A steel for large single-weight wind power and a method for manufacturing the same

Abstract

The application relates to a large single-weight wind power steel and a preparation method thereof, the method comprising the following steps: first heating and first rolling at least two first billets with a set chemical composition to obtain corresponding second billets; compounding all the corresponding second billets to obtain a composite billet; second heating and second rolling of the composite billet to obtain a hot-rolled plate; first cooling, normalizing and second cooling of the hot-rolled plate to obtain the large single-weight wind power steel. The large single-weight wind power steel prepared by the application meets the following performances: the yield strength at different thickness positions is greater than or equal to 390 MPa, the yield strength difference at different thickness positions is less than or equal to 50 MPa; the tensile strength is greater than or equal to 530 MPa, the tensile strength difference at different thickness positions is less than or equal to 30 MPa; the impact value is greater than or equal to 120 J; and the thickness direction section shrinkage rate is greater than or equal to 45%.

Description

Technical Field

[0001] This application relates to the field of medium and heavy plate manufacturing technology, and in particular to a large single-weight wind power steel and its preparation method. Background Technology

[0002] Wind power, as a renewable energy source, boasts advantages such as short construction cycles, flexible installed capacity, and low operating and maintenance costs, offering broad development prospects. In recent years, with the rapid advancement of the national carbon peaking and carbon neutrality strategies, the wind power industry has achieved rapid development. Looking at the industry's development trend, the capacity of single wind turbine units is continuously increasing. This necessitates increasingly thicker and wider steel plates for wind power applications, requiring high strength, low yield strength ratio, excellent low-temperature toughness, and good mechanical properties in the thickness direction. Furthermore, higher requirements are placed on the uniformity of mechanical properties in the thickness direction, necessitating normalized delivery.

[0003] To meet the requirements for large unit weight and performance of wind turbine steel, traditional processes use ingot casting, which results in low yield, high cost, and poor uniformity of mechanical properties in the thickness direction. Due to limitations in billet size and rolling mill capacity, continuous casting of wind turbine steel can hardly meet the required unit weight, and also results in poor low-temperature toughness and mechanical properties in the thickness direction. Summary of the Invention

[0004] This application provides a steel for large single-unit wind power and its preparation method to solve the following technical problem: how to improve the uniformity of mechanical properties in the thickness direction of steel for large single-unit wind power.

[0005] In a first aspect, this application provides a method for preparing steel for large single-unit wind power applications, the method comprising:

[0006] At least two first steel billets with a set chemical composition are subjected to a first heating and a first rolling process to obtain a corresponding second steel billet;

[0007] All the corresponding second steel billets are combined to obtain composite steel billets;

[0008] The composite steel billet is subjected to a second heating and a second rolling process to obtain a hot-rolled plate.

[0009] The hot-rolled plate is subjected to a first cooling, normalizing, and a second cooling process to obtain steel for large single-weight wind power applications.

[0010] Optionally, the temperature of the first heating is 1210℃~1250℃.

[0011] Optionally, the process parameters for the first rolling process include: a single-pass reduction rate of ≥10% for the last two passes and a rolling speed of 1.0m / s to 1.2m / s.

[0012] Optionally, the temperature of the second heating is 1120℃~1160℃.

[0013] Optionally, the process parameters for the second rolling process include: a single-pass reduction rate of ≥20% for the last two passes, a rolling speed of 1.0m / s to 1.2m / s, and a final rolling temperature of ≥980℃.

[0014] Optionally, the process parameters for the first cooling include: a cooling rate of 10℃ / s to 20℃ / s and a final cooling temperature of 600℃ to 660℃.

[0015] Optionally, the normalizing temperature is 875℃~885℃.

[0016] Optionally, the process parameters for the second cooling include: a cooling rate of 5℃ / s to 12℃ / s and a final cooling temperature of 530℃ to 600℃.

[0017] Optionally, the specified chemical composition includes: C, Si, Mn, Alt, Nb, Ti, V, Cu, P, S, and Fe;

[0018] Of which, in terms of mass fraction,

[0019] The C content is 0.16%~0.18%, the Si content is 0.40%~0.50%, and the Mn content is 1.50%~1.60%.

