A short-process preparation method of high-strength TC6 titanium alloy large-size rod

Abstract

The present application relates to non-ferrous metal processing field, specifically to a kind of short process high-strength TC6 titanium alloy large specification bar preparation method, comprising the following steps: TC6 titanium alloy ingot is carried out to open upsetting forging, intermediate forging, forming forging, finally obtain diameter between Φ220mm-Φ350mm, length is not less than 1000mm high-strength TC6 titanium alloy large specification bar.The present application realizes TC6 titanium alloy grain fully uniform refinement by less fire, and the finished bar prepared has good organization and performance consistency, its tensile strength is (1050-1200) MPa, surface shrinkage average 37%, realizes strength promotion, and plasticity level is not obviously reduced.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal processing, specifically to a short-process method for preparing large-diameter TC6 titanium alloy bars. Background Technology

[0002] TC6 titanium alloy, with a nominal composition of Ti-6Al-2.5Mo-1.5Cr-0.5Fe-0.3Si, possesses high strength, good ductility and toughness, and excellent corrosion resistance. It is widely used in high-pressure compressor discs, blades, and fasteners, and is one of the main titanium alloys in the aerospace field. Due to the high content and variety of alloying elements, TC6 titanium alloy is difficult to break down. Traditional forging methods often involve multiple upsetting and drawing processes to break down the microstructure, resulting in long production cycles, low yields, and high production costs. The multiple upsetting and drawing processes also make forging process control difficult, leading to poor batch stability and affecting the service life and safety of aerospace components. The room temperature tensile strength range of TC6 titanium alloy bars forged using traditional processes is generally (935~1050) MPa.

[0003] The use of a short-process forging technique to rapidly and thoroughly refine the original grains, uniformly deform the intermediate billet, and ensure that the tensile strength of the finished bar is in the range of (1050-1200) MPa with a reduction in area of ​​≥33% meets the requirements of aero-engines and other industries. This shortens the production cycle and reduces overall costs, making it a critical challenge for TC6 titanium alloy materials used in the aerospace field. Therefore, it is necessary to design and optimize the production process for large-diameter bars based on traditional forging techniques. This involves developing accurate forging process routes and deformation parameters, and adopting appropriate forging methods to obtain large-diameter TC6 titanium alloy bars. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the above-mentioned traditional technologies and propose a short-process method for preparing large-size TC6 titanium alloy bars. The prepared bars have a diameter between Ф220mm and Ф350mm, a length of not less than 1000mm, a tensile strength of (1050~1200)MPa, and an average area shrinkage of 37%, achieving improved strength without significantly reducing plasticity. The bar preparation cycle is short, the process control is easy, the process stability is high, the production cost is low, the yield is high, and the microstructure and properties meet the requirements of aerospace material standards, making it suitable for industrial production.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a short-process method for preparing large-diameter TC6 titanium alloy bars, comprising the following steps:

[0006] Step 1, Forging the billet

[0007] The TC6 titanium alloy ingot is subjected to 1 to 3 rounds of forging and then cooled. The forging temperature is 100°C to 190°C above the phase transformation point, the holding time is 150 min to 510 min, and the forging ratio is controlled at 1.4 to 2.0.

[0008] Step 2, intermediate forging

[0009] The billet forged in step 1 is subjected to 1 to 3 forging passes at a temperature between 60°C below the phase transformation point and 120°C above the phase transformation point, followed by cooling. For the forging passes below the phase transformation point, the holding time is 420 min to 540 min, and the forging ratio is controlled at 1.2 to 1.6. For the forging passes above the phase transformation point, the holding time is 270 min to 390 min, and the forging ratio is controlled at 1.4 to 1.8.

[0010] Step 3: The billet forged in Step 2 is subjected to one heat treatment and forging in a temperature range of 30℃ to 60℃ below the phase transformation point. The heat treatment time is 300 min to 420 min. After forging, the billet is cooled and the billet structure is observed to be fully broken. Then, the subsequent forming forging can be carried out.

