A method for producing gap-free atomic steel by using a full scrap + electric arc furnace process

Abstract

The application discloses a method for producing gapless atomic steel by adopting a full scrap steel+electric arc furnace process, and comprises scrap steel proportioning, electric arc furnace steelmaking, LF refining, RH refining and slab continuous casting. The short process technology realizes industrialized batch production of high-grade, low-carbon emission gapless atomic steel with C≤0.0025%, N≤0.005% and O≤0.004%. The finished product has good strength and forming performance, solves the technical problems of producing ultra-low-carbon steel and ultra-low-nitrogen steel by the electric arc furnace, fills the technical blank in the field, and greatly reduces the carbon emission in the production process of the gapless atomic steel compared with the conventional long-process smelting method of the blast furnace+converter, and has obvious environmental benefits.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel metallurgy technology, specifically relating to a method for producing interstitial steel using a full scrap steel + electric arc furnace process. Background Technology

[0002] Interstitial atom-free (IF) steel is a type of steel developed by controlling the interstitial atoms C, N, and impurity elements that seriously impair deep drawing performance in steel to the lowest possible level, and eliminating interstitial atoms in ferrite through alloying with Nb or Ti elements, thereby obtaining ultra-deep drawing performance. It is a new generation of deep drawing steel following the first generation of rimmed steel and the second generation of aluminum-killed steel, with excellent deep drawing performance, and is widely used as raw material for stamped parts such as automotive sheets and home appliance sheets.

[0003] Currently, the conventional long-process method of blast furnace + converter is mainly used to produce IF steel both domestically and internationally. The main processes include iron ore sintering, pelletizing, blast furnace ironmaking, and oxygen converter steelmaking. From iron ore to qualified continuous casting billets of IF steel, the production process is very long, involves many processes, has a large amount of carbon emissions, and is not environmentally friendly.

[0004] The steel industry faces immense pressure to transition to a low-carbon model, and effectively reducing carbon emissions during steel production has become a critical issue that urgently needs to be addressed by the industry and the nation as a whole. Compared to the blast furnace + converter long process, the all-scrap steel + electric arc furnace short process reduces energy consumption per ton of steel by approximately 50% and carbon emissions by approximately 70%. Therefore, developing the all-scrap steel + electric arc furnace short process steelmaking is one of the major trends for the future development of my country's steel industry.

[0005] However, compared to oxygen converter steelmaking, electric arc furnace steelmaking inevitably ionizes nitrogen in the air due to the use of an electric arc to heat scrap steel, leading to increased nitrogen content in the molten steel and making it difficult to produce ultra-low nitrogen steel, especially IF steel. Currently, no relevant technologies for producing IF steel using a full scrap steel + electric arc furnace process have been found domestically or internationally. Therefore, researching the full scrap steel + electric arc furnace steelmaking process and developing a method for producing IF steel using this process to reduce dependence on the blast furnace + converter process and lower carbon emissions has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] To address the technical problems existing in the prior art, the present invention provides a method for producing interstitial steel using a full scrap steel + electric arc furnace process, comprising the following steps:

[0007] (1) Scrap steel ratio

[0008] The amount of scrap steel added is controlled to ensure that the mass percentage of chemical composition in the molten steel after melting in the electric arc furnace meets the following requirements: P≤0.015%, S≤0.015%, Al≤0.08%, Cr≤0.05%, Ni≤0.05%, Mo≤0.03%, Cu≤0.05%, N≤0.010%, B≤0.0005%, Sn≤0.01%, Nb≤0.01%, V≤0.01%, Ti≤0.01%.

