Ultra-fine grain micro-deformation high-hardness bainite type wind power main shaft bearing material and manufacturing process

Abstract

The invention discloses an ultra-fine grain micro-deformation high-hardness bainite type wind power main shaft bearing material and a manufacturing process, and belongs to the technical field of metal material machining. On the basis of traditional high-carbon-chromium bearing steel, the contents of Mo and Si elements are properly increased, a proper amount of AlN element is added, a bainite isothermal quenching process is used for producing the fan main shaft bearing ring forging, a lower bainite structure higher in obdurability and smaller in deformation amount is obtained, high hardness and high toughness of the ring forging are guaranteed, deformation is remarkably reduced, and the service life of the ring forging is prolonged. And the size precision is improved. The original austenite grain size of the core part of the produced ring forging is not less than 10.5 grade, the hardness is 59-61 HRC, the room temperature impact value is not less than 83 J, the low-temperature impact value at-40 DEG C is not less than 33 J, the single-side machining allowance is not more than 0.52 mm, and the deformation is not more than 0.18 mm / m.

Description

Technical Field

[0001] The invention relates to an ultrafine-grained, micro-deformed, high-hardness bainite type wind turbine main shaft bearing material and a manufacturing process, belonging to the technical field of metal material processing. Background Art

[0002] Wind turbine main shaft bearings are core components of wind turbine generators, requiring high strength, toughness, hardness, wear resistance, and dimensional accuracy. With the rapid expansion of wind turbines, the size of wind turbine main shaft bearings has also gradually increased. In recent years, the diameter of wind turbine main shaft bearings has increased from less than 1m to 2m and above. This puts higher requirements on the toughness, hardness, deformation, and uniformity of bearings and ring forgings before machining. Traditional wind turbine main shaft bearings use quenched and tempered steel, carburized steel, etc. The hardness and wear resistance of quenched and tempered steel bearings are insufficient, making it difficult to meet the requirements of high-power wind turbines above 8MW for main shaft bearings. Lowering the tempering temperature still results in insufficient hardness and toughness cannot be guaranteed. Although carburized steel solves the problem of matching surface hardness and toughness, the carburizing time is long and the workpiece size deformation is large, which cannot meet the dimensional accuracy requirements of large wind turbine main shaft bearings.

[0003] Wind turbine main shaft bearings are usually made through processes such as roughing and drawing of blanks, punching and ring rolling, heat treatment, and machining. Therefore, the hot forming process and heat treatment process of forged ring rolling have an impact on the strength, hardness, wear resistance, and dimensional accuracy of the ring forgings. Compared with quenching into martensite, the deformation caused by phase transformation expansion and thermal stress is significantly smaller in bainite transformation, and the hardness is reduced very little. Therefore, bainite isothermal quenching has been applied to small-sized bearings as a heat treatment process with high hardness, high toughness, and low deformation. However, the insufficient degree of microstructure refinement and homogenization after ring forgings are rolled, the deformation anisotropy caused by metal streamlines, and the lack of uniformity of isothermal quenching are the key factors that limit the application of bainite isothermal quenching in the manufacture of main shaft bearings for high-power wind turbines above 8MW.

[0004] Therefore, there is an urgent need for a material suitable for ultrafine-grained, micro-deformation, high-hardness bainite wind turbine main shaft bearings and the corresponding forging, ring rolling and bainite isothermal quenching processes, which can significantly refine the austenite grains of ring forgings, ring rolling and heat treatment, improve strength and toughness, hardness, and reduce the deformation of ring forgings. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a manufacturing process for a ring forging for a wind turbine main shaft bearing, in which Mo and Si elements are appropriately added to the traditional 100CrMnMo material to expand the bainite isothermal quenching process window, and appropriate amounts of Al and N are added to form a second phase to refine the grains. The hot rotary forging technology is introduced to refine the core structure, destroy the metal streamline, and improve the uniformity of the structure. The isothermal quenching process is controlled to obtain a ring forging for a wind turbine main shaft bearing with ultrafine grains, micro deformation and high hardness.

[0006] At the same time, the present invention provides an ultrafine grain, micro-deformation and high hardness bainite type wind turbine main shaft bearing material.

[0007] At the same time, the present invention provides an application of an ultrafine-grained, micro-deformed, high-hardness bainite wind turbine main shaft bearing material in a ring forging for a wind turbine main shaft bearing.

[0008] At the same time, the present invention provides a ring forging for a wind turbine main shaft bearing for use in a main shaft bearing of a high-power wind turbine unit above 8MW.

[0009] At the same time, the present invention provides a main shaft bearing ring of a high-power wind turbine set with a power of more than 8MW, which is prepared by the manufacturing process of the ring forging for the main shaft bearing of the wind turbine of the present invention, and the main shaft bearing ring is a lower bainite structure.

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

[0011] The invention discloses an ultrafine-grained, micro-deformed, high-hardness bainite wind turbine main shaft bearing material, which has the following chemical compositions, measured by mass percentage: C: 0.93%-1.05%, Si: 0.40%-0.60%, Mn: 0.80%-1.10%, Cr: 1.80%-2.05%, Mo: 0.50%-0.60%, Al: 0.02%-0.04%, N: 0.008%-0.012%, and the remainder is Fe and unavoidable impurities.

[0012] A ring forging for a wind turbine main shaft bearing made of ultrafine-grained, micro-deformed, high-hardness bainite wind turbine main shaft bearing material, the original austenite grain size at the core of the ring forging is not less than grade 10.5, the hardness is 59-61HRC, the room temperature impact value is not less than 83J, the -40℃ low-temperature impact value is not less than 33J, the single-sided machining allowance is not more than 0.52mm, and the deformation is not more than 0.18mm / m.

