Preparation method of high-strength Ti662 titanium alloy bar

Abstract

The invention relates to the technical field of titanium alloy processing, in particular to a preparation method of a high-strength Ti662 titanium alloy bar. Through stepped heating, upsetting and drawing treatment and two times of intermediate forging, thermal stress concentration and internal cracks caused by rapid heating of the titanium alloy can be avoided, then the cast ingot structure is homogenized, composition segregation and residual stress are reduced, the upsetting and drawing treatment can crush original as-cast coarse grains, refine the grain size and eliminate casting defects (such as shrinkage cavities and looseness), and the casting quality of the titanium alloy is improved. The material density is improved, the anisotropy is preliminarily improved, and the forging streamline distribution is optimized; the solid solution treatment and the aging treatment can dissolve a residual intermediate phase of the Ti662 alloy to provide conditions for precipitation of a strengthening phase, heat preservation is carried out at a low temperature, precipitation of a fine and dispersed alpha phase is promoted, the strength of the Ti662 alloy is remarkably improved, the problems that a large-specification Ti662 bar is large in anisotropy, composition segregation is caused, and the batch stability is poor are solved, and the production cost is reduced. And the application range and field of the alloy are expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium alloy processing, and in particular to a method for preparing a high-strength Ti662 titanium alloy bar. Background Art

[0002] Ti662 titanium alloy boasts excellent mechanical properties, heat resistance, good corrosion resistance, and weldability, and is widely used in aircraft fuselages, rocket engines, nuclear reactor components, and oil exploration equipment. The alloy exhibits excellent corrosion resistance and good overall performance in media such as seawater and crude oil containing sulfides, ammonia, and chlorine. When operating in humid environments and seawater, its corrosion resistance far exceeds that of 1Cr18Ni9Ti, and its resistance to pitting, acid corrosion, and stress corrosion is particularly strong. Compared to Ti-6Al-4V alloy, Ti662 alloy offers superior overall performance, making Ti662 alloy bar ideally suited for offshore oil exploration, where strength, plasticity, and impact toughness are paramount, and offers a broad market prospect.

[0003] Ti662 titanium alloy, with a nominal composition of Ti-6Al-6V-2Sn-0.5Fe-0.5Cu, is a two-phase, high-strength titanium alloy developed based on Ti-6Al-4V and rich in β-stabilizing elements. Compared to Ti-6Al-4V titanium alloy, the addition of β-stabilizing elements in Ti662 significantly improves its heat treatment properties. Due to the high content of β-stabilizing elements, its annealed strength exceeds that of Ti-6Al-4V, and its hardenability is also superior to that of Ti-6Al-4V. Furthermore, Ti662 exhibits excellent overall performance after solution aging heat treatment.

[0004] With the rapid development of my country's high-end equipment manufacturing industry, higher technical requirements have been put forward for Ti662 titanium alloy products. In the process of engineering application, large-size Ti662 bars still have engineering problems such as large anisotropy, composition segregation, and poor batch stability. It is urgent to optimize the Ti662 titanium alloy bar forming process to further solve the above-mentioned problems and promote the application scope and field of this alloy.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] In response to the problems existing in the prior art, the present invention aims to develop a method for preparing high-strength Ti662 titanium alloy bars, which can solve the engineering problems of large-size Ti662 bars still existing in large anisotropy, composition segregation, and poor batch stability.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for preparing a high-strength Ti662 titanium alloy bar, which is characterized by comprising the following steps:

[0009] S1, performing a stepwise heating process on a Ti662 titanium alloy ingot and then performing an upsetting process to obtain a first forging blank;

[0010] S2, performing two intermediate forgings on the first forging blank to obtain a second forging blank;

[0011] S3, reforging the second forging blank to obtain a third forging blank;

[0012] S4, stretching the third forging blank to obtain a first bar;

[0013] S5, performing solution treatment and aging treatment on the first bar in sequence to obtain a second bar;

[0014] S6. Surface machining the second bar to the finished size.

[0015] Specifically, in S1, the stepwise heating process is as follows: heating the Ti662 titanium alloy ingot to 650° C. to 850° C., keeping the temperature for 30 min to 120 min, then heating the ingot to Tβ+200° C. to Tβ+250° C., and keeping the temperature for 20 h to 24 h;

[0016] During the upsetting process, the single upsetting ratio is 1.6 to 1.9, and the final forging temperature is ≥850°C.

