A mandrel die and its application in the rotary forging process of thin-walled, slender hollow shafts

Abstract

This invention relates to a mandrel mold and its application in the rotary forging process of thin-walled, slender hollow shafts. The mold includes a mandrel and a guide sleeve. A cam is fixed on the mandrel. Both the mandrel and the cam are located inside the guide sleeve. Both ends of the mandrel are connected to a rotating support frame. The cam has several cam tops and several cam grooves, with each cam top and cam groove arranged adjacent to each other. The guide sleeve has several through holes, each containing a support rod. One end of each support rod has a first sphere, and the other end has a second sphere. The first sphere is located within the cam groove, and a rolled-up elastic metal gasket is disposed outside the second sphere. The mandrel mold of this invention is used to process thin-walled, slender hollow shafts with internal stepped structures, significantly improving the coaxiality, wall thickness difference, material utilization, and processing efficiency of the thin-walled, slender hollow shafts, while simultaneously increasing the mechanical properties of the workpiece.

Description

Technical Field

[0001] This invention relates to a mandrel mold and its application in the rotary forging process of thin-walled, slender hollow shafts, belonging to the field of rotary forging technology. Background Technology

[0002] With the increasing demands for lightweight structures and carbon emission reduction, hollow shafts have gained widespread attention in rotating mechanisms. Compared to solid shafts, hollow shafts offer advantages in terms of lighter weight and higher strength under the same load, making them promising for applications in various fields such as automobiles, ships, and aerospace. In particular, thin-walled, slender hollow shafts used in aero engines and gas turbines are typically made of high-temperature alloys and feature internal stepped bore structures. During high-speed rotation in service, the requirements for the coaxiality and wall thickness difference of the internal stepped bore are even more stringent.

[0003] Currently, thin-walled, slender hollow shafts are mainly produced using a process of drilling, boring, and honing cylindrical blanks, which is a mechanical cutting method. This process suffers from drawbacks such as low efficiency, material waste, and disruption of structural continuity. In particular, thin-walled, slender hollow shafts are prone to deformation during machining, especially when using deep-hole drilling and honing to machine internal stepped holes. Problems arise such as drill rod deformation during deep-hole machining and difficulty in controlling positioning accuracy during repeated clamping, making it difficult to meet the corresponding requirements for coaxiality and wall thickness variation. The machining quality is largely constrained by machine tool equipment, cutting tools, and process parameters. Summary of the Invention

[0004] The purpose of this invention is to provide a mandrel mold and its application in the rotary forging process of thin-walled slender hollow shafts. By applying this mandrel mold to the rotary forging process of thin-walled slender hollow shafts, the rotary-forged thin-walled slender hollow shafts with internal stepped structures have higher coaxiality, wall thickness difference and good mechanical properties.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows: a mandrel mold, comprising a mandrel and a guide sleeve, wherein a cam is fixed on the mandrel, and both the mandrel and the cam are located inside the guide sleeve. Both ends of the mandrel are connected to a rotating support frame. The cam is provided with a plurality of cam tops and a plurality of cam grooves, each of the cam tops and cam grooves being arranged adjacent to each other. The guide sleeve is provided with a plurality of through holes, and a support rod is provided in each through hole. A first ball is provided at one end of each support rod, and a second ball is provided at the other end. The first ball is located in the cam groove, and a rolled-up elastic metal gasket is provided on the outside of the second ball.

[0006] In the above scheme, the elastic metal gasket is rectangular in shape after being unfolded, and a bevel is reserved where the two sides of the rectangle meet after the elastic metal gasket 505 is rolled up.

[0007] In the above scheme, both the first sphere and the second sphere are magnetic spheres.

[0008] In the above scheme, the number of cam tops and cam grooves is 6.

