Uniformly-oriented small-grain polycrystalline titanium alloy bar and preparation method thereof

Abstract

The invention belongs to the technical field of titanium alloy machining, and particularly relates to a uniformly-oriented small-grain polycrystalline titanium alloy bar and a preparation method thereof.The preparation method comprises the steps that a titanium alloy cast ingot is subjected to beta single-phase region cogging forging, and an intermediate billet cast ingot is obtained; performing cross-phase region forging on the intermediate billet cast ingot to obtain a first intermediate billet; (alpha + beta) two-phase region reversing upsetting forging is conducted on the first intermediate blank, and a second intermediate blank is obtained; (alpha + beta) two-phase region drawing-out forging is conducted on the second intermediate blank, and a titanium alloy bar is obtained; according to the method, the pass deformation of a beta single-phase region and an (alpha + beta) two-phase region is reduced, grains are effectively refined through cross-phase region circulating forging, and the texture strength is greatly reduced while the structure is refined, so that the isotropy of the bar is greatly enhanced, and the use requirement is met.

Description

Technical Field

[0001] The present invention belongs to the technical field of titanium alloy processing, and particularly relates to an oriented-uniform small-grain polycrystalline titanium alloy bar and a preparation method thereof. Background Art

[0002] Titanium alloy is a polycrystalline advanced metal material with very broad application prospects in the fields of aviation, aerospace, ocean and chemical industry due to its excellent characteristics such as low density, high specific strength and good corrosion resistance. With the complication of the application environment, the randomness of the bearing angles of titanium alloy equipment components is continuously increasing, and it is required that the mechanical properties of titanium alloy bars are isotropic. However, in the traditional titanium alloy bar processing process, in order to reduce the number of deformation heats, the single-pass deformation amount is large, and the upsetting and drawing deformation regions overlap, resulting in coarse grain size (see the appendix Figure 2 ) and serious deformation texture, so that the finally obtained titanium alloy bar has serious mechanical anisotropy and cannot meet the use requirements.

[0003] In view of the stringent requirements for the isotropy of the mechanical properties of titanium alloy bars, those skilled in the art have carried out research on the optimization of heat treatment and forging processes. The existing research mainly focuses on the improvement of tissue uniformity, but the improvement of tissue uniformity has a very limited effect on the improvement of the isotropy of the mechanical properties of titanium alloy bars. Texture uniformity is a decisive factor affecting property anisotropy, but how to control texture is a challenging problem faced by this field.

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

[0005] Aiming at the deficiencies of the prior art, the present invention provides an oriented-uniform small-grain polycrystalline titanium alloy bar and a preparation method thereof. Compared with the traditional hot working process, the prepared titanium alloy bar has uniform texture and isotropic properties.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a preparation method of an oriented-uniform small-grain polycrystalline titanium alloy bar, comprising the following steps:

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

[0009] Step 2: Perform cross-phase region forging on the intermediate ingot to obtain a first intermediate blank;

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

[0011] Step 4: Perform (α + β) two-phase region drawing forging on the second intermediate blank to obtain a titanium alloy bar.

[0012] Specifically, in step 1, the titanium alloy ingot is subjected to cogging forging in 4 to 6 heats, and is air-cooled after forging in each heat; among them, cogging and upsetting forging is adopted in no less than 3 heats.

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

[0014] Specifically, during the forging process of the titanium alloy ingot, the heating temperature in the first heat is 1150 to 1200 °C, the heating temperatures in the remaining heats are all reduced by 30 to 50 °C compared with the previous heat, and the heating temperature in the last heat is not lower than T β + 30 °C, T β is the β phase transformation point temperature.

[0015] Specifically, in step 2, the intermediate ingot is subjected to 3 to 6 times of cross-phase region forging. The process of each cross-phase region forging is as follows: first, forge in one heat at T β -(30 to 70) °C, and then forge in one heat at T β +(20 to 80) °C; during the cross-phase region forging process of the intermediate ingot, cogging and upsetting forging is adopted in no less than 4 heats.

