Method for preparing aerospace TC4 ELI ultra-low temperature titanium alloy plate

Abstract

The application discloses a preparation method of a TC4ELI ultra-low-temperature titanium alloy plate for aerospace, and belongs to the technical field of titanium alloy material preparation. The preparation method of the TC4ELI ultra-low-temperature titanium alloy plate for aerospace comprises the following steps: step 1, selecting a finished product ingot with a diameter specification of phi 720 to 840*L and subjected to at least three times of melting; step 2, performing at least three times of forging treatment on the finished product ingot to obtain a finished product slab; step 3, performing at least three times of hot rolling treatment on the finished product slab to obtain a semi-finished product plate; step 4, performing annealing and polishing treatment on the semi-finished product plate to obtain a finished product plate; and step 5, performing temperature and flaw detection on the finished product plate. The forging and rolling process parameters are controlled, so that the plate has good structure and performance, the strength and toughness are improved, the work hardening and residual stress are effectively eliminated through reasonable annealing treatment, the room temperature plasticity and the ultra-low-temperature toughness of the plate are improved, and the preparation technology of the ultra-low-temperature TC4ELI titanium alloy plate for aerospace is perfected.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of titanium alloy material preparation, in particular to a preparation method of TC4ELI ultra-low-temperature titanium alloy plate for aerospace. BACKGROUND

[0002] With the continuous development of aerospace technology, the performance requirements of materials in an ultra-low-temperature environment are higher and higher. Liquid oxygen (boiling point -183 DEG C) and liquid hydrogen (boiling point -253 DEG C) or liquid oxygen kerosene are commonly used as propellant fuel in aerospace liquid fuel engines. Therefore, the titanium alloy material for aerospace ultra-low-temperature service environment (-183 DEG C, -196 DEG C and -253 DEG C) is an important research direction in the field of titanium alloy at home and abroad. The TC4ELI titanium alloy is widely used in the production of liquid rocket engine fuel tanks due to its good low-temperature performance, and has a wide application prospect in the field of aerospace.

[0003] At present, the research and use of the ultra-low-temperature titanium alloy material for aerospace mainly focus on the TA7ELI titanium alloy (Ti-5Al-2.5SnELI), and the in-depth research and preparation method of the ultra-low-temperature TC4ELI (Ti-6Al-4VELI) titanium alloy plate for aerospace are still lacking. SUMMARY

[0004] The application aims at solving the problem of the imperfect preparation technology of the ultra-low-temperature TC4ELI titanium alloy plate in the prior art, and provides a preparation method of a TC4ELI ultra-low-temperature titanium alloy plate for aerospace.

[0005] In order to achieve the above-mentioned purpose, the application adopts the following technical scheme:

[0006] The application provides a preparation method of a TC4ELI ultra-low-temperature titanium alloy plate for aerospace, which comprises the following steps:

[0007] Step 1: selecting a finished ingot with a diameter specification of phi 720-840*L, which is subjected to at least three times of melting;

[0008] Step 2: performing at least three times of forging treatment on the finished ingot to obtain a finished plate blank;

[0009] Step 3: performing at least three times of hot rolling treatment on the finished plate blank to obtain a semi-finished plate;

[0010] Step 4: performing annealing and polishing treatment on the semi-finished plate to obtain a finished plate;

[0011] Step 5: performing temperature and flaw detection on the finished plate.

[0012] Preferably, the deformation temperature formed by the forging treatment and the hot rolling treatment satisfies the form of high-high-low+high-low-low.

[0013] Preferably, the three-time forging treatment in step 2 comprises:

[0014] First time: open forging, initial forging temperature is 1050-1150℃, holding time is 6-8 hours, final forging temperature is greater than or equal to 850℃, upsetting and drawing forging, forging ratio is greater than 5, air cooling after forging;

[0015] Second time: forging blank modification, initial forging temperature is 1000-1100℃, holding time is 6-8 hours, final forging temperature is greater than or equal to 800℃, upsetting and drawing forging, forging ratio is greater than 5, air cooling after forging;

[0016] Third time: plate blank forming forging, temperature is 920-970℃, holding time is 5-7 hours, final forging temperature is greater than or equal to 800℃, forging ratio is greater than 2, to get plate blank roughcast.

[0017] Further, the plate blank roughcast is milled, single-side milling depth is greater than or equal to 5mm, then surface polishing is performed, plate blank surface roughness Ra is less than or equal to 3.2μm, to get finished plate blank.

