A high-temperature titanium alloy bar and low-cost preparation method thereof

Abstract

The present invention discloses a low-cost method for preparing high-temperature titanium alloy bars. The titanium alloy is composed of the following components by mass: Al 8.0% to 10.5%, Zr 1.0% to 2.5%, Nb 0.5% to 1.0%, Mo 0.1% to 0.5%, Si 0.1% to 0.45%, O 0.15% to 0.25%, C ≤ 0.15%, with the balance being Ti and unavoidable impurities. The method comprises: 1. ingot smelting; 2. ingot forging and grinding; 3. bar billet radial forging; and 4. bar billet heat treatment and machining. The present invention designs the titanium alloy composition, employs a single-fire billet forging process combined with a multi-fire radial forging process, and controls process parameters and production processes such as deformation temperature and deformation amount. This results in a titanium alloy bar with high-strength room-temperature mechanical properties and excellent high-temperature performance. The bar is suitable for high-temperature applications such as aerospace engine components, aircraft structural parts, and fasteners.

Description

Technical Field

[0001] The present invention relates to the technical field of nonferrous metal material processing, and in particular to a high-temperature titanium alloy bar and a low-cost preparation method thereof. Background Art

[0002] High-temperature titanium alloys are widely used in high-temperature environments, such as aerospace, energy, petrochemicals, and automotive manufacturing, due to their excellent thermal stability and heat resistance, as well as their inherent advantages such as low density, excellent corrosion resistance, strong creep resistance, and excellent fracture toughness. While meeting the same requirements, high-temperature titanium alloys can reduce weight by approximately 70%, perform well in good working order, and play an indispensable role in modern industry. In recent years, with the rapid development of various high-temperature alloy application fields, the demand for high-temperature alloys has increased, and the requirements for their performance have become more stringent. Near-alpha titanium alloys, with their high high-temperature strength and stability, have become the main high-temperature titanium alloys currently in use. Examples include Ti-1100 developed in the United States, IMI834 developed in the United Kingdom, BT36 developed in Russia, and Ti60, Ti600, TG6, Ti65, and Ti750 developed in my country. Although high-temperature titanium alloys can be used at certain high temperatures, as the service temperature increases, titanium alloys become more susceptible to oxidation, and their oxide layer will significantly reduce the alloy properties. Therefore, the current conventional service temperature of high-temperature titanium alloys is difficult to exceed 600°C, the room temperature strength is about 1100MPa, and the optimal high-temperature tensile strength at 600°C is about 650MPa. This also makes the development of high-temperature titanium alloys face more severe challenges. Near-α titanium alloys have a high aluminum equivalent. With the increase of α stabilizing elements, especially the increase of aluminum content, the substitutional solid solution strengthening effect can significantly improve the room temperature and high temperature strength and thermal strength of titanium alloys. However, when the aluminum content exceeds a certain limit, brittle Ti3Al phase is easily formed in the titanium alloy. This brittle phase will significantly reduce the plasticity and toughness of the material, making it easy to form severe surface cracks during hot working. Traditional grinding will also aggravate crack propagation, increase invisible loss, lead to long processing cycle, reduced yield rate, and increased cost, which to a certain extent limits engineering applications. This is also one of the bottlenecks restricting the development of high-temperature titanium alloys. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art and provide a low-cost method for preparing high-temperature titanium alloy bars. This method designs the composition of the titanium alloy, adopts a process of single-fire open forging combined with multi-fire radial forging, and controls process parameters and production processes such as deformation temperature and deformation amount during the preparation process to avoid crack propagation during deformation, ensuring the smooth progress of the preparation process. A titanium alloy bar with high-strength room temperature mechanical properties and good high-temperature performance at 700°C is obtained, thereby improving the processing yield of the high-temperature titanium alloy bar, reducing production costs, and solving the problem of poor plasticity in the hot working process of near-α titanium alloys.

