A large gauge non-annealed b steel rod and a method of producing the same

Abstract

This invention discloses a type of non-annealed B steel wire rod suitable for large-size applications. The wire rod is based on Fe and also contains the following chemical composition (wt%): C: 0.28~0.34%, Si: 0.07~0.15%, Mn: 0.60~0.90%, P: ≤0.0025%, S: ≤0.0025%, Cr: 0.30~0.40%, Mo: 0.05~0.10%, Ni: 0.05~0.12%, B: 0.0005~0.0060%, Al: 0.015~0.040%, O: ≤0.0015%, N: 0.0040~0.0090%, H: ≤0.0002%. The production method is as follows: KR hot metal pretreatment—converter smelting—LF+RH refining—continuous casting—warm or hot feeding of continuously cast billets—heating and billet opening of continuously cast billets—cleaning of continuously cast billets—heating—high-pressure water descaling—controlled rolling and temperature control—Stelmore cooling—wire rod. The microstructure of this B steel wire rod is F+P, with uniform structure, ferrite content ≥40%, actual grain size 6~8, tensile strength ≤620Mpa, reduction of area ≥53%, hardness ≤88HRB, excellent through-bar performance, no softening annealing is required before drawing, and it can be directly drawn with a large reduction in area, reducing production costs and saving energy and protecting the environment.

Description

Technical Field

[0001] This invention relates to the field of steel material preparation technology, specifically to a method for producing large-size, non-annealed B steel wire rod. Background Technology

[0002] B steel, due to its good strength, toughness, and machinability, is widely used in machinery manufacturing, automotive parts, fasteners, and other fields. However, due to the hardenability of B steel, traditional production techniques make it difficult to manufacture large-diameter B steel wire rods with a diameter of φ15mm or more. According to ASTM 29 standard, the chemical composition of traditional B steel wire rods contains only C: 0.28~0.34%, Si: 0.07~0.15%, and Mn: 0.60~0.90%. The resulting product has poor hardenability, uneven microstructure, low ferrite content, high tensile strength, low reduction of area, and high hardness, making it unsuitable for direct drawing.

[0003] To meet drawing requirements, existing technologies typically require prolonged annealing heat treatment for large-diameter B-steel wire rods. This not only increases production cycle time and energy consumption, raising production costs, but also leads to surface oxidation and decarburization, affecting product quality. Meanwhile, controlled rolling and controlled cooling technology, as an effective means to improve the microstructure and mechanical properties of materials, is currently only applied to low-carbon carbon steel and low-carbon alloy steel. Due to the compositional characteristics and process sensitivity of large-diameter B-steel, this technology has not yet been successfully applied to the production of large-diameter B-steel wire rods.

[0004] Therefore, developing a large-size B-type steel wire rod with a reasonable composition design, optimized production process, and the ability to be directly drawn with a large reduction in surface area without annealing has become a pressing technical problem for the steel industry. It is of great significance for enhancing the industry's competitiveness and practicing the concept of green and low-carbon production. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for producing large-size non-annealed B steel wire rods, which is in contrast to the above-mentioned prior art. Through precise composition design and optimized process scheme, large-size B steel wire rods with uniform microstructure, high ferrite content, low tensile strength, high area reduction ratio, low hardness and good through-strand performance are obtained. They can be directly drawn with large area reduction without annealing treatment, thereby reducing production costs and saving energy and protecting the environment.

[0006] The technical solution adopted by the present invention to solve the above problems is as follows: a type of non-annealed B steel wire rod suitable for large specifications, wherein the wire rod is based on Fe and also contains the following chemical composition by mass percentage (wt%): C: 0.28~0.34%, Si: 0.07~0.15%, Mn: 0.60~0.90%, P: ≤0.0025%, S: ≤0.0025%, Cr: 0.30~0.40%, Mo: 0.05~0.10%, Ni: 0.05~0.12%, B: 0.0005~0.0060%, Al: 0.015~0.040%, O: ≤0.0015%, N: 0.0040~0.0090%, H: ≤0.0002%, with the remainder being impurity elements; The design basis and main functions of each chemical element are as follows: C: Carbon directly affects the strength, plasticity, and toughness of materials. Solid solution strengthening and precipitation strengthening can significantly improve the strength of steel, but excessively high carbon content will reduce the plasticity and toughness of the steel. In this invention, the carbon content range is set at 0.28-0.34%.

