Preparation method of gh4730 alloy shaft forgings and shaft forgings

Abstract

This invention relates to the field of alloy processing technology, and in particular to a method for preparing GH4730 alloy shaft forgings and the shaft forgings themselves. Specifically, it includes: (a) hot extruding GH4730 alloy bars at 1100~1190℃ to obtain shaft forgings; during hot extrusion, the extrusion ratio is 1:(4~6), and the extrusion rate is 5~20s. ‑1 (b) The shaft forging is subjected to solution treatment and aging treatment; the GH4730 alloy contains 0.005%~0.018% C, 0.003%~0.01% P, and 0.005%~0.05% Cu by mass percentage. This invention adjusts the content of specific elements C, P, and Cu in the GH4730 alloy, which not only effectively improves the hot working performance of the GH4730 alloy, but also significantly enhances the creep and fatigue resistance of the prepared GH4730 alloy shaft forging at 750℃, thus meeting higher service performance requirements.

Description

Technical Field

[0001] This invention relates to the field of alloy processing technology, and in particular to a method for preparing GH4730 alloy shaft forgings and the shaft forgings themselves. Background Technology

[0002] The turbine shaft is a core rotating component of an aero-engine, playing a crucial role in converting the rotational kinetic energy of the turbine blades into mechanical energy. This drives the compressor blades to continuously pressurize the intake air, ensuring stable and efficient engine operation. GH4730 alloy is a new type of nickel-based wrought high-temperature alloy with a maximum service temperature of 750℃. It not only possesses excellent high-temperature strength but also meets stringent service requirements such as fatigue resistance and creep resistance, making it an ideal material for manufacturing high-performance shaft forgings such as aero-engine turbine shafts.

[0003] Hot extrusion technology is mainly used to manufacture long parts with ordinary constant cross-sections of high-temperature alloys. It can effectively ensure that long parts achieve high dimensional accuracy and surface quality, thereby achieving near-net-shape forming. The hot extrusion process places stringent requirements on the thermoplasticity of high-temperature alloys. Controlling the uniformity of microstructure from the core to the outer edge and from the head to the tail of the shaft forging is a key challenge in the extrusion process.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing GH4730 alloy shaft forgings and the shaft forgings themselves. By combining the processing characteristics of shaft forgings and adjusting the content of specific elements in GH4730 alloy, the hot deformation capability of GH4730 alloy is effectively improved, thereby ensuring the formability of shaft forgings. Furthermore, the creep and fatigue resistance of the prepared GH4730 alloy shaft forgings at 750°C are significantly improved, which can meet higher service performance requirements.

[0006] To achieve the above-mentioned objectives of the present invention, a first aspect of the present invention provides a method for preparing a GH4730 alloy shaft forging, comprising the following steps:

[0007] (a) GH4730 alloy bars are hot-extruded at 1100~1190℃ to obtain shaft forgings; in the hot extrusion, the extrusion ratio is 1:(4~6) and the extrusion rate is 5~20s. -1 ;

[0008] (b) The shaft forging is subjected to solution treatment and aging treatment;

[0009] In the GH4730 alloy, the content of C is 0.005%~0.018% by mass percentage, the content of P is 0.003%~0.01% and the content of Cu is 0.005%~0.05%.

[0010] In a specific embodiment of the present invention, the Mn content in the GH4730 alloy is 0.001% to 0.15% by mass percentage.

[0011] In a specific embodiment of the present invention, during the hot extrusion, the front end of the bar is processed to form a conical surface, and the cone angle of the conical surface is 90°~120°.

[0012] In a specific embodiment of the present invention, during the hot extrusion, the extrusion cylinder is preheated to a temperature not lower than 400°C.

[0013] In a specific embodiment of the present invention, the solution treatment is performed at a temperature of 1070~1110℃ for 1~8h; the aging treatment is performed at a temperature of 850~870℃ for 4~18h.

[0014] In a specific embodiment of the present invention, step (a) includes the following method for preparing the GH4730 alloy bar: after homogenizing the GH4730 alloy ingot, upsetting and drawing it along the axial direction to obtain a bar blank; and then forging the bar blank to obtain the GH4730 alloy bar.