[0013] The manufacturing process of the ring forging for the fan main shaft bearing includes the following steps:

[0014] S01, heat the forging billet to 1150℃~1180℃, keep warm for 3~5h;

[0015] S02, the forging blank is upset and stretched, the starting forging temperature is 1120-1150°C, the final forging temperature is 860-930°C, the total forging ratio is not less than 6, and the forging blank is finally upset into a pancake-shaped forging blank with a thickness not exceeding 25 cm;

[0016] S03, the forging blank is reheated to 1150℃~1180℃ and kept warm for 1~2h;

[0017] S04, the forging blank is drilled, expanded and ring rolling begins. The expansion core mold is conical and connected to the vertical rod. The core mold rotates and moves downward with the vertical rod. When the expansion is completed, the vertical rod enters the center hole of the forging blank, and then the ring rolling begins. The starting temperature of the ring rolling is 1120℃~1150℃.

[0018] S05, the inner and outer walls of the ring are first rolled using traditional vertical rods, with a single-turn reduction of not less than 20%, and a total reduction of not less than 60%, to form a ring forging, and the wall thickness of the ring forging is 120% to 150% of the final wall thickness of the forged product. The final temperature of the traditional vertical rod ring rolling is not less than 1050°C. Subsequently, a hot forging press is introduced into the inner and outer walls of the ring forging, and air is blown to control cooling, so that the ring forging is cooled to 900°C at a cooling rate of not less than 20°C / s, and the inner and outer walls are hot forged until the wall thickness of the finished product is reached and the inner and outer shapes are formed. The final temperature of hot forging is 800°C to 850°C;

[0019] S06, the ring forging is placed horizontally, and air is blown to 680℃ from 2-3m above and below the center of the ring forging. It is placed horizontally in a heating furnace for spheroidizing annealing, and the ring forging is fixed with a stopper. The temperature is raised to 790℃~810℃ at a rate of no more than 20℃ / h for spheroidizing annealing, and the temperature is kept isothermal for 4-6h. Then, it is cooled to 690℃ at a cooling rate of no more than 20℃ / h, and the temperature is kept isothermal for 2-3h. Then, it is cooled to 400℃ at a cooling rate of no more than 20℃ / h. After taking it out, it is air-cooled to room temperature.

[0020] S07, the ring forging is heated to 850℃~870℃ at a rate of no more than 20℃ / h and kept at this temperature for 1~2h. The ring forging is fixed with a stopper, and then placed horizontally in a nitrate quenching tank for isothermal quenching. The nitrate has a support stopper to fix the ring forging. The nitrate temperature is 220-240℃ and the temperature is isothermal for 25-30h. After being taken out, it is air-cooled to room temperature and the attached nitrate is cleaned.

[0021] A manufacturing process for an ultrafine-grained, micro-deformed, high-hardness bainite type wind turbine main shaft bearing material, wherein the hot forging head working surface in S05 is spherical, and the diameter of the spherical working surface is not greater than the width of the inner wall and outer wall of the finished ring forging. The hot forging reduction is not less than 20%, the head rotation speed is not less than 120 revolutions per minute, the head is stepped along the width direction of the ring forging, the step interval is not less than the time required for the ring forging to roll one circle, and the step distance is half the diameter of the contact surface between the hot forging head and the workpiece.

[0022] A manufacturing process for an ultrafine-grained micro-deformation high-hardness bainite type wind turbine main shaft bearing material, wherein, in S05, when processing special-shaped steps, hot rotary forging rams can be added to the upper and lower sides of the existing hot rotary forging rams on the inner wall and outer wall as needed. The diameter of the ram is not greater than 50% of the width of its processing surface, the single-turn pressing amount is not less than 15%, the ram speed is not less than 120 rpm, the ram is stepped along the diameter direction and vertical direction of the ring forging, the step interval is not less than the time required for the ring forging to roll one circle, and the step distance is half of the contact surface diameter of the hot rotary forging ram and the workpiece.

[0023] The structure of the hot forging ram is as follows: the hot forging round ram is connected to the ring rolling machine by a transmission rod that can be extended and adjusted in angle. The hot forging ram rotates and moves with the transmission rod as the axis. The diameter of the hot forging ram is selected according to needs and is not larger than the size of the special-shaped step or channel. The hot forging ram is made of cemented carbide.

[0024] A manufacturing process for an ultrafine-grained, micro-deformed, high-hardness bainite type wind turbine main shaft bearing material, wherein in S07, the nitrate salt uses 50% potassium nitrate + 50% sodium nitrate, and a stirring device is provided in the quenching tank to ensure that the nitrate salt is in a flowing and uniform temperature state. The ring forging is suspended horizontally, and the nitrate salt circulates from top to bottom.

[0025] A manufacturing process of an ultrafine-grained, micro-deformed, high-hardness bainite wind turbine main shaft bearing material, which is applicable to ring forgings with a diameter of 1m to 3m, which may be without special shapes, with internal special shapes, with external special shapes, or with internal and external special shapes.

[0026] A manufacturing process for an ultrafine-grained, micro-deformed, high-hardness bainite wind turbine main shaft bearing material, wherein the original austenite grain size at the core of the produced ring forging is not less than grade 10.5, the hardness is 59-61HRC, the room temperature impact value is not less than 83J, the -40°C low-temperature impact value is not less than 33J, the single-sided machining allowance is not more than 0.52mm, and the deformation is not more than 0.18mm / m.

[0027] An ultrafine-grained, micro-deformed, high-hardness bainite wind turbine main shaft bearing material is used in ring forgings for wind turbine main shaft bearings.

[0028] The ring forgings for wind turbine main shaft bearings obtained by the manufacturing process of the present invention are used in main shaft bearings of high-power wind turbines above 8MW.

