Method for controlling corner of triangular region of titanium alloy four-layer structure superplastic forming diffusion bonding

Abstract

A control method for a titanium alloy four-layer structure superplastic forming / diffusion bonding triangular area fillet, belonging to the field of precision plastic processing, comprising: making a solder resist pattern for a core layer and a skin; processing a strip; positioning the core layer and the skin according to the solder resist pattern and the structure of the four-layer structure, applying the solder resist, and fixing the strip to the diffusion bonding position of the skin inner surface corresponding to the core layer to obtain a four-layer plate blank; edge welding the four-layer plate blank, and welding the core layer vent block and the skin vent block to the four-layer plate blank to obtain a post-welding four-layer plate; installing the post-welding four-layer plate into a mold, heating the mold to a superplastic forming / diffusion bonding temperature; after the mold is heated, applying pressure to the mold to seal the mold cavity; superplastic forming / diffusion bonding; and in the last stage of the superplastic forming / diffusion bonding, reducing or even closing the triangular area through the core layer vent pipe. The titanium alloy four-layer structure superplastic forming / diffusion bonding triangular area fillet can be reduced or even eliminated.

Description

Technical Field

[0001] This invention belongs to the field of precision plastic forming and relates to a method for controlling the fillet radius of the diffusion bonding triangular region in the superplastic forming of a four-layer titanium alloy structure. This method is mainly used in the diffusion bonding process of a four-layer titanium alloy structure during superplastic forming. Background Technology

[0002] The hollow four-layer structure of titanium alloy is a typical lightweight integral structure, which is difficult to manufacture using conventional methods. Superplastic forming diffusion bonding technology utilizes the fact that the optimal superplastic temperature and optimal diffusion bonding temperature of titanium alloy are the same. It achieves diffusion bonding and superplastic forming of the sheet metal within a single heating cycle, enabling the integral manufacturing of the hollow four-layer structure. The superplastic forming diffusion bonding process of the titanium alloy four-layer structure mainly includes three steps: the first step is diffusion bonding of the core layer to connect the core layer ribs; the second step is superplastic forming of the core layer to form the core layer and reinforcing ribs; the third step is diffusion bonding between the core layer and the skin to connect the core layer to the skin after superplastic molding. The hollow vertical ribs in the four-layer structure are formed by bonding two adjacent cells during the superplastic forming process of the core layer. Because the two adjacent cells of the core layer cannot completely close in the final stage of bonding to the skin, a triangular area is formed at this location. The size of the triangular area affects both quality and precision, and also reduces the performance of the part. Therefore, controlling or even eliminating the size of the superplastic forming diffusion bonding triangular area is particularly important. Summary of the Invention

[0003] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a method for controlling the fillet radius of the diffusion connection triangle region in the superplastic forming of a four-layer titanium alloy structure. This method can reduce or even eliminate the fillet radius of the triangle region after diffusion connection in the superplastic forming of a four-layer titanium alloy structure, thereby improving the performance of the parts and ensuring product quality and precision.

[0004] The technical solution of this invention is:

[0005] A method for controlling the fillet radius of the diffusion bonding triangle region in the superplastic forming of a four-layer titanium alloy structure, including:

[0006] S1: Cut and manufacture two core layers and two skin layers for the four-layer structure, and make solder resist patterns according to the structure of the four-layer structure;

[0007] S2: Process the strips according to the triangular cross-sectional shape of the four-layer structure;

[0008] S3: According to the solder resist pattern and the four-layer structure, position the core layer and skin, apply solder resist, and fix the strip to the diffusion connection point of the core layer on the inner surface of the skin to obtain the four-layer plate blank;

[0009] S4: edge-welding the four-layer plate blank, and welding the core vent block and the skin vent block to the four-layer plate blank, ensuring that one end of the core vent block communicates with the cavities between the two core layers, and the other end connects the core vent pipe; one end of the skin vent block simultaneously communicates with the cavities between the upper skin and the upper core layer and the cavities between the lower skin and the lower core layer, and the other end connects the upper and lower skin vent pipes, to obtain the post-weld four-layer plate;

[0010] S5: installing the post-weld four-layer plate into the mold, and heating the mold to the superplastic forming / diffusion bonding temperature of the four-layer structure material;

[0011] S6: after the mold is heated, mechanical pressure is applied to the mold to seal the mold cavity; superplastic forming and diffusion bonding of the post-weld four-layer plate are performed, and in the last stage of superplastic forming and diffusion bonding, the core vent pipe is used to reduce or even close the triangular area.

