Small-specification low-chromium high-carbon steel wire rod and preparation method thereof

Abstract

The invention relates to a small-specification low-chromium high-carbon steel wire rod and a preparation method thereof. The diameter of the wire rod is # imgabs0. Chemical components of the wire rod comprise 0.79%-0.84% of C, 0.20%-0.30% of Si, 0.70%-0.90% of Mn, smaller than or equal to 0.020% of P, smaller than or equal to 0.020% of S, 0.18%-0.23% of Cr, smaller than or equal to 0.0040% of O, smaller than or equal to 0.0050% of N and the balance Fe and impurities. The production technology process mainly including KR molten iron pretreatment, converter smelting, LF refining furnace smelting, continuous casting, controlled rolling and controlled cooling and heat preservation channel slow cooling is adopted, the sorbite rate of the product reaches 90% or above through the measures of Cr micro-combination, the stelmor cooling technology and the like, the requirements of the high strength and the drawing technology of the wire rod are met, and the product quality is improved. The problems that in the wire rod production process, due to the fact that abnormal structure martensite appears, the strength is high, and brittle failure is caused in the wire rod drawing process are solved.

Description

Technical Field

[0001] The invention relates to the technical field of wire rod preparation, and in particular to a small-sized low-chromium high-carbon steel wire rod and a preparation method thereof. Background Art

[0002] SWRH82B and C82D2 wire rods, the main raw materials for prestressed steel wire and stranded wire, are widely used in railways, highways, bridges, urban overpasses, large cement water pipes, high-rise earthquake-resistant buildings, mine support and other fields. Export wire rods require high strength without reducing plasticity. In actual production, the diameter Some high-carbon steel wire rods (such as SWRH82B wire rods, C82D2 wire rods, etc.) have abnormal martensite structure, which leads to high strength and prominent brittle fracture during wire rod drawing.

[0003] The Chinese invention patent with application number 200910187459.6 discloses "a method for controlled cooling of high carbon steel wire rod after rolling". After spinning, controlled cooling is carried out on the roller. The cooling roller is concave, and a water tank is set in the concave part. The roller is wrapped in the water tank containing water. After spinning, the wire rod enters the water tank for controlled cooling. After exiting the water tank, the wire rod is air-cooled to room temperature. After adopting the controlled cooling process after rolling of high carbon steel wire rod, the troostitization rate of high carbon steel wire rod is increased from 80% to 85% of the air cooling process to more than 95%. Because the water tank is set on the roller after spinning, and the roller is wrapped in the water tank containing water, the equipment occupies a large area, the water consumption in the production process is increased, and the cost is increased relative to the ordinary production process.

[0004] The Chinese invention patent with application number 201410176803.2 discloses "a method for controlling the cooling of small-sized high-Cr 82B wire rod after rolling", which involves a controlled cooling process of a high-Cr (alloy content 0.30-0.35%) SWRH82B wire rod after rolling. The goal of stable production is achieved by combining the post-rolling spinning temperature, the cooling rate before the spinning phase change, the phase change temperature range, the cooling rate in the phase change zone, the Stelmor roller speed, the fan air volume and the Jialing air volume distribution, and adjusting the stable spinning mode of the production equipment. The spinning temperature is controlled at 860-880°C, the cooling rate before phase change after rolling is controlled in the range of 10.0-14.0°C / s, the phase change temperature range is controlled in the range of 580-620°C, the cooling rate in the phase change zone is controlled in the range of 1.5-3.0°C / s, and the base speed of the entrance section of the Stelmor roller is controlled in the range of 0.6-1.0m / s. After the application of the controlled cooling method after wire rod rolling, it can ensure that high strength is obtained while the plasticity is not reduced but improved, avoiding uneven cooling of the wire rod and causing the formation of low-temperature transformation organizations such as martensite in local positions, and ensuring the uniformity of the wire rod organization and mechanical properties. The "small specification" mentioned here refers to the diameter The wire rod has a Cr content in the steel ranging from 0.30% to 0.40% (internal control content 0.30-0.35%), and the cross-sectional size of the steel billet ranges from 100mm×100mm to 260mm×260mm. The Cr content is higher than that of the wire rod described in the present application. High carbon steel is added with the hardenability microalloying element Cr (Cr is a carbide-forming element), which mainly exists in the cementite lamellae in the steel, and forms alloy cementite through substitution, which has the characteristics of lowering the pearlite transformation temperature, and can reduce the pearlite lamella spacing of hypereutectoid steel to improve the strength of the steel, and improve plasticity by reducing and inhibiting the precipitation of proeutectoid cementite and refining the grains. The price of ferrochrome is lower than other microalloys, and it has the effect of improving the hardenability of the wire rod, so adding Cr has become one of the main measures for the development of 82B series wire rods. However, the Cr content cannot be too high, especially for small-sized wire rods, it must be controlled within a reasonable range. Compared with large-sized wire rods, small-sized wire rods have a smaller cross-sectional diameter and stronger hardenability, which will cause the CCT curve of the wire rod to move seriously to the lower right after continuous cooling, and then greatly reduce the critical cooling rate of martensite formation. If the cooling control process is slightly improper, it will be very easy to produce low-temperature transformation structures such as martensite and bainite. For small-sized wire rods, higher requirements are also placed on the uniformity of cooling, which brings great difficulties to the control of abnormal structures and fluctuations in mechanical properties during post-rolling cooling.

