A high-performance, thick steel plate for wind turbine piles and its manufacturing method

Abstract

This application provides a method for producing high-performance, thick steel plates for wind turbine piles, characterized by the following steps: steelmaking, continuous casting, stacking cooling, billet heating, rolling, post-rolling cooling, and heat preservation; wherein the rolling process adopts a one-stage high-reduction rolling; the post-rolling cooling process adopts a three-stage cooling, with the first stage being high-pressure water cooling, the second stage being air cooling, and the third stage also being high-pressure water cooling; the extra-thick steel plate prepared by the above method has a surface microstructure of ferrite + bainite dual-phase microstructure with an average grain size of 6μm; the core microstructure is a multiphase microstructure of ferrite + bainite + a small amount of pearlite with an average grain size of 12μm; it has both excellent strength and toughness, and also has a high flaw detection pass rate and high surface quality.

Description

Technical Field

[0001] This application relates to the field of iron and steel metallurgy technology, and in particular to a high-performance, thick steel plate for wind power pipe piles and its production method. Background Technology

[0002] Wind turbine pipe piles are exposed to extreme marine environments with high salinity seawater corrosion and strong typhoon impacts for extended periods. They must withstand enormous static loads, dynamic loads, and cyclic fatigue loads. In addition, the increase in wind turbine power has led to a sharp increase in bending moment and overturning force. As a result, wind turbine pipe piles are developing towards ultra-large diameter, large wall thickness, and high strength.

[0003] Thermomechanical rolling (TMCP) can support low-carbon equivalent design without relying on offline heat treatment and has excellent microstructure control capabilities, enabling the preparation of high-performance materials with both high strength and high toughness. Therefore, it is an ideal technology for producing high-performance thick plates. However, when practically applied to the large-scale stable production of steel for thick, high-strength wind turbine piles, several prominent challenges remain, such as: low flaw detection pass rate; the relatively small compression ratio during rolling of thick steel plates makes it difficult to fully roll together defects such as cracks, porosity, and segregation inside the continuously cast billet; slow core cooling rate, which easily leads to the formation of coarse microstructures or harmful phases, resulting in defects such as center segregation and delamination frequently observed during ultrasonic flaw detection, making it difficult to meet stringent internal quality requirements; difficulty in plate shape control; extremely uneven temperature and deformation distribution during rolling; enormous rolling force; asymmetric shrinkage caused by the surface-core temperature difference during cooling, easily producing defects such as waviness and warping; high straightening difficulty; and low yield. The thickness effect is significant; the thicker the steel plate, the slower the core cools, resulting in a clear gradient in microstructure and properties along the thickness direction. While surface properties are excellent, core strength, toughness, and especially low-temperature impact toughness decrease significantly, making it difficult to meet the requirements for consistent performance across the entire cross-section. Surface quality control is challenging. The high reduction rate, low final rolling temperature, and ultra-fast cooling processes used to ensure material strength are prone to defects such as oxide scale indentation, pitting, and microcracks, affecting the steel plate's appearance and potential fatigue performance. Summary of the Invention

[0004] This application aims to address the technical problems in the existing technology of manufacturing thick-walled wind turbine pipe piles, such as low flaw detection pass rate, difficulty in plate shape control, significant thickness effect, and difficulty in surface quality control. It proposes a high-performance steel plate for thick-walled wind turbine pipe piles and its production method, which effectively reduces the impact of thickness effect on material properties. The steel plate obtained has both excellent strength and toughness, and at the same time has a high flaw detection pass rate and high surface quality.

[0005] To achieve the above objectives, this application adopts the following technical solution:

[0006] A method for producing high-performance, thick-walled steel plates for wind turbine piles includes the following steps: steelmaking, continuous casting, stacking and cooling, billet heating, rolling, post-rolling cooling, and heat preservation.

[0007] The rolling process employs a one-stage high-reduction rolling process, with a first-stage initial rolling temperature >1100℃ and a first-stage final rolling temperature >T. nr +40℃; the bite speed during the rolling process is 1.0~1.5m / s, the rolling speed is 2.5~3.5m / s, and the rolling acceleration is 0.75m / s². 2 The steel throwing speed is 1.0~1.5m / s, the single-pass reduction is ≥32mm, and the rolling pass interval is <5s; the T nr This is the recrystallization temperature of austenite;