[0012] The mold comprises an upper mold and a lower mold, the upper mold is provided with an upper cavity and a sealing stem, the sealing stem is located outside the upper cavity for sealing between the upper cavity and the lower cavity; the lower mold is provided with a lower cavity opposite to the upper cavity, and grooves for accommodating the core vent block and the skin vent block.

[0013] The upper mold is further provided with an upper exhaust hole and an upper exhaust pipe, the upper exhaust pipe communicates with the space of the upper cavity through the upper exhaust hole for exhaust and vacuumization of the upper cavity; the lower mold is further provided with a lower exhaust hole and a lower exhaust pipe, the lower exhaust pipe communicates with the space of the lower cavity through the lower exhaust hole for exhaust and vacuumization of the lower cavity.

[0014] The lower mold is provided with a pressing block, the pressing block comprises a skin pipe pressing block and a core layer pipe pressing block, and two grooves are arranged, the skin vent pipe is pressed in one groove by the skin pipe pressing block, and the core vent pipe is pressed in the other groove by the core layer pipe pressing block.

[0015] The sealing stem is arranged to press against the outer edges of the core vent block and the skin vent block.

[0016] The thickness of the pressing block is arranged to be 2mm higher than the mold surface after assembly, when the mold is closed, the pressing block is subjected to upsetting plastic deformation under the pressure of the upper mold and is completely embedded in the groove of the lower mold at the superplastic forming temperature, so as to seal the lower mold cavity.

[0017] The superplastic forming and diffusion bonding of the post-weld four-layer plate in step S6 comprises, in sequence: diffusion bonding between the core layers;

[0018] superplastic forming of the core layer and diffusion bonding between the core layer and the skin;

[0019] reduction or even closure of the triangular area.

[0020] The diffusion connection between the core layers comprises: introducing 2MPa high pressure argon into the skin air pipe, and maintaining the pressure for 2 hours to realize the diffusion connection between the core layers.

[0021] After the diffusion connection of the core layers is completed, the air pressure in the skin air pipe is unloaded to 0.1MPa-0.2MPa, and 1.5MPa-2.5MPa high pressure argon is introduced into the core layer air pipe, and the pressure is maintained for 60min-120min to realize the superplastic forming of the core layer and the diffusion connection between the core layer and the skin.

[0022] The 3 / 4 time of the pressure maintaining for 60min-120min, the upper exhaust pipe, the lower exhaust pipe and the skin air pipe are vacuumed, and the core layer continues to be maintained at 1.5MPa-2.5MPa, to realize the reduction or even closure of the triangular area.

[0023] In summary, the present application at least includes the following beneficial technical effects:

[0024] Through the method, the triangular area of the titanium alloy four-layer structure superplastic forming diffusion connection can be reduced or even eliminated. Compared with the conventional method, the triangular area can be reduced or closed, thereby improving the comprehensive mechanical properties of the product; the defects such as groove and depression caused by the too large triangular area can be avoided, thereby improving the profile accuracy of the product; finally, the method can improve the qualified rate of the four-layer structure superplastic forming diffusion connection, thereby shortening the processing cycle and reducing the production cost. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a schematic diagram of the overall structure of the titanium alloy four-layer structure superplastic forming diffusion connection mold;

[0026] Figure 2 It is a schematic diagram of the structure of the upper mold;

[0027] Figure 3 It is a schematic diagram of the structure of the lower mold;

[0028] Figure 4 It is a schematic diagram of the structure of the titanium alloy four-layer structure;

[0029] Figure 5 The upper diagram is a schematic diagram of the assembly of the four-layer structure and the mold, Figure 5 The lower diagram is a schematic diagram of the assembly of the four-layer structure, which is hidden, and the position of the sealing stem and the core layer air block and the skin air block;

[0030] Figure 6 It is a schematic diagram of the connection of the four-layer structure air pipe;

[0031] Figure 7 The upper diagram is a schematic diagram of the overall structure of the upper core layer and the lower core layer, Figure 7 The lower diagram is a schematic diagram of the assembly relationship between the triangular area and the strip block.

