Highly homogenized steel for high-power wind power yaw bearing ring, bearing ring and production process

Abstract

The invention discloses a high-homogenization steel for a high-power wind power yaw bearing ring, a bearing ring and a production process, and belongs to the field of alloy steel. The steel contains C0.47%-0.57%, Si0.40%-0.70%, Mn1.30%-1.50%, Cr0.50%-0.70%, Mo0.35%-0.45%, Ni0.25%-0.35%, Cu0.030%-0.050%, Nb0.010%-0.030%, Ti0.0040%-0.0060%, Al0.015%-0.025%, P≤0.015%, S≤0.010%, N≤0.0080%, O≤0.0040% by weight. In the production method of the steel, normalizing and quenching and tempering are used for heat treatment. The produced bearing ring steel has excellent strength, toughness and contact fatigue performance, and is suitable for yaw bearings for 6MW wind power.

Description

Technical Field

[0001] The present invention relates to alloy steel, and more specifically, to a highly homogenized steel for a high-power wind power yaw bearing ring, a bearing ring and a production process. Background Art

[0002] Under the background of "dual carbon", the demand for clean energy is increasing, and wind power as a clean energy has attracted much attention. By 2021, my country's wind power installed capacity will exceed 300,000 megawatts, accounting for more than one-third of the world. However, the unit power of wind power in my country is relatively low, generally concentrated at 4 megawatts. The unit power of foreign wind power has reached 8 megawatts, and my country's marine wind power development resource potential at a height of 70 meters and a water depth of 5 to 50 meters is about 500,000 megawatts. Therefore, the in-depth development of large offshore wind turbines is the development trend of the wind power industry in the future.

[0003] The large-scale development of wind power has led to an increase in the size of the bearings of key wind power components. According to research, the outer diameter of the yaw bearing ring of a 1.5MW wind power is about 2.1m, while the outer diameter of the yaw bearing ring of a 6MW wind power is 4.5 meters, which is 2.1 times larger. In addition, as the bearing size increases, the wall thickness of the bearing ring increases, resulting in poor consistency in the cross-sectional performance of the bearing ring. Therefore, the requirements for strength, toughness and uniformity of high-power wind power bearing rings are increased. JB / T 10705 also points out that "materials with equivalent or better performance can be used" to manufacture wind power yaw bearing rings. my country's offshore wind power has developed rapidly, but it is generally lower than 6MW at present, mainly because the key equipment materials cannot be completely self-sufficient. Therefore. It is urgent to develop steel for high-power offshore wind power yaw bearing rings.

[0004] Patent CN 101230441A points out that 42CrMoVNb steel is used to manufacture wind turbine yaw and pitch bearing rings. The material has a V-type impact energy of ≥91J at -40℃ and a tensile strength of ≥835MPa. However, the patent does not explain the application of wind power to the steel, and the material performance is not clear whether it is the actual dissection value of the bearing ring or the value of a small sample test. It is inferred from the performance value that it is used in wind turbines below 3MW.

[0005] Patent CN1426490A is a thin-walled bearing steel, and it uses carburizing treatment. At present, wind power yaw bearings are all thick-walled bearings, with a wall thickness of ≥100mm and a bearing diameter of ≥3m. This patent requires carburizing treatment, which is not feasible for wind power yaw bearings. In addition, this patent is made of cold-rolled strips, which requires welding technology. The bearings in the wind power industry all use integrated rings, so this patent cannot be applied to wind power yaw bearings, and it is essentially different from the patent applied for. The component system of patent CN1745188A is high-carbon chromium steel, which is used to produce bearings with smaller diameters. The material steel pipe is used for bearing ring processing. At present, the maximum diameter of steel pipes in the world is about 1.5m, which cannot meet the needs of wind power yaw bearing rings. In addition, this patent uses spheroidizing annealing, which consumes a lot of process energy and has a long process cycle, which is different from the patent applied for. The bearings in the CN110257717A patent are machine tool bearings, which have the characteristics of fast speed and small size. Compared with the yaw bearing, which has the characteristics of large size and low speed, the application environment is different and the requirements for materials and processes are different.

