Composite forging forming method and device for aluminum-steel bimetallic gear with nearly uniform wall thickness
Through the reverse design, the design of steel layer blanks and forming devices is optimized, and the problem of uneven wall thickness during the composite forging of aluminum steel bimetal gears is solved, and the formation of near-uniform wall thickness is achieved, which improves the reliability and lightweight effect of the structure.
Patent Information
- Application Number
- CN202510412279.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-02
- Publication Date
- 2025-06-13
AI Technical Summary
During the composite forging process, aluminum steel bimetal gears have uneven wall thickness due to non-uniform deformation, and there are local weak areas, which are prone to fatigue damage.
Through the reverse design, the non-uniform wall thickness of the steel layer blank is optimized, the roots of the prefabricated steel layer blank are set with inward arc, the tops of the teeth are set with straight wall structure, and the slope and step structure of the forming device are used to achieve near-uniform wall thickness forming of the aluminum alloy core and the steel layer through closed die forging.
The near-uniform wall thickness forming of aluminum steel bimetal gear is achieved, eliminating local weak areas of the tooth root, improving the lightweight effect and overall structural reliability, and meeting the lightweight and high-performance needs of aerospace.
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Figure CN120133419A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to a method in the technical field of material processing, specifically a method and device for composite forging and forming of an aluminum-steel bimetallic gear with a nearly uniform wall thickness. Background Art
[0002] The aerospace industry has an increasing demand for lightweight and high-performance components, which is beneficial for improving mobility and reducing launch and operation costs. However, due to the advantages of high-strength steel in terms of stiffness, wear resistance, etc., high-strength steel still cannot be completely replaced by lightweight materials at present. Steel gears, as traditional high-density components, are still widely used in various drive transmission mechanisms, steering mechanisms and other devices, and are the key breakthrough points for lightweight design and manufacturing.
[0003] An aluminum-steel bimetallic gear is a lightweight functional composite component in which a steel material forms a tooth-shaped surface layer and an aluminum-based material is the core. It has good weight reduction effect and high load-bearing capacity, and is the first choice to replace high-density steel gears. The composite forging and forming technology is the first choice for realizing the near-net forming of lightweight aluminum-steel bimetallic gears, and the developed soft-core composite forging technology in China has solved key breakthroughs such as the coordinated deformation of aluminum-steel bimetals and the controllability of the metallurgical bonding interface. However, during composite forging and forming, when the steel layer fills the tooth-shaped cavity, after the tooth root contacts the die first, it bears a stress state of "compressed axially / radially and tensioned circumferentially", and when passing through the fillet area, the curvature center transfers from the inner side to the outer side, resulting in serious thinning. The tooth top part bears a stress state of "compressed axially / circumferentially" and the thickness increases. The non-uniform wall thickness distribution leads to extremely uneven mechanical properties of the gear and there are local weak areas, which are prone to fatigue failure under extreme service conditions of cyclic alternating loads, and have become a bottleneck problem hindering the application of aluminum-steel bimetallic gears.
[0004] Therefore, it is necessary to propose a new process method to address the technical bottleneck of active control of non-uniform deformation of aluminum-steel bimetallic gears. Summary of the Invention
[0005] The purpose of the present application is to provide a composite forging and forming method for actively controlling the non-uniform deformation of aluminum-steel bimetallic gears.
[0006] The embodiments of the present application can be realized by the following technical solutions:
[0007] A composite forging and forming method for an aluminum-steel bimetallic gear with a nearly uniform wall thickness, comprising the following steps:
[0008] Step 1, design and reverse design: Design the structural characteristics of the steel layer of the aluminum-steel bimetallic gear with a nearly uniform wall thickness, and reverse design the shape of the non-uniform wall thickness prefabricated steel layer blank of the aluminum-steel bimetallic gear based on the steel layer structure;
[0009] Step 2, forming a prefabricated steel layer blank: Form a prefabricated steel layer blank with a non-uniform wall thickness;
[0010] Step 3, compound forging: Heat the prefabricated steel layer blank to the thermoplastic range, heat the thixoformed aluminum alloy core to the semi-solid range, and form the aluminum alloy into a gear core and the steel layer into a gear surface through closed-die forging.
