A method of forging a passenger aircraft wheel hub

Abstract

The present application mainly relates to a passenger plane wheel hub forging forming method, comprising the following steps: S1: adopting a backward extrusion forming process to perform rough pressing forming treatment on a round cake blank in a rough pressing upper die and rough pressing lower die combination to obtain a rough pressing piece of the wheel hub; S2: performing pre-pressing forming treatment on the rough pressing piece using a pre-pressing upper die and pre-pressing lower die combination to obtain a pre-pressing piece; S3: performing final-pressing forming treatment on the pre-pressing piece using a final-pressing upper die and final-pressing lower die combination to obtain a final-pressing piece; the method adopts a process division forming method for two positions prone to defects such as folding in the wheel hub forming process, that is, the forming steps of rough pressing, pre-pressing and final-pressing are sequentially adopted to form the barrel wall, the upper end material gathering area of the barrel wall and the final wheel hub forging piece as a whole, thereby greatly reducing the difficulty of forging piece forming. The method avoids the deviation prone part in the actual forming condition through the die structure, so that the whole forging process is stable and controllable, and the stability of the forging piece forming quality of each process is improved and ensured.

Description

Technical Field

[0001] This invention belongs to the field of forging technology, and in particular relates to a forging method for a thin-walled deep-cavity passenger aircraft wheel hub with a flange structure. Background Technology

[0002] As a crucial component of aircraft wheels, the wheel hub bears the static loads, impact loads, and frictional forces generated during takeoff, landing, and taxiing. Due to the extremely harsh service conditions of aircraft wheels, the requirements for the dimensions, mechanical properties, and microstructure of wheel components are extremely high. Wheel hubs made of aluminum alloy are typically designed with thin walls and deep cavities, and feature a flange structure at the top of the cylinder wall. During forging, problems such as incomplete filling, disordered flow lines, excessive loads, and uneven microstructure are prone to occur.

[0003] Forging thin-walled, deep-cavity wheel hubs with flanges at the top of the cylindrical wall presents several challenges, including the reverse extrusion process of the thin-walled, deep cavity and the forming of the flange structure. During the initial forming of the cylindrical structure of the wheel hub forging, the thin wall thickness and high height mean that issues such as the inability to center the circular blank in the lower die before forming, and uneven lubrication on the sidewalls of the forming die at the cylindrical position, can lead to varying reverse extrusion speeds of the forged cylindrical metal, resulting in folding defects. Furthermore, since the metal at the flange position needs to be concentrated before forming the flange structure, and the wall thickness at this location must be greater than that at other parts of the cylindrical wall, how to concentrate the metal at the flange position at the top of the thin cylindrical wall is a key issue determining the precise forming of the forged flange structure. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a simple and effective forging method for passenger aircraft wheel hubs, which can effectively solve the problem of folding defects forming on the inner side of the cylinder wall during the forging process of thin-walled deep-cavity passenger aircraft wheel hubs with flange structures.

[0005] The present invention provides a method for forging a passenger aircraft wheel hub, comprising the following steps:

[0006] Step S1: Place the round blank into the combination of the upper and lower die for pressing, and use the reverse extrusion forming process to press the round blank for pressing to obtain the pressed part of the wheel hub; the pressed part is a thin-walled cylindrical structure, and the axial section of the pressed part is a U-shaped structure;

[0007] Step S2: Use the combination of pre-pressing upper die and pre-pressing lower die to pre-press the rough part to obtain a pre-pressed part; during the pre-pressing process, a circular groove is provided at the root of the protrusion structure of the pre-pressing upper die to upset the top of the cylinder wall of the rough part, and at the same time to reverse extrude the bottom of the rough part, so that the shape of the pre-pressed part is close to the shape of the final pressed part, and a material accumulation area is formed at the flange structure position of the pre-pressed part;

[0008] Step S3: Use the combination of the final pressure upper die and the final pressure lower die to perform final pressure forming on the pre-pressed part to obtain the final pressed part; during the final pressure forming process, the bottom of the pre-pressed part is further subjected to reverse extrusion to form a complete flange structure.

[0009] Preferably, the dimensions of the round cake blank are φ540mm×180mm.

