A steel for a wind turbine gearbox bearing and a method of producing the same

Abstract

The present application relates to a kind of wind turbine gear box bearing steel and its production method, belong to the field of wind power steel.The steel is φ180-φ250mm round steel, metallographic structure is ferrite+pearlite, and a small amount of bainite.Adopting molten iron pretreatment-converter or electric arc furnace smelting-LF refining-RH or VD furnace vacuum degassing-large section continuous casting CCM large billet-rolled into round steel-finishing production process.The macrostructure of round steel: loose center ≤1.5 level, general loose ≤1.0 level, center crack ≤1.0 level, center segregation ≤1.0 level, no shrinkage cavity and subsurface crack.Inclusion: B fine ≤1.5 level, B coarse ≤0.5 level, D fine ≤1.0 level, D coarse ≤0.5 level, Ds ≤1.5 level.Macroscopic inclusion: image defect density ≤10mm / dm³, image single defect length ≤3mm, except 15% D in the center of bar.The banded structure is ≤3 levels.The present application is a kind of wind power steel with excellent purity, uniformity and density.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically relating to wind power steel and its production method. Background Technology

[0002] Wind power, as an ideal renewable and clean energy source with abundant resources, is a major force in my country's efforts to achieve its "dual carbon" goals. A development path focused on "high quality, large-scale, lightweight, low cost, and long lifespan" has become an inevitable trend. Due to the harsh operating environment and inconvenient installation, maintenance, and repair of wind power equipment, bearings, as core components of wind turbines, face even stricter quality requirements. They must not only possess sufficient strength and load-bearing capacity but also have a lifespan of at least 20 years. Currently, domestically produced wind turbine bearings are limited to yaw and pitch bearings, which have relatively lower technological barriers in wind turbines. Main shaft and gearbox bearings are largely dependent on imports. The domestic gearbox bearing market is still mainly controlled by traditional international companies from Germany, Sweden, and Japan, with domestic manufacturers holding less than 30% market share. Furthermore, the domestic wind turbine gearbox bearing sector is primarily concentrated in areas below 3MW. For gearbox bearings for 3MW and above wind turbines, domestic production is still in its early stages due to the high technical difficulty. The quality of bearing materials is the most crucial factor determining the performance of wind turbine bearings. The gap between Chinese and foreign wind turbine bearings is primarily due to materials, followed by wind turbine bearing design, manufacturing processes, and equipment. The future localization of wind turbine main shaft bearings and gearbox bearings in China requires first overcoming the technical challenges in the production of wind turbine bearing materials. Wind turbines operate outdoors year-round under harsh conditions, with significant variations in temperature, humidity, and bearing load. Therefore, bearings require excellent sealing and lubrication performance, impact resistance, long lifespan, and high reliability. Because wind turbine gearbox bearings are subjected to axial and radial loads from the turbine's weight, as well as impact loads from wind variations, the bearing rings and rolling elements undergo constant relative motion, experiencing severe contact fatigue and frictional wear. The bearing surfaces must not only have high hardness but also be properly matched. Therefore, bearing materials need to possess high hardenability, quenchability, and good impact toughness to meet the requirements for resistance to contact fatigue. Currently, imported materials mainly consist of steel produced using electroslag remelting and ingot casting processes. While these processes offer advantages in purity and uniformity of structure, enabling the production of highly stable materials for wind turbine gearbox bearings, they also suffer from significant disadvantages such as low production efficiency, yield, and capacity, as well as high energy consumption and production costs. Furthermore, the fatigue life of imported materials is unstable, still leading to premature failure of wind turbine gearbox bearings. Summary of the Invention

