A preparation method for improving the high uniformity of large-size Ti55531 titanium alloy bars

Abstract

The present invention relates to the field of bar forging, and specifically to a preparation method for improving the high uniformity of large-size Ti55531 titanium alloy bars, comprising the following steps: S1, high-temperature forging, air cooling after forging; S2, low-temperature forging, air cooling after forging; S3, high-temperature forging, air cooling after forging; S4, low-temperature forging; in S4, firstly perform step a: two-phase zone 2-fire widening + square closing operation; then perform step b: 1-fire upsetting followed by diagonal drawing operation, air cooling after forging; finally perform step c: drawing and forming, drawing and forging to the finished product size, air cooling after forging. This solution solves the problem that the product structure and performance uniformity and stability produced by the current general forging method of ordinary upsetting are not high.

Description

Technical Field

[0001] The invention relates to the field of bar forging, and in particular to a preparation method for improving the high uniformity of large-size Ti55531 titanium alloy bars. Background Art

[0002] Ti55531 titanium alloy is mainly used in large-scale main load-bearing structural parts such as aircraft landing gear, wings, frame beams, etc. It has significant advantages in meeting the requirements of aviation structural materials for weight reduction, high strength and high toughness, and reliability. At present, the manufacturing of Ti55531 titanium alloy in China is still in the research and development stage, and the technology is not mature. There are still some problems in the forging process of Ti55531 titanium alloy. For example, the conventional size of Ti55531 large-size bars is 300-400mm. Due to the low phase transition point, the forging temperature is low when forging in the two-phase zone, the deformation resistance is large, and the forging penetration is poor, which makes it difficult to control the uniformity of the cross-section of the billet. The improvement by increasing the number of fires is limited, and the processing process is long, resulting in poor uniformity of the finished bar structure and performance, high forging cost, low yield rate, and poor batch stability.

[0003] In addition, all brands of titanium alloys are currently forged using ordinary upsetting and drawing methods, and Ti55531 titanium alloy forging is no exception. However, the uniformity of the edge and core of the titanium alloy forged using ordinary upsetting and drawing methods is not high, and the uniformity and stability of the product's organization and performance are not high. The uniformity and stability of the product's organization and performance still need to be improved. Summary of the invention

[0004] The present invention aims to provide a preparation method for improving the high uniformity of large-size Ti55531 titanium alloy bars, so as to solve the problem that the products currently produced by the general forging method of ordinary upsetting and drawing have low uniformity and stability in organization and performance.

[0005] To achieve the above object, the present invention adopts the following technical scheme: A preparation method for improving the high uniformity of large-size Ti55531 titanium alloy bars, comprising the following steps: S1, high temperature forging, air cooling after forging; S2, low temperature forging, air cooling after forging; S3, high temperature forging, air cooling after forging; S4, low temperature forging;

[0006] In S4, firstly, step a is performed: two-phase zone widening + squaring operation for 2 times; then step b is performed: one-time upsetting followed by diagonal drawing operation, and air cooling after forging; finally, step c is performed: drawing and forming, drawing and forging to the finished product size, and air cooling after forging.

[0007] In this scheme, high temperature forging refers to forging above the β temperature, and low temperature forging refers to forging at a temperature below the β temperature. In this scheme, S1 can break the cast grains through high temperature forging to obtain a relatively fine and uniform β structure. Through S2, the temperature difference at different positions of the billet cross section can be reduced to obtain a fine and uniform equiaxed structure. Through S3, relatively uniform β grains can be obtained, and recrystallization forging above the β phase transformation point temperature can be performed. Through S4, the forgeability of Ti55531 large-size billets can be increased, deformation dead zones can be eliminated, and the entire cross section can obtain a uniform and fine two-phase processing structure.

[0008] The creativity of this scheme is that during the forging process of large-size Ti55531 titanium alloy bars, a two-phase zone two-fire widening + squaring operation is performed in S4 instead of the ordinary upsetting and drawing forging method. Through the two-phase zone two-fire widening + squaring operation, compared with the ordinary upsetting and drawing forging method in the prior art (the ordinary upsetting and drawing method in the prior art is X-axis upsetting and Y-axis drawing), the widening in this scheme is that the bar is upset along the X-axis, upset into a flat square along the Y-axis, and then upset into a flat square along the Z-axis. This makes it easier to break the grains in the core of the billet, which is beneficial to improving the forgeability and uniformity of the core structure. Compared with the ordinary upsetting and drawing method, the plastic deformation is more uniform, thereby greatly improving and improving the uniformity of the core and surface structures of the billet, and improving the yield rate and product batch stability.