[0009] (2) Electric arc furnace steelmaking

[0010] The proportioned scrap steel is loaded into the electric arc furnace, and the furnace is heated by power. During the tapping process, slag blocking is performed to control the slag thickness to ≤40mm. The composition of the tapped steel from the electric arc furnace is controlled as follows:

[0011] C To Mn P S Al Cr ≤0.04 ≤0.04 ≤0.10 ≤0.013 ≤0.015 ≤0.07 ≤0.05 In Know Cu N B Sn ≤0.05 ≤0.03 ≤0.05 ≤0.010 ≤0.0005 ≤0.010

[0012] (3) LF Refining

[0013] When the ladle enters the LF station, it is powered on and heated. During the heating process, a slag-forming agent is added to form slag. Aluminum wire or aluminum particles are added to the molten steel for pre-deoxidation. The amount of aluminum wire or aluminum particles added must ensure that the O content in the molten steel is 600-700 ppm. The LF refining process uses bottom-blown argon to stir the molten steel. Before leaving the LF station, an aluminum-containing pre-melted steel slag modifier is evenly added to the slag surface on the top of the ladle. After adding, it is weakly stirred with bottom-blown argon for 1-2 minutes before leaving the station.

[0014] (4) RH refining

[0015] The ladle enters the RH station, where it is evacuated and undergoes molten steel circulation and decarburization. After decarburization, Al alloy, electrolytic manganese, ferrotitanium, and ferroniobium alloys are added to the molten steel for alloying. After alloying, circulation continues for ≥20 minutes. After circulation, a vacuum breaking operation is performed. The molten steel is then blown with argon gas and weakly stirred before exiting the station. The composition of the RH-exit steel is controlled as follows:

[0016] C To Mn P S Al Of Cr ≤0.0015 ≤0.03 0.10～0.20 ≤0.013 ≤0.015 0.04～0.06 0.04～0.08 ≤0.05 In Know Cu N B Sn Nb V ≤0.05 ≤0.05 ≤0.05 ≤0.005 ≤0.0005 ≤0.01 ≤0.01 ≤0.01

[0017] (5) Slab continuous casting

[0018] The tundish of continuous casting uses an ultra-low carbon covering agent with a total carbon content of ≤1.5%, and the mold flux uses an ultra-low carbon flux with a total carbon content of ≤2.0%. Protective casting is implemented during the opening process of the continuous casting ladle. The superheat of the tundish is controlled at 20-30℃, and the continuous casting speed is controlled at 1.10-1.15m / min.

[0019] Preferably, in the slab continuous casting process, the first heat in the tundish uses other ultra-low carbon steel with C ≤ 0.0050% for casting, and the second and subsequent heats in the tundish use molten steel obtained through the scrap steel proportioning, electric arc furnace steelmaking, LF refining, and RH refining processes for casting.

[0020] As a specific implementation method, in the above-mentioned method for producing gapless atomic steel using the all-scrap steel + electric arc furnace process, in the scrap steel proportioning process, scrap steel accounts for ≥95% of all smelting raw materials. This scrap steel includes ≥45% by weight of cold-rolled steel briquettes, and / or ≥30% by weight of premium-grade crushed material, and / or ≥10% by weight of pure iron scrap. The scrap steel proportioning should meet the following requirements for characteristic elements in the molten steel after electric arc furnace smelting: P≤0.015%, S≤0.015%, Al≤0.08%, Cr≤0.05%, Ni≤0.05%, Mo≤0.03%, Cu≤0.05%, N≤0.010%, B≤0.0005%, Sn≤0.01%, Nb≤0.01%, V≤0.01%, Ti≤0.01%.

[0021] Furthermore, in the above-mentioned method of producing gapless atomic steel using the whole scrap steel + electric arc furnace process, in the electric arc furnace steelmaking process, lime, fluorite, and red mud balls are added during the smelting process to form slag. Coke, ferrosilicon, and silicon carbide slag are added during the smelting process. After the molten steel is heated by power and melted, power is supplied at a low level and oxygen is blown into the molten pool to stir it. Lime and fluorite are added again to increase the slag basicity. Oxygen is blown to dephosphorize. After the slag is discharged, the steel is tapped.

