A GH4698 alloy bar, its preparation method and application

Abstract

This application provides a GH4698 alloy bar, its preparation method, and its application, relating to the field of alloy technology. The method for preparing GH4698 alloy bars includes the following steps: a) homogenizing a GH4698 alloy billet to obtain a homogenized billet; b) hot-rolling the homogenized billet to obtain a hot-rolled bar billet; c) solution-annealing and cold-drawing the hot-rolled bar billet to obtain a cold-drawn bar; d) heat-treating the cold-drawn bar to obtain the GH4698 alloy bar. The preparation method provided by this application not only achieves uniform grain structure in the GH4698 alloy bar but also meets the tensile performance requirements at 750℃, fully satisfying the application requirements of aerospace fasteners; furthermore, it improves the overall yield of GH4698 alloy bars in the final product.

Description

Technical Field

[0001] This application relates to the field of alloy technology, specifically to a GH4698 alloy bar, its preparation method, and its application. Background Technology

[0002] GH4698 is a nickel-based age-hardening alloy with the γ' phase as the strengthening phase. It was developed from GH4033 and IE69. Due to its excellent creep strength and comprehensive mechanical properties, it is widely used in the aerospace field, and in China, it was originally mainly used to manufacture turbine disks for aero engines. In recent years, the use of GH4698 alloy hot-rolled bars to manufacture various aero-engine fasteners has added requirements for tensile properties at 750℃, requiring a tensile strength ≥740MPa, elongation ≥5%, and reduction of area ≥8%. Simultaneously, the bars are required to have uniform grain size after standard heat treatment, controlled within grade 2-6 (optimally grade 3-5), free of coarse grain bands and abnormally coarse grains larger than grade 0.5.

[0003] In existing technologies, GH4698 bars are generally produced using a multi-pass pure hot processing process on a transverse rolling mill. For example, patent CN115213251A discloses a method that uses only hot processing, through multiple passes of billet forging and rolling, with a reasonable combination of forging and rolling deformation, to produce bars with a diameter of Φ5mm to 30mm, and a grain size that barely reaches the 2-6 grade range. However, in actual industrial production, residual stress concentrates inside the bars after rolling. If the finished product is directly heat-treated, the residual stress will induce irregular and abnormal grain growth, easily generating a mixed-grain structure containing grade 0 ultra-large grains, which seriously reduces high-temperature mechanical properties and service stability. At the same time, the dimensional accuracy and yield of transverse rolling mills are low, and the influence of human intervention and operation is significant. As a result, the grain size qualification rate and the comprehensive qualification rate of high-temperature plasticity at 750℃ for GH4698 bars produced using this process are less than 20%, which is completely unable to meet the requirements for mass supply of high-end aerospace fasteners. Another technique improves the high-temperature plasticity of GH4698 alloy by adjusting the alloy's chemical composition. Although this technique improves the high-temperature plasticity to some extent, the addition of new components can easily lead to compositional deviations. Furthermore, this technique does not address the core issues of uneven microstructure during hot working and abnormal grain growth induced by residual stress, and therefore cannot fundamentally eliminate the problems of mixed crystals and excessive grain size. Summary of the Invention

[0004] In view of this, this application provides a GH4698 alloy bar, its preparation method, and its application. The preparation method provided in this application fundamentally solves the technical problems of uneven grain structure, insufficient high-temperature plasticity at 750℃, and extremely low overall yield of GH4698 alloy bars.

[0005] This application provides a method for preparing GH4698 alloy bars, comprising the following steps: a) The GH4698 alloy square billet is homogenized to obtain a homogenized billet; b) The homogenized billet is subjected to hot continuous rolling to obtain a hot-rolled bar billet; c) After solution annealing and cold drawing, the hot-rolled billet is obtained as a cold-drawn bar. d) The cold-drawn bar is heat-treated to obtain GH4698 alloy bar.

[0006] In some specific implementations, the rolling speed of the hot continuous rolling is 3 m / s to 3.5 m / s, and the final rolling temperature of the hot continuous rolling is 980℃ to 1020℃.

