12.9-grade wind power bolt material as well as preparation method and application thereof

Abstract

The invention provides a 12.9-grade wind power bolt material and a preparation method and application thereof, and belongs to the technical field of fastener steel. The 12.9-grade wind power bolt material is prepared from the following element components in percentage by mass: 0.38 to 0.45 percent of C, 0.20 to 0.30 percent of Si, 0.52 to 0.58 percent of Mn, less than or equal to 0.010 percent of P, less than or equal to 0.005 percent of S, 1.10 to 1.15 percent of Cr, 0.22 to 0.28 percent of Mo, less than or equal to 0.10 percent of Cu, 0.30 to 0.40 percent of Ni, 0.10 to 0.15 percent of V, 0.02 to 0.03 percent of Nb, 0.02 to 0.03 percent of Al and the balance of Fe and inevitable impurities. By redesigning the components and optimizing the heat treatment process, the wind power bolt material with the mechanical property meeting the 12.9-grade high strength and the M42-M72 large specification is produced.

Description

Technical Field

[0001] The present invention belongs to the technical field of fastener steel materials, and in particular relates to a 12.9-grade wind power bolt material and a preparation method and application thereof. Background Art

[0002] Wind power generation is a key renewable energy source. my country's cumulative installed wind power capacity exceeded 500 GW in 2024, with a target of 3,000 GW by 2060. Wind power generation has entered a period of rapid development. Bolts are a crucial component of wind turbines, primarily providing connections and fastening. These bolts include tower bolts, blade bolts, and ground anchor bolts. 42CrMo is a typical structural alloy steel. After quenching and tempering, it exhibits excellent overall mechanical properties and is widely used in the manufacture of grade 10.9 and 12.9 high-strength bolts. However, the critical through-hardening diameter of 42CrMo is approximately 40 mm, making it difficult to meet the performance requirements of large-size bolts (M42-M72).

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The critical hardenability diameter of currently used 42CrMo is approximately φ40mm. As wind turbine capacity increases, the use of bolts also increases, making it difficult for this material to meet the performance requirements of large-scale M42-M72 bolts. The present invention aims to provide a 12.9-grade wind turbine bolt material, its preparation method, and its application. By redesigning its composition and optimizing its heat treatment process, this material is produced with mechanical properties that meet the requirements of 12.9-grade high-strength, large-scale M42-M72 wind turbine bolts, thereby resolving the problem that 42CrMo cannot meet the performance requirements of large-scale M42-M72 12.9-grade wind turbine bolts.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The first aspect of the present invention provides a 12.9 grade wind power bolt material, which includes the following elemental components by mass percentage: C: 0.38-0.45%, Si: 0.20-0.30%, Mn: 0.52-0.58%, P: ≤0.010%, S: ≤0.005%, Cr: 1.10-1.15%, Mo: 0.22-0.28%, Cu: ≤0.10%, Ni: 0.30-0.40%, V: 0.10-0.15%, Nb: 0.02-0.03%, Al: 0.02-0.03%, and the rest is Fe and unavoidable impurities.

[0007] The second aspect of the present invention provides a preparation method of the 12.9 grade wind power bolt material described in the first aspect, wherein the round steel material prepared by the converter, LF refining, RH vacuum degassing, continuous casting and rolling process is subjected to heat treatment and tempering by quenching and tempering. During the rolling process, a controlled rolling and controlled cooling process is adopted, and the final rolling temperature during the controlled rolling is not less than 810°C, and the cooling rate during the controlled cooling is 0.5-0.8°C / s.

[0008] Furthermore, the final rolling temperature is 810-840°C.

[0009] Furthermore, the finishing temperature is controlled by water cooling;

[0010] And / or, the cooling rate is controlled by a heat-insulating cover during the controlled cooling.

[0011] Furthermore, the continuous casting adopts a soft reduction technology.

[0012] Furthermore, the temperature of the continuous casting billet before rolling is 1180-1220°C.

[0013] Furthermore, the quenching adopts a quenching temperature of not less than 880° C. and a water cooling process;

[0014] And / or, the tempering adopts a tempering temperature not higher than 630° C. and a water cooling process.

[0015] Furthermore, the quenching temperature is 880-900°C;

[0016] And / or, the tempering temperature is 570-630°C.

