Precision forming method of built-in reinforcing block thin-walled member

Abstract

The present application belongs to the field of plastic forming of metal thin-walled components, and relates to a precise forming method of a thin-walled component with built-in reinforcing blocks. The present application cooperatively uses pre-forming and final forming processes, first performs hot forming to complete the manufacturing of preformed rib cells, and then performs SPF / DB process to complete the manufacturing of the final component. The existence of the pre-formed rib cells improves the stability of the reinforcing block fixation, improves the consistency of the welding rate and quality of the diffusion bonding between the reinforcing block and the skin, suppresses the final sagging and shrinkage defects of the component by controlling the protruding height size of the placed reinforcing block, and improves the overall forming quality of the component.

Description

Technical Field

[0001] This invention belongs to the field of plastic forming of thin-walled metal components, and relates to a precise forming method for thin-walled components with built-in reinforcing blocks. Background Technology

[0002] Superplastic forming / diffusion bonding (SPF / DB) components, characterized by lightweight and high strength, have been widely used in the manufacturing of vehicle components. With the development of vehicle design and manufacturing technology, vehicles suitable for multiple scenarios have become a major trend, posing new challenges to the design and manufacturing of new vehicles. Gradient structural components, with their good adaptability to complex and varied operating conditions, have gradually become an important choice for lightweight, high-strength components. The introduction of thin-walled structures with built-in reinforcing blocks has achieved a perfect coupling of lightweight and high-strength characteristics in thin-walled structure manufacturing, greatly expanding the application areas of SPF / DB technology and improving the adaptability of thin-walled components to complex service environments. Currently, the main process flow for forming thin-walled structures with built-in reinforcing blocks is as follows: the reinforcing block is fixed to the inner skin using spot welding; then, a weld inhibitor is sprayed onto the non-diffusion area, and the outer skin and inner skin are sealed at the edges using welding; finally, the component is placed in an SPF / DB forming machine to complete the manufacturing process. Using this method, due to the presence of the built-in reinforcing block, a large gap appears at the location of the built-in reinforcing block in the unformed structure after welding and sealing. During diffusion bonding, the gap is subjected to external pressure, causing the inner and outer skins to adhere towards the center. However, due to the rigidity of the reinforcing block, the amount of skin adhesion at the reinforcing block is much less than that without the reinforcing block. This difference ultimately leads to grooves on the outer surface of the skin, affecting the overall forming quality of the component. The grooves create significant stress concentration during use, reducing the product's performance. Therefore, there is an urgent need to find a more suitable SPF / DB forming method for thin-walled components with built-in reinforcing blocks to solve existing problems in production and improve quality and efficiency. Summary of the Invention

[0003] To address the aforementioned defects that easily occur in the traditional SPF / DB manufacturing process, a precision forming method for thin-walled components with built-in reinforcing blocks is proposed. This invention employs a method that combines preforming and final forming, controlling the preforming and final forming processes separately to improve the forming efficiency, quality, and precision of the components. Preforming refers to pre-forming a rib cell in the placement area of ​​the reinforcing block while the plate is in a flat state. By rationally designing the configuration of the preforming mold and controlling the depth and outer dimensions of the pre-formed rib cell, the relative position of the reinforcing block and the plate is positioned, improving the positional accuracy of the reinforcing block diffusion connection. At the same time, the separate state of the reinforcing block and the skin before diffusion connection improves the quality consistency of the reinforcing block and the skin after diffusion forming. Final forming refers to introducing three inert gases into the inner and outer skin surfaces and the mold contact surfaces, as well as the reinforcing block rib cell, during SPF / DB forming. The inert gas flow rate at the reinforcing block rib package and the contact surfaces of the two skins and the tooling is adjusted respectively, controlling the gas pressure and the opening and closing of each gas path at the contact surfaces of the skin and the tooling and the reinforcing block rib package. This guides the flow direction and flow behavior of the metal during superplastic forming, improves the stability of superplastic forming, suppresses groove defects on the outer surface of the component, and ultimately achieves high-quality manufacturing of SPF / DB forming of thin-walled components with built-in reinforcing blocks.