[0020] The content of Alt is 0.02%~0.05%, the content of Nb is 0.015%~0.025%, the content of Ti is 0.01%~0.02%, the content of V is 0.03%~0.06%, the content of Cu is 0.2%~0.3%, the content of P is 0.01%~0.02%, and the content of S is <0.003%.

[0021] Secondly, this application provides a large single-weight wind power steel prepared by the method described in any embodiment of the first aspect, wherein the large single-weight wind power steel meets the following properties: yield strength at different positions of thickness ≥390MPa, yield strength difference at different positions of thickness ≤50MPa; tensile strength ≥530MPa, tensile strength difference at different positions of thickness ≤30MPa; impact value ≥120J; reduction of area in the thickness direction ≥45%.

[0022] The technical solutions provided in this application have the following advantages compared with the prior art:

[0023] The method for preparing the large single-weight wind power steel provided in this application includes: subjecting at least two first steel billets with a set chemical composition to a first heating and a first rolling to obtain corresponding second steel billets; combining all the corresponding second steel billets to obtain a composite steel billet; subjecting the composite steel billet to a second heating and a second rolling to obtain a hot-rolled plate; and subjecting the hot-rolled plate to a first cooling, normalizing, and a second cooling to obtain the large single-weight wind power steel. The first heating of the first steel billet with the set chemical composition softens the billet, thereby reducing the deformation resistance of subsequent rolling mills and increasing the single-pass reduction rate, while also allowing the alloying elements in the first steel billet to dissolve fully, thus improving the internal quality and performance of the steel plate; the first rolling of the first heated billet allows recrystallization throughout its thickness, refining the billet's microstructure and improving its internal quality; combining at least two second steel billets increases the billet thickness, thereby increasing the rolling compression ratio and billet weight, thus improving the target large single-weight wind power steel. Internal quality and unit weight; the second heating of the composite billet further refines its microstructure, and the second rolling of the heated composite billet allows for recrystallization throughout its thickness, refining its microstructure and improving its internal quality; the first cooling of the hot-rolled plate results in a refined ferrite and pearlite microstructure; normalizing further refines the grain size and homogenizes the microstructure through austenitization; the second cooling refines the microstructure of the normalized hot-rolled plate and increases the pearlite content, improving its impact toughness and strength. In summary, this improves the uniformity of mechanical properties in the thickness direction of the large-unit-weight wind power steel. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 A schematic flowchart illustrating a method for preparing large single-weight wind power steel provided in this application embodiment;

[0027] Figure 2 Microstructure diagram of a large single-unit wind turbine steel provided in Embodiment 1 of this application;

[0028] Figure 3 Microstructure of a large single-unit wind turbine steel provided in Embodiment 2 of this application;

[0029] Figure 4 Microstructure diagram of a large single-weight wind power steel provided in Embodiment 3 of this application. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0032] In this application, the terms "comprising," "including," etc., mean "including but not limited to." Relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0033] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0034] Firstly, this application provides a method for preparing steel for large single-unit wind turbines. Figure 1 A schematic flowchart illustrating a method for preparing large-scale wind power steel according to an embodiment of this application; please refer to... Figure 1 The method includes:

[0035] S1. At least two first steel billets with a set chemical composition are subjected to a first heating and a first rolling process to obtain a corresponding second steel billet;

[0036] In some embodiments, the specified chemical composition includes: C, Si, Mn, Alt, Nb, Ti, V, Cu, P,

[0037] S and Fe; wherein, by mass fraction,

[0038] The C content is 0.16%~0.18%, the Si content is 0.40%~0.50%, and the Mn content is 1.50%~1.60%.

[0039] The content of Alt is 0.02%~0.05%, the content of Nb is 0.015%~0.025%, the content of Ti is 0.01%~0.02%, the content of V is 0.03%~0.06%, the content of Cu is 0.2%~0.3%, the content of P is 0.01%~0.02%, and the content of S is <0.003%.