[0029] A main shaft bearing ring of a high-power wind turbine set with a capacity of more than 8MW is prepared by the manufacturing process of the invention, and the main shaft bearing ring is a lower bainite structure.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] (1) The bainite isothermal quenching process is used to produce the fan main shaft bearing ring forgings to obtain a lower bainite structure with higher toughness and smaller phase transformation deformation, which not only ensures the high hardness and toughness of the ring forgings, but also significantly reduces deformation and improves dimensional accuracy. The present invention adopts an isothermal quenching process in which the ring forgings are placed horizontally in a salt bath and the nitrate salt is circulated vertically. The phase transformation temperature of the ring forgings is stable and uniform, which further reduces the additional deformation caused by uneven temperature and uneven phase transformation, and has higher dimensional accuracy. When the ring forgings are air-cooled, air is blown from the center of the circle at the same time from top to bottom. The heating rate is limited during spheroidizing annealing, quenching heating and nitrate salt quenching, and a stop block is used to further reduce the possible dimensional deformation. During spheroidizing annealing cooling, the isothermal temperature is 690℃ for 2-3h, so that the size of the spherical cementite obtained is more uniform, the size of the ferrite grains is closer, the uniformity of the phase transformation during quenching heating and isothermal is improved, and then the uniformity of the organizational properties is improved, and the dimensional deformation is reduced.

[0032] (2) The forging heating temperature and deformation temperature are significantly reduced and controlled within a narrow range, which refines the austenite grains from the source. In the ring rolling process, hot rotary forging is introduced. In addition to the normal flow of the ring rolling metal in the direction of expanding the diameter, the local metal in contact with the hot rotary forging punch also flows in the direction of the punch rotation, which significantly increases the metal deformation and deformation penetration efficiency, breaks the ring forging structure, and makes the ring forging present ultrafine crystallization, providing a finer microstructure foundation for subsequent heat treatment processes. At the same time, the ring rolling temperature is further reduced to enter the two-phase region, and the newly generated carbides are fully broken by hot rotary forging to achieve the effect of fine dispersed distribution, improve toughness, and realize online spheroidizing annealing, which significantly shortens the spheroidizing annealing time. In addition, hot rotary forging also destroys the metal streamlines of the ring forging, so that defects such as segregation are evenly distributed, avoiding structural anisotropy, and further reducing the deformation of bainite after isothermal quenching.

[0033] (3) By adding an appropriate amount of AlN to the material, it is controlled to precipitate in large quantities during hot rotary forging, further hindering the growth of austenite grains during hot rotary forging and subsequent spheroidizing annealing and quenching heating, and refining the isothermal quenching structure. Increasing the content of Mo and Si elements in the material, expanding the bainite transformation temperature range, expanding the bainite isothermal transformation process window, making the bainite transformation more uniform and sufficient, reducing the content of residual austenite, and improving the dimensional stability of the ring forging.

[0034] The main principles of the present invention are as follows:

[0035] The forging billet is heated to 1150℃~1180℃, kept warm for 3~5h, and then upsetting and drawing are performed to avoid the austenite grains of the forging billet growing fully before forging when the heating temperature is too high, which is conducive to grain refinement. The starting forging temperature is 1120~1150℃, the final forging temperature is 860~930℃, and the total forging ratio is not less than 6. The purpose is to fully heat and break the cast structure of the forging billet and weld internal defects. The final upsetting into a pancake-shaped forging billet with a thickness of no more than 25cm is conducive to the smooth development of subsequent drilling, hole expansion and ring rolling, avoiding the problems of excessive thickness of the forging billet, difficulty in drilling and hole expansion, and the inability of the ring rolling rod to enter the center hole.

[0036] The integrated forming process of drilling, reaming and ring rolling greatly shortens the forming time. After ring rolling, hot rotary forging is used, which has low deformation temperature and good deformation penetration. It can fully refine the core structure of the ring forging, crush the carbides generated during the deformation of the two-phase region, destroy the metal flow line, improve the uniformity of defects such as segregation, and avoid uneven deformation during isothermal quenching. By adding multiple sets of hot rotary forging rams, the shape and size of the internal and external special shapes of the ring forging can be independently and accurately controlled, the dimensional accuracy can be improved, and the subsequent machining allowance can be reduced.

[0037] During the hot rotary forging process, in order to ensure that all positions of the ring forging can be fully deformed during the ring rolling process, the hot rotary forging ram adopts step-by-step displacement, that is, it is ensured that the hot rotary forging is completed at least one circle of the ring forging before stepping, and the displacement is half of the diameter of the contact surface between the hot rotary forging ram and the workpiece, ensuring that the hot rotary forging deformation can cover each position of the workpiece twice, so that the deformation is uniform, and the surface quality and surface dimensional accuracy are uniform.

[0038] The end temperature of the traditional vertical roller ring rolling is higher than 1050℃, at which time aluminum nitride just begins to precipitate. Replacing the hot forging head and blowing air to 900℃ to suppress the precipitation of aluminum nitride in this temperature range to form a large-sized second phase, but inducing aluminum nitride to precipitate at below 900℃ to form a finer and more dispersed second phase, which improves the hindering effect on austenite grain boundary migration during spheroidizing annealing and quenching heating, and further refines the austenite grains.

