A uniformly oriented, small-grained polycrystalline titanium alloy rod and its preparation method

Abstract

This invention belongs to the field of titanium alloy processing technology, specifically relating to a uniformly oriented, small-grained polycrystalline titanium alloy bar and its preparation method. The preparation method includes the following steps: forging a titanium alloy ingot in the β single-phase region to obtain an intermediate billet ingot; forging the intermediate billet ingot in the cross-phase region to obtain a first intermediate billet; forging the first intermediate billet in the (α+β) two-phase region by reversing upsetting to obtain a second intermediate billet; and forging the second intermediate billet in the (α+β) two-phase region by drawing to obtain a titanium alloy bar. This invention reduces the amount of deformation per pass in the β single-phase region and the (α+β) two-phase region. Through cross-phase region cyclic forging, the grains are effectively refined. While refining the microstructure, the texture strength is significantly reduced, thereby greatly enhancing the isotropy of the bar and meeting the application requirements.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy processing technology, specifically relating to a uniformly oriented small-grained polycrystalline titanium alloy rod and its preparation method. Background Technology

[0002] Titanium alloys, due to their excellent characteristics such as low density, high specific strength, and good corrosion resistance, are polycrystalline advanced metallic materials with very broad application prospects in aerospace, marine, and chemical industries. With the increasing complexity of application environments, the randomness of the load-bearing angles of titanium alloy equipment components is constantly increasing, requiring isotropic mechanical properties of titanium alloy bars. However, traditional titanium alloy bar processing methods, in order to reduce the number of deformation heat treatments, result in large deformation amounts per heat treatment, overlapping upsetting and drawing deformation areas, leading to coarse grain sizes (see Appendix). Figure 2 Furthermore, the severe deformation and texture result in significant anisotropy in the mechanical properties of the final titanium alloy bar, which fails to meet the application requirements.

[0003] Those skilled in the art have conducted research on optimizing heat treatment and forging processes to address the stringent requirements for isotropic mechanical properties of titanium alloy bars. Existing research mainly focuses on improving microstructure uniformity, but the effect of improving microstructure uniformity on enhancing the isotropic mechanical properties of titanium alloy bars is very limited. Texture uniformity is a decisive factor affecting the anisotropy of properties, but how to control texture is a challenging problem in this field.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a uniformly oriented, small-grained polycrystalline titanium alloy rod and its preparation method. Compared with traditional hot working processes, this preparation method produces titanium alloy rods with uniform texture and isotropic properties.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention proposes a method for preparing polycrystalline titanium alloy rods with uniformly oriented small grains, comprising the following steps:

[0008] Step 1: Perform β single-phase region forging on the titanium alloy ingot to obtain intermediate billet ingot;

[0009] Step 2: Forge the intermediate billet ingot in a cross-phase region to obtain the first intermediate billet;

[0010] Step 3: Perform (α+β) two-phase region reversing upsetting and forging on the first intermediate billet to obtain the second intermediate billet;

[0011] Step 4: Perform (α+β) two-phase elongation forging on the second intermediate billet to obtain titanium alloy bars.

[0012] Specifically, in step 1, the titanium alloy ingot is subjected to 4 to 6 forging passes, and air-cooled after each forging pass; among them, no less than 3 passes are forging by reversing upsetting.

[0013] Specifically, during the forging process of the titanium alloy ingot, the single-hammer upsetting ratio is 1.02 to 1.3, the upsetting rate is 10 to 30 mm / s, the single-pass drawing ratio is 1.02 to 1.2, the drawing rate is 30 to 90 mm / s, the number of remelting cycles per furnace is 3 to 15, and the cumulative forging ratio from each furnace exit to the next remelting is 2.6 to 4.2.

[0014] Specifically, during the forging process of the titanium alloy ingot, the heating temperature for the first heating pass is 1150–1200°C, the heating temperature for each subsequent heating pass is 30–50°C lower than the previous heating pass, and the heating temperature for the final heating pass is not lower than T. β +30℃, T β is the β phase transition temperature.

[0015] Specifically, in step 2, the intermediate billet ingot undergoes 3 to 6 cross-phase region forgings. Each cross-phase region forging process is as follows: first, in T... β - (30~70)℃ for a single forging, then at T β The intermediate billet ingot is forged at 20-80℃ in a single forging process; during the cross-phase forging process, the intermediate billet ingot is forged at least 4 times using reverse upsetting forging.

