Method for improving three-direction uniformity of GH350 forged structure

Abstract

The invention discloses a method for improving the three-way uniformity of a forged structure of a GH350 alloy, which adopts a multi-way dynamic recrystallization regulation and control forging and gradient aging heat treatment composite process and comprises the following steps: adopting gradient aging heat treatment, accurately controlling a phase change process and improving the uniformity. Under the condition of a certain total deformation amount, a strain path is optimized through a staged multi-pass multi-direction forging technology, and three-dimensional uniform deformation and dynamic recrystallization regulation and control are achieved in combination with a gradient temperature control strategy; compared with a traditional one-way forging and single-stage temperature control process, composition segregation can be remarkably reduced, the three-way structure uniformity is improved, and the subsequent forging performance is more stable. Through heat treatment-forging process coupling regulation and control, collaborative optimization of high strength, high ductility and excellent high-temperature performance is achieved. The method is particularly suitable for high-temperature and high-stress environments such as aero-engine hot end parts, and a reliable process scheme is provided for preparation of high-performance nickel-based alloy forgings.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature alloy forging technology, specifically relating to a method for improving the three-dimensional uniformity of the forged microstructure of GH350. Background Technology

[0002] With the rapid development of my country's high-end equipment manufacturing in aviation, aerospace, and shipbuilding, extreme service environments pose challenges to the performance of critical structural components, leading to increasingly prominent early failures of core parts. This is particularly true in critical load-bearing components such as aero-engine turbine disks, marine gas turbine blades, and launch vehicle connecting rings. Taking high-strength fasteners for aero-engines as an example, these critical connecting components must simultaneously withstand extremely complex loads during service: on the one hand, they must resist high-intensity pre-tensioning stress, and on the other hand, they must cope with vibration fatigue loads generated during flight. Especially in the hot-end region of the engine, fasteners also face problems such as stress corrosion. Fasteners manufactured using traditional cold heading processes often experience stress relaxation and fatigue fracture, leading to connection failures and potentially catastrophic accidents. While nickel-based superalloys, represented by GH350, possess excellent high-temperature strength, they still face some bottlenecks in practical applications. Traditional forging, with its lack of directional deformation design and repeated forging in a single direction, easily leads to the agglomeration and coarsening of the η phase along the stress direction at grain boundaries, forming a brittle layer. This significantly increases the risk of intergranular cracking during high-temperature service. The traditional process also lacks directional deformation design, resulting in uneven grain size and large fluctuations in the alloy's mechanical properties. Furthermore, the use of single-stage heating or uncontrolled temperature heat treatment in traditional processes leads to significant elemental segregation. Unidirectional forging also causes imbalances in three-dimensional mechanical properties and insufficient high-temperature stability. These defects restrict the application of GH350 alloy in new aerospace equipment, necessitating the development of innovative forging processes that can simultaneously ensure microstructure uniformity, consistent three-dimensional properties, and high-temperature stability. Summary of the Invention