[0017] Specifically, in S2, the process of the first intermediate forging is as follows: heating the first forging blank to 650°C to 800°C, holding the temperature for 30min to 90min, then heating the blank to Tβ+100°C to Tβ+150°C, holding the temperature for 150min to 210min, and then performing an upsetting process to obtain an intermediate forging blank;

[0018] The second intermediate forging process is as follows: first, the intermediate forging blank is heated to 700℃~800℃, kept at this temperature for 30min~90min, then heated to Tβ+30℃~Tβ+50℃, kept at this temperature for 150min~210min, and then subjected to the upsetting process;

[0019] During the two intermediate forging processes, the single upsetting ratio of the upsetting and drawing process is 1.6 to 1.9, and the final forging temperature is ≥800℃.

[0020] Specifically, in S3, the process of the reforging treatment is: first heat the second forging blank to 650℃~800℃, keep it warm for 30min~90min, then heat it to Tβ-30℃~Tβ-100℃, keep it warm for 210min~270min and then reforge it, then perform 3~5 fire upsetting and drawing processes, two upsetting and two drawing per fire, the single upsetting ratio is 1.4~1.7, and the final forging temperature is ≥750℃.

[0021] Specifically, in S4, the process of the drawing treatment is: first heat the third forging blank to 650℃~800℃, keep it warm for 30min~90min, then heat it to Tβ-30℃~Tβ-100℃, keep it warm for 90min~270min, and then perform 3 to 5 fire drawing treatments. The drawing treatment uses three-way asynchronous deformation technology, with an axial deformation rate of 15-20mm / s and a radial rotation speed of 5-8rpm. The total forging ratio of the process is ≥7.0, and the final forging temperature is ≥750℃.

[0022] Specifically, in S5, the process of the solution treatment is as follows: firstly, the first bar is heated to Tβ-30°C to 50°C, then kept at this temperature for 1h to 3h, and then cooled to room temperature after being taken out of the furnace;

[0023] The aging treatment process is as follows: heating the solution treated bar to 520° C. to 560° C., keeping the temperature for 4 to 8 hours, and then air cooling the bar to room temperature.

[0024] Specifically, in S1, the preparation process of the Ti662 titanium alloy ingot is: the Ti662 titanium alloy ingot is obtained by three times of vacuum consumable arc furnace melting.

[0025] Specifically, in S3, multi-directional forging is performed during the reforming forging process, and the tolerance of the third forging blank finally formed satisfies ±3 mm, and the curvature is ≤3 mm / m.

[0026] Specifically, in S5, the time from the first bar being taken out of the furnace to entering the water during the solution treatment is ≤30s, and the bar is quenched in flowing water with a water flow rate of ≥143m 3 / h.

[0027] Specifically, in S6, the second rod needs to be straightened before surface machining, with a curvature of ≤3 mm / m.

[0028] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0029] (1) The present invention can avoid thermal stress concentration and internal cracking of titanium alloy caused by rapid heating through step-by-step heating, thereby homogenizing the ingot structure and reducing component segregation and residual stress. The upsetting treatment can break the coarse grains in the original cast state, refine the grain size, eliminate casting defects such as shrinkage cavities and looseness, improve the material density, preliminarily improve the anisotropy, and optimize the forging streamline distribution; the two intermediate forgings and the reforming forging treatment can form a uniform equiaxed crystal structure through dynamic recrystallization. This process can also reduce the anisotropy remaining in the upsetting process, improve the transverse mechanical properties of the material, and prevent the strength differentiation caused by deformation in a single direction; the solid solution and aging treatment can dissolve the residual intermediate phase of the Ti662 alloy, provide conditions for the precipitation of the strengthening phase by aging, and maintain the heat at a lower temperature to promote the precipitation of fine and dispersed α phase, significantly improving the strength of the Ti662 alloy.

[0030] (2) During the drawing process, three-way asynchronous deformation technology is used to achieve differentiated deformation of the material in three dimensions through the synergistic effect of axial deformation, radial rotation, and temperature gradient control, thereby optimizing the microstructure and mechanical properties and increasing the {0001} basal surface texture strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the original low-magnification microstructure diagram of the Ф118×1700mm bar;

[0032] Figure 2 This is the transverse microstructure diagram of the Ф118×1700mm bar;

[0033] Figure 3 This is the longitudinal microstructure diagram of the Ф118×1700mm bar;

[0034] Figure 4 This is a typical waveform diagram of ultrasonic testing of Ф118×1700mm bar. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] The following is an embodiment of the present invention for preparing a Ti662 titanium alloy bar having a specification of Ø118 mm×1700 mm:

[0037] Example 1

[0038] S1. The Ti662 ingot, which had been melted in a vacuum consumable arc melting furnace three times, was first heated to 800°C in a natural gas furnace, kept warm for 120 minutes, then raised to 1150°C, kept warm for another 20 hours, and then taken out of the furnace. It was then forged on a 45 / 50MN fast forging unit using a two-upset and three-draw forging process with a single upsetting ratio of 1.75 and a final forging temperature of 880°C to fully break up the as-cast structure.

