High-cleanliness high-carbon steel and low-carbon-emission production method therefor

Abstract

High-cleanliness high-carbon steel and a low-carbon-emission production method therefor. The high-cleanliness high-carbon steel comprises the following components in percentage by mass: 0.5-1.0% of C, less than or equal to 0.006% of P, and less than or equal to 0.0030% of N. The low-carbon-emission production method for the steel comprises the steps of smelting in an electric furnace, RH vacuum processing, bloom continuous casting, cogging and grinding, high-speed wire rolling, Stelmor air cooling, and finished product wire rod obtaining. The present invention achieves the control objectives of low C emission, low gas content, low impurity elements, and high cleanliness under the condition of a high steel scrap ratio.

Description

A high-cleanliness high-carbon steel and a low-carbon emission production method thereof Technical Field

[0001] The invention relates to high-cleanliness high-carbon steel and a low-carbon emission production method thereof, belonging to the technical field of steelmaking. Background Art

[0002] As the goal of carbon neutrality progresses, the steel industry is actively seeking manufacturing process technologies and methods to reduce carbon emissions. The electric furnace process, which uses all-scrap steel or a low iron-to-metal ratio (≤30%) for smelting, can eliminate blast furnace ironmaking or reduce iron consumption, significantly reducing carbon emissions. However, when using all-scrap steel or a low iron-to-metal ratio for smelting in an electric furnace, the small amount of iron makes KR desulfurization impossible, placing high pressure on deep desulfurization during refining. Furthermore, the large amount of scrap steel used increases the difficulty of controlling impurity elements such as Al, Ti, and Cu. Furthermore, a high scrap ratio in an electric furnace requires long power-on times, which can easily lead to a significant increase in nitrogen content in the molten steel. Conventional processes have limited RH denitrification capabilities, while the VD denitrification process results in a violent slag-metal reaction, exacerbating refractory corrosion and making inclusions uncontrollable. Consequently, the production ratio of high-quality, high-carbon steel wire products, such as high-strength spring steel, cord steel, and cable steel, is relatively low when using all-scrap steel or a low iron-to-metal ratio in the electric furnace process. Furthermore, the production of high-quality high-carbon steel wire products using only scrap steel or a low iron-to-metal ratio in an electric furnace requires not only controlling the cleanliness of the molten steel but also comprehensively controlling the segregation and cracking of the continuous casting billet, the structure of the wire rod, and the surface quality of the wire rod to obtain high-quality high-carbon steel wire products. To address the above technical issues, the present invention provides a method for producing high-purity high-carbon steel and its low-carbon emissions.

[0003] High-carbon steel wire products come in many varieties and are used in a wide range of applications. Mid- to high-end high-carbon steel products, such as spring steel, cord steel, and cable steel, require extremely stringent control over cleanliness, segregation, cracks, and surface quality during the production process. Springs are important foundational components, widely used in the automotive, machinery, and railway industries. As safety-bearing components, springs are subject to high-cycle alternating loads during service, and their primary mode of failure is fatigue fracture. Numerous studies have shown that for high-strength, high-cycle fatigue springs, gas content, impurity elements, large-sized inclusions, brittle inclusions, segregation, and surface quality are the primary causes of fatigue failure. As the skeleton-like support material in automotive tire rubber, cord steel has extremely high requirements for quality stability. Large-sized inclusions, segregation, and abnormal microstructures are the primary causes of pull-out and torsional strand fractures, severely impacting product quality stability and, in turn, vehicle safety. Bridge cable steel is mainly used in large-scale bridge projects. It is sensitive to phosphorus content, large-size inclusions, segregation, carbon mesh, surface quality, etc. During the drawing process, these defects may cause brittle fracture or torsional fracture, affecting product quality and, in turn, project quality and safety.

[0004] High-quality, high-carbon steel wire rod is typically produced using a lengthy process involving blast furnace (BF) – hot metal pretreatment (KR) – converter (BOF) – refining (LF or LF-VD / RH) – and continuous casting. This is primarily due to the difficulty in reliably controlling impurities, gas content, and inclusions during the EAF smelting process. When using all scrap steel or a low molten iron ratio for smelting, the refining desulfurization pressure is high because KR desulfurization treatment cannot be carried out. Long-term deep desulfurization treatment during refining will increase the molten steel's air intake and cause slag contamination of the molten steel. At the same time, in order to control hard inclusions such as alumina, magnesia spinel, titanium oxide and titanium nitride in the molten steel, high-end wire products have extremely strict control over the Al and Ti contents in the molten steel. At the same time, to stabilize product performance, elements such as Cu, Mo, and Sn also need to be strictly controlled. The increase in the scrap steel ratio makes it more difficult to control impurity elements. In addition, the increase in the scrap steel ratio prolongs the power-on time of electric furnace smelting, resulting in a higher nitrogen content in the molten steel than the converter process. The conventional process RH has poor decarburization ability, while VD has better denitrification ability than RH. However, if VD is used for long-term stirring and degassing, the erosion of the refractory material is aggravated and the slag-metal reaction is intense, which leads to uncontrollable inclusion types and poor molten steel cleanliness. In addition, in order to ensure the quality of high carbon steel wire products, in addition to controlling gas content, impurity elements, etc., it is necessary to strictly control the segregation and cracks of continuous casting billets, wire rod structure and surface quality, so as to obtain high purity and high quality wire products.

[0005] Patent 2022111781023 provides a process for producing medium-quality, thin-gauge carbon tool steel. This process utilizes a low-emission, short-process, endless strip production process, including a quantum electric furnace smelting process, LF refining for off-furnace molten steel refining, VOD or RH refining for off-furnace molten steel refining, and ESP continuous casting and rolling for endless strip production. This effectively combines these production processes to form a novel endless strip production process for producing medium-quality, thin-gauge carbon tool steel and high-carbon steel below the specified specifications. This invention effectively reduces energy consumption and harmful emissions during strip production. However, the electric furnace primarily utilizes a large charge rate and steel is retained after tapping. Because scrap steel types are not categorized, impurity element content cannot be guaranteed, resulting in high levels of impurities such as P, Cu, and Ni in the finished product. Furthermore, the process route utilizes RH or VOD followed by LF refining. During the refining process, extensive bottom blowing and agitation are used, resulting in intense slag-metal reactions, which negatively impacts both inclusion control and cleanliness control in the molten steel.

[0006] Patent 202110338648X discloses a high-cleanliness spring steel and its production method. This method utilizes a process involving deep desulfurization of molten iron, converter dephosphorization, LF refining, RH vacuum refining, and continuous casting. The molten iron is desulfurized to a sulfur content of ≤0.0015%. Converter blowing produces molten steel with a phosphorus content of ≤0.011%. Precise control of bottom blowing during converter tapping and refining is employed. Combined with RH vacuum treatment and tundish induction heating technology, inclusion control is achieved throughout the entire process, resulting in highly clean spring steel wire rod. However, this method utilizes a high-basicity slag system, containing 55-60% CaO and 20-25% SiO₂. Due to the high carbon and silicon content in spring steel, under high-basic conditions, Si reduces Al₂O₃ in the slag or refractory, increasing the alumina content in the molten steel inclusions. This significantly increases the probability of high-melting-point aluminosilicate inclusions and brittle inclusions, adversely affecting the fatigue life of the spring steel.

[0007] Patent 2022109583109 provides a spring steel wire rod and its production method. This process controls the content of impurity elements such as P, S, Al, and Ti, as well as gases, in the molten steel through the smelting process and certain auxiliary materials. Segregation of the ingot is controlled through continuous casting and high reduction. Combined with heating, the overall quality of the spring steel is controlled by shortening the holding time, heating at low temperatures, controlling the furnace atmosphere, and controlling surface decarburization through full grinding. Although this process controls resulfurization through KR and converters, and uses a high-basicity slag system for desulfurization during the refining and vacuum processes, the high-basicity slag system significantly increases the Al2O3 and CaO components in the molten steel, hindering the control of inclusion types. In addition, since it is silicon-manganese deoxidized steel, acidic inclusions have a certain corrosive effect on refractory materials. At the same time, the reduction corrosion of refractory oxides by C in high carbon steel under vacuum is also relatively serious. The method provided by this patent does not provide a control technology method for refractory materials such as vacuum and continuous casting, which is not conducive to the control of foreign large-sized inclusions; at the same time, the continuous casting reduction is simply divided into three sections according to the solidification center. If the reduction amount of a single section is too large, it may cause problems such as cracks inside the ingot; and the use of low holding time and low heating temperature to heat the ingot in the heating furnace is not conducive to the weakening and elimination of element diffusion and segregation; in addition, the use of wire as a strapping tape can easily cause marks and scratches on the surface of the spring coil.

[0008] Patent 2016102603055 provides a smelting process for controlling inclusions in spring steel, including: 1) primary refining in an electric furnace; 2) argon blowing; 3) refining in a LF furnace; 4) refining in a VD furnace; and 5) continuous casting. During the tapping process, the steel is pre-deoxidized using a Si / Mn aluminum-free deoxidation process, along with the use of activated lime, a composite agent, and refined slag. While this effectively controls brittle inclusions in the steel, the slag basicity in the later stages of refining is controlled at 0.7-1.4. Acidic slag severely corrodes the refractory materials in the ladle and continuous casting tundish, easily causing excessive foreign inclusions and impacting the fatigue life of the spring.

[0009] Patent 2018115248243 discloses a hot-rolled spring steel wire rod for ultra-heavy-load die springs and its production method. The method includes converter smelting, LF furnace refining, bloom continuous casting, bloom opening, hot-rolled bloom shot blasting, grinding, bloom heating, controlled rolling, and controlled cooling. The hot-rolled spring steel wire rod for ultra-heavy-load die springs produced by this invention exhibits excellent surface decarburization, internal segregation, and cleanliness control. The processed spring steel wire with a special cross-section can be used to coil ultra-heavy-load die springs. However, the low superheat casting temperature of 10-20°C hinders the removal of inclusions and hinders the reduction and post-press microcrack control of the cast billet. Furthermore, the use of acidic pre-melted refining slag without proper control of refractory materials and auxiliary materials leads to increased refractory erosion and an increase in foreign impurities and inclusions, negatively impacting the overall quality control of high-strength spring steel.

[0010] Patent 2020111278482 provides a 2300MPa wire rod for prestressed steel strand and its production method. Wire rod production proceeds sequentially through the following processes: molten iron pre-desulfurization → converter smelting → refining → bloom continuous casting → blooming → high-speed wire rolling → air cooling → salt bath treatment. The molten steel in the continuous casting tundish is superheated to 12-25°C. Electromagnetic stirring and dynamic soft reduction are used to minimize solidification segregation. A two-pass bloom rolling process is employed, with strong cooling before phase transformation to suppress the formation of network cementite. After salt bath treatment, the wire rod exhibits sorbite ≥95% and network carbon ≤1. However, casting at a low superheat level hinders the control of cracks caused by inclusion uptake and high reduction. After rolling, the ingot undergoes a salt bath treatment, resulting in a lengthy process and high production costs.

[0011] Patent 2021110884598 provides a method for producing deep-drawn high-carbon steel wire rod. The steel's chemical composition is: 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 balance being iron and unavoidable impurities. Continuous casting utilizes specialized mold slag and a large-chamfered mold. High-speed wire heating utilizes high temperatures, controlled holding times, and an oxidizing atmosphere to minimize surface burnout in the heating furnace. The resulting surface cementite network is ≤ 0.5. However, the high-carbon steel wire rod used for this purpose has high impurity levels of P and S, resulting in poor cleanliness. The use of a strong oxidizing atmosphere in the heating furnace can lead to severe surface decarburization of the billet, increasing grinding time and negatively impacting 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 products have stringent requirements for impurity elements, inclusions, composition, and microstructure uniformity, especially for high-end applications such as automotive suspension springs, high-grade cord steel and diamond wire, and high-strength bridge cable steel. Therefore, to achieve high-quality high-carbon steel products under the high scrap ratio smelting conditions of the electric furnace process, comprehensive research and design of the electric furnace process manufacturing process is required to control impurity element content, inclusion type and size, composition and microstructure uniformity, and wire rod surface quality. Analysis shows that brittle inclusions and large-sized silicate inclusions are key factors that degrade the quality and performance of high-carbon steel products. Therefore, controlling the Al, Ti, and N contents in the molten steel is crucial to prevent the formation of hard inclusions such as alumina, magnesia spinel, and titanium nitride. Inclusions formed by deoxidation products and slag-metal reactions also require control from the perspectives of plasticization and size reduction. Furthermore, controlling the P and S contents is crucial to reduce product quality issues such as cold and hot brittleness. At the same time, precise control of the wire rod composition, structural uniformity, and surface quality is also required. This is primarily achieved through the continuous casting and rolling processes. During the continuous casting process, high-composition uniformity ingots are obtained by controlling the superheat of the molten steel, the intensity of the cooling water, and the reduction process. Combined with ingot grinding, controlled rolling, and controlled cooling technologies, segregation, carbon slurry, and surface quality issues are mitigated. This results in high-purity, high-quality, and low-carbon-emission high-carbon steel wire rods.

[0013] Summary of the Invention

[0014] In order to solve the above problems, the present invention discloses a high-cleanliness high-carbon steel and a low-carbon emission production method thereof, and the specific technical solution is as follows:

[0015] A high-cleanliness high-carbon steel. The high-cleanliness high-carbon steel wire rod, in addition to Si, Mn, Cr, V alloy elements and Fe elements, also includes the following chemical components in 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%.

[0016] Furthermore, the inclusions in the high-cleanliness high-carbon steel wire rod are mainly SiO2-MnO type low-melting point inclusions, and the number density of inclusions larger than 1 μm is ≤5 / mm 2 , the number density of inclusions larger than 5μm is ≤0.12 pieces / mm 2 The maximum size of transverse inclusions is ≤15μm, the rating of longitudinal inclusions A, B, C, D, and Ds are all ≤1, and the size of brittle inclusions is ≤5μm.

