Steel for wind power main shaft bearing ring and production method thereof

Abstract

The invention discloses steel for a wind power main shaft bearing ring and a production method of the steel, the steel comprises the following chemical components in percentage by mass: 0.46 to 0.53 percent of C, 0.15 to 0.35 percent of Si, 0.70 to 1.00 percent of Mn, 1.10 to 1.30 percent of Cr, 0.40 to 0.70 percent of Ni, 0.25 to 0.35 percent of Mo, 0.020 to 0.050 percent of Al, 0.05 to 0.10 percent of V and 0.005 to 0.012 percent of N. The steel for the soft-belt-free quenched wind power main shaft bearing ring with high hardenability, high hardenability and high low-temperature impact toughness is produced by proportioning the C, the Si, the Mn, the Cr, the Ni, the Mo and the V; after hardening and tempering, good strength, plasticity and low-temperature impact toughness can be obtained, high hardness and deep quenching hardness layer depth can be obtained through soft-belt-free medium-frequency quenching, and the use requirement of the wind power main shaft bearing ring is met.

Description

Technical Field

[0001] The invention belongs to the technical field of steel for wind turbine main shaft bearing rings, and in particular relates to steel for wind turbine main shaft bearing rings and a production method thereof. Background Art

[0002] The main shaft bearing of a wind turbine is a key component of a wind turbine, supporting the impeller and main shaft in the wind turbine to ensure its normal operation. Due to the harsh operating environment and complex operating conditions of wind turbines, the service life of wind turbines is required to be 25 years, so the requirements for the materials of wind turbine parts are relatively high, especially for the raw materials used in the main shaft bearing rings of wind turbines.

[0003] At present, the steel used for wind turbine main shaft bearings in the industry mainly adopts 100CrMnSiMo8-6-4, 100CrMnMo7-3 and other electroslag high carbon chromium bearing steels after bainite quenching treatment, or G20Cr2Ni4 electroslag steel after carburizing quenching treatment to meet the performance requirements of wind turbine main shaft bearing rings.

[0004] However, the raw material cost of 100CrMnSiMo8-6-4, 100CrMnMo7-3, and G20Cr2Ni4 electroslag steel is high, and the subsequent bearing processing technology is complex and the process cost is high. With the cost reduction of the wind power industry, the industry urgently needs raw materials with more cost advantages. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a steel for wind turbine main shaft bearing rings and a production method thereof. Steel for wind turbine main shaft bearing rings with high hardenability, high hardenability, high and low temperature impact toughness and non-soft band quenching is produced through the ratio of C, Si, Mn, Cr, Ni, Mo and V. After quenching and tempering, the material can obtain good strength, plasticity and low temperature impact toughness. Through non-soft band medium frequency quenching, higher hardness and deeper quenching hardness layer depth can be obtained, which meets the use requirements of wind turbine main shaft bearing rings.

[0006] The present invention also provides a method for preparing a wind turbine main shaft bearing ring, which is prepared by forging → ring rolling → machining → tempering treatment of the steel for the wind turbine main shaft bearing ring described in the present invention. The wind turbine main shaft bearing ring has good strength, plasticity, low-temperature impact toughness, high hardness and deep quenching hardness layer depth, and can meet the use requirements of the wind turbine main shaft bearing ring.

[0007] The technical solution adopted by the present invention is as follows: A wind turbine main shaft bearing ring steel, the wind turbine main shaft bearing ring steel comprising the following chemical components in mass percentage: C: 0.46-0.53%, Si: 0.15-0.35%, Mn: 0.70-1.00%, Cr: 1.10-1.30%, Ni: 0.40~0.70%, Mo: 0.25~0.35%, Al: 0.020~0.050%, V: 0.05%~0.10%, N: 0.005~0.012%, P≤0.015%, S≤0.010%, Cu≤0.20%, Ti≤0.0020%, Ca≤0.0010%, O≤0.0010%, H≤0.00015%, As≤0.015%, Sn≤0.010%, Sb≤0.003%, Pb≤0.002%, Bi≤0.005%, As+Sn+Sb+Pb+Bi≤0.030%, others are Fe and unavoidable impurities.

