Metastable beta titanium alloy thin strip and preparation method thereof

Abstract

The invention discloses a metastable beta titanium alloy thin strip and a preparation method thereof. The method comprises the steps that firstly, a beta titanium alloy cast ingot is subjected to four-heating-number forging, and a forged plate blank is obtained; secondly, the forged plate blank is subjected to three-heating-number hot rolling, and a hot-rolled plate is obtained; thirdly, the hot-rolled plate is subjected to annealing treatment; fourthly, the annealed hot-rolled plate is subjected to multi-rolling-process tension cold rolling, and a cold-rolled strip is obtained; and fifthly, the cold-rolled strip is subjected to solution annealing treatment, and the metastable beta titanium alloy thin strip is obtained. According to the method, by adjusting the forging process, the temperature and the deformation amount and optimizing the hot rolling temperature, the cold rolling deformation amount and the solution treatment system, omega brittle phase precipitation is effectively restrained, the cold forming and cold machining capacity is improved, the metastable beta titanium alloy thin strip uniform in thickness, good in surface quality, stable in performance and excellent in plasticity is obtained, and the application requirements of different fields are met.

Description

Technical Field

[0001] The invention belongs to the technical field of nonferrous metal material processing, and in particular relates to a metastable beta titanium alloy thin strip and a preparation method thereof. Background Art

[0002] β-titanium alloy has the characteristics of high specific strength, excellent forming performance and corrosion resistance, and has a good development prospect. TB5 (Ti-15V-3Cr-3Sn-3Al) is a metastable β-type titanium alloy with broad application prospects in the aerospace industry. The main advantages of this alloy are excellent casting performance and cold formability, high specific strength, and disadvantages are low elastic modulus, large rebound during cold deformation, and strong anisotropy. In the actual production process of TB5 alloy plate, due to improper hot working and heat treatment process, the room temperature processing plasticity of the alloy deteriorates, making cold working difficult and product performance difficult to meet the requirements. In the plate rolling link, in order to ensure the consistency of the cold forming performance of the plate, the plate needs to have stable mechanical properties, good plate shape and plate difference. Especially when preparing thin plates or strips, how to control the cold rolling process and heat treatment process urgently needs in-depth research. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for preparing a metastable β titanium alloy thin strip in view of the deficiencies of the above-mentioned prior art. The method sequentially performs four-stage forging, three-stage hot rolling, and belt tension multi-pass cold rolling and solution treatment on the β titanium alloy ingot, and by adjusting the forging process, temperature, and deformation, optimizing the hot rolling temperature, cold rolling deformation, and solution treatment system, effectively inhibits the precipitation of the ω brittle phase, improves the cold forming and cold processing capabilities, and obtains a metastable β titanium alloy thin strip with uniform thickness, good surface quality, stable performance, and excellent plasticity, thereby solving the technical problems of cold rolling cracking of titanium alloy thin strips and the difficulty in producing high-plasticity thin strips.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a metastable β titanium alloy thin strip, characterized in that the method comprises the following steps:

[0005] Step 1, slab forging: remove the riser and oxide scale from the β-titanium alloy ingot obtained by three vacuum arc melting processes as a blank, and perform four-time forging to obtain a forged slab;

[0006] Step 2, hot rolling of the plate: the forged slab obtained in step 1 is subjected to three-time hot rolling to obtain a hot-rolled plate; the temperature of the three-time hot rolling is above the phase transformation point temperature of the β titanium alloy, and the holding time is t=h×b, wherein h is the thickness of the corresponding processed slab, in mm, and b is the time coefficient, b takes a value of 0.8min / mm~1.5min / mm, and the thickness of the hot-rolled plate is 2.5mm~3.0mm;

[0007] Step 3, sheet annealing: annealing the hot-rolled sheet obtained in step 2; the annealing temperature is 20°C to 40°C above the phase transition point of the β titanium alloy, and the holding time is 30min to 40min;

[0008] Step 4, cold rolling of the strip: the hot-rolled sheet after annealing in step 3 is subjected to multi-pass tension cold rolling, and then leveled and trimmed to obtain a cold-rolled strip; the total deformation of each rolling process in the multi-pass tension cold rolling is 33% to 50%, and the cold-rolled billet is cleaned, degreased and annealed after each rolling process; the thickness of the strip is 0.15 mm to 0.8 mm;

[0009] Step 5: Heat treatment of the strip: The cold-rolled strip obtained in step 4 is heat treated by online solution annealing to obtain a metastable β titanium alloy thin strip.