[0040] In the embodiments of this application, Nb, V, and Ti microalloying is employed, while Cu and V precipitation strengthening are utilized simultaneously. A high C (0.16-0.18%) composition design is used, increasing the pearlite content to improve strength. C is the cheapest and best strengthening element; increasing the C content reduces the need for alloy additions. More Si and Mn are added to improve strength through solid solution strengthening and reduce strength loss after normalizing. Less Nb is added to leverage its grain-refining strengthening effect while reducing its inhibitory effect on recrystallization. Cu and V are added to improve strength through grain-refining and precipitation strengthening. P is a harmful element, having a very negative impact on toughness and plasticity, and its content should be reduced. However, P is also a very good strengthening element; therefore, the upper and lower limits of P content are controlled, as are the Alt and S contents in the steel. For example, the content of C can be 0.16%, 0.17%, 0.18%, etc.; the content of Si can be 0.40%, 0.45%, 0.50%, etc.; the content of Mn can be 1.50%, 1.55%, 1.60%, etc.; the content of Alt can be 0.02%, 0.03%, 0.04%, 0.05%, etc.; the content of Nb can be 0.015%, 0.017%, 0.019%, 0.021%, 0.023%, 0.025%, etc.; the content of Ti can be 0.01%, 0.015%, 0.02%, etc.; the content of V can be 0.03%, 0.04%, 0.05%, 0.06%, etc.; the content of Cu can be 0.2%, 0.25%, 0.3%, etc.; the content of P can be 0.01%, 0.015%, 0.02%, etc.; and the content of S can be 0.002%, 0.0015%, etc. In addition, the carbon equivalent (CEV) of the aforementioned wind power steel is 0.450~0.480; its calculation formula is as follows: CEV=C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15, where it is calculated based on the mass fraction of chemical elements.

[0041] In some embodiments, the temperature of the first heating is 1210°C to 1250°C.

[0042] In this embodiment, the first steel billet is cold-charged into the furnace and heated at a high temperature. This softens the billet, reduces the deformation resistance of subsequent rolling mills, increases the single-pass reduction rate, and improves the internal quality of the billet. Simultaneously, the high-temperature heating allows the alloying elements to dissolve fully, further enhancing the billet's internal quality and performance. If the first heating temperature is too low, it can lead to high deformation resistance in subsequent rolling mills and a low single-pass reduction rate in recrystallization rolling, resulting in poorer internal quality and performance of the billet. Furthermore, if the first heating temperature is too low, it can hinder the complete solidification of Nb, preventing the full utilization of solid solution strengthening and precipitation strengthening effects during subsequent rolling, thus reducing the uniformity of mechanical properties in the thickness direction of the billet. Conversely, if the first heating temperature is too high, it can cause abnormal growth of the billet's microstructure, ultimately further reducing the uniformity of mechanical properties in the thickness direction. For example, the temperature of the first heating can be 1210℃, 1220℃, 1230℃, 1240℃, 1250℃, etc.; the time of the first heating can be 400min~600min.

[0043] In some embodiments, the process parameters for the first rolling process include: a single-pass reduction rate of ≥10% for the last two passes and a rolling speed of 1.0 m / s to 1.2 m / s.

[0044] In this embodiment, the first steel billet is directly rolled into the required steel plate size after exiting the furnace. The aforementioned first rolling process parameters are used, namely, a high-temperature, low-speed, and high-reduction fully recrystallized rolling process, which causes recrystallization throughout the entire thickness of the first steel billet, refining its microstructure and improving its internal quality. Furthermore, the rolling process is not temperature-controlled, preventing the first steel billet from growing excessively during the warming process, while simultaneously improving rolling efficiency. For example, in the aforementioned first rolling process parameters: the single-pass reduction rate for the last two passes can be 10%, 11%, 12%, 13%, etc., and the rolling speed can be 1.0 m / s, 1.1 m / s, 1.2 m / s, etc.

[0045] In addition, the steps before step S1 include: (1) Smelting: using a converter for smelting and top and bottom combined blowing; using LF furnace and VD furnace for vacuum treatment to reduce the content of harmful gases such as O, N, and H; (2) Continuous casting: designing the billet shape of the continuous casting billet (first billet), with a thickness of 400mm and a width of 1650-2400 (mm), controlling the inclusions of type A, type B, and type Ds to not exceed 2.0, the inclusions of type C to not exceed 1.0, and the inclusions of type D to not exceed 1.5.