[0039] Since the hot rotary forging has a larger deformation amount, better deformation penetration effect, and the deformation temperature is lower than the Acm temperature of the material, the carbides formed during the deformation process are fully broken, which not only improves the toughness of the material, but also increases the carbide nucleation core. The ring forging can be directly put into the heating furnace for spheroidizing annealing, without cooling to room temperature to form lamellar pearlite and then spheroidizing annealing. The total time of traditional spheroidizing annealing of about 20 hours is shortened to 4-6 hours, significantly shortening the process cycle and energy consumption of spheroidizing annealing. After the ring rolling is completed, the ring forging is air-cooled to 680℃ to inhibit the continued precipitation of carbides, and then spheroidized annealing temperature is 790℃~810℃, isothermal for 4-6h, and then cooled to 690℃ at a cooling rate of no more than 20℃ / h, isothermal for 2-3h, with the broken carbides as the core, precipitated to form granular carbides, and then cooled to 400℃ at a cooling rate of no more than 20℃ / h. After being taken out, it is air-cooled to room temperature to avoid the formation of lamellar pearlite in the untransformed structure, and the spheroidizing annealing is completed.

[0040] The bainite isothermal quenching heating temperature is 850℃~870℃, and the temperature is kept for 1~2h. Then, it is placed horizontally in a nitrate quenching tank for isothermal quenching. The nitrate temperature is 220-240℃, and the temperature is kept for 25-30h. The ring forging is partially austenitized in the two-phase region, and the C element content entering the austenite is controlled to obtain a lower bainite structure with better performance, high hardness, high toughness, and low deformation. At the same time, fine carbides are retained to improve the hardness and wear resistance of the bearing. The material of the present invention expands the temperature range of bainite, especially the transformation of lower bainite, by increasing the content of Mo and Si, so that the ring forging is fully transformed into lower bainite without producing harmful structures such as upper bainite. By circulating nitrate and long-term temperature balancing, austenite is transformed into lower bainite as much as possible, and will not be retained in the bearing to cause deformation.

[0041] The ring forgings applicable to the present invention have a diameter of 1m to 3m and may be without special shapes, with internal special shapes, external special shapes, or internal and external special shapes. For ring forgings with smaller sizes, the traditional martensitic quenching process can meet the requirements, and the performance improvement by using the present invention is not obvious; larger ring forgings are limited by equipment capacity, and the forging heating and thermal deformation temperature cannot be controlled to the lower temperature range required by the present invention, and upsetting and drawing may require multiple reheatings to ensure the degree of microstructure refinement. In addition, the deformation of ring forgings with larger diameters after isothermal quenching is greater and cannot be controlled within the range required by the present invention.

[0042] The present invention appropriately increases the content of Mo and Si elements and adds an appropriate amount of AlN elements on the basis of traditional high-carbon chromium bearing steel, and uses a bainite isothermal quenching process to produce a fan main shaft bearing ring forging, thereby obtaining a lower bainite structure with higher toughness and smaller deformation, which not only ensures the high hardness and high toughness of the ring forging, but also significantly reduces deformation and improves dimensional accuracy. The original austenite grain size of the core of the produced ring forging is not less than 10.5, the hardness is 59-61HRC, the room temperature impact value is not less than 83J, the -40℃ low temperature impact value is not less than 33J, the single-sided machining allowance is not more than 0.52mm, and the deformation is not more than 0.18mm / m. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The phase change law calculated for the material in Example 1;

[0044] Figure 2 The AlN solid solution precipitation law calculated for the material in Example 1;

[0045] Figure 3 TTT curve calculated for the material of Example 1;

[0046] Figure 4 This is the original austenite grain morphology of the spindle bearing core in Example 1;

[0047] Figure 5 This is the lower bainite structure of the spindle bearing core of Example 1 and a small amount of white retained austenite. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings, comparative examples and embodiments. The specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0049] Example 1

[0050] A manufacturing process of an ultrafine-grained, micro-deformed, high-hardness bainite wind turbine main shaft bearing material, specifically, manufacturing a ring forging for a wind turbine main shaft bearing with internal and external special shapes, with a final size requirement of Φ2100*Φ1840*193mm (wherein Φ2100 is the outer diameter of the ring forging, Φ1840 is the inner diameter of the ring forging, and 193mm is the height of the ring forging, that is, the height of the cross section, the height perpendicular to the wall thickness direction), the material used has the following chemical composition by mass percentage: C: 1.0%, Si: 0.5%, Mn: 1.0%, Cr: 1.95%, Mo: 0.55%, Al: 0.02%, N: 0.01%, and the remainder is Fe and unavoidable impurities;

[0051] The forging blank is first heated to 1160℃ and kept for 3.5h. After being taken out, it is upset and stretched at 1130℃. The total forging ratio of upsetting and stretching is 7, and the final forging temperature is 900℃. Finally, it is upset into a pancake-shaped forging blank with a thickness of about 20cm.

[0052] The forging blank is reheated to 1160℃ and kept for 1h before drilling. After completion, it is moved to the hole expansion and ring rolling station. The hole expansion mandrel is conical and connected to the vertical rod. The mandrel rotates and moves downward with the vertical rod. While completing the punching, the hole expansion is achieved and the vertical rod enters the center hole of the forging blank. Then the ring rolling begins. The starting temperature of the ring rolling is about 1130℃.

[0053] The inner and outer walls of the ring are first rolled using traditional vertical rods, with a single-turn reduction of 25% and a total reduction of 65% to form a ring forging. The wall thickness of the ring forging is about 130% (about 260mm) of the final forging wall thickness. The end temperature of the traditional vertical rod ring rolling is 1070℃. The hot forging head is introduced into the inner and outer walls of the ring forging, and the air is blown to control the cooling, so that the ring forging is cooled to 900℃ at a cooling rate of 25℃ / s, and the inner and outer walls are hot forged until the wall thickness reaches the finished product and the inner and outer shapes are formed. The end temperature of hot forging is 820℃.