[0008] The post-rolling cooling process employs a three-stage cooling method. The first stage is high-pressure water cooling, after which the steel plate temperature is (B). s +60)℃~(A r3 -20)℃; the second stage of cooling is air cooling, and the temperature of the steel plate after cooling is (B)℃. s +45)℃~(A r3 During the second stage of cooling, the steel plate is straightened at -35℃; the third stage of cooling is also high-pressure water cooling, and the temperature of the steel plate after cooling is M. s ~B f ;

[0009] Among them, A r3 A is the temperature at which the austenite-ferrite transformation begins. r3 =910-310C-80Mn-20Cu-15Cr;B s B is the temperature at which the austenite undergoes a bainite transformation. s =830-270C-90Mn-70Cr-37Ni; B f B is the temperature at which the austenite undergoes a bainitic transformation. f =B s -120; M s M is the temperature at which the austenite undergoes a martensitic transformation. s =539-423C-30.4Mn-12.1Cr-17.7Ni;

[0010] In the above formula, C, Mn, Cu, Cr, and Ni refer to the mass percentage values ​​of C, Mn, Cu, Cr, Mo, and Ni elements in the steel plate, respectively. For example, when the mass percentage of C is 0.12%, then C in the above formula is 0.12.

[0011] Furthermore, the austenite recrystallization temperature satisfies the following condition: T nr =887+464C-357Si+(6445Nb-644 )+(732V-230 )+890Ti+363Al; In the above formula, C, Si, Nb, V, Ti, and Al refer to the mass percentage values ​​of C, Si, Nb, V, Ti, and Al elements in the steel plate, respectively. For example, when the mass percentage of C is 0.12%, then C in the above formula is 0.12; 843℃<T nr <947℃.

[0012] During hot deformation, niobium dissolves in austenite or segregates at grain boundaries and subgrain boundaries, simultaneously forming fine Nb(C,N) precipitates. These precipitates strongly delay or even completely inhibit the recrystallization process of the deformed austenite, a phenomenon particularly important during rolling in the non-recrystallization zone. This application requires ensuring complete recrystallization of austenite in the rolled steel sheet, forming fine equiaxed grains. Therefore, strict control of the Nb content is necessary to ensure the steel sheet's temperature (T) is within acceptable limits. nr The temperature should be lowered as much as possible to expand the temperature window for complete austenite recrystallization, ensuring that recrystallization can still occur at the set final rolling temperature. Therefore, the above two conditions are used for T nr And the various important elemental components are mutually limited.

[0013] Furthermore, the post-rolling cooling process adopts a finished product exit mode at the mill exit, with a steel conveying speed at the mill exit ≥4.0m / s.

[0014] Furthermore, the cooling water pressure used in the first stage of cooling is 0.75~0.95MPa, and the water volume is 12000~14000m³. 3 The third stage of cooling uses cooling water at a pressure of 1.00~1.20MPa and a flow rate of 14500~16500m³ / h. 3 / h.

[0015] Furthermore, the steelmaking process is as follows: molten iron is subjected to pre-desulfurization treatment, converter smelting, ladle refining, and RH vacuum refining to obtain refined molten steel; wherein, during RH vacuum refining, the vacuum degree is set to ≤2mbar, the degassing time is 20~25min, the net circulation treatment time is 8~10min, and the ladle is placed on the rotary table for 15~18min before continuous casting begins.

[0016] By increasing the RH vacuum refining degassing time and net circulation treatment time, the purity of steel plates can be improved, thereby enhancing their comprehensive mechanical properties.

[0017] Furthermore, the continuous casting process is as follows: the refined molten steel is continuously cast into a billet with a thickness of 320±10mm. The continuous casting process adopts dynamic light reduction, and the reduction amount is 1.5%~3.0% of the billet thickness.

[0018] In the continuous casting process, the use of dynamic light reduction can significantly reduce center segregation, eliminate center porosity, and mitigate internal cracks. Meanwhile, due to the large shrinkage and high crack sensitivity of peritectic reactions, the reduction amount under dynamic light reduction should be controlled at 1.5% to 3.0% of the billet thickness. This can improve the quality of the continuously cast billet while preventing the induction of longitudinal surface cracks.

[0019] Furthermore, the stack cooling time is ≥48 hours.

[0020] Furthermore, in the billet heating process, the heating temperature is 1190~1220℃, the furnace time is 380~420min, and the temperature difference between the upper and lower surfaces is ≤20℃ when the billet is removed from the furnace.

[0021] By limiting the heating temperature and furnace time during the billet processing, it is possible to ensure that the billet is fully "burnt through," which not only improves the temperature uniformity of the billet but also ensures the complete dissolution of alloying elements. Temperature uniformity is a prerequisite for ensuring uniform deformation of the steel plate, and whether the deformation is uniform directly affects the shape quality of the steel plate; in addition, the complete dissolution of alloying elements is also an important prerequisite for ensuring the strength of the steel plate.