[0003] This invention provides a method to improve the three-dimensional uniformity of the microstructure of GH350 forging, solving the problems of microstructure inhomogeneity, three-dimensional mechanical property imbalance and insufficient high-temperature stability of GH350 nickel-based high-temperature alloy for aerospace fasteners in traditional forging processes. This method belongs to a multi-dimensional dynamic recrystallization controlled forging + gradient aging heat treatment composite process, which significantly improves the comprehensive performance of forgings through multi-dimensional strain path optimization and precise phase transformation control.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention includes the following steps: a method for improving the triaxial uniformity of the forged microstructure of GH350, the method including the following steps: Step 1: Perform surface peeling treatment on the GH350 triple casting ingot to remove defects such as oxide scale, cracks, and pits from the surface of the billet; the triple casting ingot refers to the process of vacuum induction melting (VIM) + protective atmosphere electroslag remelting (ESR) + vacuum arc remelting (VAR). Step 2: Perform a stepped heating heat treatment on the GH350 triple casting ingot, specifically including: first, raise the temperature to 300-500℃ and hold for 0.5-1h; then raise the temperature to 700-850℃ and hold for 1-2h; finally, raise the temperature to 1100-1180℃ and hold for 2-5h. Step 3: Multi-directional forging. The billet, heated to a fully heated state, is taken out of the furnace and then placed on a forging press for forging operations. The initial forging temperature is controlled at 1100-1180℃, and the final forging temperature is ≥900℃. First Z-axis forging pass: The billet is laid flat, and the hammer is pressed down along the Z-axis, with a forging ratio range of 1.2 to 2.5; rotate 90° around the X-axis: flip the billet with the front and back sides centered on the X-axis, turning the original front and back sides into the top and bottom surfaces (the surface to be deformed switches to the X-axis); Second Z-axis forging pass: The hammer is pressed down along the Z-axis, compressing the original front-back dimension (reduction in the X-axis, extension in the Y / Z-axis), with a forging ratio range of 1.2 to 2.5; rotate 90° around the Y-axis: flip the billet with the left and right sides centered on the Y-axis, turning the original left and right sides into the top and bottom surfaces (the surface to be deformed switches to the Y-axis); Third Z-axis forging pass: The hammer is pressed down along the Z-axis, compressing the original left-right dimension (reduction in the Y-axis, extension in the X / Z-axis), with a forging ratio range of 1.2 to 2.5; repeat the above process 1 to 3 times; (Z-axis: perpendicular to the worktable, X-axis: parallel to the front-back direction of the worktable, Y-axis: parallel to the left-right direction of the worktable (perpendicular to the X-axis)) Step 4: Cooling. After the final forging is completed, the forging is immediately transferred to an annealing furnace preheated to 700-780°C. After cooling to 350-400°C, it is left to cool in the air to room temperature to obtain GH350 forging billet.

[0005] In step two of this invention, the stepped heating method is furnace heating. The heating rate in the first stage is 60-100℃ / h, the heating rate in the second stage is maintained in the range of 80-150℃ / h, and the temperature is held for 1-2 hours; the heating rate in the third stage is controlled at 100-200℃ / h.

[0006] In step three of this invention, the temperature is monitored in real time during the forging process. If the final forging temperature drops, timely reheating should be carried out. If the billet temperature drops below 900°C, it needs to be reheated in the furnace to 1100-1150°C, held for 0.5-1 hour, and then forging should continue.

[0007] In step four of this invention, the cooling rate is maintained at 300°C / h or higher.

[0008] The chemical composition and mass percentage of the GH350 triple casting ingot described in this invention are as follows: carbon: 0.01%–0.025%, chromium: 15.3%–16.5%, molybdenum: 2.95%–3.25%, titanium: 1.65%–2.35%, iron: 0.6%–1.25%, cobalt: 23.0%–27.0%, tantalum: 3.5%–4.6%, with the remainder being nickel and unavoidable impurities.

[0009] The GH350 forging billet described in this invention has a tensile strength of 1156-1403 MPa and a difference in X, Y, and Z dimensional properties of ≤5.6%.

[0010] The GH350 forging billet described in this invention has a yield strength of 997-1168 MPa and a difference in X, Y, and Z dimensional properties of ≤5.6%.

[0011] The GH350 forging billet described in this invention has an elongation of 15.8% to 20.5% and a difference in X, Y, and Z dimensional properties of ≤9.8%.

[0012] The GH350 forging billet described in this invention has a hardness of 36.5 to 43.5 HRC, at which point the difference in X, Y, and Z-axis properties is ≤6.9%.