[0017] Furthermore, the high-cleanliness high-carbon steel ingot has a C segregation index of 0.96-1.04 and no crack defects; in the metallographic structure of the wire rod, the volume percentage of sorbite and pearlite is ≥97%, and the grain size is 8-10; the carbon content ratio of the most severely segregated area and other matrix areas on the cross section of the wire rod is ≤1.04, the Si content ratio is ≤1.15, the Mn content ratio is ≤1.12, the Cr content ratio is ≤1.10, and the V content ratio is ≤1.15, and the hardness difference is ≤25HV.

[0018] Furthermore, the total carbon emissions from steelmaking, continuous casting and steel rolling of the low-carbon emission production method are less than 180kg / ton of steel.

[0019] A method for producing low-carbon emissions of high-purity high-carbon steel, the production process of which includes: electric furnace smelting - RH vacuum - bloom continuous casting - blooming and grinding - high-speed wire rolling - Stelmor air cooling - finished wire rod; specifically, the following steps are included:

[0020] Step 1: Electric furnace smelting: put the scrap steel into the electric furnace for smelting until it is completely molten steel. The furnace loading capacity is 115±5t, and the steel retention rate is 15-30%. High-quality scrap steel is used for smelting, and the electricity used is all derived from hydropower or photovoltaic power generation;

[0021] Step 2: Electric furnace tapping. Slide plates are used to block slag during the tapping process. At the beginning of tapping, the pre-deoxidation method is selected according to the C content of the molten steel. When the C content is ≤0.35%, 10-20% low-nitrogen carburizer and 20-30% metallic manganese are first added to the ladle for pre-deoxidation. Bottom blowing is not turned on during the tapping process. When tapping is completed, the bottom blowing flow rate is controlled at 400-800NL / min. When the C content is greater than 0.35%, boiling tapping is performed, and the bottom blowing flow rate during the entire tapping process is 200-300NL / min. When 90% of the tapping is completed, silicon carbide, synthetic slag, and lime are added to deoxidize and slag the slag. After tapping, the molten steel is transported to RH treatment.

[0022] Step 3: RH furnace refining, RH station temperature ≥ 1595℃, RH station rapid vacuum treatment, then deoxidation and desulfurization treatment, after net circulation treatment, breaking the air and tapping the steel, transported to the continuous casting platform and let it stand for more than 8 minutes before starting casting;

[0023] Step 4: Continuous casting of square billets is adopted, and the continuous casting is protected throughout the casting process. A high-alkalinity, low-alumina tundish covering agent is used. The superheat of the molten steel in the tundish is controlled to fluctuate ≤5°C by electromagnetic induction heating equipment, and the tundish superheat is 15-40°C. An integral submerged nozzle is used for casting, and the submerged nozzle insertion depth is 10-15mm. The crystallizer electromagnetic stirring current is 500-900A, the frequency is 6-8Hz, and the crystallizer taper is adjusted to 1.05-1.15% according to the alloying element content. The continuous casting speed is controlled at 0.50-0.65m / min, the billet reduction is controlled at 15-28mm, and the billet C segregation index is obtained to be 0.96-1.04. The billet is hot charged and hot transported, and the billet surface temperature is ≥450°C, and the corner temperature is ≥400°C.

[0024] Step 5: Open the blank and grind it to control the surface quality;

[0025] Step 6: High-speed wire rolling to improve surface decarburization;

[0026] Step 7: Stelmor air cooling, control cooling intensity, improve structure and performance.

[0027] Furthermore, in step 1, the electric furnace is powered on to heat up, lime is added in the early stage of smelting, slag is lightly burned, bottom blowing is started for stirring, and the bottom blowing argon flow rate is 5-10Nm 3 / min; After all the scrap steel is melted, lime, light burning and pelletizing are added in batches to make slag. After the scrap steel is melted, the bottom blowing is switched to oxygen, and the bottom blowing oxygen flow rate is 30-60Nm 3 / min, adjust the oxygen blowing time according to the Al, Ti and Si content of the scrap steel, open the side wall gun to blow argon during the whole smelting process, and the flow rate is 2-5Nm 3 / min; during the bottom blowing oxygen process, lime, light burning, and pelletizing are added to adjust the temperature and dephosphorize. The T.Fe content in the slag is 15-25%. Foamed slag is made by bottom blowing oxygen and stirring is enhanced to promote slag flow and strengthen dephosphorization. The power supply is controlled to keep the molten steel temperature at 1520-1550℃ and reduce the P content in the molten steel to below 0.005%. Then, the slag is poured. After the slag is poured, lime, light burning, and pelletizing are added to make slag. The slag basicity is controlled to be above 5.0 and the TFe content is 8-15%. The bottom blowing oxygen is stopped and switched to argon blowing again with a flow rate of 5-10Nm 3 / min, high power is applied to increase the temperature, and appropriate amount of low nitrogen recarburizer is added to adjust the C content of the molten steel. When the temperature of the molten steel rises to above 1645℃, the C content is 0.10-0.50%, and the oxygen content is ≤0.03%, steel is tapped.

[0028] Furthermore, in step 2, 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 during steel tapping from the electric furnace.

[0029] Furthermore, in step 3, the RH station rapid vacuum treatment is specifically as follows: turn on the three water ring pumps and E4, E3, E2, and E1 steam pumps in sequence, reduce the vacuum chamber working pressure to below 1 mbar within 5 minutes, and increase the gas flow rate to 200-250 Nm 3 / min, deep vacuum treatment time ≥20min.

[0030] Furthermore, in step 3, the deoxidation treatment is specifically as follows: based on the incoming composition, if the C content is ≥0.35%, natural carbon decarburization and oxygenation are first performed under deep vacuum for more than 5 minutes; if the C content is <0.35%, a low-nitrogen recarburizer is added according to the target value of 0.45% for deoxidation for more than 5 minutes, and then silicon carbide is added to continue deoxidation, and sampling is performed to test the composition. Based on the composition test results, one or more of a low-nitrogen recarburizer, ultrapure silicon, metallic manganese, ferrochrome, and ferrovanadium are added for alloying to achieve the target composition;

[0031] The specific desulfurization treatment is as follows: After the alloying is completed, continue deep vacuum treatment for more than 5 minutes, then turn off the three water ring pumps and E4 steam pump, lower the ladle by 15-25cm, increase the vacuum chamber pressure to more than 20mbar, and increase the gas flow rate to 100-120Nm 3 / min, determine the amount of desulfurizer added according to the S content of molten steel. After the desulfurizer is added in batches, the net circulation should be ≥5min, and the steel can be tapped.

[0032] Furthermore, the step 4 adopts billet continuous casting, the continuous casting machine is a straight arc rectangular billet continuous casting machine, the cross-sectional size of the continuous casting billet is 300mm×390mm, and the arc radius is 12.5m;

[0033] The induction heating power of the tundish is 2500-3500KW. The tonnage fluctuation of the normal pouring tundish is ≤1 ton, and the tonnage drops ≤5 tons when changing tundishes. The water volume of the crystallizer is 2700-3000NL / min. The secondary cooling section adopts strong cooling within 1.5 meters with a water volume of 600-800NL / min, and the latter section adopts slow cooling with a water volume of 400-600NL / min.

[0034] Furthermore, in step 5, when the billet is opened and ground, the continuous casting billet is heated and heat-insulated in a billet opening heating furnace when large square billets are used for casting. After the billet is opened and rolled, a 140mm×140mm rolled billet is obtained. The rolled billet is subjected to magnetic particle inspection, and then the entire surface is ground. The positions with obvious flaws detected on the surface are further repaired, and the average grinding depth is ≥0.5mm.

[0035] Furthermore, in step 6, the surface of the milled billet is sprayed with a high-temperature resistant coating, but when the Si content of the high carbon steel is ≤0.6%, the coating thickness is 0.1-0.3 mm, when the Si content is 0.6-1.0%, the coating thickness is 0.3-0.5 mm, and when the Si content is >1.0%, the coating thickness is 0.5-1.0 mm;

[0036] The sprayed billet is heated and heat-insulated in a steel rolling heating furnace using natural gas for heating, with an air-fuel ratio of 9.5-10.1. The rolling temperature of the billet out of the heating furnace is 1000-1150°C, the finishing rolling inlet temperature is 850-970°C, and the finishing rolling outlet temperature is 1000-1060°C.

[0037] Furthermore, in step 7: Stelmor air cooling, the wire rod obtained in the high-speed wire rolling process is subjected to an air cooling process controlled by a Stelmor air cooling line, and the spinning temperature of the Stelmor air cooling line is controlled at 850-950°C.

[0038] Furthermore, the high-quality scrap steel used in the electric furnace includes but is not limited to silicon steel, pipeline steel, bridge steel, automobile plate, spring steel, cord steel, and cable steel, and its composition includes P≤0.035%, S≤0.008%, Ti≤0.015%, Ni≤0.025%, Cu≤0.018%, Mo≤0.006%, Sn≤0.015%, As≤0.01%, and the rest are conventional C, Si, Al, Mn and Fe elements.

[0039] Furthermore, the low-carbon recarburizer added during steel tapping in the electric furnace has an N content of ≤0.035%, a C content of ≥99%, and the remainder being unavoidable impurity elements;

[0040] Manganese metal contains Mn element content ≥ 98.5%, P content ≤ 0.006%, S content ≤ 0.003%, Ti content ≤ 0.0035%, Al content ≤ 0.005%, and the rest are iron and unavoidable impurity elements;

[0041] The SiC content in silicon carbide is ≥98%, and other unavoidable impurity elements;

[0042] The main components of the synthetic slag added to the electric furnace for steelmaking include: CaO: 55-65%, SiO2 10-20%, CaF2 3-8%, MnO 1-3%, MgO 1-5%, Al2O3≤3%, and other inevitable impurities; synthetic slag and lime are added for slag making, the slag basicity is 2.0-3.5, the synthetic slag particle size is less than or equal to 3mm, accounting for ≥90%, 3-5mm accounting for ≥5%, and the rest is 5mm and above, and the moisture content is ≤1.0%.

[0043] Furthermore, the low-carbon recarburizer used in the RH has an N content of ≤0.035%, a C content of ≥99%, and the rest are unavoidable impurity elements;

[0044] Manganese metal contains Mn element content ≥ 99%, Ti content ≤ 0.003%, Al content ≤ 0.005%, P content ≤ 0.0065%, S content ≤ 0.0035%, and the rest are iron and unavoidable impurity elements;

[0045] The SiC content in silicon carbide is ≥98%, and other unavoidable impurity elements;

[0046] Ultrapure silicon contains 80-85% Si, ≤0.0035% Al, ≤0.001% Ti, ≤0.005% P, ≤0.0025% S, and the remainder is iron and unavoidable impurity elements.

[0047] The Cr content in ferrochrome is 55-60%, the C content is ≤1.8%, the S content is ≤0.006%, the P content is ≤0.013%, and the rest is iron and unavoidable impurity elements;

[0048] The V content in ferrovanadium is 45-50%, the C content is ≤1.6%, the S content is ≤0.005%, the P content is ≤0.012%, and the rest is iron and unavoidable impurity elements;

[0049] Desulfurizer ingredients include: CaO 70-80%, CaF 2 15-25%, MgO 1-3%, SiO2≤2%, and other inevitable impurities, particle size 3-8mm accounts for ≥90%, and the maximum does not exceed 10mm.

[0050] Furthermore, 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 / cm 3 , porosity ≤9.0%, of which MgO content ≥85%, C content 3-8%, Al2O3 content ≤3.0%, and the rest are other inevitable components.

[0051] Furthermore, the refractory materials used in the immersion pipe and bottom tank of the RH vacuum furnace are mainly high-quality ultra-low carbon magnesia-chrome bricks with a flexural strength of ≥48MPa and a density of 3.2-3.6g / cm 3 , porosity ≤8.0%, C content ≤1.5%, MgO: 85-95%, Cr2O3: 5-12, and other inevitable impurity components.

[0052] Furthermore, the composition of the continuous casting high basicity, low alumina tundish covering agent includes: basicity CaO / SiO2 of 1.2-1.5, Al2O3≤2%, CaF2 3-8%, MgO 3-6%, and other inevitable components;

[0053] The particle size of the magnesium spray coating on the inner wall of the tundish is ≤2mm, accounting for 70-80%, 2-3mm accounts for more than 20%, and 3mm and above accounts for ≤5%. The composition includes MgO ≥80%, CaO 5-10%, SiO2 1-3%, and other unavoidable components;

[0054] The mold protection slag has a melting point of 1000-1100°C and a viscosity of 0.3-0.45 Pa•s, and includes the following mass components: C: 15-20%, CaO / SiO2: 0.6-0.8%, Na2O: 10-15%, Al2O3 ≤3%, MgO ≤1%, CaF2: 3-6%, and other inevitable impurity components.

[0055] Furthermore, the stopper rod and nozzle material include magnesium carbon, the stopper rod material also includes MgO content 80-85%, C content 8-12%, Al2O3 content ≤1.5%, SiC content 1-4%, SiO2 content 2-3%, and other inevitable impurity components, with a density of 2.4-2.7g / cm 3 , porosity ≤ 14%, flexural strength ≥ 40MPa;

[0056] The inner wall thickness of the submerged nozzle is 5-7mm, and the density is 2.5-2.8g / cm 3 , porosity ≤13%, composition includes MgO and C total content ≥90%, of which SiC content is 3-5%, and other unavoidable impurity components.