[0054] The working surface of the hot forging ram is spherical, and the diameter of the spherical working surface is not greater than the width of the inner and outer walls of the finished ring forging. The hot forging reduction is 20%, the ram rotation speed is 120 rpm, the ram moves stepwise along the width direction of the ring forging, the stepping interval is not less than the time required for the ring forging to roll one circle, and the stepping distance is half of the contact surface diameter between the hot forging ram and the workpiece.

[0055] When processing the special-shaped step in this embodiment, hot forging rams can be added on both sides of the existing hot forging rams of the inner wall and outer wall as needed. The ram diameter is 50% of the width of the processing surface, the single-turn pressing amount is 15%, the ram speed is 120 rpm, the ram moves stepwise along the diameter direction and vertical direction of the ring forging, the stepping interval is not less than the time required for the ring forging to roll one circle, and the stepping distance is half of the contact surface diameter of the hot forging ram and the workpiece.

[0056] The ring forging is placed horizontally, and air is blown to 680℃ from 2m above and below the center of the ring forging. It is placed horizontally in a heating furnace for spheroidizing annealing, and the ring forging is fixed with a stopper. The temperature is raised to 800℃ at a rate of 15℃ / h for spheroidizing annealing, and the temperature is kept isothermal for 5h. Then, it is cooled to 690℃ at a cooling rate of 15℃ / h, and the temperature is kept isothermal for 2.5h. Then, it is cooled to 400℃ at a cooling rate of 10℃ / h. After taking it out, it is air-cooled to room temperature.

[0057] The ring forgings were heated to 860℃ at a rate of 15℃ / h, kept warm for 1h, and then placed horizontally in a nitrate quenching tank for isothermal quenching. There were support limit blocks in the nitrate to fix the ring forgings. The nitrate temperature was 230℃ and the temperature was isothermal for 26h. After being taken out, they were air-cooled to room temperature and the attached nitrate was cleaned.

[0058] The nitrate salt uses 50% potassium nitrate + 50% sodium nitrate. A stirring device is installed in the quenching tank to ensure that the nitrate salt is in a flowing and uniform temperature state. The ring forging is placed horizontally in the air, and the nitrate salt circulates from top to bottom.

[0059] An ultrafine-grained, micro-deformed, high-hardness bainite wind turbine main shaft bearing material is obtained in this embodiment.

[0060] The ultrafine-grained, micro-deformed, high-hardness bainite wind turbine main shaft bearing material obtained in this embodiment is used in ring forgings for wind turbine main shaft bearings.

[0061] The ring forgings for wind turbine main shaft bearings obtained by the manufacturing process of this embodiment are used in main shaft bearings of high-power wind turbines above 8MW.

[0062] A main shaft bearing ring of a high-power wind turbine with a capacity of more than 8MW is prepared by the manufacturing process of this embodiment, and the main shaft bearing ring has a lower bainite structure.

[0063] The material phase change law, AlN solid solution precipitation law and TTT curve of this embodiment are shown in Figure 1 to Figure 3 .from Figure 1 It can be seen that the A1 temperature is about 750℃ and the Acm temperature is about 900℃. For hypereutectoid bearing steel, the quenching heating temperature should be between A1 and Acm to ensure that the remaining undissolved carbides increase wear resistance. Figure 2 It can be seen that the AlN precipitation temperature range is about 1100℃~780℃, among which the AlN precipitated at high temperature tends to grow, significantly reducing the effect of refining austenite grains. Therefore, hot rotary forging heads are introduced into the inner and outer walls of the ring forgings, and air is blown to control cooling, so that the ring forgings are cooled to 900℃ at a cooling rate of 25℃ / s, forming more finely dispersed AlN, improving the hindering effect on austenite grain boundary migration during spheroidizing annealing and quenching heating, and further refining austenite grains. Figure 3 It can be seen that the transformation temperature range of lower bainite is about 210-300℃. In order to obtain finer bainite and less residual austenite, the austempering temperature is selected to be 230℃. Figure 3 It can also be seen that the bainite transformation starts at 230℃ no earlier than 3h, and the transformation completion time is significantly longer, so the insulation is 26h.

[0064] The original austenite grain morphology and microstructure morphology of the core of the ring forging are as follows: Figure 4 , Figure 5 As shown, Figure 4 As shown in Figure 1, the austenite grains are very small and uniform. Figure 5 As shown in the figure, a very small amount of white retained austenite can be seen on the bainite matrix. The austenite grain size, hardness, impact performance, single-sided machining allowance and deformation are shown in Table 1.

[0065] Example 2

[0066] A manufacturing process of an ultrafine-grained, micro-deformed, high-hardness bainite wind turbine main shaft bearing material, specifically, manufacturing a ring forging for a wind turbine main shaft bearing with a final size requirement of Φ1200*Φ1000*85mm, wherein the material has the following chemical composition by mass percentage: C: 0.93%, Si: 0.4%, Mn: 0.8%, Cr: 1.8%, Mo: 0.50%, Al: 0.04%, N: 0.008%, and the remainder is Fe and unavoidable impurities;

[0067] The forging blank is first heated to 1150℃ and kept at this temperature for 3h. After being taken out, it is upset and stretched at 1120℃. The total forging ratio of upsetting and stretching is 6, and the final forging temperature is 860℃. Finally, it is upset into a pancake-shaped forging blank with a thickness of about 6cm.

[0068] The forging blank is reheated to 1150℃, kept warm for 2 hours before drilling, and then moved to the hole expansion and ring rolling station. The hole expansion mandrel is conical and connected to the vertical rod. The mandrel rotates and moves downward with the vertical rod. When the hole is punched, the hole expansion is achieved and the vertical rod enters the center hole of the forging blank, and then the ring rolling begins. The starting temperature of the ring rolling is about 1120℃.