[0010] The above-mentioned method for preparing a metastable β titanium alloy thin strip is characterized in that the first and second fire forging processes of the four-fire forging in step one are two upsetting and two drawing, the third fire forging process is reversing three upsetting and three drawing, and the deformation from the first to the third fire forging is 40% to 50%, and the fourth fire forging process is side drawing.

[0011] Generally, the final forging temperature of the four-step forging in the present invention is greater than 850°C.

[0012] The above-mentioned method for preparing a metastable β-titanium alloy thin strip is characterized in that the first hot rolling temperature in the three hot rollings in step 2 is 80°C to 120°C above the phase transformation point temperature of the β-titanium alloy, the holding time is 1 to 1.5 times the thickness of the corresponding processed slab, the unit is min, and the rolling deformation is 75% to 80%.

[0013] The above-mentioned method for preparing a metastable β titanium alloy thin strip is characterized in that the second hot rolling in the three hot rollings in step 2 is reversing rolling, the temperature is 80°C to 120°C above the phase transformation point temperature of the β titanium alloy, the holding time is 0.8 to 1.2 times the thickness of the corresponding processed slab, the unit is min, and the rolling deformation is 65% to 80%.

[0014] The above-mentioned method for preparing a metastable β-titanium alloy thin strip is characterized in that the third hot rolling temperature in the three-hot rolling in step 2 is 50°C to 100°C above the phase transformation point temperature of the β-titanium alloy, the holding time is 0.8 to 1.2 times the thickness of the corresponding processed slab, the unit is min, and the rolling deformation is 57% to 68%.

[0015] Preferably, the rolling deformation of each pass of the three-pass hot rolling in the present invention is 10% to 20%.

[0016] The above-mentioned method for preparing a metastable β titanium alloy thin strip is characterized in that the total deformation of the first rolling process and the second rolling process in the multi-rolling process strip tension cold rolling in step four is 40% to 50%, and after each rolling process is completed, the cold-rolled billet is cleaned, degreased, stress-relieved annealed, and the cracked edges and heads of the strip are removed. After that, the total deformation of each rolling process is 33% to 43%, and after each rolling process is completed, the cold-rolled billet is cleaned, degreased, stress-relieved annealed, and the cracked edges and heads of the strip are removed.

[0017] The above-mentioned method for preparing a metastable β titanium alloy thin strip is characterized in that the rolling deformation of each pass of the first rolling pass and the second rolling pass in the multi-pass strip tension cold rolling in step four is 10% to 15%, and the rolling deformation of each pass of the third rolling pass and the fourth rolling pass is 5% to 10%.

[0018] The above-mentioned method for preparing a metastable β titanium alloy thin strip is characterized in that the temperature of the online solution annealing in step 5 is 25°C to 40°C above the phase transformation point temperature of the β titanium alloy, the holding time is 10min to 30min, and then high-purity argon gas quenching is used for cooling.

[0019] At the same time, the present invention also discloses a metastable β titanium alloy thin strip prepared by the above method, characterized in that it is composed of the following components in percentage by mass: Al 3.02% to 3.34%, Cr 3.10% to 3.17%, Sn 2.99% to 3.16%, V 14.98% to 15.06%, Fe≤0.25%, C≤0.05%, N≤0.05%, H≤0.015%, O≤0.15%, and the balance is Ti. The phase transition point of the β titanium alloy is 780°C to 790°C. The tensile strength of the metastable β titanium alloy thin strip after solution annealing is 704MPa to 740MPa, the yield strength is 696MPa to 736MPa, the elongation is 26.5% to 32.5%, and the thickness is uniform, the surface quality is good, and the performance is stable.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. The present invention adopts four-fire forging to make the as-cast structure of the β-titanium alloy ingot undergo repeated deformation to achieve the purpose of grain refinement, and at the same time adjusts the deformation temperature and the overall deformation amount during the forging process to achieve overall regulation of the deformation capacity of the forged slab; compared with the one- to two-fire unidirectional drawing forging process in the prior art, the three-time upsetting + one-time drawing preparation process of the present invention can fully crush the as-cast structure of the ingot, and the obtained forged slab has a more uniform structure and finer grains, which is beneficial to the subsequent improvement of the processing performance of the forged plate, thereby improving the stability of the performance of the product β-titanium alloy thin strip.