[0016] Specifically, in T β When forging at -(30~70)℃, the single hammer upsetting ratio is 1.02~1.3, the upsetting rate is 10~30mm / s, the single pass drawing ratio is 1.02~1.2, the drawing rate is 30~90mm / s, the number of times to remelt per forging is 3~15, the cumulative forging ratio from each forging to the next remelting is 2.6~4.2, and air cooling is performed after each forging.

[0017] In T β When forging at +(20~80)℃, the single hammer upsetting ratio is 1.02~1.2, the upsetting rate is 10~30mm / s, the single pass drawing ratio is 1.02~1.2, the drawing rate is 30~90mm / s, the number of times to remelt per forging is 3~15, the cumulative forging ratio from each exit from the furnace to the next remelting is 1.6~4.3, and water cooling is performed after each forging.

[0018] Specifically, in step 3, the first intermediate billet is subjected to 1 to 3 rounds of reverse upsetting and drawing forging, and air-cooled after each round of forging;

[0019] During the reverse upsetting and drawing forging process of the first intermediate billet, the single hammer upsetting ratio is 1.02 to 1.1, the upsetting rate is 10 to 30 mm / s, the single pass drawing ratio is 1.02 to 1.2, and the drawing rate is 30 to 90 mm / s; the number of times the billet is reheated per furnace is 3 to 15, and the cumulative forging ratio from each furnace exit to the next furnace reheat is 1.6 to 2.2.

[0020] Specifically, during the reversing upsetting and forging process of the first intermediate billet, the heating temperature for each heat is T. β -(30~60)℃.

[0021] Specifically, in step 4, the second intermediate billet is forged 1 to 3 times, with a single-pass drawing ratio of 1.02 to 1.2 and a drawing rate of 30 to 90 mm / s. During each forging process, the billet is returned to the furnace after every 1 to 4 drawing passes. The heating temperature for each forging is T. β -(30~60)℃, air-cooled after each forging.

[0022] The present invention also proposes a small-grained polycrystalline titanium alloy rod with uniform orientation, wherein the titanium alloy rod is prepared by the above-described preparation method.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) The present invention reduces the amount of pass deformation in the β single-phase region and (α+β) two-phase region. Through cross-phase region cyclic forging, the grains are effectively refined. While refining the structure, the texture strength is greatly reduced, thereby greatly enhancing the isotropy of the bar and meeting the application requirements.

[0025] (2) This invention obtains a full fine lamellar layer by multiple low-high cycle forging and water cooling in the β phase region. The deformation in the two phase region is fast and effective in refining the grain size. At the same time, a small amount of deformation is applied to each forging to avoid strong deformation texture. The deformation uniformity is increased by reversing upsetting. During each forging process, when the amount of deformation accumulates to a certain extent, the material is returned to the furnace for heating and timely recrystallization annealing to weaken the deformation texture. This ensures that the mechanical properties of the prepared titanium alloy bar are isotropic. Compared with steps 1 and 2, steps 3 and 4 reduce the amount of deformation from each forging process to the next return to the furnace, thereby avoiding strong α texture and further ensuring the isotropic mechanical properties of the titanium alloy bar.

[0026] (3) The present invention has strong process adaptability, does not require the addition of new equipment, and the preparation process is simple and clear, and can be used for continuous and batch industrial production. Attached Figure Description

[0027] Figure 1 This is a temperature control diagram of the preparation method of the present invention;

[0028] Figure 2 This is an orientation distribution diagram of the TC4 titanium alloy rod prepared in Example 1 of the present invention;

[0029] Figure 3 The orientation pole diagram of the TC4 titanium alloy rod prepared in Example 1 of this invention;

[0030] Figure 4 The orientation distribution diagram of the TC4 titanium alloy rod prepared for comparison is shown.

[0031] Figure 5 The orientation pole diagram is shown for the TC4 titanium alloy rod prepared in comparison. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1

[0034] refer to Figure 1 A method for preparing a uniformly oriented, small-grained polycrystalline TC4 titanium alloy rod, specifically implemented according to the following steps:

[0035] Step 1: Perform four upsetting and drawing forging processes on a 4-ton TC4 titanium alloy ingot to obtain an intermediate billet ingot.