[0069] The inner and outer walls of the ring are first rolled using traditional vertical rods, with a single-turn reduction of 20% and a total reduction of 60% to form a ring forging. The wall thickness of the ring forging is about 120% of the wall thickness of the final forging product. The end temperature of the traditional vertical rod ring rolling is 1050℃. The hot forging head is introduced into the inner and outer walls of the ring forging, and the air is blown to control the cooling, so that the ring forging is cooled to 900℃ at a cooling rate of 20℃ / s, and the inner and outer walls are hot forged until the wall thickness reaches the finished product. The end temperature of hot forging is 800℃.

[0070] The working surface of the hot forging ram is spherical, and the diameter of the spherical working surface is not greater than the width of the inner and outer walls of the finished ring forging. The hot forging reduction is 25%, the ram rotation speed is 150 rpm, the ram moves stepwise along the width direction of the ring forging, the stepping interval is not less than the time required for the ring forging to roll one circle, and the stepping distance is half of the contact surface diameter of the hot forging ram and the workpiece.

[0071] The ring forging is placed horizontally, and air is blown to 680℃ from 3m above and below the center of the ring forging. It is placed horizontally in a heating furnace for spheroidizing annealing, and the ring forging is fixed with a stopper. The temperature is raised to 790℃ at a rate of 20℃ / h for spheroidizing annealing, and the temperature is kept isothermal for 4h. Then, it is cooled to 690℃ at a cooling rate of 20℃ / h, and the temperature is kept isothermal for 2h. Then, it is cooled to 400℃ at a cooling rate of 20℃ / h. After being taken out, it is air-cooled to room temperature.

[0072] The ring forging is heated to 850℃ at a rate of 20℃ / h, kept warm for 2h, and then placed horizontally in a nitrate quenching tank for isothermal quenching. There are support limit blocks in the nitrate to fix the ring forging. The nitrate temperature is 220℃ and the temperature is isothermal for 25h. After being taken out, it is air-cooled to room temperature and the attached nitrate is cleaned.

[0073] The nitrate salt uses 50% potassium nitrate + 50% sodium nitrate. A stirring device is installed in the quenching tank to ensure that the nitrate salt is in a flowing and uniform temperature state. The ring forging is placed horizontally in the air, and the nitrate salt circulates from top to bottom.

[0074] An ultrafine-grained, micro-deformed, high-hardness bainite wind turbine main shaft bearing material is obtained in this embodiment.

[0075] The ultrafine-grained, micro-deformed, high-hardness bainite wind turbine main shaft bearing material obtained in this embodiment is used in ring forgings for wind turbine main shaft bearings.

[0076] The ring forgings for wind turbine main shaft bearings obtained by the manufacturing process of this embodiment are used in main shaft bearings of high-power wind turbines above 8MW.

[0077] A main shaft bearing ring of a high-power wind turbine with a capacity of more than 8MW is prepared by the manufacturing process of this embodiment, and the main shaft bearing ring has a lower bainite structure.

[0078] Example 3

[0079] A manufacturing process of an ultrafine-grained, micro-deformed, high-hardness bainite type wind turbine main shaft bearing material, specifically, manufacturing a ring forging for a wind turbine main shaft bearing with a final size requirement of Φ3000*Φ2640*350mm, wherein the material used has the following chemical composition by mass percentage: C: 1.05%, Si: 0.6%, Mn: 1.10%, Cr: 2.05%, Mo: 0.60%, Al: 0.03%, N: 0.012%, and the remainder is Fe and unavoidable impurities;

[0080] The forging billet is first heated to 1180℃ and kept at this temperature for 5h. After being taken out, it is upset and stretched at 1150℃, with a total forging ratio of 7 and a final forging temperature of 930℃. Finally, it is upset into a pancake-shaped forging billet with a thickness of about 24cm.

[0081] The forging blank is reheated to 1180℃, kept warm for 1.5h and then drilled. After completion, it is moved to the hole expansion and ring rolling station. The hole expansion mandrel is conical and connected to the vertical rod. The mandrel rotates and moves downward with the vertical rod. When the punching is completed, the hole expansion is achieved and the vertical rod enters the center hole of the forging blank. Then the ring rolling begins. The starting temperature of the ring rolling is about 1150℃.

[0082] The inner and outer walls of the ring are first rolled using traditional vertical rods, with a single-turn reduction of 25% and a total reduction of 70% to form a ring forging. The wall thickness of the ring forging is about 150% of the wall thickness of the final forging product. The end temperature of the traditional vertical rod ring rolling is 1080℃. The hot forging head is introduced into the inner and outer walls of the ring forging, and the air is blown to control the cooling, so that the ring forging is cooled to 900℃ at a cooling rate of 30℃ / s, and the inner and outer walls are hot forged until the wall thickness reaches the finished product. The end temperature of hot forging is 850℃.

[0083] The working surface of the hot forging ram is spherical, and the diameter of the spherical working surface is not greater than the width of the inner and outer walls of the finished ring forging. The hot forging reduction is 25%, the ram rotation speed is 140 rpm, the ram moves stepwise along the width direction of the ring forging, the stepping interval is not less than the time required for the ring forging to roll one circle, and the stepping distance is half of the contact surface diameter of the hot forging ram and the workpiece.

[0084] The ring forging is placed horizontally, and air is blown to 680℃ from 2.5m above and below the center of the ring forging. It is placed horizontally in a heating furnace for spheroidizing annealing, and the ring forging is fixed with a stopper. The temperature is raised to 810℃ at a rate of 20℃ / h for spheroidizing annealing, and the temperature is kept isothermal for 6h. Then, it is cooled to 690℃ at a cooling rate of 10℃ / h, and the temperature is kept isothermal for 3h. Then, it is cooled to 400℃ at a cooling rate of 15℃ / h. After being taken out, it is air-cooled to room temperature.