[0004] The technical means adopted in this invention are as follows:

[0005] A precise forming method for thin-walled components with built-in reinforcing blocks is characterized by: firstly, designing a thermoforming fixture for prefabricated rib cells based on the dimensions of the built-in reinforcing blocks and the specifications of the thin-walled skin, and designing an SPF / DB final forming fixture based on the final shape requirements of the component; secondly, after the prefabricated rib cells are formed, placing the reinforcing blocks at the prefabricated rib cells, determining the area for applying the anti-weld flux, and completing the application of the anti-weld flux; thirdly, completing the laser welding sealing of the cavities of the inner and outer skins before superplastic forming of the component to form a prefabricated integral part; fourthly, placing the formed prefabricated integral part into the SPF / DB final forming fixture and fixing it into the SPF / DB forming equipment, connecting each control gas path, controlling the gas flow rate and the on / off state of each gas path, and completing the final SPF / DB forming of the component.

[0006] 1. Determination of precast reinforcing block reinforcement cell specifications

[0007] The prefabricated reinforcing block rib cell is part of the final component reinforcing block rib cell. The outer contour dimensions of the prefabricated reinforcing block rib cell are determined based on the planned height H of the prefabricated reinforcing block rib cell. After the height H of the prefabricated reinforcing block rib cell is determined, a virtual cross section is constructed by measuring the height H of the final component reinforcing block rib cell towards the skin side with the rib cell protrusion plane as the reference. The outer contour of the segmented body is the outer contour of the prefabricated reinforcing block rib cell.

[0008] The height H of the prefabricated reinforcing block rib cell is determined by the thickness c of the reinforcing block. In order to improve the manufacturing accuracy of the subsequent manufacturing process, the two should satisfy the relationship shown in equation (1).

[0009] c + 0.1 mm ≤ H ≤ c + 0.5 mm (1)

[0010] 2. Design Guidelines for Precast Reinforcing Block Cell Forming Tooling

[0011] The aforementioned prefabricated reinforcing block cell forming fixture is a thermoforming fixture used to pre-form the outline of the reinforcing block cell based on a flat raw material. Its overall configuration is divided into an upper mold and a lower mold. The forming surface of the upper mold is generally flat, with protrusions made at the corresponding positions of the proposed reinforcing block cells. The forming surface of the lower mold is also generally flat, with depressions made at the corresponding positions of the proposed reinforcing block cells. The outer dimensions and height of the protrusions and the outer dimensions and depth of the depressions are all determined based on the already determined dimensions of the proposed prefabricated reinforcing block cells.

[0012] The bottom of the precast reinforcing block rib cell should have a chamfer of approximately R5 to suppress excessive stress concentration at the bottom of the rib cell during the subsequent final component forming.

[0013] 3. Fabrication of precast reinforcing block rib cells

[0014] The flat sheet is placed in the prefabricated reinforcing block forming fixture, and the prefabricated reinforcing block rib is formed by thermoforming. Then, the reinforcing block is placed into the prefabricated reinforcing block rib, ensuring that the reinforcing block is about 0.1 to 0.5 mm lower than the height of the rib, so as to facilitate the fixing of the reinforcing block during subsequent forming. The upper surface of the reinforcing block is coated with a weld stop agent. The outer skin is placed on the skin of the prefabricated reinforcing block rib, and the inner and outer skins are sealed by laser welding using the external corner joint method to form a prefabricated integral part.

[0015] 4. Integral component SPF / DB forming

[0016] (1) After the prefabricated integral part with the sealing weld is placed on the SPF / DB forming fixture, it is put into the forming furnace together. The inert gas path connection of the reinforcing block rib and the two skins and the tooling contact surface is completed. First, it is extracted from the reinforcing block rib cell to complete the tight contact of the inner surface of the skin. The furnace temperature is raised to complete the diffusion connection of the reinforcing block and inner skin of the prefabricated integral part and the skin contact area other than the prefabricated rib cell.

[0017] (2) Inert gas is injected into the precast rib cell and the gap between the outer surface of the rib cell and the cavity. The flow rate of the inert gas is adjusted and the pressure of the two external inert gases is controlled during the forming process. Under the action of the inert gas pressure, the forming of the reinforcing block rib cell is completed. The forming process should be carried out at a uniform rate to avoid the forming rate being too fast, which will cause the thin wall to become unstable under stress and eventually produce tearing defects.

