High-purity, high-carbon steel and its low-carbon emission production method

Abstract

This invention provides high-purity, high-carbon steel and a low-carbon emission production method thereof, wherein the high-purity, high-carbon steel has a mass percentage of C: 0.5-1.0%, P: ≤0.006%, and N: ≤0.0030%. The low-carbon emission production method includes electric furnace smelting, RH vacuum treatment, large square billet continuous casting, bract grinding, high-speed wire rod rolling, Stermor air cooling, and finished wire rod formation. Under conditions of a high scrap steel ratio, the control targets of low carbon emissions, low gas content, low impurity element content, and high purity are achieved.

Description

[Technical Field]

[0001] This invention relates to high-purity, high-carbon steel and a low-carbon emission production method thereof, and belongs to the technical field of steelmaking. [Background technology]

[0002] As carbon neutrality targets progress, the steel industry is actively exploring manufacturing process technologies to reduce carbon emissions. In electric arc furnace processes, smelting only scrap steel or with a low molten iron ratio (≤30%) can eliminate blast furnace steelmaking or reduce the amount of molten iron used, thereby significantly reducing carbon emissions. However, in electric arc furnaces, when smelting only scrap steel or with a low molten iron ratio, the amount of molten iron is small, making KR desulfurization treatment impossible. This results in high deep desulfurization pressure during refining, and the large amount of scrap steel used makes it difficult to control impurity elements such as Al, Ti, and Cu. Furthermore, a high scrap steel ratio in electric arc furnaces leads to longer energizing times, which can significantly increase the nitrogen content in the molten steel. The conventional RH denitrification capacity is limited, and in the VD denitrification process, the reaction between slag and metal is vigorous, accelerating refractory erosion and making it difficult to control inclusions. As a result, the production ratio of high-quality high-carbon steel wire rod products, such as high-strength spring steel, cord steel, and cable steel, using only scrap steel or a low molten iron ratio in the electric furnace process is low. Furthermore, when producing high-quality high-carbon steel wire rod products using only scrap steel or a low molten iron ratio in the electric furnace process, comprehensive control of segregation and cracking of continuous casting billets, wire structure, and surface quality is required in addition to controlling the cleanliness of the molten steel in order to obtain high-quality high-carbon steel wire rod products. To solve the above technical problems, the present invention provides high-cleanliness high-carbon steel and a low-carbon emission production method thereof.

[0003] High-carbon steel wire rods come in many varieties and have a wide range of applications. Mid-to-high-grade high-carbon steel products, such as spring steel, cord steel, and cable steel, require relatively strict control over cleanliness, segregation, cracking, and surface quality during production. Springs are essential basic components and are widely used in fields such as automobiles, machinery, and railways. As safety support members, springs must withstand high-cycle alternating loads during use, and their failure mechanism is primarily fatigue fracture. Extensive research indicates that in high-strength, high-cycle fatigue springs, gas content, impurity elements, large inclusions, brittle inclusions, segregation, and surface quality are the main causes of fatigue fracture. Cord steel, which supports the framework of automobile tire rubber, requires extremely high quality stability. Large inclusions, segregation, and abnormal structures are major causes of wire drawing failure and torsional joint failure, seriously impacting product quality stability and, consequently, the safety of automobile use. Steel for bridge cables is primarily used in large bridge projects and is sensitive to phosphorus content, large inclusions, segregation, mesh cementite, and surface quality. During the wire drawing process, these defects can cause brittle fracture or torsional fracture, affecting product quality and, consequently, the quality and safety of the project.

[0004] High-quality high-carbon steel wire rods are generally produced through a blast furnace-KR molten iron pretreatment-converter-refining (LF or LF-VD / RH)-continuous casting process, resulting in a long production process. This is mainly due to the inability to stably control impurity elements, gas content, and inclusions in the electric furnace smelting process. When smelting only scrap steel or with a low molten iron ratio, KR desulfurization cannot be performed, leading to high refining and desulfurization pressures. Prolonged deep desulfurization during refining increases the amount of gas drawn into the molten steel, contaminating it through slag inclusion. Furthermore, in high-grade wire rod products, the Al and Ti content in the molten steel is strictly controlled to control hard inclusions such as alumina, magnesium aluminum spinel, titanium oxide, and titanium nitride. Additionally, elements such as Cu, Mo, and Sn are also carefully controlled to stabilize product performance. Strict control is required, and as the scrap steel ratio increases, the difficulty in controlling impurity elements increases. Furthermore, as the scrap steel ratio increases, the energizing time in electric furnace smelting increases, resulting in a higher nitrogen content in the molten steel compared to the converter process. In conventional processes, rhodium disulfide decarburization capacity is poor, while volatile distillate (VD) denitrification capacity is stronger than rhodium disulfide. However, if denitrification is performed by stirring with VD for a long time, corrosion of refractories becomes severe, the reaction between slag and metal becomes more intense, and as a result, the types of inclusions become uncontrollable, and the cleanliness of the molten steel decreases. In addition, in order to guarantee the quality of high-carbon steel wire rod products, it is necessary to strictly control not only the gas content and impurity elements, but also the segregation and cracking of continuous casting billets, the wire rod structure, and the surface quality. In this way, high-purity, high-quality wire rod products can be obtained.

[0005] Patent application 2022111781023 provides a production process for medium to high quality thin carbon tool steel. This production process uses a low-emission, short-process headless strip steel production process and includes a molten steel smelting process using a quantum electric furnace, an out-of-furnace molten steel refining process using LF refining, an out-of-furnace molten steel refining process using VOD or RH refining, and an ESP continuous casting and rolling headless strip steel rolling process. By effectively combining these production processes, a completely new, headless strip steel production process is formed to create high-quality thin carbon tool steel, enabling the production of high-carbon steel below set specifications. This invention can effectively reduce energy consumption and harmful emissions in the strip steel product production process. However, electric furnaces mainly produce steel through large charging volumes, tapping, and molten steel residue. Because classification and management are not performed for the type of scrap steel, control of the content of impurity elements cannot be guaranteed, and the content of impurity elements such as P, Cu, and Ni in the finished product is generally high. Furthermore, the process involves selecting either RH or VOD followed by LF refining, and during the refining process, a large flow rate is injected from the bottom while stirring, resulting in a vigorous reaction between the slag and the metal, which is unfavorable for controlling inclusions and the cleanliness of the molten steel.

[0006] Patent application 202110338648X provides high-purity spring steel and a method for producing the same, the method of production using the processes of deep desulfurization of molten iron, dephosphorization in a converter, LF refining, RH vacuum, and continuous casting, desulfurizing the molten iron until the sulfur content in the molten iron is ≤0.0015%, refining in a converter to obtain molten steel with P ≤0.011%, precisely controlling bottom blowing in the converter tapping and refining process, and controlling inclusions in the molten steel throughout the entire process by an RH vacuum treatment process and tundish induction heating technology to obtain high-purity spring steel wire. However, when high-basicity slag containing 55-60% CaO and 22-25% SiO2 is used, the high C and Si content in the spring steel means that under high-basicity conditions, the Si element reduces Al2O3 in the slag or refractory material, increasing the alumina component in the molten steel inclusions. This significantly increases the probability of high-melting-point aluminosilicate inclusions and brittle inclusions, which is unfavorable for controlling the fatigue life of the spring steel.

[0007] Patent application 2022109583109 provides a spring steel wire rod and a method for producing the same. This process controls the content of impurities such as P, S, Al, and Ti, as well as gases, in the molten steel through the smelting process and some auxiliary materials. It controls segregation of the cast billet through a large reduction ratio in continuous casting, and controls the furnace atmosphere by shortening the holding time and heating at a low temperature in combination with the degree of heating. It also controls decarburization of the surface through overall polishing, thereby achieving control of the overall quality of the spring steel. This process controls desulfurization using KR and a converter, and desulfurizes using high-basicity slag in the smelting and vacuum processing processes. However, high-basicity slag significantly increases the Al2O3 and CaO components of inclusions in the molten steel, making it unfavorable to control the types of inclusions. Furthermore, because it is a silicon-manganese deoxidized steel, acidic inclusions have a certain corrosive effect on the refractory material, and under vacuum, the reductive erosion of refractory oxides by carbon in high-carbon steel is also serious. The method provided by the patent application does not provide control technology for refractory materials such as vacuum treatment and continuous casting, and is disadvantageous for controlling large external inclusions. Also, the reduction in continuous casting is easily divided into three sections according to the solidification center, and if the reduction amount in a single section is too large, it can cause problems such as cracking inside the casting billet. In the heating furnace, the casting billet is heated with a short holding time and low heating temperature, which is disadvantageous for reducing and removing elemental diffusion and segregation. Also, when wire is used as packing tape, it is prone to causing tightening marks and scratches on the surface of the spring wire.

[0008] Patent application 2016102603055 provides a smelting process for controlling inclusions in spring steel, which includes 1) electric furnace primary smelting, 2) argon gas injection, 3) LF furnace refining, 4) VD furnace refining, and 5) continuous casting, wherein preliminary deoxidation is performed in the electric furnace primary smelting process using a Si / Mn aluminum-free deoxidation process, and activated lime, a composite agent, and refining slag are used. While brittle inclusions in the steel can be well controlled, the basicity of the slag in the later stages of refining is controlled to 0.7-1.4, and the acidic slag severely erodes the refractories of the ladle and continuous casting tundish, leading to the generation of excessive foreign inclusions and easily affecting the fatigue life of the spring.

[0009] Patent application 2018115248243 provides a hot-rolled spring wire rod for super-heavy-duty mold springs and a method for producing the same, the production method comprising the steps of converter smelting, LF furnace smelting, continuous casting of large square billets, mass separation, shot blasting and polishing of hot-rolled billets, billet heating, rolling control, and cooling control. The hot-rolled spring wire rod for super-heavy-duty mold springs produced by this invention exhibits good surface decarburization, internal segregation, and cleanliness control, and the processed irregular-section spring wire rod is used for coiling super-heavy-duty mold springs. However, casting at a low superheat of 10-20°C is disadvantageous for the surfacing and removal of inclusions, as well as for controlling the reduction amount and small cracks in the cast billet after reduction. Furthermore, although acidic pre-molten slag is used, the refractories and auxiliary materials are not controlled, leading to severe erosion of the refractories, an increase in foreign impurity elements and inclusions, and thus unfavorable quality control for the high-strength spring steel as a whole.

[0010] Patent application 2020111278482 provides wire rods for wires made from 2300 MPa class prestressed steel and a method for producing the same. The wire rod production process involves the following steps in order: "molten iron pre-desulfurization → converter smelting → out-of-furnace refining → continuous casting of large square billets → ingot splitting → high-speed wire rod rolling → air cooling → salt bath treatment". The superheating of the molten steel in the continuous casting tundish is 12-25°C, and solidification segregation is reduced using means such as electromagnetic stirring and dynamic light reduction. A two-pass heating and forming rolling process of large square billets is used, and strong cooling is performed before the phase change to suppress the formation of network cementite. After salt bath treatment, the wire rod structure has sorbite ≥ 95% and network cementite ≤ Grade 1. However, casting at low superheating levels is disadvantageous for controlling cracks due to the floating of inclusions and large reduction ratios. After rolling the cast billet, it needs to be treated in a salt bath process, resulting in a long overall process flow and high production costs.

[0011] Patent application 2021110884598 provides a method for producing high-carbon steel wire rods with excellent deep-drawability. The chemical composition of the steel includes C: 0.69-1.02%, Si: 0.15-0.35%, Mn: 0.40-0.90%, Cr: ≤0.35%, P: ≤0.025%, S: ≤0.025%, with the remainder being iron and unavoidable impurities. Continuous casting is performed using a dedicated protective slag and a large chamfer crystallizer. High-speed heating of the wire rods is performed using high temperatures, with controlled holding time, and an oxidizing atmosphere is used to promote combustion of the steel billet surface in the heating furnace. The mesh cementite on the wire rod surface is ≤0.5 grade. However, the overall content of impurity elements such as P and S in the applied high-carbon steel wire rods is high, resulting in low purity. Because the heating furnace uses a strong oxidizing atmosphere, decarburization of the billet surface becomes severe, increasing the need for polishing, which is detrimental to production costs and wire rod quality control, making it unsuitable for the production of high-quality high-carbon steel wire rod products.

[0012] High-carbon steel wire rod products have stringent requirements regarding impurity elements, inclusions, composition, and microstructure uniformity, particularly for high-grade applications such as automotive suspension springs, high-grade cord steel and diamond wire, and high-strength bridge cable steel. Therefore, in order to obtain high-quality high-carbon steel products under the conditions of a high-scrap steel ratio smelting mode in an electric furnace process, it is necessary to comprehensively study and design the electric furnace manufacturing process by controlling the content of impurity elements, the type and size of inclusions, the microstructure uniformity of the composition, and the surface quality of the wire rod. Surface analysis results show that brittle inclusions and large silicate inclusions are important factors that cause a decrease in the quality and performance of high-carbon steel products. Therefore, in order to prevent the formation of hard inclusions such as alumina, magnesium aluminum spinel, and titanium nitride, it is necessary to control the content of Al, Ti, and N in the molten steel, and it is also necessary to control inclusions formed by deoxidation products and reactions between slag and metal through both plasticization and miniaturization. Furthermore, to reduce quality issues such as cold and hot brittleness of the product, it is necessary to control the content of P and S. It is also necessary to precisely control the wire rod composition, microstructure uniformity, and surface quality. These are mainly controlled by the continuous casting and rolling processes. In the continuous casting process, by controlling the degree of superheating of the molten steel, the strength of the cooling water, and the reduction process, a casting billet with high compositional uniformity is obtained. Furthermore, problems such as segregation, network cementite, and surface quality are reduced through split polishing, controlled rolling, and controlled cooling technologies. In addition, high-purity, high-quality, and low-carbon emission high-carbon steel wire rods are obtained. [Overview of the project]

[0013] To solve the above problems, the present invention discloses high-purity, high-carbon steel and a low-carbon emission production method thereof, the specific technical means being as follows.