[0010] Preferably, the height of the cylinder wall of the pressed part is 210.3mm and the thickness is 41.6mm; the top surface and the inner side of the cylinder wall adopt a 20° transition slope and a 12mm rounded corner transition, and the top surface and the outer side of the cylinder wall adopt a 9mm rounded corner transition. A 150mm×71mm pressed groove is provided at the center of the bottom of the pressed part.

[0011] Preferably, the height of the pre-pressed component's cylinder wall is the same as that of the rough-pressed component, and the thickness is 40.5 mm; the upper end of the pre-pressed component's cylinder wall is provided with a material gathering area with an axial cross section in the shape of a goose's head, and a pre-pressed ring protrusion structure with an outer contour of φ248 mm and a height of 161 mm is provided at the center of the bottom of the pre-pressed component, and the middle of the pre-pressed ring protrusion structure is a pre-pressed through hole with an inner diameter of φ135 mm.

[0012] Preferably, the top of the cylinder wall of the final pressing component is 256mm above the inner bottom surface of the hub, and the thickness is 40mm. A final pressing ring protrusion structure with an outer contour of φ240mm and a height of 192mm is provided at the center of the bottom of the final pressing component, and the center of the final pressing ring protrusion structure is a final pressing through hole with an inner diameter of φ132mm.

[0013] Preferably, the forging material is made of 2040 aluminum alloy, the mold material is 5CrNiMo, the billet forming temperature in each process from step S1 to step S3 is 420°C to 450°C, the mold temperature is 350°C to 400°C, and the forming speed is 2mm / s to 5mm / s; and the draft angle of the inner and outer sides of the cylinder wall of the rough pressing part, the pre-pressing part and the final pressing part is 3°.

[0014] Preferably, in step S2, during the initial forming stage, the top surface and the inner bottom surface of the U-shaped cylindrical wall structure of the pressed part simultaneously contact the bottom of the circular groove provided at the root of the pre-pressing upper die and the top of the protrusion structure of the upper die, respectively. Most of the inner side of the pressed part's cylindrical wall contacts the outer side of the protrusion structure, and there is a gap between the root of the protrusion structure of the pre-pressing upper die and the upper side of the U-shaped structure of the pressed part.

[0015] Preferably, the pre-press die and the final press die are also provided with a cylindrical inner flash structure.

[0016] Preferably, after steps S1 to S3, an edge trimming process needs to be completed. After trimming the rough pressed part obtained in step S1, the outer edge of the top of the rough pressed part cylinder wall needs to be rounded, and then the rough pressed groove is processed into a rough pressed through hole.

[0017] Preferably, the underpressure value of the mold used in steps S1 to S3 is set to 0mm.

[0018] The aircraft wheel hub forging method described in this invention achieves the following beneficial effects: The forging difficulties of thin-walled, deep-cavity aircraft wheel hubs with flanges are mainly concentrated in the back extrusion of the cylinder wall and the forming of the corresponding material accumulation zone in the flange area. Specifically, uneven blank placement and cylinder wall lubrication in the initial forming stage can lead to folding defects during the back extrusion process, and excessively large height-to-diameter ratios during upsetting in the material accumulation zone can cause instability defects at that location. Therefore, this invention employs a step-by-step forming process of initial pressing, pre-pressing, and final pressing to form the forged cylinder wall, the upper material accumulation zone, and the final forging. This method reduces the difficulty of forging by forming the two areas prone to folding defects in a separate process. This invention utilizes the simple shape of the initial pressing part to avoid folding defects caused by unstable workmanship and uneven lubrication in actual working conditions. By using the initial pressing part in conjunction with the pre-pressing die, the flow of metal in the material accumulation zone is limited and guided, preventing instability and bending caused by excessively large height-to-diameter ratios during upsetting in this location. Based on the structural characteristics, forming process and on-site conditions of this type of wheel hub, the present invention provides a stable, reliable forging process for thin-walled deep cavity aircraft wheel hubs with flanges that is less affected by subjective factors. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the three-dimensional structure of the final pressed part processed using an embodiment of the present invention;

[0020] Figure 2 A schematic diagram showing a folding defect on the inner wall of a wheel hub when it is formed using other forming methods.

[0021] Figure 3 This is a process flow diagram of an embodiment of the present invention;

[0022] Figure 4 This is a schematic cross-sectional view of the pressure die used in an embodiment of the present invention, taken from the main view direction.

