Preparation method of high-efficiency and low-cost TC4 titanium alloy fine-grain rod

Abstract

The application discloses a high-efficiency and low-cost TC4 titanium alloy fine-grain rod preparation method, which precisely controls the microstructure evolution in the hot working process of the rod through a mode of 'rolling instead of forging and forging-rolling combination', and finally obtains the TC4 titanium alloy fine-grain rod with uniform and fine microstructure and excellent performance through three times of ingot breaking and forging and four times of low-temperature and low-speed large-deformation rolling forming. The TC4 titanium alloy fine-grain rod prepared by the application reaches a leading level in the uniform and fine transverse and longitudinal microstructure. The application breaks through the difficulties in the forging-rolling combination process and the microstructure regulation, reduces the preparation process from about 20 times of the traditional radial forging process to four times of rolling, and provides a high-efficiency and low-cost TC4 titanium alloy fine-grain rod preparation method.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of titanium alloy processing, and particularly relates to a high-efficiency and low-cost preparation method of a titanium alloy fine-grain rod. BACKGROUND

[0002] A typical application of advanced high-performance titanium alloy in the field of aviation is engine blades. The rod for the blades requires that the primary alpha phase content be greater than 60%, the average grain size in the transverse and longitudinal directions be less than 10 mu m, and the performance indicators such as the room temperature tensile strength be higher than 930 MPa and the room temperature impact energy be greater than 31 J. The common preparation process of the titanium alloy fine-grain rod is free forging + radial forging process. Because the accumulated deformation in the whole hot deformation process is small, the spheroidization and recrystallization effect of the alpha phase is poor, and the primary alpha phase grain size of the prepared rod is 20-30 mu m, which still cannot meet the use requirements. Moreover, the radial forging process has problems such as many heating times, low forming efficiency, poor deformation uniformity, and poor consistency of the structure. The "forging-rolling combination" method instead of the "free forging + radial forging" process becomes a more low-cost and high-efficiency method for preparing the TC4 titanium alloy fine-grain rod. SUMMARY

[0003] Therefore, the purpose of the application is to provide a high-efficiency and low-cost preparation method of a TC4 titanium alloy fine-grain rod.

[0004] In order to achieve the above-mentioned purpose, the application provides the following technical scheme:

[0005] On the one hand, the application provides a high-efficiency and low-cost preparation method of a TC4 titanium alloy fine-grain rod, which comprises the following steps:

[0006] Step 1: 3 heating times of ingot breakdown forging:

[0007] The first heating time: the TC4 titanium alloy ingot is forged at a temperature above the beta phase transformation point, and then air-cooled after forging;

[0008] The second heating time: the blank obtained in the first heating time is forged at a temperature below the beta phase transformation point, and then air-cooled after forging;

[0009] The third heating time: the blank obtained in the second heating time is forged at a temperature above the beta phase transformation point, and then water-cooled after forging, to obtain a forged blank with a cross-sectional size of (350-400) * (350-400) mm;

[0010] Step 2: 4 heating times of low-temperature and low-speed large deformation rolling:

[0011] The first heating time: the forged blank obtained in step 1 is rolled at a temperature below the beta phase transformation point, and then air-cooled after rolling, to obtain a square blank with a cross-sectional size of (200-250) mm * (200-250) mm;

[0012] The second fire: the square billet obtained in the first fire is rolled at a temperature below the beta transus point, and after rolling, air cooling is performed to obtain a rod billet with a cross-sectional size of Φ(100-160) mm;

[0013] The third fire: the rod billet obtained in the second fire is rolled at a temperature below the beta transus point, and after rolling, air cooling is performed to obtain a rod billet with a cross-sectional size of Φ(50-80) mm.

[0014] The fourth fire: the rod billet obtained in the third fire is rolled at a temperature below the beta transus point, and after rolling, air cooling is performed to obtain a TC4 titanium alloy fine-grained rod with a cross-sectional size of Φ(20-45) mm.