[0009] The prior art also uses widening forging when forging Ti55531 titanium alloy, but the purpose of widening in the prior art is that the finished product of Ti55531 titanium alloy is in a flat square shape, so it needs to be widened. Therefore, the purpose of widening in the prior art is to form it into a flat square shape, rather than to improve the forgeability and uniformity of the core structure. The purpose of widening in this solution is to improve the forgeability and uniformity of the core structure. Although it is also a flat square after widening, it still needs to go through step c and be stretched into a rod instead of keeping the flat square shape. Therefore, the function of widening in this solution is not forming, and no similar forging process is disclosed in the prior art.

[0010] In addition, in the prior art, when forging Ti55531 titanium alloy large-size bars, the reason why ordinary upsetting is used for forging instead of widening is that Ti55531 titanium alloy is different from other grades of titanium alloys. Ti55531 titanium alloy has large deformation resistance and high requirements for forging. If improperly operated, it is easy to cause uneven deformation and uneven organizational properties. Therefore, there are high requirements for deformation amount, final forging temperature, heating, remelting temperature and the skill level of on-site operators. Unqualified organizational properties caused by uneven deformation will bring great economic losses, so ordinary upsetting is usually used in the prior art. In this application, the inventors accurately control the parameters such as the widening fire number, the widening deformation amount, the final forging temperature, the heating or remelting temperature, so that the widening forging can be applied to the forging of Ti55531 titanium alloy bars, which greatly improves the forging quality of Ti55531 titanium alloy large-size bars.

[0011] Preferably, as an improvement, in step a, the heating temperature is Tβ-(30-50)°C, the cold material heating coefficient is 0.65-0.80, the hot material return insulation coefficient is 0.25-0.40, and the single-fire forging ratio is 1.5-1.7. Therefore, by accurately controlling the temperature, heating coefficient, insulation coefficient and forging ratio of this step, the quality of widening forging in step a can be guaranteed.

[0012] Preferably, as an improvement, in step b, the heating temperature is Tβ-(30-50)°C, the heat preservation coefficient of the hot material is 0.25-0.40, and the single-fire forging ratio is 1.5-1.7. Thus, through step b, the forging and extrusion of the corners of the bar are achieved to ensure the forging uniformity of the corners of the bar. At the same time, after diagonal forging and extrusion, it is beneficial to restore the flat square structure to a round bar.

[0013] By accurately controlling the temperature, heating coefficient, insulation coefficient and forging ratio of this step, the quality of the diagonal stretch forging in step b can be guaranteed and the problem of poor uniformity during forging can be avoided.

[0014] Preferably, as an improvement, in step c, the heating temperature is Tβ-(30-50)°C, the cold material heating coefficient is 0.65-0.80, the hot material return furnace insulation coefficient is 0.25-0.40, the single fire forging ratio is 1.15-1.35, and the cumulative forging ratio is 1.5-2.5.

[0015] By precisely controlling the temperature, heating coefficient, insulation coefficient and forging ratio of step c, the quality of forging in step c can be ensured, the problem of poor uniformity during forging can be avoided, and the drawing and forming of titanium alloy can be facilitated.

[0016] Preferably, as an improvement, in S1, two rounds of high temperature forging are performed, the heating temperature of the first round is 1100-1200°C, the heating coefficient is 0.65-0.80, one round of two upsetting and two drawing are performed, and the upsetting amount does not exceed 20%; after forging, the hot material is returned to the furnace, the heating temperature of the second round is 1000-1100°C, the heating coefficient is 0.25-0.40, one round of two upsetting and two drawing are performed, and the upsetting amount does not exceed 28%;

[0017] The single fire forging ratio in S1 is 2.00~3.00.

[0018] Therefore, through this step, the as-cast grains can be fully broken and a relatively fine and uniform β structure can be obtained. In the S1 high-temperature forging stage of this scheme, only two rounds of high-temperature step-down forging are performed, the heating temperature of the first round is 1100-1200°C, and the heating temperature of the second round is 1000-1100°C, which is conducive to ensuring the gradual breaking and refinement of the as-cast grains.

[0019] Preferably, as an improvement, in S2, two forgings are performed, and the heating temperature is Tβ-(30~50)℃; the heating coefficient of the cold material in the first fire is 0.65~0.80, and the heating coefficient of the second fire is 0.25~0.40; each fire is one upsetting and one drawing, and the single-fire forging ratio of the two-phase zone forging is 1.5~2.0.

