A method for preparing a large-size thin-walled double-layer titanium alloy nozzle

Abstract

This invention provides a method for manufacturing a large-size thin-walled double-layer titanium alloy nozzle, mainly solving the technical problems of low efficiency and difficulty in guaranteeing precision in traditional manufacturing methods. The method includes: preparing blanks; machining the blanks into corresponding arc-shaped structures using a thermal creep process; removing excess material from both sides of the width direction of each blank and welding them to obtain an inner tube blank and an outer tube blank; spraying a heat-protective coating onto the inner and outer wall surfaces of the inner and outer tube blanks; performing profile correction on the inner and outer tube blanks; profile inspection; removing excess material from both ends of the length direction of the inner and outer tube blanks; removing the heat-protective coating from the surfaces of the inner and outer tube blanks to obtain a semi-finished inner tube and a semi-finished outer tube; performing non-destructive testing on the semi-finished inner and outer tubes; and assembling the semi-finished inner and outer tubes to obtain a large-size thin-walled double-layer titanium alloy nozzle. Compared with traditional manufacturing methods, this invention improves both processing efficiency and processing precision.

Description

Technical Field

[0001] This invention relates to a method for manufacturing rocket engine nozzles, specifically to a method for preparing a large-size thin-walled double-layer titanium alloy nozzle. Background Technology

[0002] Nozzles are crucial components for guiding flowing media and are widely used in aviation, aerospace, and energy fields. In certain specific applications, double-layered nozzles are required to adapt to varying temperature and pressure conditions. Currently, titanium alloys are commonly used for nozzles due to their lightweight and high strength. However, the manufacturing of titanium alloy nozzles, especially large-diameter double-layered titanium alloy nozzles, remains a significant challenge for the manufacturing industry.

[0003] The traditional manufacturing method for double-layer titanium alloy nozzles involves machining the inner and outer layers separately and then assembling them. However, because the inner and outer layers are machined using independent tooling, design errors in the tooling, as well as machining and part forming errors, can easily lead to significant deviations in the surface profiles of the formed inner and outer layers, making it difficult to meet subsequent application requirements. Furthermore, since all tooling needs to be manufactured individually, the processing cycle is long and manufacturing efficiency is low. In addition, because double-layer titanium alloy nozzles are mostly large-size, thin-walled structures, they require extremely high machining precision. Traditional methods cannot guarantee the required precision and are prone to deformation and cracking. Therefore, developing a method for simultaneous precision forming of the inner and outer walls of large-size, thin-walled double-layer titanium alloy nozzles is of great significance for improving the manufacturing efficiency and product quality of nozzles. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problems of low efficiency, difficulty in ensuring accuracy, and easy occurrence of deformation and cracks in traditional double-layer titanium alloy nozzle manufacturing methods, and to provide a method for preparing large-size thin-walled double-layer titanium alloy nozzles.

[0005] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0006] A method for preparing a large-size thin-walled double-layer titanium alloy nozzle, characterized by the following steps:

[0007] Step 1: Based on the size requirements of the nozzle and the width of a single blank, prepare a corresponding number of blanks; the blanks include multiple inner tube blanks and multiple outer tube blanks. Each blank is a flat plate structure that is wide at one end and narrow at the other, and there is a margin on all four sides.

[0008] Step 2: Using a thermal creep process, each inner tube blank and outer tube blank is machined into an arc-shaped structure with a pre-set arc cross-section.

[0009] Step 3: Based on Step 2, the excess material on both sides of the width direction of each inner tube blank and each outer tube blank is removed by machining, and then welded in sequence to obtain hollow conical inner tube blank and outer tube blank.

[0010] Step 4: Spray a heat-protective coating onto the inner and outer wall surfaces of each inner tube blank and outer tube blank respectively;

[0011] Step 5: Place the inner tube blank and the outer tube blank in the same straightening mold in sequence, and perform surface correction on the inner tube blank and the outer tube blank with the sprayed heat protection coating simultaneously through the thermoforming process.

[0012] Step 6: Perform surface inspection on the inner tube blank and outer tube blank after surface correction. If the inspection is qualified, proceed to step 7; otherwise, return to step 5 and adjust the hot forming temperature.

[0013] Step 7: Remove the excess material at both ends of the inner tube blank and the outer tube blank along their length by machining.

