A method for producing a thick-gauge high-strength clean steel structural steel plate for a wind power generation tower

Abstract

The application discloses a production method of a thick-gauge high-strength clean steel structural steel plate for a wind power tower, discloses related production processes and parameters, and limits the chemical components of the steel plate according to weight percentage as follows: C: 0.15-0.17%; Si: 0.20-0.35%; Mn: 1.40-1.50%; Nb: 0.030-0.040%; Cr: 0.20-0.30%; Ti: 0.010-0.020%; B: 0.0005-0.0.0010%; P: <=0.015%; S: <=0.005%; Als: 0.017-0.027%; N: <=0.0050%; and the rest is iron and inevitable impurities. The application aims to provide a production method of a thick-gauge high-strength clean steel structural steel plate for a wind power tower, which is stable in production, excellent in toughness and good in welding performance with a thickness of 60-80 mm.

Description

Technical Field

[0001] This invention belongs to the field of hot rolling technology, and particularly relates to a method for producing structural steel plates for thick-gauge high-strength clean steel wind power towers. Background Technology

[0002] With the rapid development of my country's power grid construction and the increasing requirements for weight reduction, high-strength structural steel is widely used in the production and construction of power grid towers. High-strength clean steel differs from ordinary low-alloy steel. It is a new generation of low-alloy high-strength steel produced based on the smelting process of ordinary low-alloy steel. This is achieved through the application of strong carbide-forming elements such as alloying elements, and the establishment of a steel strengthening and toughening mechanism primarily focused on grain refinement and precipitation strengthening. Q500 steel is a micro-alloyed steel characterized by low carbon and high purity. It possesses excellent mechanical properties, maintaining good toughness while maintaining high strength, and can significantly improve the stability of power grid tower structures.

[0003] Taking into account the impact toughness, shape, and weldability of the steel plate, the production of 60-80mm thick wind power steel on a wide and thick plate production line is quite difficult and requires a high level of technical control.

[0004] Patent CN 119956254 A, entitled "A 500MPa Grade Wind Power Steel with High Strength, Toughness, and Crack Arrest Toughness and Its Production Method," provides a method for preparing wind power steel. This method employs controlled rolling and controlled cooling to design steel plates for wind tower structures that meet standard requirements. However, this method utilizes a controlled rolling and controlled cooling process, resulting in significant fluctuations in performance stability. This patent uses a TMCP (Transformer Metal Processing) + tempering heat treatment method, which ensures the uniformity of steel plate performance and, with stable processes, improves production efficiency.

[0005] Patent CN 116536580 B, entitled "An Easily Weldable High-Strength and Tough 500MPa Grade Wind Power Steel Plate and Its Preparation Method," provides a TMCP+critical annealing heat treatment process. This process employs an ultra-low carbon + alloy composition design, adding Nb, V, Ti, Ni, and Cr to the alloy, resulting in higher alloy costs and requiring more sophisticated cooling equipment. This patent, however, uses a TMCP+tempering heat treatment method, saving on the quenching process and reducing costs. Furthermore, this patent employs a low-carbon composition design and adds a small amount of alloy components, resulting in lower costs.

[0006] Patent CN 118147412 A, entitled "A Method for Preparing Q500ME High-Strength and High-Toughness Wind Power Steel Plate," provides a method for producing 16-50mm thick wind power steel. However, the rolling process has a narrow control window, leading to potential fluctuations in performance stability. This patent, targeting thicker wind power plates, employs a TMCP + tempering heat treatment method, resulting in stable performance and excellent low-temperature impact toughness. Summary of the Invention

[0007] The purpose of this invention is to provide a method for producing thick, high-strength, clean steel structural steel plates for wind power towers. The plates have a thickness of 60-80mm, stable production, excellent toughness, and good weldability.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] This invention discloses a method for producing thick-gauge, high-strength, clean steel structural steel plates for wind turbine towers, comprising:

[0010] 1) Desulfurization of molten iron is required, with sulfur content ≤0.005% after desulfurization and slag content ≤5% after slag removal; carbon removal requirements for converter include C ≥0.05%, oxygen content at furnace head ≤600ppm, and tapping temperature ≥1600℃; ≥800kg of quicklime should be produced during converter tapping; 150-350kg of synthetic slag should be added during slag washing operation according to actual conditions; molten steel must be deoxidized to ensure a permeability of 0.070% ≥Als ≥0.030%; after tapping from the converter, 30-50kg of aluminum granules should be manually sprinkled on the slag surface and stirred with argon for 2 minutes. Spot blowing is not allowed, and slag discharge is strictly prohibited during converter tapping. The phosphorus recovery rate during the treatment process must be ≤0.003%. For RH furnace treatment of molten steel, hot slag recovery process can be adopted. The amount of quicklime added must be ≥2000kg. Aluminum granules are added during the refining process to promote the formation of white slag. 2-5 bags of aluminum granules are added each time the electrode is lowered for heating. When the steel is fed into the RH furnace for refining, all components must be included. The RH vacuum refining sequence must be ≥40min, the vacuum time ≥20min, and the soft blowing time ≥15min.

[0011] 2) The thickness of the continuously cast billet is 250mm. The superheat during steel pouring is controlled at 15–28℃, and the casting speed is 0.9–1.1 m / min. Electromagnetic stirring and light reduction are used during continuous casting. The light reduction is applied in the third and fourth stages before the solidification endpoint, with a total reduction of 8.0mm. Electromagnetic stirring is used in stages 4 and 5, with a stirring frequency of 5Hz and a current of 380A. The water flow rate on the wide side of the crystallizer is 4500L / min, and the water flow rate on the narrow side is 370L / min. The crystallizer inlet water temperature is controlled at 36±2℃. The inlet water temperature is controlled at 38±1℃, and the secondary cooling water temperature is controlled at 22~25℃. The water quality indicators must meet the process requirements. Protective casting is adopted. The argon pressure for sealing the long nozzle is controlled at ≥0.2MPa, and the flow rate is controlled at 130~160L / min. The argon pressure for sealing the tundish immersion nozzle is 0.1-0.4Mpa, and the flow rate is 6~10L / min. The billet straightening temperature is controlled at 950~1000℃, and the temperature difference along the width of the billet must not exceed 50℃. Protective casting is carried out to prevent secondary oxidation of molten steel and nitrogen absorption.

[0012] 3) heating process: using 250mm thick continuous casting billet for production, slab into the furnace surface temperature is not more than 120℃, slab heating using step heating furnace, continuous casting billet out of furnace temperature 1210~1250℃, heating time ≥ 250 minutes, slab in the heating section of the heating time is not less than 20 minutes; slab in the heating furnace moving speed of 1.10~1.20m / min;

[0013] 5) 60mm~80mm thick steel plate rolling process: after the slab heating control rolling, the first stage opening rolling thickness is the slab thickness, the first stage opening rolling temperature 1100~1220℃, the first stage final rolling temperature ≥ 950℃, the first stage high temperature elongation rolling single pass reduction rate ≥ 12%, the first stage rolling speed is 1.7~3.1m / s, the first stage rolling set torque is 2150kN·m; the second stage steel plate opening rolling thickness is 2.5 times the finished steel plate thickness, the second stage steel plate opening rolling temperature is 865~905℃, the second stage final rolling temperature is 790~860℃; the second stage rolling speed is 3.5~4.5m / s, the second stage rolling set torque is 2280kN·m, the second stage last pass reduction rate ≥ 5.5%. After the steel plate rolling, laminar cooling is carried out, ACC water temperature is 17~19℃, cooling speed is 8~12℃ / s, final cooling temperature is 650~700℃, ACC roller speed is 1.70~1.90m / s, the cooling water flow ratio of ACC lower spray beam and upper spray beam is 2.00;

[0014] 6) using tempering heat treatment process, tempering holding temperature 500~600℃, holding time > 40 minutes, furnace time 160~200min. After discharging, air cooling to 200℃, then using stacking slow cooling, slow cooling time is greater than 6 hours;

[0015] The chemical composition of the steel plate is: C: 0.15~0.17%; Si: 0.20~0.35%; Mn: 1.40~1.50%; Nb: 0.030~0.040%; Cr: 0.20~0.30%; Ti: 0.010~0.020%; B: 0.0005~0.0.0010%; P ≤ 0.015%; S ≤ 0.005%; Als: 0.017~0.027%; N: ≤ 0.0050%; the rest is iron and inevitable impurities.