[0014] High-purity high-carbon steel is provided. In addition to Si, Mn, Cr, V alloy elements and Fe element, the high-purity high-carbon steel further contains, by mass percentage, C: 0.5 - 1.0%, P: ≤0.006%, S: ≤0.0035%, T.O: ≤0.0010%, N: ≤0.0030%, H: ≤0.0002%, Alt: ≤0.0015%, Ti: ≤0.0008%, Ni: ≤0.02%, Cu: ≤0.015%, Mo: ≤0.005%, Sn: ≤0.010%, As: ≤0.008%.

[0015] Furthermore, the inclusions in the high-purity high-carbon steel are mainly SiO2-MnO-based low-melting-point inclusions, and the number density of inclusions with a size of 1 μm or more is ≤5 pieces / mm 2 and the number density of inclusions with a size of 5 μm or more is ≤0.12 pieces / mm 2 and the maximum dimension of inclusions in the transverse direction is ≤15 μm, the grades of inclusions in the longitudinal direction of A, B, C, D systems are all ≤1 class, and the dimension of brittle inclusions is ≤5 μm.

[0016] Furthermore, the casting billet of the high-purity high-carbon steel has a C segregation degree of 0.96 - 1.04, no crack defects, in the metal structure of the wire rod, by volume percentage, sorbite and pearlite ≥97%, the crystal grain size is 8 - 10 grades, in the most severe segregation region and other matrix regions in the cross-section of the wire rod, by mass percentage, the carbon content ≤1.04, the Si content ≤1.15, the Mn content ≤1.12, the Cr content ≤1.10, the V content ≤1.15, and the hardness difference ≤25 HV.

[0017] Furthermore, in the low-carbon emission production method, the total C emission in steelmaking, continuous casting, and steel rolling is less than 180 kg / ton steel.

[0018] A low-carbon emission production method of high-purity high-carbon steel is provided. The production process flow of the low-carbon emission production method includes electric furnace smelting - RH vacuum treatment - large square billet continuous casting - block grinding - high-speed wire rod rolling - Stelmor air cooling - finished product wire rod forming, specifically including the following steps 1 - 7.

[0019] In Step 1, electric furnace smelting is carried out. Scrap steel is charged into the electric furnace and smelted until it completely becomes molten steel. The charging amount of the electric furnace is 115 ± 5 t, and the molten steel residue rate is 15 - 30%. High-quality scrap steel is selected for smelting, and all the electricity used is derived from hydroelectric power or solar power generation.

[0020] In Step 2, steel is tapped from the electric furnace. During the tapping process, a slide gate plate is used to stop the slag. At the start of tapping, a preliminary deoxidation method is selected according to the C content in the molten steel. When the C content ≤ 0.35%, first, 10 - 20% of low-nitrogen carburizer and 20 - 30% of metallic manganese are added to the ladle for preliminary deoxidation. Bottom blowing is not carried out during the tapping process, and after tapping, the bottom blowing flow rate is controlled at 400 - 800 NL / min. When the C content > 0.35%, tapping is carried out with boiling, and the bottom blowing flow rate is set at 200 - 300 NL / min throughout the tapping process. When the tapping rate reaches 90%, silicon carbide, synthetic slag, and lime are added to carry out slag deoxidation and slag formation. After tapping, the molten steel is transported for RH treatment.

[0021] In Step 3, RH furnace refining is carried out. The RH arrival temperature is set at ≥ 1595°C. After reaching RH, rapid vacuum pumping treatment is carried out, and then deoxidation and desulfurization treatments are carried out. After the washing and circulation treatment, the vacuum is broken and steel is tapped, and it is transported to the continuous casting platform and left standing for 8 minutes or more before starting casting.

[0022] In Step 4, continuous casting of square billets is used, protective casting is performed throughout the entire continuous casting process, a high-basicity, low-alumina tundish coating is used, an electromagnetic induction heating device for the tundish is used to control the fluctuation range of the molten steel superheating temperature in the tundish to ≤5°C, the tundish superheating temperature is set to 15-40°C, casting is performed with an integrated immersion nozzle, the insertion depth of the immersion nozzle is set to 10-15 mm, and the electromagnetic stirring current of the crystallizer is set to 500-900 A. The frequency is set to 6-8 Hz, the taper of the crystallizer is adjusted to 1.05-1.15% according to the alloy element content, the continuous casting and wire drawing speed is controlled to 0.50-0.65 m / min, and the reduction amount of the cast billet is controlled to 15-28 mm, thereby setting the degree of carbon segregation in the cast billet to 0.96-1.04, and the cast billet is subjected to hot loading and hot conveying, resulting in a billet surface temperature of ≥450°C and a corner temperature of ≥400°C.

[0023] In step 5, clump polishing is performed to control the surface quality.

[0024] In step 6, high-speed wire rolling is performed to improve decarburization of the surface layer.

[0025] In step 7, Stermore air cooling is performed to control the cooling intensity and improve the structure and performance.

[0026] Furthermore, in step 1, the electric furnace is energized to raise the temperature, lime is added in the initial stages of smelting, light calcination and slag formation are performed, and the mixture is stirred while bottom blowing is carried out, with an argon gas bottom blowing flow rate of 5-10 Nm 3 Set the flow rate to / min, and after all the scrap steel has melted, lime is added in batches, followed by light calcination, pelletization, and slag formation. After the scrap steel has melted, the bottom-blowing gas is switched to oxygen gas, and the bottom-blowing oxygen gas flow rate is set to 30-60 Nm. 3 Set the oxygen injection time to / min and adjust it according to the Al, Ti, and Si content in the scrap steel. Throughout the entire smelting process, argon gas is injected from the side wall using a lance, with a flow rate of 2-5 Nm³. 3The flow rate is set to / min, and during the oxygen gas bottom blowing process, lime is added, light calcination, pelletization, temperature adjustment, and dephosphorization are performed to bring the T.Fe content in the slag to 15-25%. Foam slag is formed by bottom blowing of oxygen gas, stirring is intensified to promote slag flow in the process and enhance dephosphorization, and the power supply is controlled to control the molten steel temperature to 1520-1550°C. After bringing the P content in the molten steel to 0.005% or less, the slag is discharged, and after slag discharge is completed, lime is added, light calcination, pelletization, and slag formation are performed to control the basicity of the slag to 5.0 or higher, the TFe content to 8-15%, bottom blowing of oxygen gas is stopped, and the flow rate is switched back to argon gas at 5-10 Nm³. 3 The process involves setting the flow rate to / min, applying high power to raise the temperature, adding an appropriate amount of low-nitrogen carburizing agent to adjust the carbon content in the molten steel, raising the temperature of the molten steel to 1645°C or higher, setting the carbon content to 0.10-0.50%, the oxygen content to ≤0.03%, and then tapping the steel.

[0027] Furthermore, in step 2, during the process of tapping steel from the electric furnace, 1.0 to 2.0 kg / t of silicon carbide, 10 to 12 kg / t of synthetic slag, and 1.5 to 3.5 kg / t of lime are added.

[0028] Furthermore, in step 3, the rapid vacuuming process after reaching RH is specifically performed by sequentially turning on three water-sealed pumps and E4, E3, E2, and E1 steam pumps, reducing the operating pressure of the vacuum chamber to below 1 mbar within 5 minutes, and increasing the rising gas flow rate to 200-250 Nm 3 The solution is to set the time to / min and the deep vacuum processing time to ≥20 min.

[0029] Furthermore, in step 3, the deoxidation treatment is specifically carried out according to the target composition: if the C content is ≥ 0.35%, first, spontaneous decarbonization and deoxidation are performed for 5 minutes or more under deep vacuum; if the C content is < 0.35%, a low nitrogen carbonizer is added according to the target value of 0.45% and deoxidation is performed for 5 minutes or more; then, silicon carbide is added and deoxidation is continued; a sample is taken and the composition is examined; and based on the composition examination results, one or more of the low nitrogen carbonizer, ultrapure silicon, metallic manganese, ferrochrome, and ferrovanadium are added to form an alloy and achieve the target composition.

[0030] The desulfurization process specifically involves continuing deep vacuum treatment for 5 minutes or more after alloying is complete, then switching off the three water-sealed pumps and the E4 steam pump, lowering the ladle by 15-25 cm, raising the vacuum chamber pressure to over 20 mbar, and increasing the rising gas flow rate to 100-120 Nm 3 The process involves reducing the pressure to / min, determining the amount of desulfurizing agent to add according to the sulfur content in the molten steel, performing a washing cycle for ≥5 minutes after the desulfurizing agent has been added in the batch, and then tapping the steel by breaking the vacuum.

[0031] Furthermore, in step 4, continuous casting of rectangular billets is used. The continuous casting machine is a straight-arc rectangular billet continuous casting machine, and the cross-sectional dimensions of the continuously cast billet are 300 mm x 390 mm, with an arc radius of 12.5 m.

[0032] The induction heating power for the tundish is 2500-3500 kW, the tonnage fluctuation range when casting normally in the tundish is ≤1 ton, the tonnage drop range during replacement is ≤5 ton, the water flow rate in the crystallizer is 2700-3000 NL / min, strong cooling is used within 1.5 meters of the secondary cooling zone with a water flow rate of 600-800 NL / min, and slow cooling is used at the rear with a water flow rate of 400-600 NL / min.

[0033] Furthermore, in step 5, if casting is performed using a large rectangular billet after bloc polishing, the continuous casting billet is heated, soaked, and kept warm in a bloc heating furnace. After bloc rolling, a 140mm x 140mm rolled billet is obtained, magnetic particle testing is performed on the rolled billet, and then the entire surface is polished. Areas with obvious flaws on the surface are further spot-polished to achieve an average polishing depth of ≥0.5mm.

[0034] Furthermore, in step 6, high-speed wire rolling is performed, and a high-temperature resistant coating is sprayed onto the surface of the polished rolled billet. If the Si content of the high-carbon steel is ≤0.6%, the coating thickness is set to 0.1-0.3 mm; if the Si content is 0.6-1.0%, the coating thickness is set to 0.3-0.5 mm; and if the Si content is >1.0%, the coating thickness is set to 0.5-1.0 mm.

[0035] The sprayed rolled billet is heated, soaked, and maintained in a steel rolling furnace, heated with natural gas, and the air-fuel ratio is controlled to 9.5-10.1. The bloc rolling temperature of the rolled billet after it exits the furnace is set to 1000-1150°C, the inlet temperature of the finishing mill is set to 850-970°C, and the outlet temperature of the finishing mill is set to 1000-1060°C.

[0036] Furthermore, in step 7, Stermore air cooling is performed, and the rolled wire obtained in the high-speed wire rolling process is cooled using a controlled cooling process by the Stermore air cooling line, controlling the laing temperature of the Stermore air cooling line to 850-950°C.

[0037] Furthermore, the high-quality scrap steel used in the electric furnace includes, but is not limited to, silicon steel, pipeline steel, bridge steel, automotive steel sheets, spring steel, cord steel, and cable steel. Its composition includes P: ≤0.035%, S: ≤0.008%, Ti: ≤0.015%, Ni: ≤0.025%, Cu: ≤0.018%, Mo: ≤0.006%, Sn: ≤0.015%, and As: ≤0.01%, with the remainder typically being C, Si, Al, Mn, and Fe elements.

[0038] Furthermore, the low-nitrogen carburizing agent added during the process of tapping steel from the electric furnace has an N content of ≤0.035% and a C content of ≥99%, with the remainder being unavoidable impurity elements.

[0039] Metallic manganese has a Mn content of ≥98.5%, P content of ≤0.006%, S content of ≤0.003%, Ti content of ≤0.0035%, and Al content of ≤0.005%, with the remainder being iron and unavoidable impurity elements.

[0040] Silicon carbide has a SiC content of ≥98%, with the remaining elements being unavoidable impurities.

[0041] The main components of the synthetic slag added during the tapping process from the electric furnace are CaO: 55-65%, SiO2: 10-20%, CaF2: 3-8%, MnO: 1-3%, MgO: 1-5%, and Al2O3: ≤3%, with the remaining components being unavoidable impurities. Slag is formed by adding synthetic slag and lime. The basicity of the slag is 2.0-3.5, the particle size of the synthetic slag is ≥90% for particles 3mm or smaller, ≥5% for particles 3-5mm, and the remainder for particles 5mm or larger, and the moisture content is ≤1.0%.

[0042] Furthermore, the low-nitrogen carbonizer used in the aforementioned RH has an N content of ≤0.035% and a C content of ≥99%, with the remainder being unavoidable impurity elements.

[0043] Metallic manganese has a Mn content of ≥99%, Ti content of ≤0.003%, Al content of ≤0.005%, P content of ≤0.0065%, and S content of ≤0.0035%, with the remainder being iron and unavoidable impurity elements.

[0044] Silicon carbide has a SiC content of ≥98%, with the remaining elements being unavoidable impurities.