[0007] In some specific implementations, the chemical composition of the GH4698 alloy billet, by mass percentage, includes: C: 0.03%~0.07%; Mo: 2.80%~3.20%; Cr: 13.0%~16.0%; Ti: 2.35%~2.75%; Al: 1.45%~1.80%; Nb: 1.80%~2.20%; Fe: 0%~2.0%; Ni: balance; The side length of the GH4698 alloy square billet is 120mm~150mm.

[0008] In some specific implementations, step a) specifically includes the following steps: The GH4698 alloy billet is heated to a first temperature and held for the first stage. After the first stage of holding is completed, it is cooled to a second temperature and held for the second stage to obtain a homogenized billet.

[0009] In some specific implementations, the heating method is furnace heating, and the heating rate is 50℃ / h~150℃ / h; The first temperature is 1190℃~1210℃, and the first stage of heat preservation time is 8h~32h; The second temperature is 1130℃~1170℃, and the second stage of heat preservation time is 2h~4h.

[0010] In some specific implementations, the solution annealing temperature is 1150℃~1170℃, and the holding time is 10min~30min.

[0011] In some specific implementations, the total deformation of the cold drawing is 25% to 32%; the cold drawing is completed in three passes, and the deformation of each pass is 8% to 12%.

[0012] In some specific implementations, the heat treatment specifically includes: After holding at 1110℃ for 8 hours, air-cooled; then, after holding at 1000℃ for 4 hours, air-cooled; and finally, after holding at 775℃ for 16 hours, air-cooled.

[0013] This application also provides a GH4698 alloy bar, which is prepared by the preparation method described in the above technical solution.

[0014] This application also provides an aero-engine fastener, comprising a GH4698 alloy bar prepared by the preparation method described above or the GH4698 alloy bar described above.

[0015] This application provides a method for preparing GH4698 alloy bars, comprising the following steps: a) homogenizing a GH4698 alloy billet to obtain a homogenized billet; b) hot-rolling the homogenized billet to obtain a hot-rolled bar billet; c) solution annealing and cold drawing the hot-rolled bar billet to obtain a cold-drawn bar; d) heat-treating the cold-drawn bar to obtain a GH4698 alloy bar. This application, through the matching of homogenization, hot rolling, solution annealing, cold drawing, and heat treatment processes, especially the synergistic control of the "hot rolling + cold drawing" process, not only achieves uniformity in the grain structure of the GH4698 bar but also meets the tensile performance requirements at 750℃, fully satisfying the application requirements of aerospace fasteners; furthermore, it improves the overall yield of GH4698 alloy bars in the final product. Experimental results show that the GH4698 alloy rods prepared by the preparation method provided in this application have uniform grain size after standard heat treatment, which is stable and meets the requirements of grade 3 to 5. There are no abnormal coarse grains or coarse grain bands of grade 0.5. The tensile strength at 750℃ is ≥880MPa, the elongation is ≥7.5%, and the reduction of area is ≥10%. The overall qualification rate of GH4698 alloy rods in the final product is ≥95%. Attached Figure Description

[0016] Figure 1 This is a grain structure diagram of the GH4698 rod prepared in Example 1 of this application; Figure 2 This is a grain structure diagram of the GH4698 rod prepared in Example 2 of this application; Figure 3 This is a grain structure diagram of the GH4698 rod prepared in Example 3 of this application; Figure 4 This is a grain structure diagram of the GH4698 rod prepared in Comparative Example 1 of this application; Figure 5 This is a grain structure diagram of the GH4698 rod prepared in Comparative Example 2 of this application. Detailed Implementation

[0017] It should be understood that the expression “one or more of…” individually includes each of the objects described after the expression, as well as various different combinations of two or more of the described objects, unless otherwise understood from the context and usage. The expression “and / or” combined with three or more described objects should be understood to have the same meaning, unless otherwise understood from the context.

[0018] The terms “including,” “having,” or “containing,” including the use of their grammatical synonyms, should generally be understood as open-ended and non-restrictive, for example, not excluding other unstated elements or steps, unless otherwise specifically stated or understood from the context.