[0003] The technical problem to be solved by this invention is to provide a steel for wind turbine gearbox bearings and its production method, which addresses the above-mentioned prior art and meets the requirements for steel used in large wind turbine gearbox bearings. Specifically, an optimized continuous casting process is used to produce carburized bearing steel rolled round bars with a specification of φ180mm-φ250mm, and the internal quality of the continuously cast billet is improved through reasonable composition design. The technical solution of this invention is: a steel for bearings of wind turbine gearboxes, the chemical composition of which, by mass percentage, is: C: 0.19~0.23%, Si: 0.25~0.40%, Mn: 0.55~0.70%, P≤0.020%, S≤0.010%, Cr: 0.45~0.65%, Mo: 0.20~0.30%, Ni: 1.65~2.00%, Cu≤0.20%, Ti≤0.0025%, N: 0.0070~0.0120%, Al≤0.050%, H≤0.0002%, O≤0.0009%, Ca≤0.0010%, with the balance being Fe and other unavoidable impurity elements. The steel is rolled round steel, and the properties of the rolled round steel meet the following requirements: the metallographic structure is ferrite + pearlite, with a small amount of bainite. Samples are taken from the steel, and after quenching and tempering, the tensile strength is ≥980MPa, the elongation after fracture is ≥13%, the reduction of area is ≥45%, and the room temperature impact energy (AKU) is ≥63J. The low-magnification microstructure of rolled round steel is rated according to ASTM E381, and meets the following requirements: central porosity ≤ 1.5, general porosity ≤ 1.0, central crack ≤ 1.0, central segregation ≤ 1.0, and no shrinkage cavities or subcutaneous cracks. The inclusions in rolled round steel are graded according to GB / T 10561, and the following conditions must be met: B fine ≤ 1.5 grade, B coarse ≤ 0.5 grade, D fine ≤ 1.0 grade, D coarse ≤ 0.5 grade, and Ds ≤ 1.5 grade. The grain size of rolled round steel is inspected using the ASTM E112 method, and the following condition must be met: grain size ≥ grade 6. The end-quenching test shall be carried out in accordance with GB / T 225 and shall meet the following requirements: 42 HRC≤J1.5≤48HRC, 35 HRC≤J5≤46HRC, J9≥33HRC, J25≥21HRC. The SEP 1927 method was used to inspect the macroscopic inclusions in rolled round bars, meeting the following requirements: image defect density ≤ 10 mm / dm³, and the length of a single image defect ≤ 3 mm (except for the 15%D core of the bar stock). The microstructure of rolled round steel was inspected according to GB / T 13299, and the following condition was met: the banded structure in the hot-rolled state was ≤ grade 3. The elemental composition of this application is based on: 1) Determination of C content Carbon (C) is an essential element for ensuring the wear resistance of steel. Increasing the carbon content in steel will increase its martensitic transformation ability, thereby improving its hardness and strength, and thus its wear resistance. However, excessively high C content is detrimental to the toughness of steel. Furthermore, excessively high C content can also lead to severe central C segregation, thus affecting the core toughness of the steel. This invention controls its content to 0.19~0.23%. The steel of this invention belongs to the category of low-carbon steel. 2) Determination of Si content Si is the key element in this invention. Si, dissolved in the ferrite phase, has a strong solid solution strengthening effect, significantly improving the strength of ferrite, but simultaneously reducing its plasticity and toughness. Si is added to steel as a deoxidizing element during steelmaking. The steel of this invention is intended for cold working, requiring good cold working properties, which means excellent plasticity and toughness of the ferrite in the steel. Therefore, the Si content of the steel in this invention should be as low as possible to minimize the amount of Si dissolved in the ferrite and maximize the plasticity limit of ferrite; thus, the Si content is set within the range of 0.25~0.40%. 3) Determination of Mn content Mn, as a deoxidizing element in the steelmaking process, is an effective strengthening element for steel, playing a role in solid solution strengthening. Furthermore, Mn can improve the hardenability and hot working properties of steel. Mn can eliminate the influence of sulfur (S): in steelmaking, Mn can combine with S to form high-melting-point MnS, thereby weakening and eliminating the adverse effects of S. However, high Mn content will reduce the toughness of steel. In this invention, the Mn content is controlled at 0.55~0.70%. 4) Determination of Al content Al is added as a deoxidizing element in steel. Besides reducing dissolved oxygen in molten steel, Al combines with N to form fine, dispersed aluminum nitride inclusions, which can refine the grain size. However, excessive Al content can easily lead to the formation of large, brittle inclusions such as Al₂O₃ particles during steelmaking, reducing the purity of the steel and affecting the service life of the finished product. In this invention, the Al content is defined as ≤0.05%. 5) Determination of Ni content In steel, nickel can reduce the surface's ability to absorb carbon atoms, accelerate the diffusion of carbon atoms in austenite, and reduce the carbon concentration in the carburized layer, thus slowing down the carburizing rate. Simultaneously, the addition of nickel can improve the toughness of the steel. In this invention, the nickel content is determined to be in the range of 1.65~2.00%. 6) Determination of Cr content Cr is a carbide-forming element that can improve the hardenability, wear resistance, and corrosion resistance of steel. However, excessive Cr content can lead to the formation of large, insoluble carbides by combining with carbon in the steel, which reduces the toughness of the steel. In carburized bearing steel, chromium can adjust hardenability, improve the wear resistance of the carburized layer, and enhance the mechanical properties of the steel. Furthermore, chromium can stabilize the heat treatment process of the steel, achieve good carburizing performance, and reduce the inhomogeneity of carbides. In this invention, the Cr content is determined to be in the range of 0.45% to 0.65%. 7) Determination of Mo content The main function of molybdenum in carburized bearing steel is to improve hardenability and enhance the steel's mechanical properties, particularly its toughness. It also improves the steel's wear resistance and carburizing properties. In this invention, the Mo content is determined to be in the range of 0.20% to 0.30%. 