[0011] Preferably, the tooth root of the prefabricated steel layer blank has an inward curvature.
[0012] Preferably, the tooth tip of the prefabricated steel layer blank has a straight wall structure.
[0013] Preferably, the height of the prefabricated steel layer blank is 2 - 3 mm higher than the height of the aluminum alloy core.
[0014] Preferably, the unilateral clearance between the inner diameter of the prefabricated steel layer blank and the outer diameter of the aluminum alloy core is 0.5 - 1 mm.
[0015] Further, the temperature corresponding to the thermoplastic range is 1000°C - 1200°C.
[0016] Further, the aluminum alloy core is converted into a semi-solid state with a liquid phase fraction of 0.1 - 0.4.
[0017] A forming device for implementing the compound forging step includes a first platform, a second platform, and a punch, a die, a counter-punch, and a ejector rod arranged from top to bottom between the first platform and the second platform;
[0018] The punch is installed on one side of the first platform facing the second platform. The ejector rod is connected to the second platform and its top end abuts against the bottom end of the counter-punch. The top end of the counter-punch can extend into the die and is movably connected to the die. The bottom end of the punch can extend into the die. A forging cavity for the forging blank is formed between the punch, the counter-punch, and the die.
[0019] Preferably, the lower surface of the punch and the upper surface of the die are provided with mutually cooperating inclined surface structures, and the upper surface of the counter-punch is also provided with an inclined surface structure.
[0020] Preferably, the lower surface of the punch and the upper surface of the counter-punch are provided with step structures, and the outer diameter of the step structure is slightly smaller than the inner diameter of the prefabricated steel layer blank.
[0021] The near-uniform wall thickness aluminum-steel bimetallic gear compound forging method and device provided by the embodiments of the present application at least have the following beneficial effects:
[0022] Based on the technical idea of active control of non-uniform deformation, this application utilizes the characteristics of local thickening at the tooth tips and local thinning near the tooth roots in the steel layer during the compound forging process of aluminum-steel bimetallic gears. It reversely optimizes and designs the initial non-uniform wall thickness of the steel layer blank (pre-thinning at the tooth tips and pre-thickening at the tooth root parts), solves the problem of uneven steel layer thickness, eliminates the local weak areas at the tooth roots, and improves the lightweight effect and overall structural reliability.
[0023] In this application, an inward arc is set at the tooth roots of the prefabricated steel layer blank, so that the tooth roots tend to move outward, avoiding excessive buckling simply according to the original circular ring shape. This outward movement trend helps to achieve near-uniform wall thickness of the gear during the forging process, effectively alleviating the wall thickness difference caused by the significant thinning due to the tension at the tooth roots, and further ensuring the near-uniformity of the gear wall thickness.
[0024] The lower surface of the punch, the upper surface of the die, and the upper surface of the counter-punch in the forming device of this application are all designed with inclined surface structures, making the die cavity in the shape of a dovetail at the outer edge of the gear, promoting the flow of the steel layer towards the end of the tooth-shaped cavity and improving the forming quality.
[0025] In this application, a stepped structure is preset on the lower surface of the punch and the upper surface of the counter-punch of the forming device. The outer diameter of the stepped structure is slightly smaller than the inner diameter of the non-uniform steel preform to ensure that the radial position of the non-uniform thickness steel preform does not shift. Description of the Drawings
[0026] Figure 1 It is a structural diagram of an aluminum-steel bimetallic gear prepared by a method for compound forging and forming of an aluminum-steel bimetallic gear with near-uniform wall thickness in this application;
[0027] Figure 2 It is a schematic diagram of the principle of the active control technology for non-uniform structures of aluminum-steel bimetallic components;
[0028] Figure 3 It is a partial schematic diagram of a prefabricated steel layer blank with non-uniform wall thickness in this application from two different angles;
[0029] Figure 4 It is an overall structural diagram of the compound forging and forming device in this application;
[0030] Figure 5 It is a sectional view of the compound forging and forming device in this application.