[0022] Furthermore, in the heat preservation process, the steel plate temperature is ≥400℃, the heat preservation time is ≥36 hours, and the stacking height is ≥1 meter.

[0023] Furthermore, the chemical composition of the steel plate, by mass percentage, includes:

[0024] C: 0.10%-0.13%, Si: 0.16%-0.26%, Mn: 1.45%-1.65%, P: 0.007%-0.017%, S≤0.003%, Nb: 0.010%-0.020%, Ti: 0.010%-0.020%, Al: 0.03%-0.05%, Ni: 0.30%-0.40%, Cr: 0.30%-0.40%, Cu: 0.30%-0.40%, V: 0.03%-0.04%, N≤0.005%, H≤0.0002%, the remainder being iron and unavoidable impurities;

[0025] The content of each chemical component in the steel plate also meets the following conditions:

[0026] 26.01Cu+3.88Ni+1.20Cr+1.49Si+17.28P-7.29CuNi-9.10NiP-33.39Cu 2 ≥6.0; where Cu, Ni, Cr, Si, and P refer to the mass percentage values ​​of Cu, Ni, Cr, Si, and P elements in the steel plate, respectively. For example, when the mass percentage of Cu is 0.35%, then Cu in the above formula is 0.35.

[0027] By coordinating the content of Cr, Ni, Cu, P, and Si elements, the steel plate is guaranteed to have good resistance to seawater corrosion and its service life is extended.

[0028] The beneficial effects of this application are:

[0029] The method described in this application produces extra-thick steel plates with a thickness of 80-120 mm that possess both excellent strength and toughness, while also exhibiting a high pass rate in flaw detection and high surface quality. Specifically, the plate unevenness is ≤2 mm / m; the near-surface microstructure is a ferrite + bainite multiphase structure with an average grain size <8 μm; the core microstructure is a ferrite + bainite + a small amount of pearlite multiphase structure with an average grain size <15 μm; the near-surface yield strength is 580~620 MPa, and the tensile strength is 690~740 MPa; under room temperature conditions, the stress ratio is R=0.1, and the cycle life is 10... 7 The fatigue limit is 430~470 MPa; elongation ≥25%; Brinell hardness of the steel plate surface is 185~215 HBW; yield strength of the steel plate core is 530~580 MPa; tensile strength is 640~690 MPa; under normal temperature conditions, stress ratio is R=0.1; 10 cycles 7 The fatigue limit is 380~430MPa, elongation ≥27%, and the average impact energy (KV2) at -60℃ in the core is ≥280J; the crack arrest toughness at -10℃ for the entire thickness of the steel plate is ≥8000 N / mm. 3 / 2 The Z-direction tensile reduction of area is ≥60%; the surface quality of the steel plate meets the Class A, subclass 3 requirements of EN 10163-2 standard; the flaw detection results of the steel plate meet the Body: Class S2, Edge: Class E3 requirements of EN 10160 standard; the average annual corrosion rate of the steel plate under full seawater immersion conditions is ≤0.15mm / a.

[0030] This application first controls the final rolling temperature at T during the rolling stage. nrAt temperatures above +40℃, a safety margin is maintained to ensure rolling is performed within the fully recrystallized region. Secondly, increasing the single-pass reduction promotes dynamic recrystallization of austenite. Large deformation combined with high-temperature rolling strongly promotes dynamic recrystallization, thereby driving repeated grain refinement. Furthermore, high-speed rolling ensures a high deformation rate, increasing dislocation density and energy storage, further promoting dynamic recrystallization. Finally, shortening the pass interval suppresses static recrystallization and grain growth.

[0031] This application first achieves high undercooling and introduces defects through rapid cooling in the post-rolling cooling stage; then, through slow cooling, nucleation is stimulated at intragranular defects under low temperature and high driving force, breaking the dominance of grain boundary nucleation in traditional processes and achieving a large number of dispersed nucleations within the grains. Segmented cooling, through a sophisticated three-step control of "suppressing grain growth, promoting nucleation, and refining the microstructure," solves the persistent problem of coarse grains and uneven microstructure caused by slow cooling rates in the core of thick steel plates, thus achieving a breakthrough improvement in low-temperature toughness. This results in steel plates with both excellent strength and toughness, as well as high flaw detection pass rate and high surface quality. Details are as follows:

[0032] The final cooling temperature of the first stage high-pressure water cooling: (B) s +60)℃~(A r3 -20)℃. High-pressure water cooling ensures that the cooling water can effectively penetrate the vapor film and retention layer, increasing the cooling rate and penetration. This allows the temperature of the steel plate to rapidly cross the austenite coarsening stability zone from the surface to the core, "freezing" the austenite in its fine initial state during rolling. It also inhibits the excessive grain growth caused by prolonged austenite residence in the high-temperature zone; allows the austenite to enter a lower temperature range, increasing undercooling and providing a significant driving force for subsequent phase transformation; rapid cooling can also introduce non-equilibrium structural defects such as dislocations, strain energy, and micro-region compositional fluctuations. The upper limit temperature should not exceed (A). r3 -20)℃, the primary purpose of this temperature setting is to ensure that the core temperature of the steel plate can effectively exceed A. r3 Below the phase transformation point, the fine austenite structure in the rolled state is forcibly "frozen" in an untransformed state. If the final cooling temperature is too high, the austenite will coarsen in the high-temperature region, losing its basis for refinement. Below A... r3 -20℃ ensures sufficient supercooling to suppress austenite recovery recrystallization and grain boundary migration, creating the prerequisite for subsequent nucleation under low temperature and high driving force. The lower limit temperature is not lower than (B s +60)℃, this setting is to precisely avoid entering the bainitic phase transformation region. If the first stage of cooling is excessive and the steel plate temperature is too low, the bainitic phase transformation will be triggered prematurely. This phase transformation is usually dominated by grain boundary nucleation, and the transformation products will consume the defect energy in austenite, making it impossible to achieve the desired "intragranular nucleation". Controlling the temperature at (B)℃... sTemperatures above +60℃ ensure that the microstructure remains in an austenitic state without phase transformation, but a large number of defects such as dislocations have accumulated, providing sufficient driving force and nucleation sites for the second stage of intracrystalline nucleation.

[0033] The final cooling temperature of the second stage air cooling (which is also the straightening stage): (B) s +45)℃~(A r3 -35)℃. This temperature window is crucial for stimulating intragranular nucleation, and this temperature range is precisely set above the bainite transformation initiation temperature (B). s However, it is still far below the austenite coarsening temperature range. The upper limit of the final cooling temperature is limited to ≤(A). r3 -35℃ is used to provide a high driving force. The temperature is gradually cooled from the final cooling temperature of the first stage to this point, further increasing the supercooling. The phase transformation driving force is sufficient to overcome the energy barrier for nucleation at intragranular defects. Compared to grain boundary nucleation, which can only occur at higher temperatures, the high driving force at this temperature is the core condition for activating intragranular defects as effective nucleation sites. The lower limit of the final cooling temperature is limited to ≥(B s +45℃ is used to suppress rapid grain boundary growth and diffusion; the temperature is still higher than B. s The temperature at this point signifies that the phase transformation is primarily a diffusion-type transformation, but the low diffusion rate provided by slow cooling inhibits the rapid growth of newly formed grains. This allows sufficient time for the numerous nucleation sites within the grains to develop simultaneously, ultimately resulting in a fine, dispersed microstructure, rather than the abnormal growth of a few grains. Simultaneously, this temperature avoids the shear-type bainitic transformation, which is detrimental to the formation of a dispersed ferrite microstructure. Furthermore, the steel plate retains good plasticity at this temperature, but its yield strength is significantly higher than at high temperatures. Straightening the steel plate at this temperature effectively releases internal stress and improves plate shape, while avoiding new shape problems caused by incomplete stress relaxation after high-temperature straightening, as well as the risk of excessive straightening force and cracking that may result from low-temperature straightening. This process arrangement organically combines deformation heat treatment with microstructure control. In addition, heat transfer from the core to the surface of the steel plate occurs at this stage, resulting in temperature homogenization along the thickness direction, which is a crucial step in achieving uniform microstructure and properties in thick plates.

[0034] The final cooling temperature of the third-stage high-pressure water cooling system: M s ~B f The final cooling temperature is limited to M. s Points above to B f The purpose of the final cooling point is to ensure the steel plate has excellent strength: High-pressure water cooling rapidly transforms the untransformed retained austenite from the first and second stages into high-strength bainite, thus ensuring the final strength performance of the steel plate. It also prevents the formation of martensite, ensuring that the steel plate possesses both excellent strength and excellent toughness by strictly controlling the final cooling temperature at the martensite initiation temperature (M). sAbove a certain point, the formation of hard and brittle martensite was successfully avoided. This is key to ensuring the steel plate's excellent low-temperature toughness and superior processing and forming properties. The final cooling temperature is below B. f This ensures that the bainitic phase transformation is basically complete, avoids the presence of unstable residual austenite in the microstructure, and guarantees the strength and microstructure stability of the steel plate.