[0013] The beneficial effects of adopting the above technical solution are as follows: 1. Pre-forging heat treatment using a stepped heating method eliminates residual stress, promotes partial dissolution of carbides, and heat preservation redistributes dislocations, promotes the gradual dissolution of the γ' phase, prevents local component segregation, and achieves complete austenitization before forging. 2. The "forging-heat compensation" process eliminates accumulated strain through multiple reheating in the furnace, rehomogenizing the billet temperature and microstructure, and avoiding performance fluctuations caused by local overcooling or overheating. By strictly monitoring the final forging temperature and timely reheating in the furnace when approaching the critical temperature, the material is always kept in the optimal thermoplastic range, thereby obtaining a uniform and fine recrystallized microstructure and improving the mechanical properties and high-temperature stability of the forging. 3. Segmented controlled cooling significantly reduces thermal stress and inhibits the precipitation of harmful phases. It can effectively eliminate metallurgical defects such as porosity and shrinkage cavities inside the ingot, significantly optimize the microstructure of the material, and thus obtain a more uniform strain distribution in the ingot during plastic deformation. The final forging has good strength and exhibits stable thermal expansion properties, meeting the dimensional stability requirements under high-temperature environments. 4. Multi-directional forging: Within the phase transformation temperature range, multiple forging passes are performed alternately along the X, Y, and Z directions to dynamically recrystallize and refine the grains. This method, through the synergistic control of deformation and heat treatment, achieves tri-directional microstructure uniformity while ensuring fine-grain strengthening, thereby improving overall mechanical properties. Attached Figure Description

[0014] Figure 1 The image shows the microstructure of the forging blank obtained in Example 5 of this invention. Figure 2 The η phase is uniformly distributed at the grain boundaries of the forged billet obtained in Example 5 of the present invention. Detailed Implementation

[0015] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Example 1

[0016] A method for improving the triaxial uniformity of the microstructure of GH350 in the forged state includes the following steps: Step 1: Perform surface peeling treatment on the GH350 triple casting ingot to remove defects such as oxide scale, cracks, and pits from the surface of the billet; Step 2: Perform a stepped heating heat treatment on the GH350 triple casting ingot, specifically including: heating with the furnace in a stepped heating method. In the first stage, the temperature is raised to 300℃ at a rate of 60℃ / h and held for 1 hour; in the second stage, the temperature is raised to 700℃ at a rate of 80℃ / h and held for 2 hours; in the third stage, the temperature is raised to 1180℃ at a rate of 100℃ / h and held for 2 hours.

[0017] Step 3: Multi-directional forging. The billet, heated to a fully heated state, is taken out of the furnace and then placed on a forging press for forging operations; the initial forging temperature is controlled at 1180℃. First Z-axis forging pass: The billet is laid flat, and the hammer is pressed down along the Z-axis. The forging ratio is 1.65, and the final forging temperature is 980℃. Rotate 90° around the X-axis: Flip the billet with the front and back sides centered on the X-axis, turning the original front and back sides into the top and bottom surfaces (the surface to be deformed switches to the X-axis). Second Z-axis forging pass: The hammer is pressed down along the Z-axis, compressing the original front-back dimension (reduction in the X-axis, extension in the Y / Z-axis), with a forging ratio of 1.65 and a final forging temperature of 960℃. Rotate 90° around the Y-axis: Flip the billet with the left and right sides centered on the Y-axis, turning the original left and right sides into the top and bottom surfaces (the surface to be deformed switches to the Y-axis). Third Z-axis forging pass: The hammer is pressed down along the Z-axis, compressing the original left-right dimension (reduction in the Y-axis, extension in the X / Z-axis), with a forging ratio of 1.65 and a final forging temperature of 920℃. Repeat the above process once.

[0018] Step 4: Cooling. After final forging, the forging is immediately transferred to an annealing furnace preheated to 710℃. A segmented controlled cooling process is used, with a cooling rate maintained at 300℃ / h, cooling to 390℃. After being removed from the furnace, it is allowed to cool to room temperature in air to obtain the GH350 forging billet. The mechanical properties of this embodiment are shown in Table 1 below, and the chemical composition of the GH350 triple casting ingot (the same as the GH350 forging billet) is shown in Table 2. Example 2

[0019] A method for improving the triaxial uniformity of the microstructure of GH350 in the forged state includes the following steps: Step 1: Perform surface peeling treatment on the GH350 triple casting ingot to remove defects such as oxide scale, cracks, and pits from the surface of the billet; Step 2: Perform a stepped heating heat treatment on the GH350 triple casting ingot, specifically including: heating the furnace in a stepped heating method. In the first stage, the temperature is increased to 350℃ at a rate of 100℃ / h and held for 0.5h; in the second stage, the temperature is increased to 780℃ at a rate of 90℃ / h and held for 1.5h; in the third stage, the temperature is increased to 1160℃ at a rate of 110℃ / h and held for 3h.

