Process method for cooperatively regulating and controlling structure performance of high-toughness wind power steel through trace Ce-Nb

Abstract

The invention discloses a process method for cooperatively regulating and controlling the structure performance of high-toughness wind power steel through trace Ce-Nb, and belongs to the technical field of wind power structural steel. According to the invention, by compositely adding trace rare earth Ce and Nb and on the basis of a two-stage hot rolling and air cooling process, austenite grains are effectively refined, grain boundary migration is inhibited, dislocation density is enhanced, and uniform refining of ferrite and pearlite structures is realized; the high-strength and high-toughness steel is prepared from the following components in percentage by mass: 0.05 to 0.15 percent of C, 1.2 to 1.5 percent of Mn, 0.1 to 0.4 percent of Si, 0 to 0.02 percent of Nb, 0.0011 to 0.0066 percent of Ce, 0 to 0.07 percent of V and the balance of iron and impurities. Under the condition that high-cost elements such as Ti and Cr are not introduced, the performance indexes that the yield strength is larger than or equal to 460 MPa and the impact energy at the temperature of-40 DEG C is larger than or equal to 280 J are achieved, and excellent low-temperature toughness and industrialization cost control are both considered.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wind power structural steel materials, and particularly relates to a process method for synergistically regulating the microstructure and performance of high-strength and high-toughness wind power steel by trace Ce-Nb. BACKGROUND

[0002] China still has broad room for improvement in the treatment of steel with rare earth. Breakthroughs are urgently needed in the following aspects: first, the optimal addition amount of rare earth and its adaptability to different process routes and equipment should be determined; second, the limitations of existing characterization and measurement techniques should be broken through, and the basic research on the mechanism of rare earth in steel should be deepened to accurately grasp the strengthening mechanism and microstructure evolution law of rare earth; third, the stability and yield of rare earth utilization should be improved to promote the stable casting and large-scale application of rare earth steel in industrial production. On this basis, new types of rare earth micro-alloyed steel with independent intellectual property rights should be developed to fully leverage China's strategic advantage in rare earth resources, promote the transformation of rare earth resources into product and economic advantages in steel materials, and effectively improve the innovation ability and core competitiveness of China's steel industry. This not only has important economic value, but also has far-reaching practical significance.

[0003] The addition of an appropriate amount of rare earth in steel can purify the molten steel and modify the inclusions. The combination of rare earth with harmful elements in steel can make harmful substances float and be removed, modify inclusions, and improve the cleanliness of molten steel. The combination of rare earth with O and S in steel forms high-melting-point compounds, and dispersed rare earth inclusions can pin grain boundaries, promote the nucleation of ferrite, and refine the grain size. Due to the differences in atomic size and electronegativity between rare earth and iron atoms, rare earth has a micro-alloy solid solution strengthening effect. However, it is necessary to further study the coordinated control of rare earth and O and S, the effective control of the size of rare earth inclusions, and the stable control of the content of rare earth in steel. The addition of rare earth can improve the microstructure of steel and thus improve the comprehensive mechanical properties of metal materials. The addition of rare earth elements in steel can improve the morphology of sulfide inclusions, the segregation of Cr, V, and Mo, reduce the eutectic carbide of network structure, refine the grain size, and have other effects, which can comprehensively improve the mechanical properties of steel, effectively change the ductile-brittle transition temperature and pearlite transformation rate of steel, refine the ferrite grain size to improve the uniformity of the structure, and improve the strength and toughness of steel. Rare earth can significantly improve the corrosion resistance, impact resistance, fatigue resistance, and wear resistance of steel.

[0004] In Chinese invention patent CN102433495A, the inventors proposed improving the corrosion resistance of marine wind turbine structural components by adding rare earth element Ce (0.01-0.03 wt.%) to steel and combining it with Al and Ca to purify the molten steel and control inclusions, thereby inhibiting the formation of inferior inclusions such as MnS and Al2O3. However, this approach does not delve into the microscopic mechanisms of rare earth elements in grain evolution, nor does it establish the intrinsic relationship between composition, microstructure, and properties by incorporating microstructural parameters. The Ce content is too high and mainly used for inclusion purification, failing to constitute a systematic strengthening system.