[0035] In summary, the ingenuity of this application's technical solution lies not only in the three-stage cooling method, but also in its temperature parameter design, which is precisely correlated with the material's phase transformation point. The first-stage temperature window effectively suppresses growth and stores defects; the second-stage temperature window precisely triggers the promotion of core development and refinement of the microstructure; and the third-stage temperature window achieves the balance between strength and brittleness. The coordinated control of these three temperature parameters forms an interconnected organic whole, jointly achieving the refinement and homogenization of the microstructure within the thick steel plate's core, ultimately breaking through the simultaneous improvement of strength and toughness, while ensuring a high flaw detection pass rate and surface quality. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a metallographic diagram of the surface layer of the steel plate obtained in an embodiment of this application;

[0038] Figure 2 This is a metallographic diagram of the core of the steel plate obtained in an embodiment of this application;

[0039] Figure 3 This is a metallographic diagram of the surface layer of the steel plate obtained in the comparative example of this application;

[0040] Figure 4 This is a metallographic diagram of the core of the steel plate obtained as a comparative example in this application. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. In the description of this application, the experimental methods, unless otherwise specified, are conventional methods; the reagents and materials, unless otherwise specified, are all commercially available.

[0042] The following disclosure provides many different implementations or examples for carrying out this application. To simplify the disclosure of this application, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the scope of this application. Those skilled in the art will recognize the application of other processes and / or the use of other materials. Example

[0043] A high-performance, thick-walled steel plate for wind turbine piles comprises, by mass percentage: C: 0.12%, Si: 0.22%, Mn: 1.55%, P: 0.012%, S: 0.002%, Nb: 0.015%, Ti: 0.015%, Al: 0.035%, Ni: 0.35%, Cr: 0.35%, Cu: 0.35%, V: 0.034%, N: 0.003%, H: 0.00010%, with the remainder being iron and unavoidable impurities. Its austenite recrystallization temperature and corrosion resistance index are as follows: T nr ≈891℃, I≈6.4.

[0044] The preparation method of the above-mentioned high-performance, thick-walled wind turbine pile steel plate includes the following steps:

[0045] steelmaking

[0046] The molten iron is pre-desulfurized, smelted in a converter, refined in a ladle, and then RH vacuum refined to obtain refined molten steel. During the RH vacuum refinement, the vacuum degree is set to ≤2mbar, the degassing time is 25min, the net circulation treatment time is 10min, and the ladle is placed on the rotary table for 15min before continuous casting begins.

[0047] Continuous casting

[0048] The refined molten steel is continuously cast into a 320mm thick billet. The continuous casting process adopts dynamic light reduction with a reduction amount of 8mm.

[0049] Stack and cool for 48 hours.

[0050] billet heating

[0051] The heating temperature is 1200℃, the furnace time is 420min, and the temperature difference between the upper and lower surfaces of the steel plate when it is taken out of the furnace is ≤20℃.

[0052] Rolling

[0053] A one-stage high-reduction rolling process was adopted, with the first-stage initial rolling temperature set at 1100℃ and the first-stage final rolling temperature at 950℃. The bite speed during the rolling process was 1.0 m / s, the rolling speed was 2.5 m / s, and the rolling acceleration was 0.75 m / s². 2The steel throwing speed is 1.0 m / s, the single-pass reduction is ≥32 mm, and the rolling pass interval is <5 s. The rolling pass interval refers to the time interval between the end of the previous rolling pass and the start of the next rolling pass.

[0054] Post-rolling cooling

[0055] The rolling mill adopts a finished product exit mode, with a steel conveying speed ≥4.0m / s. The ACC cooling system is activated in advance to ensure that the post-rolling cooling start time of the steel plate is ≤3 seconds. Water temperature is strictly controlled, and the cooling tower is activated promptly to ensure that the water temperature is ≤25℃. A three-stage cooling system is employed. The first stage is high-pressure water cooling using high-pressure nozzles, with a water pressure of 0.95MPa and a water flow rate of 14000m³. 3 The spraying speed is [number] hours, ensuring full coverage of the steel plate surface. The final cooling temperature of the steel plate after the first stage is 700℃. The second stage is air cooling, where heat transfer from the core of the steel plate to the surface is achieved, resulting in temperature homogenization. The final cooling temperature of the steel plate in this stage is 686℃, and the steel plate is straightened during air cooling. The third stage is also high-pressure water cooling, using high-pressure nozzles, with a water pressure of 1.20 MPa and a water flow rate of 16500 m³ / h. 3 / h, ensuring spray coverage of the entire steel plate surface, with the third stage final cooling temperature of the steel plate at 465℃. In the post-rolling cooling process, the starting temperature for the ferrite transformation of austenite, the starting temperature for the bainite transformation of austenite, and the ending temperature for the bainite transformation of austenite are respectively A r3 =736.55℃, B s =620.65℃, B f =500.65℃, M s =430.69℃.