[0015] Further, in step 1, the specific steps of the first fire for high-temperature forging above the beta transus point of the titanium alloy ingot are as follows: the TC4 titanium alloy ingot is heated, the heating temperature is T β +100-200℃, the heating coefficient is 0.6-0.8 min / mm, after discharging, 4-6 times of upsetting and elongation forging are performed, and intermediate tempering is performed twice, the heating temperature for tempering is T β +100-200℃, the heating coefficient is 0.2-0.4 min / mm, the upsetting and elongation deformation amount is controlled to be 30-80%, and the final forging temperature is controlled to be above 800℃, and after forging, air cooling is performed.

[0016] Further, in step 1, the second fire low-temperature forging is as follows: the billet obtained in the first fire is heated, the heating temperature is T β - (20-50) ℃, the heating coefficient is 0.6-0.8 min / mm, after discharging, two times of upsetting and elongation are performed, the upsetting and elongation deformation amount is controlled to be 30-80%, the final forging temperature is controlled to be above 800℃, and after forging, air cooling is performed.

[0017] Further, in step 1, the third fire high-temperature forging above the beta transus point is as follows: the billet obtained in the second fire is heated, the heating temperature is T β +50-150℃, after discharging, two times of continuous elongation forging are performed, the elongation deformation amount is controlled to be 30-80%, the final forging temperature is controlled to be above 800℃, and after forging, water cooling is performed to obtain a forging billet with a cross-sectional size of (350-400) *(350-400) mm.

[0018] Further, in step 2, the low-temperature rolling of the first fire is specifically as follows: the forged blank obtained in step 1 is heated to 900-960 DEG C, the heating coefficient is 0.6-0.8 min / mm, after discharging, 11-15 passes of rolling are carried out by using a reciprocating rolling mill with a roller diameter of 1000-1500 mm, the rolling is stopped until the square billet with a size of (200-250) mm * (200-250) mm is obtained, the rolling deformation is controlled to be 60-70%, and the rolling speed is controlled to be 1-2 mm / s.

[0019] Further, in step 2, the low-temperature rolling of the second fire is specifically as follows: the rod blank obtained in the first fire of step 2 is heated to 900-960 DEG C, the heating coefficient is 0.6-0.8 min / mm, after discharging, 11-15 passes of rolling are carried out by using a reciprocating rolling mill with a roller diameter of 800-1200 mm, the rolling is stopped until the rod blank with a size of Φ (100-160) mm is obtained, the rolling deformation is controlled to be 60-80%, and the rolling speed is controlled to be 1-2 mm / s.

[0020] Further, in step 2, the low-temperature rolling of the third fire is specifically as follows: the rod blank obtained in the second fire of step 2 is heated to 790-830 DEG C, the heating coefficient is 0.6-0.8 min / mm, after discharging, 4-7 passes of rolling are carried out by using a reciprocating rolling mill with a roller diameter of 500-800 mm, the rolling is stopped until the rod blank with a size of Φ (50-80) mm is obtained, the rolling deformation is controlled to be 60-80%, and the rolling speed is controlled to be 1-2 mm / s.

[0021] Further, in step 2, the low-temperature rolling of the fourth fire is specifically as follows: the rod blank obtained in the third fire of step 2 is heated to 900-960 DEG C, the heating coefficient is 0.6-0.8 min / mm, after discharging, 4-7 passes of rolling are carried out by using a reciprocating rolling mill with a roller diameter of 500-800 mm, the rolling is stopped until the finished rod material with a size of Φ (20-45) mm is obtained, the rolling deformation is controlled to be 50-60%, and the rolling speed is controlled to be 1-2 mm / s.

[0022] On the other hand, the application also provides a TC4 titanium alloy fine-grained rod prepared by the above preparation method.

[0023] Further, the cross-sectional size of the TC4 titanium alloy fine-grained rod is Φ (20-45) mm.