[0019] It should be understood that the order of steps or the sequence of actions is not important as long as this application remains operational. Furthermore, two or more steps or actions may be performed simultaneously.

[0020] The use of any and all instances or exemplary language such as “e.g.” or “including” herein is merely intended to better illustrate the application and does not constitute a limitation on the scope of the application unless the claims are made. No language in this specification should be construed as indicating that any unclaimed element is essential to the practice of this application.

[0021] Furthermore, the numerical ranges and parameters used to define this application are approximate values, and the relevant values ​​in the specific embodiments have been presented as precisely as possible. However, any numerical value inevitably contains standard deviations due to individual test methods. Therefore, unless otherwise explicitly stated, it should be understood that all ranges, quantities, values, and percentages used in this disclosure are modified with the word "approximately." Here, "approximately" generally means that the actual value is within plus or minus 10%, 5%, 1%, or 0.5% of a specific value or range.

[0022] This application provides a method for preparing GH4698 alloy bars, comprising the following steps: a) The GH4698 alloy square billet is homogenized to obtain a homogenized billet; b) The homogenized billet is subjected to hot continuous rolling to obtain a hot-rolled bar billet; c) After solution annealing and cold drawing, the hot-rolled billet is obtained as a cold-drawn bar. d) The cold-drawn bar is heat-treated to obtain GH4698 alloy bar.

[0023] Based on the grain growth law of GH4698 alloy: the larger the initial grain size, the slower the grain growth rate during heat treatment, the more uniform the pinning effect of grain boundary precipitates, and the less likely it is to produce abnormal coarse grains and mixed grain structures. This application adopts a process approach of synergistic control of hot working and cold working. While maintaining the standard chemical composition of GH4698 alloy, it achieves precise control of the microstructure and mechanical properties of bars through the matching of high-temperature homogenization treatment, hot continuous rolling, cold deformation, and heat treatment. This solves the technical problems existing in the current transverse pure hot working process for preparing GH4698 bars, such as prominent surface mixed grains, excessive grain size due to high residual stress, insufficient plasticity at 750℃, and extremely low overall yield. At the same time, it avoids the technical problems of standard composition deviation and difficulty in composition control that may arise from composition adjustment schemes.

[0024] This application uses GH4698 alloy billet as raw material. This application does not impose special restrictions on the source or side length of the GH4698 alloy billet; any GH4698 alloy billet commonly used by those skilled in the art can be used. In some specific implementations, the side length of the GH4698 alloy billet is 120mm~150mm. For example, the side length of the GH4698 alloy billet is 120mm, 125mm, 130mm, 135mm, 140mm, 145mm, or 150mm, etc. In some specific implementations, the chemical composition of the GH4698 alloy billet, by mass percentage, includes: C: 0.03%~0.07%; Mo: 2.80%~3.20%; Cr: 13.0%~16.0%; Ti: 2.35%~2.75%; Al: 1.45%~1.80%; Nb: 1.80%~2.20%; Fe: 0%~2.0%; Ni: balance; Preferably, the chemical composition of the GH4698 alloy billet, by mass percentage, includes: C: 0.04%~0.06%; Mo: 2.80%~3.00%; Cr: 13.0%~15.0%; Ti: 2.35%~2.75%; Al: 1.50%~1.80%; Nb: 1.90%~2.10%; Fe: 1.0%~2.0%; Ni: balance.

[0025] This application first homogenizes the GH4698 alloy billet to obtain a homogenized billet. Specifically, the GH4698 alloy billet is heated to a first temperature and held for a first stage; after the first stage holding, it is cooled to a second temperature and held for a second stage to obtain a homogenized billet. In some specific implementations, the first temperature is 1190℃~1210℃, preferably 1190℃~1200℃, and the first stage holding time is 8h~32h, preferably 10h~30h. In some specific implementations, the second temperature is 1130℃~1170℃, preferably 1140℃~1170℃, and the second stage holding time is 2h~4h, preferably 3h~3.5h. In some specific implementations, the heating method is furnace heating, preferably furnace heating at 0℃~700℃, more preferably furnace heating at 500℃~700℃. In some specific implementations, the heating rate is 50℃ / h to 150℃ / h, preferably 80℃ / h to 120℃ / h, and more preferably 100℃ / h. In some specific implementations, the heating time is preferably controlled to be more than 3 hours. The furnace heating described in this application involves loading the workpiece into the furnace when the furnace temperature is ≤700℃, and then the furnace and workpiece are heated together at a set heating rate until the preset target temperature is reached.