[0008] The metallographic structure of the wind turbine main shaft bearing ring steel after quenching and tempering treatment is tempered troostite.

[0009] The present invention also provides a production method for the wind turbine main shaft bearing ring steel, which comprises the following steps: electric furnace smelting→LF refining→VD vacuum degassing→continuous casting→slow cooling.

[0010] In the electric furnace smelting step, the phosphorus content of the steel tapped from the electric furnace is controlled to be ≤0.010%, and the carbon content is controlled to be 0.15-0.25%; the tapping temperature is controlled to be ≥1610°C; Al blocks are added for deep deoxidation when the steel tapped from the electric furnace reaches 1 / 4 to 1 / 3, and 1.2-1.5 kg of Al is added per ton of steel.

[0011] In the LF refining step, a CaO-SiO2-Al2O3 ternary slag system with a CaO content of 45-55%, a SiO2 content of 7-12%, and an Al2O3 content of 25-32% is used, the basicity is controlled at 5-7, and the LF refining white slag time is ≥30 minutes; carbon powder and silicon carbide are used for slag surface diffusion deoxidation during the refining process, and the amount of carbon powder and silicon carbide added per ton of steel is controlled at 1.8-2.2 kg; the LF refining time is controlled within 100 minutes.

[0012] In the VD vacuum degassing step, the high vacuum holding time of vacuum degree ≤67pa is controlled to be 12-20min, Al wire is fed once after breaking the air, rare earth ferrocerium is added for modification after feeding Al wire, and 0.1-0.2kg cerium carbonate rare earth wire is fed per ton of steel; the soft blowing time after VD vacuum degassing is ≥25min.

[0013] In the continuous casting step, protective casting is adopted, the superheat of molten steel is controlled at 15° C. to 30° C., and crystallizer electromagnetic stirring, casting strand stirring and end electromagnetic stirring are adopted at the same time.

[0014] In the slow cooling step, the billet is put into a slow cooling pit for slow cooling, the surface temperature of the billet entering the slow cooling pit is controlled at 500-550°C, the billet slow cooling rate is lower than 5°C / h, and the exit temperature from the pit is lower than 200°C.

[0015] The present invention also provides a method for preparing a wind turbine main shaft bearing ring, which uses the wind turbine main shaft bearing ring steel of the present invention to undergo forging → ring rolling → machining → quenching and tempering treatment.

[0016] Furthermore, the method of the quenching and tempering treatment is: first quenching at 840-880°C, and then tempering at 580-620°C.

[0017] The wind turbine main shaft bearing ring prepared according to the method of the present invention has a tensile strength of 980-1050MPa, a yield strength of 830-870MPa, an elongation after fracture ≥17%, a cross-sectional shrinkage rate ≥55%, and an impact energy Akv2 of 60-70J at 25.4mm below the skin; a tensile strength of 940-990MPa, a yield strength of 780-840MPa, an elongation after fracture ≥16%, a cross-sectional shrinkage rate ≥55%, and an impact energy Akv2 of 45-65J at -40℃ in the middle of the ring cross section; a hardened layer depth of ≥7.5mm, and a surface hardness of 58-63 HRC.

[0018] The wind turbine main shaft bearing ring steel provided by the present invention adopts the combination of strong carbide forming elements Cr, Mo, etc. that stabilize austenite and strong ferrite elements Ni and Mn in the composition design, so as to effectively improve the martensite hardenability of the steel. At the same time, by adding Al, V, and N to refine the grains, the center of the bearing can obtain a uniform tempered bainite structure after quenching and tempering, and the austenite grain size can reach more than level 6; by adding Ni and Mn and refining the grains, the impact toughness of the steel is improved, especially the low-temperature impact toughness.

[0019] The wind turbine main shaft bearing ring steel provided by the present invention has the following components: C: According to the requirement of 57-63HRC for the raceway hardness of the wind turbine main shaft bearing ring after heat treatment, C is determined to be 0.46-0.53% to ensure that the surface hardness of the raceway is 57-63HRC after medium frequency quenching and tempering at 180-200℃.

