Hollow part superplastic forming method with thickness steps

Abstract

The application provides a hollow part superplastic forming method with thickness steps, comprising the following steps: diffusion bonding multiple plates to form a superplastic forming blank, the superplastic forming blank has a hollow area for filling high-pressure gas and a solid area for realizing diffusion bonding, and the hollow area forms N thickness steps; and designing N superplastic forming molds corresponding to the N thickness steps according to a forming numerical model of the hollow part. The application designs and processes multiple superplastic forming molds on the basis of the forming numerical model of the hollow part, sequentially superplastic forms each thickness step from thick to thin through the multiple superplastic forming molds, makes each thickness step sequentially thin from thick to thin, reduces the thickness gradient difference between each thickness step, makes the thickness distribution of the finally superplastically formed hollow part more uniform, and improves the deformation coordination of different areas, and solves the problem of severe thinning of the thinner area generated by one-time superplastic forming.

Description

Technical Field

[0001] This invention relates to the field of superplastic forming technology, and more specifically, to a method for superplastic forming hollow parts with thickness gradients. Background Technology

[0002] As aircraft performance requirements increase, they become increasingly sensitive to weight, making lightweight structural design a growing goal for modern aircraft design and manufacturing engineers.

[0003] Superplastic forming is a manufacturing technology that utilizes the low deformation resistance and excellent ductility of materials under specific temperature conditions. Its process is simple, allowing for the one-time forming of complex parts with near-zero allowance. Diffusion bonding is a unique fixed-joining process often used in combination with superplastic forming to form highly flexible and lightweight titanium alloy parts. The superplastic forming / diffusion bonding (SPF / DB) process significantly reduces manufacturing costs and component weight, while substantially improving the overall integrity, specific strength, forming accuracy, and load-bearing efficiency of the parts.

[0004] With the development of the aviation industry, the trend of larger and more integrated sheet metal parts is becoming increasingly apparent. Cabin doors and hatches are important components of aircraft sheet metal parts and a major key technology in aircraft development. Aircraft cabin doors and hatches are subject to complex stresses, directly contacting the external environment, bearing heavy loads, and requiring extremely high dimensional accuracy. Simultaneously, to meet strength and rigidity requirements, aircraft hatches and hatches are generally thin-plate parts, designed with varying thicknesses. They exhibit a large thickness gradient near the reinforced areas and have hollow structures distributed throughout. Therefore, achieving welding and integral forming of the reinforced areas while ensuring the surface quality of the parts is a challenge. Superplastic forming / diffusion bonding (SPF / DB) technology is a relatively good method to solve this problem.

[0005] For novel large-thickness gradient hollow structures, the traditional superplastic forming / diffusion bonding (SPF / DB) technology was initially used. This involves welding multiple layers using diffusion bonding and then forming the hollow structure in a single step using superplastic forming. However, compared to traditional SPF / DB multi-layer hollow structures made of uniform-thickness plates, the deformation inconsistency in the large-thickness gradient region (i.e., the boundary between thick and thin areas) of the novel SPF / DB structure increases significantly under the influence of temperature and stress fields during superplastic forming. The thinner areas exhibit a clear trend of thickness reduction, causing deformation to concentrate primarily in the thinner areas. Figure 1As shown. If the superplastic forming / diffusion bonding process is not properly implemented, it will cause drastic thinning in thin areas, forming a severely thinned zone C, or even cracking, resulting in an excessively high thinning rate. The remaining thickness will not meet the structural load-bearing requirements. At the same time, the uneven deformation of the material in the large thickness gradient area will lead to surface defects such as wrinkles, concavities, and non-adherence to the mold, which will affect the part's shape accuracy, surface quality, structural integrity, and structural load-bearing capacity. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] The technical problem to be solved by the present invention is that the existing superplastic forming / diffusion bonding process tends to form a drastic thinning zone when forming hollow parts with thickness gradients, resulting in an excessively high structural thinning rate, and the remaining thickness cannot meet the structural load-bearing and other usage requirements.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] This invention provides a method for superplastic forming of hollow parts with thickness gradients, which includes the following steps:

[0011] Step 1: Diffusion bonding of multiple sheet materials to form a superplastic forming blank. The superplastic forming blank has a hollow area that has not been diffusely bonded and a solid area that has been diffusely bonded. The hollow area forms N thickness steps, which are defined as the 1st step, ... the (N-1)th step and the Nth step from thinnest to thickest.

