Forging method for large annular cake piece

Abstract

The invention relates to the technical field of ring cake part forging, in particular to a large ring cake part forging method which comprises the following steps: upsetting and punching a cylindrical blank to form an annular blank; the annular blank is placed on a rotary workbench, and local loading continuous deformation is conducted on the annular blank in the circumferential direction in a rotary unfolding and pressing mode through a special-shaped anvil; reheating the annular blank subjected to a whole circle of rotary expansion to a forging temperature, placing the annular blank on a rotary worktable and turning over relative to the previous heating number, taking the lower surface, in contact with the special-shaped anvil, of the previous heating number as the upper surface, in contact with the special-shaped anvil, of the heating number, and repeating the rotary expansion process; and the steps of reheating, overturning and rotary unfolding and pressing are repeated till the height of the annular blank reaches the height of the target annular cake piece. According to the method, through combination of the working procedures of upsetting, drawing-out, upsetting, punching and rotary unfolding and pressing, deformation targets of all stages are clear and high in pertinence, and structure performance regulation and control are taken into consideration while precise forming is achieved.

Description

Technical Field

[0001] This invention relates to the field of ring forging technology, and more specifically, to a method for forging large rings. Background Technology

[0002] Large ring-shaped components (such as mirror plates and shaft rings of hydro generators) are key basic components in the field of heavy equipment manufacturing. Their internal structure and performance uniformity are directly related to the operating accuracy and service life of the entire machine. Due to the large size and significant differences in wall thickness of these forgings, they are prone to defects such as grain coarsening and mixed structure due to uneven deformation during the hot forming process. Therefore, extremely high requirements are placed on their deformation uniformity.

[0003] Currently, the forging of large ring-shaped components typically follows a stopgap approach of "forging large disc-shaped components + punching." This involves first forming a disc-shaped billet using conventional disc forging technology, and then using punching as the final forging pass to complete the ring structure. However, this method requires reheating the billet to a high temperature before punching. The punching deformation is limited and mainly concentrated near the hole wall, leaving most of the billet in a state of little or no deformation. This results in a lack of effective large deformation within the billet after high-temperature heating to promote dynamic recrystallization, leading to significant grain growth. Consequently, the forging exhibits an inhomogeneous structure with a mixture of coarse and fine grains, severely deteriorating its mechanical properties and reliability. Summary of the Invention

[0004] The purpose of this application is to provide a method for forging large ring-shaped parts to solve the above-mentioned technical problems.

[0005] This application provides a method for forging a large ring-shaped billet. The method includes: upsetting and punching a cylindrical billet to form a ring-shaped billet; placing the ring-shaped billet on a rotary worktable and using a shaped anvil with variable contact surface and variable curvature to continuously deform the ring-shaped billet along the circumference through rotary pressing, so that the deformation covers the entire circumference of the ring-shaped billet; wherein the working surface of the shaped anvil has a cylindrical side surface in the middle and frustum side surfaces at both ends, the axial length of the cylindrical side surface is less than the inner diameter of the target ring-shaped billet, and the axial length of the frustum side surface is greater than the wall thickness of the target ring-shaped billet; reheating the ring-shaped billet after completing a full rotation of rotary pressing to the forging temperature, placing it on the rotary worktable and flipping it relative to the previous pressing, so that the lower surface that contacted the shaped anvil in the previous pressing becomes the upper surface that contacts the shaped anvil in this pressing, and repeating the above rotary pressing process; repeating the above reheating, flipping and rotary pressing steps until the height of the ring-shaped billet reaches the height of the target ring-shaped billet.

[0006] Furthermore, before the cylindrical billet is upset and punched to form a ring-shaped billet, the process further includes: heating the steel ingot to 1250±20℃, performing upset and drawing forging, breaking the coarse grains inside the steel ingot, and obtaining the cylindrical billet by cutting.

[0007] Further, upsetting the cylindrical billet includes: heating the cylindrical billet to the forging temperature and placing it on a press platform; placing a circular upsetting plate on the cylindrical billet; controlling the press to compress the cylindrical billet through the circular plate until the upper surface of the circular plate reaches a first preset height, thereby obtaining an upset disc-shaped billet.

[0008] Further, the punching process includes: heating the upset billet to the forging temperature and placing it on a punching pad ring; placing a hollow punch on the upset billet, such that the axis of the billet coincides with the axis of the punching pad ring and the axis of the hollow punch; punching the billet with the hollow punch until the upper surface of the hollow punch reaches a second preset height, thereby obtaining the annular billet.

[0009] Furthermore, the step of punching the blank with the hollow punch until the upper surface of the hollow punch reaches a second preset height includes: controlling the hollow punch to press down until its upper surface reaches the second preset height, the second preset height being determined based on the inner diameter of the target annular blank and the height of the punching pad ring, so that the annular blank after punching has a target wall thickness.

[0010] Furthermore, the method of using a shaped anvil with variable contact surface and variable curvature to perform localized loading and continuous deformation of the annular billet in the circumferential direction through a rotary pressing method includes: controlling the single anvil reduction rate of the shaped anvil to be 15%~20% and loading the annular billet anvil by anvil.

[0011] Furthermore, in the process of using a shaped anvil with variable contact surface and variable curvature to continuously deform the annular billet by rotating and pressing, the method further includes: during the anvil loading process, when there are local protrusions on the upper surface of the annular billet due to uneven local deformation, the local protrusions are leveled by adjusting the pressing position of the shaped anvil until the overall height of the annular billet reaches a uniform third preset height.

[0012] Furthermore, flipping the annular billet includes: after each rotational pressing that covers the entire circumference of the annular billet, immediately reheating the annular billet to the forging temperature, and then, when placing it on the rotary worktable for the next heat deformation, flipping the annular billet 180 degrees relative to the position of the previous heat, so that the lower surface that contacted the shaped anvil in the previous heat becomes the upper surface that contacts the shaped anvil in this heat, thereby achieving alternating loading of the upper and lower surfaces.

[0013] Furthermore, the repetition of the above-mentioned reheating, flipping, and rotary pressing steps includes: repeating the flipping and rotary pressing steps multiple times, wherein each time includes reheating the annular billet that has been deformed in the previous time to the forging temperature, placing it on the rotary worktable and flipping it 180 degrees relative to the previous time, and then using the shaped anvil to perform local loading and continuous deformation of the annular billet along the circumference by rotary pressing, so that the deformation amount of each time accumulates and superimposes until the height of the annular billet reaches the target annular part height.