[0015] The second aspect of the present invention provides a GH4730 alloy shaft forging, which is prepared by any of the methods for preparing GH4730 alloy shaft forgings described in the first aspect of the present invention.

[0016] In a specific embodiment of the present invention, the average grain size of the GH4730 alloy shaft forging is not lower than ASTM grade 6, and the grain size difference between each part does not exceed 2 grades.

[0017] In a specific embodiment of the present invention, the GH4730 alloy shaft forging has a creep rupture life of not less than 50 hours under conditions of 750°C and 600MPa.

[0018] In a specific embodiment of the present invention, the fatigue life of the GH4730 alloy shaft forging under conditions of 750°C and α=0~0.6% is not less than 20,000 cycles.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] This invention, by combining the processing characteristics of shaft forgings and adjusting the content of specific elements C, P, and Cu in GH4730 alloy, effectively improves the hot deformation capability of GH4730 alloy, thereby ensuring the formability of shaft forgings. At the same time, by rationally controlling the distribution of crystallizing elements, the high-temperature creep life and fatigue resistance of the prepared GH4730 alloy shaft forgings are significantly improved, which can meet higher service performance requirements. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0022] The first aspect of this invention provides a method for preparing GH4730 alloy shaft forgings, comprising the following steps:

[0023] (a) GH4730 alloy bars are hot-extruded at 1100~1190℃ to obtain shaft forgings; in the hot extrusion, the extrusion ratio is 1:(4~6) and the extrusion rate is 5~20s. -1 ;

[0024] (b) The shaft forging is subjected to solution treatment and aging treatment;

[0025] In the GH4730 alloy, the content of C is 0.005%~0.018% by mass percentage, the content of P is 0.003%~0.01% and the content of Cu is 0.005%~0.05%.

[0026] This invention, by combining the processing characteristics of shaft forgings and adjusting the content of specific elements C, P, and Cu in GH4730 alloy, not only effectively improves the hot deformation capability of GH4730 alloy, thus ensuring the formability of shaft forgings, but also rationally controls the distribution of grain boundary elements, significantly improving the creep life and fatigue life of the prepared GH4730 alloy shaft forgings at 750℃, which can meet higher service performance requirements.

[0027] In some specific embodiments, the carbon content in the GH4730 alloy, by mass percentage, is 0.005% to 0.018%, specifically within the range of 0.005%, 0.008%, 0.01%, 0.012%, 0.015%, 0.018%, or any combination thereof. Adjusting the carbon content within this range ensures that the shaft forging has excellent high-temperature strength, while simultaneously promoting dynamic recrystallization of the alloy to enhance its hot deformation capability.

[0028] In some specific embodiments, the phosphorus (P) content in the GH4730 alloy, by mass percentage, is 0.003% to 0.01%, specifically within the range of 0.003%, 0.005%, 0.006%, 0.008%, 0.01%, or any combination thereof. Adjusting the P content within this range ensures that the shaft forgings possess both excellent thermoplasticity and high grain boundary strength and creep rupture life.

[0029] In some specific embodiments, the Cu content in the GH4730 alloy, by mass percentage, is 0.005% to 0.05%, specifically within the range of 0.005%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, or any combination thereof. Adjusting the Cu content within this range can effectively improve the high-temperature plasticity and fatigue strength of the shaft forging.

[0030] In some specific embodiments, the Mn content in the GH4730 alloy is 0.001% to 0.15% by mass percentage, specifically 0.001%, 0.003%, 0.005%, 0.008%, 0.01%, 0.012%, 0.015%, or any combination thereof.

[0031] In practice, apart from C, P, Cu, and Mn, the other elements can refer to the existing GH4730 alloy. For example, in some embodiments, the GH4730 alloy, by mass percentage, includes: C 0.005%~0.018%, P 0.003%~0.01%, Cu 0.005%~0.05%, Mo 2.5%~3.5%, W 2.3%~3.3%, Fe 3.5%~5.0%, Co 8%~10%, Cr 15%~17%, Zr 0.01%~0.05%, Ti 3.2%~3.8%, Al 2%~2.6%, Nb 0.8%~1.4%, B 0.005%~0.025%, Mn 0.001%~0.15%, N≤0.002%, O≤0.002%, S≤0.0005%, with the balance being Ni.