[0024] Compared with the prior art, the application has the following beneficial effects:

[0025] 1) The application provides a high-efficiency and low-cost preparation method of a TC4 titanium alloy fine-grained rod by adopting a 3-fire free forging + 4-fire rolling process, and the number of fires is reduced by more than a dozen compared with the traditional process.

[0026] 2) The titanium alloy fine-grained rod prepared by the process has a primary alpha phase content greater than 60%, the average grain size in the transverse and longitudinal directions is increased to less than 10 microns compared with 20-30 microns obtained by the existing process, and meets various indicators of the TC4 fine-grained rod for an aero-engine blade, such as a room temperature tensile strength higher than 930 MPa, a room temperature impact energy greater than 35 J, and leaves a certain margin. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 (a)-(c) are low-magnification microstructure diagrams of the head, middle and tail cross sections of the Φ30mm TC4 titanium alloy fine-grained rod prepared in Example 1 of the application.

[0028] Figure 2 (a)-(c) are high-magnification microstructure diagrams of the R / 2 positions of the head, middle and tail cross sections of the Φ30mm TC4 titanium alloy fine-grained rod prepared in Example 1 of the application.

[0029] Figure 3 (a)-(c) are high-magnification microstructure diagrams of the R / 2 positions of the head, middle and tail longitudinal sections of the Φ30mm TC4 titanium alloy fine-grained rod prepared in Example 1 of the application. DETAILED DESCRIPTION

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0031] In the present application, when a numerical interval (i.e. a numerical range) is involved, without specific indication, the numerical values distributed in the above numerical interval are considered to be continuous, and include the two numerical end points (i.e. the minimum value and the maximum value) of the numerical range, and every numerical value between the two numerical end points. Without specific indication, when a numerical interval only refers to integers in the numerical interval, including the two end point integers of the numerical range, and every integer between the two end points, in this article, it is equivalent to directly listing each integer, such as t is an integer selected from 1 10, which means that t is any integer selected from the group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. In addition, when multiple ranges are provided to describe a feature or characteristic, these ranges can be combined. In other words, unless otherwise indicated, the ranges disclosed herein should be understood to include any and all sub-ranges therein.

[0032] The temperature parameters in the present application, if not particularly limited, allow for both constant temperature treatment and for variations within a certain temperature interval. It is to be understood that the constant temperature treatment allows for fluctuations within the accuracy range of the instrument control. Fluctuations within a range of, for example, ±5°C, ±4°C, ±3°C, ±2°C, ±1°C are allowed.

[0033] The present application provides a high-efficiency and low-cost preparation method of TC4 titanium alloy fine-grain rods, characterized in that the method comprises:

[0034] Step 1: 3 heating times of ingot breaking down and forging:

[0035] First heating time: high-temperature forging above the beta transus point of the TC4 titanium alloy ingot, and air cooling after forging;

[0036] Second heating time: low-temperature forging below the beta transus point of the blank obtained in the first heating time, and air cooling after forging;

[0037] Third heating time: high-temperature forging above the beta transus point of the blank obtained in the second heating time, and water cooling after forging, to obtain a forged blank with a cross-sectional size of (350-400) * (350-400) mm;

[0038] Step 2: 4 heating times of low-temperature and low-speed large deformation rolling:

[0039] First heating time: low-temperature rolling below the beta transus point of the forged blank obtained in step 1, and air cooling after rolling, to obtain a square blank with a cross-sectional size of (200-250) mm * (200-250) mm;

[0040] Second heating time: low-temperature rolling below the beta transus point of the square blank obtained in the first heating time, and air cooling after rolling, to obtain a rod blank with a cross-sectional size of Φ(100-160) mm;

[0041] Third heating time: low-temperature rolling below the beta transus point of the rod blank obtained in the second heating time, and air cooling after rolling, to obtain a rod blank with a cross-sectional size of Φ(50-80) mm.

[0042] Fourth heating time: low-temperature rolling below the beta transus point of the rod blank obtained in the third heating time, and air cooling after rolling, to obtain a TC4 titanium alloy fine-grain rod with a cross-sectional size of Φ(20-45) mm.