[0005] The present invention is directed to diameter The small-sized high-carbon steel wire rod is added with a small amount of Cr element to ensure the strength and toughness of the wire rod, while achieving the purpose of cost saving. In addition, the controlled cooling process after wire rod rolling is optimized to reduce the generation of network cementite. The troostitization rate of the small-sized low-chromium high-carbon steel wire rod produced reaches more than 90%, which not only meets the high-strength requirements, but also has good drawing performance. Summary of the invention

[0006] The present invention provides a small-size low-chromium high-carbon steel wire rod and a preparation method thereof, adopting a production process mainly based on "KR molten iron pretreatment + converter smelting + LF refining furnace + continuous casting + controlled rolling and controlled cooling + slow cooling in an insulation channel", and through measures such as Cr micro-combination and Stelmor cooling process, the troostitization rate of the product reaches more than 90%, meeting the high strength and drawing process requirements of the wire rod, and solving the problem of high strength and brittle fracture during the wire rod drawing process caused by the abnormal structure martensite in the wire rod production process.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A small-sized low-chromium high-carbon steel wire rod with a diameter of The chemical composition of the wire rod is C: 0.79% ~ 0.84%, Si: 0.20% ~ 0.30%, Mn: 0.70% ~ 0.90%, P ≤ 0.020%, S ≤ 0.020%, Cr: 0.18% ~ 0.23%, O ≤ 0.0040%, N ≤ 0.0050%, and the balance is Fe and inevitable impurities; the wire rod production process includes blast furnace smelting molten iron, KR molten iron pretreatment, converter smelting molten steel, ladle alloying and static argon blowing, LF furnace refining, square billet continuous casting and billet slow cooling, heating, rolling and wire laying, coiling, and insulation channel slow cooling; the tensile strength of the finished wire rod is 1162 ~ 1230MPa, the cross-sectional shrinkage is 27% ~ 35%, and the sorbitization rate is ≥ 90%; non-metallic inclusions A + C ≤ 1.5 level, B + D ≤ 1.5 level.

[0009] A method for preparing a small-size low-chromium high-carbon steel wire rod, wherein the wire rod production process includes blast furnace smelting of molten iron, KR molten iron pretreatment, converter smelting of molten steel, ladle alloying and static argon blowing, LF furnace refining, billet continuous casting and billet slow cooling, heating, rolling and wire laying, coiling, and insulation channel slow cooling; the specific control process is as follows:

[0010] 1) KR molten iron pretreatment: spray desulfurizer into the molten iron ladle for desulfurization, and the sulfur content in the molten iron after treatment is ≤0.030%;

[0011] 2) Converter smelting molten steel: in terms of weight percentage, scrap steel accounts for 10% to 12% of the steelmaking raw materials, molten iron accounts for 88% to 90%, and 4 to 6 tons of slag steel is added; top and bottom double-blown converter is used for smelting, the tapping temperature is 1600 to 1650°C, the tapping end point [C] ≥ 0.08%, P ≤ 0.012%;

