment is 1.9. Then, the LF refining molten steel is subjected to soft blowing. The soft blowing argon blowing time is 10min and the soft blowing argon flow rate is 40L / min to obtain low-sulfur and low-carbon steel.

[0069] Example 2 Molten iron is smelted in a converter to obtain the first molten steel. Converter smelting includes bottom-blowing gas control, endpoint control, and temperature and composition control. The bottom-blowing gas uses nitrogen and argon; when the blowing time reaches 70% of the total oxygen blowing volume, the nitrogen is automatically switched to argon. In endpoint control, the final slag basicity is 2.9. During the final carbon removal stage, the oxygen lance position is lowered to 1.7m. In temperature and composition control, the endpoint temperature is 1642℃, and the endpoint carbon content is 0.081 wt%. The first molten steel is pre-blown with argon, which includes argon gas stirring and slag addition to obtain pretreated molten steel. The argon gas flow rate is 200 L / min and the argon pressure is 0.37 MPa. The amount of quicklime added during slag addition is 5.5 kg / t, and the treatment time for adding sintered ore is 9 min. The pretreated molten steel was subjected to vacuum degassing (VD), which included vacuum decarburization and vacuum desulfurization, to obtain VD-treated molten steel. The vacuum degree of VD degassing was 20 Pa, and the holding time was 8 min. VD degassing included argon blowing and stirring at an argon flow rate of 70 L / min. The carbon content of the VD-treated molten steel was 0.0068 wt%. The VD-treated molten steel was then subjected to LF refining, which included deoxidation, desulfurization, and temperature control to obtain LF-refined molten steel. The deoxidizers used in LF refining were aluminum granules, a high-efficiency deoxidizer, and aluminum blocks. The LF refining time was 42 minutes, the LF refining temperature was 1573℃, the LF refining slag was white slag with a basicity of 9.6, and the sulfur content of the LF-refined molten steel was 0.0019 wt%. After LF refining, the molten steel is subjected to calcium treatment. The wire feeding material for calcium treatment is pure calcium-aluminum wire, and the wire feeding length is 480m for the first heat after start-up and 348m for subsequent heats. The calcium-aluminum ratio of the slag after calcium treatment is 1.8. Then, the LF refining molten steel is subjected to soft blowing. The soft blowing argon blowing time is 11min and the soft blowing argon flow rate is 43L / min to obtain low-sulfur and low-carbon steel.

[0070] Example 3 Molten iron is smelted in a converter to obtain the first molten steel. Converter smelting includes bottom-blowing gas control, endpoint control, and temperature and composition control. The bottom-blowing gas uses nitrogen and argon; when the blowing time reaches 70% of the total oxygen blowing volume, the nitrogen is automatically switched to argon. In endpoint control, the final slag basicity is 3.0. During the final carbon removal stage, the oxygen lance position is lowered to 1.7m. In temperature and composition control, the endpoint temperature is 1648℃, and the endpoint carbon content is 0.082 wt%. The first molten steel is pre-blown with argon, which includes argon gas stirring and slag addition to obtain pretreated molten steel. The argon gas flow rate is 170 L / min and the argon pressure is 0.36 MPa. The amount of quicklime added during slag addition is 5.7 kg / t, and the treatment time for adding sintered ore is 8.5 min. The pretreated molten steel was subjected to vacuum degassing (VD), which included vacuum decarburization and vacuum desulfurization, to obtain VD-treated molten steel. The vacuum degree of VD degassing was 20 Pa, and the holding time was 9 min. VD degassing also included argon blowing and stirring at an argon flow rate of 90 L / min. The carbon content of the VD-treated molten steel was 0.0072 wt%. The VD-treated molten steel was then subjected to LF refining, which included deoxidation, desulfurization, and temperature control to obtain LF-refined molten steel. The deoxidizers used in LF refining were aluminum granules, a high-efficiency deoxidizer, and aluminum blocks. The LF refining time was 43 minutes, the LF refining temperature was 1579℃, the LF refining slag was white slag with a basicity of 9.8, and the sulfur content of the LF-refined molten steel was 0.0018 wt%. The molten steel after LF refining is subjected to calcium treatment. The wire feeding material for calcium treatment is pure calcium-aluminum wire, and the wire feeding length is 460m for the first heat after start-up and 341m for subsequent heats. The calcium-aluminum ratio of the slag after calcium treatment is 2.0. Then, the molten steel after LF refining is subjected to soft blowing. The argon blowing time for soft blowing is 11min, and the argon flow rate for soft blowing is 38L / min, to obtain low-sulfur and low-carbon steel.

