Process for smelting ultra-low sulphur steel with low specific consumption of liquid iron
By employing a process flow of converter smelting, ladle refining, and RH vacuum treatment, combined with the use of lime, alloys, aluminum blocks, and modifiers, the problem of producing ultra-low sulfur steel with low iron consumption was solved, achieving efficient and low-cost production of ultra-low sulfur steel.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUNAN VALIN LIANYUAN IRON & STEEL CO LTD
- Filing Date
- 2024-11-15
- Publication Date
- 2026-06-26
AI Technical Summary
Traditional ultra-low sulfur steel production processes suffer from problems such as long production routes, high production costs, long smelting times, and mismatched furnaces and machines, making it difficult to stably control the sulfur content in steel under conditions of low iron consumption.
The process involves converter smelting, ladle refining, and RH vacuum treatment. By adding lime, alloys, aluminum blocks, and modifiers, and combining ladle slag recycling, the deoxidation and desulfurization processes are optimized, reducing the consumption of molten iron and improving desulfurization efficiency.
Ultra-low sulfur steel with a sulfur content of ≤0.0015% was produced under low iron consumption conditions, which shortened the production time, reduced the cost, and met the requirements for mass production of ultra-low sulfur steel.
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Abstract
Description
Technical Field
[0001] This application belongs to the field of steel technology, specifically relating to a method for smelting ultra-low sulfur steel with low molten iron consumption. Background Technology
[0002] Iron consumption per unit volume is a key factor restricting steel production. Effectively reducing iron consumption per unit volume can not only increase billet production and reduce the consumption of raw materials and auxiliary materials such as dolomite in steelmaking, but also reduce emissions of waste gas, wastewater, and slag. Studies have shown that replacing 1 ton of iron with 1 ton of scrap steel in a converter can save at least 550 kg of standard coal. Therefore, reducing iron consumption per unit volume has significant environmental benefits.
[0003] Ultra-low sulfur steel refers to steel with a sulfur content of ≤0.0015% in molten steel. High sulfur content in steel adversely affects its hot working properties, causing "hot brittleness." Traditional production processes for ultra-low sulfur steel include KR pretreatment of molten iron, converter smelting, LF furnace refining, RH furnace vacuum treatment, and continuous casting. This process suffers from problems such as long production routes, high production costs, long smelting times, and furnace-machine mismatch. With the continuous development of iron and steel metallurgical technology, the requirements for sulfur content in finished products are becoming increasingly stringent, with ultra-low sulfur steel, represented by sulfur-resistant pipeline steel, having even higher requirements. Summary of the Invention
[0004] This application provides a method for smelting ultra-low sulfur steel with low iron consumption, which can obtain ultra-low sulfur steel with a sulfur mass percentage of ≤0.0015% under the condition that the iron consumption is 680kg~830kg / ton of steel, thereby improving production efficiency and quality and enhancing environmental benefits.
[0005] This application provides a method for smelting ultra-low sulfur steel with low iron consumption, comprising:
[0006] Converter smelting: Molten iron and scrap steel are added to a converter for smelting to obtain molten steel and ladle top slag;
[0007] Converter tapping: The molten steel and ladle top slag are transferred out of the converter, and lime, alloy, aluminum blocks and modifier are added to the transferred molten steel and ladle top slag to obtain pretreated molten steel and ladle top slag;
[0008] Ladle refining: The pretreated molten steel and ladle top slag are transferred to the refining furnace, where scrap steel and recycled ladle slag are added for refining to obtain refined molten steel;
[0009] RH vacuum treatment: Refined molten steel is subjected to vacuum treatment to obtain molten steel to be cast;
[0010] Continuous casting: Molten steel to be poured is cast into a slab through continuous casting to obtain ultra-low sulfur steel; the mass percentage of sulfur in the ultra-low sulfur steel is ≤0.0015%.
[0011] In a feasible embodiment of this application, during the converter smelting step, the iron consumption of ultra-low sulfur steel is 680 kg to 830 kg / ton of steel; and / or the sulfur content of the molten iron is 0.04% to 0.1% by mass.
[0012] In a feasible embodiment of this application, in the converter smelting step: the amount of molten iron added is 150t / furnace to 170t / furnace; the amount of scrap steel added is 40t / furnace to 60t / furnace, the total amount added is 200t / furnace to 210t / furnace, and the initial amount of molten steel is 185t / furnace to 195t / furnace.
[0013] In a feasible embodiment of this application, in the step of tapping steel from the converter, the modifier comprises the following composition by mass percentage: Al: 35%–50%, Al2O3: 12%–25%, CaO: 18%–28%, SiO2: 2.5%–7.5%, MgO: 1.5%–5.5%, with the remainder being trace elements.
[0014] In a feasible embodiment of this application, during the converter tapping step, the binary basicity of the ladle top slag is 2 to 5.
[0015] In a feasible embodiment of this application, the steps of tapping steel from the converter include: adding 2 kg / ton to 3.3 kg / ton of steel lime for slag washing when the steel is tapped to 1 / 4 to 1 / 3; adding alloy and 1.6 kg / ton to 2.2 kg / ton of steel aluminum blocks for deoxidation and alloying when the steel is tapped to 1 / 2 to 4 / 5; and adding 0.95 kg / ton to 1.7 kg / ton of steel modifier to modify the top slag of the ladle after tapping.
[0016] In a feasible embodiment of this application, during the converter tapping step, the bottom-blown argon gas flow rate in the ladle is controlled at 60 Nm³. 3 / h~120Nm 3 / h.
[0017] In a feasible embodiment of this application, during the converter tapping process, a dual-stage operation with front and rear slag baffles is adopted to strictly control the amount of slag fed and prevent over-oxidation of the top slag of the ladle.
[0018] In a feasible embodiment of this application, the ladle slag in the ladle refining step comprises the following composition by mass percentage: CaO: 50%–58%, SiO2: 5%–12%, MgO: 4.8%–6.5%, MnO: 0.05%–0.16%, P2O5: 0.02%–0.1%, TiO2: 0.2%–0.8%, Fe... t O t 0.2% to 0.9%.
