A production method of a gear ring forging for wind power

Abstract

The application discloses a production method of a gear ring forge piece for wind power, which takes a continuous casting round billet of 42CrMo as a blank, sequentially comprises a forging process and a normalizing treatment process after forging, and the forging process comprises upsetting, punching, trimming forming, mandrel hole expanding and ring rolling steps; and the element composition of the continuous casting round billet is limited. The large-diameter continuous casting round billet is used as the forging blank of the large wind power gear ring, the lower limit values of main elements C, Si, Mn, Cr and Mo are improved, the upper limit values of elements such as P and S are reduced to a certain extent, the element segregation in the alloy is reduced, the as-cast structure of the continuous casting round billet is easy to be broken and internal defects are easy to be forged, and the weight percentage of Al and Ti in the continuous casting round billet is preferably selected to help refining grains, reducing dendritic segregation, improving the compactness of the material and the strength of the gear ring product in the forging and normalizing processes.

Description

Technical Field

[0001] This invention relates to the field of gear ring forging technology, and specifically to a method for producing gear ring forgings for wind power applications. Background Technology

[0002] The function of the large internal gear ring in wind turbines includes not only transmitting power but also changing the rotational speed and direction of rotation. The performance requirements for the internal gear ring include: a dense material structure with excellent wear resistance, fatigue strength, and low-temperature impact toughness.

[0003] In traditional wind turbine gear ring production, ingot-cast steel billets are used as raw materials. Ingot-cast steel ingots meet the high density requirements of large-scale production and provide high yield strength and impact energy. However, their drawback is that the larger the ingot, the greater the difference in raw material composition between the riser end and the gate end, such as a large difference in carbon weight percentage. After forging and post-forging heat treatment, the difference in raw material composition ultimately leads to localized hardness differences in the flange product. Generally, the hardness and wear resistance of metallic materials are positively correlated. Replacing ingot-cast steel billets with continuously cast round billets faces the following obstacles: the solidification mode of continuously cast round billets makes them prone to internal defects such as center segregation, porosity, and shrinkage cavities, which affect the performance of forgings. This is especially true for large-sized continuously cast round billets with a length approximately twice the diameter. The larger the ingot, the more severe the defects, and the more difficult it is to improve them during forging, thus increasing the difficulty of forging.

[0004] The raw material for the gear ring forging is designated as 42CrMo. CN114289675A discloses a manufacturing method for gear ring forgings with similar elemental compositions used in wind turbine gearboxes. The method specifies a forging ratio of upsetting to drawing of not less than 1:2 and not more than 2.5:1. Using this method in continuously cast billets can lead to excessive deformation of the forgings, resulting in the loss of some inherent mechanical properties, such as low-temperature toughness. Furthermore, the cooling method for normalizing is air cooling. Although the cooling rate is not specified, forced air cooling can cause differences in the microstructure distribution within the gear ring, thus adversely affecting the average austenite grain size. Summary of the Invention

[0005] One of the objectives of this invention is to overcome the defects in the prior art and provide a method for producing wind turbine gear ring forgings. The method uses continuously cast round billets as forging blanks, and by controlling element segregation, the as-cast structure is easily broken up, internal defects are easily forged together, and the elemental composition of the round billet is conducive to the refinement of the gear ring grains.

[0006] To achieve the above-mentioned technical effects, the technical solution of the present invention is as follows: a production method of a wind power gear ring forging, using a 42CrMo continuously cast round billet as the billet, and sequentially including a forging process and a post-forging normalizing process, wherein the forging process includes upsetting, punching, finishing and shaping, reaming, and ring rolling steps. The elemental composition of the continuously cast round billet, by weight percentage, is as follows: C: 0.42%~0.45%, Si: 0.25%~0.35%, Mn: 0.8%~0.9%, Cr: 1.1%~1.2%, Mo: 0.2%~0.25%, Al: 0.02%~0.04%, P: ≤0.02%, S: ≤0.015%, Cu: ≤0.2%, H: ≤2ppm, O: ≤20ppm, Ti: ≤80ppm, Ca: ≤10ppm, As+Sn+Pb+Sb+Bi: ≤0.035%, Sn: ≤100ppm, Pb: ≤100ppm, Bi: ≤100ppm, Sb: ≤30ppm, As: ≤150ppm, balance Fe.

[0007] The preferred technical solution is that the forging steps include N alternating upsetting and N+1 drawing operations; where N is 3 or 4. Taking the ratio of the forging length before and after upsetting as the single upsetting forging ratio, the sum of the upsetting forging ratios for N upsetting operations is 6.2 to 7.1. Further, the sum of the upsetting forging ratios for N upsetting operations is 6.5 to 7.0. The sum of the upsetting forging ratios for N upsetting operations is also called the total upsetting forging ratio.

