Thin-wall lining metal plate stretching forming process

Abstract

The invention provides a thin-wall lining metal plate stretching forming process which comprises the following steps: carrying out primary stretching forming at a pre-forming position of a blank at a preset stretching depth to form a primary blank; the primary blank is subjected to seven times of stretching, an opening of a middle finished product obtained after each time of stretching treatment shrinks inwards, the longitudinal height of the middle finished product is increased, the stretching length from the second time of stretching forming to the fifth time of stretching forming is gradually increased, and the stretching length in the fifth time of stretching forming procedure reaches the maximum value; the stretching length from the fifth time of stretching forming to the eighth time of stretching forming is gradually reduced; and the middle finished product obtained after the last time of stretching treatment is subjected to corner trimming and shaping, and a thin-wall lining finished product is obtained. Cracking and wrinkling caused by too large local deformation of the blank are avoided, the surface of the lining is good in quality, free of air holes and full in shape, the product quality and the production efficiency are remarkably improved, and the use performance and the safety performance of equipment are ensured.

Description

Technical Field

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

[0002] As a key Fe-Ni-Cr-based high-temperature alloy, GH2132 alloy is widely used in aviation parts due to its excellent yield strength, endurance strength, creep strength below 650°C, as well as good processing plasticity and welding performance. However, its outstanding material properties also bring significant processing challenges. Plate forming is extremely difficult, and serious defects such as folding, wrinkling, and cracking are very likely to occur during traditional processing.

[0003] The processing die structure of GH2132 high-precision thin-walled bushing is relatively complex, especially the deep drawing process with flange is difficult to achieve, and the production efficiency is low. In addition, the bushing parts require a flat and smooth surface without wrinkles, indentations, and scratches. The surface quality of the parts processed by existing mold equipment is difficult to guarantee, and must be considered 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 mold, and 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 the traditional processing process.

[0005] To achieve the above purpose, the technical solution of this application is implemented as follows: 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 pre-blank, wherein the pre-blank has an opening at the top, the edge of the opening is folded outward to form a flange edge, and the bottom has a closed surface, forming a cylindrical pre-blank with a cavity inside; The preform is stretched seven times, wherein the opening of the intermediate product after each stretching process shrinks inward and stretches in longitudinal height, the stretching length increases gradually 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, and in the fifth stretching process, the connection between the flange edge and the side wall is chamfered; The intermediate product obtained after the last stretching treatment is subjected to corner trimming and shaping to obtain a finished thin-walled bushing.

[0006] Furthermore, the first stretching forming depth is less than the preset stretching depth, wherein the preset stretching depth is 15 mm.

[0007] Furthermore, before the first stretching forming, the blank is pre-cut, including cutting the four corners of the blank.

[0008] Furthermore, 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 through cooperation between a male mold and a female mold.

[0009] 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 carried out at different deformation speeds to obtain the stress-strain distribution and deformation resistance. The plastic deformation reliability was predicted based on the simulation results.

[0010] Furthermore, the stretching length during the stretching forming process is ≤3.5 mm.

[0011] Compared with the prior art, the thin-walled bushing sheet metal stretching forming process described in this application has the following beneficial effects: The thin-walled bushing sheet metal stretching forming process described in the present application adopts a cold heading forming process to process the high-precision thin-walled bushing, and distributes the large deformation to each workstation, thereby avoiding cracking and wrinkling caused by excessive local deformation of the blank. The surface quality of the bushing is intact without pores and the shape is full, which significantly improves the product quality and production efficiency, and ensures the performance and safety of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings: Figure 1 This is a geometric dimension diagram of the bushing during processing described in an embodiment of the present application. DETAILED DESCRIPTION

[0013] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0014] 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 words "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 "comprises" and other 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 other similar words are not limited to physical or mechanical connections, but can be Including electrical connections, whether direct or indirect. "Up", "down", "left", "right", etc. are only used to indicate relative position relationships. When the absolute position of the object being described changes, the relative position relationship may also change accordingly.

[0015] See also Figure 1 As shown, this embodiment provides a thin-walled bushing sheet metal stretching forming process, including the following process steps: Step S101, performing the first stretching forming at a preset stretching depth at the 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 initial stage. After the first stretching, a primary blank is formed, and the primary blank has an opening at the top, and the edge of the opening is folded outward to form a flange edge, and the bottom has a closed surface, forming a cylindrical primary blank with a cavity inside.

[0016] In this step, the preform is an intermediate transition form. The key to the preform is its stretching depth. Since the preform has not reached 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.

[0017] 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. 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.

[0018] In this embodiment, the blank holder is only used in the deep 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 structure and better quality.

[0019] 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.

[0020] In some embodiments, before the first stretching and forming, the blank is pre-cut, including cutting four corners of the blank.

[0021] Specifically, in this embodiment, the purpose of pre-cutting in this step is mainly the following: 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.

[0022] Second, the excess material in the corner area may cause additional friction or interference with the mold during the molding process, aggravating the wear of the mold and affecting the molding accuracy. By pre-cutting, the interference of excess material can be reduced, the load on the mold can be reduced, the mold life can be extended, and the accuracy of the molded parts can be improved.

[0023] 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.