[0019] In a feasible embodiment of this application, the ladle refining step includes: transferring pretreated molten steel and ladle top slag into a refining furnace, adding scrap steel and recovered ladle slag, adding lime and low-silicon refining pre-melted slag, and controlling the binary basicity of the final refining slag to be 6-8. The CaO mass percentage in the final refining slag is 52%-58%, and the Fe content is... t O t The mass percentage content is 0.24% to 0.59%.
[0020] In a feasible embodiment of this application, the ladle refining step includes: heating the pretreated molten steel to 1580℃~1620℃, adding 20t / furnace~35t / furnace of scrap steel, 205t / furnace~220t / furnace of molten steel, and 2.9kg / ton of steel~5.0kg / ton of steel ladle slag, controlling the argon flow rate to 980NL / min~220NL / min, adding 9kg / ton of steel~12kg / ton of steel lime and 0.9kg / ton of steel~1.9kg / ton of steel low-silicon refining pre-melting slag, and refining to obtain refined molten steel.
[0021] In a feasible embodiment of this application, the RH vacuum treatment step includes: transferring refined molten steel into an RH furnace, controlling the RH ultimate vacuum degree to ≤133Pa, and the circulating argon flow rate to 150Nm³. 3 / h~220Nm 3 / h, RH smelting time is 18min~25min; to obtain vacuum smelting molten steel.
[0022] In a feasible embodiment of this application, the continuous casting process includes: transferring vacuum-smelted molten steel to a continuous casting table for slab continuous casting, controlling the back pressure of the long nozzle sealing argon and the inter-plate argon to be >0 MPa, and the superheat of the tundish to be 10°C to 20°C. Detailed Implementation
[0023] To make the inventive objectives, technical solutions, and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the embodiments described in this specification are merely illustrative and not intended to limit the scope of this application.
[0024] For simplicity, this paper only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, just as any upper limit can be combined with any other upper limit to form an undefined range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can serve as its own lower or upper limit and be combined with any other point or individual value, or with other lower or upper limits, to form an undefined range.
[0025] In the description herein, when a composition is described as containing, comprising, or including a specific component, or when a process is described as containing, comprising, or including a specific process step, it is anticipated that the composition of this application is also primarily composed of or consisting of the said component, and that the process of this application is also primarily composed of or consisting of the said process step.
[0026] Unless otherwise expressly stated, the use of the terms “including,” “contains,” “comprising,” “containing,” and “having” should generally be interpreted as open-ended and non-restrictive.
[0027] In this description, it should be noted that, unless otherwise stated, "above" and "below" include the stated number, and "multiple" in "one or more" means two or more.
[0028] The foregoing description of this invention is not intended to describe every disclosed embodiment or implementation. Instead, the following description provides more specific examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments that can be used in various combinations. The examples listed are merely representative and should not be construed as exhaustive.
[0029] Molten iron is the primary heat source in converter smelting, providing the energy required for steelmaking. A decrease in molten iron consumption per unit area means less molten iron enters the converter, affecting the energy supply during smelting. Furthermore, low molten iron consumption may lead to reduced stability in the smelting process, increasing technological complexity and making it more difficult to obtain steel with ultra-low sulfur content. While adding scrap steel can compensate for reduced molten iron consumption, scrap steel has a complex composition and high sulfur content, necessitating further optimization of the preparation process.
[0030] In view of this, based on theoretical calculation and analysis, the inventors organically combined diffusion deoxidation and precipitation deoxidation in the smelting process, giving full play to the thermodynamic and kinetic conditions of desulfurization. After multiple field tests, they developed a method for smelting ultra-low sulfur steel under low iron consumption conditions, without the need for iron pretreatment.
[0031] This application provides a method for smelting ultra-low sulfur steel with low iron consumption, which can obtain ultra-low sulfur steel with a sulfur mass percentage of ≤0.0015% under the condition that the iron consumption is 680kg~830kg / ton of steel, thereby improving production efficiency and quality and enhancing environmental benefits.
[0032] This application provides a method for smelting ultra-low sulfur steel with low iron consumption, comprising:
[0033] Converter smelting: Molten iron and scrap steel are added to a converter for smelting to obtain molten steel and ladle top slag;
[0034] Converter tapping: The molten steel and ladle top slag are transferred out of the converter, and lime, alloy, aluminum blocks and modifier are added to the transferred molten steel and ladle top slag to obtain pretreated molten steel and ladle top slag;
[0035] Ladle refining: The pretreated molten steel and ladle top slag are transferred to the refining furnace, where scrap steel and recycled ladle slag are added for refining to obtain refined molten steel;
[0036] RH vacuum treatment: Refined molten steel is subjected to vacuum treatment to obtain molten steel to be cast;
[0037] Continuous casting: Molten steel to be poured is cast into a slab through continuous casting to obtain ultra-low sulfur steel; the mass percentage of sulfur in the ultra-low sulfur steel is ≤0.0015%, and can be selected from 0.0008% to 0.0010%.
[0038] In this method, the molten iron does not require KR pretreatment. In the converter smelting process, lime, alloys, aluminum blocks, and modifiers are added to the molten steel and ladle top slag produced by the converter smelting. The lime, alloys, and aluminum blocks are used for deoxidation and alloying to reduce the oxygen content in the molten steel. The modifiers are used to modify the ladle top slag, improve the quality and binary basicity of the ladle slag, improve deoxidation efficiency, and reduce the oxygen content in the ladle. In the ladle refining process, the ladle slag remaining after continuous casting is recycled and used as slag-forming material in the refining process. The calcium oxide and silicon dioxide in the ladle slag can reduce refining time and accelerate the deoxidation efficiency in the refining process, thereby improving the overall desulfurization efficiency and reducing the sulfur content. This method can efficiently obtain ultra-low sulfur steel with a sulfur mass percentage of 0.0008% to 0.0010%.