[0045] Ultrapure silicon has a Si content of 80-85%, Al content of ≤0.0035%, Ti content of ≤0.001%, P content of ≤0.005%, and S content of ≤0.0025%, with the remainder being iron and unavoidable impurity elements.

[0046] Ferrochrome has a Cr content of 55-60%, C content of ≤1.8%, S content of ≤0.006%, and P content of ≤0.013%, with the remainder being iron and unavoidable impurity elements.

[0047] Ferrovanadium has a V content of 45 - 50%, a C content of ≤1.6%, a S content of ≤0.005%, and a P content of ≤0.012%, with the balance being iron and inevitable impurity elements.

[0048] The components of the desulfurizing agent include CaO: 70 - 80%, CaF2: 15 - 25%, MgO: 1 - 3%, SiO2: ≤2%, and other inevitable impurity components. The particle size is such that 3 - 8 mm is ≥90%, and it does not exceed 10 mm at most.

[0049] Furthermore, the ladle bricks used for the ladle are high-strength, high-density magnesia-carbon bricks, with a flexural strength of ≥45 MPa, a density of 2.8 - 3.5 g / cm 3 and a porosity of ≤9.0%, an MgO content of ≥85%, a C content of 3 - 8%, an Al2O3 content of ≤3.0%, and the balance being other inevitable components.

[0050] Furthermore, the refractory materials used for the immersion tube and bottom tank of the RH vacuum furnace used for the RH vacuum treatment are mainly high-quality ultra-low-carbon magnesia-chrome bricks, with a flexural strength of ≥48 MPa, a density of 3.2 - 3.6 g / cm 3 and a porosity of ≤8.0%, a C content of ≤1.5%, an MgO content of 85 - 95%, a Cr2O3 content of 5 - 12%, and the rest being inevitable impurity components.

[0051] Furthermore, the components of the high basicity and low alumina tundish coating agent used for the continuous casting include a basicity CaO / SiO2 of 1.2 - 1.5, an Al2O3 content of ≤2%, a CaF2 content of 3 - 8%, an MgO content of 3 - 6%, and other inevitable components.

[0052] The particle size of the magnesium material sprayed on the inner wall of the tundish is such that ≤2 mm is 70 - 80%, 2 - 3 mm is 20% or more, and ≥3 mm is 5% or less. The components include MgO: ≥80%, CaO: 5 - 10%, SiO2: 1 - 3%, and other inevitable components.

[0053] The protective slag of the crystallizer has a melting point of 1000-1100°C, a viscosity of 0.3-0.45 Pa·s, and contains, by mass percentage, C: 15-20%, CaO / SiO2: 0.6-0.8%, Na2O: 10-15%, Al2O3: ≤3%, MgO: ≤1%, CaF2: 3-6%, and other unavoidable impurity components.

[0054] Furthermore, the material of the stopper and nozzle contains magnesium carbon, and the stopper material further contains MgO content of 80-85%, C content of 8-12%, Al2O3 content of ≤1.5%, SiC content of 1-4%, SiO2 content of 2-3%, and other unavoidable impurity components, with a density of 2.4-2.7 g / cm³. 3 It has a porosity of ≤14% and a flexural strength of ≥40MPa.

[0055] The inner wall of the immersion nozzle has a thickness of 5-7 mm and a density of 2.5-2.8 g / cm³. 3 The porosity is ≤13%, the total content of MgO and C is ≥90%, the SiC content is 3-5%, and the rest are unavoidable impurities.

[0056] Furthermore, in the continuous casting process, the continuous casting machine includes 11 tension levelers arranged sequentially along the drawing direction of the billet. The first to fourth tension levelers are distributed in the straightening section, with the pressure of the first tension leveler being 30-40 bar, and the pressure of each tension leveler after it gradually increasing by 5-15 bar. The fifth to eleventh tension levelers are distributed in the horizontal section, with the pressure of the fifth tension leveler being 75-85 bar, and the pressure of each tension leveler after it gradually increasing by 5-10 bar, with the pressure of the tenth and eleventh tension levelers decreasing by 10-20 bar from the pressure of the ninth tension leveler.

[0057] Furthermore, before entering the heating furnace, the rolled billet is sprayed with a protective coating. The coating has a particle size of 120-200 mesh for over 90% of its particles, and its components include calcium silicate, calcium aluminate, magnesium aluminum spinel, zirconia, graphite carbon, and small amounts of alkali metal oxides, inorganic binders, surfactants, etc. It does not decompose at temperatures below 1600°C.

[0058] Furthermore, the rolled billet is heated in a heating furnace. In the preheating section, the furnace temperature is controlled to 750-850°C for 40-60 minutes. In the heating section, the temperature is raised to 900-1100°C for 60-80 minutes. In the soaking section, the temperature is raised to 1100-1250°C for 60-80 minutes.

[0059] Furthermore, using a controlled cooling process with a Stermore line, in the air-cooled line, the airflow of fans 1# to 3# is 100%, the airflow of fans 4# to 7# is 60-80%, the airflow of fans 8# and 9# is 40-50%, and the airflow of the remaining fans is 10-20% on or off.

[0060] Furthermore, a high-purity, high-carbon steel wire rod manufactured by the above method is provided.

[0061] Furthermore, the aforementioned high-purity, high-carbon steel wire rod has a TO content of ≤10 ppm, sorbite and pearlite ≥97%, a C content segregation value of ≤1.04, and its surface is free from defects such as small cracks, pits, blemishes, and scratches, and has no completely decarburized layer. It can be used in the manufacture of high-strength spring steel with a strength of 1600-2200 MPa, bridge cable steel with a strength of 1800-2200 MPa, cord steel with a drawing diameter of 0.05 mm or more, or high-strength diamond wire.

[0062] The present invention further seeks to protect high-purity, high-carbon steel produced by the method of the present invention.

[0063] The present invention further seeks to protect wire rods manufactured from high-purity, high-carbon steel.

[0064] Furthermore, the wire has a TO content of ≤10 ppm, sorbite and perlite ≥97%, a C content segregation value of ≤1.04, and the surface is free of defects such as small cracks, pits, blemishes, and scratches, and there is no total decarburization layer.

[0065] The present invention further seeks protection for high-strength spring steel with a strength of 1600-2200 MPa, bridge cable steel with a strength of 1800-2200 MPa, cord steel with a wire diameter of 0.05 mm or more, or high-strength diamond wire, all manufactured from wire.

[0066] The principle of the smelting process of the present invention is as follows:

[0067] Cord steel requires good drawability and torsional strength, spring steel requires high fatigue resistance, and cable steel has high requirements for material torsional strength. High-carbon steel wire rod products with such high performance requirements have very high demands regarding gas content, cleanliness, segregation, decarburization, and surface quality. In order to obtain high-purity molten steel, highly homogenized cast billets, and high-purity wire rods under low-carbon emission conditions, the present invention innovatively designs a short-process, high-efficiency, low-carbon emission smelting technology consisting of electric furnace-RH vacuum treatment, based on conventional smelting processes.

[0068] First, in the smelting stage, scrap steel raw materials with low content of sulfur, phosphorus, and elements that are difficult to oxidize are selected, and the sulfur content in the molten steel is controlled by light desulfurization and RH desulfurization operations of the molten iron. In the electric furnace, argon gas is blown in from the furnace wall with a lance, and oxygen gas is blown in from the bottom, reducing the intake during the electric furnace smelting stage. By blowing in an appropriate amount of oxygen gas from the bottom, decarburization occurs, generating a large amount of CO gas, further enhancing the denitrification of the molten steel, removing impurity elements such as Al, Ti, and P that have been introduced into the scrap steel, providing chemical heat to the molten steel, and reducing the temperature rise due to the application of electricity. Furthermore, blowing in oxygen gas from the bottom has a very high stirring effect on the molten steel, enabling dephosphorization by stirring while performing high-flow bottom blowing through lime addition, pelletization, and slag formation, thereby achieving ultra-low phosphorus smelting. Impurity elements are completely removed by slag flow and slag discharge operations during the electric furnace smelting process.

[0069] Next, tapping from the electric furnace involves a molten steel retention operation to improve the smelting efficiency of the next charge. In the tapping process, weak deoxidation or boiling tapping is used to ensure a certain amount of oxygen is present in the molten steel, significantly reducing the absorption of nitrogen from the air during the tapping process. After tapping, RH treatment is performed directly. Deoxidation is performed using carbon in the initial stages of RH, and the N content in the molten steel is further reduced by deep vacuum operation. After deoxidation and alloying in the middle and later stages, the oxygen content in the molten steel is removed to an extremely low level. The circulation flow rate and strength of the molten steel are reduced according to process parameter conditions, and the backflow problem of inclusions is mitigated by washing away refractories and turbulence, promoting further floating of inclusions. After tapping by weak deoxidation or boiling in the electric furnace, the molten steel is directly fed into an RH vacuum furnace for treatment. By deoxidizing with carbon, silicon, and manganese, precise control of inclusions can be achieved, mainly by controlling them to SiO2-MnO-based inclusions with a high SiO2 component, precise control of inclusion composition is achieved. The present invention's technology enables the achievement of control targets such as low gas content, low impurity element content, and high cleanliness. The present invention overcomes technical challenges in electric furnace processes, such as high gas and impurity element content and difficulty in controlling cleanliness.

[0070] Furthermore, through bottom-blowing and weak-blowing processes of oxygen gas in the electric furnace, operations such as slag flow and slag discharge reduce the Al, Ti, and P content to extremely low levels. The design of weak deoxidation or boiling slag extraction and high basicity slag enhances the oxidation of Al and Ti elements, adsorbs deoxidation products such as Al and Ti, weakens erosion of the refractory, and reduces the generation of intrinsic or exogenous brittle inclusions such as alumina, magnesium aluminum spinel, titanium oxide, and titanium nitride in subsequent processes. By using three main components—ladle refractories with low alumina content, vacuum furnace refractories, and continuous casting—the source of alumina inclusions is further reduced, the requirements for improving refractory quality are lowered, erosion of the refractory is reduced, and magnesium exogenous inclusions are avoided. According to relevant research, high-melting-point exogenous inclusions such as alumina, magnesium oxide, and magnesium aluminum spinel are significant problems causing wire drawing failure and fatigue failure in high-grade wire products. Therefore, by using a weak circulation stirring mode in the mid- and late stages of the vacuum furnace, continuous high-intensity washing of the refractory material by the molten steel is avoided, small amounts of composite inclusions formed by erosion of the refractory material are further floated and removed, and after the vacuum is broken, the mixture is further gently stirred and allowed to stand to promote the floating of inclusions, thereby obtaining molten steel with high cleanliness.

[0071] Furthermore, in the continuous casting process, inclusions are adsorbed using a high-magnesium spray material, and the floating and removal of inclusions are further promoted by using techniques such as electromagnetic induction heating of the tundish and electromagnetic stirring of the crystallizer. In the continuous casting process, casting is performed using a stable superheating degree in a narrow section, and the appropriate superheating degree is adjusted according to the C and Si content in the molten steel. By lowering the C content, increasing the Si content, and improving the superheating degree to an appropriate level, it is possible to avoid the billet becoming excessively hard due to a low superheating degree, which makes it prone to cracking during reduction or straightening. By improving the superheating degree to an appropriate level, it contributes to reduction, and by appropriately controlling the amount of reduction, the segregation problem of the cast billet can be significantly improved. Although the carbon content is high and the silicon content is low, and the degree of superheating is reduced to an appropriate level, it is still higher than in conventional processes. By using an appropriate reduction process and cooling water volume, the proportion of the liquid phase region in each section is ensured, and by using a mode in which the reduction amount gradually decreases, the total reduction amount is kept constant, weakening central segregation and avoiding problems such as internal cracking caused by excessive reduction. This allows for stable control of the liquid level fluctuations in the crystallizer and avoids the occurrence of slag entrapment problems in the crystallizer. Technologies such as a weak deoxidation process for converter-fired steel and RH vacuum degassing, along with technologies for controlling the cooling intensity during continuous casting and constant wire drawing speed casting, reduce the generation of precipitates.

[0072] Finally, by employing the technical concept of heating at high temperatures and extending the heat retention time, the heating furnace further promotes the uniformity of alloy element diffusion, reducing problems such as segregation and network cementite. Furthermore, by employing overall polishing techniques after billet division, the surface quality problems of the original cast billet are resolved, and by applying high-temperature delamination resistance to the rolled billet, surface decarburization problems of the cast billet are mitigated, improving the uniformity of the microstructure performance. By utilizing controlled rolling and controlled cooling technologies, sorbite and pearlite structures are obtained, martensite and ferrite structures are reduced, and high-cleanliness, high-carbon steel wire rod products are obtained.

[0073] The beneficial effects of the present invention are as follows:

[0074] (1) Compared to the conventional production process for high-carbon steel wire rods, the blast furnace, KR molten iron pretreatment, and LF refining processes are omitted, enabling short-process production. Furthermore, the electric furnace uses only scrap steel, a green electricity energy refining mode, and a high-efficiency carbon deoxidation mode, reducing carbon emissions and alloy consumption during steelmaking. The high-efficiency hot loading and hot conveying mode of continuous casting significantly reduces energy consumption in the steel rolling process. The newly developed short-process production mode for high-carbon steel wire rods has low carbon emissions and low alloy consumption, which is of great significance to environmental protection, cost, and quality.

