High-purity high-carbon steel wire rod and production method therefor

Abstract

The present invention belongs to the technical field of steelmaking. Disclosed are a high-purity high-carbon steel wire rod and a production method therefor. In addition to alloying elements and Fe, the high-purity high-carbon steel wire rod further comprises the following chemical components in percentage by mass: C: 0.5-1.0%, P≤0.008%, S≤0.0025%, T.O≤0.0010%, N≤0.0020%, H≤0.0002%, Alt≤0.0010%, and Ti≤0.0005%. The production method comprises: hot-metal pretreatment, converter smelting, RH vacuum treatment, continuous casting of large billets, cogging and grinding, high-speed wire rolling, Stelmor air cooling, and obtainment of a finished wire rod. In the present invention, highly homogenized casting blanks and high-quality wire rods are obtained, and high-purity base materials are provided for high-end wire rod products. Provided in the present invention are a high-purity high-carbon steel wire rod and a production method therefor, which can be used for producing highly homogenized wire rod products having high cleanliness.

Description

A high-purity high-carbon steel wire and its production method Technical Field

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

[0002] High-purity high-carbon steel wire rods have very strict technical requirements for impurity element content, inclusions, and segregation. Applications such as high-strength automotive suspension springs, cord steel, and bridge cable steel directly affect the fatigue life and drawing performance of the product, thereby affecting the overall lifespan and operational safety of the equipment or project. To achieve high-strength, high-performance high-carbon steel wire rod products, it is necessary to improve the control of impurity elements and inclusions during the production process, and to address the composition uniformity, internal and surface quality of the ingots during the continuous casting process, thereby comprehensively improving the quality of high-carbon steel wire rod products.

[0003] Springs are important basic components, widely used in automobiles, machinery, railways and other fields. As safety-bearing components, springs have to bear high-cycle alternating loads during their service life, and their main failure mode is fatigue fracture. A large number of studies have shown that for high-strength, high-cycle fatigue springs, impurity elements, large-sized inclusions, segregation, surface quality, etc. are the main causes of fatigue failure. As the skeleton support material in automobile tire rubber, cord steel has extremely high requirements for its quality stability. Large-sized inclusions, segregation, abnormal structure, etc. are the main causes of pull-out fracture and torsional fracture, which seriously affect the stability of product quality and thus the safety of automobile use. Bridge cable steel is mainly used in large-scale bridge projects. It is relatively sensitive to phosphorus content, large-sized inclusions, segregation, and network carbon. During the drawing process, these defects will cause brittle fracture or torsional fracture, affecting product quality and thus the quality and safety of the project.

[0004] High-quality, high-carbon steel wire rod, such as spring steel, cable steel, and cord steel, is generally produced using a lengthy process: KR-BOF-LF refining-VD / RH-continuous casting. The KR process pre-desulfurizes the molten iron, followed by decarburization and dephosphorization in the converter, followed by tapping from the converter and slagging through LF refining, deoxidation, and alloying. The VD / RH process then vacuum degasses and removes inclusions. Some spring steel manufacturers use acidic slag systems to control inclusions to low-melting calcium aluminosilicates. However, acidic slag systems severely corrode refractory materials, easily causing excessive inclusions, leading to fatigue fractures and impacting spring performance. Because some cable steel grades contain aluminum, inclusions are primarily calcium aluminosilicates and calcium aluminates. These inclusions fluctuate widely, resulting in poor control stability. Due to the coarseness of the product, fractures due to inclusions are generally not a problem during drawing. However, fractures caused by large inclusions can occur during torsion. Cord steel is generally produced using the KR-converter-LF refining-continuous casting process, using acidic slag to control the melting point of inclusions and improve drawing performance. However, the acidic slag seriously corrodes the refractory material, and foreign brittle inclusions are the main cause of wire breakage during cord steel drawing. At the same time, large-sized, low-melting-point silicate inclusions can also cause breakage during the cord steel stranding and twisting process, affecting the product processing performance and quality stability.

[0005] 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%; molten steel is then blown in the converter to a phosphorus content of ≤0.011%. Bottom blowing during the converter tapping and refining processes is precisely controlled. Combined with RH vacuum treatment and tundish induction heating technology, inclusions in the molten steel are fully controlled, 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.

[0006] Patent 2022101243433 provides a method for controlling brittle inclusions in cord steel. The method utilizes a low-alkalinity, moderately oxidizing slag (basicity 0.9-1.2) with a 2-5% T.Fe+MnO content in the slag. Furthermore, low-aluminum alloys and low-alumina refractory materials are selected for production. This method effectively controls alumina and magnesia-alumina spinel inclusions in the molten steel, significantly improving the drawability of the cord steel wire rod. However, due to the acidic slag system used, despite the low-aluminum alloys and refractory materials, the slag exhibits a certain degree of oxidizing properties, resulting in a significantly high T.Fe+MnO content and a high total oxygen content in the molten steel. Consequently, this increases the corrosion of the refractory materials in the ladle and tundish during the smelting process. In addition to controlling the composition of the refractory materials, higher physical properties such as strength and density must be met. Otherwise, the refractory materials will corrode the molten steel, introducing large magnesia inclusions, which can cause the cord product to break during drawing.

[0007] Patent 202010061162.1 provides a method for controlling ultra-low melting point plastic inclusions in cord steel. By controlling the oxygen content in the molten steel, deoxidation is first performed through manganese alloy during the tapping process, and then an appropriate amount of carbon powder is added to assist in deoxidation. During the refining process, Mn and C elements are first adjusted to meet the standards, and then silicon alloy is added to adjust the Si content of the molten steel to reach the target composition. By designing the deoxidation and alloying process, an ultra-low melting point SiO 2+ MnO inclusions. However, this process utilizes an acidic, low-alkalinity slag system, and utilizes Mn for pre-deoxidation, followed by Si deoxidation. This results in poor overall deoxidation of the molten steel, significantly oxidizing the carbon in the refractory. This can cause decarburization and erosion of the refractory during steelmaking and continuous casting, increasing the risk of refractory particles entering the molten steel and causing excessive brittle inclusions. Furthermore, the MnO content in the slag reaches 3-5%, while the SiO2 content reaches 40-50%, further reacting with components such as MgO and Al2O3 in the refractory to form low-melting-point silicates, exacerbating refractory erosion and leading to an increase in brittle inclusions or large-sized silicate inclusions in the molten steel.

[0008] Patent 2013106819801 provides a spring steel wire production process for controlling inclusions, comprising the following steps: 1) smelting using an aluminum-free deoxidation process; 2) combined top and bottom blowing in a converter; 3) argon blowing in an Ar station; 4) argon refining in a LF ladle, with a basicity target of 0.7-2.0; 5) vacuum treatment; 6) pouring into billets, which are then rolled into wire through a high-speed wire rolling process. Although this process utilizes aluminum-free deoxidation, the low-basicity slag used in this process does not effectively absorb silicate inclusions generated by Si / Mn deoxidation. Furthermore, low-basicity slags can exacerbate refractory corrosion, increasing the number of foreign inclusions introduced into the refractory, such as alumina and magnesia-alumina spinel. These inclusions pose the greatest threat to fatigue life.

[0009] Patent 2012102042739 discloses a method for controlling inclusions in spring steel wire rod. The process involves: 1) high-carbon steel tapping from a converter (BOF); 2) post-BOF silicon-manganese deoxidation; 3) LF refining, with the oxygen content of the final steel controlled at 20-40 ppm; 4) continuous casting with low-superheat pouring; and 5) continuous rolling and wire rod rolling. The steel inclusions are limited to a width of no more than 10 μm, and the aspect ratio is greater than 3. However, the high oxygen content (20-40 ppm) and the acid-soluble aluminum content in the molten steel, ranging from 0.01% to 0.02%, can lead to an increase in non-metallic brittle inclusions in the spring steel, significantly impacting the fatigue life of the spring during service.

[0010] Patent 2016102603055 provides a smelting process for controlling inclusions in spring steel, comprising 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 in the electric furnace, a Si / Mn aluminum-free deoxidation process is used for pre-deoxidation, along with the use of activated lime, a composite agent, and refined slag. While this process effectively controls brittle inclusions in the steel, the slag basicity in the later stages of refining is controlled at 0.7-1.4. The acidic slag severely corrodes the refractory materials in the ladle and continuous casting tundish, easily causing excessive foreign inclusions.

[0011] Patent 2020111278482 discloses 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 structure exhibits sorbite ≥95% and network carbon ≤1. Low superheat casting is also used, which hinders crack control 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.

[0012] 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-temperature heating is achieved through controlled holding time 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 in this process exhibits high levels of impurities such as 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.

[0013] Patent 2022109583109 discloses a spring steel wire rod and its production method, involving a process flow consisting of hot metal pre-desulfurization, converter smelting, LF refining, RH vacuum treatment, bloom continuous casting, bloom opening and grinding, high-speed wire rolling, and air cooling. During the smelting process, the alloy and slag composition are controlled, resulting in inclusions of calcium aluminosilicates with Al2O3 content of 10-25%, SiO2 content of 45-65%, and CaO content of 15-30%. The reduction is controlled by dividing the solidification center fraction fs of the continuous casting into three stages, effectively controlling the segregation of the cast ingot. Furthermore, the internal and surface quality of the wire rod is controlled by controlling grinding, the heating furnace atmosphere, and the rolling process, thereby improving the performance of the spring steel wire rod and its products. However, the overall alkalinity of its slag is relatively high, and the inclusions are calcium aluminosilicate inclusions with an Al2O3 content of 10-25%, a SiO2 content of 45-65%, and a CaO content of 15-30%. This type of inclusion has a melting point of 1400-1500°C. Although it is a low-melting-point liquid inclusion at the molten steel temperature, it is solid at the rolling temperature and hardly deforms, which is not conducive to the control of the fatigue performance of the spring. In addition, the use of a medium-alkalinity slag system of 1.6-2.0 and the high SiO2 content of inclusions in the molten steel have a certain corrosive effect on the refractory material, especially under strong vacuum stirring, which will aggravate the erosion of the refractory material. In addition, no further restrictions are made on the refractory materials and other auxiliary materials used, and the quality of the refractory materials and auxiliary materials cannot be controlled. Foreign high-melting-point brittle inclusions will significantly affect the fatigue life of the spring. The three-stage distributed pressure control makes it difficult to accurately control the pressure reduction effect of the casting billet; at the same time, the billet has no coating protection, and the surface of the billet in the heating furnace is severely oxidized and decarburized. It relies on a lot of grinding to control it, which is not conducive to production efficiency and quality control stability.