[0022] Furthermore, in the above-mentioned method of producing interstitial steel using the whole scrap steel + electric arc furnace process, during the LF refining process, 800-1000 kg of lime and 200-400 kg of fluorite are added during the heating process to adjust the slag condition, 150-300 m of aluminum wire is added for pre-deoxidation, the total flow rate of bottom-blown argon is 100-500 NL / min, and the temperature of the molten steel at the LF outlet is controlled at 1660-1670℃.

[0023] Furthermore, in the above method for producing interstitial steel using all scrap steel + electric arc furnace process, in the RH refining process:

[0024] When the ladle enters the RH station, vacuuming and molten steel circulation begin. When the vacuum level reaches ≤150Pa, timing begins. Decarburization is performed after 6-10 minutes of vacuum circulation.

[0025] After decarburization, the steel liquid composition is sampled and analyzed. When the mass percentage of C in the steel liquid is ≤0.0015%, a high-precision oxygen analyzer is used to determine the O content in the steel liquid. Based on the O content, the Al content required for deoxidation and alloying is calculated, and the required amount of Al alloy is added to the steel liquid. Then, the mixture is circulated for 3 to 6 minutes.

[0026] Based on the target composition of the interstitial steel, electrolytic manganese, ferrotitanium, and ferroniobium alloys were added for alloying. After cycling for 3 to 4 minutes, the composition of the molten steel was sampled and analyzed. The steel composition was then finely adjusted based on the target composition of the interstitial steel.

[0027] After alloying is completed, when the vacuum degree reaches ≤150Pa, continue to circulate for ≥20 minutes. After the circulation is completed, perform the vacuum breaking operation. During the vacuum breaking operation, when the vacuum tank leaves the molten steel surface, quickly add an appropriate amount of aluminum-containing steel slag modifier to the molten steel surface.

[0028] The molten steel temperature at the RH station outlet is controlled at 1595~1610℃.

[0029] Furthermore, in the above method for producing interstitial steel using all scrap steel + electric arc furnace process, in the slab continuous casting process:

[0030] Before continuous casting, the tundish and nozzle are baked online for 2 hours, with a maximum of 4 hours. The calming time of the ladle fork arm is controlled to be ≥5 minutes.

[0031] The liquid level fluctuation in the crystallizer is required to be ±5mm. The argon flow rate of the stopper rod is controlled to be ≤10NL / min. Dynamic light pressure and roller electromagnetic stirrer are used to control the central looseness and central segregation. The dynamic light pressure process parameters are: applying pressure in the two-phase region with a solid phase ratio of 50-95% and a total pressure reduction of 3.2mm. The roller electromagnetic stirrer process parameters are: 300A, 6Hz, no reversing.

[0032] Furthermore, the present invention also provides an interstitial steel, wherein the chemical composition of the interstitial steel by mass percentage is: C≤0.0025%, Si≤0.03%, Mn≤0.25%, P≤0.015%, S≤0.015%, Al≤0.08%, Ti: 0.03~0.10%, Cr≤0.05%, Ni≤0.05%, Mo≤0.03%, Cu≤0.05%, N≤0.005%, B≤0.0005%, Sn≤0.01%, Nb≤0.01%, V≤0.01%, with the remainder being Fe and unavoidable impurities.

[0033] The method for producing interstitial steel using a full scrap steel + electric arc furnace process of the present invention has the following advantages and beneficial effects: it achieves mass production of high-grade, low-carbon emission IF steel with C≤0.0025%, N≤0.005%, and O≤0.004% using a short-process technology. The finished product has good strength and formability, solves the technical problem of producing ultra-low carbon steel and ultra-low nitrogen steel in electric arc furnace, and fills the technical gap in this field. Compared with the conventional long-process smelting method of blast furnace + converter, the method of the present invention significantly reduces carbon emissions in the IF steel production process and has obvious environmental benefits. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0035] This invention aims to develop an industrial smelting method for producing high-grade, low-carbon emission interstitial steel using a full scrap steel + electric arc furnace process. This method enables the mass production of high-grade IF steel with C≤0.0025%, N≤0.005%, and O≤0.004%, solving the technical challenges of producing ultra-low carbon steel and ultra-low nitrogen steel using electric arc furnaces, and significantly reducing carbon emissions during the IF steel production process.

