A punching and extruding forming device and processing method for large high-performance hollow shaft

Abstract

The application discloses a punching and extruding forming device and a processing method for a large high-performance hollow shaft, and relates to the technical field of hollow shaft processing.The device comprises a press machine workbench, an outer forming assembly is arranged on the press machine workbench, and the outer forming assembly comprises a shaping die, a top block, a stop block and a flange die.A punching and extruding assembly is further arranged on the outer forming assembly, and the punching and extruding assembly comprises a round anvil, an upper flat anvil, a lower flat anvil, a large punch, a small punch and a heightening ring.The device integrates the outer forming assembly and the punching and extruding assembly, greatly simplifies a process flow and improves production efficiency.A flange forming process combining step-by-step anvil pressing and rolling is adopted, and the precision problem of insufficient filling of the flange part is solved.The device is provided with a step punching function and a whole-process temperature control function, a continuous ideal streamline organization is formed on the shaft body, the quality defect of uneven microstructure is improved, and the efficient, high-precision and high-performance integrated manufacturing of the large hollow shaft is realized.

Description

Technical Field

[0001] This invention relates to the field of hollow shaft processing technology, and specifically discloses a punching and extrusion forming device and processing method for large high-performance hollow shafts. Background Technology

[0002] Against the backdrop of continuously growing global demand for renewable energy, clean energy sources such as wind power, hydropower, and nuclear power are playing an increasingly important role in the energy structure. As a core transmission component of generator sets, the performance of hollow shafts directly affects the reliability and service life of the units. However, traditional manufacturing processes for large hollow spindles often involve multiple drawing, upsetting, punching, mandrel drawing, and flange upsetting, resulting in problems such as difficulty in achieving standard flange dimensions, poor forming quality, complex processes, long production cycles, and significant material waste. Especially for large shaft forgings such as hollow wind turbine spindles, traditional free forging processes lead to low material utilization, uneven internal structure, and unstable mechanical properties. Furthermore, the difficulty in precisely controlling material flow results in insufficient flange forming precision, and the shaft's microstructure cannot achieve an ideal continuous streamline distribution, severely restricting performance improvement and failing to meet the rapidly developing industry's demand for high-performance spindles.

[0003] While some existing invention patents have made improvements to the main shaft forging process to address the aforementioned issues, limitations still exist. For example, invention CN119843172A discloses a microstructure-controlled wind turbine main shaft steel and its heat treatment preparation method and application. This prior art focuses on controlling the microstructure of the steel through smelting and heat treatment to improve mechanical properties, but it does not solve the problems of insufficient flange filling and simplification of the forging process. Invention CN112705667B discloses a forging process for wind turbine shafts. While this prior art improves the durability and efficiency of the forging process, it does not address the optimization of key processes such as punching and shaft forming for hollow main shafts. Invention CN118699258A discloses a forging process for hollow wind turbine main shafts. This prior art proposes a flange upsetting combined with wide anvil pressing method, but in practical applications, it suffers from uneven metal rheology, non-ideal circular flange end face contours, and localized insufficient filling of the flange portion, affecting the geometric accuracy and mechanical properties of the component.

[0004] Therefore, in the current manufacturing field of large shaft forgings such as hollow wind turbine main shafts, existing technologies still have several shortcomings that urgently need to be addressed. Regarding flange forming, traditional processes and some improved solutions struggle to precisely control material flow, leading to insufficient filling of the flange and poor end-face forming accuracy. Especially during multi-directional deformation, due to uneven metal rheology, non-ideal circular profiles often appear, directly affecting the geometric accuracy and connection reliability of the components. In terms of shaft microstructure and properties, existing forging methods struggle to achieve an ideal continuous streamline distribution, resulting in insufficient internal microstructure uniformity and limited mechanical stability, thus restricting the service life of the main shaft under long-term heavy-load conditions. Furthermore, the overall process flow remains relatively complex, involving multiple processes such as drawing, upsetting, punching, and mandrel drawing. This not only results in long production cycles and low efficiency but also significant material waste, making it difficult to simultaneously meet the dual requirements of high-precision forming and efficient manufacturing. These interconnected problems collectively restrict further improvements in the overall performance of hollow main shafts, necessitating breakthroughs in key forming processes. Summary of the Invention

[0005] In order to address the technical defects of existing technologies in the manufacturing of large shaft forgings such as wind turbine hollow shafts, which are characterized by insufficient filling of the flange and uneven micro-flow structure of the shaft body, resulting in insufficient forming precision and low production efficiency of hollow shafts, this invention provides a punching and extrusion forming device and processing method for large high-performance hollow shafts.

[0006] To address the above problems, in a first aspect, the present invention provides the following technical solution: A punching and extrusion forming device for a large, high-performance hollow shaft includes a press worktable. A forming assembly is provided on the press worktable, comprising a shaping mold fixedly placed on the press worktable. The inner cavity of the shaping mold is used to hold a steel ingot. A top block is provided at the bottom of the inner cavity of the shaping mold, and a stop block is provided inside the top block. A flange mold is provided at the top of the shaping mold. In addition to the forming assembly, a punching and extrusion assembly is also provided. The punching and extrusion assembly includes a round anvil, an upper flat anvil, a lower flat anvil, a large punch, and a small punch. The upper flat anvil is used to press down the flange portion of the hollow shaft piece by piece. The upper and lower flat anvils are used to roll and form the flange portion of the hollow shaft. The large and small punches are used to punch holes in the main body of the hollow shaft.

[0007] Preferably, the top block is steppedly assembled with the inner wall of the shaping mold, the bottom end of the stop block is limitedly assembled with the press worktable, and the flange mold is steppedly assembled with the top of the shaping mold.

[0008] Preferably, both the large punch and the small punch have internal cooling water channels, which are spiral structures, and the top outer diameters of the large punch and the small punch are the same.

[0009] Preferably, the punching and extrusion assembly includes a shim ring, which is used to raise the arrangement height of the shaping mold.