[0017] Further, the quenching temperature is 880°C, and the tempering temperature is 570-630°C; further, the quenching temperature is 880°C, and the tempering temperature is 630°C;

[0018] And / or, the quenching temperature is 900°C, and the tempering temperature is 600-630°C.

[0019] The third aspect of the present invention provides an application of the 12.9-grade wind power bolt material described in the first aspect or the 12.9-grade wind power bolt material prepared by the preparation method of the second aspect, wherein the 12.9-grade wind power bolt material is used for the preparation of M42-M72 specification, 12.9-grade high-strength wind power bolts.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The 12.9-grade wind power bolt material of the present invention ensures the hardenability of the material by adding elements Mn, Cr, and Mo that improve hardenability, and controlling their contents to Mn: 0.52-0.58%, Cr: 1.10-1.15%, and Mo: 0.22-0.28%, respectively; adding microalloying elements V and Nb can refine the grain size and improve the comprehensive performance of the material; adding the element Ni can improve the hardenability of steel and ensure the low-temperature impact toughness of the material.

[0022] 2. The preparation method of the 12.9-grade wind power bolt material of the present invention optimizes the heat treatment process, including the controlled rolling and controlled cooling process during the rolling process, the final rolling temperature during controlled rolling is not less than 810°C, and the cooling rate during controlled cooling is 0.5-0.8°C / s, thereby obtaining uniform and stable ferrite F and pearlite P structures, which is more conducive to improving the subsequent tempering heat treatment performance; further, by controlling the quenching and tempering heat treatment temperatures during heat treatment tempering, the mechanical properties of the material are improved, and a material that meets the performance requirements of 12.9-grade wind power bolts is obtained.

[0023] 3. The 12.9-grade wind power bolt material of the present invention can be used to produce wind power bolts that meet the 12.9-grade high strength and large specifications of M42-M72, so as to solve the problem that 42CrMo is difficult to meet the performance of large-size 12.9-grade wind power bolts of M42-M72. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 The metallographic structure of the material after light reduction rolling provided in Example 5 of the present invention Figure 1 ;

[0026] Figure 2 The metallographic structure of the tempered material provided in Example 5 of the present invention Figure 2 ;

[0027] Figure 3 This is a macrostructure diagram of the material after light reduction rolling provided in Example 5 of the present invention;

[0028] Figure 4 This is a low-magnification microstructure diagram of the material after not using soft reduction rolling provided in Example 9 of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. The process parameters for which specific conditions are not specified in the following examples are generally in accordance with conventional conditions.

[0030] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the present invention.

[0031] According to the first aspect of the present invention, the present invention provides a 12.9 grade wind power bolt material, which includes the following elemental components by mass percentage: C: 0.38-0.45%, Si: 0.20-0.30%, Mn: 0.52-0.58%, P: ≤0.010%, S: ≤0.005%, Cr: 1.10-1.15%, Mo: 0.22-0.28%, Cu: ≤0.10%, Ni: 0.30-0.40%, V: 0.10-0.15%, Nb: 0.02-0.03%, Al: 0.02-0.03%, and the rest is Fe and unavoidable impurities.

[0032] In the present invention, since the critical hardenability diameter of the existing 42CrMo is about φ40mm, and the chemical composition directly affects the performance of the material product, the inventors mainly consider the strength and low-temperature impact performance of the material after heat treatment when designing the composition. Therefore, (1) elements Mn, Cr, and Mo are added to improve the hardenability of the wind power bolt material, and the contents of Mn, Cr, and Mo are controlled to Mn: 0.52-0.58%, Cr: 1.10-1.15%, and Mo: 0.22-0.28%, respectively, to ensure the hardenability of the material; (2) micro-alloying elements V and Nb are added to refine the grain size and improve the comprehensive performance of the material; (3) element Ni is added to improve the hardenability of steel and ensure the low-temperature impact toughness of the material. Therefore, in the 12.9 grade wind power bolt material of the present invention, calculated by mass percentage, the C content can be typically but not limited to: 0.38-0.45% (for example, 0.40%, 0.42%, 0.44%), Si can be typically but not limited to: 0.17-0.37% (for example, 0.20%, 0.22%, 0.24%, 0.26%, 0.28%, 0.30%, 0.32%, 0.34%, 0.36%), Mn can be typically but not limited to: 0.50-0.80% (for example, 0.55%, 0.60%, 0.65%, 0.70%, 0.75%), S can be typically but not limited to: ≤0.035% (for example, 0.030%, 0.020%, 0.010%, 0.005%, 0 ), P can be typically but not limitedly selected as: ≤0.035% (for example, 0.030%, 0.020%, 0.010%, 0.005%, 0), Cr can be typically but not limitedly selected as: 0.90-1.20% (for example, 0.95%, 1.00%, 1.05%, 1.10%, 1.15%), Mo can be typically but not limitedly selected as: 0.15-0.25% (for example, 0.18%, 0.20%, 0.22%, 0.24%), Ni can be typically but not limitedly selected as: 0.02-0.05% (for example, 0.03%, 0.04%), Cu can be typically but not limitedly selected as: ≤0.30% (for example, 0.20%, 0.10%, 0.05%, 0), and the rest are Fe and unavoidable impurities.