[0039] S2. First heat the billet that has completed S1 to 650℃, keep it warm for 90min, then heat it to 1050℃, keep it warm for 150min, and then perform the upsetting and drawing process, two upsetting and two drawing, with a single upsetting ratio of 1.9 and a final forging temperature of 810℃ to obtain the intermediate forging billet.

[0040] The intermediate forging blank was first heated to 750°C and kept warm for 60 minutes, then heated to 990°C and kept warm for 200 minutes before performing the upsetting and drawing process, with one upsetting and one drawing being performed, the single upsetting ratio being 1.7, and the final forging temperature being 804°C to obtain the Ti662 forging blank.

[0041] S3, the Ti662 forging blank obtained in S2 is subjected to three-stage reforging treatment:

[0042] In the first fire, the Ti662 billet after S3 was heated to 650℃ in a resistance heating furnace, kept at this temperature for 30 minutes, then raised to 900℃, and kept at this temperature for another 210 minutes before being made into a two-phase zone billet. Two upsetting and two drawing processes were performed, with a single upsetting ratio of 1.7 and a final forging temperature of 754℃.

[0043] For the second heat, the Ti662 billet that has completed the first heat is first heated to 700℃ in a resistance heating furnace, kept at this temperature for 30 minutes, then raised to 880℃, and kept at this temperature for another 270 minutes before being made into a two-phase zone billet. Two upsetting and two drawing processes are performed, with a single upsetting ratio of 1.5 and a final forging temperature of 760℃.

[0044] For the third fire, the Ti662 billet that has completed the second fire is first heated to 650℃ in a resistance heating furnace, kept at this temperature for 60 minutes, then raised to 850℃, and kept at this temperature for another 210 minutes before being made into a two-phase zone billet. Two upsetting and two drawing processes are performed, with a single upsetting ratio of 1.4 and a final forging temperature of 752℃.

[0045] In order to further ensure that the grains are fully broken, multi-directional forging is performed in S3 to minimize the anisotropy generated during the forging process.

[0046] S4, subjecting the Ti662 forging blank obtained in S3 to a three-stage drawing treatment:

[0047] In the first heat, the Ti662 billet obtained in S3 was heated to 650°C in a resistance heating furnace, kept at this temperature for 90 minutes, then raised to 900°C, and kept at this temperature for another 210 minutes before being stretched. The stretching process used a three-way asynchronous deformation technology with an axial deformation rate of 15 mm / s, a radial rotation speed of 5 rpm, a forging ratio of 3.0, and a final forging temperature of 752°C.

[0048] For the second heat treatment, the Ti662 billet that has completed the first heat treatment is heated to 700°C in a resistance heating furnace, kept at this temperature for 30 minutes, then raised to 880°C, and kept at this temperature for another 270 minutes before being stretched. The stretching process uses a three-way asynchronous deformation technology with an axial deformation rate of 18 mm / s, a radial rotation speed of 6 rpm, a forging ratio of 2.7, and a final forging temperature of 763°C.

[0049] For the third fire, the Ti662 billet that has completed the second fire is first heated to 650°C in a resistance heating furnace, kept warm for 90 minutes, then heated to 850°C, and kept warm for another 90 minutes before being drawn. A 45 / 50MN fast forging machine is used with a Ф110-170mm spring hammer for the drawing process. The drawing process uses three-way asynchronous deformation technology, with an axial deformation rate of 20mm / s, a radial rotation speed of 8rpm, and a single upsetting ratio of 1.7. The titanium alloy bar with a specification of Ф130mm is prepared, and the final forging temperature is 758°C.

[0050] The three-way asynchronous deformation technology can achieve differentiated deformation of the material in three dimensions through the synergistic effect of axial deformation, radial rotation and temperature gradient control, thereby optimizing the microstructure and mechanical properties.

[0051] S5. First heat the formed rod obtained in S4 to 910℃, keep it warm for 1.5 hours, then take it out of the furnace and water cool it to room temperature; then heat the rod to 540℃, keep it warm for 5 hours, then take it out of the furnace and straighten it to a curvature of ≤3mm / m, and then air cool it to room temperature.

[0052] S6, after completing S5, the Ti662 titanium alloy bar is surface machined to prepare the bar into a size of Ti662 titanium alloy bar.

