Titanium alloy block blank isothermal forming construction method based on diffusion bonding

Abstract

The invention discloses a titanium alloy block blank isothermal forming construction method based on diffusion bonding, and belongs to the technical field of metal material machining. According to the titanium alloy block blank isothermal forming construction method based on diffusion bonding, diffusion bonding of two or more large titanium alloy casting and forging raw materials is achieved through the isothermal forming process, and the problems that traditional smelting raw materials are limited in size and prone to generating defects, and traditional welding causes low connecting strength, stress concentration and the like are solved; according to the invention, material performance stability, residual stress inhibition under isothermal conditions, structure isotropy and excellent high-temperature performance can be realized; the structure is light in weight and high in strength, a heat affected zone of traditional welding is avoided, and the high specific strength characteristic of titanium alloy is kept; the three bottlenecks of many raw material defects, low connection strength and poor forming efficiency of a large titanium alloy component are solved through isothermal field cooperation and diffusion-plasticity coupling mechanisms, and an efficient and reliable solution is provided for aerospace high-end equipment manufacturing.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material processing, and in particular relates to an isothermal forming construction method of a titanium alloy block blank based on diffusion bonding. Background Art

[0002] Titanium alloy has good thermal stability and welding performance, moderate room temperature or high temperature strength and good high temperature plasticity. It is an advanced structural material widely used in the aerospace field. Diffusion bonding technology is an important forming method for complex integral structural parts. It not only meets the structural design and manufacturing requirements but also has the advantages of improving material utilization. Therefore, scholars at home and abroad have conducted research on titanium alloy diffusion bonding technology.

[0003] Chinese invention patent CN101392363A, “A method for low-temperature vacuum diffusion bonding of titanium alloys,” uses magnetron sputtering to sputter a nanoscale film layer on the surface of the sample to reduce the diffusion bonding temperature, successfully obtaining TA15 and TC4 diffusion bonded joints. However, due to high cost and size limitations, it is difficult to apply in industrial manufacturing processes. The metal construction method proposed in Chinese invention patent CN105618506, “Metal construction forming method,” is a non-isothermal forming technology for cold mold hot billets, while the present invention uses an isothermal forming construction method for hot mold hot billets, which is more suitable for forming metal billets with narrow processing windows such as titanium alloys. Chinese invention patent CN44006393, “A method for isothermal near-net forming of a TC4 titanium alloy aircraft engine integral blade disk,” improves the performance of the TC4 blade disk through multi-stage isothermal forging, but does not involve diffusion bonding construction of bulk billets. Chinese invention patent CN118848192A, "A mechanical diffusion bonding superplastic forming integrated die and forming method," mentions the die design and forming method for diffusion bonding and superplastic forming of multi-layer hollow structures, but does not address diffusion bonding and superplastic forming of large bulk billets. Chinese invention patent CN118682261A, "A mechanical / pneumatic composite diffusion bonding superplastic forming method for dissimilar titanium alloys," addresses the issue of diffusion resistance in hollow internal structures of difficult-to-diffuse titanium alloys through a mechanical / pneumatic composite diffusion bonding superplastic forming process, but does not address diffusion bonding and superplastic forming of large bulk billets.

[0004] Defects in raw materials for large titanium alloy castings and forgings: Due to limitations of traditional smelting equipment, the casting size of raw materials for large castings and forgings is limited, and shrinkage cavities and segregation are prone to occur; integrated forming is difficult: Currently, complex structural parts require multi-component welding or mechanical connection, resulting in low interface strength (such as welded joint strength is only 60% of the parent material), increased weight, and the risk of stress concentration; low process efficiency: conventional rolling connection has high energy consumption and short mold life, which increases costs in industrial production. Summary of the Invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the present invention provides a method for isothermal forming and constructing titanium alloy block billets based on diffusion bonding; the present invention realizes diffusion bonding of two or even multiple large titanium alloy casting and forging raw materials through an isothermal forming process, thereby solving the problems of limited size and easy defects of traditional smelting raw materials, low connection strength and stress concentration caused by traditional welding, and improving production efficiency and product quality.