[0006] Therefore, it is urgent to develop a steel for high-power wind power yaw bearing ring and its heat treatment process with high strength, toughness and contact fatigue life according to the service characteristics of 6MW yaw bearings to meet the needs of high-power wind power development. Summary of the invention

[0007] 1. Problem to be solved

[0008] In view of the problem of poor homogeneity of existing large-sized wind turbine bearings, the present invention provides a highly homogenized steel for a high-power wind turbine yaw bearing ring, a bearing ring and a production process. The difference between the tensile strength of the surface layer of the bearing ring at 12.5 mm and the strength at 1 / 2 of the wall thickness is ≤80 MPa, the grain size is consistent, and the homogenization is good.

[0009] 2. Technical solution

[0010] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0011] The invention discloses a high-homogenization steel for a high-power wind power yaw bearing ring, which contains, by weight percentage, C0.47%-0.57%, Si 0.40%-0.70%, Mn 1.30%-1.50%, Cr 0.50%-0.70%, Mo0.35%-0.45%, Ni 0.25%-0.35%, Cu 0.030%-0.050%, Nb 0.010%-0.030%, Ti0.0040%-0.0060%, Al 0.015%-0.025%, P≤0.015%, S≤0.010%, N≤0.0080%, O≤0.0040%, and the rest is Fe and other inevitable impurities.

[0012] The chemical composition ratio complies with:

[0013] 1) 12.5 ≤ (0.54 × C%) × (1 + 3.34 × Mn%) × (1 + 0.7 × Si%) × (1.2 + 0.36 × Cu%) × (1 + 0.37 × Ni%) ×

[0014] (1+2.61×Cr%)×(1+3×Mo%)×(1+0.7×Nb%)≤18.0;

[0015] 2)0.54%≤C%+(Mn%) / 6-(Cr%+Mo%+Nb%+Ti%) / 5+(Ni%+Cu%) / 15≤0.60%.

[0016] Heat treatment process parameters should meet the following requirements:

[0017] 1) Normalizing, S-T1 / 20≤t1≤S-T1 / 80;

[0018] 2) For quenching and tempering, S-T2 / 10≤t2≤S-T2 / 50; for tempering and tempering, 1.5×S-T3 / 10≤t3≤1.5×S-T3 / 50.

[0019] The invention also provides a production method of the steel. The produced bearing ring steel has excellent toughness and contact fatigue performance and is suitable for manufacturing yaw bearings for 6MW wind power (shaft ring wall thickness ≥ 240mm).

[0020] C: C is the cheapest strengthening element in steel. Every increase of 0.1% of solid solution C can increase the strength by about 450MPa. C forms precipitation phase with alloy elements in steel, which plays a precipitation strengthening role. C can significantly improve hardenability and obtain martensite structure in the center of the thick wall periodic ring. However, as its content increases, plasticity and toughness decrease, so the C content is controlled at 0.47% to 0.57%.

[0021] Si: Si is an effective solid solution strengthening element in steel, which improves the strength and hardness of steel. Si can play a deoxidizing role during steelmaking and is a commonly used deoxidizer. However, Si is easy to segregate at austenite grain boundaries, reduce grain boundary bonding strength, and cause brittleness. In addition, Si is easy to cause element segregation in steel. Therefore, the Si content is controlled at 0.40% to 0.70%.

[0022] Mn: Mn can play a role in solid solution strengthening, and its solid solution strengthening ability is weaker than that of Si. Mn is an austenite stabilizing element that can significantly improve the hardenability of steel and reduce the decarburization of steel. Mn combined with S can prevent hot brittleness caused by S. However, excessive Mn will reduce the plasticity of steel. Therefore, the Mn content is controlled at 1.30% to 1.50%.

[0023] Cr: Cr is a carbide-forming element. Cr can improve the hardenability and strength of steel, but it is easy to cause temper brittleness. Cr can improve the oxidation resistance and corrosion resistance of steel, but too high Cr content will increase crack sensitivity. The Cr content should be controlled between 0.50% and 0.70%.

[0024] Mo: Mo mainly improves the hardenability and heat resistance of steel. Mo dissolved in the matrix can keep the structure of steel stable during tempering, and can effectively reduce the segregation of impurity elements such as P, S and As at the grain boundaries, thereby improving the toughness of steel and reducing temper brittleness. Mo reduces the stability of M7C3. When the Mo content is high, needle-shaped Mo2C will be formed, which will lead to a decrease in the Mo content of the matrix. Mo can improve the strength of steel through the combined effects of solid solution strengthening and precipitation strengthening, and can also change the toughness of steel by changing the precipitation of carbides. Therefore, Mo is controlled at 0.35% to 0.45%.