[0022] 2. The present invention adopts a three-pass hot rolling process. By optimizing the hot rolling temperature and deformation amount, and controlling the second pass hot rolling to be reversing rolling, it not only improves the uniformity of the organization of the hot-rolled plate, but also effectively breaks and refines the grains, making the microstructure of the hot-rolled plate more uniform, which is beneficial to reducing the difference in performance of the hot-rolled plate in different directions, making the mechanical properties of the hot-rolled plate in various directions closer, and improving the overall quality and reliability of the hot-rolled plate. At the same time, it avoids excessive accumulation of stress in a single direction, reduces the residual stress inside the plate, reduces the risk of deformation and cracking of the plate during subsequent processing or use, and improves the subsequent cold processing performance of the hot-rolled plate, thereby obtaining a hot-rolled plate with better deformation organization and comprehensive performance.

[0023] 3. The present invention adopts high-purity argon gas quenching cooling after solution annealing, strictly controls the cooling rate, and effectively avoids the α phase precipitation and grain growth phenomenon occurring in the slow cooling process of the β titanium alloy thin strip, thereby completely retaining the β phase fine grain structure, which is beneficial to improving the strength-plasticity matching of the β titanium alloy thin strip.

[0024] 4. The present invention optimizes the hot rolling temperature, controls the strip tension, multi-rolling cold rolling deformation and the solution annealing system, effectively inhibits the precipitation of the ω brittle phase, thereby improving the cold working and cold forming capabilities, and achieving the regulation of the dimensional accuracy, microstructure and mechanical properties of the metastable β titanium alloy thin strip.

[0025] 5. The preparation method of the present invention is simple, has strong process applicability, is not limited by production equipment, is easy to operate and implement, saves costs, can realize mass production, and has broad application prospects.

[0026] 6. The metastable β titanium alloy thin strip prepared by the present invention has a tensile strength of 704MPa-740MPa, a yield strength of 696MPa-736MPa, an elongation of 26.5%-32.5% in the solid solution state, uniform thickness, good surface quality, stable performance, excellent plasticity, good plate shape and small difference in performance anisotropy, which meets the technical requirements of GB / T 3621-2007 "Titanium and Titanium Alloy Plates", meets the application needs of different fields, and is conducive to the industrial promotion and application of high-strength and high-plasticity TB5 titanium alloy thin strips.

[0027] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a microstructure diagram of the metastable β titanium alloy thin strip prepared in Example 2 of the present invention.

[0029] Figure 2 This is the microstructure diagram of the metastable β titanium alloy thin strip prepared in Example 4 of the present invention. DETAILED DESCRIPTION

[0030] Example 1

[0031] This embodiment includes the following steps:

[0032] Step 1, slab forging: a β-titanium alloy ingot obtained by three vacuum arc melting is selected, the ingot is composed of the following components by mass percentage: Al 3.34%, Cr 3.11%, Sn 2.99%, V14.98%, Fe 0.19%, C 0.008%, N 0.01%, H 0.009%, O 0.04%, and the balance is Ti, and the phase transition point of the β-titanium alloy is 780°C;

[0033] The β-titanium alloy ingot is surface treated to remove the riser and oxide scale as a blank, and the blank with a diameter × height of Φ235mm × 435mm is placed in a heating furnace and heated at 800℃ for 90min, and then heated to 1050℃ for 360min, and then the blank is forged, i.e., the first fire forging, and the forging process is two upsetting and two drawing, and the upsetting ratio is greater than 1.8. After the forging is completed, the product is ground to remove surface defects, and a first fire forging blank with a side length × length of □230mm × 470mm is obtained;

[0034] The first-fire forging billet is sequentially subjected to the second-fire and third-fire forgings, and the second-fire forging process is two upsetting and two drawing, and the third-fire forging process is reversing three upsetting and three drawing. After forging, the product is ground to remove surface defects to obtain a three-fire forging billet with a side length × length of □230mm×470mm;

[0035] The three-fire forging billet is subjected to the fourth-fire forging, and the fourth-fire forging process is drawing. After the forging is completed, the product is ground to remove surface defects to obtain a four-fire forging billet, i.e., a forging slab, with a thickness × width × length of δ90 mm × 250 mm × 1100 mm;