[0006] A method for isothermal forming of a titanium alloy block billet based on diffusion bonding is specifically completed in the following steps:

[0007] 1. Construction of large titanium alloy block billets:

[0008] Two or more titanium alloy block billets are subjected to surface activation treatment to obtain a clean and flat metal interface, and then arranged together, and then spot welded around the connection surface to prevent relative movement, thereby obtaining a large titanium alloy block billet that is initially fixed by spot welding;

[0009] 2. Vacuum diffusion connection:

[0010] The connection surface of the large titanium alloy block blank that has been initially fixed by spot welding is sealed along the outer ring, leaving only a groove for connecting the vacuum pipe; after ensuring that the vacuum pipe is connected to the inner cavity of the connection surface but completely isolated from the outside world, vacuum is performed to obtain a preform;

[0011] 3. Isothermal forging:

[0012] The vacuum-evacuated preform is forged in an isothermal forging device to achieve diffusion bonding of the titanium alloy material, so that the interfaces between the titanium alloy block billets are bonded at the atomic level to form an integrated billet, thus completing an isothermal forming construction method for titanium alloy block billets based on diffusion bonding.

[0013] Principle of the present invention:

[0014] The present invention provides a method for isothermal forming of titanium alloy block billets based on diffusion bonding, which realizes diffusion bonding of two or even multiple large titanium alloy casting and forging raw materials through an isothermal forming process. By simultaneously applying a high temperature and high pressure isothermal forming process to the titanium alloy billets, the metal surface structure of the connection surface can be restored and statically recrystallized, and the recrystallized grains nucleate and grow at the connection interface, thereby promoting the complete fusion of the metals on both sides to achieve diffusion bonding.

[0015] Advantages of the present invention:

[0016] 1. The present invention provides a method for isothermal forming of titanium alloy block billets based on diffusion bonding. The method achieves diffusion bonding of two or more large titanium alloy casting and forging raw materials through an isothermal forming process, thereby solving the problems of limited size and easy defects of traditional smelting raw materials, low connection strength and stress concentration caused by traditional welding, and improving production efficiency and product quality.

[0017] Second, this invention achieves material performance stability: Isothermal conditions suppress residual stress, resulting in isotropic microstructure and excellent high-temperature performance. Lightweight and high-strength structures: Diffusion bonding forms a metallurgical bond, avoiding the heat-affected zone of traditional welding and maintaining the high specific strength of titanium alloys. Through the mechanisms of "isothermal field synergy" (mold / blank is at the same temperature) and "diffusion-plastic coupling" (SPF / DB synchronization), it addresses the three major bottlenecks of large titanium alloy components: numerous raw material defects, low connection strength, and poor forming efficiency.

[0018] 3. This invention solves the problems of raw material defects and forming size of large titanium alloy castings and forgings through the integrated process of "block construction-isothermal shaping". Compared with traditional technologies, the material utilization rate is increased by 35% and the overall cost is reduced by 40%, providing an efficient and reliable solution for the manufacturing of high-end aerospace equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of a unit after stacking the titanium alloy block billets in Example 1;

[0020] Figure 2 This is the morphology and organization diagram of the TC4ELI titanium alloy base material before diffusion bonding in Example 1;

[0021] Figure 3 This is a morphology and organization diagram of the connection surface of the TC4ELI titanium alloy unit after diffusion bonding in Example 1;

[0022] Figure 4 This is a diagram of the mechanical properties of the TC4ELI titanium alloy unit connection surface after diffusion bonding in Example 1;

[0023] Figure 5 Provide ultrasonic scanning test weld rate report;

[0024] Figure 6 This is the morphology and organization diagram of the connection surface of the Ti60 titanium alloy unit after diffusion bonding in Example 2. DETAILED DESCRIPTION

[0025] Specific embodiment 1: This embodiment is a method for isothermal forming of a titanium alloy block billet based on diffusion bonding, which is specifically completed in the following steps:

[0026] 1. Construction of large titanium alloy block billets:

[0027] Two or more titanium alloy block billets are subjected to surface activation treatment to obtain a clean and flat metal interface, and then arranged together, and then spot welded around the connection surface to prevent relative movement, thereby obtaining a large titanium alloy block billet that is initially fixed by spot welding;

[0028] 2. Vacuum diffusion connection:

[0029] The connection surface of the large titanium alloy block blank that has been initially fixed by spot welding is sealed along the outer ring, leaving only a groove for connecting the vacuum pipe; after ensuring that the vacuum pipe is connected to the inner cavity of the connection surface but completely isolated from the outside world, vacuum is performed to obtain a preform;

[0030] 3. Isothermal forming forging:

[0031] The vacuum-evacuated preform is forged in an isothermal forging device to achieve diffusion bonding of the titanium alloy material, so that the interfaces between the titanium alloy block billets are bonded at the atomic level to form an integrated billet, thus completing an isothermal forming construction method for titanium alloy block billets based on diffusion bonding.

[0032] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the weight of a single titanium alloy block billet in step 1 is greater than 5 tons. The other steps are the same as those in specific embodiment 1.

[0033] Specific embodiment 3: This embodiment differs from specific embodiment 1 or 2 in that the titanium alloy block blank described in step 1 is TC4ELI alloy or Ti60 alloy. The other steps are the same as specific embodiment 1 or 2.

[0034] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the titanium alloy block material in step 1 is a cast billet, a forged billet, or a rolled billet. The other steps are the same as those in specific embodiments 1 to 3.

[0035] Specific Embodiment 5: This embodiment differs from Specific Embodiments 1 to 4 in that the surface activation treatment method described in step 1 is: first, the surface of the titanium alloy block is machined to a smooth and bright surface, then dust and impurities are cleaned with an organic solvent, and then the oxide layer and impurities are removed by acid or alkaline washing. Finally, the surface is rinsed with water and dried. The other steps are the same as Specific Embodiments 1 to 4.

[0036] Specific embodiment 6: This embodiment differs from specific embodiments 1 to 5 in that, in step 1, two or more titanium alloy block blanks are cut into cuboids or cylinders, which are then stacked into a large-sized cuboid or cylinder with their edges aligned. The other steps are the same as specific embodiments 1 to 5.

[0037] Specific Embodiment 7: This embodiment differs from Specific Embodiments 1 to 6 in that the ratio of the height to width or thickness of the large rectangular parallelepiped or cylinder does not exceed 3:1; and the spot welding on the four sides of the connecting surface described in step 1 includes welds in at least four directions. The other steps are the same as Specific Embodiments 1 to 6.

[0038] Specific embodiment eight: The difference between this embodiment and specific embodiments one to seven is that in step two, vacuuming is performed after ensuring that the vacuumed pipe is connected to the inner cavity of the connection surface but completely isolated from the outside world, and the vacuum degree is 10 -3 ~10 - 1 MPa, and a preform is obtained. The other steps are the same as those in the first to seventh embodiments.

[0039] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that, in step 2, the connection surfaces of the large titanium alloy block blank, initially fixed by spot welding, are seal-welded along the outer ring, with the weld depth of the seal-welded interface being at least greater than 10 mm. The other steps are the same as specific embodiments 1 to 8.

[0040] Specific Embodiment 10: This embodiment differs from Specific Embodiments 1 to 9 in that the forging process described in step 3 is as follows: Under vacuum conditions, the temperature is first raised from room temperature to 840-900°C at a heating rate of 8-10°C / min, then to 0.8-0.9°C at a heating rate of 3-5°C / min. A hydraulic pump is then activated to apply pressure, which is maintained for 1-8 hours, followed by cooling to room temperature in the furnace. The applied pressure is calculated as 20 kg / cm². The other steps are the same as Specific Embodiments 1 to 9.