[0007] Si: Silicon is an important reducing agent and deoxidizer in the steelmaking process. Silicon can dissolve in ferrite and austenite to increase the hardness and strength of steel, but at the same time it will reduce the plasticity and toughness of ferrite. Taking into account the effects of silicon on strength and plasticity, the silicon content range of this invention is set to 0.07-0.15%.

[0008] Mn: As a strengthening element in steel, manganese improves the strength of the material while having a relatively small impact on its plasticity. Furthermore, manganese is relatively inexpensive. In the steelmaking process, manganese is an excellent deoxidizer and desulfurizer. Mn can combine with sulfur (S) to form high-melting-point MnS, thereby weakening and eliminating the adverse effects of sulfur. In this invention, the manganese content is set at 0.60-0.90%.

[0009] Cr: Chromium increases the hardenability of steel and has a secondary hardening effect, improving the hardness and wear resistance of carbon steel without making it brittle. However, increasing the chromium content affects the microstructure transformation curve of the steel, causing changes in the spheroidization principle and method. In this invention, the chromium content is set at 0.30-0.40%. Mo: Molybdenum has solid solution strengthening and grain refinement properties. It can inhibit the growth of austenite grains. After grain refinement, the overall performance of steel can be improved. Because refined grains have higher strength, toughness and better processing performance, etc.

[0010] Ni: Nickel can improve the toughness of steel and stabilize austenite. It can expand the austenite phase region and stabilize the austenite structure, resulting in better plasticity and toughness. In this invention, the nickel content is set at 0.05~0.12%.

[0011] B: Boron has an effective hardening effect and a grain refining effect. Boron combines with other elements in steel to form borides, which pin grain boundaries and prevent grain growth.

[0012] Al: Aluminum is a commonly used deoxidizer that can effectively reduce the oxygen content of molten steel. At the same time, aluminum fixes nitrogen in steel to form AlN, which plays a role in refining grains. However, excessive aluminum will lead to an increase in Al2O3 inclusions, reducing the purity of molten steel and deteriorating its cold working performance. In this invention, the aluminum content is set at 0.015-0.040%.

[0013] Nitrogen (N) combines with aluminum to form fine, dispersed AlN, which can refine grains and improve steel properties. However, as the nitrogen content increases, plasticity and toughness decrease significantly, while cold brittleness intensifies. In this invention, the nitrogen content is set at 0.0040-0.0090%.

[0014] P, S, O, and H are all harmful elements. P causes cold brittleness, S causes hot brittleness, O forms oxide inclusions, and H causes hydrogen embrittlement. This invention strictly controls their content: P ≤ 0.0025%, S ≤ 0.0025%, O ≤ 0.0015%, and H ≤ 0.0002%, thereby improving the purity and safety of the steel.

[0015] The specifications of this wire rod are φ5.5~23mm. The microstructure is uniform and fine ferrite + pearlite (F+P). The ferrite content is ≥40%, the actual grain size is 6~8, the tensile strength is ≤620Mpa, the reduction of area is ≥53%, the hardness is ≤88HRB, and the wire rod has excellent performance and can be directly drawn with a large reduction in area.

[0016] The above-mentioned method for manufacturing large-diameter non-annealed B steel wire rod includes the following specific steps: Step 1: Raw material preparation and smelting The smelting raw materials are precisely formulated according to the above chemical composition to ensure that the content of each element meets the design requirements. The smelting process includes the following steps: KR molten iron pretreatment: Deep desulfurization and dephosphorization of molten iron is carried out using mechanical stirring to ensure full contact between the desulfurizing agent and the molten iron. After treatment, the sulfur content of the molten iron is ≤0.0050%, ensuring the high purity of the molten iron entering the converter.

[0017] Converter smelting: The pretreated molten iron is fed into the converter, heated and slag is formed to remove carbon and phosphorus. The carbon content at the end point is strictly controlled (matching the carbon content in the design composition). When tapping the steel, devices such as slag cones are used to prevent slag from falling and to avoid secondary pollution of the molten steel.

[0018] LF+RH refining: The molten steel from the converter is fed into the LF refining furnace. By adjusting the composition of the refining slag, the intensity and time of argon blowing and stirring, the inclusions in the molten steel are removed, and the temperature and composition of the molten steel are made uniform. Then it is transferred to the RH vacuum refining furnace for vacuum treatment to control the hydrogen content of the molten steel to ≤1.0ppm, thereby further improving the purity of the molten steel.