[0016] Specifically, when forging at T β -(30 to 70) °C, the upsetting forging ratio per hammer is 1.02 to 1.3, the upsetting rate is 10 to 30 mm / s, the drawing forging ratio per single pass is 1.02 to 1.2, the drawing rate is 30 to 90 mm / s, the number of reheating times per heat is 3 to 15 times, the cumulative forging ratio from each furnace discharge to the next reheating is 2.6 to 4.2, and it is air-cooled after forging in each heat;

[0017] When forging at T β +(20 to 80) °C, the upsetting forging ratio per hammer is 1.02 to 1.2, the upsetting rate is 10 to 30 mm / s, the drawing forging ratio per single pass is 1.02 to 1.2, the drawing rate is 30 to 90 mm / s, the number of reheating times per heat is 3 to 15 times, the cumulative forging ratio from each furnace discharge to the next reheating is 1.6 to 4.3, and it is water-cooled after forging in each heat.

[0018] Specifically, in step 3, the first intermediate blank is subjected to 1 to 3 heats of cogging and upsetting forging, and is air-cooled after forging in each heat;

[0019] During the process of cross - direction upsetting and drawing forging of the first intermediate blank, the upsetting forging ratio per hammer is 1.02 - 1.1, the upsetting rate is 10 - 30 mm / s, the drawing forging ratio per single pass is 1.02 - 1.2, and the drawing rate is 30 - 90 mm / s; the number of reheating times per heat treatment is 3 - 15 times, and the cumulative forging ratio from each furnace tapping to the next reheating is 1.6 - 2.2.

[0020] Specifically, during the process of cross - direction upsetting and drawing forging of the first intermediate blank, the heating temperature per heat treatment is T β -(30 - 60) °C.

[0021] Specifically, in step 4, the second intermediate blank is forged for 1 - 3 heat treatments. The drawing forging ratio per single pass is 1.02 - 1.2, and the drawing rate is 30 - 90 mm / s. During each heat treatment, after every 1 - 4 passes of drawing, it is reheated. The heating temperature per heat treatment is T β -(30 - 60) °C, and it is air - cooled after each heat treatment.

[0022] The present invention also provides an oriented - uniform fine - grained polycrystalline titanium alloy bar, which is prepared by the above - mentioned 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 pass deformation amount 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, so that the isotropy of the bar is greatly enhanced, meeting the usage requirements.

[0025] (2) Through multiple low - high cyclic forging in the present invention, water - cooling in the β - phase region obtains a fully fine - lamellar structure. Deformation in the two - phase region can quickly and effectively refine the grain size. At the same time, a small deformation amount is applied per heat treatment to avoid generating strong deformation textures. By cross - direction upsetting and drawing, the deformation uniformity is increased. During each heat treatment, when the deformation amount accumulates to a certain extent, it is reheated, and recrystallization annealing is carried out in a timely manner to weaken the deformation texture, thus ensuring the isotropy of the mechanical properties of the prepared titanium alloy bar. Compared with steps 1 and 2, the deformation amount from each furnace tapping to the next reheating during the forging process is reduced in steps 3 and 4, thus avoiding the generation of strong α - textures and further ensuring the isotropy of the mechanical properties of the titanium alloy bar.

[0026] (3) The present invention has strong process adaptability, does not require adding new equipment, the preparation process is simple and clear, and it can be used for continuous and batch industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0028] Figure 2 Orientation distribution map of the TC4 titanium alloy bar prepared in Example 1 of the present invention;

[0029] Figure 3 Orientation pole figure of the TC4 titanium alloy bar prepared in Example 1 of the present invention;

[0030] Figure 4 Orientation distribution map of the TC4 titanium alloy bar prepared in the comparative example;

[0031] Figure 5 Orientation pole figure of the TC4 titanium alloy bar prepared in the comparative example. Detailed implementation manners

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] Example 1

[0034] Reference Figure 1 , a preparation method of a small-grain polycrystalline TC4 titanium alloy bar with uniform orientation, which is specifically implemented according to the following steps:

[0035] Step 1: Perform upsetting and drawing forging on a 4-ton TC4 titanium alloy ingot for 4 heat treatments to obtain an intermediate billet ingot;

[0036] During the forging process of the TC4 titanium alloy ingot, the upsetting forging ratio per hammer is 1.3, the upsetting rate is 10 mm / s, the drawing forging ratio per pass is 1.02, the drawing rate is 30 mm / s, the number of reheating times per heat treatment is 15 times, and the cumulative forging ratio from each furnace discharge to the next reheating is 2.6; after each heat treatment of forging, air cooling is performed, wherein, in the 2nd to 4th heat treatments, reverse upsetting and drawing forging are used; the heating temperatures of the 1st to 4th heat treatments are 1150 °C, 1120 °C, 1090 °C, and 1060 °C in sequence;

