Low-temperature titanium alloy material and preparation method

Abstract

The invention discloses a low-temperature titanium alloy material and a preparation method, the low-temperature titanium alloy material is an alpha + beta type two-phase titanium alloy, an alpha stable element (Al), a beta stable element (Mo / Nb / V) and a neutral element (Zr) are used as main composition elements, and the content (O) of interstitial elements is controlled. The influence mechanism of each component element on the low-temperature mechanical property and the low-temperature deformation mechanism is determined, so that the mass percentage content of each component and the interstitial element content are accurately controlled. On the basis, the low-temperature titanium alloy material involved in the invention can be used for manufacturing profiles or components in various forms, and low-temperature titanium alloy components in different forms can be manufactured by combining a numerical simulation technology optimization process scheme. The low-temperature mechanical properties of the low-temperature titanium alloy material under the condition of 20K can meet the requirements that the tensile strength Rm is larger than or equal to 1500MPa, the elongation A is larger than or equal to 12%, and the low-temperature strength and plasticity matching is excellent.

Description

Technical Field

[0001] The invention relates to a low-temperature titanium alloy, a rod, a product and a preparation method, and belongs to the technical field of advanced materials. Background Art

[0002] Low-temperature titanium alloy components are the core components of the launch vehicle engine system. Due to the sharp increase in the service capability of launch vehicles, traditional low-temperature titanium alloy materials and manufacturing processes can no longer meet the needs of some core components due to increased engine speed. In addition, in today's international situation where scientific and technological competition is increasingly fierce, foreign countries have been strictly blocking my country in the design of high-strength and tough low-temperature titanium alloy composition, forming process and mechanism research. It is particularly important to develop domestically produced low-temperature titanium alloy materials and corresponding manufacturing processes with independent intellectual property rights.

[0003] At present, although the relatively mature TC4ELI, TA7ELI, and CT20 low-temperature titanium alloys developed at home and abroad have been applied, they have more or less some practical engineering problems and cannot meet the new and higher service requirements. TC4ELI, as an α+β type dual-phase titanium alloy, has high hot processing performance and excellent low-temperature specific strength and fracture toughness. However, the high β phase content makes the alloy have a certain ductile-brittle transition phenomenon, resulting in the low-temperature service temperature of TC4ELI titanium alloy being mostly concentrated at 77K, which cannot meet the use requirements of 20K in liquid hydrogen environment. As a near-α type low-temperature titanium alloy, TA7ELI has excellent strength and extremely low notch sensitivity under low temperature conditions of 20K, and has both ideal weldability and economy. It has been used in the development of hydrogen pump impellers and cold helium cylinder components of launch vehicle liquid engines. However, due to the lack of β-stabilizing elements, it has practical problems such as poor strength-plasticity matching and low mechanical property margin under 20K low temperature environment. CT20 titanium alloy is a near-α-type medium-strength low-temperature titanium alloy successfully developed in recent years. Its certain content of β-stabilizing elements not only makes CT20 exhibit good cold and hot processing properties, but also has excellent room temperature and low-temperature properties, process properties and welding properties. It has been successfully applied to the mass production of liquid hydrogen pipeline components for launch vehicle engines. However, the tensile strength of this alloy is only 1300MPa at the low temperature of 20K, and it does not have the characteristics of high-strength and high-toughness low-temperature mechanical properties.

[0004] Foreign countries have always imposed strict blockades on my country in the composition design, preparation technology, forming process and mechanism research of low-temperature high-strength plastic titanium alloys, resulting in my country not yet being at the advanced echelon of low-temperature titanium alloy research. There is an urgent need to develop new high-strength plastic titanium alloys with better performance and stability in low-temperature environments. Summary of the invention

[0005] The technical problem solved by the present application is: to overcome the deficiencies of the prior art, to provide a method for optimizing the performance of low-temperature titanium alloys and an advanced manufacturing technology, to provide a low-temperature titanium alloy material with higher performance, and to provide a more effective manufacturing process solution for the mismatch between the manufacturing process and the service environment.