[0071] Example 4 Molten iron is smelted in a converter to obtain the first molten steel. Converter smelting includes bottom-blowing gas control, endpoint control, and temperature and composition control. The bottom-blowing gas uses nitrogen and argon; when the blowing time reaches 70% of the total oxygen blowing volume, the nitrogen is automatically switched to argon. In endpoint control, the final slag basicity is 3.2. During the final carbon removal stage, the oxygen lance position is lowered to 1.69m. In temperature and composition control, the endpoint temperature is 1650℃, and the endpoint carbon content is 0.085 wt%. The first molten steel is pre-blown with argon, which includes argon gas stirring and slag addition to obtain pretreated molten steel; wherein, the argon gas flow rate of the pre-blown argon is 180L / min, the pre-blown argon pressure is 0.37MPa; the amount of quicklime added in the slag addition is 5.4kg / t, and the treatment time for adding sintered ore is 11.3min. The pretreated molten steel was subjected to vacuum degassing (VD), which included vacuum decarburization and vacuum desulfurization, resulting in VD-treated molten steel. The vacuum level of the VD degassing was 19 Pa, and the holding time was 8.6 min. The VD degassing process included argon blowing and stirring at an argon flow rate of 99 L / min. The carbon content of the VD-treated molten steel was 0.0055 wt%. The VD-treated molten steel was then subjected to LF refining, which included deoxidation, desulfurization, and temperature control to obtain LF-refined molten steel. The deoxidizers used in LF refining were aluminum granules, a high-efficiency deoxidizer, and aluminum blocks. The LF refining time was 41 minutes, the LF refining temperature was 1580℃, the LF refining slag was white slag with a basicity of 10, and the sulfur content of the LF-refined molten steel was 0.0020 wt%. The LF-refined molten steel is subjected to calcium treatment. The wire feeding material for the calcium treatment is pure calcium-aluminum wire, and the wire feeding length is 458m for the first heat after start-up and 335m for subsequent heats. The calcium-aluminum ratio of the slag after calcium treatment is 2.1. The LF-refined molten steel is then subjected to soft blowing. The soft blowing argon time is 10min and the soft blowing argon flow rate is 36L / min to obtain low-sulfur and low-carbon molten steel.