[0010] On the other hand, the present invention also provides a method for punching and extruding large high-performance hollow shafts, comprising the following steps: S1. The steel ingot undergoes preheating and preforming treatment; S2. Assemble the shape forming components and place the pre-treated steel ingot into the inner cavity of the forming mold; S3. Use a round anvil to perform upsetting on the steel ingot, and the flange part of the hollow shaft is initially formed; S4. The upper anvil presses the steel ingot down one by one, and the flange of the hollow shaft is fully formed. S5. The upper and lower flat anvils perform rounding and forming operations on the steel ingots and correct the outer diameter of the hollow shaft flange. S6. Carbon powder is evenly applied to the inner wall of the forming mold, the outer wall of the large punch, and the outer wall of the small punch to lubricate and prevent the steel ingot from sticking to the mold. S7. The steel ingot is punched in sequence with the large punch and the small punch. S8. The top of the steel ingot is upset with the upper flat anvil, so that the steel ingot is in close contact with the flange mold, and the hollow shaft punching and extrusion forming process is completed.

[0011] Preferably, S1 specifically comprises: S101. The initial surface temperature of the steel ingot is 550℃. The steel ingot is heated to 850℃ and held for 3 hours. S102. After the first heat preservation is completed, the steel ingot is continuously heated at a heating rate of 90℃ / h until the temperature of the steel ingot reaches 1230℃, and then a second heat preservation is carried out for 8 hours to keep the average temperature of the steel ingot at 1230℃. S103. The steel ingot is subjected to staggered extrusion using an upper and lower flat anvil, and the sprue part of the steel ingot is upsetting and separated. The riser part of the steel ingot is plastically deformed using a drawing process to form a clamp structure. The clamp structure is used for subsequent gripping and transfer operations of the steel ingot. S104. Use a hydraulic press to upset and draw the steel ingot to eliminate the looseness and porosity defects inside the steel ingot, and process the steel ingot into a cylindrical billet, so that the outer diameter of the top of the steel ingot is larger than its outer diameter of the bottom. S105. Repeat the operation method in S103 to perform upsetting on the clamp structure of the steel ingot, and completely remove the clamp structure of the steel ingot by controlling the pressing amount and misalignment distance of the upper and lower flat anvils.

[0012] Preferably, S3 specifically includes: S301. Place the steel ingot into a heating furnace at a temperature of 1230℃ and maintain this temperature environment for 5 hours to allow the steel ingot to fully recover to 1230℃ and reach the hot forging temperature. S302. After the steel ingot is heated, it is hoisted into the inner cavity of the forming mold. The circular anvil is driven by a hydraulic press to compress the steel ingot in the forming mold. Under the continuous pressure applied by the circular anvil, the steel ingot undergoes plastic deformation, completing the preliminary forming process of the flange part of the hollow shaft.

[0013] Preferably, S4 specifically includes: S401. Place the upper flat anvil in the center area of ​​the flange on the top of the steel ingot and press it down. Then, using the upper flat anvil as the base point, move the upper flat anvil to the outer area of ​​the steel ingot flange one by one from the inside to the outside and press it down in sequence. S402. Rotate the steel ingot and the shaping mold synchronously around their axis by 90°. Use an upper flat anvil to press down the rotated steel ingot one anvil at a time. Under pressure, the steel ingot will extend evenly in the circumferential and radial directions, so that the top of the steel ingot fully fits the inner surface of the flange mold, and the flange part of the hollow shaft is fully formed.

[0014] Preferably, S7 specifically includes: S701. Place the steel ingot back into the forming mold. First, use a large punch as the first punching tool to apply axial pressure to the steel ingot, causing the steel ingot to undergo plastic deformation and complete the forming operation of the first step structure. Then, replace it with a small punch to perform the second punching operation and complete the forming operation of the second step structure. S702. After the steel ingot is punched twice, the shaping mold is lifted as a whole using a shim ring, so that the stop block is removed from the shaping mold and falls onto the press worktable. The steel ingot is punched again with a small punch to form the main through hole structure of the hollow shaft. The punching residue falls above the stop block and is collected.

[0015] Preferably, S8 specifically includes: S801. Use a shim ring to lift the forming mold and steel ingot as a whole, so that the steel ingot is in a suspended state. Use the upper flat anvil to apply pressure to the center area of ​​the flange of the steel ingot. In the order from the inside to the outside, gradually move the upper flat anvil towards the edge of the flange of the steel ingot and press it down in sequence. S802. After the flange part of the steel ingot is formed, the steel ingot and the flange mold are rotated 90° around their axis synchronously. The upper flat anvil is used again to press down one anvil at a time to process the material. This ensures that the steel ingot is completely filled into the inner cavity of the flange mold, thereby eliminating the round corner defects of the steel ingot flange part and obtaining the hollow shaft finished product.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention, through the synergistic cooperation of the forming component and the punching and extrusion component, constructs a complete integrated forming device and processing method from steel ingot pretreatment to finished product forming, effectively solving the technical problems of lengthy process, low efficiency, and serious material waste in the traditional hollow shaft manufacturing process; the punching and extrusion forming device in this invention systematically integrates the closed mold cavity composed of the shaping mold, flange mold, top block, and stop block with punching and extrusion tools such as round anvil, upper and lower flat anvil, large and small punches, and shim rings, realizing multiple processes such as overall upsetting, local forming, rounding and straightening, stepped punching, and final upsetting. Continuous operation at the same workstation eliminates the need for multiple heating and mold changes, completely eliminating the complex processes of repeated stretching, upsetting, and mandrel stretching in traditional processes. This highly integrated forming method not only significantly shortens the production cycle and reduces energy consumption, but more importantly, through the precise constraint of the mold cavity, it ensures that the material is effectively utilized in each deformation, avoiding the large amount of flash and excess material waste caused by the uncontrollable material flow in traditional free forging. The material utilization rate is significantly improved, and production costs are effectively controlled, providing a brand-new technical solution for the efficient and green manufacturing of large hollow shafts.