[0037] Step 2: Perform 3 times of cross-phase-region forging on the intermediate billet ingot to obtain a first intermediate billet; the process of each cross-phase-region forging is: first perform one heat treatment of forging at 960 °C, and then perform one heat treatment of forging at 1010 °C; during the 1st to 2nd cross-phase-region forging processes, reverse upsetting and drawing forging are used for each heat treatment;

[0038] When forging at 960°C, the upsetting forging ratio per single hammer is 1.3, the upsetting rate is 10 mm / s, the drawing forging ratio per single pass is 1.02, the drawing rate is 30 mm / s, the number of reheating times per heat is 15, the cumulative forging ratio from each furnace tapping to the next reheating is 2.6, and air cooling is carried out after forging in each heat;

[0039] When forging at 1010°C, the upsetting forging ratio per single hammer is 1.02, the upsetting rate is 10 mm / s, the drawing forging ratio per single pass is 1.2, the drawing rate is 30 mm / s, the number of reheating times per heat is 15, the cumulative forging ratio from each furnace tapping to the next reheating is 1.6, and water cooling is carried out after forging in each heat;

[0040] Step 3: Perform 1 heat of upsetting and drawing forging on the first intermediate blank to obtain a second intermediate blank; during the forging process of the first intermediate blank, the upsetting forging ratio per single hammer is 1.02, the upsetting rate is 10 mm / s, the drawing forging ratio per single pass is 1.2, the drawing rate is 30 mm / s; the heating temperature is 960°C, the number of reheating times is 15, and the cumulative forging ratio from each furnace tapping to the next reheating is 1.6; air cooling is carried out after forging.

[0041] Step 4: Perform 1 heat of drawing forging on the second intermediate blank to obtain a TC4 titanium alloy bar with a diameter of Φ210 mm; when forging the second intermediate blank, the heating temperature is 960°C, the drawing forging ratio per single pass is 1.2, the drawing rate is 90 mm / s, and reheating is carried out after each pass of drawing until the process requirement specifications are reached, and air cooling is carried out after forging.

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

[0043] The orientation distribution map and orientation pole figure of the TC4 titanium alloy bar prepared in this embodiment are respectively as Figure 2 and Figure 3 shown.

[0044] Example 2

[0045] A method for preparing a small - grain polycrystalline TA15 titanium alloy bar with uniform orientation is specifically implemented according to the following steps:

[0046] Step 1: Perform 5 heats of upsetting and drawing forging on a 4 - ton TA15 titanium alloy ingot to obtain an intermediate blank ingot;

[0047] During the forging process of TA15 titanium alloy ingots, the upsetting forging ratio per hammer is 1.25, the upsetting rate is 13 mm / s, the drawing forging ratio per pass is 1.06, the drawing rate is 40 mm / s, the number of reheating times per heat treatment is 9 times, and the cumulative forging ratio from each furnace tapping to the next reheating is 4.0; after each heat treatment, it is air-cooled. Among them, the 2nd to 5th heat treatments adopt reverse upsetting and drawing forging; the heating temperatures for the 1st to 5th heat treatments are 1180 °C, 1150 °C, 1110 °C, 1080 °C, and 1030 °C in sequence.

[0048] Step 2: Perform 4 times of cross-phase-region forging on the intermediate ingot to obtain the first intermediate blank; the process of each cross-phase-region forging is as follows: first, perform one heat treatment of forging at 955 °C, and then perform one heat treatment of forging at 1025 °C.

[0049] When forging at 955 °C, the upsetting forging ratio per hammer is 1.25, the upsetting rate is 13 mm / s, the drawing forging ratio per pass is 1.06, the drawing rate is 40 mm / s, each heat treatment adopts reverse upsetting and drawing forging, the number of reheating times per heat treatment is 9 times, the cumulative forging ratio from each furnace tapping to the next reheating is 4.0, and after each heat treatment, it is air-cooled.

[0050] When forging at 1025 °C, the upsetting forging ratio per hammer is 1.06, the upsetting rate is 13 mm / s, the drawing forging ratio per pass is 1.18, the drawing rate is 40 mm / s, each heat treatment adopts reverse upsetting and drawing forging; the number of reheating times per heat treatment is 9 times, the cumulative forging ratio from each furnace tapping to the next reheating is 2.0, and after each heat treatment, it is water-cooled.