[0005] Chinese invention patent CN103014501A discloses another rare-earth-treated high-strength wind power steel. Its alloy system employs a combination of microalloying elements such as Ce, Nb, and Ti for strengthening, focusing on improving low-temperature toughness and yield strength. This patent uses Nb / Ti precipitates as the primary source of strengthening, while relying on Ce to synergistically refine grains. However, it does not provide systematic microstructural evidence to support the rare-earth action pathway, nor does it establish a theoretical model of the strengthening mechanism. The alloy system is relatively complex and highly dependent on controlled rolling and cooling. In contrast, this invention employs a synergistic design of trace amounts of rare-earth Ce (0.0011-0.0066 wt.%) with microalloying elements such as Nb, V, and Mg to construct a three-dimensional composite strengthening mechanism integrating grain boundary segregation, precipitation control, and dislocation modulation. Among them, Ce element segregates at the austenite grain boundaries, effectively refining grains and enhancing grain boundary strength by inhibiting recrystallization and promoting ferrite nucleation; Nb and V synergistically form stable carbide / nitride precipitates, enhancing the matrix strengthening ability; Mg element, under the action of Ce, induces the formation of Ce2O2S-like rare earth inclusions, optimizing the inclusion morphology and further improving toughness.

[0006] The Chinese invention patent CN114635085A specifies a product yield strength ≥355MPa and an impact energy ≥135J at -40℃, but it does not provide systematic microstructural evidence to support the rare earth effect pathway, nor does it establish a theoretical model for the strengthening mechanism. In contrast, this invention achieves a product yield strength ≥460MPa and an impact energy ≥280J at -40℃ without introducing high-cost elements such as Ti and Cr, balancing excellent low-temperature toughness with industrialization cost control.

[0007] To verify the above mechanism, this invention introduces electron backscatter diffraction (EBSD) for the first time to perform microscopic analysis of the microstructure. Combined with the mean orientation difference (KAM), grain size distribution and dislocation density evolution, the specific role of Ce in grain evolution and strengthening path is systematically revealed, and a comprehensive integrated process preparation and microstructure performance verification is established from alloy composition design to final performance.

[0008] Furthermore, this invention, while ensuring performance (yield strength ≥ 460 MPa, impact absorption energy at -40℃ ≥ 280 J), achieves microstructure control using a conventional hot rolling + air cooling process, eliminating the need for controlled rolling and cooling or multiple heat treatments, thus possessing high potential for industrialization. Compared with existing technologies, this invention exhibits significant differences in alloy design system, rare earth utilization efficiency, strengthening mechanism construction, and microstructure empirical analysis, demonstrating clear novelty and inventiveness. It is of positive significance for promoting the development of key technology industries in my country, which is also the challenge this invention aims to overcome. Summary of the Invention

[0009] The purpose of this invention is to provide a process method for synergistic regulation of the microstructure and properties of high-strength and high-toughness wind power steel by adding rare earth Ce. By adding rare earth Ce, the austenite grains can be effectively refined, and the ferrite grains generated by the phase transformation can be made smaller, ultimately resulting in fine and uniform ferrite + pearlite grains. Combined with the rolling process, the yield strength and other properties of the alloy can be greatly improved while effectively controlling the cost.

[0010] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0011] This invention discloses a process for synergistic regulation of the microstructure and properties of high-strength and high-toughness wind power steel using trace amounts of Ce-Nb, comprising the following steps:

[0012] S1, Weigh the raw materials according to the formula ratio;

[0013] S2, C, Mn, Si, Nb and Fe raw materials are added to a vacuum induction melting furnace in an orderly manner for smelting;

[0014] S3, after deoxidation by Al, pure rare earth Ce is added to the molten steel and cast into an ingot;

[0015] S4 is heated at 1250±10℃, then held at that temperature for a total of 3-5 hours, and then cooled to 1150℃ to forge into a forging billet;

[0016] S5, after two-stage hot rolling, the forged billet is air-cooled to obtain finished wind power steel with UTS≥460MPa and -40℃ impact energy≥280J;

[0017] It consists of the following components by mass percentage: C: 0.05-0.15%, Mn: 1.2-1.5%, Si: 0.1-0.4%, Nb: 0-0.02%, Ce: 0.0011-0.0066%, V: 0-0.07%, with the balance being Fe and unavoidable impurities.

