A forging method to improve the uniformity of microstructure in GH4169 series high-temperature alloy ring forgings

Abstract

This invention belongs to the field of forging hot working and relates to a forging method for improving the uniformity of the microstructure of GH4169 series high-temperature alloy ring forgings. The method obtains a ring billet with a uniform microstructure by controlling the billet heating temperature and forging deformation. Pre-forging is then performed. The pre-forging die is designed to pre-allocate the deformation amount of each part, ensuring that the deformation amount of each part meets the requirement of 30%-70% during final forging, eliminating the existence of dead deformation zones or critical deformation zones, thus ensuring uniform microstructure throughout the part. Both pre-forging and final forging are performed using a soft-sleeving method to prevent excessively rapid temperature drop of the billet and reduce the formation of cold die microstructure.

Description

Technical Field

[0001] This invention belongs to the field of forging hot working and relates to a forging method for improving the uniformity of the microstructure of GH4169 series high temperature alloy ring forgings. Background Technology

[0002] GH4169 series high-temperature alloys are among the most widely used alloys in aero-engines, primarily for combustion chamber components. Due to their long-term operation under high temperature and pressure conditions, the microstructure and performance requirements for these parts are extremely stringent. Ring forgings themselves have a relatively simple structure. In conventional forging, either a disc forging process is used, with the center hole area being a continuous forging layer, or a ring blank is directly forged into the final forging. Production practice has shown that these forging methods have low material utilization and significant variations in deformation across different parts of the forging, resulting in large deformation dead zones. This leads to insufficient or no dynamic recrystallization in these dead zones, resulting in uneven grain structure or severe mixed grains in the forging microstructure, failing to meet standard requirements. This further affects the performance of different parts of the forging, making it difficult to meet the application requirements of the parts. Therefore, studying the impact of forging processes on the uniformity of the forging microstructure and controlling grain size is of great significance for improving the performance of ring forgings. Summary of the Invention

[0003] Objective of the invention: To provide a forging method that improves the uniformity of the microstructure of GH4169 series high-temperature alloy ring forgings, thereby enhancing the uniformity of the microstructure of GH4169 series high-temperature alloy ring forgings to meet standard requirements and further ensuring good and stable performance of various parts of the parts.

[0004] Technical solution:

[0005] A forging method for improving the microstructure uniformity of GH4169 series high-temperature alloy ring forgings, comprising:

[0006] Step 1: Make two sets of molds, one set as the final forging mold and the other set as the pre-forging mold. The mold material is 5CrNiMo. The cavity of the pre-forging mold is a ring, and the upper and lower end faces of the cavity are gradually inclined upward from the inside to the outside.

[0007] Step 2: Perform billet preparation and one-fire forging: Heat the GH4169 series bars of the specified specifications to a forging temperature of 980℃-1020℃ in an electric furnace and hold until fully heated. Preheat the free forging hammer and anvil to ≥150℃, and complete the upsetting deformation of the first deformation amount on the free forging hammer. Then, complete the billet preparation and one-fire forging by rolling and punching. Air cool to room temperature, machine the inner hole to the required size, remove the burrs and defects of the inner hole, and obtain the first ring billet.

[0008] Step 3: Perform billet preparation and second-stage forging: Heat the first ring billet in an electric furnace to a forging temperature of 980℃-1020℃ and hold it until it is fully heated. Preheat the free forging hammer anvil to ≥150℃. Place the billet on the frame reaming fixture and expand the inner hole size through the free forging hammer to obtain the second ring billet. The deformation amount of the frame reaming ring billet is the second deformation amount, which is less than the first deformation amount. Air cool to room temperature.

[0009] Step 4: Pre-forging the second ring billet using a pre-forging die: Preheat the pre-forging die to ≥250℃, heat the second ring billet in an electric furnace to a forging temperature of 980℃-1020℃ and hold it until fully heated. After being fully heated, remove it from the furnace and softly wrap it with insulation material of appropriate size. After returning it to the furnace and holding it for 0.5-1h, forge it in the pre-forging die using a hammer, forming it with a single hammer blow. The interval between each hammer blow is 2-5s. The forging deformation is the third deformation. After forging, air cool it to room temperature and remove the burrs using water jet cutting to obtain the pre-forged part.