[0075] (2) In conventional processes for smelting high-quality high-carbon steel wire rods, the desulfurization task is generally mainly performed at the KR and LF refining stations. The present invention shortens the smelting process by omitting the KR and LF refining processes and controlling the sulfur content in the molten steel to an extremely low level in both the electric furnace and RH treatment processes. This effectively avoids slag entrapment and changes in the type of inclusions due to large-scale desulfurization during refining, effectively reduces the size of inclusions, and allows for precise control of the type of inclusions. Furthermore, by omitting the refining process, production efficiency can be greatly improved and smelting costs can be greatly reduced.

[0076] (3) By using a smelting mode in which argon gas is blown in from the side walls for protection and oxygen gas is blown in from the bottom, the increase in nitrogen in the molten steel during the electric furnace smelting process can be effectively controlled. By using a process in which RH treatment is performed directly after tapping by weak deoxidation or boiling in the electric furnace, the problem of nitrogen absorption in the molten steel during the tapping process can be greatly reduced. CO can be generated by utilizing the carbon deoxidation reaction under deep vacuum RH, and the denitrification of the molten steel can be promoted. In addition, bubbles from argon gas blown in with a large rising gas flow rate can also promote denitrification, further reducing the N and O content, which is very advantageous for controlling the N content and the cleanliness of the molten steel.

[0077] (4) The bottom-blowing oxygen gas mode of the electric furnace provides greater stirring strength to the molten steel, higher decarburization and dephosphorization efficiency compared to blowing oxygen gas from the side wall with a lance, removes harmful elements such as Al and Ti introduced into the scrap steel, provides a heat source for the electric furnace smelting process, reduces the energizing time, and since the ladle, RH vacuum furnace, refractory and auxiliary materials for continuous casting are all made of high-purity standard materials, it reduces erosion problems caused by high-carbon and silicate inclusions, effectively controls foreign inclusions, and provides an effective method for suppressing foreign harmful inclusions in high-quality wire rods.

[0078] (5) In designing the entire flow system, the control of each type of impurity element and inclusion in the steel is taken into consideration to reduce the content of impurity elements and gases in the steel, and to significantly reduce the size and number of endogenous and foreign inclusions. Furthermore, by performing RH vacuum treatment directly after tapping steel by weak deoxidation or boiling in an electric furnace, and by using calcium silicate-based stable phase high basicity synthetic slag in the electric furnace tapping process, the transmission of CaO-based inclusions to the molten steel is further reduced, the adsorption of SiO2-based acidic inclusions is enhanced, and by performing deoxidation and alloying under RH vacuum conditions, precise control of inclusions with a high SiO2 component can be achieved.

[0079] (6) By employing process technology that precisely controls the superheating of the molten steel in the tundish and precisely controls the reduction amount in each section, segregation of the cast billet is reduced. By using billet coating protection technology, high temperature and long-term heat retention technology of the heating furnace is implemented to further promote the uniformity of elemental diffusion and effectively control the decarburization problem of the surface of the cast billet. Furthermore, by using the Stermore air cooling control process, the performance of the wire structure is controlled, reducing wire segregation and network cementite problems, and comprehensively improving the quality of the wire.

[0080] The electric furnace of the present invention smelts only scrap steel, then discharges high-carbon steel from the electric furnace at high temperature and smelts with green electricity, thereby reducing the amount of oxygen gas blown into the electric furnace, controlling the scrap steel in the electric furnace, employing low-phosphorus steel smelting technology, and using a technique to control weak deoxidation or no deoxidation by adding some carbon powder and some metallic manganese to the steel discharged from the electric furnace, thereby controlling the oxygen content in the molten steel, reducing the Al and Ti content, and reducing nitrogen absorption in the molten steel. Subsequently, by adding a high-basicity synthetic slag of a specific phase, adsorption to inclusions is enhanced, the type of inclusions is controlled, and the molten steel is directly fed into an RH vacuum furnace without refining, employing stepwise deoxidation in the RH treatment process, first using silicon carbide for deoxidation. By reducing carbon emissions, controlling the total oxygen content and types of inclusions, turning off some steam pumps, reducing the insertion depth of the immersion tubes and the rising gas flow rate, the circulation flow rate is reduced, erosion of refractories is mitigated, inclusion removal is enhanced, and cleanliness is improved. By controlling the physicalization index of the tundish refractories, alloys, and auxiliary material parts, brittle inclusions are reduced. During continuous casting, coatings and protective slag are controlled to adsorb inclusions and improve cleanliness. Continuous casting reduces segregation through techniques such as tundish induction heating, superheat control, crystallizer taper, large reduction ratio, and precise control of cooling water volume. Segregation is also reduced by high-temperature heating, billet protection, increased heating time, and fan airflow control, improving wire rod quality. [Brief explanation of the drawing]

[0081] [Figure 1] This is a flowchart of the present invention. [Modes for carrying out the invention]

[0082] The present invention will be further described below with reference to the drawings and specific embodiments. It should be understood that the following specific embodiments are merely illustrative and do not limit the scope of the present invention.

[0083] High-purity high-carbon steel is provided, which, in addition to Si, Mn, Cr, V alloying elements and Fe elements, further comprises, by mass percentage, C: 0.5~1.0%, P: ≤0.006%, S: ≤0.0035%, TO: ≤0.0010%, N: ≤0.0030%, H: ≤0.0002%, Alt: ≤0.0015%, Ti: ≤0.0008%, Ni: ≤0.02%, Cu: ≤0.015%, Mo: ≤0.005%, Sn: ≤0.010%, and As: ≤0.008%.

[0084] Inclusions in high-purity, high-carbon steel are mainly SiO2-MnO-based low-melting-point inclusions, with a number density of inclusions 1 μm or larger being ≤ 5 inclusions / mm². 2 Therefore, the number density of inclusions larger than 5 μm is ≤ 0.12 inclusions / mm³. 2 The dimensions of the largest transverse inclusion are ≤15 μm, the grades of the longitudinal A, B, C, and D type inclusions are all ≤1 class, and the dimensions of the brittle inclusions are ≤5 μm.

[0085] The cast billets of high-purity, high-carbon steel have a carbon segregation degree of 0.96 to 1.04, are free of crack defects, and in the metal structure of the wire, sorbite and pearlite are ≥97% by volume percentage, the grain size is 8 to 10, and in the most severely segregated region and other matrix regions of the cross-section of the wire, the carbon content is ≤1.04, Si content is ≤1.15, Mn content is ≤1.12, Cr content is ≤1.10, V content is ≤1.15 by mass percentage, and the hardness difference is ≤25HV.

[0086] In low-carbon emission production methods, the total carbon emissions from steelmaking, continuous casting, and steel rolling are less than 180 kg / ton of steel.

[0087] A low-carbon emission production method for high-purity, high-carbon steel is provided, and the production process flow of the low-carbon emission production method includes electric furnace smelting - RH vacuum treatment - large square billet continuous casting - bract grinding - high-speed wire rod rolling - Stermor air cooling - finished wire rod formation, and specifically includes the following steps 1 to 7.

[0088] Step 1 involves electric furnace smelting, where scrap steel is fed into an electric furnace and smelted until it is completely molten. The electric furnace charge capacity is 115 ± 5 tons, and the molten steel residue rate is 15-30%. High-quality scrap steel is selected for smelting, and the electricity used is either hydroelectric or solar power.

[0089] The electric furnace is energized and heated, lime is added in the initial stages of smelting, followed by light calcination and slag formation. The mixture is stirred while bottom blowing is performed, with a bottom blowing argon gas flow rate of 5-10 Nm. 3 Set the flow rate to / min, and after all the scrap steel has melted, lime is added in batches, followed by light calcination, pelletization, and slag formation. After the scrap steel has melted, the bottom-blowing gas is switched to oxygen gas, and the bottom-blowing oxygen gas flow rate is set to 30-60 Nm. 3 Set the oxygen injection time to / min and adjust it according to the Al, Ti, and Si content in the scrap steel. Throughout the entire smelting process, argon gas is injected from the side wall using a lance, with a flow rate of 2-5 Nm³. 3 The flow rate is set to / min, and during the oxygen gas bottom blowing process, lime is added, light calcination, pelletization, temperature adjustment, and dephosphorization are performed to bring the T.Fe content in the slag to 15-25%. Foam slag is formed by bottom blowing of oxygen gas, stirring is intensified to promote slag flow in the process and enhance dephosphorization, and the power supply is controlled to control the molten steel temperature to 1520-1550°C. After bringing the P content in the molten steel to 0.005% or less, the slag is discharged, and after slag discharge is completed, lime is added, light calcination, pelletization, and slag formation are performed to control the basicity of the slag to 5.0 or higher, the T.Fe content to 8-15%, bottom blowing of oxygen gas is stopped, and the flow rate is switched back to argon gas at 5-10 Nm³. 3 The process involves setting the flow rate to / min, applying high power to raise the temperature, adding an appropriate amount of low-nitrogen carburizing agent to adjust the carbon content in the molten steel, raising the temperature of the molten steel to 1645°C or higher, setting the carbon content to 0.10-0.50%, the oxygen content to ≤0.03%, and then tapping the steel.

[0090] High-quality scrap steel used in electric furnaces includes, but is not limited to, silicon steel, pipeline steel, bridge steel, automotive steel sheets, spring steel, cord steel, and cable steel. Its composition typically includes P: ≤0.035%, S: ≤0.008%, Ti: ≤0.015%, Ni: ≤0.025%, Cu: ≤0.018%, Mo: ≤0.006%, Sn: ≤0.015%, and As: ≤0.01%, with the remainder usually being C, Si, Al, Mn, and Fe.

[0091] In Step 2, the molten steel is tapped from the electric furnace, and a slide gate plate is used to stop the slag during the tapping process. At the start of tapping, a preliminary deoxidation method is selected according to the carbon content in the molten steel. If the carbon content is ≤0.35%, preliminary deoxidation is performed by first adding 10-20% low nitrogen carburizer and 20-30% metallic manganese to the ladle, and bottom blowing is not performed during the tapping process. After tapping is completed, the bottom blowing flow rate is controlled to 400-800 NL / min. If the carbon content is >0.35%, the molten steel is tapped by boiling, and the bottom blowing flow rate is set to 200-300 NL / min throughout the entire tapping process. When the tapping rate reaches 90%, 1.0-2.0 kg / t of silicon carbide, 10-12 kg / t of synthetic slag, and 1.5-3.5 kg / t of lime are added to deoxidize the slag and create slag. After tapping is completed, the molten steel is transported for RH treatment.

[0092] Furthermore, the low-nitrogen carburizing agent added during the process of tapping steel from the electric furnace has an N content of ≤0.035% and a C content of ≥99%, with the remainder being unavoidable impurity elements.

[0093] Metallic manganese has a Mn content of ≥98.5%, P content of ≤0.006%, S content of ≤0.003%, Ti content of ≤0.0035%, and Al content of ≤0.005%, with the remainder being iron and unavoidable impurity elements.

[0094] Silicon carbide has a SiC content of ≥98%, with the remaining elements being unavoidable impurities.

[0095] The main components of the synthetic slag added during the tapping process from the electric furnace are CaO: 55-65%, SiO2: 10-20%, CaF2: 3-8%, MnO: 1-3%, MgO: 1-5%, and Al2O3: ≤3%, with the remaining components being unavoidable impurities. Slag is formed by adding synthetic slag and lime. The basicity of the slag is 2.0-3.5, the particle size of the synthetic slag is ≥90% for particles 3mm or smaller, ≥5% for particles 3-5mm, and the remainder for particles 5mm or larger, and the moisture content is ≤1.0%.

[0096] The ladle bricks used are high-strength, high-density magnesia-carbon bricks with a flexural strength of ≥45 MPa and a density of 2.8-3.5 g / cm³. 3 The porosity is ≤9.0%, the MgO content is ≥85%, the C content is 3-8%, the Al2O3 content is ≤3.0%, and the remainder consists of other unavoidable components.

[0097] In step 3, RH furnace refining is performed to reach an RH temperature of ≥1595°C. After reaching RH, a vacuum treatment is quickly performed, followed by deoxidation and desulfurization treatments. After a cleaning and circulation treatment, the vacuum is broken to tap the steel, which is then transported to a continuous casting platform where it is left to stand for 8 minutes or more before casting begins.

[0098] The rapid vacuuming process after reaching RH specifically involves sequentially switching on three water-sealed pumps and E4, E3, E2, and E1 steam pumps to reduce the operating pressure of the vacuum chamber to below 1 mbar within 5 minutes, and increasing the rising gas flow rate to 200-250 Nm. 3 The solution is to set the time to / min and the deep vacuum processing time to ≥20 min.

[0099] Depending on the desired composition, if the carbon content is ≥0.35%, first, natural decarburization and deoxidation are performed under deep vacuum for 5 minutes or more. If the carbon content is <0.35%, a low nitrogen carbonizer is added according to the target value of 0.45%, and deoxidation is performed for 5 minutes or more. Then, silicon carbide is added and deoxidation is continued, samples are taken and the composition is examined, and based on the composition examination results, one or more of the low nitrogen carbonizer, ultrapure silicon, metallic manganese, ferrochrome, and ferrovanadium are added to form an alloy and achieve the target composition.