[0011] Step 4, Forming and Forging

[0012] The billet forged in step 3 is heated to a temperature range of 40℃ to 70℃ below the phase transformation point and held for 210 min to 330 min. After forging, it is returned to the furnace to be heated to the original temperature and held for 60 min to 120 min. After being taken out of the furnace, it is shaped into a billet and then cooled and processed into a bar. The diameter of the bar is between Ф220 mm and Ф350 mm, and the length is not less than 1000 mm.

[0013] Preferably, step 1 includes a high-temperature homogenization treatment. Before the high-temperature homogenization, the surface of the billet needs to be coated with a high-temperature coating. The high-temperature homogenization holding time is 45h to 70h.

[0014] Preferably, in step 1, before the blanking forging, the four corners of the blank are upsetting. During the blanking forging, the deformation per pass is 30% to 40%, and the cumulative deformation should be greater than 60%.

[0015] Preferably, the forging method used in steps 1 and 2 is upsetting forging, wherein the upsetting forging adopts slow hammer upsetting with an upsetting rate of 10mm / s to 25mm / s.

[0016] Preferably, in step 1, the first elongation of each fire is radial elongation, and the second elongation is axial elongation. The feed amount during axial elongation is 200mm to 300mm, and the elongation rate is 40mm / s to 80mm / s.

[0017] Preferably, in step 2, when drawing the billet below the phase change point, a flat square drawing method is used, and when drawing the billet above the phase change point, a diagonal drawing method is used. The drawing feed amount is 250mm to 300mm, and the drawing rate is 40mm / s to 80mm / s. The cross-section of the billet after drawing is square.

[0018] Preferably, in step 2, during forging, the deformation per pass is 25% to 45%, and the cumulative deformation should be greater than 65%.

[0019] Preferably, the forging method in step 3 is direct drawing, the deformation per pass during forging is 20% to 40%, the direct drawing length is 250mm to 300mm, the drawing rate is 40mm / s to 80mm / s, and the cross-sectional shape of the forged billet is angular or round.

[0020] Preferably, the forging method in step 4 is direct drawing, with a single-pass deformation of 10% to 25%, a drawing length of 200 mm to 250 mm, and a drawing rate of 40 mm / s to 80 mm / s.

[0021] Preferably, the cooling method after forging is air cooling.

[0022] The beneficial effects of this invention are:

[0023] 1) Based on the recrystallization theory of titanium alloys, this invention precisely controls the heating and forging process by rationally designing the heating temperature, deformation amount, and deformation method. This not only solves the problem of increased deformation inhomogeneity caused by repeated upsetting and drawing, but also fully realizes the refinement of the microstructure through recrystallization, and improves the strength level of the bar and the overall uniformity.

[0024] 2) During the billet forging process, a high-temperature homogenization treatment is performed. The compositional uniformity of the billet is improved by utilizing the thermal diffusion properties of atoms under high-temperature conditions. The reversing upsetting forging method is adopted to improve the structural uniformity of the billet.

[0025] 3) During the intermediate forging process, the flat square drawing and diagonal drawing are combined to fully deform the difficult deformation area of ​​the billet. The furnace is used for reheating to reduce the energy consumption of heating cold material and the material loss during grinding, shorten the alloy preparation cycle, and avoid grain growth caused by excessive heat holding time.

[0026] 4) In the forming forging process, a smaller deformation amount is combined with the straight drawing forging method to ensure uniform deformation of the metal in all directions during the forging process;

[0027] 5) The TC6 alloy rods prepared by the processing method of the present invention have a short process flow, which can reduce the number of firing steps by 4 to 5 compared with the traditional process. The processing cost is low, the yield can be increased by about 7% to 8%, and the rods have high strength and good overall uniformity.

