A thin-walled bushing sheet metal stretching forming process

Abstract

The present application provides a thin-walled bushing sheet metal stretching forming process, comprising: performing a first stretching forming at a preset stretching depth at a pre-forming position of the blank to form a preliminary blank; stretching the preliminary blank seven times, wherein the opening of the intermediate finished product after each stretching process shrinks inward and stretches in longitudinal height, the stretching length gradually increases from the second stretching forming to the fifth stretching forming, reaches a maximum value in the fifth stretching forming process, and then gradually decreases from the fifth stretching forming to the eighth stretching forming; trimming and shaping the intermediate finished product obtained after the last stretching process to obtain a thin-walled bushing finished product. The present application avoids cracking and wrinkling caused by excessive local deformation of the blank, and the surface quality of the bushing is intact without air holes and the shape is full, which significantly improves product quality and production efficiency, and ensures the performance and safety performance of the equipment.

Description

Technical Field

[0001] The present application belongs to the field of metal precision processing technology, and in particular relates to a thin-walled bushing sheet metal stretching forming process. Background Art

[0002] GH2132 alloy, a key Fe-Ni-Cr-based superalloy, is widely used in aviation components due to its exceptional yield strength, rupture strength, creep strength below 650°C, as well as good processing ductility and weldability. However, its outstanding material properties also present significant processing challenges. Sheet forming is extremely difficult, and severe defects such as folding, wrinkling, and cracking are easily formed during traditional processing.

[0003] The processing mold structure of the GH2132 high-precision thin-walled bushing is relatively complex, especially the deep drawing process with flanges is difficult to achieve, and the production efficiency is low. In addition, the bushing parts require a flat and smooth surface without wrinkles, indentations, or scratches. The surface quality of the parts processed using existing mold equipment is difficult to guarantee, and must be given special consideration in the forming method and mold design. The sheet metal progressive die can complete multiple stamping processes such as blanking, bending, forming, and deep drawing in one die, and can decompose complex parts into simple stamping. Therefore, the sheet metal progressive die has become the best choice for achieving large-scale production and reducing production costs. Therefore, extending the life of the sheet metal progressive die, improving material utilization, and realizing automated production are the key issues to improve the production efficiency of the bushing. Summary of the Invention

[0004] In view of this, the present application aims to propose a thin-walled bushing sheet metal stretching forming process to solve the problem of bushing stretching cracking occurring in traditional processing.

[0005] To achieve the above objectives, the technical solution of this application is implemented as follows:

[0006] The present application provides a thin-walled bushing sheet metal stretching forming process, comprising:

[0007] A first stretching process is performed at a pre-forming position of the blank at a preset stretching depth to form a preform. The preform has an opening at the top, with the edge of the opening folded outward to form a flange, and a closed surface at the bottom, forming a cylindrical preform with a cavity inside.

[0008] The preform is stretched seven times, wherein the opening of the intermediate product shrinks inward and the longitudinal height is extended after each stretching process, the stretching length gradually increases from the second stretching process to the fifth stretching process, reaches a maximum stretching length in the fifth stretching process, and then gradually decreases from the fifth stretching process to the eighth stretching process, and in the fifth stretching process, a chamfering process is performed on the connection between the flange edge and the side wall;

[0009] The intermediate product obtained after the last stretching treatment is trimmed and shaped to obtain a thin-walled bushing product.

[0010] Furthermore, the first stretching depth is less than the preset stretching depth, wherein the preset stretching depth is 15 mm.

[0011] Furthermore, before the first stretching and forming, the blank is pre-cut, including cutting the four corners of the blank.

[0012] Furthermore, during the first stretching process, a pressure ring is provided below the blank, and the male and female dies cooperate to fold the edge of the opening of the blank to form a flange.

[0013] Furthermore, a simulation model of a 100° countersunk deep hole thin-walled GH2132 bushing was established. During the simulation, the gap between the convex and concave molds was set to 0.05 mm. The deformation distribution strategy for each process was determined based on the simulation results. Multiple simulations were performed at different deformation speeds to obtain the stress-strain distribution and deformation resistance. The plastic deformation reliability was predicted based on the simulation results.

[0014] Furthermore, the stretching length during the stretching forming process is ≤3.5 mm.