[0072] Example 5 Molten iron is smelted in a converter to obtain the first molten steel. Converter smelting includes bottom-blowing gas control, endpoint control, and temperature and composition control. The bottom-blowing gas uses nitrogen and argon; when the blowing time reaches 70% of the total oxygen blowing volume, the nitrogen is automatically switched to argon. In endpoint control, the final slag basicity is 2.8. During the final carbon removal stage, the oxygen lance position is lowered to 1.7m. In temperature and composition control, the endpoint temperature is 1648℃, and the endpoint carbon content is 0.094 wt%. The first molten steel is pre-blown with argon, which includes argon gas stirring and slag addition to obtain pretreated molten steel. The argon gas flow rate is 190 L / min and the argon pressure is 0.35 MPa. The amount of quicklime added during slag addition is 5.4 kg / t, and the treatment time for adding sintered ore is 10.5 min. The pretreated molten steel was subjected to vacuum degassing (VD), which included vacuum decarburization and vacuum desulfurization, to obtain VD-treated molten steel. The vacuum degree of VD degassing was 20 Pa, and the holding time was 7.4 min. VD degassing also included argon blowing and stirring at an argon flow rate of 96 L / min. The carbon content of the VD-treated molten steel was 0.0073 wt%. The VD-treated molten steel was then subjected to LF refining, which included deoxidation, desulfurization, and temperature control to obtain LF-refined molten steel. The deoxidizers used in LF refining were aluminum granules, a high-efficiency deoxidizer, and aluminum blocks. The LF refining time was 38 minutes, the LF refining temperature was 1572℃, and the LF refining slag was white slag with a basicity of 9.5. The sulfur content of the LF-refined molten steel was 0.0019 wt%. The LF-refined molten steel is subjected to calcium treatment. The wire feeding material for the calcium treatment is pure calcium-aluminum wire, and the wire feeding length is 483m for the first heat after start-up and 347m for subsequent heats. The calcium-aluminum ratio of the slag after calcium treatment is 1.7. The LF-refined molten steel is then subjected to soft blowing. The soft blowing argon time is 12min and the soft blowing argon flow rate is 45L / min to obtain low-sulfur and low-carbon molten steel.

[0073] Comparative Example 1 Molten iron is smelted in a converter to obtain the first molten steel. Converter smelting includes bottom-blowing gas control, endpoint control, and temperature and composition control. The bottom-blowing gas uses nitrogen and argon; when the blowing time reaches 70% of the total oxygen blowing volume, the nitrogen is automatically switched to argon. In endpoint control, the converter slag basicity is 2.3; during the endpoint carbon removal stage, the oxygen lance position is lowered to 2.0m. In temperature and composition control, the endpoint temperature is 1660℃, and the endpoint carbon content is 0.062wt%. The first molten steel is pre-blown with argon, which includes argon gas stirring and slag addition to obtain pre-treated molten steel; wherein, the argon gas flow rate of the pre-blown argon is 350L / min, the pre-blown argon pressure is 0.30MPa; the amount of quicklime added in the slag addition is 4.0kg / t, and the treatment time for adding sintered ore is 6min; The pretreated molten steel was subjected to vacuum degassing (VD), which included vacuum decarburization and vacuum desulfurization, resulting in VD-treated molten steel. The vacuum level of the VD degassing was 53 Pa, and the holding time was 6 min. The VD degassing also included argon blowing and stirring at an argon flow rate of 150 L / min. The carbon content of the VD-treated molten steel was 0.0078 wt%. The VD-treated molten steel was then subjected to LF refining, which included deoxidation, desulfurization, and temperature control to obtain LF-refined molten steel. The deoxidizers used in LF refining were aluminum granules, a high-efficiency deoxidizer, and aluminum blocks. The LF refining time was 45 minutes, the LF refining temperature was 1565℃, and the LF refining slag was white slag with a basicity of 7.1. The sulfur content of the LF-refined molten steel was 0.0054 wt%. After LF refining, the molten steel is subjected to calcium treatment. The wire feeding material for calcium treatment is pure calcium-aluminum wire, and the wire feeding length is 416m for the first heat after start-up and 3.1m for subsequent heats. The calcium-aluminum ratio of the slag after calcium treatment is 1.4. Then, the LF refining molten steel is subjected to soft blowing. The soft blowing argon blowing time is 5min and the soft blowing argon flow rate is 23L / min to obtain low-sulfur and low-carbon steel.