[0057] Furthermore, the continuous casting machine in the continuous casting process includes 11 drawing and straightening machines, which are arranged in sequence along the casting direction, wherein the 1st to 4th drawing and straightening machines are distributed in the straightening section, and the pressure of the 1st drawing and straightening machine is 30-40 bar, and thereafter the pressure of each drawing and straightening machine gradually increases by 5-15 bar; the 5th to 11th drawing and straightening machines are distributed in the horizontal section, and the pressure of the 5th drawing and straightening machine is 75-85 bar, and thereafter each drawing and straightening machine increases to 5-10 bar, and the 10th and 11th drawing and straightening machines reduce the pressure by 10-20 bar under the pressure of the 9th drawing and straightening machine.

[0058] Furthermore, the rolling mill is sprayed with a protective coating before entering the heating furnace. The particle size of the coating is more than 90% in the range of 120-200 mesh. The components include calcium silicate, calcium aluminate, magnesium aluminum spinel, zirconium oxide, graphite carbon and a small amount of alkali metal oxides, inorganic binders, surfactants and other substances. It does not decompose within 1600°C.

[0059] Furthermore, the rolled billet is heated in a heating furnace. In the preheating section, the furnace temperature is controlled at 750-850°C for 40-60 minutes; in the heating section, the temperature is controlled at 900-1100°C for 60-80 minutes; and in the soaking section, the temperature is controlled at 1100-1250°C for 60-80 minutes.

[0060] Furthermore, the Stelmore line is used to control the air cooling process. The air volume of fans 1# to 3# on the air cooling line is 100%, the air volume of fans 4# to 7# is 60-80%, the air volume of fans 8# and 9# is 40-50%, and the air volume of the remaining fans is turned on by 10-20% or turned off.

[0061] Furthermore, the method can produce high-purity high-carbon steel wire rod.

[0062] Furthermore, the high-cleanliness high-carbon steel wire rod has a TO content of ≤10ppm, sorbite and pearlite ≥97%, a C content segregation value ≤1.04, no microcracks, pits, scars, scratches on the surface, and no complete decarburization layer on the surface of the wire rod. It can be used to prepare high-strength spring steel with a strength of 1600-2200MPa, bridge cable steel with a strength of 1800-2200MPa, and cord steel wire or high-strength diamond wire with a drawn diameter of 0.05mm or more.

[0063] The present invention also applies for protection of: high-cleanliness high-carbon steel prepared by the method of the present invention.

[0064] The present invention also applies for protection of: a wire rod made of high-cleanliness high-carbon steel.

[0065] Furthermore, the wire rod has a TO content of ≤10ppm, sorbite and pearlite ≥97%, a C content segregation value of ≤1.04, no microcracks, pits, scars, scratches or defects on the surface, and no complete decarburization layer on the wire rod surface.

[0066] The present invention also applies for protection of: high-strength spring steel with a strength of 1600-2200 MPa, bridge cable steel with a strength of 1800-2200 MPa, cord steel wire or high-strength diamond wire with a drawn diameter of 0.05 mm or more prepared from wire rods.

[0067] The principle of the smelting process of the present invention is as follows:

[0068] Cord steel requires excellent drawing and twisting properties, spring steel requires high fatigue resistance, and cable steel has high torsional requirements. These high-performance high-carbon steel wire products place very high demands on gas content, cleanliness, segregation, decarburization, and surface quality. To achieve high-purity molten steel, highly homogenized ingots, and high-purity wire rods while maintaining low carbon emissions, this invention innovatively designs a short-process, high-efficiency, low-carbon-emission electric furnace-RH vacuum smelting technology based on conventional smelting processes.

[0069] First, during the smelting stage, scrap steel with low sulfur, low phosphorus, and low content of non-oxidizable elements is selected. Combined with light iron desulfurization and RH desulfurization, the sulfur content of the molten steel is controlled. The electric furnace uses side-blowing argon and bottom-blowing oxygen through wall lances to reduce air intake during the smelting phase. The bottom-blowing introduces an appropriate amount of oxygen, which decarburizes and produces a large amount of CO, further enhancing denitrification of the molten steel. It also removes impurities such as Al, Ti, and P introduced from the scrap steel, provides chemical heat to the molten steel, and reduces the need for electrical heating. Furthermore, the bottom-blown oxygen creates a strong agitation effect on the molten steel. Combined with lime and pellet slag formation, this allows for extensive bottom-blowing agitation dephosphorization, enabling ultra-low phosphorus smelting. Combined with slag flow and pouring during the smelting process, impurity elements are more thoroughly removed.

[0070] Secondly, the EAF tapping process utilizes steel retention to prepare for the next heat, improving the efficiency of the next heat. Weak deoxidation or boiling tapping is employed during the tapping process, resulting in a certain amount of oxygen in the molten steel, significantly reducing nitrogen absorption from air. After tapping, the steel is directly fed to the RH furnace. Carbon deoxidation is used in the early stages of the RH furnace, combined with deep vacuum operation, to further reduce the steel's nitrogen content. Deoxidation and alloying in the middle and late stages further reduce the steel's oxygen content to extremely low levels. Process parameters are then used to reduce the steel's circulation flow rate and intensity, mitigating erosion of refractory materials and turbulent inclusion backflow, thereby promoting further inclusion uptake. Weak deoxidation or boiling tapping in the EAF directly into the RH vacuum furnace, utilizing carbon, silicon, and manganese for deoxidation, allows for precise control of inclusion levels, primarily targeting SiO2-MnO inclusions with high SiO2 content. This allows for precise control of inclusion composition. The present technology achieves the control objectives of low gas content, low impurity elements, and high cleanliness. This overcomes technical challenges associated with the EAF process, such as high gas and impurity content and the difficulty in controlling cleanliness.

[0071] Thirdly, through the weak oxygen blowing process at the bottom of the electric furnace, combined with slag flow and slag discharge operations, the Al, Ti, and P contents are reduced to extremely low levels. At the same time, weak deoxidation or boiling steelmaking and high-alkalinity slag system design enhance the oxidation of Al and Ti elements, while adsorbing deoxidation products such as Al and Ti, and reducing the erosion of refractory materials, thereby reducing the formation of endogenous or exogenous brittle inclusions such as alumina, magnesia spinel, titanium oxide, and titanium nitride in subsequent processes. The use of ladle refractory materials, vacuum furnace refractory materials, and continuous casting components with low alumina content further reduces the source of alumina inclusions. At the same time, the quality requirements for refractory materials are improved, refractory erosion is reduced, and magnesium exogenous inclusions are avoided. According to relevant research results, high-melting-point exogenous inclusions such as alumina, magnesia, and magnesia spinel are the key issues causing pull-out fractures and fatigue failures in high-end wire products. Therefore, a weak circulation stirring mode is adopted in the middle and late stages of the vacuum furnace to avoid continuous high-intensity scouring of the refractory by the molten steel, so that a small amount of complex inclusions formed by the erosion of the refractory can be further floated up and removed. After breaking the air, further soft stirring and calming are carried out to promote the floating of inclusions and obtain high-purity molten steel.

[0072] In addition, the continuous casting process utilizes high-magnesium gunning material to absorb inclusions, while electromagnetic induction heating of the tundish and electromagnetic stirring of the mold further promote inclusion removal. The continuous casting process utilizes stable superheat casting within a narrow range, adjusting the appropriate superheat based on the C and Si contents of the molten steel. Low C content and high Si content lead to a moderately increased superheat, avoiding excessive billet hardness due to low superheat, which can easily cause cracks due to reduction or straightening. A moderately increased superheat facilitates reduction, and combined with controlled reduction, can significantly improve billet segregation. High C content and low Si content moderately reduce superheat, but still higher than traditional processes. Appropriate reduction processes and cooling water volumes are used to ensure the proportion of liquid phase zones in each section. A gradually decreasing reduction mode is used to ensure a constant total reduction, reduce center segregation, and avoid problems such as internal cracks caused by excessive reduction. Controlling stable mold liquid level fluctuations can prevent mold slag rolls. The converter steelmaking weak deoxidation process, RH vacuum degassing and other technologies, combined with continuous casting cooling intensity control and constant casting speed casting technology, can reduce the generation of precipitates.

[0073] Finally, the heating furnace utilizes high-temperature heating and extended holding times to further promote uniform diffusion of alloying elements and reduce segregation and carbon lattice issues. Furthermore, full grinding is employed after billet opening to eliminate surface quality issues with the original ingot. High-temperature delamination is employed for the rolled ingot to mitigate surface decarburization and improve microstructure and performance uniformity. Controlled cooling technology is employed to achieve sorbite and pearlite structures, while reducing martensite and ferrite, resulting in a high-cleanliness, high-carbon steel wire rod product.

[0074] The beneficial effects of the present invention are:

[0075] (1) Compared with the conventional high carbon steel wire production process, the blast furnace, KR hot metal pretreatment and LF refining processes are eliminated, and short-process production is realized. At the same time, the electric furnace adopts a full scrap steel green electricity energy smelting mode and a high-efficiency carbon deoxidation mode, which reduces the carbon emissions and alloy consumption of steelmaking; the continuous casting high-efficiency hot charging and hot delivery mode greatly reduces the energy consumption of the rolling process. The developed and designed high carbon steel wire short-process production mode has low carbon emissions and low alloy consumption, which is of great significance to environmental protection, cost and quality.

[0076] (2) Conventional processes are used to smelt high-quality high-carbon steel wire rods. Generally, the desulfurization task is mainly carried out at the KR and LF refining stations. The present invention eliminates the KR and LF refining processes, and controls the S content in the molten steel at an extremely low level in the electric furnace and RH processes. This shortens the smelting process and effectively avoids the changes in slag rolls and inclusion types caused by large-scale desulfurization during refining. It can effectively reduce the size of inclusions and accurately control the type of inclusions. At the same time, eliminating the refining process can greatly improve production efficiency and reduce smelting costs.

[0077] (3) Side wall air blowing protection combined with bottom blowing argon oxygen smelting mode can effectively control the nitrogen increase of molten steel during the electric furnace smelting process. Combined with the weak deoxidation of the electric furnace or the boiling steel-tapping RH treatment process, the problem of nitrogen absorption of molten steel during the steel-tapping process is greatly reduced. The carbon deoxidation reaction under RH deep vacuum is used to produce CO to assist in denitrification of molten steel. At the same time, the argon bubbles blown by the large gas flow rate can also assist in denitrification, further reducing the N and O contents, which is very beneficial to controlling the N content and the cleanliness of molten steel.

[0078] (4) The bottom oxygen blowing mode of the electric furnace has a stronger stirring intensity on the molten steel than the side wall gun oxygen blowing mode, and has a higher decarburization and dephosphorization efficiency. At the same time, it removes harmful elements such as Al and Ti brought in by scrap steel, and provides a heat source for the electric furnace smelting process, reducing the power-on time; combined with the ladle, RH vacuum furnace, continuous casting refractory and auxiliary materials all made of high-purity standard materials, it reduces the erosion problem caused by high carbon and silicate inclusions, effectively controls foreign inclusions, and provides an effective control method for foreign harmful inclusions in high-quality wire.

[0079] (5) The whole process system design takes into account the control of various impurity elements and inclusions in steel, reduces the content of impurity elements and gas in steel, and significantly reduces the size and number of endogenous and exogenous inclusions. On the basis of weak deoxidation in electric furnace or boiling steel-tapping directly to RH vacuum, the electric furnace steel-tapping process adopts calcium silicate-based stable phase high-alkalinity synthetic slag, which further reduces the transmission of CaO-type inclusions into molten steel and enhances the adsorption of SiO2-type acidic inclusions. Deoxidation and alloying are carried out under RH vacuum conditions, which can achieve precise control of high SiO2 component inclusions.

[0080] (6) Adopt precise control of the superheat of the molten steel in the tundish and the segmented precise pressure control process technology to reduce the segregation of the ingot; combine the ingot coating protection technology and implement the high temperature and long-term insulation technology of the heating furnace to further promote the uniform diffusion of elements and effectively control the decarburization problem on the surface of the ingot; and combine the Stelmor air cooling control process to control the microstructure and performance of the wire rod, and reduce the segregation and carbon network problems of the wire rod, thereby comprehensively improving the quality of the wire rod.

[0081] The electric furnace of the present invention adopts all scrap steel for smelting, and then the electric furnace has high carbon and high temperature steelmaking, adopts green electricity smelting, reduces the oxygen blowing amount of the electric furnace; adopts the electric furnace scrap steel control and low phosphorus steel smelting process technology; adds part of carbon powder and part of metal manganese for weak deoxidation or no deoxidation control technology during the electric furnace tapping, controls the oxygen content of molten steel, reduces the Al and Ti contents, and reduces the nitrogen absorption of molten steel; then adds high basicity basicity synthetic slag of a specific phase to enhance the adsorption of inclusions and control the type of inclusions; does not go through refining treatment, directly puts into RH vacuum furnace, adopts step-by-step deoxidation in the RH process, uses silicon carbide for deoxidation first, reduces carbon emissions, controls the total oxygen content and inclusions The types of impurities can be reduced by shutting down some steam pumps, reducing the insertion depth of the immersion tube, increasing the gas flow, etc., so as to reduce the circulation flow, reduce the erosion of refractory materials, strengthen the removal of inclusions, and improve the cleanliness; combine the physical and chemical index control of refractory materials, alloys and auxiliary materials in the middle package to reduce foreign brittle inclusions; control the absorption of inclusions such as covering agents and protective slag in continuous casting to improve the cleanliness; use the technology of middle package induction heating, superheat control, crystallizer taper, large pressure and precise control of cooling water volume in continuous casting to reduce segregation; high temperature heating, billet protection, increased heating time, control of fan air volume, etc. to reduce segregation and improve the quality of wire rod.

[0082] BRIEF DESCRIPTION OF THE DRAWINGS

[0083] FIG1 is a flow chart of the present invention.

