Preparation method of high-uniformity large-specification TA19 titanium alloy bar

Abstract

The invention discloses a preparation method of a high-uniformity large-specification TA19 titanium alloy bar, and belongs to the technical field of high-quality titanium alloy material manufacturing. The process route comprises the processes of two-heating-number cogging, three-heating-number modified forging, one-heating-number preforming and one-heating-number forming, three-time forging deformation is conducted at the position above the beta phase transformation point in the first heating number, an original structure is completely broken, and it is guaranteed that a microscopic structure is fine and uniform; according to the second heating number, primary forging deformation is carried out below the beta phase transformation point, remelting forging is carried out above the beta phase transformation point, the temperature is accurately controlled during remelting forging, beta grains are prevented from being too large, and the transverse and longitudinal uniformity of a microscopic structure is guaranteed. All properties of the finally prepared TA19 titanium alloy bar with the diameter of 400 mm meet index requirements, the transverse and longitudinal structures and properties of the bar have no difference, the uniformity is good, and the properties are more excellent.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-quality titanium alloy material manufacturing, relates to the manufacture of TA19 titanium alloy, and specifically relates to a method for preparing high-uniformity large-size TA19 titanium alloy bars. Background Art

[0002] TA19 titanium alloy is a near-alpha heat-resistant titanium alloy with excellent comprehensive properties. It boasts high specific strength, excellent creep resistance, and high-temperature durability. It is widely used in the manufacture of annular components such as compressor discs and engine cases in aircraft engines. However, with the growing demand for integrated, lightweight, and integrated aircraft engines, commonly available TA19 titanium alloy bars are no longer sufficient for larger aircraft engines. Therefore, the development of larger-sized TA19 bars is needed.

[0003] However, the alloy contains a wide variety of alloying elements at high concentrations, along with a low content of β-stabilizing elements. This results in poor hot working performance, a narrow processing window, and a high tendency to crack when forged below the phase transformation point. Furthermore, to prevent crack propagation, the cracks must be ground after firing, resulting in significant grinding losses. This not only prolongs the production cycle but also increases energy consumption, resulting in significant production cost waste and severely impacting product quality and yield. Furthermore, conventional forging methods for large-sized bars with diameters exceeding 400 mm require numerous firings and are prone to producing non-uniformity in both the transverse and longitudinal structures. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a method for preparing large-size TA19 titanium alloy bars with high uniformity, so as to solve the technical problems in the existing technology that the TA19 titanium alloy has poor thermal processing performance, narrow processing window, and conventional forging methods have many firing times, which easily lead to uneven transverse and longitudinal microstructures of TA19 titanium alloys with a diameter greater than or equal to 400 mm, as well as the problems of large grinding amount and high production cost.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A method for preparing large-size TA19 titanium alloy bars with high uniformity, comprising:

[0007] Step 1: Perform two-fire forging to obtain square billets:

[0008] Step 1.1, first fire blank forging: keep the temperature at 130-160°C above the β transformation point of TA19 titanium alloy for 6-10 hours, and perform upsetting forging deformation; after forging, return the hot material to the furnace, the furnace temperature is 80-110°C above the β transformation point of TA19 titanium alloy, the holding time is 2-5 hours, and after taking out of the furnace, perform upsetting forging deformation; after forging, return the hot material to the furnace, the furnace temperature is 30-60°C above the β transformation point of TA19 titanium alloy, the holding time is 2-5 hours, and after taking out of the furnace, perform upsetting forging deformation.

[0009] Step 1.2, the second fire forging includes: keeping the temperature at 20-50°C below the β transformation point of TA19 titanium alloy for 6-10 hours, performing at least two upsetting forging deformations, and controlling the upsetting deformation amount of each upsetting within 30-40%; returning the hot material to the furnace after forging, the furnace temperature is 30-60°C above the β transformation point of TA19 titanium alloy, the holding time is 4-6 hours, and upsetting forging deformation is performed after taking out of the furnace.