[0020] Si: Adding Si to steel can improve strength, elastic limit and hardenability, and improve the low temperature tempering stability of steel, but Si increases the overheating sensitivity, cracking and decarburization tendency of steel. The range of Si content in the present invention is determined to be 0.15-0.35%.

[0021] Mn: Mn can effectively improve the strength of steel and significantly improve the hardenability of steel. For wind turbine main shaft bearings, it can improve the strength and toughness of the ring center after quenching and tempering. However, too high Mn will increase the tendency of grain coarsening and temper brittleness. The Mn content of the present invention is controlled at 0.70-1.00%.

[0022] Cr: Cr is a carbide-forming element that can improve the hardenability, wear resistance and corrosion resistance of steel. However, if the Cr content is too high, it will combine with the carbon in the steel. On the one hand, it will reduce the carbon content in the martensite and reduce the quenching hardness after medium-frequency quenching. On the other hand, it is easy to form large carbides. This insoluble carbide reduces the toughness of the steel and shortens the bearing life.

[0023] Ni: Ni improves plasticity and toughness, especially low-temperature toughness. Ni is also an element that effectively improves austenite stability and inhibits austenite transformation. Ni addition is beneficial to the core of large-section wind turbine main shaft bearing rings after quenching to obtain martensite, but Ni is a precious alloy, and too high a content will increase the cost. Therefore, under the premise of achieving both design performance and cost savings, the present invention controls its content to 0.40-0.70%, which is conducive to achieving the best cost performance.

[0024] Mo: Mo can refine the grains of steel, improve hardenability and heat resistance, improve the bearing core structure and properties, and improve the toughness and impact resistance of the bearing core material. Mo is not only a precious alloy, but also a ferrite-forming element. When the molybdenum content is high, ferrite delta phase or other brittle phases are likely to appear, which reduces toughness. The range of Mo content in the present invention is determined to be 0.25-0.35% Al: Al is added as a deoxidizing element in steel. In addition to reducing the dissolved oxygen in the molten steel, Al and N form dispersed and fine aluminum nitride inclusions, which can refine the grains. However, when the Al content is too high, large particles of Al2O3 and other brittle inclusions are easily formed during the molten steel smelting process, and the purity of the molten steel deteriorates, which affects the service life of the bearing, especially the contact fatigue life. The present invention controls its content to 0.020~0.050%.

[0025] V: solid solution in austenite can improve the hardenability of steel, but vanadium in a chemical state will reduce the hardenability of steel. V and C, N form fine C, N compounds, which can play a role in dispersion strengthening and grain refinement, and can improve the strength and toughness of steel. V is not only a precious alloy, but also too high V reduces the carbon content in martensite, which will reduce the quenching hardness after medium frequency quenching and affect the surface quality. Therefore, the present invention controls its V content: 0.050~0.10%.

[0026] N: N is a harmful element in steel. N and Fe generate Fe4N, which can easily cause the steel to become blue and brittle during deformation. However, if there are nitride-forming elements such as Al and V in the steel, they can form AlN and VN compounds, which play a role of precipitation strengthening in the steel, which is beneficial to refine the grains and improve the strength and toughness. However, if the N content is too high, it is easy to generate large block nitrides with alloy elements. These large block nitrides will affect the life of the bearing and reduce the effect of the alloy elements. Therefore, the N content of the present invention is controlled in the range of 0.005~0.012%.

[0027] The Ca content will increase the number and size of the point oxides in the steel. At the same time, since the point oxides have high hardness and poor plasticity, they do not deform during plastic deformation, which affects the service life of the bearing. Therefore, the Ca content of the present invention is required to be ≤0.0010%.

[0028] Ti can easily react with N to form TiN inclusions, which have high hardness and are in the shape of sharp corners, and can easily cause stress concentration and affect the service life of the bearing. Therefore, the Ti content in the present invention is required to be ≤0.0020%.

[0029] O is the source of oxide inclusions in steel, so the O content in the present invention is required to be ≤0.0010%. H is the main factor causing white spots and hydrogen embrittlement in steel, and is extremely harmful to steel, so the H content in the present invention is required to be ≤0.00015%.