[0039] Furthermore, this application eliminates the need for KR pretreatment of molten iron, resulting in a shorter process flow and reduced production costs. It also addresses issues such as the difficulty in desulfurizing ultra-low sulfur steel, long smelting time, difficulty in stabilizing sulfur content in the steel, and furnace-machine mismatch, all while meeting the requirement of low molten iron consumption in converters. This application features a short production process, low molten iron consumption, no need for secondary slag formation in the LF furnace, controlled smelting rhythm, stable desulfurization effect, and low production costs, greatly satisfying the requirements for mass production of ultra-low sulfur steel.
[0040] In some embodiments, the main equipment includes ladles, steel ladles, overhead cranes, converters, LF refining furnaces, RH vacuum furnaces, slab continuous casting machines, etc.
[0041] In some embodiments, during the converter smelting step, the hot metal consumption of ultra-low sulfur steel is 680 kg to 830 kg / ton of steel, and can be selected as 682 kg / ton of steel to 743 kg / ton of steel; and / or, the mass percentage of sulfur in the hot metal is 0.04% to 0.1%.
[0042] The sulfur content of the molten iron fed into the furnace in this application is relatively high because it has not been pretreated, which increases the difficulty of smelting ultra-low sulfur steel with low molten iron consumption.
[0043] In some implementations, during the converter smelting process: the amount of molten iron added is 150t / furnace to 170t / furnace; the amount of scrap steel added is 40t / furnace to 60t / furnace, the total amount added is 200t / furnace to 210t / furnace, and the initial amount of molten steel is 185t / furnace to 195t / furnace.
[0044] In some implementations, the amount of scrap steel added during the converter smelting step is 28% to 40% of the molten iron.
[0045] In a feasible embodiment of this application, in the step of tapping steel from the converter, the modifier comprises the following composition by mass percentage: Al: 35%–50%, Al2O3: 12%–25%, CaO: 18%–28%, SiO2: 2.5%–7.5%, MgO: 1.5%–5.5%, with the remainder being trace elements.
[0046] Aluminum can undergo a reduction reaction with iron oxide in steel slag to produce Al2O3 and iron, thereby reducing the oxygen content in the steel. The aforementioned mass percentage of aluminum can increase the Al2O3 content in the synthetic slag. The added lime can increase the CaO content in the slag, thereby increasing the binary basicity of the slag and reducing the CaO / Al2O3 ratio. [S] in the molten steel reacts chemically with CaO to form calcium sulfide, which is insoluble in molten steel. Due to the low solubility of calcium sulfide in molten steel, it precipitates as a solid and, with the aid of argon blowing from the bottom of the ladle, enters the steel slag, ultimately achieving desulfurization. Simultaneously, aluminum can also combine with [S] in the molten steel to form high-melting-point sulfides. These compounds have high stability in molten steel, thus accelerating the transfer of sulfur from the molten steel to the steel slag, further improving the desulfurization effect.
[0047] Alumina can reduce slag viscosity and promote desulfurization, but excessive alumina can inhibit CaO activity. The above-mentioned mass percentage of alumina and aluminum can keep the alumina content in the ladle within a suitable range to achieve good desulfurization results.
[0048] CaO can increase the calcium oxide content in the slag, and the lower oxygen potential at the slag-steel interface will promote the desulfurization reaction to proceed in the positive direction, thereby improving the desulfurization effect.
[0049] Silica also affects slag basicity, but it reacts with calcium oxide to reduce desulfurization efficiency. Magnesium oxide can increase slag fluidity, which is beneficial for the desulfurization reaction, but it tends to deposit at the bottom of the furnace, reducing the desulfurization effect. Modifiers combining silica, magnesium oxide, aluminum, alumina, and calcium oxide within the above range complement each other to increase slag quantity and basicity in the ladle, promoting the desulfurization reaction.
[0050] In some implementations, during the converter tapping step, the binary basicity of the ladle top slag is 2 to 5, and can be selected as 2.7 to 3.2.
[0051] When the binary basicity of the ladle top slag in this application is within the above-mentioned range, it is beneficial to balance the flowability and activity of the slag material, giving the steel slag suitable kinetic conditions and reactivity, thereby improving the desulfurization effect. When the basicity of the slag material increases further, the viscosity will decrease, worsening the reaction kinetic conditions and reducing the desulfurization effect.
[0052] In some embodiments, the steps of tapping steel from the converter include: adding 2 kg / ton to 3.3 kg / ton of steel lime for slag washing when the steel is tapped to 1 / 4 to 1 / 3; adding alloy and 1.6 kg / ton to 2.2 kg / ton of steel aluminum blocks for deoxidation and alloying when the steel is tapped to 1 / 2 to 4 / 5; calculating the amount of aluminum blocks added based on the oxygen content at the converter endpoint (600-950 ppm); and performing pre-deoxidation of the molten steel by adding 30 kg of aluminum blocks at a deoxidation rate of 100 ppm; and adding 0.95 kg / ton to 1.7 kg / ton of steel modifier to modify the top slag of the ladle after tapping.
[0053] The inventors discovered that the addition of lime, aluminum blocks, and modifiers also affects the reaction effect. In this application, the above-mentioned materials are combined with the above-mentioned timing of addition, so that ultra-low sulfur steel can be prepared under low iron molten conditions.
[0054] In some implementations, during the converter tapping step, the bottom-blown argon gas flow rate in the ladle is controlled at 60 Nm³. 3 / h~120Nm 3 / h.
[0055] In some implementations, during the converter tapping process, a dual-stage slag-blocking operation is used to strictly control the amount of slag fed and prevent over-oxidation of the top slag of the ladle.
[0056] In some embodiments, during the ladle refining step, the ladle slag comprises the following composition by mass percentage: CaO: 50%–58%, SiO2: 5%–12%, MgO: 4.8%–6.5%, MnO: 0.05%–0.16%, P2O5: 0.02%–0.1%, TiO2: 0.2%–0.8%, Fe... t O t 0.2% to 0.9%.