[0010] Step 2: Perform three-stage reforging on the billet to obtain the reforged billet:

[0011] The first fire forging includes: keeping the temperature at 20-50℃ below the β phase transformation point of TA19 titanium alloy for 6-10 hours, and performing upsetting forging deformation; returning the hot material to the furnace after forging, the furnace temperature is 20-50℃ below the β phase transformation point of TA19 titanium alloy, and the holding time is 2-4 hours; performing upsetting forging deformation after taking out of the furnace; returning the hot material to the furnace after forging, the furnace temperature is 20-50℃ below the β phase transformation point of TA19 titanium alloy, and the holding time is 2-4 hours, and performing upsetting forging deformation after taking out of the furnace; asbestos is used to wrap the square billet during the forging process.

[0012] The specific process of the second and third fire forging is exactly the same as that of the first fire forging.

[0013] Step 3: Perform one-time pre-forming forging on the reformed billet to obtain a pre-formed billet:

[0014] Drawing forging is carried out below the β phase transformation point. The conditions for drawing forging are: keeping warm at 20-40°C below the β phase transformation point of TA19 titanium alloy for 4-7 hours; the deformation amount of each upsetting and drawing is controlled at 25%-35%, the pressing speed during drawing is controlled at 25-35mm / s, the reduction amount is controlled at 75-150mm, and the feed amount is controlled at 300-400mm; after forging, the hot material is returned to the furnace, the returning temperature is 20-40°C below the β phase transformation point of TA19 titanium alloy, the holding time is 1-3 hours, and diagonal drawing is carried out after taking out of the furnace.

[0015] Step 4: Perform one-shot forging on the preformed billet:

[0016] The material is kept at 20-40°C below the β phase transformation point of TA19 titanium alloy for 4-6 hours and then rounded. During rounding, the pressing speed is 25-30 mm / s, the reduction is 10-20 mm, and the feed amount is 50-150 mm. After rounding, the hot material is returned to the furnace at a temperature of 20-40°C below the β phase transformation point of TA19 titanium alloy and the holding time is 0.5-2 hours.

[0017] The preparation method described above is applicable to TA19 titanium alloy bars with a diameter greater than or equal to 400 mm.

[0018] The beneficial technical effects of the present invention compared with the prior art are as follows:

[0019] (I) The present invention adopts two-fire forging. In the first fire, three forging deformations are performed above the β phase transformation point, so that the original structure is completely broken, ensuring that the microstructure is fine and uniform. In the second fire, one forging deformation is performed below the β phase transformation point and a re-forging is performed above the β phase transformation point. The temperature is precisely controlled during the re-forging to prevent the β grains from being too large, thereby ensuring the transverse and longitudinal uniformity of the microstructure.

[0020] (II) The process of the present invention includes two burns for blanking, three burns for forging, one burn for preforming, and one burn for forming. The number of burns for drawing is minimal. The final large-scale TA19 titanium alloy bar with a diameter of 400 mm meets all performance requirements. The bar exhibits no differences in microstructure and properties in the transverse and longitudinal directions, exhibits good uniformity, and exhibits superior performance. By optimizing the bar processing technology, the present invention improves bar quality and material utilization, which is of great significance for improving aircraft engine performance and reducing the risk of engine accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a macroscopic morphology of the TA19 titanium alloy rod prepared in Example 1 under a low-power microscope. Figure 1 Middle: (a) is a low-magnification macroscopic image of the rod head. (b) is a low-magnification macroscopic image of the rod tail.

[0022] Figure 2 This is the microstructure diagram of the TA19 titanium alloy rod prepared in Example 1 under a high-power microscope. Figure 2 Middle: (a) is a high-magnification microstructure image at the edge of a cross-section of the rod head. (b) is a high-magnification microstructure image at the R / 2 position of a cross-section of the rod head. (c) is a high-magnification microstructure image at the center of a cross-section of the rod head. (d) is a high-magnification microstructure image at the edge of a longitudinal section of the rod tail. (e) is a high-magnification microstructure image at the R / 2 position of a longitudinal section of the rod tail. (f) is a high-magnification microstructure image at the center of a longitudinal section of the rod tail.