[0006] The technical solutions provided by this application are as follows:

[0007] A low-temperature titanium alloy material, based on 100% content of each component, includes: Al: 3.3-4.5%, Zr: 1.5-3%, Mo: 0.5-1.5%, V: 0.5-1.5%, Nb: 0.5-1.5%, oxygen content ≤0.12%, unavoidable impurities ≤0.4%, and the balance is Ti.

[0008] The raw materials are titanium sponge, Al-Mo alloy, Al-V alloy, Al-Nb alloy, zirconium sponge, aluminum beans and aluminum foil.

[0009] The low-temperature properties of low-temperature titanium alloys under liquid hydrogen 20K conditions meet the following requirements: tensile strength Rm ≥ 1500MPa, elongation A ≥ 12%.

[0010] A method for preparing a low-temperature titanium alloy material, using any of the above-mentioned low-temperature titanium alloy materials for preparation, comprises the following steps:

[0011] The raw materials are subjected to vacuum melting to obtain an ingot;

[0012] The ingot is at the β phase transition point T β The forging blank is obtained by performing multiple upsetting-stretching processes at 50-150°C.

[0013] The primary forging billet cooled to room temperature is heated at T β + (0~50℃) to repeatedly upsetting-drawing to obtain a round billet, and finally air-cooling the round billet to room temperature;

[0014] If the diameter of the target bar is greater than 80 mm, the round billet is made into a bar by forging;

[0015] If the diameter of the target bar is less than 80 mm, the round billet is made into a bar by rolling.

[0016] The method of forging a round billet into a bar comprises:

[0017] Place the round billet at T β -(0~50℃) keep warm for 3~4h, take out of the furnace and repeatedly roll, forge and stretch, the final forging temperature is not less than 800℃, until the required diameter is reached, then anneal at 650±50℃, adjust the shape, cut and peel.

[0018] The method of rolling the round billet into a bar comprises: rolling the round billet into a bar β -(0~50℃) keep warm for 3~4h, roll into round shape according to product diameter, the final rolling temperature shall not be lower than 820℃, until the required diameter is reached, then anneal, adjust shape, cut and peel at 650±50℃ / 900±30℃ for 1~2h.

[0019] The ingot is at the β phase transformation point T β The forging blank is obtained by performing multiple upsetting-drawing processes at 50-150°C, including:

[0020] The ingot is at the β phase transition point T β The billet is heated with the furnace, and after being taken out of the furnace, it is first upset to a height-to-diameter ratio ≤ 2, returned to the furnace and kept warm for 1.5±0.5h, and then drawn to a height-to-diameter ratio of 2 to 2.5; the above upsetting-drawing process is repeated 2 to 3 times, and then placed in an annealing furnace at 600 to 700°C and kept warm for 6 to 8h, and finally air-cooled to room temperature to obtain a primary forging billet.

[0021] The primary forging billet cooled to room temperature is heated to T β + (0~50℃) for repeated upsetting-drawing to obtain a round billet, and finally air-cooling the round billet to room temperature, including:

[0022] The primary forging billet cooled to room temperature is heated again to T β + (0-50°C) for 3-4 hours to fully recrystallize it, and then repeatedly upsetting and drawing at this temperature for 3-5 times, wherein the upsetting height-to-diameter ratio is ≤2, and the drawing is to a height-to-diameter ratio of 2-2.5, and finally to a length-to-diameter ratio of 6-8, and then placed in a 600-700°C annealing furnace for 6-8 hours to obtain a round billet, and finally the round billet is air-cooled to room temperature.

[0023] In summary, this application at least includes the following beneficial technical effects:

[0024] (1) The present invention provides a new type of low-temperature titanium alloy material. Starting from the influence mechanism of each component element on the low-temperature mechanical properties and its influence on the hot processing forming performance of the material, the influence of each element on the low-temperature mechanical properties and the low-temperature cooperative deformation mechanism of the α phase / β phase is clearly analyzed, and the corresponding relationship between multi-factor, multi-level parameters and its mechanical properties is established, so as to reasonably control the proportion of each element and the content of interstitial elements according to the specific service environment of the low-temperature titanium alloy. Thereby avoiding the cost waste caused by the simple trial and error method.