[0018] Preferably, the finished plate blank in step 2 is subjected to ultrasonic flaw detection, and the flaw detection meets the A-level requirement of GB / T5193.

[0019] Preferably, the three-time hot rolling treatment in step 3 comprises:

[0020] First time: plate blank heating temperature is 1050-1100℃, holding time is 3.5-4.5 hours, rolling deformation is 50-65%, rolling speed is 2-3mm / s, final rolling temperature is greater than or equal to 850℃, residual temperature straightening and leveling, air cooling after rolling, surface roughness Ra is less than or equal to 3.2μm, to get first-time intermediate blank semi-finished product;

[0021] Second time: rolling first-time intermediate blank semi-finished product heating temperature is 920-970℃, holding time is 1.5-2 hours, rolling deformation is 60-70%, rolling speed is 1-2mm / s, final rolling temperature is greater than or equal to 800℃, residual temperature straightening and leveling, air cooling after rolling, surface roughness Ra is less than or equal to 3.2μm, to get second-time intermediate blank semi-finished product;

[0022] Third time: rolling second-time intermediate blank semi-finished product heating temperature is 920-970℃, holding time is 0.5-1 hours, rolling deformation is 60-70%, rolling speed is 1-2mm / s, final rolling temperature is greater than or equal to 800℃, residual temperature straightening and leveling, air cooling after rolling, to get semi-finished plate;

[0023] Preferably, the annealing treatment in step 4 is: annealing temperature is 700-800℃, holding time is 1-2 hours, air cooling, straightening and leveling after discharging.

[0024] Preferably, the surface roughness Ra of the polishing treatment in step 4 is less than or equal to 1.6 microns.

[0025] Preferably, the temperature parameters of the temperature detection of the finished plate in step 5 are 20 DEG C, -196 DEG C and -253 DEG C.

[0026] Preferably, the ultrasonic flaw detection of the finished plate in step 5 meets the AA level requirements of GB / T5193.

[0027] Compared with the prior art, the present application provides a preparation method of TC4ELI ultra-low temperature titanium alloy plate for aerospace, which has the following beneficial effects:

[0028] 1. The preparation method of TC4ELI ultra-low temperature titanium alloy plate for aerospace, by selecting a finished ingot with qualified chemical composition and subjected to 3 times of VAR melting, ensures the product quality from the raw material and ensures the stability and controllability of the subsequent processing parameters.

[0029] 2. The preparation method of TC4ELI ultra-low temperature titanium alloy plate for aerospace, by controlling the multi-fire forging and rolling process parameters, the plate obtains good organization and performance, and the strength and toughness are improved.

[0030] 3. The preparation method of TC4ELI ultra-low temperature titanium alloy plate for aerospace, by reasonable annealing treatment, effectively eliminates the work hardening and residual stress, and improves the room temperature plasticity and low temperature toughness of the plate. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The finished product diagram of the TC4ELI ultra-low temperature titanium alloy plate according to the present application;

[0032] Figure 2 The longitudinal microstructure diagram of the TC4ELI ultra-low temperature titanium alloy plate according to the present application;

[0033] Figure 3 The bending performance test diagram of the TC4ELI ultra-low temperature titanium alloy plate after annealing according to the present application;

[0034] Figure 4 The ultrasonic flaw detection waveform diagram of the TC4ELI ultra-low temperature titanium alloy plate according to the present application. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all.

[0036] Example 1:

[0037] Reference Figures 1-4The application discloses a preparation method of a TC4ELI ultra-low-temperature titanium alloy plate for aerospace, and comprises the following steps:

[0038] Step 1: selection of TC4ELI ingot components, TC4ELI titanium alloy ingots produced from high-purity titanium sponge and high-quality intermediate alloy are selected, and the main chemical components (mass fraction) of the TC4ELI titanium alloy ingots are as follows: Al: 5.5-6.8%, V: 3.5-4.5%, Fe≤0.30%, C≤0.10%, N≤0.05%, H≤0.015%, O≤0.20%, Ti balance, the product quality is ensured by selecting raw materials, and the stability and controllability of subsequent processing parameters are ensured;

[0039] Step 2: selection of the ingot, the finished ingot with a specification of φ720-840×L is selected, and the finished ingot is subjected to three times of vacuum consumable electrode arc melting and has qualified chemical components;

