A method for forging a high-pressure compressor disc of GH738 with L-shaped cross section

Abstract

This invention relates to the field of forging technology, and more particularly to a forging method for a GH738 high-pressure compressor disc with an L-shaped cross-section. The method includes: Step 1: Determining the shape and size of the forging based on the disc shape, wherein the upper end face of the forging is a sloping surface with a lower inner surface and a higher outer surface; Step 2: Determining the shape and size of the billet based on the shape, size, and deformation amount of the forging, wherein the upper end of the billet is a large end, and the lower end is a small end; the large end is a columnar structure with a draft angle, and the lower end is a frustum with a predetermined angle; Step 3: Determining the bar stock size based on the billet shape, size, and deformation amount; Step 4: Blanking; Step 5: Forging the bar stock in a die to obtain a billet; Step 6: Forging the billet in a final forging die to obtain a forging; Step 7: Performing heat treatment and machining on the forging to obtain the disc.

Description

Technical Field

[0001] This invention relates to the field of forging technology, and in particular to a forging method for a GH738 high-pressure compressor disc with an L-shaped cross-section. Background Technology

[0002] Nickel-based superalloys are widely used in various high-performance engine components and high-temperature hot-end components of various industrial gas turbines, such as turbine disks, turbine casings, working blades and combustion chambers, due to their excellent comprehensive properties such as high heat resistance, resistance to hot corrosion, resistance to high-temperature oxidation, good fatigue performance and fracture toughness. GH738 is a nickel-based superalloy with a high degree of alloying. During hot working, it often suffers from microstructure inhomogeneity problems such as microstructure segregation, coarse grains, mixed grains and surface cracks. The uniformity of the microstructure and grain size are well correlated with the ultrasonic longitudinal wave velocity, attenuation coefficient, and noise frequency. Some GH738 engine discs have extremely high requirements for water immersion ultrasonic flaw detection. The acceptance standard is Φ0.4 flat bottom hole, with noise and bottom loss both at -6dB, and noise and bottom loss ≤50%. Traditional manufacturing processes involve multiple forgings of raw materials, and direct forging of blanks with the same hot working parameters. The deformation and grain size of different parts of the forging vary greatly, resulting in a very uneven microstructure. It is difficult to meet the ultrasonic flaw detection and metallographic structure acceptance requirements of the forgings. The scrap rate of the produced engine discs is high, the raw material loss is large, and the number of forgings is high. After forging, heat treatment is not effective in improving the microstructure. Therefore, the water immersion ultrasonic flaw detection results of the forgings are not ideal. Summary of the Invention

[0003] Purpose of the invention: This invention provides a forging method for L-shaped GH738 high-pressure compressor discs, which solves the problems of large differences in deformation and grain size among different parts of the forging caused by traditional hot working process parameters and direct forging of blanks. These problems result in extremely uneven microstructure, making it difficult to meet the requirements of ultrasonic testing and metallographic structure acceptance, leading to a high scrap rate. Furthermore, it addresses the issues of high raw material reforging losses, numerous forging cycles, and long processing times (to achieve a Φ0.4 flat-bottom hole, with noise and bottom loss both at -6dB, and noise and bottom loss ≤50%, the raw material undergoes as many as 10-20 reforging cycles). This method reduces the scrap rate, the number of forging cycles, improves production efficiency, reduces energy consumption, increases raw material utilization, and lowers production costs.

[0004] Technical solution: A forging method for a GH738 high-pressure compressor disc with an L-shaped cross-section, wherein the upper and lower end faces of the disc are flat, comprising: Step 1: Determine the shape and size of the forging based on the shape of the disc, wherein the upper end face of the forging is an inclined surface with a lower inner surface and a higher outer surface; Step 2: Determine the shape and size of the billet based on the shape, size and deformation of the forging. The upper end of the billet is the large end and the lower end is the small end. The large end is a columnar structure with a draft angle and the lower end is a frustum with a predetermined angle. Step 3: Determine the bar stock dimensions based on the billet shape, size, and deformation amount; Step 4: Unloading; Step 5: Place the bar stock into the die and forge it to obtain the billet; Step 6: Place the billet into the final forging die to forge the forging to obtain the forging; Step 7: Heat treat and machine the forging to obtain the disc.