[0036] In the method of producing gapless atomic steel using the all-scrap steel + electric arc furnace process of the present invention, "all-scrap steel" refers to scrap steel accounting for ≥95% of all smelting raw materials. Scrap steel includes, but is not limited to, cold-rolled plate briquettes, premium crushed material, pure iron scrap steel, and silicon steel scrap steel.

[0037] Specifically, the method of producing gapless atomic steel using the all-scrap steel + electric arc furnace process of the present invention includes the following steps:

[0038] (1) Scrap steel ratio

[0039] The amount of scrap steel added is controlled to ensure that the mass percentage of the chemical composition in the molten steel after melting in the electric arc furnace meets the following requirements: P≤0.015%, S≤0.015%, Al≤0.08%, Cr≤0.05%, Ni≤0.05%, Mo≤0.03%, Cu≤0.05%, N≤0.010%, B≤0.0005%, Sn≤0.01%, Nb≤0.01%, V≤0.01%, Ti≤0.01%.

[0040] (2) Electric arc furnace steelmaking

[0041] The properly proportioned scrap steel is loaded into the electric arc furnace, the electrodes are lowered, and electricity is applied to raise the temperature. During the electric arc furnace steelmaking process, appropriate amounts of auxiliary materials such as limestone and coke can be added, and a suitable amount of oxygen is introduced to assist in heating and melting. Slag-blocking operations are performed during tapping to minimize slag accumulation and control the slag thickness to ≤40mm. Deoxidation and alloying operations are not performed during tapping to avoid phosphorus reversion.

[0042] The composition of steel produced from electric arc furnaces is controlled as shown in Table 1 below:

[0043] Table 1. Composition of steel tapped from electric arc furnace (mass percentage, the remainder being Fe and unavoidable impurities).

[0044] C To Mn P S Al Cr ≤0.04 ≤0.04 ≤0.10 ≤0.013 ≤0.015 ≤0.07 ≤0.05 In Know Cu N B Sn ≤0.05 ≤0.03 ≤0.05 ≤0.010 ≤0.0005 ≤0.010

[0045] (3) LF Refining

[0046] The ladle is heated at the LF station. Based on the molten steel temperature, electrodes are used to raise the temperature, and appropriate amounts of lime, fluorite, and other slag-forming agents are added during this process. A suitable amount of aluminum wire or aluminum granules can be added to the molten steel for pre-deoxidation, but the oxygen content must be maintained at 600-700 ppm for RH decarburization. Bottom-blown argon is used to agitate the molten steel throughout the LF refining process. Before leaving the LF station, an appropriate amount of aluminum-containing pre-melted steel slag modifier is evenly added to the slag surface on top of the ladle. After addition, it is gently stirred with bottom-blown argon for 1-2 minutes before leaving the station. The molten steel temperature at the LF station is 1660-1670℃. The molten steel in the LF process only undergoes heating and slag-forming operations; desulfurization and alloying are not performed.

[0047] (4) RH refining

[0048] The ladle is brought into the RH station for temperature measurement, vacuuming, and molten steel circulation and decarburization. After decarburization, according to the target composition of IF steel, Al alloy, as well as electrolytic manganese, ferrotitanium, ferroniobium, and other alloys are added to the molten steel for alloying. After alloying, circulation continues for ≥20 minutes. After circulation, a vacuum breaking operation is performed. The molten steel outlet temperature at the RH station is 1595–1610℃.