[0014] High-grade, high-carbon steel wire products for critical applications have stringent requirements for impurity elements, inclusions, composition, and microstructure uniformity. Therefore, controlling impurity element content, inclusion type and size, and compositional and microstructure uniformity has always been a key focus in the research and development of high-grade, high-carbon steel wire. Analysis shows that impurity elements primarily require controlling phosphorus and sulfur to reduce product quality issues such as cold and hot brittleness. Al, titanium, and nitrogen content in the molten steel also need to be controlled to prevent the formation of hard inclusions such as alumina, magnesia spinel, and titanium nitride. Inclusions formed by deoxidation products, slag-metal reactions, and refractory spalling also require control from the perspectives of plasticization and minimization. Compositional and microstructure uniformity, as well as surface quality, are primarily controlled during the continuous casting and rolling processes. During the continuous casting process, high-composition uniformity is achieved by controlling the steel superheat, cooling water intensity, and reduction process. Combined with slab grinding, controlled rolling, and controlled cooling techniques, segregation, carbon lattice, and surface quality issues can be mitigated, resulting in high-purity, high-carbon steel wire products.

[0015] Summary of the Invention

[0016] In order to solve the above problems, the present invention discloses a high-purity high-carbon steel wire and a production method thereof. The specific technical solution is as follows:

[0017] A high-purity high-carbon steel wire comprises, in addition to alloying elements and Fe, the following chemical components calculated by mass percentage: C: 0.5-1.0%, P≤0.008%, S≤0.0025%, TO≤0.0010%, N≤0.0020%, H≤0.0002%, Alt≤0.0010%, and Ti≤0.0005%.

[0018] Furthermore, the mass content of the inclusions in the high carbon steel wire, except for SiO2-MnO inclusions, is ≤20%, and the number density of inclusions larger than 1 μm is ≤3.5 / mm 2 , the number density of inclusions larger than 5μm is ≤0.06 pieces / mm 2 , the maximum transverse inclusion size ≤12μm, the maximum longitudinal inclusion width ≤10μm, length ≤25μm, brittle inclusion size ≤3μm, C segregation index of ingot 0.95-1.05, C segregation index of wire rod ≤1.05.

[0019] A method for manufacturing high-purity high-carbon steel wire rod, which is produced according to the process flow of molten iron pretreatment - converter smelting - RH vacuum - bloom continuous casting - blooming and grinding - high-speed wire rolling - Stelmor air cooling - finished wire rod, specifically comprising the following steps:

[0020] Step 1: Pre-treat KR hot metal to obtain low-sulfur hot metal, which is then fed into the converter;

[0021] Step 2: Converter smelting, the converter charge is 145±5t, the molten iron ratio is 80-90%, clean scrap steel is used for smelting, and double slag dephosphorization is used in the converter;

[0022] Step 3: Tapping from the converter. At the beginning of tapping, 30-40% of a low-nitrogen recarburizer and then 20-30% of metallic manganese are added to the ladle for pre-deoxidation. The low-nitrogen recarburizer and metallic manganese are completely dissolved in the molten steel, and no carbon powder particles are floating on the surface. Tapping is then completed. Silicon carbide and synthetic slag are then added to the slag surface of the ladle in sequence to deoxidize and slag the slag surface. The ladle bottom blowing is kept open throughout the converter tapping process. In the double bottom blowing of the ladle, the maximum flow rate of one air brick is 600-800 NL / min, and the flow rate of the other air brick is 30-50% of the maximum flow rate. The two air bricks are distributed at a 135-degree angle at the bottom of the ladle, starting from the center of the ladle and located at 55% of the radius. Argon is blown into the molten steel to stir the molten steel and slag.

[0023] After the converter tapping is completed, silicon carbide is added to deoxidize the ladle slag in an amount of 0.5-1.5 kg / t. After the addition of silicon carbide, synthetic slag is added for slagging in an amount of 8-12 kg / t. After the synthetic slag is added, the double bottom blowing flow of the ladle is controlled at 150-250 NL / min. The synthetic slag is evenly spread and transported to the RH for treatment.

[0024] Step 4: RH furnace refining, RH furnace inlet temperature ≥1590℃, C content ≥0.2%, Mn content 0.15-0.35%, oxygen content ≤0.020%, RH inlet rapid vacuum treatment vacuum chamber working pressure ≤1mbar, increase gas flow rate to 150-200Nm 3 / min, then add silicon carbide for deoxidation according to the incoming composition, deep vacuum treatment time ≥15min, and take samples for composition testing. According to the composition test results and the composition requirements of the smelted steel, one or more of low nitrogen recarburizer, ultrapure silicon, metallic manganese, ferrochrome, and ferrovanadium are selected for alloying. After the composition meets the standard, the RH vacuum system's pumping capacity is reduced by 40-60%, and the gas flow rate is reduced to 80-100Nm 3 / min, the vacuum chamber pressure rises to above 50mbar, and after a net cycle of ≥5min, the vacuum chamber is broken;

[0025] After RH breaks through the air, the soft stirring time is ≥6min, the maximum air brick flow rate of the double air brick is 60-80NL / min, and the flow rate of the other air brick is 40-50% of the maximum air brick flow rate. Then it is transported to the continuous casting platform and left to stand for more than 10 minutes before starting pouring;

[0026] Step 5: Continuous casting of large square blooms. The cross-section of the large square blooms is 300mm×390mm. The continuous casting is protected throughout the entire process. A low-alkalinity, low-alumina tundish covering agent is used. The tundish electromagnetic induction heating equipment is used to control the superheat of the molten steel in the tundish to fluctuate ≤5°C. The tundish induction heating current is 1500-1800A and the voltage is 1600-2000V. When the steel grade is 0.5≤C<0.8%, the superheat of the molten steel is 20-35°C. When the steel grade is 0.8≤C<1.0%, the superheat of the molten steel is 30-45°C. The tundish tonnage is maintained at 48±1 tons, and the tonnage during the tundish change is 40-45 tons.

[0027] The crystallizer electromagnetic stirring current used is 450-650A, frequency is 6-8Hz, crystallizer water volume is 2750-3050NL / min, secondary cooling section water volume is 550-650NL / min, crystallizer liquid level fluctuation is ≤2mm, continuous casting is cast at a constant casting speed, and the continuous casting speed is controlled at 0.6-0.7m / min.

[0028] The solid phase ratio fs at the solidification center of the continuous casting billet is divided into three sections. When 0.1≤fs<0.3, the reduction rate is 10-15%; when 0.3≤fs<0.5, the reduction rate is 20-30%; when 0.5≤fs<0.8, the reduction rate is 50-60%; when 0.8≤fs<1, the reduction rate is 10-20%. The total reduction is controlled at 15-30mm, and the C segregation index of the billet is 0.95-1.05.

[0029] Step 6: Opening and grinding;

[0030] Step 7: Rolling and air cooling, control cooling intensity, improve structure and performance.

[0031] Furthermore, in the step 2, in the early stage of converter blowing, large bottom blowing and stirring are carried out, high lance position and low oxygen flow are used, a medium alkalinity slag system with alkalinity of 1.8-2.2 is used, and pellets are added to control the slag T.Fe ≥ 25%. After the early blowing is completed, oxygen blowing is stopped, the temperature is 1380-1430°C, bottom blowing and stirring are carried out for more than 3 minutes, the P content is ≤ 0.016%, and the slag is poured; after the slag is poured, blowing is continued, a low lance position and a large oxygen flow are used for blowing, lime is added to make a high alkalinity slag system, pellets are added, and the minimum T.Fe during the blowing process is controlled to be ≥ 15%. The blowing end temperature is ≥ 1650°C, T.Fe ≥ 25%, and the alkalinity is ≥ 6. The slag is poured first, and a slide plate is used to block the slag for tapping after the slag is poured.

[0032] Furthermore, the step 6: blanking and grinding: heating and soaking the continuous casting blank in a blanking heating furnace, controlling the blank temperature to 1100-1200°C and the rolling temperature to 1040-1180°C, blanking and rolling to obtain a rolled blank, performing magnetic particle inspection on the rolled blank, and then fully grinding the surface, and performing spot repair on the locations with obvious flaws detected on the surface, with an average grinding depth of ≥0.5mm;

[0033] Rolling billet spray coating: spray the surface of the ground rolling billet with a high temperature resistant coating with a coating thickness of 0.3-1.5mm.

[0034] Under the condition of controlling the atmosphere in the heating furnace, the sprayed billet is heated and heat-insulated in a steel rolling heating furnace, and the billet temperature in the steel rolling heating furnace is controlled to be 1030-1190°C, the start rolling temperature is 910-1170°C, the finishing rolling entrance temperature is 840-960°C, and the finishing rolling exit temperature is 990-1050°C, wherein in the atmosphere composition in the heating furnace, the total content of H2O and O2 is ≤2.5% by volume.

[0035] Furthermore, in step 7: rolling and air cooling, the rolled wire obtained in the high-speed wire rolling process is subjected to temperature-controlled air cooling, and the air-cooled wire spinning temperature is controlled at 820-925°C.