[0017] 2. In terms of device structure, the flange mold is precisely assembled with the top of the forming mold through a stepped structure, forming a flange forming cavity with good sealing. Combined with the separable bottom support design of the top block and stop block, it ensures rigid support in the initial stage of flange forming and provides a channel for excess material to fall during subsequent through-hole forming. In terms of process method, this invention creatively uses a flange precision forming process of pressing down anvils from the inside out and simultaneously rotating 90° for rounding and correction. First, the upper flat anvil is used to press down gradually from the center area of ​​the flange outwards, guiding the material to flow orderly from the center to the edge, avoiding premature material blockage and insufficient bottom filling. Then, the steel ingot and mold are rotated 90° simultaneously and pressed down anvils again, allowing the material to extend evenly along the circumference. Finally, the upper and lower flat anvils are rotated at a small angle of 10° for rounding, precisely straightening the outer edge of the flange. This combined process effectively solves the problems of non-circular contours and local filling defects caused by uneven material rheology in traditional methods, ensuring that the outer edge dimensions of the flange bottom are accurately met, and the rounded corner area is completely filled, significantly improving the geometric accuracy and mechanical properties of the flange forming.

[0018] 3. This invention constructs a full-process stepped heating and insulation system, which, in conjunction with the punching and extrusion process, abandons the traditional crude mode of simple heating followed by deformation. Instead, it establishes a gradient heating process to ensure full dissolution of carbides and uniform refinement of austenite grains. By setting a reheating process of 1230℃ for 5 hours between each forming process, the steel ingot achieves sufficient static recrystallization after large deformation, eliminating the uneven microstructure caused by accumulated work hardening. Simultaneously, in the punching process, through two stepped punching operations and precise temperature control, the material in the inner hole flows directionally at the optimal plasticity temperature, promoting a continuous and smooth distribution of metal flow lines along the shaft direction, completely avoiding the interruption and folding of flow lines caused by uneven temperature drop in traditional processes. The aforementioned full-process precision temperature control system fundamentally solves the persistent quality problems of insufficient internal microstructure uniformity and significant differences in mechanical properties between the core and surface layers in large forgings, constituting a key innovation that distinguishes it from existing technologies.

[0019] 4. This invention achieves a breakthrough improvement in the structural properties of the shaft body through a two-step punching scheme and the coordinated design of the punch cooling system. In terms of process method, a large punch is first used to perform the first punching to form the first step structure, then a small punch is used to perform the second punching to form the second step structure. Finally, the die is raised by a shim ring to achieve through hole penetration. The above-mentioned step-by-step punching method cleverly utilizes the constraint effect of the die cavity, so that the material in the inner hole flows orderly towards the shaft body under the action of punching pressure. While gradually raising the shaft body, a continuous metal streamline structure is formed along the shaft body direction. This streamline structure can significantly improve the fatigue strength and impact resistance of the hollow shaft under heavy load conditions. In terms of device structure, both the large and small punches are equipped with spiral cooling water channels. Compared with straight water channels, spiral water channels have a longer heat exchange path and a larger heat exchange area, which can efficiently remove the heat generated by the punch during operation, effectively preventing the punch from bending and deforming due to excessively high punch temperature caused by continuous punching, ensuring punching accuracy and tool life, and providing reliable equipment guarantee for the stable formation of high-performance shaft body structure. Attached Figure Description

[0020] To more clearly illustrate the technical solution of the present invention, the drawings used in the description will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 This is a schematic diagram showing the placement of the pre-molding shaping mold, stop block, top block, and flange mold for the steel ingot before it is inserted into the mold according to the present invention. Figure 2 This is a schematic diagram of the steel ingot being placed into the shaping mold according to the present invention; Figure 3 This is a schematic diagram showing the placement of the steel ingot and the anvil in this invention; Figure 4 for Figure 3 Material simulation modal diagrams; Figure 5 This is a preliminary forming schematic diagram of the steel ingot flange portion of the present invention; Figure 6 for Figure 5 Material simulation modal diagrams; Figure 7 for Figure 5 Enlarged schematic diagram of the structure at point A in the middle; Figure 8 This is a schematic diagram of the working structure of the large punch and small punch of the present invention; Figure 9 for Figure 8 Material simulation modal diagrams; Figure 10 This is a schematic diagram showing the placement of the large punch of the present invention for the first punching operation on a steel ingot; Figure 11 for Figure 10 Material simulation modal diagrams Figure 12 This is a schematic diagram of the placement of the small punch of the present invention for secondary punching of steel ingots; Figure 13 for Figure 12 Material simulation modal diagrams Figure 14 This is a schematic diagram of the arrangement of punching waste material according to the present invention; Figure 15 for Figure 14 Material simulation modal diagrams; Figure 16 This is a schematic diagram of the flange upsetting process of the present invention; Figure 17 for Figure 16 Material simulation modal diagrams; In the diagram: 1. Press worktable, 2. Top block, 3. Stop block, 4. Shaping mold, 5. Flange mold, 6. Steel ingot, 7. Round anvil, 8. Upper flat anvil, 9. Lower flat anvil, 10. Large punch, 11. Small punch, 12. Shaping ring, 13. Punching residue. Detailed Implementation

[0021] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the specific embodiments. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0022] This specific embodiment provides a punching and extrusion forming apparatus for large, high-performance hollow shafts, such as... Figures 1-17 As shown, this device is the core hardware foundation for implementing the processing method of this invention. Its structural design fully considers the comprehensive requirements for precision, strength, thermal stability, and ease of operation during the forming of large hollow shafts. The device as a whole includes a press worktable 1, and an outline forming component and a punching and extrusion component mounted on it.

[0023] The forming assembly includes a shaping mold 4, a top block 2, a stop block 3, and a flange mold 5, all fixedly placed on the press worktable 1. The inner cavity of the shaping mold 4 is used to hold a steel ingot 6, and its inner cavity dimensions match the outer diameter of the main shaft of the target hollow shaft. The top block 2 is located at the bottom of the inner cavity of the shaping mold 4, and the stop block 3 is located inside the top block 2. The flange mold 5 is located at the top of the shaping mold 4.