[0084] DETAILED DESCRIPTION

[0085] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0086] A high-cleanliness high-carbon steel. The high-cleanliness high-carbon steel wire rod, in addition to Si, Mn, Cr, V alloy elements and Fe elements, also includes the following chemical components in 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%.

[0087] The inclusions in high-cleanliness high-carbon steel wire rod are mainly SiO2-MnO type low melting point inclusions, and the number density of inclusions larger than 1μm is ≤5 / mm 2 , the number density of inclusions larger than 5μm is ≤0.12 pieces / mm 2 The maximum size of transverse inclusions is ≤15μm, the rating of longitudinal inclusions A, B, C, D, and Ds are all ≤1, and the size of brittle inclusions is ≤5μm.

[0088] The C segregation index of high-cleanliness high-carbon steel ingot is 0.96-1.04, with no crack defects; in the metallographic structure of the wire rod, the volume percentage of sorbite and pearlite is ≥97%, and the grain size is 8-10; the carbon content ratio between the most severely segregated area and other matrix areas on the cross section of the wire rod is ≤1.04, Si content ratio ≤1.15, Mn content ratio ≤1.12, Cr content ratio ≤1.10, V content ratio ≤1.15, and the hardness difference is ≤25HV, by mass percentage.

[0089] Low-carbon production methods, the total carbon emissions from steelmaking, continuous casting and rolling are less than 180kg / ton of steel.

[0090] A method for producing low-carbon emissions of high-purity high-carbon steel, the production process of which includes: electric furnace smelting - RH vacuum - bloom continuous casting - blooming and grinding - high-speed wire rolling - Stelmor air cooling - finished wire rod; specifically, the following steps are included:

[0091] Step 1: Electric furnace smelting: put the scrap steel into the electric furnace for smelting until it is completely molten steel. The furnace loading capacity is 115±5t, and the steel retention rate is 15-30%. High-quality scrap steel is used for smelting, and the electricity used is all derived from hydropower or photovoltaic power generation;

[0092] The electric furnace is powered on to heat up. In the early stage of smelting, lime is added and slag is lightly burned. Bottom blowing is started for stirring. The bottom blowing argon flow rate is 5-10Nm 3 / min; After all the scrap steel is melted, lime, light burning and pelletizing are added in batches to make slag. After the scrap steel is melted, the bottom blowing is switched to oxygen, and the bottom blowing oxygen flow rate is 30-60Nm 3 / min, adjust the oxygen blowing time according to the Al, Ti and Si content of the scrap steel, open the side wall gun to blow argon during the whole smelting process, and the flow rate is 2-5Nm 3 / min; during the bottom blowing oxygen process, lime, light burning, and pelletizing are added to adjust the temperature and dephosphorize. The T.Fe content in the slag is 15-25%. Foamed slag is made by bottom blowing oxygen and stirring is enhanced to promote slag flow and strengthen dephosphorization. The power supply is controlled to keep the molten steel temperature at 1520-1550℃ and reduce the P content in the molten steel to below 0.005%. Then, the slag is poured. After the slag is poured, lime, light burning, and pelletizing are added to make slag. The slag basicity is controlled to be above 5.0 and the TFe content is 8-15%. The bottom blowing oxygen is stopped and switched to argon blowing again with a flow rate of 5-10Nm 3 / min, high power is applied to increase the temperature, and appropriate amount of low nitrogen recarburizer is added to adjust the C content of molten steel. When the temperature of molten steel rises to above 1645℃, the C content is 0.10-0.50%, and the oxygen content is ≤0.03%, steel is tapped;

[0093] The high-quality scrap steel used in the electric furnace includes but is not limited to silicon steel, pipeline steel, bridge steel, automobile plates, spring steel, cord steel, and cable steel. The composition includes P≤0.035%, S≤0.008%, Ti≤0.015%, Ni≤0.025%, Cu≤0.018%, Mo≤0.006%, Sn≤0.015%, As≤0.01%, and the rest are conventional C, Si, Al, Mn and Fe elements.

[0094] Step 2: Electric furnace tapping. Slide plates are used to block slag during the tapping process. At the beginning of tapping, the pre-deoxidation method is selected according to the C content of the molten steel. When the C content is ≤0.35%, 10-20% low-nitrogen carburizer and 20-30% metallic manganese are first added to the ladle for pre-deoxidation. Bottom blowing is not turned on during the tapping process. When tapping is completed, the bottom blowing flow rate is controlled at 400-800NL / min. When the C content is greater than 0.35%, boiling tapping is performed, and the bottom blowing flow rate during the entire tapping process is 200-300NL / min. When 90% of the tapping is completed, 1.0-2.0kg / t of silicon carbide, 10-12kg / t of synthetic slag, and 1.5-3.5kg / t of lime are added to deoxidize and slag the slag. After tapping, the molten steel is transported to RH treatment.

[0095] The low carbon recarburizer added during steelmaking in an electric furnace contains ≤0.035% N and ≥99% C, with the remainder being unavoidable impurity elements.

[0096] Manganese metal contains Mn element content ≥ 98.5%, P content ≤ 0.006%, S content ≤ 0.003%, Ti content ≤ 0.0035%, Al content ≤ 0.005%, and the rest are iron and unavoidable impurity elements;

[0097] The SiC content in silicon carbide is ≥98%, and other unavoidable impurity elements;

[0098] The main components of the synthetic slag added to the electric furnace for steelmaking include: CaO: 55-65%, SiO2 10-20%, CaF2 3-8%, MnO 1-3%, MgO 1-5%, Al2O3 ≤ 3%, and other unavoidable impurities. Synthetic slag and lime are added to form the slag. The slag basicity is 2.0-3.5. The synthetic slag particle size is ≤ 3mm, accounting for ≥ 90%, 3-5mm accounting for ≥ 5%, and the rest is 5mm and above. The moisture content is ≤ 1.0%.

[0099] 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 / cm 3 , porosity ≤9.0%, of which MgO content ≥85%, C content 3-8%, Al2O3 content ≤3.0%, and the rest are other inevitable components.

[0100] Step 3: RH furnace refining, RH station temperature ≥ 1595℃, RH station rapid vacuum treatment, then deoxidation and desulfurization treatment, after net circulation treatment, breaking the air and tapping the steel, transported to the continuous casting platform and let it stand for more than 8 minutes before starting casting;

[0101] The specific steps of the RH station rapid vacuum treatment are as follows: open the three water ring pumps and E4, E3, E2, and E1 steam pumps in sequence, reduce the working pressure of the vacuum chamber to below 1mbar within 5 minutes, and increase the gas flow rate to 200-250Nm 3 / min, deep vacuum treatment time ≥20min;

[0102] According to the incoming composition, if the C content is ≥0.35%, first decarburize and deoxidize naturally under deep vacuum for more than 5 minutes; if the C content is <0.35%, add low-nitrogen recarburizer according to the target value of 0.45% for deoxidation for more than 5 minutes, then add silicon carbide to continue deoxidation, and take samples for composition testing. Based on the composition test results, add one or more of low-nitrogen recarburizer, ultra-pure silicon, metallic manganese, ferrochrome, and ferrovanadium for alloying to achieve the target composition;

[0103] The specific desulfurization treatment is as follows: After the alloying is completed, continue deep vacuum treatment for more than 5 minutes, then turn off the three water ring pumps and E4 steam pump, lower the ladle by 15-25cm, increase the vacuum chamber pressure to more than 20mbar, and increase the gas flow rate to 100-120Nm 3 / min, determine the amount of desulfurizer added according to the S content of molten steel, add the desulfurizer in batches, and after the net circulation is ≥5min, break the air and tap the steel;

[0104] The low carbon recarburizer used in RH has a nitrogen content of ≤0.035%, a carbon content of ≥99%, and the rest are unavoidable impurity elements;

[0105] Manganese metal contains Mn element content ≥ 99%, Ti content ≤ 0.003%, Al content ≤ 0.005%, P content ≤ 0.0065%, S content ≤ 0.0035%, and the rest are iron and unavoidable impurity elements;

[0106] The SiC content in silicon carbide is ≥98%, and other unavoidable impurity elements;

[0107] Ultrapure silicon contains 80-85% Si, ≤0.0035% Al, ≤0.001% Ti, ≤0.005% P, ≤0.0025% S, and the remainder is iron and unavoidable impurity elements.

[0108] The Cr content in ferrochrome is 55-60%, the C content is ≤1.8%, the S content is ≤0.006%, the P content is ≤0.013%, and the rest is iron and unavoidable impurity elements;

[0109] The V content in ferrovanadium is 45-50%, the C content is ≤1.6%, the S content is ≤0.005%, the P content is ≤0.012%, and the rest is iron and unavoidable impurity elements;

[0110] Desulfurizer ingredients include: CaO 70-80%, CaF 2 15-25%, MgO 1-3%, SiO2≤2%, and other inevitable impurities, with a particle size of 3-8mm accounting for ≥90%, and a maximum of no more than 10mm;

[0111] The refractory materials used in the immersion tube and bottom tank of the RH vacuum furnace are mainly high-quality ultra-low carbon magnesia-chrome bricks with a flexural strength of ≥48MPa and a density of 3.2-3.6g / cm 3 , porosity ≤8.0%, C content ≤1.5%, MgO: 85-95%, Cr2O3: 5-12, and other inevitable impurity components.

[0112] Step 4: Use billet continuous casting, the continuous casting machine is a straight arc rectangular billet continuous casting machine, the cross-sectional size of the continuous casting billet is 300mm×390mm, and the arc radius is 12.5m;

[0113] The continuous casting process is fully protected by using a high-alkalinity, low-alumina tundish covering agent. The tundish electromagnetic induction heating equipment is used to control the superheat of the molten steel in the tundish to a fluctuation of ≤5°C. The tundish superheat is 15-40°C, and the tundish induction heating power is 2500-3500K. The tonnage fluctuation of the tundish during normal casting is ≤1 ton, and the tonnage drop is ≤5 tons when changing tundishes.

[0114] The casting process uses an integral submerged nozzle with an insertion depth of 10-15mm. The crystallizer electromagnetic stirring current is 500-900A, the frequency is 6-8Hz, the crystallizer taper is adjusted according to the alloy element content within 1.05-1.15%, the crystallizer water volume is 2700-3000NL / min, the secondary cooling section within 1.5 meters adopts strong cooling with a water volume of 600-800NL / min, and the subsequent section adopts slow cooling with a water volume of 400-600NL / min.

[0115] The continuous casting speed is controlled at 0.50-0.65m / min, the billet reduction is controlled at 15-28mm, the billet C segregation index is 0.96-1.04, the billet is hot charged and hot transported, the billet surface temperature is ≥450℃, and the corner temperature is ≥400℃;

[0116] The continuous casting process includes 11 straightening machines, which are arranged in sequence along the casting direction. The 1st to 4th straightening machines are distributed in the straightening section. The pressure of the 1st straightening machine is 30-40 bar, and the pressure of each straightening machine increases gradually by 5-15 bar. The 5th to 11th straightening machines are distributed in the horizontal section. The pressure of the 5th straightening machine is 75-85 bar, and the pressure of each straightening machine increases gradually to 5-10 bar. The pressure of the 10th and 11th straightening machines decreases by 10-20 bar under the pressure of the 9th straightening machine.

[0117] The composition of the continuous casting high basicity, low alumina tundish covering agent includes: basicity CaO / SiO2 of 1.2-1.5, Al2O3≤2%, CaF2 3-8%, MgO 3-6%, and other inevitable components;

[0118] The particle size of the magnesium spray coating on the inner wall of the tundish is ≤2mm, accounting for 70-80%, 2-3mm accounts for more than 20%, and 3mm and above accounts for ≤5%. The composition includes MgO ≥80%, CaO 5-10%, SiO2 1-3%, and other unavoidable components;

[0119] The mold powder has a melting point of 1000-1100°C and a viscosity of 0.3-0.45 Pa•s, and includes the following mass components: C: 15-20%, CaO / SiO2: 0.6-0.8%, Na2O: 10-15%, Al2O3 ≤3%, MgO ≤1%, CaF2: 3-6%, and other inevitable impurity components;

[0120] The stopper rod and nozzle material include magnesium carbon, the stopper rod material also includes MgO content 80-85%, C content 8-12%, Al2O3 content ≤1.5%, SiC content 1-4%, SiO2 content 2-3%, and other inevitable impurity components, with a density of 2.4-2.7g / cm 3 , porosity ≤ 14%, flexural strength ≥ 40MPa;

[0121] The inner wall thickness of the submerged nozzle is 5-7mm, and the density is 2.5-2.8g / cm 3 , porosity ≤13%, composition includes MgO and C total content ≥90%, of which SiC content is 3-5%, and other unavoidable impurity components.

[0122] Step 5: Opening and grinding to control surface quality. When large square blooms are used for casting, the continuous casting slab is heated and heat-insulated in a slab heating furnace. After opening and rolling, a 140 mm × 140 mm slab is obtained. The slab is subjected to magnetic particle inspection and then the entire surface is ground. Spot repair is performed on the locations with obvious flaws detected on the surface. The average grinding depth is ≥ 0.5 mm.

[0123] For billet rolling, the billet enters the heating furnace and is kept warm after reaching the target temperature. In the preheating section, the furnace temperature is controlled at 600-800℃ and the heating rate is 10-20℃ / min; the temperature in the heating section is 850-1150℃ and the heating rate is 20-30℃ / min; the soaking section is 1150-1250℃ and the total time in the furnace is 280-320min; then billet rolling is carried out, with the starting rolling temperature at 1100-1220℃, and the billet is a square billet with a cross-section of 140mm×140mm.