[0014] Furthermore, the working surface of the irregularly shaped anvil is an arc surface with gradually changing curvature along its length.

[0015] The advantages or beneficial effects of the above technical solutions include at least the following: First, in response to the special conditions of extremely high requirements for the deformation uniformity of large ring-shaped parts, a special process chain consisting of billet forging and forming forging was constructed. Through the combination of upsetting, drawing, upsetting, punching and rotary pressing, the deformation targets at each stage are clear and targeted, achieving precise forming while taking into account the control of microstructure and properties. Second, the rotary pressing is used as the final forming process. The large deformation generated by it promotes dynamic recrystallization and grain refinement, avoiding the grain coarsening phenomenon caused by the lack of effective large deformation inside the billet after high-temperature heating when punching is used as the last firing process in the existing technology. Third, by designing an irregularly shaped anvil with variable curvature characteristics, its arc-shaped surface gradually contacts the billet to produce an effect similar to upsetting with a conical plate, overcoming the deformation dead zone formed by the large contact area and strong friction effect during the traditional strip-shaped flat anvil pressing, thus expanding the effective deformation area. Fourth, by utilizing the geometric structure of the irregularly shaped anvil with gradually changing curvature along its length, a boundary condition is created in which the contact surface gradually increases with the radius during the deformation process. This compensates for the uneven metal flow caused by the difference in rigid end constraint at different radii of the annular billet, and improves the uniformity of radial deformation. Fifth, by using a rotary pressing method, each anvil forms a strip-shaped deformation area along the diameter of the billet. After multiple anvils are stacked, a deformation field symmetrical about the axis is constructed inside the billet. Combined with a 180-degree flip, the upper and lower surfaces are alternately loaded, which improves the uniformity of tangential and axial deformation.

[0016] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the embodiments of this application. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic flowchart illustrating the forging method for large ring-shaped discs provided in this application embodiment; Figure 2 This is a schematic diagram of the structure of the large annular disc component provided in the embodiments of this application; Figure 3 This is a schematic diagram of the main structure of a cylindrical billet after upsetting deformation according to an embodiment of this application; wherein, the left half is a schematic diagram before upsetting, and the right half is a schematic diagram after upsetting; Figure 4 The main view of the upsetting billet provided in this application embodiment is shown on the punching pad ring, and punching is performed under the action of a hollow punch; wherein, the left half is a schematic diagram before punching, and the right half is a schematic diagram after punching; Figure 5 The main view of the annular billet provided in this application embodiment is shown on a rotary worktable and deformed under the action of a rotary anvil. The left half is a schematic diagram before the single anvil is pressed down during the rotary pressing process, and the right half is a schematic diagram after the single anvil is pressed down during the rotary pressing process. Figure 6 This is a top view of the annular billet undergoing compressive deformation under the action of a rotary compressive anvil, as provided in the embodiments of this application.

[0019] The numbers in the diagram are as follows: 1. Cylindrical billet; 2. Circular flat plate for upsetting; 3. Upset billet; 4. Punching washer ring; 5. Hollow punch; 6. Ring-shaped billet after punching; 7. Rotary worktable; 8. Rotary pressing anvil; C8-1. The middle part of the working surface of the rotary pressing anvil is a cylindrical side surface; C8-2. The two ends of the working surface of the rotary pressing anvil are frustum side surfaces. Detailed Implementation

[0020] The embodiments of the technical solution of the present invention will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only examples, not intended to limit the scope of protection of the present invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and the foregoing description of the accompanying drawings, are intended to cover non-exclusive inclusion. In the description of the embodiments of this application, technical terms such as "first," "second," etc., are only used to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order, or primary or secondary relationship of the indicated technical features. In the description of the embodiments of this application, "a plurality of" means two or more, unless otherwise explicitly specified. The reference to "embodiment" herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the present invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0021] like Figure 1 As shown in the figure, this application provides a method for forging a large ring-shaped disc, including: Step S110: The cylindrical blank is upsetting and punched to form a ring blank.

[0022] The aforementioned ring-shaped forging is a forging with a central through hole and an outer profile in the shape of a disc. Its geometric characteristics are characterized by a small axial height and a large radial dimension, and an overall flat ring structure. Figure 2 The diagram shows an axial cross-section of a ring-shaped forging. The blank area in the center represents the central through hole, the shaded areas on both sides represent the solid wall thickness, and the dashed line represents the geometric central axis of the ring-shaped forging. This type of forging has wide applications in heavy machinery manufacturing, such as mirror plates and shaft rings in hydroelectric generator sets. The mirror plate, as a key load-bearing component of the thrust bearing, requires extremely high flatness and uniformity of structure to ensure the stability and accuracy of the unit's operation. The shaft ring, as a connecting and positioning component, transmits enormous torque, and its dimensional accuracy and performance consistency directly affect the assembly quality and operational reliability of the entire machine. For these large ring-shaped forgings, due to their large cross-sectional dimensions and significant differences in wall thickness, inconsistent microstructure and properties are easily caused by uneven temperature gradients and deformation resistance distribution during hot forming. Therefore, extremely high requirements are placed on the uniformity of internal deformation.

[0023] The aforementioned cylindrical billet refers to a pre-formed billet with a regular cylindrical geometry obtained by heating a steel ingot to the forging temperature, then upsetting and drawing it to break up the internal coarse-grained structure, and finally cutting it into blanks. The ratio of its axial height to its diameter is usually less than 1. The specific dimensions are calculated and determined based on the volume of the target ring-shaped part and the forming process requirements. This billet serves as the initial blank for subsequent forming processes, used to prepare a disc-shaped pre-formed billet through upsetting deformation, or directly as an intermediate billet before punching. Its structural uniformity and dimensional accuracy directly affect the forming quality and performance consistency of the final ring-shaped part.

[0024] The aforementioned upsetting is an axial compression forming process that reduces the height and expands radially of the billet by applying pressure along the axial direction, transforming a cylindrical billet into a disc-shaped geometry with a larger diameter and smaller height. This process is accompanied by the plastic flow and recrystallization of the metal, which can effectively improve the internal density of the billet and provide a preform with regular end faces for subsequent forming.