[0053] Example 2

[0054] S1. The Ti662 ingot, which had been melted in a vacuum consumable arc melting furnace three times, was first heated to 655°C in a natural gas furnace, kept warm for 120 minutes, then raised to 1180°C, kept warm for another 24 hours, and then taken out of the furnace. It was then forged on a 45 / 50MN fast forging unit using a two-upset and three-draw forging process with a single upsetting ratio of 1.9 and a final forging temperature of 900°C to fully break up the as-cast structure.

[0055] S2. First heat the billet that has completed S1 to 700℃, keep it warm for 30min, then heat it to 1070℃, keep it warm for 180min, and then perform the upsetting and drawing process, two upsetting and two drawing, with a single upsetting ratio of 1.7 and a final forging temperature of 830℃ to obtain the intermediate forging billet.

[0056] The intermediate forging blank was first heated to 700°C and kept warm for 30 minutes, then heated to 980°C and kept warm for 150 minutes before performing the upsetting and drawing process, with one upsetting and one drawing being performed, the single upsetting ratio being 1.6, and the final forging temperature being 808°C to obtain the Ti662 forging blank.

[0057] S3. The Ti662 forging blank obtained in S2 is subjected to 4-fire reforging treatment:

[0058] In the first heat, the Ti662 billet after S3 was heated to 800℃ in a resistance heating furnace, kept at this temperature for 60min, then raised to 840℃, kept at this temperature for another 210min, and then made into a two-phase blank. The billet was subjected to two upsetting and two drawing processes, with a single upsetting ratio of 1.4 and a final forging temperature of 780℃.

[0059] For the second heat, the Ti662 billet that has completed the first heat is heated to 750℃ in a resistance heating furnace, kept at this temperature for 90 minutes, then raised to 860℃, and kept at this temperature for another 240 minutes before being made into a two-phase zone billet. Two upsetting and two drawing processes are performed, with a single upsetting ratio of 1.55 and a final forging temperature of 770℃.

[0060] For the third heat, the Ti662 billet that has completed the second heat is first heated to 650℃ in a resistance heating furnace, kept at this temperature for 30 minutes, then raised to 890℃, and kept at this temperature for another 270 minutes before being made into a two-phase zone billet. Two upsetting and two drawing processes are performed, with a single upsetting ratio of 1.68 and a final forging temperature of 755℃.

[0061] For the fourth heat, the Ti662 billet that has completed the third heat is first heated to 700℃ in a resistance heating furnace, kept at this temperature for 45 minutes, then raised to 910℃, and kept at this temperature for another 255 minutes before being made into a two-phase zone billet. Two upsetting and two drawing processes are performed, with a single upsetting ratio of 1.7 and a final forging temperature of 760℃.

[0062] In order to further ensure that the grains are fully broken, multi-directional forging is performed in S3 to minimize the anisotropy generated during the forging process.

[0063] S4, subjecting the Ti662 forging blank obtained in S3 to 5-time drawing treatment:

[0064] In the first heat, the Ti662 billet obtained in S3 was heated to 800°C in a resistance heating furnace, kept at this temperature for 45 minutes, then raised to 900°C, and kept at this temperature for another 180 minutes before being stretched using a 45 / 50MN fast forging machine with a spring hammer of Ø110-170mm. The stretching process used a three-way asynchronous deformation technology with an axial deformation rate of 15mm / s, a radial rotation speed of 5rpm, a forging ratio of 3.0, and a final forging temperature of 760°C.

[0065] For the second heat treatment, the Ti662 billet that has completed the first heat treatment is heated to 750°C in a resistance heating furnace, held at that temperature for 30 minutes, then raised to 910°C. After holding at that temperature for another 90 minutes, it is stretched using a 45 / 50MN fast forging machine with a Ø110-170mm spring hammer. The stretching process uses a three-way asynchronous deformation technology with an axial deformation rate of 20mm / s, a radial rotation speed of 7rpm, a forging ratio of 1.0, and a final forging temperature of 750°C.

[0066] For the third fire, the Ti662 billet that has completed the second fire is first heated to 650℃ in a resistance heating furnace, kept warm for 90 minutes, then heated to 840℃, and kept warm for 270 minutes. It is then drawn using a 45 / 50MN fast forging machine with a Ф110~170mm spring hammer. The drawing process uses three-way asynchronous deformation technology, with an axial deformation rate of 18mm / s, a radial rotation speed of 6rpm, an upsetting ratio of 1.5, and a final forging temperature of 770℃.