[0012] 3) Ladle alloying and static argon blowing: alloying is carried out in the order of ferrosilicon alloy, silicon-manganese alloy, high carbon ferrochrome and low nitrogen carburizer, without adding deoxidizer, argon blowing time ≥ 5min, medium blowing for 4min first, and then weak blowing; the temperature of molten steel after treatment is 1500℃~1520℃;

[0013] 4) LF furnace refining: maintain a slight positive pressure of 40-70 kPa in the furnace; adopt submerged arc heating; add 5.6-6.0 kg / t steel of active lime, 0.9-1.2 kg / t steel of fluorite, 20-30 kg / furnace of calcium carbide slag to make white slag refining; then add 0.8-1.0 kg / t steel of high carbon ferromanganese, 0.8-1.1 kg / t steel of ferrosilicon, 28-32 kg / furnace of ferrosilicon powder to make alloy fine adjustment; soft blowing time ≥15 min, LF furnace leaving station temperature 1520℃~1535℃;

[0014] 5) Billet continuous casting and billet slow cooling: adopt the whole process protection casting process, use argon to clean the tundish before casting, the purge time is ≥2min; the crystallizer electromagnetic stirring current is ≥320A, frequency is ≥3Hz, and it runs continuously; the electromagnetic stirring current at the end of continuous casting is ≥400A, frequency is ≥8Hz, and it runs alternately in forward and reverse directions; the crystallizer protective slag uses high carbon steel protective slag, and aluminum carbon water nozzle is used for casting. The platform ladle temperature is 1540±5℃, the tundish temperature is 1490℃~1512℃, and the superheat is maintained at 20℃~30℃. The continuous casting adopts a constant pulling speed of 2.0~2.2m / min, and the billet is put into the insulation pit for slow cooling for more than 72h after it comes off the line;

[0015] 6) Heating: Use a walking beam heating furnace for heating, with the preheating section temperature at 880±20℃, the heating section temperature at 1120±20℃, the soaking section temperature at 1150±20℃, and the total heating time at 1.5 to 2.5h;

[0016] 7) Rolling and spinning: Rough rolling temperature is 1020±20℃; Finishing rolling inlet temperature is 920±20℃; Spinning temperature is 860±20℃; Air-cooled roller speed is set as: Head roller speed 0.80~0.85m / s, roller speed increase 2%~5%; Insulation cover is fully open; Fan air volume is set as: 1st to 3rd fan air volume is 178700~179700m 3 / h, the air volume of the 4th and 5th fans is 133900~134900m 3 / h, the air volume of the 6th to 8th fans is 73900~74000m 3 / h, and other fans are fully closed; the air volume of the first half fans is controlled by frequency modulation, and the air volume of the second half fans is controlled by dampers.

[0017] During the KR molten iron pretreatment process, the composition of the desulfurizer is 88% to 92% lime powder + 8% to 12% fluorite powder by weight.

[0018] Auxiliary materials are added during the ladle alloying and static argon blowing treatment, including 4.2-6.24 kg / t of lime, 30-44 kg / t of limestone, and 4.2-4.4 kg / t of dolomite.

[0019] During the ladle alloying and static argon blowing treatment, the amount of ferrosilicon alloy added is 0.56-0.73 kg / t steel, the amount of silicon manganese alloy added is 7.2-8.9 kg / t steel, the amount of high carbon ferrochrome added is 2.8-3.2 kg / t steel, and the amount of low nitrogen recarburizer added is 480-520 kg / t steel.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1) The production process mainly consists of "KR molten iron pretreatment + converter smelting + LF refining furnace + continuous casting + controlled rolling and controlled cooling + slow cooling in an insulation channel". Through measures such as Cr micro-combination and Stelmor cooling process, the sorbitization rate of the product reaches more than 90%, which meets the high strength and drawing process requirements of the wire rod, and solves the problem of high strength and brittle fracture during the wire rod drawing process caused by the abnormal martensite structure in the wire rod production process.