[0014] Step 8: Remove the heat protection coating from the surface of the inner tube blank and the outer tube blank after removing the excess material to obtain the inner tube semi-finished product and the outer tube semi-finished product.

[0015] Step 9: Perform composition analysis on the surfaces of the inner tube semi-finished product and the outer tube semi-finished product to determine whether the heat protection coating has been effectively removed. If the analysis is qualified, proceed to step 10; otherwise, return to step 7 to remove the heat protection coating on the surfaces of the inner tube blank and the outer tube blank again.

[0016] Step 10: Assemble the inner tube semi-finished product and the outer tube semi-finished product to obtain a large-size thin-walled double-layer titanium alloy nozzle.

[0017] Further, in step 1, the number of the blanks... ,in, C This indicates the circumference of the large end of the nozzle. D This indicates the width of the wider end of the corresponding blank, and the length of the blank is adapted to the length of the nozzle.

[0018] Further, step 3 specifically involves, based on step 2, firstly removing the excess material on both sides of the width direction of each inner tube blank and each outer tube blank by machining, then pairing all the blanks in sequence according to the principle of similar wall thickness, then machining the seam edges of each blank, and finally welding the paired blanks in sequence to obtain the inner tube blank and the outer tube blank.

[0019] Furthermore, in step 3, the gap between the seam edges of two adjacent blanks is ≤0.1mm; the welding adopts laser welding process.

[0020] Furthermore, in step 3, when removing the excess material on both sides of the width direction of each inner tube blank and each outer tube blank, a tolerance allocation technique is used to adjust the cutting dimension tolerance of the last blank.

[0021] Furthermore, in step 4, the inner tube blank and the outer tube blank are made of the same material, and a heat protection material containing graphite and silicon dioxide is used as the heat protection coating on the inner and outer wall surfaces of each inner tube blank and the outer tube blank, and the thickness of the heat protection coating is 0.05~0.1mm.

[0022] Step 5 specifically involves placing the inner tube blank and the outer tube blank coated with the heat-protective coating into the same pre-prepared calibration mold, and then placing them together with the calibration mold into a thermoforming furnace. The furnace is first heated to a preset temperature and held for 2-3 hours, then cooled to below 40°C and removed, thereby completing the simultaneous calibration of the inner tube blank and the outer tube blank. The preset temperature is the recommended annealing temperature of the materials selected for the inner tube blank and the outer tube blank minus 100°C.

[0023] Furthermore, in step 4, the inner tube blank and the outer tube blank are made of the same material, and a heat-protective material containing boron nitride is used as the heat-protective coating on the inner and outer wall surfaces of each inner tube blank and the outer tube blank, and the thickness of the heat-protective coating is 0.05~0.1mm.

[0024] Step 5 specifically involves placing the inner tube blank and the outer tube blank coated with the heat-protective coating into the same pre-prepared calibration mold, and then placing them together with the calibration mold into a thermoforming furnace. The furnace is first heated to a preset temperature and held for 2-3 hours, and then cooled to below 40°C before being removed, thereby completing the simultaneous calibration of the inner tube blank and the outer tube blank. The preset temperature is below the temperature of the material selected for the inner tube blank and the outer tube blank, which has the lower phase transformation temperature.

[0025] Furthermore, in step 6, the surface inspection includes using an inner and outer wall powder coating method to inspect the surface fitting gap between the inner tube blank and the outer tube blank, and using a pressing and tapping method to inspect the surface quality of the inner tube blank and the outer tube blank.

[0026] Furthermore, in step 7, the excess material at both ends of the inner tube blank and the outer tube blank in the length direction is removed by flame cutting or turning.

[0027] Furthermore, in step 8, the heat-protective coating is removed by water blowing or polishing.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. This invention involves sequentially subjecting inner and outer tube blanks to thermal creep, width-direction allowance removal, and welding steps to obtain hollow conical inner and outer tube blanks. Then, through spraying a heat-protective coating, profile correction, profile inspection, length-direction allowance removal, and removal of the heat-protective coating, simultaneously forming inner and outer tube semi-finished products are obtained. Finally, the inner and outer tube semi-finished products are assembled to obtain a large-size thin-walled double-layer titanium alloy nozzle that meets the required dimensions and precision. Compared to traditional manufacturing methods, this invention improves both processing efficiency and processing precision.