[0028] In summary, this invention achieves fully uniform and refined grains in TC6 titanium alloy with fewer firing cycles. The resulting finished bars exhibit excellent microstructure and property consistency, with a tensile strength of (1050–1200) MPa and an average shrinkage of 37%, demonstrating improved strength without a significant decrease in plasticity. Furthermore, the bar preparation process is short, yield is high, and processing costs are low, meeting the stringent requirements of aero-engines and other industries for this alloy bar, making it suitable for industrial-scale mass production. Attached Figure Description

[0029] Figure 1 This is a physical image of the TC6 titanium alloy Ф220mm bar stock of this invention.

[0030] Figure 2 This is a diagram showing the sampling location of the metallographic sample of the bar material according to the present invention.

[0031] Figure 3 The low-magnification structure of the bar in Embodiment 1 of the present invention includes: (a) low-magnification structure of the head bar; (b) low-magnification structure at 1 / 2R of the head bar; (c) low-magnification structure of the tail bar; and (d) low-magnification structure at 1 / 2R of the tail bar.

[0032] Figure 4 The microstructure of the bar in heat-treated state in Embodiment 1 of the present invention includes (a) the microstructure of the edge of the head bar, (b) the microstructure at 1 / 2R of the head bar, and (c) the microstructure of the core of the head bar.

[0033] Figure 5 The low-magnification structure of the bar in Embodiment 2 of the present invention includes: (a) low-magnification structure of the head bar; (b) low-magnification structure at 1 / 2R of the head bar; (c) low-magnification structure of the tail bar; and (d) low-magnification structure at 1 / 2R of the tail bar.

[0034] Figure 6 The microstructure of the bar in heat treatment state in Embodiment 2 of the present invention includes (a) the microstructure of the edge of the head bar, (b) the microstructure at 1 / 2R of the head bar, and (c) the microstructure of the core of the head bar.

[0035] Figure 7 The low-magnification structure of the bar in Embodiment 3 of the present invention includes: (a) low-magnification structure of the head bar; (b) low-magnification structure at 1 / 2R of the head bar; (c) low-magnification structure of the tail bar; and (d) low-magnification structure at 1 / 2R of the tail bar.

[0036] Figure 8 The microstructure of the bar in heat treatment state in Embodiment 3 of the present invention includes (a) the microstructure of the edge of the head bar, (b) the microstructure at 1 / 2R of the head bar, and (c) the microstructure of the core of the head bar. Detailed Implementation

[0037] The present invention provides a short-process method for preparing large-diameter high-strength TC6 titanium alloy bars, comprising the following steps:

[0038] Step 1, Forging the billet

[0039] The TC6 titanium alloy ingot has a diameter of 720mm. After sawing, the single billet weighs approximately 1500kg, and its phase transformation point is 980℃. It is held at 100℃–190℃ above the phase transformation point for 150–510 minutes. After being removed from the furnace, it undergoes 1–3 rounds of forging, including one high-temperature homogenization treatment with a holding time of 45–70 hours. High-temperature homogenization effectively achieves sufficient diffusion of easily segregating elements Cr and Fe within and between grains, reducing the risk of microscopic segregation during ingot smelting. Before high-temperature homogenization, a high-temperature coating is applied to the billet surface to improve the titanium alloy's resistance to high-temperature oxidation. During forging, the deformation per pass is 30%–40%, and the cumulative deformation should be greater than 60%. Before forging, the four corners of the billet are upset, with the upsetting-to-drawing ratio controlled at 1.4–2.0. After forging, the billet is cooled. During upsetting, slow hammer upsetting is used, with an upsetting rate of 10mm / s to 25mm / s. The first drawing in each firing cycle is radial drawing, and the second drawing is axial drawing. During axial drawing, the feed amount is 200mm to 300mm, and the drawing rate is 40mm / s to 80mm / s.