[0036] During the forging process of TC4 titanium alloy ingots, the upsetting ratio per hammer is 1.3, the upsetting rate is 10 mm / s, the drawing ratio per pass is 1.02, the drawing rate is 30 mm / s, the number of reheats per forging is 15, and the cumulative forging ratio from each forging to the next reheat is 2.6. After each forging, air cooling is performed. Among them, the second to fourth forgings adopt reverse upsetting and drawing forging. The heating temperatures of the first to fourth forgings are 1150℃, 1120℃, 1090℃, and 1060℃ respectively.

[0037] Step 2: Perform three cross-phase zone forgings on the intermediate billet ingot to obtain the first intermediate billet. The process of each cross-phase zone forging is as follows: first, perform one forging at 960℃, and then perform one forging at 1010℃. In the first and second cross-phase zone forging processes, each forging is performed by reversing upsetting.

[0038] When forging at 960℃, the single-hammer upsetting ratio is 1.3, the upsetting rate is 10mm / s, the single-pass drawing ratio is 1.02, the drawing rate is 30mm / s, the number of re-forgings per forging is 15, the cumulative forging ratio from each forging to the next re-forging is 2.6, and air cooling is performed after each forging.

[0039] When forging at 1010℃, the single-hammer upsetting ratio is 1.02, the upsetting rate is 10mm / s, the single-pass drawing ratio is 1.2, the drawing rate is 30mm / s, the number of re-forgings per forging is 15, the cumulative forging ratio from each forging to the next re-forging is 1.6, and water cooling is performed after each forging.

[0040] Step 3: Perform a single-pass reverse upsetting and drawing forging on the first intermediate billet to obtain the second intermediate billet; during the forging process of the first intermediate billet, the single-hammer upsetting ratio is 1.02, the upsetting rate is 10mm / s, the single-pass drawing ratio is 1.2, and the drawing rate is 30mm / s; the heating temperature is 960℃, the number of reheats is 15, and the cumulative forging ratio from each reheat to the next reheat is 1.6; after forging, air cooling is performed;

[0041] Step 4: Perform a single-pass drawing forging on the second intermediate billet to obtain a 210mm TC4 titanium alloy bar. When forging the second intermediate billet, the heating temperature is 960℃, the single-pass drawing ratio is 1.2, the drawing rate is 90mm / s, and the billet is returned to the furnace after each drawing pass until it is drawn to the required specifications. After forging, the billet is air-cooled.

[0042] In this embodiment, the nominal composition of the TC4 titanium alloy ingot is Ti-6Al-4V, T β =990℃.

[0043] The orientation distribution diagram and orientation pole figure of the TC4 titanium alloy rod prepared in this embodiment are as follows: Figure 2 and Figure 3 As shown.

[0044] Example 2

[0045] A method for preparing a uniformly oriented, small-grained polycrystalline TA15 titanium alloy rod is specifically implemented according to the following steps:

[0046] Step 1: Perform five upsetting and drawing forging processes on a 4-ton TA15 titanium alloy ingot to obtain an intermediate billet ingot.

[0047] During the forging process of TA15 titanium alloy ingots, the upsetting ratio per hammer blow is 1.25, the upsetting rate is 13 mm / s, the drawing ratio per pass is 1.06, the drawing rate is 40 mm / s, the number of reheating cycles per forging is 9, and the cumulative forging ratio from each forging to the next reheat is 4.0. After each forging cycle, air cooling is performed. Among them, the 2nd to 5th forging cycles adopt reverse upsetting and drawing forging. The heating temperatures of the 1st to 5th forging cycles are 1180℃, 1150℃, 1110℃, 1080℃, and 1030℃, respectively.

[0048] Step 2: Perform four cross-phase zone forgings on the intermediate billet ingot to obtain the first intermediate billet; the process of each cross-phase zone forging is as follows: first, perform one forging at 955℃, and then perform one forging at 1025℃.

[0049] When forging at 955℃, the single-hammer upsetting ratio is 1.25, the upsetting rate is 13mm / s, the single-pass drawing ratio is 1.06, the drawing rate is 40mm / s, the reverse upsetting and drawing forging is used in each forging, the number of times the forging is reheated in each forging is 9, the cumulative forging ratio from each forging to the next reheat is 4.0, and the forging is air-cooled after each forging.