[0018] (3) After the superplastic forming process of the component is completed, inert gas is introduced into the reinforcing block and the two skin and tooling contact surfaces to ensure a certain pressure until the component cools down to room temperature, so as to avoid the component from being dented due to the sudden drop in air pressure when the component is in a high temperature state.

[0019] Beneficial effects of the present invention

[0020] This invention proposes a precise forming method for thin-walled components with built-in reinforcing blocks. It employs pre-forming and final forming processes in synergy. First, pre-formed ribs are manufactured by thermoforming, and then the final component is manufactured by SPF / DB process. The presence of pre-formed ribs improves the stability of the reinforcing block fixation, and enhances the welding rate and quality consistency of the diffusion connection between the reinforcing block and the skin. By controlling the protrusion height of the reinforcing block, the final sagging and shrinkage defects of the component are suppressed, thereby improving the overall forming quality of the component. Attached Figure Description

[0021] Figure 1 Schematic diagram of a thin-walled component with built-in reinforcing blocks;

[0022] Figure 2 Schematic diagram of prefabricated reinforcing ribs;

[0023] Figure 3 For prefabricated reinforcing rib cell formation;

[0024] Figure 4 Schematic diagram of prefabricated integral component;

[0025] Figure 5 SPF / DB molding diagram.

[0026] In the figure: 1 is the pneumatic skin panel; 2 is the non-pneumatic skin panel; 3 is the built-in reinforcing block; 4 is the prefabricated reinforcing block rib; 5 is the rib protrusion plane; 6 is the virtual cross section; 7 is the corner at the bottom of the rib; 8 is the upper mold of the prefabricated reinforcing block rib forming fixture; 9 is the lower mold of the prefabricated reinforcing block rib forming fixture; 10 is the protrusion of the upper mold of the prefabricated reinforcing block rib forming fixture; 11 is the depression of the upper mold of the prefabricated reinforcing block rib forming fixture; 12 is the outer skin; 13 is the prefabricated integral part; 14 is the upper mold of the SPF / DB forming fixture; 15 is the lower mold of the SPF / DB forming fixture. Detailed Implementation

[0027] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. The following examples are used to illustrate the present invention, but are not intended to limit the scope of application of the present invention.

[0028] Built-in reinforcing thin-walled components such as Figure 1 As shown, its overall structure consists of three parts: a pneumatic skin panel 1, a non-pneumatic skin panel 2, and an internal reinforcing block 3. The specific forming and manufacturing steps are as follows:

[0029] Step 1: Determine the specifications of the precast reinforcing block reinforcement cells

[0030] Open the digital model of the proposed component in the 3D modeling software, measure the thickness c of the reinforcing block 3 to be 8mm, and calculate the height H of the precast reinforcing block rib cell 4 according to formula (1) to be 8.1~8.5mm. Determine to take 8.5mm. In the digital model of the component, construct a virtual section 6 based on the rib cell protrusion plane 5. At this time, the outline of the segmented body is the outline of the precast reinforcing block rib cell 4. And the corner 7 at the bottom of the precast reinforcing block rib cell needs to be preset as R5 chamfer.

[0031] Step 2: Design of tooling for prefabricated reinforcing block rib cell forming

[0032] The forming tooling for the precast reinforcing block rib cell is divided into two parts: an upper mold 8 and a lower mold 9. The forming surface of the upper mold 8 has a protrusion 10 that is consistent with the shape of the precast reinforcing block at the corresponding position of the cell of the proposed reinforcing block. The forming surface of the lower mold 9 has a depression 11 that is consistent with the shape of the precast reinforcing block at the corresponding position of the cell of the proposed reinforcing block.

[0033] Step 3: Fabrication of prefabricated reinforcing cells

[0034] The flat sheet is placed in the prefabricated reinforcing block forming fixture, and the prefabricated reinforcing block rib cell 4 is formed by thermoforming process. Then, the reinforcing block 3 is placed in the prefabricated reinforcing block rib cell, ensuring that the reinforcing block is about 0.1 to 0.5 mm lower than the height of the rib cell. The upper surface of the reinforcing block 3 is coated with anti-weld flux. The outer skin 12 is placed above the skin of the prefabricated reinforcing block rib cell, and the inner and outer skins are sealed by laser welding using the outer corner joint method to form the prefabricated integral part 13.