[0036] Furthermore, the KR arrival temperature is ≥1380°C, the molten iron S content is ≤0.045%, the C content is 4.1-4.6%, the Si content is 0.25-0.60%, the Ti content is ≤0.03%, the P content is ≤0.11%, and the rest are Fe and other inevitable impurity elements; when the KR arrives at the station, the blast furnace slag is first removed, and the slag removal rate is ≥95%, and then a desulfurizer is added for desulfurization. After the desulfurization is completed, the slag is removed again, and the slag removal rate is ≥95%. Then, a desulfurizer is added for the second desulfurization, and the slag removal rate is ≥98%. The KR exit temperature is ≥1330°C, and the exit S content is ≤0.0008%.

[0037] Furthermore, the composition of the clean scrap steel used in the converter includes P≤0.015%, S≤0.0050%, Ti≤0.01%, and also includes conventional C, Si, Al, Mn and Fe elements; the C content at the end of converter blowing is 0.03-0.07%, the O content is 0.035-0.075%, the P content is ≤0.008%, and the converter steel output is 135±5t.

[0038] Furthermore, the nitrogen content of the low-carbon recarburizer added during the converter tapping process is ≤0.045%, with the remainder being carbon and unavoidable impurity elements;

[0039] 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;

[0040] The SiC content in silicon carbide is ≥98%, and other unavoidable impurity elements;

[0041] The synthetic slag composition includes: CaO: 45-55%, SiO2 20-30%, CaF2 5-10%, MnO 1-3%, MgO ≤3%, Al2O3 ≤1.5%, and other inevitable impurity components. The basicity of the synthetic slag is 1.5-2.0. Among the main phases of the synthetic slag, monocalcium silicate accounts for 35-45%, dicalcium silicate accounts for 15-25%, and the rest are CaO, CaF2, MnO and inevitable phases.

[0042] Furthermore, the N content of the low-carbon recarburizer added during the RH vacuum treatment process is ≤0.045%, with the remainder being C and unavoidable impurity elements;

[0043] 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;

[0044] The SiC content in silicon carbide is ≥98%, and other unavoidable impurity elements;

[0045] 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.

[0046] 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;

[0047] 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.

[0048] Furthermore, the ladle bricks used in step 3 are magnesia carbon bricks, wherein the magnesia alumina spinel content is ≤3.0%, the C content is ≤3%, and the rest are unavoidable impurity components;

[0049] The refractory materials used for the immersion tube and bottom tank of the RH vacuum furnace in step 4 are magnesia-chromium ultra-low carbon bricks, wherein the C content is ≤1.5%, MgO: 85-95%, Cr2O3: 5-12%, magnesia-alumina spinel ≤3%, and other inevitable impurity components.

[0050] Furthermore, in step 5, the main components of the continuous casting low basicity low alumina tundish covering agent include: CaO 40-50%, SiO2 30-40%, CaF2: 3-6%, Al2O3 ≤ 2%, MgO 3-6%, and other inevitable components;

[0051] The composition of the tundish inner wall magnesium spray coating includes MgO ≥ 80%, CaO 5-10%, SiO2 1-3%, and other inevitable components.

[0052] Furthermore, in step 5, an integral submerged nozzle is used for casting, the submerged nozzle insertion depth is 10-15 mm, the thickness of the mold protective slag layer is 10-20 mm, and the consumption is 0.15-0.25 kg / ton;

[0053] The stopper rod and nozzle are made of magnesium carbon. The components of the stopper rod head are calculated by mass percentage: MgO content 80-85%, C content 8-12%, Al2O3 content ≤1.5%, SiC content 1-4%, SiO2 content 2-3%, and other inevitable impurities;

[0054] The inner wall thickness of the submerged nozzle is 5-7 mm, and the composition, calculated by mass percentage, includes MgO content of 75-80%, C content of 6-10%, SiC content of 3-5%, SiO25-10%, and other unavoidable impurities.

[0055] Furthermore, in step 6, a protective coating is sprayed before the rolled billet enters the heating furnace. The coating thickness is 0.3-1.5 mm, and the high-temperature coating composition includes CaO, SiO2, Al2O3, MgO, ZrO, C, and a small amount of alkali metal oxides, inorganic binders, surfactants and other substances.

[0056] The large square bloom is opened into billets with a cross-section of 140mm×140mm, and is subjected to flaw detection and grinding, heating in a heating furnace, rolling, and temperature-controlled cooling on a Stelmor air-cooling line. The obtained wire rod has no folding, scarring, or scratch defects on its surface, and no complete decarburization layer on its surface.

[0057] The present invention also applies for protection of: high-purity high-carbon steel wire prepared by the method of the present invention.

[0058] The present invention also applies for protection of: wire rods made from the high-purity high-carbon steel wire rods, the wire rods including high-quality cord steel wire rods with a C content of ≤0.87% and a drawing diameter of 0.1 mm or more, and high-quality gold wire rods with a C content of 0.87% <1.0% and a drawing diameter of 0.05 mm or more.

[0059] The present invention also applies for protection of: 1600-2400MPa grade spring steel and 1800-2200MPa grade cable steel made from the high-purity high-carbon steel wire.

[0060] Cord steel requires good drawing and twisting properties, spring steel requires high fatigue resistance, and cable steel has high requirements for the torsional performance of the material. Such high-carbon steel wire products with high performance requirements have very high requirements for cleanliness, segregation, decarburization, surface quality, etc. In order to obtain high-purity molten steel, highly homogenized ingots and high-purity wire rods, the present invention, based on conventional smelting processes, first removes the S in the molten steel to an extremely low level during the molten iron smelting stage. At the same time, the converter uses high-quality scrap steel to reduce the amount of resulfurization and comprehensively reduce desulfurization in the refining process. Refining desulfurization mainly relies on large bottom blowing and strong stirring to promote slag-metal reaction desulfurization. This method is very likely to cause slag rolling or slag-metal reaction to change the type of inclusions. Therefore, the present invention reduces the S content to a lower level in the KR and converter, avoiding strong slag-metal reaction, so that large-sized inclusions are generated in the molten steel for easy removal. Cold-rolled silicon steel and titanium-free thick plate scrap (pipeline steel, bridge steel, etc.) are selected for smelting. At the same time, the converter uses a slide plate to block the slag, which can effectively avoid problems such as Al, Ti, and P returning due to slag discharge, and further avoid the precipitation of brittle inclusions such as titanium oxide and titanium nitride during the continuous casting process.

[0061] Secondly, in addition to using low-phosphorus, clean scrap steel to reduce the introduction of impurities during the converter smelting process, lime and pellets are precisely added to the slag during each stage of the converter blowing process to maintain appropriate slag basicity and oxidizing properties in the early, middle, and late stages of the blowing process, thereby enhancing slag dephosphorization. Dephosphorization during the early stages of the converter blowing process is particularly important. Building on traditional dephosphorization techniques, bottom blowing is performed during the early stages of the converter blowing process, with a period of extensive bottom blowing and stirring to promote slag-metal reactions. This ensures effective dephosphorization control in the early stages. The mid-stage of the converter blowing process primarily involves high-speed decarburization, which can easily dry out the slag. Therefore, precise control of lime and pellet addition during the blowing process, maintaining the oxidizing and basicity of the slag during the mid-stage blowing process, can significantly reduce phosphorus reversion during the high-speed decarburization period. Ultra-high-basicity, highly oxidizing slag is used in the late stages of the converter blowing process to ensure high-temperature, low-phosphorus tapping, resulting in low-phosphorus molten steel. At the same time, the tapping temperature meets the requirements for direct transport to RH treatment. This avoids nitrogen absorption and slag curling during the LF heating process, thereby improving high-quality water cleanliness.

[0062] Secondly, when smelting high-carbon steel wire in a converter, a low-carbon tapping process is used to appropriately increase the oxidizability of the molten steel, thereby completely oxidizing and removing any small amounts of elements such as Al and Ti introduced into the alloy. Furthermore, a small amount of carbon powder and metallic manganese are added during the pre-tapping process to pre-deoxidize the molten steel, further reducing its oxidizability and significantly reducing the total amount of silicon oxide, aluminum oxide, and other elements formed during the subsequent deoxidation and alloying process. Incomplete deoxidation using carbon powder and metallic manganese prevents significant air intake in the molten steel and reduces its nitrogen content. Combined with asymmetric small and medium bottom blowing in the ladle, this prevents the formation of biased flow and accelerates the dissolution of carbon powder into the molten steel. Silicon carbide is added to deoxidize and modify the slag at the end of tapping. Sliders are used to control the amount of slag released, keeping the slag oxidizability low after silicon carbide modification. Simultaneously, medium-alkalinity silicate synthetic slag is added to cover the silicon carbide, preventing air burn and improving the slag deoxidation and modification effect. At the same time, the synthetic slag in the form of calcium silicate compounds has a low CaO content, which can reduce the inclusion of CaO in the molten steel, and form a deoxidation product mainly composed of SiO2 and MnO in the molten steel.

[0063] The semi-deoxidized molten steel is directly transported to RH treatment. The carbon in the molten steel is used to remove the oxygen content to a low level under high vacuum. At the same time, silicon carbide is added to strengthen the C and Si composite deoxidation, so that the total oxygen in the molten steel is reduced to an extremely low level. Then, low-carbon recarburizer, ultra-pure silicon, metallic manganese, ferrochrome, ferrovanadium and other alloying agents are added in sequence. Silicon carbide can increase C and Si in the molten steel, reduce the amount of C powder added, and alleviate the problem of molten steel temperature drop caused by adding a large amount of carbon powder. At the same time, after the addition of silicon carbide, the Si element and the C element are deoxidized at the same time, which can reduce the oxygen content to an extremely low level. A small amount of Si element oxidizes and releases heat to stabilize the molten steel temperature. Under high vacuum, carbon element participates in deoxidation in large quantities, which also reduces the oxidation of other alloying elements such as Mn and Cr, improves the recovery rate of alloying elements, and reduces the total amount of oxide inclusions generated. Si element reduces the final oxygen content of molten steel. A small amount of metallic aluminum may be needed to add in a few high-carbon steels. Adding metallic aluminum after Si and C deoxidation in the vacuum furnace is completed can greatly reduce the oxidation of aluminum, reduce alumina inclusions, and improve the cleanliness of molten steel.

