A method of forging a low pressure turbine casing of FV535 alloy

Abstract

The present application relates to a kind of FV535 alloy low-pressure turbine casing forging method, comprising the following forging steps: modeling step, product is modeled to obtain model data;Heating step;Processing step;Pre-rolling step, raw material is pre-rolled and then air-cooled to room temperature;Model calculation step, superimposed model profile data and forging profile data, calculate the deformation direction and deformation allowance of forging forming;Tire mold forming step: the forging is placed in die and is formed by forging pressing;Then air-cooled to room temperature;Pre-forming step: the linear profile and non-linear profile of forging are sequentially formed by rolling;Special-shaped finish rolling step: forging is heated and kept, and closed rolling is carried out;Then air-cooled to room temperature.Solve the uneven force distribution of existing scheme die pressing, the wall thickness of casing forging is uneven, cause the fracture or crack of forging and if the forged streamline of machined part cannot be distributed along the part profile, the cut-off forging streamline will affect the performance of forging.

Description

Technical Field

[0001] This invention relates to the field of forging, and more particularly to a forging method for an FV535 alloy low-pressure turbine casing. Background Technology

[0002] FV535 alloy is one of the main alloys currently used in casing forgings for civil aircraft engines. The low-pressure turbine casing ring is an important component of aircraft engines, providing a safe and sealed space for the turbine, the core component of the engine.

[0003] The casing forging is a complex multi-step cross-section forging with differences in diameter along the height direction, and the wall thickness distribution is also uneven. If an integral molding process using an irregularly shaped mold is used, the irregular mold surface will cause some parts of the mold surface to contact the raw material first, while others will contact it later during the molding process. This will result in uneven force distribution during molding. Furthermore, because the wall thickness of the casing forging is uneven, it can cause the forging to fracture or crack during forging.

[0004] To reduce the difficulty of casing forming, a rough product shape is usually forged first, followed by machining to complete the final product shape. However, the forging flow lines of the machined part cannot be distributed along the part's profile, and the cut forging flow lines will affect the performance of the forging. Solving the above problems becomes crucial. Summary of the Invention

[0005] To address the shortcomings of the prior art, the present invention aims to provide a forging method for FV535 alloy low-pressure turbine casing, thereby solving the problems of uneven force distribution during die pressing, uneven wall thickness of casing forgings causing forging fractures or cracks during forging, and the inability of machining forging flow lines to be distributed along the part profile, which can affect the performance of forgings.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A forging method for an FV535 alloy low-pressure turbine casing;

[0008] The forging process includes the following steps:

[0009] The modeling process involves creating a model of the product based on the dimensions and shape requirements of the drawings to obtain model data.

[0010] The heating process involves feeding the raw materials and heating them, followed by heat preservation.

[0011] The processing steps involve upsetting and punching the raw materials sequentially, followed by air cooling to room temperature.

[0012] Pre-rolling step: The raw material is pre-rolled to Φ555±5*Φ465±5*260±5; the final forging temperature is ≥850℃; the deformation amount is 25-30%; then it is air-cooled to room temperature to form the forging;

[0013] The model calculation steps are as follows: 1. Measure the dimensions of the forging to obtain measurement data; 2. Superimpose the measurement data onto the model data to obtain the forming machining amount; 3. Mark the cross-sectional contour according to the model data to obtain model contour data; 4. Mark the cross-sectional contour of the forging according to the measurement data to obtain forging contour data; 5. Superimpose the model contour data and the forging contour data to calculate the deformation direction and deformation allowance of the forging.

[0014] The die forming process is as follows: heat the forging and the die separately; place the forging in the die for forging and pressing; then air cool the forging to room temperature;

[0015] Pre-forming step: Divide the model contour data into straight contours and non-straight contours; heat the forging to 1120-1150℃ and heat the rolling die to 300-320℃; roll the straight contours and non-straight contours of the forging in sequence; final forging temperature ≥800℃.

[0016] The special-shaped final rolling process is as follows: the forging is heated to 1120-1150℃ and held for 40-160 minutes; the special-shaped die is heated to 150-250℃ and closed rolling is performed; the final forging temperature is ≥850℃; the deformation is 20-27%; then the forging is air-cooled to room temperature to obtain the product.

[0017] A further technical solution is as follows: In the heating step: the raw material is fed to Φ250*420mm and heated to 1120-1150℃; then it is kept at that temperature for 120-240 minutes.