[0025] Ni: Ni can form an infinitely miscible solid solution with Fe. It is an austenite stabilizing element. It has the function of expanding the phase region, increasing the stability of supercooled austenite, shifting the C curve to the right, and improving the hardenability of steel. Ni can refine the width of martensite laths and improve strength. Ni can significantly reduce the toughness-brittleness transition temperature of steel and improve low-temperature toughness. However, Ni is a precious metal element, and excessive addition leads to excessive cost. The Ni content is controlled at 0.25% to 0.35%.

[0026] Nb: Nb is a strong C, N compound forming element. Nb (C, N) forms fine dispersion and maintains a coherent relationship with the matrix, which can play a role in strengthening and refining the structure. The Nb content is controlled at 0.010% to 0.030%.

[0027] Ti: Ti plays a wide range of roles in steel. It can be used as a deoxidizer for deoxidation. Ti, C and N can form carbonitrides that precipitate in steel to strengthen precipitation. It can also pin grain boundaries to hinder grain growth. The Ti content is controlled at 0.0040% to 0.0060%.

[0028] Al: Al is the main deoxidizer in steelmaking. Al combines with N to form fine dispersed AlN, which maintains a coherent relationship with the matrix, can strengthen and refine the structure, increase the resistance to fatigue crack initiation and expansion, and thus improve the endurance strength of steel. The Al content is controlled at 0.015% to 0.035%.

[0029] O and N: TO forms oxide inclusions in steel, and TO is controlled to be ≤0.0040%; N can form nitrides in steel, forming fine precipitation phases to refine the structure, and can also precipitate Fe4N, but the diffusion rate is slow, which causes the steel to become aging and reduces the processing performance. Therefore, N is controlled within 0.008%.

[0030] The 6MW-class yaw bearing is large in size and needs to ensure sufficient toughness. The addition of alloying elements can effectively improve hardenability and thus toughness. According to research, adding Mn to the alloying elements is the most effective to improve hardenability and strength, with a coefficient of 3.34; Mo improves stability by improving tempering, and it interacts with Mn, and contributes greatly to hardenability and strength, that is, the outermost electrons of the atomic structure of Mn and Mo are 2 and 1 respectively, and both are easy to lose electrons. In steel, Mn only forms a solid solution and cannot form carbides. After the interaction between Mo and Mn, the electrons of Mo are competed for by Mn, making Mo positive and able to form carbides. After Mn obtains electrons, its stability is improved and the solid solution effect is enhanced, with a coefficient of 3.0; Cr is the main substitutional solid solution element and carbide-forming element, which replaces Fe atoms into the crystal structure of iron to enhance the strength of iron, and at the same time When the steel is tempered, it precipitates to form carbides for precipitation strengthening, which improves the toughness and has a contribution coefficient of 2.16 to the strength; Ni and Cu do not form carbides in the steel, but change the lattice morphology through solid solution strengthening, so that the lattice is deformed from a complete cubic structure to an incomplete hexahedral structure, and the lattice parameters change, that is, the size and spacing of the lattice change, which reduces the microscopic consistency of the crystal, thereby improving the hardenability and strength of the steel, with coefficients of 0.37 and 0.36 respectively; C is a non-metallic element and the most important interstitial solid solution strengthening element in steel, which affects both strength and toughness, so the coefficient is 0.54; Si is a non-metallic element and the main solid solution strengthening element in steel, and its contribution to the performance of steel is 0.70. Nb and Ti can form carbonitrides, which can help increase the resistance to dislocation movement in steel, increase strength and significantly improve the fracture toughness of steel. Since the strength of steel is inversely proportional to its plasticity and toughness, that is, high strength will lead to reduced plasticity and toughness, in order to ensure the comprehensive performance of steel, it is not enough to simply increase strength, but also necessary to consider its plasticity and toughness. Let A represent the strengthening factor in steel, then 12.5%≤A≤18.5%,

[0031] A=(0.54×C%)×(1+3.34×Mn%)×(1+0.7×Si%)×(1.2+0.36×Cu%)×(1+0.37×Ni%)×(1+2.61×Cr%)×(1+3×Mo%)×(1+0.7×Nb%).