[0012] Step 2: Based on the forming model of the hollow part, design N superplastic forming molds corresponding to N thickness steps, wherein the Nth superplastic forming mold has an Nth cavity for forming the Nth step, the (N-1)th superplastic forming mold has an N-1th cavity for forming the (N-1)th step, and so on, and the 1st superplastic forming mold has a 1st cavity for forming the hollow part;

[0013] Step 3: Position and install the superplastic forming blank on the Nth superplastic forming mold. Under a preset temperature environment, introduce high-pressure gas into the hollow area. The high-pressure gas causes the Nth step to stretch and deform and adhere to the mold in the Nth cavity. Cool and remove from the furnace to form the Nth preform blank.

[0014] Step 4: Position and install the Nth preform blank on the (N-1)th pre-superplastic forming mold. Under a preset temperature environment, introduce high-pressure gas into the hollow area. The high-pressure gas causes the Nth preform blank to stretch and deform and adhere to the mold in the (N-1)th cavity. Cool and remove from the furnace to form the (N-1)th preform blank.

[0015] ...;

[0016] Step N+3: Position and install the second preform blank on the first pre-superplastic forming mold. Under a preset temperature environment, introduce high-pressure gas into the hollow area. The high-pressure gas stretches and deforms the second preform blank and attaches it to the first cavity. Cool and remove it from the furnace to form the hollow part.

[0017] Further, step 1 specifically includes: cutting multiple plates into blanks, and pickling and shaping the cut plates according to the forming numerals of the hollow parts to form diffusion blanks, then diffusion connecting the diffusion blanks to form blanks, trimming the blanks, sealing the edges and vacuuming to form superplastic forming blanks.

[0018] Furthermore, the superplastic forming method further includes:

[0019] Step N+4: Perform a welding rate test on the hollow part. After passing the test, perform surface treatment and trim the edges. Then, inspect its shape, contour, thickness, and surface quality.

[0020] Furthermore, the superplastic forming mold includes a first half mold and a second half mold, the first half mold and the second half mold together forming a cavity.

[0021] Furthermore, the second half of the mold has an mounting plane for mounting the superplastic forming blank, and the first half of the mold has a forming groove, the inner wall of the forming groove and the mounting plane forming a cavity.

[0022] (III) Beneficial Effects

[0023] The above-described technical solution of the present invention has at least the following advantages:

[0024] 1. This invention designs and processes multiple superplastic forming molds based on the forming model of hollow parts. By using multiple superplastic forming molds to superplastic form each thickness step from thick to thin, the thickness step is thinned from thick to thin, reducing the thickness gradient difference between each thickness step. This results in a more uniform thickness distribution of the final superplastic formed hollow part, improves the deformation coordination of different areas, and solves the problem of severe thinning in thinner areas caused by one-time superplastic forming.

[0025] 2. Since the total deformation of hollow parts is constant, during superplastic forming, the total deformation of materials located in the thinner thickness gradient region decreases, while the total deformation of materials located in the thicker thickness gradient region increases, thereby achieving uniform deformation control of hollow parts with thickness gradients.

[0026] 3. Each superplastic forming mold is installed at each thickness step area, which is consistent with the thickness distribution of the superplastic forming blank. Moreover, each superplastic forming mold can only form the corresponding thickness step area, which can restrict the participation of thickness step areas with a thickness thinner than it in forming. This enables superplastic forming of each thickness step from thickest to thinnest. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a superplastic forming effect diagram of hollow parts in existing technology.

[0029] Figure 2 This is one of the implementation steps of the superplastic forming method for hollow parts with thickness gradients provided in this embodiment of the invention.

[0030] Figure 3 This is the second step diagram of the superplastic forming method for hollow parts with thickness gradients provided in this embodiment of the invention.

[0031] Figure 4 This is the third step diagram of the superplastic forming method for hollow parts with thickness gradients provided in this embodiment of the invention.

[0032] Figure 5 This is the fourth step diagram of the superplastic forming method for hollow parts with thickness gradients provided in this embodiment of the invention.

[0033] The labels for the attached figures are as follows:

[0034] 100. Superplastic forming blank; 101. First stage; 102. Second stage; 200. Second preform blank; 300. Hollow part; A. Hollow area; B. Solid area; 1. First pre-superplastic forming mold; 2. Second superplastic forming mold; 11. First cavity; 12. First half mold; 13. Second half mold; 21. Second cavity; 121. Forming groove; 131. Mounting plane. Detailed Implementation

[0035] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present 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 present invention and are not intended to limit the present invention.