[0040] Preferably, the ingot forging method is upsetting and drawing forging, the purpose of which is to obtain a uniform and controllable recrystallized structure by deforming and breaking coarse columnar crystals; preferably, the cooling method after forging is air cooling.

[0041] Step 2, intermediate forging

[0042] To obtain an alloy billet with a uniform microstructure, the billet forged in step 1 is subjected to 1 to 3 forging cycles at a temperature between 60°C below the phase transformation point and 120°C above the phase transformation point. For the cycles below the phase transformation point, the holding time is 420 min to 540 min, the upsetting-drawing ratio is controlled at 1.2 to 1.6, the upsetting is performed by slow hammer upsetting at a rate of 10 mm / s to 25 mm / s, and the drawing is performed by flat square drawing at a feed rate of 250 mm to 300 mm and a drawing rate of 40 mm / s to 80 mm / s. For forging above the phase transformation point, the holding time is 270-390 minutes. The upsetting-drawing-forging ratio is controlled at 1.4-1.8. Slow-speed hammer upsetting is used, with an upsetting rate of 10-25 mm / s. Diagonal drawing is used, with a drawing feed of 250-300 mm and a drawing rate of 40-80 mm / s. After drawing, the billet cross-section is square to ensure uniform deformation of all parts of the billet. During forging, the deformation per pass is 25%-45%, and the cumulative deformation should be greater than 65%. Air cooling is used after forging.

[0043] Step 3: After grinding and removing surface cracks from the forged billet from Step 2, perform 1-2 heat treatments and forgings within a temperature range of 30℃ to 60℃ below the phase transformation point. The holding time is 300-420 minutes. The forging method is direct drawing, with a single-pass deformation of 20%-40%, and the cumulative deformation should be greater than 60%. The feed rate during the drawing process is 250mm-300mm, and the drawing rate is 40mm / s-80mm / s. The cross-sectional shape of the forged billet is either angular or round. The cooling method after forging is air cooling. After air cooling, the end face of the billet is observed at low magnification. When the low magnification structure shows a uniform and fine structure, it indicates that the billet structure has been fully broken up, and the billet can be further formed and forged.

[0044] Step 4, Forming and Forging

[0045] After grinding to remove surface cracks from the forged billet from step 3, it is heated to 40℃~70℃ below the phase transformation point and held for 210min~330min. The forging method is direct drawing, with a single-pass deformation of 10%~25%. The feed rate during the drawing process is 200mm~250mm, and the drawing rate is 40mm / s~80mm / s. The relatively small deformation combined with direct drawing forging ensures uniform deformation of the metal in all directions during the forging process. The cross-section of the forged billet is circular. It is then reheated to the original temperature in the furnace and held for 60min~120min. After exiting the furnace, it is shaped into a bar using an anvil and air-cooled after forming. The bar is then machined into finished bars. The obtained bars have a diameter between Ф220mm and Ф350mm and a length of not less than 1000mm.

[0046] The present invention will be further described in detail below with reference to specific embodiments.

[0047] Example 1

[0048] A short-process method for preparing large-diameter high-strength TC6 titanium alloy bars includes the following steps:

[0049] Step 1, Forging the billet

[0050] The TC6 titanium alloy ingot has a diameter of 720mm. After sawing, the single billet weighs approximately 1500kg, and its phase transformation point is 980℃. The ingot is heated to 1170℃ in a stepped manner and held for approximately 510 minutes. After exiting the furnace, the four corners of the billet are first upset, followed by upset drawing forging, with a cumulative deformation of approximately 65% ​​and an upset-drawing-forging ratio controlled at 1.4. Subsequently, it is held at 1080℃ for approximately 150 minutes and then upset drawing forging again, with a single-pass deformation of approximately 35% and a cumulative deformation of approximately 60%, again with an upset-drawing-forging ratio controlled at 1.4. After forging, it is air-cooled. During upseting, slow, multi-hammer upseting is used at a rate of 10mm / s. The first drawing in each pass is radial, and the second drawing is axial. For axial drawing, the feed is 250mm, and the drawing rate is 60mm / s.