[0031] Reference Signs: 1. First platform, 2. Second platform, 3. Punch, 4. Die, 5. Counter-punch, 6. Ejector rod, 7. Inclined surface structure, 8. Stepped structure. Detailed Embodiments
[0032] The following further describes the present application based on preferred embodiments with reference to the accompanying drawings.
[0033] The terms used in this specification are for the purpose of describing the embodiments of the present application, but are not intended to limit the present application. Unless otherwise clearly specified and defined, if the terms "arranged", "connected", or "coupled" appear, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those skilled in the art, the specific meanings of the above terms in the present application can be specifically understood.
[0034] In addition, in the description of the embodiments of the present application, for the convenience of understanding, various components on the drawings are enlarged or reduced, but this approach is not intended to limit the protection scope of the present application.
[0035] Figure 2 The upper part of the drawing file in is a partial schematic diagram of an existing gear with non-uniform wall thickness. As Figure 2 shown, in the existing aluminum-steel bimetallic gear, the tooth tip part of the steel layer is locally thickened, and the part near the tooth root is locally thinned. The non-uniform wall thickness distribution will cause extremely uneven mechanical properties of the gear and there are local weak areas. During actual use, under the extreme service conditions of cyclic alternating loads, it is prone to fatigue damage, thus affecting the application of the aluminum-steel bimetallic gear. The reason for the non-uniform wall thickness is that during the compound forging process, when the steel layer fills the tooth profile cavity, the part near the tooth root will first contact the mold, thus bearing a stress state of "axially / radially compressed and circumferentially tensioned", and when the tooth root passes through the fillet area, the curvature center transfers from the inner side to the outer side, causing the tooth root to be severely thinned; the tooth tip part bears a stress state of "axially / circumferentially compressed" and the thickness increases, resulting in local thickening of the tooth tip part of the existing aluminum-steel bimetallic gear produced, and local thinning of the tooth root part.
[0036] As Figure 2 shown, based on the problem of non-uniform wall thickness existing in the existing aluminum-steel bimetallic gear, through the technical idea of active control of non-uniform deformation, using the characteristics of local thickening of the tooth tip part and local thinning near the tooth root of the steel layer during the compound forging process of the aluminum-steel bimetallic gear, the initial non-uniform wall thickness of the steel layer blank is reversely optimized (pre-thinning of the tooth tip part and pre-thickening of the tooth root part) to solve the problem of non-uniform steel layer thickness, thereby eliminating the local weak area at the tooth root, improving the lightweight effect and the overall structural reliability, and realizing the compound forging of the aluminum-steel bimetallic gear with nearly uniform wall thickness to meet the lightweight and high-performance requirements of aerospace.
[0037] Based on Figure 2 the technical schematic diagram in, the present application can produce and manufacture asFigure 1 The nearly uniform aluminum-steel bimetallic gear shown is composed of Figure 1 and Figure 2 As shown, the aluminum-steel bimetal gear includes an outer steel layer and an inner aluminum alloy core. The aluminum core at the tooth top of the nearly uniform aluminum-steel bimetal gear is much more uniform and substantial than the existing non-uniform aluminum-steel bimetal gear. Combined with the pre-thickening of the tooth root part of the steel layer blank, the wall thickness of the formed aluminum-steel bimetal component reaches a nearly uniform level, thereby solving the uneven thickness of the steel layer and eliminating the local weak area at the tooth root.
[0038] Specifically, the non-uniform deformation in the composite forging process mainly occurs during the tooth filling process. The pre-thickened tooth root will first contact the die and be subjected to the stress state of "axial / radial compression and circumferential tension". When the pre-thickened tooth root passes through the fillet area, the center of curvature shifts from the inside to the outside, resulting in drastic thinning. The pre-thinned tooth top part is subjected to the pressure state of "axial / circumferential compression" and is locally thickened, making the gear wall thickness tend to be uniform, that is, nearly uniform.