[0050] When forging at 1025℃, the single-hammer upsetting ratio is 1.06, the upsetting rate is 13mm / s, the single-pass drawing ratio is 1.18, the drawing rate is 40mm / s, and the reverse upsetting and drawing forging is used for each forging pass; the number of reheating passes per forging pass is 9, the cumulative forging ratio from each exit from the furnace to the next reheating pass is 2.0, and water cooling is performed after each forging pass;

[0051] Step 3: Perform two-pass reverse upsetting and drawing forging on the first intermediate billet to obtain the second intermediate billet; during the forging process of the first intermediate billet, the single-hammer upsetting ratio is 1.06, the upsetting rate is 13mm / s, the single-pass drawing ratio is 1.18, and the drawing rate is 40mm / s; the heating temperature of each pass is 955℃, the number of times each pass is reheated is 9, and the cumulative forging ratio from each exit from the furnace to the next reheat is 1.7; after each forging pass, air cooling is performed;

[0052] Step 4: Perform two-pass drawing forging on the second intermediate billet to obtain 410mm TA15 titanium alloy bar. When forging the second intermediate billet, the single-pass drawing ratio is 1.18 and the drawing rate is 80mm / s. During each forging process, the billet is returned to the furnace after every two drawing passes until it is drawn to the required specifications. After each forging, the billet is air-cooled and the heating temperature for each forging is 955℃.

[0053] In this embodiment, the nominal composition of the TA15 titanium alloy ingot is Ti-6.5Al-1Mo-1V-2Zr, T β =995℃.

[0054] Example 3

[0055] A method for preparing a uniformly oriented, small-grained polycrystalline TC21 titanium alloy rod is specifically implemented according to the following steps:

[0056] Step 1: Perform six rounds of reverse upsetting and drawing forging on a 4-ton TC21 titanium alloy ingot to obtain an intermediate billet ingot.

[0057] During the forging process of TC4 titanium alloy ingots, the upsetting ratio per hammer blow is 1.2, the upsetting rate is 16 mm / s, the drawing ratio per pass is 1.1, the drawing rate is 50 mm / s, the number of remelting cycles per forging is 7, and the cumulative forging ratio from each forging to the next remelting is 3.6; air cooling is performed after each forging cycle; the heating temperatures for the 1st to 6th forging cycles are 1200℃, 1170℃, 1130℃, 1080℃, 1050℃, and 1010℃, respectively.

[0058] Step 2: Perform five cross-phase zone forgings on the intermediate billet ingot to obtain the first intermediate billet. The process of each cross-phase zone forging is as follows: first, perform one forging at 910℃, and then perform one forging at 1000℃. In the second to fourth cross-phase zone forging processes, each forging is performed by reversing upsetting forging.

[0059] When forging at 910℃, the single hammer upsetting ratio is 1.2, the upsetting rate is 16mm / s, the single pass drawing ratio is 1.1, the drawing rate is 50mm / s, the number of times the furnace is reheated per forging is 7, the cumulative forging ratio from each furnace exit to the next furnace reheat is 3.6, and air cooling is performed after each forging.

[0060] When forging at 1000℃, the single hammer upsetting ratio is 1.1, the upsetting rate is 16mm / s, the single pass drawing ratio is 1.14, the drawing rate is 50mm / s, the number of times the furnace is reheated per forging is 7, the cumulative forging ratio from each furnace exit to the next furnace reheat is 2.4, and water cooling is performed after each forging.

[0061] Step 3: Perform three-pass reverse upsetting and drawing forging on the first intermediate billet to obtain the second intermediate billet; during the forging process of the first intermediate billet, the single hammer upsetting ratio is 1.1, the upsetting rate is 16mm / s, the single-pass drawing ratio is 1.14, and the drawing rate is 50mm / s; the heating temperature of each pass is 915℃, the number of times each pass is reheated is 7, and the cumulative forging ratio from each exit from the furnace to the next reheat is 1.8; after each forging pass, air cooling is performed;

[0062] Step 4: Perform three-pass drawing and forging on the second intermediate billet to obtain a 360mm TC21 titanium alloy bar. When forging the second intermediate billet, the single-pass drawing ratio is 1.15, the drawing rate is 70mm / s, and after each three-pass drawing process, the billet is returned to the furnace until it is drawn to the required specifications. After each forging, the billet is air-cooled, and the heating temperature for each forging is 915℃.

[0063] In this embodiment, the nominal composition of the TC21 titanium alloy ingot is Ti-6Al-2Mo-2Nb-2Zr-2Sn-1.5Cr, T β =960℃.