[0004] To solve the above technical problems, the technical solution adopted by the present invention is: a low-cost preparation method for a high-temperature titanium alloy bar, characterized in that the high-temperature titanium alloy bar is composed of the following components by mass: Al 8.0% to 10.5%, Zr 1.0% to 2.5%, Nb 0.5% to 1.0%, Mo 0.1% to 0.5%, Si 0.1% to 0.45%, O 0.15% to 0.25%, C ≤ 0.15%, and the balance is Ti and unavoidable impurities. The method comprises the following steps:

[0005] Step 1, ingot melting: a consumable electrode is prepared by vacuum argon arc welding, and then the consumable electrode is melted three times in a vacuum consumable arc furnace to obtain a titanium alloy ingot, and then the ingot riser is sawed and the surface pores and surface oxide scale are removed; the phase transition point of the titanium alloy ingot is 1100°C ± 5°C;

[0006] Step 2, ingot forging: the titanium alloy ingot from which the surface pores and surface oxide scale have been removed in step 1 is heated to a high temperature and then subjected to a first-fire forging process to obtain a billet, which is then slowly cooled;

[0007] Step 3, radial forging of the rod blank: The rod blank slowly cooled in step 2 is subjected to radial forging for 3 to 4 times, and is ground and de-scratched after each radial forging. After the first two radial forging times, the rod blank is slowly cooled to obtain a radial forged rod blank; the diameter of the radial forged rod blank is 2 mm to 4 mm larger than the diameter of the target titanium alloy bar;

[0008] Step 4: Heat treatment and machining of the rod blank: Use an electric heating furnace to perform atmospheric annealing on the radial forging rod blank obtained in step 3. After annealing, straighten the rod blank at residual heat and turn it to the target size to obtain a high-temperature titanium alloy rod: the high-temperature titanium alloy rod has a room temperature yield strength of more than 1150 MPa, a tensile strength of more than 1250 MPa, an elongation of more than 8%, a cross-sectional shrinkage rate of more than 10%, a high-temperature tensile strength of more than 640 MPa at 700°C, an elongation of more than 55%, a uniform structure, an average grain size of about 20 μm, and a yield rate of 60% to 70%.

[0009] The above-mentioned low-cost preparation method for high-temperature titanium alloy rods is characterized in that the three vacuum consumable arc furnace smeltings in step one adopt a 500kg vacuum consumable arc furnace, and the vacuum degree is less than 0.3Pa, and the stable smelting current is 7500A~12000A; the size of the titanium alloy ingot is Φ360mm×1050mm in diameter×height, and the size of the ingot after sawing the ingot riser and removing the surface pores and surface oxide scale is Φ340mm×1000mm in diameter×height, and the surface is flat and smooth, without untreated subcutaneous pores or obvious turning steps caused by sampling.

[0010] The above-mentioned low-cost preparation method of high-temperature titanium alloy bars is characterized in that the high-temperature heating system described in step 2 is: placing it in a box-type resistance furnace at 600℃~900℃ and keeping it warm for 60min~90min, then heating it with the furnace to 1150℃ and keeping it warm for 240min~360min, and the single-fire blanking forging process is: after high-temperature heating, taking it out of the furnace and directly drawing and rounding it to a bar billet with a diameter of Φ180mm~200mm, the single hammer pressing amount does not exceed 70mm, and it can be returned to the furnace for heating during the forging process, and the holding time for returning to the furnace for heating is 30min~60min; the slow cooling is to use insulation cotton wrapping for cooling, or placing it in a box-type resistance furnace with a temperature not exceeding 950℃ and cooling it with the furnace to 300℃~400℃, then taking it out of the furnace for air cooling, and then using a grinding wheel machine to grind and remove the oxide scale on the surface of the bar billet, and water cooling during grinding to avoid local areas being ground for too long due to temperature rise and secondary cracking.