[0067] For the fourth fire, the Ti662 billet that has completed the second fire is first heated to 700°C in a resistance heating furnace, kept warm for 60 minutes, then heated to 850°C, and kept warm for 220 minutes before being drawn. A 45 / 50MN fast forging machine is used with a Ф110-170mm spring hammer for drawing. The drawing process uses three-way asynchronous deformation technology, with an axial deformation rate of 17mm / s, a radial rotation speed of 8rpm, an upsetting ratio of 1.6, and a final forging temperature of 765°C.

[0068] In the fifth fire, the Ti662 billet that has completed the second fire is first heated to 720℃ in a resistance heating furnace, kept warm for 55 minutes, then heated to 880℃, and kept warm for 130 minutes before being drawn. A 45 / 50MN fast forging machine is used with a Ф110~170mm spring hammer for drawing. The drawing process uses three-way asynchronous deformation technology, with an axial deformation rate of 16mm / s, a radial rotation speed of 6rpm, and an upsetting ratio of 2.0. It is prepared into a titanium alloy bar with a specification of Ф130mm, and the final forging temperature is 759℃.

[0069] The three-way asynchronous deformation technology can achieve differentiated deformation of the material in three dimensions through the synergistic effect of axial deformation, radial rotation and temperature gradient control, thereby optimizing the microstructure and mechanical properties.

[0070] S5. First heat the formed rod obtained in S4 to 900℃, keep it warm for 1 hour, and then cool it to room temperature with water; then heat the rod to 520℃, keep it warm for 4 hours, and then straighten it with a curvature of ≤3mm / m, and then air cool it to room temperature.

[0071] S6, after completing S5, the Ti662 titanium alloy bar is surface machined to prepare the bar into a size of Ti662 titanium alloy bar.

[0072] Example 3

[0073] S1. The Ti662 ingot, which had been melted in a vacuum consumable arc melting furnace three times, was first heated to 750°C in a natural gas furnace, kept warm for 60 minutes, then raised to 1190°C, kept warm for another 22 hours, and then taken out of the furnace. It was then forged on a 45 / 50MN fast forging unit using a two-upset and three-draw forging process with a single upsetting ratio of 1.6 and a final forging temperature of 860°C to fully break up the as-cast structure.

[0074] S2: First heat the billet that has completed S1 to 655℃, keep it warm for 55min, then heat it to 1030℃, keep it warm for 205min, and then perform the upsetting and drawing process, two upsetting and two drawing, with a single upsetting ratio of 1.8 and a final forging temperature of 820℃ to obtain the intermediate forging billet.

[0075] The intermediate forging blank was first heated to 750°C and kept at this temperature for 60 minutes. The temperature was then raised to 950°C and kept at this temperature for 180 minutes before performing the upsetting and drawing process. The upsetting and drawing process was repeated once, with a single upsetting ratio of 1.7 and a final forging temperature of 810°C to obtain the Ti662 forging blank.

[0076] S3, the Ti662 forging blank obtained in S2 is subjected to 5-fire reforging treatment:

[0077] In the first fire, the Ti662 billet after S3 was heated to 800℃ in a resistance heating furnace, kept at this temperature for 50min, then raised to 850℃, kept at this temperature for another 220min, and then made into a two-phase blank. The blank was made by two upsetting and two drawing, with a single upsetting ratio of 1.42 and a final forging temperature of 750℃.

[0078] For the second heat, the Ti662 billet that has completed the first heat is heated to 650℃ in a resistance heating furnace, kept at this temperature for 90 minutes, then raised to 880℃, and kept at this temperature for another 210 minutes before being made into a two-phase blank. The billet is then subjected to two upsetting and two drawing operations, with a single upsetting ratio of 1.5 and a final forging temperature of 760℃.

[0079] For the third fire, the Ti662 billet that has completed the second fire is first heated to 700℃ in a resistance heating furnace, kept at this temperature for 30 minutes, then raised to 910℃, and kept at this temperature for another 270 minutes before being made into a two-phase zone billet. Two upsetting and two drawing processes are performed, with a single upsetting ratio of 1.7 and a final forging temperature of 765℃.

[0080] For the fourth heat, the Ti662 billet that has completed the third heat is first heated to 750℃ in a resistance heating furnace, kept at this temperature for 60 minutes, then raised to 890℃, and kept at this temperature for another 250 minutes before being made into a two-phase zone billet. Two upsetting and two drawing processes are performed, with a single upsetting ratio of 1.6 and a final forging temperature of 755℃.

[0081] In the fifth heat, the Ti662 billet that has completed the third heat is first heated to 720℃ in a resistance heating furnace, kept at this temperature for 75 minutes, then raised to 860℃, and kept at this temperature for another 260 minutes before being made into a two-phase zone billet. Two upsetting and two drawing processes are performed, with a single upsetting ratio of 1.4 and a final forging temperature of 770℃.