[0018] The further technical solution is as follows: In the processing steps: the raw material is upset to 290mm, and then punched; the punching size is Φ160-180mm; the final forging temperature is ≥850℃; the deformation amount is 30%; and then it is air-cooled to room temperature.

[0019] A further technical solution is as follows: In the die forming step: the forging is heated to 1120-1150℃; then held at that temperature for 40-160 minutes; the die is heated to 150-250℃; the forging is placed in the die for forging; the final forging temperature is ≥850℃; then the forging is air-cooled to room temperature.

[0020] A further technical solution is as follows: In the die forming step, the forging of the forging workpiece within the die includes multiple processes:

[0021] Planning process: Based on the amount of deformation required for the forging in the mold forming process, divide the forming process into N forming processes and determine the amount of deformation in each forming process;

[0022] First forming process: Based on the deformation of the forging in the first forming process, the amount of graphite to be sprayed on the forging and the mold is obtained and sprayed; the deformation of the forging is positively correlated with the amount of graphite sprayed.

[0023] Nth forming process: Based on the deformation of the forging in the Nth forming process, the amount of graphite sprayed on the forging and the mold is obtained and sprayed; the deformation of the forging is positively correlated with the amount of graphite sprayed.

[0024] A further technical solution is as follows: In the pre-forming step, the straight contour and non-straight contour of the forging are rolled four times in sequence:

[0025] First rolling process: Rolling is performed on the straight contour lines of the forging;

[0026] Second rolling process: Rolling is performed on one side of the non-linear profile of the forging;

[0027] The third rolling process: Rolling is performed on the other side of the non-linear profile of the forging;

[0028] The fourth rolling process: Rolling is performed on the middle position of the non-linear contour of the forging.

[0029] A further technical solution is as follows: In the pre-forming step, the non-linear contour is divided into oblique contour, concave curve contour and convex curve contour; in the second to fourth rolling process, the rolling pressure decreases sequentially according to the different contours.

[0030] A further technical solution is as follows: In the pre-forming step, during the first to fourth rolling processes: the rolling force is positively correlated with the forging deformation; the rolling force is negatively correlated with the forging temperature; and the forging temperature is positively correlated with the rolling die temperature.

[0031] Compared with the prior art, the beneficial technical effects of the present invention are as follows: (1) In the modeling step, by modeling the product, the final shape and size model data of the product can be obtained. Then, based on the model data, the deformation amount and size of the raw materials and forgings in the subsequent steps are restricted, thereby enabling accurate control of the entire forging process; (2) After the pre-rolling step, the rolling of the overall structure of the forging is completed. The forging of the irregular structure of the forging is completed in sequence in the die forming step, the pre-forming step, and the irregular final rolling step. In order to ensure the stability of the deformation direction of the forging and the accuracy of the deformation allowance in the subsequent steps, and to eliminate the influence of the processing error generated by the processing step and the pre-rolling step on the subsequent steps; (3) In the model calculation step, the size of the forging is obtained by measuring the forging, which is the measurement data. Due to the processing error of the processing step and the pre-rolling step, there is a difference between the measurement data and the model data. By superimposing the measurement data with the model data, the size of the forging is calibrated, thereby obtaining the forming processing amount for subsequent steps; (4) In order to avoid the temperature of the mold being low when the forging contacts the mold, and the temperature of the forging contacting the mold dropping sharply, which would affect the surface quality of the forging after forging, the mold is heated to 150-250℃ to avoid the sudden drop in surface temperature of the forging; (5) The forging first passes through a mold of a larger size, and then the forging is placed into molds of gradually decreasing size to complete the molding. In the die forming step of this application, the forging gradually transitions to the required shape in molds of different sizes, avoiding excessive deformation of the forging in a single step, which would cause local cracks or defects in the forging.

[0032] During the molding process, the forging and the mold will generate a large frictional force. In order to avoid excessive friction during molding, graphite is sprayed on the forging and the mold to reduce the friction between them. Attached Figure Description

[0033] Figure 1 A process flow diagram of the forging method of FV535 alloy low-pressure turbine casing according to an embodiment of the present invention is shown.

[0034] Figure 2 A structural diagram of the product is shown.

[0035] Figure 3 A structural diagram of the mold is shown.

[0036] Figure 4 The diagram shows the changes in the structural state of the forging in each step of the forging method of the FV535 alloy low-pressure turbine casing according to an embodiment of the present invention.

[0037] The attached diagram is labeled as follows: 1. Base mold; 11. Mold groove; 12. Mold hole; 13. Bottom block; 2. Cover plate mold. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the device proposed by this invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, only for the purpose of conveniently and clearly illustrating the embodiments of this invention. Please refer to the accompanying drawings to make the objectives, features, and advantages of this invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the implementation conditions of this invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention.

