A process for producing a fine-grained GH4169 alloy disc-shaped forging

Abstract

The application discloses a process method for producing a fine-grain GH4169 alloy disc-shaped forge piece, and the method comprises the following steps: (1) performing solid solution treatment on a GH4169 alloy blank; (2) performing aging treatment on the blank after the solid solution treatment; (3) keeping the blank after the aging treatment at 970-990 DEG C for 90-180 min; (4) performing die forging on the blank treated in the step 2, the total deformation amount is controlled to be more than 40%, the pressing speed of a hydraulic machine is controlled to be 5-20 mm / s, and then air cooling is performed; (5) performing aging treatment on the forge piece; (6) when the furnace temperature rises to 1005-1020 DEG C, keeping the temperature for 10-20 min, lowering the furnace temperature to 990-1005 DEG C for 5-20 min, and then lowering the furnace temperature to 970-985 DEG C for 30-60 min. The method can obtain the GH4169 alloy disc-shaped forge piece with a uniform fine-grain structure.

Description

Technical Field

[0001] This invention relates to a process for producing fine-grained GH4169 alloy disc forgings, belonging to the field of nickel-based alloy hot working technology. Background Technology

[0002] GH4169 alloy, with its excellent strength, toughness, and corrosion resistance at high temperatures, has become the preferred material for critical hot-end components such as turbine disks in aero-engines. GH4169 alloy exhibits high deformation resistance at room temperature, so turbine disks are typically formed by hot forging. However, the complex shape of turbine disks leads to extremely uneven strain distribution in the forgings after hot forging, and the narrow forming process parameters of GH4169 make it difficult to achieve complete recrystallization during forging. This results in uneven grain structure in turbine disk forgings, severely affecting their mechanical properties and service life. Therefore, obtaining GH4169 alloy forgings with a fine-grained structure is a problem that urgently needs to be solved.

[0003] Due to the static and sub-dynamic recrystallization behavior during annealing, the coarse / mixed grains formed during die forging can be effectively and uniformly refined through annealing. For GH4169 alloy, the δ phase promotes recrystallization nucleation during annealing while inhibiting grain growth. Therefore, before recrystallization annealing, aging treatment is performed on the forging to precipitate a large amount of δ phase, fully utilizing the promoting effect of δ phase on static recrystallization and the inhibiting effect on grain growth, thereby refining the mixed grain structure of the forging. However, the uneven strain distribution of the forging after die forging leads to the formation of mixed grain structures of varying degrees in different regions. Current heat treatment processes are insufficient to simultaneously and uniformly refine the mixed grain structure in different regions of GH4169 alloy die forgings. Therefore, there is an urgent need to propose a new, economical, and efficient method to obtain GH4169 alloy disc forgings with a uniform and fine grain structure. Summary of the Invention

[0004] The purpose of this invention is to provide a process for producing fine-grained GH4169 alloy disc forgings. This method obtains disc forgings through ordinary die forging, and then performs "δ-phase aging + multi-stage cooling recrystallization annealing" on the forgings to eliminate coarse and mixed grain structures in different regions of ordinary die forgings, thus solving the problems of high cost or unsatisfactory grain refinement effect of existing processes.

[0005] The solution of the present invention to the above problems is:

[0006] Step 1: Perform a solution treatment on the GH4169 alloy billet to dissolve the solute atoms into the matrix and distribute the solute atoms evenly. After the solution treatment is completed, remove the billet and air cool it.

[0007] Step 2: Aging treatment is performed on the cooled forgings from Step 1. The aging temperature is controlled at 890-910℃ and the aging time is controlled at 20-25 hours to uniformly precipitate the δ phase.

[0008] Step 3: Heat the GH4169 alloy billet treated in Step 2 to 970-990℃ and hold for 90-180 minutes;

[0009] Step 4: Transfer the GH4169 alloy billet processed in Step 3 to a die forging machine for die forging. The hydraulic press pressing rate is 5-20 mm / s, and the total deformation is controlled to be above 40%. After die forging, air cool.

[0010] Step 5: Perform a second aging treatment on the cooled forgings from Step 4. The aging temperature is controlled at 890-910℃ and the aging time is controlled at 6-12 hours.