[0041] The following examples are used to verify the beneficial effects of the present invention:

[0042] Example 1: A method for isothermal forming of a titanium alloy block blank based on diffusion bonding is specifically completed by the following steps:

[0043] 1. Construction of large titanium alloy block billets:

[0044] Two TC4ELI titanium alloy ingots with a size of Φ160×100mm were selected as units, and then surface activation treatment was performed on them to obtain a clean and flat metal interface. They were then stacked into a large-scale cylinder with the edges aligned, as shown in Figure 2. Figure 1As shown, a hole with a diameter of Φ8×60mm is machined at the height of h / 2 on the upper piece to facilitate the subsequent installation of the temperature measuring thermocouple, and then spot welding is performed around the connecting surface to prevent relative movement. At the same time, a hole with a diameter of Φ6×10mm is milled out with a milling machine, and the position is just above the hole for installing the thermocouple on the connecting surface to facilitate the installation of the vacuum tube during subsequent vacuuming, thereby obtaining a large titanium alloy block blank that is initially fixed by spot welding.

[0045] The TC4ELI titanium alloy ingot described in step 1 is a casting blank;

[0046] The surface activation treatment method described in step 1 is as follows: first, the surface of the TC4ELI titanium alloy block blank is processed to be flat and bright (roughness Ra ≤ 0.8) by mechanical processing, then the dust and impurities on the surface are cleaned with acetone, and then the oxide layer and impurities are removed by pickling, and finally, the surface is rinsed with water and blown dry;

[0047] The acid used in the pickling step 1 is a mixture of HF and water, wherein the volume ratio of HF to water is 2:8;

[0048] The four-sided spot welding described in step 1 has welding spots in at least four directions;

[0049] 2. Vacuum diffusion connection:

[0050] A circle of cold welding is performed on the large titanium alloy block blank that has been initially fixed by spot welding, and only the groove is reserved for connecting the vacuum pipe. To ensure the sealing, a 50A current and a 1mm diameter welding wire are used. Then, the thermocouple and vacuum tube are installed and welded firmly. The connection surface is vacuumed through the vacuum tube to increase the tightness. After ensuring that the vacuum pipe is connected to the inner cavity of the connection surface but completely isolated from the outside world, vacuum is performed and the vacuum degree is guaranteed to be 10 -3 ~10 -1 MPa, and a preform is obtained;

[0051] In step 2, a circle of seal welding is performed on the connection surface of the large titanium alloy block blank that is initially fixed by spot welding, and the welding depth of the seal welding interface is 10 mm;

[0052] 3. Isothermal forging:

[0053] The vacuum-evacuated preform is forged in an isothermal forging device to achieve diffusion bonding of the titanium alloy material, so that the interfaces between the titanium alloy block billets are bonded at the atomic level to form an integrated billet, and a diffusion-bonded TC4ELI titanium alloy unit is obtained, completing a method for isothermal forming of titanium alloy block billets based on diffusion bonding.

[0054] The forging process described in step three is: in a vacuum state, first heat the temperature from room temperature to 840°C at a heating rate of 10°C / min, then heat the temperature to 900°C at a heating rate of 5°C / min, start the hydraulic pump to apply pressure and keep the temperature and pressure for 2 hours, and finally cool to room temperature with the furnace; the applied pressure is calculated as 20 kg per square centimeter.

[0055] Figure 2 This is the morphology and organization diagram of the TC4ELI titanium alloy base material before diffusion bonding in Example 1;

[0056] Figure 3 This is a morphology and organization diagram of the connection surface of the TC4ELI titanium alloy unit after diffusion bonding in Example 1;

[0057] from Figure 3 It can be seen that the morphology and organization diagram of the connection surface of the TC4ELI titanium alloy unit after diffusion bonding shows that there is no original interface at the interface, the overall interface is well bonded, and no defects such as holes are found.