[0064] Finally, the use of low-alumina ladle refractory materials, vacuum furnace refractory materials, and continuous casting components further reduces the sources of alumina inclusions. Simultaneously, higher quality standards for refractory materials are being implemented to reduce refractory erosion and avoid magnesia-containing foreign inclusions. Research has shown that high-melting-point foreign inclusions such as alumina, magnesia, and magnesia-alumina spinel are the primary causes of spring fatigue fracture, cord pullout brittle fracture, and cable steel torsional brittle fracture. In the early stages of the RH vacuum furnace process, deep vacuum and a medium-alkalinity slag system are used to rapidly adsorb and remove acidic, low-melting-point SiO2-MnO inclusions. A weak circulation agitation mode is employed in the middle and late stages to prevent continuous, high-intensity erosion of the refractory material by the molten steel, allowing a small amount of complex inclusions formed by refractory erosion to float up and be removed. After the slag is ruptured, asymmetric soft stirring and molten steel sedation are further employed to rapidly float the slag coils disturbed by the ruptured slag surface and any inclusions present in the molten steel, resulting in high-purity molten steel.

[0065] The continuous casting process uses high-alkalinity magnesia gunning material to absorb inclusions, and at the same time uses technologies such as electromagnetic induction heating of the tundish and electromagnetic stirring of the crystallizer to further promote the floating and removal of inclusions.

[0066] The continuous casting process utilizes a narrow, stable superheat range. The appropriate superheat is adjusted based on the carbon and silicon content of the molten steel. For low carbon and high silicon contents, the superheat is appropriately increased. This avoids excessive billet hardness due to low superheat, which can easily lead to cracking during reduction or straightening. A moderately increased superheat also facilitates reduction, and combined with controlled reduction, it can significantly improve billet segregation. While high carbon and low silicon contents can moderately reduce superheat, it remains higher than traditional processes. Appropriate reduction techniques and cooling water volumes are used to ensure the proportion of liquid phase in each section. A gradual reduction pattern is employed to maintain a constant total reduction, minimizing central segregation while avoiding internal cracking caused by excessive reduction. Stable mold level fluctuations can prevent mold slag entanglement. Technologies such as weak deoxidation during converter tapping and RH vacuum degassing, combined with continuous casting cooling intensity control and constant casting speed, reduce the formation of precipitates.

[0067] 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 problems. Furthermore, full grinding is employed after billet opening to eliminate surface quality issues with the original ingot. High-temperature-resistant coatings are applied to rolled ingots to mitigate surface decarburization and improve microstructure and performance uniformity. Controlled rolling and cooling techniques are utilized to achieve sorbite and pearlite structures while reducing martensite and ferrite structures, resulting in high-purity, high-quality high-carbon steel wire rod for processing and manufacturing various high-carbon steel products.

[0068] (1) In the conventional process of smelting spring steel, the desulfurization task is generally mainly carried out in the LF refining station. The present invention controls the S content in the molten steel at an extremely low level in the KR and converter, effectively avoiding the change of slag rolls and inclusion types caused by large-scale desulfurization during refining, effectively reducing the size of inclusions, and accurately controlling the type of inclusions.

[0069] (2) A double-slag high-efficiency dephosphorization process was developed for the converter. By designing the slag alkalinity, oxidizability, and bottom blowing stirring in the early stage of blowing, combined with the temperature control of the molten steel, low-phosphorus semi-steel molten steel was obtained. A slag oxidation control technology for the converter's high-speed decarburization period was developed to avoid the problem of slag drying and phosphorus regeneration. Combined with the high-alkalinity and high-oxidizability slag control technology in the late stage of the converter, high-temperature low-phosphorus molten steel was obtained.

[0070] (3) The ladle, RH vacuum furnace, continuous casting refractory and auxiliary materials are all made of high-purity standard materials to reduce the erosion problems caused by high carbon, acidic slag, silicate inclusions, etc., effectively control foreign inclusions, and provide an effective control method for foreign harmful inclusions in high-quality wire.

[0071] (4) An original asymmetric flow control method for the entire process of the double bottom blowing ladle was proposed, which effectively reduced the dead zone of molten steel stirring caused by convection, greatly promoted the floating removal of inclusions, and reduced gas consumption, which has positive significance for the quality of molten steel and cost reduction.

[0072] (5) The full-process system design takes into account the control of various impurity elements and inclusions in the steel, reduces the impurity element content and gas content in the steel, and at the same time greatly reduces the size and number of endogenous and exogenous inclusions, significantly improving the cleanliness of the molten steel.

[0073] (6) Accurately design the semi-quiet deoxidation process for high carbon steel converter steelmaking, breaking the traditional process method, designing the converter steelmaking to first use a small amount of carbon powder and metallic manganese for weak deoxidation, combined with strong deoxidation and carbonization of silicon carbide under RH vacuum conditions, to avoid the intake of air during the converter steelmaking deoxidation and alloying process and accurately control the SiO2-MnO type low-melting point inclusions; RH vacuum furnace C, Si composite deoxidation and variable vacuum intensity operation, which not only reduces the number and size of inclusions, but also controls the type of low-melting point plastic inclusions.

[0074] (7) The precise segmented pressing process is adopted, combined with the high temperature and long-time heat preservation technology of the heating furnace to further promote the uniform diffusion of elements, and the high temperature resistant coating technology is adopted to effectively control the decarburization problem of the surface of the ingot, thereby comprehensively improving the quality of the ingot.

[0075] This invention primarily reduces the content of impurity elements in molten steel through systematic design of smelting processes and control standards for raw and auxiliary materials. It also develops efficient deoxidation, alloying, and refining technologies to produce high-purity molten steel while simultaneously plasticizing and minimizing inclusions. Precise continuous casting and rolling control technologies produce highly homogenized ingots and high-quality wire rod, providing high-purity parent material for high-end wire products. This invention provides a high-purity, high-carbon steel wire and its production method, which can be used to produce highly clean, homogenized wire products.

[0076] The present invention adopts deep desulfurization and converter double slag dephosphorization technology; part of carbon powder and part of metallic manganese are added to the converter steel for weak deoxidation and alloying to control the oxygen content of the molten steel, reduce the Al and Ti contents, and reduce the nitrogen absorption of the molten steel; then medium-alkalinity synthetic slag of a specific phase is added to enhance the adsorption of inclusions and control the type of inclusions; without refining treatment, it goes directly to the RH vacuum furnace, first adopts deep vacuum degassing and removal of inclusions, and then reduces the circulation flow by reducing the RH pumping capacity and increasing the gas flow, thereby reducing the erosion of the refractory material, enhancing the removal of inclusions, and improving the cleanliness; combines the control of physicochemical indicators of refractory materials, alloys and auxiliary materials to reduce foreign brittle inclusions; controls the adsorption of inclusions by covering agents, protective slags, etc. in continuous casting to improve cleanliness; adopts precise reduction according to the solid phase ratio and other technologies in continuous casting to reduce segregation; high-temperature heating, billet protection, increased heating time, etc. to reduce segregation and improve the quality of wire rods. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] FIG1 is a flow chart of the present invention. DETAILED DESCRIPTION

[0078] The present invention will be further described below in conjunction with 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.

[0079] Referring to FIG1 , the method for manufacturing high-purity high-carbon steel wire rod is produced according to the process flow of molten iron pretreatment - converter smelting - RH vacuum - bloom continuous casting - blooming and grinding - high-speed wire rolling - Stelmor air cooling - finished wire rod, and specifically includes the following steps:

[0080] Step 1: KR hot metal is pretreated to produce low-sulfur hot metal for feeding into the converter. The KR arrival temperature is ≥1380°C, with a sulfur content ≤0.045%, a carbon content of 4.1-4.6%, a silicon content of 0.25-0.60%, a titanium content ≤0.03%, and a phosphorus content ≤0.11%. The remainder is Fe and other unavoidable impurities. Upon arrival, the KR is first stripped of blast furnace slag to a slag removal rate of ≥95%. Desulfurization is then performed with a desulfurizer. After desulfurization is complete, slag is removed to a slag removal rate of ≥95%. A second desulfurization with a desulfurizer is then added to achieve a slag removal rate of ≥98%. The KR exit temperature is ≥1330°C, with an exiting sulfur content of ≤0.0008%.

[0081] Step 2: Converter smelting: The converter charge is 145±5t, with a hot metal ratio of 80-90%. Clean scrap steel is used for smelting, and double slag dephosphorization is applied to the converter. During the initial blowing phase of the converter, high bottom blowing and agitation are applied, with a high lance position and low oxygen flow rate. A medium-basic slag system with a basicity of 1.8-2.2 is used. Pellets are added to control the slag T.Fe ≥ 25%. At the end of the initial blowing phase, oxygen blowing is stopped. The temperature is 1380-1430°C, and bottom blowing and agitation are maintained for at least 3 minutes. The slag is then drained. After draining, the process continues with a low lance position and high oxygen flow rate. Lime is added to create a high-basicity slag system, and pellets are added. The minimum T.Fe during the blowing phase is controlled to ≥ 15%. The final blowing temperature is ≥ 1650°C, T.Fe ≥ 25%, and basicity ≥ 6. Slag is drained first, and a slide plate is used to block the slag for tapping.