[0023] The technical solution of the present invention is further described below in conjunction with embodiments. DETAILED DESCRIPTION

[0024] It should be noted that all materials used in the present invention, unless otherwise specified, are materials known in the art. For example, TA19 titanium alloy is a titanium alloy known in the prior art, and its composition is: Al is 6.0wt%, Sn is 2.0wt%, Zr is 4.0wt%, Mo is 2.0wt%, Si is 0.12wt%, and the balance is Ti. Its β phase transition point (T β ) is 990~1020℃; T β The following refers to below 1005℃, T β The above refers to above 1005℃.

[0025] In accordance with the above technical solution, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0026] Example 1:

[0027] This embodiment provides a method for preparing a large-size TA19 titanium alloy bar with high uniformity. The method is used to prepare a titanium alloy bar with a diameter of 400 mm, and specifically includes the following steps:

[0028] Step 1: Perform two-fire forging to obtain a square billet with fine β structure:

[0029] Step 1.1, first time forging: forge the TA19 titanium alloy ingot at a high temperature above the β phase transformation point. β Above 150℃, keep warm for 7h, carry out two upsetting and two drawing forging deformations, the deformation amounts are: 37%, 30%, 36%, 36% respectively; after forging, the hot material is returned to the furnace, and the furnace temperature is T β Above 100℃, keep warm for 3h, and then carry out two upsetting and two drawing forging deformation for a total of 4 times after being taken out of the furnace. In the process of drawing, reversing is added to better break the grains and obtain uniform structure. The deformation of each upsetting and drawing is controlled at 36%. After forging, the hot material is returned to the furnace at a temperature of T β The steel is heated to 50°C or higher and held for 3 hours. After exiting the furnace, it undergoes two upsetting and two drawing forgings. After the second drawing, it is forged in an eight-sided manner to reduce the deformation dead zone. The deformation of each upsetting and drawing process is controlled at 36%. After forging, it is air-cooled and polished. During the forging process, the pressing speed is controlled at 40mm / s, the pressing reduction is controlled at 120mm, and the feed rate is controlled at 450mm. A β structure with a grain size distribution of 5 to 15mm is obtained.

[0030] Step 1.2, second fire forging: low temperature forging below the β phase transformation point, heating temperature is T β The temperature is kept below 30℃ for 8 hours, and two upsetting and two drawing forgings are carried out. In the upsetting and drawing process, the billet is wrapped with heat-insulating asbestos to prevent the surface temperature from dropping and causing cracking. The deformation of each upsetting and drawing is controlled at 36%. After forging, the hot material is returned to the furnace at a temperature of T β The temperature is above 50℃, kept warm for 5h, and after being taken out of the furnace, it is forged by upsetting and drawing, and after drawing, it is turned into eight directions to reduce the deformation dead zone. The deformation of each upsetting and drawing is controlled at 36%. After forging, it is air-cooled and polished. The pressing speed of the forging process is controlled at 40mm / s, the reduction is controlled at 120mm, and the feed rate is controlled at 450mm. A β structure with a grain size distribution of 2 to 4mm is obtained.

[0031] Step 2: Perform three-stage reforging on the billet obtained in step 1 to obtain a reforged billet:

[0032] The first heat is low temperature forging below the β phase transformation point, and the heating temperature is T β The temperature is kept below 30℃ for 8 hours, and the billet is forged by upsetting and drawing. In the process of upsetting and drawing, the billet is wrapped with heat-insulating asbestos to prevent the surface temperature from dropping and causing cracking. The deformation of each upsetting and drawing is controlled at 36%. After forging, the hot material is returned to the furnace at a temperature of T β The temperature is kept below 30℃ for 3 hours. After being taken out of the furnace, the billet is forged by upsetting and drawing. In the process of upsetting and drawing, the billet is wrapped with heat-insulating asbestos. The deformation of each upsetting and drawing is controlled at 36%. After forging, the hot material is returned to the furnace at a temperature of T β The temperature is below 30℃, kept warm for 3h, and after being taken out of the furnace, it is forged by one upsetting and one drawing, and after the drawing is completed, it is turned into eight directions to reduce the deformation dead zone. The deformation of each upsetting and drawing is controlled at 36%. After forging, it is air-cooled and polished. The pressing speed of the forging process is controlled at 30mm / s, the pressing amount is controlled at 120mm, and the feed amount is controlled at 450mm. The forging process of the second and third fires is the same as the first fire.