[0057] In some embodiments, the ladle refining steps include: transferring pretreated molten steel and ladle top slag into a refining furnace, adding scrap steel and recovered ladle slag, adding lime and low-silicon refining pre-melted slag, and controlling the binary basicity of the final refining slag to 6-8, optionally 6.8-7.1. In some embodiments, the final refining slag contains 52%-58% CaO, 6%-9% SiO2, 21%-36% Al2O3, and Fe... t O t The mass percentage content is 0.24% to 0.59%.
[0058] This application achieves better desulfurization effect and shortens refining time when the alkalinity and composition of the refining slag are within the above-mentioned suitable range, thereby improving production quality and achieving high production efficiency.
[0059] In some embodiments, the refining time in the ladle refining step is 80 to 110 minutes. This application can obtain ultra-low sulfur steel S with a shorter refining time and low iron consumption.
[0060] In some embodiments, the ladle refining steps include: heating the pretreated molten steel to 1580℃~1620℃, adding 20t / furnace~35t / furnace of scrap steel, molten steel amount of 205t / furnace~220t / furnace, and ladle slag of 2.9kg / ton steel~5.0kg / ton steel, controlling the argon flow rate to 980NL / min~220NL / min, adding 9kg / ton steel~12kg / ton steel of lime and 0.9kg / ton steel~1.9kg / ton steel of low-silicon refining pre-melting slag, and refining to obtain refined molten steel.
[0061] By adopting the recycling of slag from large ladles, combined with a reasonable power supply system for the LF furnace, a reasonable argon bottom blowing flow rate, and timely addition of lime to control the refining slag system of the LF furnace, the sulfur content of molten steel can be rapidly reduced to ≤0.0015%.
[0062] In some embodiments, the RH vacuum treatment steps include: transferring refined molten steel into the RH furnace, controlling the RH ultimate vacuum to ≤133 Pa, and the circulating argon flow rate to 150 Nm³. 3 / h~220Nm 3 / h, RH smelting time is 18min~25min; to obtain vacuum smelting molten steel.
[0063] In some embodiments, the continuous casting process includes: transferring vacuum-smelted molten steel to a continuous casting table for slab continuous casting, controlling the back pressure of the long nozzle sealing argon and the inter-plate argon to be >0 MPa, and the superheat of the tundish to be 10°C to 20°C.
[0064] Example
[0065] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.
[0066] Example 1
[0067] Steel grade: GC9012A3
[0068] Composition: By mass percentage, C: 0.13-0.18%, Si: 0.2-0.4%, Mn: 1.3-1.5%, P≤0.02%, S≤0.0015%, Als: 0.02-0.06%, Cr: 0.2-0.5%, Mo: 0.3-0.6%, V: 0.02-0.045%, Nb: 0.02-0.04%, N≤0.006%, B: 0.001-0.003%, Ti: 0.01-0.03%, with the balance being iron and other unavoidable impurities.
[0069] The ladle capacity is 210t, and the smelting process is: molten iron → converter smelting → LF refining → RH vacuum smelting → slab continuous casting. The smelting method for ultra-low sulfur steel without pretreatment under low molten iron consumption conditions is as follows:
[0070] (1) In the converter process, the amount of molten iron added is 162t, the amount of scrap steel added is 47t, the total amount of charging is 209t, the oxygen at the converter endpoint is 743ppm, the tapping temperature is 1605℃, and the amount of molten steel tapped is 190t.
[0071] (2) During the steel tapping process in the converter, the flow rate of bottom-blown argon gas in the ladle is controlled at 82 Nm. 3 / h, a dual-stage slag-blocking operation is adopted during tapping to strictly control the amount of slag discharged and prevent over-oxidation of the top slag of the ladle; when the steel is tapped to 1 / 3, 400kg (2.11kg / ton of steel) of lime is added for slag washing; when the steel is tapped to 1 / 2, 591kg of metallic manganese, 896kg of high-carbon ferrochrome, 1300kg of ferromolybdenum, and 354kg (1.86kg / ton of steel) of aluminum blocks are added for deoxidation and alloying; after tapping, 200kg (0.95kg / ton of steel) of modifier is added to modify the top slag of the ladle.
[0072] (3) The molten steel obtained from the converter is transferred to the LF furnace. After the molten steel is heated to 1608℃ upon entering the station, 25t of scrap steel is added, resulting in a molten steel volume of 218t and a hot metal consumption of 743kg / ton of steel. After adding the scrap steel, the ladle slag of the molten steel is recycled, with a recovery amount of 650kg (2.98kg / ton of steel). Then, the temperature of the molten steel is raised to 1625℃. In the early stage of power supply, a low current is used for arc initiation, and after arc initiation, a high current is used for heating. During the power supply process, lime and low-silicon refined pre-melted slag (with a chemical composition of Al2O3: 30%, CaO: 42%, SiO2: 3.2% by mass percentage) are added in batches. (MgO: 4.5%, the remainder being trace elements), during power transmission, the bottom-blown argon flow rate is 200 NL / min. After the molten steel reaches the required temperature, rapid slag formation and desulfurization are carried out. Lime is added promptly according to the slag consistency. During desulfurization, the bottom-blown argon flow rate is 900 NL / min, and the total amount of lime added is 2452 kg (11.24 kg / ton of steel). The amount of low-silicon refining pre-melted slag added is 395 kg (1.81 kg / ton of steel). The binary basicity of the final refining slag is 6.8, the CaO content in the slag is 58%, the SiO2 mass percentage is 8.5%, the Al2O3 mass percentage is 26.6%, and the Fe content is... t O t The sulfur content is 0.43%, with the remainder being trace elements. The above techniques can be used to rapidly reduce the sulfur content of molten steel to 0.0010%.
[0073] (4) The molten steel obtained from the LF furnace is transferred to the RH furnace. During the RH vacuum smelting process, the ultimate vacuum of the RH furnace is 68 Pa, and the circulating argon flow rate is 175 Nm³. 3 / h, RH smelting time is 20min.
[0074] (5) The molten steel obtained from RH is transferred to continuous casting, which is slab continuous casting. During the casting process, protective casting is carried out to prevent secondary oxidation of the molten steel. The argon back pressure of the long nozzle is 0.48 Bar, the argon back pressure between plates is 0.16 Bar, and the average superheat of the tundish is 18°C.