[0082] The composition of the clean scrap steel used in the converter includes P≤0.015%, S≤0.0050%, Ti≤0.01%, and also includes conventional C, Si, Al, Mn and Fe elements; the C content at the end of converter blowing is 0.03-0.07%, O content is 0.035-0.075%, P content ≤0.008%, and the converter steel output is 135±5t.

[0083] Step 3: Tapping from the converter. At the beginning of tapping, 30-40% of a low-nitrogen recarburizer and then 20-30% of metallic manganese are added to the ladle for pre-deoxidation. The low-nitrogen recarburizer and metallic manganese are completely dissolved in the molten steel, and no carbon powder particles are floating on the surface. Tapping is then completed. Silicon carbide and synthetic slag are then added to the slag surface of the ladle in sequence to deoxidize and slag the slag surface. The ladle bottom blowing is kept open throughout the converter tapping process. In the double bottom blowing of the ladle, the maximum flow rate of one air brick is 600-800 NL / min, and the flow rate of the other air brick is 30-50% of the maximum flow rate. The two air bricks are distributed at a 135-degree angle at the bottom of the ladle, starting from the center of the ladle and located at 55% of the radius. Argon is blown into the molten steel to stir the molten steel and slag.

[0084] The ladle bricks used are magnesia carbon bricks, in which the magnesia alumina spinel content is ≤3.0%, the C content is ≤3%, and the rest are unavoidable impurity components;

[0085] The low-carbon recarburizer added during the converter tapping process has a nitrogen content of ≤0.045%, with the remainder being carbon and unavoidable impurities. The manganese metal has a Mn content of ≥99%, a Ti content of ≤0.003%, an Al content of ≤0.005%, a P content of ≤0.0065%, and a S content of ≤0.0035%, with the remainder being iron and unavoidable impurities. The silicon carbide has a SiC content of ≥98%, and other unavoidable impurities. The synthetic slag composition includes: CaO: 45-55%, SiO2 20-30%, CaF2 5-10%, MnO 1-3%, MgO ≤3%, Al2O3 ≤1.5%, and other unavoidable impurities. The synthetic slag has a basicity of 1.5-2.0, and the main phases of the synthetic slag are monocalcium silicate accounting for 35-45%, dicalcium silicate 15-25%, and the remainder being CaO, CaF2, MnO, and unavoidable phases.

[0086] After the converter tapping is completed, silicon carbide is added to deoxidize the ladle slag in an amount of 0.5-1.5 kg / t. After the addition of silicon carbide, synthetic slag is added for slagging in an amount of 8-12 kg / t. After the synthetic slag is added, the double bottom blowing flow of the ladle is controlled at 150-250 NL / min. The synthetic slag is evenly spread and then transported to the RH for treatment.

[0087] Step 4: RH furnace refining, RH furnace inlet temperature ≥1590℃, C content ≥0.2%, Mn content 0.15-0.35%, oxygen content ≤0.020%, RH inlet rapid vacuum treatment vacuum chamber working pressure ≤1mbar, increase gas flow rate to 150-200Nm 3 / min, then add silicon carbide for deoxidation according to the incoming composition, deep vacuum treatment time ≥15min, and take samples for composition testing. According to the composition test results and the composition requirements of the smelted steel, one or more of low nitrogen recarburizer, ultrapure silicon, metallic manganese, ferrochrome, and ferrovanadium are selected for alloying. After the composition meets the standard, the RH vacuum system's pumping capacity is reduced by 40-60%, and the gas flow rate is reduced to 80-100Nm 3 / min, the vacuum chamber pressure rises to above 50mbar, and after a net cycle of ≥5min, the vacuum chamber is broken;

[0088] The refractory materials used for the immersion tube and bottom tank of the RH vacuum furnace are magnesia-chrome ultra-low carbon bricks, with C content ≤1.5%, MgO: 85-95%, Cr2O3: 5-12%, magnesia-alumina spinel ≤3%, and other unavoidable impurities;

[0089] The N content of the low-carbon recarburizer added during the RH vacuum treatment process is ≤0.045%, and the rest is C and unavoidable impurities; the Mn content of 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 impurities; the SiC content of silicon carbide is ≥98%, and other unavoidable impurities; the Si content of ultrapure silicon is 80-85%, and the Al content is ≤0.00 35%, Ti content ≤ 0.001%, P content ≤ 0.005%, S content ≤ 0.0025%, the rest are iron and inevitable impurity elements; ferrochrome has a Cr content of 55-60%, a C content ≤ 1.8%, a S content ≤ 0.006%, a P content ≤ 0.013%, the rest are iron and inevitable impurity elements; ferrovanadium has a V content of 45-50%, a C content ≤ 1.6%, a S content ≤ 0.005%, a P content ≤ 0.012%, the rest are iron and inevitable impurity elements;

[0090] After RH breaks the air, the soft stirring time is ≥6min, the maximum air brick flow of the double air brick is 60-80NL / min, and the flow of the other air brick is 40-50% of the maximum air brick flow. Then it is transported to the continuous casting platform and left to stand for more than 10 minutes before starting pouring.

[0091] Step 5: Bloom continuous casting is adopted. The cross section of the bloom is 300mm×390mm. The continuous casting is protected throughout the casting process. A low-alkalinity, low-alumina tundish covering agent is used. The tundish electromagnetic induction heating equipment is used to control the superheat of the molten steel in the tundish to fluctuate ≤5°C. The tundish induction heating current is 1500-1800A and the voltage is 1600-2000V. When the steel grade is 0.5≤C<0.8%, the superheat of the molten steel is 20-35°C. When the steel grade is 0.8≤C<1.0%, the superheat of the molten steel is 30-45°C. The tundish tonnage is maintained at 48±1 tons. The tonnage during the tundish change is 40-45 tons.

[0092] The crystallizer electromagnetic stirring current used is 450-650A, the frequency is 6-8Hz, the crystallizer water volume is 2750-3050NL / min, the secondary cooling section water volume is 550-650NL / min, the crystallizer liquid level fluctuation is ≤2mm, the continuous casting casting is performed at a constant casting speed, and the continuous casting speed is controlled at 0.6-0.7m / min;

[0093] The solid phase ratio fs of the continuous casting slab solidification center is divided into three sections. When 0.1≤fs<0.3, the reduction ratio is 10-15%; when 0.3≤fs<0.5, the reduction ratio is 20-30%; when 0.5≤fs<0.8, the reduction ratio is 50-60%; when 0.8≤fs<1, the reduction ratio is 10-20%, and the total reduction is controlled at 15-30mm, obtaining a slab C segregation index of 0.95-1.05.

[0094] The main components of the continuous casting low basicity low alumina tundish covering agent include: CaO 40-50%, SiO2 30-40%, CaF2: 3-6%, Al2O3 ≤ 2%, MgO 3-6%, and other inevitable components;

[0095] The composition of the tundish inner wall magnesium spray coating includes MgO ≥ 80%, CaO 5-10%, SiO2 1-3%, and other inevitable components;

[0096] Adopt integral submerged nozzle casting, the submerged nozzle insertion depth is 10-15mm, the thickness of the mold protection slag layer is 10-20mm, and the consumption is 0.15-0.25kg / ton;

[0097] The stopper rod and nozzle are made of magnesium carbon. The components of the stopper rod head are calculated by mass percentage: MgO content 80-85%, C content 8-12%, Al2O3 content ≤1.5%, SiC content 1-4%, SiO2 content 2-3%, and other inevitable impurities;

[0098] The inner wall thickness of the submerged nozzle is 5-7 mm, and the composition, calculated by mass percentage, includes MgO content of 75-80%, C content of 6-10%, SiC 3-5%, SiO2 5-10%, and other unavoidable impurities.

[0099] Step 6: slab grinding: heating and soaking the continuous casting slab in a slab heating furnace, controlling the slab temperature at 1100-1200°C and the rolling temperature at 1040-1180°C, rolling the slab to obtain a rolled slab, performing magnetic particle inspection on the rolled slab, and then grinding the entire surface. Spot repairing is performed on the locations with obvious flaws detected on the surface, with an average grinding depth of ≥0.5mm;

[0100] Rolling billet spray coating: spray the surface of the ground rolling billet with a high temperature resistant coating with a coating thickness of 0.3-1.5mm.

[0101] Under the condition of controlling the atmosphere in the heating furnace, the sprayed billet is heated and heat-insulated in a steel rolling heating furnace, and the billet temperature in the steel rolling heating furnace is controlled to be 1030-1190°C, the start rolling temperature is 910-1170°C, the finishing rolling entrance temperature is 840-960°C, and the finishing rolling exit temperature is 990-1050°C, wherein in the atmosphere composition in the heating furnace, the total content of H2O and O2 is ≤2.5% by volume.

[0102] Step 7: rolling and air cooling, the rolled wire obtained in the high-speed wire rolling process is subjected to temperature-controlled air cooling, and the air-cooled wire spinning temperature is controlled at 820-925°C.

[0103] The rolling mill is sprayed with protective coating before entering the heating furnace. The coating thickness is 0.3-1.5mm. The high-temperature coating composition includes CaO, SiO2, Al2O3, MgO, ZrO, C and a small amount of alkali metal oxides, inorganic binders, surfactants and other substances.

[0104] The large square bloom is opened into billets with a cross-section of 140mm×140mm, and is subjected to flaw detection and grinding, heating in a heating furnace, rolling, and temperature-controlled cooling on a Stelmor air-cooling line. The obtained wire rod has no folding, scarring, or scratch defects on its surface, and no complete decarburization layer on its surface.

[0105] Example

[0106] The components of the high-purity high-carbon steel wire produced include, in addition to alloy elements and Fe elements, the following chemical compositions by mass percentage: C: 0.5-1.0%, P≤0.008%, S≤0.0025%, TO≤0.0010%, N≤0.0020%, H≤0.0002%, Alt≤0.0010%, Ti≤0.0005%.