[0023] Figure 5 This is a schematic diagram of the blank material arrangement state during pre-pressing forming using a pre-pressing mold, according to an embodiment of the present invention.

[0024] Figure 6 for Figure 5 A magnified view of a portion of the image;

[0025] Figure 7This is a schematic cross-sectional view of the main view of the pressed part processed using an embodiment of the present invention;

[0026] Figure 8 This is a schematic cross-sectional view of the pre-compression part processed and formed according to an embodiment of the present invention, taken from the main view direction.

[0027] Figure 9 This is a schematic cross-sectional view of the final pressed part processed using an embodiment of the present invention, taken from the main view direction.

[0028] In the figure, 1 is the rough pressing part, 4 is the flange structure, 5 is the circular ring protrusion structure, 6 is the cylinder wall, 7 is the rough pressing upper die, 8 is the rough pressing lower die, 9 is the rough pressing flash structure, 10 is the pre-pressing upper die, 11 is the pre-pressing lower die, 12 is the inner flash structure, 13 is the cylinder wall gap, 14 is the transition slope, 15 is the rough pressing through hole, 16 is the material accumulation area, 17 is the pre-pressing through hole, 18 is the pre-pressing ring protrusion structure, 19 is the final pressing ring protrusion structure, and 20 is the folding defect. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0030] Depend on Figure 1 As shown, the aircraft wheel hub forged in this invention is a thin-walled, deep-cavity aircraft wheel hub with a flange structure 4. When forged using conventional methods, the cylinder wall 6 is prone to folding. Due to the high height of the hub cylinder wall 6 and the flange structure 4 at the top of the cylinder wall 6, if this type of hub is formed in one step, it often results in a long metal flow distance, high flow resistance, and uneven forming, leading to numerous forging defects such as folding, incomplete filling, and transgranularity.

[0031] Therefore, the current main forging method for forming this type of wheel hub forging is the pre-pressing plus final pressing forming process, and the forming method is also isothermal forging. When the pre-pressing plus final pressing forming process is adopted, the metal needs to be divided in the pre-pressing process. During the forming of the cylinder wall 6 structure, sufficient metal is stored for the forming of the flange structure 4 by the material accumulation method. The main process of the pre-pressing process is as follows: the round blank is placed in the center of the pre-pressing lower die 11, and the round blank is first made to flow laterally by the pre-pressing upper die 10. After contacting the side wall of the pre-pressing lower die 11, it begins to flow upward to the cylinder wall 6 structure until it contacts the root of the protruding structure of the pre-pressing upper die 10 and fills the material accumulation area 16, finally forming the flash. At this time, the height of the cylinder wall 6 of the pre-pressed part after pre-pressing is the same as that of the final pressed part.

[0032] The aforementioned pre-pressing process often presents two unavoidable problems during forming: First, to ensure the round blank can be smoothly placed into the pre-pressing lower die 11 with its deep groove, the maximum diameter of the round blank is often smaller than the groove diameter of the pre-pressing lower die 11, resulting in a gap between the round blank and the pre-pressing lower die 11 during placement, and the size of this gap is unevenly distributed. Second, due to the deep sidewall of the groove in the pre-pressing lower die 11, significant uneven lubrication occurs. Therefore, the uneven gap around the round blank and the uneven lubrication of the sidewall of the pre-pressing lower die 11 lead to inconsistent reverse extrusion forming speeds of the metal in the cylinder wall 6 during pre-pressing. The metal with the faster forming speed will first contact the root of the protruding structure of the pre-pressing upper die 10, forming flash, while the metal with the slower forming speed will contact the root of the protruding structure of the pre-pressing upper die 10 later, also forming flash. Consequently, the forming area with the slower forming speed will form fold defects 20 on the inner side of the cylinder wall 6. Fold defects 20, such as... Figure 2 As shown. At the same time, due to the inconsistent forming speed of the cylinder wall 6, the top of the cylinder wall 6 at the faster forming speed will contact the pre-pressing upper mold 10 in advance. This will result in an excessively large height-to-diameter ratio at the position where the material gathering area 16 first contacts the upper mold during forming, leading to instability and folding defects 20.