[0025] (2) Compared with the currently commonly used low-temperature titanium alloy materials, the low-temperature titanium alloy powder metallurgy material involved in the present invention has excellent low-temperature mechanical properties. Its low-temperature performance under 20K conditions meets the following requirements: tensile strength Rm ≥ 1500MPa, elongation A ≥ 12%, and has excellent low-temperature strength and plasticity matching.

[0026] (3) The low-temperature titanium alloy material involved in the present invention can be manufactured into profiles and components of different forms, has strong adaptability, and can provide solutions for different service environments and manufacturing solutions. For example, by rolling low-temperature titanium alloy bars, direct mechanical processing of parts can be achieved; low-temperature titanium alloy atomization powder making and powder metallurgy forming process technology are combined to produce high-performance hydrogen pump impeller components, solve the service performance obstacles of carrier aircraft impeller components produced by traditional casting technology, and promote technological upgrading.

[0027] (4) The present invention can solve the current research shortcomings in my country in terms of unreasonable design of low-temperature titanium alloy composition and backward forming process technology. The research results involved can be extended to the development and production of high-performance low-temperature titanium alloy structural parts for aerospace such as impellers, rotors, and gas cylinders, so as to promote the upgrading of my country's new generation of aerospace vehicles, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart of the preparation method of the low-temperature titanium alloy rod and powder metallurgy material of the present invention;

[0029] Figure 2 This is a microstructure photograph of the low-temperature titanium alloy rod in Example 1 of the present invention;

[0030] Figure 3 This is a microstructure photograph of the low-temperature titanium alloy powder metallurgy material in Example 3 of the present invention;

[0031] Figure 4 TEM microstructures of alloys with different Al / Mo element contents, where a is the TEM microstructure of the alloy with low Al / Mo element content, and b is the TEM microstructure of the alloy with high Al / Mo element content. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0033] The present embodiment discloses a low-temperature titanium alloy, which is an α+β two-phase titanium alloy, with α-stabilizing elements (Al), β-stabilizing elements (Mo / Nb / V), and neutral elements (Zr) as main components; based on the content of each component being 100%, it includes: Al: 3.3~4.5%, Zr: 1.5~3%, Mo: 0.5~1.5%, V: 0.5~1.5%, Nb: 0.5~1.5%, oxygen content ≤0.12%, unavoidable impurities ≤0.4%, and the balance is Ti.

[0034] Orthogonal tests were used to analyze the influence of each element on low-temperature mechanical properties and the low-temperature cooperative deformation mechanism of α phase / β phase. Taking α-stabilizing element Al and β-stabilizing element Mo as examples, as shown in Table a (in the low-temperature titanium alloy in Table a, the sum of all components is 100%, Zr: 2.0%, V: 1.0%, Nb: 0.5%, oxygen content 0.11%, unavoidable impurities ≤ 0.4%, and the remainder is Ti; the total mass percentage of Al, Mo and Ti is considered to be the same), it was found that with the increase of Al content and Mo content, the tensile strength at 20K increased, but when the Al content and Mo content were at the maximum value at the same time, the elongation decreased. After the oxygen content increased by more than 0.12%, the maximum strength reached 1686MPa, but the elongation also showed this phenomenon. Mainly, with the coordinated increase of Al / Mo element content, the proportion of twin deformation in its low-temperature deformation mode gradually decreased, and dislocation slip became dominant. At this time, dislocation entanglement became an inevitable trend, so there was an increase in 20K low-temperature tensile strength. Figure 4 (a) is the TEM microstructure of the alloy with low Al / Mo content (3.3% Al, 0.5% Mo). Figure 4 (b) is the TEM microstructure of the alloy with high Al / Mo content (4.5% Al, 1.5% Mo).