[0030] As, Sn, Sb, Pb and Bi are low melting point elements, which have influence on the plasticity, toughness and pressure processing performance of steel. Therefore, the present invention requires: As≤0.015%, Sn≤0.010%, Sb≤0.003%, Pb≤0.002%, Bi≤0.005%, and As+Sn+Sb+Pb+Bi≤0.030%.

[0031] The production method of the wind turbine main shaft bearing ring steel provided by the present invention is produced through the process flow of blast furnace molten iron → electric furnace smelting → LF refining → VD vacuum treatment → continuous casting of Φ350-800mm round billets → slow cooling.

[0032] In the electric furnace smelting step, 1) in order to control the harmful residual elements in the steel, a reasonable combination of high-quality molten iron, pure scrap steel and nickel-containing pig iron is used, requiring the P content in the molten iron and scrap steel to be ≤0.15%, S≤0.05%, Ti content≤0.006%, As content≤0.008%, Pb content≤0.005%, Sn content≤,0.005%, Sb content≤0.005%, Bi content≤0.005%. The proportion of molten iron charging is 75~80%, the scrap charging is 15~20%, and the nickel pig iron charging is 5~10%. 2) Electric furnace smelting uses high-basicity slag dephosphorization and uses slag flow operation to quickly remove P in the steel. The phosphorus content of the electric furnace steel is ≤0.010%: in order to reduce the oxygen source of oxidized inclusions in the steel, the carbon content in the molten steel must be not less than 0.15% when the electric furnace is tapped, and the carbon content of the electric furnace is controlled at 0.15-0.25%. 3) The electric furnace uses an eccentric furnace bottom to tap steel to prevent slag from falling during tapping, and to prevent high phosphorus and high oxidizing agents from entering the molten steel and affecting the purity of the steel. 4) In order to ensure the rapid melting of deoxidizers and alloys added during the tapping process and the rapid slag slagging of slag materials, the tapping temperature of the electric furnace is ≥1610℃.

[0033] Alloying is performed during the tapping process of electric steel. 1) When the steel tapping of the electric furnace reaches 1 / 4-1 / 3, Al blocks are added for deep deoxidation. The amount of Al added per ton of steel is 1.2-1.5 kg, ensuring that the Al content of LF is 0.030-0.050% at the station. No more Al is added to LF for deoxidation. After adding the aluminum blocks, silicon-manganese alloy, ferromanganese, high-carbon ferrochrome, and carburizer are added. Finally, top slag is added. In order to control the Ti content in the steel, high-carbon ferrochrome uses low-titanium high-carbon ferrochrome, and its Ti content is ≤0.035%. 2) Large argon stirring is used during the tapping process. After the alloy and slag are added, the argon stirring is adjusted to soft blowing within 2 minutes.

[0034] In the LF refining step, 1) by making foamed white slag, the inclusions in the steel are effectively adsorbed. The CaO-SiO2-Al2O3 ternary slag system is used, and the basicity is controlled at 5-7. Through this slag system, the S content in the steel is effectively reduced to below 0.005%, and the sulfur content that forms Class A inclusions in the steel is effectively reduced. 2) In order to reduce the formation of oxidized inclusions in the refining process, Al precipitation deoxidation is no longer used in the refining process. Carbon powder and silicon carbide are used for slag surface diffusion deoxidation to effectively reduce the oxygen content in the steel. The amount of carbon powder and silicon carbide added per ton of steel is controlled at 1.8-2.2kg. 3) In order to ensure sufficient deoxidation and removal of inclusions during refining, the LF refining white slag time is ≥30min. In order to reduce the impact of molten steel on the purity of molten steel and production rhythm control caused by the erosion of molten steel on the ladle refractory, the LF refining time is controlled within 100min.

[0035] In the VD vacuum degassing step, under the premise of ensuring effective dehydrogenation effect, the argon stirring and high vacuum holding time are reduced as much as possible, and the high vacuum holding time of vacuum degree ≤67pa is controlled within 12-20min to reduce the mixing of steel slag and reduce the inclusions in the steel. After breaking the air, feed Al wire once to adjust the Al content in the steel to the target value; after feeding Al wire, add rare earth ferrocerium for denaturation treatment, feed 0.1-0.2kg cerium carbonate rare earth wire per ton of steel for inclusion denaturation treatment, use the sulfides and oxides in the steel to effectively denature, form high melting point inclusions, float up and remove them during the soft blowing process, and the soft blowing time after VD is ≥25min.