[0033] This invention provides a forging process for thin-walled deep-cavity aircraft aluminum alloy wheel hubs with flanges. By optimizing the wheel hub forging process and rationally planning the forming sequence of each structure of the wheel hub, the folding defect that occurs on the inner side of the wheel hub cylinder wall 6 during the forging process is effectively solved. The invention will be further described below with reference to specific embodiments.

[0034] Example

[0035] like Figure 1 As shown, the wheel hub formed by final pressing in this embodiment is a thin-walled, deep-cavity aluminum alloy wheel hub with a flange structure 4, including the flange structure 4, the annular protrusion structure 5 at the center position, and the cylindrical wall 6. Its forging process includes the following steps:

[0036] like Figure 3 and Figure 4 As shown, step S1: The round blank is placed into the combination of the upper die 7 and the lower die 8, and the round blank is subjected to a reverse extrusion forming process to obtain the blank part 1 of the wheel hub. The blank part 1 is a thin-walled cylindrical structure, and the axial section of the blank part 1 is a U-shaped structure; the height of the cylindrical wall 6 of the blank part 1 is greater than the height of the cylindrical wall 6 of the final pressed part. Figure 7As shown, in this embodiment, the height of the cylinder wall 6 of the pressed part 1 is 210.3mm and the thickness is 41.6mm. The top surface of the cylinder wall 6 and the inner surface of the cylinder wall 6 are transitioned by a 20° transition slope 14 and a radius of 12mm. The top surface of the cylinder wall 6 and the outer surface of the cylinder wall 6 are transitioned by a radius of 9mm. A φ150mm×71mm pressed groove is provided at the center of the bottom of the pressed part 1. Before pre-pressing, the pressed groove is processed into a φ150mm pressed through hole 15.

[0037] Step S2: The rough part 1 is pre-pressed using a combination of the upper pre-press die 10 and the lower pre-press die 11 to obtain a pre-pressed part. During the pre-pressing process, a circular groove is provided at the root of the protruding structure of the upper pre-press die 10 to upset the top of the cylinder wall 6 of the rough part 1, and simultaneously to reverse-extrude the bottom of the rough part 1, so that the shape of the pre-pressed part is close to the shape of the final pressed part, and a material accumulation area 16 is formed at the flange structure 4 of the pre-pressed part. Figure 8 As shown, in this embodiment, the height of the pre-pressed component's cylinder wall 6 is the same as that of the rough-pressed component 1, which is 210.3 mm. The thickness of the cylinder wall 6 is 40.5 mm. The upper end of the pre-pressed component's cylinder wall 6 is provided with a material gathering area 16 with an axial cross section in the shape of a goose's head. At the bottom center of the pre-pressed component, a pre-pressed ring protrusion structure 18 with an outer contour of φ248 mm and a height of 161 mm is provided. The middle of the pre-pressed ring protrusion structure 18 is a pre-pressed through hole 17 with an inner diameter of φ135 mm.

[0038] During pre-pressing, since the height of the cylinder wall 6 of the blank 1 is the same as the height of the protruding structure of the pre-pressing upper die 10, the initial arrangement of the blank 1 in the pre-pressing process is as follows: Figure 5 and Figure 6 As shown. At this time, to ensure that the blank part 1 can be smoothly placed into the mold, there is a 0.2mm gap between the outer side of the blank part 1 cylinder wall 6 and the pre-pressing mold. At the same time, the top surface of the blank part 1 cylinder wall 6 contacts the bottom surface of the groove at the root of the protrusion structure of the pre-pressing upper mold 10, and the inner bottom surface of the blank part 1 contacts the top surface of the protrusion structure of the pre-pressing upper mold 10, so that in the early stage of pre-pressing, the pre-pressing mold can directly upset the material accumulation area 16 at the top of the cylinder wall 6.