[0085] The ring forgings are heated to 870℃ at a rate of 15℃ / h, kept warm for 1.5h, and then placed horizontally in a nitrate quenching tank for isothermal quenching. There are support limit blocks in the nitrate to fix the ring forgings. The nitrate temperature is 240℃ and the temperature is isothermal for 30h. After being taken out, air cool to room temperature and clean the attached nitrate.

[0086] The nitrate salt uses 50% potassium nitrate + 50% sodium nitrate. A stirring device is installed in the quenching tank to ensure that the nitrate salt is in a flowing and uniform temperature state. The ring forging is placed horizontally in the air, and the nitrate salt circulates from top to bottom.

[0087] An ultrafine-grained, micro-deformed, high-hardness bainite wind turbine main shaft bearing material is obtained in this embodiment.

[0088] The ultrafine-grained, micro-deformed, high-hardness bainite wind turbine main shaft bearing material obtained in this embodiment is used in ring forgings for wind turbine main shaft bearings.

[0089] The ring forgings for wind turbine main shaft bearings obtained by the manufacturing process of this embodiment are used in main shaft bearings of high-power wind turbines above 8MW.

[0090] A main shaft bearing ring of a high-power wind turbine with a capacity of more than 8MW is prepared by the manufacturing process of this embodiment, and the main shaft bearing ring has a lower bainite structure.

[0091] Example 4

[0092] The difference between this embodiment and embodiment 1 is only that:

[0093] The ring forging is placed horizontally, and air is blown to 680℃ from 2m above and below the center of the ring forging. It is placed horizontally in a heating furnace for spheroidizing annealing, and the ring forging is fixed with a stopper. The temperature is raised to 800℃ at a rate of 15℃ / h for spheroidizing annealing, and the temperature is kept isothermal for 4.5h. Then, it is cooled to 690℃ at a cooling rate of 20℃ / h, and the temperature is kept isothermal for 3h. Then, it is cooled to 400℃ at a cooling rate of 15℃ / h. After being taken out, it is air-cooled to room temperature.

[0094] Comparative Example 1

[0095] The final size, material and heating system of the workpiece are the same as those of Example 1. The difference between this comparative example and Example 1 is that the temperature is raised to 800°C at a rate of 15°C / h for spheroidizing annealing, isothermal for 5 hours, then cooled to 700°C at a cooling rate of 15°C / h, isothermal for 18 hours, and then cooled to 400°C at a cooling rate of 25°C / h. After being taken out, it is air-cooled to room temperature. The original austenite grain size, hardness, impact performance, single-side machining allowance and deformation of the core of the ring forging are shown in Table 1.

[0096] Comparative Example 2

[0097] The final size, material and heating system of the workpiece are the same as those of Example 1. The only difference between this comparative example and Example 1 is that the ring forging is heated to 860°C at a rate of 15°C / h, kept at this temperature for 1h, then placed horizontally in a quenching tank, cooled to 150°C, taken out, put into a 200°C furnace for tempering for 7h, and then air-cooled to room temperature. The original austenite grain size, hardness, impact performance, single-side machining allowance and deformation of the core of the ring forging are shown in Table 1.

[0098] Comparative Example 3

[0099] The final size, material and heating system of the workpiece are the same as those in Example 1. The only difference between this comparative example and Example 1 is that the ring forging is heated to 860°C at a rate of 15°C / h, kept warm for 1h, and then placed horizontally in a nitrate quenching tank for isothermal quenching. There are support limit blocks in the nitrate to fix the ring forging. The nitrate temperature is 200°C and the temperature is isothermal for 35h. After being taken out, it is air-cooled to room temperature and the attached nitrate is cleaned. The original austenite grain size, hardness, impact performance, single-sided machining allowance and deformation of the core of the ring forging are shown in Table 1.

[0100] Comparative Example 4

[0101] The final size, material and heating system of the workpiece are the same as those of Example 1. The only difference between this comparative example and Example 1 is that the ring forging is heated to 860°C at a rate of 15°C / h, kept warm for 1h, and then placed horizontally in a nitrate quenching tank for isothermal quenching. There are support limit blocks in the nitrate to fix the ring forging. The nitrate temperature is 250°C and the temperature is isothermal for 23h. After being taken out, it is air-cooled to room temperature and the attached nitrate is cleaned. The original austenite grain size, hardness, impact performance, single-sided machining allowance and deformation of the core of the ring forging are shown in Table 1.

[0102] Comparative Example 5

[0103] The final size and hot working system of the workpiece are the same as those in Example 1, only the material is different. The chemical composition of the materials used is as follows: C: 1.0%, Si: 0.25%, Mn: 1.0%, Cr: 1.95%, Mo: 0.15%, and the balance is Fe and unavoidable impurities; no elements such as Al and N are added. The original austenite grain size, hardness, impact performance, single-side machining allowance and deformation of the core of the ring forging are shown in Table 1.

[0104] Table 1 Grain size, hardness, impact performance, machining allowance and deformation of ring forgings

[0105]

[0106] Note: The austenite grain size refers to the national standard GB / T 6394-2017 "Method for determination of average grain size of metals".

[0107] The impact energy refers to the national standard GB / T 229-2020 "Charpy Pendulum Impact Test Method for Metal Materials".

[0108] It should be understood that in order to streamline the present disclosure and aid in understanding one or more of the various inventive aspects, in the above description of exemplary embodiments of the present invention, various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting the intention that the claimed invention requires more features than those expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in less than all of the features of the previously disclosed embodiments. Therefore, the claims that follow the detailed description are hereby expressly incorporated into the detailed description, with each claim itself serving as a separate embodiment of the present invention.