[0040] Step 3: determination of the plate blank preparation process, the finished ingot is subjected to three times of forging, and the process parameters of each time of forging are as follows:

[0041] Step 3.1: the first time of forging is open-die forging, the initial forging temperature of the open-die forging is 1050-1150 DEG C, the holding time is 6-8 hours, the final forging temperature is not lower than 850 DEG C, upsetting and drawing are adopted, the forging ratio is greater than 5, and the blank is air-cooled after the forging;

[0042] Step 3.2: the surface of the intermediate forged blank after the first time of open-die forging is polished to remove surface cracks, and a forged first-time forging blank semi-product is obtained;

[0043] Step 3.3: the second time of forging is upsetting of the blank, the initial forging temperature of the upsetting of the blank is 1000-1100 DEG C, the holding time is 6-8 hours, the final forging temperature is not lower than 800 DEG C, upsetting and drawing are adopted, the forging ratio is greater than 5, and the blank is air-cooled after the forging;

[0044] Step 3.4: the surface of the intermediate forged blank after the second time of upsetting of the blank is polished to remove surface cracks, and a forged second-time forging blank semi-product is obtained;

[0045] Step 3.5: the third time of forging is plate blank forming forging, the forging temperature of the plate blank forming is 920-970 DEG C, the holding time is 5-7 hours, the final forging temperature is not lower than 800 DEG C, the forging ratio is greater than 2, and the size of the plate blank blank is controlled in the range of 200-220×800-1000×1300-1500 mm;

[0046] Step 3.6: plate blank machining, the plate blank blank is machined by a milling machine, the single-side milling depth is greater than or equal to 5 mm, the oxidation layer and the pollution layer of the plate blank are removed, and then the surface is polished, the surface roughness Ra of the plate blank is less than or equal to 3.2 microns, and a forged plate blank for rolling is obtained;

[0047] Step 3.7: slab flaw detection, the ultrasonic flaw detection is carried out on the machined forging slab to ensure that the slab meets the A level of GB / T 5193, and the intermediate product flaw detection link is a quality control means before the production process is transferred, and the qualified product is a finished slab;

[0048] Step 4: plate hot rolling process, the finished slab is hot rolled for 3 times, and the process parameters of each time are as follows:

[0049] Step 4.1: the slab heating temperature of the first time is 1050-1100℃, the holding time is 3.5-4.5 hours, the deformation amount of the first time is 50-65%, the rolling pass is 8-11, the pass deformation amount is 6-15%, the rolling speed is 2-3mm / s, the final rolling temperature is not lower than 850℃, the remaining temperature is straightened and leveled, and the air cooling is carried out after rolling;

[0050] Step 4.2: the surface of the intermediate blank after the first time rolling is polished to remove surface cracks and oxide skin, the surface roughness Ra is less than or equal to 3.2μm, and the first time rolling intermediate blank semi-finished product is obtained;

[0051] Step 4.3: the second time rolling operation is to heat the first time intermediate blank semi-finished product to 920-970℃, the holding time is 1.5-2 hours, the deformation amount of the second time is 60-70%, the rolling pass is 8-11, the pass deformation amount is 6-14%, the rolling speed is 1-2mm / s, the final rolling temperature is not lower than 800℃, the remaining temperature is straightened and leveled, and the air cooling is carried out after rolling;

[0052] Step 4.4: the intermediate blank after the second time rolling is cut and discharged;

[0053] Step 4.5: the surface of the intermediate blank after discharging is polished to remove surface cracks and oxide skin, the surface roughness Ra is less than or equal to 3.2μm, and the second time rolling intermediate blank semi-finished product is obtained.

[0054] Step 4.6: the third time rolling is to heat the second time intermediate blank semi-finished product to 920-970℃, the holding time is 0.5-1 hour, the deformation of the third time is 60-70%, the rolling pass is 8-11, the pass deformation amount is 6-14%, the rolling speed is 1-2mm / s, the final rolling temperature is not lower than 800℃, the remaining temperature is straightened and leveled, and the air cooling is carried out after rolling, and the semi-finished product plate with oxide skin is obtained;

[0055] Step 5: annealing process is to anneal the semi-finished product plate with oxide skin at 700-800℃, the holding time is 1-2 hours, the straightening and leveling are carried out after discharging, and the cooling mode is air cooling;

[0056] Step 6: polishing the annealed plate, the surface roughness of the product plate is Ra≤1.6 μm, and a 2-fold size plate with smooth surface is obtained;

[0057] Step 7: cutting the 2-fold size plate after polishing into product plates with a specified size by a cold working method, and a 10*1100*2200 mm TC4ELI ultra-low temperature titanium alloy product plate for aerospace is obtained;

[0058] Step 8: performance detection: the performance of the obtained 10*1100*2200 mm product plate is detected, including the performance detection at room temperature, -196 DEG C and -253 DEG C;

[0059] Step 9: flaw detection: the ultrasonic flaw detection of the obtained 10*1100*2200 mm product plate is performed, and it is ensured that the flaw detection of the product plate meets the AA level of GB / T5193.

