A method of producing a microalloyed low alloy steel hot strip

Abstract

The application discloses a production method of micro-alloyed low-alloy steel hot continuous rolling steel strips, which comprises the following steps: blast furnace molten iron, molten iron desulfurization pretreatment, 120-ton combined blown converter smelting, LF refining, continuous casting, heating, rough scale removal, width setting, rough rolling, fine scale removal, TMCP six-rack fine rolling, laminar cooling, coiling, inspection and warehousing; wherein the chemical components of the micro-alloyed low-alloy steel are as follows: C: 0.11-0.14wt%, Si: ≤0.25wt%, Mn: 0.90-1.10wt%, P: ≤0.025wt%, S: ≤0.015wt%, Als: 0.015-0.035wt%, V: 0.033-0.048wt%, Re: 0.002-0.004wt%; wherein the laminar cooling adopts a multi-section high-efficiency laminar cooling system of encryption section+rough adjustment section+encryption section+fine adjustment section.

Description

Technical Field

[0001] This invention relates to the field of microalloyed steel technology, and in particular to a method for producing hot-rolled strip of microalloyed low-alloy steel. Background Technology

[0002] Q420MD is a type of low-alloy high-strength steel, characterized by high strength, high toughness, wear resistance, fatigue resistance, impact resistance, easy machinability, good wear resistance, weldability, and mechanical properties. It also features reduced structural weight and lower construction costs, making it a low-carbon and environmentally friendly material. Q420MD is widely used in power transmission towers, various types of cranes, heavy-duty trucks, oil derricks, dump trucks and drilling rigs, coal mine hydraulic supports, steel structures, and more.

[0003] Current standards require low-alloy steel Q420MD to have a yield strength ≥420MPa, tensile strength 520-680MPa, elongation after fracture ≥19%, and longitudinal impact energy ≥55J at 20℃. However, producing Q420MD hot-rolled strip steel requires the addition of different types of alloys to achieve the required mechanical properties. This inevitably increases Q420MD production costs, reduces enterprise profits, and hinders market competitiveness. To ensure product quality meets user needs while simultaneously reducing costs and increasing efficiency, [further measures are needed]. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for producing microalloyed low-alloy steel hot-rolled strip.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: A method for producing microalloyed low alloy steel hot-rolled strip includes the following steps: blast furnace hot metal → hot metal desulfurization pretreatment → 120-ton combined blowing converter smelting → LF refining → continuous casting → heating → rough descaling → width setting → rough rolling → fine descaling → TMCP six-stand fine rolling → laminar flow cooling → coiling → inspection and warehousing. The chemical composition of the microalloyed low alloy steel is as follows (by weight percentage): C: 0.11–0.14 wt%, Si: ≤0.25 wt%, Mn: 0.90–1.10 wt%, P: ≤0.025 wt%, S: ≤0.015 wt%, Als: 0.015–0.035 wt%, V: 0.033–0.048 wt%, Re: 0.002–0.004 wt%, with the remainder being Fe and unavoidable trace elements. The laminar flow cooling system employs a multi-stage high-efficiency, high-density laminar flow cooling system consisting of a high-density section, a coarse adjustment section, a high-density section, and a fine adjustment section. This system enables flexible control of the laminar cooling process and adapts to the cooling process requirements of all product specifications.

[0006] In the converter smelting process, the S content of the molten iron is ≤0.035wt%; argon gas is blown from the bottom throughout the smelting process, with a flow rate of 0.02m³. 3 / (t·min)<bottom-blown gas supply intensity≤0.05m 3 / (t·min); Deoxidation alloying steel grit aluminum deoxidation, using SiMnFe, SiFe, LCMnFe to prepare Si and Mn.

[0007] In the LF refining process, molten steel undergoes aluminum deoxidation, V microalloying, and calcium treatment in an LF furnace. The wire feeding speed is 3-3.5 m / s. After calcium treatment, rare earth alloys are added, and the soft blowing time after adding rare earths is 3 min.