[0020] Through this step, the temperature difference at different positions of the cross section of the blank can be reduced to obtain a relatively fine and uniform equiaxed structure. By controlling the heating temperature, heating coefficient, heating times and forging ratio of this step within the above range, the quality of forging can be guaranteed, and the obtained equiaxed structure is relatively finer and more uniform.

[0021] Preferably, as an improvement, in S3, the forging temperature is set to Tβ+(80-100)°C, the heating coefficient is 0.65-0.80, the current firing is a one-upsetting-one-drawing process, and the forging ratio is 1.2-1.8.

[0022] Through this step, relatively uniform β grains can be obtained, and recrystallization forging above the β phase transformation point temperature is achieved. This fire is high-temperature forging. Although it is high-temperature forging, the forging temperature is lower than the temperature of the second fire in S1. The temperature of high-temperature forging is further reduced, which is conducive to ensuring the uniformity of the billet forging structure, and the grain size is further refined. Therefore, the first fire, the second fire in S1, and the high-temperature forging temperature in S3 are reduced successively, that is, gradient cooling, so as to ensure the uniformity of the forging structure.

[0023] In addition, the firing number of this step is one, which also reduces the firing number of high-temperature forging and greatly improves the forging efficiency.

[0024] Preferably, as an improvement, in S1, the high temperature final forging temperature is 850°C.

[0025] Preferably, as an improvement, in S2 and S4, the low-temperature final forging temperature is 700°C.

[0026] Preferably, as an improvement, in S3, the high temperature final forging temperature is 750°C.

[0027] Therefore, by controlling the final forging temperature in the corresponding steps respectively, the quality of titanium alloy forging can be avoided by avoiding too low a temperature after forging, thereby ensuring the uniformity of the forging structure.

[0028] In summary, the present application adopts a high-low-high process, fully utilizing the cooling gradient above the β phase transformation point temperature (the temperature of each fire of high-temperature forging gradually decreases), through S2 low-temperature forging + S3 high-temperature forging (recrystallization), combined with the deformation mode of widening the two-phase zone (flattening) in S4, and then combined with the relationship between the reheating time, heating temperature, heating coefficient, heating fires and forging ratio in the entire forging process, effectively realizes the refinement of the casting structure, improves the uniformity of the core and surface structure of the billet, increases the forgeability of the billet, reduces anisotropy, thereby reducing the problems of uneven finished product structure and performance caused by large deformation of multiple fires and difficult control of the final forging temperature, and improves the yield rate and product batch stability.

[0029] By adopting the technical solution of the present application, there is no need to use many high-temperature forging fires. In the present application, the number of high-temperature forging fires will not exceed 3 fires, and the other stages are low-temperature forging stages. The purpose is to obtain a uniform and fine two-phase processing structure in the entire cross-section of the rod. Compared with the prior art, in order to fully crush the cast grains of the titanium alloy, the forging temperature is generally and consistently very high, and the number of forging fires is large. The process scheme of high temperature and multiple fires to crush the cast structure used in traditional titanium alloy forging is abandoned, which greatly improves the forging efficiency, saves forging energy, and has a high manufacturing success rate and good quality stability for titanium alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the forged macrostructure of a typical φ350mm bar.

[0031] Figure 2 This is a schematic diagram of the macrostructure of a typical φ350mm bar after β annealing and aging heat treatment.

[0032] Figure 3 This is a schematic diagram of the high-magnification structure of the edge of a typical φ350mm bar after β annealing and aging heat treatment.

[0033] Figure 4 This is a schematic diagram of the high-magnification structure at D / 4 of a typical φ350mm bar after β annealing and aging heat treatment.

[0034] Figure 5 This is a schematic diagram of the high-magnification structure of the core of a typical φ350mm bar after β annealing and aging heat treatment.

[0035] Figure 6 This is a schematic diagram of the bar after upsetting in the X-axis direction.

[0036] Figure 7 For Figure 6 Schematic diagram of the bar transformation direction and widening and upsetting in the Y direction.

[0037] Figure 8 For Figure 7 Schematic diagram of the bar transformation direction and widening and upsetting in the Z direction.

[0038] Fig. 9 This is a schematic diagram of the forged macrostructure of a typical φ400mm bar.

[0039] Fig.10 This is a schematic diagram of the macrostructure of a typical φ400mm bar after β annealing and aging heat treatment.