[0039] Figure 1 A process flow diagram of the forging method of FV535 alloy low-pressure turbine casing according to an embodiment of the present invention is shown. Figure 2 A structural diagram of the product is shown. Figure 3 A structural diagram of the mold is shown. Figure 4 This diagram illustrates the changes in the structural state of the forging during each step of the forging method for the FV535 alloy low-pressure turbine casing according to an embodiment of the present invention. (Combined with...) Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, this invention discloses a forging method for an FV535 alloy low-pressure turbine casing.

[0040] The forging method for the FV535 alloy low-pressure turbine casing includes the following forging steps:

[0041] The modeling process involves creating a model of the product based on the dimensions and shape requirements of the drawings, thereby obtaining model data.

[0042] The heating process involves feeding the raw materials and heating them, followed by heat preservation.

[0043] The processing steps involve upsetting and punching the raw materials in sequence, followed by air cooling to room temperature.

[0044] The pre-rolling process involves pre-rolling the raw material to Φ555±5*Φ465±5*260±5. The final forging temperature is ≥850℃. The deformation amount is 25-30%. The forging is then air-cooled to room temperature to form the final product.

[0045] The model calculation steps are as follows: First, measure the dimensions of the forging to obtain measurement data. Then, superimpose the measurement data onto the model data to obtain the forming machining allowance. Next, annotate the cross-sectional contour based on the model data to obtain the model contour data. Finally, annotate the cross-sectional contour of the forging based on the measurement data to obtain the forging contour data. Then, superimpose the model contour data and the forging contour data to calculate the deformation direction and deformation allowance of the forging.

[0046] The die forming process involves heating the forging and the die separately. The forging is then placed inside the die and forged. Afterward, the forging is air-cooled to room temperature.

[0047] Pre-forming step: Divide the model contour data into straight contours and non-straight contours. Heat the forging to 1120-1150℃ and the rolling die to 300-320℃. Roll-form the straight contours and non-straight contours of the forging sequentially. Final forging temperature ≥800℃.

[0048] The final rolling process for irregular shapes involves heating the forging to 1120-1150℃ and holding it at that temperature for 40-160 minutes. The irregular-shaped die is then heated to 150-250℃ for closed-circuit rolling. The final forging temperature is ≥850℃. The deformation is 20-27%. The forging is then air-cooled to room temperature to obtain the final product.

[0049] In the modeling step, by modeling the product, we can obtain the model data of the final shape and size of the product. Then, based on the model data, we can limit the deformation and size of the raw materials and forgings in subsequent steps, thereby enabling accurate control of the entire forging process.

[0050] During the heating process: the raw material is fed into a diameter of Φ250*420mm and heated to 1120-1150℃. Then it is held at that temperature for 120-240 minutes.

[0051] The heating step is the initial heating of the raw material, and it is necessary to ensure that the internal and external temperatures of the raw material are consistent. At this stage, the raw material has not been punched and is relatively thick, so the holding time in the heating step is also longer.

[0052] In the processing steps: the raw material is upset to 290mm, then punched. The punching size is Φ160-180mm. The final forging temperature is ≥850℃. The deformation amount is 30%. It is then air-cooled to room temperature.

[0053] Strict dimensional control is required during upsetting and punching processes to ensure the uniformity of raw material wall thickness in subsequent pre-rolling steps.

[0054] The pre-rolling process involves pre-rolling the raw material to Φ555±5*Φ465±5*260±5. The final forging temperature is ≥850℃. The deformation amount is 25-30%. The forging is then air-cooled to room temperature to form the final product.

[0055] The pre-rolling step results in a cylindrical structure with a relatively short height and a large diameter. The pre-rolling step enlarges the aperture of the raw material and thins its wall thickness, thereby reducing the deformation of the forging in subsequent die forming, pre-forming, and final rolling steps, facilitating the forming of the forging.

[0056] After the pre-rolling step, the overall structure of the forging is rolled. The irregular structure of the forging is then forged sequentially in the die forming step, the pre-forming step, and the final rolling step. This process is designed to ensure the stability of the deformation direction and the accuracy of the deformation allowance in subsequent steps, and to eliminate the influence of machining errors generated in the machining and pre-rolling steps on subsequent steps.