[0008] Specifically, the sum of the upsetting forging ratios for N upsetting operations are 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, and 7.1, as well as the range with the above two values ​​as the maximum and minimum values.

[0009] A preferred technical solution is that the punching step involves punching a hole in the center of the blank, with the ratio of the hole diameter to the radial diameter of the blank being (0.26–0.34):1. Further, the ratio of the hole diameter to the radial diameter of the blank is (0.28–0.32):1. Specifically, the ratio of the hole diameter to the radial diameter of the blank is defined as 0.26:1, 0.27:1, 0.28:1, 0.29:1, 0.30:1, 0.31:1, 0.32:1, 0.33:1, 0.34:1, and the range between these two values ​​as the maximum and minimum values.

[0010] The preferred technical solution is that N is 4; The upsetting forging ratio for the first upsetting is 1.63 to 1.86; The upsetting forging ratio for the second upsetting is 1.58 to 1.82; The upsetting forging ratio for the third upsetting is 1.48 to 1.71; The upsetting forging ratio for the fourth upsetting is 1.71 to 1.95.

[0011] Furthermore, the upsetting forging ratio for the first upsetting is 1.69–1.79; the upsetting forging ratio for the second upsetting is 1.65–1.75; the upsetting forging ratio for the third upsetting is 1.55–1.65; and the upsetting forging ratio for the fourth upsetting is 1.77–1.86.

[0012] The preferred technical solution is to use the ratio of the forging length before and after drawing as the single-drawing forging ratio. The drawing-out forging ratio for the first drawing stage is 0.65–0.89; The drawing-out forging ratio for the second drawing stage is 0.51–0.75; The elongation forging ratio for the third time was 0.55 to 0.79.

[0013] Furthermore, the drawing-forging ratio for the first drawing is 0.71–0.80; the drawing-forging ratio for the second drawing is 0.58–0.66; and the drawing-forging ratio for the third drawing is 0.62–0.70.

[0014] A preferred embodiment is that the diameter of the blank is 860–940 mm; the inner diameter of the gear ring is 2000–2350 mm, and the difference between the inner and outer diameters is 410–460 mm. Further, the diameter of the blank is 880–920 mm; the inner diameter of the gear ring is 2150–2320 mm, and the difference between the inner and outer diameters is 410–445 mm.

[0015] The preferred technical solution is that the forging temperature in the forging process is 1220-850℃, and the forging process adopts three-stage forging, with heating times before the upsetting and drawing step, between the finishing and shaping and the reaming step, and between the reaming and rolling step.

[0016] A preferred technical solution is that the normalizing treatment includes: After the forgings are loaded into the furnace, the temperature is raised to 900±20℃. The holding time is determined according to the effective thickness of 0.7~1.0h / 25mm. After the first stage of air cooling to 700±40℃, the forgings are transferred to furnace cooling for a period of not less than 6 hours to 620±40℃. Then the forgings are transferred to the second stage of air cooling.

[0017] Furthermore, after the forgings are loaded into the furnace, they are heated to 900±10℃. The holding time is determined according to the effective thickness of 0.7~1.0h / 25mm. After the first stage of air cooling to 700±30℃, they are transferred to furnace cooling for a period of not less than 6 hours to 620±20℃, and then transferred to the second stage of air cooling.

[0018] The preferred technical solution is that the ratio of the outer diameter of the blank before and after the expansion hole of the lever is 1:(2.07~2.2), and the ratio of the inner diameter is 1:(1.92~2.15).

[0019] Furthermore, the ratio of the outer diameter of the blank before and after the expansion of the lever is 1:(2.09~2.16), and the ratio of the inner diameter is 1:(1.97~2.08).

[0020] Specifically, the ratio of the outer diameter of the blank before and after reaming the lever is 1:2.07, 1:2.1, 1:2.13, 1:2.15, 1:2.17, 1:2.19, and 1:2.2, along with the range where the above two values ​​are the maximum and minimum values. The ratio of the inner diameter of the blank before and after reaming the lever is 1:1.92, 1:1.95, 1:1.97, 1:2, 1:2.03, 1:2.05, 1:2.07, 1:2.1, 1:2.12, and 1:2.15, along with the range where the above two values ​​are the maximum and minimum values.

[0021] The preferred technical solution is that the heat treatment and holding time between the reaming and ring rolling steps is 3 to 5 hours, and the forging is heated to 1140 to 1190°C; further, it is 4 to 5 hours; and even further, the heat treatment between the reaming and ring rolling steps is heated to 1150 to 1180°C.