[0082] In order to further ensure that the grains are fully broken, multi-directional forging is performed in S3 to minimize the anisotropy generated during the forging process.

[0083] S4, subjecting the Ti662 forging blank obtained in S3 to a 4-time drawing treatment:

[0084] In the first heat, the Ti662 billet obtained in S3 was heated to 800°C in a resistance heating furnace, kept at this temperature for 30 minutes, then raised to 950°C, and kept at this temperature for another 90 minutes before being stretched using a 45 / 50MN fast forging machine with a spring hammer of Ø110-170mm. The stretching process used a three-way asynchronous deformation technology with an axial deformation rate of 20mm / s, a radial rotation speed of 5rpm, a forging ratio of 2.0, and a final forging temperature of 755°C.

[0085] For the second heat treatment, the Ti662 billet that has completed the first heat treatment is heated to 650°C in a resistance heating furnace, held at that temperature for 90 minutes, then raised to 840°C. After holding at that temperature for another 270 minutes, it is stretched using a 45 / 50MN fast forging machine with a Ø110-170mm spring hammer. The stretching process uses a three-way asynchronous deformation technology with an axial deformation rate of 15mm / s, a radial rotation speed of 6rpm, a forging ratio of 5.5, and a final forging temperature of 760°C.

[0086] For the third fire, the Ti662 billet that has completed the second fire is first heated to 700°C in a resistance heating furnace, kept warm for 60 minutes, then heated to 910°C, and kept warm for 180 minutes. It is then drawn using a 45 / 50MN fast forging machine with a Ф110-170mm spring hammer. The drawing process uses three-way asynchronous deformation technology, with an axial deformation rate of 18mm / s, a radial rotation speed of 8rpm, an upsetting ratio of 2.2, and a final forging temperature of 758°C.

[0087] For the fourth fire, the Ti662 billet that has completed the second fire is first heated to 750°C in a resistance heating furnace, kept warm for 75 minutes, then heated to 880°C, and kept warm for 210 minutes before being drawn. A 45 / 50MN fast forging machine is used with a Ф110-170mm spring hammer for drawing. The drawing process uses three-way asynchronous deformation technology, with an axial deformation rate of 17mm / s, a radial rotation speed of 7rpm, an upsetting ratio of 2.6, and a final forging temperature of 778°C.

[0088] The three-way asynchronous deformation technology can achieve differentiated deformation of the material in three dimensions through the synergistic effect of axial deformation, radial rotation and temperature gradient control, thereby optimizing the microstructure and mechanical properties.

[0089] S5. First heat the formed rod obtained in S4 to 890℃, keep it warm for 2 hours, then take it out of the furnace and water cool it to room temperature; then heat the rod to 545℃, keep it warm for 8 hours, then take it out of the furnace and straighten it to a curvature of ≤3mm / m, and then air cool it to room temperature.

[0090] S6, after completing S5, the Ti662 titanium alloy bar is surface machined to prepare the bar into a size of Ti662 titanium alloy bar.

[0091] Example 4

[0092] S1. The Ti662 ingot, which had been melted in a vacuum consumable arc melting furnace three times, was first heated to 700°C in a natural gas furnace, kept warm for 90 minutes, then raised to 1160°C, kept warm for another 23 hours, and then taken out of the furnace. It was then forged on a 45 / 50MN fast forging unit using a two-upset and three-draw forging process with a single upsetting ratio of 1.86 and a final forging temperature of 870°C to fully break up the as-cast structure.

[0093] S2. First heat the billet that has completed S1 to 800℃ and keep it warm for 85min. Then heat it to 1090℃ and keep it warm for 150min. Then perform the upsetting and drawing process. The process is two upsetting and two drawing. The upsetting ratio of each time is 1.6. The final forging temperature is 840℃ to obtain the intermediate forging billet.

[0094] The intermediate forging blank was first heated to 800°C and kept warm for 90 minutes, then heated to 970°C and kept warm for 160 minutes before performing the upsetting and drawing process, with one upsetting and one drawing being performed, the single upsetting ratio being 1.9, and the final forging temperature being 820°C to obtain the Ti662 forging blank.

[0095] S3, the Ti662 forging blank obtained in S2 is subjected to three-stage reforging treatment:

[0096] In the first heat, the Ti662 billet after S3 was heated to 650℃ in a resistance heating furnace, kept at this temperature for 60min, then raised to 910℃, and kept at this temperature for 270min before being made into a two-phase zone billet. The billet was subjected to two upsetting and two drawing operations, with a single upsetting ratio of 1.4 and a final forging temperature of 760℃.