[0026] The high-temperature homogenization treatment provided in this application can effectively eliminate the segregation of elements such as Nb and Mo in the alloy, avoid the formation of dense MC carbide strips during subsequent unidirectional drawing, and ensure the uniformity of the billet structure from the source.

[0027] After obtaining the homogenized billet, the homogenized billet is subjected to hot continuous rolling to obtain a hot-rolled bar. Specifically, the homogenized billet is continuously deformed sequentially through transfer rolls on a roughing mill, intermediate mill, finishing mill, and sizing mill. To avoid core cracking due to high-speed rolling and surface cracking due to low-speed rolling, the rolling speed is optimized to 3.0 m / s to 3.5 m / s, and the final rolling temperature is ≥980℃. In some specific implementations, the rolling speed of the hot continuous rolling is 3.0 m / s to 3.5 m / s. For example, the rolling speed of the hot continuous rolling is 3.0 m / s, 3.1 m / s, 3.2 m / s, 3.3 m / s, 3.4 m / s, or 3.5 m / s, etc. In some specific implementations, the final rolling temperature of the hot continuous rolling is 980℃ to 1020℃, preferably 990℃ to 1010℃. A uniform, low-stress billet microstructure with a diameter of Φ18mm~28mm and a grain size of grade 6 is obtained by hot continuous rolling. Combined with cold drawing to induce uniform recrystallization in subsequent processes, the final grain size is stably controlled at grade 3~5.

[0028] The hot continuous rolling described in this application refers to a rolling method in which metal billets heated to the target temperature are passed sequentially and unidirectionally through multiple rolling mill stands arranged continuously in the rolling direction, undergoing compression deformation only once on each stand, and directly rolled into finished products through continuous deformation. The traditional transverse rolling described in this application refers to a rolling method in which metal billets heated to the target temperature are repeatedly and cross-transported between one or more sets of transversely arranged rolling mill stands by guiding devices or manual operation, causing the workpiece to repeatedly pass through the same or adjacent stands, undergoing compression deformation pass-by-pass, and requiring turning or reversing operations after each deformation pass, until the cumulative deformation reaches the required finished product amount, at which point the rolling process terminates.

[0029] This application replaces traditional tandem rolling with hot continuous rolling, avoiding the problems of high residual stress, uneven microstructure, and unstable quality associated with tandem rolling mills. Hot continuous rolling features continuous deformation, uniform temperature field, and low residual stress, and can stably control the rolled grain size at level 6, thereby obtaining a uniform, low-stress, and highly stable initial microstructure, providing a high-quality microstructure and suitable dimensions for subsequent cold drawing. Simultaneously, hot continuous rolling eliminates the drawbacks of tandem rolling mills, such as human intervention, uneven surface heat dissipation, and concentrated residual stress. The overall pass rate for grain size and high-temperature plasticity is increased from less than 20% in traditional processes to over 95%, with good process repeatability, making it suitable for large-scale, stable industrial production.

[0030] After obtaining the hot-rolled billet, the billet is solution annealed and cold-drawn to obtain cold-drawn bars. Specifically, the hot-rolled billet is solution annealed, water-cooled, straightened, polished, and then cold-drawn to obtain cold-drawn bars. In some specific implementations, the solution annealing temperature is 1150℃~1170℃, preferably 1150℃~1165℃, and the holding time is 10min~30min, preferably 15min~20min. In some specific implementations, it is preferable to uniformly apply a water-based composite lubricant to the surface of the billet before cold drawing, and then perform cold drawing after the surface lubricant has dried. In some specific implementations, the total deformation of the cold drawing is 25%~32%, preferably 28%~30%; the cold drawing is completed in three passes, and the deformation of each pass is 8%~12%, preferably 9%~12%. In the cold drawing process, the deformation amount of each pass and the total deformation amount are controlled within ±0.5% of the target value.