[0043] In some embodiments, the present application provides a high-efficiency and low-cost preparation method of TC4 titanium alloy fine-grain rods, which comprises:

[0044] Step 1: 3 heating times of ingot breaking down and forging:

[0045] The first fire: the beta phase point above high temperature forging of TC4 titanium alloy ingot, the TC4 titanium alloy ingot is heated, the heating temperature is T β +100~200℃, the heating coefficient is 0.6~0.8min / mm, after discharging, 4~6 times of upsetting and elongation forging is carried out, twice intermediate tempering, the heating temperature of tempering is T β +100~200℃, the heating coefficient is 0.2~0.4min / mm, the upsetting and drawing deformation is controlled to be 30~80%, the final forging temperature is controlled to be above 800℃, air cooling after forging;

[0046] The second fire: the billet obtained in the first fire is forged below the beta phase point, the billet obtained in the first fire is heated, the heating temperature is T β -(20~50)℃, the heating coefficient is 0.6~0.8min / mm, after discharging, two times of upsetting and elongation are carried out, the upsetting and drawing deformation is controlled to be 30~80%, the final forging temperature is controlled to be above 800℃, air cooling after forging;

[0047] The third fire: the billet obtained in the second fire is forged above the beta phase point, the billet obtained in the second fire is heated, the heating temperature is T β +50~150℃, after discharging, two times of continuous elongation forging is carried out, the elongation deformation is controlled to be 30~80%, the final forging temperature is controlled to be above 800℃, water cooling after forging, the forging billet with the cross section size of (350~400) * (350~400)mm is obtained;

[0048] Step 2: low temperature and low speed large deformation rolling forming 4 fires:

[0049] The first fire: the forging billet obtained in step 1 is rolled below the beta phase point, the forging billet obtained in step 1 is heated to 900~960℃, the heating coefficient is 0.6~0.8min / mm, after discharging, 11~15 passes of rolling is carried out by using a reciprocating rolling mill with the rolling mill diameter of 1000~1500mm, the square billet with the size of (200~250) mm * (200~250) mm is rolled, the rolling deformation is controlled to be 60~70%, the rolling speed is controlled to be 1~2mm / s, air cooling after rolling, the square billet with the cross section size of (200~250) mm * (200~250) mm is obtained;

[0050] The billet obtained in the first heating is low-temperature rolled below the beta transus point, the billet obtained in the second heating of step 2 is heated to 900-960 DEG C, the heating coefficient is 0.6-0.8 min / mm, after discharging, the reciprocating rolling mill with a roller diameter of 800-1200 mm is used to carry out 11-15 pass rolling, the billet with a specification of Phi (100-160) mm is rolled, the rolling deformation is controlled to be 60-80%, the rolling speed is controlled to be 1-2 mm / s, after rolling, air cooling is carried out, and the billet with a cross section size of Phi (100-160) mm is obtained.

[0051] The billet obtained in the second heating is low-temperature rolled below the beta transus point, the billet obtained in the second heating of step 2 is heated to 790-830 DEG C, the heating coefficient is 0.6-0.8 min / mm, after discharging, the reciprocating rolling mill with a roller diameter of 500-800 mm is used to carry out 4-7 pass rolling, the billet with a specification of Phi (50-80) mm is rolled, the rolling deformation is controlled to be 60-80%, the rolling speed is controlled to be 1-2 mm / s, after rolling, air cooling is carried out, and the billet with a cross section size of Phi (50-80) mm is obtained.

[0052] The billet obtained in the third heating is low-temperature rolled below the beta transus point, the billet obtained in the third heating of step 2 is heated to 900-960 DEG C, the heating coefficient is 0.6-0.8 min / mm, after discharging, the reciprocating rolling mill with a roller diameter of 500-800 mm is used to carry out 4-7 pass rolling, the finished rod with a specification of Phi (20-45) mm is rolled, the rolling deformation is controlled to be 50-60%, the rolling speed is controlled to be 1-2 mm / s, after rolling, air cooling is carried out, and the TC4 titanium alloy fine-grain rod with a cross section size of Phi (20-45) mm is obtained.