[0100] The desulfurization process specifically involves continuing deep vacuum treatment for 5 minutes or more after alloying is complete, then switching off the three water-sealed pumps and the E4 steam pump, lowering the ladle by 15-25 cm, raising the vacuum chamber pressure to over 20 mbar, and increasing the rising gas flow rate to 100-120 Nm 3 The process involves reducing the pressure to / min, determining the amount of desulfurizing agent to add according to the sulfur content in the molten steel, performing a washing cycle for ≥5 minutes after the desulfurizing agent has been added in the batch, and then tapping the steel by breaking the vacuum.

[0101] The low-nitrogen carbonizers used in RH have an N content of ≤0.035% and a C content of ≥99%, with the remainder being unavoidable impurity elements.

[0102] Metallic manganese has a Mn content of ≥99%, Ti content of ≤0.003%, Al content of ≤0.005%, P content of ≤0.0065%, and S content of ≤0.0035%, with the remainder being iron and unavoidable impurity elements.

[0103] Silicon carbide has a SiC content of ≥98%, with the remaining elements being unavoidable impurities.

[0104] Ultrapure silicon has a Si content of 80-85%, Al content of ≤0.0035%, Ti content of ≤0.001%, P content of ≤0.005%, and S content of ≤0.0025%, with the remainder being iron and unavoidable impurity elements.

[0105] Ferrochrome has a Cr content of 55-60%, C content of ≤1.8%, S content of ≤0.006%, and P content of ≤0.013%, with the remainder being iron and unavoidable impurity elements.

[0106] Ferrovanadium has a V content of 45-50%, C content of ≤1.6%, S content of ≤0.005%, and P content of ≤0.012%, with the remainder being iron and unavoidable impurity elements.

[0107] The desulfurizing agent consists of CaO: 70-80%, CaF2: 15-25%, MgO: 1-3%, SiO2: ≤2%, and other unavoidable impurities. The particle size is ≥90% between 3 and 8 mm, and does not exceed 10 mm.

[0108] The refractory materials used in the immersion tubes and bottom tanks of RH vacuum furnaces are mainly high-quality ultra-low carbon magnesium-chromium bricks with a flexural strength of ≥48 MPa and a density of 3.2-3.6 g / cm³. 3 The porosity is ≤8.0%, with C: ≤1.5%, MgO: 85-95%, Cr2O3: 5-12%, and the rest being unavoidable impurity components.

[0109] In Step 4, continuous casting of rectangular billets is used. The continuous casting machine is a straight-arc rectangular billet continuous casting machine, and the cross-sectional dimensions of the continuously cast billets are 300 mm x 390 mm, with an arc radius of 12.5 m.

[0110] Protective casting is performed throughout the entire continuous casting process, a high-basicity, low-alumina tundish coating agent is used, and an electromagnetic induction heating device for the tundish is used to control the fluctuation range of the molten steel superheating temperature in the tundish to ≤5°C, maintaining the tundish superheating temperature at 15-40°C, with an induction heating power of 2500-3500KW, a tonnage fluctuation range of ≤1 ton when casting normally in the tundish, and a tonnage drop range of ≤5 tons when replacing the tundish.

[0111] Casting is performed using an integrated immersion nozzle, with an insertion depth of 10-15 mm for the immersion nozzle, the electromagnetic stirring current of the crystallizer set to 500-900 A, the frequency set to 6-8 Hz, the taper of the crystallizer adjusted to 1.05-1.15% according to the alloy element content, the water flow rate of the crystallizer is 2700-3000 NL / min, strong cooling is used within 1.5 meters of the secondary cooling zone with a water flow rate of 600-800 NL / min, and slow cooling is used in the rear section with a water flow rate of 400-600 NL / min.

[0112] By controlling the continuous casting and wire drawing speed to 0.50-0.65 m / min and the reduction amount of the cast billet to 15-28 mm, the carbon segregation degree in the cast billet is set to 0.96-1.04. Hot loading and hot conveying are performed on the cast billet to set the surface temperature of the billet to ≥450°C and the corner temperature to ≥400°C.

[0113] In the continuous casting process, the continuous casting machine includes 11 tension levelers arranged sequentially along the drawing direction of the billet. The first to fourth tension levelers are distributed in the straightening section, with the pressure of the first tension leveler being 30-40 bar, and the pressure of each tension leveler thereafter gradually increasing by 5-15 bar. The fifth to eleventh tension levelers are distributed in the horizontal section, with the pressure of the fifth tension leveler being 75-85 bar, and the pressure of each tension leveler thereafter gradually increasing by 5-10 bar, with the pressure of the tenth and eleventh tension levelers decreasing by 10-20 bar from the pressure of the ninth tension leveler.

[0114] The components of the high-basicity, low-alumina tundish coating used in the aforementioned continuous casting include basicity CaO / SiO2: 1.2-1.5, Al2O3: ≤2%, CaF2: 3-8%, MgO: 3-6%, and other unavoidable components.

[0115] The particle size of the magnesium material sprayed onto the inner wall of the tundish is such that 70-80% are 2mm or smaller, 20% or more are 2-3mm, and 5% or less are 3mm or larger. The composition includes MgO: ≥80%, CaO: 5-10%, SiO2: 1-3%, and other unavoidable components.

[0116] The protective slag of the crystallizer has a melting point of 1000-1100°C, a viscosity of 0.3-0.45 Pa·s, and contains, by mass percentage, C: 15-20%, CaO / SiO2: 0.6-0.8%, Na2O: 10-15%, Al2O3: ≤3%, MgO: ≤1%, CaF2: 3-6%, and other unavoidable impurity components.

[0117] The material of the stopper and nozzle contains magnesium carbon. The stopper's material further contains 80-85% MgO, 8-12% C, ≤1.5% Al2O3, 1-4% SiC, 2-3% SiO2, and other unavoidable impurities, with a density of 2.4-2.7 g / cm³. 3 It has a porosity of ≤14% and a flexural strength of ≥40MPa.

[0118] The inner wall of the immersion nozzle has a thickness of 5-7 mm and a density of 2.5-2.8 g / cm³. 3 The porosity is ≤13%, the total content of MgO and C is ≥90%, the SiC content is 3-5%, and the rest are unavoidable impurities.

[0119] In step 5, when casting with a large rectangular billet, the continuous casting billet is heated, soaked, and maintained in a bloc heating furnace, and after bloc rolling, a 140mm x 140mm rolled billet is obtained. Magnetic particle testing is performed on the rolled billet, and then the entire surface is polished, and any obvious flaws on the surface are further spot polished to make the average polishing depth ≥ 0.5mm.

[0120] In bract rolling, the billet enters the heating furnace, reaches the target temperature, and is then kept warm. In the preheating section, the furnace temperature is controlled to 600-800°C and the heating rate is set to 10-20°C / min. In the heating section, the temperature is raised to 850-1150°C and the heating rate is set to 20-30°C / min. In the soaking section, the temperature is raised to 1150-1250°C and the total time spent in the furnace is 280-320 min. After that, bract rolling is performed, and the bract rolling temperature is set to 1100-1220°C to form a bract-rolled billet into a rectangular billet with a cross-section of 140 mm x 140 mm.

[0121] In step 6, high-speed wire rolling is performed to improve surface decarburization, and a high-temperature resistant coating is sprayed onto the surface of the polished rolled billet. If the Si content of the high-carbon steel is ≤0.6%, the coating thickness is set to 0.1-0.3 mm; if the Si content is 0.6-1.0%, the coating thickness is set to 0.3-0.5 mm; and if the Si content is >1.0%, the coating thickness is set to 0.5-1.0 mm.

[0122] Before entering the heating furnace, the rolled billets are sprayed with a protective coating. The coating has a particle size of 120-200 mesh for over 90% of the particles and contains calcium silicate, calcium aluminate, magnesium aluminum spinel, zirconia, graphite carbon, and small amounts of alkali metal oxides, inorganic binders, and surfactants. It does not decompose at temperatures below 1600°C.

[0123] The rolled billet is placed in a heating furnace and heated. In the preheating section, the furnace temperature is controlled to 750-850°C for 40-60 minutes. In the heating section, the temperature is raised to 900-1100°C for 60-80 minutes. In the soaking section, the temperature is raised to 1100-1250°C for 60-80 minutes.

[0124] The sprayed rolled billet is heated, soaked, and maintained in a steel rolling furnace, heated with natural gas, and the air-fuel ratio is controlled to 9.5-10.1. The bloc rolling temperature of the rolled billet after it exits the furnace is set to 1000-1150°C, the inlet temperature of the finishing mill is set to 850-970°C, and the outlet temperature of the finishing mill is set to 1000-1060°C.

[0125] In step 7, Stermore air cooling is performed to control the cooling intensity, improve the structure and performance, and the rolled wire obtained in the high-speed wire rolling process is subjected to a controlled cooling process using the Stermore air cooling line, controlling the laing temperature of the Stermore air cooling line to 850-950°C.

[0126] In the air-cooling line, the airflow of fans 1# to 3# is 100%, the airflow of fans 4# to 7# is 60-80%, the airflow of fans 8# and 9# is 40-50%, and the airflow of the remaining fans is 10-20% on or off.

[0127] The high-purity, high-carbon steel wire rod produced by the above method has a TO content of ≤10 ppm, sorbite and pearlite ≥97%, a C content segregation value of ≤1.04, and the surface is free from defects such as small cracks, pits, blemishes, and scratches, and there is no complete decarburization layer. It can be used to manufacture high-strength spring steel with a strength of 1600-2200 MPa, bridge cable steel with a strength of 1800-2200 MPa, cord steel with a drawing diameter of 0.05 mm or more, or high-strength diamond wire.

[0128] (Examples) The aforementioned high-purity high-carbon steel further contains, in addition to Si, Mn, Cr, V alloying elements and Fe elements, C: 0.5~1.0%, P: ≤0.006%, S: ≤0.0035%, TO: ≤0.0010%, N: ≤0.0030%, H: ≤0.0002%, Alt: ≤0.0015%, Ti: ≤0.0008%, Ni: ≤0.02%, Cu: ≤0.015%, Mo: ≤0.005%, Sn: ≤0.010%, and As: ≤0.008% by mass percentage.

[0129] The steps of the technical production process of the present invention will be explained using spring steel 55SiCr / 65Mn, cord steel 72A / 82A / 97A, and cable steel 87B / 92Si as examples.

[0130] The chemical composition and mass percentages of spring steel 55SiCr are as follows: C: 0.50-0.60%, Si: 1.35-1.65%, Mn: 0.60-0.80%, Cr: 0.55-0.80%, V: 0.15-0.35%.

[0131] The chemical composition and mass percentages of spring steel 65Mn are C: 0.60-0.70%, Si: 0.20-0.40%, and Mn: 0.90-1.00%.

[0132] The chemical composition and mass percentages of cord steel 72A are C: 0.70-0.78%, Si: 0.15-0.30%, and Mn: 0.50-0.60%.

[0133] The chemical composition and mass percentages of the cord steel 82A are C: 0.78~0.86%, Si: 0.15~0.35%, and Mn: 0.50~0.65%.

[0134] The chemical composition and mass percentages of Cord steel 97A are C: 0.95~1.00%, Si: 0.15~0.30%, and Mn: 0.35~0.45%.

[0135] The chemical composition and mass percentages of cable steel 87B are as follows: C: 0.85~0.90%, Si: 0.45~0.60%, Mn: 0.70~0.85%, Cr: 0.20~0.35%, V: 0.02~0.05%.

[0136] The chemical composition and mass percentages of cable steel 92Si are as follows: C: 0.90-0.95%, Si: 1.1-1.3%, Mn: 0.75-0.90%, Cr: 0.20-0.35%, V: 0.01-0.04%.

[0137] A low-carbon emission production method for high-purity, high-carbon steel is provided, and the production process flow of the low-carbon emission production method includes electric furnace smelting - RH vacuum treatment - large square billet continuous casting - bract grinding - high-speed wire rod rolling - Stermor air cooling - finished wire rod formation, and specifically includes the following steps 1 to 7.

[0138] Step 1 involves electric furnace smelting.

[0139] High-quality scrap steel is fed into an electric furnace for smelting. Throughout the entire smelting process, argon gas is blown in from the side wall using a lance until the steel is completely molten. The electricity used in the electric furnace is either hydroelectric or solar power. In the initial stages of electric furnace smelting, the furnace is heated by applying electricity, lime is added, light calcination and slag are formed, and the furnace is stirred while bottom blowing is performed. Argon gas is blown in from the bottom while stirring is performed. After all the scrap steel has melted, lime is added, light calcination and pelletization and slag are performed in batches. After the scrap steel has melted, the bottom blowing gas is switched to oxygen gas, and the furnace is stirred while oxygen gas is blown in from the bottom. The oxygen gas blowing time is adjusted according to the Al, Ti, and Si content in the scrap steel to remove alloying elements and C elements from the scrap steel. In the process of blowing oxygen gas from the bottom, dephosphorization is performed by adjusting the temperatures of lime addition, light calcination, and pelletization. The high basicity and high oxidation properties of the slag are controlled by lime and pellets, foam slag is formed by blowing oxygen gas from the bottom, and stirring is enhanced to promote slag flow in the process and enhance dephosphorization. By controlling the power supply, the temperature of the molten steel is stabilized in a relatively low temperature range, which is suitable for dephosphorization by the reaction of slag and metal. P-containing slag is discharged by the flow of the slag, and the P content in the molten steel is reduced to 0.005% or less, after which the slag is discharged. After the slag discharge is complete, lime addition, light calcination, pelletization, and slag formation are performed to produce high basicity, medium oxidation slag and continue dephosphorization. At the same time, the blowing of oxygen gas from the bottom is stopped and switched to blowing argon gas, and the temperature is raised by applying a large amount of power. An appropriate amount of low nitrogen carburizer is added to adjust the C content in the molten steel, so that the temperature, C content, and oxygen content of the molten steel reach the target discharge steel.