[0032] In some embodiments, in step (a), the hot extrusion temperature can be 1100~1190℃, specifically 1100℃, 1110℃, 1120℃, 1130℃, 1140℃, 1150℃, 1160℃, 1170℃, 1180℃, 1190℃, or any combination thereof. Controlling the temperature within the above range ensures both uniform microstructure of the forging during extrusion and effective grain refinement.

[0033] In some embodiments, in step (a), the hot extrusion ratio is 1:(4~6), specifically a range of 1:4, 1:4.5, 1:5, 1:5.5, 1:6, or any combination thereof. Adjusting the hot extrusion ratio within the above range can effectively achieve synergistic control of the forging composition and uniform microstructure.

[0034] In some embodiments, in step (a), the hot extrusion rate is 5~20s. -1 Specifically, it can be 5s -1 8s -1 10s -1 12s -1 15s -1 18s -1 20s -1 Or a range consisting of any two of these. By controlling the hot extrusion rate within the above range, and by adjusting the C and P element content, the forging structure can fully complete dynamic recrystallization, achieving uniform fine-grained structure control.

[0035] In some embodiments, during hot extrusion, the front end of the bar is machined into a conical surface with a cone angle of 90° to 120°, specifically 90°, 95°, 100°, 105°, 110°, 115°, 120°, or any combination thereof. The diameter difference between the small end and the large end (i.e., the bar body) of the conical surface is 50 to 100 mm (e.g., 80 mm, but not limited thereto); the distance between the small end and the large end of the conical surface along the axial direction of the bar is 10 to 50 mm (e.g., 30 mm, but not limited thereto).

[0036] In some embodiments, hot extrusion involves preheating the extrusion cylinder to a temperature not lower than 400°C, specifically within the range of 400°C, 450°C, 500°C, 550°C, 600°C, or any combination thereof. Further, during hot extrusion, a high-temperature lubricating coating is applied to the inner wall of the extrusion cylinder, and an anti-oxidation coating is applied to the surface of the bar stock to be extruded. Both the high-temperature lubricating coating and the anti-oxidation coating are conventional commercially available products used in high-temperature alloy hot extrusion processes and can be adjusted according to actual needs; therefore, they will not be elaborated upon here.

[0037] In practice, hot extrusion can be carried out on an extrusion press, including but not limited to 20,000~80,000t extrusion presses.

[0038] In some embodiments, in step (b), during the solution treatment, the holding temperature is 1070~1110℃, specifically 1070℃, 1080℃, 1090℃, 1100℃ or any combination thereof; the holding time is 1~8h, specifically 1h, 2h, 4h, 5h, 6h or 8h.

[0039] In some embodiments, the solution treatment includes: placing the shaft forging in a furnace at 300-500°C, then heating it to a holding temperature at a heating rate of 5-10°C / min, and then air-cooling or oil-cooling it to room temperature. In other embodiments, the shaft forging may be placed in a furnace at a temperature range of 300°C, 350°C, 400°C, 450°C, 500°C, or any combination thereof, and then heated to a holding temperature at a heating rate range of 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, or any combination thereof.

[0040] In some implementations, in step (b), during the aging process, the heat preservation temperature is 850~870℃, specifically 850℃, 855℃, 860℃, 865℃, 870℃ or any combination thereof; the heat preservation time is 4~18h, specifically 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h or any combination thereof.

[0041] In some embodiments, the aging treatment includes: placing the shaft forging in a furnace at 100~300°C, then heating it to the holding temperature at a heating rate of 2~5°C / min for holding treatment, and then air-cooling or oil-cooling to room temperature. In other embodiments, the shaft forging may be placed in a furnace at a temperature range of 100°C, 150°C, 200°C, 250°C, 300°C, or any combination thereof, and then heated to the holding temperature at a heating rate range of 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min, 4°C / min, 4.5°C / min, 5°C / min, or any combination thereof for holding treatment.