[0053] For the purpose, technical scheme and advantages of the present application, the present application will be described in detail below in combination with specific examples and the drawings of the specification. The specific examples described herein are only used to explain the present application, and the present application is not limited thereto.

[0054] Example 1: Preparation of TC4 titanium alloy Phi 30 mm fine-grain rod

[0055] The present embodiment provides a preparation method of TC4 titanium alloy fine-grain rod, which comprises the following steps:

[0056] Step 1: 3-heating of ingot breaking down forging:

[0057] The first heating: the TC4 titanium alloy ingot is subjected to high-temperature forging above the beta transus point, the TC4 titanium alloy ingot is heated, the heating temperature is T β+120℃, heating coefficient is 0.75min / mm, after furnace discharge, two times of upsetting and drawing are carried out, upsetting and drawing deformation is controlled in 30%~40%. After forging, hot material is recycled, recycling temperature is T β +70℃, heating coefficient is 0.35min / mm, after furnace discharge, two times of upsetting and drawing are carried out, upsetting and drawing deformation is controlled in 30%~40%. After forging, hot material is recycled, heating coefficient is 0.35min / mm, recycling temperature is T β +20℃, after furnace discharge, two times of upsetting and drawing are carried out, upsetting and drawing deformation is controlled in 30%~40%, final forging temperature is controlled above 800℃, after forging, air cooling is carried out;

[0058] The 2nd fire: the square billet obtained in the 1st fire is forged at low temperature below the beta phase transformation point. The heating temperature is T β -50℃, heating coefficient is 0.75min / mm, after furnace discharge, two times of upsetting and drawing are carried out, upsetting and drawing deformation is controlled in 30%~40%, final forging temperature is controlled above 800℃, after forging, air cooling is carried out;

[0059] The 3rd fire: the billet obtained in the 2nd fire is forged at high temperature above the beta phase transformation point. The heating temperature is T β +30℃, heating coefficient is 0.75min / mm, after furnace discharge, drawing forging is carried out, drawing deformation is controlled in 30%~40%, final forging temperature is controlled above 800℃, the size is forged to (350±3)*(350±3)*L mm, after forging, water cooling is carried out;

[0060] Step 2: low temperature and low speed large deformation rolling forming 4 fires:

[0061] The 1st fire: the forged billet obtained in step 1 is rolled at low temperature below the beta phase transformation point, the heating temperature is 900℃, the heating coefficient is 0.75min / mm, after furnace discharge, 13 times of rolling is carried out by using reciprocating rolling mill with rolling diameter of 1200mm, the square billet with specification of 200*200 mm is rolled, rolling deformation is controlled in 60%, rolling speed is controlled in 1~2mm / s. After rolling, air cooling is carried out, the square billet with section size of 200*200 mm is obtained;

[0062] The 2nd fire: the square billet obtained in the 1st fire of step 2 is rolled at low temperature below the beta phase transformation point, the heating temperature is 900℃, the heating coefficient is 0.75min / mm, after furnace discharge, 13 times of rolling is carried out by using reciprocating rolling mill with rolling diameter of 1200mm, the rod billet with specification of Φ120 mm is rolled, rolling deformation is controlled in 60%, rolling speed is controlled in 1~2mm / s. After rolling, air cooling is carried out, the rod billet with section size of Φ120 mm is obtained;

[0063] Third pass: The billet obtained in the second pass of step 2 is subjected to low-temperature rolling below the β phase transformation point. The heating temperature is 800℃, and the heating coefficient is 0.75 min / mm. After exiting the furnace, it is rolled in 5 passes using a reciprocating rolling mill with a roll diameter of 500mm to obtain a billet with a specification of Φ70 mm. The rolling deformation is controlled at 70%, and the rolling speed is controlled at 1~2 mm / s. After rolling, it is air-cooled to obtain a billet with a cross-sectional dimension of Φ70 mm.