[0005] Furthermore, in step 1, the upper end face of the forging is an inclined plane of about 7~15°.

[0006] Furthermore, in step 2, the ratio of the billet height to the forging height is greater than or equal to 45%.

[0007] Furthermore, in step 2, the weight of the disc is 0.88 to 0.92 times the weight of the blank.

[0008] Furthermore, in step 3, the weight of the billet is 0.88 to 0.92 times the weight of the bar stock, and the height of the billet is 0.3 to 0.45 times the length of the bar stock. Furthermore, in step 5, the heating temperature is 1045~1060℃, the heat preservation coefficient is 0.5~0.7mm / min, and the forging transfer time is ≤30s.

[0009] Furthermore, in step 5, the cooling method is air cooling.

[0010] Furthermore, in step 6, the heating temperature is 1060~1075℃, the heat preservation coefficient is 0.5~0.7mm / min, and the forging transfer time is ≤30s.

[0011] Furthermore, in step 6, the cooling method is air cooling.

[0012] Furthermore, in step 7, the heat treatment process consists of solution treatment and aging.

[0013] Beneficial effects: The design of the billet increases the overall deformation of the disc to between 38% and 65%. By designing the high ribs of the disc as bevels, the deformation of the lower deformation areas (high ribs) is increased to over 45%, thus increasing the overall deformation of the disc to between 45% and 65%. Different processes are used to correspond to different heating temperature ranges, solving the difficulties of achieving uniform microstructure and meeting ultrasonic testing requirements in forged discs. It also addresses the problems of high scrap rates, numerous forging passes, low production efficiency, low raw material utilization, and high production costs associated with traditional disc production. This design is applicable to the manufacture of all L-type GH738 discs. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram comparing the structure of a traditional forging with the forging structure of the present invention; Figure 2 This is a schematic diagram of the billet structure; Figure 3 This is a schematic diagram of the forging process of a forging according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the high-magnification metallographic structure of the forging. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. 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. Numerous specific details are set forth in the following detailed description 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 setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0018] In the description of this invention, it should be noted that the directions or positional relationships indicated by terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing and simplifying the invention, and should not be construed as limiting the invention. Furthermore, the use of ordinal numbers (e.g., "first and second," etc.) is for distinguishing objects and is not limited to this 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 in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] To meet the requirements of ultrasonic flaw detection and microstructure analysis for GH738 engine discs, a local bevel design was adopted instead of the traditional planar design to eliminate the deformation dead zone (the metal does not flow much on the horizontal surface of the disc during forging, resulting in a large area of ​​deformation dead zone, which leads to extremely uneven microstructure in the forging in this area). At the same time, a manufacturing process with different forging heating temperatures corresponding to different deformation ranges was adopted, which can effectively improve the microstructure of the forging and produce products that meet the acceptance requirements of the discs.

[0022] This invention provides a forging method for a GH738 high-pressure compressor disc with an L-shaped cross-section, comprising: 1. The horizontal plane design of the high ribs of the disc is changed to an inclined plane with an included angle of about 7~15°. The rest of the disc is designed normally with a certain machining allowance. After the metal flows to the high rib area of ​​the disc, if the high rib area is a plane, the metal will not flow and deform much, resulting in a small amount of deformation at the top of the high rib and poor microstructure and properties of the forging. However, after the top of the high rib is changed to an inclined plane, the metal flows to the top of the rib and rolls along the inclined plane, changing the flow mode of the metal and greatly improving the microstructure and properties of the high rib area of ​​the forging.

[0023] 2. Calculate the minimum billet height H based on the required deformation amount (≥45%) for GH738. The calculation formula is as follows: (Bill height / Forging height) × 100% ≥ 45% The formula for calculating the weight of the billet is: weight of the disc / (0.88~0.92). The specific dimensions of the billet diameter D are determined by the height and weight of the billet.