[0025] Optionally, step S110 above for upsetting the cylindrical billet includes: heating the cylindrical billet to the forging temperature and placing it on the press platform; placing the upsetting circular plate on the cylindrical billet; controlling the press to compress the cylindrical billet through the circular plate until the upper surface of the circular plate reaches the first preset height, thereby obtaining the upset disc-shaped billet.

[0026] The aforementioned upsetting process is the initial deformation step in the forming forging stage. Its purpose is to transform the cylindrical billet obtained after blanking into a disc-shaped geometry with a large radial dimension and a small axial height, thereby providing a pre-fabricated blank with a flat end face and uniform height for the subsequent punching process. This process induces radial flow in the metal through axial compression, improving the billet's density while establishing regular geometric boundaries, ensuring that the billet has an axisymmetric stress state and a uniform microstructure distribution before punching.

[0027] In practice, the cylindrical billet is heated to a suitable forging temperature. This temperature range is determined based on the phase transformation characteristics and recrystallization behavior of the steel used, ensuring the metal is in a fully plastic state and reducing deformation resistance. The billet is placed on a press platform, using a special upsetting circular plate as the upper anvil. This plate is designed with a flat working surface to apply uniformly distributed compressive force along the billet's axis, avoiding stress concentration and uneven deformation caused by localized contact in traditional strip anvils. By precisely controlling the press's downward stroke, the upper surface of the circular plate reaches a first preset height. This height parameter is calculated based on the volume conservation principle of the target annular billet and the billet thickness required for subsequent punching. This process achieves precise control over the height of the pre-formed billet, ensuring that the disc-shaped billet has uniform axial dimensions and a dense internal structure, providing a geometrically consistent basis for uniform shearing and flow of the metal during punching. Furthermore, the disc-shaped billet obtained through this process has flat upper and lower end faces perpendicular to the axis, and the internal grains are refined through sufficient dynamic recrystallization, effectively eliminating microstructural defects that may remain from the billet-making process. This dual uniformity of geometry and structure avoids differences in hole wall thickness caused by billet tilting or uneven height during subsequent punching, improves the concentricity and dimensional accuracy of the annular billet, and lays a key technological foundation for obtaining high-performance annular parts through rotary pressing.

[0028] The aforementioned punching is a localized plastic forming process. It utilizes a hollow punch to penetrate the central region of the blank along the axial direction, removing the metal material in the central part through shearing and extrusion, forming a through-hole structure inside the disc-shaped blank, thereby transforming it into an annular blank with target inner and outer diameter dimensions, providing a semi-finished product with a continuous annular cross-section for the final forming of the annular disc.

[0029] Optionally, the punching in step S110 above includes: heating the upset billet to the forging temperature and placing it on the punching pad ring; placing the hollow punch on the upset billet and aligning the billet axis with the punching pad ring axis and the hollow punch axis; punching the billet with the hollow punch until the upper surface of the hollow punch reaches the second preset height to obtain an annular billet.

[0030] The aforementioned punching process, as a crucial transitional step connecting preform forming and final rotary pressing, is technically based on the creation of a through-hole structure in the central region of the disc-shaped billet through precise axial pressing deformation, thereby transforming it into an annular billet with a continuous ring-shaped cross-section. This process not only achieves the geometric transformation from a solid to a hollow body, but more importantly, by controlling the punching deformation parameters, it ensures the uniformity of the wall thickness and the coaxiality of the inner and outer contours of the annular billet, providing an initial blank with regular geometric boundaries and uniform metal distribution for subsequent multi-stage rotary pressing.

[0031] The punching process relies on a specialized tooling system consisting of a punching pad ring and a hollow punch. The punching pad ring acts as a lower die support, its inner diameter matching the inner diameter of the target annular blank. It supports the blank and defines the formed dimensions of the inner hole after punching. The hollow punch acts as an upper die actuator, its outer diameter fitting with the inner hole of the punching pad ring. It performs a combined shearing and extrusion deformation on the central region of the blank through axial pressing. The axial positioning accuracy of the two tooling components directly determines the uniformity of the wall thickness distribution of the annular blank after punching.

[0032] In the above scheme, the billet axis, the punching pad ring axis, and the hollow punch axis are all triple-coincident, i.e., triaxial concentricity control. This geometric constraint ensures that the punch is symmetrically distributed along the billet center during the pressing process, so that the metal material is subjected to uniform circumferential shear force and radial extrusion force at the shearing edge, avoiding the aggravation of unilateral metal flow or tearing caused by eccentricity. Strict concentricity control effectively suppresses billet warping and hole wall tilting caused by uneven force during punching, ensures the concentricity of the inner and outer cylindrical surfaces of the annular billet, and eliminates the hidden dangers of uneven loading and deformation that may occur in subsequent pressing due to differences in wall thickness.

[0033] The termination condition for punching deformation is determined by the second preset height reached by the upper surface of the hollow punch. This height parameter is calculated and set based on the inner diameter of the target annular blank and the structural height of the punched pad ring, aiming to ensure that the annular blank after punching has the target wall thickness and axial height. When the lower surface of the punch penetrates the blank and contacts the working surface of the punched pad ring, the central skin is cut off to form a through hole, thus completing the morphological transformation from a disc-shaped blank to an annular blank, obtaining an annular pre-formed blank with precise inner and outer diameter dimensions, uniform wall thickness, and a flat end face.

[0034] Optionally, the above-mentioned punching of the blank with a hollow punch until the upper surface of the hollow punch reaches a second preset height includes: controlling the hollow punch to press down until its upper surface reaches the second preset height, the second preset height being determined according to the inner diameter of the target annular blank and the height of the punching pad ring, so that the annular blank after punching has a target wall thickness.