[0074] Comparative Example 2 Molten iron is smelted in a converter to obtain the first molten steel. Converter smelting includes bottom-blowing gas control, endpoint control, and temperature and composition control. The bottom-blowing gas uses nitrogen and argon; when the blowing time reaches 70% of the total oxygen blowing volume, the nitrogen is automatically switched to argon. In endpoint control, the final slag basicity is 3.3. During the final carbon removal stage, the oxygen lance position is lowered to 1.5m. In temperature and composition control, the endpoint temperature is 1623℃, and the endpoint carbon content is 0.061 wt%. The first molten steel is pre-blown with argon, which includes argon gas stirring and slag addition to obtain pretreated molten steel. The argon gas flow rate is 500 L / min and the argon pressure is 0.60 MPa. The amount of quicklime added during slag addition is 5.5 kg / t, and the treatment time for adding sintered ore is 6 min. The pretreated molten steel was subjected to vacuum degassing (VD), which included vacuum decarburization and vacuum desulfurization, to obtain VD-treated molten steel. The vacuum degree of VD degassing was 33 Pa, and the holding time was 15 min. VD degassing also included argon blowing and stirring at an argon flow rate of 250 L / min. The carbon content of the VD-treated molten steel was 0.0066 wt%. The VD-treated molten steel was then subjected to LF refining, which included deoxidation, desulfurization, and temperature control to obtain LF-refined molten steel. The deoxidizers used in LF refining were aluminum granules, a high-efficiency deoxidizer, and aluminum blocks. The LF refining time was 54 minutes, the LF refining temperature was 1590℃, and the LF refining slag was white slag with a basicity of 6.3. The sulfur content of the LF-refined molten steel was 0.0046 wt%. After LF refining, the molten steel is subjected to calcium treatment. The wire feeding material for calcium treatment is pure calcium-aluminum wire, and the wire feeding length is 700m for the first heat after start-up and 500m for subsequent heats. The calcium-aluminum ratio of the slag after calcium treatment is 2.5. Then, the molten steel after LF refining is subjected to soft blowing. The soft blowing argon blowing time is 19min and the soft blowing argon flow rate is 60L / min to obtain low-sulfur and low-carbon steel.

[0075] As shown in the above embodiments and comparative examples, the technical advancements of the present application's technical solution include: Examples 1-5 demonstrate that optimizing the bottom-blowing mode and endpoint control strategy significantly improves the stability of converter endpoint carbon content (≥95%), achieving precise carbon control under high-carbon steelmaking conditions. The low-oxygen, high-carbon endpoint control technology substantially reduces the carbon-oxygen product and deoxidizer consumption (deoxidizer consumption reduced by more than 10%), while simultaneously suppressing inclusion formation. The pre-blown argon + VD + LF multi-stage refining synergistic system effectively blocks the carbon increase path during refining, ensuring stable carbon content in the finished product (C≤0.035wt%). Deep desulfurization technology, combined with vacuum degassing and white slag refining, achieves stable control of ultra-low sulfur (S≤0.0020wt%). Metal recovery is significantly improved, reducing steel feedstock consumption (metal recovery increased by 0.5%~1.5%, steel feedstock consumption reduced by 0.72kg / t), effectively optimizing the production cost per ton of steel (cost reduced by 4.65 yuan per ton of steel). The purity of molten steel has been comprehensively improved, with the oxygen content at the endpoint and the oxygen content in the finished product both reaching ultra-low levels (O≤0.0015wt%), ultimately achieving high-quality, low-sulfur steel manufacturing at low cost.

[0076] As can be seen from Comparative Examples 1 and 2, when the process parameters deviate from the optimized range, such as the converter endpoint carbon being too low or too high, the refining slag basicity being inappropriate, the calcium treatment being insufficient or excessive, or the treatment time and gas flow rate being unreasonable, it will lead to a decrease in the purity of molten steel, unstable desulfurization effect, increased deoxidizer consumption, increased production costs, or excessive carbon and sulfur content in the finished product, thus making it impossible to stably achieve the manufacture of high-quality low-sulfur and low-carbon steel.

[0077] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this application.