[0008] In the continuous casting process, the following requirements apply: the casting process requires ladle protection casting and ladle slag detection and control; the continuous casting tundish temperature is 1540~1560℃; the billet casting speed is 1.2m / min; carbon-free covering agent is used in the tundish; the crystallizer uses special protection made of low alloy steel; dynamic light pressure is selected with a pressure reduction mode of 4mm; and the liquid level fluctuation in the crystallizer is controlled within ±3mm.

[0009] The heating process employs a three-stage heating method: a preheating stage with a temperature of 1070–1150°C, a heating stage with a temperature of 1150–1250°C, and a soaking stage with a temperature of 1200–1250°C. The heating time is 160–240 minutes, and the furnace exit temperature is controlled at 1180–1240°C to ensure the billet is held in the furnace for the required time, allowing microalloying elements to dissolve and controlling the austenite grain size.

[0010] In the rolling process, a six-stand hot continuous rolling process using a roughing mill and TMCP is adopted, with a focus on controlling the reduction per pass to ensure that a large reduction in rolling forms a deformation zone, increases the nucleation sites, and refines the grains. At least one high-pressure water descaling is ensured during the rolling process, with an inlet pressure of 200-260 bar and an outlet pressure of 300-380 bar. Water cooling is used between the finishing mills, and the final rolling temperature is 870-930℃.

[0011] In the winding process, the winding tension is 10–23 kN, and the winding temperature is 570–610 °C.

[0012] The role of chemical components in this invention and their impact on material properties: C: C is an important solid solution strengthening element in steel and contributes the most to its strength. Increasing the C content can significantly improve the strength of steel. However, excessively high C content is detrimental to controlling the plasticity, toughness, and formability of steel. Reducing the C content can improve plasticity and increase the toughness of steel. Therefore, to ensure the strength and formability of Q420MD, the C content of this invention is controlled at 0.11–0.14 wt%.

[0013] Si: Si has a certain solid solution strengthening effect in steel, which is beneficial to improving the strength of steel, but not conducive to the control of toughness. However, if the Si content is too high, due to its strong diffusion ability, it will form the Fe2SiO4 spinel phase with the surface iron oxide scale above 1173℃. This phase is not easy to remove during the dephosphorization process, and microcracks caused by oxide indentation are easily formed on the surface. This is detrimental to the control of the surface quality of the steel plate. In order to obtain a steel plate with high strength, good formability and good surface quality, the Si content of this invention is controlled at ≤0.25wt%.

[0014] Mn: In steel, Mn partially dissolves with iron to form a solid solution (ferrite or austenite), and partially combines with iron and carbon to form cementite, which can strengthen ferrite and refine pearlite, thereby improving the strength of steel. Appropriate amounts of Mn can lower the γ→α phase transformation temperature, helping to obtain finer phase transformation products and improving strength and toughness. Simultaneously, due to the strong affinity between manganese and sulfur, it can cause sulfur in steel to form MnS, which has a higher melting point than FeS, preventing FeS precipitation at grain boundaries, reducing hot brittleness, and improving hot working performance. In this invention patent, the Mn content is controlled at 0.90–1.10 wt%.

[0015] V: V is a strong carbon and nitride forming element. It mainly inhibits austenite grain growth and refines the final microstructure by forming dispersed and fine carbonitrides (V(C,N)) during hot rolling or cooling, thus achieving significant fine grain strengthening. At the same time, the precipitated phase can hinder dislocation movement and provide precipitation strengthening effect, thereby effectively improving the strength and toughness of steel without significantly impairing its plasticity and toughness. The V content in this invention patent is controlled at 0.033 to 0.048 wt%.

[0016] Re: The main functions of rare earth elements in steel are to purify molten steel (deoxidation and desulfurization), modify inclusions (transforming long, brittle inclusions such as MnS and Al2O3 into fine, dispersed spherical rare earth inclusions), refine grains, and microalloy. In this invention, the characteristics of rare earth-modified inclusions are mainly utilized to improve the low-temperature impact toughness of low-alloy steel. In this invention, the Re content is controlled at 0.002–0.004 wt%.