[0010] Step 5: Final forging of the pre-forged part using the final forging die: Preheat the pre-forging die to ≥250℃, heat the pre-forged billet in an electric furnace to a forging temperature of 980℃-1010℃ and hold it until fully heated. After being fully heated, remove it from the furnace and softly wrap it with insulation material of appropriate size. After returning it to the furnace for 0.5-1h, forge it in the final forging die using a hammer. The first 5 hammer blows are forged in one stroke, with an interval of 3-5 seconds between each blow. Subsequent hammer blows are forged in one stroke, with an interval of 2-4 seconds between each blow. The forging deformation is the fourth deformation, which is greater than the third deformation. The final forging temperature is controlled to ≥910℃. After forging, air cool it to room temperature and remove the burrs using water jet cutting to obtain the final forging.

[0011] Furthermore, in step 1, the inclination angle of the upper and lower end faces of the pre-forging mold cavity is 10° to 20°.

[0012] Furthermore, in step 1, the upper and lower end faces of the pre-forging mold cavity are curved surfaces.

[0013] Furthermore, the first deformation amount is 30%-60%.

[0014] Furthermore, the second deformation amount is 25%-40%.

[0015] Furthermore, the third deformation amount is 20%-30%.

[0016] Furthermore, the fourth deformation amount is 30%-70%.

[0017] Furthermore, the forging equipment used in the pre-forging and die forging processes is a 400KJ hammer with an air pressure of 0.6-0.5Mpa.

[0018] Beneficial effects:

[0019] The forging method for improving the uniformity of the microstructure of GH4169 series high-temperature alloy ring forgings described in this invention obtains a ring billet with uniform microstructure by controlling the billet heating temperature and forging deformation. Pre-forging is then performed. The purpose of the pre-forging die is to pre-allocate the deformation amount of each part, ensuring that the deformation amount of each part of the part meets the requirement of 30%-70% during final forging, eliminating the existence of deformation dead zones or critical deformation zones, thus ensuring uniform microstructure in all parts of the part. Pre-forging and final forging are performed using a soft-sleeve method to prevent excessively rapid temperature drop of the billet and reduce the formation of cold die microstructure. When using a hammer for pre-forging and final forging, the hammering rhythm and interval are controlled. Pre-forging is single-shot forming with an interval of 2-5 seconds between each hammer shot, achieving a forging deformation amount ≥20%. Final forging requires the first 5 hammer shots to be single-shot forming with an interval of 3-5 seconds between each hammer shot, followed by subsequent single-shot forming with an interval of 2-4 seconds between each hammer shot, achieving a forging deformation amount of 25%-60%. The final forging temperature is controlled at ≥910℃. The forging is finally produced. The GH4169 series high-temperature alloy ring forging produced by the process has a uniform microstructure, excellent and stable mechanical properties, and meets the requirements of aviation standards. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the final forging of the sealing ring for the engine in Example 1;

[0021] Figure 2 This is a schematic diagram of the pre-forged sealing ring for engine in Example 1. Detailed Implementation

[0022] A forging method for improving the microstructure uniformity of GH4169 series high-temperature alloy ring forgings, the method comprising the following steps:

[0023] Step 1: Fabricate two sets of molds, one for final forging and one for pre-forging, both made of 5CrNiMo material. The cavity of the pre-forging mold is annular, with both the upper and lower end faces gradually sloping upwards from the inside out. If a conventional ring billet is used for direct final forging, the deformation direction of the ring billet at the protruding positions of the upper and lower molds is a vertical translation, with virtually no deformation. This creates a deformation dead zone, leading to coarse grains and decreased performance. To achieve a uniform microstructure, the amount of deformation is crucial. The upper and lower end faces of the pre-forging mold cavity slope upwards from the inside out to oppose the deformation direction during final forging, thus increasing the deformation at that location during final forging. The relationship between the inclination angle of the upper and lower end faces of the pre-forging mold and the amount of deformation during final forging is as follows:

[0024]

[0025] Step 2: Perform billet preparation and one-fire forging: Heat the GH4169 series bars of the specified specifications to a forging temperature of 980℃-1020℃ in an electric furnace and hold until fully heated. Preheat the free forging hammer and anvil to ≥150℃. Complete the upsetting deformation of 30%-60% on the free forging hammer. Then, complete the billet preparation and one-fire forging by rolling and punching. Air cool to room temperature, machine the inner hole to the required size, remove the burrs and defects of the inner hole, and obtain the first ring billet.

[0026] Step 3: Perform billet preparation and secondary forging: Heat the first ring billet in an electric furnace to a forging temperature of 980℃-1020℃ and hold until fully heated. Preheat the free forging hammer anvil to ≥150℃. Place the billet on the frame forging fixture and enlarge the inner hole size with the free forging hammer to obtain the second ring billet. The deformation of the frame forged ring billet is 25%-40%. Air cool to room temperature. The frame forging is mainly achieved by local radial forging and rotation. Within the deformation range of 25%-40%, dynamic recrystallization occurs inside the metal, and the degree of recrystallization is relatively sufficient, resulting in better equiaxed grains.