[0020] Step 3: Multi-directional forging. The billet, heated to a fully heated state, is taken out of the furnace and then placed on a forging press for forging operations; the initial forging temperature is controlled at 1180℃.

[0021] First Z-axis forging pass: The billet is laid flat, and the hammer is pressed down along the Z-axis. The forging ratio is 1.2, and the final forging temperature is 990℃. Rotate 90° around the X-axis: Flip the billet with the front and back sides as the center, turning the original front and back sides into the top and bottom surfaces (the surface to be deformed switches to the X-axis). Second Z-axis forging pass: The hammer is pressed down along the Z-axis, compressing the original front-back dimension (reduction in the X-axis, extension in the Y / Z-axis). The forging ratio is 1.2, and the final forging temperature is 980℃. Rotate 90° around the Y-axis: Flip the billet with the left and right sides as the center, turning the original left and right sides into the top and bottom surfaces (the surface to be deformed switches to the Y-axis). Third Z-axis forging pass: The hammer is pressed down along the Z-axis, compressing the original left-right dimension (reduction in the Y-axis, extension in the X / Z-axis). The forging ratio is 1.2, and the final forging temperature is 950℃. Repeat the above process once, with a forging ratio of 1.9 for each pass.

[0022] Step 4: Cooling. After final forging, the forging is immediately transferred to an annealing furnace preheated to 720℃. A segmented controlled cooling process is used, with a cooling rate maintained at 310℃ / h, cooling to 380℃. After being removed from the furnace, it is allowed to cool to room temperature in air to obtain the GH350 forging billet. The mechanical properties of this embodiment are shown in Table 1 below, and the chemical composition of the GH350 triple casting ingot (the same as the GH350 forging billet) is shown in Table 2. Example 3

[0023] A method for improving the triaxial uniformity of the microstructure of GH350 in the forged state includes the following steps: Step 1: Perform surface peeling treatment on the GH350 triple casting ingot to remove defects such as oxide scale, cracks, and pits from the surface of the billet; Step 2: Perform a stepped heating heat treatment on the GH350 triple casting ingot, specifically including: heating with the furnace in a stepped heating method. The first stage is to heat to 380℃ at a rate of 75℃ / h and hold for 1 hour; the second stage is to heat to 750℃ at a rate of 105℃ / h and hold for 1.2 hours; the third stage is to heat to 1150℃ at a rate of 120℃ / h and hold for 3 hours.

[0024] Step 3: Multi-directional forging. The billet, heated to a fully heated state, is taken out of the furnace and then placed on a forging press for forging operations; the initial forging temperature is controlled at 1180℃.

[0025] First Z-axis forging pass: The billet is laid flat, and the hammer is pressed down along the Z-axis. The forging ratio is 1.5, and the final forging temperature is 960℃. Rotate 90° around the X-axis: Flip the billet with the front and back sides centered on the X-axis, turning the original front and back sides into the top and bottom surfaces (the surface to be deformed switches to the X-axis). Second Z-axis forging pass: The hammer is pressed down along the Z-axis, compressing the original front-back dimension (reduction in the X-axis, extension in the Y / Z-axis), with a forging ratio of 1.5 and a final forging temperature of 930℃. Rotate 90° around the Y-axis: Flip the billet with the left and right sides centered on the Y-axis, turning the original left and right sides into the top and bottom surfaces (the surface to be deformed switches to the Y-axis). Third Z-axis forging pass: The hammer is pressed down along the Z-axis, compressing the original left-right dimension (reduction in the Y-axis, extension in the X / Z-axis), with a forging ratio of 1.5 and a final forging temperature of 910℃. Repeat the above process once, with a forging ratio of 1.6 for each pass.