[0030] 2. This invention eliminates the deformation problems that may occur in traditional splicing methods by synchronous forming, avoids cracking and other problems during the forming process, and greatly improves the product qualification rate.

[0031] 3. In the process of profile correction, this invention achieves synchronous precision manufacturing of the inner and outer walls of the nozzle by precisely controlling the forming temperature and time, and simultaneously cooling the inner and outer tubes. This solves the problem of differences in the inner and outer wall profiles after forming in traditional manufacturing methods.

[0032] 4. To ensure the surface smoothness of the product, the present invention selects a corresponding high-temperature resistant coating material to spray a heat protection coating on the inner and outer wall surfaces of each inner tube blank and outer tube blank, so as to prevent the titanium alloy material from oxidizing during the hot forming process, thereby ensuring product quality.

[0033] 5. The surface composition detection of the inner tube semi-finished product and the outer tube semi-finished product before assembly is a non-destructive test according to the present invention. This test method will not cause any damage to the product, thereby improving the product quality. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure in step 2 of the present invention, in which the inner tube blank is processed into a cross-section with a preset arc shape;

[0035] Figure 2 This is a schematic diagram of the hollow conical inner tube blank structure obtained in step 3 of the present invention.

[0036] Figure 3 This is a schematic diagram of the structure of the calibration mold used in step 5 of the present invention. Detailed Implementation

[0037] To make the objectives, advantages, and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0038] Example 1

[0039] This embodiment provides a method for preparing a large-size thin-walled double-layer titanium alloy nozzle, including the following steps:

[0040] Step 1: Determine the dimensions of the inner and outer tube blanks based on the size requirements of the nozzle, and then prepare the corresponding number of blanks based on the width of a single blank.

[0041] The blanks described in this embodiment include multiple inner tube blanks and multiple outer tube blanks, each blank being a flat plate structure that is wider at one end and narrower at the other. The number of inner tube blanks and outer tube blanks... N The calculation is performed using the following formula:

[0042]

[0043] in, C This indicates the circumference of the large end of the nozzle. D This indicates the width of the wider end of the corresponding blank, and the length of the blank is adapted to the length of the nozzle.

[0044] The nozzle to be prepared in this embodiment is used in a liquid rocket engine. The nozzle is a conical cylindrical structure with one end larger than the other. The opening diameter of the larger end is generally ≥1800mm, and the length of the nozzle is ≥1400mm. The inner and outer tubes of the nozzle can be of the same thickness or different thicknesses, but the total thickness of the inner and outer tubes must be ≤6mm. The surface difference between the finished inner and outer tubes is ≤0.1mm, and the wall thickness difference between different parts of the inner and outer tubes after forming is ≤0.2mm.

[0045] Based on the usage environment and required functions of the inner and outer walls of the nozzle, this embodiment selects TA15 titanium alloy as the inner and outer tube blanks, with thicknesses of 3.5mm and 1.1mm respectively. The thickness can be tested using ultrasonic testing to ensure the raw materials meet requirements. Additionally, each blank has a allowance of approximately 30mm in both length and width. The nozzle's large end opening diameter is 1800mm, and the nozzle length is 1600mm. Based on this, the number of inner and outer tube blanks in this embodiment is... N They were each designated as 6.

[0046] Step 2: Using a thermal creep process, each inner tube blank and outer tube blank is machined into an arc-shaped structure with a pre-defined arc cross-section (e.g., Figure 1 As shown in the figure, the curvature of each arc structure is adapted to the profile of the corresponding position of the nozzle expansion section.

[0047] Step 3: Based on Step 2, firstly, CNC milling is used to remove the excess material on both sides of the width direction of each inner tube blank and each outer tube blank. Then, all blanks are paired sequentially according to the principle of similar wall thickness. Next, the seam edges of each blank are trimmed sequentially using a clamping method to ensure that the gap between the seam edges of two adjacent blanks is ≤0.1mm. Finally, the paired blanks are sequentially welded using laser welding to obtain the inner tube blank and the outer tube blank, as shown below. Figure 2 As shown.

[0048] In actual production, in order to ensure product quality, the quality of welds can be inspected by radiographic testing. If the welds do not meet the preset process requirements, they can be repaired or treated in other ways according to the actual welding situation.