[0024] Step S102, stretching the embryo seven times, the stretching length in the stretching process is ≤3.5mm, wherein the opening of the intermediate product after each stretching treatment shrinks inward and stretches in longitudinal height, the stretching length increases gradually from the second stretching to the fifth stretching, reaches a maximum value in the fifth stretching process, and then gradually decreases from the fifth stretching to the eighth stretching. 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.

[0025] Specifically, in this embodiment, the second to fourth processes are all thinning and drawing processes. When the upper die (i.e., male die) just contacts the lower die (i.e., female die), a certain stress will be generated at the fillet of the blank. As the amount of downward pressure increases, the blank gradually elongates, and the stress concentration area is mainly in the upper part. If the gap between the male and female dies is too large, the workpiece is prone to wrinkling and poor precision; if the gap between the male and female dies is too small, the friction will increase, and the surface of the workpiece will be easily scratched, resulting in severe thinning or even cracking. Considering the product precision requirements, the drawing die gap is set to 0.05 mm during simulation. At this time, the height h of the bushing body is 16.4 mm, with an error within 0.5 mm, and the outer diameter φ is 21.46 mm, with an error within 0.2 mm.

[0026] In the fifth process, the upper part is chamfered while thinning and drawing. Chamfering helps to improve the mechanical properties of the product, especially in the connection parts, which can improve the structural strength of the product and ensure the durability and stability of the finished product. In addition, chamfering can also improve the matching accuracy and aesthetics during subsequent assembly, especially in places where it needs to be connected with other parts. Chamfering will make the assembly smoother and reduce damage. At this time, the height h of the bushing body is 19.9mm, with an error within 0.5mm, and the outer diameter φ is 20.34mm, with an error within 0.2mm.

[0027] The drawing distance after the fifth step is gradually shortened, so that the overall deformation of the blank in the sixth step is reduced, thereby avoiding wrinkles and cracks. At this time, the height h of the bushing body is 23.19mm, with an error within 0.5mm, and the outer diameter φ is 19.42mm, with an error within 0.2mm.

[0028] The seventh and eighth steps are to continue drawing the bushing to increase its depth. 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-tuning of dimensions or the forming of thin-walled parts.

[0029] It should be noted that, since the bushing needs to be further drawn, the amount of the punch pressing down is larger than that in the previous forming step, and the fan-shaped part that was deformed in the previous step needs to be deformed and drawn downward; but 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, so that the residual stress of the part where the bottom of the bushing intersects with the side wall is concentrated, resulting in cracking and structural damage. However, the present application gradually reduces the stretching length after the fifth process, and 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.

[0030] 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.

[0031] In this step, the present embodiment performs multiple stretching forming processes, and by gradually increasing and decreasing the stretching length, it is possible to achieve a gradual improvement in forming accuracy while ensuring the shape and structure of the product. The gradual adjustment of each stretching makes the morphology of the product at each stage more uniform, reducing the risk of uneven deformation, thereby improving the consistency and quality of the final product.

[0032] Step S103, performing corner trimming and shaping on the intermediate product obtained after the last stretching treatment to obtain a finished thin-walled bushing.

[0033] Specifically, in this embodiment, after multiple stretching, the intermediate product may have sharp corners or irregular edges, which need to be removed or rounded by corner trimming. Corner trimming helps to ensure that the appearance of the thin-walled bushing is smoother and neater, meeting the design requirements. At the same time, sharp corners will cause stress concentration and increase the risk of cracking or breaking. Corner trimming at the flange edge, joints and other locations of the bushing can effectively reduce stress concentration, improve the structural strength of the product, and enhance its durability.

[0034] In this step, the corner shaping can ensure that the bushing can better fit other components during the subsequent assembly process and avoid damage or poor assembly caused by sharp angles.

[0035] The thin-walled bushing sheet metal stretching forming process described in this embodiment adopts a cold heading forming process to process the high-precision thin-walled bushing, and distributes the large deformation to each workstation, avoiding cracking and wrinkling caused by excessive local deformation of the blank. The surface quality of the bushing is intact without pores and the shape is full, which significantly improves the product quality and production efficiency, and ensures the performance and safety of the equipment.

[0036] 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.

[0037] Specifically, in this embodiment, by analyzing the GH2132 bushing forming process, the 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.

[0038] 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 plastic deformation reliability was predicted based on the simulation results to avoid defects such as folding, wrinkling, and rupture, and to optimize the mold design and process flow.

[0039] 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.

[0040] 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate 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 specification of the present invention.

[0041] 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 the present application.

Claims

1. A thin-walled bushing sheet metal stretching forming process, characterized in that: include: Performing a first stretching forming at a preset stretching depth at a pre-forming position of the blank to form a pre-blank, wherein the pre-blank has an opening at the top, the edge of the opening is folded outward to form a flange edge, and the bottom has a closed surface, forming a cylindrical pre-blank with a cavity inside; The preform is stretched seven times, wherein the opening of the intermediate product after each stretching process shrinks inward and stretches in longitudinal height, the stretching length increases gradually 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, and in the fifth stretching process, the connection between the flange edge and the side wall is chamfered; The intermediate product obtained after the last stretching treatment is subjected to corner trimming and shaping to obtain a finished thin-walled bushing.

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

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

5. A 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 carried out 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. A 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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