[0031] This application softens the billet and reduces deformation resistance through a high-temperature solution annealing process before drawing; eliminates surface microcracks and improves the surface quality of the bar through straightening and polishing, while maintaining precise control; and introduces a cold drawing process with parameters specifically optimized for the high deformation resistance and poor plasticity of GH4698 alloy. Appropriate cold deformation enhances the strength of the bar through work hardening and utilizes the energy stored in cold deformation to induce uniform recrystallization in subsequent solution treatment, avoiding abnormal grain growth (grade 0 coarse grains) and ensuring stable grain size control at grade 3 to 5. It also avoids surface cracking and microstructure distortion caused by excessive deformation.

[0032] After obtaining the cold-drawn bar, the cold-drawn bar is subjected to heat treatment to obtain GH4698 alloy bar. In some specific implementations, the heat treatment is specifically as follows: holding at 1110℃ for 8 hours and then air-cooling, then holding at 1000℃ for 4 hours and then air-cooling, and finally holding at 775℃ for 16 hours and then air-cooling.

[0033] This application also provides a GH4698 alloy bar, which is prepared by the preparation method described in the above technical solution.

[0034] This application also provides an aero-engine fastener, comprising a GH4698 alloy bar prepared by the preparation method described above or the GH4698 alloy bar described above.

[0035] This application provides a method for preparing GH4698 alloy bars, comprising the following steps: a) homogenizing a GH4698 alloy billet to obtain a homogenized billet; b) hot-rolling the homogenized billet to obtain a hot-rolled bar billet; c) solution annealing and cold drawing the hot-rolled bar billet to obtain a cold-drawn bar; d) heat-treating the cold-drawn bar to obtain a GH4698 alloy bar. This application, through the matching of homogenization, hot rolling, solution annealing, cold drawing, and heat treatment processes, especially the synergistic control of the "hot rolling + cold drawing" process, not only achieves uniformity in the grain structure of the GH4698 bar but also meets the tensile performance requirements at 750℃, fully satisfying the application requirements of aerospace fasteners; furthermore, it improves the overall yield of GH4698 alloy bars in the final product. Experimental results show that the GH4698 alloy rods prepared by the preparation method provided in this application have uniform grain size after standard heat treatment, which stably meets the requirements of grade 3 to 5, with no abnormal coarse grains or coarse grain bands of grade 0.5. The tensile strength at 750℃ is ≥880MPa, the elongation is ≥7.5%, and the reduction of area is ≥10%. The overall pass rate of GH4698 alloy rods in the final product is ≥95%.

[0036] The present invention is further illustrated below with reference to the embodiments. The scope of protection of the present invention is not limited to the following embodiments.

[0037] Example 1

[0038] A precipitation-hardening high-temperature alloy bar for high-performance fasteners and its preparation method are disclosed. First, a Φ28mm hot-rolled bar billet is obtained through hot continuous rolling, and then a Φ22mm GH4698 bar is prepared by cold drawing with a total deformation of 28.4%. The specific implementation steps are as follows: S1. Homogenization treatment: A 150mm GH4698 alloy billet is loaded into a natural gas furnace at 680℃, then heated to 1200℃ at a heating rate of 100℃ / h over 5.2h and held for 30h. After holding, the furnace is cooled to 1170℃ and held for 3.5h. The chemical composition of the GH4698 alloy billet, by mass percentage, includes: C: 0.049%; Mo: 2.92%; Cr: 14.20%; Ti: 2.56%; Al: 1.62%; Nb: 2.01%; Fe: 1.80%; Ni: balance.

[0039] S2. Hot Continuous Rolling: The billet, after homogenization in step S1, is fed into a continuous rolling mill. The billet undergoes continuous deformation sequentially through transfer rolls on the roughing mill, intermediate mill, finishing mill, and sizing mill. The rolling speed is 3.2 m / s, the final rolling temperature is 1000℃, and it is continuously rolled into Φ28mm round steel, resulting in a stable rolled grain size of grade 6.