[0058] Figure 4 This is a diagram of the mechanical properties of the TC4ELI titanium alloy unit connection surface after diffusion bonding in Example 1;

[0059] Figure 4 The shear mechanical properties test is carried out in different areas from the center to the edge. Figure 4 The mechanical properties diagram of the TC4ELI titanium alloy unit connection surface after diffusion bonding shows good tensile strength and shear strength.

[0060] Figure 5 Provide ultrasonic scanning test weld rate report;

[0061] from Figure 5 It can be seen from the ultrasonic scanning detection welding rate report that the diffusion bonding welding rate of titanium alloy units is relatively high, which meets the actual industrial production requirements.

[0062] Example 2: A method for isothermal forming of a titanium alloy block blank based on diffusion bonding is specifically completed in the following steps:

[0063] 1. Construction of large titanium alloy block billets:

[0064] Two Ti60 titanium alloy ingots with a size of Φ100×50mm were selected as units, and then surface activation treatment was performed on them to obtain a clean and flat metal interface. They were then stacked into a large-scale cylinder with the edges aligned, as shown in Figure 2. Figure 1As shown, a hole with a diameter of Φ8×60mm is machined at the height of h / 2 on the upper piece to facilitate the subsequent installation of the temperature measuring thermocouple, and then spot welding is performed around the connecting surface to prevent relative movement. At the same time, a hole with a diameter of Φ6×10mm is milled out with a milling machine, and the position is just above the hole for installing the thermocouple on the connecting surface to facilitate the installation of the vacuum tube during subsequent vacuuming, thereby obtaining a large titanium alloy block blank that is initially fixed by spot welding.

[0065] The Ti60 titanium alloy ingot described in step 1 is a casting blank;

[0066] The surface activation treatment method described in step 1 is as follows: first, the surface of the Ti60 titanium alloy block blank is processed to be flat and bright (roughness Ra ≤ 0.8) by mechanical processing, then the dust and impurities on the surface are cleaned with acetone, and then the oxide layer and impurities are removed by pickling, and finally, the surface is rinsed with water and blown dry;

[0067] The acid used in the pickling step 1 is a mixture of HF and water, wherein the volume ratio of HF to water is 2:8;

[0068] The four-sided spot welding described in step 1 has welding spots in at least four directions;

[0069] 2. Vacuum diffusion connection:

[0070] A circle of cold welding is performed on the large titanium alloy block blank that has been initially fixed by spot welding, and only the groove is reserved for connecting the vacuum pipe. To ensure the sealing, a 50A current and a 1mm diameter welding wire are used. Then, the thermocouple and vacuum tube are installed and welded firmly. The connection surface is vacuumed through the vacuum tube to increase the tightness. After ensuring that the vacuum pipe is connected to the inner cavity of the connection surface but completely isolated from the outside world, vacuum is performed and the vacuum degree is guaranteed to be 10 -3 ~10 -1 MPa, and a preform is obtained;

[0071] In step 2, a circle of seal welding is performed on the connection surface of the large titanium alloy block blank that is initially fixed by spot welding, and the welding depth of the seal welding interface is 10 mm;

[0072] 3. Isothermal forging:

[0073] The vacuum-evacuated preform is forged in an isothermal forging device to achieve diffusion bonding of the titanium alloy material, so that the interfaces between the titanium alloy block billets are bonded at the atomic level to form an integrated billet, thereby obtaining a diffusion-bonded Ti60 titanium alloy unit, thus completing a method for isothermal forming of titanium alloy block billets based on diffusion bonding.

[0074] The forging process described in step three is: in a vacuum state, first heat the temperature from room temperature to 860°C at a heating rate of 8°C / min, then heat the temperature to 920°C at a heating rate of 3°C / min, start the hydraulic pump to apply pressure and keep the temperature and pressure for 2 hours, and finally cool to room temperature with the furnace; the applied pressure is calculated as 20 kg per square centimeter.

[0075] Figure 6 This is the morphology and organization diagram of the connection surface of the Ti60 titanium alloy unit after diffusion bonding in Example 2.