[0039] Since the top surface and the inner bottom surface of the cylindrical wall 6 of the pressed part 1 are in contact with the pre-pressing mold at the same time, the material gathering area 16 is mainly a backward upsetting process with limited ends during pre-pressing. The upsetting height-to-diameter ratio of the material gathering area 16 is directly determined by the distance between the inner bottom surface and the top surface of the pressed part 1. The deformation of the material gathering area 16 is directly determined by the pre-pressing mold and is no longer affected by actual working conditions such as forming lubrication and blank placement. Secondly, a transition slope 14 combined with a rounded corner is used when the inner side surface and the top surface of the cylindrical wall 6 of the pressed part 1 transition. In the early stage of pre-pressing, a large cylindrical wall gap 13 is also provided between the upper end of the inner surface of the cylindrical wall 6 and the mold. This allows some of the metal in the cylindrical wall 6 to fill the inner side of the cylindrical wall 6 during the upsetting process of the material gathering area 16, avoiding the folding defect 20 of the cylindrical wall 6 caused by only the flash area where metal can flow.

[0040] Step S3: Use a combination of final pressure upper and final pressure lower dies to perform final pressure forming on the pre-compressed part to obtain the final compressed part; during the final pressure forming process, the bottom of the pre-compressed part is further subjected to reverse extrusion to form a complete flange structure 4. Figure 9 As shown, in this embodiment, the maximum outer diameter of the final pressing component is 616mm, the outer height of the cylinder wall 6 is 300mm, the distance from the top of the cylinder wall 6 to the inner bottom surface of the hub is 256mm, and the thickness of the cylinder wall 6 is 40mm. A final pressing ring protrusion structure 19 with an outer contour of φ240mm and a height of 192mm is provided at the bottom center of the final pressing component, and the center of the final pressing ring protrusion structure 19 has a final pressing through hole of φ132mm.

[0041] During the forming process from steps S1 to S3, the draft angles of the inner and outer sides of the cylinder wall 6 of the rough pressing part 1, the pre-pressing part, and the final pressing part are all 3°. The shape of the rough pressing part 1 is the key factor in determining whether folding occurs during the rough pressing and pre-pressing forming process. Figure 4 This is a schematic diagram of the press forming die structure. The flash of the press forming part 1 is located at the top of the cylinder wall 6. The top of the cylinder wall 6 has no complex structure, except for a 20° slope at the root of the protrusion structure of the upper press forming die 7. Therefore, the structure of the cylinder wall 6 of the press forming part 1 gradually thins from bottom to top. During press forming, the metal of the cylinder wall 6 is extruded upwards, and the excess metal is discharged through the press forming flash structure 9. Because the cylinder wall 6 gradually thins from bottom to top, the metal of the press forming part 1 is always in contact with the press forming die assembly before the flash is formed, thus avoiding folding defects in press forming.

[0042] The molds used in steps S2 and S3 are also equipped with a cylindrical inner flash structure 12 to accommodate excess metal, such as... Figure 5 and Figure 6 As shown, in the pre-pressing process, the inner flash structure 12 is located on the top of the central protrusion structure of the pre-pressing lower mold 11 and is adjacent to the position of the rough pressing through hole 15 in the center of the rough pressing part 1 placed in the pre-pressing lower mold 11.

[0043] In this embodiment, the forging is made of 2040 aluminum alloy, and the die is made of 5CrNiMo. In each step from S1 to S3, the forming temperature of the billet is 420°C to 450°C, the die temperature is 350°C to 400°C, the forming speed is 2mm / s to 5mm / s, and the die underpressure during the forming process is set to 0mm to avoid metal flow defects at the flange position due to excessive metal.

[0044] Correspondingly, after each forming process from steps S1 to S3, a trimming process must be performed. The trimming locations include the flash at the top edge of the outer side of the cylinder wall 6 and the cylindrical flash at the center. In step S1, the trimming process also includes cutting the crimping groove at the bottom of the crimped part 1 into a crimping through hole 15 and rounding the outer edge of the top edge of the cylinder wall 6 of the crimped part 1. The purpose of this is to ensure that the top surface of the cylinder wall 6 of the crimped part 1 can fully contact the bottom of the circular groove at the root of the protrusion structure of the pre-pressing upper mold 10 while the crimped part 1 is smoothly placed into the pre-pressing lower mold 11 in step S2.

[0045] In this embodiment, two areas prone to defects such as folding are formed using a step-by-step forming method. Specifically, the wheel hub's cylinder wall, the upper material accumulation zone of the cylinder wall, and the final wheel hub forging are formed sequentially through rough pressing, pre-pressing, and final pressing. This significantly reduces the difficulty of forging. Furthermore, the mold structure avoids deviations that are prone to occur during actual forming, ensuring a stable and controllable forging process and improving and guaranteeing the stability of the forging quality at each stage.