[0024] Specifically, the top block 2 is assembled with the inner cavity wall of the forming mold 4 through a stepped structure. This stepped structure serves multiple purposes: firstly, it precisely limits the axial position of the top block 2 within the mold cavity, preventing it from sinking or shifting under pressure; secondly, the stepped structure facilitates the quick installation and removal of the top block 2, improving the efficiency of mold replacement and adjustment. The top block 2 is embedded in the bottom step of the forming mold 4, and is fixed and limited by the stepped structure. Its top surface forms the bottom plane of the mold cavity, directly affecting the forming quality of the hollow shaft bottom.

[0025] The bottom end of the stop block 3 is in direct contact with the press worktable 1, and is positioned and limited by the press worktable 1. The stop block 3 and the top block 2 together constitute the bottom support structure of the mold cavity. In the initial stage of punching, the stop block 3 supports the top block 2 and transmits pressure; when punching reaches the later stage and a through hole needs to be formed, the entire mold is lifted by the shim ring 12, the stop block 3 detaches from the press worktable 1 and falls naturally, thus providing space for the punching residue 13 to fall and for the formation of the through hole. This detachable bottom support structure design is one of the important innovations of this invention in achieving efficient through hole forming.

[0026] The flange mold 5 and the top of the shaping mold 4 are assembled via a stepped structure. The flange mold 5 engages with the top step of the shaping mold 4 to form the flange portion of the hollow shaft. The inner cavity shape of the flange mold 5 is completely consistent with the outer contour of the target hollow shaft flange. A local upsetting process is used to fill the cavity with steel ingot material, thereby obtaining a high-precision flange shape. The top block 2, the stop block 3, the shaping mold 4, and the flange mold 5 together form a complete hollow shaft mold cavity.

[0027] To ensure the dimensional stability and assembly accuracy of the mold during hot processing and to prevent thermal deformation or cracking due to excessive temperature differences, the top block 2, stop block 3, shaping mold 4, and flange mold 5 are all preheated in a heating furnace before assembly, heated to approximately 200°C and held at that temperature. Preheating reduces the temperature gradient between the mold and the steel ingot being processed, minimizing the impact of thermal shock on the mold's lifespan. It also helps maintain a stable temperature field for the steel ingot during forming, improving the uniformity of material flow.

[0028] The punching and extrusion assembly includes a round anvil 7, an upper flat anvil 8, a lower flat anvil 9, a large punch 10, a small punch 11, and a shim ring 12. These tools perform different functions during the processing, working together to complete all processes from overall upsetting and local forming to punching through the hole.

[0029] The upper anvil 8 is used to perform a step-by-step pressing operation on the flange portion of the hollow shaft. Step-by-step pressing is a local forming process. By precisely controlling the pressing position and amount of the upper anvil 8 each time, the material in the flange portion can be gradually and uniformly flowed, avoiding defects such as folding and cracking caused by a large deformation at once. The upper anvil 8 is used in conjunction with the lower anvil 9 to perform a rounding forming operation on the flange portion of the hollow shaft. During the rounding process, by controlling the rotation angle of the steel ingot, the upper and lower anvils continuously compress and round the outer edge of the flange, effectively correcting the roundness error of the flange and ensuring that its external dimensions meet the design requirements.

[0030] The large punch 10 and the small punch 11 are used to punch holes in the main body of the hollow shaft. The large punch 10 is used for the first punching, forming the first stepped structure; the small punch 11 is used for the second punching and the final through hole forming. The design of punching twice instead of forming a hole in one step is mainly based on the following considerations: First, the step-by-step punching can significantly reduce the axial pressure and thermal load on the punch during each punching, preventing the punch from bending and deforming due to excessive load or temperature; second, the two-step punching is conducive to guiding the inner hole material to flow orderly in the direction of the shaft, promoting the shaping of the shaft and forming a continuous distribution of metal flow lines along the direction of the shaft, which is crucial for improving the mechanical properties and service life of the hollow shaft.

[0031] In a preferred embodiment of the present invention, both the large punch 10 and the small punch 11 are internally equipped with spiral cooling channels and can be fitted with an intelligent temperature monitoring system. Compared to straight-through channels, spiral cooling channels have a longer heat exchange path and a larger heat exchange area, resulting in higher cooling efficiency. The intelligent temperature monitoring system can collect real-time temperature data of the working part of the punch. When the temperature exceeds a set threshold, the system can automatically adjust the flow rate or velocity of the cooling medium or issue a warning signal. The spiral cooling channels and the intelligent temperature monitoring system work together to monitor and control the temperature of the punch during operation in real time, effectively preventing the punch from bending and deforming due to excessive temperature during continuous punching operations, ensuring punching accuracy and tool life.

[0032] The shim ring 12 is used to raise the arrangement height of the forming mold 4 in the later stage of punching. The shim ring 12 is placed between the press worktable 1 and the forming mold 4. By increasing the mold's height above the ground, the stop block 3, which was originally in contact with and limited by the press worktable 1, loses its support and falls naturally, providing operating space for through-hole forming. The thickness of the shim ring 12 can be designed according to actual needs to meet the processing requirements of hollow shafts of different specifications.

[0033] In summary, the external forming assembly provides precise external contour constraints for the steel ingot 6 through the shaping mold 4 and the flange mold 5, ensuring the dimensional accuracy of the shaft and flange. The punching and extrusion assembly uses the round anvil 7, upper flat anvil 8, and lower flat anvil 9 to upset, partially form, and round and calibrate the steel ingot 6, and the large punch 10 and small punch 11 to complete the stepped forming of the inner hole. The coordinated use of the top block 2, the stop block 3, and the shim ring 12 enables the switching from closed-die forging to through-hole punching. These components work collaboratively under the drive of the hydraulic press to achieve efficient, precise, and high-performance forming of large hollow shafts.

[0034] The foregoing has described in detail an embodiment of a punching and extrusion forming apparatus for large, high-performance hollow shafts. Based on the punching and extrusion forming apparatus for large, high-performance hollow shafts described above, this invention also provides a punching and extrusion forming method corresponding to the apparatus, comprising the following steps: S1 and steel ingot 6 undergo preheating and preforming treatment.

