Forming method for controlling grain size of ring forge piece through GH4738 heat treatment system

Abstract

The invention belongs to the field of hot working, and particularly relates to a forming method for controlling the grain size of a ring forging through a GH4738 heat treatment system. Comprising the steps that after forging forming of a GH4738 alloy forge piece is finished, preheating treatment is conducted in a direct remelting mode; and the forge piece obtained after preheat treatment is subjected to solid solution treatment and two times of aging treatment, and the oil temperature before oil entering during solid solution treatment, the oil cooling time during solid solution treatment and the furnace discharging transfer time during solid solution treatment are determined according to the weight of the forge piece.

Description

Technical Field

[0001] This invention belongs to the field of hot working, specifically relating to a forming method for controlling the grain size of ring forgings using the GH4738 heat treatment process. Background Technology

[0002] GH4738 alloy is a precipitation-hardening nickel-based wrought superalloy. It exhibits high tensile and creep strength, as well as good oxidation resistance, within the temperature range of 650–900℃. It is suitable for manufacturing parts requiring high strength below 870℃ and oxidation resistance below 980℃. Simultaneously, it possesses excellent high-temperature strength and creep strength, making it widely used in fields such as aero-engines. Typically used as critical components such as support discs and turbine discs, it operates under harsh conditions. To meet the requirements of these practical applications, high demands are placed on the microstructure and properties of GH4738 forgings.

[0003] Further improvements are needed to the microstructure of GH4738 forgings and to increase the grain size requirements. Summary of the Invention

[0004] Purpose of the invention: To provide a forming method for controlling the grain size of ring forgings using the GH4738 heat treatment process, thereby improving the quality of forgings and reducing product scrap and the resulting significant waste of resources.

[0005] Technical solution: A forming method for controlling the grain size of ring forgings using a GH4738 heat treatment process, comprising: After the GH4738 alloy forging is forged, it is preheated by directly returning it to the furnace. Forgings that have undergone pre-heat treatment are subjected to solution treatment and two aging treatments. The oil temperature before immersion in oil, the oil cooling time during solution treatment, and the transfer time after removal from the furnace during solution treatment are determined based on the weight of the forgings.

[0006] Furthermore, the pre-treatment temperature is determined based on the effective thickness δ of the forging: .

[0007] Furthermore, the holding time T in the furnace at the pre-heat treatment temperature is determined based on the effective thickness (δ) mm of the forging: .

[0008] Furthermore, the cooling method after preliminary heat treatment is determined based on the weight of the forging: .

[0009] Furthermore, the oil temperature before adding the solution during solid solution treatment should be controlled according to the following table: .

[0010] Furthermore, the oil cooling time during solution treatment is controlled according to the following table: .

[0011] Furthermore, the transfer time during solution treatment should be controlled according to the following table: .

[0012] Further, solution treatment: ≤700℃ is put into the furnace and heated to 850±10℃, held for 60±6min, then heated to 980±10℃, held for 60±6min, then heated to 1030±10℃, held for 240±15min, and then removed from the furnace and cooled in oil.

[0013] Furthermore, the first aging process is as follows: the furnace is heated to 750±10℃ at a temperature of ≤700℃, and after holding at that temperature, the temperature is raised to 845±10℃, and after holding for a certain period of time, the furnace is removed and air-cooled.

[0014] Furthermore, the second aging process involves: ≤600℃ entering the furnace and heating it to 750±10℃, holding it at that temperature, then raising the temperature again to 760±10℃, holding it for that time, and then removing it from the furnace and air cooling it.

[0015] Beneficial effects: This invention provides a method for forming GH4738 alloy ring forgings. This method incorporates pre-treatment heat treatment and strict control over final heat treatment parameters, particularly the parameters at each stage. These parameters include pre-treatment temperature (°C), holding time (min), cooling time (min), cooling method, oil cooling time (s), oil temperature before oil immersion (°C), and transfer time (s). The heat treatment parameters are determined based on the forging's own parameters, such as wall thickness (δ) mm, effective parameter (γ) mm, and forging weight (G). The aim is to strictly control the influence of these parameters on the internal microstructure and grain size of the forging, ensuring the product meets final requirements and effectively improving the product yield. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments 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.

[0017] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setup and method set forth below, but covers any improvements, substitutions, and modifications to the structures, methods, and devices without departing from the spirit of the invention.

[0018] In the description of this invention, the use of ordinal numbers (e.g., "first and second", etc.) is for distinguishing objects and is not limited to the order, and should not be construed as indicating or implying relative importance.

[0019] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly, encompassing both direct connection and indirect connection via an intermediate medium. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0020] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited from each other.

[0021] The present invention discloses a forming method for controlling the grain size of ring forgings using a GH4738 heat treatment process. By setting different pre-heat treatment temperature parameters and cooling methods for different forging wall thicknesses, and by adding a pre-heat treatment process, the pre-heat treatment process parameters are controlled to meet the grain size requirements of the forgings, thereby achieving the final requirements of the forgings and reducing product scrap and thus avoiding significant resource waste.