[0016] Further, the center segregation of the continuous casting billet is not greater than B1.0.

[0017] Further, the performance of the steel plate meets: yield strength is between 515~550MPa, tensile strength is between 620~690MPa, elongation is ≥ 16%, -40℃ impact energy is ≥ 130J.

[0018] Further, the steel plate has the following chemical composition in terms of weight percentage: C 0.16%, Si 0.31%, Mn 1.45%, P 0.012%, S 0.002%, Als 0.024%, Nb 0.035%, Cr 0.22%, Ti 0.010%, B 0.0008%, N: 0.0041%; the balance being Fe and inevitable impurities.

[0019] Further, the steel plate has the following chemical composition in terms of weight percentage: C 0.15%, Si 0.30%, Mn 1.42%, P 0.014%, S 0.004%, Als 0.027%, Nb 0.032%, Cr 0.26%, Ti 0.016%, B 0.0007%, N: 0.0035%; the balance being Fe and inevitable impurities.

[0020] Further, the steel plate has the following chemical composition in terms of weight percentage: C 0.17%, Si 0.28%, Mn 1.49%, P 0.011%, S 0.003%, Als 0.029%, Nb 0.032%, Cr 0.28%, Ti 0.018%, B 0.0006%, N: 0.0032%; the balance being Fe and inevitable impurities.

[0021] Further, the steel plate is rolled to a thickness of 60 mm or 70 mm.

[0022] Compared with the prior art, the present application has the following beneficial technical effects:

[0023] 1) The present application adopts a low composition design, only using cheap alloys such as Nb, Ti, Cr, etc., to produce a yield strength 500 MPa grade wind power steel with good comprehensive performance through suitable smelting, continuous casting, heating, controlled rolling, and controlled cooling processes. Through tempering heat treatment process, the process is stable, and the process manufacturing cost is low.

[0024] 2) The steel plate has good strength, plasticity, and toughness, and the microstructure is tempered bainite. The yield strength of the steel plate is between 515-550 MPa, the tensile strength is between 620-690 MPa, the elongation is ≥ 16%, and the -40℃ impact energy is ≥ 130J. DETAILED DESCRIPTION

[0025] The present application is further described below in conjunction with examples.

[0026] Example 1

[0027] The slab after smelting and continuous casting was put into a heating furnace, the heating time was 240 minutes, and the soaking time was 35 minutes. The mass percentage of the chemical composition of the slab was: C 0.16%, Si 0.31%, Mn 1.45%, P 0.012%, S 0.002%, Als 0.024%, Nb 0.035%, Cr 0.22%, Ti 0.010%, B 0.0008%, N: 0.0041%; the balance was Fe and inevitable impurities. The slab was rolled into a steel plate with a thickness of 60 mm, the detailed rolling and heat treatment process was shown in Table 1, and the mechanical properties were shown in Table 2.

[0028] Example 2

[0029] The slab after smelting and continuous casting was put into a heating furnace, the heating time was 230 minutes, and the soaking time was 33 minutes. The mass percentage of the chemical composition of the slab was: C 0.15%, Si 0.30%, Mn 1.42%, P 0.014%, S 0.004%, Als 0.027%, Nb 0.032%, Cr 0.26%, Ti 0.016%, B 0.0007%, N: 0.0035%; the balance was Fe and inevitable impurities. The slab was rolled into a steel plate with a thickness of 70 mm, the detailed rolling and heat treatment process was shown in Table 1, and the mechanical properties were shown in Table 2.