[0057] In the model calculation step, the dimensions of the forging are obtained by measuring it; these are the measurement data. Due to processing errors in the machining and pre-rolling steps, there are discrepancies between the measurement data and the model data. By superimposing the measurement data onto the model data, the dimensions of the forging are calibrated, thereby obtaining the forming and machining allowances for subsequent steps.

[0058] To ensure the final dimensional accuracy of the product, this application requires precise control of the deformation direction and deformation allowance during forging. The cross-section of the product in the model is obtained from the model data, and its contour is annotated. The cross-section of the forging is obtained through measurement, and its contour is also annotated. By superimposing the two contour shapes, the non-overlapping areas are identified as the deformation region.

[0059] Because the product has an irregular shape, the deformation direction and amount of the forging are different at different positions during the forging process. The deformation direction and deformation allowance of the forging can be accurately calculated through the model calculation steps.

[0060] In the die forming process: heat the forging to 1120-1150℃. Then hold at that temperature for 40-160 minutes. Heat the die to 150-250℃. Place the forging in the die for forging. The final forging temperature is ≥850℃. Afterward, air cool the forging to room temperature.

[0061] To prevent a sudden drop in temperature at the point of contact between the forging and the die when the die is at a low temperature, which could affect the surface quality of the forging after forging, the die is heated to 150-250℃ to avoid this sudden temperature drop.

[0062] There are multiple sets of molds used to complete multiple molding processes. The dimensions of the multiple sets of molds are different, and the dimensions of the multiple sets of molds gradually decrease.

[0063] The mold includes a base mold 1 and a cover mold 2 that covers the base mold 1. A mold groove 11 is formed around the upper surface of the base mold 1. Mold holes 12 are formed side by side on the lower surface of the base mold 1. A bottom block 13 is placed in the mold hole 12. During the die forming process, the bottom block 13 is placed in the mold hole 12, the forging is placed in the mold groove 11, the cover mold 2 is placed on the base mold 1, and the cover mold 2 is pressed down by the forging equipment, pressing down the forging. After pressing is completed, the base mold 1 is flipped over, and another set of bottom blocks 13 is stacked at the position of the bottom block 13. The bottom blocks 13 are pressed down by the forging equipment, pressing out the forging.

[0064] The forgings first pass through a larger mold, and then are placed into molds of progressively smaller sizes to complete the molding process. In the die-forming step of this application, the forgings gradually transition to the required shape through molds of different sizes, avoiding excessive deformation of the forgings in a single step, which could cause localized cracks or defects in the forgings.

[0065] During the molding process, the forging and the mold will generate a large frictional force. In order to avoid excessive friction during molding, graphite is sprayed on the forging and the mold to reduce the friction between them.

[0066] In the die forming process, the forging of the workpiece involves several steps, including placing the workpiece in the die for forging.

[0067] Planning process: Based on the amount of deformation required for the forging in the mold forming process, divide the forming process into N forming processes and determine the amount of deformation in each forming process.

[0068] First forming process: Based on the deformation of the forging in the first forming process, the amount of graphite to be sprayed on the forging and the mold is obtained and sprayed. The deformation of the forging is positively correlated with the amount of graphite sprayed.

[0069] Nth forming process: Based on the deformation of the forging in the Nth forming process, the amount of graphite to be sprayed on the forging and the mold is obtained and sprayed. The deformation of the forging is positively correlated with the amount of graphite sprayed.

[0070] The planning process requires knowing the deformation amount in each forming process. The deformation of the forging gradually decreases from the first forming process to the Nth forming process. This also means that the amount of graphite sprayed gradually decreases from the first forming process to the Nth forming process. Simultaneously, after the forming process, a certain amount of graphite will adhere to the mold and the surface of the forging. To ensure accurate control of the graphite spraying amount, the graphite inside the mold and on the surface of the forging needs to be blown away after the forging is removed from the die.

[0071] After determining the amount of graphite based on the deformation of the forging, a uniform coating is applied inside the mold and onto the surface of the forging. The greater the deformation of the forging during the forming process, the greater the amount of graphite sprayed; conversely, the smaller the deformation, the smaller the amount of graphite sprayed.

[0072] The cross-sectional profile of the final product consists of straight lines and non-straight lines, and the thickness distribution of the product is uneven. Therefore, when the special-shaped final rolling step is carried out directly, the deformation of the forging is also uneven. In the thinner parts of the product, cracks or defects will be generated due to the deformation.

[0073] Through a pre-forming step, the straight contours of the forging are first rolled, and then the non-straight contours are rolled, so that the deformation of the non-straight contours is evenly distributed and dispersed towards the straight contours. Then, during the final shaped rolling step, the deformation of the forging is uniformly distributed and will not cause cracks or defects in the non-straight contours.