[0019] Continuous casting: Full-process protective casting is adopted to prevent secondary oxidation of molten steel; the liquid level in the crystallizer is controlled by automatic technology to maintain a stable liquid level; low superheat (≤30℃) and low casting speed (0.8~1.2m / min) casting are adopted, combined with light reduction technology and electromagnetic stirring technology to improve billet segregation and obtain a continuous casting billet with uniform composition and excellent internal quality.

[0020] Step 2: Continuous casting billet processing After the continuously cast billet exits the crystallizer, it is transferred to the heating furnace by warm conveying (temperature ≥ 600℃) or hot conveying (temperature ≥ 800℃) to reduce temperature loss and save energy.

[0021] The continuously cast billet is heated to 1150~1200℃ and rolled into a small square billet of □150mm²~□200mm² to ensure the compression ratio requirement for subsequent rolling.

[0022] After the billet is cut off from the production line, it undergoes slow cooling treatment for ≥24 hours to eliminate internal stress. After slow cooling, the surface of the billet is peeled (to remove the oxide scale and defect layer, with a peeling thickness ≥3mm) and then manually ground to ensure that the surface of the billet is smooth, the corners are rounded, and there are no defects such as cracks, inclusions, or oxide scale, so as to avoid overheating of the corners and decarburization during the heating process.

[0023] Step 3: Heating The processed small square billets are then fed into a heating furnace for three-stage heating, specifically: Preheating section: The temperature is gradually increased from room temperature to 800~900℃, and the temperature is increased slowly to avoid excessive thermal stress on the billet and cracks. Heating section: The temperature rises to 1000~1080℃, and the temperature rises rapidly to ensure that the billet temperature quickly reaches the solution temperature of the alloying elements; Soaking zone: The temperature is controlled at 1080℃~1100℃, the holding time is ≥40min, and the residual oxygen content in the furnace is ≤2.0% to ensure uniform billet temperature, full solid solution and uniform distribution of alloying elements in steel, while avoiding excessive surface decarburization.

[0024] Step 4: Descaling and Rolling After the heated billet is taken out of the furnace, it is immediately subjected to high-pressure water descaling treatment with a pressure of ≥15MPa to remove the oxide scale generated on the surface and prevent the oxide scale from being pressed into the surface of the billet and affecting the product quality.

[0025] Rough rolling: After descaling, the steel billet enters the rough rolling mill. The initial rolling temperature is controlled at 880~950℃. Large reduction rolling is adopted, with a total compression ratio of ≥65%, so that the deformation penetrates to the center of the steel billet and ensures uniform core properties.

[0026] Intermediate and finishing mill: After being cooled by a water tank, the rough-rolled workpiece enters the intermediate and finishing mill. The temperature of the workpiece entering the finishing mill is controlled at 860~900℃ by adjusting the water tank pressure (0.8~1.2MPa) and the water valve opening. The workpiece passes through 2~3 rolling mills before the intermediate and finishing mill to make the surface and core temperatures uniform. The total compression ratio of the intermediate and finishing mill is ≥95%, which further refines the grains and improves the uniformity of the microstructure.

[0027] Sizing and reducing: The rolled piece after intermediate and finishing rolling enters the sizing and reducing mill. The entry temperature is controlled at 850~880℃. The compression ratio of the last two passes is ≥35% to ensure the dimensional accuracy and surface quality of the rolled piece, while further optimizing the microstructure.

[0028] Step 5: Cooling The sizing-reduced rolled piece enters the Stellm cooling line at a wire drawing temperature of 840℃~860℃, employing a slow cooling process. The roller conveyor speed is maintained at a constant speed of 0.10m / s to 0.20m / s to ensure uniform cooling of the wire rod; 0-2 insulation covers are opened according to cooling requirements, and the rest are closed. The wire rod stays in the cover for 7-14 minutes, and the cooling rate is controlled at 0.2-0.6℃ / s to ensure that the F+P structure transformation is complete and uniform and fine. After the wire rod exits the insulation cover, it is naturally air-cooled to room temperature to obtain the finished large-size non-annealed B steel wire rod.

[0029] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention provides a solid compositional basis for the anneal-free performance of large-size B steel wire rods by using precise compositional design to coordinate the proportions of multiple alloying elements and combining strict control of harmful elements, thus breaking through the limitations of traditional B steel compositional design.