[0035] Step 4: SPF / DB forming of the integral component

[0036] (1) Place the prefabricated integral part 13 with the sealing weld completed between the upper mold 14 and the lower mold 15 of the SPF / DB forming fixture, and put them into the forming furnace together to complete the connection of the inert gas path at the reinforcing block rib and the two skins and the tooling contact surface. First, extract it from the reinforcing block rib cell to complete the tight contact of the inner surface of the skin. Raise the furnace temperature to complete the diffusion connection of the reinforcing block and inner skin of the prefabricated integral part and the skin contact area other than the prefabricated rib cell.

[0037] (2) Inert gas is injected into the precast rib cell and the gap between the outer surface of the rib cell and the cavity. The flow rate of the inert gas is adjusted and the pressure of the inert gas on both sides is controlled during the forming process. Under the action of the inert gas pressure, the forming of the reinforcing block rib cell is completed. The forming process should be carried out at a uniform rate to avoid the forming rate being too fast, which will cause the thin wall to become unstable under stress and eventually produce tearing defects.

[0038] (3) After the superplastic forming process of the component is completed, inert gas is introduced into the reinforcing block and the two skin and tooling contact surfaces to ensure a certain pressure until the component cools down to room temperature, so as to avoid the component from being dented due to the sudden drop in air pressure when the component is in a high temperature state.

Claims

1. A method for precise forming of thin-walled components with built-in reinforcing blocks, characterized in that, The steps are as follows: Step 1: Design the prefabrication tooling for reinforcing block rib forming based on the dimensions of the built-in reinforcing block and the specifications of the thin-walled skin, and design the SPF / DB final forming tooling based on the final shape requirements of the component; Step 2: After the precast reinforcement cells are formed, place the reinforcing block at the precast reinforcement cells, determine the coating area of ​​the anti-weld flux, and complete the coating of the anti-weld flux. Step 3: Laser welding and sealing of the cavities of the inner and outer skins before superplastic forming of the component to form a prefabricated integral part; The fourth step is to place the precast integral part after forming into the SPF / DB final forming fixture and fix it into the SPF / DB forming equipment. Connect each control air path, control the gas flow rate and the on / off of each air flow path, and complete the SPF / DB forming of the final component. In the first step, the specifications of the precast reinforcing block rib cells are determined as follows: The prefabricated reinforcing block rib cell is part of the final component reinforcing block rib cell. The outer contour dimensions of the prefabricated reinforcing block rib cell are determined based on the planned height H of the prefabricated reinforcing block rib cell. After determining the height H of the prefabricated reinforcing block rib cell, a virtual cross section is constructed by measuring the height H of the final component reinforcing block rib cell towards the skin side with the rib cell protrusion plane as the reference. The outer contour of the segmented body is the outer contour of the prefabricated reinforcing block rib cell. The height H of the prefabricated reinforcing block rib cell is determined by the thickness c of the reinforcing block, and the two should satisfy the relationship shown in equation (1). c+0.1 mm≤H≤c+0.5 mm (1).

2. The method for precise forming of a thin-walled component with built-in reinforcing blocks as described in claim 1, characterized in that, In the first step, the prefabricated reinforcing block rib forming tooling is a thermoforming tooling. Its overall configuration is divided into an upper mold and a lower mold. The forming surface of the upper mold is generally flat, and a protrusion is made at the corresponding position of the proposed reinforcing block rib. The forming surface of the lower mold is also generally flat, and a depression is made at the corresponding position of the proposed reinforcing block rib. The outer dimensions and height of the protrusion and the outer dimensions and depth of the depression are all determined according to the already determined dimensions of the proposed prefabricated reinforcing block rib. The bottom of the precast reinforcing block rib cell should have a chamfer of approximately R5 to suppress excessive stress concentration at the bottom of the rib cell during the subsequent final component forming.