[0039] Furthermore, the composite forging forming method in the present application is specifically as follows:
[0040] Step 1, design and reverse design: design the steel layer structure characteristics of the aluminum-steel bimetal gear with nearly uniform wall thickness, and reversely design the shape of the prefabricated steel layer blank of the aluminum-steel bimetal gear with non-uniform wall thickness based on the steel layer structure;
[0041] Step 2, forming a prefabricated steel layer blank: forming a prefabricated steel layer blank with a non-uniform wall thickness;
[0042] Step three, composite forging: heating the prefabricated steel layer blank to a thermoplastic range, heating the thixotropic aluminum alloy core to a semi-solid range, and using closed die forging to make the aluminum alloy core form the gear core and the steel layer form the gear surface.
[0043] In some preferred embodiments of the present application, Figure 3 As shown in the figure, the tooth root of the prefabricated steel layer blank has an inward curvature. This is based on the understanding of the deformation behavior of the ring-shaped blank when subjected to force. Specifically, when the ring-shaped blank is subjected to pressure, it tends to bend outward and become a drum shape. In order to cope with this deformation trend and optimize the overall performance and structural uniformity of the gear, an arc-shaped inner wall protruding inward is set at the tooth root.
[0044] When the forming device applies pressure to the blank for forging, since the inner wall of the tooth root is preset to be arc-shaped, it tends to move outward, avoiding excessive buckling simply according to the original circular ring shape. This outward movement trend helps to achieve near-uniformity of the gear wall thickness during forging, effectively alleviating the wall thickness difference caused by uneven stress due to the outward expansion of the inner wall of the tooth root, and further ensuring near-uniformity of the gear wall thickness.
[0045] In some specific embodiments of the present application, such as Figure 3 shown, the tooth tip of the prefabricated steel layer blank has a straight wall structure, which is beneficial to guiding the initial deformation of the steel layer, avoiding inward bending of the material, and also facilitating the placement of the blank into the mold cavity during the blank transfer process.
[0046] In some preferred embodiments of the present application, in order to address the problem that the thixotropic aluminum alloy core may cause material to overflow from the mold cavity during the forming process due to shear thinning, thereby affecting the forming effect, preventive measures are taken: ensuring that the height of the prefabricated steel layer blank is higher than that of the aluminum alloy core, specifically set to be slightly higher than the aluminum alloy core by 2-3 mm, which can not only effectively prevent material overflow but also avoid instability of the overly high prefabricated steel layer blank during the compression deformation process.
[0047] In some preferred embodiments of the present application, after the preform is placed into the guiding device and the steel layer blank is placed, the aluminum core blank needs to be manually placed. To minimize the influence caused by the offset during the blank transfer, the outer diameter of the aluminum core should be close to the minimum inner diameter of the steel layer blank. Considering the operability during the blank placement, the unilateral clearance between the outer diameter of the aluminum core blank and the inner diameter of the steel layer is set to 0.5-1 mm.
[0048] In some specific embodiments of the present application, the temperature corresponding to the thermoplastic range is 1000°C to 1200°C, causing the steel layer to change from a solid state to a thermoplastic state, providing a prerequisite for the metallurgical bonding with the aluminum alloy core.
[0049] In some specific embodiments of the present application, the aluminum alloy core is converted into a semi-solid state with a liquid phase ratio of 0.1 to 0.4. At this time, the aluminum alloy core not only has a low deformation resistance but also is not in an unstable state where it can flow freely. Thus, under the action of external force, the aluminum alloy core can be more easily filled into the tooth tip part.
[0050] In some specific embodiments of the present application, the structural characteristics of the steel layer include at least one of wall thickness distribution, outer dimension, number of teeth, and modulus. Based on the structural characteristics of the steel layer, precise reverse design can be achieved.
[0051] In some specific embodiments of the present application, the forming die, blank size, and prefabricated shape are set according to the parameters of the required aluminum-steel bimetallic gear, and the initial microstructure state, structural conditions, loading rate, etc. of the blank are optimized.