[0022] 2) Applicable to diameter specifications By adding a small amount of Cr element to high carbon steel wire rod (such as SWRH82B, C82D2 wire rod), the purpose of cost saving is achieved while ensuring the strength and toughness of the wire rod; by optimizing the controlled cooling process after wire rod rolling, the sorbitization rate is achieved to reach more than 90%, the generation of network cementite is reduced, and the wire rod has high strength and good drawing properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a metallographic structure photograph of a small-sized low-chromium high-carbon steel wire rod described in the present invention.

[0024] Figure 2 yes Figure 1 The figure shows the thickness of the decarburized layer of a small-sized low-chromium high-carbon steel wire rod. DETAILED DESCRIPTION

[0025] The small-size low-chromium high-carbon steel wire rod described in the present invention adopts a process with the process of "blast furnace smelting molten iron → KR molten iron pretreatment (desulfurization and slag removal) → converter (top and bottom double blowing) smelting molten steel → ladle alloying and argon blowing treatment → LF furnace refining → eight-stream square billet continuous casting (electromagnetic stirring of crystallizer and electromagnetic stirring at the end of solidification) → slow cooling of steel billet → (walking beam heating furnace) heating → rolling → wire laying → inspection → coiling → slow cooling in insulation channel → sampling, inspection and judgment → packaging and delivery to warehouse", and the product produced is high-performance prestressed steel wire wire rod (SWRH82B, C82D2 wire rod).

[0026] The chemical composition design (mass percentage) of the small-size low-chromium high-carbon steel wire rod described in the present invention is C: 0.79%-0.84%, Si: 0.20%-0.30%, Mn: 0.70%-0.90%, P≤0.020%, S≤0.020%, Cr: 0.18%-0.23%, O≤0.0040%, N≤0.0050%, and the balance is Fe and unavoidable impurities.

[0027] The reasons for the composition design are as follows:

[0028] C: Carbon can improve the strength and hardness of steel, but as the carbon content increases, the plasticity and toughness of steel decrease. The present invention controls the C content to 0.79% to 0.84%.

[0029] Si: Silicon can also improve the strength and hardness of steel, reduce the plasticity and toughness of steel, and also has a deoxidizing effect in the steelmaking process. The present invention controls the Si content to 0.20% to 0.30%.

[0030] Mn: Manganese can improve the strength of steel, can combine with sulfur to form manganese sulfide to eliminate the "hot brittleness" of steel, and can also improve the hardenability and wear resistance of steel. In the present invention, the Mn content is controlled to 0.70% to 0.90%.

[0031] P, S: Phosphorus and sulfur are harmful elements in steel. Phosphorus dissolves in ferrite. Although it can improve the strength and hardness of steel, its biggest harm is serious segregation, increased temper brittleness, and significantly reduced plasticity and toughness of steel, making steel easy to crack during cold working, which is the so-called "cold brittle" phenomenon; sulfur can reduce the plasticity of steel, increase the brittleness of steel, and deteriorate the quality of steel. The present invention controls P≤0.020%, S≤0.020%.

[0032] Cr: Chromium is a carbide-forming element. When properly matched with carbon and manganese, it can strengthen the matrix, refine the grains, improve the strength, hardness, hardenability and wear resistance of steel, and improve the corrosion resistance and oxidation resistance of steel. The addition of a small amount of chromium can increase the solubility of vanadium in austenite and enhance the solid solution strengthening effect of vanadium. The present invention controls the Cr content to 0.18% to 0.23%.

[0033] The production process of a small-sized low-chromium high-carbon steel wire rod described in the present invention mainly controls the following processes:

[0034] (1) KR hot metal pretreatment: After smelting hot metal in a blast furnace, a desulfurizing agent (composition of 88% to 92% lime powder + 8% to 12% fluorite powder) is sprayed into the hot metal ladle for desulfurization. After treatment, the S content of the hot metal is required to be ≤ 0.030%.

[0035] (2) Converter smelting of molten steel: In terms of weight percentage, scrap steel accounts for 10% to 12% of the steelmaking raw materials, and molten iron accounts for 88% to 90%. In addition, 4 to 6 tons of slag steel are added. Desulfurized slag steel and nickel-copper scrap steel are prohibited. The top and bottom combined blowing converter is used for smelting. The tapping temperature is 1600 to 1650°C. The tapping end point [C] ≥ 0.08%, P ≤ 0.012%. Slag is strictly prohibited: avoid spot blowing. Ensure that the end point carbon content and temperature are hit once. In case of secondary spot blowing, the cover must be lowered first.