[0011] The above-mentioned low-cost preparation method of high-temperature titanium alloy bars is characterized in that the process of 3 to 4 rounds of radial forging in step three is: placing it in a box-type resistance furnace at 600℃ to 900℃ and keeping it warm for 60min to 90min, then heating it with the furnace to 1000℃ to 1050℃ and keeping it warm for 120min to 180min, and then performing radial forging, and the deformation of each round of radial forging is 40% to 60%. After the first two rounds of radial forging are completed, it is wrapped with insulation cotton for cooling, or placed in a box-type resistance furnace with a temperature not exceeding 950℃ and cooled with the furnace to 300℃ to 400℃ before being taken out of the furnace for air cooling.

[0012] The above-mentioned low-cost preparation method for high-temperature titanium alloy bars is characterized in that the heating temperature of the atmospheric annealing in step 4 is 800°C to 850°C, the holding time is 90min to 120min, and the residual temperature is straightened after being taken out of the furnace.

[0013] The above-mentioned low-cost preparation method of a high-temperature titanium alloy rod is characterized in that the diameter of the high-temperature titanium alloy rod in step 4 is Φ30mm to Φ80mm.

[0014] The present invention also discloses a high-temperature titanium alloy bar, characterized by being prepared by the above method. The high-temperature titanium alloy bar of the present invention is suitable for use in high-temperature environments of 700°C and is suitable for use in aerospace engine parts, aircraft structural parts, fasteners, and many other high-temperature environments.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. The high-temperature titanium alloy in the present invention is a typical near-α titanium alloy. By increasing the Al content in its components to 8.0% to 10.5%, its room temperature and high-temperature properties are significantly improved. By adding a small amount of β-interstitial stabilizing element Si, the high-temperature properties and oxidation resistance of the titanium alloy are greatly improved. By adding a large amount of neutral element Zr, it is solid-solved in α-titanium, which has the effect of refining the grains and effectively improving the strength and plasticity of the titanium alloy. By adding titanium alloy β-stabilizing elements Mo and Nb, the thermal strength and thermal stability of the titanium alloy are improved. By adding C, the elements in the matrix are uniformly diffused and the processing window of the two-phase region is widened. The strength of the titanium alloy is further improved by doping interstitially strengthened O.

[0017] 2. The present invention adopts a process of single-fire open forging combined with multi-fire radial forging. First, a single-fire large deformation forging is performed by utilizing the characteristics of good deformation plasticity and low resistance at the phase transformation point of titanium alloy, and then multi-fire radial forging is performed at the phase transformation point, so that the billet is subjected to three-dimensional compressive stress during deformation, effectively avoiding further expansion of cracks during deformation. At the same time, a slow cooling method is adopted after forging and after the first two fires of radial forging are completed to reduce the change in temperature gradient during the cooling process of the billet, and prevent further expansion of cracks generated during the processing process, thereby ensuring the smooth progress of the preparation process. Under the condition that the Al content in the titanium alloy increases and its processing plasticity is reduced, the yield of high-temperature titanium alloy bars is guaranteed by regulating the preparation process.

[0018] 3. The present invention adopts a staged heating process for both single-fire blank forging and multi-fire radial forging, which effectively avoids the adverse phenomena such as excessive temperature gradient from the surface to the core of the blank during high-temperature heating and heat preservation due to poor thermal conductivity of titanium alloy, resulting in poor structural uniformity, and even cracking of the blank due to uneven temperature.

[0019] 4. During the single-fire forging of the blank of the present invention, the amount of single hammer reduction is controlled and processing measures such as remelting and heating are taken to control the processing deformation and deformation temperature of the blank. At the same time, the temperature of the grinding process is controlled to effectively avoid the adverse effects caused by the poor processing plasticity of the near-α alloy.

[0020] 5. After the rod blanks that have obtained a certain processing plasticity through forging and radial forging are subjected to atmospheric annealing, the present invention adopts conventional air cooling to ensure that the surface of the high-temperature titanium alloy rods is good and simplify the process; at the same time, the preparation process route of the present invention is short, the product rate is high, and the production cost is effectively reduced.