[0033] According to the second aspect of the present invention, the present invention provides a method for preparing the 12.9-grade wind power bolt material described in the first aspect, wherein the round steel material prepared by the converter, LF refining, RH vacuum degassing, continuous casting and rolling process is subjected to heat treatment and tempering by quenching and tempering, and the controlled rolling and controlled cooling process is adopted during the rolling process, and the final rolling temperature during the controlled rolling is not less than 810°C (such as 812°C, 815°C, 817°C, 820°C, 822°C). ℃, 824℃, 826℃, 828℃, 830℃, 832℃, 834℃, 836℃, 838℃, 840℃), and the cooling rate during the controlled cooling is 0.5-0.8℃ / s (for example, 0.6℃ / s, 0.62℃ / s, 0.64℃ / s, 0.66℃ / s, 0.68℃ / s, 0.7℃ / s, 0.72℃ / s, 0.74℃ / s, 0.76℃ / s, 0.78℃ / s).

[0034] As an optional implementation method of the preparation method of grade 12.9 wind power bolt material of the present invention, the final rolling temperature is 810-840°C (812°C, 815°C, 817°C, 820°C, 822°C, 825°C, 827°C, 830°C, 832°C, 835°C, 837°C).

[0035] In the preparation method of the present invention, a uniform and stable ferrite F and pearlite P structure is obtained through a controlled rolling and controlled cooling process during the rolling process, which is more conducive to improving the performance of subsequent tempering heat treatment. Conventional rolling and air cooling processes will produce bainite structure, which is an unstable structure. Specifically, the final rolling temperature is controlled to be no less than 810°C, and can be specifically controlled at 810-840°C. This is because if the temperature is too low, the deformation resistance will be large and the equipment will be easily damaged; and the temperature should not be too high, because if the temperature is too high, it will not only increase energy consumption, but also lead to a significant trend of grain size growth, which will easily produce coarse grains. The cooling rate is controlled to 0.5-0.8°C / s to ensure slow cooling and provide sufficient favorable time for the formation of ferrite F and pearlite P.

[0036] As an optional embodiment of the method for preparing the 12.9 grade wind power bolt material of the present invention, the final rolling temperature is controlled by water cooling;

[0037] And / or, the cooling rate is controlled by using a heat-insulating cover during the controlled cooling.

[0038] In the present invention, the cooling rate can be controlled by using a heat-insulating cover, or by other methods that can achieve a slow cooling effect.

[0039] As an optional implementation of the method for preparing the 12.9-grade wind power bolt material of the present invention, the continuous casting adopts a soft reduction technology.

[0040] In the above technical solution, a light reduction technique can be used during continuous casting to improve the density of the center of the continuous casting billet and improve the quality of the core of the material. The light reduction technique is a process method in which a small pressure is applied to the liquid core billet during the continuous casting and ironmaking process to obtain a defect-free billet when the continuous casting billet is straightened with liquid core straightening. Specifically, in order to reduce center segregation, a light reduction technique can be applied to the center segregation section (the final stage of billet solidification) during the continuous casting process. That is, the billet is slightly reduced (e.g., 6 to 8 mm) at the point where it is about to completely solidify to avoid center segregation from seriously affecting the internal quality of the billet. Because the formation of center segregation is due to the inward-growing solidification front forming a "bridge" that blocks the downward transport of molten steel, solidification and cooling contraction will cause the solidification contraction force to absorb the S and P-rich liquid between the surrounding dendrites, resulting in center segregation.