[0017] Sulfur (S) and phosphorus (P): For most steels, sulfur (S) and phosphorus (P) are harmful elements. S mainly affects the plasticity of steel, while P mainly affects the impact toughness and ductile-brittle transition temperature. Furthermore, sulfide inclusions in steel also significantly influence the properties of the steel in different directions. According to research by Japanese scholar Yukimasa Ozawa, the sulfur content in hot-rolled low-alloy steel plates should be controlled between 0.010 and 0.015 wt%. The development trend of modern steel materials is to minimize the sulfur content and control sulfide inclusions. In this invention, S is controlled below 0.015 wt%, and P is controlled below 0.025 wt%.

[0018] The beneficial effects of this invention are: 1. This invention adopts the design concept of medium carbon, high manganese, V microalloyed steel. By controlling the design of reasonable alloy composition, it obtains stable chemical composition and mechanical properties, high strength, good plasticity and toughness, etc., which meet the requirements of general steel structures.

[0019] 2. This invention uses V microalloying to control strength, controls grain size through precipitation strengthening and grain refinement of V alloying elements, and further refines the microstructure through recrystallization controlled rolling technology and ultra-fast cooling technology.

[0020] 3. This invention uses Re to control the properties of inclusions, reduce long strip-shaped inclusions, and improve the low-temperature impact toughness, fatigue resistance and cold working performance of steel.

[0021] 4. This invention uses a chamfered crystallizer to produce billets, which reduces cracks at the edges of the billets and effectively prevents defects such as cracks at the edges of the final steel strip.

[0022] 5. This invention employs a low-Si composition process, using high-pressure water descaling before roughing and finishing rolling, and employing secondary descaling during finishing rolling, effectively reducing the thickness of the iron oxide scale on the final steel strip surface. Attached Figure Description

[0023] Figure 1 This is a metallographic image of Embodiment 1 of the present invention.

[0024] Figure 2 This is a metallographic image of Embodiment 2 of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of the invention.

[0026] Example 1 The chemical composition of the low-alloy steel strip Q420MD is shown in the table below: , The continuously cast billet is 230 mm thick; hot-sent. The heating process employs a three-stage heating method: a preheating stage with a temperature of 1100℃, a heating stage with a temperature of 1210℃, and a soaking stage with a temperature of 1220℃. The heating time is 155–240 min. The roughing rolling process: Roughing rolling temperature: 1112℃, six passes of rolling R1→R2→R2→R1→R1→R2, three passes of vertical rolling; , Intermediate billet air cooling: The intermediate billet is naturally cooled on the intermediate roller table, and the temperature drop is controlled at 20-50℃; The descaling and finishing rolling processes are as follows: Temperature before descaling: 1031℃, pressure in the manifold before descaling machine: 212 bar, pressure in the manifold after descaling machine: 324 bar, starting temperature of finishing mill: 980℃; The finishing mill adopts a TMCP six-pass continuous rolling process; , Finishing rolling temperature: 898℃; Immediately after finishing rolling, the material enters the laminar flow cooling stage, employing a control mode of "ultra-fast cooling in the front section, air cooling in the middle section, and fine-tuning in the rear section." The front section utilizes a large volume of water for rapid cooling to inhibit grain growth; the middle section uses air cooling to homogenize the temperature; and the rear section precisely adjusts the cooling rate according to the target performance, achieving refined control over the material's microstructure and mechanical properties to ensure stable product performance. The total water volume is 12,000 m³. 3 / h, actual floor cooling water volume 4733m³ 3 / h, chilled water temperature 30.5℃; The winding temperature is 585℃, the winding tension is 14.64KN, and the resulting high-strength low-alloy Q4200B hot-rolled steel strip has a thickness of 5.50mm.

[0027] The hot-rolled strip steel obtained in this embodiment has the following key indicators: Mechanical properties of the hot-rolled strip steel: yield strength 434 MPa, tensile strength 542 MPa, elongation after fracture 24.5%; thickness did not meet the standard for impact energy testing; edge defect rate: 0; metallographic structure of the hot-rolled strip steel as follows... Figure 1 As shown: F+P; Grain size: 10.5 grade; Fully compliant with general engineering structural steel.