[0021] 6. The room temperature yield strength of the high-temperature titanium alloy rod prepared by the present invention is above 1150 MPa, the tensile strength is above 1250 MPa, the elongation is above 8%, the cross-sectional shrinkage is above 10%, the high temperature tensile strength at 700°C is above 640 MPa, the elongation is above 55%, the structure is uniform, the average grain size is about 20 μm, the finished product rate is 60% to 70%, and the batch consistency is good.

[0022] 7. The high-temperature titanium alloy rods prepared by the present invention have higher processing plasticity during subsequent hot working deformation, and the optional processing methods are less limited. It is expected to prepare smaller-sized high-temperature titanium alloy rods and wires, which will further expand its application field.

[0023] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a high-magnification microstructure diagram of the high-temperature titanium alloy rod prepared in Example 1 of the present invention.

[0025] Figure 2 This is a high-magnification microstructure diagram of the high-temperature titanium alloy rod prepared in Example 2 of the present invention.

[0026] Figure 3 This is a high-magnification microstructure diagram of the high-temperature titanium alloy rod prepared in Example 3 of the present invention.

[0027] Figure 4 This is a high-magnification microstructure diagram of the high-temperature titanium alloy rod prepared in Example 4 of the present invention. DETAILED DESCRIPTION

[0028] Example 1

[0029] The high-temperature titanium alloy rod of this embodiment is composed of the following components by mass: Al 9.2%, Zr 1.1%, Nb 0.6%, Mo 0.32%, Si 0.10%, O 0.15%, C 0.12%, and the balance is Ti and unavoidable impurities. The preparation method of the high-temperature titanium alloy rod comprises the following steps:

[0030] Step 1, ingot melting: vacuum argon arc welding is used to prepare a consumable electrode, and then the consumable electrode is placed in a 500kg vacuum consumable arc furnace for three vacuum consumable arc furnace melting, and the vacuum degree is less than 0.3Pa, the stable melting current is 7520A, and a titanium alloy ingot with a diameter × height of Φ360mm × 1050mm is obtained. The ingot riser is then sawed and the surface pores and surface oxide scale are removed to a diameter × height of Φ340mm × 1000mm, and the surface is flat and smooth, without untreated subcutaneous pores or obvious turning steps caused by sampling;

[0031] Step 2, ingot forging: the titanium alloy ingot after removing the surface pores and surface oxide scale in step 1 is placed in a box-type resistance furnace at 600°C and kept warm for 60 minutes, then heated to 1150°C with the furnace and kept warm for 240 minutes, then taken out of the furnace and directly drawn and rounded to a rod billet with a diameter of Φ180mm, with a single hammer pressing amount of 60mm. During the forging process, after the rod billet is forged to a diameter of Φ220mm, it is returned to the furnace for heating, and the holding time for returning to the furnace for heating is 30 minutes. It is then placed in a box-type resistance furnace at a temperature of 950°C and cooled to 300°C with the furnace, then taken out of the furnace for air cooling, and ground with a grinding wheel to remove the surface oxide scale; water cooling is applied during the grinding to avoid secondary cracking caused by excessive grinding time in local areas resulting in temperature rise;

[0032] Step 3, radial forging of the rod: the rod from which the surface oxide scale was removed in step 2 was placed in a box-type resistance furnace at 600°C and kept warm for 60 minutes, then heated to 1000°C and kept warm for 120 minutes, and then radial forging was performed four times, with the deformation of each radial forging being 59%, 57%, 56%, and 56% respectively. After each radial forging, the rod was ground and scratched. After the first two radial forgings, the rod was wrapped with insulation cotton and cooled to obtain a radial forging rod with a diameter of Φ33 mm.