[0026] Step 4: Cooling. After final forging, the forging is immediately transferred to an annealing furnace preheated to 730℃. A segmented controlled cooling process is used, with the cooling rate maintained above 300℃ / h, cooling to 370℃. After being removed from the furnace, it is allowed to cool to room temperature in air to obtain the GH350 forging billet. The mechanical properties of this embodiment are shown in Table 1 below, and the chemical composition of the GH350 triple casting ingot (the same as the GH350 forging billet) is shown in Table 2. Example 4

[0027] A method for improving the triaxial uniformity of the microstructure of GH350 in the forged state includes the following steps: Step 1: Perform surface peeling treatment on the GH350 triple casting ingot to remove defects such as oxide scale, cracks, and pits from the surface of the billet; Step 2: Perform a stepped heating heat treatment on the GH350 triple casting ingot, specifically including: heating with the furnace in a stepped heating method. The first stage is to heat to 430℃ at a rate of 80℃ / h and hold for 0.8h; the second stage is to heat to 780℃ at a rate of 110℃ / h and hold for 1.8h; the third stage is to heat to 1130℃ at a rate of 150℃ / h and hold for 3.5h.

[0028] Step 3: Multi-directional forging. The billet, heated to a fully heated state, is taken out of the furnace and then placed on a forging press for forging operations; the initial forging temperature is controlled at 1180℃.

[0029] First Z-axis forging pass: The billet is laid flat, and the hammer is pressed down along the Z-axis. The forging ratio is 1.8, and the final forging temperature is 980℃. Rotate 90° around the X-axis: Flip the billet with the front and back sides centered on the X-axis, turning the original front and back sides into the top and bottom surfaces (the surface to be deformed switches to the X-axis). Second Z-axis forging pass: The hammer is pressed down along the Z-axis, compressing the original front-back dimension (reduction in the X-axis, extension in the Y / Z-axis), with a forging ratio of 1.8 and a final forging temperature of 950℃. Rotate 90° around the Y-axis: Flip the billet with the left and right sides centered on the Y-axis, turning the original left and right sides into the top and bottom surfaces (the surface to be deformed switches to the Y-axis). Third Z-axis forging pass: The hammer is pressed down along the Z-axis, compressing the original left-right dimension (reduction in the Y-axis, extension in the X / Z-axis), with a forging ratio of 1.8 and a final forging temperature of 910℃. Repeat the above process once, with a forging ratio of 1.5 for each pass.

[0030] Step 4: Cooling. After final forging, the forging is immediately transferred to an annealing furnace preheated to 740℃. A segmented controlled cooling process is used, with the cooling rate maintained above 300℃ / h, cooling to 360℃. After being removed from the furnace, it is allowed to cool to room temperature in air to obtain the GH350 forging billet. The mechanical properties of this embodiment are shown in Table 1 below, and the chemical composition of the GH350 triple casting ingot (the same as the GH350 forging billet) is shown in Table 2. Example 5

[0031] A method for improving the triaxial uniformity of the microstructure of GH350 in the forged state includes the following steps: Step 1: Perform surface peeling treatment on the GH350 triple casting ingot to remove defects such as oxide scale, cracks, and pits from the surface of the billet; Step 2: Perform a stepped heating heat treatment on the GH350 triple casting ingot, specifically including: heating with the furnace in a stepped heating method. The first stage is to heat to 490℃ at a rate of 85℃ / h and hold for 0.8h; the second stage is to heat to 790℃ at a rate of 115℃ / h and hold for 2h; the third stage is to heat to 1120℃ at a rate of 150℃ / h and hold for 4h.

[0032] Step 3: Multi-directional forging. The billet, heated to a fully heated state, is taken out of the furnace and then placed on a forging press for forging operations; the initial forging temperature is controlled at 1180℃.

[0033] First Z-axis forging pass: The billet is laid flat, and the hammer is pressed down along the Z-axis. The forging ratio is 2.1, and the final forging temperature is 970℃. Rotate 90° around the X-axis: Flip the billet with the front and back sides centered on the X-axis, turning the original front and back sides into the top and bottom surfaces (the surface to be deformed switches to the X-axis). Second Z-axis forging pass: The hammer is pressed down along the Z-axis, compressing the original front-back dimension (reduction in the X-axis, extension in the Y / Z-axis), with a forging ratio of 2.1 and a final forging temperature of 940℃. Rotate 90° around the Y-axis: Flip the billet with the left and right sides centered on the Y-axis, turning the original left and right sides into the top and bottom surfaces (the surface to be deformed switches to the Y-axis). Third Z-axis forging pass: The hammer is pressed down along the Z-axis, compressing the original left-right dimension (reduction in the Y-axis, extension in the X / Z-axis), with a forging ratio of 2.1 and a final forging temperature of 905℃. Repeat the above process once, with a forging ratio of 1.2 for each pass.