[0049] In the RH refining process, argon is used as the vacuum lifting gas, and the flow rate is 90-100% of the limit flow rate. The composition of the RH-finished steel is controlled as shown in Table 2 below:

[0050] Table 2. RH steel composition (mass percentage, the remainder being Fe and unavoidable impurities)

[0051] C To Mn P S Al Of Cr ≤0.0015 ≤0.03 0.10～0.20 ≤0.013 ≤0.015 0.04～0.06 0.04～0.08 ≤0.05 In Know Cu N B Sn Nb V ≤0.05 ≤0.03 ≤0.05 ≤0.005 ≤0.0005 ≤0.01 ≤0.01 ≤0.01

[0052] (5) Slab continuous casting

[0053] The tundish uses an ultra-low carbon covering agent with a total carbon content ≤1.5%, and the mold flux uses an ultra-low carbon mold flux with a total carbon content ≤2.0%. Protective casting is implemented during the initial pouring process of the continuous casting ladle, and the increase in nitrogen (N) and carbon (C) is strictly controlled. The superheat of the tundish is maintained at 20–30°C. The casting speed of the twin-strand continuous casting machine is controlled at 1.10–1.15 m / min.

[0054] Specifically, during continuous casting, molten steel comes into direct contact with various carbon-containing raw and auxiliary materials in the tundish and crystallizer, such as tundish covering agents, tundish coating materials, and crystallizer protective slag. The carbon (C) in these materials inevitably transfers to the molten steel, leading to an increase in carbon content. Typically, the first heat in the tundish during continuous casting shows a significant increase in carbon, usually 7–12 ppm. From the second heat onwards, the increase decreases noticeably. This 7–12 ppm increase in carbon during the first heat can very likely result in the final molten steel having a carbon content exceeding 0.0025%. Therefore, to ensure the production of high-grade interstitial steel and minimize or eliminate carbon increase during continuous casting, the first heat in the tundish uses other ultra-low carbon steel with a carbon content ≤ 0.0050%. The second heat and subsequent heats use molten steel produced through the aforementioned scrap steel blending, electric arc furnace steelmaking, LF refining, and RH refining processes.

[0055] In the slab continuous casting process, when the remaining weight of molten steel in the ladle is 40-60% of the total weight of molten steel in the ladle, the chemical composition of the produced IF steel can be obtained by sampling from the tundish, as shown in Table 3 below:

[0056] Table 3 Chemical composition of IF steel (mass percentage, the remainder being Fe and unavoidable impurities)

[0057] C To Mn P S Al Of Cr ≤0.0025 ≤0.03 ≤0.25 ≤0.015 ≤0.015 ≤0.08 0.03～0.10 ≤0.05 In Know Cu N B Sn Nb V ≤0.05 ≤0.03 ≤0.05 ≤0.005 ≤0.0005 ≤0.01 ≤0.01 ≤0.01

[0058] The following describes the method for producing gapless atomic steel using the all-scrap steel + electric arc furnace process according to the present invention, with reference to Examples 1 and 2. The method for producing gapless atomic steel using the all-scrap steel + electric arc furnace process in Examples 1 and 2 of the present invention is carried out according to the aforementioned scrap steel proportioning, electric arc furnace steelmaking, LF refining, RH refining, slab continuous casting and other processes. The specific implementation process is as follows:

[0059] In the scrap steel proportioning process, the scrap steel proportions of Example 1 and Example 2 are shown in Table 4 below:

[0060] Table 4. Scrap steel composition of Examples 1 and 2

[0061]

[0062] In the electric arc furnace steelmaking process, pre-mixed scrap steel is loaded into the furnace using a basket. The electrodes are lowered, and electricity is applied to raise the temperature. During smelting, auxiliary materials such as lime, fluorite, and red mud balls are added to form slag. Coke, ferrosilicon, and silicon carbide slag are also added. After the molten steel is heated and melted, electricity is applied at a low setting, and a suitable amount of oxygen is blown in to stir the molten pool, ensuring uniform temperature and preventing steel adhesion within the furnace. A suitable amount of lime and fluorite is added again to increase the slag basicity, and oxygen is blown in for dephosphorization. After slag discharge, the steel is tapped. No deoxidation or alloying operations are performed during tapping to avoid phosphorus reversion. Slag blocking is performed during tapping to minimize slag runoff, controlling the slag thickness to ≤40mm. If slag blocking fails and a large amount of slag runoff occurs, slag removal can be performed during tapping, ensuring the slag thickness after removal is ≤40mm.