[0022] The advantages and beneficial effects of this invention are as follows: The large wind turbine gearbox gear ring uses a large-diameter continuously cast round billet as the forging billet. In addition to limiting the weight percentage of Cu, H, O, Ca and the six conventional residual elements, as well as the sum of their weight percentages, the lower limit values ​​of the main elements C, Si, Mn, Cr and Mo are increased, and the upper limit values ​​of elements such as P and S are reduced to a certain extent. This reduces element segregation in the alloy, making the as-cast structure of the continuously cast round billet easier to break and the internal defects easier to forge together. Determining the content of Al and Ti, and selecting the optimal weight percentage of Al and Ti in continuously cast round billets, helps to refine grains, reduce dendrite segregation, improve the density of materials, and enhance the strength of gear ring products during forging and normalizing processes. Attached Figure Description

[0023] Figure 1 This is a 100x magnified tissue photograph of the gear ring of the wind turbine gearbox in Example 1. Detailed Implementation

[0024] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0025] Continuous casting round billet Compared to ingot casting, continuous casting is more conducive to narrowing the content range of various elements in the billet, thereby reducing element segregation in the alloy material. Based on the optimized continuous casting round billet, the optimal upsetting and drawing ratio breaks down the as-cast structure far from the center of the billet and generates a forged structure, fully forging internal defects far from the center of the billet, reducing the impact of internal defects such as center segregation, porosity, and shrinkage cavities on the grain size, microstructure distribution, and density of the final product.

[0026] Furthermore, based on the known product dimensions and specifications, a continuously cast round billet of a predetermined size is selected. Compared with ingot casting, continuously cast round billets have a higher material utilization rate as forging blanks, which helps to reduce production costs.

[0027] Forging ratio and center punch size Upsetting and drawing eliminate casting defects and form fibrous structures.

[0028] Based on the predetermined composition and size of the continuously cast round billet, the optimized sum of forging ratios, along with further upsetting and drawing ratios, concentrates internal defects such as center segregation, porosity, and shrinkage cavities at the center of the forging, which can be effectively removed by center punching. If the center punch size is too large, it increases material waste; if it is too small, defects are likely to remain at the punch edge, increasing the likelihood that the mechanical properties of the inner radial layer of the gear ring are inferior to those of the outer layer.

[0029] For forgings of the same size, the size of the center hole in a continuously cast billet is larger than that in a die-cast billet, in order to ensure that center defects are fully removed.

[0030] After upsetting and drawing, the circumferential surface of the blank surrounding the central punch hole is an arc surface, and the diameter of the blank in the radial direction of the hole is the maximum diameter of the arc surface in the radial direction of the central punch hole.

[0031] Expanding the hole in the mast After upsetting and drawing, the process moves to the reaming step to ensure sufficient plastic deformation in the core of the forging, improve the forging penetration of the entire cross section, and facilitate the obtaining of a uniformly distributed forged microstructure.

[0032] The third heating and heat preservation To avoid the formation of tiny holes and cracks on the inner surface of the gear ring, which would further degrade the mechanical strength of subsequent gear insertion, the optimal holding time and temperature for the third firing stage are selected.

[0033] Zheng Huo Based on production requirements, the gear ring is only subjected to normalizing treatment. The cooling after normalizing adopts the cooling method of air cooling + furnace cooling + air cooling, which is conducive to obtaining equiaxed fine and uniform grains of 42CrMo, reducing the internal stress of the forging, and thus ensuring the stability of the gear ring flaw detection results. Example

[0034] Example 1

[0035] Material grade: 42CrMo; Material specifications: Xingcheng Φ900 continuous casting billet; Material weight: 11345kg; The chemical composition is specified for continuous casting according to the following element weight percentages: C: 0.42%~0.45%, Si: 0.25%~0.35%, Mn: 0.8%~0.9%, Cr: 1.1%~1.2%, Mo: 0.2%~0.25%, Al: 0.02%~0.04%, P: ≤0.02%, S: ≤0.015%, Cu: ≤0.2%, H: ≤2ppm, O: ≤20ppm, Ti: ≤80ppm, Ca: ≤10ppm, As+Sn+Pb+Sb+Bi: ≤0.035%, Sn: ≤100ppm, Pb: ≤100ppm, Bi: ≤100ppm, Sb: ≤30ppm, As: ≤150ppm, with the balance being Fe.