[0107] 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.

[0108] 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%.

[0109] 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%.

[0110] The chemical composition mass percentages of the cord 72A are as follows: C: 0.70-0.78%, Si: 0.15-0.30%, and Mn: 0.50-0.60%.

[0111] The chemical composition mass percentages of cord 82A are as follows: C: 0.78-0.86%, Si: 0.15-0.35%, and Mn: 0.50-0.65%.

[0112] The chemical composition mass percentage of cord 97A is: C: 0.95-1.00%, Si: 0.15-0.30%, Mn: 0.35-0.45%.

[0113] 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%.

[0114] 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%.

[0115] High-purity high-carbon steel wire rod is produced according to the process flow of molten iron pretreatment - converter smelting - RH vacuum - bloom continuous casting - blooming and grinding - high-speed wire rolling - Stelmor air cooling - finished wire rod.

[0116] Step 1: KR hot metal pretreatment

[0117] The molten iron is transported to the KR processing station, and after three slag removals and two deep desulfurizations, low-sulfur molten iron is obtained, which is then added to the converter for smelting.

[0118] Table 1 Main parameters of spring steel KR molten iron arriving at the station

[0119] Table 2 Main parameters of spring steel KR desulfurization treatment

[0120] Table 3 Main parameters of molten iron at the arrival station of cord steel KR

[0121] Table 4 Main parameters of KR desulfurization treatment of cord steel

[0122] Table 5 Main parameters of cable steel KR molten iron at the station

[0123] Table 6 Main parameters of KR desulfurization treatment for cable steel

[0124] Step 2: Converter smelting

[0125] After the converter is charged with molten iron and clean scrap, double slag dephosphorization is performed. During the initial blowing phase of the converter, high bottom blowing and agitation are employed, with a high lance position and low oxygen flow rate. A medium-basic, highly oxidizing slag system is used. Bottom blowing and agitation are performed at the end of the initial blowing phase, and the slag is drained. Blowing continues after the slag is drained, using a low lance position and high oxygen flow rate. Lime is added to create a high-basic, highly oxidizing slag system. The T and Fe content is controlled during the blowing process. Slag is drained first at the end of the blowing phase, and a slide plate is used to block the slag before tapping. The clean scrap used in the converter contains P ≤ 0.015%, S ≤ 0.0050%, and Ti ≤ 0.01%, along with the conventional elements C, Si, Al, Mn, and Fe.

[0126] Table 7 Main parameters of the first stage of spring steel converter smelting

[0127] Table 8 Main parameters of the second stage of spring steel converter smelting

[0128] Table 9 Main parameters of the first stage of converter smelting of cord steel

[0129] Table 10 Main parameters of the second stage of converter smelting of cord steel

[0130] Table 11 Main parameters of the first stage of cable steel converter smelting

[0131] Table 12 Main parameters of the second stage of cable steel converter smelting

[0132] Step 3: Tapping Steel from Converter

[0133] At the beginning of tapping from the converter, some low-nitrogen recarburizer and metallic manganese are added to the ladle for pre-deoxidation. The low-nitrogen recarburizer and metallic manganese to be added are completely dissolved in the molten steel, and there are no floating carbon powder particles on the surface, and the tapping is completed. Then silicon carbide and synthetic slag are added to the slag surface of the ladle in sequence to deoxidize and slag the slag surface. The bottom blowing of the ladle is turned on throughout the tapping process of the converter. The maximum flow rate of one air brick in the double bottom blowing of the ladle is 600-800NL / min, and the flow rate of the other air brick is 30-50% of the maximum flow rate. The two air bricks are distributed at an angle of 135 degrees at the bottom of the ladle, starting from the center of the ladle, at 55% of the radius, and argon is blown into the molten steel to stir the molten steel and slag; the ladle bricks used are magnesia-carbon bricks, of which the magnesia-alumina spinel content is ≤3.0%, the C content is ≤3%, and the rest are unavoidable impurity components; converter The nitrogen content of the low-carbon recarburizer added during the steel tapping process is ≤0.045%, with the remainder being carbon and inevitable impurities. The manganese metal contains ≥99% Mn, ≤0.003% Ti, ≤0.005% Al, ≤0.0065% P, and ≤0.0035% S, with the remainder being iron and inevitable impurities. The silicon carbide contains ≥98% SiC, along with other inevitable impurities. The synthetic slag comprises 45-55% CaO, 220-30% SiO, 25-10% CaF, 1-3% MnO, ≤3% MgO, ≤1.5% Al2O3, and other inevitable impurities. The synthetic slag has a basicity of 1.5-2.0, and the main phases of the synthetic slag are 35-45% monocalcium silicate, 15-25% dicalcium silicate, with the remainder being CaO, CaF2, MnO, and inevitable phases.

[0134] After the converter tapping is completed, silicon carbide is added to deoxidize the ladle slag. After the silicon carbide is added, synthetic slag is added to make slag. After the synthetic slag is added, the ladle flow rate is lowered, the double bottom blowing flow rates are consistent, and the synthetic slag is evenly spread and transported to the RH for treatment.

[0135] Table 13 Main parameters of spring steel converter tapping

[0136] Table 14 Main parameters of cord steel converter tapping

[0137] Table 15 Main parameters of cable steel converter tapping

[0138] Step 4: RH furnace refining

[0139] The RH furnace is quickly vacuumed and a large lifting gas flow rate is set. Then, silicon carbide is added for deoxidation according to the incoming composition. The deep vacuum treatment is maintained for a certain period of time, and samples are taken for composition testing. Based on the composition test results and the composition requirements of the smelted steel, one or more of low-nitrogen recarburizer, ultra-pure silicon, metallic manganese, ferrochrome, and ferrovanadium are added for alloying. After the composition meets the standards, the RH vacuum system's pumping capacity is reduced, the lifting gas flow rate is reduced, and the vacuum chamber pressure is increased. After a clean cycle, the vacuum chamber is broken.

[0140] The refractory materials used for the immersion tube and bottom tank of the RH vacuum furnace are magnesia-chrome ultra-low carbon bricks, with C content ≤1.5%, MgO: 85-95%, Cr2O3: 5-12%, magnesia-alumina spinel ≤3%, and other unavoidable impurities;

[0141] The nitrogen content of the low-carbon recarburizer added during the RH vacuum treatment process is ≤0.045%, with the remainder being carbon and unavoidable impurities. The manganese metal has a Mn content ≥99%, a Ti content ≤0.003%, an Al content ≤0.005%, a P content ≤0.0065%, and a S content ≤0.0035%, with the remainder being iron and unavoidable impurities. The silicon carbide has a SiC content ≥98%, and other unavoidable impurities. The ultrapure silicon has a Si content of 80-85%, an Al content ≤0.0035%, a Ti content ≤0.001%, a P content ≤0.005%, and a S content ≤0.0025%, with the remainder being iron and unavoidable impurities. The chromium content of the ferrochrome is 55-60%, a C content ≤1.8%, a S content ≤0.006%, and a P content ≤0.013%, with the remainder being iron and unavoidable impurities.

[0142] After RH breaks through the air, soft stirring is carried out, and the bottom blowing flow rate of double-permeable bricks is set differently, among which the smaller flow rate bottom blowing value is 40-50% of the large flow rate bottom blowing. Then it is transported to the continuous casting platform and left to stand for more than 10 minutes before pouring.

[0143] Table 16 RH station and deep vacuum treatment parameters for spring steel

[0144] Table 17 Spring steel RH treatment and tapping parameters

[0145] Table 18 Cord steel RH station and deep vacuum treatment parameters

[0146] Table 19 Cord steel RH treatment late stage and tapping parameters

[0147] Table 20 Cable steel RH station entry and deep vacuum treatment parameters

[0148] Table 21 Cable steel RH treatment late stage and tapping parameters

[0149] Step 5: Bloom Continuous Casting

[0150] The cross-section of the large square bloom is 300mm x 390mm. Protective pouring is used throughout the continuous casting process. A low-alkalinity, low-alumina tundish covering agent is used. The tundish electromagnetic induction heating equipment is used to maintain a stable superheat of the molten steel. The tundish induction heating current and voltage are set. The superheat of the molten steel in the tundish is adjusted according to the sulfur content of steel grade C. The tundish tonnage is kept stable during the pouring and tundish changing process.

[0151] Set the crystallizer electromagnetic stirring current and frequency to 6-8Hz to strengthen stirring, set the crystallizer water volume and the secondary cooling section water volume to control the cooling effect of the billet, and cast at a constant casting speed to keep the crystallizer liquid level stable;

[0152] The solid phase ratio fs of the solidification center of the continuous casting billet is divided into three sections, and the reduction ratio is allocated to different sections. When 0.1≤fs<0.3, the reduction ratio is 10-15%; when 0.3≤fs<0.5, the reduction ratio is 20-30%; when 0.5≤fs<0.8, the reduction ratio is 50-60%; when 0.8≤fs<1, the reduction ratio is 10-20%. By controlling the reduction ratio, a billet with a C segregation index of 0.95-1.05 is obtained;

[0153] The main components of the low-basicity, low-alumina tundish covering agent used in continuous casting include: CaO 40-50%, SiO2 30-40%, CaF2: 3-6%, Al2O3≤2%, MgO 3-6%, and other inevitable components. The components of the magnesia spray coating on the inner wall of the tundish include MgO≥80%, CaO 5-10%, SiO2 1-3%, and other inevitable components.