[0032] Bearings need good contact fatigue performance during service, so the ratio of C, Mn, Cr, Mo, Ni, Cu, and V needs to be limited. C and Mn can significantly improve the shallow hardness and wear resistance of steel, thereby improving contact fatigue performance; Cr and Mo can form a second phase with C and N in steel. Although the second phase can increase the strength in steel, it is still different from the steel matrix. If the second phase is large in size, it will form a contact fatigue crack source, so it is not conducive to improving contact fatigue. Ni and Cu are beneficial to contact fatigue performance by combining with the matrix at the atomic scale through solid solution strengthening. The compounds formed by Nb and Ti in steel after heat treatment can reduce the structural stress of steel, thereby improving the contact fatigue performance of steel. Let the contact fatigue factor in steel be represented by Y, then 0.54%≤Y≤0.60%, Y=C%+(Mn%) / 6-(Cr%+Mo%+Nb%+Ti%) / 5+(Ni%+Cu%) / 15.

[0033] The present invention also discloses a production process of steel for a yaw bearing ring and a yaw bearing ring: electric arc furnace or converter smelting → LF furnace refining → RH or VD vacuum degassing → Φ380mm-Φ700mm round billet continuous casting → round billet heating → forging → punching → ring rolling (semi-finished product) → heat treatment → machining → flaw detection → packaging and warehousing.

[0034] Among them, the heat treatment adopts normalizing + quenching and tempering, and the heat treatment process is:

[0035] Normalizing: The furnace temperature of the semi-finished yaw bearing ring after ring rolling is ≤600℃, the normalizing heating temperature (T1, ℃) is 1100-1200℃, the normalizing holding time (t1, min) is determined by the bearing ring wall thickness (S, mm) and the normalizing heating temperature (T1, ℃), S-T1 / 20≤t1≤S-T1 / 80, water cooling.

[0036] Quenching and tempering: Quenching heating temperature (T2, ℃) is 850~950℃, quenching holding time (t2, min) is determined by bearing ring wall thickness (S, mm) and quenching heating temperature (T2, ℃), S-T2 / 10≤t2≤S-T2 / 50, water cooling; tempering heating temperature (T3, ℃) is 650~750℃, tempering holding time (t3, min) is determined by bearing ring wall thickness (S, mm) and tempering heating temperature (T3, ℃), 1.5×S-T3 / 10≤t3≤1.5×S-T3 / 50, water cooling.

[0037] The normalizing temperature of steel is related to the composition of steel, which directly affects the austenite transformation point of steel. As for the tempering heating temperature, it is more closely related to the composition of the steel grade. Different compositions produce different types of phases, so the tempering heating temperature is different.

[0038] The present invention controls the normalizing heating temperature at 1100-1200°C to ensure that the bearing ring is completely austenitized at this temperature, and at the same time controls the heating temperature not higher than 1200°C to ensure that the size of the second phase precipitated in the steel during the forging process is not too coarse, thereby improving the homogeneity of the material.

[0039] The heating temperature for quenching and tempering treatment is 850-950℃. On the one hand, it ensures that the temperature reaches above the austenitizing temperature, so that the steel can be recrystallized on the basis of normalizing, and the grains are further refined; on the other hand, it ensures that the size of the precipitate generated in normalizing is not coarse during the quenching and tempering process, which is conducive to improving strength, toughness and fatigue performance. The tempering temperature of 650-750℃ is used to ensure the type of precipitate phase while controlling the size of the precipitate phase, improve the homogenization of the grains, and thus improve toughness and fatigue performance.

[0040] The bearing ring produced by the above process has a tensile strength of ≥950MPa, a yield strength of ≥850MPa, and a -40℃ KV2 of ≥100J at 1 / 2 wall thickness (wall thickness ≥240mm); and has good cross-sectional uniformity, with the difference between the tensile strength at 12.5mm on the surface and the strength at 1 / 2 wall thickness ≤80MPa; and has good contact fatigue performance. Under the action of 2000MPa contact stress, the contact fatigue life is ≥1 million times, which meets the 20-year service requirement of large-power wind power.