[0056] Insulation

[0057] After the third stage of cooling is completed, the steel plates are placed inside an insulation cover for heat preservation. The temperature of the steel plates when they are placed inside the insulation cover is 428℃, the heat preservation time is 36 hours, and the stacking height is 1.2 meters.

[0058] After the insulation is completed, an extra-thick steel plate with a thickness of 120mm can be obtained. Comparative Example

[0059] A thick steel plate for wind turbine piles, with the same chemical composition as in the above embodiments, is prepared by the following steps:

[0060] steelmaking

[0061] The molten iron is pre-desulfurized, smelted in a converter, refined in a ladle, and then RH vacuum refined to obtain refined molten steel. During the RH vacuum refinement, the vacuum degree is set to ≤2mbar, the degassing time is 25min, the net circulation treatment time is 10min, and the ladle is placed on the rotary table for 15min before continuous casting begins.

[0062] Continuous casting

[0063] The refined molten steel is continuously cast into a 320mm thick billet. The continuous casting process adopts dynamic light reduction with a reduction amount of 8mm.

[0064] Stack and cool for 48 hours.

[0065] billet heating

[0066] The heating temperature is 1200℃, the furnace time is 420min, and the temperature difference between the upper and lower surfaces of the steel plate when it is taken out of the furnace is ≤20℃.

[0067] Rolling

[0068] The rolling process is carried out in two stages. The first stage starts at a rolling temperature of 1110℃ and ends at a rolling temperature of 1020℃, with a thickness of 200mm. The second stage starts at a rolling temperature of 830℃ and ends at a rolling temperature of 800℃.

[0069] The bite speed during the first-stage rolling process is 0.5 m / s, the rolling speed is 1.5 m / s, and the rolling acceleration is 0.40 m / s². 2 The steel-throwing speed is 0.5 m / s, the single-pass reduction is ≥28 mm, and the rolling pass interval is <10 s. The steel-biting speed in the two-stage rolling process is 1.0 m / s, the rolling speed is 2.5 m / s, and the rolling acceleration is 0.75 m / s². 2 The steel throwing speed is 1.0 m / s, the single-pass reduction is ≥5 mm, and the rolling pass interval is <10 s. The rolling pass interval refers to the time interval between the end of the previous rolling pass and the start of the next rolling pass.

[0070] Post-rolling cooling

[0071] A single-stage high-pressure water cooling system is employed, with strict temperature control and timely activation of the cooling tower to ensure the water temperature remains ≤25℃. High-pressure nozzles are used, with a water pressure set at 1.20 MPa and a water flow rate of 16500 m³ / h. 3 / h, ensuring that the spray covers the entire surface of the steel plate, and the final cooling temperature of the steel plate after cooling is 468℃.

[0072] Insulation

[0073] After cooling, the steel plates are placed inside an insulation cover for heat preservation. The steel plate temperature is 430℃ when it enters the insulation cover, the heat preservation time is 36 hours, and the stacking height is 1.3 meters.

[0074] After the insulation is completed, an extra-thick steel plate with a thickness of 120mm can be obtained.

[0075] Performance testing

[0076] To better compare the performance of the extra-thick steel plates obtained in the above embodiments and comparative examples, the extra-thick steel plates obtained in the above embodiments and comparative examples were tested for various properties, including unevenness, mechanical properties, corrosion resistance, surface quality, and flaw detection. The standards and conditions for each test are as follows: unevenness was tested using the ASTM A1030 standard method; mechanical property testing was conducted according to the ISO 6892-1 standard, where yield strength and tensile strength were taken from the standard tensile test, and elongation was the total elongation after fracture; fatigue limit test conditions were: at room temperature, stress ratio R=0.1, 10 cycles. 7 Weekly testing was conducted; the surface quality inspection standard was Class A, subclass 3 of EN 10163-2; the flaw detection standard was S2 / E3 (i.e., Body: Class S2, Edge: Class E3) of EN 10160; corrosion resistance was tested according to ASTM G50 standard, with a 90-day exposure test under full seawater immersion conditions, and the annual average corrosion rate (mm / a) was calculated based on the weight loss of the samples. The test results are shown in Table 1 below.