[0036] (3) Ladle alloying: Alloying is carried out in the order of ferrosilicon alloy, silicomanganese alloy, high carbon ferrochrome, and low nitrogen carburizer, without adding deoxidizer, and the argon blowing time is ≥5 minutes. The target amount of alloy added per ton of steel is: silicomanganese alloy 7.2-8.9 kg / t steel, ferrosilicon alloy 0.56-0.73 kg / t steel, high carbon ferrochrome 2.8-3.2 kg / t steel, and low nitrogen carburizer 500 kg / t steel. In addition, auxiliary materials are added, including lime 4.2-6.24 kg / t steel, limestone 30-44 kg / t steel, and dolomite 4.2-4.4 kg / t steel.

[0037] (4) Static argon blowing: The argon blowing time is ≥ 5 minutes, first medium blowing for 4 minutes, then weak blowing; the temperature of the molten steel after argon blowing treatment is 1500℃~1520℃.

[0038] (5) LF furnace refining: The furnace is kept at a slight positive pressure of 40-70 kPa, and submerged arc heating is used, and the arc light does not leak out. Active lime 5.6-6.0 kg / t steel, fluorite 0.9-1.2 kg / t steel, carbide slag 20-30 kg / furnace are added to make white slag refining, and high carbon ferromanganese 0.8-1.0 kg / t steel, ferrosilicon 0.8-1.1 kg / t steel, ferrosilicon powder 30 kg / furnace are added to fine-tune the alloy. The soft blowing time is ≥15 min. The temperature of the LF furnace leaving the station is 1520℃~1535℃.

[0039] (6) Billet continuous casting and slow cooling of billets: In order to ensure the quality of billets, measures such as controlling the superheat of molten steel, billet drawing speed, electromagnetic stirring of continuous casting crystallizer and electromagnetic stirring at the end are taken to control defects such as carbon center segregation, looseness or shrinkage of billet center. Protect the casting during the whole process. Use argon to clean the tundish before casting. The purge time is ≥2min. The electromagnetic stirring current of the crystallizer is ≥320A, the frequency is ≥3Hz, and it runs continuously; the electromagnetic stirring current at the end of continuous casting is ≥400A, the frequency is ≥8Hz, and it runs alternately in forward and reverse directions. High carbon steel protective slag is used for the crystallizer protective slag. Aluminum carbon water nozzle must be used for casting. The platform ladle temperature is 1540±5℃, the tundish temperature is 1490℃~1512℃, the superheat is maintained at 20℃~30℃, and the pulling speed is controlled at 2.0~2.2m / min; a constant pulling speed is used to reduce liquid level fluctuations. The billet is put into the insulation pit for slow cooling for more than 72 hours after it is off the line.

[0040] (7) Heating: Use a walking beam heating furnace for heating, with the preheating section temperature at 880±20℃, the heating section temperature at 1120±20℃, the soaking section temperature at 1150±20℃, and the total heating time at 1.5 to 2.5 hours.

[0041] (8) Rolling and spinning: Rough rolling temperature is 1020±20℃; Finishing rolling inlet temperature is 920±20℃; Spinning temperature is 860±20℃; Air-cooled roller speed is set as: Head roller speed 0.85m / s; Roller speed increase 2~5%. Insulation cover is fully open; Fan air volume is set as: 1st to 3rd fan air volume is 178700~179700m 3 / h, the air volume of the 4th and 5th fans is 133900~134900m 3 / h, the air volume of the 6th to 8th fans is 73900~74000m 3 / h, and other fans are fully closed; the air volume of the first half fans is controlled by frequency modulation, and the air volume of the second half fans is controlled by dampers.

[0042] (9) Insulation channel slow cooling: Insulation channel slow cooling is used to effectively release tissue stress and internal stress, ensuring product performance and the performance requirements of the pass rod.