[0076] from Figure 6 It can be seen from the morphology and organization diagram of the Ti60 titanium alloy unit connection surface after diffusion bonding that there is no original interface at the interface, the overall interface is well bonded, and no defects such as holes are found.

Claims

1. A method for isothermal forming of titanium alloy block blanks based on diffusion bonding, characterized in that The method is specifically completed according to the following steps:

1. Construction of large titanium alloy block billets: Two or more titanium alloy block billets are subjected to surface activation treatment to obtain a clean and flat metal interface, and then arranged together, and then spot welded around the connection surface to prevent relative movement, thereby obtaining a large titanium alloy block billet that is initially fixed by spot welding; 2. Vacuum diffusion connection: The connection surface of the large titanium alloy block blank that has been initially fixed by spot welding is sealed along the outer ring, leaving only a groove for connecting the vacuum pipe; after ensuring that the vacuum pipe is connected to the inner cavity of the connection surface but completely isolated from the outside world, vacuum is performed to obtain a preform; 3. Isothermal forming forging: The vacuum-evacuated preform is forged in an isothermal forging device to achieve diffusion bonding of the titanium alloy material, so that the interfaces between the titanium alloy block billets are bonded at the atomic level to form an integrated billet, thus completing an isothermal forming construction method for titanium alloy block billets based on diffusion bonding.

2. The isothermal forming method for titanium alloy block blanks based on diffusion bonding according to claim 1 is characterized in that The weight of a single titanium alloy block blank in step 1 is greater than 5 tons.

3. The isothermal forming method for titanium alloy block blanks based on diffusion bonding according to claim 1 is characterized in that The titanium alloy block blank described in step 1 is TC4ELI alloy or Ti60 alloy.

4. The isothermal forming method for titanium alloy block blanks based on diffusion bonding according to claim 1 is characterized in that The titanium alloy block billet described in step 1 is a cast billet, a forged billet or a rolled billet.

5. The isothermal forming method for titanium alloy block blanks based on diffusion bonding according to claim 1, characterized in that The surface activation treatment method described in step 1 is: first, the surface of the titanium alloy block blank is processed to be smooth and bright by mechanical processing, then the dust and impurities on the surface are cleaned with an organic solvent, and then the oxide layer and impurities are removed by acid washing or alkali washing, and finally, it is rinsed with water and blown dry.

6. The isothermal forming method for titanium alloy block blanks based on diffusion bonding according to claim 1 is characterized in that In step 1, two or more titanium alloy block blanks are cut into cuboids or cylinders, and then stacked into large-sized cuboids or cylinders with their edges aligned.

7. The isothermal forming method for titanium alloy block blanks based on diffusion bonding according to claim 1, characterized in that The ratio of the height to the width or thickness of the large-sized rectangular parallelepiped or cylinder does not exceed 3:1; the spot welding around the connecting surface in step 1 has welding spots in at least four directions.

8. The isothermal forming method for titanium alloy block blanks based on diffusion bonding according to claim 1, characterized in that In step 2, after ensuring that the vacuum pipe is connected to the inner cavity of the connection surface but completely isolated from the outside world, vacuum is performed, and the vacuum degree is 10 -3 ~10 -1 MPa, and a preform is obtained.

9. The isothermal forming method for titanium alloy block blanks based on diffusion bonding according to claim 1, characterized in that In step 2, the connection surface of the large titanium alloy block blank that is initially fixed by spot welding is seal-welded along the outer ring, and the welding depth of the seal-welded interface is at least greater than 10 mm.

10. The isothermal forming method for titanium alloy block blanks based on diffusion bonding according to claim 1, characterized in that The forging process described in step 3 is as follows: in a vacuum state, first heat the temperature from room temperature to 840~900℃ at a heating rate of 8~10℃ / min, then heat the temperature to 0.8~0.9Tm at a heating rate of 3~5℃ / min, start the hydraulic pump to apply pressure and keep the temperature and pressure for 1h~8h, and finally cool to room temperature with the furnace; the applied pressure is calculated as 20kg per square centimeter.

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