[0124] Step 6: high-speed wire rolling to improve surface decarburization, spray a high-temperature resistant coating on the surface of the milled billet after grinding. However, when the Si content of the high carbon steel is ≤0.6%, the coating thickness is 0.1-0.3mm; when the Si content is 0.6-1.0%, the coating thickness is 0.3-0.5mm; when the Si content is greater than 1.0%, the coating thickness is 0.5-1.0mm;

[0125] The coating is sprayed before the rolling mill enters the heating furnace. The particle size of the coating is more than 90% in the range of 120-200 mesh. The composition includes calcium silicate, calcium aluminate, magnesium aluminum spinel, zirconium oxide, graphite carbon and a small amount of alkali metal oxides, inorganic binders, surfactants and other substances. It does not decompose within 1600℃.

[0126] The rolled billet is heated in the heating furnace. In the preheating section, the furnace temperature is controlled at 750-850℃ for 40-60min; in the heating section, the temperature is controlled at 900-1100℃ for 60-80min; in the soaking section, the temperature is controlled at 1100-1250℃ for 60-80min.

[0127] The sprayed billet is heated and heat-insulated in a steel rolling heating furnace using natural gas for heating, with an air-fuel ratio of 9.5-10.1. The rolling temperature of the billet out of the heating furnace is 1000-1150°C, the finishing rolling inlet temperature is 850-970°C, and the finishing rolling outlet temperature is 1000-1060°C.

[0128] Step 7: Stelmor air cooling, controlling the cooling intensity, improving the structure and performance, the wire rod obtained in the high-speed wire rolling process is subjected to a Stelmor air cooling line controlled air cooling process, and the spinning temperature of the Stelmor air cooling line is controlled at 850-950°C;

[0129] On the air cooling line, the air volume of fans 1# to 3# is 100%, the air volume of fans 4# to 7# is 60-80%, the air volume of fans 8# and 9# is 40-50%, and the air volume of the remaining fans is turned on by 10-20% or turned off.

[0130] The high-cleanliness high-carbon steel wire rod prepared by the method has a TO content of ≤10ppm, sorbite and pearlite ≥97%, a C content segregation value ≤1.04, no microcracks, pits, scars, scratches or other defects on the surface, and no complete decarburization layer on the surface of the wire rod. The wire rod can be used to prepare high-strength spring steel with a strength of 1600-2200MPa, bridge cable steel with a strength of 1800-2200MPa, and cord steel wire or high-strength diamond wire with a drawn diameter of 0.05mm or more. Example

[0131] The high-cleanliness high-carbon steel wire rod includes, in addition to Si, Mn, Cr, V alloy elements and Fe elements, the following chemical components in 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%.

[0132] Taking spring steel 55SiCr / 65Mn, cord steel 72A / 82A / 97A, and cable steel 87B / 92Si as examples, the production process of the technology of the present invention is introduced.

[0133] The chemical composition mass percentage of spring steel 55SiCr is: 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%.

[0134] The chemical composition mass percentage of spring steel 65Mn is: C: 0.60-0.70%, Si: 0.20-0.40%, Mn: 0.90-1.00%.

[0135] The chemical composition mass percentage of cord 72A is: C: 0.70-0.78%, Si: 0.15-0.30%, Mn: 0.50-0.60%.

[0136] The chemical composition mass percentage of cord 82A is: C: 0.78-0.86%, Si: 0.15-0.35%, Mn: 0.50-0.65%.

[0137] The chemical composition mass percentage of cord 97A is: C: 0.95-1.00%, Si: 0.15-0.30%, Mn: 0.35-0.45%.

[0138] The chemical composition mass percentage of cable steel 87B is: 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%.

[0139] The chemical composition mass percentage of cable steel 92Si is: 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%.

[0140] A method for producing low-carbon emissions of high-purity high-carbon steel, the production process of which includes: electric furnace smelting - RH vacuum - bloom continuous casting - blooming and grinding - high-speed wire rolling - Stelmor air cooling - finished wire rod; specifically, the following steps are included:

[0141] Step 1: Electric furnace smelting

[0142] High-quality scrap steel is fed into an electric furnace for smelting. Argon is blown through the sidewalls throughout the smelting process until the steel is completely molten. Electricity for the furnace is generated entirely by hydropower or photovoltaics. In the early stages of the furnace, the furnace is heated, lime and light calcining are added to create slag, and bottom blowing and argon stirring are activated. After all the scrap steel is melted, lime, light calcining, and pelletizing are added in batches to create slag. After the scrap steel is melted, the bottom blowing is switched to oxygen for stirring. The oxygen blowing time is adjusted based on the Al, Ti, and Si content of the scrap steel to remove alloying elements and carbon. During the bottom blowing process, lime, light calcining, and pelletizing are added to adjust the temperature and dephosphorize. Lime and pelletizing control the high alkalinity and oxidizing properties of the slag. Combined with bottom blowing, oxygen foaming and enhanced stirring promote slag flow and enhance dephosphorization. Power is controlled to maintain a relatively low temperature for molten steel dephosphorization, ideal for slag-metal reaction. Phosphorus-containing slag is discharged from the slag flow, reducing the phosphorus content in the molten steel to below 0.005%, and then the slag is discharged. After slag pouring is complete, lime is added, light burning is performed, and pellets are formed to create a high-basic, medium-oxidizing slag, and dephosphorization is continued. At the same time, bottom oxygen blowing is stopped and switched back to argon blowing. High power is applied to increase the temperature, and an appropriate amount of low-nitrogen recarburizer is added to adjust the carbon content of the molten steel. Once the molten steel temperature, carbon content, and oxygen content reach the target, steel can be tapped.

[0143] The high-quality scrap steel used in the electric furnace includes but is not limited to silicon steel, pipeline steel, bridge steel, automobile plates, spring steel, cord steel, and cable steel. The composition includes P≤0.035%, S≤0.008%, Ti≤0.015%, Ni≤0.025%, Cu≤0.018%, Mo≤0.006%, Sn≤0.015%, As≤0.01%, and the rest are conventional C, Si, Al, Mn and Fe elements.

[0144] Table 1 Main parameters of spring steel electric furnace smelting

[0145] Steel type parameters Loading amount, tRetained steel amount, % Bottom blowing argon flow rate in the early stage of smelting, Nm 3 / min bottom blowing oxygen flow rate, Nm 3 / min Side wall gun argon flow rate, Nm 3 / min Oxygen blowing stage Slag T.Fe,% Oxygen blowing stage Molten steel temperature, °C 55SiCr Example 1 115205302151520 Example 2 120159553181540 Example 3 11820740525153565Mn Example 4 1103010605221550 Example 5 116256502171546 Example 6 11928845321541

[0146] Table 2 Main parameters of spring steel electric furnace smelting endpoint

[0147] Steel type parameters Slag basicity Slag T.Fe Temperature, °C Tapping C, % Tapping O, % Tapping P, % 55SiCr Example 1 5.51016650.150.03000.0033 Example 2 6.31416500.350.01450.0060 Example 3 5.0816580.280.01160.003865Mn Example 4 8.5916530.500.00850.0045 Example 5 7.61316450.100.02790.0055 Example 6 9.31516700.46001320.0043

[0148] Table 3 Main parameters of electric furnace smelting of cord steel

[0149] Steel type parameters Loading amount, tRetained steel amount, % Bottom blowing argon flow rate in the early stage of smelting, Nm 3 / min bottom blowing oxygen flow rate, Nm 3 / min Side wall gun argon flow rate, Nm 3 / min Oxygen blowing stage Slag T.Fe,% Oxygen blowing stage Molten steel temperature, °C 72A Example 71181810383181528 Example 8116236524211539 Example 911520830515152082A Example 10120307455251545 Example 11119276604161541 Example 1211019955319155097A Example 13114157462231537 Example 14110255585201542 Example 15113236474171530

[0150] Table 4 Main parameters of the end point of electric furnace smelting of cord steel

[0151] Steel type parameters Slag basicity Slag T.Fe Temperature, °C Tapping C, % Tapping O, % Tapping P, % 72A Example 7 5.891663 0.19 0.0277 0.0039 Example 8 8.3111657 0.37 0.0164 0.0041 Example 9 6.581669 0.49 0.0115 0.0032 82A Example 10 5.0101650 0.38 0.0197 0.0056 Example 119.51316710.200.02530.0057 Example 127.31116660.360.01280.003397A Example 1310.61416580.500.00890.0045 Example 146.81016650.100.03000.0060 Example 157.01216450.470.01120.0046

[0152] Table 5 Main parameters of cable steel electric furnace smelting

[0153] Steel type parameters Loading amount, tRetained steel amount, % Bottom blowing argon flow rate in the early stage of smelting, Nm 3 / min bottom blowing oxygen flow rate, Nm 3 / min Side wall gun argon flow rate, Nm 3 / min Oxygen blowing stage Slag T.Fe,% Oxygen blowing stage Molten steel temperature, °C 87B Example 16120276363191535 Example 171182510502211520 Example 1811020860423154692Si Example 19115159555181539 Example 2117237565251550 Example 21119265303151541

[0154] Table 6 Main parameters of cable steel electric furnace smelting end point

[0155] Steel type parameters Slag basicity Slag T.Fe Temperature, ℃ Tapping C, % Tapping O, % Tapping P, % 87B Example 166.51316580.100.03000.0043 Example 177.3816690.360.01570.0051 Example 185.81516500.320.01760.003792 Si Example 195.01016450.500.00980.0060 Example 206.21216670.45001420.0055 Example 218.6916640.2700209000042

[0156] Step 2: Electric furnace tapping

[0157] The electric furnace tapping process uses a slide plate to block slag. At the beginning of tapping, the pre-deoxidation method is selected according to the C content of the molten steel. When the C content is ≤0.35%, 10-20% low-nitrogen recarburizer and 20-30% metallic manganese are first added to the ladle for pre-deoxidation. Bottom blowing is not turned on during the tapping process. After tapping is completed, medium and large bottom blowing is turned on for stirring. When the C content is greater than 0.35%, boiling tapping is carried out and medium and small bottom blowing is turned on for stirring. When 90% of the tapping is completed, silicon carbide, synthetic slag and lime are added to deoxidize and slag the slag. After tapping is completed, the molten steel is transported to RH treatment.

[0158] The low-carbon recarburizer added to the electric furnace for steelmaking has a N content of ≤0.035%, a C content of ≥99%, and the rest are unavoidable impurities; the Mn content in metallic manganese is ≥98.5%, the P content is ≤0.006%, the S content is ≤0.003%, the Ti content is ≤0.0035%, the Al content is ≤0.005%, and the rest are iron and unavoidable impurities; the SiC content in silicon carbide is ≥98%, and other unavoidable impurities; the main components of the synthetic slag added to the electric furnace for steelmaking include: CaO: 55-65%, SiO2 10-20%, CaF2 3-8%, MnO 1-3%, MgO 1-5%, Al2O3≤3%, and other unavoidable impurities; synthetic slag particle size is less than or equal to 3mm, accounting for ≥90%, 3-5mm accounting for ≥5%, and the rest is 5mm or above, moisture ≤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 / cm 3 , porosity ≤9.0%, of which MgO content ≥85%, C content 3-8%, Al2O3 content ≤3.0%, and the rest are other inevitable components.

[0159] Table 7 Main parameters of spring steel electric furnace tapping

[0160] Steel grade parameters Steel tapping C, % Bottom blowing flow rate, NL / min Silicon carbide addition, kg / t Synthetic slag addition, kg / t Lime addition, kg / t Slag basicity 55SiCr Example 1 0.15800 1.210 1.5 2.3 Example 2 0.35400 1.61 22.7 2.8 Example 3 0.28350 1.81 13.5 3.26 5Mn Example 4 0.50200 1.01 11.8 2.0 Example 5 0.10500 2.01 0 3.2 3.5 Example 6 0.46300 1.51 22.3 2.5

[0161] Table 8 Main parameters of cord steel electric furnace tapping

[0162] Steel grade parameters Steel tapping C, % Bottom blowing flow rate, NL / min Silicon carbide addition, kg / t Synthetic slag addition, kg / t Lime addition, kg / t Slag basicity 72A Example 7 0.19600 1.31 11.7 3.3 Example 8 0.37200 1.01 0 2.5 2.5 Example 9 0.49300 1.81 2 1.9 2.0 82A Example 10 0.38250 1.71 2 1.5 2.8 Example 11 0.20600 2.01 0 3.3 3.5 Example 12 0.36300 1.51 13.5 3.19 7A Example 13 0.50200 1.91 11.8 2.7 Example 14 0.10800 1.41 2 2.3 2.3 Example 15 0.47250 1.21 0 2.8 3.2

[0163] Table 9 Main parameters of cable steel electric furnace tapping

[0164] Steel grade parameters Steel tapping C, % Bottom blowing flow rate, NL / min Silicon carbide addition, kg / t Synthetic slag addition, kg / t Lime addition, kg / t Slag basicity 87B Example 16 0.10 700 1.91 23.0 2.5 Example 17 0.36 250 1.51 0 1.8 2.0 Example 18 0.32 800 1.01 0 2.9 2.8 9 2Si Example 19 0.50 200 1.61 11.5 2.7 Example 20 0.45 300 2.01 12.6 3.5 Example 21 0.27 400 1.31 23.5 3.2

[0165] Step 3: RH furnace refining

[0166] RH enters the station for rapid vacuum treatment, then deoxidation and desulfurization treatment, and after net circulation treatment, it is broken into steel and transported to the continuous casting platform for a certain period of time before pouring.