[0075] Example 2:
[0076] Steel grade: GC9012A4
[0077] Composition: By mass percentage, C: 0.13-0.18%, Si: 0.2-0.4%, Mn: 1.3-1.5%, P≤0.02%, S≤0.0015%, Als: 0.02-0.06%, Cr: 0.3-0.6%, Mo: 0.4-0.7%, V: 0.02-0.045%, Nb: 0.02-0.04%, N≤0.006%, B: 0.001-0.003%, Ti: 0.01-0.03%, with the balance being iron and other unavoidable impurities.
[0078] The ladle capacity is 210t, and the smelting process is: molten iron → converter smelting → LF refining → RH vacuum smelting → slab continuous casting. The smelting method for ultra-low sulfur steel without pretreatment under low molten iron consumption conditions is as follows:
[0079] (1) In the converter process, the amount of molten iron added is 150t, the amount of scrap steel added is 55t, the total amount of charging is 205t, the oxygen at the converter endpoint is 896ppm, the tapping temperature is 1602℃, and the amount of molten steel tapped is 185t.
[0080] (2) During the steel tapping process in the converter, the flow rate of bottom-blown argon gas in the ladle is controlled at 95 Nm. 3 / h, a dual-stage slag-blocking operation is adopted during tapping to strictly control the amount of slag fed and prevent over-oxidation of the top slag of the ladle; when the steel is tapped to 1 / 3, 604 kg (3.2 kg / ton of steel) of lime is added for slag washing; when the steel is tapped to 1 / 2, 653 kg of metallic manganese, 1320 kg of high-carbon ferrochrome, 1580 kg of ferromolybdenum, and 396 kg (2.14 kg / ton of steel) of aluminum blocks are added for deoxidation and alloying; after tapping, 302 kg (1.63 kg / ton of steel) of modifier is added to modify the top slag of the ladle.
[0081] (3) The molten steel obtained from the converter is transferred to the LF furnace. After the molten steel is heated to 1615℃ by power supply, 32t of scrap steel is added, and the molten steel volume is 220t. The iron consumption is 682kg / ton of steel. After adding the scrap steel, the ladle slag of the molten steel is recycled, and the recovery amount is 720kg (3.27kg / ton of steel). Then the temperature of the molten steel is raised to 1620℃. In the early stage of power supply, a low current is used for arc initiation. After arc initiation, a high current is used for heating. During the power supply process, lime and low-silicon refining pre-melted slag are added in batches. The bottom blowing argon flow rate during power supply is... The flow rate was 260 NL / min. Rapid slag formation and desulfurization were performed after the molten steel reached the required temperature. Lime was added promptly based on the slag consistency. During desulfurization, the bottom-blown argon flow rate was 980 NL / min. The total amount of lime added was 2236 kg (10.16 kg / ton of steel). The amount of low-silicon refining pre-melted slag added was 278 kg (1.26 kg / ton of steel). The binary basicity of the final refining slag was 7.1. The slag contained 52% CaO, 7.3% SiO2, 27.3% Al2O3, and Fe... t O t The sulfur content is 0.24%, with the remainder being trace elements. The above techniques can rapidly reduce the sulfur content of molten steel to 0.0008%.
[0082] (4) The molten steel obtained from the LF furnace is transferred to the RH furnace. During the RH vacuum smelting process, the ultimate vacuum of the RH furnace is 75 Pa, and the circulating argon flow rate is 190 Nm³. 3 / h, RH smelting time is 18min.
[0083] (5) The molten steel obtained from RH is transferred to continuous casting, which is slab continuous casting. During the casting process, protective casting is carried out to prevent secondary oxidation of the molten steel. The argon back pressure of the long nozzle is 0.43 Bar, the argon back pressure between plates is 0.29 Bar, and the average superheat of the tundish is 15°C.
[0084] Example 3:
[0085] Steel grade: GC9011A1
[0086] Composition: By mass percentage, C: 0.13-0.18%, Si: 0.1-0.3%, Mn: 1.3-1.5%, P≤0.02%, S≤0.0015%, Als: 0.02-0.06%, Cr: 0.2-0.5%, Mo: 0.3-0.6%, V: 0.02-0.045%, Nb: 0.02-0.04%, N≤0.006%, B: 0.001-0.003%, Ti: 0.01-0.03%, with the balance being iron and other unavoidable impurities.
[0087] The ladle capacity is 210t, and the smelting process is: molten iron → converter smelting → LF refining → RH vacuum smelting → slab continuous casting. The smelting method for ultra-low sulfur steel without pretreatment under low molten iron consumption conditions is as follows:
[0088] (1) In the converter process, the amount of molten iron added is 169t, the amount of scrap steel added is 40t, the total amount of charging is 209t, the oxygen at the converter endpoint is 883ppm, the tapping temperature is 1597℃, and the amount of molten steel tapped is 185t.
[0089] (2) During the steel tapping process in the converter, the flow rate of bottom-blown argon gas in the ladle is controlled at 75 Nm. 3 / h, a dual-stage slag-blocking operation is adopted during tapping to strictly control the amount of slag discharged and prevent over-oxidation of the top slag of the ladle; when the steel is tapped to 1 / 3, 592kg (3.2kg / ton of steel) of lime is added for slag washing; when the steel is tapped to 1 / 2, 608kg of metallic manganese, 865kg of high-carbon ferrochrome, 1050kg of ferromolybdenum, and 296kg (1.6kg / ton of steel) of aluminum blocks are added for deoxidation and alloying; after tapping, 289kg (1.56kg / ton of steel) of modifier is added to modify the top slag of the ladle.