[0011] Step 6: After the furnace temperature rises to 1005-1020℃ in 50-70 minutes, hold it at that temperature for 10-20 minutes. Then, after a cooling time of 3-10 minutes, lower the furnace temperature to 990-1005℃ and hold it for 5-20 minutes. After another cooling time of 3-10 minutes, lower the furnace temperature again to 970-985℃ and hold it for 30-60 minutes. Finally, remove the forging and air cool it.

[0012] The design concept of this invention is to further refine the coarse / mixed-grain structure formed during die forging through a static and sub-dynamic recrystallization mechanism. Furthermore, the forging is subjected to δ-phase aging treatment before recrystallization annealing to precipitate sufficient δ-phase to promote static recrystallization nucleation and slow down grain growth during subsequent recrystallization annealing. Addressing the problems of uneven strain distribution in die forgings leading to varying degrees of mixed grains in different regions and difficulties in heating large forgings, a multi-stage cooling recrystallization annealing method is proposed. The first stage of high temperature accelerates the heating of the forging while stimulating static recrystallization nucleation in the low-strain region. Subsequently, the high temperature is slightly reduced to ensure the nucleation rate and prevent excessive grain growth. Finally, the annealing temperature is lowered again to achieve a relatively controllable recrystallization rate. Holding at this temperature for a period allows the recrystallized grains to slowly engulf the deformed coarse grains, ultimately obtaining a GH4169 alloy disc forging with uniform fine grains.

[0013] Patent CN 115261753 A, entitled "A Hot Working Method for Producing Highly Uniform Ultrafine-Grained Nickel-Based High-Temperature Alloys"; Patent CN 116005087 A, entitled "A Heat Treatment Method for GH4169 Alloy Forgings"; Patent CN 109457201 A, entitled "A Method for Refining the Grain Size of Nickel-Based Alloy Forgings and Improving the Uniformity of the Microstructure"; Patent CN 109252120 B, entitled "A Method for Uniformly Refining the Microstructure of GH4169 Alloy Forgings"; Patent CN 111575620 B, entitled "A Method for Obtaining Ultrafine-Grained GH4169 Alloy Forgings"; and Patent CN 116657067 A, entitled "A Heat Treatment Method for Uniformly Refining the Mixed-Grain Microstructure of GH4169 Alloy Forgings and Controlling the δ-Phase Content," all six patents disclose hot working methods for producing fine-grained GH4169 alloy forgings. Patent CN 115261753 A uses a method of "δ-phase aging treatment + isothermal forging" to obtain fine-grained forgings. Patent CN116005087 A uses a method of "ordinary forging + isothermal recrystallization annealing" to refine the grain structure of forgings, which can refine the mixed-grain structure after forging to a certain extent. Patents CN 109252120 B and CN 111575620 B propose heat treatment methods of "δ-phase aging + multiple isothermal recrystallization annealing" and "δ-phase aging + continuous cooling recrystallization annealing," respectively, to refine the mixed-grain structure after forging. In order to control the residual content of δ-phase while refining grains, patent CN 116657067 A proposes "δ-phase aging + three-stage recrystallization annealing." This invention utilizes a process of "ordinary die forging + δ-phase aging + multi-stage cooling recrystallization annealing" to obtain GH4169 alloy disc forgings with a fine-grained microstructure. Its key technical highlight is the multi-stage cooling recrystallization annealing. This process consists of two high-temperature stages at different temperatures, three cooling stages, and one low-temperature stage. Unlike other heat treatment methods, the two high-temperature stages in the multi-stage cooling recrystallization annealing accelerate the heating rate of the forging and the nucleation rate in the small strain region, effectively solving the problems of difficult heating during the annealing process of large forgings and unsatisfactory grain refinement in the small strain region. The "ordinary die forging + δ-phase aging + multi-stage cooling recrystallization annealing" method proposed in this invention is more suitable for the production of large GH4169 alloy fine-grained forgings, and can economically and efficiently obtain GH4169 alloy disc forgings with uniform fine grains.