[0040] Fig.11 This is a schematic diagram of the high-magnification structure of the edge of a typical φ400mm bar after β annealing and aging heat treatment.

[0041] Fig.12 This is a schematic diagram of the high-magnification structure at D / 4 of a typical φ400mm bar after β annealing and aging heat treatment.

[0042] Fig.13 This is a schematic diagram of the high-magnification structure of the core of a typical φ400mm bar after β annealing and aging heat treatment. DETAILED DESCRIPTION

[0043] The following is further described in detail through specific implementation methods:

[0044] Example 1

[0045] Ti55531 titanium alloy ingot was selected with specification of φ720mm and phase transition point of 850℃.

[0046] This embodiment discloses a preparation method for improving the high uniformity of large-size Ti55531 titanium alloy bars, comprising the following steps:

[0047] S1. High temperature forging

[0048] The ingot was heated at 1200℃, with a heating coefficient of 0.80. The first forging process was two upsetting and two drawing forgings, with a cumulative forging ratio of 3.0. During the forging process, the final forging temperature was ensured to be 850℃.

[0049] Then the hot material is returned to the furnace, the heating temperature is set at 1100℃, the heating coefficient is 0.40, the second fire is two upsetting and two drawing forging, the cumulative forging ratio is 3.0, and air cooling is performed after forging.

[0050] In this step, the final forging temperature (the final forging temperature refers to the temperature at which the main forging deformation ends) is controlled at 850°C.

[0051] S2. Low temperature forging

[0052] The billet heating temperature in S1 is set at 820°C, the heating coefficient is 0.80, and the first fire-up and one-draw forging is carried out, with a cumulative forging ratio of 2.0.

[0053] Then the hot material is returned to the furnace for heating at a temperature of 820°C, with a heating coefficient of 0.40, and the second forging of one upsetting and one drawing is carried out, with a cumulative forging ratio of 2.0, and air cooling after forging.

[0054] In this step, the final forging temperature is controlled at 700°C.

[0055] S3, high temperature forging

[0056] The heating temperature of the billet in S2 is set at 950°C, the heating coefficient is 0.80, and one-time forging, one-upsetting and one-drawing forging is performed, the cumulative forging ratio is 1.8, and the billet is slowly pressed in batches at a uniform speed, and air-cooled after forging.

[0057] The final forging temperature in this step is controlled at 750°C.

[0058] S4, low temperature forging

[0059] Step a, two-phase zone 2-fire widening + squaring operation: Set the billet heating temperature to 820℃, heating coefficient to 0.80, widen forging in the first fire, width-to-thickness ratio to 1.8, square and chamfer after widening. Then set the hot material back to the furnace heating temperature to 820℃, heating coefficient to 0.40, widen forging in the second fire, width-to-thickness ratio to 1.8, square and chamfer after widening.

[0060] Combination Figure 6 As shown, the axial direction of the bar is defined as X square, the radial direction is defined as Y square, and the radial direction perpendicular to the Y direction is defined as Z square. Figure 7 and Figure 8 As shown, in the first widening forging, widening upset forging in the Y direction is performed first, and then widening upset forging in the Z direction is performed. In the second widening forging, widening upset forging in the Y direction is also performed first, and then widening upset forging in the Z direction is performed. This embodiment adopts this unique widening forging method, and the bar can be forged and extruded in different directions (two directions are cross directions), the bar structure is fully integrated, the uniformity of the bar structure can be ensured, and the grains in the core of the billet are more easily broken.

[0061] Step b, then the hot material is returned to the furnace, the heating temperature is set at 820°C, and one fire, one upsetting and one drawing are performed to eight sides, and air cooling is performed after forging. In step a and step b, the single fire forging ratio is 1.7.

[0062] Step c: then multi-fire forging is performed at 820°C, stretched to 365mm and then air-cooled (Note: the finished product size after machining is φ350mm). In step c, the heating coefficient of the cold material is 0.80, the heat preservation coefficient of the hot material is 0.40, the single-fire forging ratio is 1.35, and the cumulative forging ratio is 2.5.

[0063] In step S4, the final forging temperature is controlled at 700°C.

[0064] from Figure 1 and Figure 2 It can be seen that the macroscopic structure of the forged state is uniform, and there are no visible cracks, folds, pores, inclusions, segregation, shrinkage holes and other metallurgical defects that affect the use. The macroscopic structure after β annealing + aging heat treatment is uniform and has no stratification. Figure 3-Figure 5 It can be seen that after β annealing + aging heat treatment, the high-magnification microstructures in different parts of the rod are composed of recrystallized network primary β grains and α bundles, without primary α phase, the microstructures in different parts of the rod are relatively uniform, and the room temperature mechanical properties of the rod meet the index requirements.

