A forging method for large-diameter titanium alloy bars

Abstract

This invention provides a forging method for large-diameter titanium alloy bars. Compared with existing technologies, this invention leverages the inherent good fracture toughness and excellent machinability of titanium alloys. It employs large deformation, repeated upsetting and drawing, flattened upsetting and drawing, and recrystallization annealing processes to achieve uniform deformation of the core, edges, and multiple directions of the thick cross-section forging billet. Furthermore, by matching the forging strain rate during each upsetting and drawing process, and controlling the comprehensive balance between dynamic recrystallization, static recrystallization, and grain nucleation and growth, this method successfully addresses the technical challenges of homogenizing and refining the microstructure of titanium alloy bars with fewer forging passes. While ensuring the excellent mechanical properties of titanium alloys, it reduces forging process costs and meets the demands of various aerospace, aviation, and weaponry fields for low-cost, high-performance titanium alloy structural components.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy material processing technology, and particularly relates to a forging method for large-diameter titanium alloy bars. Background Technology

[0002] Titanium alloys, due to their high specific strength, specific modulus, excellent corrosion resistance, high toughness, and weldability, are widely used in important industrial fields such as aviation, aerospace, shipbuilding, weaponry, and nuclear industry. Titanium is relatively abundant in nature, ranking tenth among all elements. However, corresponding to its vast reserves, the usage of titanium alloys is far lower than that of steel and aluminum alloys, and also far lower than that of copper and magnesium alloys. The main factor limiting its widespread application is its relatively high cost. Titanium is not only widely dispersed and difficult to extract, but its complex processing and relatively low yield also contribute to the high cost of titanium alloys, limiting their use in civilian fields such as construction, automobiles, and sports and leisure.

[0003] In recent years, new-generation weapons and equipment have begun to use titanium alloys extensively to meet their design and application requirements of high weight reduction, long service life and low cost. The demand for titanium alloys is also increasing. However, the high processing and use costs of titanium alloys have become the main obstacle to their expanded application. There is an urgent need to develop low-cost titanium alloy materials and their processing technologies.

[0004] The processing of titanium alloys generally involves sponge titanium smelting, ingot melting, forging / rolling, and other processes. Currently, reducing the cost of titanium alloys mainly focuses on two aspects: reducing the cost of titanium alloying elements and shortening the processing steps. For example, in the forging process of titanium alloy bars for aerospace applications, to produce high-quality bars that meet the aforementioned technical requirements, it is often necessary to perform 2-4 forging passes in the β single-phase region, 5-10 repeated upsetting passes in the α+β two-phase region, and 1-2 forming passes. This results in a long production cycle, significant grinding losses, and low yield, leading to high production costs. Therefore, how to reduce the number of forging passes from titanium alloy ingots to qualified bars through reasonable short-process forging design, achieving a good match between low cost and high comprehensive performance, has become a key challenge in the development of low-cost titanium alloy technologies. There is an urgent need to develop low-cost titanium alloy processing technologies to solve the bottleneck problem of high titanium alloy material costs and expand the application areas of titanium alloys. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a low-cost, high-performance forging method for large-size titanium alloy bars. The purpose is to successfully solve the technical problems of homogenization and grain refinement of large-size bars by reducing the number of forging passes. While ensuring the excellent mechanical properties of titanium alloys, the cost of forging process is reduced, thus meeting the needs of various fields such as aviation, aerospace, and weaponry for low-cost, high-performance titanium alloy structural parts.

[0006] This invention provides a forging method for large-diameter titanium alloy bars, comprising the following steps:

[0007] S1) Heat the titanium alloy ingot to 1100℃~1200℃ and perform one-time forging. The number of forging upsetting and drawing in this forging does not exceed three upsetting and three drawing. The single upsetting deformation is 40%~65%, and a forged billet after opening is obtained.