[0046] S2. Combine all the corresponding second steel billets to obtain composite steel billets;

[0047] In this embodiment, at least two second steel billets are combined to increase the billet thickness, thereby increasing the rolling compression ratio and billet weight, and thus improving the internal quality and weight of the target large-unit wind power steel. For example, S2 specifically includes: after the second steel billets are cooled to room temperature, one side of each of the two second steel billets is ground until smooth and free of iron oxide scale; the ground surfaces of the two second steel billets are then combined; the four sides of the stacked billets are welded and a vacuum is applied to ensure the bonding surface is in a vacuum state, thus completing the preparation of the composite steel billet.

[0048] S3. The composite steel billet is subjected to a second heating and a second rolling process to obtain a hot-rolled plate;

[0049] In some embodiments, the temperature of the second heating is 1120°C to 1160°C.

[0050] In this embodiment, the composite steel billet is heated in the furnace using a second heating temperature at a low temperature. The first heating has already fully dissolved the alloying elements; the purpose of the second heating at a low temperature is to obtain a finer microstructure and improve the mechanical properties of the composite steel billet. If the second heating temperature is too low, it may cause the entire rolling process to be difficult to occur entirely within the recrystallization zone, resulting in mixed crystals and affecting impact toughness. If the second heating temperature is too high, it may lead to abnormal microstructure growth, causing a decrease in the uniformity of the composite steel billet's mechanical properties in the thickness direction. For example, the second heating temperature can be 1120℃, 1130℃, 1140℃, 1150℃, 1160℃, etc.; the second heating time can be 500min~700min.

[0051] In some embodiments, the process parameters for the second rolling process include: a single-pass reduction rate of ≥20% for the last two passes, a rolling speed of 1.0 m / s to 1.2 m / s, and a final rolling temperature of ≥980°C.

[0052] In this embodiment, the composite steel billet is directly rolled into the required steel plate size after exiting the furnace, using the aforementioned second rolling process parameters, namely, a low-speed, high-reduction fully recrystallized rolling process, to allow recrystallization to occur throughout the thickness of the composite steel billet, refining the microstructure and improving internal quality. Furthermore, the rolling process is not temperature-controlled, avoiding microstructure growth of the composite steel billet during the warming process, while simultaneously improving rolling efficiency. For example, in the aforementioned second rolling process parameters: the single-pass reduction rate for the last two passes can be 20%, 21%, 22%, 23%, etc.; the rolling speed can be 1.0 m / s, 1.1 m / s, 1.2 m / s, etc.; and the final rolling temperature can be 980℃, 990℃, 1000℃, 1010℃, etc.

[0053] S4. The hot-rolled plate is subjected to first cooling, normalizing and second cooling to obtain large single-weight wind power steel.

[0054] In some embodiments, the process parameters for the first cooling include: a cooling rate of 10°C / s to 20°C / s and a final cooling temperature of 600°C to 660°C.

[0055] In this embodiment, a post-rolling accelerated cooling control system (ACC) is used to achieve the first cooling. Using the process parameters of the first cooling, the hot-rolled plate can have a refined ferrite and pearlite structure. If the final cooling temperature is too low, bainite or martensite structures may appear in the hot-rolled plate to some extent, resulting in poor mechanical properties of the hot-rolled plate after normalizing. If the final cooling temperature is too high, the structure of the hot-rolled plate may be too coarse to some extent, resulting in poor uniformity of the thickness-direction mechanical properties of the hot-rolled plate after normalizing. For example, the process parameters of the first cooling can include: cooling rates of 10℃ / s, 12℃ / s, 14℃ / s, 16℃ / s, 18℃ / s, 20℃ / s, etc.; and final cooling temperatures of 600℃, 610℃, 620℃, 630℃, 640℃, 650℃, 660℃, etc.

[0056] In some embodiments, the normalizing temperature is 875°C to 885°C.