[0042] In some embodiments, step (a) of the preparation method of GH4730 alloy bar includes: homogenizing GH4730 alloy ingot, upsetting and drawing it along the axial direction to obtain a bar blank; and forging the bar blank to obtain GH4730 alloy bar.

[0043] In some embodiments, the homogenization treatment includes: holding the GH4730 alloy ingot at 1120~1210℃ for 70~130h, then cooling it in the furnace to below 500℃ before removing it from the furnace, and then air-cooling it to room temperature. Further, the 70~130h holding at 1120~1210℃ includes: holding at 1120~1140℃ for 30~50h, then raising the temperature to 1150~1170℃ and holding for 20~40h, and then raising the temperature to 1180~1210℃ and holding for 20~40h. Through multi-stage homogenization diffusion annealing under the above conditions, the segregation degree of various elements can be significantly reduced, controlling the segregation coefficient to 0.8~1.2, thus laying a good foundation for subsequent hot working and optimization of the final microstructure and properties.

[0044] In some embodiments, the upsetting and drawing temperature can be between 1110 and 1160°C, specifically within the ranges of 1110°C, 1120°C, 1130°C, 1140°C, 1150°C, 1160°C, or any combination thereof. Maintaining the temperature within this range is more conducive to balancing the uniformity of the microstructure and the grain size during the upsetting and drawing process. If the upsetting and drawing temperature is too low, the material's plasticity is low, its deformation resistance increases, and it is prone to forging cracks or uneven microstructure; if the upsetting and drawing temperature is too high, it will cause excessive grain growth and microstructure coarsening.

[0045] In some embodiments, during the upset drawing process, the single deformation amount for both upsetting and drawing is independently 30% to 60%, specifically within the range of 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any combination thereof. Furthermore, the final forging temperature during upset drawing is not lower than 1000℃. If the single deformation amount is too low, the upset drawing process cannot adequately break up the as-cast structure, resulting in incomplete dynamic recrystallization and potentially leading to uneven microstructure, affecting subsequent processing. If the single deformation amount is too high, it may cause excessively high local temperature rise, overheating of the microstructure, or an increased risk of cracking, which is detrimental to process stability and forging quality consistency.

[0046] In practice, upsetting and drawing of billets can be carried out on high-speed forging machines, including but not limited to 4000~10000t high-speed forging machines.

[0047] In some implementations, the total number of upsetting and drawing operations during the upsetting and drawing process is 5 to 7 times, specifically 5, 6 or 7 times.

[0048] In some embodiments, the diameter of the bar blank is 200 to 400 mm, specifically 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, or any combination thereof.

[0049] In some embodiments, the forging temperature is 1110~1160℃, specifically a range of 1110℃, 1120℃, 1130℃, 1140℃, 1150℃, 1160℃, or any combination thereof. Maintaining the temperature within this range is beneficial for achieving uniform and refined microstructure and ensuring the overall performance of the forgings.

[0050] In some embodiments, the total deformation of radial forging is 10% to 30%, specifically 10%, 15%, 20%, 25%, 30%, or any combination thereof. If the total deformation of radial forging is too low, it is difficult to sufficiently refine the grains and eliminate structural defects; if the deformation is too high, it may lead to abnormal grain growth or the formation of microcracks.

[0051] In some embodiments, the final forging temperature of radial forging is not lower than 1000°C.

[0052] In some embodiments, the diameter of the bar is 150 to 350 mm, specifically a range of 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, or any combination thereof.

[0053] In some implementations, the average grain size of the bar is finer than ASTM grade 4, and the grain size difference between different portions does not exceed 2 grades.

[0054] In some embodiments, the GH4730 alloy ingot has a diameter of 406~508mm and a length of 1000~2000mm.

[0055] In some embodiments, the preparation method of GH4730 alloy ingots includes at least one of two-stage smelting and three-stage smelting. Two-stage smelting includes vacuum induction melting (VIM) and vacuum arc remelting (VAR), while three-stage smelting includes VIM, protective atmosphere electroslag remelting (ESR), and VAR. Specific preparation parameters for conventional GH4730 alloy ingots can be referred to.