[0049] Step 4: Spray a heat-protective coating on the inner and outer wall surfaces of each inner tube blank and outer tube blank to prevent oxidation of the titanium alloy material during subsequent hot forming. At the same time, the heat-protective coating can also play a lubricating role between the inner and outer tubes and between the inner and outer tubes and the forming mold during the forming process, preventing damage to the surfaces of the inner and outer tubes during the forming process.

[0050] In this embodiment, the thickness of the thermal protective coating is generally 0.05~0.1mm, and the thermal protective coating uses a thermal protective material containing graphite and silicon dioxide.

[0051] Step 5: Place the inner tube blank and the outer tube blank in the same straightening mold in sequence, and perform surface correction on the inner tube blank and the outer tube blank with the sprayed heat protection coating simultaneously through the thermoforming process.

[0052] Specifically, the inner tube blank and the outer tube blank, coated with a heat-protective coating, are sequentially placed into a pre-prepared shaping mold. The shaping mold is a fixture capable of simultaneously correcting the profiles of the inner and outer tube blanks, such as... Figure 3As shown, the calibration mold in this embodiment mainly includes a female mold and a male mold located inside the female mold. The male mold, inner tube blank, outer tube blank, and female mold are sequentially nested from the inside out, and finally assembled by components such as limiting devices. Afterwards, the inner tube blank and outer tube blank, together with the calibration mold, are placed into a thermoforming furnace, and then subjected to overall heating, holding, and cooling in sequence, similar to solution heat treatment. In principle, the forming temperature is approximately equal to the annealing temperature of the part minus 100°C, so that the required shape and size of the double-layer nozzle can be obtained. For example, the recommended annealing temperature for TA15 titanium alloy is 700℃~850℃, so its hot forming temperature can be selected as 600℃~750℃. In this embodiment, the temperature in the hot forming furnace is first raised to 600℃, held for 2 hours, and then cooled to below 40℃. The inner tube blank and the outer tube blank are taken out together with the forming mold to complete the surface correction. The purpose is to correct the welding deformation and the forming difference in the hot creep process of step 2, so as to ensure the final forming accuracy.

[0053] Step 6: Perform surface inspection on the inner tube blank and outer tube blank after surface correction. If the inspection is qualified, proceed to step 7; otherwise, return to step 5 and adjust the hot forming temperature to perform surface correction again.

[0054] The inspection in this embodiment mainly includes checking the surface fit gap and surface quality of the inner and outer tube blanks. The surface fit gap refers to the radial fit gap between the two blanks, and is checked using an inner and outer wall powder coating method. The surface quality of the inner and outer tube blanks mainly refers to parameters such as the circumferential curvature at various points, which must be compatible with the overall requirements of the nozzle. This can be checked using a pressure tester and a surface template. If the inspection fails, appropriate processing is performed based on the results. Generally, this involves adjusting the corresponding thermoforming temperature and returning to step 5 for thermoforming until the inspection is passed.

[0055] In this embodiment, if the test fails, the thermoforming temperature can be adjusted according to the specific test results and the heat treatment can be performed again, and the holding time can be appropriately extended until the test passes.

[0056] Since the inner tube blank and the outer tube blank are tightly bonded together after forming, with a bonding gap of <0.1mm, after passing the inspection, the inner tube blank and the outer tube blank need to be pried apart by physical methods before proceeding to the following process.

[0057] Step 7: Remove the excess material at both ends (i.e., large and small ends) of the inner tube blank and outer tube blank along their length by flame cutting or turning.

[0058] Step 8: For the inner tube blank and the outer tube blank after removing the surplus, remove the thermal protection coating on their surfaces to obtain the inner tube semi-finished product and the outer tube semi-finished product. Among them, the thermal protection coating is removed by physical methods such as water jet blasting or grinding, or by chemical methods such as alkali pickling.

[0059] Step 9: Conduct a composition detection on the surfaces of the inner tube semi-finished product and the outer tube semi-finished product to determine whether the thermal protection coating has been effectively removed. If the detection is qualified, proceed to Step 10; otherwise, return to Step 8 to remove the thermal protection coating on the surfaces of the inner tube blank and the outer tube blank again.