[0033] Step 3: Perform a pre-forming forging on the billet obtained in step 2:

[0034] The square billet with an octagonal cross section is subjected to low temperature drawing and forging below the β phase transformation point. The heating temperature is T β The temperature is below 30℃, kept warm for 5h, and diagonal drawing forging is carried out. The deformation of each drawing is controlled at 30%, the pressing speed is controlled at 30mm / s, the pressing amount is controlled at 100mm, and the feed amount is controlled at 350mm. After forging, the hot material is returned to the furnace at a temperature of T βThe temperature is below 30℃, kept warm for 2h, and then drawn diagonally after being taken out of the furnace. After the drawing is completed, the steel is turned into eight directions. The deformation of each upsetting and drawing is controlled at 25%, the pressing speed is controlled at 30mm / s, the pressing amount is controlled at 70mm, the feed amount is controlled at 300mm, and the steel is air-cooled and polished after forging.

[0035] Step 4: Perform a first-time forming forging on the billet that has been preformed in step 3:

[0036] The rod with an octagonal cross section is rounded at low temperature below the β phase transformation point, and the heating temperature is T β Below 30℃, keep warm for 5h, control the deformation of each rounding and upsetting at 12%, the pressing speed at 30mm / s, the reduction at 15mm, and the feed at 100mm. In this process, in order to prevent cracking caused by too low temperature, the hot material is allowed to be returned to the furnace, and the returning temperature is 30℃ below the β phase transformation point of TA19 titanium alloy, and the returning holding time is 1.5h; air cooling and grinding after forging.

[0037] Effect verification of Example 1:

[0038] Figure 1 TA19 titanium alloy prepared by this preparation method From the macroscopic microstructure of the cross section of the head and tail of the large-size bar, it can be seen that the macroscopic microstructure has no cracks, folds, pores, metal or non-metallic inclusions, segregation, shrinkage and other metallurgical defects visible to the naked eye. There are no obvious visually visible clear grains, and the structure is uniformly blurred.

[0039] Figure 2 TA19 titanium alloy prepared by this preparation method From the high-magnification microstructures at the head and tail cross sections, longitudinal section edges, R / 2, and center of large-size bars, it can be seen that the high-magnification microstructure is composed of equiaxed α phase and a small amount of lamellar primary α phase. The high-magnification microstructure is uniform, no abnormal thermal structure is seen, and there is no continuous α network structure on the original β grain boundary.

[0040] Table 3 is the TA19 titanium alloy prepared by this preparation method From the mechanical properties of the large-size bar cross-section at the R / 2 position, the horizontal and vertical sampling results show that they meet the requirements of aviation standards, with good uniformity and a certain margin.

[0041] Table 3 Mechanical properties of horizontal and vertical samples taken at the R / 2 position on the cross section of the bar

[0042]

[0043] Comparative Example 1 (the blanking forging temperature in step 1.1 is different):

[0044] This comparative example provides a method for preparing large-size TA19 titanium alloy bars with high uniformity. The method is basically the same as that in Example 1, with the only difference being that the blanking forging temperature in step 1.1 is different.