[0035] This step is the pretreatment stage for hollow shaft forming, designed to eliminate internal defects in the steel ingot, optimize the billet shape, refine the grain structure, and provide a billet with uniform structure and precise dimensions for subsequent forming. Specifically, it includes the following sub-steps: S101. A hot-delivered steel ingot 6 with a surface temperature of approximately 550℃ is selected as the processing object. Utilizing residual heat from smelting significantly reduces heating energy consumption. First, the heating furnace is heated to 850℃, and then the steel ingot 6 is placed inside the furnace and held at this temperature for 3 hours for a first holding period. The purpose of this stage is to homogenize the temperature of the ingot's core and prevent cracking due to excessive thermal stress caused by rapid heating. After the holding period, the heating furnace is continuously heated at a rate of 90℃ / hour until the furnace temperature reaches 1230℃, followed by a second holding period of 8 hours. This heating rate has been optimized to ensure sufficient austenitization of the ingot while avoiding excessive grain coarsening. The final result is a steel ingot with an average temperature of approximately 1230℃, which is the ideal forging temperature for subsequent hot forging.

[0036] S102. For the steel ingot 6 heated in step S101, perform sprue removal and riser forming operations. During the casting process, the sprue area of ​​the steel ingot often contains numerous non-metallic inclusions and porosity defects, which need to be removed; the riser area can be used to design a clamping structure for convenient subsequent handling. In this step, the sprue area of ​​the steel ingot 6 is upset and separated using a staggered extrusion method with an upper flat anvil 8 and a lower flat anvil 9. Compared to direct cutting, staggered extrusion allows for better control of the quality and shape of the sheared surface. Subsequently, the riser area of ​​the steel ingot 6 is plastically deformed using a drawing process to form a clamping structure, for example, a clamping handle with a diameter of 900 mm. This clamping structure has sufficient strength and rigidity for subsequent gripping and handling operations of the steel ingot 6, facilitating convenient handling and processing of the steel ingot.

[0037] S103. A large hydraulic press is used to perform multiple (e.g., two) upsetting and drawing operations on the steel ingot 6. Upsetting and drawing are fundamental deformation methods in forging. Through periodic upsetting and drawing, the following effects can be achieved: firstly, effectively closing the porosity and pore defects inside the steel ingot 6, significantly improving the material density; secondly, breaking up coarse grains in the as-cast structure, refining the grain size; and thirdly, distributing non-metallic inclusions along the deformation direction, improving the material's anisotropy. Subsequently, based on the actual size requirements of the target hollow shaft, the steel ingot 6 is precisely machined into a cylindrical billet that is thicker at the top and thinner at the bottom, meaning the outer diameter of the top of the steel ingot 6 is larger than its outer diameter at the bottom. This shape design, thicker at the top and thinner at the bottom, matches the material distribution requirements of the subsequent flange and shaft body. The larger volume at the top provides sufficient metal reserves for flange forming, while the smaller volume at the bottom facilitates the precise forming of the shaft body. During the processing, the diameter of the cylindrical blank is strictly controlled to be slightly smaller than the inner diameter of the forming mold 4 (usually with a 2-5mm gap) to ensure that the blank is smoothly placed into the mold cavity and fits tightly against the inner wall of the mold, preventing the blank from shifting or tilting after entering the mold, and providing a stable and reliable blank base for subsequent processing and forming.

[0038] S104. Repeat the staggered extrusion method in S102, using the upper flat anvil 8 and lower flat anvil 9 to perform upsetting on the clamp structure of the steel ingot 6. The purpose of this step is to remove the clamp handles retained in S102 for transport, making the two ends of the steel ingot flat and avoiding interference from the clamp handles with subsequent punching and flange forming. During the operation, by precisely controlling the pressing amount and staggered spacing of the upper flat anvil 8 and lower flat anvil 9, the clamp handles can be cleanly removed without damaging the main body of the steel ingot.

[0039] S2. Assemble the shape-forming components.

[0040] like Figure 1 As shown, the pretreated steel ingot 6 is placed in the inner cavity of the shaping mold 4. Before placing the steel ingot, the top block 2, the stop block 3, the shaping mold 4, and the flange mold 5 are placed in a heating furnace and heated to approximately 200°C and held at that temperature to complete the mold preheating treatment. The purpose of the preheating treatment is to reduce the temperature difference between the mold and the hot steel ingot, reduce the influence of heat conduction on the temperature field of the steel ingot, and prevent the mold from developing thermal fatigue cracks due to sudden heating. After preheating, the shaping mold 4 is placed on the press worktable 1, and the top block 2 is embedded into the bottom stepped structure of the shaping mold 4 for limiting and fixing. At the same time, the stop block 3 is positioned and limited by the press worktable 1, forming the bottom support structure of the mold cavity. Then, the flange mold 5 is installed on the top of the shaping mold 4, and the stepped structure on the top of the shaping mold 4 is used for precise positioning and limiting to form a complete hollow shaft mold cavity. After assembly, the fitting clearance between each component should be checked to ensure the dimensional accuracy and sealing of the mold cavity.

[0041] S3. Use the round anvil 7 to perform upsetting on the steel ingot, and the flange part of the hollow shaft is initially formed.

[0042] This step, through overall upsetting, induces initial plastic flow in the material, laying the foundation for flange forming. Specifically, it includes: S301. The steel ingot 6, after being processed in step S104, is placed back into a heating furnace with the temperature set at 1230℃ and kept at this temperature for 5 hours to allow the steel ingot 6 to fully reheat to 1230℃ and reach the appropriate hot forging temperature. Since the steel ingot loses some heat during the transfer and removal of the clamps, it needs to be reheated again to ensure that it has good plasticity.