3. The precise forming method for a thin-walled component with built-in reinforcing blocks as described in claim 1, characterized in that, The manufacturing method of the prefabricated reinforcing block rib cell is as follows: The flat sheet is placed in the prefabricated reinforcing block forming fixture, and the prefabricated reinforcing block rib is formed by thermoforming. Then, the reinforcing block is placed into the prefabricated reinforcing block rib, ensuring that the reinforcing block is about 0.1 to 0.5 mm lower than the height of the rib, so as to facilitate the fixing of the reinforcing block during subsequent forming. The upper surface of the reinforcing block is coated with anti-weld flux. The outer skin is placed on the skin of the prefabricated reinforcing block rib, and the inner and outer skins are sealed by laser welding using the external corner joint method to form a prefabricated integral part.

4. The method for precise forming of a thin-walled component with built-in reinforcing blocks as described in claim 2, characterized in that, The manufacturing method of the prefabricated reinforcing block rib cell is as follows: The flat sheet is placed in the prefabricated reinforcing block forming fixture, and the prefabricated reinforcing block rib is formed by thermoforming. Then, the reinforcing block is placed into the prefabricated reinforcing block rib, ensuring that the reinforcing block is about 0.1 to 0.5 mm lower than the height of the rib, so as to facilitate the fixing of the reinforcing block during subsequent forming. The upper surface of the reinforcing block is coated with anti-weld flux. The outer skin is placed on the skin of the prefabricated reinforcing block rib, and the inner and outer skins are sealed by laser welding using the external corner joint method to form a prefabricated integral part.

5. The method for precise forming of a thin-walled component with built-in reinforcing blocks as described in any one of claims 1 or 4, characterized in that, The SPF / DB forming method is as follows: (1) After the prefabricated integral part with the sealing weld is placed on the SPF / DB forming fixture, it is put into the forming furnace together. The inert gas path connection of the reinforcing block rib and the two skins and the tooling contact surface is completed. First, it is extracted from the reinforcing block rib cell to complete the tight contact of the inner surface of the skin. The furnace temperature is raised to complete the diffusion connection of the reinforcing block and inner skin of the prefabricated integral part and the skin contact area other than the prefabricated rib cell. (2) Inert gas is injected into the precast ribs and the gap between the outer surface of the ribs and the cavity, and the flow rate of the inert gas is adjusted to control the pressure of the two external inert gases during the forming process. (3) After the superplastic forming process of the component is completed, inert gas is introduced into the reinforcing block and the two skin and tooling contact surfaces to ensure that the pressure is maintained until the component cools to room temperature.

6. The method for precise forming of a thin-walled component with built-in reinforcing blocks as described in claim 2, characterized in that, The SPF / DB forming method is as follows: (1) After the prefabricated integral part with the sealing weld is placed on the SPF / DB forming fixture, it is put into the forming furnace together. The inert gas path connection of the reinforcing block rib and the two skins and the tooling contact surface is completed. First, it is extracted from the reinforcing block rib cell to complete the tight contact of the inner surface of the skin. The furnace temperature is raised to complete the diffusion connection of the reinforcing block and inner skin of the prefabricated integral part and the skin contact area other than the prefabricated rib cell. (2) Inert gas is injected into the precast ribs and the gap between the outer surface of the ribs and the cavity, and the flow rate of the inert gas is adjusted to control the pressure of the two external inert gases during the forming process. (3) After the superplastic forming process of the component is completed, inert gas is introduced into the reinforcing block and the two skin and tooling contact surfaces to ensure that the pressure is maintained until the component cools to room temperature.

7. The method for precise forming of a thin-walled component with built-in reinforcing blocks as described in claim 3, characterized in that, The SPF / DB forming method is as follows: (1) After the prefabricated integral part with the sealing weld is placed on the SPF / DB forming fixture, it is put into the forming furnace together. The inert gas path connection of the reinforcing block rib and the two skins and the tooling contact surface is completed. First, it is extracted from the reinforcing block rib cell to complete the tight contact of the inner surface of the skin. The furnace temperature is raised to complete the diffusion connection of the reinforcing block and inner skin of the prefabricated integral part and the skin contact area other than the prefabricated rib cell. (2) Inert gas is injected into the precast ribs and the gap between the outer surface of the ribs and the cavity, and the flow rate of the inert gas is adjusted to control the pressure of the two external inert gases during the forming process. (3) After the superplastic forming process of the component is completed, inert gas is introduced into the reinforcing block and the two skin and tooling contact surfaces to ensure that the pressure is maintained until the component cools to room temperature.

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