[0028] Example 2 The chemical composition of the low-alloy steel strip Q420MD is shown in the table below: , The continuously cast billet is 230 mm thick; hot-sent. The heating process employs a three-stage heating method: a preheating stage with a temperature of 1100℃, a heating stage with a temperature of 1150℃, and a soaking stage with a temperature of 1220℃. The heating time is 155–240 min. The roughing rolling process: Roughing rolling temperature: 1146℃, six passes of rolling R1→R2→R2→R1→R1→R2, three passes of vertical rolling; , Intermediate billet air cooling: The intermediate billet is naturally cooled on the intermediate roller table, and the temperature drop is controlled at 20-50℃; The descaling and finishing rolling processes are as follows: Temperature before descaling: 1053℃, pressure in front of the descaling machine manifold: 212 bar, pressure in the rear manifold: 324 bar, starting temperature of the finishing mill: 1004℃; The finishing mill adopts a TMCP six-pass continuous rolling process; , Finishing rolling temperature: 875℃; Immediately after finishing rolling, the material enters the laminar flow cooling stage, employing a control mode of "ultra-fast cooling in the front section, air cooling in the middle section, and fine-tuning in the rear section." The front section utilizes a large volume of water for rapid cooling to inhibit grain growth; the middle section uses air cooling to homogenize the temperature; and the rear section precisely adjusts the cooling rate according to the target performance, achieving refined control over the material's microstructure and mechanical properties to ensure stable product performance. The total water volume is 12,000 m³. 3 / h, actual floor cooling water volume 4152m³ 3 / h, chilled water temperature 27℃; The winding temperature is 583℃, the winding tension is 12.31KN, and the resulting high-strength low-alloy Q420MD hot-rolled steel strip has a thickness of 7.50mm.

[0029] The hot-rolled strip steel obtained in this embodiment has the following key indicators: Mechanical properties of hot-rolled strip steel: yield strength 436MPa, tensile strength 560MPa, elongation after fracture 24.0%; impact energy at -20℃ 79J; edge defect rate: 0; metallographic structure of hot-rolled strip steel as follows: Figure 2 As shown: F+P; Grain size: Grade 10; Fully compliant with general engineering structural steel.

[0030] .

[0031] Example 3 A method for producing microalloyed low alloy steel hot-rolled strip includes the following steps: blast furnace hot metal → hot metal desulfurization pretreatment → 120-ton combined blowing converter smelting → LF refining → continuous casting → heating → rough descaling → width setting → rough rolling → fine descaling → TMCP six-stand fine rolling → laminar flow cooling → coiling → inspection and warehousing. The chemical composition of the microalloyed Q420MD low alloy steel by weight percentage is C: 0.11wt%, Si: 0.25wt%, Mn: 0.90wt%, P: 0.025wt%, S: 0.015wt%, Als: 0.015wt%, V: 0.033wt%, Re: 0.002wt%, with the remainder being Fe and unavoidable trace elements; The laminar flow cooling system employs a multi-stage high-efficiency, high-density laminar flow cooling system consisting of a high-density section, a coarse adjustment section, a high-density section, and a fine adjustment section. This system enables flexible control of the laminar cooling process and adapts to the cooling process requirements of all product specifications.

[0032] In the converter smelting process, the S content of the molten iron is 0.035 wt%; argon gas is blown from the bottom throughout the smelting process, with a bottom-blowing gas supply intensity of 0.02 m³ / min. 3 / (t·min); Deoxidation alloying steel grit aluminum deoxidation, using SiMnFe, SiFe, LCMnFe to prepare Si and Mn.

[0033] In the LF refining process, molten steel undergoes aluminum deoxidation, V micro-alloying, and calcium treatment in an LF furnace. The wire feeding speed is 3 m / s. After calcium treatment, rare earth alloys are added, and the soft blowing time after adding rare earths is 3 min.

[0034] In the continuous casting process, the following requirements apply: the casting process requires ladle protection casting and ladle slag detection and control; the continuous casting tundish temperature is 1540℃; the billet casting speed is 1.2m / min; carbon-free covering agent is used in the tundish; the crystallizer uses special protection made of low alloy steel; the dynamic light pressure is selected with a pressure reduction mode of 4mm; and the liquid level fluctuation in the crystallizer is controlled within ±3mm.