[0063] The composition of steel produced from electric arc furnaces is controlled as shown in Table 5 below:

[0064] Table 5. Composition of steel tapped from electric arc furnace (mass percentage, the remainder being Fe and unavoidable impurities).

[0065]

[0066] In the LF refining process, the ladle is brought into the LF station for temperature measurement. Based on the temperature of the molten steel, electrodes are used to supply electricity to raise the temperature. During the heating process, 800-1000 kg of lime and 200-400 kg of fluorite are added to adjust the slag condition. 150-300 m of aluminum wire is added for pre-deoxidation to ensure that 600-700 ppm of oxygen remains in the molten steel for subsequent RH decarburization. The LF refining process uses bottom-blown argon to stir the molten steel, with a total argon flow rate of 100-500 NL / min. Before leaving the LF station, an appropriate amount of aluminum-containing pre-melted steel slag modifier is evenly added to the slag surface on the top of the ladle. After the addition, the ladle is gently stirred with bottom-blown argon for 1-2 minutes before leaving the station. The temperature of the molten steel leaving the LF station is 1660-1670℃.

[0067] In the RH refining process, the ladle is brought into the RH station for temperature measurement, vacuuming begins, and molten steel is circulated. When the vacuum level reaches ≤150Pa, timing begins, and decarburization is performed after 6-10 minutes of vacuum circulation. After decarburization, a sample of the molten steel is taken for analysis. When the mass percentage of carbon in the molten steel is ≤0.0015%, a high-precision oxygen analyzer is used to determine the oxygen content in the molten steel. Based on the oxygen content, the required Al content for deoxidation and alloying is calculated, and the necessary amount of Al alloy is added to the molten steel. Circulation continues for 3-6 minutes. Based on the target composition of IF steel, appropriate amounts of electrolytic manganese, ferrotitanium, ferroniobium, etc., are added for alloying. After 3-4 minutes of circulation, a sample of the molten steel is taken for analysis, and the steel composition is fine-tuned based on the target composition of IF steel. After alloying is completed, when the vacuum level reaches ≤150Pa, circulation continues for ≥20 minutes. After the cycle is completed, a vacuum breaking operation is performed. During the vacuum breaking operation, as the vacuum ladle leaves the molten steel surface, an appropriate amount of aluminum-containing steel slag modifier is quickly added to the molten steel surface to improve the oxidizability of the steel slag in direct contact with the molten steel and reduce the TFe content in the slag. The molten steel outlet temperature at RH is 1595–1610℃.

[0068] The RH-treated steel composition is controlled as shown in Table 6 below:

[0069] Table 6. RH steel composition (mass percentage, the remainder being Fe and unavoidable impurities)

[0070]

[0071] In the slab continuous casting process, the tundish and nozzles are preheated online for 2 hours, with a maximum of 4 hours. The ladle fork arm is allowed to settle for at least 5 minutes. An ultra-low carbon covering agent with a total carbon content ≤1.5% is used in the tundish, and an ultra-low carbon protective slag with a total carbon content ≤2.0% is selected for the crystallizer. Protective casting is implemented during the ladle opening process, strictly controlling nitrogen and carbon increases. The tundish superheat is controlled at 20–30°C. The continuous casting speed of the twin-strand continuous casting machine is [not specified]. The flow rate is controlled at 1.10–1.15 m / min, the liquid level fluctuation in the crystallizer is required to be ±5 mm, and the argon flow rate of the stopper rod is ≤10 NL / min to reduce the disturbance of the liquid level in the crystallizer by argon. Dynamic light pressure and roller electromagnetic stirrer are used to control the central looseness and central segregation. The dynamic light pressure process parameters are: applying pressure in the two-phase region with a solid phase content of 50–95% and a total pressure reduction of 3.2 mm. The roller electromagnetic stirrer process parameters are: 300 A, 6 Hz, no reversing.