8) Determination of N content When supersaturated nitrogen is dissolved in steel, it precipitates as nitrides after a prolonged period, increasing the steel's hardness and strength while decreasing its plasticity, leading to aging. Adding an appropriate amount of aluminum to steel can generate stable AlN, suppressing the formation and precipitation of Fe4N. This not only improves the aging properties of the steel but also prevents austenite grain growth, thus refining the grain size. However, nitrogen reacts with alloying elements in the steel to form nitride nonmetallic inclusions, and more importantly, reduces the effect of the alloying elements. High nitrogen content in steel increases strength but decreases impact toughness. The N content in this invention is determined to be 0.0070~0.0120%. 9) Determination of Ti content Ti in steel forms TiN inclusions, which are hard and angular, severely affecting the fatigue life of the material. However, Ti can preferentially react with N in molten steel, reducing the failure caused by the reaction of N with B in molten steel due to the addition of B element. Therefore, this invention requires the addition of Ti element. After comprehensive calculation, the Ti content range of this invention is determined to be ≤0.0025%. 10) Determination of Ca content The Ca content increases the number and size of dot oxides in steel. Furthermore, because dot oxides have high hardness and poor plasticity, they do not deform during steel deformation and easily form voids at interfaces, thus degrading the steel's properties. In this invention, the Ca content range is determined to be ≤0.001%. 11) Determination of O content Oxygen content represents the total amount of oxide inclusions. The brittle inclusions of oxides limit the service life of the finished product. Numerous experiments have shown that reducing oxygen content is significantly beneficial for improving the purity of steel, especially for reducing the content of brittle oxide inclusions in the steel. In this invention, the oxygen content range is defined as ≤0.0009%. 12) Determination of P and S content Phosphorus (P) severely causes segregation during solidification in steel. P dissolves in ferrite, causing grain distortion and coarsening, and increasing cold brittleness. In this invention, the P content is defined as ≤0.020%. Sulfur (S) causes hot brittleness in steel, reducing its ductility and toughness. In this invention, the S content is defined as ≤0.010%. 13) Determination of H content Hydrogen readily melts into molten steel at high temperatures. During cooling, it cannot escape in time and accumulates in the microstructure, forming high-pressure micropores. This reduces the steel's plasticity, toughness, and fatigue strength. Furthermore, hydrogen easily causes white spots to appear on the steel. Therefore, this invention requires hydrogen content to be ≤0.0002%. Another objective of this invention is to provide a method for producing the steel used in the bearings of wind turbine gearboxes. The production process is as follows: molten iron pretreatment – ​​converter or electric arc furnace smelting – LF refining – RH or VD furnace vacuum degassing – large-section continuous casting CCM Dalian casting billet – rolling into finished products – finishing. The main characteristics of the production process are as follows: Steelmaking: The raw materials must be processed sequentially through KR hot metal pretreatment, converter or electric arc furnace smelting, LF refining, and RH or VD furnace vacuum degassing. First, the molten iron must undergo KR molten iron pretreatment to initially reduce the content of harmful elements S and P (P content range ≤0.020%, S content range ≤0.010%) and obtain clean molten iron. Molten iron pretreatment can also reduce the amount of slag-forming agent added in subsequent smelting, shorten smelting time, and improve production efficiency. Secondly, primary refining is carried out in a converter or electric arc furnace, mainly to reduce the carbon content and convert molten iron into molten steel. Simultaneously, the content of Si and Mn elements is adjusted (target adjustment range: Si: 0.25~0.40%, Mn: 0.55~0.70%) to further remove the content of P and S elements. Clean scrap steel is added, and the content of residual elements in the scrap steel and the residual harmful elements in the molten steel are strictly controlled. The final carbon content at tapping is controlled at around 0.10%. Based on the final carbon content, Al-iron is added for pre-deoxidation, ensuring that the Al content in the refining furnace is controlled at ≤0.05%, and the final P content is controlled at ≤0.020%, with a tapping temperature above 1600℃. Slag-blocking plugs and slag removal techniques are used in converter or electric arc furnace tapping to address the problem of high content of harmful elements such as As, Sn, Pb, and Sb in bearing steel. In the LF refining furnace, the content of each element is precisely controlled, with low-Ti and low-Ca alloys being preferred. The Ti content in the molten steel is strictly controlled to be ≤0.0012wt%. High-performance refining synthetic slag is used in the LF process. The synthetic slag is a ternary slag system of CaO-Al2O3-SiO2, and argon gas is used for stirring. This accelerates the transfer of substances between the molten steel and the refining slag, which is beneficial for desulfurization and deoxygenation reactions. Furthermore, argon blowing ensures that Al2O3 non-metallic inclusions are fully floated and removed. High-quality refractory materials are used, the amount of MgO in the molten steel is controlled, and a long LF refining time (≥1 hour) is maintained to ensure that inclusions are fully floated and removed. After LF refining, the molten steel must undergo vacuum degassing in an RH or VD furnace. It is essential to ensure that the furnace reaches a sufficient vacuum level and maintains a sufficient circulation time to further remove harmful gases and non-metallic inclusions from the molten steel and improve its purity. The maximum vacuum level should be ≤1.5 mbar, and the high vacuum time should be ≥15 min. After breaking the vacuum, argon gas is used for soft blowing and stirring for ≥25 min. This ensures both vacuum degassing and sufficient floating and removal of inclusions. (2) Continuous casting: Large cross-sectional square continuous casting billets are used, with billet specifications of 300mm×340mm and above, to ensure a large compression ratio of the steel in the subsequent forging and rolling process, thereby ensuring the density of the material; before the continuous casting process, a tundish covering agent with a thickness of ≥100mm is added to the tundish to