[0035] The aforementioned second preset height, as a key process parameter for controlling the termination of deformation in the punching process, directly determines the axial height and wall thickness distribution of the annular blank after punching. This parameter precisely limits the termination position of the hollow punch, ensuring that the depth of the punch penetration into the blank is sufficient to completely remove the central skin to form a through hole, while avoiding hole wall deformation or end face damage caused by excessive pressing. This provides an annular pre-formed blank with precise wall thickness dimensions for the subsequent rotary pressing process. The value of the second preset height needs to comprehensively consider the inner diameter of the target annular blank and the structural height of the punching pad. The inner diameter of the target annular blank determines the inner diameter of the annular blank after punching, while the height of the punching pad limits the support reference position of the blank during the punching process. Together, they constitute the geometric boundary conditions for punching deformation. Based on the principle of volume conservation, and combined with the initial height and diameter of the disc-shaped billet, the second preset height calculated through geometric relationships ensures that the wall thickness of the annular billet after punching strictly meets the target wall thickness requirement, eliminating the phenomenon of residual skin due to insufficient punching depth or wall thinning caused by excessive punching. Precise control of the target wall thickness has a decisive impact on subsequent forming processes, and its uniformity directly relates to the symmetry of metal flow and the consistency of deformation resistance distribution during rotary pressing. When the annular billet has a circumferentially uniform wall thickness, the radial compressive force applied by the shaped anvil during subsequent multi-stage rotary pressing can form a balanced stress field on the circumference of the billet, avoiding uneven loading, uneven metal flow, or expansion of deformation dead zones caused by local wall thickness differences, thereby ensuring the uniformity of the final annular disc part in both radial and tangential directions.

[0036] In the above scheme, the height control parameters and the triaxial concentricity requirements form a process synergy. While ensuring strict alignment between the punch and the geometric center of the blank, precise axial displacement control ensures that the punched annular blank not only has accurate inner and outer diameter dimensions but also a uniform wall thickness distribution along the circumference. This dual guarantee of geometric accuracy and structural uniformity lays a crucial foundation for high-uniformity forming of large annular blanks through rotary pressing.

[0037] Optionally, before upsetting and punching the cylindrical billet into a ring-shaped billet, the process further includes: heating the steel ingot to 1250±20℃, performing upsetting and drawing forging, breaking the coarse grains inside the steel ingot, and obtaining the cylindrical billet by cutting.

[0038] It is understandable that the billet forging process is the initial stage of the process flow, aiming to transform the original steel ingot into a cylindrical billet with refined grains and a uniform microstructure, providing a high-quality initial blank for subsequent forming processes. The as-cast microstructure formed during the solidification process of the steel ingot typically contains coarse columnar crystals, well-developed dendritic segregation, and metallurgical defects such as porosity and shrinkage cavities. These microstructure characteristics directly lead to directional differences in the material's mechanical properties and a tendency towards brittleness, failing to meet the stringent requirements for internal quality and performance consistency in large ring-shaped components. Therefore, this process first heats the steel ingot to a specific temperature range of 1250±20℃. This temperature range is set based on the austenitizing temperature and recrystallization kinetics of the steel grade used, aiming to ensure that both the core and surface of the steel ingot reach a uniform single-phase austenitic state, achieving sufficient plasticity to reduce deformation resistance while avoiding abnormal grain growth or overheating defects caused by excessively high temperatures. The ±20℃ temperature tolerance control reflects the stringent requirements for heating uniformity, ensuring consistent temperature distribution in large-section steel ingots before deformation and preventing the risk of uneven local deformation or cracking caused by temperature gradients. Under this temperature condition, a combination of upsetting and elongation deformation is applied to the steel ingot. Upsetting deformation, through axial compression, induces dynamic recrystallization of the as-cast coarse grains, breaking down the original columnar crystal structure; elongation deformation, through axial extension and radial contraction, further increases the deformation amount, allowing core as-cast defects to weld and densify under multidimensional stress. The combined application of these two deformation methods achieves the transformation from large-section ingots to medium- and small-section billets, achieving homogenization and densification of the microstructure, effectively eliminating dendritic segregation and refining grain size.

[0039] The billet obtained through the above-mentioned forging process is then separated into individual billets with regular cylindrical geometric shapes through a cutting process. The cutting process ensures the perpendicularity of the billet end faces and the accuracy of its length dimensions, meeting the geometric requirements of subsequent forming processes. This cylindrical billet, serving as an intermediate blank, no longer possesses the original as-cast microstructure characteristics, but instead exhibits a fine and uniform equiaxed crystal structure, exhibiting excellent thermoplastic deformation capabilities. This provides the foundation for the subsequent upsetting, punching, and rotary pressing processes to produce high-performance large ring-shaped parts with both microstructure and geometric homogenization.

[0040] Furthermore, the determination of the aforementioned temperature parameter 1250±20℃ is primarily based on the austenitic phase transformation characteristics and high-temperature mechanical behavior of the steel used. Specifically, 1250℃ falls within the single-phase austenite region of typical structural steel, far exceeding the material's recrystallization temperature and dynamic recovery temperature. At this temperature, the as-cast coarse-grained structure inside the ingot is in a thermally activated state, dislocation movement resistance is reduced, and deformation resistance is at a low level. This provides the necessary plasticity conditions for subsequent large deformations (such as upsetting and drawing) to break dendrites and weld internal porosity. Simultaneously, this temperature point is within a sufficiently safe range below the material's solidus line, avoiding the overheating-sensitive region of rapid grain growth and the overheating critical temperature of grain boundary oxidation or even melting, ensuring that good plasticity is achieved without compromising the material's structural integrity. The ±20℃ tolerance range stems from engineering considerations regarding the thermal conductivity characteristics during the heating of large steel ingots. Specifically, due to the large mass and thick cross-section of the steel ingot, an unavoidable temperature gradient exists from the surface to the core in the heating furnace. The ±20℃ fluctuation range allows for a temperature difference between the core and the surface during the heat penetration process. This ensures that the core reaches a temperature sufficient for dynamic recrystallization while preventing the surface from prematurely entering the grain coarsening or oxidation zone due to localized overheating. Furthermore, this tolerance also takes into account the temperature control accuracy of industrial heating furnaces and the thermal inertia fluctuations in mass production. It ensures that under actual production conditions, whether the steel ingot is in the homogenized zone of the furnace or has slight temperature field inhomogeneity, its overall temperature can be maintained within a suitable forging process window, providing a stable thermodynamic environment for the full fragmentation and homogenization of the as-cast structure.

[0041] Step S120: Place the annular billet on a rotary worktable, and use a shaped anvil with variable contact surface and variable curvature to perform localized continuous deformation of the annular billet along the circumference through rotary pressing, so that the deformation covers the entire circumference of the annular billet; the middle part of the working surface of the shaped anvil is a cylindrical side surface, and the two ends are frustum side surfaces. The axial length of the cylindrical side surface is less than the inner diameter of the target annular piece, and the axial length of the frustum side surface is greater than the wall thickness of the target annular piece.