[0040] S3. Solution annealing and cold drawing: The Φ28mm hot-rolled bar billet is solution annealed at 1160℃, held for 20min, and then water-cooled. After solution annealing, the bar is straightened and polished to 26.0mm. Then, a water-based lubricant is applied to the bar, and it is drawn in 3 passes using a drawing machine. The bar dimensions change to 26.0mm, 24.8mm, 23.4mm, and 22.0mm respectively. The deformation of each pass is 9.0%, 10.9%, and 11.6% respectively, with a total deformation of 28.4%, resulting in a Φ22.0mm cold-drawn bar.

[0041] S4. Heat treatment: The Φ22.0mm cold-drawn bar is subjected to 1110℃×8h / air cooling + 1000℃×4h / air cooling + 775℃×16h / air cooling to obtain GH4698 alloy bar.

[0042] The grain structure of the prepared GH4698 alloy rods was analyzed, and the results are shown in [reference needed]. Figure 1 , Figure 1 This is a grain structure diagram of the GH4698 rod prepared in Example 1 of this application. Figure 1 It can be seen that the resulting finished bar has a grain size of grade 4, is uniform and free of mixed crystals, and meets the standard requirements.

[0043] The high-temperature tensile properties of the prepared GH4698 alloy rods at 750℃ were tested. The tensile strength was 886MPa / 894MPa, the elongation was 7.8% / 9.0%, and the reduction of area was 12.5% / 10.2%, which met the performance requirements of aerospace fasteners. The comprehensive pass rate of grain size and high-temperature plasticity was 98.4%.

[0044] Example 2

[0045] A method for preparing precipitation-hardening high-temperature alloy bars for high-performance fasteners involves first hot rolling to obtain a Φ24mm hot-rolled billet, and then cold-drawing with a total deformation of 29.3% to prepare a Φ18.5mm GH4698 bar. The specific implementation steps are as follows: S1. Homogenization treatment: A 120mm GH4698 alloy billet is loaded into a natural gas furnace at 650℃, then heated to 1190℃ at a heating rate of 100℃ / h over 5.4h and held for 10h. After holding, the furnace is cooled to 1150℃ and held for 3h. The chemical composition of the GH4698 alloy billet, by mass percentage, includes: C: 0.052%; Mo: 2.94%; Cr: 14.24%; Ti: 2.58%; Al: 1.67%; Nb: 2.07%; Fe: 1.30%; Ni: balance.

[0046] S2. Hot Continuous Rolling: The billet, homogenized in step S1, is fed into a continuous rolling mill. The billet undergoes continuous deformation sequentially through transfer rolls on the roughing mill, intermediate mill, finishing mill, and sizing mill. The rolling speed is 3.5 m / s, the final rolling temperature is 1005℃, and it is continuously rolled into Φ24mm round steel, resulting in a stable rolled grain size of grade 6.

[0047] S3. Solution annealing and cold drawing: The Φ24mm hot-rolled bar billet is solution annealed at 1150℃, held for 10 minutes, and then water-cooled. After solution annealing, the bar is straightened and polished to 22.0mm. Then, a water-based lubricant is applied to the bar, and it is drawn in 3 passes using a drawing machine. The bar dimensions change to 22.0mm, 20.9mm, 19.7mm, and 18.5mm respectively. The deformation of each pass is 9.8%, 11.1%, and 11.8%, respectively, with a total deformation of 29.3%, resulting in a Φ18.5mm cold-drawn bar.

[0048] S4. Heat treatment: The Φ18.5mm cold-drawn bar is subjected to 1110℃×8h / air cooling + 1000℃×4h / air cooling + 775℃×16h / air cooling to obtain GH4698 alloy bar.

[0049] The grain structure of the prepared GH4698 alloy rods was analyzed, and the results are shown in [reference needed]. Figure 2 , Figure 2 This is a grain structure diagram of the GH4698 rod prepared in Example 2 of this application. Figure 2 It can be seen that the resulting finished bar has a grain size of grade 4, is uniform and free of mixed crystals, and meets the standard requirements.