prevent the molten steel from being oxidized before continuous casting; protective slag is added throughout the continuous casting process for protective casting to protect the molten steel from secondary oxidation and contamination; low superheat casting is used in the continuous casting process, with the superheat controlled at ≤35℃, which can reduce the columnar crystal zone and expand the range of the equiaxed crystal zone, which can not only reduce the grain size, but also effectively reduce the compositional segregation of the continuous casting billet, significantly improving the uniformity of the structure of the continuous casting billet; the casting speed is 0.40-0.55min / m, and the liquid level fluctuation is stable at ≤5mm; tundish induction heating, light pressing, and electromagnetic stirring technology are used to effectively improve low-magnification defects such as central porosity and shrinkage cavities. (3) Rolling of continuously cast billets into finished products: After heating in a furnace with a neutral or weakly oxidizing atmosphere, the continuously cast billets are rolled into φ180-φ250mm rolled products by a continuous rolling mill. The heating temperature is controlled at 1050-1260℃, the total heating time is not less than 12 hours, and the high-temperature diffusion time is guaranteed to be not less than 7 hours, so that carbides and alloying elements can be fully diffused and the billet can be fully austenitized. After the face rolling process, the frame segregation of the rolled product tends to be square, improving the isotropic properties of the material, thereby improving the heat treatment deformation of the finished rings. At the same time, this rolling process also has an improving effect on the banded structure, and the strip structure is more uniformly distributed. After rolling, the rolled material should be placed in a cooling pit for slow cooling for no less than 60 hours to achieve uniform microstructure. The temperature of the material exiting the cooling pit must be less than 200℃. (4) Finishing: After rolling, the bar stock must undergo finishing processes such as straightening, chamfering, and non-destructive testing of surface and internal quality. Only after the surface and internal quality testing are qualified can the final product be delivered. Attached Figure Description Figure 1 This is a typical macrostructure of the steel used in the wind turbine gearbox bearings in this embodiment of the invention; Figure 2 This is a typical microstructure of the steel used in the bearings of wind turbine gearboxes in this embodiment of the invention. Detailed Implementation The present invention will be further described in detail below with reference to the embodiments. The embodiments are exemplary and intended to explain the present invention, but should not be construed as limiting the present invention. Table 1 shows the chemical composition (wt%) of G20CrNi2Mo produced by various embodiments of the present invention and (for comparison) by the current commercially available die casting process. Table 1 Table 1 Table 2 Inclusions in the steel of each embodiment Table 3. End hardenability and macroscopic inclusion data of steels from each embodiment. Table 4. Grain size, hardness, and mechanical property data for each embodiment. Table 5 Low-magnification data of steel in each embodiment The manufacturing process of the steel for large wind turbine gearbox bearings in this invention is as follows: a method for producing large-size rolled round steel for wind turbine gearbox bearings using arc continuous casting. The process involves smelting molten iron through pretreatment, oxygen converter smelting, LF ladle refining, and RH vacuum circulation degassing, followed by casting into square billets using an arc continuous casting machine. The continuously cast square billets undergo subsequent heating, rolling, flaw detection, and warehousing. The user's processing steps are: blanking, heating, forging (upsetting, drawing, center punching), ring rolling, carburizing, heat treatment (quenching and tempering), machining, grinding, and final finishing of the bearing rings. Specifically, high-quality molten iron, scrap steel, and raw materials are selected during smelting, along with high-quality deoxidizers and refractory materials. During converter production, the tapping endpoint C in the three embodiments is controlled to ≥0.05%, the endpoint P is controlled to ≤0.018%, and the continuous casting superheat is controlled within 20-40℃. The produced continuous casting billets are then slowly cooled in a pit, with a pit temperature greater than 500℃, a pit cooling time greater than 48 hours, and a tapping temperature less than 200℃. The continuous casting billet is heated, rolled, inspected for flaws, and then stored. It then undergoes further processing at the client's location: blanking, heating, forging (upsetting, drawing, center punching), ring rolling, carburizing, heat treatment (quenching and tempering), machining, and grinding to produce the final bearing. As shown in Tables 1-5, the gearbox bearings in the embodiments of the present invention exhibit significantly better control of harmful elements such as oxygen and titanium, as well as non-metallic inclusions, compared to G20CrNi2Mo steel produced by the die-casting process. This indicates significantly higher steel purity. Low-magnification testing results also show superior quality, reflecting better uniformity and density. In summary, the wind turbine gearbox bearing steel produced by the vacuum degassing and continuous casting process of the present invention can replace the original die-casting process, significantly improving production efficiency, reducing production costs, and significantly enhancing product competitiveness. In summary, this invention relates to a steel for wind turbine gearbox bearings and its production method. By improving the overall purity of the steel and adopting a high-efficiency, high-capacity, and low-cost process route involving vacuum degassing, continuous casting, and rolling, and by optimizing and controlling key processes, the steel achieves high purity, high microstructure uniformity, and high density, completely replacing the original ingot casting process. This results in a more competitive product in terms of production efficiency, production cost, and product quality stability. In addition to the above embodiments, the present invention also includes other embodiments. All technical solutions formed by equivalent transformation or equivalent substitution should fall within the protection scope of the claims of the present invention.