[0056] The second aspect of the present invention provides a GH4730 alloy shaft forging, which is prepared by any of the preparation methods of the GH4730 alloy shaft forging in the first aspect of the present invention.

[0057] In some embodiments, the average grain size of the GH4730 alloy shaft forging is not lower than ASTM grade 6, specifically grade 6, 7, 8, 9, 10 or finer; the grain size difference between each part does not exceed 2 grades, specifically grade 2, grade 1, such as grade 1~2.

[0058] In some embodiments, the GH4730 alloy shaft forging has a creep rupture life of not less than 50 hours under conditions of 750°C and 600MPa, specifically a range of 50 hours, 70 hours, 80 hours, 100 hours, 120 hours, 136 hours, 140 hours, or any combination thereof.

[0059] In some embodiments, the fatigue life of the GH4730 alloy shaft forging at 750°C and α=0~0.6% is not less than 20,000 cycles, specifically a range of 20,000 cycles, 40,000 cycles, 60,000 cycles, 65,000 cycles, 70,000 cycles, 75,000 cycles, 80,000 cycles, or any combination thereof.

[0060] Example 1

[0061] This embodiment provides a method for preparing GH4730 alloy shaft forgings, including the following steps:

[0062] (1) GH4730 alloy ingots were obtained by a three-stage process of vacuum induction melting, protective atmosphere electroslag remelting and vacuum consumable remelting. The ingot size was Φ508mm. The GH4730 alloy included the following components by mass percentage: C 0.011%, P 0.005%, Cu 0.02%, Mo 3.0%, W 2.8%, Fe 4.0%, Co 9.0%, Cr 16.0%, Zr 0.03%, Ti 3.6%, Al 2.3%, Nb 1.1%, B 0.01%, Mn 0.07%, N 0.0009%, O 0.0009%, S 0.0003%, with the balance being Ni.

[0063] (2) Hold the ingot from step (1) at 1130℃ for 40h; then heat it to 1160℃ at a heating rate of 8℃ / min and hold it at 1160℃ for 30h; then heat it to 1195℃ at a heating rate of 8℃ / min and hold it at 1195℃ for 30h; then furnace cool it to 500℃ and take it out of the furnace, cover it with asbestos and air cool it to room temperature.

[0064] (3) The ingot processed in step (2) is upset and drawn 7 times along the axial direction using a 4000t fast forging machine to prepare a billet with a diameter of 300mm. Specifically, after the ingot is kept at 1135℃ for 4h, it is upset and drawn alternately for a total of 7 times. The deformation amount of each upset is 40%, and the deformation amount of each drawing is 40%. The final forging temperature is not lower than 1000℃.

[0065] (4) The billet obtained in step (3) is subjected to radial forging using a 2200t radial forging machine to prepare a bar with a diameter of 300mm; specifically, the billet is kept at 1135℃ for 4h and then subjected to radial forging with a total deformation of 30% on the radial forging machine, and the final forging temperature is not lower than 1000℃.

[0066] (5) The front end of the bar obtained in step (4) is machined into a conical surface with a cone angle of 90°. The bar is hot-extruded using an 80,000t extrusion press to prepare a shaft forging with a diameter of 150mm. Specifically, the extrusion cylinder is preheated to a temperature not lower than 400℃ (e.g., 500℃). Conventional high-temperature lubricating coating is applied to the inner wall of the extrusion cylinder, and conventional anti-oxidation coating is applied to the surface of the extruded billet. After the bar is kept at 1150℃ for 4 hours, it is hot-extruded at an extrusion rate of 10 s. -1 .

[0067] (6) The shaft forging obtained in step (5) is placed in the furnace at 400°C, and then heated to 1080°C at a rate of 8°C / min. After holding at the temperature for 6 hours, it is air-cooled to room temperature.

[0068] (7) The shaft forgings processed in step (6) are placed in a furnace at 200°C, and then heated to 860°C at a rate of 3°C / min. After holding at this temperature for 12 hours, they are air-cooled to room temperature.

[0069] Example 2

[0070] This embodiment provides a method for preparing GH4730 alloy shaft forgings, referring to Embodiment 1, except that the contents of C, P and Cu in the GH4730 alloy are different.