[0064] Example 4

[0065] A method for preparing a uniformly oriented, small-grained polycrystalline TC19 titanium alloy rod is specifically implemented according to the following steps:

[0066] Step 1: Perform four upsetting and drawing forging processes on a 4-ton TC19 titanium alloy ingot to obtain an intermediate billet ingot;

[0067] During the forging process of TC19 titanium alloy ingots, the upsetting ratio per hammer is 1.12, the upsetting rate is 20 mm / s, the drawing ratio per pass is 1.14, the drawing rate is 60 mm / s, the number of reheats per forging is 5, and the cumulative forging ratio from each forging to the next reheat is 4.2; after each forging, air cooling is performed. Among them, the first to third forgings use reverse upsetting and drawing forging; the heating temperatures for the first to fourth forgings are 1160℃, 1120℃, 1070℃, and 1020℃ respectively.

[0068] Step 2: Perform six cross-phase zone forgings on the intermediate billet ingot to obtain the first intermediate billet. The process of each cross-phase zone forging is as follows: first, perform one forging at 905℃, and then perform one forging at 1015℃. In the second to sixth cross-phase zone forging processes, each forging is performed by reversing upsetting forging.

[0069] When forging at 905℃, the single-hammer upsetting ratio is 1.12, the upsetting rate is 20mm / s, the single-pass drawing ratio is 1.14, the drawing rate is 60mm / s, the number of times the furnace is reheated per forging is 5, the cumulative forging ratio from each furnace exit to the next furnace reheat is 4.2, and air cooling is performed after each forging is completed.

[0070] When forging at 1015℃, the single hammer upsetting ratio is 1.14, the upsetting rate is 20mm / s, the single pass drawing ratio is 1.1, the drawing rate is 60mm / s, the number of times the furnace is reheated per forging is 5, the cumulative forging ratio from each furnace exit to the next furnace reheat is 4.2, and water cooling is performed after each forging.

[0071] Step 3: Perform a single-pass reverse upsetting and drawing forging on the first intermediate billet to obtain the second intermediate billet; during the forging process of the first intermediate billet, the single-hammer upsetting ratio is 1.08, the upsetting rate is 20mm / s, the single-pass drawing ratio is 1.1, and the drawing rate is 60mm / s; the heating temperature is 915℃, the number of reflows is 5, and the cumulative forging ratio from each reflow to the next reflow is 1.9; after each forging pass, air cooling is performed;

[0072] Step 4: Perform a single-pass drawing forging on the second intermediate billet to obtain a 460mm TC19 titanium alloy bar. When forging the second intermediate billet, the heating temperature is 915℃, the single-pass drawing ratio is 1.1, the drawing rate is 60mm / s, and the billet is returned to the furnace after every 4 passes of drawing until it reaches the required specifications. After forging, the billet is air-cooled.

[0073] In this embodiment, the nominal composition of the TC19 titanium alloy ingot is Ti-6Al-2Sn-4Zr-6Mo, T β =965℃.

[0074] Example 5

[0075] A method for preparing a uniformly oriented, small-grained polycrystalline TC17 titanium alloy rod is specifically implemented according to the following steps:

[0076] Step 1: Perform five upsetting and drawing forging processes on a 6-ton TC17 titanium alloy ingot to obtain an intermediate billet ingot.

[0077] During the forging process of TC17 titanium alloy ingots, the upsetting ratio per hammer blow is 1.07, the upsetting rate is 25 mm / s, the drawing ratio per pass is 1.18, the drawing rate is 70 mm / s, the number of reheating cycles per forging is 3, and the cumulative forging ratio from each forging to the next reheating is 3.3. After each forging cycle, air cooling is performed. Among them, the first to fourth forging cycles adopt reverse upsetting and drawing forging. The heating temperatures for the first to fifth forging cycles are 1190℃, 1140℃, 1090℃, 1040℃, and 990℃, respectively.

[0078] Step 2: Perform four cross-phase zone forgings on the intermediate billet ingot to obtain the first intermediate billet. The process of each cross-phase zone forging is as follows: first, perform one forging at 830℃, and then perform one forging at 960℃. In the third and fourth cross-phase zone forging processes, each forging is performed by reversing upsetting forging.

[0079] When forging at 830℃, the single-hammer upsetting ratio is 1.07, the upsetting rate is 25mm / s, the single-pass drawing ratio is 1.18, the drawing rate is 70mm / s, the number of times the furnace is reheated per forging is 3, the cumulative forging ratio from each furnace exit to the next furnace reheat is 3.3, and air cooling is performed after each forging is completed.