[0008] S2) The forging billet after the initial forging is heated to 1000℃~1100℃ and forged in one heat. The number of forging upsetting and drawing in this heat shall not exceed two upsetting and two drawing. The deformation amount of a single upsetting is 45%~60%. Then, recrystallization annealing treatment is performed to obtain the first intermediate forging billet.

[0009] S3) Heat the first intermediate forging billet to 20°C to 50°C below the β phase transformation temperature, and perform 2 to 3 forging cycles. The number of upsetting and drawing cycles in each cycle shall not exceed two upsetting and two drawing cycles, and the single upsetting deformation amount shall be 35% to 50%, to obtain the second intermediate forging billet.

[0010] S4) The second intermediate forging billet is heated to 30°C to 60°C below the β phase transformation temperature and subjected to one-time forming forging to obtain large-size titanium alloy bars.

[0011] Preferably, the titanium alloy ingot is a TC32 titanium alloy ingot.

[0012] Preferably, in step S1), the forging blank after each upsetting is pressed into a flat square; the aspect ratio of the flat square is 1:(1.5~3.5).

[0013] Preferably, in step S1), each pier extraction is carried out according to the pier extraction process of axial pier thickening, pressing flat piers, pier thickening flat piers, and axial elongation.

[0014] Preferably, in step S1), the forging strain rate during the upsetting and drawing process gradually decreases, with the forging strain rate of the first upsetting and drawing process being 0.15–0.2S. -1 The forging strain rate during the final upsetting and pulling process was 0.05–0.1 s. -1 The final forging temperature shall not be lower than 850℃.

[0015] Preferably, when the forging and pulling process in step S2) is performed one forging and pulling at a time, the forging strain rate of the forging and pulling is 0.05 to 0.1 s.-1 The final forging temperature shall not be lower than 850℃;

[0016] In step S2), when the forging and pulling process involves two forging and pulling operations, the forging strain rate gradually decreases, with the forging strain rate of the first forging and pulling operation being 0.08–0.1 s⁻¹. -1 The forging strain rate during the second upsetting and pulling process was 0.05–0.07 s. -1 The final forging temperature shall not be lower than 850℃.

[0017] Preferably, the recrystallization annealing temperature in step S2) is 800℃~950℃; and the recrystallization annealing time is 120~300min.

[0018] Preferably, in step S3), when each forging pass is a single forging pass, the forging strain rate during forging is 0.03–0.1 s. -1 The final forging temperature shall not be lower than 800℃;

[0019] In step S3), when each pass involves two passes and two pulls, the forging strain rate gradually decreases, with the forging strain rate of the first pass being 0.08–0.1 s. -1 The forging strain rate during the second upsetting and pulling process was 0.03–0.06 s. -1 The final forging temperature shall not be lower than 800℃.

[0020] Preferably, the forging strain rate during forming and forging in step S4) is 0.05 to 0.01 s. -1 The final forging temperature shall not be lower than 800℃.

[0021] Preferably, in step S3), if no cracks appear in the forging billet after each forging cycle, the hot material is returned to the furnace for the next heating forging cycle.