[0035] The heating process employs a three-stage heating method: a preheating stage temperature of 1070℃, a heating stage temperature of 1150℃, and a soaking stage temperature of 1200℃. The heating time is 160 minutes, and the furnace exit temperature is controlled at 1180℃ to ensure the billet is held in the furnace for the required time, allowing microalloying elements to dissolve and controlling the austenite grain size.

[0036] In the rolling process, a roughing mill + TMCP six-stand hot continuous rolling process is adopted, with a focus on controlling the reduction per pass to ensure that a large reduction in rolling forms a deformation zone, increases the nucleation site, and refines the grains. At least one high-pressure water descaling is guaranteed during the rolling process, with a descaling inlet pressure of 200 bar and an outlet pressure of 300 bar. Water cooling between the finishing mills is used, and the final rolling temperature is 870℃.

[0037] In the winding process, the winding tension is 10 kN and the winding temperature is 570°C.

[0038] The hot-rolled strip steel obtained in this embodiment has the following key indicators: mechanical properties of hot-rolled strip steel: yield strength 436MPa, tensile strength 520MPa, elongation after fracture 24.0%; impact energy at -20℃ 79J; edge defect rate: 0; metallographic structure of hot-rolled strip steel: F+P; grain size: grade 10; fully conforms to general engineering structural steel.

[0039] Example 4 A method for producing microalloyed low alloy steel hot-rolled strip includes the following steps: blast furnace hot metal → hot metal desulfurization pretreatment → 120-ton combined blowing converter smelting → LF refining → continuous casting → heating → rough descaling → width setting → rough rolling → fine descaling → TMCP six-stand fine rolling → laminar flow cooling → coiling → inspection and warehousing. The chemical composition of the microalloyed Q420MD low alloy steel by weight percentage is as follows: C: 0.14wt%, Si: 0.25wt%, Mn: 1.10wt%, P: 0.025wt%, S: 0.015wt%, Als: 0.035wt%, V: 0.048wt%, Re: 0.004wt%, with the remainder being Fe and unavoidable trace elements. The laminar flow cooling system employs a multi-stage high-efficiency, high-density laminar flow cooling system consisting of a high-density section, a coarse adjustment section, a high-density section, and a fine adjustment section. This system enables flexible control of the laminar cooling process and adapts to the cooling process requirements of all product specifications.

[0040] In the converter smelting process, the S content of the molten iron is ≤0.035wt%; argon gas is blown from the bottom throughout the smelting process, with a bottom-blowing gas supply intensity of 0.05m³ / min. 3 / (t·min); Deoxidation alloying steel grit aluminum deoxidation, using SiMnFe, SiFe, LCMnFe to prepare Si and Mn.

[0041] In the LF refining process, molten steel undergoes aluminum deoxidation, V micro-alloying, and calcium treatment in the LF furnace. The wire feeding speed is 3.5 m / s. After calcium treatment, rare earth alloys are added, and the soft blowing time after adding rare earths is 3 min.

[0042] In the continuous casting process, the following requirements apply: the casting process requires ladle protection casting and ladle slag detection and control; the continuous casting tundish temperature is 1560℃; the billet casting speed is 1.2m / min; carbon-free covering agent is used in the tundish; the crystallizer uses special protection made of low alloy steel; the dynamic light pressure is selected with a pressure reduction mode of 4mm; and the liquid level fluctuation in the crystallizer is controlled within ±3mm.

[0043] The heating process employs a three-stage heating method: a preheating stage temperature of 1150℃, a heating stage temperature of 1250℃, and a soaking stage temperature of 1250℃. The heating time is 240 minutes, and the furnace exit temperature is controlled at 1240℃ to ensure the billet is held in the furnace for the required time, allowing microalloying elements to dissolve and controlling the austenite grain size.

[0044] In the rolling process, a roughing mill + TMCP six-stand hot continuous rolling process is adopted, with a focus on controlling the reduction per pass to ensure that the large reduction during rolling forms a deformation zone, increases the nucleation site, and refines the grains. At least one high-pressure water descaling is guaranteed during the rolling process, with a descaling inlet pressure of 260 bar and an outlet pressure of 380 bar. Water cooling between the finishing mills is used, and the final rolling temperature is 930℃.