[0077] Table 1. Performance test results of the examples and comparative examples

[0078]

[0079] As can be clearly seen from the test results in Table 1 above, the preparation method described in the application can effectively reduce the influence of thickness effect on the performance of steel plates. The prepared steel plates have both excellent strength and toughness, and at the same time have a high failure rate, high surface quality, and good corrosion resistance.

[0080] To further investigate the differences between the steel plates obtained in the embodiments and the comparative examples, the surface and core microstructures of the steel plates obtained in the embodiments and the comparative examples were examined, and the results are as follows. Figures 1 to 4 As shown, by Figure 1-2 It can be seen that the surface microstructure of the steel plate obtained in the example is a dual-phase microstructure of ferrite + bainite, with an average grain size of 6 μm; the core microstructure of the steel plate is a multiphase microstructure of ferrite + bainite + a small amount of pearlite, with an average grain size of 12 μm. Then, from... Figure 3-4It is evident that the surface microstructure of the steel plate obtained in the comparative example is lath bainite with an average grain size of 10 μm; the core microstructure is a multiphase microstructure of ferrite, pearlite, and a small amount of bainite, with an average grain size of 50 μm. This demonstrates that the preparation method described in this application effectively suppresses grain growth within the steel plate, successfully achieving significant refinement (average 12 μm) and optimization of the core microstructure (obtaining a ferrite + bainite multiphase microstructure), completely changing the inferior structure of the comparative example, which was coarse (average 50 μm) and dominated by ferrite and pearlite in the core. This fundamental shift from "grain boundary nucleation-dominated" to "intragranular dispersed nucleation-dominated" is key to overcoming the "thickness effect" of thick steel plates. The refinement and homogenization of the core microstructure directly translates into a comprehensive and superior improvement in performance. While maintaining high strength (yield strength 568MPa, tensile strength 687MPa), the core exhibits an impact energy of up to 325J at -60℃, nearly an order of magnitude higher than the control group (36J), achieving a perfect combination of high strength and ultra-high and low temperature toughness. The fatigue limit of the core is increased to 416MPa, and the crack arrest toughness of the entire steel plate at -10℃ reaches 9000 N / mm². 3 / 2 This demonstrates its extremely strong ability to resist alternating loads and suppress crack propagation, significantly improving safety and reliability. The performance gradient between the surface and core of the example is much smaller than that of the comparative example, proving its excellent microstructure uniformity. Simultaneously, higher core elongation (29%), Z-axis reduction of area (68%), excellent shape control (roughness 2 mm / m), and satisfactory surface and flaw detection results collectively demonstrate that the steel plate prepared by this process possesses an unprecedented balance of comprehensive performance.

[0081] In summary, the significant differences in microstructure and macroscopic properties between the embodiments and the comparative examples definitively prove that the "intragranular dispersion nucleation" mechanism achieved by the present invention through precise one-stage high-reduction rolling + three-stage controlled pressure and temperature cooling fundamentally solves the industry problem of core performance degradation in thick steel plates, and ultimately obtains steel plates with excellent comprehensive performance.

[0082] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0083] The preparation method of a high-performance, thick-walled steel plate for wind turbine piles provided in the embodiments of this application has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for producing a high-performance large-thickness steel plate for a wind power tubular pile, characterized by, It comprises the following steps: steelmaking, continuous casting, stacking cooling, blank heating, rolling, post-rolling cooling and heat preservation. The rolling process adopts one-stage large reduction rolling, one-stage rough rolling temperature > 1100℃, and one-stage finish rolling temperature > T nr +40℃; the biting speed in the rolling process is 1.0-1.5 m / s, the rolling speed is 2.5-3.5 m / s, and the rolling acceleration is 0.75 m / s 2 ; the throwing speed is 1.0-1.5 m / s, the single pass reduction is > 32 mm, and the rolling pass interval time is < 5 s; the T nr is the austenite recrystallization temperature; the austenite recrystallization temperature satisfies the following condition: T nr = 887+464C-357Si+(6445Nb-644 )+(732V-230 )+890Ti+363Al; in the above formula, C, Si, Nb, V, Ti, and Al respectively represent the mass percentage values of C element, Si element, Nb element, V element, Ti element, and Al element in the steel plate; 843℃ < T nr < 947℃; The post-rolling cooling process adopts three-stage cooling, the first stage cooling is high-pressure water cooling, the temperature of the steel plate after cooling is (B s +60) ℃~(A r3 -20) ℃; the second stage cooling is air cooling, the temperature of the steel plate after cooling is (B s +45) ℃~(A r3 -35) ℃, the steel plate is straightened during the second stage cooling; the third stage cooling is also high-pressure water cooling, the temperature of the steel plate after cooling is M s ~B f ; wherein A r3 is the start temperature of ferrite transformation of austenite, A r3 = 910 - 310C - 80Mn - 20Cu - 15Cr; B s is the start temperature of bainite transformation of austenite, B s = 830 - 270C - 90Mn - 70Cr - 37Ni; B f is the finish temperature of bainite transformation of austenite, B f = B s - 120; M s is the start temperature of martensite transformation of austenite, M s = 539 - 423C - 30.4Mn - 12.1Cr - 17.7Ni; In the formula, C, Mn, Cu, Cr, Mo and Ni respectively represent the mass percentage values of C element, Mn element, Cu element, Cr element, Mo element and Ni element in the steel plate.