[0060] In the application, the TC4ELI ultra-low temperature titanium alloy plate for aerospace prepared by the above preparation technology has a tensile strength at room temperature of not less than 895 MPa, an elongation of not less than 10%, an impact toughness of not less than 45 J / cm 2 , and a bending of not less than 70 DEG; at -196 DEG C and -253 DEG C ultra-low temperature environment, the tensile strength is not less than 1324 MPa, the elongation is not less than 8%, and the impact toughness is not less than 30 J / cm 2 , which has the advantages of stable process, high product quality and good batch stability, can meet the use requirements of aerospace field in ultra-low temperature environment, and perfects the preparation technology of the ultra-low temperature TC4ELI titanium alloy plate for aerospace, and provides reliable material guarantee for the development of aerospace industry.

[0061] Example two:

[0062] Based on the example one, one of the parameter values is selected, and the specific product and test results are made, and the steps are as follows:

[0063] Step 1: selecting the TC4ELI ingot component, a TC4ELI titanium alloy ingot produced by high-purity titanium sponge and high-quality intermediate alloy is selected, and the main chemical components (mass fraction) of the TC4ELI titanium alloy ingot are as follows: Ti balance, Al: 6.0%, V: 4.0%, Fe: 0.10%, C: 0.08%, N: 0.04%, H: 0.002%, O: 0.10%;

[0064] Step 2: the selected TC4ELI ingot is prepared by three times of vacuum consumable arc furnace smelting, and the ingot with a specification of φ760*L is obtained; after the ingot blank is machined, the skin is removed, the flaw is detected, and the ingot is sawed, the finished ingot is produced;

[0065] Step 3: slab preparation process: the ingot is subjected to multi-pass open forging, and the process parameters of each pass are as follows:

[0066] Step 3.1: first pass: open forging: the initial forging temperature of open forging is 1150℃, the holding time is 7 hours, the final forging temperature is not lower than 850℃, upsetting and drawing forging, the forging ratio is greater than 5, and air cooling after forging;

[0067] Step 3.2: surface polishing is performed on the intermediate forging blank after the first pass of open forging to remove surface cracks, and a first-pass forging blank semi-finished product is obtained;

[0068] Step 3.3: second pass: forging blank modification: the initial forging temperature of the blank modification is 1050℃, the holding time is 6-7 hours, the final forging temperature is not lower than 800℃, upsetting and drawing forging, the forging ratio is greater than 5, and air cooling after forging;

[0069] Step 3.4: surface polishing is performed on the intermediate forging blank after the second pass of blank modification to remove surface cracks, and a second-pass forging blank semi-finished product is obtained;

[0070] Step 3.5: third pass: slab forming forging: the forging temperature of slab forming is 940℃, the holding time is 5 hours, the final forging temperature is not lower than 800℃, the forging ratio is greater than 2, the size of the slab blank after forming forging is controlled to be 220×890×1420mm, and air cooling after forging;

[0071] Step 3.6: slab machining: the slab blank is machined by a milling machine, the single-side milling depth is greater than or equal to 5mm, the oxidation layer and the pollution layer of the slab are removed, and then surface polishing is performed, the surface roughness of the slab is Ra≤3.2μm, and a 210×880×1400mm forging slab for rolling is obtained;

[0072] Step 3.7: slab flaw detection: ultrasonic flaw detection is performed on the machined slab to ensure that the slab meets the A-level of GB / T5193. This is an intermediate product flaw detection link and a quality control means before the production process is transferred. The qualified product is a finished slab;

[0073] Step 4: slab hot rolling process: the finished slab is subjected to 3-pass hot rolling, and the process parameters of each pass are as follows:

[0074] Step 4.1: first pass: the slab heating temperature is 1080℃, the holding time is 4 hours, the total deformation of this pass is 59%, the specification of the slab after the first pass is 86×880×3410mm, the rolling passes are 8, the deformation of each pass is 6.2%, 6.6%, 10.9%, 12.2%, 13.9%, 12.9%, 12.0%, 9.5% respectively, the rolling speed is 2-3mm / s, the final rolling temperature is not lower than 850℃, and air cooling after rolling;

[0075] Step 4.2: Surface polishing of the intermediate blank after the first rolling pass is performed to remove the surface scale, with a surface roughness Ra≤3.2μm, to obtain the first-pass intermediate blank semi-product;

[0076] Step 4.3: Second pass: the first-pass intermediate blank semi-product is heated to 930℃ for 1.5 hours, with a total deformation of 65% in this pass. After the second pass, the plate has a size of 30×880×9770mm, with 10 passes, each with a deformation of 5.8%, 7.4%, 10.7%, 13.4%, 13.8%, 12.0%, 11.4%, 10.3%, 8.6%, and 6.3%, respectively. The rolling speed is 1-2mm / s, and the final rolling temperature is not less than 800℃. The plate is straightened and leveled at room temperature after rolling, and is air-cooled after rolling;

[0077] Step 4.4: The intermediate blank after the second rolling pass is cut to a size of 30×880×2300mm;

[0078] Step 4.5: Surface polishing of the cut intermediate blank is performed to remove the surface scale, with a surface roughness Ra≤3.2μm, to obtain the second-pass intermediate blank semi-product;

[0079] Step 4.6: Third pass: the second-pass intermediate blank semi-product is heated to 930℃ for 0.6 hours, with a total deformation of 65% in this pass. The third pass is a reversing rolling pass, and after the third pass, the plate has a size of 10.5×2300×2510mm, with 10 passes, each with a deformation of 5.3%, 7.0%, 11.4%, 13.7%, 13.9%, 12.1%, 11.8%, 11.1%, 7.5%, and 5.4%, respectively. The rolling speed is 1-2mm / s, and the final rolling temperature is not less than 800℃. The plate is straightened and leveled at room temperature after rolling, and is air-cooled after rolling, to obtain the semi-product plate with scale;

[0080] Step 5: Plate annealing process: the semi-product plate with scale is annealed at 750℃ for 1 hour, and is straightened and leveled after annealing. The cooling method is air cooling;

[0081] Step 6: Plate surface polishing: the annealed plate is polished to a depth of 0.25mm on one side, with a surface roughness Ra≤1.6μm for the finished plate, to obtain the 2x size plate with a smooth surface;

[0082] Step 7: The 2x size plate after polishing is cut into finished plates of a specified size using cold working methods, to obtain the finished TC4ELI super-low-temperature titanium alloy plate for aerospace use, with a size of 10×1100×2200mm;

[0083] Step 8: plate performance detection: the performance of the finished plate with the specification of 10*1100*2200mm is detected, including the room temperature performance at 20℃ and the ultralow temperature performance detection at-196℃ and-253℃;

[0084] The following table is the room temperature (20℃) mechanical property and-196℃, -253℃ ultralow temperature mechanical property data of TC4ELI ultralow temperature titanium alloy plate after annealing:

[0085]

[0086] Step 9: plate flaw detection test: the ultrasonic flaw detection test is carried out on the finished plate to ensure that the flaw detection of the finished plate meets the AA level of GB / T5193.

[0087] In the application, the multiple forging and rolling process parameters are controlled, so that the plate obtains good organization and performance, the strength and toughness are improved, the reasonable annealing treatment effectively eliminates the work hardening and residual stress, the room temperature plasticity and low temperature toughness of the plate are improved, the TC4ELI aerospace ultralow temperature titanium alloy plate has excellent comprehensive performance, can meet the complex working condition requirements of aerospace field under ultralow temperature environment, and provides reliable material guarantee for the development of aerospace industry.

[0088] The above is only the preferred specific embodiment of the application, but the protection scope of the application is not limited to this, any skilled person in the art can make equivalent replacement or change according to the technical scheme and the inventive concept of the application within the technical range disclosed by the application, which should be covered in the protection scope of the application.