[0014] The beneficial effects of this invention are as follows: Compared with isothermal forging of GH4169 alloy disc forgings, this method uses "ordinary forging + heat treatment" to refine the mixed-grain structure of the forging, which can effectively save time and economic costs. Furthermore, the method uses a heat treatment approach of "δ-phase aging + multi-stage cooling recrystallization annealing" to uniformly refine the mixed-grain structure formed in different regions of the GH4169 alloy disc forging, providing a new method for forming and manufacturing next-generation, higher-performance turbine disc forgings. Attached Figure Description

[0015] Figure 1 The hot working process of the GH4169 alloy disc forging in Example 1;

[0016] Figure 2 Strain distribution diagram of GH4169 alloy after forging in Example 1;

[0017] Figure 3 The grain structure at various characteristic locations of the GH4169 disc forging after heat treatment in Example 1;

[0018] Figure 4 Hot working process of GH4169 alloy disc forging in Comparative Example 1;

[0019] Figure 5 Strain distribution diagram of GH4169 alloy after forging in Comparative Example 1;

[0020] Figure 6 The grain structure at various characteristic locations of the GH4169 disc forging in Comparative Example 1 after heat treatment. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0022] This invention is a process for producing fine-grained GH4169 alloy disc forgings. The following examples all use typical industrial GH4169 billets as the subject.

[0023] Example 1

[0024] Step 1: The GH4169 alloy billet with dimensions of φ220mm×133mm is subjected to solution treatment at a temperature of 1040±5℃ for 150min. The billet is then removed and air-cooled.

[0025] Step 2: Heat the GH4169 alloy billet that has been cooled to room temperature in Step 1 to 900℃ and hold it at that temperature for 24 hours;

[0026] Step 3: Heat the GH4169 alloy billet treated in Step 2 to 980±5℃ and hold for 105 min;

[0027] Step 4: Transfer the GH4169 alloy billet processed in Step 3 to a die forging machine for die forging. The hydraulic press lowering rate is 10 mm / s, reducing the billet height to 68 mm (deformation of approximately 51%). After die forging, air cool. The process method for processing the GH4169 alloy billet in steps 1, 2, 3, and 4 is as follows: Figure 1 As shown, the strain distribution diagram of the cross-section of the forging after die forging is as follows: Figure 2 As shown;

[0028] Step 5: Heat the GH4169 alloy forging, which has been cooled to room temperature in Step 4, to 900℃ and hold for 9 hours;

[0029] Step 6: After completing step 5, raise the furnace temperature to 1010-1020℃ over 60 minutes and hold for 15 minutes. Then, after a 5-minute cooling period, lower the furnace temperature to 995-1005℃ and hold for 10 minutes. After another 5-minute cooling period, lower the furnace temperature again to 975-985℃ and hold for 40 minutes. Finally, remove the forging and air cool it.

[0030] Comparative Example 1

[0031] In this comparative example, the hot working method for the GH4169 alloy disc forging includes the following steps:

[0032] Step 1: The GH4169 alloy billet with dimensions of φ220mm×133mm is subjected to solution treatment at a temperature of 1040±5℃ for 150min. The billet is then removed and air-cooled.

[0033] Step 2: Heat the GH4169 alloy billet that has been cooled to room temperature in Step 1 to 900℃ and hold it at that temperature for 24 hours;

[0034] Step 3: Heat the GH4169 alloy billet treated in Step 2 to 950±5℃ and hold for 105 min;

[0035] Step 4: Transfer the GH4169 alloy billet processed in Step 3 to a die forging machine for die forging. The hydraulic press lowering rate is 10 mm / s, reducing the billet height to 68 mm (deformation of approximately 51%). After die forging, air cool. The process method for processing the GH4169 alloy billet in steps 1, 2, 3, and 4 is as follows: Figure 4 As shown, the strain distribution diagram of the cross-section of the forging after die forging is as follows: Figure 5 As shown;

[0036] Step 5: Heat the GH4169 alloy forging, which has been cooled to room temperature in Step 4, to 900℃ and hold for 9 hours;

[0037] Step 6: After completing step 4, raise the furnace temperature to 975-985℃ over 40 minutes and hold for 90 minutes. Then remove the forging and air cool it.