[0036] Step 2, hot rolling of the plate: the forged slab obtained in step 1 is heated to 860°C and kept at this temperature for 135 minutes, and then the slab is quickly hot rolled after being taken out of the furnace, with a total rolling deformation of 78% and a single rolling deformation of no more than 20%. After cooling, the slab is ground to obtain a first hot rolled slab with a thickness of 20 mm;

[0037] The first hot rolled slab is heated to 860°C and kept at this temperature for 24 minutes, and then quickly hot-rolled for the second hot rolling after being taken out of the furnace to obtain the second hot rolled slab with a thickness of 7 mm;

[0038] The second hot rolling slab was heated to 830℃ and kept at this temperature for 8min, and then the third hot rolling was carried out immediately after it came out of the furnace to obtain a hot-rolled plate with a thickness of 3mm.

[0039] Step 3, plate annealing: the hot-rolled plate obtained in step 2 is placed in a roller-bottom heating furnace for annealing; the annealing temperature is 800°C, the holding time is 40 minutes, and the plate is air-cooled after being taken out of the furnace, and the surface defects such as cracks, indentations and oxide scale of the plate are removed by sanding;

[0040] Step 4, cold rolling of the strip: the heads of both ends of the hot-rolled plate after annealing and defect removal in step 3 are cut off, and three-pass strip tension cold rolling is performed by welding the lead strips at both ends, wherein the total deformation of the first rolling process is 50%, and a first cold-rolled billet with a thickness of δ1.5 mm is obtained. The first cold-rolled billet is intermediately annealed, and the intermediate annealing system is 820°C / 30min. The total deformation of the second rolling process is 40%, and a second cold-rolled billet with a thickness of δ0.9 mm is obtained. The second cold-rolled billet is intermediately annealed, and the intermediate annealing system is 820°C / 20min. The rolling deformation of each pass of the first to second rolling processes is 10% to 15%, the total deformation of the third rolling process is 33%, and the rolling deformation of each pass is 5% to 10%, and a third cold-rolled billet with a thickness of δ0.6 mm is obtained. After each rolling process, the cold-rolled billet is cleaned, degreased, and stress-relieved annealed, and the cracked edge and head of the strip are leveled and removed to obtain a cold-rolled strip with a thickness of 0.6 mm;

[0041] Step 5: Heat treatment of the strip: The cold-rolled strip obtained in step 4 is heat treated by online solution annealing at a temperature of 820° C. for 30 min, and then cooled by high-purity argon gas quenching to obtain a metastable β titanium alloy thin strip.

[0042] According to the test, the thickness tolerance of the metastable β titanium alloy thin strip prepared in this embodiment is less than ±0.05 mm.

[0043] Example 2

[0044] This embodiment includes the following steps:

[0045] Step 1, slab forging: a β-titanium alloy ingot obtained by three vacuum arc melting is selected, the ingot is composed of the following components by mass percentage: Al 3.28%, Cr 3.17%, Sn 3.16%, V15.06%, Fe 0.15%, C 0.009%, N 0.01%, H 0.009%, O 0.03%, and the balance is Ti, and the phase transition point of the β-titanium alloy is 780°C;

[0046] The β-titanium alloy ingot is surface treated to remove the riser and oxide scale and used as a blank. The blank with a diameter × height of Φ330mm × 500mm is placed in a heating furnace and heated at 800°C for 90 minutes, then heated to 1150°C and kept for 180 minutes, and then forged, i.e., first fire forging, is performed. The forging process is two upsetting and two drawing, and the upsetting ratio is greater than 1.8. After the forging is completed, the product is ground to remove surface defects, and a first fire forging blank with a side length × length of □300mm × 470mm is obtained.

[0047] The first-fire forging billet is sequentially subjected to the second-fire and third-fire forgings, and the second-fire forging process is two upsetting and two drawing, and the third-fire forging process is reversing three upsetting and three drawing. After forging, the product is ground to remove surface defects to obtain a three-fire forging billet with a side length × length of □300mm×470mm;

[0048] The three-fire forging billet is subjected to the fourth-fire forging, and the fourth-fire forging process is drawing. After the forging is completed, the product is ground to remove surface defects to obtain a four-fire forging billet, i.e., a forging slab, with a thickness × width × length of δ100 mm × 300 mm × 1400 mm;

[0049] Step 2, hot rolling of the plate: the forged slab obtained in step 1 is heated to 900°C and kept at this temperature for 120 minutes, and then the slab is quickly hot rolled after being taken out of the furnace, with a total rolling deformation of 80%, and a single rolling deformation of no more than 20%. After cooling, the slab is ground to obtain a first hot rolled slab with a thickness of 20 mm;

[0050] The first hot rolled slab was heated to 900℃ and kept at this temperature for 16min, and then quickly hot-rolled for the second hot rolling after being taken out of the furnace to obtain the second hot rolled slab with a thickness of 7mm;

[0051] The second hot rolled slab was heated to 880°C and kept at this temperature for 6 minutes, and then quickly hot rolled for the third time after being taken out of the furnace to obtain a hot rolled plate with a thickness of 2.5 mm.