Claims

1. A type of steel for wind turbine gearbox bearings, characterized in that: The steel composition by mass percentage is as follows: C: 0.19~0.23%, Si: 0.25~0.40%, Mn: 0.55~0.70%, P≤0.020%, S≤0.010%, Cr: 0.45~0.65%, Mo: 0.20~0.30%, Ni: 1.65~2.00%, Cu≤0.20%, Ti≤0.0025%, N: 0.0070~0.0120%, Al≤0.050%, H≤0.0002%, O≤0.0009%, Ca≤0.0010%, with the balance being Fe and other unavoidable impurity elements. The metallographic structure of the steel is ferrite + pearlite, and a small amount of bainite.

2. The steel for wind turbine gearbox bearings according to claim 1, characterized in that: We produce round steel bars with diameters ranging from φ180mm to φ250mm.

3. The steel for wind turbine gearbox bearings according to claim 1, characterized in that: Samples were taken from the steel and, after quenching and tempering, met the following requirements: tensile strength ≥ 980 MPa, elongation after fracture ≥ 13%, reduction of area ≥ 45%, and room temperature impact absorption energy AKU ≥ 63 J.

4. The steel for wind turbine gearbox bearings according to claim 1, characterized in that: The low-magnification microstructure of rolled round steel is rated according to ASTM E381, and meets the following requirements: central porosity ≤ 1.5, general porosity ≤ 1.0, central crack ≤ 1.0, central segregation ≤ 1.0, and no shrinkage cavities or subcutaneous cracks. The inclusions in rolled round steel are graded according to GB / T 10561, and the following conditions must be met: B fine ≤ 1.5 grade, B coarse ≤ 0.5 grade, D fine ≤ 1.0 grade, D coarse ≤ 0.5 grade, Ds ≤ 1.5 grade; The grain size of rolled round steel is inspected using ASTM E112 and meets the following requirement: grain size ≥ grade 6; The end-quench test shall be carried out in accordance with GB / T 225 and shall meet the following requirements: 42 HRC≤J1.5≤48HRC, 35 HRC≤J5≤46HRC, J9≥33HRC, J25≥21HRC; The SEP 1927 method was used to inspect the macroscopic inclusions of rolled round steel, which met the following requirements: image defect density ≤10mm / dm³, image single defect length ≤3mm, except for 15%D in the core of the round steel; The microstructure of rolled round steel was inspected according to GB / T 13299, and the following condition was met: the banded structure in the hot-rolled state was ≤ grade 3.