[0140] High-quality scrap steel used in electric furnaces includes, but is not limited to, silicon steel, pipeline steel, bridge steel, automotive steel sheets, spring steel, cord steel, and cable steel. Its composition typically includes P: ≤0.035%, S: ≤0.008%, Ti: ≤0.015%, Ni: ≤0.025%, Cu: ≤0.018%, Mo: ≤0.006%, Sn: ≤0.015%, and As: ≤0.01%, with the remainder usually being C, Si, Al, Mn, and Fe.

[0141] Table 1 Main parameters of electric furnace smelting of spring steel [Table 1]

[0142] Table 2 Main parameters of the electric furnace smelting endpoint for spring steel [Table 2]

[0143] Table 3 Main parameters of electric furnace smelting of steel for cords [Table 3]

[0144] Table 4 Main parameters of the electric furnace smelting endpoint for steel used for cord. [Table 4]

[0145] Table 5 Main parameters of electric furnace smelting of steel for cables [Table 5]

[0146] Table 6 Main parameters of the electric furnace smelting endpoint for cable steel [Table 6]

[0147] In step 2, the steel is tapped out of the electric furnace.

[0148] In Step 2, a slide gate plate is used to stop the slag during the electric furnace tapping process. At the start of tapping, a preliminary deoxidation method is selected according to the carbon content in the molten steel. If the carbon content is ≤0.35%, first, 10-20% low nitrogen carburizer and 20-30% metallic manganese are added to the ladle to perform preliminary deoxidation. Bottom blowing is not performed during the tapping process, and after tapping is completed, bottom blowing is performed at a moderate to high flow rate while stirring. If the carbon content is >0.35%, tapping is performed by boiling, and bottom blowing is performed at a moderate to low flow rate while stirring. When the tapping rate reaches 90%, silicon carbide, synthetic slag, and lime are added to deoxidize the slag and create slag. After tapping is completed, the molten steel is transported for RH treatment.

[0149] The low-nitrogen carburizing agent added during the tapping process from the electric furnace has an N content of ≤0.035% and a C content of ≥99%, with the remainder being unavoidable impurity elements. The metallic manganese has a Mn element content of ≥98.5%, a P content of ≤0.006%, a S content of ≤0.003%, a Ti content of ≤0.0035%, and an Al content of ≤0.005%, with the remainder being iron and unavoidable impurity elements. The silicon carbide has a SiC content of ≥98%, with the remainder being unavoidable impurity elements. The main components of the synthetic slag are CaO: 55-65%, SiO2: 10-20%, CaF2: 3-8%, MnO: 1-3%, MgO: 1-5%, and Al2O3: ≤3%, with the rest being unavoidable impurities. The particle size of the synthetic slag is ≥90% for particles 3mm or smaller, ≥5% for particles 3-5mm, and the remainder for particles 5mm or larger. The moisture content is ≤1.0%. The ladle bricks used are high-strength, high-density magnesia-carbon bricks with a flexural strength of ≥45MPa and a density of 2.8-3.5g / cm³. 3 The porosity is ≤9.0%, the MgO content is ≥85%, the C content is 3-8%, the Al2O3 content is ≤3.0%, and the remainder consists of other unavoidable components.

[0150] Table 7 Main parameters of electric furnace discharged spring steel [Table 7]

[0151] Table 8 Main parameters of electric furnace discharged steel for cords [Table 8]

[0152] Table 9 Main parameters of electric furnace discharged steel for cable use [Table 9]

[0153] Step 3 involves RH furnace smelting.

[0154] After reaching RH, a vacuum treatment is quickly performed, followed by deoxidation and desulfurization treatment. After a cleaning and circulation treatment, the vacuum is broken to tap the steel, which is then transported to a continuous casting platform where it is left to stand for a certain period of time before casting begins.

[0155] Rapid vacuuming after reaching RH specifically involves sequentially switching on three water-sealed pumps and E4, E3, E2, and E1 steam pumps to rapidly reduce the pressure in the vacuum chamber to an extremely low level, setting a large rising gas flow rate, and controlling the deep vacuum processing time. Depending on the resulting composition, if the C content is ≥0.35%, first, natural decarburization and deoxidation are performed under deep vacuum. If the C content is <0.35%, deoxidation is performed by adding a low nitrogen carburizer according to the target value of 0.45%, and then deoxidation is continued by adding silicon carbide. Sampling is performed to check the composition, and based on the composition check results, one or more of the low nitrogen carburizer, ultrapure silicon, metallic manganese, ferrochrome, and ferrovanadium are added to alloy and achieve the target composition. The desulfurization process specifically involves, after alloying is complete, maintaining a deep vacuum for a certain period of time, then turning off three water-sealed pumps and an E4 steam pump, lowering the ladle, increasing the pressure in the vacuum chamber, decreasing the rising gas flow rate, determining the amount of desulfurizing agent to add according to the sulfur content in the molten steel, and after the addition of the desulfurizing agent in batches is complete, performing a cleaning and circulation, breaking the vacuum, and tapping the steel.

[0156] Low nitrogen carbonizers used in RH have an N content of ≤0.035%, a C content of ≥99%, with the remainder being unavoidable impurity elements. Metallic manganese has an Mn element content of ≥99%, a Ti content of ≤0.003%, an Al content of ≤0.005%, a P content of ≤0.0065%, a S content of ≤0.0035%, with the remainder being iron and unavoidable impurity elements. Silicon carbide has a SiC content of ≥98%, with the remainder being unavoidable impurity elements. Ultrapure silicon has a Si content of 80-85%, an Al content of ≤0.0035%, a Ti content of ≤0.001%, a P content of ≤0.005%, a S content of ≤0.0025%, with the remainder being iron and unavoidable impurity elements. Ferrochrome has a Cr content of 55-60%, a C content of ≤0.0035%. The composition of the refractory material is ≤1.8%, with S content ≤0.006% and P content ≤0.013%, with the remainder being iron and unavoidable impurity elements. The composition of the ferrovanadium is 45-50% V content, ≤1.6% C content, ≤0.005% S content, and ≤0.012% P content, with the remainder being iron and unavoidable impurity elements. The components of the desulfurizer include CaO: 70-80%, CaF2: 15-25%, MgO: 1-3%, SiO2: ≤2%, and other unavoidable impurity components. The particle size is ≥90% between 3-8 mm and does not exceed 10 mm at most. The refractory material used in the immersion tubes and bottom tanks of RH vacuum furnaces is mainly high-quality ultra-low carbon magnesium chromium brick with a flexural strength of ≥48 MPa and a density of 3.2-3.6 g / cm³. 3 The porosity is ≤8.0%, with C: ≤1.5%, MgO: 85-95%, Cr2O3: 5-12%, and the rest being unavoidable impurity components.

[0157] Table 10 Parameters for RH attainment and deep vacuum processing of spring steel [Table 10]

[0158] Table 11 Parameters of spring steel after RH treatment alloying and tapping. [Table 11]

[0159] Table 12 Parameters for RH attainment and deep vacuum processing of steel for cords [Table 12]

[0160] Table 13 Parameters of steel for cord after RH treatment alloying and tapping [Table 13]

[0161] Table 14 Parameters for RH attainment and deep vacuum processing of cable steel [Table 14]

[0162] Table 15 Parameters of cable steel after RH treatment alloying and tapping [Table 15]

[0163] In step 4, continuous casting of large rectangular billets is performed.

[0164] The continuous casting machine is a straight-arc rectangular billet continuous casting machine. The cross-sectional dimensions of the continuous casting billet are 300 mm x 390 mm, and the arc radius is 12.5 m. Protective casting is performed throughout the entire continuous casting process. A high-basicity, low-alumina tundish coating agent is used, and an electromagnetic induction heating device for the tundish is used to control the fluctuation range of the molten steel overheating in the tundish and the overheating of the tundish. The tundish is efficiently replaced, and the stability of the tonnage is controlled during normal casting and tundish replacement. An integrated immersion nozzle is used. By controlling the insertion depth of the immersion nozzle during casting, adjusting the electromagnetic stirring current and frequency of the crystallizer, and increasing the taper of the crystallizer to a range of 1.05-1.15% as the carbon content or alloying element content increases, controlling the water volume of the crystallizer and the nozzle of the secondary cooling zone, casting at a constant wire drawing speed during continuous casting, and controlling the reduction amount, high-quality cast billets are obtained. Hot loading and hot conveying are performed on the cast billets to maintain a surface temperature of ≥450°C and a corner temperature of ≥400°C, thereby reducing the energy consumption of the heating furnace.

[0165] In the continuous casting process, the continuous casting machine includes 11 tension levelers arranged sequentially along the drawing direction of the billet. The first to fourth tension levelers are distributed in the straightening section, with the pressure of the first tension leveler being 30-40 bar, and the pressure of each tension leveler thereafter gradually increasing by 5-15 bar. The fifth to eleventh tension levelers are distributed in the horizontal section, with the pressure of the fifth tension leveler being 75-85 bar, and the pressure of each tension leveler thereafter gradually increasing by 5-10 bar, with the pressure of the tenth and eleventh tension levelers decreasing by 10-20 bar from the pressure of the ninth tension leveler.

[0166] The components of the high-basicity, low-alumina tundish coating used in the aforementioned continuous casting are: basicity CaO / SiO2: 1.2-1.5, Al2O3: ≤2%, CaF2: 3-8%, MgO: 3-6%, and other unavoidable components; the particle size of the magnesium material sprayed onto the inner wall of the tundish is 70-80% 2mm or less, 20% or more 2-3mm, and 5% or less 3mm or larger, and its components are MgO: ≥80%, CaO: 5-10%, SiO2: 1-3%, and other unavoidable components; and the protective slag for the crystallizer has a melting point of 1000-1100°C. The material has a viscosity of 0.3-0.45 Pa·s and contains, by mass percentage, C: 15-20%, CaO / SiO2: 0.6-0.8%, Na2O: 10-15%, Al2O3: ≤3%, MgO: ≤1%, CaF2: 3-6%, and other unavoidable impurities. The material of the stopper and nozzle contains magnesium carbon, and the stopper further contains MgO content of 80-85%, C content of 8-12%, Al2O3 content of ≤1.5%, SiC content of 1-4%, SiO2 content of 2-3%, and other unavoidable impurities, with a density of 2.4-2.7 g / cm³. 3 The porosity is ≤14%, the flexural strength is ≥40MPa, the inner wall of the immersion nozzle is 5-7mm thick, and the density is 2.5-2.8g / cm³. 3 The porosity is ≤13%, the total content of MgO and C is ≥90%, the SiC content is 3-5%, and the rest are unavoidable impurities.

[0167] Table 16 Main parameters of continuous casting tundishes for spring steel [Table 16]

[0168] Table 17 Continuous casting crystallizer and reduction control parameters for spring steel. [Table 17]

[0169] Table 18 Main parameters of continuous casting tundishes for cord steel [Table 18]

[0170] Table 19 Continuous casting crystallizer and reduction control parameters for steel used in cords [Table 19]

[0171] Table 20 Main parameters of continuous casting tundishes for cable steel [Table 20]

[0172] Table 21 Continuous casting crystallizer and reduction control parameters for cable steel [Table 21]

[0173] Step 5 involves performing clump grinding.

[0174] When casting with a large rectangular billet, the continuous casting billet is heated in a bloc heating furnace, the heating rate of the preheating section is set to 10-20°C / min, the heating rate of the heating section is set to 20-30°C / min, then soaking and heat retention are performed, a 140mm x 140mm rolled billet is obtained after bloc rolling, magnetic particle testing is performed on the rolled billet, the entire surface is polished, and any obvious flaws on the surface are further spot polished.

[0175] Table 22 Main process parameters for split polishing of spring steel [Table 22]

[0176] Table 23 Main process parameters for block polishing of steel for cords [Table 23]

[0177] Table 24 Main process parameters for splitting and polishing of steel for cables [Table 24]

[0178] Step 6 involves high-speed wire rolling.

[0179] The decarburization of the surface layer is improved, and a high-temperature resistant coating is sprayed onto the surface of the polished rolled billet. When the Si content of the high-carbon steel is ≤0.6%, the coating thickness is 0.1 to 0.3 mm; when the Si content is 0.6 to 1.0%, the coating thickness is 0.3 to 0.5 mm; and when the Si content is >1.0%, the coating thickness is 0.5 to 1.0 mm.

[0180] Before entering the heating furnace, the rolled billets are sprayed with a protective coating. The coating has a particle size of 120-200 mesh for over 90% of the particles and contains calcium silicate, calcium aluminate, magnesium aluminum spinel, zirconia, graphite carbon, and small amounts of alkali metal oxides, inorganic binders, and surfactants. It does not decompose at temperatures below 1600°C.

[0181] The rolled billet is placed in a heating furnace and heated using natural gas, with the air-fuel ratio controlled to 9.5-10.1. The furnace stay time in the preheating section is 40-60 minutes, the furnace stay time in the heating section is 60-80 minutes, and the furnace stay time in the soaking section is 60-80 minutes, after which the billet is rolled.

[0182] Table 25 Main process parameters for rolling spring steel [Table 25]

[0183] Table 26 Main process parameters for rolling steel for cords [Table 26]

[0184] Table 27 Main process parameters for rolling cable steel [Table 27]

[0185] Step 7 involves performing Stelmore air cooling.