[0022] The preheating process in the preheating stage employs a two-stage preheating method, wherein the preheating temperature remains constant, and the heating temperature varies according to the deformation of the forging in the forging step described above.

[0023] The present invention discloses a forming method for controlling the grain size of ring forgings using a GH4738 heat treatment process, the specific steps of which are as follows: Step 1: After forging the part using conventional forging methods, the formed billet is directly returned to the furnace for pre-heat treatment after ring rolling. Among these steps... Based on the effective thickness δ of the forging, the setting of the pre-heat treatment temperature after the completion of the forming forging step is determined;

[0024] Step 2: Determine the holding time T in the furnace at the pre-heat treatment temperature based on the effective thickness (δ) mm of the forging.

[0025] Step 3: Select and control the cooling time after pre-heat treatment according to the weight of the forging:

[0026] Step 4: Select and control the cooling method after pre-heat treatment according to the weight of the forging:

[0027] Step 5: Forgings that have undergone preliminary heat treatment according to the table above need to be solution treated and aged twice. The cooling method for solution treatment is based on the weight of the forging, and the heat treatment parameters are controlled accordingly. Solution treatment: ≤700°C is placed in the furnace and heated to 850±10°C, held for 60±6 min, then heated to 980±10°C, held for 60±6 min, then heated to 1030±10°C, held for 240±15 min, and then oil-cooled after removal from the furnace.

[0028] The oil temperature before solution treatment should be controlled according to the table below.

[0029]

[0030] The oil cooling time during solution treatment should be controlled according to the table below.

[0031]

[0032] The transfer time during solution treatment should be controlled according to the table below.

[0033]

[0034] Step 8: Forgings that have undergone preliminary heat treatment according to the table above need to undergo final heat treatment: that is, solution treatment followed by the first aging treatment. First aging: ≤700°C is placed in the furnace and heated to 750±10°C. After holding at this temperature, the temperature is raised to 845±10°C and held for a specified time. Then, the parts are removed from the furnace and air-cooled.

[0035] Step 9: Forgings that have undergone preliminary heat treatment according to the table above need to be solution treated before undergoing a second aging treatment. Second aging: ≤600°C is placed in the furnace and heated to 750±10°C. After holding at this temperature, the temperature is further increased to 760±10°C. After holding at this temperature for the specified time, the parts are removed from the furnace and air-cooled.

[0036] Step 10: Conduct physical and chemical tests on the forgings. All performance indicators must meet the standards and the grain size must meet the requirements.

[0037] This paper optimizes the pre-heat treatment process for GH4738 forgings by adding a preliminary heat treatment before the final heat treatment. Different preliminary heat treatment parameters are set according to the forging wall thickness. The improvement in grain size of the forgings before and after optimization is characterized by processing the embrittled layer after heat treatment. The results show that the optimized process achieves a relatively finer grain size and significantly improved mechanical properties compared to conventional methods. The optimized GH4738 forging process can lay a foundation for applications in aerospace and other materials fields.

[0038] This paper uses heat treatment technology to optimize different pre-heat treatment parameters for different forging wall thicknesses. Under the same forging process parameters, the grain size of GH4738 forgings can be tested and compared using the above method. By evaluating the test results of grain size, mechanical properties, and other aspects of the forgings, optimal forging process parameters can be obtained. Furthermore, the influence of different process parameters on the microstructure and properties of forgings is preliminarily analyzed from a theoretical perspective.

[0039] The technical solution of the present invention will be further described in detail below with reference to examples: The low-vortex level 6 baffle ring forging of the present invention has the following dimensions: φ763×682×60; material: GH4738, category II; process specification requires blanking specification: φ220×162; weight: 55.33Kg; the overall performance indicators and grain size requirements of the forging shall meet the requirements of AMS7124 standard (grain size requirement level 4 or finer).

[0040] The forging process is detailed below: Step 1: Place the batch of φ230×162mm material into the electric furnace and hold at 850±50℃ for 100 minutes. Then heat to 1080℃ and hold for 130 minutes. Shape the material into φ330×80mm (completed in one heat). Place the material back into the electric furnace and hold at 850±50℃ for 100 minutes. Then heat to 1070℃ and hold for 65 minutes. Punch holes ≤φ130×30mm (completed in one heat). Step 2: Machine the inner hole to φ140; and chamfer the upper and lower end faces of the inner hole to R10; sand and polish.

[0041] Step 3: After machining, the forging is placed in the furnace at 850℃ and held for 55 minutes, then the temperature is increased to 1070℃ for 65 minutes (completed in 2 heats); the roughing end face is flattened to the rough shape dimensions: φ470×φ300×61mm; Step 4: After reaming the hole, heat it in the furnace at 850±50℃ for 50 minutes, then raise the temperature to 1080℃ and hold for another 50 minutes (step 1 is complete); ream the hole to the dimensions shown in the forging drawing: φ763×φ682×60mm; Step 5: Preliminary heat treatment temperature; Based on the forging wall thickness δ of 40.5, determine the preliminary heat treatment temperature setting after the completed forming forging step; 1015.5℃ Step 6: Determine the holding time in the furnace for the pre-heat treatment temperature according to the effective heating parameters of the forging; the effective heating parameters refer to the comparison between the forging height of 60 min and the wall thickness of 40.5 mm. The minimum effective heating parameter γ is selected as 40.5 mm to complete the pre-heat treatment holding time of 80 min.