5. A method for producing the steel for wind turbine gearbox bearings as described in claim 1, characterized in that: This includes steel smelting, continuous casting, rolling of continuously cast billets into finished products, and finishing. Specifically: Steelmaking: The raw materials must sequentially pass through KR hot metal pretreatment, converter or electric arc furnace smelting, LF refining, and vacuum degassing in a vacuum furnace. First, KR hot metal pretreatment initially reduces the content of harmful elements S and P, lowering P content to ≤0.020% and S content to ≤0.010%, thus obtaining clean hot metal. Second, primary smelting is carried out in the converter or electric arc furnace. The main purpose of primary smelting is to reduce the C content, transforming the hot metal into steel, while simultaneously adjusting the Si and Mn content to the desired steel composition. To achieve the target content, further dephosphorize and desulfurize the molten steel. The final carbon content at tapping is controlled at 0.10±0.02%. Based on the final carbon content, Al iron is added for pre-deoxidation, so that the Al content in the refining furnace is controlled at ≤0.05%, and the final phosphorus content is controlled at ≤0.020%. The tapping temperature is controlled above 1600℃. Slag is blocked by slag plugs and slag removal is carried out after the furnace when tapping from the converter or electric furnace. During LF refining, the content of each element is precisely controlled, and the Ti content in the molten steel is strictly controlled so that Ti≤0.0012wt%. The synthetic slag used in the LF process is a ternary slag system of CaO-Al2O3-SiO2, and argon gas is used for stirring. On the one hand, it accelerates the transfer of substances between molten steel and refining slag, which is beneficial to the desulfurization and deoxygenation reactions. On the other hand, argon blowing promotes the full flotation and removal of Al2O3 non-metallic inclusions, and the LF refining time is controlled to be ≥1h. After LF refining, the molten steel is vacuum degassed to remove light elements. After vacuum degassed, argon gas is passed through to stir the molten steel to make the inclusions float to the surface and remove them, thereby improving the purity of the molten steel. Continuous casting: Large-section square continuous casting billets are used, with billet specifications of 300mm×340mm or larger. Before continuous casting begins, a tundish covering agent with a thickness of ≥100mm is added to the tundish to prevent the molten steel from being oxidized before continuous casting. Protective slag is added throughout the continuous casting process to protect the molten steel from secondary oxidation and contamination. Low superheat casting is used, with superheat controlled at ≤35℃, and the casting speed controlled at 0.40-0.55min / m, with the liquid level fluctuation stable at ≤5mm. Tundish induction heating, light pressure reduction, and electromagnetic stirring technology are employed. (3) Rolling of continuous casting billets into finished products: After heating in a furnace with a neutral or weakly oxidizing atmosphere, the continuous casting billets are rolled into φ180-φ250mm rolled products by a continuous rolling mill. The heating temperature is controlled at 1050-1260℃, the total heating time is not less than 12 hours, and the high-temperature diffusion time is not less than 7 hours, so that carbides and alloying elements can be fully diffused and the structure can be fully austenitized. The face rolling process is adopted so that the frame segregation of the rolled product tends to be square. After rolling, the rolled product is slowly cooled in a pit for not less than 60 hours, and the temperature of the product leaving the slow cooling pit is <200℃. (4) Finishing: After rolling, the bar must be straightened, chamfered and subjected to non-destructive testing for surface and internal quality. The finished product is obtained after the surface and internal quality tests are qualified.

6. The method for producing steel for wind turbine gearbox bearings according to claim 5, characterized in that: During LF refining, low-Ti and low-Ca alloys are selected to control the elemental composition, and high-quality refractory materials are used to control MgO in the molten steel.

7. The method for producing steel for wind turbine gearbox bearings according to claim 5, characterized in that: Molten steel is degassed under vacuum in an RH or VD furnace, with a maximum vacuum degree ≤1.5mbar and a high vacuum time ≥15min. After degassing, it is stirred by argon gas soft blowing for ≥25min.

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