[0024] The billet positioning table is made to match the lower die of the final forging cavity, with a height of 10~20mm.

[0025] The weight of the bar stock is 0.88~0.92 times the weight of the billet, and the length is 0.3~0.45 times the height of the billet. The specifications are determined by the height and the weight of the raw materials.

[0026] 3. Preheat the die before forging at 400℃. The die material is 55CrNiMoV7. The preheating time is ≥8 hours. Place the preheated bar in a thermal furnace at 100~150℃ for 10~20 minutes. After removal, evenly spray with heat-insulating coating. Then place the bar into the forging furnace and heat at 1045~1060℃. Calculate the holding time using a holding coefficient of 0.5~0.7 mm / min. Simultaneously calculate the bar removal time to ensure the die is properly installed when the bar is removed, preventing excessive die temperature loss and the formation of a cold die structure. The die cavity should be designed according to... Figure 2 The design specifies a forging transfer time of ≤30s for billet forging. The forging equipment is selected based on the area of ​​the disc diameter D. For diameters ≤0.03m², a 5t die forging hammer is used; for 0.03~0.1m², a 250kJ counter-hammer is used; for 0.1~0.25m², a 630kJ counter-hammer is used; and for diameters above 0.25m², a 200NM hydraulic press is used. If hammer forging is used, the billet should be placed upright during forging, and the air pressure should be controlled at 60%~80%. First, perform 1~2 light blows, then heavy blows. The interval between blows must be controlled at 1~2 seconds to prevent excessive temperature rise and uneven microstructure. If a press is used, the speed should not exceed 5mm / s, and air cooling should be used.

[0027] 4. Preheat the die before forging at 400℃. The die material is 55CrNiMoV7. The preheating time is ≥8h. After spraying the insulating coating as described in step 3, place the billet into the forging furnace and heat it at 1060~1075℃. Calculate the holding time using a holding coefficient of 0.5~0.7mm / min. Calculate the billet tapping time so that the die is just installed when the billet taps out, preventing excessive die cooling and the formation of a cold die structure. The die cavity is designed according to the forging shape. The forging transfer time is ≤30s. The equipment selection is based on the area of ​​the forging diameter, using the same method as in step 3. Then, process the coiled parts. Forging: During forging, the billet is placed on the positioning table. If hammer forging is used, the air pressure is controlled at 60%~80%. First, lightly strike once, then strike heavily. The interval between hammer blows must be controlled at 1~2 seconds to prevent excessive temperature rise and uneven microstructure. If a press is used, the speed should not exceed 10mm / s. Air cooling is used to obtain the final disc. After forging, solution treatment, stabilization and aging heat treatment are performed. Finally, the part is machined according to its shape and subjected to physical and chemical tests to obtain the final part. Water immersion ultrasonic flaw detection is performed. After the flaw detection is qualified, it is delivered to the customer.

[0028] Heat treatment process: Solid solution: 8~32℃ below the initial γ phase dissolution temperature, heat preservation time 4h, cooling method oil cooling.

[0029] Stabilization: Hold at 843℃ for 4 hours, then air cool.

[0030] Duration: 760℃ heat preservation time for 16 hours, air cooling.

[0031] 5. If the standard sample used for flaw detection is close to and has a uniform microstructure of the forging, the accuracy of the water immersion ultrasonic flaw detection result will be higher. This can avoid scrapping caused by the difference between the microstructure of the standard sample and the microstructure of the forging. The uniform microstructure of the disc forged by the above method can reach the standard sample usage level. Therefore, the standard sample can be cut from the disc forged by the above method, sent to a certified third party for machining and testing, and after passing the certification and obtaining the certificate, the standard sample can be used for water immersion ultrasonic flaw detection.

[0032] The present invention will now be described in further detail with reference to specific embodiments.