[0057] In this embodiment, normalizing can refine the grains and homogenize the microstructure in the hot-rolled sheet after the first cooling by austenitizing. For example, the normalizing temperature can be 875°C, 880°C, 885°C, etc. The furnace temperature time for normalizing can be 1.9 to 2.0 times the final steel sheet thickness (min).

[0058] In some embodiments, the process parameters for the second cooling include: a cooling rate of 5°C / s to 12°C / s and a final cooling temperature of 530°C to 600°C.

[0059] In this embodiment, the hot-rolled plate after normalizing undergoes a second cooling process, which is water cooling. The process parameters for this second cooling can further refine the ferrite and pearlite microstructure in the normalized hot-rolled plate. Using this low cooling rate and low final cooling can refine the microstructure of the normalized hot-rolled plate and increase its pearlite content, thereby improving its impact toughness and strength. If the final cooling temperature is too low, it can lead to the formation of bainite or martensite on the surface of the normalized hot-rolled plate, resulting in poor impact toughness; if the final cooling temperature is too high, the microstructure becomes too coarse, leading to poor mechanical properties. For example, the process parameters for the second cooling can include: cooling rates of 5℃ / s, 7℃ / s, 9℃ / s, 11℃ / s, 12℃ / s, etc., and final cooling temperatures of 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, etc.

[0060] Secondly, this application provides a large single-weight wind power steel prepared by the method described in any embodiment of the first aspect, wherein the large single-weight wind power steel meets the following properties: yield strength at different positions of thickness ≥390MPa, yield strength difference at different positions of thickness ≤50MPa; tensile strength ≥530MPa, tensile strength difference at different positions of thickness ≤30MPa; impact value ≥120J; reduction of area in the thickness direction ≥45%.

[0061] Currently, traditional processes use ingot casting. The thickness of the ingot-cast billet makes it difficult for the rolling force to penetrate to the core of the steel plate during the rolling process, resulting in poor mechanical properties and uniformity in the thickness direction. However, in this embodiment, through post-rolling composite rolling and then re-rolling, high strength and good low-temperature toughness are achieved in the steel plate, while maintaining excellent and uniform mechanical properties in the thickness direction. This enables large-scale wind power steel plates to simultaneously meet the requirements of high strength, low yield strength ratio, good low-temperature toughness, and uniform mechanical properties in the thickness direction. Specifically, the mechanical properties in the thickness direction of this embodiment are: yield strength at different locations ≥ 390 MPa, yield strength difference at different locations ≤ 50 MPa; tensile strength difference at different locations ≤ 30 MPa; and reduction of area in the thickness direction ≥ 45%.

[0062] The large single-weight wind power steel is realized based on the above-mentioned preparation method of the large single-weight wind power steel. The specific steps of the preparation method of the large single-weight wind power steel can be referred to the above embodiments. Since the large single-weight wind power steel adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be repeated here.

[0063] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0064] This application provides a method for preparing steel for large single-unit wind power applications. Please refer to Table 1 for the chemical composition (wt%) of the steel for large single-unit wind power applications, Table 2 for the preparation process parameters of the steel for large single-unit wind power applications, and Table 3 for the mechanical properties of the steel for large single-unit wind power applications.

[0065] Table 1 Chemical composition (wt%) of steel for large single-unit wind turbines, the remainder being Fe and unavoidable impurities.

[0066]

[0067] Table 2. Process parameters of a high-performance steel plate for large single-unit wind power applications.

[0068]

[0069] Table 2. Process parameters of a high-performance steel plate for large single-unit wind power applications (continued)

[0070]

[0071] Table 3 Mechanical properties of steel for large single-unit wind turbines

[0072]