[0030] (2) This invention optimizes the complete production process chain and successfully applies controlled rolling and cooling technology to the production of large-size B steel wire rod for the first time. Through the coordinated control of process parameters such as three-stage heating, multi-stage controlled rolling, and precise slow cooling, the precise control of the fine and uniform F+P structure is realized, solving the technical problems of poor uniformity of large-size B steel structure, insufficient ferrite precipitation, and poor performance of the wire rod.

[0031] (3) The product of this invention has a ferrite content of ≥40%, an actual grain size of 6~8, a tensile strength of ≤620Mpa, a shrinkage of area of ​​≥53%, a hardness of ≤88HRB, excellent through-strand performance, and can be directly drawn with a large reduction in area without annealing. Each ton of wire rod can reduce energy consumption by about 300kWh, shorten the production cycle by 12~24 hours, significantly reduce production costs, reduce waste gas emissions, and conform to the concept of green and low-carbon production.

[0032] (4) The specifications of the wire rod produced by this invention cover φ5.5~23mm, especially the large specifications of φ15~23mm, which fills the gap of the prior art, broadens the application range of B steel wire rod, and enhances the market competitiveness of the product. Attached Figure Description

[0033] Figure 1 The image shows the microstructure (×500) of the hot-rolled wire rod in Example 1 of this invention. As can be seen from the image, the wire rod has a microstructure consisting of uniform and fine ferrite (light-colored area) + pearlite (dark-colored area). The ferrite content is high, the grains are fine and uniform, and there are no obvious defects. Detailed Implementation

[0034] The technical solution of the present invention will be described in more detail below with reference to preferred embodiments. However, these embodiments are merely descriptions of preferred implementations of the present invention and should not be construed as limiting the scope of the present invention. Example 1

[0035] The embodiment involves a large-size, non-annealed B steel wire rod with a diameter of ∮5.5mm. The composition and its mass percentage are as follows: C: 0.31%, Si: 0.12%, Mn: 0.70%, P: 0.002%, S: 0.002%, Cr: 0.35%, Mo: 0.08%, Ni: 0.08%, B: 0.035%, Al: 0.025%, N: 0.0056%, O: 0.0008%, H: 0.0001%, with the balance being iron and unavoidable impurity elements.

[0036] The production process suitable for large-size non-annealed B steel wire rod is as follows: According to the chemical composition of the wire rod, the smelting raw materials are configured and carried out in sequence as follows: KR molten iron pretreatment—converter smelting—LF+RH refining—continuous casting—continuous casting billet warm or hot delivery—continuous casting billet heating and billet opening—continuous casting billet cleaning—heating—high pressure water descaling—controlled rolling and temperature control—Stelmo cooling—wire rod.

[0037] In further detail, the specific processes for the heating, rolling, and cooling stages are as follows: The produced continuous casting billet (□200mm2) is heated to 1090℃ and held for 40 minutes, with a residual oxygen content of 1.0% in the furnace. After exiting the furnace, it is descaled by high-pressure water and then rolled. The roughing rolling temperature is 950℃, and the total compression ratio is 68%. The water tank pressure and water valve are adjusted, and after cooling, the billet is passed through several rolling mills to ensure uniform surface and core temperatures. The finishing rolling temperature is 890℃, and the total compression ratio of the intermediate and finishing rolling is 98%. The sizing temperature is 870℃, and the compression ratio of the last two passes is 36%. The wire drawing temperature is 830℃, and a slow cooling process is adopted. The roller speed is constant at 0.15m / s, one heat preservation hood is opened, and the rest are closed. The heat preservation time is 9.5 minutes, and the cooling rate is 0.32℃ / s. The billet is then air-cooled to room temperature after exiting the hood. The finished wire rod produced by the above process has a fine F+P microstructure, uniform structure, high ferrite content, low tensile strength, high reduction of area, and low hardness, and good through-bar performance. Its properties are shown in Table 1. Example 2

[0038] The embodiment involves a large-size, non-annealed B steel wire rod with a diameter of ∮14mm (intermediate size of 5.5~23mm). The composition and its mass percentage are as follows: C: 0.30%, Si: 0.10%, Mn: 0.80%, P: 0.0022%, S: 0.0021%, Cr: 0.33%, Mo: 0.09%, Ni: 0.10%, B: 0.0030%, Al: 0.030%, N: 0.0065%, O: 0.0009%, H: 0.0001%, with the balance being iron and unavoidable impurity elements.