[0051] Step 3: Perform 2 heat treatments of reverse upsetting and drawing forging on the first intermediate blank to obtain the second intermediate blank; during the forging process of the first intermediate blank, the upsetting forging ratio per hammer is 1.06, the upsetting rate is 13 mm / s, the drawing forging ratio per pass is 1.18, the drawing rate is 40 mm / s; the heating temperature for each heat treatment is 955 °C, the number of reheating times per heat treatment is 9 times, the cumulative forging ratio from each furnace tapping to the next reheating is 1.7; after each heat treatment, it is air-cooled.

[0052] Step 4: Perform 2 heat treatments of drawing forging on the second intermediate blank to obtain a TA15 titanium alloy bar with a diameter of Φ410 mm; when forging the second intermediate blank, the drawing forging ratio per pass is 1.18, the drawing rate is 80 mm / s. During each heat treatment, after every 2 passes of drawing, it is reheated until it is drawn to the required process specifications. After each heat treatment, it is air-cooled, and the heating temperature for each heat treatment is 955 °C.

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

[0054] Example 3

[0055] A preparation method for a small-grained polycrystalline TC21 titanium alloy bar with uniform orientation is specifically implemented according to the following steps:

[0056] Step 1: Perform six-pass reverse upsetting and drawing forging on a 4-ton TC21 titanium alloy ingot to obtain an intermediate blank ingot;

[0057] During the forging process of the TC4 titanium alloy ingot, the upsetting forging ratio per hammer is 1.2, the upsetting rate is 16 mm / s, the drawing forging ratio per pass is 1.1, the drawing rate is 50 mm / s, the number of reheating times per heat treatment is 7 times, and the cumulative forging ratio from each furnace discharge to the next reheating is 3.6; after each heat treatment, air cooling is carried out; the heating temperatures for the first to sixth heat treatments are 1200 °C, 1170 °C, 1130 °C, 1080 °C, 1050 °C, and 1010 °C in sequence;

[0058] Step 2: Perform five cross-phase-region forging operations on the intermediate blank ingot to obtain a first intermediate blank; the process of each cross-phase-region forging operation is as follows: first, perform one heat treatment at 910 °C, and then perform one heat treatment at 1000 °C; during the second to fourth cross-phase-region forging operations, reverse upsetting and drawing forging is adopted for each heat treatment;

[0059] When forging at 910 °C, the upsetting forging ratio per hammer is 1.2, the upsetting rate is 16 mm / s, the drawing forging ratio per pass is 1.1, the drawing rate is 50 mm / s, the number of reheating times per heat treatment is 7 times, and the cumulative forging ratio from each furnace discharge to the next reheating is 3.6; after each heat treatment, air cooling is carried out;

[0060] When forging at 1000 °C, the upsetting forging ratio per hammer is 1.1, the upsetting rate is 16 mm / s, the drawing forging ratio per pass is 1.14, the drawing rate is 50 mm / s, the number of reheating times per heat treatment is 7 times, and the cumulative forging ratio from each furnace discharge to the next reheating is 2.4; after each heat treatment, water cooling is carried out;

[0061] Step 3: Perform three-pass reverse upsetting and drawing forging on the first intermediate blank to obtain a second intermediate blank; during the forging process of the first intermediate blank, the upsetting forging ratio per hammer is 1.1, the upsetting rate is 16 mm / s, the drawing forging ratio per pass is 1.14, and the drawing rate is 50 mm / s; the heating temperature for each heat treatment is 915 °C, the number of reheating times per heat treatment is 7 times, and the cumulative forging ratio from each furnace discharge to the next reheating is 1.8; after each heat treatment, air cooling is carried out;

[0062] Step 4: Perform upsetting and drawing forging on the second intermediate blank for 3 heats to obtain a TC21 titanium alloy bar with a diameter of Φ360 mm. When forging the second intermediate blank, the upsetting forging ratio per pass is 1.15, and the drawing rate is 70 mm / s. During the forging process of each heat, after every 3 passes of drawing, it is returned to the furnace until it is drawn to the required specification. After the forging of each heat is completed, it is air-cooled, and the heating temperature for each heat is 915°C.

[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°C.