[0033] This embodiment is a high-pressure compressor disc forging of a certain type of aircraft engine. It is L-shaped, made of Waspaloy (GH738), and weighs 15kg.

[0034] First firing: billet preparation, mold preheating to 400℃, holding time 8 hours, bar preheating and placing it in the electric furnace at 100℃ for 10 minutes, after taking it out, uniformly spraying with heat-insulating coating GZH-3, then heating the bar to the forging temperature of 1050℃ and holding for 100 minutes, then placing the bar into the die cavity, forging it using a 5T die forging hammer, setting the air pressure to 60%, first lightly striking twice, then heavily striking to form the shape, and then air cooling after taking it out.

[0035] The second forging process involves preheating the die to 400℃ and holding it for 8 hours. The preheated bar stock is placed in a thermal furnace at 100℃ for 10 minutes. After removal, it is evenly sprayed with GZH-3 heat-insulating coating. The billet is then heated to the forging temperature of 1060℃ and held for 70 minutes. The billet is then aligned with the positioning table and placed into the die cavity. A 5T forging hammer is used for forging, with the equipment set to 60% air pressure. The initial blow is light, followed by a heavy blow to form the shape. After removal, the billet is air-cooled. After forging, solution treatment, stabilization, and aging heat treatment are performed. After heat treatment, the billet is machined according to the delivered drawings and subjected to water immersion ultrasonic testing. After passing the test, five forgings are put into storage and delivered for production. According to the testing standards, these forgings are sent to a customer-certified third-party company for machining with different flat-bottom hole depth gauges and testing. After passing the test and obtaining a certificate of conformity, the gauges are then used for water immersion ultrasonic testing.

[0036] Through the above forging process, the produced parts have a uniform structure, and all physical and chemical test results meet the standard acceptance requirements. The water immersion ultrasonic test results meet the requirements of Φ0.4 flat bottom hole, with noise and bottom loss both at -6dB, and noise and bottom loss ≤50%. The physical and chemical test results are qualified.

[0037] 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 forging method for a GH738 high-pressure compressor disc with an L-shaped cross-section, characterized in that, The upper and lower end faces of the disc are flat, including: Step 1: Determine the shape and size of the forging based on the shape of the disc, wherein the upper end face of the forging is an inclined surface with a lower inner surface and a higher outer surface; Step 2: Determine the shape and size of the billet based on the shape, size and deformation of the forging. The upper end of the billet is the large end and the lower end is the small end. The large end is a columnar structure with a draft angle and the lower end is a frustum with a predetermined angle. Step 3: Determine the bar stock dimensions based on the billet shape, size, and deformation amount; Step 4: Unloading; Step 5: Place the bar stock into the die and forge it to obtain the billet; Step 6: Place the billet into the final forging die to forge the forging to obtain the forging; Step 7: Heat treat and machine the forging to obtain the disc.

2. The method according to claim 1, characterized in that, In step 1, the upper end face of the forging is an inclined plane of about 7~15°.

3. The method according to claim 1, characterized in that, In step 2, the ratio of billet height to forging height is greater than or equal to 45%.

4. The method according to claim 1, characterized in that, In step 2, the weight of the disc is 0.88 to 0.92 times the weight of the blank.

5. The method according to claim 1, characterized in that, In step 3, the billet weight is 0.88 to 0.92 times the bar weight, and the billet height is 0.3 to 0.45 times the bar length.

6. The method according to claim 1, characterized in that, In step 5, the heating temperature is 1045~1060℃, the heat preservation coefficient is 0.5~0.7mm / min, and the forging transfer time is ≤30s.

7. The method according to claim 1, characterized in that, In step 5, the cooling method is air cooling.

8. The method according to claim 1, characterized in that, In step 6, the heating temperature is 1060~1075℃, the heat preservation coefficient is 0.5~0.7mm / min, and the forging transfer time is ≤30s.

9. The method according to claim 1, characterized in that, In step 6, the cooling method is air cooling.

10. The method according to claim 1, characterized in that, In step 7, the heat treatment process consists of solution treatment and aging.

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