[0052] Step 3, plate annealing: the hot-rolled plate obtained in step 2 is placed in a roller-bottom heating furnace for annealing; the annealing temperature is 820°C, the holding time is 30 minutes, and the plate is air-cooled after being taken out of the furnace, and the surface defects such as cracks, indentations and oxide scale of the plate are removed by sanding;

[0053] Step 4, cold rolling of the strip: the heads of both ends of the hot-rolled plate after annealing and defect removal in step 3 are cut off, and the strips are welded at both ends for four-pass strip tension cold rolling, wherein the total deformation of the first rolling pass is 44%, and the first cold-rolled billet with a thickness of δ1.4 mm is obtained. The first cold-rolled billet is intermediately annealed, and the intermediate annealing system is 810°C / 20min. The total deformation of the second rolling pass is 43%, and the second cold-rolled billet with a thickness of δ0.8 mm is obtained. The rolling deformation of each pass from the first to the second rolling pass is 10% to 15%, and the second cold-rolled billet is intermediately annealed. The intermediate annealing system is 810℃ / 20min, the total deformation of the third rolling process is 38%, and the third cold-rolled billet with a thickness of δ0.5mm is obtained. The third cold-rolled billet is intermediate annealed, and the intermediate annealing system is 810℃ / 20min. The total deformation of the fourth rolling process is 40%, and the fourth cold-rolled billet with a thickness of δ0.3mm is obtained. The rolling deformation of each pass of the third to fourth rolling processes is 5% to 10%. After each rolling process, the cold-rolled billet is cleaned, degreased, and stress-relief annealed, and the cracked edge and head of the strip are leveled and removed to obtain a cold-rolled strip with a thickness of 0.3mm;

[0054] Step 5: Heat treatment of the strip: The cold-rolled strip obtained in step 4 is heat treated by online solution annealing at a temperature of 820° C. for 10 min, and then cooled by high-purity argon gas quenching to obtain a metastable β titanium alloy thin strip.

[0055] According to the test, the thickness tolerance of the metastable β titanium alloy thin strip prepared in this embodiment is less than ±0.05 mm.

[0056] Figure 1 This is the microstructure of the 0.3 mm metastable β titanium alloy thin strip prepared in this example. Figure 1 It can be seen that the microstructure of the metastable β titanium alloy thin strip is a uniform and fine β phase structure.

[0057] Example 3

[0058] This embodiment includes the following steps:

[0059] Step 1, slab forging: a β-titanium alloy ingot obtained by three vacuum arc melting is selected, the ingot is composed of the following components by mass percentage: Al 3.02%, Cr 3.10%, Sn 3.08%, V15.01%, Fe 0.16%, C 0.009%, N 0.012%, H 0.008%, O 0.03%, and the balance is Ti, and the phase transition point of the β-titanium alloy is 785°C;

[0060] The β-titanium alloy ingot is surface treated to remove the riser and oxide scale and used as a blank. The blank with a diameter × height of Φ330mm × 500mm is placed in a heating furnace and heated at 800°C for 90 minutes, then heated to 1100°C and kept for 270 minutes, and then forged, i.e., first fire forging, is performed. The forging process is two upsetting and two drawing, and the upsetting ratio is greater than 1.8. After the forging is completed, the product is ground to remove surface defects, and a first fire forging blank with a side length × length of □300mm × 470mm is obtained.