[0018] Furthermore, the impurities in the alloy components are controlled to be P≤0.015wt.%, S≤0.004wt.%, total Al≤0.04wt.%, Ca≤0.0015wt.%, and Mg≤0.0004wt.%.

[0019] Furthermore, the diameter of the ingot cast in step S4 is 150–250 mm.

[0020] Furthermore, in step S5, the first stage of hot rolling is held at 1250℃ for 2 hours, the initial rolling temperature is 900~1150℃, and the reduction rate is ≤60%.

[0021] Furthermore, in step S5, the second stage of rolling temperature is below 870℃, the reduction rate is ≤30%, and then air cooling is used to obtain the finished wind power steel.

[0022] Furthermore, the steel plate has a fine and uniform ferrite + pearlite dual-phase structure with an average grain size of less than 13 μm and a dislocation density that is increased by more than 20%.

[0023] Furthermore, the longitudinal impact absorption energy at -40℃ is not less than 280J, and the transverse impact energy is not less than 290J, exhibiting isotropic low-temperature toughness.

[0024] Furthermore, the main inclusions in the steel include Ce2O2S, CaAl2O4 and 12CaO·7Al2O3, and the amount of Ce added can control the content of spinel inclusion MgAl2O4 to be reduced by at least 30%.

[0025] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0026] 1. This invention, through optimizing the alloy composition and proportions, produces an alloy with a yield strength (YS) greater than 460 MPa and low-temperature toughness with an impact energy greater than 250 J at -40℃, while controlling the carbon equivalent to 0.33 and exhibiting excellent weldability. The addition of rare-earth Ce effectively refines the austenite grains and makes the ferrite grains generated by the phase transformation smaller, ultimately resulting in fine, uniform ferrite + pearlite grains. Combined with the rolling process, this significantly improves the alloy's yield strength and other properties while effectively controlling costs.

[0027] 2. The addition of rare earth elements in this invention affects the ferrite grain state, including grain size, morphology, and intragranular dislocation state, thereby influencing the final mechanical properties. The addition of rare earth elements affects the austenite nucleation and growth process of the steel plate in the furnace. One effect is that fine, dispersed rare earth inclusions promote austenite nucleation and hinder grain growth; another is that rare earth atoms segregate at austenite grain boundaries, hindering grain boundary migration. Therefore, refined austenite grains result in finer ferrite grains generated during the phase transformation. During the air-cooled phase transformation, Ce hinders ferrite nucleation along austenite grain boundaries, promoting ferrite transformation at low temperatures and uniform nucleation. Furthermore, during the transformation, Ce segregates at ferrite grain boundaries, hindering ferrite grain boundary migration, ultimately resulting in fine, uniform ferrite + pearlite grains.

[0028] 3. This invention employs a two-stage rolling process, which increases the dislocation density in ferrite by adding modified austenitic microstructure to achieve dislocation strengthening. In addition, a certain amount of Nb is added to achieve precipitation strengthening, effectively improving the yield strength of the alloy.

[0029] Based on a scientific and reasonable process design, this invention patent describes a process method that uses trace amounts of Ce-Nb to synergistically regulate the microstructure and properties of high-strength and tough wind power steel, thereby preparing wind power steel with excellent high strength and toughness, impact resistance, uniform microstructure, and excellent mechanical properties.