[0042] The aforementioned rotary forging process, as the final forging step in the forming of large ring-shaped billets, aims to achieve overall radial widening and axial compression of the ring-shaped billet through continuous deformation under localized loading. Unlike traditional integral upsetting or strip-shaped flat anvil forging, this process relies on the rotational motion of the rotary table combined with the vertical pressing of the shaped anvil. This allows the deformation tool to apply compressive force segment by segment along the circumference of the ring-shaped billet. Through the cumulative effect of multiple anvil presses, uniform large deformation is achieved throughout the entire circumference, thus forming a symmetrical deformation field around the axis within the billet, ensuring uniform tangential deformation.

[0043] As the core tooling in this process, the irregularly shaped anvil functions to replace traditional strip or circular flat anvils. Through specific geometric contour design, it controls the contact state with the billet and the boundary conditions of metal flow. Traditional flat anvils have a planar or simple curved surface contact with the billet, resulting in a large and fixed contact area, which easily leads to friction effects and restricted metal flow under the anvil, forming deformation dead zones. The irregularly shaped anvil, through its special working surface configuration, creates a contact area and curvature distribution that varies with the loading position during deformation. This alters the metal flow path and stress field distribution, enabling differentiated control of deformation behavior in different radius regions to compensate for the uneven radial deformation caused by the geometric shape of the annular billet.

[0044] It is understandable that the above-mentioned process has strict requirements on the integrity of the deformation coverage area. It is necessary to control the rotation angle of the worktable and the pressing position of the shaped anvil to ensure that the deformation band formed by each anvil is tightly connected in the circumference, without any omissions. Only when the deformation covers the entire circumference of the annular billet can a deformation field symmetrical about the axis be established inside the billet, eliminating the differences in microstructure and properties caused by local undeformed areas, and laying the foundation for subsequent axial uniform deformation through flipping.

[0045] Optionally, the above-mentioned use of a shaped anvil with variable contact surface and variable curvature to perform local loading and continuous deformation of the annular billet in the circumferential direction by means of rotary pressing includes: controlling the single anvil reduction rate of the shaped anvil to be 15%~20% and loading the annular billet anvil by anvil.

[0046] The single-anvil reduction rate is defined as the relative compression of the billet's local height in the loading zone during a single compression by a shaped anvil, and its value is equal to the ratio of the reduction to the billet's initial height. In the rotary pressing process, this parameter, combined with the sequential anvil loading method, constitutes the core process variable for controlling the deformation penetration depth and strain distribution uniformity. Sequential anvil loading refers to the sequential local compression of the annular billet by shaped anvils at specific angular positions along its circumference. After each anvil's action, the worktable rotates the billet by a certain angle, allowing the next anvil to act on adjacent undeformed or lightly deformed areas. Through the superposition of multiple anvils, continuous deformation accumulation with full circumferential coverage is achieved. This loading mode decomposes the overall large deformation into the sequential action of multiple local small deformations, which not only reduces the equipment load requirements for a single deformation but also creates a complex three-dimensional stress state inside the billet through the overlap and interference of the deformation zones of each anvil.

[0047] In the above scheme, controlling the single-anvil reduction rate within the range of 15% to 20% is a process window optimized based on the deformation penetration characteristics and microstructure evolution law of large-section rings. When the reduction rate is below 15%, deformation is mainly concentrated on the surface layer of the billet, making it difficult to effectively transfer to the core. This leads to an increased strain difference between the core and the surface layer, failing to fully break up any remaining casting defects or coarse-grained structures in the core. When the reduction rate exceeds 20%, the surface metal experiences excessive temperature rise due to severe shearing and friction, easily forming local coarse grains or shear bands. Meanwhile, the core, due to enhanced rigid end constraint, experiences insufficient deformation, resulting in an intensified radial deformation gradient. A reduction rate of 15% to 20% ensures that the deformation energy is sufficient to penetrate a significant portion of the billet's cross-sectional thickness, allowing for sufficient dynamic recrystallization in both the core and surface metals, while avoiding microstructure inhomogeneity caused by excessive surface deformation. Within a compression range of 15% to 20%, the curvature gradient characteristics of the irregularly shaped anvil's working surface can be fully utilized, enabling the metal to generate controllable radial flow while undergoing axial compression. This effectively overcomes the deformation dead zone formed by large-area contact friction during traditional flat anvil pressing. During the anvil-by-anvil loading process, the deformation zone of each anvil appropriately overlaps with the previous thousand deformation zones to ensure continuity, while avoiding excessive overlap to prevent excessive local cumulative strain. This establishes a deformation field with uniform strain distribution in the circumference of the annular billet, providing a uniform strain basis for achieving axially symmetrical deformation through subsequent flipping.

[0048] It is understandable that the parameter range of the single anvil reduction rate (i.e., 15%~20%) is based on a deep understanding of the deformation transfer mechanism and microstructure evolution law during the rotary pressing process of large annular billets. Under local loading conditions, the reduction rate directly determines the geometric size and strain penetration depth of the plastic deformation zone, thereby affecting the uniformity of strain distribution and the degree of dynamic recrystallization within the billet cross-section. When the reduction rate is set below 15%, the deformation zone is limited to the vicinity of the contact surface. The core metal, being in a rigid zone, hardly undergoes plastic flow, resulting in a strong strain gradient between the surface and the core. This makes it impossible to effectively break up the as-cast microstructure of the core or weld the internal porosity, and is also detrimental to the uniform transfer of deformation in subsequent firing cycles. When the reduction rate exceeds 20%, although the deformation penetration depth increases, the surface metal generates a large amount of deformation heat due to severe shear deformation, resulting in a strong temperature rise effect. This easily leads to abnormal local grain growth or the formation of shear band structures. Simultaneously, excessive reduction intensifies the lateral flow of the metal under the anvil, and the increased rigid-end constraint inhibits sufficient deformation of the core, causing uneven radial deformation and easily leading to folding or crack defects on the surface. The 15%–20% range was determined through quantitative analysis of the deformation zone depth, uniformity of equivalent strain distribution, and recrystallization volume fraction under different reduction rates. This ensures that the deformation generated by a single loading effectively penetrates the main part of the billet cross-sectional thickness, allowing sufficient dynamic recrystallization in both the core and surface layers, while controlling the surface temperature rise and deformation resistance within a reasonable range to avoid surface quality deterioration. This range provides key process parameter support for establishing a circumferentially uniform strain field and obtaining a fine and uniform equiaxed grain structure.