[0041] 3. Beneficial effects

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] (1) A highly homogenized high-power wind turbine yaw bearing ring of the present invention has good cross-sectional uniformity, the difference between the tensile strength at the surface layer of 12.5 mm and the strength at 1 / 2 of the wall thickness is ≤80 MPa, the grain size at the surface layer of the bearing ring of 12.5 mm and 1 / 2 of the wall thickness is consistent, and the homogenization is good;

[0044] (2) A highly homogenized high-power wind turbine yaw bearing ring of the present invention, with a tensile strength of ≥950MPa, a yield strength of ≥850MPa, and a -40°C KV2 of ≥100J at 1 / 2 wall thickness of the bearing ring (wall thickness ≥240mm);

[0045] (3) The highly homogenized high-power wind turbine yaw bearing ring of the present invention has good contact fatigue performance. Under the contact stress of 2000MPa, the contact fatigue life is ≥1 million times, which meets the service requirement of high-power wind turbines for 20 years. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but it should be understood that these drawings are designed only for explanation purposes and are not intended to limit the scope of the present invention. In addition, unless otherwise specified, these drawings are intended only to conceptually illustrate the structural configurations described herein and are not necessarily drawn to scale.

[0047] Figure 1 This is a microstructure morphology diagram of the bearing ring surface at 12.5 mm in Example 2 of the present invention;

[0048] Figure 2 This is a microstructure morphology diagram of the 1 / 2 wall thickness of the bearing ring of Example 2 of the present invention;

[0049] Figure 3 This is the microstructure morphology at 12.5 mm on the surface of the bearing ring of Comparative Example 2 of the present invention;

[0050] Figure 4 This is a microstructure morphology diagram of the bearing ring at 1 / 2 wall thickness of Comparative Example 2 of the present invention;

[0051] Figure 5 This is a microstructure diagram of the 1 / 2 wall thickness of the bearing ring of Example 2 of the present invention;

[0052] Figure 6 This is a microstructure diagram of the 1 / 2 wall thickness of the bearing ring of comparative example 2 of the present invention. DETAILED DESCRIPTION

[0053] The following detailed description of exemplary embodiments of the present invention refers to the accompanying drawings, which form a part of the description, and in which exemplary embodiments of the present invention that can be implemented are shown as examples. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to implement the present invention, it should be understood that other embodiments can be implemented and various changes can be made to the present invention without departing from the spirit and scope of the present invention. The following more detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but is only for the purpose of illustrating and not limiting the description of the characteristics and features of the present invention, so as to propose the best mode for performing the present invention and to enable those skilled in the art to implement the present invention. Therefore, the scope of the present invention is limited only by the appended claims.

[0054] The invention discloses a high-homogenization steel for a high-power wind power yaw bearing ring, which contains, by weight percentage, C0.47%-0.57%, Si 0.40%-0.70%, Mn 1.30%-1.50%, Cr 0.50%-0.70%, Mo0.35%-0.45%, Ni 0.25%-0.35%, Cu 0.030%-0.050%, Nb 0.010%-0.030%, Ti0.0040%-0.0060%, Al 0.015%-0.025%, P≤0.015%, S≤0.010%, N≤0.0080%, O≤0.0040%, and the rest is Fe and other inevitable impurities.

[0055] The chemical composition ratio complies with:

[0056] 1) 12.5% ​​≤ (0.54 × C%) × (1 + 3.34 × Mn%) × (1 + 0.7 × Si%) × (1.2 + 0.36 × Cu%) × (1 + 0.37 × Ni%) ×

[0057] (1+2.61×Cr%)×(1+3×Mo%)×(1+0.7×Nb%)≤18.0%;

[0058] 2)0.54%≤C%+(Mn%) / 6-(Cr%+Mo%+Nb%+Ti%) / 5+(Ni%+Cu%) / 15≤0.60%.

[0059] The present invention adopts a steel grade with a specific composition to produce a bearing ring with a wall thickness of 240 mm. The steel grade compositions of the embodiment and the comparative example are shown in Table 1.