[0064] Fourth pass: The billet obtained in step 2, third pass, is subjected to low-temperature rolling below the β phase transformation point. The heating temperature is 900℃, and the heating coefficient is 0.75 min / mm. After exiting the furnace, it is rolled in 5 passes using a reciprocating rolling mill with a roll diameter of 500mm to obtain a bar with a specification of Φ30 mm. The rolling deformation is controlled at 60%, and the rolling speed is controlled at 1~2 mm / s. After rolling, it is air-cooled to obtain a TC4 titanium alloy fine-grained bar with a cross-sectional dimension of Φ30mm.

[0065] Figure 1 The image shows low-magnification microstructure images of the head, middle, and tail sections of the TC4 titanium alloy Φ30mm fine-grained rod prepared in Example 1 of this invention. Figure 1 It can be seen that the low-magnification microstructure does not show cracks, folds, pores, metallic or non-metallic inclusions, segregation, shrinkage tails or other metallurgical defects visible to the naked eye, and there are no obvious, clear grains visible to the naked eye, but rather a uniform and blurred appearance.

[0066] Figure 2 and 3 The figures show high-magnification microstructure images of the head, middle, and tail sections, and the longitudinal section at position R / 2 of the Φ30mm fine-grained TC4 titanium alloy rod prepared in Example 1 of this invention. Figure 2 and 3 It can be seen that the high-magnification structure consists of equiaxed α phase and a small amount of lamellar primary α phase. The high-magnification structure is fine and uniform in both the transverse and longitudinal directions, with no thermal structural anomalies, no continuous α network structure on the original β grain boundaries, and the primary α phase content is as high as 70%. Moreover, the average grain size in the longitudinal direction of the bar is less than 10 μm, with good equiaxing and no obvious elongation.

[0067] Table 1 shows the mechanical properties of longitudinally sampled cross-sections at position R / 2 of the 30mm TC4 titanium alloy fine-grained rod prepared in Example 1. It can be seen that the test results all meet the requirements of the TC4 fine-grained rod standard for aero-engine blades, and have a certain margin.

[0068] Table 1 Mechanical properties of longitudinal samples taken from the R / 2 position of the bar cross section

[0069]

[0070] This invention overcomes the difficulties in formulating the forging-rolling combined process and controlling the microstructure, reducing the preparation process from approximately 20 passes in the traditional radial forging process to 3-4 passes in rolling, providing a highly efficient and low-cost method for preparing fine-grained titanium alloy bars. The prepared fine-grained titanium alloy bars meet aerospace standards, exhibiting good uniformity and a certain margin of error.