[0030] The innovation of this invention is reflected in the following aspects:

[0031] (1) This invention innovatively controls the Ce content at an extremely low level of 0.0011-0.0066 wt.%, and through in-depth observation of the microstructure evolution behavior during hot deformation, it first clearly proposes the selective segregation behavior of Ce at austenite grain boundaries. This segregation behavior effectively inhibits the grain boundary migration rate, thereby delaying the dynamic recrystallization process, reducing the grain growth tendency, and forming a finer and more uniform ferrite grain structure. The strengthening behavior of Ce has shifted from inclusion purification to bulk strengthening through grain boundary regulation mechanism, changing the traditional rare earth utilization path, significantly improving the efficiency of Ce utilization, and providing a mechanism innovation paradigm for the development of other rare earth steels.

[0032] (2) Most patents for rare earth reinforced steel only provide mechanical properties or a small number of metallographic images, lacking a systematic quantitative analysis of the microstructure evolution path. This makes it difficult to support the construction of a mechanism model and is also not conducive to fully demonstrating the effectiveness of the innovative path in comparative review. This invention systematically introduces EBSD electron backscatter diffraction technology to analyze the microstructure of hot-rolled state, focusing on: grain size statistics; distribution of average orientation difference (KAM); grain boundary segregation orientation spectrum; dislocation density estimation and deformation behavior determination. At the same time, it is supplemented by SEM impact fracture morphology observation and EDS inclusion composition analysis to construct a complete causal chain from alloy design → grain boundary evolution → precipitation behavior → mechanical response, providing structural-level theoretical support for the action mechanism of Ce, Nb, V, and Mg microalloying. For the first time in published patents, a clear mechanism chain has been formed, which is significantly different from the traditional empirical rare earth wind power steel technology path.

[0033] (3) While existing Nb-Ti-Ce and Cr-Ni series wind power steels have excellent performance, they rely on high-priced elements and complex process routes, resulting in poor industrial adaptability, especially for non-controlled rolling equipment and small and medium-sized steel mills. This invention does not use high-cost alloys such as Ti, Cr, Ni, and Mo at all. It adopts an economical Ce-Nb synergistic composition design and matches it with conventional hot rolling + air cooling process. It can achieve the microstructure and performance targets without controlled rolling, controlled cooling, or secondary heat treatment. It has four major advantages: high cost performance, easy promotion, low threshold, and high performance. It is particularly suitable for large-scale wind power steel manufacturing scenarios in China and has excellent industrial application potential. Attached Figure Description

[0034] The present invention will be further described below with reference to the accompanying drawings.

[0035] Figure 1 The curves of load and energy versus displacement for different steel grades of the present invention under low-temperature impact are shown; wherein, (a) Example 1, (b) Example 2, (c) Example 3, and (d) are comparison graphs of load-displacement curves for the three steel grades.

[0036] Figure 2 These are macroscopic morphological images of the low-temperature impact fracture surfaces of Embodiments 1 and 3 of the present invention.

[0037] Figure 3 The morphology of the low-temperature impact fracture surface under SEM in Examples 1 and 3 of the present invention;

[0038] Figure 4 The morphology of the low-temperature impact fracture surface under SEM at different temperatures in Example 1 of the present invention is shown, wherein: (a)-60℃, (b)-80℃, (c)-100℃, (d)-120℃;

[0039] Figure 5The morphology of the low-temperature impact fracture surface under SEM at different temperatures in Example 3 of the present invention is shown, wherein: (a)-60℃, (b)-80℃, (c)-100℃, (d)-120℃;

[0040] Figure 6 The images shown are representative local average orientation difference distribution images of samples with different Ce contents characterized by EBSD according to the present invention, wherein: (a) Example 1, (b) Example 2, (c) Example 3, (d) statistical curves of local average orientation difference of three steels;

[0041] Figure 7 Metallographic images of the alloy of Example 4 of the present invention, wherein: (a) 100x image, (b) 500x image;

[0042] Figure 8 Metallographic images of the alloy of Example 5 of the present invention, wherein: (a) 100x image, (b) 500x image. Detailed Implementation

[0043] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below. The description in this part is only exemplary and explanatory, and should not be used to limit the scope of protection of the present invention in any way.