[0186] For the rolled wire obtained in the high-speed wire rolling process, a controlled cooling process using a Stermore air cooling line is employed, and the fan airflow of the Stermore air cooling line is precisely controlled for each section.

[0187] The high-purity, high-carbon steel wire rod produced by the above method has a TO content of ≤10 ppm, sorbite and pearlite ≥97%, a C content segregation value of ≤1.04, and the surface is free from defects such as small cracks, pits, blemishes, and scratches, and there is no complete decarburization layer. It can be used to manufacture high-strength spring steel with a strength of 1600-2200 MPa, bridge cable steel with a strength of 1800-2200 MPa, cord steel with a drawing diameter of 0.05 mm or more, or high-strength diamond wire.

[0188] Table 28 Main process parameters for air cooling of spring steel [Table 28]

[0189] Table 29 Main process parameters for air cooling of steel for cords [Table 29]

[0190] Table 30 Main process parameters for air cooling of steel for cables [Table 30]

[0191] This invention achieves the following:

[0192] (1) Develop a process route that produces high-quality high-carbon steel wire rods in a short number of steps, with a short process flow, low carbon emissions, omitting the blast furnace or reducing the amount of molten iron used, and omitting the LF refining furnace.

[0193] (2) By classifying and selecting scrap steel, the problems of desulfurization and dephosphorization in electric furnaces are solved, and by the process scheme of bottom blowing of oxygen gas in the electric furnace, slag flow, and slag discharge, harmful elements such as Al and Ti are effectively controlled, and control of impurity elements and intrinsic brittle inclusions is ensured.

[0194] (3) The electric furnace uses a mode in which oxygen gas is blown in from the bottom and argon gas is blown in from the side walls to control the problem of nitrogen intake in the electric furnace smelting process, and by performing RH treatment directly after boiling and tapping steel at the end of the electric furnace, the problem of large amounts of gas intake in the deoxidation and alloying processes of the discharged steel in the conventional process is effectively solved, and the conventional LF refining operation of high carbon steel wire rods is canceled to further reduce gas intake, and in the RH process, carbon deoxidation, high vacuum and large flow rate argon injection operations are used to further reduce the nitrogen content in the molten steel, solving the technical challenges of low nitrogen smelting in the electric furnace process.

[0195] (4) In terms of controlling cleanliness, by using a process in which high-carbon steel is boiled in an electric furnace and then directly subjected to RH treatment, and by using RH deep vacuum carbon deoxidation, the number of inclusions generated during the alloying stage can be significantly reduced. Furthermore, by not performing bottom blowing of the ladle during the RH vacuum treatment stage, and by using a synthetic slag with a very weak reaction between the slag and the metal and composed of calcium silicate and dicalcium silicate phases, calcium silicate inclusions can be further prevented from entering the molten steel, and the inclusions in the molten steel can be precisely controlled to be inclusions with a high SiO2 content. Such inclusions have poor wettability with the molten steel and can be easily removed by circulating and stirring the molten steel, thereby significantly improving the cleanliness of the molten steel.

[0196] (5) In terms of controlling foreign inclusions, the source of alumina-based inclusions is reduced by controlling auxiliary materials such as ladles, vacuum tanks, and refractories used in continuous casting, thereby improving the quality of the refractories and reducing the amount of large foreign brittle inclusions caused by erosion of the refractories. Furthermore, inclusions are removed using a variable circulation strength method in the RH process, and low-melting-point acidic inclusions are removed in the initial stages using high vacuum and high rising gas flow rates. Such inclusions have a certain erosive effect on the refractories. By using low-carbon materials for the refractories, deoxidation erosion is reduced, and erosion of the refractories is reduced by using weak circulation stirring in the middle and later stages, promoting the floating of large silicate-based composite inclusions formed by initial erosion. The floating of inclusions is further promoted by soft stirring and standing after vacuum breaking, continuous casting electromagnetic stirring, etc.

[0197] (6) Continuous casting achieves precise reduction control for each section by employing techniques such as stable superheating in narrow sections, matching control of alloy elements and superheating, and constant wire drawing speed casting, thereby reducing segregation of various elements in the cast billet, i.e., reducing the formation of precipitate inclusions, and avoiding problems such as internal cracking due to inappropriate stress distribution.

[0198] (7) The bract rolling process utilizes high temperature and long-duration heating technology to promote uniformity of elemental diffusion and eliminate problems such as elemental segregation. Furthermore, by applying overall polishing of the billet and new coating material technology, decarburization of the wire surface is reduced, and the controlled rolling and controlled cooling processes are optimized to obtain a superior wire with a high content of sorbite and pearlite structures.

[0199] The technical means disclosed in this invention are not limited to the technical means disclosed above, but also include any combination of the technical features described above.

[0200] Those skilled in the art can use the above-described ideal embodiment of the present invention as a revelation and make various changes and modifications without departing from the scope of the technical idea of ​​the present invention. The technical scope of the present invention is not limited to what is described in the specification and should be determined based on the claims.

Claims

1. A low-carbon emission production method for high-purity, high-carbon steel, The aforementioned high-purity high-carbon steel further contains, in addition to Si, Mn, Cr, V alloy elements and Fe elements, C: 0.5-1.0%, P: ≤0.006%, S: ≤0.0035%, T.O: ≤0.0010%, N: ≤0.0030%, H: ≤0.0002%, Alt: ≤0.0015%, Ti: ≤0.0008%, Ni: ≤0.02%, Cu: ≤0.015%, Mo: ≤0.005%, Sn: ≤0.010%, As: ≤0.008%, in addition to Si, Mn, Cr, V alloy elements and Fe elements, by mass percentage. The production process flow of the low-carbon emission production method includes electric furnace smelting - RH vacuum treatment - large rectangular billet continuous casting - bract grinding - high-speed wire rod rolling - Stermor air cooling - finished wire rod formation, and specifically includes the following steps 1 to 7: Step 1 involves electric furnace smelting, where scrap steel is fed into an electric furnace and smelted until it is completely molten. The electric furnace charge is 115 ± 5 tons, and the molten steel residue rate is 15-30%. High-quality scrap steel is selected for smelting, and the electricity used is derived from either hydroelectric or solar power. In step 2, the molten steel is tapped from the electric furnace, and a slide gate plate is used to stop the slag during the tapping process. At the start of tapping, a preliminary deoxidation method is selected according to the carbon content in the molten steel. If the carbon content is ≤0.35%, first, 10-20% low nitrogen carburizer and 20-30% metallic manganese are added to the ladle to perform preliminary deoxidation, and bottom blowing is not performed during the tapping process. After tapping is complete, the bottom blowing flow rate is controlled to 400-800 NL / min. If the carbon content is >0.35%, the molten steel is tapped by boiling, and the bottom blowing flow rate is set to 200-300 NL / min throughout the entire tapping process. When the tapping rate reaches 90%, silicon carbide, synthetic slag, and lime are added to deoxidize the slag and create slag. After tapping is complete, the molten steel is transported for RH treatment. In step 3, RH furnace refining is performed to raise the RH temperature to ≥1595°C, followed by rapid vacuuming after reaching RH, then deoxidation and desulfurization, followed by cleaning and circulation, vacuum breaking to tap the steel, and then transporting it to the continuous casting platform where it is allowed to stand for 8 minutes or more before casting begins. The deoxidation process specifically involves, depending on the target composition, first performing spontaneous deoxidation under deep vacuum for 5 minutes or more if the carbon content is ≥0.35%, adding a low nitrogen carbonizer according to the target value of 0.45% and deoxidizing for 5 minutes or more, then continuing deoxidation by adding silicon carbide, sampling and compositional analysis, and based on the compositional analysis results, adding one or more of the low nitrogen carbonizer, ultrapure silicon, metallic manganese, ferrochrome, and ferrovanadium to form an alloy and achieve the target composition. The desulfurization process specifically involves continuing deep vacuum treatment for 5 minutes or more after alloying is complete, then turning off the three water-sealed pumps and the E4 steam pump, lowering the ladle by 15-25 cm, raising the vacuum chamber pressure to 20 mbar or more, and increasing the rising gas flow rate to 100-120 Nm ３ The process involves reducing the flow rate to / min, determining the amount of desulfurizing agent to add according to the sulfur content in the molten steel, performing a washing cycle for ≥5 min after the addition of the desulfurizing agent in the batch is complete, and then tapping the steel by breaking the vacuum. In step 4, continuous casting of square billets is used, protective casting is performed throughout the entire continuous casting process, a high-basicity, low-alumina tundish coating is used, an electromagnetic induction heating device for the tundish is used to control the fluctuation range of the molten steel in the tundish to ≤5°C, the tundish temperature is set to 15-40°C, casting is performed with an integrated immersion nozzle, the insertion depth of the immersion nozzle is set to 10-15 mm, and the electromagnetic stirring current of the crystallizer is set to 500-900 A. The frequency is set to 6-8 Hz, the taper of the crystallizer is adjusted to 1.05-1.15% according to the alloy element content, the continuous casting and drawing speed is controlled to 0.50-0.65 m / min, and the reduction amount of the cast billet is controlled to 15-28 mm, thereby setting the degree of carbon segregation in the cast billet to 0.96-1.04, hot loading and hot conveying are performed on the cast billet, the surface temperature of the billet is set to ≥450°C, and the corner temperature is set to ≥400°C. In step 5, we perform clump polishing to control the surface quality. In step 6, high-speed wire rolling is performed to improve surface decarburization. Step 7 involves performing Stermore air cooling to control the cooling intensity and improve the structure and performance. A low-carbon emission production method for high-purity, high-carbon steel, characterized by the following features.

2. In step 1, the electric furnace is energized to raise the temperature, lime is added in the initial stages of smelting, light calcination and slag formation are performed, and the mixture is stirred while bottom blowing is carried out, with an argon gas bottom blowing flow rate of 5 to 10 Nm ３ / min, After all the scrap steel has melted, lime is added in batches, followed by light calcination, pelletization, and slag formation. After the scrap steel has melted, the bottom-blowing gas is switched to oxygen gas, and the bottom-blowing oxygen gas flow rate is set to 30-60 Nm. ３ Set the flow rate to / min, adjust the oxygen blowing time according to the Al, Ti, and Si content in the scrap steel, and blow argon gas from the side wall with a lance throughout the entire smelting process, with a flow rate of 2-5 Nm ３ / min, During the oxygen gas bottom blowing process, lime is added, light calcination is performed, pelletization is carried out, temperature is adjusted, and dephosphorization is performed to bring the T.Fe content in the slag to 15-25%, and foam slag is formed by bottom blowing of oxygen gas. Agitation is intensified to promote slag flow during the process and enhance dephosphorization, and the power supply is controlled to control the temperature of the molten steel to 1520-1550°C. After bringing the P content in the molten steel to 0.005% or less, the slag is discharged, and after slag discharge is completed, lime is added, light calcination is performed, pelletization is carried out, and slag formation is performed to control the basicity of the slag to 5.0 or higher, bringing the T.Fe content to 8-15%, bottom blowing of oxygen gas is stopped, and argon gas is switched back, with a flow rate of 5-10 Nm ３ The molten steel is heated by applying high power to the molten steel at a minimum power of / min, an appropriate amount of low-nitrogen carburizing agent is added to adjust the carbon content in the molten steel, the temperature of the molten steel is raised to 1645°C or higher, the carbon content is set to 0.10-0.50%, the oxygen content to ≤0.03%, and then the steel is tapped. A low-carbon emission production method for high-purity, high-carbon steel according to feature 1.

3. In step 2, during the process of tapping steel from the electric furnace, 1.0 to 2.0 kg / t of silicon carbide, 10 to 12 kg / t of synthetic slag, and 1.5 to 3.5 kg / t of lime are added. A low-carbon emission production method for high-purity, high-carbon steel according to feature 1.

4. In step 3, the rapid vacuuming process after reaching RH is specifically performed by sequentially turning on three water-sealed pumps and steam pumps E4, E3, E2, and E1, reducing the operating pressure of the vacuum chamber to 1 mbar or less within 5 minutes, and increasing the rising gas flow rate to 200-250 Nm ３ The solution is to set the processing time to ≥ 20 mins and the deep vacuum processing time to ≥ 20 mins. A low-carbon emission production method for high-purity, high-carbon steel according to feature 1.

5. In step 4, continuous casting of rectangular billets is used. The continuous casting machine is a straight-arc rectangular billet continuous casting machine, and the cross-sectional dimensions of the continuously cast billet are 300 mm x 390 mm, with an arc radius of 12.5 m. The induction heating power for the tundish is 2500-3500 kW, the tonnage fluctuation range when casting normally in the tundish is ≤1 ton, the tonnage drop during replacement is ≤5 ton, the water flow rate in the crystallizer is 2700-3000 NL / min, strong cooling is used within 1.5 meters of the secondary cooling zone with a water flow rate of 600-800 NL / min, and slow cooling is used at the rear with a water flow rate of 400-600 NL / min. A method for producing a low-carbon series of high-purity, high-carbon steel according to feature 1.

6. In step 5, when casting with a large rectangular billet after bloc grinding, the continuous casting billet is heated, soaked, and maintained in a bloc heating furnace, and after bloc rolling, a 140 mm x 140 mm rolled billet is obtained. Magnetic particle testing is performed on the rolled billet, and then the entire surface is polished, and any obvious flaws on the surface are further spot-polished to make the average polishing depth ≥ 0.5 mm. A low-carbon emission production method for high-purity, high-carbon steel according to feature 1.