[0035] Table a 20K low temperature tensile strength of titanium alloys with different Al and Mo contents / MPa

[0036]

[0037] The applicable temperature of the low-temperature titanium alloy material under liquid hydrogen conditions is 20K and above, and at the same time, it still has a high strength-plasticity matching effect under room temperature conditions. The mechanical properties should have a synergistic effect under both room temperature and low temperature conditions.

[0038] The low-temperature titanium alloy material (such as rod material, powder metallurgy material) and corresponding components have low-temperature properties under liquid hydrogen 20K conditions that meet the following requirements: tensile strength Rm≥1500MPa, elongation A≥12%.

[0039] The manufacturing technology includes but is not limited to the form and manufacturing method of raw materials or components, such as Figure 1 As shown, including:

[0040] (1) The low-temperature titanium alloy and its preparation method include but are not limited to precision casting components, bars obtained by ingot casting-forging-rolling, forged cakes obtained by ingot casting-forging and other forms of profiles, blanks for powder forging, and pre-alloyed spherical powders suitable for powder metallurgy and additive manufacturing. That is, on the one hand, the required parts can be manufactured by near-net forming; on the other hand, profiles / blanks (bars, forgings), etc. can also be manufactured for subsequent mechanical processing to manufacture the required parts to meet the corresponding accuracy and service requirements.

[0041] (2) The low-temperature titanium alloy and its preparation method, the raw materials can be commercially available high-cleanliness ultra-soft sponge titanium, Al-Mo master alloy, Al-V master alloy, Al-Nb master alloy, sponge zirconium, aluminum beans and aluminum foil through at least three vacuum melting to obtain ingots, which meet the requirements of subsequent forging and precision casting. Or large particles of TiH2 etc. replace sponge titanium, and the raw material particles are mixed, hot pressed, dehydrogenated and other steps to obtain powder metallurgy billets or parts.

[0042] (3) The low-temperature titanium alloy and its preparation method, the manufacture of high-performance low-temperature titanium alloy rods; sponge titanium, Al-Mo alloy, Al-V alloy, Al-Nb alloy, sponge zirconium, aluminum beans and aluminum foil are vacuum melted three times to obtain an ingot. The ingot is at the β phase transition point T β Keep it at 50-150℃ for 3-4h, heat the billet with the furnace, and transfer it to the fast forging machine immediately after it comes out of the furnace. First, upset it to a height-to-diameter ratio of ≤2, return it to the furnace and keep it for 1.5±0.5h, and then stretch it to a height-to-diameter ratio of 2-2.5; repeat the above upsetting-stretching process 2-3 times, then put it in a 600-700℃ annealing furnace and keep it for 6-8h, finally put it in a sand pit and air-cool it to room temperature, and grind the surface; heat the billet cooled to room temperature again to T β + (0 ~ 50 ℃) for 3 ~ 4h to fully recrystallize, and then repeatedly upsetting and drawing at this temperature for 3 to 5 times, wherein the upsetting height-diameter ratio is ≤2, drawn to a height-diameter ratio of 2 to 2.5, and finally drawn to a length-diameter ratio of 6 to 8, then placed in a 600 ~ 700 ℃ annealing furnace for 6 to 8h, and finally placed in a sand pit for air cooling to room temperature, and the surface is polished; the final deformation by the last fire determines the final preparation process according to the final rod diameter, and the large diameter Forged bars are used, and rolled bars are used for bars (<80mm). Forged bars: The round billet obtained by the previous deformation fire is rolled into a T β -(0~50℃) for 3~4h, then take out of the furnace and repeatedly roll, forge and stretch, the final forging temperature is not less than 800℃, until the required diameter is reached, then anneal, adjust, cut and peel at 650±50℃. β-(0~50℃) for 3~4h, and then roll the product into a round shape according to the diameter. The final rolling temperature is not less than 820℃. After reaching the required diameter, anneal, shape correction, cutting and peeling are carried out at 650±50℃ / 900±30℃ for 1~2h. The low-temperature titanium alloy bar with excellent low-temperature strength matching is obtained, which can be used for the processing and production of different types of low-temperature components.