[0039] The production process of wire rod is as follows: Continuous casting billet (□200mm) 2 Heated to 1095℃ and held for 42 minutes, residual oxygen in the furnace: 1.1%. After exiting the furnace, it was descaled by high-pressure water and then rolled: roughing rolling temperature 940℃, total compression ratio 68%; water tank pressure 1.0MPa and water valve opening were adjusted, and after cooling, it was passed through two rolling mills to make the surface and core temperature of the rolled piece uniform. The finishing rolling temperature was 885℃, and the total compression ratio of the intermediate and finishing rolling was 96%. The sizing temperature was 865℃, and the compression ratio of the last two passes was 33%. The wire drawing temperature was 845℃, and a slow cooling process was adopted. The roller speed was 0.16m / s constant. One heat preservation hood was opened and the others were closed. The heat preservation time was 10 minutes, and the cooling rate was 0.35℃ / s. After exiting the hood, it was air-cooled to room temperature.

[0040] The finished wire rod produced by the above process has a uniform and fine F+P microstructure, high ferrite content, and excellent through-bar performance. It can be directly drawn with a large reduction in surface area. Its properties are shown in Table 1. Example 3

[0041] The embodiment involves a large-size, non-annealed B steel wire rod with a diameter of ∮23mm. The composition and its mass percentage are as follows: C: 0.32%, Si: 0.13%, Mn: 0.60%, P: 0.002%, S: 0.002%, Cr: 0.35%, Mo: 0.07%, Ni: 0.08%, B: 0.032%, Al: 0.025%, N: 0.0058%, O: 0.0007%, H: 0.0001%, with the balance being iron and unavoidable impurity elements.

[0042] The production process of wire rod is basically the same as in Example 1, but the rolling and cooling processes differ, as follows: Continuous casting billet (□200mm) 2 Heated to 1080℃ and held for 45 minutes, residual oxygen in the furnace: 1.2%. After exiting the furnace, it was descaled by high-pressure water and then rolled. The roughing rolling temperature was 900℃ and the total compression ratio was 68%. The water tank pressure and water valve were adjusted, and after cooling, it was passed through several rolling mills to make the surface and core temperature of the rolled piece uniform. The finishing rolling temperature was 886℃ and the total compression ratio of the intermediate and finishing rolling was 98%. The sizing temperature was 875℃ and the compression ratio of the last two passes was 36%. The wire drawing temperature was 850℃. A slow cooling process was adopted, with a constant roller speed of 0.18m / s. Two heat preservation hoods were opened and the rest were closed. The heat preservation time was 9 minutes and the cooling rate was 0.36℃ / s. After exiting the hoods, it was air-cooled to room temperature.

[0043] The finished wire rod produced by the above process has a fine F+P microstructure, uniform structure, high ferrite content, low tensile strength, high reduction of area and low hardness, and good through-bar performance. Its properties are shown in Table 1.

[0044] Comparative Example 1 This comparative example uses the composition and manufacturing process of traditional ASTM 29 standard B steel wire rod, with a specification of ∮14mm (the same specification as Example 2, ensuring the validity of the comparison). The components and their mass percentages are as follows: C: 0.30%, Si: 0.10%, Mn: 0.80%, P: 0.0022%, S: 0.0021%, Cr: 0.33%, Mo: 0.09%, Ni: 0.10%, B: 0.0030%, Al: 0.030%, N: 0.0065%, O: 0.0009%, H: 0.0001%, with the balance being iron and unavoidable impurities.

[0045] The production process of wire rod is as follows: The continuously cast billet (□200mm²) is heated to 1050℃ and held for 45 minutes. The residual oxygen content in the furnace is 1.0%. After exiting the furnace, it is descaled by high-pressure water and then rolled: the roughing rolling start temperature is 950℃ and the total compression ratio is 68%. The water tank pressure is adjusted to 1.0MPa and the water valve opening is adjusted. After cooling, it passes through two rolling mills without controlled rolling and controlled cooling technology. The roughing rolling start temperature is 1050℃ and the total compression ratio is 50%. The intermediate and finishing rolling total compression ratio is 85%. The compression ratio of the last two passes of sizing is 25%. It is then naturally air-cooled to room temperature.