[0036] Specifically: C: 0.42%, Si: 0.29%, Mn: 0.83%, Cr: 1.14%, Mo: 0.2%, Al: 0.031%, P: 0.013%, S: 0.001%, Cu: 0.02%, Ni: 0.03%, H: 0.5ppm, O: 11.3ppm, Ti: 22ppm, Ca: 3ppm, Sn: 11ppm, Pb: 10ppm, Bi: 10ppm, Sb: 10ppm, As: 42ppm, with the balance being Fe.

[0037] The production method of wind turbine gear ring forgings includes the following steps: S1: The first heating is brought to a maximum temperature of 1220℃; S2: A round billet with a diameter of 900 mm and a length of approximately 2270 mm is subjected to a four-upsetting and three-drawing operation. First, it is upset to 1300±15 mm, then drawn to 1700±15 mm, then upset to 1000±15 mm, then drawn to 1600±15 mm, then upset to 1000±15 mm, then drawn to 1500±15 mm, and finally upset to 820±15 mm. S3: Center punch hole Φ465mm; S4: Trimming and shaping; S5: The second heating is carried out to a maximum temperature of 1220°C; S6: Using a hydraulic press and lever, supplemented by a manipulator, to enlarge the hole, the size after enlarging and leveling is Φ(1750±50)*Φ(950±50)*820; S7: The third heating is carried out to 1650℃, and the holding time is 4 hours; S8: The forging is rolled to the following dimensions using a ring rolling mill: outer diameter: 2730±15mm, inner diameter: 2275±15mm, length: 767±15mm; S9: Normalizing: After the forging is loaded into the furnace, the temperature is raised to 900±10℃. The holding time is determined according to the effective thickness of 0.7~1.0h / 25mm. After the first stage of air cooling to 700±30℃, it is transferred to furnace cooling for 6 hours to 620±20℃, and then transferred to the second stage of air cooling.

[0038] The performance test results for Example 1 are as follows: 1. For the testing of non-metallic inclusions using ISO 4967 standard method A, the inclusion levels should meet the following requirements: fine series A / B / C / D: 0.5 / 0.5 / 0.0 / 1.0; coarse series A / B / C / D: 0.0 / 0.0 / 0.0 / 0.5. 2. Low magnification: Central porosity 1, shrinkage pores 0, central cracks 0, intermediate cracks 0, subcutaneous cracks 0, subcutaneous bubbles 0; 3. The austenite grain size was tested according to DIN EN ISO 643, and the average austenite grain size reached 6.5 in 90% of the test area.

[0039] 4. Metallographic structure evaluated according to GB / T13320 standard: Pearlite grade 3 + small amount of ferrite, such as... Figure 1 As shown; 5. Sampling location: 1 / 2 radius. The banded structure should be inspected under equilibrium microstructure conditions. Recommended heat treatment temperature: 920℃, hold for 30 minutes, air cool to 650℃, hold for 60 minutes, then air cool. Evaluation and testing should be carried out according to GB / T 34474.1 standard. The delivered condition for the toothed ring should have a banded structure of 1.0.

[0040] 6. Hardness is tested according to ISO 6506-2014 standard, and the delivered hardness is 189-196HB; 7. The test specimens were produced using the same process as the forgings. The holding time in the normalizing process parameters of the test specimens was a predetermined multiple of the effective thickness, which was consistent with the normalizing holding time of the gear ring. Tensile mechanical properties of the test specimen (size Φ10.02mm): maximum force (Fm) 96.1kN, tensile strength (Rm) 1219MPa, specified plastic elongation (Fp) 87.311kN, specified plastic elongation (Rp0.2) 1107MPa, elongation after fracture (A) 14%, reduction of area (Z) 51%, impact 1: 41J, impact 2: 45J, impact 3: 46J.

[0041] 8. The hardenability of the gear ring was tested according to ISO 642 standard (end quenching temperature 850±5℃): the hardness at 1.5mm from the quenched end was 60.5HRC, the hardness at 5mm from the quenched end was 56.5HRC, and the hardness at 25mm from the quenched end was 53HRC. 9. Perform ultrasonic testing according to QJ / NGC 70011.2 standard. The area within 1.5 times the tooth height of the tooth is grade 1, and the remaining areas are grade 2.

[0042] Example 2

[0043] 42CrMo die-cast steel ingots were used as raw materials. The sample was produced using the same process as the example. The elements of the die-cast steel ingots are as follows: C: 0.395%, Si: 0.25%, Mn: 0.73%, Cr: 1.14%, Mo: 0.2%, Al: 0.031%, P: 0.014%, S: 0.002%, Cu: 0.05%, Ni: 0.1 5%, H: 0.83ppm, O: 10ppm, Ti: 16ppm, Ca: 1ppm, Sn: 45ppm, Pb: 8ppm, Bi: 2ppm, Sb: 17ppm, As: 57ppm, the balance is Fe.