[0065] Example 2

[0066] Ti55531 titanium alloy ingot was selected with specification of φ720mm and phase transition point of 845℃.

[0067] This embodiment discloses a preparation method for improving the high uniformity of large-size Ti55531 titanium alloy bars, comprising the following steps:

[0068] S1. High temperature forging

[0069] The ingot was heated at 1100°C with a heating coefficient of 0.65. The first forging process was two upsetting and two drawing forgings with a cumulative forging ratio of 2.0.

[0070] Then the hot material is returned to the furnace, the heating temperature is set at 1000°C, the heating coefficient is 0.25, the second fire is two upsetting and two drawing forging, and the cumulative forging ratio is 2.0. The rest is the same as Example 1.

[0071] S2. Low temperature forging

[0072] The heating temperature of the billet in S1 is set at 815°C, the heating coefficient is 0.65, and the first fire-up and one-draw forging is carried out, with a cumulative forging ratio of 1.5.

[0073] Then the hot material was returned to the furnace for heating at a temperature of 815°C, a heating coefficient of 0.25, and the second forging of upsetting and drawing was performed, with a cumulative forging ratio of 1.5. The rest was the same as in Example 1.

[0074] S3, high temperature forging

[0075] The heating temperature of the blank in S2 is set at 930°C, the heating coefficient is 0.65, and one-time forging, one-upsetting and one-drawing forging is performed, with a cumulative forging ratio of 1.2. The rest is the same as in Example 1.

[0076] S4, low temperature forging

[0077] Step a, two-phase zone 2-fire widening + square operation: Set the billet heating temperature to 815℃, heating coefficient to 0.65, and perform the first fire widening forging, with a width-to-thickness ratio of 1.5. Then set the hot material heating temperature to 815℃, heating coefficient to 0.25, and perform the second fire widening forging, with a width-to-thickness ratio of 1.5.

[0078] Step b, then the hot material is returned to the furnace, the heating temperature is set at 815°C, and one fire, one upsetting and one drawing are performed to eight sides. In step a and step b, the single fire forging ratio is 1.5.

[0079] Step c, then multi-fire forging is performed at 815°C, stretched to 415mm and then air-cooled (Note: the finished product size after machining is φ400mm). In step c, the heating coefficient of the cold material is 0.65, the heat preservation coefficient of the hot material is 0.25, the single-fire forging ratio is 1.15, and the cumulative forging ratio is 1.5. The rest is the same as in Example 1.

[0080] from Fig. 9 and Fig.10 It can be seen that the macroscopic structure of the forged state is uniform, and there are no visible cracks, folds, pores, inclusions, segregation, shrinkage holes and other metallurgical defects that affect the use. The macroscopic structure after β annealing + aging heat treatment is uniform and has no stratification. Figure 11-13 It can be seen that the high-magnification microstructures at different parts of the rod after β annealing + aging heat treatment are composed of recrystallized network primary β grains and α bundles, without primary α phase. The microstructures at different parts of the rod are relatively uniform, and the room temperature mechanical properties of the rod meet the index requirements.

[0081] Tables 1-2 below are the mechanical property results of the β-annealing state of the rods of Example 1-2. It can be seen from Tables 1-2 below that the room temperature mechanical property test results of Example 1-2 all meet the index requirements, and the strength and toughness matching is high. In addition, the measurement results of Example 1-2 all meet the technical index requirements and have a certain margin. Therefore, the high uniformity of the organization and performance of the material of Example 1-2 is guaranteed.

[0082] Table 1

[0083]

[0084] Table 2

[0085]

[0086] In summary, compared with the existing preparation methods, the preparation method of the present application abandons the forging process scheme used in the prior art in which the traditional titanium alloy forging is subjected to high temperature and multiple fires to break the cast structure, and the number of fires and deformation is small, and the remelting time is short, resulting in uneven deformation at different positions of the entire cross section. In Examples 1-2 of the present application, the low-magnification structure of the forged state is uniform, and there are no visually visible cracks, folds, pores, inclusions, segregation, shrinkage holes, and other metallurgical defects that affect use. The high-magnification structure of different parts of the rod is composed of recrystallized network primary β grains and α bundles, without primary α phase, and the structure of different parts of the rod is relatively uniform, and the room temperature mechanical properties of the rod meet the index requirements.