[0109] Although the present invention has been described according to a limited number of embodiments, it will be apparent to those skilled in the art, with the benefit of the above description, that other embodiments may be envisioned within the scope of the invention thus described. In addition, it should be noted that the language used in this specification is selected primarily for readability and teaching purposes, rather than for explaining or defining the subject matter of the present invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the present invention is illustrative, not restrictive, with respect to the scope of the present invention, which is defined by the appended claims.

[0110] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An ultrafine-grained, micro-deformed, high-hardness bainite wind turbine main shaft bearing material, characterized in that: The chemical composition, in mass percentage, is as follows: C: 0.93% ~ 1.05%, Si: 0.40% ~ 0.60%, Mn: 0.80% ~ 1.10%, Cr: 1.80% ~ 2.05%, Mo: 0.50% ~ 0.60%, Al: 0.02% ~ 0.04%, N: 0.008% ~ 0.012%, and the balance is Fe and unavoidable impurities.

2. The ring forging for wind turbine main shaft bearing made of ultrafine grain micro-deformation high hardness bainite wind turbine main shaft bearing material according to claim 1 is characterized in that: The original austenite grain size of the core of the ring forging shall not be less than grade 10.5, the hardness shall be 59-61HRC, the room temperature impact value shall not be less than 83J, the -40℃ low temperature impact value shall not be less than 33J, the single-sided machining allowance shall not exceed 0.52mm, and the deformation shall not exceed 0.18mm / m.

3. The manufacturing process of the ring forging for the fan main shaft bearing according to claim 2 is characterized in that: The following steps are involved: S01, heat the forging billet to 1150℃~1180℃, keep warm for 3~5h; S02, the forging blank is upset and stretched, the starting forging temperature is 1120-1150°C, the final forging temperature is 860-930°C, the total forging ratio is not less than 6, and the forging blank is finally upset into a pancake-shaped forging blank with a thickness not exceeding 25 cm; S03, the forging blank is reheated to 1150℃~1180℃ and kept warm for 1~2h; S04, drilling and expanding the forging blank and starting ring rolling, the ring rolling starting temperature is 1120℃~1150℃; S05, the inner and outer walls of the ring are first rolled using traditional vertical rods, with a single-turn reduction of not less than 20% and a total reduction of not less than 60% to form a ring forging, the wall thickness of the ring forging is 120% to 150% of the wall thickness of the final forging product; the end temperature of the traditional vertical rod ring rolling is not less than 1050°C; then, a hot rotary forging head is introduced into the inner and outer walls of the ring forging, and air is blown to control cooling, so that the ring forging is cooled to 900°C at a cooling rate of not less than 20°C / s, and the inner and outer walls are hot forged until the wall thickness reaches the finished product and the inner and outer shapes are formed; the end temperature of the hot rotary forging is 800°C to 850°C; S06, the ring forging is placed horizontally, and air is blown to 680℃ from 2-3m above and below the center of the ring forging, and then placed horizontally in a heating furnace for spheroidizing annealing. The ring forging is fixed with a stopper; the temperature is raised to 790℃~810℃ at a rate of no more than 20℃ / h for spheroidizing annealing, and the temperature is kept constant for 4-6h, and then the temperature is cooled to 690℃ at a cooling rate of no more than 20℃ / h, and the temperature is kept constant for 2-3h, and then the temperature is cooled to 400℃ at a cooling rate of no more than 20℃ / h; after being taken out, the temperature is air-cooled to room temperature; S07, the ring forging is heated to 850℃~870℃ at a speed of no more than 20℃ / h, kept warm for 1~2h, fixed with a limit block, and then placed horizontally in a nitrate quenching tank for isothermal quenching. The nitrate has a support limit block to fix the ring forging, the nitrate temperature is 220-240℃, and the temperature is kept warm for 25-30h; after being taken out, it is air-cooled to room temperature, and the attached nitrate is cleaned to obtain the product.

4. The manufacturing process according to claim 3, characterized in that: In S05, the working surface of the hot forging ram is spherical, and the diameter of the spherical working surface is not greater than the width of the inner and outer walls of the finished ring forging; the hot forging reduction is not less than 20%, the ram rotation speed is not less than 120 rpm, the ram is stepped along the width direction of the ring forging, the step interval is not less than the time required for the ring forging to roll one circle, and the step distance is half of the diameter of the contact surface between the hot forging ram and the workpiece.

5. The manufacturing process according to claim 3, characterized in that: In S07, the nitrate salt used is 50% potassium nitrate + 50% sodium nitrate, and a stirring device is provided in the quenching tank to ensure that the nitrate salt is in a flowing and uniform temperature state; the ring forging is placed horizontally in the air, and the nitrate salt circulates from top to bottom.

6. The manufacturing process according to claim 3, characterized in that: The diameter of the ring forging is 1m to 3m.

7. The manufacturing process according to claim 3, characterized in that: In S04, the hole expansion core mold is conical and connected to the vertical rod. The hole expansion core mold rotates and moves downward with the vertical rod. While the hole expansion is completed, the vertical rod enters the center hole of the forging blank and then starts ring rolling.

8. Application of the ultrafine-grained, micro-deformed, high-hardness bainite wind turbine main shaft bearing material according to claim 1 in ring forgings for wind turbine main shaft bearings.

9. Application of the ring forging for wind turbine main shaft bearing obtained by the manufacturing process according to any one of claims 3 to 7 in the main shaft bearing of a high-power wind turbine unit above 8MW.

10. A main shaft bearing ring of a high-power wind turbine with a capacity of 8 MW or more, prepared by the manufacturing process according to any one of claims 3 to 7, wherein the main shaft bearing ring is a lower bainite structure.

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