[0154] Adopt integral submerged nozzle casting, the submerged nozzle insertion depth is 10-15mm, the thickness of the mold protection slag layer is 10-20mm, and the consumption is 0.15-0.25kg / ton;

[0155] The stopper rod and nozzle are made of magnesium carbon. The components of the stopper rod head are calculated by mass percentage: MgO content 80-85%, C content 8-12%, Al2O3 content ≤1.5%, SiC content 1-4%, SiO2 content 2-3%, and other inevitable impurities;

[0156] The inner wall thickness of the submerged nozzle is 5-7 mm, and the composition, calculated by mass percentage, includes MgO content of 75-80%, C content of 6-10%, SiC 3-5%, SiO2 5-10%, and other unavoidable impurities.

[0157] Table 22 Main parameters of spring steel continuous casting tundish

[0158] Table 23 Spring steel continuous casting mold and pressure control parameters

[0159] Table 24 Main parameters of cord steel continuous casting tundish

[0160] Table 25 Cord steel continuous casting mold and pressure control parameters

[0161] Table 26 Main parameters of cable steel continuous casting tundish

[0162] Table 27 Cable steel continuous casting mold and pressure control parameters

[0163] Step 6: Cutting and grinding

[0164] The continuous casting slab is heated and heat-insulated in a slab heating furnace, the slab temperature is controlled at 1100-1200° C., the rolling temperature is controlled at 1040-1180° C., and a rolled slab is obtained after slab rolling. The rolled slab is subjected to magnetic particle inspection, and then the surface is fully ground. Locations with obvious flaws detected on the surface are further spot-grinded, and the average grinding depth is ≥0.5 mm.

[0165] Under the condition of controlling the atmosphere in the heating furnace, the sprayed billet is heated and heat-insulated in the steel rolling heating furnace, and the heating time, billet temperature and start rolling temperature in the steel rolling heating furnace are controlled, wherein, in the atmosphere composition in the heating furnace, the total content of H2O and O2 is ≤2.5% by volume.

[0166] Table 28 Main process parameters for spring steel blanking and grinding

[0167] Table 29 Main process parameters for cord steel blanking and grinding

[0168] Table 30 Main process parameters for cable steel blanking and grinding

[0169] Step 7: Rolling and air cooling

[0170] The 140mm×140mm rolling blank obtained by the blanking is ground, and then a high-temperature resistant coating is sprayed on the surface of the rolling blank with a coating thickness of 0.3-1.5mm.

[0171] The rolled wire obtained in the high-speed wire rolling process is subjected to temperature-controlled air cooling, and the air-cooled wire spinning temperature is controlled at 820-900°C.

[0172] The components of high-temperature coatings include CaO, SiO2, Al2O3, MgO, ZrO, C, as well as a small amount of alkali metal oxides, inorganic binders, surfactants and other substances.

[0173] The large square bloom is opened into a rolling billet, and then subjected to flaw detection and grinding, heating in a heating furnace, rolling, and temperature-controlled cooling in a Stelmor air cooling line. The obtained wire rod has no defects such as folding, scarring, and scratches on its surface, and has no complete decarburization layer on its surface.

[0174] Wire rods made of high-purity high-carbon steel wire rods include high-quality cord steel wire rods with a C content of ≤0.87% and a drawing diameter of 0.1mm or more, and high-quality gold wire rods with a C content of 0.87% <1.0% and a drawing diameter of 0.05mm or more.

[0175] 1600-2400MPa grade spring steel and 1800-2200MPa grade cable steel made from high-purity high-carbon steel wire.

[0176] Table 31 Main process parameters of spring steel rolling and air cooling

[0177] Table 32 Main process parameters of cord steel rolling and air cooling

[0178] Table 33 Main process parameters of cable steel rolling and air cooling

[0179] The present invention realizes:

[0180] (1) KR and converter reduce the S content to a lower level to avoid the desulfurization of high-basicity slag during the refining process. During the desulfurization process, the slag-gold reaction is intense and the inclusion component system changes. KR and converter control the S content well to achieve precise control of the inclusion component type.

[0181] (2) The converter adopts a double slag process. By precisely controlling the temperature of the molten pool in the early stage of blowing, the basicity and oxidizability of the slag, and bottom blowing and stirring, low-phosphorus semi-steel molten steel is obtained, and high-basicity and high-oxidizability slag is further produced. In particular, by precisely adding pellets during the blowing process, the oxidizability of the slag is controlled throughout the entire process, the problem of rephosphorization is avoided, and low-phosphorus molten steel is obtained.

[0182] (3) Carbon powder and metallic manganese are first used for weak deoxidation during steelmaking in the converter to reduce the problem of nitrogen absorption by the molten steel. At the same time, MnO inclusions are mainly formed in the inclusions. Silicon carbide, ultrapure silicon, and carbon powder are used for deoxidation and alloying under RH deep vacuum conditions to reduce the total amount of inclusions generated, reduce the RH pumping capacity, weaken the stirring intensity of the molten steel, reduce the reduction of MnO inclusions by Si elements, and obtain SiO2-MnO inclusions with a high MnO component. Combined with the control of alloy, refractory material, and low basicity slag system, the content of high melting point components such as CaO, Al2O3, and MgO in the inclusions is further reduced.

[0183] (4) The entire refining process adopts an asymmetric flow stirring mode with a limited maximum flow rate to reduce the dead zone of molten steel, promote molten steel circulation, accelerate the temperature and composition uniformity, shorten the time of intense reaction between slag and metal, reduce the introduction of inclusions such as slag rolls, and promote the efficient removal of inclusions.

[0184] (5) Control of auxiliary materials such as ladle, vacuum tank, and continuous casting refractory materials to reduce the source of alumina inclusions, improve the quality of refractory materials, and reduce the erosion of refractory materials to form 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. Weak circulation stirring is used in the middle and late stages 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.

[0185] (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.

[0186] (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 cooling process is optimized and controlled to obtain wire rods with excellent organizational properties.

[0187] 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.

[0188] 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 manufacturing high-purity high-carbon steel wire, characterized in that: The production is carried out according to the process flow of molten iron pretreatment - converter smelting - RH vacuum - large square billet continuous casting - billet opening and grinding - high-speed wire rolling - Stelmor air cooling - finished wire rod, which specifically includes the following steps: Step 1: Pre-treat KR molten iron to obtain low-sulfur molten iron, and add it into the converter; Step 2: converter smelting, the converter loading is 145±5t, the molten iron ratio is 80-90%, clean scrap steel is used for smelting, and the converter adopts double slag dephosphorization; Step 3: tapping from the converter. When tapping begins, add 30-40% of a low-nitrogen recarburizer and then 20-30% of metallic manganese to the ladle for pre-deoxidation. The low-carbon recarburizer and metallic manganese to be added are completely dissolved in the molten steel, and there are no floating carbon powder particles on the surface. The tapping is completed. Then, silicon carbide and synthetic slag are added to the slag surface of the ladle in sequence to deoxidize and slag the slag surface. During the tapping of the converter, the ladle bottom blowing is turned on throughout the process. The maximum flow rate of one air brick in the double bottom blowing of the ladle is 600-800NL / min, and the flow rate of the other air brick is 30-50% of the maximum flow rate. The two air bricks are distributed at an angle of 135 degrees at the bottom of the ladle, starting from the center of the ladle, at the 55% position of the radius, and argon is blown into the molten steel to stir the molten steel and slag; After the converter tapping is completed, silicon carbide is added to deoxidize the ladle slag, the addition amount is 0.5-1.5kg / t, and after the silicon carbide is added, synthetic slag is added for slag making, the addition amount is 8-12kg / t. After the synthetic slag is added, the double bottom blowing flow of the ladle is controlled to 150-250NL / min. The synthetic slag is spread evenly and then transported to the RH for treatment; Step 4: RH furnace refining, RH furnace station temperature ≥1590℃, C content ≥0.2%, Mn content 0.15-0.35%, oxygen content ≤0.020%, RH station rapid vacuum treatment, then add silicon carbide for deoxidation, and take samples to test the composition. According to the composition test results and the composition requirements of the smelted steel, one or more of low nitrogen carburizer, ultrapure silicon, metallic manganese, ferrochrome, and ferrovanadium are selected for alloying. After the composition meets the standard, the RH vacuum system's pumping capacity is reduced by 40-60%, the vacuum chamber pressure is increased, and the gas flow rate is reduced to 80-100Nm 3 / min, after a net circulation of ≥5min, break the air, open the bottom of the ladle for soft blowing and stirring, and then transport it to the continuous casting platform to stand for more than 10 minutes before starting pouring; The working pressure of the vacuum chamber for RH station rapid vacuum treatment is ≤1mbar, and the lifting gas flow is 150-200Nm 3 / min, deep vacuum treatment time ≥15min, after the composition meets the standard, the vacuum chamber pressure rises to above 50mbar; In step 4, the soft stirring time after RH breaking is ≥6min, the maximum air brick flow rate of the double air brick is 60-80NL / min, and the flow rate of the other air brick is 40-50% of the maximum air brick flow rate; Step 5: Continuous casting of large square billets; Step 6: Grind and improve the surface quality; Step 7: Rolling and air cooling, control cooling intensity, improve structure and performance.

2. The method for manufacturing high-purity high-carbon steel wire according to claim 1, characterized in that: In the step 2, the converter is blown at the beginning with large bottom blowing and stirring, high lance position and low oxygen flow, a medium basicity slag system is used, the basicity is 1.8-2.2, pellets are added to control the slag T.Fe ≥ 25%, oxygen blowing is stopped at the end of the early blowing, the temperature is 1380-1430°C, the bottom blowing and stirring are performed for more than 3 minutes, the P content is ≤ 0.016%, and the slag is poured; after the slag is poured, the blowing is continued, the low lance position and large oxygen flow are used for blowing, lime is added to make a high basicity slag system, pellets are added, the minimum T.Fe of the blowing process is controlled to be ≥ 15%, the blowing end temperature is ≥ 1650°C, T.Fe ≥ 25%, the basicity is ≥ 6, the slag is poured first, and a slide plate is used to block the slag for steelmaking after the slag is poured.