[0044] Example 1 (Comparative Example)

[0045] S1, according to the formula ratio, weigh the raw materials as follows: 0.088% C, 1.26% Mn, 0.32% Si, 0.017% Nb, without adding Ce and V, with the balance being Fe and unavoidable impurities. Specifically, control the impurities in the alloy components to be P≤0.015wt.%, S≤0.004wt.%, total Al≤0.04wt.%, Ca≤0.0015wt.%, Mg≤0.0004wt.%.

[0046] S2, raw materials C, Mn, Si, Nb and Fe are added to a vacuum induction melting furnace for smelting;

[0047] S3 is deoxidized with Al and cast into ingots with a diameter of 210mm.

[0048] S4 is heated at 1250℃, then held at that temperature for a total of 4 hours, and then cooled to 1150℃ to forge a thickness of 100 mm × 120 mm. 2 Forged billets;

[0049] S5 involves hot rolling the forged billet from S4 in two stages. The first stage of hot rolling is a holding temperature of 1250℃ for 2 hours, followed by an initial rolling temperature of 1150℃. The billet is rolled to 40mm at 900-1150℃ with a reduction rate of 60%. The second stage of hot rolling is a rolling temperature below 870℃ to 13mm with a reduction rate of 27%. The billet is then air-cooled to obtain the finished wind power steel.

[0050] Example 2

[0051] S1, according to the formula ratio, weigh the raw materials as follows: 0.088% C, 1.23% Mn, 0.3% Si, 0.014% Nb, 0.0022% Ce, without adding V, with the balance being Fe and unavoidable impurities. Specifically, control the impurities in the alloy components to be P≤0.015wt.%, S≤0.004wt.%, total Al≤0.04wt.%, Ca≤0.0015wt.%, Mg≤0.0004wt.%.

[0052] S2, raw materials C, Mn, Si, Nb and Fe are added to a vacuum induction melting furnace for smelting;

[0053] S3 is deoxidized with Al, pure rare earth Ce is added, and then cast into an ingot with a diameter of 210mm.

[0054] S4 is heated at 1250℃, then held at that temperature for a total of 4 hours, and then cooled to 1150℃ to forge a thickness of 100 mm × 120 mm. 2 Forged billets;

[0055] S5 involves hot rolling the forged billet from S4 in two stages. The first stage of hot rolling is a holding temperature of 1250℃ for 2 hours, followed by an initial rolling temperature of 1150℃. The billet is rolled to 40mm at 900-1150℃ with a reduction rate of 60%. The second stage of hot rolling is a rolling temperature below 870℃ to 13mm with a reduction rate of 27%. The billet is then air-cooled to obtain the finished wind power steel.

[0056] Example 3

[0057] S1, according to the formula ratio, weigh the raw materials as follows: 0.088% C, 1.24% Mn, 0.31% Si, 0.017% Nb, 0.0066% Ce, without adding V, with the balance being Fe and unavoidable impurities. Specifically, control the impurities in the alloy components to be P≤0.015wt.%, S≤0.004wt.%, total Al≤0.04wt.%, Ca≤0.0015wt.%, Mg≤0.0004wt.%.

[0058] S2, raw materials C, Mn, Si, Nb and Fe are added to a vacuum induction melting furnace for smelting;

[0059] S3 is deoxidized with Al, pure rare earth Ce is added, and then cast into an ingot with a diameter of 210mm.

[0060] S4 is heated at 1250℃, then held at that temperature for a total of 4 hours, and then cooled to 1150℃ to forge a thickness of 100 mm × 120 mm. 2 Forged billets;

[0061] S5 involves hot rolling the forged billet from S4 in two stages. The first stage of hot rolling is a holding temperature of 1250℃ for 2 hours, followed by an initial rolling temperature of 1150℃. The billet is rolled to 40mm at 900-1150℃ with a reduction rate of 60%. The second stage of hot rolling is a rolling temperature below 870℃ to 13mm with a reduction rate of 27%. The billet is then air-cooled to obtain the finished wind power steel.