7. In step 6, high-speed wire rolling is performed, and a high-temperature resistant coating is sprayed onto the surface of the polished rolled billet. If the Si content of the high-carbon steel is ≤0.6%, the coating thickness is set to 0.1 to 0.3 mm; if the Si content is 0.6 to 1.0%, the coating thickness is set to 0.3 to 0.5 mm; and if the Si content is >1.0%, the coating thickness is set to 0.5 to 1.0 mm. The sprayed rolled billet is heated, soaked, and maintained in a steel rolling furnace, heated with natural gas, and the air-fuel ratio is controlled to 9.5 to 10.

1. The bloc rolling temperature of the rolled billet after it exits the furnace is set to 1000 to 1150°C, the inlet temperature of the finishing mill is set to 850 to 970°C, and the outlet temperature of the finishing mill is set to 1000 to 1060°C. A low-carbon emission production method for high-purity, high-carbon steel according to feature 1.

8. In step 7, Stermore air cooling is performed, and the rolled wire obtained in the high-speed wire rolling process is cooled using a controlled cooling process with a Stermore air cooling line, controlling the laing temperature of the Stermore air cooling line to 850-950°C. A low-carbon emission production method for high-purity, high-carbon steel according to feature 1.

9. The high-quality scrap steel used in the aforementioned electric furnace includes, but is not limited to, silicon steel, pipeline steel, bridge steel, automotive steel sheets, spring steel, cord steel, and cable steel. Its composition is typically P: ≤0.035%, S: ≤0.008%, Ti: ≤0.015%, Ni: ≤0.025%, Cu: ≤0.018%, Mo: ≤0.006%, Sn: ≤0.015%, As: ≤0.01%, with the remainder being C, Si, Al, Mn, and Fe. A low-carbon emission production method for high-purity, high-carbon steel according to feature 1.

10. The low-nitrogen carburizing agent added during the process of tapping steel from an electric furnace has an N content of ≤0.035% and a C content of ≥99%, with the remainder being unavoidable impurity elements. Metallic manganese has a Mn content of ≥98.5%, P content of ≤0.006%, S content of ≤0.003%, Ti content of ≤0.0035%, and Al content of ≤0.005%, with the remainder being iron and unavoidable impurity elements. Silicon carbide has a SiC content of ≥ 98%, with the rest being unavoidable impurity elements. In the process of steel tapping from an electric furnace, the main components of the synthetic slag added are: CaO: 55 - 65%, SiO ２ : 10 - 20%, CaF ２ : 3 - 8%, MnO: 1 - 3%, MgO: 1 - 5%, Al ２ O ３ : ≤ 3%, and the rest are inevitable impurity components, Slag formation was carried out by adding synthetic slag and lime. The basicity of the slag was 2.0 to 3.5, the particle size of the synthetic slag was ≥90% for particles 3 mm or smaller, ≥5% for particles between 3 and 5 mm, and the remainder for particles 5 mm or larger, and the moisture content was ≤1.0%. A low-carbon emission production method for high-purity, high-carbon steel according to feature 1.

11. In terms of mass percentage, the low nitrogen carbonizer used in the RH has an N content of ≤0.035% and a C content of ≥99%, with the remainder being unavoidable impurity elements. Metallic manganese has a Mn content of ≥99%, Ti content of ≤0.003%, Al content of ≤0.005%, P content of ≤0.0065%, and S content of ≤0.0035%, with the remainder being iron and unavoidable impurity elements. Silicon carbide has a SiC content of ≥ 98%, with the rest being unavoidable impurity elements. Ultrapure silicon has a Si content of 80-85%, Al content of ≤0.0035%, Ti content of ≤0.001%, P content of ≤0.005%, and S content of ≤0.0025%, with the remainder being iron and unavoidable impurity elements. Ferrochrome has a Cr content of 55-60%, C content of ≤1.8%, S content of ≤0.006%, and P content of ≤0.013%, with the remainder being iron and unavoidable impurity elements. Ferrovanadium has a V content of 45-50%, C content of ≤1.6%, S content of ≤0.005%, and P content of ≤0.012%, with the remainder being iron and unavoidable impurity elements. The components of the desulfurizing agent are CaO: 70-80%, CaF ２ :15~25%, MgO:1~3%, SiO ２ It contains ≤2% and other unavoidable impurities, with particle size ≥90% being between 3 and 8 mm and not exceeding 10 mm. A low-carbon emission production method for high-purity, high-carbon steel according to feature 1.

12. The ladle bricks used in the ladle are high-strength, high-density magnesia-carbon bricks with a flexural strength of ≥45 MPa and a density of 2.8–3.5 g / cm³. ３ The porosity is ≤9.0%, and the mass percentage is MgO content ≥85%, C content 3-8%, Al ２ O ３ The content is ≤3.0%, and the remainder consists of other unavoidable components. A low-carbon emission production method for high-purity, high-carbon steel according to feature 1.

13. The refractory material used in the immersion tubes and bottom tank of the RH vacuum furnace used in the aforementioned RH vacuum processing is high-quality ultra-low carbon magnesium-chromium brick, with a flexural strength of ≥48 MPa and a density of 3.2–3.6 g / cm³. ３ The porosity is ≤8.0%, and the mass percentage is C: ≤1.5%, MgO: 85-95%, Cr ２ O ３ : 5-12%, with the remainder being unavoidable impurities. A low-carbon emission production method for high-purity, high-carbon steel according to feature 1.

14. The components of the high-basicity, low-alumina tundish coating used in the aforementioned continuous casting are CaO / SiO ２ :1.2~1.5, Al ２ O ３ ≤2%, CaF ２ It contains 3-8% of :, 3-6% of MgO, and other unavoidable components. The particle size of the magnesium material sprayed onto the inner wall of the tundish is 70-80% for particles 2 mm or smaller, 20% or more for particles 2-3 mm, and 5% or less for particles 3 mm or larger. The composition is MgO: ≥80%, CaO: 5-10%, SiO ２ : Contains 1-3% and other unavoidable components, The protective slag for the crystallizer has a melting point of 1000-1100°C, a viscosity of 0.3-0.45 Pa·s, and is composed of C: 15-20% and CaO / SiO₂ by mass percentage. ２ :0.6-0.8%, Na ２ O: 10-15%, Al ２ O ３ :≦3%, MgO:≦1%, CaF ２ : Contains 3-6% and other unavoidable impurities. A low-carbon emission production method for high-purity, high-carbon steel according to feature 1.

15. The stopper and nozzle are made of magnesium carbon, with the stopper material containing 80-85% MgO, 8-12% C, and Al. ２ O ３ Content≦1.5%, SiC content 1-4%, SiO ２ It contains 2-3% of the active ingredient, plus other unavoidable impurities, and has a density of 2.4-2.7 g / cm³. ３ The porosity is ≤14%, and the flexural strength is ≥40 MPa. The inner wall of the immersion nozzle has a thickness of 5-7 mm and a density of 2.5-2.8 g / cm³. ３ The porosity is ≤13%, the total content of MgO and C is ≥90%, the SiC content is 3-5%, and the rest are unavoidable impurities. A low-carbon emission production method for high-purity, high-carbon steel according to feature 1.

16. In the continuous casting process described above, the continuous casting machine includes 11 tension levelers arranged sequentially along the drawing direction of the billet. The first to fourth tension levelers are distributed across the orthodontic area, with the pressure of the first tension leveler being 30-40 bar, and the pressure of each subsequent tension leveler gradually increasing by 5-15 bar. The fifth to eleventh tension levelers are distributed horizontally, with the fifth tension leveler having a pressure of 75-85 bar, and each tension leveler behind it gradually increasing by 5-10 bar, so that the pressures of the tenth and eleventh tension levelers decrease by 10-20 bar from the pressure of the ninth tension leveler. A low-carbon emission production method for high-purity, high-carbon steel according to feature 1.

17. In the aforementioned bract rolling process, the billet enters a heating furnace, reaches the target temperature, and is then kept warm. In the preheating section, the furnace temperature is controlled to 600-800°C, and the heating rate is set to 10-20°C / min. In the heating section, the temperature is set to 850-1150°C, and the heating rate is set to 20-30°C / min. In the heating section, the temperature is set to 1150-1250°C, and the total time spent in the furnace is set to 280-320 min. Subsequently, bloc rolling is performed, with the bloc rolling temperature set to 1100-1220°C, to form the bloc-rolled billet into a rectangular billet with a cross-section of 140 mm x 140 mm. A low-carbon emission production method for high-purity, high-carbon steel according to feature 5.

18. The aforementioned rolled billet is sprayed with a protective coating before entering the heating furnace. The coating has a particle size of 120-200 mesh for more than 90% of its composition and contains substances such as calcium silicate, calcium aluminate, magnesium aluminum spinel, zirconia, graphite carbon, and small amounts of alkali metal oxides, inorganic binders, and surfactants, and does not decompose at temperatures below 1600°C. A low-carbon emission production method for high-purity, high-carbon steel according to feature 17.

19. The rolled billet is placed in a heating furnace and heated, In the preheating section, the furnace temperature is controlled to 750-850°C, and the time is set to 40-60 min. In the heating section, the temperature is set to 900-1100°C and the time to 60-80 min. In the heating section, the temperature is set to 1100-1250°C and the time to 60-80 minutes. A low-carbon emission production method for high-purity, high-carbon steel according to feature 17.

20. In step 7, a controlled cooling process using a Stermore line is employed, where the airflow of fans 1# to 3# is 100%, the airflow of fans 4# to 7# is 60-80%, the airflow of fans 8# and 9# is 40-50%, and the airflow of the remaining fans is 10-20% on or off. A low-carbon emission production method for high-purity, high-carbon steel according to feature 1.

21. High-purity, high-carbon steel manufactured by the method described in any one of claims 1 to 20.

22. A wire rod manufactured from high-purity, high-carbon steel as described in claim 21.

23. The aforementioned wire has a T.O content of ≤10 ppm, sorbite and perlite ≥97%, a C content segregation value of ≤1.04, and the surface is free of defects such as small cracks, pits, blemishes, and scratches, and there is no total decarburization layer. The wire material according to feature 22.

24. A high-strength spring steel with a strength of 1600 to 2200 MPa, a bridge cable steel with a strength of 1800 to 2200 MPa, a cord steel with a drawing diameter of 0.05 mm or more, or a high-strength diamond wire, manufactured from the wire material described in claim 23.

25. When high-purity high-carbon steel is spring steel 55SiCr, it further contains, by mass percentage, C: 0.50-0.60%, Si: 1.35-1.65%, Mn: 0.60-0.80%, Cr: 0.55-0.80%, and V: 0.15-0.35%. When high-purity high-carbon steel is used as spring steel 65Mn, it further contains, by mass percentage, C: 0.60-0.70%, Si: 0.20-0.40%, and Mn: 0.90-1.00%. When the high-purity high-carbon steel is cord steel 72A, it further contains, by mass percentage, C: 0.70-0.78%, Si: 0.15-0.30%, and Mn: 0.50-0.60%. When the high-purity high-carbon steel is steel 82A for cords, it further contains, by mass percentage, C: 0.78-0.86%, Si: 0.15-0.35%, and Mn: 0.50-0.65%. When the high-purity high-carbon steel is steel 97A for cords, it further contains, by mass percentage, C: 0.95-1.00%, Si: 0.15-0.30%, and Mn: 0.35-0.45%. When the high-purity high-carbon steel is cable steel 87B, it further contains, by mass percentage, C: 0.85-0.90%, Si: 0.45-0.60%, Mn: 0.70-0.85%, Cr: 0.20-0.35%, and V: 0.02-0.05%. When the high-purity high-carbon steel is cable steel 92Si, it further contains the following mass percentages: C: 0.90-0.95%, Si: 1.1-1.3%, Mn: 0.75-0.90%, Cr: 0.20-0.35%, V: 0.01-0.04%. The high-purity, high-carbon steel according to feature 21.

26. The inclusions in the wire rod manufactured from the aforementioned high-purity high-carbon steel are mainly SiO ２ - These are MnO-based low-melting-point inclusions, and the number density of inclusions 1 μm or larger is ≤ 5 inclusions / mm². ２ Therefore, the number density of inclusions larger than 5 μm is ≤ 0.12 inclusions / mm². ２ The dimensions of the largest transverse inclusion are ≤15 μm, the grades of the longitudinal A, B, C, and D type inclusions are all ≤1 class, and the dimensions of the brittle inclusions are ≤5 μm. A wire rod manufactured from high-purity, high-carbon steel according to feature 22.

27. The aforementioned high-purity, high-carbon steel casting billets have a carbon segregation degree of 0.96 to 1.04 and are free from crack defects. In the metallographic structure of the wire, sorbite and pearlite are ≥ 97% by volume percentage, and the grain size is between 8 and 10. In the most severely segregated region and other matrix regions of the wire cross-section, the mass percentages are: carbon content ≤ 1.04, Si content ≤ 1.15, Mn content ≤ 1.12, Cr content ≤ 1.10, V content ≤ 1.15, and hardness difference ≤ 25 HV. A wire rod manufactured from high-purity, high-carbon steel according to feature 22.

28. The total amount of carbon (C) emitted during steelmaking, continuous casting, and steel rolling is less than 180 kg / ton of steel. A low-carbon emission production method for high-purity, high-carbon steel, characterized by the following features.

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