[0041] As an optional implementation of the preparation method of grade 12.9 wind power bolt material of the present invention, the temperature of the continuous casting billet before rolling is 1180-1220°C (for example, 1185°C, 1190°C, 1195°C, 1200°C, 1205°C, 1210°C, 1215°C).

[0042] As an optional embodiment of the method for preparing the grade 12.9 wind power bolt material of the present invention, the quenching adopts a quenching temperature of not less than 880°C (such as 882°C, 884°C, 886°C, 888°C, 890°C, 892°C, 894°C, 896°C, 898°C, 900°C) and a water cooling process;

[0043] And / or, the tempering adopts a tempering temperature not higher than 630° C. (such as 610° C., 615° C., 620° C., 625° C., 630° C.) and a water cooling process.

[0044] As an optional embodiment of the method for preparing the grade 12.9 wind power bolt material of the present invention, the quenching temperature is 880-900°C (e.g., 882°C, 884°C, 826°C, 828°C, 890°C, 892°C, 894°C, 896°C, 898°C);

[0045] And / or, the tempering temperature is 570-630°C (e.g., 575°C, 580°C, 585°C, 590°C, 595°C, 600°C, 605°C, 610°C, 615°C, 620°C, 625°C).

[0046] As an optional embodiment of the method for preparing grade 12.9 wind power bolt material of the present invention, the quenching temperature is 880°C, and the tempering temperature is 570-630°C (for example, 575°C, 580°C, 585°C, 590°C, 595°C, 600°C, 605°C, 610°C, 615°C, 620°C, 625°C); further, the quenching temperature is 880°C, and the tempering temperature is 630°C;

[0047] And / or, the quenching temperature is 900°C, and the tempering temperature is 600-630°C (e.g., 602°C, 604°C, 606°C, 608°C, 610°C, 612°C, 614°C, 616°C, 618°C, 620°C, 622°C, 624°C, 626°C, 628°C).

[0048] The preparation method of the present invention achieves material that meets the 12.9 grade performance requirements through quenching and tempering. Specifically, by using a quenching temperature of no less than 880°C and a tempering temperature of no more than 630°C, bolts exceeding 40 mm in diameter, such as 72 mm in diameter, can be obtained. The inventors conducted extensive quenching and tempering heat treatment experiments and determined the optimal heat treatment process for achieving the 12.9 grade performance requirements for bolt materials and the M42-M72 large-size requirements: a quenching temperature of 880°C and a tempering temperature of 630°C.

[0049] According to the third aspect of the present invention, the present invention provides the application of the 12.9-grade wind power bolt material described in the first aspect or the 12.9-grade wind power bolt material prepared by the preparation method of the second aspect, and the 12.9-grade wind power bolt material is used for the preparation of M42-M72 specification, 12.9-grade high-strength wind power bolts.

[0050] The present invention will be further described in detail below with reference to specific examples and comparative examples.

[0051] Examples 1-8 and Comparative Examples 1-8

[0052] The process of 120t top and bottom combined blowing converter → LF refining → RH vacuum degassing → continuous casting of 410mm×530mm → continuous rolling mill is adopted to produce φ72mm round steel (YGFD12.9, i.e. 12.9 grade M72 large-size wind power bolt material (42CrMoVNb)).

[0053] The composition of the round steel, calculated by mass percentage, is: w[C]: 0.42%, w[Si]: 0.27%, w[Mn]: 0.55%, w[P]: 0.007%, w[S]: 0.002%, w[Cr]: 1.10%, w[Mo]: 0.25%, w[Cu]: 0.02%, w[Ni]: 0.36%, w[V]: 0.12%, w[Nb]: 0.025%, w[Al]: 0.024%, and the rest is Fe and unavoidable impurities.

[0054] The continuous casting process uses a 410mm×530mm continuous casting machine, and a soft reduction technique (reduction of 7mm) is used in the final stage of solidification of the ingot.

[0055] Before rolling, a walking-beam heating furnace is used for heating. To ensure uniform heating of the ingot, the total heating time is controlled at about 10 hours, of which the high-temperature holding temperature is controlled at 1180-1220°C, and the high-temperature holding time is 120 minutes. A controlled rolling and controlled cooling process is adopted, and the final rolling temperature is controlled by water cooling during rolling. The final rolling temperature is 830°C, and an insulation cover is used for slow cooling at a cooling rate of 0.5-0.8°C / s to obtain a stable ferrite F + pearlite P structure.