[0045] In this comparative example, step 1.1 includes: the first blanking temperature is T β Above 200℃, keep warm for 7h, carry out two upsetting and two drawing forging deformations, the deformation amounts are: 37%, 30%, 36%, 36% respectively; after forging, the hot material is returned to the furnace, and the furnace temperature is T β Above 150℃, keep warm for 3h, and then carry out two upsetting and two drawing forging deformations for a total of 4 times after being taken out of the furnace. In the process of drawing, reversing is added to better break the grains and obtain uniform structure. The deformation of each upsetting and drawing is controlled at 36%. After forging, the hot material is returned to the furnace at a temperature of T β The temperature is kept above 80℃ for 3 hours. After being taken out of the furnace, it is forged by two upsetting and two drawing. After the second drawing, it is turned into eight squares to reduce the deformation dead zone. The deformation of each upsetting and drawing is controlled at 36%. After forging, it is air-cooled and polished. The pressing speed of the forging process is controlled at 40mm / s, the pressing amount is controlled at 120mm, and the feed rate is controlled at 450mm.

[0046] In this comparative example, due to deformation at a relatively high temperature, the original structure was not completely broken, the density was low, and the microstructure was uneven. The microstructure of the titanium alloy rod finally obtained was uneven and could not meet the technical requirements.

[0047] Comparative Example 2 (forging process in step 1.2 is different):

[0048] This comparative example provides a method for preparing a large-size TA19 titanium alloy bar with high uniformity. The method is basically the same as that in Example 1, with the only difference being that the first forging process in step 1.2 is different.

[0049] In this comparative example, step 1.2 includes: performing low temperature forging below the β phase transformation point, and heating the temperature to T β The temperature is kept below 30℃ for 8 hours, and the billet is forged in one upsetting and one drawing process. In the upsetting and drawing process, the billet is wrapped with heat-insulating asbestos to prevent the surface temperature from dropping and causing cracking. The deformation of each upsetting and drawing process is controlled at 36%. After forging, the hot material is returned to the furnace at a temperature of T β The temperature is above 50℃, kept warm for 5h, and after being taken out of the furnace, it is forged by upsetting and drawing, and after drawing, it is turned to eight directions to reduce the deformation dead zone. The deformation of each upsetting and drawing is controlled at 36%. After forging, it is air-cooled and polished. The pressing speed of the forging process is controlled at 40mm / s, the pressing amount is controlled at 120mm, and the feed amount is controlled at 450mm.

[0050] In this comparative example, since the steel bar only underwent upsetting deformation once at 30°C below the phase transformation point, the deformation amount was insufficient, resulting in the inability to recrystallize the β grains during subsequent deformation at 50°C above the phase transformation point. The microstructure of the titanium alloy bar finally obtained was uneven, with microtexture, and large differences in the transverse and longitudinal properties of the bar, making it difficult to meet the technical requirements.

[0051] Comparative Example 3 (the re-forging temperature in step 1.2 is different):

[0052] This comparative example provides a method for preparing large-size TA19 titanium alloy bars with high uniformity. The method is basically the same as that in Example 1, with the only difference being that the second re-melting forging temperature in step 1.2 is different.

[0053] In this comparative example, step 1.2 includes: performing low temperature forging below the β phase transformation point, and heating the temperature to T β The temperature is kept below 30℃ for 8 hours, and two upsetting and two drawing forgings are carried out. In the upsetting and drawing process, the billet is wrapped with heat-insulating asbestos to prevent the surface temperature from dropping and causing cracking. The deformation of each upsetting and drawing is controlled at 36%. After forging, the hot material is returned to the furnace at a temperature of T β The temperature is above 80℃, kept warm for 5h, and after being taken out of the furnace, it is forged by upsetting and drawing, and after drawing, it is turned to eight directions to reduce the deformation dead zone. The deformation of each upsetting and drawing is controlled at 36%. After forging, it is air-cooled and polished. The pressing speed of the forging process is controlled at 40mm / s, the pressing amount is controlled at 120mm, and the feed amount is controlled at 450mm.

[0054] In this comparative example, due to the second β Deformation at a high temperature above 80°C causes the β grains to grow, and the microstructure of the titanium alloy rod finally obtained is uneven, with microtexture, and large differences in the transverse and longitudinal properties of the rod, making it difficult to meet the technical requirements.