[0097] For the second heat, the Ti662 billet that has completed the first heat is first heated to 725°C in a resistance heating furnace, kept at this temperature for 30 minutes, then raised to 845°C, and kept at this temperature for another 210 minutes before being made into a two-phase blank. Two upsetting and two drawing operations are performed, with a single upsetting ratio of 1.58 and a final forging temperature of 758°C.

[0098] For the third heat, the Ti662 billet that has completed the second heat is first heated to 800℃ in a resistance heating furnace, kept at this temperature for 90 minutes, then raised to 875℃, and kept at this temperature for another 240 minutes before being made into a two-phase zone billet. Two upsetting and two drawing processes are performed, with a single upsetting ratio of 1.7 and a final forging temperature of 776℃.

[0099] In order to further ensure that the grains are fully broken, multi-directional forging is performed in S3 to minimize the anisotropy generated during the forging process.

[0100] S4, subjecting the Ti662 forging blank obtained in S3 to a three-time drawing treatment:

[0101] In the first heat, the Ti662 billet obtained in S3 was heated to 650°C in a resistance heating furnace, kept at this temperature for 90 minutes, then raised to 910°C, and kept at this temperature for another 180 minutes before being stretched using a 45 / 50MN fast forging machine with a spring hammer of Ø110-170mm. The stretching process used a three-way asynchronous deformation technology with an axial deformation rate of 15mm / s, a radial rotation speed of 5rpm, a forging ratio of 2.2, and a final forging temperature of 753°C.

[0102] For the second heat treatment, the Ti662 billet that has completed the first heat treatment is heated to 720°C in a resistance heating furnace, held at that temperature for 60 minutes, then raised to 845°C. After holding at that temperature for another 90 minutes, it is stretched using a 45 / 50MN fast forging machine with a 110-170mm Ø spring hammer. The stretching process uses a three-way asynchronous deformation technology with an axial deformation rate of 18mm / s, a radial rotation speed of 8rpm, a forging ratio of 3.0, and a final forging temperature of 760°C.

[0103] For the third fire, the Ti662 billet that has completed the second fire is first heated to 799°C in a resistance heating furnace, kept warm for 30 minutes, then heated to 875°C, and kept warm for 270 minutes before being drawn. A 45 / 50MN fast forging machine is used with a Ф110-170mm spring hammer for drawing. The drawing process uses three-way asynchronous deformation technology, with an axial deformation rate of 20mm / s, a radial rotation speed of 6rpm, an upsetting ratio of 1.9, and a final forging temperature of 759°C.

[0104] The three-way asynchronous deformation technology can achieve differentiated deformation of the material in three dimensions through the synergistic effect of axial deformation, radial rotation and temperature gradient control, thereby optimizing the microstructure and mechanical properties.

[0105] S5. First heat the formed bar obtained in S4 to 910℃, keep it warm for 3 hours, then take it out of the furnace and water cool it to room temperature; then heat the bar to 560℃, keep it warm for 6 hours, then take it out of the furnace and straighten it with a curvature of ≤3mm / m, and then air cool it to room temperature.

[0106] S6, after completing S5, the Ti662 titanium alloy bar is surface machined to prepare the bar into a size of Ti662 titanium alloy bar.

[0107] refer to Figures 1 to 4 As shown in Table 1, the Ti662 titanium alloy bars with a diameter of 118 mm × 1700 mm obtained in each embodiment were subjected to microstructure, mechanical properties and ultrasonic testing. Figure 1 , in line with level 20 in AMS2380; the transverse microstructure of the rod in Example 1 is shown in Figure 2 , the β transformation structure content is 79.70%, the α grain size is 9.5, rated according to ETTC2, the macrostructure is rated according to AMS2380, and the grade is ≤30; the longitudinal microstructure of the rod of Example 1 is shown in Figure 3 , the β transformation structure content is 84.02%, and the α grain size is 10.5; the typical waveform of the ultrasonic testing of the rod in Example 1 is shown in Figure 4 The noise level is Ø0.8-24 to -18dB, meeting the AA-level requirements of AMS2631F and AMS-STD-2154E. The longitudinal room-temperature tensile test results of the core of the bar of each embodiment are shown in Table 1. The preparation process of the present invention can achieve longitudinal room-temperature tensile properties of Rm ≥ 1120MPa, RP0.2 ≥ 1050MPa, A4D ≥ 10%, and Z ≥ 25% for the core of Ti662 bars with a diameter greater than Ø100mm. In the present invention, the furnace temperature uniformity requirements of all heating equipment involved meet the requirements of AMS2750 "Pyrometry Methods."