[0045] In the winding process, the winding tension is 23 kN and the winding temperature is 610°C.

[0046] The hot-rolled strip steel obtained in this embodiment has the following key indicators: mechanical properties of hot-rolled strip steel: yield strength 436MPa, tensile strength 680MPa, elongation after fracture 24.0%; impact energy at -20℃ 79J; edge defect rate: 0; metallographic structure of hot-rolled strip steel: F+P; grain size: grade 11; fully conforms to the general engineering structural steel.

[0047] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for producing hot-rolled strip of microalloyed low-alloy steel, characterized in that, Includes the following steps: Blast furnace hot metal → Hot metal desulfurization pretreatment → 120-ton combined blowing converter smelting → LF refining → continuous casting → heating → rough descaling → width setting → rough rolling → fine descaling → TMCP six-stand fine rolling → laminar flow cooling → coiling → inspection and warehousing; The chemical composition of the microalloyed low alloy steel is as follows (by weight percentage): C: 0.11–0.14 wt%, Si: ≤0.25 wt%, Mn: 0.90–1.10 wt%, P: ≤0.025 wt%, S: ≤0.015 wt%, Als: 0.015–0.035 wt%, V: 0.033–0.048 wt%, Re: 0.002–0.004 wt%, with the remainder being Fe and unavoidable trace elements. The laminar flow cooling system employs a multi-stage high-efficiency, high-density laminar flow cooling system consisting of a high-density section, a coarse adjustment section, a high-density section, and a fine adjustment section. This system enables flexible control of the laminar cooling process and adapts to the cooling process requirements of all product specifications.

2. The method for producing microalloyed low-alloy steel hot-rolled strip according to claim 1, characterized in that, In the converter smelting process: the S content of the molten iron is ≤0.035wt%; argon gas is blown from the bottom throughout the smelting process, with a flow rate of 0.02m³. 3 / (t·min)<bottom-blown gas supply intensity≤0.05m 3 / (t·min); Deoxidation alloying steel grit aluminum deoxidation, using SiMnFe, SiFe, LCMnFe to prepare Si and Mn.

3. The method for producing microalloyed low-alloy steel hot-rolled strip according to claim 1, characterized in that, In the LF refining process: molten steel undergoes aluminum deoxidation, V microalloying and calcium treatment in the LF furnace. The wire feeding speed is 3-3.5 m / s. After calcium treatment, rare earth alloys are added, and the soft blowing time after adding rare earths is 3 min.

4. The method for producing microalloyed low-alloy steel hot-rolled strip according to claim 1, characterized in that, In the continuous casting process: the casting process requires ladle protection casting and ladle slag detection and control, the continuous casting tundish temperature is 1540~1560℃, the billet casting speed is 1.2m / min, the tundish uses carbon-free covering agent, the crystallizer uses low alloy steel special protection, the dynamic light pressure is selected with a pressure reduction mode of 4mm, and the crystallizer liquid level fluctuation is controlled within ±3mm.

5. The method for producing microalloyed low-alloy steel hot-rolled strip according to claim 1, characterized in that, The heating process employs a three-stage heating method: a preheating stage temperature of 1070–1150°C, a heating stage temperature of 1150–1250°C, and a soaking stage temperature of 1200–1250°C. The heating time is 160–240 minutes, and the furnace exit temperature is controlled at 1180–1240°C to ensure the billet is held in the furnace for the required time, allowing microalloying elements to dissolve and controlling the austenite grain size.

6. The method for producing microalloyed low-alloy steel hot-rolled strip according to claim 1, characterized in that, In the rolling process: a roughing mill + TMCP six-stand hot continuous rolling process is adopted, with a focus on controlling the reduction per pass to ensure that the large reduction during rolling forms a deformation zone, increases the nucleation sites, and refines the grains; at least one high-pressure water descaling is ensured during the rolling process, with an inlet pressure of 200-260 bar and an outlet pressure of 300-380 bar. Water cooling is used between the finishing mills, and the final rolling temperature is 870-930℃.

7. The method for producing microalloyed low-alloy steel hot-rolled strip according to claim 1, characterized in that, During the winding process: the winding tension is 10-23 kN, and the winding temperature is 570-610℃.

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