[0064] Example 4

[0065] A method for preparing a small-grained polycrystalline TC19 titanium alloy bar with uniform orientation is specifically implemented according to the following steps:

[0066] Step 1: Perform upsetting and drawing forging on a 4-ton TC19 titanium alloy ingot for 4 heats to obtain an intermediate blank ingot.

[0067] During the forging process of the TC19 titanium alloy ingot, the upsetting forging ratio per hammer is 1.12, and the upsetting rate is 20 mm / s. The drawing forging ratio per pass is 1.14, and the drawing rate is 60 mm / s. The number of times of returning to the furnace for each heat is 5 times, and the cumulative forging ratio from each furnace discharge to the next furnace return is 4.2. After the forging of each heat is completed, it is air-cooled. Among them, the first to the third heats adopt reverse upsetting and drawing forging. The heating temperatures for the first to the fourth heats are 1160°C, 1120°C, 1070°C, and 1020°C in sequence.

[0068] Step 2: Perform 6 times of cross-phase-region forging on the intermediate blank ingot to obtain a first intermediate blank. The process of each cross-phase-region forging is as follows: First, perform forging for one heat at 905°C, and then perform forging for one heat at 1015°C. Among them, during the 2nd to 6th cross-phase-region forging processes, reverse upsetting and drawing forging are adopted for each heat.

[0069] When forging at 905°C, the upsetting forging ratio per single hammer is 1.12, and the upsetting rate is 20 mm / s. The drawing forging ratio per single pass is 1.14, and the drawing rate is 60 mm / s. The number of times of returning to the furnace for each heat is 5 times, and the cumulative forging ratio from each furnace discharge to the next furnace return is 4.2. After the forging of each heat is completed, it is air-cooled.

[0070] When forging at 1015°C, the upsetting forging ratio per single hammer is 1.14, and the upsetting rate is 20 mm / s. The drawing forging ratio per single pass is 1.1, and the drawing rate is 60 mm / s. The number of times of returning to the furnace for each heat is 5 times, and the cumulative forging ratio from each furnace discharge to the next furnace return is 4.2. After the forging of each heat is completed, it is water-cooled.

[0071] Step 3: Perform one-pass reverse upsetting and drawing forging on the first intermediate blank to obtain a second intermediate blank; during the forging process of the first intermediate blank, the upsetting forging ratio per hammer is 1.08, the upsetting rate is 20 mm / s, the drawing forging ratio per single pass is 1.1, and the drawing rate is 60 mm / s; the heating temperature is 915 °C, the number of reheating times is 5 times, and the cumulative forging ratio from each furnace discharge to the next reheating is 1.9; after each forging pass, air cooling is performed.

[0072] Step 4: Perform one-pass drawing forging on the second intermediate blank to obtain a TC19 titanium alloy bar with a diameter of Φ460 mm; when forging the second intermediate blank, the heating temperature is 915 °C, the drawing forging ratio per single pass is 1.1, the drawing rate is 60 mm / s, and after every 4 passes of drawing, reheating is carried out until the drawing reaches the process requirement specifications, and after forging is completed, air cooling is performed.

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

[0074] Example 5

[0075] A method for preparing a small-grained polycrystalline TC17 titanium alloy bar with uniform orientation is specifically implemented according to the following steps:

[0076] Step 1: Perform 5 passes of upsetting and drawing forging on a 6-ton TC17 titanium alloy ingot to obtain an intermediate blank ingot;

[0077] During the forging process of the TC17 titanium alloy ingot, the upsetting forging ratio per hammer is 1.07, the upsetting rate is 25 mm / s, the drawing forging ratio per single pass is 1.18, the drawing rate is 70 mm / s, the number of reheating times per pass is 3 times, and the cumulative forging ratio from each furnace discharge to the next reheating is 3.3; after each forging pass, air cooling is performed, where in the 1st to 4th passes, reverse upsetting and drawing forging is used; the heating temperatures for the 1st to 5th passes are 1190 °C, 1140 °C, 1090 °C, 1040 °C, and 990 °C in sequence;

[0078] Step 2: Perform 4 times of cross-phase region forging on the intermediate blank ingot to obtain a first intermediate blank; the process of each cross-phase region forging is: first perform one-pass forging at 830 °C, and then perform one-pass forging at 960 °C; among the 3rd to 4th cross-phase region forging processes, reverse upsetting and drawing forging is used per pass;

[0079] When forging at 830 °C, the upsetting forging ratio per hammer is 1.07, the upsetting rate is 25 mm / s, the drawing forging ratio per single pass is 1.18, the drawing rate is 70 mm / s, the number of reheating times per pass is 3 times, and the cumulative forging ratio from each furnace discharge to the next reheating is 3.3, and after each forging pass, air cooling is performed;

[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 re-melting times per fire is 3, the cumulative forging ratio from each time out of the furnace to the next re-melting is 3.3, and water cooling is performed after each fire forging.