[0036] During the continuous casting step, the continuous casting process adopts measures such as long water inlet argon protection, integral submerged water inlet, covering agent and crystallizer protective slag in the tundish to achieve protective casting and prevent secondary oxidation. In order to control the low weight and composition segregation of the continuous casting billet, low superheat casting and electromagnetic stirring technology are adopted. The superheat is controlled at 15℃~30℃. At the same time, crystallizer electromagnetic stirring + casting strand stirring + end electromagnetic stirring are used to improve the crystal structure of the billet.

[0037] In the slow cooling step, the billet is quickly placed into the slow cooling pit for slow cooling after cutting, which reduces the internal stress of the billet on the one hand and facilitates the precipitation of hydrogen in the steel on the other hand. The surface temperature of the billet entering the slow cooling pit is controlled at 500-550℃, the billet slow cooling rate is less than 5℃ per hour, and the temperature out of the pit is less than 200℃.

[0038] Compared with the prior art, the present invention has the following beneficial effects: The present invention adds C, Mn, Cr, Ni, Mo, V, and N to make the steel have good hardenability and hardenability. After quenching and tempering, good comprehensive mechanical properties can be obtained. After medium frequency quenching, higher hardenability and deeper hardened layer depth can be obtained. The requirements of wind turbine main shaft bearing steel for strength, low temperature toughness, surface hardness and hardened layer depth after medium frequency quenching can be met. Through the process flow of blast furnace molten iron → electric furnace smelting → LF refining → VD vacuum treatment → continuous casting to obtain large round billets → slow cooling, large round billets that meet the processing of wind turbine main shaft bearing rings are produced. The large round billets have high purity, and the inclusions reach the level of electroslag re-melted steel. The continuous casting round billets have dense structure. After the continuous casting round billets are cut, they can be directly heated to forge the wind turbine main shaft bearing rings, meeting the high flaw detection requirements of the wind turbine main shaft bearing rings. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a low-magnification microstructure diagram of a round steel billet for a wind turbine main shaft bearing ring in Example 1; Figure 2 This is a quenched and tempered microstructure diagram of the cross section center of a bearing ring made from the steel for the wind turbine main shaft bearing ring in Example 1, and the microstructure is tempered troostite; Figure 3The medium frequency quenching structure of the bearing ring raceway in Example 1 is needle-shaped martensite; Figure 4 The quenched bainite structure of the bearing ring raceway in Comparative Example 3 is lower bainite; Figure 5 The quenched and tempered structure of the carburized layer of the bearing ring in Comparative Example 4 is needle-shaped martensite; Figure 6 This is the quenched and tempered structure of the core of the cross section of the bearing ring in Comparative Example 4, and the structure is lath martensite. DETAILED DESCRIPTION

[0040] The present invention provides a wind turbine main shaft bearing ring steel, the wind turbine main shaft bearing ring steel comprises the following chemical components in mass percentage: C: 0.46-0.53%, Si: 0.15-0.35%, Mn: 0.70-1.00%, Cr: 1.10-1.30%, Ni: 0.40~0.70%, Mo: 0.25~0.35%, Al: 0.020~0.050%, V: 0.05%~0.10%, N: 0.005~0.012%, P≤0.015%, S≤0.010%, Cu≤0.20%, Ti≤0.0020%, Ca≤0.0010%, O≤0.0010%, H≤0.00015%, As≤0.015%, Sn≤0.010%, Sb≤0.003%, Pb≤0.002%, Bi≤0.005%, As+Sn+Sb+Pb+Bi≤0.030%, others are Fe and unavoidable impurities.

[0041] The production method of the wind turbine main shaft bearing ring steel comprises the following steps: electric furnace smelting→LF refining→VD vacuum degassing→continuous casting→slow cooling.