[0043] (4) The low-temperature titanium alloy and its preparation method, the powder metallurgy material and component shape-property integrated control technology can be prepared from the high-performance billet obtained in (3) above by plasma gun rotating electrode atomization method, and the powder diameter is controlled at 53 to 250 microns. Combined with numerical simulation software such as Marc., the powder metallurgy forming process parameters are optimized to manufacture structural parts that meet the requirements of liquid hydrogen temperature environment.

[0044] The low-temperature titanium alloy and its preparation method described in (5) can realize the manufacture of high-performance low-temperature titanium alloy forging cakes through the forging scheme described in (3) and the subsequent large deformation upsetting technology. On this basis, the Deform 3D software is combined to realize the optimization of the die forging process of structural parts and the design of the process scheme, and realize the production and manufacturing of die forgings.

[0045] Example 1

[0046] In this embodiment, low temperature titanium alloy rods are first used, and the rods can be used for parts processing. The specific preparation process is as follows:

[0047] The titanium alloy powder metallurgy material prepared in this embodiment is a new type of α+β two-phase low-temperature titanium alloy. Based on the content of each component being 100%, the content is Al: 3.3%, Zr: 2.0%, Mo: 0.5%, V: 1.0%, Nb: 0.5%, oxygen content is 0.11%, unavoidable impurities are ≤0.4%, and the balance is Ti.

[0048] The method for preparing the above-mentioned low-temperature titanium alloy rod comprises the following steps:

[0049] (1) Ingot preparation: The ingots are prepared in a three-stage vacuum consumable arc furnace. The raw materials for the ingots are ultra-pure and ultra-soft sponge titanium, high-cleanliness aluminum beans, aluminum foil, Al-Mo, Al-V, Al-Nb master alloys and sponge zirconium.

[0050] (2) Rolling: The ingot is at the β phase transformation point T βThe billet is kept at 1050℃ for 3-4 hours, and then heated with the furnace. After being taken out of the furnace, it is immediately transferred to the fast forging machine. First, it is upset to a height-to-diameter ratio of 1.8, returned to the furnace for 1.5 hours, and then drawn to a height-to-diameter ratio of 2.2. This is repeated twice, and then placed in a 650℃ annealing furnace for 6.5 hours, and finally placed in a sand pit for air cooling to room temperature, and the surface is polished; the billet cooled to room temperature is heated to 1000℃ again for 3 hours to fully recrystallize, and repeated upsetting-drawing is performed at this temperature for 4 times, wherein the upsetting height-to-diameter ratio is 1.8, drawn to a height-to-diameter ratio of 2.2, and finally drawn Grow to an aspect ratio of 8, then put it in a 650℃ annealing furnace for 6.5 hours, and finally put it in a sand pit for air cooling to room temperature, and polish the surface; keep the round billet obtained from the previous deformation fire at 920℃ for 4 hours, and roll it into a round shape. The deformation amount is 15-25% each time, and the final rolling temperature is not less than 820℃. The final billet diameter is 25mm, and annealing, shaping, cutting, and peeling are carried out at 650±50℃ / 900±30℃ for 1-2 hours. The diameter of the obtained product is 20±0.5mm.

[0051] (3) The performance of the rod obtained in this example was tested. The microstructure of the low-temperature titanium alloy rod is shown in FIG. Figure 2 The test results are shown in Table 1 below.

[0052] Table 1 Low temperature mechanical properties of new low temperature titanium alloy bars

[0053]

[0054] Example 2

[0055] The only difference from Example 1 is that the alloy element contents are Al: 4.0%, Zr: 2.0%, Mo: 1.0%, V: 1.0%, Nb: 0.5%, the balance is Ti, and the oxygen content is 0.11%.

[0056] The preparation method of the above-mentioned low-temperature titanium alloy rod is the same as that of Example 1.

[0057] The rod obtained in this embodiment was subjected to performance testing, and the testing structure is shown in Table 2 below.