[0032] Explanation of reference numerals in the attached drawings: 1. Upper mold; 11. Upper vent pipe; 12. Upper vent hole; 13. Upper cavity; 14. Sealing pin;

[0033] 2. Lower mold; 21. Lower vent pipe; 22. Lower vent hole; 23. Lower cavity; 24. Skin tube pressing block; 25. Core tube pressing block;

[0034] 31. Lower skin; 32. Lower core layer; 33. Upper core layer; 34. Upper skin;

[0035] 41. Core layer vent block; 42. Core layer vent pipe; 43. Skin vent block; 44. Skin vent pipe;

[0036] 5. Strips; 6. Four-layer slab blanks. Detailed Implementation

[0037] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments:

[0038] This invention addresses the superplastic forming diffusion bonding process of a four-layer titanium alloy structure. This embodiment proposes a method for controlling the rounded corners of the triangular region in the superplastic forming diffusion bonding of a four-layer TA15 titanium alloy structure.

[0039] First, such as Figure 4 As shown, the four-layer titanium alloy structure includes two core layers and two skins located outside the two core layers, namely, the lower skin 31, the lower core layer 32, the upper core layer 33, and the upper skin 34 arranged in sequence. The lower core layer 32 and the upper core layer 33 have opposite stiffening plates on their opposite sides.

[0040] like Figures 1-3 As shown, the mold controlling the rounded corners of the triangular area mainly consists of an upper mold 1 and a lower mold 2. The upper mold 1 includes four upper vent pipes 11, four upper vent holes 12, a sealing rod 14, and an upper cavity 13. The sealing rod 14 is located around the outside of the upper cavity 13. The upper vent pipes 11 communicate with the upper cavity 13 through the upper vent holes 12. The lower mold 2 includes four lower vent pipes 21, four lower vent holes 22, and a lower cavity 23. The lower vent pipes 21 communicate with the lower cavity 23 through the lower vent holes 22. The four-layer titanium alloy structure is located within the cavity formed by the upper cavity 13 of the upper mold 1 and the lower cavity 23 of the lower mold 2.

[0041] The four corners of the upper cavity 13 have four exhaust holes of the upper die 1, and the four exhaust holes of the upper die 1 are communicated with four exhaust pipes outside the mold, for exhausting and vacuumizing the upper cavity 13. The four corners of the lower cavity 23 have four exhaust holes of the lower die 2, and the four exhaust holes of the lower die 2 are communicated with four exhaust pipes outside the mold, for exhausting and vacuumizing the lower cavity 23. In order to realize sealing, a sealing stem 14 is arranged on the upper die 1. The lower die 2 is provided with a pressing block for sealing assembly of the four-layer structure core layer pipe and the skin pipe vent block.

[0042] As shown in Figure 5 In order to realize sealing of the upper and lower die 2 cavities in cooperation with the sealing stem 14, the four-layer structure core layer and skin venting device are arranged in the form of a vent block, and the vent block specifically includes a core layer vent pipe 42 and a skin vent block 43. One end of the core layer vent block 41 is communicated with the cavity between the two core layers, and one end is connected with the core layer vent pipe 42, so as to realize venting of the core layer cavity. One end of the skin vent block 43 is communicated with the cavities between the upper skin 34 and the upper core layer 33 and between the lower skin 31 and the lower core layer 32, and one end is connected with the skin vent pipe 44, so as to realize venting of the upper and lower skin 31 cavities. As shown in Figure 3 Specifically, the pressing block arranged on the lower die 2 includes a skin pipe pressing block 24 and a core layer pipe pressing block 25. The lower die 2 is provided with a groove, and the core layer pipe pressing block 25 and the skin pipe pressing block 24 are arranged in the groove. The core layer vent pipe 42 is clamped between the core layer pipe pressing block 25 and the bottom of the groove, and the skin vent pipe 44 is clamped between the skin pipe pressing block 24 and the bottom of the groove. The skin pipe pressing block 24 and the core layer pipe pressing block 25 support the core layer vent pipe 42 and the skin vent pipe 44, and at the same time, improve the sealing performance of the outer periphery of the core layer vent pipe 42 and the skin vent pipe 44.

[0043] As shown in Figure 6 Due to the existence of the sealing stem 14, the upper die 1 cavity can be sealed after the mold is closed under high temperature and high pressure. In order to realize sealing of the lower die 2 cavity, the sealing stem 14 is arranged to press the outer edge of the core layer vent block 41 and the skin vent block 43, and the vent holes of the two vent blocks are all within the sealing stem 14, so as to ensure that the gas can enter the internal area of the sealing stem 14. The thickness of the pressing block is arranged to be 2mm higher than the mold surface after assembly. When the mold is closed, the pressing block is subjected to upsetting plastic deformation under the pressure of the upper die 1 and is completely embedded in the groove of the lower die 2, so as to realize sealing of the lower die 2 cavity. After the upper and lower die 2 cavities are sealed, the upper die 1 cavity and the lower die 2 cavity can be vacuumized through the upper exhaust pipe 11 and the lower exhaust pipe 21.