[0042] In the electric furnace smelting step, the phosphorus content of the steel tapped from the electric furnace is controlled to be ≤0.010%, and the carbon content is controlled to be 0.15-0.25%; the tapping temperature is controlled to be ≥1610°C; Al blocks are added for deep deoxidation when the steel tapped from the electric furnace reaches 1 / 4 to 1 / 3, and 1.2-1.5 kg of Al is added per ton of steel.

[0043] In the LF refining step, a CaO-SiO2-Al2O3 ternary slag system with a CaO content of 45-55%, a SiO2 content of 7-12%, and an Al2O3 content of 25-32% is used, the basicity is controlled at 5-7, and the LF refining white slag time is ≥30 minutes; carbon powder and silicon carbide are used for slag surface diffusion deoxidation during the refining process, and the amount of carbon powder and silicon carbide added per ton of steel is controlled at 1.8-2.2 kg; the LF refining time is controlled within 100 minutes.

[0044] In the VD vacuum degassing step, the high vacuum holding time of vacuum degree ≤67pa is controlled to be 12-20min, Al wire is fed once after breaking the air, rare earth ferrocerium is added for modification after feeding Al wire, and 0.1-0.2kg cerium carbonate rare earth wire is fed per ton of steel; the soft blowing time after VD vacuum degassing is ≥25min.

[0045] In the continuous casting step, protective casting is adopted, the superheat of molten steel is controlled at 15° C. to 30° C., and crystallizer electromagnetic stirring, casting strand stirring and end electromagnetic stirring are adopted at the same time.

[0046] In the slow cooling step, the billet is put into a slow cooling pit for slow cooling, the surface temperature of the billet entering the slow cooling pit is controlled at 500-550°C, the billet slow cooling rate is lower than 5°C / h, and the exit temperature from the pit is lower than 200°C.

[0047] The present invention is described in detail below with reference to the embodiments. Example

[0048] The chemical composition and weight percentage of the steel for the wind turbine main shaft bearing ring in each embodiment and comparative example are shown in Table 1, and the remainder is iron and unavoidable impurities.

[0049] Table 1 Chemical composition and weight percentage

[0050] The process parameters of the smelting and continuous casting process of the steel for the wind turbine main shaft bearing ring in each embodiment are shown in Table 2. Comparative Examples 1 to 4 adopt the conventional process of casting steel ingots and then electroslag remelting.

[0051] Table 2 Process parameters of smelting and continuous casting

[0052] Samples were taken from the ingots obtained in each embodiment to examine macrostructure, non-metallic inclusions, and hardenability. The test data are shown in Tables 3, 4, and 5.

[0053] Table 3 Macrostructure / Grade

[0054] Table 4 Non-metallic inclusions / grade

[0055] Table 5 Hardenability

[0056] The round blanks prepared in Examples 1 to 3 were forged → ring rolled → machined → tempered to obtain wind turbine main shaft bearing rings, tempered, quenched: 860±10℃ for 5.5±0.5h for water quenching, water cooling for 20min, the water outlet temperature of the forging surface was 150±20℃, tempered: 600±10℃ for 7±0.5h, tempered and then air cooled to room temperature, samples were taken from 25.4mm below the ring skin to test the longitudinal tensile and impact properties, the data are shown in Table 6, and samples were taken from the middle of the ring section to test the mechanical properties, see Table 7.

[0057] Table 6 Mechanical properties of subcutaneous 25.4 mm quenched and tempered

[0058] Table 7 Mechanical properties of ring cross-section intermediate sampling quenched and tempered

[0059] The wind turbine main shaft bearing rings prepared in Examples 1 to 3 were heated at 880±10°C and subjected to medium frequency quenching at 2500±200kHz and 300kW, and the surface hardness and the depth of the hardened layer were tested. The results are shown in Table 8.

[0060] Table 8 Surface hardness and hardened layer depth after medium frequency quenching

[0061] It can be seen from the above test results that the steel round billet for wind turbine main shaft bearing rings obtained according to the technical solution of the present invention has dense low-magnification structure, good material hardenability, high purity, high strength after tempering, good low-temperature impact toughness, high surface hardness and deep hardened layer after medium frequency quenching, which meets the performance requirements of wind turbine bearing rings and has a large margin.