[0036] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be located directly on or indirectly on the other component. When a component is referred to as "connected to" another component, it can be directly or indirectly connected to the other component.

[0037] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate that the device or element must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0038] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating relative importance or the number of technical features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. The specific implementation of this invention will be described in more detail below with reference to specific embodiments:

[0039] like Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown, this embodiment of the invention provides a superplastic forming method for hollow parts with thickness gradients, used for superplastic forming of hollow parts 300, including the following steps:

[0040] Step 1: Diffusion bonding of multiple sheet materials forms a superplastic forming blank 100. The superplastic forming blank 100 has a hollow region A without diffusion bonding and a solid region B with diffusion bonding. The hollow region A forms N thickness steps, which are defined sequentially from thinnest to thickest as step 101, ..., step N-1, and step N; Figure 2 Taking the illustrated embodiment as an example, the superplastic forming blank 100 in this embodiment has 2N thickness steps, namely the first step 101 and the second step 102.

[0041] Step 2: Based on the forming model of the hollow part, design N superplastic forming molds corresponding to N thickness levels. The Nth superplastic forming mold has an Nth cavity for forming the Nth thickness level, the (N-1)th superplastic forming mold has an (N-1)th cavity for forming the (N-1)th thickness level, and so on. The first superplastic forming mold 1 has a first cavity 11 for forming the hollow part. Figure 2 Taking the superplastic forming blank 100 shown as an example, in this embodiment there are two superplastic forming molds, namely as follows: Figure 3 The first superplastic molding die 1 shown and as follows Figure 4The second superplastic forming mold 2 shown has a first cavity 11 for forming the first step 101 and a second cavity 21 for forming the second step 102.

[0042] Step 3: Position and install the superplastic forming blank 100 on the Nth superplastic forming mold. Under the preset temperature environment, introduce high-pressure gas into the hollow area A. The high-pressure gas causes the Nth step to stretch and deform and adhere to the mold in the Nth cavity. Cool and remove from the furnace to form the Nth preform blank.

[0043] Step 4: Position and install the Nth preform blank on the (N-1)th pre-superplastic forming mold. Under a preset temperature environment, introduce high-pressure gas into the hollow area. The high-pressure gas causes the Nth preform blank to stretch and deform and adhere to the mold in the (N-1)th cavity. Cool and remove from the furnace to form the (N-1)th preform blank.

[0044] ...;

[0045] Step N+3: Position and install the second preform blank on the first pre-superplastic forming mold. Under a preset temperature environment, introduce high-pressure gas into the hollow area. The high-pressure gas causes the second preform blank to stretch and deform and adhere to the mold in the first cavity. Cool and remove from the furnace to form a hollow part.

[0046] Step N+4: Perform welding rate testing on hollow parts. After passing the test, perform surface treatment and trim the edges. Then, inspect the shape, contour, thickness, and surface quality of the hollow parts.

[0047] In one embodiment, when the superplastic forming blank 100 has two thickness steps, Figure 2 Taking the superplastic forming blank 100 as an example, firstly, the superplastic forming blank 100 is positioned and installed on the second superplastic forming mold 2, so that the second step 102 is directly opposite the second cavity 21, and the first step 101 is limited by the second superplastic forming mold to prevent deformation. Under a preset temperature environment, high-pressure gas is introduced into the hollow region A. The high-pressure gas stretches and deforms the second step 102 and molds it into the second cavity 21. After cooling and exiting the furnace, the second preform blank 200 is formed. Then, the second preform blank 20 is positioned and installed on the first pre-superplastic forming mold 10. Under a preset temperature environment, high-pressure gas is introduced into the hollow region A. The high-pressure gas stretches and deforms the second preform blank 200 and molds it into the first cavity 11. After cooling and exiting the furnace, the hollow part 300 is formed.

[0048] In another embodiment, when the superplastic forming blank 100 has three thickness steps, the superplastic forming blank 100 is first positioned and installed on the third superplastic forming mold, such that the third step is directly opposite the third cavity, and the second and first steps are restrained by the third superplastic forming mold to prevent deformation. Under a preset temperature environment, high-pressure gas is introduced into the hollow region A. The high-pressure gas stretches and deforms the third step, causing it to adhere to the mold in the third cavity. After cooling and removal from the furnace, the third preform is formed. Then, the third preform is positioned and installed on the second superplastic forming mold, such that the second step is directly opposite the second cavity, and the first step is restrained by the second superplastic forming mold to prevent deformation. Under a preset temperature environment, high-pressure gas is introduced into the hollow region A. The high-pressure gas stretches and deforms the third preform blank and molds it into the second cavity. After cooling and exiting the furnace, the second preform blank is formed. Finally, the second preform blank is positioned and installed on the first pre-superplastic forming mold blank. Under a preset temperature environment, high-pressure gas is introduced into the hollow region A. The high-pressure gas stretches and deforms the second preform blank and molds it into the first cavity. After cooling and exiting the furnace, the hollow part is formed.