2. The production method of high-performance large-thickness steel plate for wind power pipe piles according to claim 1, characterized in that: The post-rolling cooling process adopts a finished product mode at the outlet of the rolling mill, and the steel conveying speed out of the rolling mill is greater than or equal to 4.0 m / s.

3. The production method of high-performance large-thickness steel plate for wind power pipe piles according to claim 1, characterized in that: The cooling water pressure for the first stage cooling is 0.75-0.95 MPa, and the water quantity is 12000-14000 m 3 / h, and the cooling water pressure for the third stage cooling is 1.00-1.20 MPa, and the water quantity is 14500-16500 m 3 / h.

4. The production method of high-performance large-thickness steel plate for wind power pipe piles according to claim 1, characterized in that: The steelmaking process is as follows: the molten iron is subjected to pre-desulfurization treatment, converter smelting, ladle refining and RH vacuum refining to obtain refined molten steel; during the RH vacuum refining, a vacuum degree of less than or equal to 2 mbar is set, the degassing time is 20-25 min, the net circulation treatment time is 8-10 min, and the ladle is placed on the rotating table for 15-18 min before continuous casting is started.

5. The method of producing a high-performance large-thickness steel plate for wind power pipe piles according to claim 4, characterized in that: The continuous casting process is as follows: the refined molten steel is continuously cast into a 320±10 mm thick casting blank, and the dynamic soft reduction is adopted during the continuous casting process, and the reduction amount is 1.5%-3.0% of the thickness of the casting blank.

6. The production method of high-performance large-thickness steel plate for wind power pipe piles according to claim 1, characterized in that: The stacking cooling time is greater than or equal to 48 hours.

7. The production method of high-performance large-thickness steel plate for wind power pipe piles according to claim 1, characterized in that: In the blank heating process, the heating temperature is 1190-1220℃, the furnace time is 380-420 min, and the temperature difference between the upper and lower surfaces when leaving the furnace is less than or equal to 20℃.

8. The production method of high-performance large-thickness steel plate for wind power pipe piles according to claim 1, characterized in that: In the heat preservation process, the steel plate temperature is greater than or equal to 400℃, the heat preservation time is greater than or equal to 36 hours, and the stacking height is greater than or equal to 1 meter.

9. The production method of high-performance large-thickness steel plate for wind power pipe piles according to claim 1, characterized in that, The chemical composition of the steel plate comprises, in terms of mass percentage: C element: 0.10%-0.13%, Si element: 0.16%-0.26%, Mn element: 1.45%-1.65%, P element: 0.007%-0.017%, S element: less than or equal to 0.003%, Nb element: 0.010%-0.020%, Ti element: 0.010%-0.020%, Al element: 0.03%-0.05%, Ni element: 0.30%-0.40%, Cr element: 0.30%-0.40%, Cu element: 0.30%-0.40%, V element: 0.03%-0.04%, N element: less than or equal to 0.005%, H element: less than or equal to 0.0002%, and the rest is iron and inevitable impurities; The content of each chemical composition of the steel plate also satisfies the following conditions: 26.01 Cu + 3.88 Ni + 1.20 Cr + 1.49 Si + 17.28 P - 7.29 CuNi - 9.10 NiP - 33.39 Cu 2 ≥ 6.0; wherein, Cu, Ni, Cr, Si, P respectively refer to the mass percentage value of Cu element, Ni element, Cr element, Si element, P element in the steel plate.

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