[0043] The small-sized low-chromium high-carbon steel wire rod of the present invention has a tensile strength of 1162-1230 MPa, a cross-sectional shrinkage of 27%-35%, a non-metallic inclusion rating of: A+C≤1.5, B+D≤1.5, and a wire rod troostitization rate of more than 90%.

[0044] The contents not specified in the present invention are all by mass.

[0045] The metallographic structure photo of a small-sized low-chromium high-carbon steel wire rod described in the present invention is as follows: Figure 1 As shown, the decarburized layer thickness is marked as Figure 2 shown.

[0046] The following embodiments are implemented on the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0047] [Example]

[0048] The chemical composition of the wire rod of each embodiment is shown in Table 1, the converter smelting-LF furnace refining process parameters of each embodiment are shown in Table 2, the continuous casting process parameters of each embodiment are shown in Table 3, the heating process parameters of each embodiment are shown in Table 4, the rolling and spinning process parameters of each embodiment are shown in Table 5, the low-magnification defect inspection results of the ingots of each embodiment are shown in Table 6, the finished product properties of the wire rod of each embodiment are shown in Table 7, and the inspection results of the wire rod microstructure and non-metallic inclusions of each embodiment are shown in Table 8.

[0049] Table 1 Chemical composition of wire rod (mass percentage, %)

[0050] Example C Si Mn P S Cr O N 1 0.82 0.23 0.75 0.009 0.005 0.20 0.0031 0.0029 2 0.79 0.24 0.74 0.011 0.009 0.21 0.0035 0.0025 3 0.80 0.26 0.70 0.010 0.012 0.19 0.0020 0.0035 4 0.81 0.20 0.90 0.007 0.014 0.18 0.0019 0.0030 5 0.83 0.28 0.82 0.008 0.008 0.22 0.0025 0.0032 6 0.84 0.30 0.85 0.013 0.010 0.23 0.0035 0.0038

[0051] Table 2 Converter smelting-LF furnace refining process parameters

[0052]

[0053] Table 3 Continuous casting process parameters

[0054]

[0055] Table 4 Heating process parameters

[0056]

[0057] Table 5 Rolling and laying process parameters

[0058]

[0059] Table 6 Results of macroscopic defects inspection of ingot

[0060]

[0061] Table 7 Wire rod finished product properties

[0062] Example Diameter(mm) Tensile strength(MPa) Sectional shrinkage (%) 1 8 1184 28 2 12 1230 29 3 8 1193 27 4 10 1195 29 5 8 1162 30 6 8 1174 32

[0063] Table 8 Wire rod microstructure and non-metallic inclusion inspection results

[0064]

[0065] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A small-sized low-chromium high-carbon steel wire rod, characterized in that: The diameter of the wire rod is The chemical composition of the wire rod is C: 0.79% ~ 0.84%, Si: 0.20% ~ 0.30%, Mn: 0.70% ~ 0.90%, P ≤ 0.020%, S ≤ 0.020%, Cr: 0.18% ~ 0.23%, O ≤ 0.0040%, N ≤ 0.0050%, and the balance is Fe and inevitable impurities; the wire rod production process includes blast furnace smelting molten iron, KR molten iron pretreatment, converter smelting molten steel, ladle alloying and static argon blowing, LF furnace refining, square billet continuous casting and billet slow cooling, heating, rolling and wire laying, coiling, and insulation channel slow cooling; the tensile strength of the finished wire rod is 1162 ~ 1230MPa, the cross-sectional shrinkage is 27% ~ 35%, and the sorbitization rate is ≥ 90%; non-metallic inclusions A + C ≤ 1.5 level, B + D ≤ 1.5 level.