[0009] This invention also provides a process for rotary forging of thin-walled, slender hollow shafts using a mandrel mold, comprising the following steps: 1) Preparing a tubular blank: The inner hole of the prepared tubular blank 1 is d, the outer diameter is D+Δ1, and the length is L-Δ2, where Δ1 is the reduction in outer diameter due to rotary forging, and Δ2 is the axial elongation due to rotary forging; 2) Inserting the combined mandrel mold: The assembled cam mandrel, support frame, guide sleeve, support rod, and metal washer are inserted together into the center hole of the tubular blank; 3) Adjusting the mandrel mold: By rotating the cam mandrel, the first ball on the support rod rotates along the inner wall of the cam groove. At this time, the second ball gradually unfolds against the elastic metal washer. When the first ball rotates to the top of the cam, the elastic metal washer just unfolds into a cylindrical shape. 4) Rotary forging: The tubular billet 1 and the combined mandrel mold are clamped in the rotary forging equipment. The rotary forging chuck clamps both ends of the mandrel mold. The rotary forging hammer forges radially from the middle of the tubular billet to both sides, thinning the wall thickness until the workpiece is formed. At this time, the outer diameter of the workpiece is D. 5) Extracting the combined mandrel mold: The rotary forging chuck clamps the workpiece, rotates and vibrates the cam mandrel, so that the first ball slides from the top of the cam into the cam groove. At this time, the elastic metal pad relies on its own elastic contraction to separate from the inner surface of the workpiece, and the mandrel mold is extracted. 6) Machining the outer diameter: The workpiece 2 is clamped on the lathe for machining the outer diameter to the design required size.

[0010] The present invention also protects the application of the above-mentioned mandrel mold in the rotary forging process of thin-walled slender hollow shafts.

[0011] The beneficial effects of this invention are as follows: 1) This invention uses tubular blanks as raw materials, and the combined mandrel mold is tightly attached to the inner surface of the tubular blank as a support. During the rotary forging process, due to the protection of the inner surface by metal gaskets, the inner step surface of the formed workpiece does not undergo any deformation, thus improving the overall coaxiality of the workpiece and the machining accuracy of the wall thickness difference. 2) It improves material utilization and processing efficiency. Since the raw material is tubular, the drilling-boring-honing process is eliminated, improving the material utilization and processing efficiency of the parts. 3) It improves the mechanical properties of the parts. After rotary forging, the part structure is dense and the grains are refined, and compressive stress exists on the surface of the part, improving the service performance of the part. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the mandrel structure.

[0013] Figure 2 This is a schematic diagram of the guide sleeve.

[0014] Figure 3 This is a schematic diagram of the support rod.

[0015] Figure 4 This is a schematic diagram of the support frame.

[0016] Figure 5 This is a schematic diagram of the overall structure of the mandrel mold.

[0017] Figure 6 This is a schematic diagram of the extended state of the elastic metal gasket.

[0018] Figure 7 for Figure 6 A magnified view of a section at point C.

[0019] Figure 8 for Figure 6 A magnified view of a section at point D.

[0020] Figure 9 This is a schematic diagram of the tubular blank structure.

[0021] Figure 10 for Figure 9 Side view at point A in the middle.

[0022] Figure 11 This is a schematic diagram of the assembled mandrel mold.

[0023] Figure 12 A schematic diagram of inserting the combined mandrel mold.

[0024] Figure 13 This is a schematic diagram of the combined mandrel mold principle.

[0025] Figure 14 A schematic diagram showing the process of enlarging the outer diameter of the combined mandrel mold.

[0026] Figure 15 This is a schematic diagram of the rotary forging device.

[0027] Figure 16 for Figure 15 A sectional view.

[0028] Figure 17 This is a schematic diagram of the overall structure after rotary forging.