[0167] The RH inlet rapid vacuum treatment involves sequentially turning on the three water ring pumps and the E4, E3, E2, and E1 steam pumps, rapidly reducing the vacuum chamber pressure to an extremely low level, setting a maximum lift gas flow rate, and controlling the deep vacuum treatment time. Based on the incoming steel composition, if the carbon content is ≥0.35%, natural carbon decarburization and oxygen removal are initiated under deep vacuum. If the carbon content is <0.35%, deoxidation is performed by adding a low-nitrogen recarburizer to the target value of 0.45%, followed by the addition of silicon carbide. Samples are then taken for composition testing. Based on the test results, alloying is performed with one or more of the following: low-nitrogen recarburizer, ultrapure silicon, metallic manganese, ferrochrome, or ferrovanadium to achieve the target composition. Desulfurization treatment involves continuing deep vacuum treatment for a specified period after alloying. The three water ring pumps and E4 steam pump are then turned off, the ladle is lowered, the vacuum chamber pressure is increased, the gas flow rate is increased, and the amount of desulfurizer added is determined based on the sulfur content of the molten steel. After the desulfurizer is added in batches, a clean cycle is performed and the steel is tapped.

[0168] The low carbon recarburizer used in RH has a N content of ≤0.035%, a C content of ≥99%, and the rest are unavoidable impurity elements; the Mn content in metallic manganese is ≥99%, the Ti content is ≤0.003%, the Al content is ≤0.005%, the P content is ≤0.0065%, the S content is ≤0.0035%, and the rest are iron and unavoidable impurity elements; the SiC content in silicon carbide is ≥98%, and other unavoidable impurity elements; the Si content in ultrapure silicon is 80-85%, the Al content is ≤0.0035%, the Ti content is ≤0.0065%, and the P content is ≤0.0035%. The content of Cr in ferrochrome is ≤0.001%, the content of P is ≤0.005%, the content of S is ≤0.0025%, and the rest are iron and inevitable impurities; the content of Cr in ferrochrome is 55-60%, the content of C is ≤1.8%, the content of S is ≤0.006%, the content of P is ≤0.013%, and the rest are iron and inevitable impurities; the content of V in ferrovanadium is 45-50%, the content of C is ≤1.6%, the content of S is ≤0.005%, the content of P is ≤0.012%, and the rest are iron and inevitable impurities; the desulfurizer composition includes: CaO 70-80%, CaF 2 15-25%, MgO 1-3%, SiO2≤2%, and other inevitable impurities, with a particle size of 3-8mm accounting for ≥90%, and a maximum of no more than 10mm; the refractory materials used in the immersion tube and bottom tank of the RH vacuum furnace are mainly high-quality ultra-low carbon magnesia-chrome bricks with a flexural strength of ≥48MPa and a density of 3.2-3.6g / cm 3 , porosity ≤8.0%, C content ≤1.5%, MgO: 85-95%, Cr2O3: 5-12, and other inevitable impurity components.

[0169] Table 10 RH station and deep vacuum treatment parameters of spring steel

[0170] Steel type parameters Inlet temperature, ℃ Minimum vacuum, mbar Minimum vacuum time, min Lifting gas, Nm 3 / min Deep vacuum time, min Carbon deoxidation time, min 55SiCr Example 1 1595 0.55.0 200 225.5 Example 2 1598 0.34.5 250 216.0 Example 3 1606 0.84.0 210 208.0 65Mn Example 4 1597 0.74.2 230 255.0 Example 5 1603 0.64.6 220 237.5 Example 6 1610 1.040 240 246.5

[0171] Table 11 Spring steel RH treatment alloying and tapping parameters

[0172] Steel parameters Deep vacuum time after alloying, min Ladle drop, cm Vacuum chamber pressure, mbar Lifting gas, Nm 3 / min net cycle, min rest, min 55SiCr Example 1 6.0 1530 11068 Example 2 7.5 20 25 120 510 Example 3 5.5 20 45 100 78 65Mn Example 4 5.0 2520 10589 Example 5 8.0 1535 115611 Example 6 6.0 20 40 11069

[0173] Table 12 Cord steel RH station and deep vacuum treatment parameters

[0174] Steel type parameters Inlet temperature, ℃ Minimum vacuum, mbar Minimum vacuum time, min Lifting gas, Nm 3 / min Deep vacuum time, min Carbon deoxidation time, min 72A Example 7 1611 0.73.5 220 236.5 Example 8 1595 0.34.0 210 225.0 Example 9 1610 1.04.2 250 205.5 82A Example 10 1608 0.65.0 200 257.0 Example 11 1606 0.54.6 210 266.5 Example 12 1613 0.83.8 230 236.0 97A Example 13 1595 0.44.7 250 225.0 Example 14 1598 0.740 240 215.5 Example 15 1607 0.945 230 247.5

[0175] Table 13 Parameters of cord steel after RH treatment and alloying and tapping

[0176] Steel parameters Deep vacuum time after alloying, min Ladle drop, cm Vacuum chamber pressure, mbar Lifting gas, Nm 3 / minNet cycle, minStanding, min72AExample 75.5203511059Example 85.0152010578Example 96.025251006882AExample 107.51830100610Example 115.0224511089Example 128.0164012071197AExample 135.5173512069Example 146.02330115711Example 156.52020100612

[0177] Table 14 Cable steel RH entry and deep vacuum treatment parameters

[0178] Steel type parameters Inlet temperature, ℃ Minimum vacuum, mbar Minimum vacuum time, min Lifting gas, Nm 3 / min Deep vacuum time, min Carbon deoxidation time, min 87B Example 161598 0.64.0 250 235.0 Example 171600 0.85.0 230 207.0 Example 181603 0.34.5 220 256.5 92Si Example 191590 0.54.8 200 226.0 Example 201605 1.04.1 220 247.5 Example 211612 0.53.6 210 228.0

[0179] Table 15 Cable steel RH treatment alloying and tapping parameters

[0180] Steel parameters Deep vacuum time after alloying, min Ladle drop, cm Vacuum chamber pressure, mbar Lifting gas, Nm 3 / minNet cycle, minStanding, min87BExample 165.5163511058Example 176.02040100710Example 187.025451108992SiExample 196.5152012078Example 207.52135115610Example 215.01825105811

[0181] Step 4: Bloom Continuous Casting

[0182] The continuous casting machine is a straight arc rectangular billet casting machine with a cross-sectional dimension of 300mm×390mm and an arc radius of 12.5m. The continuous casting process is protected by using a high-alkalinity, low-alumina tundish covering agent. The tundish electromagnetic induction heating device controls the fluctuation of the molten steel superheat and the tundish superheat, and efficiently changes tundishes, ensuring stable tundish tonnage during normal casting and tundish changes. The machine uses an integral submerged nozzle for casting, with controlled nozzle insertion depth and adjustable electromagnetic stirring current and frequency in the mold. The higher the carbon content or alloying element content, the larger the mold taper within the range of 1.05-1.15%. The mold water volume and secondary cooling section nozzle are controlled. The casting process is carried out at a constant casting speed, with controlled reduction, to produce high-quality billets. Billets are hot-charged and hot-delivered, with billet surface temperatures ≥450°C and corner temperatures ≥400°C, reducing energy consumption in the heating furnace.

[0183] The continuous casting process includes 11 straightening machines, which are arranged in sequence along the casting direction. The 1st to 4th straightening machines are distributed in the straightening section. The pressure of the 1st straightening machine is 30-40 bar, and the pressure of each straightening machine increases gradually by 5-15 bar. The 5th to 11th straightening machines are distributed in the horizontal section. The pressure of the 5th straightening machine is 75-85 bar, and the pressure of each straightening machine increases gradually to 5-10 bar. The pressure of the 10th and 11th straightening machines decreases by 10-20 bar under the pressure of the 9th straightening machine.

[0184] The composition of the continuous casting high basicity, low alumina tundish covering agent includes: basicity CaO / SiO2 of 1.2-1.5, Al2O3≤2%, CaF2 3-8%, MgO 3-6%, and other inevitable components; the magnesia spray coating material on the inner wall of the tundish has a particle size of ≤2mm accounting for 70-80%, 2-3mm accounting for more than 20%, and 3mm and above accounting for ≤5%, and the composition includes MgO≥80%, CaO 5-10%, SiO2 1-3%, and other inevitable components; the crystallizer protection slag has a melting point of 1000-1100℃ and a viscosity of 0.3-0.45Pa•s, and includes the following mass components: C: 15-20%, CaO / SiO2: 0.6-0.8%, Na2O: 10-15%, Al2O3 ≤3%, MgO ≤1%, CaF2: 3-6%, and other inevitable impurity components; the stopper rod and nozzle material include magnesia carbon, the stopper rod material also includes MgO content 80-85%, C content 8-12%, Al2O3 content ≤1.5%, SiC content 1-4%, SiO2 content 2-3%, and other inevitable impurity components, density 2.4-2.7g / cm 3 , porosity ≤ 14%, flexural strength ≥ 40MPa; the inner wall thickness of the submerged nozzle is 5-7mm, and the density is 2.5-2.8g / cm 3 , porosity ≤13%, composition includes MgO and C total content ≥90%, of which SiC content is 3-5%, and other unavoidable impurity components.

[0185] Table 16 Main parameters of spring steel continuous casting tundish

[0186] Steel parameters Casting speed, m / min Tundish tonnage fluctuation, t Tundish tonnage reduction, t Tundish superheat, °C Superheat fluctuation, °C Induction heating power, KW 55SiCr Example 1 0.65 1.0 4.5 1 5 4 2 8 0 0 Example 2 0.60 0.5 3.6 2 0 5 3 0 0 0 Example 3 0.50 0.65.0 2 5 4 3 2 0 0 65Mn Example 4 0.63 0.83 1 8 3 2 9 0 0 Example 5 0.58 0.72.83 5 5 3 5 0 0 Example 6 0.53 0.93.7 4 0 4 2 5 0

[0187] Table 17 Spring steel continuous casting mold and pressure control parameters

[0188] Steel grade parameters Mold water volume, NL / min Electromagnetic stirring current, A Electromagnetic stirring frequency, Hz Front section secondary cooling water, NL / min Rear section secondary cooling water, NL / min Reduction, mm Ingot C Segregation index 55SiCr Example 1 30006006600600150.98 Example 2 29007007750450221.04 Example 3 27008008800400281.01 65Mn Example 4 29509006650550190.96 Example 5 28255008700500201.02 Example 6 27507507750550231.03

[0189] Table 18 Main parameters of cord steel continuous casting tundish

[0190] Steel grade parameters Casting speed, m / min Tundish tonnage fluctuation, t Tundish tonnage reduction, t Tundish superheat, °C Superheat fluctuation, °C Induction heating power, KW 72A Example 7 0.55 0.5 2.5 40 42 500 Example 8 0.50 0.8 3.6 2 5 3 2 700 Example 9 0.65 1.0 4.5 3 0 4 2 600 82A Example 10 0.60 0.64.0 3 5 5 3 000 Example 11 0.65 0.75.0 3 0 3 3 3 00 Example 12 0.55 0.93.9 2 8 5 2 9 00 97A Example 13 0.50 0.64.2 40 43 500 Example 14 0.60 0.8 3.3 3 0 5 3 2 00 Example 15 0.55 0.53 2 5 43 000

[0191] Table 19 Cord steel continuous casting mold and pressure control parameters

[0192] Steel grade parameters Mold water volume, NL / min Electromagnetic stirring current, A Electromagnetic stirring frequency, Hz Front section secondary cooling water, NL / min Rear section secondary cooling water, NL / min Reduction, mm Ingot C Segregation index 72A Example 7 27505506650500180.96 Example 8 27006808700450151.02 Example 9 30006007800400201.0482A Example 10 29007508750450230.97 Example 11 29509007600550281.03 Example 12 28008207630600251.0497A Example 13 27508506720480261.02 Example 14 29507508780450231.03 Example 15 28005007670500281.02

[0193] Table 20 Main parameters of cable steel continuous casting tundish

[0194] Steel type parameters Casting speed, m / min Tundish tonnage fluctuation, t Tundish tonnage reduction, t Tundish superheat, °C Superheat fluctuation, °C Induction heating power, KW87B Example 160.6547403041600 Example 170.6048443551800 Example 180.554943435165092Si Example 190.5048444541750 Example 200.6049453631700 Example 210.5548424051650

[0195] Table 21 Cable steel continuous casting mold and pressure control parameters

[0196] Steel grade parameters Mold water volume, NL / min Electromagnetic stirring current, A Electromagnetic stirring frequency, Hz Front section secondary cooling water, NL / min Rear section secondary cooling water, NL / min Reduction, mm Ingot C Segregation index 87B Example 1630005508800500230.98 Example 1729005009750600151.03 Example 1828507507700450201.0492Si Example 1927008508600400260.97 Example 2028508009700550250.96 Example 2128009008650500281.03

[0197] Step 5: Cutting and grinding

[0198] When large square billets are used for casting, the continuous casting billets are heated in a billet heating furnace with a heating rate of 10-20°C / min in the preheating section and a heating rate of 20-30°C / min in the heating section, followed by uniform heating and heat preservation. After billet rolling, 140mm×140mm billets are obtained, which are subjected to magnetic particle inspection, and then the surface is fully ground, and locations with obvious flaws detected on the surface are spot-repaired.