[0043] S302. After the steel ingot 6 has been heated, it is precisely transferred into the inner cavity of the shaping mold 4 using hoisting equipment. A large hydraulic press (e.g., a 15000t hydraulic press) drives the anvil 7 to perform a comprehensive compression operation on the steel ingot 6 within the shaping mold 4. The anvil 7 has a large contact area, allowing for uniform compression of the steel ingot. Under the continuous pressure applied by the anvil 7, the steel ingot 6 undergoes axial compression and radial expansion plastic deformation. Due to the constraint of the inner wall of the shaping mold 4, the radial expansion of the steel ingot 6 is restricted, thus forcing the material to flow upwards (towards the flange end), completing the preliminary forming process of the flange portion of the hollow shaft.

[0044] S4 and the upper anvil 8 perform a step-by-step pressing operation on the steel ingots, and the flange part of the hollow shaft is fully formed.

[0045] This step, involving localized, step-by-step pressing down to precisely control the material flow and shape filling of the flange, is one of the key steps in achieving precise flange forming using this method. Specifically, it includes: S401. Place the upper flat anvil 8 in the center area of ​​the flange on top of the steel ingot 6 and press it down. Then, using the upper flat anvil 8 as a base point, move the upper flat anvil 8 to the outer area of ​​the flange of the steel ingot 6 one by one from the inside out and press it down sequentially. This pressing sequence from the inside out helps to push the material from the center to the edge gradually, avoiding premature sealing of the material at the edge and resulting in insufficient filling of the center area. During the entire pressing process, in order to meet the requirements of subsequent processing or technology, the total pressing amount of the flange needs to be reasonably planned, and a certain amount of pressing allowance (usually 3%-5% of the final size) needs to be reserved for subsequent dimensional accuracy adjustments.

[0046] S402. Rotate the steel ingot 6 and the forming mold 4 synchronously around their axis by 90°, and then use the upper flat anvil 8 to press down on the rotated steel ingot 6 one anvil at a time. Through the above operation, the material of the steel ingot 6 is made to extend evenly in the circumferential and radial directions under pressure, so that the top of the steel ingot 6 fully fits the inner cavity surface of the flange mold 5, and the flange part of the hollow shaft is fully formed. If non-uniform material extension occurs during the forming process, that is, some areas have already fitted the inner surface of the flange mold, while other areas have not been fully extended and filled, the rotation angle parameters of the steel ingot and the mold and the number of presses of the upper flat anvil need to be adjusted accordingly. For example, the rotation angle can be adjusted to 45° or 60°, or the number of presses in local areas can be increased until the material completely fills the cavity.

[0047] S5, upper anvil 8, and lower anvil 9 perform rounding and forming operations on steel ingot 6 to correct the outer diameter of the hollow shaft flange.

[0048] After step S4, the flange is basically formed, but the outer edge of the flange may have a non-circular profile due to uneven material flow, and some areas may have excess flash. This step uses an upper flat anvil 8 and a lower flat anvil 9 to roll the initially formed hollow shaft flange into a round shape. During processing, the rotation angle of the steel ingot is controlled at 10°. After each rotation, the upper and lower flat anvils lightly press down on the outer edge of the flange. Through multiple rotations and presses, on the one hand, excess material extending beyond the flange mold cavity is upset and brought back within the dimensional range; on the other hand, through continuous accumulation of small deformations, the non-circular flange profile formed in the previous process is gradually corrected into a circular structure that meets the design requirements, achieving dimensional correction and shape optimization of the hollow shaft flange.

[0049] S6. Carbon powder is evenly applied to the inner wall of the shaping mold 4, the outer wall of the large punch 10, and the outer wall of the small punch 11.

[0050] Before the punching operation begins, lubrication is required. Using specialized spraying equipment or application tools, a layer of carbon powder coating is evenly applied to the inner wall of the forming die 4 and the working surfaces of the large punch 10 and small punch 11. Carbon powder is a high-temperature solid lubricant with good thermal stability and lubrication performance. By controlling the coating thickness and uniformity of the carbon powder, a continuous and consistent lubricating layer is formed on the die and punch surfaces. This carbon powder coating serves the following functions in subsequent processing: firstly, it acts as an isolation layer, preventing the steel ingot 6 from sticking to the die or punch under high temperature and pressure; secondly, it lubricates, effectively reducing the frictional resistance between the billet and the die, and reducing the forming load; thirdly, it protects the die and punch surfaces, reducing wear and extending their service life. This step is crucial for ensuring the surface quality of the hollow shaft and the lifespan of the die.

[0051] S7. The large punch 10 and the small punch 11 are used to punch the steel ingot 6 in sequence.

[0052] This step is the core of hollow shaft inner hole forming, employing a two- or multiple-punching method to guide the inner hole material to flow towards the shaft body, forming a continuous streamline structure. Specifically, it includes: S701. The rounded steel ingot 6 is placed back into the shaping mold 4. First, a large punch 10 is used as the initial punching tool. The large punch 10, driven by a press, applies axial pressure to the steel ingot 6, causing plastic deformation and completing the first stepped structure formation. Then, a small punch 11 is used for the second punching operation, completing the second stepped structure formation. Some dimensions of the small punch 11 are consistent with the large punch 10 to ensure the connection accuracy between the two punching processes, achieving progressively precise machining of the internal hole diameter of the steel ingot. This stepped punching design effectively reduces the shear and extrusion forces on the material during a single punching operation, preventing tearing or folding defects during the punching process.

[0053] After the secondary punching of steel ingot 6 (S702) is completed, the shaping mold 4 is lifted as a whole using the shim ring 12. This causes the stop block 3, which was originally limited by the press worktable 1, to disengage from the shaping mold 4 and fall onto the press worktable 1, providing operating space for through-hole forming. The small punch 11 is then used again to perform the final punching operation on the steel ingot 6, forming the main through-hole structure of the hollow shaft. The punching residue 13 generated during the punching process naturally falls above the stop block 3 and can be collected and cleaned.

[0054] During this process, due to the constraint of the mold cavity, the material inside the hollow shaft flows towards the shaft body under the punching force. The length of the hollow shaft gradually extends due to the directional flow of the material, while the radial dimension of the shaft body remains stable due to the constraint of the mold cavity, thus accurately achieving the dimensional design requirements of the hollow shaft. This method of using material flow during punching to achieve shaft heightening is a key innovation that distinguishes this method from the traditional process of punching first and then lengthening the mandrel, greatly simplifying the process flow.