[0046] The wire rod produced by the above process has an uneven F+P microstructure (coarse ferrite), a large difference in tensile strength, a low reduction of area, and a slightly higher hardness. The performance of the wire rod is uneven, as shown in Table 1.

[0047] Table 1. Microstructure and mechanical properties of non-annealed B steel wire rods produced in the examples.

[0048] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A large gauge non-annealed B steel wire rod suitable for, Based on Fe, it also contains the following chemical composition by mass percentage: C: 0.28~0.34%, Si: 0.07~0.15%, Mn: 0.60~0.90%, P: ≤0.0025%, S: ≤0.0025%, Cr: 0.30~0.40%, Mo: 0.05~0.10%, Ni: 0.05~0.12%, B: 0.0005~0.0060%, Al: 0.015~0.040%, O: ≤0.0015%, N: 0.0040~0.0090%, H: ≤0.0002%, with the remainder being impurity elements.

2. The method for producing large-diameter, non-annealed B steel wire rod according to claim 1, characterized in that, The specifications of the wire rod are Φ5.5~23mm.

3. The method for producing large-diameter, anneal-free B steel wire rod according to claim 1, characterized in that, The microstructure of the wire rod is ferrite + pearlite (F+P), with a ferrite content ≥40% and an actual grain size of 6~8.

4. The method for producing large-diameter, non-annealed B steel wire rod according to claim 1, characterized in that, The mechanical properties of the wire rod meet the following requirements: tensile strength ≤ 620 MPa, reduction of area ≥ 53%, and hardness ≤ 88 HRB.

5. A method for manufacturing large-diameter non-annealed B steel wire rod as described in any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Smelting: The raw materials for smelting are sequentially subjected to KR hot metal pretreatment, converter smelting, LF+RH refining and continuous casting to obtain steel billets; (2) Continuous casting billet treatment: The continuous casting billet obtained in step (1) is warmly or hotly fed, heated and opened, and then slowly cooled after being taken off the line. After the slow cooling is completed, the surface of the billet is cleaned. (3) Heating: The continuously cast billet cleaned in step (2) is heated in three temperature sections in a heating furnace. The temperature of the soaking section is 1080℃~1100℃, the holding time of the soaking section is not less than 40min, and the residual oxygen content in the furnace is ≤2.0%; (4) Rolling: After the continuous casting billet heated in step (3) is descaled by high-pressure water, it is subjected to rough rolling, intermediate and finishing rolling and sizing rolling in sequence; wherein, the rough rolling start temperature is 880~950℃ and the total compression ratio is ≥65%; the intermediate and finishing rolling temperature is 860~900℃ and the total compression ratio is ≥95%; the sizing rolling start temperature is 850~880℃ and the compression ratio of the last two passes is ≥35%; (5) Cooling: The rolled piece after step (4) enters the Stellmore cooling line at a wire drawing temperature of 840℃~860℃. The slow cooling process is adopted, the roller speed is constant at 0.10m / s~0.20m / s, 0~2 heat insulation covers are opened, the wire rod stays in the cover for 7min~14min, and the cooling rate is 0.2~0.6℃ / s. After cooling, the large-size non-annealed B steel wire rod is obtained.

6. A method for manufacturing large-diameter non-annealed B steel wire rod according to claim 5, characterized in that, In step (1), the sulfur content of KR molten iron after pretreatment is less than 0.0050%; during the LF+RH refining process, the inclusions in the molten steel are controlled by reasonably configuring the refining slag and blowing argon to stir, and the hydrogen content is controlled to be less than 1.0ppm by vacuum treatment; the continuous casting adopts low superheat and low casting speed, combined with light reduction and electromagnetic stirring process, and the entire continuous casting process adopts protective casting.

7. A method for manufacturing large-diameter non-annealed B steel wire rod according to claim 5, characterized in that, In step (2), after the continuous casting billet is heated and opened, a small square billet with a diameter of □150mm²~□200mm² is obtained; the billet surface is cleaned by peeling and manual grinding to ensure that the billet surface is smooth and the corners are rounded.

8. A method for manufacturing large-diameter non-annealed B steel wire rod according to claim 5, characterized in that, In step (4), the temperature of the rolled piece is controlled by adjusting the water tank pressure and water valve during the roughing and intermediate rolling processes. The rolled piece passes through several rolling mills before intermediate rolling to make the surface and core temperatures of the rolled piece uniform.

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