[0061] The first-fire forging billet is sequentially subjected to the second-fire and third-fire forgings, and the second-fire forging process is two upsetting and two drawing, and the third-fire forging process is reversing three upsetting and three drawing. After forging, the product is ground to remove surface defects to obtain a three-fire forging billet with a side length × length of □300mm×470mm;

[0062] The three-fire forging billet is subjected to the fourth-fire forging, and the fourth-fire forging process is drawing. After the forging is completed, the product is ground to remove surface defects to obtain a four-fire forging billet, i.e., a forging slab, with a thickness × width × length of δ100 mm × 300 mm × 1400 mm;

[0063] Step 2, hot rolling of the plate: the forged slab obtained in step 1 is heated to 865°C and kept at this temperature for 130 minutes, and the first hot rolling is carried out quickly after being taken out of the furnace, the total rolling deformation is 80%, and the single-pass rolling deformation does not exceed 20%, and the first hot rolling slab with a thickness of 20 mm is obtained after being cooled and ground;

[0064] The first hot rolled slab is heated to 865°C and kept at this temperature for 20 minutes, and then quickly hot-rolled for the second hot rolling after being taken out of the furnace to obtain the second hot rolled slab with a thickness of 7 mm;

[0065] The second hot rolled slab was heated to 860°C and kept at this temperature for 7 minutes, and then quickly hot rolled for the third time after being taken out of the furnace to obtain a hot rolled plate with a thickness of 2.5 mm.

[0066] Step 3, plate annealing: the hot-rolled plate obtained in step 2 is placed in a roller-bottom heating furnace for annealing; the annealing temperature is 820°C, the holding time is 30 minutes, and the plate is air-cooled after being taken out of the furnace, and the surface defects such as cracks, indentations and oxide scale of the plate are removed by sanding;

[0067] Step 4, cold rolling of the strip: the heads of both ends of the hot-rolled plate after annealing and defect removal in step 3 are cut off, and five-pass strip tension cold rolling is performed with welding strips at both ends, wherein the total deformation of the first rolling pass is 48%, and a first cold-rolled billet with a thickness of δ1.3 mm is obtained. The first cold-rolled billet is intermediately annealed, and the intermediate annealing system is 810°C / 20min. The total deformation of the second rolling pass is 46%, and a second cold-rolled billet with a thickness of δ0.7 mm is obtained. The deformation of each rolling pass from the first to the second rolling pass is 10% to 15%. The second cold-rolled billet is intermediately annealed, and the intermediate annealing system is 810°C / 20min. The total deformation of the third rolling pass is 43%, and a second cold-rolled billet with a thickness of δ0.7 mm is obtained. The third cold-rolled billet with a thickness of δ0.4 mm is subjected to intermediate annealing at a temperature of 810°C / 20 min, and the total deformation of the fourth rolling process is 38%, so as to obtain a fourth cold-rolled billet with a thickness of δ0.25 mm. The rolling deformation of each pass of the third to fourth rolling processes is 5% to 10%, and the fourth cold-rolled billet is subjected to intermediate annealing at a temperature of 810°C / 20 min. The total deformation of the fifth rolling process is 40%, so as to obtain a fifth cold-rolled billet with a thickness of δ0.15 mm. After each rolling process, the cold-rolled billet is cleaned and degreased, and subjected to stress relief annealing treatment, and the cracked edge and head of the strip are leveled and removed, so as to obtain a cold-rolled strip with a thickness of 0.15 mm.

[0068] Step 5: Heat treatment of the strip: The cold-rolled strip obtained in step 4 is heat treated by online solution annealing at a temperature of 810° C. for 30 min, and then cooled by high-purity argon gas quenching to obtain a metastable β titanium alloy thin strip.

[0069] According to the test, the thickness tolerance of the metastable β titanium alloy thin strip prepared in this embodiment is less than ±0.05 mm.

[0070] Example 4

[0071] This embodiment includes the following steps:

[0072] Step 1, slab forging: a β-titanium alloy ingot obtained by three vacuum arc melting is selected, the ingot is composed of the following components by mass percentage: Al 3.30%, Cr 3.21%, Sn 3.02%, V14.96%, Fe 0.18%, C 0.009%, N 0.01%, H 0.008%, O 0.03%, and the balance is Ti, and the phase transition point of the β-titanium alloy is 790°C;

[0073] The β-titanium alloy ingot is surface treated to remove the riser and oxide scale as a blank, and the blank with a diameter × height of Φ235mm × 435mm is placed in a heating furnace and heated at 800℃ for 90min, and then heated to 1100℃ and kept for 180min, and then the blank is forged, i.e., the first fire forging, and the forging process is two upsetting and two drawing, and the upsetting ratio is greater than 1.8. After the forging is completed, the product is ground to remove surface defects, and a first fire forging blank with a side length × length of □230mm × 470mm is obtained;