[0055] S8, the upper flat anvil 8 upsets the top of the steel ingot 6, so that the steel ingot 6 is in close contact with the flange mold 5, and the hollow shaft punching and extrusion forming process is completed.

[0056] After punching, the flange may have slight incomplete fillet radius or insufficient profile. This step, through final local upsetting, eliminates these fillet radius defects, ensuring the flange completely fills the cavity. Specifically, this includes: S801. Disassemble the flange mold 5 and hollow shaft from the shaping mold 4. Use the lifting ring 12 to lift the flange mold 5 and hollow shaft as a whole, so that the hollow shaft is in a suspended state. Apply pressure to the central area of ​​the flange of the steel ingot 6 using the upper flat anvil 8, and gradually move the upper flat anvil 8 towards the edge of the flange of the steel ingot 6 from the inside out, and perform the pressing operation in sequence. In order to meet the requirements of subsequent processing accuracy and compensate for springback deformation, a certain amount of pressing allowance needs to be reserved.

[0057] S802. After the flange portion of the steel ingot 6 is initially formed, the steel ingot 6 and the flange mold 5 are rotated 90° around their axis synchronously, and the upper flat anvil 8 is used again to process it by pressing down one anvil at a time. This operation promotes the full flow of material in the flange portion, ensuring that the steel ingot 6 completely fills the inner cavity of the flange mold 5, especially the rounded corner area at the flange root, so as to eliminate the rounded corner defects of the flange portion of the steel ingot 6, thereby obtaining a hollow shaft finished product with accurate flange dimensions and a full shape.

[0058] To further verify the feasibility and reliability of the above process, this embodiment also provides a numerical simulation verification method for each step of the hollow shaft machining process. Numerical simulation can predict material flow, stress-strain distribution, temperature field changes, and mold stress during the forming process without actual production, providing a scientific basis for optimizing process parameters.

[0059] S901. Numerical simulations were performed on each step of the hollow shaft machining process to establish a simulation model. In the finite element simulation software, the molds (including the shaping mold, flange mold, punch, and anvil) were set as rigid body models because their stiffness is much greater than that of the steel ingot, and they can be considered as not deforming during the forming process. The steel ingot was set as a deformable body, and tetrahedral elements were used for mesh discretization, with the number of tetrahedrons controlled between 150,000 and 200,000. This mesh size ensures both computational accuracy and avoids excessive computation time due to overly dense meshes. In terms of mesh generation strategy, fine meshes with smaller mesh sizes were used for areas expected to undergo severe deformation (such as the flange root and punching area); coarse meshes with larger mesh sizes were used for non-critical and non-deformable areas to improve computational efficiency while ensuring computational accuracy.

[0060] S902. Assign material property parameters to the steel ingot. These parameters include thermophysical parameters such as density, elastic modulus, Poisson's ratio, coefficient of thermal expansion, thermal conductivity, and specific heat capacity, as well as rheological stress-strain curves characterizing plastic deformation behavior. Rheological stress-strain curves are usually obtained through high-temperature compression tests, reflecting the deformation resistance characteristics of the material at different temperatures and strain rates.

[0061] Numerical simulation can yield the equivalent strain distribution of the material, temperature field changes, mold load curves, and the final shape profile of the component throughout the forming process. Simulation results (such as...) Figure 4 , 6 Figures 9, 11, 13, 15, and 17 show that during the entire forming process, the main deformation is concentrated on the inner surface of the hollow shaft flange and the through hole. The material at the bottom of the flange can effectively fill the mold cavity, without problems such as insufficient filling or non-ideal circular contours. The equivalent strain distribution diagram shows that the strain distribution in the transition area between the flange and the shaft body is relatively uniform, indicating good material flow coordination. In the final flange forming simulation results, the bottom diameter of the hollow shaft flange completely fills the mold cavity, and the dimensions meet the design requirements. These simulation results theoretically verify the effectiveness of this process in improving the uniformity of metal rheology and enhancing the flange forming accuracy, providing reliable technical guidance for actual production.

[0062] In summary, the punching and extrusion forming apparatus and processing method for large, high-performance hollow shafts provided by this invention effectively solves problems such as insufficient flange filling, poor forming accuracy, and complex process flow in traditional processes through the coordinated operation of the shape forming component and the punching and extrusion component, combined with optimized processing technology. This method eliminates complex processes such as traditional mandrel drawing, achieving efficient and high-quality forming of hollow shafts, and has significant economic benefits and application prospects.

[0063] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A punching and extrusion forming apparatus for large high-performance hollow shafts, comprising a press worktable (1), characterized in that, The press workbench (1) is provided with an outline forming component, which includes a shaping mold (4) fixedly placed on the press workbench (1). The inner cavity of the shaping mold (4) is used to place steel ingots (6). A top block (2) is provided at the bottom of the inner cavity of the shaping mold (4). A stop block (3) is provided inside the top block (2). A flange mold (5) is provided at the top of the shaping mold (4). In addition to the forming component, a punching and extrusion component is also provided. The punching and extrusion component includes a round anvil (7), an upper flat anvil (8), a lower flat anvil (9), a large punch (10), and a small punch (11). The upper flat anvil (8) is used to press down the flange part of the hollow shaft one by one. The upper flat anvil (8) and the lower flat anvil (9) are used to roll the flange part of the hollow shaft. The large punch (10) and the small punch (11) are used to punch the main body of the hollow shaft.

2. The punching and extrusion forming apparatus for a large high-performance hollow shaft according to claim 1, characterized in that, The top block (2) is steppedly assembled with the inner wall of the shaping mold (4), the bottom end of the stop block (3) is limitedly assembled with the press worktable (1), and the flange mold (5) is steppedly assembled with the top of the shaping mold (4).

3. The punching and extrusion forming apparatus for a large high-performance hollow shaft according to claim 1, characterized in that, The large punch (10) and the small punch (11) are both equipped with cooling water channels inside. The cooling water channels have a spiral structure. The outer diameter of the top of the large punch (10) and the small punch (11) is the same.