[0062] Test Example 1

[0063] The mechanical properties of the alloy hot-rolled plates obtained in Examples 1-3 were tested, and the results are shown in Table 1 below.

[0064] Table 1 Mechanical properties of hot-rolled alloy plates with different Ce contents

[0065]

[0066] The impact test specimens were tested using a pendulum impact testing machine, model PTMS4300. The longitudinal and transverse impact energies at -40℃ are shown in Table 1. It can be seen that the longitudinal impact energy does not change significantly, mainly because the longitudinal low-temperature performance of these three steels is already excellent, so the improvement effect of adding rare earth elements is not significant. However, the transverse impact energy shows a clear upward trend with increasing rare earth content, increasing from 251J to 295J, approaching the maximum range of the equipment. Furthermore, it can be seen that the difference in low-temperature impact performance between the longitudinal and transverse sides is significantly reduced after adding rare earth elements, possibly related to improved inclusion conditions, grain refinement, and dislocation state. The low-temperature impact performance of all three steel grades meets the requirements.

[0067] refer to Figure 1 As shown, (ac) is the curve of load and energy versus displacement for longitudinal low-temperature impact energy of the three steel grades, and (d) is a comparison of load-displacement curves of the three steel grades. It can be seen that although the longitudinal low-temperature impact energy of the three steel grades is similar, the displacement of the sample in Example 3 during the plastic deformation stage is smoother and the displacement is greater than that of the other steel grades, which also indirectly proves that the crack arrest performance of the steel in Example 3 under the low-temperature impact test conditions is better.

[0068] Further reference Figure 2 As shown, Figure 2The images show the macroscopic morphology of the low-temperature impact fracture surfaces of Examples 1 and 3. It can be seen that the macroscopic fracture morphology of both steels consists of an edge shear lip and a central fiber region, without a radial region, proving that both steels have excellent low-temperature toughness. It can also be seen that the shear lip area of ​​the sample in Example 3 is larger than that of the sample in Example 1. Generally speaking, when the toughness of the material is better and the fracture propagation rate is lower, the proportion of the shear lip in the fracture width is larger. Therefore, it can be seen from the macroscopic fracture surface that the low-temperature performance of the sample in Example 3 is better.

[0069] Further reference Figure 3 As shown, the fracture surfaces of the samples from Examples 1 and 3 under low-temperature impact are morphologically analyzed by SEM. It can be seen that the fracture surfaces of Examples 3 are mainly characterized by dimples, exhibiting ductile fracture characteristics. In contrast, the fracture surfaces of the Samples from Examples 1, in addition to dimples, also exhibit some cleavage fracture plane characteristics. Therefore, based on the SEM microscopic fracture surface analysis, the Samples from Examples 3 have better low-temperature toughness.

[0070] Further reference Figure 4 and Figure 5 , Figure 4 The image shows the SEM morphology of the low-temperature impact fracture surface in Example 1. It can be seen that the fracture surface of 0Ce at -60℃ to -120℃ is mainly characterized by cleavage fracture, exhibiting cleavage fracture features. However, at -100℃ and 120℃, a very small number of dimples appear at the tear points. Figure 5 The fracture surfaces of the sample in Example 3 at -60℃ and -120℃ mainly exhibited planar characteristics of cleavage fracture, with dimples also present at the tear. Furthermore, dimples were mainly observed at -80℃ and -100℃. Therefore, based on SEM microscopic fracture analysis, the 50Ce sample showed better low-temperature toughness.

[0071] Further reference Figure 6 The representative local average orientation difference distribution images of samples with different Ce contents were characterized by EBSD. The results of statistical analysis of grain size of hot-rolled plates with different Ce contents using EBSD are shown in Table 2.

[0072] Table 2 shows the grain size of hot-rolled plates with different Ce contents, statistically analyzed using EBSD.