[0081] Step 3, the first intermediate billet is subjected to two rounds of reversing upsetting and drawing forging to obtain a second intermediate billet; during the forging process of the first intermediate billet, the single hammer upsetting ratio is 1.04, the upsetting rate is 25 mm / s, the single pass drawing ratio is 1.06, and the drawing rate is 70 mm / s; the heating temperature of each round is 835°C, the number of reheating times per round is 3 times, and the cumulative forging ratio from each time out of the furnace to the next reheating is 2.0; air cooling is performed after each round of forging;

[0082] Step 4: The second intermediate billet is subjected to two drawing and forging passes to obtain a TC17 titanium alloy bar of Φ510 mm; when forging the second intermediate billet, the single-pass drawing and forging ratio is 1.06, the drawing rate is 40 mm / s, and during each forging process, it is returned to the furnace after every three drawing passes until it is drawn to the process requirements. After each forging pass, it is air-cooled, and the heating temperature of each fire is 840°C.

[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-grain polycrystalline Ti-15Mo titanium alloy rod is specifically implemented according to the following steps:

[0086] Step 1: performing six-fire upsetting forging on a 4-ton Ti-15Mo titanium alloy ingot to obtain an intermediate billet ingot;

[0087] During the forging process of Ti-15Mo titanium alloy ingot, the upsetting ratio of each hammer is 1.02, the upsetting rate is 30mm / s, the drawing ratio of each pass is 1.2, the drawing rate is 90mm / s, the number of remelting times per fire is 13 times, and the cumulative forging ratio from each time out of the furnace to the next remelting is 3.0; after each fire forging, air cooling is performed, among which, the 2nd to 6th fires adopt reversing upsetting and drawing forging; the heating temperatures of the 1st to 6th fires are 1150℃, 1120℃, 1080℃, 1030℃, 980℃, and 930℃ respectively;

[0088] Step 2: Perform 5 cross-phase-region forging operations on the intermediate blank ingot to obtain the first intermediate blank; the process of each cross-phase-region forging operation is as follows: first perform one-pass forging at 695 °C, and then perform one-pass forging at 845 °C; during the 1st to 4th cross-phase-region forging operations, reverse upsetting and drawing forging is used for each pass;

[0089] When forging at 695 °C, the single-hammer upsetting forging ratio is 1.02, the upsetting rate is 30 mm / s, the single-pass drawing forging ratio is 1.2, the drawing rate is 90 mm / s, the number of reheating times for each pass is 13 times, the cumulative forging ratio from each furnace discharge to the next reheating is 3.0, and air cooling is performed after the forging of each pass;

[0090] When forging at 845 °C, the single-hammer upsetting forging ratio is 1.2, the upsetting rate is 30 mm / s, the single-pass drawing forging ratio is 1.02, the drawing rate is 90 mm / s, the number of reheating times for each pass is 13 times, the cumulative forging ratio from each furnace discharge to the next reheating is 4.3, and water cooling is performed after the forging of each pass;

[0091] Step 3: Perform 3 passes of reverse upsetting and drawing forging on the first intermediate blank to obtain the second intermediate blank; during the forging of the first intermediate blank, the single-hammer upsetting forging ratio is 1.1, the upsetting rate is 30 mm / s, the single-pass drawing forging ratio is 1.02, the drawing rate is 90 mm / s; the heating temperature for each pass is 710 °C, the number of reheating times for each pass is 13 times, the cumulative forging ratio from each furnace discharge to the next reheating is 2.2; air cooling is performed after the forging of each pass;

[0092] Step 4: Perform 3 passes of drawing forging on the second intermediate blank to obtain a Ti-15Mo titanium alloy bar with a diameter of Φ310 mm; when forging the second intermediate blank, the single-pass drawing forging ratio is 1.02, the drawing rate is 30 mm / s, during the forging process of each pass, after every 4 passes of drawing, the material is reheated until the drawing reaches the process requirement specifications, air cooling is performed after the forging of each pass, and the heating temperature for each pass is 720 °C.