[0046] The above embodiments are merely illustrative examples to clearly illustrate the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for forging a passenger aircraft wheel hub, characterized in that... The method includes the following steps: Step S1: Place the round blank into the combination of the upper and lower die for pressing, and use the reverse extrusion forming process to press the round blank for pressing to obtain the pressed part of the passenger aircraft wheel hub; the pressed part is a thin-walled cylindrical structure, and the axial section of the pressed part is a U-shaped structure. Step S2: Use the combination of pre-pressing upper die and pre-pressing lower die to pre-press the rough part to obtain a pre-pressed part; during the pre-pressing process, a circular groove is provided at the root of the protrusion structure of the pre-pressing upper die to upset the top of the cylinder wall of the rough part, and at the same time to reverse extrude the bottom of the rough part, so that the shape of the pre-pressed part is close to the shape of the final pressed part, and a material accumulation area is formed at the flange structure position of the pre-pressed part; Step S3: Use the combination of the final pressure upper die and the final pressure lower die to perform final pressure forming on the pre-pressed part to obtain the final pressed part; during the final pressure forming process, the bottom of the pre-pressed part is further subjected to reverse extrusion to form a complete flange structure. The dimensions of the round blank are ϕ540mm×180mm; the height of the cylindrical wall of the rough-pressed part is 210.3mm, and the thickness is 41.6mm; the top surface and inner surface of the cylindrical wall adopt a 20° transition slope and a radius of 12mm, and the top surface and outer surface of the cylindrical wall adopt a radius of 9mm. A rough-pressing groove of ϕ150mm×71mm is provided at the center of the bottom of the rough-pressed part; the height of the cylindrical wall of the pre-pressed part is the same as that of the rough-pressed part, and the thickness is 40.5mm; the upper end of the cylindrical wall of the pre-pressed part is provided with a material gathering area with an axial cross section of gooseneck shape, and a pre-pressing ring protrusion structure with an outer contour of ϕ248mm and a height of 161mm is provided at the center of the bottom of the pre-pressed part. The middle of the pre-pressing ring protrusion structure is an inner... The pre-pressed part has a pre-pressed through hole with a diameter of ϕ135mm; the top of the cylinder wall of the final pressing part is 256mm above the inner bottom surface of the hub, and the thickness is 40mm; a final pressing ring protrusion structure with an outer contour of ϕ240mm and a height of 192mm is provided at the center of the bottom of the final pressing part, and the center of the final pressing ring protrusion structure is a final pressing through hole with an inner diameter of ϕ132mm; the forging material is made of 2040 aluminum alloy, the mold material is 5CrNiMo, the billet forming temperature of each process from step S1 to step S3 is 420℃ to 450℃, the mold temperature is 350℃ to 400℃, and the forming speed is 2mm / s to 5mm / s; and the draft angle of the inner and outer sides of the cylinder walls of the rough pressing part, the pre-pressed part, and the final pressing part is 3°. In step S2, during the initial forming stage, the top surface and the inner bottom surface of the U-shaped cylindrical wall structure of the rough pressed part simultaneously contact the bottom of the circular groove at the root of the pre-pressing upper die and the top of the protrusion structure of the upper die, respectively. Most of the inner side of the cylindrical wall of the rough pressed part contacts the outer side of the protrusion structure, and there is a gap between the root of the protrusion structure of the pre-pressing upper die and the upper side of the U-shaped structure of the rough pressed part.

2. The passenger aircraft wheel hub forging method according to claim 1, characterized in that, The pre-press die and the final press die are also equipped with a cylindrical inner flash structure.

3. The passenger aircraft wheel hub forging method according to claim 2, characterized in that, After steps S1 to S3, the edge trimming process needs to be completed. After trimming the rough pressed part obtained in step S1, the outer edge of the top of the rough pressed part cylinder wall needs to be rounded, and then the rough pressed groove is processed into a rough pressed through hole.

4. The passenger aircraft wheel hub forging method according to claim 3, characterized in that, The underpressure value of the mold used in steps S1 to S3 is set to 0mm.

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