[0073] Number Grain average size (pm) Example 1 16.4 Example 2 14.6 Example 3 12.0

[0074] The grain sizes of the three steels were statistically analyzed by EBSD, as shown in Table 2. It can be observed that the results are similar to those obtained through metallographic analysis, indicating that the addition of Ce can refine the grain size. Adding 0.0066 wt% Ce reduced the grain size by 24.4%. This is mainly because Ce exhibits a very negative segregation energy near grain boundaries, which hinders grain growth and thus contributes to grain refinement.

[0075] In addition, the addition of a certain amount of rare earth Ce reduced the ductile-brittle transition temperature (DBTT) from -66.1℃ to -83.6℃. Besides purifying molten steel, removing impurities, and refining grains, rare earths also have an important characteristic: the addition of rare earth Ce can regulate the dislocation state, which has a significant impact on optimizing the DBTT.

[0076] Example 4

[0077] S1, according to the formula proportions, weigh the raw materials as follows: 0.14% C, 1.46% Mn, 0.29% Si, 0.028% Nb, 0.0078% Ce, 0.064% V, with the balance being Fe and unavoidable impurities. Specifically, control the impurities in the alloy components to be P = 0.004 wt.%, S = 0.004 wt.%, total Al ≤ 0.04 wt.%, Ca ≤ 0.0015 wt.%, and Mg ≤ 0.0004 wt.%.

[0078] S2, raw materials C, Mn, Si, Nb, V and Fe are added to a vacuum induction melting furnace for smelting;

[0079] S3 is deoxidized with Al, pure rare earth Ce is added, and then cast into an ingot with a diameter of 150mm.

[0080] S4 is heated at 1250℃, then held at that temperature for a total of 4 hours, and then cooled to 1150℃ to forge a thickness of 100 mm × 120 mm. 2 Forged billets;

[0081] S5 involves hot rolling the forged billet from S4 in two stages. The first stage of hot rolling is a holding temperature of 1250℃ for 8 hours, with an initial rolling temperature of 1150℃. The billet is rolled from 100mm to 40mm at 900-1150℃. The second stage of hot rolling is a rolling temperature below 800℃ from 40mm to 13mm. The billet is then air-cooled to obtain the finished wind power steel.

[0082] Table 3 Mechanical properties of alloy hot-rolled plates in Example 4

[0083]

[0084] Combination Figure 7 The microstructure consists of polygonal ferrite and pearlite, with a grain size of ~9.055 μm. Therefore, the addition of V to the alloy system improves its performance.

[0085] Example 5

[0086] S1, according to the formula ratio, weigh the raw materials as follows: 0.0847% C, 1.48% Mn, 0.14% Si, 0.036% Nb, 0.0011% Ce, with the balance being Fe and unavoidable impurities. Specifically, control the impurities in the alloy components to be P = 0.004 wt.%, S = 0.004 wt.%, total Al ≤ 0.04 wt.%, Ca ≤ 0.0015 wt.%, and Mg ≤ 0.0004 wt.%.

[0087] S2, raw materials C, Mn, Si, Nb and Fe are added to a vacuum induction melting furnace for smelting;

[0088] S3 is deoxidized with Al, pure rare earth Ce is added, and then cast into an ingot with a diameter of 110mm.

[0089] S4 is heated at 1250℃, then held at that temperature for a total of 4 hours, and then cooled to 1150℃ to forge a thickness of 100 mm × 120 mm. 2 Forged billets;

[0090] S5, original forging billet dimensions (width: 120mm, thickness: 100mm, length: ~170mm), held at 1100℃ for 3 hours in a heating furnace (ensuring thorough heating); initial rolling temperature is 1100℃, first rolling from 100mm to 40mm thickness, with the steel plate surface temperature exceeding 900℃ during this stage (no specific requirements for the number of rolling passes). Note: If the temperature drop is too large during this stage, it can be reheated in the furnace; then, when the steel plate surface temperature drops to 820-870℃, it is rolled from 40mm to 13mm thickness at this temperature. Finally, straightening can be performed to ensure the steel plate is straight. After rolling, air cooling is performed. Note: If the steel plate surface temperature is below 820℃ at the beginning of this stage, it should be reheated in the furnace, and rolled again when the steel plate surface cools to 820-870℃. The entire hot rolling process ensures two-stage rolling, guaranteeing sufficient rolling volume below the recrystallization temperature, achieving the effects of grain refinement and dislocation strengthening. The mechanical properties of the alloy are shown in Table 4 below.