[0051] After the billet undergoes two forging cycles, surface cracks are removed by grinding. A uniform coating is then applied to the billet surface, followed by high-temperature homogenization treatment at 1150℃ for 45 hours. After exiting the furnace, upsetting and drawing forging are performed, with a cumulative deformation of approximately 65% ​​and an upsetting-drawing ratio controlled at 1.6. Subsequently, upsetting and drawing forging are performed after holding at 1080℃ for approximately 150 minutes, with a single-pass deformation of approximately 35% and a cumulative deformation of approximately 60%, with an upsetting-drawing ratio controlled at 1.5. After forging, the billet is air-cooled. During upsetting, slow-speed hammer upsetting is used at a rate of 10 mm / s. The first drawing in each cycle is radial, and the second drawing is axial. During axial drawing, the feed rate is 200 mm and the drawing rate is 40 mm / s.

[0052] Step 2, intermediate forging

[0053] To obtain an alloy billet with a uniform microstructure, the billet after the initial forging in step 1 was subjected to a single-pass upsetting and drawing forging at 920℃ for approximately 420 minutes. The upsetting-drawing ratio was controlled at 1.2, with slow, segmented hammer upsetting at a rate of 10 mm / s. For drawing, a flat, rectangular drawing method was used, with a drawing feed of 250 mm and a drawing rate of 40 mm / s. After forging, the hot billet was returned to the furnace and subjected to a single-pass upsetting and drawing forging at 1030℃ for 270 minutes. The upsetting-drawing ratio was controlled at 1.4, with slow, segmented hammer upsetting at a rate of 10 mm / s. For drawing, a diagonal drawing method was used, with a drawing feed of 250 mm and a drawing rate of 40 mm / s. After drawing, the billet had a square cross-section. The deformation per pass during forging was approximately 25%, and the cumulative deformation was approximately 68%. After forging, the billet was air-cooled.

[0054] Step 3: After grinding and removing surface cracks from the forged billet from Step 2, the billet is held at 920℃ for about 300 minutes for straight drawing forging. The deformation per pass is about 20%, and the cumulative deformation is 60%. The feed rate during the drawing process is 250 mm, and the drawing rate is 40 mm / s. The cross-sectional shape of the forged billet is a round bar. After forging, the billet is air-cooled.

[0055] Step 4, Forming and Forging

[0056] After grinding and removing surface cracks from the forged billet in step 3, it is forged by straight drawing at 910℃ for about 210 minutes. The deformation per pass is about 10%, the feed rate during the drawing process is 200mm, and the drawing rate is 40mm / s. The cross-section of the forged billet is circular. It is then returned to the furnace to be heated to 910℃ and held for 60 minutes. After exiting the furnace, it is shaped into a Ф230mm bar billet using an anvil and then air-cooled after forming.

[0057] The forged billet is then machined into the following shapes: Figure 1 The finished bar stock with a diameter of Ф220mm is shown.

[0058] Example 2

[0059] A short-process method for preparing large-diameter high-strength TC6 titanium alloy bars includes the following steps:

[0060] Step 1, Forging the billet

[0061] The ingot has a diameter of 720mm, and the weight of the billet after sawing is approximately 1500kg. The alloy phase transformation point is 980℃. A uniform coating is applied to the surface of the billet, followed by high-temperature homogenization treatment at 1170℃ for 55 hours. After exiting the furnace, the four corners of the billet are first upset, then upset drawing forging is performed, with a cumulative deformation of approximately 65% ​​and an upset-drawing-forging ratio controlled at 1.7. Subsequently, it is upset drawing forging at 1080℃ for approximately 180 minutes, with a single-pass deformation of approximately 30% and a cumulative deformation of approximately 60%, with an upset-drawing-forging ratio controlled at 1.7. After forging, it is air-cooled. During upseting, slow hammer upseting is used at a rate of 15mm / s. The first drawing in each pass is radial, and the second drawing is axial. The feed rate for axial drawing is 250mm, and the drawing rate is 60mm / s.