[0058] Table 2 Low temperature mechanical properties of new low temperature titanium alloy bars

[0059]

[0060] Example 3

[0061] In this embodiment, high-performance low-gap titanium alloy spherical powder is prepared by plasma gun rotating electrode atomization method, and the powder is screened and packaged before hot isostatic pressing to obtain low-temperature titanium alloy powder metallurgy material. The specific preparation process is as follows:

[0062] The titanium alloy powder metallurgy material prepared in this embodiment is a new type of α+β two-phase low-temperature titanium alloy. Based on the content of each component being 100%, its content is Al: 4.0%, Zr: 2.0%, Mo: 0.7%, V: 1.0%, Nb: 0.5%, and the balance is Ti. The oxygen content is 0.11%.

[0063] The method for preparing the above-mentioned low-temperature titanium alloy comprises the following steps:

[0064] (1) The method for preparing a low-temperature titanium alloy rod is the same as that in Example 1 to obtain a low-temperature titanium alloy rod.

[0065] (2) Powder preparation: The rod in step (1) is subjected to a plasma gun rotating electrode atomization method to prepare a new low-temperature titanium alloy spherical powder, and its chemical composition is tested and its particle morphology and internal microstructure characteristics are analyzed.

[0066] (3) Preparation of powder metallurgy materials and components: It is divided into package design - powder filling - gas outlet - hot isostatic pressing process optimization - package removal.

[0067] (3-1) Sheath design: The sheath is made of stainless steel and can be flexibly selected according to the shape of the part. The inner diameter of the sheath in this embodiment is 20 mm and the wall thickness is 2 mm. Stainless steel plugs are used at both ends for sealing welding.

[0068] (3-2) Powder filling: First, degrease and pickle the stainless steel sheath, seal one end with a plug, slowly load the new low-gap titanium alloy spherical powder into the sheath, manually knock and vibrate until the powder is compacted, weld the other end of the sheath with a plug, and leave a degassing pipe.

[0069] (3-3) High-temperature degassing: Connect the degassing pipe on the package to the vacuum unit, and place the package in the resistance furnace. Turn on the vacuum unit and the resistance furnace to heat up. The degassing temperature is selected to be 550℃ and the vacuum degree is ≤6×10 -3 Pa, the degassing time is 4h. After the degassing is completed, the degassing tube is sealed and welded under vacuum conditions.

[0070] (3-4) Hot isostatic pressing: The degassed package is subjected to hot isostatic pressing. The selected process parameters are: pressure: 140 MPa, temperature: 920 °C, and forming time: 3 h to prepare the corresponding powder metallurgy material.

[0071] (3-5) Removal of the sheath: The sheath of the material formed by hot isostatic pressing in step (7) is removed to prepare the desired powder metallurgy material.

[0072] The performance of the powder metallurgy material obtained in this example was tested, and the microstructure of the low-temperature titanium alloy powder metallurgy material is shown in the following figure: Figure 3 The test results are shown in Table 3 below.

[0073] Table 3 Low temperature mechanical properties of new low temperature titanium alloy powder metallurgy materials

[0074]

[0075] It can be seen from the low-temperature mechanical properties test results in the table that the low-temperature titanium alloy rods and powder metallurgy materials prepared in this embodiment have excellent low-temperature strength and good strength-plasticity matching. Compared with the currently commonly used TC4ELI and TA7ELI low-temperature titanium alloys, the new titanium alloy prepared in this embodiment has significant low-temperature mechanical properties advantages, which can provide a good material and process foundation for further improving the manufacturing of products in related fields in my country.

[0076] The contents not described in detail in this application specification belong to the common knowledge of those skilled in the art.

[0077] The present application is described in detail above in conjunction with specific implementation methods and exemplary examples, but these descriptions cannot be understood as limiting the present application. Those skilled in the art understand that, without departing from the spirit and scope of the present application, a variety of equivalent replacements, modifications or improvements can be made to the technical solutions and implementation methods of the present application, all of which fall within the scope of the present application. The scope of protection of the present application shall be subject to the attached claims.