[0033] Step 4: Heat treatment and machining of the rod blank: The radial forging rod blank obtained in step 3 is subjected to atmospheric annealing in an electric heating furnace at a heating temperature of 800°C and a holding time of 90 minutes. After annealing, the rod blank is straightened at residual temperature after being taken out of the furnace and turned to a diameter of Φ30 mm to obtain a high-temperature titanium alloy rod. According to statistics, the total yield of the high-temperature titanium alloy rod is 62.2%.

[0034] Figure 1 The high-magnification microstructure of the high-temperature titanium alloy rod was prepared for this example. Figure 1 It can be seen that the microstructure of the high-temperature titanium alloy rod is a two-phase processed structure, which mainly includes equiaxed α phase and a small amount of β phase, and the structure is uniform and consistent.

[0035] Example 2

[0036] The high-temperature titanium alloy rod of this embodiment is composed of the following components by mass: Al 10.1%, Zr 1.2%, Nb 0.74%, Mo 0.12%, Si 0.22%, O 0.18%, C 0.13%, and the balance is Ti and unavoidable impurities. The preparation method of the high-temperature titanium alloy rod comprises the following steps:

[0037] Step 1, ingot melting: vacuum argon arc welding is used to prepare a consumable electrode, and then the consumable electrode is placed in a 500kg vacuum consumable arc furnace for three vacuum consumable arc furnace melting, and the vacuum degree is less than 0.3Pa, and the stable melting current is 9000A to obtain a titanium alloy ingot with a diameter × height of Φ360mm × 1050mm. Then, the ingot riser is sawed and the surface pores and surface oxide scale are removed to a diameter × height of Φ340mm × 1000mm, and the surface is flat and smooth, without untreated subcutaneous pores or obvious turning steps caused by sampling;

[0038] Step 2, ingot forging: the titanium alloy ingot after removing the surface pores and surface oxide scale in step 1 is placed in a box-type resistance furnace at 780°C and kept warm for 90 minutes, then heated to 1150°C with the furnace and kept warm for 300 minutes, then taken out of the furnace and directly drawn and rounded to a rod billet with a diameter of Φ180mm, with a single hammer pressing amount of 65mm. During the forging process, after the rod billet is forged to a diameter of Φ220mm, it is returned to the furnace for heating, and the holding time for returning to the furnace for heating is 60 minutes. It is then placed in a box-type resistance furnace at a temperature of 950°C and cooled to 400°C with the furnace, then taken out of the furnace for air cooling, and ground with a grinding wheel to remove the surface oxide scale; water cooling is applied during the grinding to avoid secondary cracking caused by excessive grinding time in local areas resulting in temperature rise;

[0039] Step 3, bar billet radial forging: the bar billet after removing the surface oxide scale in step 2 is placed in a box-type resistance furnace at 600°C and kept warm for 60 minutes, then heated to 1030°C and kept warm for 150 minutes, and then subjected to three rounds of radial forging, with the radial forging deformation of each round being 56%, 50%, and 50% respectively. After each round of radial forging, the bar billet is ground and scratched. After the first two rounds of radial forging, the bar billet is placed in a box-type resistance furnace at 950°C and cooled to 300°C. The bar billet is then taken out of the furnace and air-cooled to obtain a radial forged bar billet with a diameter of Φ58 mm.

[0040] Step 4: Heat treatment and machining of the rod blank: The radial forging rod blank obtained in step 3 is subjected to atmospheric annealing in an electric heating furnace at a heating temperature of 800°C and a holding time of 120 minutes. After annealing, the rod blank is straightened at residual temperature after being taken out of the furnace and turned to a diameter of Φ55 mm to obtain a high-temperature titanium alloy rod. According to statistics, the total yield of the high-temperature titanium alloy rod is 68.2%.

[0041] Figure 2 The high-magnification microstructure of the high-temperature titanium alloy rod was prepared for this example. Figure 2It can be seen that the microstructure of the high-temperature titanium alloy rod is a two-phase processed structure, which mainly includes equiaxed α phase and a small amount of β phase, and the structure is uniform and consistent.