[0062] Step 2, intermediate forging

[0063] To obtain an alloy billet with a uniform microstructure, the billet after the initial forging in step 1 was subjected to a single-pass upsetting and drawing forging at 940℃ for 480 min, with an upsetting-to-drawing ratio controlled at 1.4. Slow, segmented hammer upsetting was used at a rate of 15 mm / s. For drawing, a flat, rectangular drawing method was employed, with a drawing feed of 280 mm and a drawing rate of 60 mm / s. After forging, the hot billet was returned to the furnace and held at 1030℃ for approximately 300 min for a single-pass upsetting and drawing forging, with an upsetting-to-drawing ratio controlled at 1.6. Slow, segmented hammer upsetting was used at a rate of 15 mm / s. For drawing, a diagonal drawing method was employed, with a drawing feed of 280 mm and a drawing rate of 60 mm / s. After drawing, the billet had a square cross-section. The deformation per pass during forging was approximately 40%, and the cumulative deformation was approximately 68%. The billet was then air-cooled after forging.

[0064] Step 3: After grinding and removing surface cracks from the billet forged in Step 2, the billet is held at 935℃ for about 360 minutes for straight drawing forging. The deformation per pass is about 30%, and the cumulative deformation is 60%. The feed rate during the drawing process is 280 mm, and the drawing rate is 60 mm / s. The cross-sectional shape of the forged billet is a round bar. After forging, the billet is air-cooled.

[0065] Step 4, Forming and Forging

[0066] After grinding and removing surface cracks from the billet forged in step 3, it is forged by straight drawing at 925℃ for about 270 minutes. The deformation per pass is about 15%, the feed rate during the drawing process is 220 mm, and the drawing rate is 60 mm / s. The cross-section of the forged billet is circular. It is then returned to the furnace to be heated to 925℃ and held for 90 minutes. After exiting the furnace, it is shaped into a Ф260 mm bar billet using an anvil and then air-cooled after forming.

[0067] The forged billet is then machined into a finished bar stock with a diameter of Ф250mm.

[0068] Example 3

[0069] A short-process method for preparing large-diameter high-strength TC6 titanium alloy bars includes the following steps:

[0070] Step 1, Forging the billet

[0071] The ingot has a diameter of 720mm, and the weight of the billet after sawing is approximately 1500kg. The alloy phase transformation point is 980℃. A uniform coating is applied to the surface of the billet, followed by high-temperature homogenization treatment at 1170℃ for 70 hours. After exiting the furnace, the four corners of the billet are first upset, then upset drawing forging is performed, with a cumulative deformation of approximately 65% ​​and an upset-drawing-forging ratio controlled at 2.0. Subsequently, it is held at 1080℃ for approximately 180 minutes and then upset drawing forging is performed, with a single-pass deformation of approximately 40% and a cumulative deformation of approximately 60%, with an upset-drawing-forging ratio controlled at 2.0. After forging, it is air-cooled. During upseting, slow hammer upseting is used at a rate of 25mm / s. The first drawing in each pass is radial, and the second drawing is axial. The feed rate for axial drawing is 300mm, and the drawing rate is 80mm / s.

[0072] Step 2, intermediate forging

[0073] To obtain an alloy billet with a uniform microstructure, the billet after the initial forging in step 1 was subjected to a single-pass upsetting and drawing forging at 940℃ for approximately 540 minutes, with an upsetting-to-drawing ratio controlled at 1.6. Slow, segmented hammer upsetting was used at a rate of 25 mm / s. For drawing, a flat, rectangular drawing method was employed, with a drawing feed of 300 mm and a drawing rate of 80 mm / s. After forging, the hot billet was returned to the furnace and held at 1100℃ for approximately 390 minutes for a single-pass upsetting and drawing forging, with an upsetting-to-drawing ratio controlled at 1.8. Slow, segmented hammer upsetting was used at a rate of 25 mm / s. For drawing, a diagonal drawing method was employed, with a drawing feed of 300 mm and a drawing rate of 80 mm / s. After drawing, the billet had a square cross-section. The deformation per pass during forging was approximately 45%, and the cumulative deformation was approximately 71%. The billet was then air-cooled after forging.