[0199] Table 22 Main process parameters for spring steel blanking and grinding

[0200] Steel parameters Preheating section, °C Heating section, °C Soaking section, °C Rolling temperature, °C Time in furnace, min Grinding depth, ≥mm 55SiCr Example 1 750 950 1 180 1 160 2 90 1.5 Example 2 700 1050 1150 1110 300 1.0 Example 3 800 1150 1250 1220 320 1.3 65Mn Example 4 600 1000 1160 1100 280 0.8 Example 5 650 850 1220 1190 290 0.5 Example 6 750 950 1200 1170 300 1.0

[0201] Table 23 Main process parameters for cord steel blanking and grinding

[0202] Steel parameters Preheating section, °C Heating section, °C Soaking section, °C Rolling temperature, °C Time in furnace, min Average grinding depth, ≥mm72A Example 7700900118011402800.4 Example 8750850115011002950.6 Example 96001050125012202900.582A Example 106501100120011 503000.7Example 118001080121011903101.0Example 127501050125012103000.897AExample 136801000116011203201.6Example 148001150122011903001.5Example 15750950119011603151.2

[0203] Table 24 Main process parameters for cable steel blanking and grinding

[0204] Steel parameters Preheating section, °C Heating section, °C Soaking section, °C Rolling temperature, °C Time in furnace, min Grinding depth, ≥mm87B Example 16650850115011002800.5 Example 176001150125012203000.8 Example 187501080120011602900.992Si Example 198001050123011803051.3 Example 20780950115011103101.5 Example 217001120119011503201.4

[0205] Step 6: High Wire Rolling

[0206] The surface of the milled billet after grinding is sprayed with a high-temperature resistant coating. When the Si content of the high carbon steel is ≤0.6%, the coating thickness is 0.1-0.3 mm; when the Si content is 0.6-1.0%, the coating thickness is 0.3-0.5 mm; when the Si content is greater than 1.0%, the coating thickness is 0.5-1.0 mm;

[0207] The coating is sprayed before the rolling mill enters the heating furnace. The particle size of the coating is more than 90% in the range of 120-200 mesh. The composition includes calcium silicate, calcium aluminate, magnesium aluminum spinel, zirconium oxide, graphite carbon and a small amount of alkali metal oxides, inorganic binders, surfactants and other substances. It does not decompose within 1600℃.

[0208] The rolled billet is heated in a heating furnace using natural gas, with an air-fuel ratio of 9.5-10.1. The preheating section is in the furnace for 40-60 minutes, the heating section is in the furnace for 60-80 minutes, the soaking section is in the furnace for 60-80 minutes, and then rolling is performed.

[0209] Table 25 Main process parameters of spring steel rolling

[0210] Steel parameters Preheating section, °C Heating section, °C Soaking section, °C Start rolling temperature, °C Finishing rolling inlet temperature, °C Finishing rolling outlet temperature, °C 55SiCr Example 1 780950115010009501050 Example 2 8001100120011308901030 Example 3 8501050125011509301060 65Mn Example 4 7501080110010308501010 Example 5 780900112010709201030 Example 6 8201000118011209001000

[0211] Table 26 Main process parameters of cord steel rolling

[0212] Steel parameters Preheating section, °C Heating section, °C Soaking section, °C Start rolling temperature, °C Finishing rolling inlet temperature, °C Finishing rolling outlet temperature, °C 72A Example 7750980110010008501010 Example 88501000115010609501000 Example 980090011301050930102082A Example 10750110011601065 9001000Example 11800950120011059101030Example 12830103012201100900101097AExample 138501060123011409501050Example 147501090125011509401060Example 158101000118010709001020

[0213] Table 27 Main process parameters of cable steel rolling

[0214] Steel grade parameters Preheating section, °C Heating section, °C Soaking section, °C Start rolling temperature, °C Finishing rolling inlet temperature, °C Finishing rolling outlet temperature, °C 87B Example 168501060115010509101050 Example 17750900110010008501010 Example 1882097011501040930104092Si Example 198501050125011509701060 Example 208001020120011109101030 Example 217801100119010808901000

[0215] Step 7: Stelmor Air Cooling

[0216] The wire rod obtained in the high-speed wire rolling process is subjected to an air-cooling process controlled by a Stelmor air-cooling line, and the air volume of the Stelmor air-cooling line fan is precisely controlled in sections.

[0217] The high-cleanliness high-carbon steel wire rod prepared by the method has a TO content of ≤10ppm, sorbite and pearlite ≥97%, a C content segregation value ≤1.04, no microcracks, pits, scars, scratches or other defects on the surface, and no complete decarburization layer on the surface of the wire rod. The wire rod can be used to prepare high-strength spring steel with a strength of 1600-2200MPa, bridge cable steel with a strength of 1800-2200MPa, and cord steel wire or high-strength diamond wire with a drawn diameter of 0.05mm or more.

[0218] Table 28 Main process parameters of spring steel air cooling

[0219] Steel type parameters Spinning temperature, ℃ 1-3# fan, % 4-7# fan, % 8-9# fan, % Other fans, % 55SiCr Example 1 850100804515 Example 2 880100705010 Example 3 8601007045 Closed 65Mn Example 4 9001006040 Closed Example 5 880100804520 Example 6 950100705010

[0220] Table 29 Main process parameters of cord steel air cooling

[0221] Steel type parameters Spinning temperature, ℃ 1-3# fan, % 4-7# fan, % 8-9# fan, % Other fans, % 72A Example 78501006540 ​​Close Example 8880100705010 Example 990010060451582A Example 108851008050 Close Example 11920100755020 Example 1293010070451597A Example 13950100654015 Example 149351008050 Close Example 15900100754510

[0222] Table 30 Main process parameters of cable steel air cooling

[0223] Steel type parameters Spinning temperature, ℃ 1-3# fan, % 4-7# fan, % 8-9# fan, % Other fans, % 87B Example 16850100804518 Example 17900100705020 Example 188801006040 Close 92Si Example 19900100704515 Example 209501008040 Close Example 21910100655010

[0224] The present invention realizes:

[0225] (1) The process flow is short and the carbon emissions are low. The blast furnace is eliminated or less molten iron is used. At the same time, the LF refining furnace is eliminated, and a short-process production process route for high-quality high-carbon steel wire is developed.

[0226] (2) Through the classification and selection of scrap steel, the problems of sulfur and phosphorus regeneration in the electric furnace are solved. Combined with the bottom oxygen blowing, slag retention and slag discharge process of the electric furnace, harmful elements such as Al and Ti are effectively controlled, providing a guarantee for controlling impurity elements and endogenous brittle inclusions;

[0227] (3) The electric furnace adopts the bottom blowing oxygen and side wall blowing argon mode to control the nitrogen absorption problem in the electric furnace smelting process. Combined with the RH treatment of boiling steel at the end of the electric furnace, it effectively solves the problem of large amounts of air absorption during the deoxidation and alloying process of steel in the conventional process. At the same time, the conventional high carbon steel wire LF refining operation is cancelled, which further reduces the air absorption. The RH process uses carbon deoxidation, high vacuum, and strong argon blowing operations to further reduce the nitrogen content of molten steel, solving the technical problem of low nitrogen smelting in the electric furnace process.

[0228] (4) In terms of cleanliness control, the use of high-carbon boiling steelmaking in an electric furnace and the RH process, and RH deep vacuum carbon deoxidation, can greatly reduce the number of inclusions produced in the alloying stage. At the same time, the ladle bottom blowing is not opened during the RH vacuum treatment stage, and the slag-metal reaction is very weak. The synthetic slag composed of monocalcium silicate and dicalcium silicate phases is used to further avoid the entry of calcium silicate inclusions into the molten steel, so that the inclusions in the molten steel are accurately controlled to be high SiO2 component inclusions. This type of inclusion has poor wettability with the molten steel and is easily removed under the circulating agitation of the molten steel, which greatly improves the cleanliness of the molten steel.

[0229] (5) In terms of control of foreign inclusions, the control of auxiliary materials such as ladle, vacuum tank, and continuous casting refractory materials can reduce the source of alumina inclusions, improve the quality of refractory materials, and reduce the erosion of refractory materials to form foreign large-sized brittle inclusions; at the same time, RH adopts a variable circulation intensity method to remove inclusions. In the early stage, high vacuum and high lifting gas flow are used to remove low-melting point acid inclusions. Such inclusions have a certain corrosive effect on refractory materials. Refractory materials are made of low-carbon materials to reduce deoxidation corrosion. In the middle and late stages, weak circulation stirring is used to reduce the corrosion of refractory materials and promote the floating of large-sized silicate composite inclusions formed by early erosion. Combined with soft stirring and calming after breaking the air, continuous casting electromagnetic stirring, etc., further promote the floating of inclusions.

[0230] (6) Continuous casting adopts narrow range superheat, alloy element and superheat matching control and constant casting speed technology to achieve precise segmented pressure reduction control, which can reduce the segregation of various elements in the ingot, that is, reduce the formation of precipitate inclusions; at the same time, avoid problems such as internal cracks caused by inappropriate stress distribution.

[0231] (7) High temperature and long time heating technology is used in the process of blanking and rolling to promote uniform diffusion of elements and eliminate problems such as element segregation. At the same time, the full grinding of blanks and the application of new coating materials are combined to reduce the decarburization of the surface of the wire rod; the controlled cooling process is optimized to obtain high-quality wire rod with high sorbite and pearlite structure.

[0232] The technical means disclosed in the solution of the present invention are not limited to the technical means disclosed in the above technical means, but also include technical solutions composed of any combination of the above technical features.

[0233] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A method for producing high-carbon steel with high cleanliness and low carbon emission, characterized in that: The high-cleanliness high-carbon steel includes, in addition to Si, Mn, Cr, V alloy elements and Fe elements, the following chemical components 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%; The production process of the low carbon emission production method includes: electric furnace smelting - RH vacuum - large square billet continuous casting - billet opening and grinding - high-speed wire rolling - Stelmor air cooling - finished wire rod; specifically includes the following steps: Step 1: Electric furnace smelting: put the scrap steel into the electric furnace for smelting until it is completely molten steel. The loading amount of the electric furnace is 115±5t, and the steel retention is 15-30%. High-quality scrap steel is selected for smelting, and the electricity used is all from hydropower or photovoltaic power generation; Step 2: Electric furnace tapping, the tapping process uses a slide plate to block slag. At the beginning of tapping, the pre-deoxidation method is selected according to the C content of the molten steel. When the C content is ≤0.35%, 10-20% of low nitrogen carburizer and 20-30% of metallic manganese are first added to the ladle for pre-deoxidation. The bottom blowing is not turned on during the tapping process. When the tapping is completed, the bottom blowing flow rate is controlled at 400-800NL / min; when the C content is greater than 0.35%, boiling tapping is performed, and the bottom blowing flow rate during the whole tapping process is 200-300NL / min. When 90% of the tapping is completed, silicon carbide, synthetic slag, and lime are added to deoxidize and slag the slag. After tapping, the molten steel is transported to RH for treatment; Step 3: RH furnace refining, RH inlet temperature ≥1595℃, RH inlet rapid vacuum treatment, then deoxidation and desulfurization treatment, after net circulation treatment, steel is broken out of the air, transported to the continuous casting platform and left to stand for more than 8 minutes before pouring; The deoxidation treatment is as follows: according to the incoming composition, if the C content is ≥0.35%, firstly, natural carbon decarburization and oxygenation are carried out under deep vacuum for more than 5 minutes; if the C content is less than 0.35%, low nitrogen recarburizer is added to deoxidize for more than 5 minutes according to the target value of 0.45%, and then silicon carbide is added to continue deoxidation, and the composition is sampled and tested. According to the composition test results, one or more of low nitrogen recarburizer, ultrapure silicon, metallic manganese, ferrochrome, and ferrovanadium are added for alloying to achieve the target composition; The specific desulfurization treatment is as follows: After alloying, continue deep vacuum treatment for more than 5 minutes, then turn off the three water ring pumps and E4 steam pump, lower the ladle by 15-25cm, increase the vacuum chamber pressure to more than 20mbar, and increase the gas flow rate to 100-120Nm 3 / min, the amount of desulfurizer added is determined according to the S content of molten steel. After the desulfurizer is added in batches, the net circulation is ≥5min, and the steel is tapped; Step 4: adopt billet continuous casting, protect the casting during the whole continuous casting process, adopt high basicity and low alumina tundish covering agent, use tundish electromagnetic induction heating equipment to control the superheat of molten steel in tundish to fluctuate ≤5°C, and the superheat of tundish is 15-40°C; adopt integral immersion nozzle casting, the immersion nozzle insertion depth is 10-15mm, the crystallizer electromagnetic stirring current is 500-900A, the frequency is 6-8Hz, and the crystallizer taper is adjusted at 1.05-1.15% according to the alloy element content; the continuous casting speed is controlled at 0.50-0.65m / min, the billet reduction is controlled at 15-28mm, and the billet C segregation index is 0.96-1.

04. The billet is hot charged and hot transported, the billet surface temperature is ≥450°C, and the corner temperature is ≥400°C; Step 5: Grind and control the surface quality; Step 6: High-speed wire rolling to improve surface decarburization; Step 7: Stelmor air cooling, control cooling intensity, improve organization and performance.

2. The low carbon emission production method of high cleanliness high carbon steel according to claim 1, characterized in that: In the step 1, the electric furnace is powered on to heat up, lime and light burning are added to make slag in the early stage of smelting, bottom blowing is turned on for stirring, and the bottom blowing argon flow rate is 5-10Nm3 / min; after all the scrap steel is melted, lime, light burning and pelletizing are added in batches to make slag, and after the scrap steel is melted, the bottom blowing is switched to oxygen, and the bottom blowing oxygen flow rate is 30-60Nm3 / min. The oxygen blowing time is adjusted according to the Al, Ti and Si contents of the scrap steel. The side wall gun is opened to blow argon throughout the smelting process, and the flow rate is 2-5Nm3 / min; lime, light burning and pelletizing are added during the bottom blowing oxygen process to adjust the temperature and dephosphorize, and the T.Fe content in the slag is 15-25%, and foamed slag and Strengthen stirring, promote slag flow during the process, strengthen dephosphorization, control the power supply to keep the molten steel temperature at 1520-1550℃, remove the P content in the molten steel to below 0.005%, then pour the slag, and after the slag pouring is completed, add lime, light burning, and pelletizing to make slag. The slag basicity is controlled to be above 5.0, and the TFe content is 8-15%. Stop bottom oxygen blowing and switch to argon blowing again, with a flow rate of 5-10Nm3 / min, turn on the power at high power to increase the temperature, add an appropriate amount of low-nitrogen recarburizer to adjust the C content of the molten steel, and the molten steel temperature rises to above 1645℃, the C content is 0.10-0.50%, the oxygen content is ≤0.03%, and the steel is tapped.