[0074] In the pre-forming step, the straight and non-straight contours of the forging are rolled four times in sequence:

[0075] First rolling process: Rolling is performed on the straight contour lines of the forging.

[0076] Second rolling process: Rolling is performed on one side of the non-linear profile of the forging.

[0077] The third rolling process: Rolling is performed on the other side of the non-linear profile of the forging.

[0078] The fourth rolling process: Rolling is performed on the middle position of the non-linear contour of the forging.

[0079] In the preforming step, there is also a molding die. The molding die is placed inside the forging and fits against the inner surface of the forging to prevent the forging from deforming inward during rolling.

[0080] The product of this application has a thicker profile in the straight lines and a thinner profile in the non-straight lines. Therefore, in the mold forming process, the deformation of the straight profile is less, while the deformation of the non-straight lines is greater. By increasing the thickness of the non-straight lines, breakage of the non-straight lines can be avoided during subsequent processing.

[0081] During the first rolling process, the outer surface of the roller is cylindrical. At this time, only the straight contour lines of the forging are rolled. Therefore, the deformation of the straight contour lines of the forging is relatively small during the first rolling process.

[0082] In the second rolling process, the upper side of the non-linear profile of the forging is rolled, and after rolling, the upper side of the non-linear profile deforms towards the straight profile above. In the third rolling process, the lower side of the non-linear profile of the forging is rolled, and after rolling, the lower side of the non-linear profile deforms towards the straight profile below. In the fourth rolling process, the middle position of the non-linear profile of the forging is rolled, and after rolling, the middle position of the non-linear profile deforms towards both the upper and lower sides of the non-linear profile.

[0083] In the pre-forming step, the deformation amount at the non-linear contour position is adjusted so that the deformation amount of the forging is evenly distributed on the linear and non-linear contours.

[0084] In the pre-forming step, non-linear profiles are divided into oblique profiles, concave curve profiles, and convex curve profiles. During the second to fourth rolling processes, the rolling pressure decreases sequentially according to the different profiles.

[0085] In the preforming process, during the first to fourth rolling processes: the rolling force is positively correlated with the forging deformation. The rolling force is negatively correlated with the forging temperature. The forging temperature is positively correlated with the rolling die temperature.

[0086] In the pre-forming step, the non-linear contour is further subdivided, with the oblique contour representing the inclined surface of the forging. The oblique contour transitions to the straight contour, forming an angle between them. The angle between the oblique and straight contours is 'a'. When 30° ≤ a ≤ 150°, it is a convex curve contour. The angle between the oblique and straight contours is 'b'. When 210° ≤ b ≤ 330°, it is a concave curve contour. There are no right angles between the oblique and straight contours.

[0087] In non-linear profiles, different profiles will have different deformation directions and deformation amounts.

[0088] When rolling a sloping profile, the larger the angle of inclination of the sloping profile, the greater the span of the deformation direction. When rolling a concave curve profile, the larger the angle between the sloping profile and the straight profile, the greater the span of the deformation direction. When rolling a convex curve profile, the larger the angle between the sloping profile and the straight profile, the smaller the span of the deformation direction.

[0089] Among non-linear profiles, oblique profiles can withstand greater rolling pressure. Concave curve profiles in non-linear profiles withstand less rolling pressure than oblique profiles. Since the transition between oblique and straight profiles is relatively gentle, concave curve profiles can withstand a certain amount of rolling pressure. Conversely, convex curve profiles in non-linear profiles withstand less rolling pressure than concave curve profiles. Since the transition between oblique and straight profiles is relatively steep, convex curve profiles can withstand less rolling pressure.

[0090] In the preforming step, when the forging needs to be deformed by a large amount, the rolling force needs to be increased. When the forging needs to be deformed by a small amount, the rolling force needs to be reduced.

[0091] When the heating temperature of the forging is high during the preforming step, the rolling force needs to be increased. When the heating temperature of the forging is low during the preforming step, the rolling force needs to be reduced.

[0092] When the heating temperature of the forging is high in the preforming step, the temperature of the die needs to be increased. When the heating temperature of the forging is low in the preforming step, the temperature of the die needs to be decreased.