[0052] In some specific embodiments of the present application, the initial microstructure state of the blank includes the temperature / liquid phase ratio / reinforcing phase of the aluminum alloy core, the temperature / grain morphology of the steel layer, etc.
[0053] In some specific embodiments of the present application, the structural conditions of the blank include the thickness of the steel layer, the initial aluminum-steel gap, the initial aluminum-steel height difference, etc.
[0054] In some specific embodiments of the present application, the prefabricated shape of the steel layer blank can be prepared by preforming or machining.
[0055] In some preferred embodiments of the present application, by optimizing the forming process, adjusting the shape of the prefabricated steel layer blank with non-uniform wall thickness, etc., the wall thickness difference of the steel layer in different parts of the gear can be reduced, local weak areas can be eliminated, and thus an aluminum-steel bimetallic gear with nearly uniform wall thickness can be obtained.
[0056] In some specific embodiments of the present application, the optimization of the forming process can be achieved by adjusting parameters such as the blank temperature and the holding pressure time.
[0057] In some specific embodiments of the present application, this compound forging forming method is applicable to various stainless steels and alloy steel materials for the outer steel layer, and various aluminum alloys and metal matrix composites based on aluminum alloys for the inner aluminum core, not limited to the aluminum-steel bimetallic gear specifically described in the present application.
[0058] Furthermore, based on the above compound forging forming method, the present application also provides a compound forging forming device for an aluminum-steel bimetallic gear with nearly uniform wall thickness, and this forming device can complete the compound forging in step three of the compound forging forming method.
[0059] Specifically, as Figure 4 and Figure 5As shown, the forming device includes a first platform 1, a second platform 2, and a punch 3, a die 4, a counter punch 5, and a ejector rod 6 that are arranged from top to bottom between the first platform 1 and the second platform 2. The punch 3 is installed on one side of the first platform 1 facing the second platform 2. The ejector rod 6 is connected to the second platform 2 and the top end thereof abuts against the bottom end of the counter punch 5 at the same time. The top end of the counter punch 5 can extend into the die 4 and is movably connected to the die 4. The bottom end of the punch 3 can extend into the die 4. A forging cavity for the forging blank is formed between the punch 3 and the counter punch 5. During the forging and forming process, the first platform 1 and the punch 3 press down to drive the die 4 to move downward, while the counter punch 5, the ejector rod 6, and the second platform 2 remain stationary. The top end and the bottom end of the prefabricated steel layer blank can be simultaneously extruded by the punch 3 and the counter punch 5, so as to realize the flow of the steel layer to the peripheral end of the forging cavity.
[0060] In some preferred embodiments of the present application, as Figure 5 shown, the lower surface of the punch 3 and the upper surface of the die 4 are provided with mutually matching inclined surface structures 7. The upper surface of the counter punch 5 also has an inclined surface structure 7, so that the forging cavity has a dovetail structure at the outer edge of the gear, further promoting the flow of the steel layer to the peripheral end of the forging cavity and ensuring the forming effect of the gear.
[0061] In some preferred embodiments of the present application, as Figure 5 shown, the upper surface of the counter punch 5 is provided with a stepped structure 8, and the outer diameter of the stepped structure 8 is slightly smaller than the inner diameter of the prefabricated steel layer blank. On the one hand, it can ensure that the radial position of the prefabricated steel layer blank does not shift, reducing the probability of the processing accuracy decreasing or even damaging the components; on the other hand, even if the material expands slightly during the processing, it will not cause an over-tight fit between the prefabricated steel layer blank and the counter punch 5, thus avoiding possible damage and processing errors.