[0049] Optionally, in the process of using a shaped anvil with variable contact surface and variable curvature to continuously deform the annular billet by rotating and pressing, the method further includes: during the anvil loading process, when there are local protrusions on the upper surface of the annular billet due to uneven local deformation, the local protrusions are leveled by adjusting the pressing position of the shaped anvil until the overall height of the annular billet reaches a uniform third preset height.

[0050] During the rotary pressing process with localized loading of the anvil, localized bulges easily appear on the upper surface of the annular billet due to the anisotropy of metal flow, the non-uniformity of the internal structure or temperature distribution of the billet, and the difference in the degree of overlap between adjacent anvil deformation zones. If these geometric defects are not eliminated in time, they will be pressed into the interior during subsequent heat deformation, forming folding defects, or causing a deterioration in the contact state between the die and the billet during subsequent loading, leading to stress concentration and further non-uniformity of deformation distribution, ultimately affecting the dimensional accuracy and internal quality of the forging. To address this type of localized deformation non-uniformity, a fixed-point leveling mechanism is introduced into the process. By precisely adjusting the horizontal position of the irregularly shaped anvil relative to the localized bulge, a specific working area of ​​the anvil directly acts on the bulge, implementing localized supplementary pressing. This fixed-point leveling utilizes the geometric characteristics of the variable curvature working surface of the irregularly shaped anvil, allowing for targeted loading based on the position and height of the bulge, effectively reducing the bulge while avoiding excessive pressing on the already leveled area, thus achieving precise control over the geometry of the upper surface of the billet.

[0051] The aforementioned leveling process terminates at a third preset height, representing the uniform axial dimension the billet should achieve after deformation in this heat. By eliminating height deviations point by point, it is ensured that the upper surface of the billet reaches a uniform and consistent level after the entire rotational pressing process, providing an ideal geometric reference for uniform deformation after the next heat's flipping and reheating. This effectively avoids dimensional deviations caused by the accumulation of initial geometric defects, ensuring that each stage in the multi-heat deformation process is based on a uniform geometric foundation, thereby improving the dimensional accuracy and microstructure uniformity of the final ring-shaped piece.

[0052] Optionally, the working surface of the aforementioned irregularly shaped anvil is an arc surface with gradually changing curvature along the length direction.

[0053] The working surface of the irregularly shaped anvil exhibits a continuously varying curvature along its length, stemming from the structural transition from the central cylindrical side surface to the frustum-shaped side surfaces at both ends. Specifically, the central cylindrical section possesses a constant curvature, while the frustum-shaped sections at both ends exhibit a gradually changing curvature along the axial direction. Together, these two features constitute a non-uniform distribution of curvature along the length of the working surface. This geometric design allows the contact state between the irregularly shaped anvil and the annular billet to continuously adjust with changes in their relative positions, creating variable contact surface boundary conditions during deformation, unlike those of traditional flat anvils. This gradually changing curvature structure plays a crucial role in the process. When the irregularly shaped anvil acts on the annular billet, different areas of the working surface, due to differences in curvature, form differentiated contact areas and contact angles with the billet surface, resulting in controlled lateral flow of the metal during axial compression. Compared to the strong frictional constraints and dead zones caused by the large-area planar contact of traditional strip anvils, the arc-shaped contact achieves a gradual transition of contact area from small to large or from large to small through curvature variation, reducing local frictional resistance and promoting uniform metal flow. The curvature distribution along the length direction matches the deformation requirements at different radial positions of the annular billet. Near the inner diameter region, the metal is strongly constrained by rigid ends and the flow space is limited; the constant curvature of the cylindrical section provides a stable contact state. In the outer diameter region, the metal has greater flow freedom; the gradual curvature of the frustum section effectively compensates for the weakening of rigid end constraints caused by the increase in radius by changing the contact angle. This synergistic spatial distribution of curvature and contact area optimizes the deformation penetration depth and strain distribution in each radial region, improves the uniformity of deformation inside the annular billet, and lays the tooling foundation for obtaining large annular billet parts with consistent microstructure and properties.

[0054] Step S130: Reheat the annular billet that has completed a full rotation and pressing to the forging temperature, place it on the rotary worktable and flip it relative to the previous pressing, so that the lower surface that contacted the anvil in the previous pressing becomes the upper surface that contacts the anvil in this pressing, and repeat the above rotation and pressing process. Optionally, the above-mentioned flipping of the annular billet includes: after each rotational pressing that covers the entire circumference of the annular billet, immediately reheating the annular billet to the forging temperature, and then when placing it on the rotary worktable for the next heat deformation, flipping the annular billet 180 degrees relative to the position of the previous heat, so that the lower surface that contacted the anvil in the previous heat becomes the upper surface that contacts the anvil in this heat, so as to achieve alternating loading of the upper and lower surfaces.

[0055] In the above scheme, after completing one full rotation and pressing cycle, the temperature of the annular billet drops below the forging temperature due to heat loss from plastic deformation caused by continuous local loading and heat exchange between the surface and the environment. The dynamic recrystallization driving force of the material is insufficient, and the deformation resistance increases. If subsequent deformation continues at this low temperature, not only will the required equipment load increase dramatically, but also a large number of dislocations will accumulate within the grains due to insufficient recrystallization, forming a work-hardened structure and deteriorating the plasticity and toughness of the forging. Therefore, the annular billet that has completed one full rotation of deformation must be reheated to the forging temperature to restore it to a hot-working state with sufficient plasticity and low deformation resistance, providing the necessary temperature conditions and microstructure preparation for the next effective deformation cycle.

[0056] When the reheated billet is placed on the rotary table, a specific orientation adjustment is required. This involves flipping the billet relative to the previous firing position, transforming the lower surface that contacted the anvil in the previous firing into the upper surface that contacts the anvil in this firing. The essence of this flipping operation is to achieve alternating loading of the upper and lower surfaces. A 180-degree rotation reverses the billet axially, turning the original pressure surface into a support surface, and vice versa. This alternating loading mechanism overcomes the deformation dead zone limitations caused by frictional constraints and asymmetrical stress states during continuous unidirectional loading. It allows the upper and lower surfaces to alternately experience compressive stress and frictional shear during deformation, thereby establishing a symmetrical strain distribution in the axial direction.