[0044] Mechanical properties of the specimen: tensile strength (Rm) 1203MPa, specified plastic elongation strength (Rp0.2) 1114MPa, elongation after fracture (A) 14%, reduction of area (Z) 51%, impact 1 42J, impact 2 44.5J, impact 3 45J.

[0045] Hardenability: The hardenability of the gear ring was tested according to ISO 642 standard (end quenching temperature 850±5℃): the hardness at 1.5mm from the quenched end was 57.5HRC, the hardness at 5mm from the quenched end was 57HRC, and the hardness at 25mm from the quenched end was 49.5HRC.

[0046] The mechanical properties of the gear ring in Example 2 are comparable to those of the gear ring in Example 1, but the hardenability is slightly worse. This indicates that using continuously cast billets as raw materials is more conducive to obtaining uniform mechanical properties across the entire cross-section of the steel part.

[0047] Example 2: The molded steel ingot needs to have the predetermined sprue and riser removed to reduce element segregation, and the raw material utilization rate is lower than that of the continuously cast round billet.

[0048] Example 3

[0049] Example 3 is based on Example 1, except that the normalizing cooling method of S9 is slow air cooling, which reduces the air cooling time by about 2 hours compared with the furnace cooling section of Example 1. Upon testing, a small amount of granular bainite was found in the metallographic structure of the sample, which affected the uniformity of the structure.

[0050] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing a forged gear ring for wind power applications, characterized in that, Using 42CrMo continuously cast round billet as the billet, the process includes a forging process and a normalizing process after forging. The forging process includes upsetting, punching, finishing and shaping, reaming with a lever, and rolling. The elemental composition of the continuously cast round billet, by weight percentage, is as follows: C: 0.42%–0.45%, Si: 0.25%–0.35%, Mn: 0.8%–0.9%, Cr: 1.1%–1.2%, Mo: 0.2%–0.25%, Al: 0.02%–0.04%, P: ≤0.02%, S: ≤0.015%, Cu: ≤0.2%, H: ≤2ppm, O: ≤20ppm, Ti: ≤80ppm, Ca: ≤10ppm, As+Sn+Pb+Sb+Bi: ≤0.035%, Sn: ≤100ppm, Pb: ≤100ppm, Bi: ≤100ppm, Sb: ≤30ppm, As: ≤150ppm, balance Fe; The forging process includes four alternating upsetting and three drawing operations; the punching process involves punching a hole in the center of the blank, with the ratio of the hole diameter to the blank diameter in the radial direction being (0.26–0.34):

1. Taking the ratio of the length of the forging before and after upsetting as the single upsetting forging ratio, the upsetting forging ratio of the first upsetting is 1.63 to 1.86; The upsetting forging ratio for the second upsetting is 1.58 to 1.82; The upsetting forging ratio for the third upsetting is 1.48 to 1.71; The upsetting forging ratio for the fourth upsetting is 1.71 to 1.95; The forging ratio for a single drawing is calculated as the ratio of the length of the forging before and after drawing. The drawing ratio for the first drawing is 0.65 to 0.

89. The drawing-out forging ratio for the second drawing stage is 0.51–0.75; The elongation forging ratio for the third time was 0.55–0.79; The diameter of the blank is 860-940mm; the inner diameter of the gear ring is 2000-2350mm, and the difference between the inner diameter and the outer diameter is 410-460mm. The ratio of the outer diameter of the blank before and after the reaming of the lever is 1:(2.07~2.2), and the ratio of the inner diameter is 1:(1.92~2.17); The normalizing process includes: Normalizing: After the forging is loaded into the furnace, the temperature is raised to 900±20℃. The holding time is determined according to the effective thickness of 0.7~1.0h / 25mm. After the first stage of air cooling to 700±40℃, it is transferred to furnace cooling. The furnace cooling time is not less than 6h to 620±40℃, and then the second stage of air cooling is transferred.

2. The method for producing wind turbine gear ring forgings according to claim 1, characterized in that, The sum of the upsetting forging ratios for the four upsetting processes is 6.2 to 7.

1.

3. The method for producing wind turbine gear ring forgings according to claim 1, characterized in that, The forging temperature in the forging process is 1220-850℃. The forging process adopts three-stage forging, with heating times before the upsetting and drawing step, between the finishing and shaping step and the reaming step, and between the reaming step and the rolling step.

4. The method for producing wind turbine gear ring forgings according to claim 3, characterized in that, The reheating and holding time between the reaming and ring rolling steps is 3-5 hours, and the forging is heated to 1140-1190℃.

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