Claims

1. A method for refining low-sulfur, low-carbon steel under low-oxygen, high-carbon conditions using argon pre-blowing + VD + LF, characterized in that, The low-sulfur, low-carbon steel has a carbon content ≤0.035wt% and a sulfur content ≤0.0020wt%, and the method includes: Molten iron is smelted in a converter to obtain the first molten steel; the converter smelting includes bottom blowing gas control, endpoint control, and temperature and composition control. The first molten steel is pre-blown with argon, the pre-blowing of argon includes argon gas stirring and slag addition, to obtain pre-treated molten steel; The pretreated molten steel is subjected to VD vacuum degassing, which includes vacuum decarburization and vacuum desulfurization, to obtain VD-treated molten steel. The VD-treated molten steel is then subjected to LF refining, which includes deoxidation, desulfurization and temperature control, to obtain LF-refined molten steel. The LF-refined molten steel is then subjected to calcium treatment and soft blowing in sequence to obtain low-sulfur, low-carbon molten steel.

2. The method according to claim 1, characterized in that, The bottom blowing gas control includes: using nitrogen and argon as the bottom blowing gas, and automatically switching from nitrogen to argon when the blowing time reaches 70% of the total oxygen blowing volume.

3. The method according to claim 1, characterized in that, The endpoint control includes: the basicity of the final slag in the converter is 2.8~3.2, and the oxygen lance position is reduced to 1.5m~1.7m during the final carbon removal stage.

4. The method according to claim 1, characterized in that, The temperature and composition control includes: an endpoint temperature of 1640℃~1660℃ and an endpoint carbon content of 0.08wt%~0.12wt%.

5. The method according to claim 1, characterized in that, The argon flow rate for the pre-blown argon is 150 L / min to 200 L / min, and the pressure of the pre-blown argon is 0.35 MPa to 0.40 MPa. And / or, The addition of slag includes: adding 5 kg / t to 6 kg / t of quicklime, and / or adding sintered ore for a processing time of 8 min to 12 min.

6. The method according to claim 1, characterized in that, The vacuum degree of the VD vacuum degassing is ≤67 Pa, and the holding time at the vacuum degree is 5 min to 12 min; and / or, The VD vacuum degassing includes argon blowing and stirring, wherein the argon flow rate for argon blowing and stirring is 30 L / min to 100 L / min; and / or, The carbon content of the molten steel after VD treatment is 0.005wt%~0.008wt%.

7. The method according to claim 1, characterized in that, The deoxidizer used in the LF refining process is at least one of aluminum granules, a high-efficiency deoxidizer, and aluminum blocks; and / or, The LF refining time is 35 min to 45 min, and the LF refining temperature is 1570℃ to 1580℃; and / or, The slag from the LF refining process is white slag, and the basicity of the white slag is 8-15; and / or, The sulfur content of the molten steel after LF refining is ≤0.0020wt%.

8. The method according to claim 1, characterized in that, The feed material for the calcium treatment is pure calcium-aluminum wire, and the feed length is 450m~500m for the first furnace and 300m~350m for subsequent furnaces; and / or, The calcium-aluminum ratio of the slag treated with calcium is 1.6~2.2; and / or, The argon blowing time for the soft blowing is ≥10 min, and the argon flow rate for the soft blowing is 30 L / min to 50 L / min.

9. A low-carbon, low-sulfur steel, characterized in that, The low-sulfur, low-carbon steel prepared by the method according to any one of claims 1 to 8 comprises the following chemical composition by mass fraction: C: 0.015wt%~0.035wt%, S: ≤0.0020wt%, O: ≤0.0015wt%, P: ≤0.015wt%, N: ≤0.0040wt%, H: ≤0.0002wt%, The balance consists of Fe and unavoidable impurities.

10. The low-sulfur, low-carbon steel according to claim 9, characterized in that, The inclusion grades of the low-sulfur, low-carbon steel shall meet the following requirements: Class A ≤ 1.5, Class B ≤ 1.5, Class C ≤ 1.0, Class D ≤ 1.5, and Class DS ≤ 1.5.

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