[0060] Table 1 Chemical composition of the present invention (wt%)

[0061]

[0062]

[0063] The production process of yaw bearing ring steel and yaw bearing ring adopts arc furnace or converter smelting → LF furnace refining → RH or VD vacuum degassing → continuous casting → round billet heating → forging → punching → ring rolling (semi-finished product) → heat treatment → machining → flaw detection → packaging and warehousing. The specific production process is as follows:

[0064] Electric furnace smelting: oxygen is determined before steel is tapped, and steel retention is adopted during the steel tapping process to avoid slag;

[0065] LF furnace refining: elements such as C, Si, Mn, Cr, Ni, Mo, Nb, and Ti are adjusted to target values;

[0066] VD vacuum degassing: pure degassing time ≥ 15 minutes, ensuring that the [H] content after vacuum treatment is ≤ 1.5ppm, avoiding the appearance of white spots in the steel and causing hydrogen embrittlement;

[0067] Continuous casting: The target temperature of the molten steel in the tundish is controlled at 10-40°C above the liquidus temperature, and round billets of φ380mm-φ700mm are continuously cast.

[0068] Bearing ring manufacturing route: round billet (diameter 600 and 700mm) heating → forging → punching → ring rolling (semi-finished product).

[0069] Bearing ring heat treatment: trolley furnace heating → insulation → normalizing → quenching → tempering → insulation → water cooling.

[0070] Bearing ring processing route: bearing ring rough turning → flaw detection → valve body fine turning → grinding → flaw detection → packaging and warehousing.

[0071] Among them, the heat treatment adopts normalizing + quenching and tempering, and the heat treatment process is:

[0072] Normalizing: The furnace temperature of the semi-finished yaw bearing ring after ring rolling is ≤600℃, the normalizing heating temperature (T1, ℃) is 1100-1200℃, the normalizing holding time (t1, min) is determined by the bearing ring wall thickness (S, mm) and the normalizing heating temperature (T1, ℃), S-T1 / 20≤t1≤S-T1 / 80, water cooling.

[0073] Quenching and tempering: quenching heating temperature (T2, ℃) is 850-950℃, quenching holding time (t2, min) is determined by the bearing ring wall thickness (S, mm) and quenching heating temperature (T2, ℃), S-T2 / 10≤t2≤S-T2 / 50, water cooling; tempering heating temperature (T3, ℃) is 650-750℃, tempering holding time (t3, min) is determined by the bearing ring wall thickness (S, mm) and tempering heating temperature (T3, ℃), 1.5×S-T3 / 10≤t3≤1.5×S-T3 / 50, water cooling. The heat treatment process parameters are shown in Table 2.

[0074] Table 2 Heat treatment process parameters of the embodiments of the present invention and comparative examples

[0075]

[0076]

[0077] The bearing ring prepared by the present invention is tested for performance by the following method:

[0078] Organization: Samples were taken from the extension of the bearing ring, and samples were taken at 12.5 mm on the surface of the extension and within 1 / 2 thickness (thickness was 240 mm) for metallographic and grain size analysis.

[0079] Performance: Samples were taken from the bearing ring extension, and tensile, impact, and contact fatigue specimens were taken from the surface 12.5 mm and 1 / 2 thickness (thickness 240 mm) of the extension. Mechanical performance tests were performed in accordance with GB / T228, GB / T229, and JB / T 10510. The performance test results are shown in Table 3. m is the tensile strength, R p0.2 is the yield strength, and the contact fatigue life is measured under a contact stress of 2000 MPa.

[0080] Table 3 Fatigue performance parameters of the embodiments of the present invention and the comparative examples

[0081]

[0082]

[0083] The chemical composition and production method of the steel in Examples 1-3 are properly controlled, and the chemical composition ensures that 12.5≤A≤18.5, 0.54%≤Y≤0.60%, and the strength, plasticity, toughness and contact fatigue performance of the steel obtained are good. The chemical composition ratio of Comparative Examples 1 and 3 is not appropriate, and the chemical composition is improperly controlled, resulting in low material strength, insufficient plasticity and toughness, and improper heat treatment process resulting in unsatisfactory overall performance; Comparative Example 2 has a reasonable component design, but an improper heat treatment process, resulting in insufficient strength and toughness of the material, and insufficient contact fatigue resistance, such as Figure 1-6 As shown, in Example 2, through reasonable component ratio and heat treatment process control, the grain size at 12.5 mm on the surface of the bearing ring and at 1 / 2 of the wall thickness is consistent, and the homogeneity is good. However, in Comparative Example 2, the grain size at 12.5 mm on the surface of the bearing ring and at 1 / 2 of the wall thickness is greatly different, and the homogeneity is poor.