[0080] When forging at 960℃, the single-hammer upsetting ratio is 1.18, the upsetting rate is 25mm / s, the single-pass drawing ratio is 1.06, the drawing rate is 70mm / s, the number of times the furnace is reheated per forging is 3, the cumulative forging ratio from each furnace exit to the next furnace reheat is 3.3, and water cooling is performed after each forging.

[0081] Step 3: Perform two-pass reverse upsetting and drawing forging on the first intermediate billet to obtain the second intermediate billet; during the forging process of the first intermediate billet, the single-hammer upsetting ratio is 1.04, the upsetting rate is 25mm / s, the single-pass drawing ratio is 1.06, and the drawing rate is 70mm / s; the heating temperature of each pass is 835℃, the number of times each pass is reheated is 3, and the cumulative forging ratio from each exit from the furnace to the next reheat is 2.0; after each forging pass, air cooling is performed;

[0082] Step 4: Perform two-pass drawing forging on the second intermediate billet to obtain a 510mm TC17 titanium alloy bar. When forging the second intermediate billet, the single-pass drawing ratio is 1.06, the drawing rate is 40mm / s, and after every three drawing passes during each forging process, the billet is returned to the furnace until it is drawn to the required specifications. After each forging, the billet is air-cooled, and the heating temperature for each forging is 840℃.

[0083] In this embodiment, the nominal composition of the TC17 titanium alloy ingot is Ti-5Al-2Sn-2Zr-4Mo-4Cr, T β =890℃.

[0084] Example 6

[0085] A method for preparing a uniformly oriented, small-grained polycrystalline Ti-15Mo titanium alloy rod is specifically implemented according to the following steps:

[0086] Step 1: The 4-ton Ti-15Mo titanium alloy ingot is subjected to 6 upsetting and drawing forging processes to obtain an intermediate billet ingot.

[0087] During the forging process of Ti-15Mo titanium alloy ingots, the upsetting ratio per hammer blow was 1.02, the upsetting rate was 30 mm / s, the drawing ratio per pass was 1.2, the drawing rate was 90 mm / s, the number of reheating cycles per forging was 13, and the cumulative forging ratio from each forging to the next reheating was 3.0. After each forging cycle, the ingots were air-cooled. For the 2nd to 6th forging cycles, reverse upsetting and drawing were used. The heating temperatures for the 1st to 6th forging cycles were 1150℃, 1120℃, 1080℃, 1030℃, 980℃, and 930℃, respectively.

[0088] Step 2: Perform five cross-phase zone forgings on the intermediate billet ingot to obtain the first intermediate billet. The process of each cross-phase zone forging is as follows: first, perform one forging at 695℃, and then perform one forging at 845℃. In the first to fourth cross-phase zone forging processes, each forging is performed by reversing upsetting forging.

[0089] When forging at 695℃, the single-hammer upsetting ratio is 1.02, the upsetting rate is 30mm / s, the single-pass drawing ratio is 1.2, the drawing rate is 90mm / s, the number of re-forgings per forging is 13, the cumulative forging ratio from each forging to the next re-forging is 3.0, and air cooling is performed after each forging.

[0090] When forging at 845℃, the single-hammer upsetting ratio is 1.2, the upsetting rate is 30mm / s, the single-pass drawing ratio is 1.02, the drawing rate is 90mm / s, the number of re-forgings per heat is 13, the cumulative forging ratio from each heat exit to the next heat return is 4.3, and water cooling is performed after each heat is completed.

[0091] Step 3: Perform three-pass reverse upsetting and drawing forging on the first intermediate billet to obtain the second intermediate billet; during the forging process of the first intermediate billet, the single-hammer upsetting ratio is 1.1, the upsetting rate is 30mm / s, the single-pass drawing ratio is 1.02, and the drawing rate is 90mm / s; the heating temperature of each pass is 710℃, the number of times each pass is reheated is 13, and the cumulative forging ratio from each exit from the furnace to the next reheat is 2.2; after each forging pass, air cooling is performed;

[0092] Step 4: Perform three-pass drawing and forging on the second intermediate billet to obtain a Φ310mm Ti-15Mo titanium alloy bar. When forging the second intermediate billet, the single-pass drawing ratio is 1.02, the drawing rate is 30mm / s, and after every four drawing passes during each forging process, the billet is returned to the furnace until it is drawn to the required specifications. After each forging, the billet is air-cooled, and the heating temperature for each forging is 720℃.

[0093] In this embodiment, the nominal composition of the Ti-15Mo titanium alloy ingot is Ti-15Mo,T β =765℃.