[0034] Step 4: Cooling. After final forging, the forging is immediately transferred to an annealing furnace preheated to 750℃. A segmented controlled cooling process is used, with the cooling rate maintained above 300℃ / h, cooling to 380℃. After being removed from the furnace, it is allowed to cool to room temperature in air to obtain the GH350 forging billet. The mechanical properties of this embodiment are shown in Table 1 below, and the chemical composition of the GH350 triple casting ingot (the same as the GH350 forging billet) is shown in Table 2. Example 6

[0035] A method for improving the triaxial uniformity of the microstructure of GH350 in the forged state includes the following steps: Step 1: Perform surface peeling treatment on the GH350 triple casting ingot to remove defects such as oxide scale, cracks, and pits from the surface of the billet; Step 2: Perform a stepped heating heat treatment on the GH350 triple casting ingot, specifically including: heating with the furnace in a stepped heating method. In the first stage, the temperature is increased to 500℃ at a rate of 90℃ / h and held for 1 hour; in the second stage, the temperature is increased to 850℃ at a rate of 130℃ / h and held for 2 hours; in the third stage, the temperature is increased to 1100℃ at a rate of 150℃ / h and held for 5 hours.

[0036] Step 3: Multi-directional forging. The billet, heated to a fully heated state, is taken out of the furnace and then placed on a forging press for forging operations; the initial forging temperature is controlled at 1180℃.

[0037] First Z-axis forging pass: The billet is laid flat, and the hammer is pressed down along the Z-axis. The forging ratio is 2.5, and the final forging temperature is 980℃. Rotate 90° around the X-axis: Flip the billet with the front and back sides as the center, turning the original front and back sides into the top and bottom surfaces (the surface to be deformed switches to the X-axis). Second Z-axis forging pass: The hammer is pressed down along the Z-axis, compressing the original front-back dimension (reduction in the X-axis, extension in the Y / Z-axis). The forging ratio is 2.5, and the final forging temperature is 960℃. Rotate 90° around the Y-axis: Flip the billet with the left and right sides as the center, turning the original left and right sides into the top and bottom surfaces (the surface to be deformed switches to the Y-axis). Third Z-axis forging pass: The hammer is pressed down along the Z-axis, compressing the original left-right dimension (reduction in the Y-axis, extension in the X / Z-axis). The forging ratio is 2.5, and the final forging temperature is 920℃. Repeat the above process once, with a forging ratio of 1.2 for each pass.

[0038] Step 4: Cooling. After final forging, the forging is immediately transferred to an annealing furnace preheated to 760℃. A segmented controlled cooling process is used, with the cooling rate maintained above 300℃ / h, cooling to 400℃. After being removed from the furnace, it is allowed to cool to room temperature in air to obtain the GH350 forging billet. The mechanical properties of this embodiment are shown in Table 1 below, and the chemical composition of the GH350 triple casting ingot (the same as the GH350 forging billet) is shown in Table 2.

[0039] Table 1. Properties of GH350 forgings obtained in Examples 1-6

[0040] Table 2 Chemical composition of GH350 triple casting ingots in Examples 1-6

[0041] Appendix Figure 1 , 2 The accompanying drawings for Embodiment 5 are shown below (the drawings for other embodiments are similar and therefore omitted). Figure 1 It is evident that the overall grain morphology of the alloy is regular and uniform, effectively avoiding fluctuations in mechanical properties caused by grain inhomogeneity, thus laying the foundation for the stability of the alloy's high-temperature strength and toughness. Figure 2 The accompanying figure shows that the η phase has a significant dispersed distribution characteristic. The η phase is uniformly dispersed in the form of fine particles without agglomeration or coarsening, thus avoiding the grain boundary embrittlement problem caused by uncontrolled η phase distribution.