[0049] Similarly, for a superplastic blank 100 with more thickness steps, superplastic forming is continuously performed on the thickness steps in descending order until the hollow part is formed.

[0050] In one embodiment, step 1 specifically includes: cutting multiple plates into blanks, and pickling and shaping the cut plates according to the forming numerals of the hollow part 300 to form diffusion blanks, then diffusion connecting the diffusion blanks to form blanks, trimming the blanks, sealing the edges and vacuuming to form a superplastic forming blank 100.

[0051] In one embodiment, the first superplastic molding die is used as an example for illustration. The first superplastic molding die 1 includes a first half mold 12 and a second half mold 13. The first half mold 12 and the second half mold 13 together form a first cavity 11.

[0052] In one embodiment, the first superplastic forming mold is used as an example for illustration. The second half mold 13 has an mounting plane 131 for mounting the superplastic forming blank 100. The first half mold 12 has a forming groove 121. The inner wall of the forming groove 121 and the mounting plane 131 together form the first cavity 11.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for superplastic forming of hollow parts with thickness gradients, used for superplastic forming of hollow parts, characterized in that, Includes the following steps: Step 1: Diffusion bonding of multiple sheet materials to form a superplastic forming blank. The superplastic forming blank has a hollow area that has not been diffusely bonded and a solid area that has been diffusely bonded. The hollow area forms N thickness steps, which are defined as the 1st step, ... the (N-1)th step and the Nth step from thinnest to thickest. Step 2: Based on the forming model of the hollow part, design N superplastic forming molds corresponding to N thickness steps, wherein the Nth superplastic forming mold has an Nth cavity for forming the Nth step, the (N-1)th superplastic forming mold has an N-1th cavity for forming the (N-1)th step, and so on, and the 1st superplastic forming mold has a 1st cavity for forming the hollow part; Step 3: Position and install the superplastic forming blank on the Nth superplastic forming mold. Under a preset temperature environment, introduce high-pressure gas into the hollow area. The high-pressure gas causes the Nth step to stretch and deform and adhere to the mold in the Nth cavity. Cool and remove from the furnace to form the Nth preform blank. Step 4: Position and install the Nth preform blank on the (N-1)th pre-superplastic forming mold. Under a preset temperature environment, introduce high-pressure gas into the hollow area. The high-pressure gas causes the Nth preform blank to stretch and deform and adhere to the mold in the (N-1)th cavity. Cool and remove from the furnace to form the (N-1)th preform blank. ……； Step N+3: Position and install the second preform blank on the first pre-superplastic forming mold. Under a preset temperature environment, introduce high-pressure gas into the hollow area. The high-pressure gas stretches and deforms the second preform blank and attaches it to the first cavity. Cool and remove it from the furnace to form the hollow part.

2. The superplastic forming method for hollow parts with thickness gradients as described in claim 1, characterized in that, Step 1 specifically includes: cutting multiple plates into blanks, and pickling and shaping the cut plates according to the forming numerals of the hollow parts to form diffusion blanks, then diffusion connecting the diffusion blanks to form a blank, trimming the blanks, sealing the edges and vacuuming to form a superplastic forming blank.

3. The superplastic forming method for hollow parts with thickness gradients as described in claim 1, characterized in that, The superplastic forming method further includes: Step N+4: Perform a welding rate test on the hollow part. After passing the test, perform surface treatment and trim the edges. Then, inspect its shape, contour, thickness, and surface quality.

4. The superplastic forming method for hollow parts with thickness gradients as described in claim 1, characterized in that, The superplastic forming mold includes a first half mold and a second half mold, which together form a cavity.

5. The superplastic forming method for hollow parts with thickness gradients as described in claim 4, characterized in that, The second half of the mold has an mounting plane for mounting the superplastic forming blank, and the first half of the mold has a forming groove, the inner wall of the forming groove and the mounting plane forming a cavity.

Images