[0042] Example 3

[0043] The high-temperature titanium alloy rod of this embodiment is composed of the following components by mass: Al 10.5%, Zr 2.4%, Nb 0.86%, Mo 0.45%, Si 0.43%, O 0.24%, C 0.09%, and the balance is Ti and unavoidable impurities. The preparation method of the high-temperature titanium alloy rod comprises the following steps:

[0044] Step 1, ingot melting: vacuum argon arc welding is used to prepare a consumable electrode, and then the consumable electrode is placed in a 500kg vacuum consumable arc furnace for three vacuum consumable arc furnace melting, and the vacuum degree is less than 0.3Pa, and the stable melting current is 10000A to obtain a titanium alloy ingot with a diameter × height of Φ360mm × 1050mm. Then, the ingot riser is sawed and the surface pores and surface oxide scale are removed to a diameter × height of Φ340mm × 1000mm, and the surface is flat and smooth, without untreated subcutaneous pores or obvious turning steps caused by sampling;

[0045] Step 2, ingot forging: the titanium alloy ingot after removing the surface pores and surface oxide scale in step 1 is placed in a box-type resistance furnace at 900°C and kept warm for 80 minutes, then heated to 1150°C with the furnace and kept warm for 350 minutes, then taken out of the furnace and directly drawn and rounded to a rod blank with a diameter of Φ200mm, with a single hammer pressing amount of 70mm, then wrapped with insulation cotton and cooled to room temperature, and ground with a grinding wheel to remove the surface oxide scale; water cooling is applied during the grinding to avoid secondary cracking caused by excessive grinding time in local areas due to temperature rise;

[0046] Step 3, radial forging of the rod: the rod after cooling in step 2 is placed in a box-type resistance furnace at 780°C and kept warm for 80 minutes, then heated to 1050°C and kept warm for 180 minutes, and then radial forging is performed three times, with the deformation of each radial forging being 42%, 42%, and 45% respectively. After each radial forging, the rod is ground and scratched. After the first two radial forgings, it is wrapped with insulation cotton and cooled to room temperature to obtain a radial forging rod with a diameter of Φ84 mm;

[0047] Step 4: Heat treatment and machining of the rod blank: The radial forging rod blank obtained in step 3 is subjected to atmospheric annealing in an electric heating furnace at a heating temperature of 850°C and a holding time of 100 minutes. After annealing, the rod blank is straightened at residual temperature after being taken out of the furnace and turned to a diameter of Φ80 mm to obtain a high-temperature titanium alloy rod. According to statistics, the total yield of the high-temperature titanium alloy rod is 65.5%.

[0048] Figure 3The high-magnification microstructure of the high-temperature titanium alloy rod was prepared for this example. Figure 3 It can be seen that the microstructure of the high-temperature titanium alloy rod is a two-phase processed structure, which mainly includes equiaxed α phase and a small amount of β phase, and the structure is uniform and consistent.

[0049] Example 4

[0050] The high-temperature titanium alloy rod of this embodiment is composed of the following components by mass: Al 8.1%, Zr 1.8%, Nb 0.97%, Mo 0.11%, Si 0.27%, O 0.20%, C 0.14%, and the balance is Ti and unavoidable impurities. The preparation method of the high-temperature titanium alloy rod comprises the following steps:

[0051] Step 1, ingot melting: vacuum argon arc welding is used to prepare a consumable electrode, and then the consumable electrode is placed in a 500kg vacuum consumable arc furnace for three vacuum consumable arc furnace melting, and the vacuum degree is less than 0.3Pa, and the stable melting current is 12000A to obtain a titanium alloy ingot with a diameter × height of Φ360mm × 1050mm. Then, the ingot riser is sawed and the surface pores and surface oxide scale are removed to a diameter × height of Φ340mm × 1000mm, and the surface is flat and smooth, without untreated subcutaneous pores or obvious turning steps caused by sampling;