3. The low carbon emission production method of high cleanliness high carbon steel according to claim 1, characterized in that: In the step 2, 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 during steel tapping from an electric furnace.

4. The low carbon emission production method of high cleanliness high carbon steel according to claim 1, characterized in that: In step 3, the RH station rapid vacuum treatment is specifically as follows: turn on the three water ring pumps and E4, E3, E2, and E1 steam pumps in sequence, reduce the vacuum chamber working pressure to below 1 mbar within 5 minutes, and increase the gas flow rate to 200-250 Nm 3 / min, deep vacuum treatment time ≥20min.

5. The low carbon emission production method of high cleanliness high carbon steel according to claim 1, characterized in that: The step 4 adopts square billet continuous casting, the continuous casting machine is a straight arc rectangular billet continuous casting machine, the cross-sectional size of the continuous casting billet is 300mm×390mm, and the arc radius is 12.5m; The induction heating power of the tundish is 2500-3500KW, the tonnage fluctuation of the normal pouring tundish is ≤1 ton, and the tonnage decreases by ≤5 tons when changing tundishes. The water volume of the crystallizer is 2700-3000NL / min. Strong cooling is used within 1.5 meters of the second cooling section, with a water volume of 600-800NL / min, and slow cooling is used in the latter section, with a water volume of 400-600NL / min.

6. The low carbon emission production method of high cleanliness high carbon steel according to claim 1, characterized in that: The step 5: grinding the billet. When casting with a large square billet, the continuous casting billet is heated and heat-insulated in a billet heating furnace. After billet rolling, a 140 mm × 140 mm billet is obtained. The billet is subjected to magnetic particle inspection, and then the surface is fully ground. Spot repair is performed on the locations with obvious flaws detected on the surface, and the average grinding depth is ≥0.5 mm.

7. The low carbon emission production method of high cleanliness high carbon steel according to claim 1, characterized in that: The step 6: high-speed wire rolling, spraying a high-temperature resistant coating on the surface of the ground billet, but when the Si content of the high carbon steel is ≤0.6%, the coating thickness is 0.1-0.3mm, when the Si content is 0.6-1.0%, the coating thickness is 0.3-0.5mm, and when the Si content is >1.0%, the coating thickness is 0.5-1.0mm; The sprayed billet is heated and heat-insulated in a steel rolling heating furnace, natural gas is used for heating, and the air-fuel ratio is controlled at 9.5-10.

1. The rolling temperature of the billet out of the heating furnace is 1000-1150°C, the finishing rolling inlet temperature is 850-970°C, and the finishing rolling outlet temperature is 1000-1060°C.

8. The low carbon emission production method of high cleanliness high carbon steel according to claim 1, characterized in that: The step 7: Stelmor air cooling, the rolled wire obtained in the high-speed wire rolling process is subjected to an air cooling process controlled by a Stelmor air cooling line, and the spinning temperature of the Stelmor air cooling line is controlled at 850-950°C.

9. The low carbon emission production method of high cleanliness high carbon steel according to claim 1, characterized in that: The high-quality scrap steel used in the electric furnace includes but is not limited to silicon steel, pipeline steel, bridge steel, automobile plates, spring steel, cord steel, and cable steel, and the composition includes P≤0.035%, S≤0.008%, Ti≤0.015%, Ni≤0.025%, Cu≤0.018%, Mo≤0.006%, Sn≤0.015%, As≤0.01%, and the rest are conventional C, Si, Al, Mn and Fe elements.

10. The low carbon emission production method of high cleanliness high carbon steel according to claim 1, characterized in that: The low carbon recarburizer added in the electric furnace for steel production has an N content of ≤0.035%, a C content of ≥99%, and the rest are unavoidable impurity elements; The Mn content in metallic manganese is ≥98.5%, the P content is ≤0.006%, the S content is ≤0.003%, the Ti content is ≤0.0035%, the Al content is ≤0.005%, and the rest is iron and unavoidable impurity elements; The SiC content in silicon carbide is ≥98%, and other unavoidable impurity elements; The main components of the synthetic slag added to the electric furnace for steelmaking include: CaO: 55-65%, SiO2 10-20%, CaF2 3-8%, MnO 1-3%, MgO 1-5%, Al2O3≤3%, and other inevitable impurity components; synthetic slag and lime are added for slag making, the slag basicity is 2.0-3.5, the synthetic slag particle size is less than or equal to 3mm, accounting for ≥90%, 3-5mm accounting for ≥5%, and the rest is above 5mm, and the moisture content is ≤1.0%.

11. The low carbon emission production method of high cleanliness high carbon steel according to claim 1, characterized in that: In terms of mass percentage, the N content of the low-carbon recarburizer used in the RH is ≤0.035%, the C content is ≥99%, and the rest are unavoidable impurity elements; The Mn content in metallic manganese is ≥99%, the Ti content is ≤0.003%, the Al content is ≤0.005%, the P content is ≤0.0065%, the S content is ≤0.0035%, and the rest is iron and unavoidable impurity elements; The SiC content in silicon carbide is ≥98%, and other unavoidable impurity elements; Ultrapure silicon contains 80-85% Si, ≤0.0035% Al, ≤0.001% Ti, ≤0.005% P, ≤0.0025% S, and the rest are iron and unavoidable impurity elements. The Cr content in ferrochrome is 55-60%, the C content is ≤1.8%, the S content is ≤0.006%, the P content is ≤0.013%, and the rest is iron and unavoidable impurity elements; The V content in ferrovanadium is 45-50%, the C content is ≤1.6%, the S content is ≤0.005%, the P content is ≤0.012%, and the rest is iron and unavoidable impurity elements; Desulfurizer ingredients include: CaO 70-80%, CaF 2 15-25%, MgO 1-3%, SiO2≤2%, and other inevitable impurities, with a particle size of 3-8mm accounting for ≥90%, and a maximum of no more than 10mm.

12. The low carbon emission production method of high cleanliness high carbon steel according to claim 1, characterized in that: 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 / cm 3 , porosity ≤9.0%, of which, by mass percentage, MgO content ≥85%, C content 3-8%, Al2O3 content ≤3.0%, and the rest are other inevitable components.

13. The low carbon emission production method of high cleanliness high carbon steel according to claim 1, characterized in that: The refractory materials used for the immersion tube and bottom tank of the RH vacuum furnace are high-quality ultra-low carbon magnesia-chrome bricks with a flexural strength of ≥48MPa and a density of 3.2-3.6g / cm 3 , porosity ≤8.0%, of which by mass percentage, C content ≤1.5%, MgO: 85-95%, Cr2O3: 5-12, and other inevitable impurity components.

14. The low carbon emission production method of high cleanliness high carbon steel according to claim 1, characterized in that: The continuous casting high basicity, low alumina tundish covering agent composition includes: basicity CaO / SiO2 of 1.2-1.5, Al2O3≤2%, CaF2 3-8%, MgO 3-6%, and other inevitable components; The particle size of magnesium spray coating on the inner wall of the tundish is ≤2mm, accounting for 70-80%, 2-3mm accounting for more than 20%, and above 3mm accounting for ≤5%. The composition includes MgO≥80%, CaO 5-10%, SiO2 1-3%, and other inevitable components; The melting point of the mold protection slag is 1000-1100℃, the viscosity is 0.3-0.45Pa•s, and the mass components include: C: 15-20%, CaO / SiO2: 0.6-0.8%, Na2O: 10-15%, Al2O3 ≤3%, MgO ≤1%, CaF2: 3-6%, and other inevitable impurity components.

15. The low carbon emission production method of high cleanliness high carbon steel according to claim 1, characterized in that: The materials of the stopper rod and nozzle include magnesium carbon. The stopper rod material also includes MgO content 80-85%, C content 8-12%, Al2O3 content ≤1.5%, SiC content 1-4%, SiO2 content 2-3%, and other inevitable impurity components, with a density of 2.4-2.7g / cm 3 , porosity ≤14%, flexural strength ≥40MPa; The inner wall thickness of the immersion nozzle is 5-7mm, and the density is 2.5-2.8g / cm 3 , porosity ≤13%, composition includes MgO and C total content ≥90%, of which SiC content is 3-5%, and other unavoidable impurity components.

16. The low carbon emission production method of high cleanliness high carbon steel according to claim 1, characterized in that: The continuous casting machine in the continuous casting process includes 11 straightening machines, which are arranged in sequence along the billet drawing direction, wherein the 1st to 4th straightening machines are distributed in the straightening section, and the pressure of the 1st straightening machine is 30-40 bar, and then the pressure of each straightening machine gradually increases by 5-15 bar; the 5th to 11th straightening machines are distributed in the horizontal section, and the pressure of the 5th straightening machine is 75-85 bar, and then each straightening machine increases to 5-10 bar, and the 10th and 11th straightening machines reduce the pressure by 10-20 bar under the pressure of the 9th straightening machine.

17. The low carbon emission production method of high cleanliness high carbon steel according to claim 5, characterized in that: The billet rolling is carried out by putting the billet into the heating furnace and keeping the billet warm after reaching the target temperature. In the preheating stage, the furnace temperature is controlled at 600-800°C and the heating rate is 10-20°C / min. The temperature in the heating stage is 850-1150°C and the heating rate is 20-30°C / min. The soaking stage is 1150-1250°C and the total time in the furnace is 280-320min. Then, the billet rolling is carried out with the rolling temperature at 1100-1220°C. The billet is a square billet with a cross-section of 140mm×140mm.

18. The low carbon emission production method of high cleanliness high carbon steel according to claim 17, characterized in that: The rolled billet is sprayed with a protective coating before entering the heating furnace. More than 90% of the coating particle size is 120-200 meshes. The components include calcium silicate, calcium aluminate, magnesium aluminum spinel, zirconium oxide, graphite carbon, and a small amount of alkali metal oxides, inorganic binders, surfactants and other substances. It does not decompose within 1600°C.

19. The low carbon emission production method of high cleanliness high carbon steel according to claim 17, characterized in that: The rolled billet is heated in a heating furnace, wherein the temperature of the preheating section is controlled at 750-850°C for 40-60 minutes; the temperature of the heating section is controlled at 900-1100°C for 60-80 minutes; and the temperature of the soaking section is controlled at 1100-1250°C for 60-80 minutes.

20. The low carbon emission production method of high cleanliness high carbon steel according to claim 1, characterized in that: The step 7 adopts the Stelmore line controlled air cooling process, the air volume of fans 1# to 3# on the air cooling line is 100%, the air volume of fans 4# to 7# is 60-80%, the air volume of fans 8# and 9# is 40-50%, and the air volume of the remaining fans is turned on by 10-20% or turned off.

21. High-cleanliness high-carbon steel obtained by the method according to any one of claims 1 to 20.

22. Wire rod made from the high-cleanliness high-carbon steel according to claim 21.

23. The wire rod according to claim 22, characterized in that The wire rod has a TO content of ≤10ppm, troostite and pearlite ≥97%, a C content segregation value of ≤1.04, no microcracks, pits, scars, scratches or defects on the surface, and no complete decarburization layer on the wire rod surface.

24. High-strength spring steel with a strength of 1600-2200 MPa, bridge cable steel with a strength of 1800-2200 MPa, cord steel wire with a drawn diameter of 0.05 mm or more, or high-strength diamond wire prepared from the wire rod according to claim 23.

25. The high-cleanliness high-carbon steel according to claim 21, characterized in that: When the high-cleanliness high-carbon steel is spring steel 55SiCr, it also contains chemical composition mass percentages 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%; When the high-cleanliness high-carbon steel is spring steel 65Mn, it also contains the following chemical composition mass percentages: C: 0.60-0.70%, Si: 0.20-0.40%, Mn: 0.90-1.00%; When high-cleanliness high-carbon steel is used as cord 72A, it also contains chemical composition mass percentages: C: 0.70-0.78%, Si: 0.15-0.30%, Mn: 0.50-0.60%; Cord 82A chemical composition mass percentage: C: 0.78-0.86%, Si: 0.15-0.35%, Mn: 0.50-0.65%; When high-cleanliness high-carbon steel is used as cord 97A, it also contains chemical composition mass percentages: C: 0.95-1.00%, Si: 0.15-0.30%, Mn: 0.35-0.45%; When the high-cleanliness high-carbon steel is cable steel 87B, it also contains the following chemical components by mass percentage: 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%; When the high-cleanliness high-carbon steel is cable steel 92Si, the chemical composition mass percentage is: 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%.

26. The high-cleanliness high-carbon steel according to claim 25, characterized in that: The inclusions in the high-cleanliness high-carbon steel wire rod are mainly SiO2-MnO type low melting point inclusions, and the number density of inclusions larger than 1 μm is ≤5 / mm 2 , the number density of inclusions larger than 5μm is ≤0.12 / mm 2 The maximum size of transverse inclusions is ≤15μm, the rating of longitudinal inclusions A, B, C, D, and Ds are all ≤1, and the size of brittle inclusions is ≤5μm.

27. The high-cleanliness high-carbon steel according to claim 25, characterized in that: The high-cleanliness high-carbon steel ingot has a C segregation index of 0.96-1.04 and is free of crack defects; in the wire rod metallographic structure, by volume percentage, troostite and pearlite are ≥97%, and the grain size is 8-10; the most severely segregated area and other matrix areas on the wire rod cross section have a carbon content ratio of ≤1.04, a Si content ratio of ≤1.15, a Mn content ratio of ≤1.12, a Cr content ratio of ≤1.10, and a V content ratio of ≤1.15, and a hardness difference of ≤25HV, by mass percentage.

28. A method for producing high-carbon steel with high cleanliness and low carbon emission, characterized in that: The total C emissions from steelmaking, continuous casting and steel rolling are less than 180kg / ton of steel.

Images