[0055] Comparative Example 4 (no insulation cotton was used in the forging process of step 2):

[0056] This comparative example provides a method for preparing large-size TA19 titanium alloy bars with high uniformity. The method is basically the same as Example 1, with the only difference being that no insulation cotton is used in the reforging process of step 2.

[0057] In this comparative example, step 2 includes: the first fire is performed at a low temperature below the β phase transformation point, and the heating temperature is T β The temperature is below 30℃, and the temperature is kept for 8 hours. The forging is carried out by upsetting and drawing. The deformation of each upsetting and drawing is controlled at 36%. After forging, the hot material is returned to the furnace at a temperature of T β The temperature is below 30℃, and the temperature is kept for 3 hours. After being taken out of the furnace, it is subjected to a forging process of upsetting and drawing. The deformation of each upsetting and drawing process is controlled at 36%. After forging, the hot material is returned to the furnace at a temperature of T βThe temperature is below 30℃, kept warm for 3h, and after being taken out of the furnace, it is forged by one upsetting and one drawing, and after the drawing is completed, it is turned into eight directions to reduce the deformation dead zone. The deformation of each upsetting and drawing is controlled at 36%. After forging, it is air-cooled and polished. The pressing speed of the forging process is controlled at 30mm / s, the pressing amount is controlled at 120mm, and the feed amount is controlled at 450mm. The forging process of the second and third fires is the same as the first fire.

[0058] In this comparative example, due to the large deformation resistance of TA19, the square billet was not wrapped with insulating asbestos during the upsetting process, resulting in a decrease in the surface temperature of the billet and cracks appearing during the forging process. The process had to be stopped for grinding, and the final titanium alloy bar had an increased grinding amount and increased cost.

[0059] Comparative Example 5 (different deformation rates in step 3):

[0060] This comparative example provides a method for preparing a large-size TA19 titanium alloy bar with high uniformity. The method is basically the same as that in Example 1, with the only difference being that the deformation rate in step three is different.

[0061] The square billet with an octagonal cross section is subjected to low temperature drawing and forging below the β phase transformation point. The heating temperature is T β The temperature is kept below 30℃ for 5 hours, and diagonal drawing forging is carried out. The deformation of each drawing is controlled at 30%, the pressing speed is controlled at 20mm / s, the pressing amount is controlled at 100mm, and the feed amount is controlled at 350mm. After forging, the hot material is returned to the furnace at a temperature of T β The temperature is below 30℃, kept warm for 2h, and then drawn diagonally after being taken out of the furnace. After the drawing is completed, the steel is turned into eight directions. The deformation of each upsetting and drawing is controlled at 25%, the pressing speed is controlled at 20mm / s, the pressing amount is controlled at 70mm, the feed amount is controlled at 300mm, and the steel is air-cooled and polished after forging.

[0062] In this comparative example, due to the low pressing speed and the long rod blank, the forming time is increased, the rod temperature is reduced, cracking occurs, and the grinding amount of the final finished rod is increased, which increases the cost.

[0063] Comparative Example 6 (step 4 without hot material remelting):

[0064] This comparative example provides a method for preparing large-size TA19 titanium alloy bars with high uniformity. The method is basically the same as Example 1, with the only difference being that the hot material is not returned to the furnace in step 4.

[0065] In this comparative example, step 4 includes: performing low-temperature rounding of the rod blank with an octagonal cross section below the β phase transition point, and heating the rod blank to a temperature of T βThe temperature is below 30℃, and the heat preservation is carried out for 5 hours. The deformation of each rounding and upsetting is controlled at 12%, the pressing speed is controlled at 30mm / s, the pressing amount is controlled at 15mm, and the feed amount is controlled at 100mm. During this process, the hot material is not returned to the furnace; after forging, it is air-cooled and polished.

[0066] In this comparative example, due to the long processing time and the fact that reheating is not allowed, the rod is later formed at a lower temperature, resulting in cracks on the surface, increased grinding amount, and increased costs.