[0062] The above-mentioned detailed description of a steel for a wind turbine main shaft bearing ring and a production method thereof with reference to the embodiments is illustrative rather than restrictive, and several embodiments can be listed according to the limited scope. Therefore, changes and modifications without departing from the overall concept of the present invention should fall within the scope of protection of the present invention.

Claims

1. A steel for a wind turbine main shaft bearing ring, characterized in that: The steel for the wind turbine main shaft bearing ring includes the following chemical components by mass percentage: C: 0.46-0.53%, Si: 0.15-0.35%, Mn: 0.70-1.00%, Cr: 1.10-1.30%, Ni: 0.40~0.70%, Mo: 0.25~0.35%, Al: 0.020~0.050%, V: 0.05%~0.10%, N: 0.005~0.012%, P≤0.015%, S≤0.010%, Cu≤0.20%, Ti≤0.0020%, Ca≤0.0010%, O≤0.0010%, H≤0.00015%, As≤0.015%, Sn≤0.010%, Sb≤0.003%, Pb≤0.002%, Bi≤0.005%, As+Sn+Sb+Pb+Bi≤0.030%, others are Fe and unavoidable impurities.

2. The steel for wind turbine main shaft bearing ring according to claim 1 is characterized in that: The metallographic structure of the wind turbine main shaft bearing ring steel after quenching and tempering treatment is tempered troostite.

3. The method for producing steel for wind turbine main shaft bearing rings according to claim 1 or 2, characterized in that: The production method comprises the following steps: electric furnace smelting→LF refining→VD vacuum degassing→continuous casting→slow cooling.

4. The production method according to claim 3, characterized in that: In the electric furnace smelting step, the phosphorus content of the steel tapped from the electric furnace is controlled to be ≤0.010%, and the carbon content is controlled to be 0.15-0.25%; the tapping temperature is controlled to be ≥1610°C; Al blocks are added for deep deoxidation when the steel tapped from the electric furnace reaches 1 / 4 to 1 / 3, and 1.2-1.5 kg of Al is added per ton of steel.

5. The production method according to claim 3, characterized in that: In the LF refining step, the CaO content is 45-55%, SiO ２ Content 7-12%, Al2O ３ The content of CaO-SiO2-Al2O3 ternary slag system is 25-32%, the basicity is controlled at 5-7, and the LF refining white slag time is ≥30min; carbon powder and silicon carbide are used for diffusion deoxidation of the slag surface during the refining process, and the amount of carbon powder and silicon carbide added per ton of steel is controlled at 1.8-2.2kg; the LF refining time is controlled within 100min.

6. The production method according to claim 3, characterized in that: In the VD vacuum degassing step, the high vacuum holding time of vacuum degree ≤67pa is controlled to be 12-20min, Al wire is fed once after breaking the air, rare earth ferrocerium is added for modification after feeding Al wire, and 0.1-0.2kg cerium carbonate rare earth wire is fed per ton of steel; the soft blowing time after VD vacuum degassing is ≥25min.

7. The production method according to claim 3, characterized in that: In the continuous casting step, protective casting is adopted, the superheat of molten steel is controlled at 15° C. to 30° C., and electromagnetic stirring of the crystallizer, casting strand stirring and terminal electromagnetic stirring are adopted at the same time.

8. The production method according to claim 3, characterized in that: In the slow cooling step, the billet is put into a slow cooling pit for slow cooling, the surface temperature of the billet entering the slow cooling pit is controlled at 500-550°C, the billet slow cooling rate is lower than 5°C / h, and the billet exit temperature is lower than 200°C.

9. A method for preparing a wind turbine main shaft bearing ring, characterized in that: The wind turbine main shaft bearing ring steel according to claim 1 or 2 is subjected to forging → ring rolling → machining → quenching and tempering treatment.

10. The method for preparing a wind turbine main shaft bearing ring according to claim 9, characterized in that: The method of the quenching and tempering treatment is: first quenching at 840-880°C, and then tempering at 580-620°C.

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