[0050] The high-temperature tensile properties of the prepared GH4698 alloy rods at 750℃ were tested. The tensile strength was 890MPa / 891MPa, the elongation was 8.8% / 8.5%, and the reduction of area was 13.5% / 14.0%, which met the performance requirements of aerospace fasteners. The overall pass rate of grain size and high-temperature plasticity was 96.7%.

[0051] Example 3

[0052] A method for preparing precipitation-hardening high-temperature alloy bars for high-performance fasteners involves first hot-rolling a Φ18mm hot-rolled billet, and then cold-drawing it with a total deformation of 28.0% to prepare a Φ14.0mm GH4698 bar. The specific implementation steps are as follows: S1. Homogenization treatment: 135mm GH4698 alloy is loaded into a natural gas furnace at 620℃, then heated to 1190℃ at a heating rate of 100℃ / h over 5.7h and held for 20h. After holding, the furnace is cooled to 1140℃ and held for 3.5h. The chemical composition of the GH4698 alloy billet, by mass percentage, includes: C: 0.055%; Mo: 3.05%; Cr: 14.32%; Ti: 2.54%; Al: 1.60%; Nb: 2.03%; Fe: 1.80%; Ni: balance.

[0053] S2. Hot Continuous Rolling: The billet, after homogenization in step S1, is fed into a continuous rolling mill. The billet undergoes continuous deformation sequentially through transfer rolls on the roughing mill, intermediate mill, finishing mill, and sizing mill. The rolling speed is 3.0 m / s, the final rolling temperature is 991℃, and it is continuously rolled into Φ18mm round steel, resulting in a stable rolled grain size of grade 6.

[0054] S3. Solution annealing and cold drawing: The Φ18mm hot-rolled bar billet is solution annealed at 1165℃, held for 15 minutes, and then water-cooled. After solution annealing, the bar is straightened and polished to 16.5mm. Then, a water-based lubricant is applied to the bar, and it is drawn in 3 passes using a drawing machine. The bar dimensions change to 16.5mm, 15.7mm, 14.8mm, and 14.0mm respectively. The deformation of each pass is 9.5%, 11.1%, and 10.5% respectively, with a total deformation of 28.0%, resulting in a Φ14.0mm cold-drawn bar.

[0055] S4. Heat treatment: Cold-drawn bars with diameter of 14.0 mm are subjected to 1110℃×8h / air cooling + 1000℃×4h / air cooling + 775℃×16h / air cooling to obtain GH4698 alloy bars.

[0056] The grain structure of the prepared GH4698 alloy rods was analyzed, and the results are shown in [reference needed]. Figure 3 , Figure 3 This is a grain structure diagram of the GH4698 rod prepared in Example 3 of this application. Figure 3 It can be seen that the resulting finished bar has a grain size of 4.5 grade, is uniform and free of mixed crystals, and meets the standard requirements.

[0057] The high-temperature tensile properties of the prepared GH4698 alloy rods at 750℃ were tested. The tensile strength was 901MPa / 895MPa, the elongation was 10.8% / 9.5%, and the reduction of area was 13.8% / 13.5%, which met the performance requirements of aerospace fasteners. The overall pass rate of grain size and high-temperature plasticity was 97.0%.

[0058] Comparative Example 1

[0059] The only difference from Example 1 is that in step S2, the hot continuous rolling process is replaced by a transverse rolling mill to roll the Φ28mm billet. The remaining process steps are the same as in Example 1, and finally, Φ22mm GH4698 alloy bars are obtained.

[0060] S2. Horizontal rolling mill: The billet that has been homogenized in step S1 is fed into the horizontal rolling mill. The billet is rolled back and forth manually. The rolling speed of the horizontal rolling mill is 1.55m / s, the final rolling temperature is 927℃, and it is rolled into Φ28mm round steel.

[0061] The grain structure of the prepared GH4698 alloy rods was analyzed, and the results are shown in [reference needed]. Figure 4 , Figure 4 This is a grain structure diagram of the GH4698 rod prepared in Comparative Example 1 of this application. Figure 4 It can be seen that the obtained finished bar material has obvious coarse grain bands on the surface, and the grain size is mixed crystal of grade 0 + grade 5, which does not meet the standard requirements.