[0090] (3) The molten steel obtained from the converter is transferred to the LF furnace. After the molten steel is heated to 1593℃ by power supply, 20t of scrap steel is added, and the molten steel volume is 205t. The iron consumption is 824kg / ton of steel. After adding the scrap steel, the ladle slag of the molten steel is recycled, and the recovery amount is 610kg (2.97kg / ton of steel). Then the temperature of the molten steel is raised to 1618℃. In the early stage of power supply, a low current is used for arc initiation. After arc initiation, a high current is used for heating. During the power supply process, lime and low-silicon refining pre-melted slag are added in batches. During the power supply, bottom blowing argon gas is used. The flow rate is 200 NL / min. After the molten steel reaches the required temperature, rapid slag formation and desulfurization are performed. Lime is added promptly based on the slag consistency. During desulfurization, the bottom-blown argon flow rate is 999 NL / min. The total amount of lime added is 2018 kg (9.84 kg / ton of steel). The amount of low-silicon refining pre-melted slag added is 198 kg (0.96 kg / ton of steel). The binary basicity of the final refining slag is 6.5. The slag contains 54% CaO, 8.3% SiO2, 28.2% Al2O3, and Fe... t O t The sulfur content is 0.59%, with the remainder being trace elements. The above techniques can rapidly reduce the sulfur content of molten steel to 0.0012%.
[0091] (4) The molten steel obtained from the LF furnace is transferred to the RH furnace. During the RH vacuum smelting process, the ultimate vacuum of the RH furnace is 95 Pa, and the circulating argon flow rate is 180 Nm³. 3 / h, RH smelting time is 22min.
[0092] (6) The molten steel obtained from RH is transferred to continuous casting, which is slab continuous casting. During the casting process, protective casting is carried out to prevent secondary oxidation of the molten steel. The argon back pressure of the long nozzle is 0.45 Bar, the argon back pressure between plates is 0.23 Bar, and the average superheat of the tundish is 13°C.
[0093] Example 4
[0094] Steel grade: GC9012A3
[0095] Composition: By mass percentage, C: 0.13-0.18%, Si: 0.2-0.4%, Mn: 1.3-1.5%, P≤0.02%, S≤0.0015%, Als: 0.02-0.06%, Cr: 0.2-0.5%, Mo: 0.3-0.6%, V: 0.02-0.045%, Nb: 0.02-0.04%, N≤0.006%, B: 0.001-0.003%, Ti: 0.01-0.03%, with the balance being iron and other unavoidable impurities.
[0096] The ladle capacity is 210t, and the smelting process is: molten iron → converter smelting → LF refining → RH vacuum smelting → slab continuous casting. The smelting method for ultra-low sulfur steel without pretreatment under low molten iron consumption conditions is as follows:
[0097] (6) In the converter process, the amount of molten iron added is 165t, the amount of scrap steel added is 48t, the total amount of charging is 213t, the oxygen at the converter endpoint is 785ppm, the tapping temperature is 1609℃, and the amount of molten steel tapped is 193t.
[0098] (7) During the steel tapping process in the converter, the flow rate of bottom-blown argon gas in the ladle is controlled at 82 Nm. 3 / h, a dual-stage slag-blocking operation is adopted during tapping to strictly control the amount of slag discharged and prevent over-oxidation of the top slag of the ladle; when the steel is tapped to 1 / 3, 400 kg of lime is added for slag washing; when the steel is tapped to 1 / 2, 595 kg of metallic manganese, 887 kg of high-carbon ferrochrome, 1310 kg of ferromolybdenum, and 354 kg of aluminum blocks are added for deoxidation and alloying; after tapping, 200 kg of modifier is added to modify the top slag of the ladle.
[0099] (8) The molten steel obtained from the converter is transferred to the LF furnace. After the molten steel is heated to 1612℃ by power supply, 25t of scrap steel is added, resulting in a molten steel volume of 218t and a hot iron consumption of 756kg / ton of steel. After adding the scrap steel, the ladle slag of the molten steel is recycled, with a recycling amount of 650kg. Then, the temperature of the molten steel is raised to 1622℃. In the early stage of power supply, a low current is used for arc initiation, and after arc initiation, a high current is used for heating. During the power supply process, lime and low-silicon refining pre-melted slag (with a chemical composition mass percentage of Al2O3: 30-45%, CaO: 40-55%) are added in batches. The slag composition is as follows: SiO2: 2-5%, MgO: 1.5-6.5%. During power transmission, the bottom-blown argon flow rate is 200 NL / min. After the molten steel reaches the required temperature, rapid slag formation and desulfurization are carried out. Lime is added promptly according to the slag consistency. During desulfurization, the bottom-blown argon flow rate is 900 NL / min, and the total amount of lime added is 2452 kg. The amount of low-silicon refining pre-melted slag added is 395 kg. The binary basicity of the final refining slag is 7.2. The slag contains 56% CaO, 7.8% SiO2, 32.6% Al2O3, and Fe. t O t The sulfur content is 0.56%, with the remainder being trace elements. The above techniques can rapidly reduce the sulfur content of molten steel to 0.0011%.
[0100] (9) The molten steel obtained from the LF furnace is transferred to the RH furnace. During the RH vacuum smelting process, the ultimate vacuum of the RH furnace is 72 Pa, and the circulating argon flow rate is 178 Nm³. 3 / h, RH smelting time is 21min.
[0101] (10) The molten steel obtained from RH is transferred to continuous casting, which is slab continuous casting. During the casting process, protective casting is carried out to prevent secondary oxidation of the molten steel. The argon back pressure of the long nozzle is 0.48 Bar, the argon back pressure between plates is 0.16 Bar, and the average superheat of the tundish is 18°C.
[0102] Comparative Example 1
[0103] Steel grade: GC9012A3
[0104] Composition: By mass percentage, C: 0.13-0.18%, Si: 0.2-0.4%, Mn: 1.3-1.5%, P≤0.02%, S≤0.0015%, Als: 0.02-0.06%, Cr: 0.2-0.5%, Mo: 0.3-0.6%, V: 0.02-0.045%, Nb: 0.02-0.04%, N≤0.006%, B: 0.001-0.003%, Ti: 0.01-0.03%, with the balance being iron and other unavoidable impurities.