[0029] Wherein: 1-tubular billet, 2-workpiece, 3-forging hammer, 4-forging chuck, 5-combined mandrel mold, 501-mandrel, 502-support frame, 503-guide sleeve, 503-1-through hole, 504-support rod, 504-1-first sphere, 504-2-second sphere, 505-elastic metal gasket, 506-cam, 506-1-cam top, 506-2-cam groove, 6-slope angle. Detailed Implementation

[0030] To make the technical problems, technical solutions, and beneficial effects of this invention clearer and more understandable, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0031] like Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown, the present invention provides a mandrel mold, including a mandrel 501, a guide sleeve 503, and a support frame 502. A cam 506 is fixed on the mandrel 501. Both ends of the mandrel 501 are connected to the support frame 502 via a rotating joint. Both the mandrel 501 and the cam 506 are located inside the guide sleeve 503. The guide sleeve 503 has several through holes 503-1. Each support rod 504 has a first ball 504-1 at one end and a second ball 504-2 at the other end. Figure 5 As shown, the cam 506 is provided with 6 cam tops 506-1 and 6 cam grooves 506-2. Each cam top 506-1 and cam groove 506-2 are arranged adjacent to each other. Each through hole 503-1 is provided with a support rod 504. One end of each support rod 504 is provided with a first sphere 504-1, and the other end is provided with a second sphere 504-2. Both the first sphere 504-1 and the second sphere 504-2 are magnetic spheres. The first sphere 504-1 is located inside the cam groove 506-2. A retractable elastic metal pad 505 is provided on the outside of the second sphere 504-2. When unfolded, the elastic metal pad 505 is rectangular in shape. Figure 6 , Figure 7 and Figure 8 As shown, the two sides of the rectangle where the elastic metal gasket 505 contacts after it is rolled up and unfolded have a bevel angle 6.

[0032] This embodiment describes a rotary forging process for a thin-walled, slender hollow shaft with an internal stepped structure, comprising the following steps.

[0033] 1) such as Figure 9 and Figure 10 As shown, prepare a tubular blank: the inner diameter of the prepared tubular blank 1 is d, the outer diameter is D+Δ1, and the length is L-Δ2, where Δ1 is the reduction value of the outer diameter due to rotary forging, and Δ2 is the axial elongation due to rotary forging.

[0034] 2) such as Figure 11 and Figure 12As shown, insert the combined mandrel mold: insert the equipped cam mandrel 501, support frame 502, guide sleeve 503, support rod 504 and metal shim 505 together into the center hole of the tubular blank 1.

[0035] 3) such as Figure 13 and Figure 14 As shown, adjusting the mandrel mold: By rotating the cam mandrel 501, the first ball 504-1 on the support rod 504 rotates along the inner wall of the cam groove 506-2. The first ball 504-1 is magnetic, ensuring that the support rod 504, the cam mandrel, and the metal washer attract each other during the rotation of the cam mandrel 501. At the same time, a spherical contact head is provided to reduce the friction between the second ball 504-2 and the metal washer, which is more conducive to the expansion and contraction of the metal washer. At this time, the second ball 504-2 pushes against the elastic metal washer 505 and gradually expands. When the first ball 504-1 rotates to the cam top 506-1, the elastic metal washer 505 just expands into a cylindrical shape and fits against the inner cylinder surface of the tubular blank 1. The second ball 504-2 provides support for the elastic metal washer 505, ensuring the rigidity of the metal washer during rotary forging.

[0036] 4) such as Figure 15 and Figure 16 As shown, rotary forging shaping: The tubular billet 1 and the combined mandrel mold 5 are clamped onto the rotary forging equipment. The rotary forging chuck 4 clamps both ends of the mandrel mold. The rotary forging hammer 3 forges radially from the middle of the tubular billet 1 to both sides. Due to the strong support of the support rod, the wall thickness of the middle part of the tubular billet 1 is gradually thinned by rotary forging until the workpiece 2 is formed (e.g., ...). Figure 17 As shown in the figure, the outer diameter of workpiece 2 is D at this time.