[0062] The high-temperature tensile properties of the prepared GH4698 alloy bars at 750℃ were tested. The tensile strength was 808MPa / 774MPa, the elongation was 3.8% / 5.2%, and the reduction of area was 6.8% / 10.3%, which did not meet the performance requirements of aerospace fasteners. Moreover, the actual production stability was poor, and the overall pass rate of grain size and high-temperature plasticity was only 15.2%.

[0063] Comparative Example 2

[0064] The only difference from Example 2 is that the cold drawing in step S3 is omitted. Instead, the Φ18.5mm billet is obtained directly through hot rolling in step S2. The remaining processes are the same as in Example 2, and finally, Φ18.5mm GH4698 alloy bars are obtained.

[0065] The grain structure of the prepared GH4698 alloy rods was analyzed, and the results are shown in [reference needed]. Figure 5 , Figure 5 This is a grain structure diagram of the GH4698 rod prepared in Comparative Example 2 of this application. As shown in Figure 5, the resulting finished rod has a relatively uniform grain size, which basically meets the standard requirements.

[0066] The high-temperature tensile properties of the prepared GH4698 alloy bars at 750℃ were tested. The tensile strength was only 710MPa / 727MPa, the elongation was 3.0% / 3.5%, and the reduction of area was 4.8% / 6.0%, which did not meet the performance requirements of aerospace fasteners. Moreover, the actual production stability was poor, and the overall pass rate of grain size and high-temperature plasticity was only 18%.

[0067] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and inventive concept of this application, should be included within the scope of protection of this application.

Claims

1. A method for preparing GH4698 alloy rods, characterized in that, Includes the following steps: a) The GH4698 alloy square billet is homogenized to obtain a homogenized billet; b) The homogenized billet is subjected to hot continuous rolling to obtain a hot-rolled bar billet; c) After solution annealing and cold drawing, the hot-rolled billet is obtained as a cold-drawn bar. d) The cold-drawn bar is heat-treated to obtain GH4698 alloy bar.

2. The preparation method according to claim 1, characterized in that, The rolling speed of the hot continuous rolling mill is 3m / s to 3.5m / s, and the final rolling temperature of the hot continuous rolling mill is 980℃ to 1020℃.

3. The preparation method according to claim 1, characterized in that, The chemical composition of the GH4698 alloy billet, by mass percentage, includes: C: 0.03%~0.07%; Mo: 2.80%~3.20%; Cr: 13.0%~16.0%; Ti: 2.35%~2.75%; Al: 1.45%~1.80%; Nb: 1.80%~2.20%; Fe: 0%~2.0%; Ni: balance; The side length of the GH4698 alloy square billet is 120mm~150mm.

4. The preparation method according to claim 1, characterized in that, Step a) specifically includes the following steps: The GH4698 alloy billet is heated to a first temperature and held for the first stage. After the first stage of holding is completed, it is cooled to a second temperature and held for the second stage to obtain a homogenized billet.

5. The preparation method according to claim 4, characterized in that, The heating method is furnace heating, and the heating rate is 50℃ / h~150℃ / h; The first temperature is 1190℃~1210℃, and the first stage of heat preservation time is 8h~32h; The second temperature is 1130℃~1170℃, and the second stage of heat preservation time is 2h~4h.

6. The preparation method according to claim 1, characterized in that, The solution annealing temperature is 1150℃~1170℃, and the holding time is 10min~30min.

7. The preparation method according to claim 1, characterized in that, The total deformation of the cold drawing is 25% to 32%; the cold drawing is completed in three passes, and the deformation of each pass is 8% to 12%.

8. The preparation method according to claim 1, characterized in that, The heat treatment specifically involves: holding at 1110℃ for 8 hours followed by air cooling, then holding at 1000℃ for 4 hours followed by air cooling, and finally holding at 775℃ for 16 hours followed by air cooling.

9. A GH4698 alloy bar, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.

10. A fastener for an aircraft engine, characterized in that, Includes GH4698 alloy rods prepared by the preparation method according to any one of claims 1 to 8 or GH4698 alloy rods according to claim 9.

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