[0071] It should be noted that the embodiments described above are merely preferred embodiments of the present invention. For those skilled in the art, various modifications, improvements, and equivalent substitutions can be made to the present invention without departing from its principles, and such modifications, improvements, and equivalent substitutions are also considered to fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing high-efficiency, low-cost TC4 titanium alloy fine-grained rods, characterized in that, include: Step 1: Forging the ingot in three stages: First forging: The TC4 titanium alloy ingot is subjected to high-temperature forging above the β-phase transformation point, followed by air cooling. The specific details of the first forging of the titanium alloy ingot at high temperature above the β-phase transformation point are as follows: The TC4 titanium alloy ingot is heated to a temperature of T. β The temperature is +100~200℃, with a heating coefficient of 0.6~0.8min / mm. After exiting the furnace, it undergoes 4~6 upsetting and drawing forging processes, with two intermediate tempering cycles. The tempering heating temperature is T. β +100~200℃, heating coefficient is 0.2~0.4min / mm, upsetting deformation is controlled at 30~80%, and final forging temperature is controlled above 800℃; Second forging: The billet obtained in the first forging is subjected to low-temperature forging below the β phase transformation point, followed by air cooling; the specific details of the second low-temperature forging are as follows: The billet obtained in the first forging is heated to a temperature of T. β - (20~50)℃, heating coefficient is 0.6~0.8min / mm, after exiting the furnace, it undergoes two upsetting and drawing processes, the upsetting and drawing deformation is controlled at 30~80%, and the final forging temperature is controlled above 800℃; Third forging: The billet obtained in the second forging is forged at a high temperature above the β phase transformation point, and then water-cooled to obtain a forged billet with a cross-sectional dimension of (350~400) * (350~400) mm; the third forging at a high temperature above the β phase transformation point is specifically as follows: The billet obtained in the second forging is heated to a temperature of T. β +50~150℃, after exiting the furnace, it undergoes two continuous drawing and forging processes, with the drawing deformation controlled at 30~80%, and the final forging temperature controlled above 800℃. Step 2: Low-temperature, low-speed, large-deformation rolling forming in 4 passes: First pass: The forging billet obtained in step 1 is subjected to low-temperature rolling below the β phase transformation point, followed by air cooling to obtain a square billet with a cross-sectional size of (200-250) mm * (200-250) mm. The low-temperature rolling of the first pass is specifically as follows: the forging billet obtained in step 1 is heated to 900-960℃ with a heating coefficient of 0.6-0.8 min / mm. After exiting the furnace, it is rolled in 11-15 passes using a reciprocating rolling mill with a roll diameter of 1000-1500 mm to obtain a square billet with a specification of (200-250) mm * (200-250) mm. The rolling deformation is controlled at 60-70%, and the rolling speed is controlled at 1-2 mm / s. Second rolling: The square billet obtained in the first rolling is subjected to low-temperature rolling below the β phase transformation point, followed by air cooling to obtain a bar billet with a cross-sectional size of Φ(100~160)mm; The low-temperature rolling of the second rolling is specifically as follows: The bar billet obtained in the first rolling in step 2 is heated to 900~960℃, with a heating coefficient of 0.6~0.8min / mm, and after exiting the furnace, it is rolled in 11~15 passes using a reciprocating rolling mill with a roll diameter of 800~1200mm to obtain a bar billet with a specification of Φ(100~160)mm, with the rolling deformation controlled at 60~80% and the rolling speed controlled at 1~2mm / s; Third rolling: The billet obtained in the second rolling is subjected to low-temperature rolling below the β phase transformation point, followed by air cooling to obtain a billet with a cross-sectional dimension of Φ(50~80)mm; The low-temperature rolling of the third rolling is specifically as follows: The billet obtained in the second rolling in step 2 is heated to 790~830℃, with a heating coefficient of 0.6~0.8min / mm, and after exiting the furnace, it is rolled in 4~7 passes using a reciprocating rolling mill with a roll diameter of 500~800mm to obtain a billet with a specification of Φ(50~80)mm. The rolling deformation is controlled at 60~80%, and the rolling speed is controlled at 1~2mm / s; Fourth rolling: The billet obtained in the third rolling is subjected to low-temperature rolling below the β phase transformation point, followed by air cooling to obtain a TC4 titanium alloy fine-grained rod with a cross-sectional size of Φ(20~45)mm; The low-temperature rolling of the fourth rolling is specifically as follows: the billet obtained in the third rolling in step 2 is heated to 900~960℃ with a heating coefficient of 0.6~0.8min / mm, and after exiting the furnace, it is rolled in 4~7 passes using a reciprocating rolling mill with a roll diameter of 500~800mm to obtain a finished rod with a specification of Φ(20~45)mm. The rolling deformation is controlled at 50~60%, and the rolling speed is controlled at 1~2mm / s.

2. A TC4 titanium alloy fine-grained rod, characterized in that, It is prepared by the preparation method according to claim 1.

3. The TC4 titanium alloy fine-grained rod according to claim 2, characterized in that, The cross-sectional dimensions of the TC4 titanium alloy fine-grained rod are Φ(20~45)mm.

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