[0030] Example 3

[0031] The slab after smelting and continuous casting was put into a heating furnace, the heating time was 260 minutes, and the soaking time was 40 minutes. The mass percentage of the chemical composition of the slab was: C 0.17%, Si 0.28%, Mn 1.49%, P 0.011%, S 0.003%, Als 0.029%, Nb 0.032%, Cr 0.28%, Ti 0.018%, B 0.0006%, N: 0.0032%; the balance was Fe and inevitable impurities. The slab was rolled into a steel plate with a thickness of 80 mm, the detailed rolling and heat treatment process was shown in Table 1, and the mechanical properties were shown in Table 2.

[0032] Table 1 Process parameters of Examples 1-3

[0033]

[0034] Table 2 Mechanical properties of Examples 1-4

[0035]

[0036] The high-strength wind power clean steel produced by using the strict smelting process meets the requirements of the new energy standard NBT47013.3-2023 ultrasonic flaw detection special class I, the steel plate non-metallic inclusion meets the requirements of A class ≤2.0 level, B class ≤2.0 level, C class ≤1.0 level, D class ≤1.5 level and Ds class ≤2.0 level, and the cleanliness of the high-strength wind power steel completely meets the requirements of the national standard and the market customers.

[0037] Table 3 Steel plate non-metallic inclusion result example

[0038]

[0039] The above-described embodiments are only used to describe the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements of the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A method for producing thick-gauge, high-strength, clean steel structural steel plates for wind power generation towers, characterized in that: include: 1) Desulfurization of molten iron is required, with sulfur content ≤0.005% after desulfurization and slag carryover ≤5% after slag removal; Carbon removal in the converter requires C ≥0.05%, pre-furnace oxygen ≤600ppm, and tapping temperature ≥1600℃; ≥800kg of quicklime should be produced at the converter tapping; 150-350kg of synthetic slag should be added during slag washing according to actual conditions; molten steel must be deoxidized to ensure a permeability of 0.070% ≥ Als ≥0.030%; after tapping, 30-50kg of aluminum granules should be manually sprinkled on the slag surface and argon should be blown and stirred for 2 minutes. Spot blowing is not allowed; slag should not be added after converter tapping; phosphorus recovery during the treatment process must be ≤0.003%; for RH furnace treatment of molten steel, a hot slag recovery process can be used, with quicklime addition ≥2000kg; aluminum granules should be added during the refining process to promote the formation of quicklime. Add 2-5 bags of aluminum granules each time the electrode is lowered and heated. When refining and feeding the steel into the RH, all components must be included. Ensure that the RH vacuum refining time is ≥40min, the vacuum time is ≥20min, and the soft blowing time is ≥15min. 2) The thickness of the continuously cast billet is 250mm. The superheat during steel pouring is controlled at 15–28℃, and the casting speed is 0.9–1.1 m / min. Electromagnetic stirring and light reduction are used during continuous casting. The light reduction is applied in the third and fourth stages before the solidification endpoint, with a total reduction of 8.0mm. Electromagnetic stirring is used in stages 4 and 5, with a stirring frequency of 5Hz and a current of 380A. The water flow rate on the wide side of the crystallizer is 4500L / min, and the water flow rate on the narrow side is 370L / min. The crystallizer inlet water temperature is controlled at 36±2℃. The inlet water temperature is controlled at 38±1℃, and the secondary cooling water temperature is controlled at 22~25℃. The water quality indicators must meet the process requirements. Protective casting is adopted. The argon pressure for sealing the long nozzle is controlled at ≥0.2MPa, and the flow rate is controlled at 130~160L / min. The argon pressure for sealing the tundish immersion nozzle is 0.1-0.4Mpa, and the flow rate is 6~10L / min. The billet straightening temperature is controlled at 950~1000℃, and the temperature difference along the width of the billet must not exceed 50℃. Protective casting is carried out to prevent secondary oxidation of molten steel and nitrogen absorption. 3) Heating process: 250mm thick continuous casting billets are used for production. The surface temperature of the billets entering the furnace is not greater than 120℃. A walking beam furnace is used for heating the billets. The temperature of the continuous casting billets exiting the furnace is 1210~1250℃, and the heating time is ≥250 minutes. The heating time of the billets in the soaking zone is not less than 20 minutes. When the billets are heated in the furnace, the moving speed of the movable beam supporting the billets is 1.10~1.20m / min. 5) Rolling process for 60mm-80mm thick steel plates: After the slab is heated, controlled rolling is performed. The initial rolling thickness in the first stage is the slab thickness, the initial rolling temperature is 1100-1220℃, the final rolling temperature in the first stage is ≥950℃, the single-pass reduction rate during the high-temperature extension rolling in the first stage is ≥12%, the rolling speed in the first stage is 1.7-3.1m / s, and the torque set during the first stage rolling is 2150kN·m. In the second stage, the initial rolling thickness of the steel plate is 2.5 times the thickness of the finished steel plate, the initial rolling temperature in the second stage is 865-905℃, the final rolling temperature in the second stage is 790-860℃, the rolling speed in the second stage is 3.5-4.5m / s, the torque set during the second stage rolling is 2280kN·m, and the final reduction rate in the second stage is ≥5.5%. After the steel plate is rolled, it undergoes laminar flow cooling. The ACC water temperature is 17-19℃, the cooling rate is 8-12℃ / s, the final cooling temperature is 650-700℃, the ACC roller speed is 1.70-1.90m / s, and the cooling water flow ratio between the lower and upper spray beams of the ACC is 2.