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

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

[0095] Comparative Example

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

[0097] Step 1: Perform upsetting and drawing forging on a 4-ton TC4 titanium alloy ingot for 2 heats to obtain an intermediate billet ingot;

[0098] During the forging process of the TC4 titanium alloy ingot, perform upsetting and drawing three times for each heat. Do not reverse the direction during the upsetting and drawing process. The upsetting forging ratio for each time is 1.4, and the drawing forging ratio is 1.4. The upsetting rate is 30 mm / s, and the drawing rate is 50 mm / s. Do not return to the furnace during the forging process of each heat. After the forging of each heat, perform air cooling. The heating temperatures for the 1st - 2nd heats are 1170 °C and 1080 °C in sequence;

[0099] Step 2: Perform one-time cross-phase region forging on the intermediate billet ingot to obtain a first intermediate billet; The process of cross-phase region forging is as follows: First, perform forging for one heat at 960 °C, and then perform forging for one heat at 1030 °C. After the forging of each heat, perform air cooling;

[0100] When forging at 960 °C, complete upsetting and drawing three times. Do not reverse the direction during the upsetting and drawing process. The upsetting forging ratio for each time is 1.3, and the drawing forging ratio is 1.6; The upsetting rate is 30 mm / s, and the drawing rate is 70 mm / s;

[0101] When forging at 1030 °C, complete upsetting and drawing three times. Do not reverse the direction during the upsetting and drawing process. The upsetting forging ratio for each time is 1.4, and the drawing forging ratio is 1.4; The upsetting rate is 30 mm / s, and the drawing rate is 70 mm / s;

[0102] Step 3: Perform upsetting and drawing forging on the first intermediate billet for 4 heats to obtain a second intermediate billet;

[0103] Complete upsetting and drawing three times for each heat. Do not reverse the direction during the upsetting and drawing process. The upsetting forging ratio for each time is 1.4, and the drawing forging ratio is 1.5. The upsetting rate is 20 mm / s, and the drawing rate is 50 mm / s. After the forging of each heat, perform air cooling; The heating temperature for each heat is 955 °C.

[0104] Step 4: Perform drawing forging on the second intermediate billet for 4 heats to obtain a titanium alloy bar with a diameter of Φ210 mm;

[0105] The heating temperature for each heat is 950 °C. During the forging process of the 1st - 2nd heats, complete drawing twice for each heat. The drawing forging ratio for each time is 1.3. The upsetting rate is 20 mm / s, and the drawing rate is 65 mm / s; During the forging process of the 3rd - 4th heats, complete drawing once for each heat. The drawing forging ratio for each time is 1.2.

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

[0107] The orientation distribution map and orientation pole figure of the TC4 titanium alloy bar prepared in this comparative example are respectively as Figure 4and Figure 5 as shown

[0108] It can be seen from Figures 2 to 4 that, compared with the traditional hot working process, the orientation uniformity of the titanium alloy bars prepared by the preparation method proposed in the present invention is significantly improved, and the texture strength is significantly weakened.

[0109] In order 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 in each direction were tested 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 bars obtained in Example 1

[0111]

[0112]

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

[0114]

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

[0116]

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

[0118]

[0119]

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

[0121]

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

[0123]

[0124] Table 7 Mechanical properties of the titanium alloy bars obtained in the comparative example

[0125]

[0126]

[0127] As can be seen from Tables 1 to 6, the mechanical properties of the titanium alloy bars prepared by the present invention have less difference in each direction. By comparing Table 1 and Table 7, it can be seen that, compared with the titanium alloy bars prepared by the traditional hot working process, the isotropy of the mechanical properties of the titanium alloy bars prepared by the preparation method proposed by the present invention has increased by more than 60%.

[0128] The specific embodiments of the present invention enable those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present 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 only limited by the appended claims.

Claims

1. A preparation method of a small-grained polycrystalline titanium alloy bar with uniform orientation, characterized in that, It includes the following steps: Step 1: Carry out cogging forging on the titanium alloy ingot in the β single-phase region to obtain an intermediate blank ingot; Step 2: Carry out cross-phase region forging on the intermediate blank ingot to obtain a first intermediate blank; Step 3: Carry out (α + β) two-phase region commutation upsetting and drawing forging on the first intermediate blank to obtain a second intermediate blank; Step 4: Carry out (α + β) two-phase region drawing forging on the second intermediate blank to obtain a titanium alloy bar.