[0060] The specific method for conducting a composition detection on the surfaces of the inner tube and the outer tube in this embodiment is as follows: Use a composition analyzer to scan the surfaces of the inner tube and the outer tube respectively, and compare them with the standard compositions of the inner tube and the outer tube materials. If there are no extra impurities, it is considered that the surface removal is qualified. When using the composition analyzer for scanning, select the most severely oxidized parts of the surfaces of the inner tube and the outer tube, melt them for gas composition detection (standard detection method), and the contents of H and O should not be higher than the standard requirements of the raw materials. If the detected components exceed the standard, select the positions close to the edges of the inner tube and the outer tube, and conduct secondary sampling and detection. Through multiple detections at multiple positions, ensure that the thermal protection coating has been effectively removed.

[0061] Step 10: Assemble the qualified inner tube semi-finished product and the outer tube semi-finished product to obtain a large-size thin-walled double-layer titanium alloy nozzle. The assembly method can be selected according to actual needs, such as welding, mechanical connection, bonding and other processes.

[0062] It should be noted that due to the large sizes of the inner and outer walls of the large-size double-layer titanium alloy nozzle and the high precision requirements, different errors will be generated in each process during its preparation process, and the final cumulative error will exceed the design precision of the nozzle. Therefore, this embodiment adopts the tolerance distribution technology. For example: reserve a forming allowance during the forming process of the arc-shaped structure. During the subsequent surplus removal process, according to the cutting size of the processed blank parts, timely adjust the cutting size tolerance of the last blank part, so as to reasonably distribute the design precision to the processing tolerances of each process. This method can ensure the final forming precision of the nozzle and is also the key technology and necessary means to reduce the product development cost.

[0063] Embodiment 2

[0064] This embodiment provides a method for preparing a large-size, thin-walled, double-layer titanium alloy nozzle. The difference from Embodiment 1 is that this embodiment selects TC4 titanium alloy as the inner tube material and TA2 titanium alloy as the outer tube material, with thicknesses of 3.5 mm and 1.5 mm, respectively. The nozzle's large-end opening diameter is 2150 mm, and the nozzle length is 1400 mm. The surface difference between the finished inner and outer tubes is ≤0.2 mm, and the wall thickness difference between different parts of the finished inner and outer tubes after forming is ≤0.2 mm. Based on these requirements, this embodiment uses 8 inner tube blanks and 8 outer tube blanks. The specific preparation method is similar to that of Embodiment 1, but with the following differences:

[0065] In step 4, a thermal protective material containing boron nitride is used as a thermal protective coating, and the thickness of the thermal protective coating is 0.05~0.1mm, which has the same function as in Example 1.

[0066] In step 5, during the thermoforming process used for profile correction, the forming temperature is controlled below the temperature of the material with the lower phase transformation temperature of the inner and outer wall materials of the nozzle. The phase transformation temperature of TC4 material is generally 700℃~850℃, and the phase transformation temperature of TA2 material is generally 550℃~750℃. If TC4 and TA2 materials are formed simultaneously, the forming temperature of the TA2 material with the lower phase transformation temperature (e.g., 500℃) is selected as the overall forming temperature, and the holding time is appropriately extended to 3 hours to obtain the required shape and size of the double-layer nozzle.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A method for preparing a large-size thin-walled double-layer titanium alloy nozzle, characterized in that, Includes the following steps: Step 1: Based on the size requirements of the nozzle and the width of a single blank, prepare a corresponding number of blanks; the blanks include multiple inner tube blanks and multiple outer tube blanks. Each blank is a flat plate structure that is wide at one end and narrow at the other, and there is a margin on all four sides. Step 2: Using a thermal creep process, each inner tube blank and outer tube blank is machined into an arc-shaped structure with a pre-set arc cross-section. Step 3: Based on Step 2, the excess material on both sides of the width direction of each inner tube blank and each outer tube blank is removed by machining, and then welded in sequence to obtain hollow conical inner tube blank and outer tube blank. Step 4: Spray a heat-protective coating onto the inner and outer wall surfaces of each inner tube blank and outer tube blank respectively; Step 5: Place the inner tube blank and the outer tube blank in the same straightening mold in sequence, and perform surface correction on the inner tube blank and the outer tube blank with the sprayed heat protection coating simultaneously through the thermoforming process. Step 6: Perform surface inspection on the inner tube blank and outer tube blank after surface correction. If the inspection is qualified, proceed to step 7; otherwise, return to step 5 and adjust the hot forming temperature. Step 7: Remove the excess material at both ends of the inner tube blank and the outer tube blank along their length by machining. Step 8: Remove the heat protection coating from the surface of the inner tube blank and the outer tube blank after removing the excess material to obtain the inner tube semi-finished product and the outer tube semi-finished product. Step 9: Perform composition analysis on the surfaces of the inner tube semi-finished product and the outer tube semi-finished product to determine whether the heat protection coating has been effectively removed. If the analysis is qualified, proceed to step 10; otherwise, return to step 8 to remove the heat protection coating on the surfaces of the inner tube blank and the outer tube blank again. Step 10: Assemble the inner tube semi-finished product and the outer tube semi-finished product to obtain a large-size thin-walled double-layer titanium alloy nozzle.