[0074] Step 3: After grinding and removing surface cracks from the billet forged in Step 2, the billet is held at 950℃ for about 420 minutes for straight drawing forging. The deformation per pass is about 40%, and the cumulative deformation is 63%. The feed rate during the drawing process is 300 mm, and the drawing rate is 80 mm / s. The cross-sectional shape of the forged billet is a round bar. After forging, the billet is air-cooled.

[0075] Step 4, Forming and Forging

[0076] After grinding and removing surface cracks from the forged billet in step 3, it is forged by straight drawing at 940℃ for about 330 minutes. The deformation per pass is about 25%, the feed rate during the drawing process is 250 mm, and the drawing rate is 80 mm / s. The cross-section of the forged billet is circular. It is then returned to the furnace to be heated to 940℃ and held for 120 minutes. After exiting the furnace, it is shaped into a Ф360 mm bar billet using an anvil and then air-cooled after forming.

[0077] The forged billet is then machined into a finished bar stock with a diameter of Ф350mm.

[0078] The product prepared according to this invention was subjected to experimental analysis. Figure 2 The diagram shows the sampling locations for microstructure observation of the finished bar stock. Metallographic samples were taken from the edge, 1 / 2R, and core of the sample for microstructure observation.

[0079] Figure 3 The image shows a low-magnification microstructure of a Ф220mm bar prepared in Example 1. It can be seen that there are no obvious metallurgical defects in the low-magnification microstructure at the head and tail of the bar, the microstructure is uniform, and it is a fuzzy crystal.

[0080] Figure 4 The image shows the microstructure of the Φ220mm bar prepared in Example 1 after heat treatment. It can be seen that the bar's microstructure is equiaxed or short rod-shaped, and the microstructure is uniform across different locations. The room temperature tensile properties of the bar were tested, and the results are shown in Table 1. Both strength and plasticity meet the standard requirements with sufficient margin.

[0081] Table 1. Room temperature tensile properties of TC6 titanium alloy bars

[0082]

[0083] Figure 5 The image shows a low-magnification microstructure of a Ф250mm bar prepared in Example 2. It can be seen that there are no obvious metallurgical defects in the low-magnification microstructure at the head and tail of the bar, the microstructure is uniform, and it is a fuzzy crystal.

[0084] Figure 6 Example 2 shows the microstructure of a Φ250mm bar in the heat-treated state. The microstructure is equiaxed or consists of short rods, and the microstructure is uniform across different locations. The room temperature tensile properties of the bar were tested, and the results are shown in Table 2. Both strength and plasticity meet the standard requirements with sufficient margin.

[0085] Table 2. Room temperature tensile properties of TC6 titanium alloy bars

[0086]

[0087] Figure 7 The image shows a low-magnification microstructure of a Ф350mm bar prepared in Example 3. It can be seen that there are no obvious metallurgical defects at the head and tail of the bar, the microstructure is uniform, and it is a fuzzy crystal.

[0088] Figure 8 The image shows the microstructure of the Ф350mm bar prepared in Example 3 after heat treatment. It can be seen that the bar's microstructure is equiaxed or short rod-shaped, and the microstructure is uniform across different locations. The room temperature tensile properties of the bar were tested, and the results are shown in Table 3. Both strength and plasticity meet the standard requirements with sufficient margin.