[0027] Step 4: Pre-forging the second ring billet using a pre-forging die: Preheat the pre-forging die to ≥250℃, heat the second ring billet in an electric furnace to a forging temperature of 980℃-1020℃ and hold it until fully heated. After being fully heated, remove it from the furnace and softly wrap it with insulation material of appropriate size. After returning it to the furnace and holding it for 0.5-1h, forge it in the pre-forging die using a hammer, forming it with a single hammer blow. The interval between each hammer blow is 2-5s, and the forging deformation is 20%-30%. After forging, air cool it to room temperature and remove the burrs using water jet cutting to obtain the pre-forged part.

[0028] Step 5: Final forging of the pre-forged part using the final forging die: Preheat the pre-forging die to ≥250℃, heat the pre-forging billet in an electric furnace to a forging temperature of 980℃-1010℃ and hold until fully heated. After fully heated, remove from the furnace and soft-wrap with insulation material of appropriate size. After returning to the furnace for holding for 0.5-1 hour, forge in the final forging die using a hammer. The first 5 hammer blows are single-shot forming with an interval of 3-5 seconds between each blow. Subsequent single-shot forming continues with an interval of 2-4 seconds between each blow. The forging deformation is 30%-70%, and the final forging temperature is controlled at ≥91℃. At 0℃, the forging is followed by air cooling to room temperature. Deburring is then removed using water jet cutting to obtain the final forging. This forging process employs counter-hammer forging, which results in a high deformation rate and a significant temperature rise in the core of the billet due to deformation. The first five hammer blows are single-shot forging with a 3-5 second interval between each blow. This allows the deformation heat and distortion energy generated by each single-shot deformation to be transferred and dissipated within this 3-5 second interval. This also allows some of the deformation heat and distortion energy to recrystallize rapidly, controlling the internal temperature of the billet and preventing excessive temperature rise that could lead to coarse grains. After five hammer blows, the overall temperature dissipation of the billet decreases due to the reduced thermal effect caused by deformation. At this point, single-shot forging continues, shortening the interval to 2-4 seconds, completing the final forging within the final forging temperature range. This achieves the goal of obtaining fully recrystallized equiaxed grains and a uniform microstructure in the forging.

[0029] The present invention will be further described in detail below through specific embodiments.

[0030] Example 1:

[0031] like Figure 1 As shown, a forging of an inner cone front sealing ring for a certain engine is made of GH4169. The forging weighs 67 kg and has an outline dimension of Φ370×106 mm. GH4169 bar stock with a diameter of Φ250×230 mm is selected.

[0032] First, a Φ250×230mm bar is heated to a forging temperature of 1020℃ in an electric furnace and held for 140 minutes. Then, it is upset to Φ320×140mm on a free forging hammer. After rolling and punching, the billet is forged in one heat. It is then air-cooled to room temperature and the inner hole is machined to the required size to obtain a ring billet of Φ330×Φ140×140mm. The forging process is carried out by preheating the hammer and anvil to 250℃ and using a 3T free forging hammer.

[0033] The aforementioned ring billet is heated to a forging temperature of 1010℃ in an electric furnace and held for 70 minutes. The billet is then placed on a frame reaming fixture and its inner diameter is enlarged by a free forging hammer to obtain a ring billet with dimensions of Φ380×Φ213×135mm. The billet is then air-cooled to room temperature. The forging process involves preheating the hammer and anvil to 250℃, and the forging equipment is a 3T free forging hammer.

[0034] The aforementioned ring billet is then heated in an electric furnace to a forging temperature of 1010℃ and held for 55 minutes. After being removed from the furnace, it is softly wrapped with insulating material and kept in the furnace for 0.5 hours before being placed into a pre-forging die for pre-forging. The number of hammer blows is 8-10, with an interval of ~3 seconds between each blow. After forging, it is air-cooled to room temperature. The pre-forging die is preheated to 300℃. The forging equipment is a 400KJ hammer with an air pressure of 0.6-0.5Mpa.

[0035] The pre-forged parts obtained above are machined to remove internal holes and burrs, and then ground to remove defects. They are then heated to a forging temperature of 1000℃ in an electric furnace and held for 50 minutes. After being taken out of the furnace, they are softly wrapped with insulating material and kept in the furnace for 0.5 hours. They are then placed in the final forging die for pre-forging, with 10 to 12 hammer blows. The first five blows are spaced about 4 seconds apart, and the subsequent blows are spaced about 2 seconds apart. After forging, they are air-cooled to room temperature. The final forging die is preheated to 300℃. The forging equipment is a 400KJ hammer with an air pressure of 0.6-0.5Mpa.