[0105] The ladle capacity is 210t, and the smelting process is: molten iron → converter smelting → LF refining → RH vacuum smelting → slab continuous casting. The smelting method for ultra-low sulfur steel without pretreatment under low molten iron consumption conditions is as follows:
[0106] (1) In the converter process, the amount of molten iron added is 165t, the amount of scrap steel added is 47t, the total amount of charging is 212t, the oxygen at the converter endpoint is 723ppm, the tapping temperature is 1607℃, and the amount of molten steel tapped is 191t.
[0107] (2) During the steel tapping process in the converter, the flow rate of bottom-blown argon gas in the ladle is controlled at 85 Nm. 3 / h, a dual-stage operation with front and rear slag baffles is adopted during tapping to strictly control the amount of slag fed and prevent over-oxidation of the top slag of the ladle; when the steel is tapped to 1 / 3, 400kg (2.09kg / ton of steel) of lime is added for slag washing; when the steel is tapped to 1 / 2, 591kg of metallic manganese, 896kg of high-carbon ferrochrome, 1300kg of ferromolybdenum, and 354kg (1.85kg / ton of steel) of aluminum blocks are added for deoxidation and alloying.
[0108] (3) The molten steel obtained from the converter is transferred to the LF furnace. After the molten steel is heated to 1612℃ upon entering the station, 27t of scrap steel is added, resulting in a molten steel volume of 218t and a hot metal consumption of 756kg / ton of steel. After adding the scrap steel, the ladle slag from the molten steel is recycled, with a recovery rate of 650kg. Then, the molten steel temperature is raised to 1625℃. In the early stage of power supply, a low current is used for arc ignition, and after arc ignition, a high current is used for heating. During the power supply process, lime and low-silicon refined pre-melted slag (with a chemical composition mass percentage of Al2O3: 32%, CaO: 43.5%, SiO2: 3.1%) are added in batches. %, MgO: 3.8%, the remainder being trace elements), during power transmission, the bottom-blown argon flow rate is 200 NL / min, after the molten steel temperature is reached, rapid slag formation and desulfurization are carried out, and lime is added in a timely manner according to the slag consistency. During desulfurization, the bottom-blown argon flow rate is 900 NL / min, the total amount of lime added is 2452 kg (11.24 kg / ton of steel), the amount of low-silicon refining pre-melted slag added is 395 kg, the binary basicity of the final refining slag is 6.9, the slag content is 56% CaO, 8.1% SiO2, 25.3% Al2O3, and Fe t O t The content is 0.52%, and the rest are trace elements.
[0109] (4) The molten steel obtained from the LF furnace is transferred to the RH furnace. During the RH vacuum smelting process, the ultimate vacuum of the RH furnace is 68 Pa, and the circulating argon flow rate is 175 Nm³. 3 / h, RH smelting time is 20min.
[0110] (5) The molten steel obtained from RH is transferred to continuous casting, which is slab continuous casting. During the casting process, protective casting is carried out to prevent secondary oxidation of the molten steel. The argon back pressure of the long nozzle is 0.48 Bar, the argon back pressure between plates is 0.16 Bar, and the average superheat of the tundish is 18°C.
[0111] Comparative Example 2
[0112] Steel grade: GC9012A3
[0113] Composition: By mass percentage, C: 0.13-0.18%, Si: 0.2-0.4%, Mn: 1.3-1.5%, P≤0.02%, S≤0.0015%, Als: 0.02-0.06%, Cr: 0.2-0.5%, Mo: 0.3-0.6%, V: 0.02-0.045%, Nb: 0.02-0.04%, N≤0.006%, B: 0.001-0.003%, Ti: 0.01-0.03%, with the balance being iron and other unavoidable impurities.
[0114] The ladle capacity is 210t, and the smelting process is: molten iron → converter smelting → LF refining → RH vacuum smelting → slab continuous casting. The smelting method for ultra-low sulfur steel without pretreatment under low molten iron consumption conditions is as follows:
[0115] (1) In the converter process, the amount of molten iron added is 158t, the amount of scrap steel added is 51t, the total amount of charging is 209t, the oxygen at the converter endpoint is 823ppm, the tapping temperature is 1601℃, and the amount of molten steel tapped is 190t.
[0116] (2) During the steel tapping process in the converter, the flow rate of bottom-blown argon gas in the ladle is controlled at 82 Nm. 3 / h, a dual-stage slag-blocking operation is adopted during tapping to strictly control the amount of slag discharged and prevent over-oxidation of the top slag of the ladle; when the steel is tapped to 1 / 3, 400kg (2.11kg / ton of steel) of lime is added for slag washing; when the steel is tapped to 1 / 2, 591kg of metallic manganese, 896kg of high-carbon ferrochrome, 1300kg of ferromolybdenum, and 354kg (1.86kg / ton of steel) of aluminum blocks are added for deoxidation and alloying; after tapping, 200kg (1.05kg / ton of steel) of modifier is added to modify the top slag of the ladle.
[0117] (3) The molten steel obtained from the converter is transferred to the LF furnace. After the molten steel is heated to 1617℃ upon entering the station, 28t of scrap steel is added, resulting in a molten steel volume of 218t and a hot metal consumption of 724kg / ton of steel. The molten steel temperature is then raised to 1625℃. A low current is used for arc ignition during the initial stage of power supply, followed by a high current for heating after arc ignition. During the power supply process, lime and low-silicon refining pre-melted slag (with the following chemical composition by mass percentage: Al2O3: 32%, CaO: 43.5%, SiO2: 3.1%, MgO: 3.8%) are added in batches. The content of the slag is 50%, with the remainder being trace elements. During power transmission, the bottom-blown argon flow rate is 200 NL / min. After the molten steel reaches the required temperature, rapid slag formation and desulfurization are carried out. Lime is added promptly according to the slag consistency. During desulfurization, the bottom-blown argon flow rate is 900 NL / min, and the total amount of lime added is 2452 kg. The amount of low-silicon refining pre-melted slag added is 395 kg. The binary basicity of the final refining slag is 6.5. The slag contains 50% CaO, 7.7% SiO2, 26.3% Al2O3, and Fe. t O t The content is 0.65%, and the rest are trace elements.