[0037] 5) Extracting the combined mandrel mold: The forging chuck 4 clamps the workpiece 2, rotates and vibrates the cam mandrel 501. Since the metal shim 505 has beveled edges on both sides when it unfolds, by rotating the cam mandrel 501, under the combined effect of external force vibration, support rod contraction, the magnetic effect of the second ball 504-2, and the elastic contraction of the metal shim itself, it is easier to achieve complete contraction of the metal shim, thereby separating it from the inner step surface of the workpiece 2, and thus smoothly extracting the mandrel mold 5 as a whole from the workpiece 2.

[0038] 6) Machining the outer diameter: Clamp workpiece 2 on a lathe and perform turning of the outer diameter until the design dimensions are met.

Claims

1. A method for forging thin-walled, slender hollow shafts using a mandrel mold, the mandrel mold comprising a mandrel (501) and a guide sleeve (503), a cam (506) fixed on the mandrel (501), both the mandrel (501) and the cam (506) being located inside the guide sleeve (503), both ends of the mandrel (501) being connected to a support frame (502) via a rotating joint, the cam (506) being provided with a plurality of cam tops (506-1) and a plurality of cam grooves (506-2), each cam top (506-1) and cam groove (506-2) being arranged adjacent to each other. The guide sleeve (503) is provided with several through holes (503-1), and a support rod (504) is provided in each through hole. One end of each support rod (504) is provided with a first sphere (504-1), and the other end is provided with a second sphere (504-2). Both the first sphere (504-1) and the second sphere (504-2) are magnetic spheres. The first sphere (504-1) is located within the cam groove (506-2), and a rolled-up elastic metal gasket (505) is provided on the outer side of the second sphere (504-2). The characteristic feature is that... Includes the following steps: 1) Prepare tubular billet: Prepare tubular billet (1) The inner hole is d, the outer diameter is D+Δ1, and the length is L-Δ2, where Δ1 is the value of the reduction of the outer diameter of the rotary forging, and Δ2 is the axial elongation of the rotary forging; 2) Insert the combined mandrel mold: Insert the equipped cam mandrel (501), support frame (502), guide sleeve (503), support rod (504) and metal gasket (505) together into the center hole of the tubular blank (1); 3) Adjusting the mandrel mold: By rotating the cam mandrel (501), the first ball (504-1) on the support rod (504) rotates along the inner wall of the cam groove (506-2). At this time, the second ball (504-2) pushes against the elastic metal pad (505) and gradually unfolds. When the first ball (504-1) rotates to the top of the cam (506-1), the elastic metal pad (505) just unfolds into a cylindrical shape and fits against the inner cylinder surface of the tubular blank (1). All the first balls (504-1) provide support for the elastic metal pad (505). 4) Rotary forging and shaping: The tubular billet (1) and the combined mandrel mold (5) are clamped into the rotary forging equipment. The rotary forging chuck (4) clamps the two ends of the mandrel mold. The rotary forging hammer (3) forges radially from the middle position of the tubular billet (1) to both sides, and the wall thickness becomes thinner until the workpiece (2) is formed. At this time, the outer diameter of the workpiece (2) is D. 5) Extract the combined mandrel mold: The forging chuck (4) clamps the workpiece (2), rotates and vibrates the cam mandrel (501), so that the first ball (504-1) slides from the cam top (506-1) into the cam groove (506-2). At this time, the elastic metal pad (505) separates from the inner surface of the workpiece (2) by its own elastic contraction, and the mandrel mold (5) is extracted. 6) Machining the outer diameter: Clamp the workpiece (2) on the lathe and machine the outer diameter to the required dimensions.

2. The method for forging thin-walled, slender hollow shafts using a mandrel die according to claim 1, characterized in that, The elastic metal pad (505) unfolds into a rectangular shape, and the two sides of the rectangle are reserved with a bevel angle when the elastic metal pad (505) is rolled up.

3. The method for forging thin-walled, slender hollow shafts using a mandrel die according to claim 1, characterized in that, The number of cam tops (506-1) and cam grooves (506-2) is 6.

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