[0094] In the above embodiments, the reversing upsetting and drawing forging process is as follows: axial upsetting → radial drawing → radial upsetting → axial drawing; the holding time after each return of the material to the furnace can be determined according to the requirements to ensure that the temperature of the material when it exits the furnace is uniform and the same as the heating temperature set in the furnace.

[0095] Comparative Example

[0096] This comparative example demonstrates the traditional hot working process for TC4 titanium alloy bars, which is implemented according to the following steps:

[0097] Step 1: Perform two upsetting and drawing forging processes on a 4-ton TC4 titanium alloy ingot to obtain an intermediate billet ingot;

[0098] During the forging process of TC4 titanium alloy ingots, three upsetting and drawing operations are completed per forging pass. The direction is not changed during the upsetting and drawing process. The upsetting ratio is 1.4 and the drawing ratio is 1.4 for each forging pass. The upsetting rate is 30 mm / s and the drawing rate is 50 mm / s. The forging passes are not reheated during each forging pass. After each forging pass, the forging is air-cooled. The heating temperatures of the first and second passes are 1170℃ and 1080℃, respectively.

[0099] Step 2: Perform one cross-phase region forging on the intermediate billet ingot to obtain the first intermediate billet; the cross-phase region forging process is as follows: first perform one forging at 960℃, then perform one forging at 1030℃, and air cool after each forging.

[0100] During forging at 960℃, three upsetting and drawing processes are completed without reversing direction. The upsetting ratio is 1.3 and the drawing ratio is 1.6 for each process. The upsetting rate is 30 mm / s and the drawing rate is 70 mm / s.

[0101] During forging at 1030℃, three upsetting and drawing processes are completed without reversing direction. The upsetting ratio is 1.4 and the drawing ratio is 1.4 for each process. The upsetting rate is 30 mm / s and the drawing rate is 70 mm / s.

[0102] Step 3: Perform four upsetting and drawing forging processes on the first intermediate billet to obtain the second intermediate billet;

[0103] Each forging cycle involves three upsetting and drawing operations without reversing direction. The upsetting ratio is 1.4, the drawing ratio is 1.5, the upsetting rate is 20 mm / s, and the drawing rate is 50 mm / s. After each forging cycle, the forging is air-cooled. The heating temperature for each cycle is 955℃.

[0104] Step 4: Perform four-stage drawing and forging on the second intermediate billet to obtain a titanium alloy bar with a diameter of 210mm.

[0105] The heating temperature for each forging is 950℃. During the first and second forging processes, two drawing operations are completed per forging, with a drawing ratio of 1.3 for each operation, an upsetting rate of 20mm / s, and a drawing rate of 65mm / s. During the third and fourth forging processes, one drawing operation is completed per forging, with a drawing ratio of 1.2 for each operation.

[0106] In this comparative example, the nominal composition of the TC4 titanium alloy ingot is Ti-6Al-4V, T β =990℃.

[0107] The orientation distribution diagram and orientation pole figure of the TC4 titanium alloy rod prepared in this comparative example are as follows: Figure 4and Figure 5 As shown.

[0108] Depend on Figures 2 to 4 It can be seen that, compared with the traditional hot working process, the titanium alloy rods prepared by the method proposed in this invention have significantly improved orientation uniformity and significantly weakened texture strength.

[0109] To better illustrate the beneficial effects of the present invention, the static mechanical properties of the titanium alloy bars obtained in Examples 1 to 6 and the comparative example were tested in various directions with reference to GB / T228.1-2021, and the dynamic mechanical properties of the titanium alloy bars obtained in Examples 1 to 6 and the comparative example were tested with reference to GB / T34108-2017. The test results are shown in Tables 1 to 7:

[0110] Table 1 Mechanical properties of the titanium alloy rods obtained in Example 1

[0111]

[0112]

[0113] Table 2 Mechanical properties of the titanium alloy rods obtained in Example 2

[0114]

[0115] Table 3 Mechanical properties of the titanium alloy rods obtained in Example 3

[0116]

[0117] Table 4 Mechanical properties of the titanium alloy rods obtained in Example 4

[0118]

[0119]

[0120] Table 5 Mechanical properties of the titanium alloy rods obtained in Example 5

[0121]

[0122] Table 6 Mechanical properties of the titanium alloy rods obtained in Example 6

[0123]

[0124] Table 7 Mechanical properties of titanium alloy bars obtained from comparative examples

[0125]

[0126]

[0127] As can be seen from Tables 1 to 6, the mechanical properties of the titanium alloy rods prepared by the present invention show little difference in all directions. Comparing Tables 1 and 7, it can be seen that compared with the titanium alloy rods prepared by the traditional hot working process, the isotropic mechanical properties of the titanium alloy rods prepared by the method proposed in this invention are improved by more than 60%.