[0044] As shown in Figure 7As shown, in order to realize the control of the corner of the triangular area of the superplastic forming and diffusion bonding, the present application firstly carries out the preparation of the core layer resist pattern when carrying out the superplastic forming and diffusion bonding of the titanium alloy four-layer structure; then carries out the processing and positioning of the strip block 5, and when the strip block 5 is positioned, the strip block 5 needs to be fixed to the diffusion bonding position of the corresponding core layer on the inner surface of the upper and lower skins 31 according to the resist pattern, so as to extrude the strip block 5 in the triangular area when the upper and lower core layers 32 are superplastically formed and die attached, and realize the reduction or closure of the triangular area; then carries out the edge welding of the four-layer plate and the welding of the core layer and the skin vent block 43; finally, carries out the superplastic forming and diffusion bonding of the four-layer plate, and in the last stage of the superplastic forming and diffusion bonding, the upper exhaust pipe 11, the lower exhaust pipe 21 and the skin vent pipe 44 can be simultaneously vacuumized, and the core layer is connected to high gas pressure, so as to realize the reduction or even closure of the triangular area.

[0045] The specific method steps are as follows:

[0046] Firstly, blanking, making a double-layer plate resist pattern. The blanking of two core layers and two skins is carried out in the form of laser cutting. Then, the resist pattern is made according to the internal structure of the model.

[0047] Secondly, the processing of the strip block 5 is carried out. The processing of the strip block 5 is realized by machining, and the cross section of the strip block 5 should be designed and processed according to the cross section shape of the triangular area.

[0048] Thirdly, the positioning of the strip block 5 is carried out. When the strip block 5 is positioned, it needs to be fixed to the diffusion bonding position of the corresponding core layer on the inner surface of the upper and lower skins 31 according to the resist pattern.

[0049] Fourthly, edge welding. The edge welding of the upper and lower skins 31 and the upper and lower core layers 32 is carried out. The core layer vent block 41 and the skin vent block 43 are welded to the four-layer plate blank 6, so as to ensure that one end of the core layer vent block 41 is communicated with the cavity between the two core layers, and one end of the core layer vent pipe 42 is connected; one end of the skin vent block 43 is communicated with the cavities between the upper skin 34 and the upper core layer 33 and between the lower skin 31 and the lower core layer 32, and one end of the skin vent pipe 44 is connected.

[0050] Fifthly, mold assembling and temperature rising. The four-layer plate blank after welding is installed on the lower die 2, at this time, the vent blocks and the vent pipes should be placed in the grooves of the lower die 2, and the vent pipes are pressed by the pressing block; finally, the upper die 1 is closed. The mold is heated to 920-930℃, which is the superplastic forming / diffusion bonding temperature of TA15 titanium alloy.

[0051] Sixthly, diffusion bonding between core layers. After the mold is heated, a mechanical pressure of 4MPa is applied to the upper die 1, so that the upper and lower die 2 cavities are sealed; at the same time, 2MPa high pressure argon gas is introduced into the skin vent pipe 44, and the pressure is maintained for 2 hours to realize the diffusion bonding between the core layers.

[0052] The superplastic forming of the core layer and the diffusion bonding of the core layer and the skin. After the diffusion bonding of the core layer is completed, the air pressure in the skin vent pipe 44 is unloaded to 0.1 MPa, and 2 MPa high-pressure argon is introduced into the core layer vent pipe 42, and the pressure is maintained for 2 hours to realize the superplastic forming of the core layer and the diffusion bonding of the core layer and the skin; after the superplastic forming and diffusion bonding pressure maintaining is completed for 1.5 hours, the upper exhaust pipe 11, the lower exhaust pipe 21 and the skin vent pipe 44 are simultaneously vacuumized, and the core layer continues to maintain 2 MPa for 0.5 hours, so as to realize the reduction or even closure of the triangular area.

[0053] Although the present application is disclosed with the preferred embodiments as above, it is not intended to limit the present application, and any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present application, therefore, the protection scope of the present application should be defined by the scope of the claims of the present application.