[0087] Example 3

[0088] The difference between this embodiment and embodiment 1 is that: during the first widening forging, widening and roughing forging in the Y direction is first performed, and at the same time, the two ends of the blank in the X direction are limited (for example, a protruding blocking portion is provided on the anvil to block the two ends of the blank in the X direction), and then widening and roughing forging in the Z direction is performed, and at the same time, the two ends of the blank in the X direction are limited. During the second widening forging, widening and roughing forging in the Y direction is also performed first, and then widening and roughing forging in the Z direction is performed. Therefore, during the first widening forging, by limiting the ends of the blank in the X direction, it is possible to avoid the blank extending in the X direction when the bar is forged in the Y and Z directions, and it can be ensured that the bar is subjected to a certain degree of forging extrusion and deformation in the Y and Z directions to the maximum extent, and the bar structure is fully extruded and fused in the two vertical directions of Y and Z, which makes it easier to break the grains in the core of the blank. During the second widening forging, the limits at both ends of the blank in the X direction are cancelled. When widening forging is performed again, the material can not only be extruded in the two vertical directions of Y and Z, but also deformed in the X direction, thereby ensuring the uniformity of the structure to a great extent. The combination of the first widening forging and the second widening forging makes the processed bar have better performance, more uniform structure, and the room temperature mechanical properties are further improved compared with Example 1.

[0089] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for improving the high uniformity of large-size Ti55531 titanium alloy bars, comprising the following steps: S1, high temperature forging, air cooling after forging; S2, low temperature forging, air cooling after forging; S3, high temperature forging, air cooling after forging; S4, low temperature forging; characterized by: In S4, firstly, step a is performed: two-phase zone widening + square operation for 2 times; then step b is performed: one-time upsetting followed by diagonal drawing operation, and air cooling after forging; finally, step c is performed: drawing and forming, drawing and forging to the finished product size, and air cooling after forging; In step a, the heating temperature is Tβ-(30-50)°C, the cold material heating coefficient is 0.65-0.80, the hot material return furnace insulation coefficient is 0.25-0.40, and the single fire forging ratio is 1.5-1.7; In step b, the heating temperature is Tβ-(30-50)°C, the heat preservation coefficient of the hot material is 0.25-0.40, and the single-fire forging ratio is 1.5-1.7; In step c, the heating temperature is Tβ-(30-50)°C, the cold material heating coefficient is 0.65-0.80, the hot material return furnace insulation coefficient is 0.25-0.40, the single fire forging ratio is 1.15-1.35, and the cumulative forging ratio is 1.5-2.

5.

2. A method for preparing a large-sized Ti55531 titanium alloy bar with high uniformity according to claim 1, characterized in that: In S1, two rounds of high temperature forging are performed. The heating temperature of the first round is 1100-1200°C, the heating coefficient is 0.65-0.80, and two upsetting and two drawing are performed in one round, and the upsetting amount does not exceed 20%; after forging, the hot material is returned to the furnace, and the heating temperature of the second round is 1000-1100°C, the heating coefficient is 0.25-0.40, and two upsetting and two drawing are performed in one round, and the upsetting amount does not exceed 28%; The single fire forging ratio in S1 is 2.00~3.

00.

3. A method for preparing a large-sized Ti55531 titanium alloy bar with high uniformity according to claim 1, characterized in that: In S2, two forgings are carried out, and the heating temperature is Tβ-(30~50)℃; the heating coefficient of the cold material in the first fire is 0.65~0.80, and the heating coefficient of the second fire is 0.25~0.40; each fire is one upsetting and one drawing, and the single-fire forging ratio of two-phase zone forging is 1.5~2.

0.

4. The method for preparing a large-sized Ti55531 titanium alloy bar with improved uniformity according to claim 1, characterized in that: In S3, the forging temperature is set to Tβ+ (80~100) ℃, the heating coefficient is 0.65~0.80, this firing is a one-upsetting-one-drawing process, and the forging ratio is 1.2~1.

8.

5. A method for preparing a large-sized Ti55531 titanium alloy bar with high uniformity according to claim 1, characterized in that: In S1, the high temperature final forging temperature is 850°C.

6. A method for preparing a large-sized Ti55531 titanium alloy bar with high uniformity according to claim 1, characterized in that: In S2 and S4, the low temperature final forging temperature is 700°C.

7. A method for preparing a large-sized Ti55531 titanium alloy bar with high uniformity according to claim 1, characterized in that: In S3, the high temperature final forging temperature is 750°C.

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