Claims

1. A method for preparing TC4ELI ultra-low temperature titanium alloy sheet for aerospace applications, characterized in that, Includes the following steps: Step 1: Select finished ingots with a diameter of φ720~840*L that have undergone at least three melting processes; Step 2: The finished ingot is forged at least three times to produce a finished slab. Step 2, the three-stage forging process includes: the first stage: billet forging, with an initial forging temperature of 1050-1150℃, a holding time of 6-8 hours, a final forging temperature greater than or equal to 850℃, upsetting and drawing forging, a forging ratio greater than 5, and air cooling after forging; Second forging: Forging billet modification, initial forging temperature is 1000-1100℃, holding time is 6-8 hours, final forging temperature is greater than or equal to 800℃, upsetting and drawing forging, forging ratio is greater than 5, and air cooling is performed after forging; Third forging: Slab forming and forging, temperature is 920-970℃, holding time is 5-7 hours, final forging temperature is greater than or equal to 800℃, forging ratio is greater than 2, to obtain slab blank; Step 3: Perform at least three hot rolling processes on the finished slab to produce semi-finished sheet material. The slab is heated to 1050-1100℃ in the first heat, and held for 3.5-4.5 hours. The deformation of the slab in this heat is 50-65%, with 8-11 passes and a deformation of 6-15% per pass. The rolling speed is 2-3 mm / s, and the final rolling temperature is greater than or equal to 850℃. The slab is then straightened and leveled with residual heat and air-cooled after rolling. The intermediate billet after the first rolling is ground and polished to remove surface cracks and oxide scale, and the surface roughness Ra≤3.2μm to obtain the semi-finished intermediate billet after the first rolling. The second rolling operation involves heating the intermediate billet semi-finished product from the first rolling operation to a temperature of 920-970℃ and holding it at that temperature for 1.5-2 hours. The deformation amount in this rolling operation is 60-70%, with 8-11 rolling passes and a deformation amount of 6-14% per pass. The rolling speed is 1-2 mm / s, and the final rolling temperature is greater than or equal to 800℃. The residual heat is used for straightening and leveling, followed by air cooling after rolling. The intermediate billet, which has been rolled in the second rolling process, is then cut and blanked. The intermediate billet after blanking is ground and polished to remove surface cracks and oxide scale, and the surface roughness Ra≤3.2μm to obtain the semi-finished intermediate billet for the second rolling process; The third rolling process involves heating the intermediate billet from the second rolling process to 920-970℃ and holding it for 0.5-1 hour. This rolling process results in a deformation of 60-70%, with 8-11 rolling passes, a deformation of 6-14% per pass, a rolling speed of 1-2 mm / s, and a final rolling temperature greater than or equal to 800℃. The billet is then straightened and leveled using residual heat, followed by air cooling to obtain a semi-finished sheet with oxide scale. Step 4: Anneal and polish the semi-finished board to produce the finished board; Step 5: Perform temperature and flaw detection tests on the finished board material.

2. The method for preparing aerospace-grade TC4ELI ultra-low temperature titanium alloy sheet according to claim 1, characterized in that, The deformation temperatures formed by forging and hot rolling meet the pattern of high-high-low + high-low-low.

3. The method for preparing aerospace-grade TC4ELI ultra-low temperature titanium alloy sheet according to claim 1, characterized in that, The slab blank is milled to a depth of ≥5mm on one side, and then polished to achieve a surface roughness Ra≤3.2μm, thus obtaining the finished slab blank.

4. A method for preparing aerospace-grade TC4ELI ultra-low temperature titanium alloy sheet according to claim 1 or 3, characterized in that, The finished slab in step 2 was subjected to ultrasonic testing, and the testing met the Class A requirements of GB / T5193.

5. The method for preparing aerospace-grade TC4ELI ultra-low temperature titanium alloy sheet according to claim 1, characterized in that, The annealing process in step 4 is as follows: annealing temperature 700-800℃, holding time 1-2 hours, followed by air cooling, straightening, and leveling after removal from the furnace.

6. The method for preparing aerospace-grade TC4ELI ultra-low temperature titanium alloy sheet according to claim 1, characterized in that, The surface roughness Ra of the polishing treatment in step 4 is ≤1.6μm.

7. The method for preparing aerospace-grade TC4ELI ultra-low temperature titanium alloy sheet according to claim 1, characterized in that, The temperature parameters for temperature detection of the finished board in step 5 are: 20℃, -196℃ and -253℃.

8. The method for preparing aerospace-grade TC4ELI ultra-low temperature titanium alloy sheet according to claim 1, characterized in that, The finished sheet material in step 5 is subjected to ultrasonic testing, and the testing meets the AA grade requirements of GB / T5193.

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