[0074] The first-fire forging billet is sequentially subjected to the second-fire and third-fire forgings, and the second-fire forging process is two upsetting and two drawing, and the third-fire forging process is reversing three upsetting and three drawing. After forging, the product is ground to remove surface defects to obtain a three-fire forging billet with a side length × length of □230mm×470mm;

[0075] The three-fire forging billet is subjected to the fourth-fire forging, and the fourth-fire forging process is drawing. After the forging is completed, the product is ground to remove surface defects to obtain a four-fire forging billet, i.e., a forging slab, with a thickness×width×length of δ100mm×250mm×1000mm;

[0076] Step 2, hot rolling of the plate: the forged slab obtained in step 1 is heated to 880°C and kept at this temperature for 100 minutes, and then the slab is quickly hot rolled after being taken out of the furnace, with a total rolling deformation of 75% and a single rolling deformation of no more than 20%. After cooling, the slab is ground to obtain a first hot rolled slab with a thickness of 25 mm;

[0077] The first hot rolled slab is heated to 880°C and kept at this temperature for 25 minutes, and then quickly hot-rolled for the second hot rolling after being taken out of the furnace to obtain the second hot rolled slab with a thickness of 8 mm;

[0078] The second hot rolled slab was heated to 850°C and kept at this temperature for 8 minutes, and then quickly hot rolled for the third time after being taken out of the furnace to obtain a hot rolled plate with a thickness of 2.6 mm.

[0079] Step 3, plate annealing: the hot-rolled plate obtained in step 2 is placed in a roller-bottom heating furnace for annealing; the annealing temperature is 815°C, the holding time is 40 minutes, and the plate is air-cooled after being taken out of the furnace, and the surface defects such as cracks, indentations and scales of the plate are removed by sanding;

[0080] Step 4, cold rolling of the strip: the heads of both ends of the hot-rolled plate after annealing and defect removal in step 3 are cut off, and the strips are welded at both ends for multi-pass strip tension cold rolling, wherein the total deformation of the first rolling process is 42%, and a first cold-rolled billet with a thickness of δ1.5 mm is obtained. The first cold-rolled billet is intermediately annealed, and the intermediate annealing system is 820°C / 30min. The total deformation of the second rolling process is 47%, and a second cold-rolled billet with a thickness of δ0.8 mm is obtained, and the rolling deformation of each pass of the first to second rolling processes is 10% to 15%. After each rolling process is completed, the cold-rolled billet is cleaned and degreased, and stress relief annealing is performed, and the cracked edge and head of the strip are leveled and removed to obtain a cold-rolled strip with a thickness of 0.8 mm;

[0081] Step 5: Heat treatment of the strip: The cold-rolled strip obtained in step 4 is heat treated by online solution annealing at a temperature of 810° C. for 10 min, and then cooled by high-purity argon gas quenching to obtain a metastable β titanium alloy thin strip.

[0082] According to the test, the thickness tolerance of the metastable β titanium alloy thin strip prepared in this embodiment is less than ±0.05 mm.

[0083] Figure 2 This is the microstructure of the 0.8 mm metastable β titanium alloy thin strip prepared in this example. Figure 2 It can be seen that the microstructure of the metastable β titanium alloy thin strip is a uniform and fine β phase structure.

[0084] The metastable β titanium alloy thin strips prepared in Examples 1 to 4 of the present invention were subjected to tensile tests, and the test results are shown in Table 1 below.

[0085] Table 1

[0086] Serial number Tensile strength / MPa Yield strength / MPa Elongation / % Example 1 740 736 28 Example 2 710 699 30.5 Example 3 704 696 26.5 Example 4 733 726 32.5

[0087] It can be seen from Table 1 in combination with Examples 1 to 4 that the metastable β titanium alloy thin strip prepared by the present invention has excellent plasticity, uniform thickness, good surface quality and stable performance.