Claims

1. A method for preparing large-scale TA19 titanium alloy bars with high uniformity, characterized in that: The method comprises: performing two-fire forging to obtain a square billet; The first round of blank forging includes: holding the temperature at 130-160°C above the β transformation point of TA19 titanium alloy for 6-10 hours, and performing upsetting forging deformation; returning the hot material to the furnace after forging, the furnace temperature is 80-110°C above the β transformation point of TA19 titanium alloy, the holding time is 2-5 hours, and upsetting forging deformation is performed after being taken out of the furnace; returning the hot material to the furnace after forging, the furnace temperature is 30-60°C above the β transformation point of TA19 titanium alloy, the holding time is 2-5 hours, and upsetting forging deformation is performed after being taken out of the furnace; The second round of blank forging includes: keeping the temperature at 20-50°C below the β phase transformation point of TA19 titanium alloy for 6-10 hours, performing at least two upsetting and drawing forging deformations, and controlling the upsetting and drawing deformation amount each time at 30-40%; after forging, the hot material is returned to the furnace, the returning temperature is 30-60°C above the β phase transformation point of TA19 titanium alloy, the holding time is 4-6 hours, and upsetting and drawing forging deformation is performed after taking out of the furnace.

2. The method for preparing a high-uniformity large-size TA19 titanium alloy bar according to claim 1, characterized in that: The method further comprises: performing three-time reforging on the square billet to obtain a reforged square billet; performing one-time preforming forging on the reforged square billet to obtain a preformed square billet; and performing one-time forming forging on the preformed square billet.

3. The method for preparing large-scale TA19 titanium alloy bars with high uniformity according to claim 2, characterized in that: Asbestos is used to wrap the square billet during the forging process.

4. The method for preparing a high-uniformity large-size TA19 titanium alloy bar according to claim 2, characterized in that: Each fire-forging process includes: keeping the temperature at 20-50℃ below the β transformation point of TA19 titanium alloy for 6-10 hours, and performing upsetting and forging deformation; returning the hot material to the furnace after forging, the furnace temperature is 20-50℃ below the β transformation point of TA19 titanium alloy, and the holding time is 2-4 hours; performing upsetting and forging deformation after taking out of the furnace; returning the hot material to the furnace after forging, the furnace temperature is 20-50℃ below the β transformation point of TA19 titanium alloy, and the holding time is 2-4 hours, and performing upsetting and forging deformation after taking out of the furnace.

5. The method for preparing large-scale TA19 titanium alloy bars with high uniformity according to claim 2, characterized in that: The preforming forging includes: drawing forging below the β phase transformation point; the pressing speed during drawing is controlled at 25 to 35 mm / s, the pressing amount is controlled at 75 to 150 mm, and the feed amount is controlled at 300 to 400 mm.

6. The method for preparing a high-uniformity large-size TA19 titanium alloy bar according to claim 5, characterized in that: The temperature and time of the drawing forging are: keeping the temperature at 20-40°C below the β phase transformation point of TA19 titanium alloy for 3-5 hours.

7. The method for preparing a high-uniformity large-size TA19 titanium alloy bar according to claim 5, characterized in that: The preform forging also includes: returning the hot material to the furnace after forging, the furnace temperature is 20 to 40°C below the β phase transformation point of TA19 titanium alloy, the holding time is 1 to 3 hours, and diagonal drawing is performed after taking out of the furnace.

8. The method for preparing large-scale TA19 titanium alloy bars with high uniformity according to claim 2, characterized in that: The forming forging includes: keeping the temperature at 20 to 40° C. below the β phase transformation point of the TA19 titanium alloy for 4 to 6 hours, and performing rounding forming.

9. The method for preparing a high-uniformity large-size TA19 titanium alloy bar according to claim 8, characterized in that: During rounding, the pressing speed is 25-30 mm / s, the pressing amount is 10-20 mm, and the feed amount is 50-150 mm.

10. The method for preparing a high-uniformity large-size TA19 titanium alloy bar according to claim 9, characterized in that: After rounding, the hot material is returned to the furnace at a temperature of 20 to 40°C below the β phase transformation point of TA19 titanium alloy, and the holding time is 0.5 to 2 hours.

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