[0062] Furthermore, the specific steps of step three in the near-uniform wall thickness aluminum-steel bimetallic gear compound forging and forming method using the above forming device specifically include the following steps:
[0063] S31: Design a forming device based on the prefabricated steel layer blank, including a punch 3, a die 4, a counter punch 5, an ejector rod 6, etc.;
[0064] S32: Assemble the forming device and set the counter punch 5 and the die 4 to the initial positions;
[0065] S33: Preheat the die cavity 4, the punch 3, and the counter punch 5 to 300° - 400°. When heated to about 120°, evenly spray a graphite release agent on the working surface of the mold;
[0066] S34: Preheat the prefabricated steel layer blank to 1000° - 2000°, perform semi-solid remelting on the aluminum alloy core, and preheat and keep the aluminum alloy core at a semi-solid state with a liquid fraction of 0.1 - 0.4;
[0067] S35: Transfer the prefabricated steel layer blank and the aluminum alloy core to the cavity of the concave die;
[0068] S36: The punch 3 drives the floating concave die 4 and the blank to move downward synchronously to complete the compound forging forming;
[0069] S37: The ejector rod 6 ejects the counter punch 5 to drive the aluminum-steel bimetallic gear out of the cavity of the concave die 4;
[0070] S38: Adopt an appropriate cooling method according to the heat treatment requirements.
[0071] The above has introduced the specific implementation manners of the present application in detail. For those skilled in the art of this technology, without departing from the principle of the present application, several improvements and modifications can still be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.
Claims
1. A composite forging method for a nearly uniform wall thickness aluminum-steel bimetallic gear, characterized in that: The following steps are involved: Step 1, design and reverse design: design the steel layer structure characteristics of the aluminum-steel bimetal gear with nearly uniform wall thickness, and reversely design the shape of the non-uniform wall thickness prefabricated steel layer blank of the aluminum-steel bimetal gear based on the steel layer structure; Step 2, forming a prefabricated steel layer blank: forming a prefabricated steel layer blank with a non-uniform wall thickness; Step three, composite forging: heating the prefabricated steel layer blank to a thermoplastic range, heating the thixotropic aluminum alloy core to a semi-solid range, and using closed die forging to make the aluminum alloy form the gear core and the steel layer form the gear surface.
2. The composite forging method for a nearly uniform wall thickness aluminum-steel bimetallic gear according to claim 1 is characterized in that: The tooth roots of the prefabricated steel layer blank have an inward curvature.
3. The composite forging method for a nearly uniform wall thickness aluminum-steel bimetallic gear according to claim 1 is characterized in that: The tooth tops of the prefabricated steel layer blank have a straight wall structure.
4. The composite forging method for a nearly uniform wall thickness aluminum-steel bimetallic gear according to claim 1 is characterized in that: The height of the prefabricated steel layer blank is 2 to 3 mm higher than the height of the aluminum alloy core.
5. The composite forging method for a nearly uniform wall thickness aluminum-steel bimetallic gear according to claim 1 is characterized in that: The single-side gap between the inner diameter of the prefabricated steel layer blank and the outer diameter of the aluminum alloy core is 0.5-1 mm.
6. The composite forging method for a nearly uniform wall thickness aluminum-steel bimetallic gear according to claim 1 is characterized in that: The temperature corresponding to the thermoplastic range is 1000°C to 1200°C.
7. The composite forging method for a nearly uniform wall thickness aluminum-steel bimetallic gear according to claim 1 is characterized in that: The aluminum alloy core is converted into a semi-solid state with a liquid phase ratio of 0.1 to 0.
4.
8. A forming device for implementing the composite forging step according to any one of claims 1 to 7, characterized in that: It comprises a first platform, a second platform, and a punch, a die, a counter punch and a push rod installed between the first platform and the second platform and arranged from top to bottom; The punch is installed on the side of the first platform facing the second platform. The top end of the push rod is connected to the second platform and abuts against the bottom end of the recoil punch. The top end of the recoil punch can be extended into the die and movably connected to the die. The bottom end of the punch can be extended into the die. A forging cavity for forging the blank is formed between the punch, the recoil punch and the die.
9. A forming device according to claim 8, characterized in that: The lower surface of the punch and the upper surface of the die are provided with mutually matching inclined surface structures, and the upper surface of the counter punch is also provided with an inclined surface structure.
10. A forming device according to claim 8, characterized in that: A step structure is provided on the lower surface of the punch and the upper surface of the counter-punch, and the outer diameter of the step structure is slightly smaller than the inner diameter of the prefabricated steel layer blank.