Claims

1. A highly homogenized steel for high-power wind power yaw bearing ring, containing by weight percentage: C 0.47%-0.57%, Si 0.40%-0.70%, Mn 1.30%-1.50%, Cr 0.50%-0.70%, Mo 0.35%-0.45%, Ni 0.25%-0.35%, Cu 0.030%-0.050%, Nb 0.010%-0.030%, Ti 0.0040%-0.0060%, Al 0.015%-0.025%, P≤0.015%, S≤0.010%, N≤0.0080%, O≤0.0040%, the rest is Fe and other inevitable impurities, and the chemical composition ratio meets the following requirements: 1) 12.5%≤(0.54×C%)×(1+3.34×Mn%)×(1+0.7×Si%)×(1.2+0.36×Cu%)×(1+0.37×Ni%) ×(1+2.61×Cr%)×(1+3×Mo%)×(1+0.7×Nb%)≤18.0%; 2) 0.54%≤C%+(Mn%) / 6-(Cr%+Mo%+Nb%+Ti%) / 5+(Ni%+Cu%) / 15≤0.60%; the wall thickness of the bearing ring is ≥240mm, the tensile strength at 1 / 2 of the wall thickness of the bearing ring is ≥950MPa, the yield strength is ≥850MPa, and the -40℃ KV2 is ≥100J; the difference between the tensile strength at 12.5mm on the surface of the bearing ring and the strength at 1 / 2 of the wall thickness of the bearing ring is ≤80MPa; under the action of 2000MPa contact stress, the contact fatigue life is ≥1 million times.

2. A process for producing bearing rings using the highly homogenized high-power wind power yaw bearing ring steel according to claim 1, characterized in that: The following steps are involved: Electric arc furnace or converter smelting → LF furnace refining → RH or VD vacuum degassing → round billet continuous casting → round billet heating → forging → punching → ring rolling → heat treatment → machining → flaw detection → packaging and warehousing.

3. According to claim 2, a production process for a high-homogenization high-power wind turbine yaw bearing ring is characterized in that: The heat treatment adopts normalizing and tempering heat treatment process, and the tempering process includes quenching and tempering.

4. According to claim 3, a production process for a high-homogenization high-power wind turbine yaw bearing ring is characterized in that: During the normalizing process, the temperature of the semi-finished yaw bearing ring after ring rolling is ≤600°C when it enters the furnace, the normalizing heating temperature (T1, °C) is 1100-1200°C, the normalizing holding time (t1, min) is determined by the bearing ring wall thickness (S, mm) and the heating temperature (T1, °C), and satisfies S-T1 / 20≤t1≤S-T1 / 80, and is water-cooled.

5. According to claim 4, a production process for a high-homogenization high-power wind turbine yaw bearing ring is characterized in that: During the quenching and tempering process, the quenching heating temperature (T2, °C) is 850-950 °C, the quenching holding time (t2, min) is determined by the bearing ring wall thickness (S, mm) and the quenching heating temperature (T2, °C), and satisfies S-T2 / 10≤t2≤S-T2 / 50, and water cooling is used; The tempering heating temperature (T3, ℃) is 650-750℃, and the tempering holding time (t3, min) is determined by the bearing ring wall thickness (S, mm) and the tempering heating temperature (T3, ℃), satisfying 1.5×S-T3 / 10≤t3≤1.5×S-T3 / 50, and water cooling.

6. A bearing ring made according to the production process of a high-homogenization high-power wind power yaw bearing ring according to any one of claims 2 to 5, characterized in that: The wall thickness of the bearing ring is ≥240mm, the tensile strength at 1 / 2 of the wall thickness of the bearing ring is ≥950MPa, the yield strength is ≥850MPa, and the -40°C KV2 is ≥100J; under the action of 2000MPa contact stress, the contact fatigue life is ≥1 million times.

7. A high-homogenization high-power wind power yaw bearing ring according to claim 6, characterized in that: After tempering, the troostite content at 12.5 mm on the surface of the bearing ring is 100%, and the troostite content at 1 / 2 of the wall thickness is ≥91%.

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