[0093] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0094] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A forging method for an FV535 alloy low-pressure turbine casing, characterized in that, The forging process includes the following steps: The modeling process involves creating a model of the product based on the dimensions and shape requirements of the drawings to obtain model data. The heating process involves feeding the raw materials and heating them, followed by heat preservation. The processing steps involve upsetting and punching the raw materials sequentially, followed by air cooling to room temperature. Pre-rolling step: The raw material is pre-rolled to Φ555±5mm*Φ465±5mm*260±5mm; the final rolling temperature is ≥850℃; the deformation is 25-30%; then it is air-cooled to room temperature to form an intermediate part. The model calculation steps are as follows:

1. Measure the dimensions of the intermediate part to obtain measurement data; 2. Superimpose the measurement data onto the model data to obtain the forming processing amount; 3. Mark the cross-sectional contour according to the model data to obtain the model contour data; 4. Mark the cross-sectional contour of the intermediate part according to the measurement data to obtain the intermediate part contour data; 5. Superimpose the model contour data and the intermediate part contour data to calculate the deformation direction and deformation allowance of the intermediate part forming. The molding process is as follows: Heat the intermediate part and the mold separately; place the intermediate part in the mold for forging; then air cool the intermediate part to room temperature. Pre-forming step: Divide the model contour data into straight contours and non-straight contours; heat the intermediate part to 1120-1150℃ and the rolling die to 300-320℃; roll the straight contours and non-straight contours of the intermediate part in sequence; final forging temperature ≥800℃. The final rolling process for irregular shapes is as follows: the intermediate part is heated to 1120-1150℃ and held for 40-160 minutes; the irregular die is heated to 150-250℃ and closed rolling is performed; the final rolling temperature is ≥850℃; the deformation is 20-27%; then the intermediate part is air-cooled to room temperature to obtain the product.

2. The forging method of the FV535 alloy low-pressure turbine casing as described in claim 1, characterized in that: During the heating step, the raw material is fed into a diameter of Φ250*420mm and heated to 1120-1150℃; then it is kept at this temperature for 120-240 minutes.

3. The forging method of the FV535 alloy low-pressure turbine casing as described in claim 2, characterized in that: In the processing steps, the raw material is upset to 290mm and then punched; the punching size is Φ160-180mm; the final forging temperature is ≥850℃; the deformation amount is 30%; and then it is air-cooled to room temperature.

4. The forging method of the FV535 alloy low-pressure turbine casing as described in claim 2, characterized in that: In the die forming process, the intermediate part is heated to 1120-1150℃; then held at that temperature for 40-160 minutes; the die is heated to 150-250℃; the intermediate part is placed in the die for forging; the final forging temperature is ≥850℃; then the intermediate part is air-cooled to room temperature.

5. The forging method of the FV535 alloy low-pressure turbine casing as described in claim 4, characterized in that: In the die-forming process, the intermediate part is placed in the die forged and formed, which includes several steps: Planning process: Based on the amount of deformation required for intermediate parts in the mold forming process, divide the forming process into N steps and determine the amount of deformation for each forming process. First molding process: Based on the deformation of the intermediate part in the first molding process, the amount of graphite to be sprayed on the intermediate part and the mold is obtained and sprayed; the deformation of the intermediate part is positively correlated with the amount of graphite sprayed. Nth molding process: Based on the deformation of the intermediate part in the Nth molding process, the amount of graphite sprayed on the intermediate part and the mold is obtained and sprayed; the deformation of the intermediate part is positively correlated with the amount of graphite sprayed.

6. The forging method of the FV535 alloy low-pressure turbine casing as described in claim 4, characterized in that: In the pre-forming step, the straight and non-straight contours of the intermediate part are rolled four times in sequence: First rolling process: Rolling is performed on the straight contour positions of the intermediate part; Second rolling process: Rolling is performed on one side of the non-linear contour of the intermediate part; The third rolling process: Rolling is performed on the other side of the non-linear contour of the intermediate part; The fourth rolling process: Rolling is performed on the middle position of the non-linear contour of the intermediate part.

7. The forging method of the FV535 alloy low-pressure turbine casing as described in claim 6, characterized in that: In the pre-forming step, the non-linear profiles are divided into oblique profiles, concave curve profiles, and convex curve profiles; in the second to fourth rolling processes, the rolling pressure decreases sequentially according to the different profiles.

8. The forging method of the FV535 alloy low-pressure turbine casing as described in claim 7, characterized in that: In the preforming step, during the first to fourth rolling processes: the rolling force is positively correlated with the deformation of the intermediate part; the rolling force is negatively correlated with the temperature of the intermediate part; and the temperature of the intermediate part is positively correlated with the temperature of the rolling die.

Images