Claims

1. A low temperature titanium alloy material, characterized in that: Taking the content of each component as 100%, it includes: Al: 3.3-4.5%, Zr: 1.5-3%, Mo: 0.5-1.5%, V: 0.5-1.5%, Nb: 0.5-1.5%, oxygen content ≤0.12%, unavoidable impurities ≤0.4%, and the balance is Ti.

2. A low temperature titanium alloy material according to claim 1, characterized in that: The raw materials of low-temperature titanium alloy materials are sponge titanium, Al-Mo alloy, Al-V alloy, Al-Nb alloy, sponge zirconium, aluminum beans and aluminum foil.

3. The low temperature titanium alloy material according to claim 1, characterized in that: The low-temperature properties of low-temperature titanium alloy materials under liquid hydrogen 20K conditions meet the following requirements: tensile strength Rm ≥ 1500MPa, elongation A ≥ 12%.

4. A method for preparing a low-temperature titanium alloy material, characterized in that: A low-temperature titanium alloy material according to any one of claims 1 to 3 is used for preparation to obtain a low-temperature titanium alloy rod, a low-temperature titanium alloy forging cake, a powder metallurgy material and / or a structural part.

5. A method for preparing a low-temperature titanium alloy material, characterized in that: The following steps are involved: The raw material of the low-temperature titanium alloy material according to any one of claims 1 to 3 is subjected to vacuum melting to obtain an ingot; The ingot is at the β phase transition point T β The forging blank is obtained by performing multiple upsetting-stretching processes at 50-150°C. The primary forging billet cooled to room temperature is heated at T β + (0~50℃) to repeatedly upsetting-drawing to obtain a round billet, and finally air-cooling the round billet to room temperature; If the diameter of the target bar is greater than 80 mm, the round billet is made into a bar by forging; If the diameter of the target bar is less than 80 mm, the round billet is made into a bar by rolling.

6. A low temperature titanium alloy rod according to claim 5, characterized in that: The method of forging a round billet into a bar comprises: The round billet is placed on the β -(0~50℃) keep warm for 3~4h, take out of the furnace and repeatedly roll, forge and stretch, the final forging temperature is not less than 800℃, until the required diameter is reached, then anneal at 650±50℃, adjust the shape, cut and peel.

7. The low-temperature titanium alloy rod according to claim 5, characterized in that: The method of rolling the round billet into a bar comprises: rolling the round billet into a bar β -(0~50℃) keep warm for 3~4h, roll into round shape according to product diameter, the final rolling temperature shall not be lower than 820℃, until the required diameter is reached, then anneal, adjust shape, cut and peel at 650±50℃ / 900±30℃ for 1~2h.

8. The low-temperature titanium alloy rod according to claim 5, characterized in that: The ingot is at the β phase transformation point T β The forging blank is obtained by performing multiple upsetting-drawing processes at 50-150°C, including: The ingot is at the β phase transition point T β The billet is heated with the furnace, and after being taken out of the furnace, it is first upset to a height-to-diameter ratio ≤ 2, returned to the furnace and kept for 1.5±0.5h, and then drawn to a height-to-diameter ratio of 2 to 2.5; the above upsetting-drawing process is repeated 2 to 3 times, and then placed in an annealing furnace at 600 to 700℃ and kept for 6 to 8h, and finally air-cooled to room temperature to obtain a primary forging billet.

9. The low-temperature titanium alloy rod according to claim 5, characterized in that: The primary forging billet cooled to room temperature is heated to T β + (0~50℃) for repeated upsetting-drawing to obtain a round billet, and finally air-cooling the round billet to room temperature, including: The primary forging billet cooled to room temperature is heated again to T β + (0-50°C) for 3-4 hours to fully recrystallize it, and then repeatedly upsetting and drawing at this temperature for 3-5 times, wherein the upsetting height-to-diameter ratio is ≤2, and the drawing is to a height-to-diameter ratio of 2-2.5, and finally to a length-to-diameter ratio of 6-8, and then placed in a 600-700°C annealing furnace for 6-8 hours to obtain a round billet, and finally the round billet is air-cooled to room temperature.

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