[0071] In this embodiment, the GH4730 alloy has a C content of 0.018%, a P content of 0.01%, and a Cu content of 0.05%.

[0072] Example 3

[0073] This embodiment provides a method for preparing GH4730 alloy shaft forgings, referring to Embodiment 1, except that the contents of C, P and Cu in the GH4730 alloy are different.

[0074] In this embodiment, the GH4730 alloy contains 0.005% C, 0.003% P, and 0.005% Cu.

[0075] Example 4

[0076] This embodiment provides a method for preparing GH4730 alloy shaft forgings. Referring to Embodiment 1, the only difference is that the heat preservation temperature of the bar is different in step (5).

[0077] In step (5) of this embodiment, the insulation temperature of the bar is 1190℃.

[0078] Example 5

[0079] This embodiment provides a method for preparing GH4730 alloy shaft forgings. Referring to Embodiment 1, the only difference is that the heat preservation temperature of the bar is different in step (5).

[0080] In step (5) of this embodiment, the insulation temperature of the bar is 1100℃.

[0081] Example 6

[0082] This embodiment provides a method for preparing GH4730 alloy shaft forgings. Referring to Embodiment 1, the only difference is that the extrusion rate in step (5) is different.

[0083] In step (5) of this embodiment, the extrusion rate is 5s. -1 .

[0084] Example 7

[0085] This embodiment provides a method for preparing GH4730 alloy shaft forgings. Referring to Embodiment 1, the only difference is that the extrusion rate in step (5) is different.

[0086] In step (5) of this embodiment, the extrusion rate is 20s. -1 .

[0087] Comparative Example 1

[0088] Comparative Example 1 follows the same preparation method as Example 1, except that the contents of C, P and Cu in the GH4730 alloy are different.

[0089] In the GH4730 alloy of Comparative Example 1, the C content is 0.02%, the P content is 0.002%, and the Cu content is 0.004%.

[0090] Comparative Example 2

[0091] Comparative Example 2 follows the same preparation method as Example 1, except that the C and P contents in the GH4730 alloy are different.

[0092] In Comparative Example 2, the GH4730 alloy contained 0.004% C and 0.002% P.

[0093] Comparative Example 3

[0094] Comparative Example 3 was prepared using the same method as Example 1, except that the contents of C and Cu in the GH4730 alloy were different.

[0095] In Comparative Example 3, the GH4730 alloy contained 0.004% C and 0.004% Cu.

[0096] Comparative Example 4

[0097] Comparative Example 4 was prepared using the same method as Example 1, except that the contents of P and Cu in the GH4730 alloy were different.

[0098] In the GH4730 alloy of Comparative Example 4, the P content is 0.002% and the Cu content is 0.004%.

[0099] Comparative Example 5

[0100] Comparative Example 5 was prepared using the same method as Example 1, except that the extrusion rate in step (5) was different.

[0101] The hot extrusion rate of Comparative Example 5 was 25 s. -1 .

[0102] Comparative Example 6

[0103] Comparative Example 6 follows the same preparation method as Example 1, except that the heat preservation temperature of the rod in step (5) is different.

[0104] In step (5) of Comparative Example 6, the insulation temperature of the bar is 1200℃.

[0105] Comparative Example 7

[0106] Comparative Example 7 follows the same preparation method as Example 1, except that the heat preservation temperature of the rod in step (5) is different.

[0107] In step (5) of Comparative Example 7, the insulation temperature of the bar is 1090℃.

[0108] Comparative Example 8

[0109] Comparative Example 8 follows the same preparation method as Example 1, except that the diameter of the shaft forging obtained by hot extrusion in step (5) is different.

[0110] The diameter of the shaft forging prepared by hot extrusion in Comparative Example 8 is 100 mm, that is, the extrusion ratio is 1:9.

[0111] Comparative Example 9

[0112] Comparative Example 9 follows the same preparation method as Example 1, except that the diameter of the shaft forging obtained by hot extrusion in step (5) is different.

[0113] The diameter of the shaft forging prepared by hot extrusion in Comparative Example 9 was 200 mm, i.e., the extrusion ratio was 1:2.25.