[0108] Table 1 Longitudinal room temperature tensile properties of the core of the rods of various examples

[0109]

[0110]

[0111] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0112] It should be understood that the present invention is not limited to the above description and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for preparing high-strength Ti662 titanium alloy bar, characterized in that: The following steps are involved: S1, performing a stepwise heating process on a Ti662 titanium alloy ingot and then performing an upsetting process to obtain a first forging blank; S2, performing two intermediate forgings on the first forging blank to obtain a second forging blank; S3, reforging the second forging blank to obtain a third forging blank; S4, stretching the third forging blank to obtain a first bar; S5, performing solution treatment and aging treatment on the first bar in sequence to obtain a second bar; S6. Surface machining the second bar to the finished size.

2. The method for preparing a high-strength Ti662 titanium alloy bar according to claim 1, characterized in that: In S1, the stepwise heating process is as follows: heating the Ti662 titanium alloy ingot to 650°C to 850°C, keeping the temperature for 30min to 120min, then heating the ingot to Tβ+200°C to Tβ+250°C, and keeping the temperature for 20h to 24h; During the upsetting process, the single upsetting ratio is 1.6~1.9, final forging temperature ≥850℃.

3. The method for preparing a high-strength Ti662 titanium alloy bar according to claim 1, characterized in that: In S2, the first intermediate forging process is as follows: heating the first forging blank to 650°C to 800°C, holding the temperature for 30min to 90min, then heating the blank to Tβ+100°C to Tβ+150°C, holding the temperature for 150min to 210min, and then performing an upsetting process to obtain an intermediate forging blank; The second intermediate forging process is as follows: first, the intermediate forging blank is heated to 700℃~800℃, kept at this temperature for 30min~90min, then heated to Tβ+30℃~Tβ+50℃, kept at this temperature for 150min~210min, and then subjected to the upsetting process; During the two intermediate forging processes, the single upsetting ratio of the upsetting and drawing process is 1.6 to 1.9, and the final forging temperature is ≥800℃.

4. The method for preparing a high-strength Ti662 titanium alloy bar according to claim 1, characterized in that: In S3, the process of the reforging treatment is: first heat the second forging blank to 650℃~800℃, keep it warm for 30min~90min, then raise the temperature to Tβ-30℃~Tβ-100℃, keep it warm for 210min~270min and then reforge, then perform 3~5 fire upsetting and drawing processes, two upsetting and two drawing per fire, the single upsetting ratio is 1.4~1.7, and the final forging temperature is ≥750℃.

5. The method for preparing a high-strength Ti662 titanium alloy bar according to claim 1, characterized in that: In S4, the drawing process is as follows: first, the third forging blank is heated to 650°C to 800°C, kept warm for 30min to 90min, then heated to Tβ-30°C to Tβ-100°C, kept warm for 90min to 270min, and then subjected to 3 to 5 fire drawing processes. The drawing process uses three-way asynchronous deformation technology, with an axial deformation rate of 15-20mm / s and a radial rotation speed of 5-8rpm. The total forging ratio of the process is ≥7.0, and the final forging temperature is ≥750°C.

6. The method for preparing a high-strength Ti662 titanium alloy bar according to claim 1, characterized in that: In S5, the process of the solution treatment is as follows: firstly, the first bar is heated to Tβ-30°C to 50°C, then kept at this temperature for 1h to 3h, and then cooled to room temperature after being taken out of the furnace; The aging treatment process is as follows: heating the solution treated bar to 520° C. to 560° C., keeping the temperature for 4 to 8 hours, and then air cooling the bar to room temperature.

7. The method for preparing a high-strength Ti662 titanium alloy bar according to claim 1, characterized in that: In S1, the preparation process of the Ti662 titanium alloy ingot is: the Ti662 titanium alloy ingot is obtained by smelting in a vacuum consumable arc furnace three times.

8. The method for preparing a high-strength Ti662 titanium alloy bar according to claim 1, characterized in that: In S3, multi-directional forging is performed during the reforming forging process, and the tolerance of the third forging blank finally formed satisfies ±3 mm, and the curvature is ≤3 mm / m.

9. The method for preparing a high-strength Ti662 titanium alloy bar according to claim 6, characterized in that: In S5, the time from the first bar being taken out of the furnace to entering the water during the solution treatment is ≤30s, and the bar is quenched in flowing water with a water flow rate of ≥143m 3 / h.

10. The method for preparing a high-strength Ti662 titanium alloy bar according to claim 1, characterized in that: In S6, the second rod needs to be straightened before surface machining, and the curvature is ≤3 mm / m.

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