[0052] Step 2, ingot forging: the titanium alloy ingot after removing the surface pores and surface oxide scale in step 1 is placed in a box-type resistance furnace at 650°C and kept warm for 90 minutes, then heated to 1150°C with the furnace and kept warm for 240 minutes, then taken out of the furnace and directly drawn and rounded to a rod blank with a diameter of Φ200mm, with a single hammer pressing amount of 70mm, then wrapped with insulation cotton and cooled to room temperature, and ground with a grinding wheel to remove the surface oxide scale; water cooling is applied during the grinding to avoid secondary cracking caused by excessive grinding time in local areas due to temperature rise;

[0053] Step 3, bar billet radial forging: the bar billet from which the surface oxide scale is removed in step 2 is placed in a 900°C box-type resistance furnace and kept warm for 90 minutes, then heated to 1050°C and kept warm for 120 minutes, and then subjected to four rounds of radial forging, with the deformation of each round being 58%, 52%, and 58% respectively. After each round of radial forging, the bar billet is ground and scratched. After the first two rounds of radial forging, the bar billet is placed in a 950°C box-type resistance furnace and cooled to 400°C. The bar billet is then taken out of the furnace and air-cooled to obtain a radial forged bar billet with a diameter of Φ58 mm.

[0054] Step 4: Heat treatment and machining of the rod blank: The radial forging rod blank obtained in step 3 is subjected to atmospheric annealing in an electric heating furnace at a heating temperature of 820°C and a holding time of 110 minutes. After annealing, the rod blank is straightened at residual temperature after being taken out of the furnace and turned to a diameter of Φ55 mm to obtain a high-temperature titanium alloy rod. According to statistics, the total yield of the high-temperature titanium alloy rod is 61%.

[0055] Figure 4 The high-magnification microstructure of the high-temperature titanium alloy rod was prepared for this example. Figure 4 It can be seen that the microstructure of the high-temperature titanium alloy rod is a two-phase processed structure, which mainly includes equiaxed α phase and a small amount of β phase, and the structure is uniform and consistent.

[0056] The mechanical properties and average grain sizes of the high-temperature titanium alloy bars prepared in Examples 1 to 4 of the present invention were tested, and the results are shown in Table 1 below.

[0057] Table 1

[0058]

[0059] As can be seen from Table 1, the phase transformation point of the titanium alloy ingots prepared in Examples 1 to 4 of the present invention is 1100°C ± 5°C, the room temperature yield strength of the prepared high-temperature titanium alloy bars is above 1150 MPa, the tensile strength is above 1250 MPa, the elongation is above 8%, the cross-sectional shrinkage is above 10%, the high-temperature tensile strength at 700°C is above 640 MPa, the elongation is above 55%, the structure is uniform, the average grain size is about 20 μm, and the batch consistency is good.

[0060] The above description 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 variation made to the above embodiment based on the essence of the invention technology shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A low-cost preparation method for high-temperature titanium alloy bars, characterized in that: The high-temperature titanium alloy rod is composed of the following components by mass: Al 8.0% to 10.5%, Zr 1.0% to 2.5%, Nb 0.5% to 1.0%, Mo 0.1% to 0.5%, Si 0.1% to 0.45%, O 0.15% to 0.25%, C ≤ 0.15%, and the balance being Ti and unavoidable impurities. The method comprises the following steps: Step 1, ingot melting: a consumable electrode is prepared by vacuum argon arc welding, and then the consumable electrode is melted three times in a vacuum consumable arc furnace to obtain a titanium alloy ingot, and then the ingot riser is sawed and the surface pores and surface oxide scale are removed; the phase transition point of the titanium alloy ingot is 1100°C ± 5°C; Step 2, ingot forging: the titanium alloy ingot from which the surface pores and surface oxide scale have been removed in step 1 is heated to a high temperature and then subjected to a first-fire forging process to obtain a billet, which is then slowly cooled; Step 3, radial forging of the rod blank: The rod blank slowly cooled in step 2 is subjected to radial forging for 3 to 4 times, and is ground and de-scratched after each radial forging. After the first two radial forging times, the rod blank is slowly cooled to obtain a radial forged rod blank; the diameter of the radial forged rod blank is 2 mm to 4 mm larger than the diameter of the target titanium alloy bar; Step 4: Heat treatment and machining of the rod blank: Use an electric heating furnace to perform atmospheric annealing on the radial forging rod blank obtained in step 3, straighten the residual heat after annealing, and turn it to the target size to obtain a high-temperature titanium alloy rod; the high-temperature titanium alloy rod has a room temperature yield strength of more than 1150 MPa, a tensile strength of more than 1250 MPa, an elongation of more than 8%, a cross-sectional shrinkage rate of more than 10%, a high-temperature tensile strength of more than 640 MPa at 700°C, an elongation of more than 55%, a uniform structure, an average grain size of about 20 μm, and a finished product rate of 60% to 70%.