[0057] By alternating loading of the upper and lower surfaces, the axial non-uniformity caused by the direct compression of the upper surface by the anvil and the delayed deformation of the lower surface due to frictional constraint of the worktable during traditional single-sided pressing is effectively overcome. The deformation of each pass forms a centrally symmetrical strain distribution along the billet thickness. After multiple passes, the deformation degree of the upper and lower surfaces tends to be consistent. The core metal is subjected to compressive stress from both the upper and lower directions in different passes, improving its grain refinement and microstructure uniformity. This cyclical operation of flipping and reheating, combined with the circumferential full-coverage deformation of rotary pressing, ultimately achieves comprehensive control over the radial, tangential, and axial deformation uniformity of the annular billet in three-dimensional space, providing a process guarantee for obtaining large annular billet parts with consistent microstructure and properties.

[0058] Step S140: Repeat the above steps of reheating, flipping and rotating pressing until the height of the annular blank reaches the target height of the annular cake.

[0059] Optionally, step S140 repeats the above-mentioned flipping and rotary pressing steps, including: repeating the flipping and rotary pressing steps multiple times, wherein each time includes reheating the annular billet that has completed the deformation of the previous time to the forging temperature, placing it on a rotary worktable and flipping it 180 degrees relative to the previous time, and then using a special-shaped anvil to perform local loading and continuous deformation of the annular billet along the circumference by rotary pressing, so that the deformation of each time accumulates and superimposes until the height of the annular billet reaches the target annular part height.

[0060] It is understandable that step S140 aims to achieve a balance between the demand for large deformation and the limitations of single-cycle processing capacity through multiple heating cycles. Since single-cycle rotary pressing is limited to a reasonable reduction rate of 15% to 20%, it is impossible to complete the total height reduction from the annular billet to the target ring-shaped part within a single heating cycle. Therefore, it is necessary to repeatedly implement a complete process cycle of reheating, flipping, and full-cycle pressing to gradually accumulate the local deformation of each heating cycle, ultimately achieving a gradual reduction in the axial dimension of the billet and cumulative optimization of its microstructure and properties. Each heating cycle constitutes an independent deformation cycle. The reheating stage restores the material's plastic state and eliminates any work hardening that may have occurred in the previous heating cycle. The flipping operation ensures alternating loading of the upper and lower surfaces to maintain axial deformation symmetry, while the full-cycle rotary pressing completes the circumferential full-coverage deformation of this cycle. This cycle is not a simple mechanical repetition, but a progressive forming process with a cumulative effect: geometrically, the billet height gradually approaches the target size as the reduction amount of each firing is superimposed; microstructure-wise, the dynamic recrystallization generated by each firing causes the grains to be continuously refined in the repeated deformation-recrystallization cycle, and since each firing covers the entire circumference and alternately loads the upper and lower surfaces, grain refinement and microstructure homogenization are simultaneously promoted in three-dimensional space.

[0061] The deformation process ends when the height of the annular billet reaches the target height of the ring-shaped part, which is determined by the forging design dimensions, marking the completion of the geometric forming process. At this point, the billet has undergone multiple heat treatments and cumulative deformation, and the internal structure has fully evolved into fine and uniform equiaxed crystals. Furthermore, due to the uniform deformation in all directions, the formation of texture or banded structures is avoided, ultimately resulting in a large ring-shaped part that combines precise geometric dimensions with excellent microstructure properties.

[0062] To facilitate understanding of the working principle of the above-described large ring forging method, this application provides a specific application example of this method in a certain application scenario. In this application scenario, the above-described large ring forging method mainly includes: S1: According to Figure 2 The relevant data of the target ring-shaped part are used to calculate and determine the shape and size of the forging blank and the mold, and to manufacture the hollow punch 5, the punching pad ring 4, and the special-shaped anvil 8 for rotary pressing.

[0063] S2: Heat the steel ingot to 1250±20℃, perform upsetting and drawing forging, break the coarse grains inside the steel ingot, and obtain cylindrical billet 1 by chopping.

[0064] S3: As Figure 3 As shown, the cylindrical billet 1 is heated to the forging temperature and then placed on the press platform. The upsetting circular plate 2 is then placed on the billet, and the press is started to compress the cylindrical billet 1 through the upsetting circular plate 2 until the upper surface of the circular plate 2 reaches the set height H1, thus obtaining the upset billet 3.

[0065] S4: As Figure 4 As shown, after the upsetting billet 3 is reheated to the forging temperature, it is placed on the punching pad ring 4. The hollow punch 5 is placed on the upsetting billet 3, and the axis of the billet 3 is aligned with the axis of the punching pad ring 4 and the axis of the hollow punch 5. The press is started, and the upsetting billet 3 is punched through the hollow punch 5 until the upper surface of the hollow punch 5 reaches the set height H2, and the punching process is completed to obtain the punched annular billet 6.

[0066] S5: As Figure 5 As shown, after the punched annular billet 6 is reheated to the forging temperature, it is placed on the rotary table 7 of the press. The rotary pressing anvil 8 is placed on the annular billet 6 along its diameter. The press is started, and pressure is applied to the annular billet 6 through the rotary pressing anvil 8 until the upper surface of the rotary pressing anvil 8 reaches the set height H3. The press's movable crossbeam is raised to separate the rotary pressing anvil 8 from the annular billet 6. The rotary table 7 of the press rotates, causing the annular billet 6 on it to rotate around its axis by a set angle. The press's movable crossbeam moves down, and the rotary pressing anvil 8 is placed on the annular billet 6 again along its diameter. The press is started again, and pressure is applied to the annular billet 6 through the rotary pressing anvil 8 until the upper surface of the rotary pressing anvil 8 reaches the set height H3. This process is repeated until a complete ring is pressed. When there are local protrusions on the upper surface of the annular billet 6, they are leveled using a rotary pressing anvil 8 until the overall height of the annular billet reaches the set height H3. Figure 6 As shown, the rotary pressing anvil 8 is geometrically symmetrical along its length. The middle of the working surface is a cylindrical side surface C8-1, and both ends are frustum side surfaces C8-2. The diameter of the smaller end of the frustum section is equal to that of the cylindrical section, and its apex angle is 8°. The angle between the axes of the frustum section and the cylindrical section is 4°, thus ensuring that the bottom of the working surface along the length of the rotary pressing anvil 8 is on the same straight line. That is, the generatrix of the bottom cylindrical side surface C8-1 of the rotary pressing anvil 8 is collinear with the generatrix of the two frustum side surfaces C8-2. There is a small transition section between the cylindrical section and the frustum section that satisfies geometric continuity. The diameter of the cylindrical section... The thickness of the annular blank 6 after punching in step S4 Decide, The length of the cylindrical segment must be less than the inner diameter of the target annular blank. The length of the frustum segment is determined by the size of the target annular blank, and the length of the frustum segment must be greater than the wall thickness of the target annular blank. This determines that the working surface of the rotary pressing anvil 8 is an arc surface with gradually changing curvature along its length, and that during deformation, the contact area gradually increases from the inside to the outside along the radial direction of the annular blank, forming a boundary condition of variable curvature and variable contact surface. The geometric center of the rotary pressing anvil 8 must always be aligned with the axis of the annular blank 6, and the single anvil reduction rate is... , .