[0128] The specific embodiments of the present invention are provided to enable those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0129] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method of producing an oriented, uniformly fine-grained polycrystalline titanium alloy rod, characterized by, The method comprises the following steps: Step 1, β single-phase zone open-die forging is performed on the titanium alloy ingot to obtain an intermediate billet ingot; The titanium alloy ingot is subjected to 4-6 times of open-die forging, and air cooling is performed after each time of forging; wherein, not less than 3 times of reversing upsetting and drawing forging is adopted; During the forging of the titanium alloy ingot, the single-ram upsetting forging ratio is 1.02-1.3, the upsetting rate is 10-30 mm / s, the single-pass elongation forging ratio is 1.02-1.2, the elongation rate is 30-90 mm / s, the number of times of return to the furnace per time is 3-15 times, and the cumulative forging ratio from each time of discharging to the next time of returning to the furnace is 2.6-4.2; The heating temperature of the first heating is 1150-1200℃, the heating temperature of the rest of the heating is reduced by 30-50℃ than the last heating, and the heating temperature of the last heating is not less than T β +30℃; Step 2, cross-phase zone forging is performed on the intermediate billet ingot to obtain a first intermediate billet; The intermediate blank ingot is forged 3-6 times across the phase zone, and the process of each time of forging across the phase zone is as follows: first, forging once at T β - (30-70) ℃, and then forging once at T β + (20-80) ℃; during the process of forging the intermediate blank ingot across the phase zone, not less than 4 times of reversing upsetting and drawing forging is adopted; In T β - when forging at (30~70) °C, the single-ram upsetting forging ratio is 1.02~1.3, the upsetting rate is 10~30 mm / s, the single-pass elongation forging ratio is 1.02~1.2, the elongation rate is 30~90 mm / s, the number of return-to-furnace is 3~15 times per fire, the cumulative forging ratio from each time of tapping to the next return-to-furnace is 2.6~4.2, and air cooling is performed after each fire of forging; In T β + (20-80) °C, the single hammer upsetting forging ratio is 1.02-1.2, the upsetting rate is 10-30 mm / s, the single pass elongation forging ratio is 1.02-1.2, the elongation rate is 30-90 mm / s, the number of return to furnace per fire is 3-15 times, the cumulative forging ratio from each time of discharging to the next return to furnace is 1.6-4.3, and water cooling is performed after each fire forging is completed; Step 3, (α+β) two-phase zone reversing upsetting and drawing forging is performed on the first intermediate billet to obtain a second intermediate billet; Step 4, (α+β) two-phase zone elongation forging is performed on the second intermediate billet to obtain a titanium alloy bar.

2. The method of producing an oriented, uniformly fine-grained polycrystalline titanium alloy bar according to claim 1, characterized in that, In step 3, the first intermediate billet is subjected to 1-3 times of reversing upsetting and drawing forging, and air cooling is performed after each time of forging; During the reversing upsetting and drawing forging of the first intermediate billet, the single-ram upsetting forging ratio is 1.02-1.1, the upsetting rate is 10-30 mm / s, the single-pass elongation forging ratio is 1.02-1.2, and the elongation rate is 30-90 mm / s; the number of times of return to the furnace per time is 3-15 times, and the cumulative forging ratio from each time of discharging to the next time of returning to the furnace is 1.6-2.

2.

3. The method of producing an oriented, uniformly fine-grained polycrystalline titanium alloy bar according to claim 2, characterized in that, Each heating temperature is T β - (30-60) °C.

4. The method of producing an oriented uniform fine-grained polycrystalline titanium alloy bar according to claim 1, characterized in that, In step 4, the second intermediate blank is forged for 1-3 times, the single pass elongation forging ratio is 1.02-1.2, the elongation rate is 30-90 mm / s, in each forging process, the blank is returned to the furnace after 1-4 passes of elongation are performed, the heating temperature for each forging is T β - (30-60) °C, air cooling after each forging process.

5. A small-grain polycrystalline titanium alloy rod material having uniform orientation, characterized by The titanium alloy bar is prepared by the method according to any one of claims 1-4.

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