2. The preparation method of the small-grained polycrystalline titanium alloy bar with uniform orientation according to claim 1, characterized in that, In Step 1, carry out cogging forging on the titanium alloy ingot for 4 to 6 heats, and air cool after each heat forging; among them, commutation upsetting and drawing forging is adopted for no less than 3 heats.

3. The preparation method of the small-grained polycrystalline titanium alloy bar with uniform orientation according to claim 2, wherein, During the forging process of the titanium alloy ingot, the single-hammer upsetting forging ratio is 1.02 to 1.3, the upsetting rate is 10 to 30 mm / s, the single-pass drawing forging ratio is 1.02 to 1.2, the drawing rate is 30 to 90 mm / s, the number of reheating times per heat is 3 to 15 times, and the cumulative forging ratio from each furnace discharge to the next reheating is 2.6 to 4.

2.

4. The preparation method of the small-grained polycrystalline titanium alloy bar with uniform orientation according to claim 2, characterized in that, The heating temperature of the first heat is 1150 - 1200 °C, and the heating temperature of the remaining heats is reduced by 30 - 50 °C compared with the previous heat. The heating temperature of the last heat is not lower than T β + 30 °C.

5. The preparation method of the small-grained polycrystalline titanium alloy bar with uniform orientation according to claim 1, characterized in that, In Step 2, the intermediate blank ingot is subjected to 3 to 6 times of cross-phase-region forging. The process of each cross-phase-region forging is as follows: First, perform one-pass forging at T β -(30 to 70)°C, and then perform one-pass forging at T β +(20 to 80)°C; during the process of subjecting the intermediate blank ingot to cross-phase-region forging, no less than 4 passes adopt reverse upsetting and drawing forging.

6. The preparation method of the small-grained polycrystalline titanium alloy bar with uniform orientation according to claim 5, characterized in that, At T β - When forging at (30 - 70)°C, the upsetting forging ratio per hammer is 1.02 - 1.3, the upsetting rate is 10 - 30 mm / s, the drawing forging ratio per single pass is 1.02 - 1.2, the drawing rate is 30 - 90 mm / s, the number of reheating times per heat is 3 - 15 times, the cumulative forging ratio from each time of taking out of the furnace to the next reheating is 2.6 - 4.2, and after forging in each heat, it is air-cooled; When forging at T β +(20 - 80)°C, the upsetting forging ratio per hammer is 1.02 - 1.2, the upsetting rate is 10 - 30 mm / s, the drawing forging ratio per single pass is 1.02 - 1.2, the drawing rate is 30 - 90 mm / s, the number of reheating times per heat is 3 - 15 times, the cumulative forging ratio from each furnace tapping to the next reheating is 1.6 - 4.3, and water cooling is carried out after forging in each heat.

7. The preparation method of the small-grained polycrystalline titanium alloy bar with uniform orientation according to claim 1, characterized in that, In Step 3, carry out commutation upsetting and drawing forging on the first intermediate blank for 1 to 3 heats, and air cool after each heat forging; During the commutation upsetting and drawing forging process of the first intermediate blank, the single-hammer upsetting forging ratio is 1.02 to 1.1, the upsetting rate is 10 to 30 mm / s, the single-pass drawing forging ratio is 1.02 to 1.2, the drawing rate is 30 to 90 mm / s; the number of reheating times per heat is 3 to 15 times, and the cumulative forging ratio from each furnace discharge to the next reheating is 1.6 to 2.

2.

8. The preparation method of the small-grained polycrystalline titanium alloy bar with uniform orientation according to claim 7, characterized in that, The heating temperature for each firing is T β -(30 to 60) °C.

9. The preparation method of the small-grained polycrystalline titanium alloy bar with uniform orientation according to claim 1, characterized in that, In step 4, the second intermediate blank is forged for 1 to 3 heats, the drawing ratio per pass is 1.02 to 1.2, the drawing rate is 30 to 90 mm / s. During the forging process of each heat, after every 1 to 4 passes of drawing, it is returned to the furnace, and the heating temperature for each heat is T β -(30 to 60)°C, and after the forging of each heat is completed, it is air-cooled.

10. A small-grained polycrystalline titanium alloy bar with uniform orientation, characterized in that, The titanium alloy bar is obtained by the preparation method according to any one of claims 1 to 9.

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