[0073] In Examples 1-3, large-capacity wind turbine steel plates were designed to simultaneously meet the requirements of high strength, low yield strength ratio, good low-temperature toughness, and good uniformity of mechanical properties in the thickness direction. Yield strength at different locations within the thickness is ≥390MPa, with a yield strength difference of ≤50MPa; tensile strength is ≥530MPa, with a tensile strength difference of ≤30MPa; impact value is ≥120J; and the reduction of area in the thickness direction is ≥45%. Figure 2 Microstructure diagram of a large single-unit wind turbine steel provided in Embodiment 1 of this application; Figure 3 Microstructure of a large single-unit wind turbine steel provided in Embodiment 2 of this application; Figure 4 Microstructure diagram of a large single-unit wind turbine steel provided in Embodiment 3 of this application; please refer to Figures 2-4This indicates that the microstructure of the large-weight wind power steel provided in this application embodiment is fine and uniform. In Comparative Example 1, the amount of Nb is excessive, and the final cooling temperature of the first cooling after rolling is too low, resulting in poor impact values ​​and reduction of area in the thickness direction at 1 / 4 and 1 / 2 thicknesses. In Comparative Example 2, the amount of C added is too small, resulting in a significant decrease in yield strength and tensile strength. In Comparative Example 3, the composite billet rolling process was not used, and the amount of C added was excessive, resulting in a small single-piece weight of steel plate and improved strength. However, the yield strength at different locations exceeded 60 MPa, the difference in tensile strength exceeded 50 MPa, and the impact at 1 / 4 and 1 / 2 thicknesses was poor, all of which are outside the scope of the embodiments in this application. In Comparative Example 4, the composite billet rolling process was not used, resulting in a small single-piece weight of steel plate, a small compression ratio, and a high final cooling temperature in the second cooling. This resulted in a significant decrease in the yield and tensile strength of the steel plate, and poor impact values ​​and reduction of area in the thickness direction at 1 / 4 and 1 / 2 thicknesses.

[0074] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for producing a steel for large single-casting wind turbines, characterized in that, The method includes: At least two first steel billets with a set chemical composition are subjected to a first heating and a first rolling to obtain a corresponding second steel billet. The temperature of the first heating is 1210℃~1250℃. All the corresponding second steel billets are combined to obtain composite steel billets; The composite steel billet is subjected to a second heating and a second rolling to obtain a hot-rolled plate, wherein the temperature of the second heating is 1120℃~1160℃. The hot-rolled plate is subjected to a first cooling, normalizing and a second cooling to obtain large single-weight wind power steel. The process parameters for the first rolling process include: a single-pass reduction rate of ≥10% for the last two passes, and a rolling speed of 1.0 m / s to 1.2 m / s; The process parameters for the second rolling process include: a single-pass reduction rate of ≥20% for the last two passes, a rolling speed of 1.0 m / s to 1.2 m / s, and a final rolling temperature of ≥980℃. The process parameters for the first cooling include: a cooling rate of 10℃ / s to 20℃ / s, a final cooling temperature of 600℃ to 660℃, and a normalizing temperature of 875℃ to 885℃. The process parameters for the second cooling include: a cooling rate of 5℃ / s to 12℃ / s, and a final cooling temperature of 530℃ to 600℃. The specified chemical composition is: C, Si, Mn, Alt, Nb, Ti, V, Cu, P, S, and Fe; wherein, by mass fraction, the content of C is 0.16%~0.18%, the content of Si is 0.40%~0.50%, the content of Mn is 1.50%~1.60%, the content of Alt is 0.02%~0.05%, the content of Nb is 0.015%~0.025%, the content of Ti is 0.01%~0.02%, the content of V is 0.03%~0.06%, the content of Cu is 0.2%~0.3%, the content of P is 0.01%~0.02%, and the content of S is <0.003%. The steel used in the large single-weight wind turbine has a thickness of ≥50mm, a yield strength difference of ≤50MPa at different locations with different thicknesses, a tensile strength difference of ≤30MPa at different locations with different thicknesses, and a reduction of area in the thickness direction of ≥45%.

2. The steel for large single heavy wind power generation prepared by the preparation method of claim 1, characterized in that, The steel for large single-unit wind power applications meets the following performance requirements: yield strength at different locations with different thicknesses ≥390MPa, yield strength difference at different locations with different thicknesses ≤50MPa; tensile strength ≥530MPa, tensile strength difference at different locations with different thicknesses ≤30MPa; impact value ≥120J; reduction of area in the thickness direction ≥45%.

Images