[0072] In addition, during slab continuous casting, the first heat in the tundish uses other ultra-low carbon steel with C ≤ 0.0050% for casting, while the second heat and subsequent heats in the tundish use molten steel obtained through the above-mentioned scrap steel proportioning, electric arc furnace steelmaking, LF refining, and RH refining processes for casting.

[0073] When the remaining molten steel in the ladle is 90-120 tons, a smelting analysis sample is taken from the tundish. The chemical composition of the produced IF steel can be obtained, as shown in Table 7 below:

[0074] Table 7 Chemical composition of IF steel (mass percentage, the remainder being Fe and unavoidable impurities)

[0075]

[0076] In summary, this invention provides an industrialized smelting method for producing high-grade, low-carbon emission interstitial steel using an all-scrap steel + electric arc furnace process. The method mainly includes a scrap steel proportioning process, an electric arc furnace steelmaking process, an LF refining process, an RH refining process, and a slab continuous casting process. This short-process technology enables the mass production of high-grade IF steel with C≤0.0025%, N≤0.005%, and O≤0.004%. The finished product exhibits good strength and formability, solving the technical challenges of producing ultra-low carbon steel and ultra-low nitrogen steel using an electric arc furnace. This fills a technological gap in the field. Compared to the conventional long-process smelting method using a blast furnace + converter, this invention significantly reduces carbon emissions during IF steel production, demonstrating significant environmental benefits.

[0077] It should be noted that, in this document, the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device.

[0078] It should also be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the present invention.

Claims

1. A method for producing interstitial steel using a full scrap steel + electric arc furnace process, characterized in that, The method includes the following steps: (1) Scrap steel ratio The amount of scrap steel added is controlled to ensure that the mass percentage of the chemical composition in the molten steel after melting in the electric arc furnace meets the following requirements: P≤0.015%, S≤0.015%, Al≤0.08%, Cr≤0.05%, Ni≤0.05%, Mo≤0.03%, Cu≤0.05%, N≤0.010%, B≤0.0005%, Sn≤0.01%, Nb≤0.01%, V≤0.01%, Ti≤0.01%; (2) Electric arc furnace steelmaking The proportioned scrap steel is loaded into the electric arc furnace, and the furnace is heated by power. During the tapping process, slag blocking is performed to control the slag thickness to ≤40mm. The composition of the tapped steel from the electric arc furnace is controlled as follows: ； (3) LF Refining When the ladle enters the LF station, it is powered on and heated. During the heating process, a slag-forming agent is added to form slag. Aluminum wire or aluminum particles are added to the molten steel for pre-deoxidation. The amount of aluminum wire or aluminum particles added must ensure that the O content in the molten steel is 600~700ppm. The LF refining process uses bottom-blown argon to stir the molten steel. Before leaving the LF station, an aluminum-containing pre-melted steel slag modifier is evenly added to the slag surface on the top of the ladle. After adding, it is weakly stirred with bottom-blown argon for 1~2 minutes before leaving the station. (4) RH refining The ladle enters the RH station, where it is evacuated and undergoes molten steel circulation and decarburization. After decarburization, Al alloy, electrolytic manganese, ferrotitanium, and ferroniobium alloys are added to the molten steel for alloying. After alloying, the steel continues to circulate under deep vacuum for ≥20 minutes. After circulation, a vacuum breaking operation is performed. The molten steel is then blown with argon gas and gently stirred before exiting the station. The composition of the RH-exported steel is controlled as follows: ； (5) Slab continuous casting The continuous casting tundish uses an ultra-low carbon covering agent with a total carbon content of ≤1.5%, and the mold flux uses an ultra-low carbon flux with a total carbon content of ≤2.0%. Protective casting is implemented during the opening process of the continuous casting ladle. The superheat of the continuous casting tundish is controlled at 20~30℃, and the continuous casting steel pulling speed is controlled at 1.10~1.15m / min.