3. The method for manufacturing high-purity high-carbon steel wire according to claim 1, characterized in that: The cross-section of the large square billet in step 5 is 300mm×390mm, and the continuous casting is protected throughout the casting process. A low-basicity and low-alumina tundish covering agent is used, and the superheat of the molten steel in the tundish is controlled to fluctuate by ≤5°C by using the tundish electromagnetic induction heating equipment. The tundish induction heating current is 1500-1800A and the voltage is 1600-2000V. When 0.5≤C<0.8% in the steel, the superheat of the molten steel is 20-35°C, and when 0.8≤C<1.0% in the steel, the superheat of the molten steel is 30-45°C. The tonnage of the tundish is maintained at 48±1 tons, and the tonnage is 40-45 tons when the tundish is changed.

4. The method for manufacturing high-purity high-carbon steel wire according to claim 1, characterized in that: In step 5, the crystallizer electromagnetic stirring current used is 450-650A, the frequency is 6-8Hz, the crystallizer water volume is 2750-3050NL / min, the secondary cooling section water volume is 550-650NL / min, the crystallizer liquid level fluctuation is ≤2mm, the continuous casting is cast at a constant pulling speed, and the continuous casting pulling speed is controlled at 0.6-0.7m / min.

5. The method for manufacturing high-purity high-carbon steel wire according to claim 4, characterized in that: In the step 5, the solid phase ratio fs of the solidification center of the continuous casting billet is divided into four sections. When 0.1≤fs<0.3, the reduction rate accounts for 10-15%; when 0.3≤fs<0.5, the reduction rate accounts for 20-30%; when 0.5≤fs<0.8, the reduction rate accounts for 50-60%; when 0.8≤fs<1, the reduction rate accounts for 10-20%, and the total reduction is controlled at 15-30mm to obtain a billet C segregation index of 0.95-1.

05.

6. The method for manufacturing high-purity high-carbon steel wire according to claim 1, characterized in that: Step 6: grinding the billet: heating and isolating the continuous casting billet in a billet heating furnace, controlling the billet temperature to be 1100-1200°C, and the rolling temperature to be 1040-1180°C, rolling the billet to obtain a rolled billet, performing magnetic particle inspection on the rolled billet, and then grinding the entire surface, and performing spot repair on the locations with obvious flaws on the surface, with an average grinding depth of ≥0.5mm; Rolling billet spray coating: spray the surface of the ground rolling billet with a high temperature resistant coating with a coating thickness of 0.3-1.5mm.

7. The method for manufacturing high-purity high-carbon steel wire according to claim 6, characterized in that: In step 6, under the condition of controlling the atmosphere in the heating furnace, the sprayed billet is heated and evenly heat-insulated in the steel rolling heating furnace, and the billet temperature in the steel rolling heating furnace is controlled to be 1030-1190°C, the start rolling temperature is 910-1170°C, the finishing rolling entrance temperature is 840-960°C, and the finishing rolling exit temperature is 990-1050°C, wherein in the atmosphere composition in the heating furnace, the total content of H2O and O2 is ≤2.5% by volume.

8. The method for manufacturing high-purity high-carbon steel wire according to claim 1, characterized in that: In the step 7, the rolled wire obtained in the high-speed wire rolling process is subjected to temperature-controlled air cooling, and the air-cooled wire spinning temperature is controlled at 820-925°C.

9. The method for manufacturing high-purity high-carbon steel wire according to claim 1, characterized in that: The KR arrival temperature is ≥1380°C, the S content of the molten iron is ≤0.045%, the C content is 4.1-4.6%, the Si content is 0.25-0.60%, the Ti content is ≤0.03%, the P content is ≤0.11%, and the rest are Fe and other inevitable impurity elements; when the KR arrives at the station, the blast furnace slag is first removed, and the slag removal rate is ≥95%, and then a desulfurizer is added for desulfurization. After the desulfurization is completed, the slag is removed again, and the slag removal rate is ≥95%. Then, a desulfurizer is added for the second desulfurization, and the slag removal rate is ≥98%. The KR exit temperature is ≥1330°C, and the exit S content is ≤0.0008%.

10. The method for manufacturing high-purity high-carbon steel wire according to claim 1, characterized in that: The components of the clean scrap steel used in the converter include P≤0.015%, S≤0.0050%, Ti≤0.01%, and also include conventional C, Si, Al, Mn and Fe elements.

11. The method for manufacturing high-purity high-carbon steel wire according to claim 1, characterized in that: At the end of the converter blowing, the C content is 0.03-0.07%, the O content is 0.035-0.075%, the P content is ≤0.008%, and the converter output is 135±5t.

12. The method for manufacturing high-purity high-carbon steel wire according to claim 1, characterized in that: The N content of the low-carbon recarburizer added in the converter steel-making process is ≤0.045%, and the rest is C and 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%, as well as other unavoidable impurity elements.

13. The method for manufacturing high-purity high-carbon steel wire according to claim 1, characterized in that: The synthetic slag added to the converter for steelmaking comprises: CaO: 45-55%, SiO2: 20-30%, CaF2: 5-10%, MnO: 1-3%, MgO≤3%, Al2O3≤1.5%, and other inevitable impurity components, with a basicity of 1.5-2.

0. Among the physical phases, monocalcium silicate accounts for 35-45%, dicalcium silicate accounts for 15-25%, and the rest are CaO, CaF2, MnO and inevitable phases.

14. The method for manufacturing high-purity high-carbon steel wire according to claim 1, characterized in that: The N content of the low-carbon recarburizer added in the RH vacuum treatment process is ≤0.045%, and the rest is C and 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.

15. The method for manufacturing high-purity high-carbon steel wire according to claim 1, characterized in that: The ladle bricks used in step 3 are magnesia carbon bricks, wherein the magnesia alumina spinel content is ≤3.0%, the C content is ≤3%, and the rest are unavoidable impurity components; In step 4, the refractory materials used for the immersion tube and the bottom tank of the RH vacuum furnace are magnesia-chrome ultra-low carbon bricks, wherein the C content is ≤1.5%, MgO: 85-95%, Cr2O3: 5-12%, magnesia-alumina spinel ≤3%, and other inevitable impurity components.

16. The method for manufacturing high-purity high-carbon steel wire according to claim 3, characterized in that: In step 5, the main components of the continuous casting low-basicity low-alumina tundish covering agent include: CaO: 40-50%, SiO2: 30-40%, CaF2: 3-6%, Al2O3≤2%, MgO: 3-6%, and other inevitable components; The composition of the magnesium spray coating for the inner wall of the tundish includes MgO≥80%, CaO: 5-10%, SiO2: 1-3%, and other inevitable components.

17. The method for manufacturing high-purity high-carbon steel wire according to claim 4, characterized in that: In the step 5, an integral immersion nozzle is used for casting, the immersion nozzle insertion depth is 10-15 mm, the thickness of the mold protective slag layer is 10-20 mm, and the consumption is 0.15-0.25 kg / ton; The materials of the stopper rod and nozzle are magnesium carbon. The components of the stopper rod head are calculated by mass percentage, MgO content is 80-85%, C content is 8-12%, Al2O3 content is ≤1.5%, SiC content is 1-4%, SiO2 content is 2-3%, and other inevitable impurities; The inner wall thickness of the submerged nozzle is 5-7mm, and the composition, by mass percentage, includes MgO: 75-80%, C: 6-10%, SiC: 3-5%, SiO2: 5-10%, and other unavoidable impurity components.

18. The method for manufacturing high-purity high-carbon steel wire according to claim 1, characterized in that: In step 6, a protective coating is sprayed before the rolled billet enters the heating furnace. The coating thickness is 0.3-1.5 mm. The high-temperature coating composition includes CaO, SiO2, Al2O3, MgO, ZrO2, C and a small amount of alkali metal oxides, inorganic binders and surfactants.

19. The method for manufacturing high-purity high-carbon steel wire according to claim 3, characterized in that: The large square bloom is opened into a billet with a cross section of 140mm×140mm, and is subjected to flaw detection and grinding, heating in a heating furnace, rolling, and temperature-controlled cooling on a Stelmor air cooling line. The obtained wire rod has no folding, scarring, or scratch defects on its surface, and has no complete decarburization layer on its surface.

20. A high-purity high-carbon steel wire made by the method according to any one of claims 1 to 19.

21. A wire rod, characterized in that: Made from the high-purity high-carbon steel wire rod as described in claim 20, the wire rod includes high-quality cord steel wire rod with a C content ≤0.87% and a drawing diameter of 0.1mm or more, and high-quality gold steel wire rod with a C content of 0.87% <1.0% and a drawing diameter of 0.05mm or more.

22. A 1600-2400 MPa spring steel or 1800-2200 MPa cable steel made from the high-purity high-carbon steel wire rod according to claim 20.

23. A high-purity high-carbon steel wire according to claim 20, characterized in that: The high-purity high-carbon steel wire component includes, in addition to alloy elements and Fe elements, the following chemical components in mass percentage: C: 0.5-1.0%, P≤0.008%, S≤0.0025%, TO≤0.0010%, N≤0.0020%, H≤0.0002%, Alt≤0.0010% and Ti≤0.0005%.

24. The high-purity high-carbon steel wire according to claim 23, characterized in that: The mass content of the inclusions in the high carbon steel wire, except for SiO2-MnO inclusions, is ≤20%, and the number density of inclusions larger than 1 μm is ≤3.5 / mm 2 , the number density of inclusions larger than 5μm is ≤0.06 / mm 2 , the maximum transverse size of inclusions ≤12μm, the maximum width of longitudinal inclusions ≤10μm, the length ≤25μm, the size of brittle inclusions ≤3μm, the C segregation index of the ingot is 0.95-1.05, and the C segregation index of the wire rod is ≤1.05.

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