[0089] Table 3. Room temperature tensile properties of TC6 titanium alloy bars

[0090]

[0091] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions recorded in the above embodiments or replace some of the technical features with equivalents. Modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should all be included within the protection scope of the present invention.

Claims

1. A method for preparing large-diameter high-strength TC6 titanium alloy bars using a short-process method, characterized in that, Includes the following steps: Step 1, Forging the billet The TC6 titanium alloy ingot is subjected to 1 to 3 rounds of forging and then cooled. The forging temperature is 100°C to 190°C above the phase transformation point, the holding time is 150 min to 510 min, and the forging ratio is controlled at 1.4 to 2.

0. In step 1, the first elongation of each fire is radial elongation, and the second elongation is axial elongation. The feed amount during axial elongation is 200mm~300mm, and the elongation rate is 40mm / s~80mm / s. Step 2, intermediate forging The billet forged in step 1 is subjected to 1 to 3 forging cycles at a temperature between 60°C below the phase transformation point and 120°C above the phase transformation point, followed by cooling. For the cycles below the phase transformation point, the holding time is 420 min to 540 min, and the forging ratio is controlled at 1.2 to 1.

6. For the cycles above the phase transformation point, the holding time is 270 min to 390 min, and the forging ratio is controlled at 1.4 to 1.

8. In step 2, when drawing the billet below the phase change point, a flat square drawing method is used, and when drawing the billet above the phase change point, a diagonal drawing method is used. The drawing feed amount is 250mm~300mm, and the drawing rate is 40mm / s~80mm / s. The cross-section of the billet after drawing is square. Step 3: The billet forged in Step 2 is subjected to one heat treatment and forging in a temperature range of 30℃~60℃ below the phase transformation point. The heat treatment time is 300min~420min. After forging, the billet is cooled and the billet structure is observed to be fully broken. Then, the subsequent forming forging can be carried out. The forging method in step 3 is direct drawing. The deformation per pass during forging is 20% to 40%. The direct drawing length feed is 250 mm to 300 mm, the drawing rate is 40 mm / s to 80 mm / s, and the cross-sectional shape of the forged billet is angular or round bar. Step 4, Forming and Forging The billet forged in step 3 is heated to a temperature range of 40℃~70℃ below the phase transformation point and held for 210min~330min. After forging, it is returned to the furnace to be heated to the original temperature and held for 60min~120min. After being taken out of the furnace, it is shaped into a billet and then cooled and processed into a bar. The diameter of the bar is between Ф220mm~Ф350mm and the length is not less than 1000mm. The forging method in step 4 is direct drawing, with a single-pass deformation of 10% to 25%, a drawing length of 200mm to 250mm, and a drawing speed of 40mm / s to 80mm / s.

2. The method for preparing large-size high-strength TC6 titanium alloy bars using a short-process method according to claim 1, characterized in that, Step 1 includes a high-temperature homogenization treatment. Before the high-temperature homogenization, a high-temperature coating needs to be applied to the surface of the billet. The high-temperature homogenization holding time is 45h~70h.

3. The method for preparing large-size high-strength TC6 titanium alloy bars using a short-process method according to claim 1, characterized in that, Before forging in step 1, the four corners of the billet are upsetting. During the forging process, the deformation per pass is 30% to 40%, and the cumulative deformation should be greater than 60%.

4. The method for preparing large-size high-strength TC6 titanium alloy bars using a short-process method according to claim 1, characterized in that, The forging method used in steps 1 and 2 is upsetting forging, which employs slow-speed hammer upsetting with an upsetting rate of 10mm / s to 25mm / s.

5. The method for preparing large-size high-strength TC6 titanium alloy bars using a short-process method according to claim 1, characterized in that, In step 2, during forging, the deformation per pass is 25% to 45%, and the cumulative deformation should be greater than 65%.

6. The method for preparing large-diameter high-strength TC6 titanium alloy bars using a short-process method according to any one of claims 1-5, characterized in that, All forging processes were cooled by air.

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