2. The method for producing interstitial steel using a full scrap steel + electric arc furnace process according to claim 1, characterized in that, In the scrap steel blending process, scrap steel accounts for ≥95% of all smelting raw materials.

3. The method for producing interstitial steel using a full scrap steel + electric arc furnace process according to claim 1, characterized in that, In the electric arc furnace steelmaking process, lime, fluorite, and red mud balls are added during the smelting process to form slag. Coke, ferrosilicon, and silicon carbide slag are added during the smelting process. After the molten steel is heated by power and melted, power is supplied at a low level and oxygen is blown in to stir the molten pool. Lime and fluorite are added again to increase the slag basicity. Oxygen is blown to dephosphorize. After the slag is discharged, the steel is tapped.

4. The method for producing interstitial steel using a full scrap steel + electric arc furnace process according to claim 1, characterized in that, In the LF refining process, 800-1000 kg of lime and 200-400 kg of fluorite are added during the heating process to adjust the slag condition. 150-300 m of aluminum wire is added for pre-deoxidation. The total flow rate of bottom-blown argon is 100-500 NL / min. The temperature of the molten steel at the LF station outlet is controlled at 1660-1670℃.

5. The method for producing interstitial steel using a full scrap steel + electric arc furnace process according to claim 1, characterized in that, In the RH refining process: When the ladle enters the RH station, vacuuming and molten steel circulation begin. When the vacuum level reaches ≤150Pa, timing begins. Decarburization is performed after 6-10 minutes of vacuum circulation. After decarburization, the steel liquid composition is sampled and analyzed. When the mass percentage of C in the steel liquid is ≤0.0015%, a high-precision oxygen analyzer is used to determine the O content in the steel liquid. Based on the O content, the Al content required for deoxidation and alloying is calculated, and the required amount of Al alloy is added to the steel liquid. Then, the mixture is circulated for 3 to 6 minutes. Based on the target composition of the interstitial steel, electrolytic manganese, ferrotitanium, and ferroniobium alloys were added for alloying. After cycling for 3-4 minutes, the composition of the molten steel was sampled and analyzed. The steel composition was then finely adjusted based on the target composition of the interstitial steel. After alloying is completed, when the vacuum degree reaches ≤150Pa, continue to circulate for ≥20 minutes. After the circulation is completed, perform the vacuum breaking operation. During the vacuum breaking operation, when the vacuum tank leaves the molten steel surface, quickly add an appropriate amount of aluminum-containing steel slag modifier to the molten steel surface. The molten steel temperature at the RH station outlet is controlled at 1595~1610℃.

6. The method for producing interstitial steel using a full scrap steel + electric arc furnace process according to claim 1, characterized in that, In the slab continuous casting process, the first heat in the tundish uses other ultra-low carbon steel with C ≤ 0.0050% for casting, while the second heat and subsequent heats in the tundish use molten steel obtained through the aforementioned scrap steel proportioning, electric arc furnace steelmaking, LF refining, and RH refining processes for casting.

7. The method for producing interstitial steel using a full scrap steel + electric arc furnace process according to claim 1, characterized in that, In the slab continuous casting process: Before continuous casting, the tundish and nozzle are baked online for 2 hours, and the calming time of the ladle fork arm is controlled to be ≥5 minutes. The liquid level fluctuation in the crystallizer is required to be ±5mm. The argon flow rate of the stopper rod is controlled to be ≤10NL / min. Dynamic light pressure and roller electromagnetic stirrer are used to control the central looseness and central segregation. The dynamic light pressure process parameters are: applying pressure in the two-phase region with a solid phase ratio of 50~95% and a total pressure reduction of 3.2mm. The roller electromagnetic stirrer process parameters are: 300A, 6Hz, no reversing.

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