00. 6) Employ a tempering heat treatment process, with a tempering holding temperature of 500–600℃ and a holding time of >40 minutes, followed by a furnace time of 160–200 minutes. After removal from the furnace, air cool, then spread out to cool to 200℃ before slow cooling in stacks for more than 6 hours. The chemical composition of the steel plate by weight percentage is as follows: C: 0.15-0.17%; Si: 0.20-0.35%; Mn: 1.40-1.50%; Nb: 0.030-0.040%; Cr: 0.20-0.30%; Ti: 0.010-0.020%. B: 0.0005~0.0.0010%; P≤0.015%; S≤0.005%; Als: 0.017~0.027%; N: ≤0.0050%; the remainder is iron and unavoidable impurities.

2. The method for producing thick-gauge high-strength clean steel structural steel plates for wind power towers according to claim 1, characterized in that: The center segregation of the billet is no greater than B1.

0.

3. The method for producing thick-gauge high-strength clean steel structural steel plates for wind power towers according to claim 1, characterized in that: The steel plate meets the following performance requirements: yield strength between 515 and 550 MPa, tensile strength between 620 and 690 MPa, elongation between ≥16%, and impact energy at -40℃ between ≥130 J.

4. The method for producing thick-gauge high-strength clean steel structural steel plates for wind power generation towers according to claim 1, characterized in that: The chemical composition of the steel plate by weight percentage is as follows: C 0.16%, Si 0.31%, Mn 1.45%, P 0.012%, S 0.002%, Als 0.024%, Nb 0.035%, Cr 0.22%, Ti 0.010%, B 0.0008%, N 0.0041%; the balance being Fe and unavoidable impurities.

5. The method for producing thick-gauge high-strength clean steel structural steel plates for wind power towers according to claim 1, characterized in that: The chemical composition of the steel plate by weight percentage is as follows: C 0.15%, Si 0.30%, Mn 1.42%, P 0.014%, S 0.004%, Als 0.027%, Nb 0.032%, Cr 0.26%, Ti 0.016%, B 0.0007%, N 0.0035%; the balance being Fe and unavoidable impurities.

6. The method for producing thick-gauge high-strength clean steel structural steel plates for wind power towers according to claim 1, characterized in that: The chemical composition of the steel plate by weight percentage is as follows: C 0.17%, Si 0.28%, Mn 1.49%, P 0.011%, S 0.003%, Als 0.029%, Nb 0.032%, Cr 0.28%, Ti 0.018%, B 0.0006%, N 0.0032%; the balance being Fe and unavoidable impurities.

7. The method for producing thick-gauge high-strength clean steel structural steel plates for wind power towers according to claim 1, characterized in that: It is rolled into steel plates with a thickness of 60mm or 70mm.

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