[0038] Microstructural observation was performed on the GH4169 alloy disc forging obtained in Example 1. The characteristic locations of the forging (special features are located in...) Figure 2 The electron backscatter diffraction (EBSD) results (marked in the middle) are as follows: Figure 3 As shown. From Figure 3 As can be seen, the grain structure at the characteristic locations of the forging consists of mostly fine recrystallized grains and a small amount of deformed grains, with the remaining deformed grains being relatively few in content and small in size. Statistical analysis showed that the average grain sizes at characteristic locations P1-P6 of the forging were 6.06 μm, 8.58 μm, 7.00 μm, 7.10 μm, 8.81 μm, and 6.61 μm, respectively, all meeting ASTM 10 standards. The two high-temperature stages of multi-stage cooling recrystallization annealing have the advantage of accelerating the recrystallization nucleation rate in the low-strain region of the forging while also accelerating the heating rate of the forging, while the growth rate of recrystallized grains is slowed down in the low-temperature stage. Therefore, a uniform and fine grain structure was obtained in both the low-strain regions (such as P1 and P5) and the central regions (P4 and P6) of the forging.

[0039] Microstructure observation was performed on the GH4169 alloy disc forging obtained in Comparative Example 1. The characteristic locations of the forging (special features) were observed in... Figure 5 The EBSD results (marked in the middle) are as follows: Figure 6 As shown. From Figure 6 As can be seen, coarse deformed grains of varying amounts are present in the grain structure at the characteristic locations of the forging. Statistical analysis shows that the average grain sizes at characteristic locations P1-P6 of the forging are 12.26 μm, 14.93 μm, 7.04 μm, 13.36 μm, 21.64 μm, and 7.01 μm, respectively. Because the recrystallization annealing uses isothermal annealing at a relatively low temperature, the nucleation rate in the small strain regions of the forging (such as P1 and P5) is too slow. The evolution of the microstructure is mainly characterized by the slow growth of recrystallized grains, thus making it difficult to eliminate a large number of coarse deformed grains. Furthermore, the isothermal annealing method results in a slow heating rate in the core of the forging, leading to a certain degree of mixed-grain structure in the core as well (such as P4).

[0040] The fineness and uniformity of the final grain structure of the forging in Example 1 are superior to those of the forging in Comparative Example 1, demonstrating the superiority of the present invention. The present invention, through a method of "ordinary die forging + δ-phase aging + multi-stage cooling recrystallization annealing," can obtain GH4169 alloy disc forgings with a uniform fine-grained structure. Compared to the fine-graining processes of other GH4169 alloy forgings, the present invention has advantages such as lower cost, better grain refinement effect, and higher efficiency.

[0041] Examples of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely exemplary and not limiting. Any invention that does not exceed the claims of the present invention is within the protection scope of the present invention.

Claims

1. A process for producing fine-grained GH4169 alloy disc forgings, characterized in that... This method obtains GH4169 alloy disc forgings with a uniform fine-grained structure through "ordinary die forging + δ-phase aging + multi-stage cooling recrystallization annealing", including the following steps: Step 1: The GH4169 alloy billet is subjected to solution treatment to dissolve solute atoms into the matrix and distribute the solute atoms evenly. Step 2: Aging treatment is performed on the solution-treated billet. The aging temperature is controlled at 890-910℃ and the aging time is controlled at 20-25 hours to uniformly precipitate the δ phase. Step 3: Heat the GH4169 alloy billet treated in Step 2 to 970-990℃ and hold for 90-180 minutes; Step 4: Forge the GH4169 alloy billet processed in Step 3 into a die forging shape, with the total deformation controlled at more than 40% and the hydraulic press pressing speed controlled at 5-20 mm / s. Step 5: After the GH4169 alloy forging treated in Step 4 is air-cooled to room temperature, the forging is subjected to aging treatment. The aging temperature is controlled at 890-910℃ and the aging time is controlled at 6-12 hours. Step 6: When the furnace temperature reaches 1005-1020℃, hold it for 10-20 minutes. After 3-10 minutes, lower the furnace temperature to 990-1005℃ and hold it for 5-20 minutes. After another 3-10 minutes, lower the furnace temperature to 970-985℃ and hold it for 30-60 minutes.

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