[0015] Compared with the prior art, the thin-walled bushing sheet metal stretching forming process described in this application has the following beneficial effects:

[0016] The thin-walled bushing sheet metal stretching forming process described in this application adopts a cold heading forming process to process high-precision thin-walled bushings, distributing large deformation to each workstation, avoiding excessive local deformation of the blank causing cracking and wrinkling. The surface quality of the bushing is intact without air holes and the shape is full, which significantly improves product quality and production efficiency, and ensures the performance and safety of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of this application. The exemplary embodiments and descriptions of this application are intended to explain this application and do not constitute an improper limitation on this application. In the accompanying drawings:

[0018] Figure 1 This is a geometric dimension diagram of the bushing during processing described in an embodiment of the present application. DETAILED DESCRIPTION

[0019] In order to make the objectives, technical solutions and advantages of this application more clear, this application is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0020] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present application should have the usual meanings understood by people with ordinary skills in the field to which the present application belongs. The "first", "second" and similar words used in the embodiments of the present application do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can be

[0021] "Up," "down," "left," "right," etc. are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0022] See also Figure 1 As shown, this embodiment provides a thin-walled bushing sheet metal stretching forming process, including the following process steps:

[0023] Step S101: Perform a first stretching forming at a preset stretching depth at a pre-forming position of the blank, wherein the first stretching forming depth is less than the preset stretching depth. In this embodiment, the preset stretching depth is set to 15 mm, that is, the preset stretching depth is used as the target stretching. During the first forming, the depth will not reach 15 mm, but a smaller depth. This is usually to avoid damage or deformation of the material caused by excessive stretching in the early stage. After the first stretching, a primary blank is formed. The primary blank has an opening at the top, and the edge of the opening is folded outward to form a flange edge. The bottom has a closed surface, forming a cylindrical primary blank with a cavity inside.

[0024] In this step, the preform is an intermediate transition form. The key to the preform is its stretching depth. Since the preform does not reach the final stretching depth, the preform ensures the initial forming shape of the material while ensuring that the material in the bottom area does not crack and the thickness of the material in the bottom area does not become transitionally thinner.

[0025] The maximum forming stress in the first process occurs in the inner arc of the bushing. When other variables remain unchanged, increasing the fillet radius can reduce the thickening rate of the outer arc and the thinning rate of the inner arc of the sheet metal. The fillet radius of the concave mold is set to 1.5mm, the height of the main body is 13.45mm, the error is within 0.5mm, and the width is 23mm, with an error within 0.2mm.

[0026] In this embodiment, the blank holder is only used in the drawing process in the first step, and the blank holder is not used in the subsequent steps. After simulation experiments, the present application can make the pressure at the flange edge position uniform by setting the blank holder, while the top edge position of the intermediate product without the blank holder will have obvious wrinkle defects. Therefore, with the help of the blank holder, the intermediate product has a fuller structural shape and better quality.

[0027] At the same time, when other variables remain unchanged, increasing the fillet radius can reduce the outer arc thickening rate and inner arc thinning rate of the sheet metal.

[0028] In some embodiments, before the first stretching and forming, the blank is pre-cut, including cutting the four corners of the blank.

[0029] Specifically, in this embodiment, the purpose of pre-cutting in this step is mainly the following:

[0030] First, during the stretching process of metal sheets, stress concentration is often prone to occur at the four corners, resulting in wrinkles, tears or other forming defects. This embodiment can effectively reduce excess material in the corner area by cutting the four corners, making the stress more evenly distributed during the stretching process, thereby reducing the generation of wrinkles and cracks.

[0031] Second, excess material in the corner area may cause additional friction or interference with the mold during the molding process, aggravating mold wear and affecting molding accuracy. By pre-cutting, the interference of excess material can be reduced, which can reduce the load on the mold, extend the mold life, and improve the accuracy of the molded parts.

[0032] Third, in stretch forming, excess material at the corners may lead to inconsistent rebound behavior of the parts after forming, affecting the precision and quality of the parts. Pre-cutting can alleviate the stress concentration problem in the corner areas, thereby reducing rebound deformation and improving the consistency and stability of the molded parts.