4. The punching and extrusion forming apparatus for a large high-performance hollow shaft according to claim 1, characterized in that, The punching and extrusion assembly includes a shim ring (12) for raising the arrangement height of the shaping mold (4).

5. A method for punching and extruding large high-performance hollow shafts, characterized in that, Includes the following steps: S1. The steel ingot (6) is preheated and pre-formed. S2. Assemble the shape forming components and place the pre-treated steel ingot (6) into the inner cavity of the shaping mold (4); S3. Use a round anvil (7) to upset the steel ingot, and the flange of the hollow shaft is initially formed; S4, the upper anvil (8) presses the steel ingot down one anvil at a time, and the flange of the hollow shaft is fully formed; S5, upper flat anvil (8), lower flat anvil (9) perform rounding and forming operations on steel ingot (6) to correct the outer diameter of hollow shaft flange; S6. Carbon powder is evenly applied to the inner wall of the shaping mold (4), the outer wall of the large punch (10), and the outer wall of the small punch (11) to lubricate and prevent the steel ingot (6) from sticking to the mold. S7. The large punch (10) and small punch (11) are used in sequence to punch the steel ingot (6); S8. The upper flat anvil (8) upsets the top of the steel ingot (6), so that the steel ingot (6) is in close contact with the flange mold (5) to complete the hollow shaft punching and extrusion forming process.

6. The method for punching and extruding large high-performance hollow shafts according to claim 5, characterized in that, Specifically, S1 is: S101. The initial surface temperature of the steel ingot (6) is 550℃. The steel ingot (6) is heated to 850℃ and then kept warm for 3 hours. S102. After the first heat preservation is completed, the heating is continued at a heating rate of 90℃ / h until the steel ingot (6) is heated to 1230℃, and then a second heat preservation is carried out for 8 hours to keep the average temperature of the steel ingot (6) at 1230℃. S103. Using an upper flat anvil (8) and a lower flat anvil (9) to perform staggered extrusion on the steel ingot (6), the sprue of the steel ingot (6) is upsetting and separated, and the riser of the steel ingot (6) is plastically deformed using a drawing process to form a clamp structure. The clamp structure is used for subsequent gripping and transfer operations of the steel ingot (6). S104. Use a hydraulic press to upset and draw the steel ingot (6) to eliminate the looseness and porosity defects inside the steel ingot (6) and process the steel ingot (6) into a cylindrical billet, so that the outer diameter of the top of the steel ingot (6) is greater than its outer diameter at the bottom. S105. Repeat the operation method in S103 to perform upsetting operation on the clamp structure of the steel ingot (6), and completely remove the clamp structure of the steel ingot (6) by controlling the pressing amount and misalignment distance of the upper flat anvil (8) and the lower flat anvil (9).

7. A method for punching and extruding large high-performance hollow shafts according to claim 5, characterized in that, Specifically, S3 is: S301. Place the steel ingot (6) into a heating furnace at a temperature of 1230°C and maintain the temperature environment for 5 hours to allow the steel ingot (6) to fully recover to 1230°C and reach the hot forging temperature. S302. After the steel ingot (6) is heated, the steel ingot (6) is hoisted into the inner cavity of the shaping mold (4). The circular anvil (7) is driven by a hydraulic press to compress the steel ingot (6) in the shaping mold (4). Under the continuous pressure applied by the circular anvil (7), the steel ingot (6) undergoes plastic deformation, and the preliminary forming process of the flange part of the hollow shaft is completed.

8. The method for punching and extruding large high-performance hollow shafts according to claim 5, characterized in that, Specifically, S4 is: S401. Place the upper flat anvil (8) in the center area of ​​the flange on the top of the steel ingot (6) and press it down. Then, using the upper flat anvil (8) as the base point, move the upper flat anvil (8) to the outer area of ​​the flange of the steel ingot (6) one by one from the inside to the outside and press it down in sequence. S402. Rotate the steel ingot (6) and the shaping mold (4) around their axis by 90° simultaneously. Use the upper flat anvil (8) to press down the rotated steel ingot (6) one anvil at a time, so that the steel ingot (6) extends evenly in the circumferential and radial directions under pressure, so that the top of the steel ingot (6) fully fits the inner surface of the flange mold (5), and the flange part of the hollow shaft is fully formed.

9. A method for punching and extruding large high-performance hollow shafts according to claim 5, characterized in that, Specifically, S7 is: S701. Place the steel ingot back into the forming mold (4). First, use the large punch (10) as the first punching tool. Apply axial pressure to the steel ingot (6) with the large punch (10) to cause the steel ingot (6) to undergo plastic deformation and complete the forming operation of the first step structure. Then, replace it with the small punch (11) to perform the second punching operation and complete the forming operation of the second step structure. S702. After the steel ingot (6) is punched twice, the shaping mold (4) is lifted as a whole using the shim ring (12), so that the stop block (3) is removed from the shaping mold (4) and falls onto the press workbench (1). The small punch (11) is used again to perform the final punching operation on the steel ingot (6), forming the main through hole structure of the hollow shaft. The punching residue (13) falls above the stop block (3) and is collected.

10. A method for punching and extruding large high-performance hollow shafts according to claim 5, characterized in that, Specifically, S8 is: S801. Use the shim ring (12) to lift the shaping mold (4) and the steel ingot (6) as a whole, so that the steel ingot (6) is suspended in the air. Use the upper flat anvil (8) to apply pressure to the center area of ​​the flange of the steel ingot (6). In the order from the inside to the outside, gradually move the upper flat anvil (8) to the edge of the flange of the steel ingot (6) and press it down in sequence. S802. After the flange part of the steel ingot (6) is formed, the steel ingot (6) and the flange mold (5) are rotated 90° around their axis in sync. The upper flat anvil (8) is used again to press down the material one anvil at a time to make the material flow fully and ensure that the steel ingot (6) is completely filled into the inner cavity of the flange mold (5) to eliminate the round corner defects of the flange part of the steel ingot (6) and thus obtain the hollow shaft finished product.

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