[0067] S6: After the annular billet 6 has completed one full rotation of the rotary forging process, it is reheated to the forging temperature and placed on the rotary worktable of the press. During placement, the annular billet 6 is rotated 180 degrees relative to its position in the previous forging cycle; that is, the upper surface in contact with the rotary forging anvil 8 in this step corresponds to the lower surface of the annular billet 6 in the previous cycle. The deformation process in step S5 is repeated. The geometric center of the rotary forging anvil 8 must always be aligned with the axis of the annular billet 6, and the single anvil reduction rate is... , .

[0068] S7: Repeat step S6 until the height of the annular blank 6 after multiple pressings reaches the target annular part height.

[0069] The above description is merely an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for forging large ring-shaped discs, characterized in that, The method includes: Cylindrical blanks are upsetting and punching to form ring-shaped blanks; The annular blank is placed on a rotary worktable, and a shaped anvil with variable contact surface and variable curvature is used to continuously deform the annular blank by local loading along the circumference through rotary pressing, so that the deformation covers the entire circumference of the annular blank; wherein, the working surface of the shaped anvil has a cylindrical side surface in the middle and frustum side surfaces at both ends, the axial length of the cylindrical side surface is less than the inner diameter of the target annular blank, and the axial length of the frustum side surface is greater than the wall thickness of the target annular blank; The annular billet, after completing a full rotation and pressing, is reheated to the forging temperature, placed on the rotary worktable, and flipped relative to the previous pressing, so that the lower surface that contacted the anvil in the previous pressing becomes the upper surface that contacts the anvil in this pressing. The above rotation and pressing process is repeated. Repeat the above steps of reheating, flipping, and rotating pressing until the height of the annular blank reaches the target height of the annular cake.

2. The forging method for large ring-shaped discs according to claim 1, characterized in that, Before the cylindrical blank is upset and punched to form a ring-shaped blank, the method further includes: The steel ingot is heated to 1250±20℃ and subjected to upsetting, drawing and forging to break up the coarse grains inside the steel ingot. The cylindrical billet is then obtained by cutting and chopping.

3. The forging method for large ring-shaped discs according to claim 1, characterized in that, Upsetting the cylindrical billet includes: After heating the cylindrical billet to the forging temperature, it is placed on the press platform. A circular plate for upsetting is placed on the cylindrical billet, and the press is controlled to compress the cylindrical billet through the circular plate until the upper surface of the circular plate reaches the first preset height, thus obtaining the upset disc-shaped billet.

4. The forging method for large ring-shaped discs according to claim 1, characterized in that, The punching includes: After the upsetting billet is heated to the forging temperature, it is placed on the punching pad ring. A hollow punch is placed on the upsetting billet, and the axis of the billet is aligned with the axis of the punching pad ring and the axis of the hollow punch. The billet is punched by the hollow punch until the upper surface of the hollow punch reaches the second preset height, thus obtaining the annular billet.

5. The forging method for large ring-shaped discs according to claim 4, characterized in that, The step of punching the blank with the hollow punch until the upper surface of the hollow punch reaches a second preset height includes: The hollow punch is controlled to press down to its upper surface to reach a second preset height. The second preset height is determined according to the inner diameter of the target annular blank and the height of the punching pad ring, so that the annular blank after punching has a target wall thickness.

6. The forging method for large ring-shaped discs according to claim 1, characterized in that, The method of using a shaped anvil with variable contact surface and variable curvature to continuously deform the annular billet along the circumferential direction through rotary pressing includes: The single-anvil reduction rate of the irregularly shaped anvil is controlled at 15%~20%, and the annular billet is loaded anvil by anvil.

7. The forging method for large ring-shaped discs according to claim 1, characterized in that, The process of using a shaped anvil with variable contact surface and variable curvature to continuously deform the annular billet along the circumferential direction through rotary pressing also includes: During the anvil loading process, when the upper surface of the annular billet has local protrusions due to uneven local deformation, the local protrusions are leveled by adjusting the pressing position of the irregular anvil until the overall height of the annular billet reaches a uniform third preset height.

8. The forging method for large ring-shaped discs according to claim 1, characterized in that, Flipping the annular blank includes: After each rotational pressing that covers the entire circumference of the annular billet is completed, the annular billet is immediately reheated to the forging temperature. Then, when it is placed on the rotary worktable for the next deformation, the annular billet is rotated 180 degrees relative to the position of the previous deformation, so that the lower surface that was in contact with the anvil in the previous deformation becomes the upper surface that is in contact with the anvil in this deformation, thereby achieving alternating loading of the upper and lower surfaces.

9. The forging method for large ring-shaped discs according to claim 1, characterized in that, The repeated reheating, flipping, and rotary pressing steps include: The flipping and rotary pressing steps are repeated multiple times. Each time, the annular billet that has been deformed in the previous time is reheated to the forging temperature, placed on the rotary worktable and flipped 180 degrees relative to the previous time. Then, the annular billet is subjected to local loading and continuous deformation along the circumference by the shaped anvil through rotary pressing. The deformation of each time is accumulated and superimposed until the height of the annular billet reaches the target annular part height.

10. The forging method for large ring-shaped discs according to any one of claims 1 to 9, characterized in that, The working surface of the irregularly shaped anvil is an arc surface with gradually changing curvature along its length.

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