[0033] Step S102: The preform is stretched seven times, and the stretching length during the stretching process is ≤3.5 mm. The opening of the intermediate product after each stretching process shrinks inward and stretches in longitudinal height. The stretching length gradually increases from the second stretching process to the fifth stretching process, reaches a maximum value in the fifth stretching process, and then gradually decreases from the fifth stretching process to the eighth stretching process. In the fifth stretching process, while the intermediate product is thinned and stretched, the connection between the flange edge and the side wall is chamfered.

[0034] Specifically, in this embodiment, steps 2 through 4 are all thinning and drawing processes. When the upper die (i.e., male die) first contacts the lower die (i.e., female die), a certain amount of stress is generated at the rounded corners of the blank. As the downward pressure increases, the blank gradually stretches, with stress concentrated primarily in the upper portion. If the gap between the male and female dies is too large, the workpiece is prone to wrinkling and poor precision. If the gap is too small, friction is intensified, easily scratching the workpiece surface, causing severe thinning or even cracking. Considering the product's precision requirements, the drawing die gap was set to 0.05 mm during the simulation. At this point, the bushing body's height h is 16.4 mm, within a 0.5 mm tolerance, and its outer diameter φ is 21.46 mm, within a 0.2 mm tolerance.

[0035] In the fifth process, the upper portion is chamfered while thinning and drawing. This chamfering helps improve the product's mechanical properties, especially at the connection points, increasing its structural strength and ensuring the durability and stability of the finished product. Chamfering also improves the fit and aesthetics during subsequent assembly, especially where connections to other components are required. Chamfering makes assembly smoother and reduces damage. At this point, the bushing's main height, h, is 19.9 mm, within a 0.5 mm tolerance, and its outer diameter, φ, is 20.34 mm, within a 0.2 mm tolerance.

[0036] The drawing distance gradually shortens from the fifth step onwards, minimizing overall deformation of the blank in the sixth step, thus preventing wrinkles and cracks. The bushing's main body height h is now 23.19 mm, within a 0.5 mm tolerance, and its outer diameter φ is 19.42 mm, within a 0.2 mm tolerance.

[0037] The seventh and eighth steps are to continue drawing the bushing to increase the depth of the bushing. The purpose is to make fine adjustments to the already formed product, reduce excess material or optimize the accuracy of the product, especially to make necessary corrections in the fine adjustment of size or the forming of thin-walled parts.

[0038] It should be noted that, since the bushing needs to be further drawn, the amount of downward pressure of the punch is larger than that of the previous forming step, and the fan-shaped part that was deformed in the previous step needs to be deformed and drawn downward; however, due to the deepening of the depth, the friction between the already formed cylindrical part and the die and punch increases, and the forming force required to deform the fan-shaped part that was deformed in the previous step is larger, which hinders the deformation of the material, thereby causing the residual stress concentration at the intersection of the bottom of the bushing and the side wall, resulting in cracking and structural damage. However, the present application gradually reduces the stretching length after the fifth process. The gradual adjustment of each stretch makes the shape of the product at each stage more uniform, reduces the risk of uneven deformation, and thus improves the consistency and quality of the final product.

[0039] The final bushing body height h is 27.5mm, with an error within 0.5mm, the outer diameter φ is 16.2mm, with an error within 0.2mm, the upper thin wall thickness is 0.51mm, the lower cylinder thin wall thickness is 0.43mm, with an error within 0.01mm, and the inner cylinder diameter φ is 7mm, with an error within 0.05mm.

[0040] In this step, the present embodiment performs multiple stretching forming processes. By gradually increasing and decreasing the stretching length, it is possible to achieve a gradual improvement in the forming accuracy while ensuring the shape and structure of the product. The gradual adjustment of each stretching makes the shape of the product at each stage more uniform, reduces the risk of uneven deformation, and thus improves the consistency and quality of the final product.

[0041] Step S103: trimming and shaping the intermediate product obtained after the last stretching process to obtain a finished thin-walled bushing.

[0042] Specifically, in this embodiment, the intermediate product may develop sharp corners or irregular edges after multiple stretching steps. These edges need to be removed or rounded through corner trimming. Corner trimming helps ensure a smoother, more uniform appearance for the thin-walled bushing, meeting design requirements. At the same time, sharp corners can cause stress concentration, increasing the risk of cracking or breaking. Trimming the bushing at locations such as flange edges and joints can effectively reduce stress concentration, improving the product's structural strength and enhancing its durability.