[0114] Experimental Example

[0115] To compare and illustrate the performance differences of GH4730 alloy shaft forgings obtained in different embodiments and comparative examples of the present invention, the grain size, creep rupture life, fatigue resistance, etc. of different GH4730 alloy shaft forgings were tested. The test methods are as follows, and the test results are shown in Table 1.

[0116] Grain size: The test was conducted in accordance with GB / T 6394 "Method for Determination of Average Grain Size of Metals". The grain size difference is the difference between the grain size of the finest grain and the grain size of the coarsest grain.

[0117] Tensile creep life: Tested in accordance with GB / T 2039 "Metallic materials - Tensile creep and creep test method";

[0118] Fatigue life: Tested in accordance with GB / T 15248 "Metallic Materials Axial Constant Amplitude Low Cyclic Fatigue Test Method".

[0119] Table 1 Performance test results of different GH4730 alloy shaft forgings

[0120]

[0121] The test results above show that by combining the processing characteristics of shaft forgings and adjusting the content of specific elements C, P, and Cu in GH4730 alloy, this invention not only effectively improves the hot working performance of GH4730 alloy, thus ensuring the formability of shaft forgings, but also significantly enhances the creep and fatigue resistance of the prepared GH4730 alloy shaft forgings at 750℃, which can meet higher service performance requirements.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing GH4730 alloy shaft forgings, characterized in that, Includes the following steps: (a) GH4730 alloy bars are hot-extruded at 1100~1190℃ to obtain shaft forgings; in the hot extrusion, the extrusion ratio is 1:(4~6) and the extrusion rate is 5~20s. -1 ; (b) The shaft forging is subjected to solution treatment and aging treatment; The GH4730 alloy comprises, by mass percentage: C 0.005%~0.018%, P 0.003%~0.01%, Cu 0.005%~0.05%, Mo 2.5%~3.5%, W 2.3%~3.3%, Fe 3.5%~5.0%, Co 8%~10%, Cr 15%~17%, Zr 0.01%~0.05%, Ti 3.2%~3.8%, Al 2%~2.6%, Nb 0.8%~1.4%, B 0.005%~0.025%, Mn 0.001%~0.15%, N≤0.002%, O≤0.002%, S≤0.0005%, with the balance being Ni; In step (a), the preparation method of the GH4730 alloy bar includes: homogenizing the GH4730 alloy ingot, upsetting and drawing it along the axial direction to obtain a bar blank; and forging the bar blank to obtain the GH4730 alloy bar. In the upsetting and drawing process, the single deformation amount of upsetting and drawing is independently 30%~60%; The total deformation of the radial forging is 10% to 30%.

2. The method for preparing the GH4730 alloy shaft forging according to claim 1, characterized in that, In the hot extrusion process, the front end of the bar is processed into a conical surface, and the cone angle of the conical surface is 90°~120°.

3. The method for preparing the GH4730 alloy shaft forging according to claim 1, characterized in that, In the hot extrusion process, the extrusion cylinder is preheated at a temperature not lower than 400°C.

4. The method for preparing the GH4730 alloy shaft forging according to claim 1, characterized in that, In the solution treatment, the holding temperature is 1070~1110℃ and the holding time is 1~8h; In the aging process, the holding temperature is 850~870℃ and the holding time is 4~18h.

5. A GH4730 alloy shaft forging, characterized in that, The GH4730 alloy shaft forging is prepared by the method described in any one of claims 1 to 4.

6. The GH4730 alloy shaft forging according to claim 5, characterized in that, The average grain size of the GH4730 alloy shaft forging is not lower than ASTM grade 6, and the grain size difference between different parts does not exceed 2 grades.

7. The GH4730 alloy shaft forging according to claim 5, characterized in that, The GH4730 alloy shaft forging has a creep rupture life of not less than 50 hours under conditions of 750℃ and 600MPa.

8. The GH4730 alloy shaft forging according to claim 5, characterized in that, The fatigue life of the GH4730 alloy shaft forging is not less than 20,000 cycles under the conditions of 750℃ and α=0~0.6%.

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