2. The method for preparing a small-sized low-chromium high-carbon steel wire rod as claimed in claim 1, characterized in that: The wire rod production process includes blast furnace smelting of molten iron, KR molten iron pretreatment, converter smelting of molten steel, ladle alloying and static argon blowing, LF furnace refining, billet continuous casting and billet slow cooling, heating, rolling and wire laying, coiling, and insulation channel slow cooling; the specific control process is as follows: 1) KR hot metal pretreatment: spray desulfurizer into the hot metal ladle for desulfurization, and the sulfur content in the hot metal after treatment is ≤0.030%; 2) Converter smelting molten steel: in terms of weight percentage, scrap steel accounts for 10% to 12% of the steelmaking raw materials, molten iron accounts for 88% to 90%, and 4 to 6 tons of slag steel is added; top and bottom double-blown converter is used for smelting, the tapping temperature is 1600 to 1650°C, the tapping end point [C] ≥ 0.08%, P ≤ 0.012%; 3) Ladle alloying and static argon blowing: alloying is carried out in the order of ferrosilicon alloy, silicon-manganese alloy, high carbon ferrochrome and low nitrogen carburizer, without adding deoxidizer, argon blowing time ≥ 5min, medium blowing for 4min first, and then weak blowing; the temperature of molten steel after treatment is 1500℃~1520℃; 4) LF furnace refining: maintain a slight positive pressure of 40-70 kPa in the furnace; adopt submerged arc heating; add 5.6-6.0 kg / t steel of active lime, 0.9-1.2 kg / t steel of fluorite, 20-30 kg / furnace of calcium carbide slag to make white slag refining; then add 0.8-1.0 kg / t steel of high carbon ferromanganese, 0.8-1.1 kg / t steel of ferrosilicon, 28-32 kg / furnace of ferrosilicon powder to make alloy fine adjustment; soft blowing time ≥15 min, LF furnace leaving station temperature 1520℃~1535℃; 5) Billet continuous casting and billet slow cooling: adopt the whole process protection casting process, use argon to clean the tundish before casting, the purge time is ≥2min; the crystallizer electromagnetic stirring current is ≥320A, frequency is ≥3Hz, and it runs continuously; the electromagnetic stirring current at the end of continuous casting is ≥400A, frequency is ≥8Hz, and it runs alternately in forward and reverse directions; the crystallizer protective slag uses high carbon steel protective slag, and aluminum carbon water nozzle is used for casting. The platform ladle temperature is 1540±5℃, the tundish temperature is 1490℃~1512℃, and the superheat is maintained at 20℃~30℃. The continuous casting adopts a constant pulling speed of 2.0~2.2m / min, and the billet is put into the insulation pit for slow cooling for more than 72h after it comes off the line; 6) Heating: Use a walking beam heating furnace for heating, with the preheating section temperature at 880±20℃, the heating section temperature at 1120±20℃, the soaking section temperature at 1150±20℃, and the total heating time at 1.5 to 2.5h; 7) Rolling and spinning: Rough rolling temperature is 1020±20℃; Finishing rolling inlet temperature is 920±20℃; Spinning temperature is 860±20℃; Air-cooled roller speed is set as: Head roller speed 0.80~0.85m / s, roller speed increase 2%~5%; Insulation cover is fully open; Fan air volume is set as: 1st to 3rd fan air volume is 178700~179700m 3 / h, the air volume of the 4th and 5th fans is 133900~134900m 3 / h, the air volume of the 6th to 8th fans is 73900~74000m 3 / h, and other fans are fully closed; the air volume of the first half fans is controlled by frequency modulation, and the air volume of the second half fans is controlled by dampers.

3. The method for preparing a small-sized low-chromium high-carbon steel wire rod according to claim 2, characterized in that: During the KR molten iron pretreatment process, the composition of the desulfurizer is 88% to 92% lime powder + 8% to 12% fluorite powder by weight.

4. The method for preparing a small-sized low-chromium high-carbon steel wire rod according to claim 2, characterized in that: Auxiliary materials are added during the ladle alloying and static argon blowing treatment, including 4.2-6.24 kg / t of lime, 30-44 kg / t of limestone, and 4.2-4.4 kg / t of dolomite.

5. The method for preparing a small-sized low-chromium high-carbon steel wire rod according to claim 2, characterized in that: During the ladle alloying and static argon blowing treatment, the amount of ferrosilicon alloy added is 0.56-0.73 kg / t steel, the amount of silicon manganese alloy added is 7.2-8.9 kg / t steel, the amount of high carbon ferrochrome added is 2.8-3.2 kg / t steel, and the amount of low nitrogen recarburizer added is 480-520 kg / t steel.

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