Claims

1. A method for controlling the corner of the triangular region of a four-layer structure of a titanium alloy superplastic formed diffusion bonded, characterized in that: Comprising S1: blanking to make two core layers and two skins of four-layer structure, and making solder resist pattern according to the structure of four-layer structure; S2: processing strip block (5) according to the cross-sectional shape of the triangular area of four-layer structure; S3: positioning core layer and skin according to solder resist pattern and the structure of four-layer structure, applying solder resist, and fixing strip block (5) to the inner surface of skin corresponding to the diffusion connection of core layer, to obtain four-layer plate blank (6); S4: edge welding four-layer plate blank (6), and welding core layer vent block (41) and skin vent block (43) to four-layer plate blank (6), to ensure that one end of core layer vent block (41) communicates with the cavity between two core layers, and the other end connects core layer vent pipe (42); one end of skin vent block (43) simultaneously communicates with the cavities between upper skin (34) and upper core layer (33) and between lower skin (31) and lower core layer (32), and the other end connects upper and lower skin vent pipe (44), to obtain post-welding four-layer plate; S5: installing post-welding four-layer plate into mold, and heating mold to superplastic forming diffusion connection temperature of four-layer structure material; S6: after the mold is heated, mechanical pressure is applied to the mold to seal the mold cavity; superplastic forming diffusion connection of post-welding four-layer plate is performed, and in the last stage of superplastic forming diffusion connection, the triangular area is reduced or even closed through core layer vent pipe (42); The superplastic forming diffusion connection of post-welding four-layer plate of step S6 comprises in sequence: diffusion connection between core layers; superplastic forming of core layer and diffusion connection between core layer and skin; reduction or even closure of triangular area; The diffusion connection between core layers comprises: high-pressure argon gas of 1.5 MPa-2.5 MPa is introduced into skin vent pipe, and pressure is maintained to realize diffusion connection between core layers; After the diffusion connection between core layers is completed, the pressure in skin vent pipe (44) is unloaded to 0.1 MPa-0.2 MPa, and high-pressure argon gas of 1.5 MPa-2.5 MPa is introduced into core layer vent pipe (42), and pressure is maintained for 60 min-120 min to realize superplastic forming of core layer and diffusion connection between core layer and skin; At 3 / 4 of the pressure maintaining for 60 min-120 min, vacuum is drawn on upper exhaust pipe (11), lower exhaust pipe (21) and skin vent pipe (44), and core layer continues to maintain pressure of 1.5 MPa-2.5 MPa, to realize reduction or even closure of triangular area; The mold comprises upper mold (1) and lower mold (2), and upper mold (1) comprises upper exhaust pipe (11), and lower mold (2) comprises lower exhaust pipe (21).

2. The method of claim 1, wherein: Upper mold (1) is provided with upper cavity (13) and sealing stem (14), and sealing stem (14) is located outside upper cavity (13) to seal between upper cavity (13) and lower cavity (23); lower mold (2) is provided with lower cavity (23) opposite to upper cavity (13), and recess for accommodating core layer vent block (41) and skin vent block (43).

3. The method of claim 2, wherein: The upper die (1) is further provided with an upper exhaust hole (12), and an upper exhaust pipe (11) is communicated with the space of the upper cavity (13) through the upper exhaust hole (12) for exhausting and vacuumizing the upper cavity (13); the lower die (2) is further provided with a lower exhaust hole (22), and a lower exhaust pipe (21) is communicated with the space of the lower cavity (23) through the lower exhaust hole (22) for exhausting and vacuumizing the lower cavity (23).

4. The method of claim 2, wherein: The lower die (2) is provided with a pressing block, which comprises a skin pipe pressing block (24) and a core layer pipe pressing block (25), and two grooves are arranged, the skin pipe pressing block (24) presses the skin vent pipe (44) in one groove, and the core layer pipe pressing block (25) presses the core layer vent pipe (42) in the other groove.

5. The method of claim 2, wherein: The sealing stem (14) is arranged to press the outer edges of the core layer vent block (41) and the skin vent block (43).

6. The method of claim 4, wherein: The thickness of the pressing block is arranged to be 1.5mm-2.5mm higher than the die surface after assembly, when the die is closed, the pressing block is subjected to upsetting plastic deformation under the pressure of the upper die (1) and is completely embedded in the groove of the lower die (2) at the superplastic forming temperature, so as to realize the sealing of the cavity of the lower die (2).

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