[0118] (4) The molten steel obtained from the LF furnace is transferred to the RH furnace. During the RH vacuum smelting process, the ultimate vacuum of the RH furnace is 68 Pa, and the circulating argon flow rate is 175 Nm³. 3 / h, RH smelting time is 20min.
[0119] (5) The molten steel obtained from RH is transferred to continuous casting. Continuous casting is slab continuous casting. During the casting process, protective casting is carried out to prevent secondary oxidation of the molten steel. The argon back pressure of the long nozzle is 0.48 Bar, the argon back pressure between plates is 0.16 Bar, and the average superheat of the tundish is 18℃.
[0120] Tables 1 and 2 below summarize the relevant technical parameters in the preparation process. Table 2 lists the main components of the calcium agent, and the rest are trace elements.
[0121] Table 1. Relevant technical parameters of each embodiment and comparative example.
[0122]
[0123] Table 2 Composition of the modifier
[0124]
[0125] In summary, the smelting method for ultra-low sulfur steel without pretreatment under low hot metal consumption conditions provided by this invention eliminates the need for KR pretreatment of hot metal, resulting in a short process flow, low hot metal consumption, no need for secondary slag formation in the LF furnace, controlled smelting rhythm, stable desulfurization effect, and low production cost. This greatly meets the requirements for mass production of ultra-low sulfur steel. Under favorable process conditions, this application can achieve an ultra-low sulfur steel with a sulfur content as low as 0.0008% when the hot metal consumption is below 700 kg / ton of steel.
[0126] The above embodiments of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.
Claims
1. A method for smelting ultra-low sulfur steel with low iron consumption, characterized in that, include: Converter smelting: Molten iron and scrap steel are added to a converter for smelting to obtain molten steel and ladle top slag; wherein, the molten iron does not require KR pretreatment; the amount of molten iron added is 150t / heat to 170t / heat; the amount of scrap steel added is 40t / heat to 60t / heat, with a total addition of 200t / heat. 210t / heat, wherein the initial amount of molten steel is 185t / heat to 195t / heat; Converter tapping: The molten steel and ladle top slag are transferred out of the converter, and lime, alloy, aluminum blocks and modifier are added to the transferred molten steel and ladle top slag to obtain pretreated molten steel and ladle top slag; Ladle refining: The pretreated molten steel and ladle top slag are transferred to the refining furnace, where scrap steel and recycled ladle slag are added for refining to obtain refined molten steel; RH vacuum treatment: Refined molten steel is subjected to vacuum treatment to obtain molten steel to be cast; Continuous casting: Molten steel is continuously cast into a slab to obtain ultra-low sulfur steel; the sulfur content of the ultra-low sulfur steel is ≤0.0015% by mass. In the converter smelting step, the iron consumption of the ultra-low sulfur steel is 680 kg to 830 kg / ton of steel; the sulfur content of the molten iron is 0.04% to 0.1% by mass. The modifier comprises the following components by mass percentage: Al: 35%–50%, Al2O3: 12%–25%, CaO: 18%–28%, SiO2: 2.5%–7.5%, MgO: 1.5%–5.5%, with the remainder being trace elements.
2. The method for smelting ultra-low sulfur steel with low iron consumption according to claim 1, characterized in that, In the converter tapping step, the binary basicity of the top slag in the ladle is 2 to 5.
3. The method for smelting ultra-low sulfur steel with low iron consumption according to claim 1, characterized in that, The steps for tapping steel from the converter include: adding 2 kg / ton to 3.3 kg / ton of steel lime for slag washing when the steel is tapped to 1 / 4 to 1 / 3; adding alloy and 1.6 kg / ton to 2.2 kg / ton of steel aluminum blocks for deoxidation and alloying when the steel is tapped to 1 / 2 to 4 / 5; and adding 0.95 kg / ton to 1.7 kg / ton of steel modifier to modify the top slag of the ladle after tapping.
4. The method for smelting ultra-low sulfur steel with low iron consumption according to claim 1, characterized in that, In the ladle refining step, the ladle slag comprises the following composition by mass percentage: CaO: 50%~58%, SiO2: 5%~12%, MgO: 4.8%~6.5%, MnO: 0.05%~0.16%, P2O5: 0.02%~0.1%, TiO2: 0.2%~0.8%, Fe... t O t 0.2%~0.9%.
5. The method for smelting ultra-low sulfur steel with low iron consumption according to claim 1, characterized in that, The ladle refining steps include: transferring pretreated molten steel and ladle top slag into a refining furnace, adding scrap steel and recovered ladle slag, adding lime and low-silicon refining pre-melted slag, and controlling the binary basicity of the final refining slag to be 6-8.
6. The method for smelting ultra-low sulfur steel with low iron consumption according to claim 1, characterized in that, The ladle refining steps include: heating the pretreated molten steel to 1580℃~1620℃, adding 20 t / furnace~35 t / furnace of scrap steel, 205 t / furnace~220 t / furnace of molten steel, and 2.9 kg / ton of steel~5.0 kg / ton of steel ladle slag, controlling the argon flow rate to 980NL / min~220NL / min, adding 9 kg / ton of steel~12 kg / ton of steel lime and 0.9 kg / ton of steel~1.9 kg / ton of steel low-silicon refining pre-melting slag, and refining to obtain refined molten steel.
7. The method for smelting ultra-low sulfur steel with low iron consumption according to claim 1, characterized in that, The RH vacuum treatment steps include: transferring the refined molten steel to the RH furnace, controlling the RH ultimate vacuum degree to ≤133Pa, and the circulating argon flow rate to 150Nm. 3 / h~220Nm 3 / h, RH smelting time is 18min~25min; to obtain vacuum smelting molten steel.
8. The method for smelting ultra-low sulfur steel with low iron consumption according to claim 7, characterized in that, The continuous casting process includes: transferring the vacuum-smelted molten steel to the continuous casting table for slab continuous casting, controlling the back pressure of the long nozzle sealing argon and the inter-plate argon to be >0 MPa, and the superheat of the tundish to be 10℃~20℃.