[0043] In this step, the corner shaping can ensure that the bushing is better adapted to other components during the subsequent assembly process, avoiding damage or poor assembly caused by sharp angles.

[0044] The thin-walled bushing sheet metal stretching forming process described in this embodiment adopts a cold heading forming process to process high-precision thin-walled bushings, distributing large deformation to each workstation, avoiding excessive local deformation of the blank causing cracking and wrinkling. The surface quality of the bushing is intact without air holes and the shape is full, which significantly improves product quality and production efficiency, and ensures the performance and safety of the equipment.

[0045] In some embodiments, a simulation model of a 100° countersunk deep hole thin-walled GH2132 bushing is established, and the gap between the male and female molds is set to 0.05 mm during simulation. The deformation distribution strategy for each process is determined based on the simulation results, and multiple simulations are performed at different deformation speeds to obtain the stress-strain distribution and deformation resistance. The plastic deformation reliability is predicted based on the simulation results.

[0046] Specifically, in this embodiment, by analyzing the GH2132 bushing forming process, DEFORM-3D software is used to establish a finite element model for simulation, and the changes in stress, strain, flow rate, etc. of key parts during the forming process are tracked at fixed points. Based on this, the sheet metal progressive die is improved to provide valuable reference for actual production.

[0047] A simulation model of a 100° countersunk high-precision deep-hole thin-walled GH2132 bushing was established. The deformation distribution scheme for each process step was determined based on the simulation results. Multiple simulations were carried out at different deformation speeds to obtain the stress-strain distribution and deformation resistance. The reliability of plastic deformation was predicted based on the simulation results to avoid defects such as folding, wrinkling, and rupture, thereby optimizing the mold design and process flow.

[0048] When the bushing is processed according to the cold heading forming process of this embodiment, the finite element simulation method can also be used to analyze the defects generated in the forming step and analyze the specific causes of the defects: if it is caused by a simulation setting problem, return to the step, reset the mold movement mode and dynamic mold speed, and then submit the calculation; if the defect still exists after the modification, it is considered to be caused by a process flow problem, then return to modify the process flow, adjust the assembly relationship between the blank and the mold, and repeat the simulation until the defect is eliminated.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

[0050] The embodiments of the present application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present application should be included in the scope of protection of this application.

Claims

1. A thin-walled bushing sheet metal stretching forming process, characterized in that: include: A first stretching process is performed at a pre-forming position of the blank at a preset stretching depth to form a preform. The preform has an opening at the top, with the edge of the opening folded outward to form a flange, and a closed surface at the bottom, forming a cylindrical preform with a cavity inside. The preform is stretched seven times, wherein the opening of the intermediate product shrinks inward and the longitudinal height is extended after each stretching process, the stretching length gradually increases from the second stretching process to the fifth stretching process, reaches a maximum stretching length in the fifth stretching process, and then gradually decreases from the fifth stretching process to the eighth stretching process, and in the fifth stretching process, a chamfering process is performed on the connection between the flange edge and the side wall; The intermediate product obtained after the last stretching treatment is trimmed and shaped to obtain a thin-walled bushing product.

2. A thin-walled bushing sheet metal stretching forming process according to claim 1, characterized in that: The first stretching depth is less than the preset stretching depth, wherein the preset stretching depth is 15 mm.

3. The thin-walled bushing sheet metal stretching forming process according to claim 1, characterized in that: Before the first stretching and forming, the blank is pre-cut, including cutting the four corners of the blank.

4. The thin-walled bushing sheet metal stretching forming process according to claim 1, characterized in that: During the first stretching process, a pressure ring is provided below the blank, and the opening edge of the blank is folded to form a flange edge through the cooperation of a male mold and a female mold.

5. The thin-walled bushing sheet metal stretching forming process according to claim 4, characterized in that: A simulation model of a 100° countersunk deep hole thin-walled GH2132 bushing was established. The gap between the convex and concave molds was set to 0.05 mm during the simulation. The deformation distribution strategy for each process was determined based on the simulation results. Multiple simulations were performed at different deformation speeds to obtain the stress-strain distribution and deformation resistance. The plastic deformation reliability was predicted based on the simulation results.

6. The thin-walled bushing sheet metal stretching forming process according to claim 1, characterized in that: The stretching length during the stretch forming process is ≤3.5mm.

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