2. The method for preparing a large-size thin-walled double-layer titanium alloy nozzle according to claim 1, characterized in that: In step 1, the number of blanks ,in, C This indicates the circumference of the large end of the nozzle. D This indicates the width of the wider end of the corresponding blank, and the length of the blank is adapted to the length of the nozzle.

3. The method for preparing a large-size thin-walled double-layer titanium alloy nozzle according to claim 1, characterized in that: Step 3 specifically involves, based on step 2, firstly removing the excess material on both sides of the width direction of each inner tube blank and each outer tube blank by machining, then pairing all the blanks in sequence according to the principle of similar wall thickness, then machining the seam edges of each blank, and finally welding the paired blanks in sequence to obtain the inner tube blank and the outer tube blank.

4. The method for preparing a large-size thin-walled double-layer titanium alloy nozzle according to claim 3, characterized in that: In step 3, the gap between the seam edges of two adjacent blanks is ≤0.1mm; the welding adopts laser welding process.

5. The method for preparing a large-size thin-walled double-layer titanium alloy nozzle according to claim 4, characterized in that: In step 3, when removing the excess material on both sides of the width direction of each inner tube blank and each outer tube blank, a tolerance allocation technique is used to adjust the cutting dimension tolerance of the last blank.

6. The method for preparing a large-size thin-walled double-layer titanium alloy nozzle according to claim 1, characterized in that: In step 4, the inner tube blank and the outer tube blank are made of the same material. A heat protection material containing graphite and silicon dioxide is used as the heat protection coating on the inner and outer wall surfaces of each inner tube blank and the outer tube blank, and the thickness of the heat protection coating is 0.05~0.1mm. Step 5 specifically involves placing the inner tube blank and the outer tube blank coated with the heat-protective coating into the same pre-prepared calibration mold, and then placing them together with the calibration mold into a thermoforming furnace. The furnace is first heated to a preset temperature and held for 2-3 hours, then cooled to below 40°C and removed, thereby completing the simultaneous calibration of the inner tube blank and the outer tube blank. The preset temperature is the recommended annealing temperature of the materials selected for the inner tube blank and the outer tube blank minus 100°C.

7. The method for preparing a large-size thin-walled double-layer titanium alloy nozzle according to claim 1, characterized in that: In step 4, the inner tube blank and the outer tube blank are made of the same material, and a heat protection material containing boron nitride is used as the heat protection coating on the inner and outer wall surfaces of each inner tube blank and the outer tube blank, and the thickness of the heat protection coating is 0.05~0.1mm. Step 5 specifically involves placing the inner tube blank and the outer tube blank coated with the heat-protective coating into the same pre-prepared calibration mold, and then placing them together with the calibration mold into a thermoforming furnace. The furnace is first heated to a preset temperature and held for 2-3 hours, and then cooled to below 40°C before being removed, thereby completing the simultaneous calibration of the inner tube blank and the outer tube blank. The preset temperature is below the temperature of the material selected for the inner tube blank and the outer tube blank, which has the lower phase transformation temperature.

8. The method for preparing a large-size thin-walled double-layer titanium alloy nozzle according to any one of claims 1 to 7, characterized in that: In step 6, the surface inspection includes using an inner and outer wall powder coating method to inspect the surface fitting gap between the inner tube blank and the outer tube blank, and using a pressing and tapping method to inspect the surface quality of the inner tube blank and the outer tube blank.

9. The method for preparing a large-size thin-walled double-layer titanium alloy nozzle according to claim 8, characterized in that: In step 7, the excess material at both ends of the inner tube blank and the outer tube blank along the length direction is removed by flame cutting or turning.

10. The method for preparing a large-size thin-walled double-layer titanium alloy nozzle according to claim 9, characterized in that: In step 8, the heat-protective coating is removed by water blowing or polishing.

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