[0056] During the quenching and tempering process, different quenching temperatures were adopted for quenching and water cooling, and different tempering temperatures were adopted for tempering and water cooling. The specific temperatures of the quenching and tempering treatments of Examples 1-8 and Comparative Examples 1-8 are shown in Table 1. With reference to GB / T228.1-2021 Metallic Materials Tensile Test Part 1: Room Temperature Test Method, and with reference to GB / T229-2020 Metallic Materials Charpy Pendulum Impact Test Method, the mechanical properties (tensile strength (Rm), yield strength (Rp)) of the obtained materials were tested. 0.2 ), elongation after fracture (A), cross-sectional shrinkage (Z), and -40℃ impact energy (KV2) were tested, and the test results are shown in Table 1.

[0057] Table 1

[0058]

[0059] It can be seen from the tempering heat treatment test that at the same tempering temperature, different quenching temperatures of 880℃ and 900℃ have little effect on the strength. At the same quenching temperature, with the increase of tempering temperature, the tensile strength and yield strength of YGFD12.9 steel gradually decrease. When the tempering temperature is higher than about 600℃, the tensile strength and yield strength decrease sharply. Different tempering temperatures have a greater influence on the impact toughness index. When the tempering temperature is increased from about 600℃ to 610℃, the impact value increases significantly. When the tempering temperature is lower than about 600℃, the tensile strength does not decrease linearly with the increase of tempering temperature, mainly due to the dispersion precipitation of Mo and V alloy carbides, which produces a secondary hardening effect. The reason for the sharp decrease in strength after the tempering temperature exceeds 610℃ is that overaging occurs, the alloy carbides aggregate and grow, and the resistance to dislocation movement is weakened. The tempering process is 880℃ quenching + 630℃ tempering, which can obtain mechanical properties of tensile strength of 1282MPa, yield strength of 1230MPa, cross-sectional shrinkage of 57%, and impact energy of 62J at -40℃. 880℃ quenching + 630℃ tempering is the best tempering process for heat treating YGFD12.9 steel to 12.9 grade and M42-M72 large-size wind power fasteners.

[0060] The YGFD12.9 with a diameter of 72 mm produced this time has the following components by mass percentage: C: 0.42%, Si: 0.27%, Mn: 0.55%, P: 0.007%, S: 0.002%, Cr: 1.10%, Mo: 0.25%, Cu: 0.02%, Ni: 0.36%, V: 0.12%, Nb: 0.025%, Al: 0.024%, and the rest is Fe and unavoidable impurities. The quenching and tempering process selected 880°C quenching + 630°C tempering to successfully obtain a material that meets the performance requirements of 12.9-grade wind power bolts. The metallographic structure of the material after rolling is shown below. Figure 1 、 2 As shown, from Figure 1 It can be seen that after the controlled rolling and controlled cooling process, uniform and stable ferrite F and pearlite P structures are obtained; Figure 2 It can be seen that after the quenching and tempering heat treatment of 880℃ quenching + 630℃ tempering, the structure of the obtained material is tempered sorbite, and the structure is uniform. In addition, the soft reduction technology is used during the continuous casting of Example 5, and the low-magnification structure diagram of the material obtained after rolling is as follows Figure 3 As shown, from Figure 3 It can be seen that the core structure of the material obtained after rolling is dense.

[0061] Example 9

[0062] The only difference between this embodiment and embodiment 5 is that the soft reduction technology is not used in the continuous casting process, and the other settings are the same as those in embodiment 5.

[0063] This embodiment does not use the soft reduction technology, and the low-magnification structure of the material after rolling is as follows: Figure 4 As shown, from Figure 4 and Figure 3 The comparison shows that Figure 4 The core structure of the material obtained after rolling is not as good as Figure 3 The core structure is dense, which shows that the light reduction technology can improve the density of the center of the continuous casting billet, improve the quality of the core of the material, and ultimately improve the mechanical properties of the material to a certain extent.

[0064] Comparative Example 9

[0065] The only difference between this comparative example and Example 5 is that the round steel composition is: Mn is 0.6%, Cr is 0.9%, and Mo is 0.15%. The remaining composition and preparation are the same as Example 5. As can be seen from Table 1, the impact energy of the φ72mm size YGFD12.9 round steel produced in this comparative example is unqualified, which is probably the result that the Mn, Cr and Mo contents affect the hardenability of the material.