[0042] The above embodiments are only used to illustrate and not limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention without departing from the spirit and scope of the present invention. Any modifications or partial substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for improving the triaxial uniformity of the microstructure of GH350 in the forged state, characterized in that, The method includes the following steps: Step 1: Perform surface peeling treatment on the GH350 triple casting ingot; Step 2: Perform a stepped heating heat treatment on the GH350 triple casting ingot, specifically including: first, raise the temperature to 300-500℃ and hold for 0.5-1h; then raise the temperature to 700-850℃ and hold for 1-2h; finally, raise the temperature to 1100-1180℃ and hold for 2-5h. Step 3: Multi-directional forging. The billet, heated to a fully heated state, is taken out of the furnace and then placed on a forging press for forging operations. The initial forging temperature is controlled at 1100-1180℃, and the final forging temperature is ≥900℃. First Z-axis forging: The billet is laid flat, and the hammer is pressed down along the Z-axis, with a forging ratio range of 1.2 to 2.5; rotate 90° around the X-axis: flip the billet back and forth towards the X-axis, turning the original front and back sides into the top and bottom surfaces; Second Z-axis forging: The hammer is pressed down along the Z-axis, compressing the original front and back dimensions, with a forging ratio range of 1.2 to 2.5; rotate 90° around the Y-axis: flip the billet left and right towards the Y-axis, turning the original left and right sides into the top and bottom surfaces; Third Z-axis forging: The hammer is pressed down along the Z-axis, compressing the original left and right dimensions, with a forging ratio range of 1.2 to 2.5; repeat the above process 1 to 3 times; Step 4: Cooling. After the final forging is completed, the forging is immediately transferred to an annealing furnace preheated to 700-780°C. After cooling to 350-400°C, it is left to cool in the air to room temperature to obtain GH350 forging billet.

2. The method for improving the triaxial uniformity of the forged microstructure of GH350 according to claim 1, characterized in that, In step two, the stepped heating method is to heat the furnace along with the furnace. The heating rate in the first stage is 60-100℃ / h, the heating rate in the second stage is maintained in the range of 80-150℃ / h, and the temperature is held for 1-2 hours; the heating rate in the third stage is controlled at 100-200℃ / h.

3. The method for improving the triaxial uniformity of the forged microstructure of GH350 according to claim 1, characterized in that, In step three, the temperature is monitored in real time during the forging process. If the final forging temperature drops, it should be replenished in time. If the billet temperature drops below 900℃, it needs to be reheated in the furnace to 1100-1150℃, held for 0.5-1 hour, and then forging can continue.

4. The method for improving the triaxial uniformity of the forged microstructure of GH350 according to claim 1, characterized in that, In step four, the cooling rate is maintained above 300°C / h.

5. A method for improving the triaxial uniformity of the forged microstructure of GH350 according to any one of claims 1-4, characterized in that, The chemical composition and mass percentage of the GH350 triple casting ingot are as follows: Carbon: 0.01%~0.025%, Chromium: 15.3%–16.5%, molybdenum: 2.95%–3.25%, titanium: 1.65%–2.35%, iron: 0.6%–1.25%, cobalt: 23.0%–27.0%, tantalum: 3.5%–4.6%, with the remainder being nickel and unavoidable impurities.

6. A method for improving the triaxial uniformity of the forged microstructure of GH350 according to any one of claims 1-4, characterized in that, The GH350 forging billet has a tensile strength of 1156-1403 MPa and a difference in X, Y, and Z dimensional properties of ≤5.6%.

7. A method for improving the triaxial uniformity of the forged microstructure of GH350 according to any one of claims 1-4, characterized in that, The GH350 forging billet has a yield strength of 997-1168 MPa and a difference in X, Y, and Z dimensional properties of ≤5.6%.

8. A method for improving the triaxial uniformity of the forged microstructure of GH350 according to any one of claims 1-4, characterized in that, The GH350 forging billet has an elongation of 15.8% to 20.5% and a three-dimensional performance difference of ≤9.8% in the X, Y, and Z directions.

9. A method for improving the triaxial uniformity of the forged microstructure of GH350 according to any one of claims 1-4, characterized in that, The GH350 forging billet has a hardness of 36.5 to 43.5 HRC, at which point the difference in X, Y, and Z-axis properties is ≤6.9%.

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