[0091] Table 4 Mechanical properties of alloy hot-rolled plates from Example 5

[0092]

[0093] refer to Figure 8 The metallographic image of Example 5 shows that the microstructure consists of polygonal ferrite and pearlite, exhibiting a banded structure of alternating ferrite and pearlite phases. The grain size is 5.4 μm. Compared with Examples 1-3, the grains are significantly refined, but the mechanical properties are not substantially improved, indicating that the strength of this alloy system is not significantly related to the grain size.

[0094] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A process for synergistically regulating the microstructure and properties of high-strength and high-toughness wind power steel by trace amounts of Ce-Nb, characterized by: The method comprises the following steps: S1, weighing raw materials according to the formula proportion; S2, sequentially adding C, Mn, Si, Nb and Fe raw materials into a vacuum induction smelting furnace for smelting; S3, after deoxidation by Al, adding pure rare earth Ce into the molten steel, and casting into ingots; S4, heating at 1250±10℃, then keeping for 3-5 hours, and then forging into a forging blank at 1150℃; S5, after two-stage hot rolling of the forging blank, air cooling to obtain a finished wind power steel with UTS≥460MPa and impact energy at-40℃≥280J; The steel is composed of the following components in percentage by mass: C: 0.05-0.15%, Mn: 1.2-1.5%, Si: 0.1-0.4%, Nb: 0-0.02%, Ce: 0.0011-0.0066%, V: 0-0.07%, and the balance of Fe and inevitable impurities.

2. The process for synergistically regulating the microstructure and properties of high-strength and high-toughness wind power steel by trace Ce-Nb according to claim 1, characterized in that: The impurities in the alloy components are controlled as follows: P≤0.015wt.%, S≤0.004wt.%, total Al≤0.04wt.%, Ca≤0.0015wt.%, and Mg≤0.0004wt.%.

3. The process for synergistically regulating the microstructure and properties of high-strength and high-toughness wind power steel by trace Ce-Nb according to claim 1, characterized in that: The diameter of the ingot cast in step S4 is 150-250mm.

4. The process for synergistically regulating the microstructure and properties of high-strength and high-toughness wind power steel by trace Ce-Nb according to claim 1, characterized in that: The first-stage hot rolling in step S5 is 1250℃ for 2h, the opening rolling temperature is 900-1150℃, and the reduction is ≤60%.

5. The process for synergistically regulating the microstructure and properties of high-strength and high-toughness wind power steel by trace Ce-Nb according to claim 1, characterized in that: The second-stage opening rolling temperature in step S5 is below 870℃, the reduction is ≤30%, and then air cooling to obtain the finished wind power steel.

6. The process for synergistically regulating the microstructure and properties of high-strength and high-toughness wind power steel by trace Ce-Nb according to claim 1, characterized in that: The microstructure of the steel plate is fine and uniform ferrite+pearlite dual-phase structure, the average grain size is less than 13μm, and the dislocation density is increased by more than 20%.

7. The process for synergistically regulating the microstructure and properties of high-strength and high-toughness wind power steel by trace Ce-Nb according to claim 1, characterized in that: The longitudinal impact absorption energy at-40℃ is not less than 280J, the transverse impact absorption energy is not less than 290J, and the steel has isotropic low-temperature toughness.

8. The process for synergistically regulating the microstructure and properties of high-strength and high-toughness wind power steel by trace Ce-Nb according to claim 1, characterized in that: The main inclusions in the steel include Ce2O2S, CaAl2O4 and 12CaO·7Al2O3, and the addition amount of Ce can control the content of spinel inclusion MgAl2O4 to be reduced by at least 30%.

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