[0036] The internal burrs and rough edges were subsequently removed by water jet cutting to obtain the final forging. The forging produced by the above process has a uniform microstructure under low magnification, and the average grain size of each part is grade 6, which meets the standard requirement of ≥4. The room temperature mechanical properties, high temperature tensile properties, creep rupture and hardness of the GH4169 ring forging fully meet the requirements.

Claims

1. A forging method for improving the microstructure uniformity of GH4169 series high-temperature alloy ring forgings, characterized in that, include: Step 1: Make two sets of molds, one set as the final forging mold and the other set as the pre-forging mold. The mold material is 5CrNiMo. The cavity of the pre-forging mold is a ring, and the upper and lower end faces of the cavity are gradually inclined upward from the inside to the outside. Step 2: Perform billet preparation and one-fire forging: Heat the GH4169 series bars of the specified specifications to a forging temperature of 980℃-1020℃ in an electric furnace and hold until fully heated. Preheat the free forging hammer and anvil to ≥150℃, and complete the upsetting deformation of the first deformation amount on the free forging hammer. Then, complete the billet preparation and one-fire forging by rolling and punching. Air cool to room temperature, machine the inner hole to the required size, remove the burrs and defects of the inner hole, and obtain the first ring billet. Step 3: Perform billet preparation and second-stage forging: Heat the first ring billet in an electric furnace to a forging temperature of 980℃-1020℃ and hold it until it is fully heated. Preheat the free forging hammer anvil to ≥150℃. Place the first ring billet on the frame reaming fixture and expand the inner hole size through the free forging hammer to obtain the second ring billet. The deformation amount of the frame reaming ring billet is the second deformation amount, which is less than the first deformation amount. Air cool to room temperature. Step 4: Pre-forging the second ring billet using a pre-forging die: Preheat the pre-forging die to ≥250℃, heat the second ring billet in an electric furnace to a forging temperature of 980℃-1020℃ and hold it until fully heated. After being fully heated, remove it from the furnace and softly wrap it with insulation material of appropriate size. After returning it to the furnace and holding it for 0.5-1h, forge it in the pre-forging die using a hammer, forming it with a single hammer blow. The interval between each hammer blow is 2-5s. The forging deformation is the third deformation. After forging, air cool it to room temperature and remove the burrs using water jet cutting to obtain the pre-forged part. Step 5: Perform final forging of the pre-forged part using the final forging die: Preheat the final forging die to ≥250℃, heat the pre-forged part in an electric furnace to a forging temperature of 980℃-1010℃ and hold until fully heated. After being fully heated, remove it from the furnace and softly wrap it with insulation material of appropriate size. After returning it to the furnace for 0.5-1h, forge it in the final forging die using a hammer. The first 5 hammer blows are forged in one stroke, with an interval of 3-5 seconds between each blow. Subsequent hammer blows are forged in one stroke, with an interval of 2-4 seconds between each blow. The forging deformation is the fourth deformation amount, which is greater than the third deformation amount. The final forging temperature is controlled to ≥910℃. After forging, air cool to room temperature and remove the burrs using water jet cutting to obtain the final forging part.

2. The forging method for improving the microstructure uniformity of GH4169 series high-temperature alloy ring forgings according to claim 1, characterized in that, In step 1, the inclination angle of the upper and lower end faces of the pre-forging mold cavity is 10° to 20°.

3. The forging method for improving the microstructure uniformity of GH4169 series high-temperature alloy ring forgings according to claim 1, characterized in that, In step 1, the upper and lower end faces of the pre-forging mold cavity are curved surfaces.

4. The forging method for improving the microstructure uniformity of GH4169 series high-temperature alloy ring forgings according to claim 1, characterized in that, The first deformation is 30%-60%.

5. The forging method for improving the microstructure uniformity of GH4169 series high-temperature alloy ring forgings according to claim 1, characterized in that, The second deformation is 25%-40%.

6. The forging method for improving the microstructure uniformity of GH4169 series high-temperature alloy ring forgings according to claim 1, characterized in that, The third deformation is 20%-30%.

7. The forging method for improving the microstructure uniformity of GH4169 series high-temperature alloy ring forgings according to claim 1, characterized in that, The fourth deformation amount is 30%-70%.

8. The forging method for improving the microstructure uniformity of GH4169 series high-temperature alloy ring forgings according to claim 1, characterized in that, The forging equipment used in the pre-forging and final forging processes is a 400KJ hammer with an air pressure of 0.6-0.5Mpa.

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