[0042] Step 7: After the forging weighs 55.33 kg, allow it to cool for 85 minutes following the initial heat treatment.

[0043] Step 8: Based on the forging weight of 55.33 kg, the pre-heat treated part is cooled by air cooling. Step 9: After preliminary heat treatment, the forgings require solution treatment and two aging treatments. The cooling method for solution treatment is based on the forging weight of 55.33 kg, with heat treatment parameters controlled accordingly: ≤700℃, enter the furnace and heat to 850±10℃, hold for 60±6 min, then heat to 980±10℃, hold for 60±6 min, then heat to 1030±10℃, hold for 240±15 min, then remove from the furnace and oil cool. The oil cooling time during solution treatment is controlled to be ≥35 min.

[0044] Step 10: After preliminary heat treatment, the forgings require solution treatment and two aging treatments. The cooling method for solution treatment is based on the forging weight of 55.33 kg, with heat treatment parameters controlled accordingly. Solution treatment: ≤700℃ is introduced into the furnace and heated to 850±10℃, held for 60±6 min, then heated to 980±10℃, held for 60±6 min, then heated to 1030±10℃, held for 240±15 min, and finally cooled in oil. The oil temperature before solution treatment is controlled to ≤45℃.

[0045] Step 11: Forgings that have undergone preliminary heat treatment require solution treatment and two aging treatments. The cooling method for solution treatment is based on the forging weight of 55.33 kg, with heat treatment parameters controlled accordingly: ≤700℃ is introduced into the furnace and heated to 850±10℃, held for 60±6 min, then heated to 980±10℃, held for 60±6 min, then heated to 1030±10℃, held for 240±15 min, and finally oil-cooled after removal from the furnace. The transfer time during solution treatment is controlled to ≤55 seconds.

[0046] Step 12: Forgings that have undergone preliminary heat treatment need to be solution treated before the first aging treatment. First aging: ≤700°C is put into the furnace and heated to 750±10°C, held for 60±6 min, then heated to 845±10°C, held for 240±30 min, and then air-cooled after being taken out of the furnace.

[0047] Step 13: Forgings that have undergone preliminary heat treatment need to be solution treated before undergoing a second aging treatment. Second aging: ≤600°C is placed in the furnace and heated to 750±10°C, held for 60±6 minutes, then heated to 760±10°C, held for 960±60 minutes, and then air-cooled after removal from the furnace.

[0048] Step 14: Conduct physical and chemical tests on the forgings. All performance indicators must meet the standards and the grain size must meet the requirements.

[0049] The grain size of GH4738 alloy ring forgings is sensitive to the pre- and final heat treatment parameters. Through production verification, this invention solves the grain size problem of GH4738 alloy by strictly controlling the forging heat treatment parameters for forgings with different grain size requirements.

[0050] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A forming method for controlling the grain size of ring forgings using a GH4738 heat treatment process, characterized in that, include: After the GH4738 alloy forging is forged, it is preheated by directly returning it to the furnace. Forgings that have undergone pre-heat treatment are subjected to solution treatment and two aging treatments. The oil temperature before immersion in oil, the oil cooling time during solution treatment, and the transfer time after removal from the furnace during solution treatment are determined based on the weight of the forgings.

2. The method according to claim 1, characterized in that, Determine the pre-heat treatment temperature based on the effective thickness δ of the forging: 。 3. The method according to claim 1, characterized in that, The holding time T in the furnace at the preheat treatment temperature is determined based on the effective thickness (δ) mm of the forging. 。 4. The method according to claim 1, characterized in that, Determine the cooling method after preliminary heat treatment based on the weight of the forging: 。 5. The method according to claim 1, characterized in that, The oil temperature before solution treatment should be controlled according to the following table: 。 6. The method according to claim 1, characterized in that, The oil cooling time during solution treatment should be controlled according to the following table: 。 7. The method according to claim 1, characterized in that, The transfer time during solution treatment should be controlled according to the following table: 。 8. The method according to claim 1, characterized in that, Solution treatment: ≤700℃ is put into the furnace and heated to 850±10℃, held for 60±6min, then heated to 980±10℃, held for 60±6min, then heated to 1030±10℃, held for 240±15min, and then removed from the furnace and cooled in oil.

9. The method according to claim 1, characterized in that, First aging: ≤700℃ enters the furnace and is heated to 750±10℃. After holding at this temperature, the temperature is raised to 845±10℃ and held for the specified time. Then, the furnace is removed and air-cooled.

10. The method according to claim 1, characterized in that, Second aging: ≤600℃ enters the furnace and is heated to 750±10℃. After holding at this temperature, the temperature is raised to 760±10℃ and held for the specified time. Then, the furnace is removed and air-cooled.

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