[0088] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a metastable β titanium alloy thin strip, characterized in that: The method comprises the following steps: Step 1, slab forging: remove the riser and oxide scale from the β-titanium alloy ingot obtained by three vacuum arc melting processes as a blank, and perform four-time forging to obtain a forged slab; Step 2, hot rolling of the plate: the forged slab obtained in step 1 is subjected to three-time hot rolling to obtain a hot-rolled plate; the temperature of the three-time hot rolling is above the phase transformation point temperature of the β titanium alloy, and the holding time is t=h×b, wherein h is the thickness of the corresponding processed slab, in mm, and b is the time coefficient, b takes a value of 0.8min / mm~1.5min / mm, and the thickness of the hot-rolled plate is 2.5mm~3.0mm; Step 3, sheet annealing: annealing the hot-rolled sheet obtained in step 2; the annealing temperature is 20°C to 40°C above the phase transition point of the β titanium alloy, and the holding time is 30min to 40min; Step 4, cold rolling of the strip: the hot-rolled sheet after annealing in step 3 is subjected to multi-pass tension cold rolling, and then leveled and trimmed to obtain a cold-rolled strip; the total deformation of each rolling process in the multi-pass tension cold rolling is 33% to 50%, and the cold-rolled billet is cleaned, degreased and annealed after each rolling process; the thickness of the strip is 0.15 mm to 0.8 mm; Step 5: Heat treatment of the strip: The cold-rolled strip obtained in step 4 is heat treated by online solution annealing to obtain a metastable β titanium alloy thin strip.

2. The method for preparing a metastable β titanium alloy thin strip according to claim 1, characterized in that: The first and second forging processes of the four-fire forging in step one are two upsetting and two drawing, the third forging process is reversing three upsetting and three drawing, and the forging deformation from the first to the third fire is 40% to 50%, and the fourth forging process is side drawing.

3. The method for preparing a metastable β titanium alloy thin strip according to claim 1, characterized in that: The first hot rolling temperature of the three hot rollings in step 2 is 80°C to 120°C above the phase transformation temperature of the β titanium alloy, the holding time is 1 to 1.5 times the thickness of the corresponding processed slab, in minutes, and the rolling deformation is 75% to 80%.

4. The method for preparing a metastable β titanium alloy thin strip according to claim 1, characterized in that: The second hot rolling in the three hot rolling in step 2 is reversing rolling, the temperature is 80°C to 120°C above the phase transformation point temperature of the β titanium alloy, the holding time is 0.8 to 1.2 times the thickness of the corresponding processed slab, the unit is min, and the rolling deformation is 65% to 80%.

5. The method for preparing a metastable β titanium alloy thin strip according to claim 1, characterized in that: The third hot rolling temperature in the three hot rolling in step 2 is 50°C to 100°C above the phase transformation point temperature of the β titanium alloy, the holding time is 0.8 to 1.2 times the thickness of the corresponding processed slab, in minutes, and the rolling deformation is 57% to 68%.

6. The method for preparing a metastable β titanium alloy thin strip according to claim 1, characterized in that: The total deformation of the first and second rolling passes in the multi-pass tension cold rolling described in step 4 is 40% to 50%, and after each rolling pass, the cold-rolled billet is cleaned, degreased, stress-relieved annealed, and the cracked edges and heads of the strip are removed. After that, the total deformation of each rolling pass is 33% to 43%, and after each rolling pass, the cold-rolled billet is cleaned, degreased, stress-relieved annealed, and the cracked edges and heads of the strip are removed.

7. The method for preparing a metastable β titanium alloy thin strip according to claim 1, characterized in that: In the multi-pass tension cold rolling described in step 4, the rolling deformation amount of each pass in the first and second rolling passes is 10% to 15%, and the rolling deformation amount of each pass in the third and fourth rolling passes is 5% to 10%.

8. The method for preparing a metastable β titanium alloy thin strip according to claim 1, characterized in that: The temperature of the online solution annealing in step 5 is 25° C. to 40° C. above the phase transformation point temperature of the β titanium alloy, the holding time is 10 min to 30 min, and then high-purity argon gas quenching is used for cooling.

9. A metastable β titanium alloy thin strip prepared by the method according to any one of claims 1 to 8, characterized in that: The invention is composed of the following components in percentage by mass: Al 3.02% to 3.34%, Cr 3.10% to 3.17%, Sn 2.99% to 3.16%, V 14.98% to 15.06%, Fe≤0.25%, C≤0.05%, N≤0.05%, H≤0.015%, O≤0.15%, and the balance is Ti. The phase transformation point of the beta titanium alloy is 780°C to 790°C. The metastable beta titanium alloy thin strip has a tensile strength of 704MPa to 740MPa after solution annealing, a yield strength of 696MPa to 736MPa, an elongation of 26.5% to 32.5%, and has uniform thickness, good surface quality, and stable performance.

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