[0066] Comparative Example 10

[0067] The only difference between this comparative example and Example 5 is that the round steel composition does not contain V and Nb, and the remaining components and preparation are the same as those in Example 5.

[0068] It can be seen from Table 1 that the impact energy of the φ72 mm YGFD12.9 round steel produced in this comparative example is unqualified. This is probably because the absence of V and Nb results in grain refinement that is not as good as in Example 5, which ultimately affects the impact energy and causes the impact energy to be unqualified.

[0069] Comparative Example 11

[0070] The only difference between this comparative example and Example 5 is that the round steel composition does not contain Ni, and the remaining components and preparation are the same as those in Example 5.

[0071] Table 1 shows the tensile strength (Rm), yield strength (Rp) and yield strength (Rm) of the φ72mm YGFD12.9 round steel produced in this comparative example. 0.2 ) and impact energy are unqualified, and the performance cannot meet the requirements of 12.9 grade fasteners.

[0072] Comparative Example 12

[0073] The only difference between this comparative example and Example 5 is that the cooling rate during rolling controlled cooling is 1.0°C / s. After controlled cooling, bainite structure is obtained, which is an unstable structure. Based on this, the optimal tempering process of 880°C quenching + 630°C tempering heat treatment is carried out. The resulting material performance barely meets the requirements of 12.9 grade fasteners, but the tensile strength (Rm) and yield strength (Rp) are 0.2 ) Especially the impact energy is not as good as Example 5.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A 12.9-grade wind power bolt material, characterized in that: The 12.9 grade wind power bolt material includes the following elemental components by mass percentage: C: 0.38-0.45%, Si: 0.20-0.30%, Mn: 0.52-0.58%, P: ≤0.010%, S: ≤0.005%, Cr: 1.10-1.15%, Mo: 0.22-0.28%, Cu: ≤0.10%, Ni: 0.30-0.40%, V: 0.10-0.15%, Nb: 0.02-0.03%, Al: 0.02-0.03%, and the rest is Fe and unavoidable impurities.

2. A method for preparing a 12.9-grade wind power bolt material according to claim 1, characterized in that: The round steel material prepared by the converter, LF refining, RH vacuum degassing, continuous casting and rolling process is subjected to heat treatment and tempering by quenching and tempering. The controlled rolling and controlled cooling process is adopted during the rolling process. The final rolling temperature during the controlled rolling is not less than 810°C, and the cooling rate during the controlled cooling is 0.5-0.8°C / s.

3. The method for preparing the 12.9-grade wind power bolt material according to claim 2, characterized in that: The final rolling temperature is 810-840°C.

4. The method for preparing the 12.9-grade wind power bolt material according to claim 2, characterized in that: The final rolling temperature is controlled by water cooling; And / or, the cooling rate is controlled by a heat-insulating cover during the controlled cooling.

5. The method for preparing the 12.9-grade wind power bolt material according to claim 2, characterized in that: The continuous casting adopts the soft reduction technology.

6. The method for preparing the 12.9-grade wind power bolt material according to claim 2, characterized in that: The temperature of the continuous casting billet before rolling is 1180-1220°C.

7. The method for preparing the 12.9-grade wind power bolt material according to claim 2, characterized in that: The quenching adopts a quenching temperature of not less than 880°C and a water cooling process; And / or, the tempering adopts a tempering temperature not higher than 630° C. and a water cooling process.

8. The method for preparing the 12.9-grade wind power bolt material according to claim 7, characterized in that: The quenching temperature is 880-900°C; And / or, the tempering temperature is 570-630°C.

9. The method for preparing the 12.9-grade wind power bolt material according to claim 8, characterized in that: The quenching temperature is 880°C, and the tempering temperature is 570-630°C; further, the quenching temperature is 880°C, and the tempering temperature is 630°C; And / or, the quenching temperature is 900°C, and the tempering temperature is 600-630°C.

10. An application of the 12.9-grade wind power bolt material according to claim 1 or the 12.9-grade wind power bolt material prepared by the preparation method according to any one of claims 2 to 9, characterized in that: The 12.9-grade wind power bolt material is used for preparing wind power bolts with M42-M72 specifications and 12.9-grade high strength.

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