2. The low-cost preparation method of a high-temperature titanium alloy bar according to claim 1, characterized in that: The three vacuum consumable arc furnace smeltings described in step one adopt a 500kg vacuum consumable arc furnace, and the vacuum degree is less than 0.3Pa, and the stable melting current is 7500A~12000A; the size of the titanium alloy ingot is Φ360mm×1050mm in diameter and height, and the size after sawing the ingot riser and removing the surface pores and surface oxide scale is Φ340mm×1000mm in diameter and height, and the surface is flat and smooth, without untreated subcutaneous pores or obvious turning steps caused by sampling.

3. The low-cost preparation method of a high-temperature titanium alloy bar according to claim 1, characterized in that: The high-temperature heating system described in step 2 is: placing it in a box-type resistance furnace at 600℃~900℃ and keeping it for 60min~90min, then heating it with the furnace to 1150℃ and keeping it for 240min~360min. The single-fire blanking forging process is: after high-temperature heating, directly pulling and rounding it to a rod billet with a diameter of Φ180mm~200mm, the single hammer pressing amount does not exceed 70mm, and it can be returned to the furnace for heating during the forging process. The holding time for returning to the furnace for heating is 30min~60min; the slow cooling is to use insulation cotton for cooling, or placing it in a box-type resistance furnace with a temperature not exceeding 950℃ and cooling it with the furnace to 300℃~400℃, then taking it out of the furnace for air cooling, and then using a grinding wheel machine to grind and remove the oxide scale on the surface of the rod billet, and water cooling during grinding to avoid local areas being ground for too long due to temperature rise and secondary cracking.

4. The low-cost preparation method of a high-temperature titanium alloy bar according to claim 1, characterized in that: The process of 3 to 4 rounds of radial forging described in step 3 is as follows: placing the steel into a box-type resistance furnace at 600°C to 900°C and keeping it warm for 60 to 90 minutes, then heating it to 1000°C to 1050°C and keeping it warm for 120 to 180 minutes, and then radial forging. The deformation of each round of radial forging is 40% to 60%. After the first two rounds of radial forging are completed, the steel is wrapped with insulation cotton and cooled, or placed in a box-type resistance furnace with a temperature not exceeding 950°C and cooled to 300°C to 400°C with the furnace, and then taken out of the furnace for air cooling.

5. The low-cost preparation method for high-temperature titanium alloy bars according to claim 1, characterized in that: The heating temperature of the atmospheric annealing in step 4 is 800° C. to 850° C., the holding time is 90 min to 120 min, and the residual temperature is used for straightening after being taken out of the furnace.

6. The low-cost preparation method for high-temperature titanium alloy bars according to claim 1, characterized in that: The diameter of the high-temperature titanium alloy rod in step 4 is Φ30mm to Φ80mm.

7. A high temperature titanium alloy bar, characterized in that: The method is prepared by any one of claims 1 to 6.

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