[0022] This invention provides a forging method for large-diameter titanium alloy bars, comprising the following steps: S1) heating a titanium alloy ingot to 1100℃~1200℃ and performing a single-pass forging, wherein the number of upsetting and drawing operations in this pass does not exceed three upsetting and three drawing operations, and the upsetting deformation in a single pass is 40%~65%, to obtain a blanked forged billet; S2) heating the blanked forged billet to 1000℃~1100℃ and performing a single-pass forging, wherein the number of upsetting and drawing operations in this pass does not exceed two upsetting and two drawing operations, and the upsetting deformation in a single pass is 40%~65%, to obtain a blanked forged billet; 45%–60%, and then recrystallization annealing treatment is performed to obtain the first intermediate forging billet; S3) The first intermediate forging billet is heated to 20°C–50°C below the β phase transformation temperature and forged in 2–3 fires, with no more than two upsetting and two drawing in each fire, and the single upsetting deformation is 35%–50%, to obtain the second intermediate forging billet; S4) The second intermediate forging billet is heated to 30°C–60°C below the β phase transformation temperature and forged in one fire to obtain large-size titanium alloy bars. Compared with existing technologies, this invention, based on the inherent good fracture toughness and excellent machinability of titanium alloys, employs large deformation, repeated upsetting and drawing, flat square upsetting and drawing, and recrystallization annealing processes to achieve uniform deformation of the core, edges, and multiple directions of thick cross-section forging billets. It also matches the forging strain rate during each upsetting and drawing process, controlling the comprehensive balance between dynamic recrystallization, static recrystallization, and grain nucleation and growth. Thus, it successfully addresses the technical challenges of homogenizing and refining the microstructure of titanium alloy bars with fewer forging passes. While ensuring the excellent mechanical properties of titanium alloys, it reduces forging process costs, meeting the needs of various aerospace, weaponry, and other fields for low-cost, high-performance titanium alloy structural components. Attached Figure Description

[0023] Figure 1 This is a microstructure diagram of the large-size titanium alloy bar obtained in Example 1 of the present invention;

[0024] Figure 2 This is a microstructure diagram of the large-size titanium alloy bar obtained in Example 2 of the present invention;

[0025] Figure 3 This is a microstructure diagram of the large-size titanium alloy bar obtained in Example 3 of the present invention. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] This invention provides a forging method for large-diameter titanium alloy bars, comprising the following steps: S1) heating a titanium alloy ingot to 1100℃~1200℃ and performing a single-pass forging, wherein the number of upsetting and drawing operations in this pass does not exceed three upsetting and three drawing operations, and the upsetting deformation in a single pass is 40%~65%, to obtain a blanked forged billet; S2) heating the blanked forged billet to 1000℃~1100℃ and performing a single-pass forging, wherein the number of upsetting and drawing operations in this pass does not exceed two upsetting and two drawing operations, and the upsetting deformation in a single pass is 40%~65%, to obtain a blanked forged billet; 45%–60%, and then recrystallization annealing treatment is performed to obtain the first intermediate forging billet; S3) The first intermediate forging billet is heated to 20°C–50°C below the β phase transformation temperature and forged in 2–3 fires, with no more than two upsetting and two drawing in each fire, and the single upsetting deformation is 35%–50%, to obtain the second intermediate forging billet; S4) The second intermediate forging billet is heated to 30°C–60°C below the β phase transformation temperature and forged in one fire to obtain large-size titanium alloy bars.

[0028] In this invention, there are no special restrictions on the source of any raw materials; they can be commercially available.

[0029] The titanium alloy ingot is heated to 1100℃~1200℃ and forged in one pass. The number of upsetting and drawing operations in this pass does not exceed three upsetting and three drawing operations, and the deformation amount in a single upsetting operation is 40%~65%, resulting in a forged blank after initial upsetting. The titanium alloy ingot is preferably a TC32 titanium alloy ingot. TC32 titanium alloy ingots have good fracture toughness and excellent machinability. In this invention, the titanium alloy ingot is preferably heated to 1140℃~1200℃, more preferably to 1160℃~1190℃, and forged in one pass. In this invention, the number of upsetting and drawing operations in this pass is preferably two upsetting and two drawing operations or three upsetting and three drawing operations, more preferably three upsetting and three drawing operations. The forged blank after each upsetting operation is preferably pressed into a flat square shape. The aspect ratio is preferably 1:(1.5-3.5), more preferably 1:(2-3.5); the aspect ratio of the flattened material pressed in each upsetting and drawing process can be the same or different, without any special restrictions; each upsetting and drawing process is preferably carried out in the following order: upsetting, pressing the flattened material, upsetting the flattened material, and axial elongation; the deformation amount of a single upsetting is preferably 40%-65%, more preferably 45%-65%, and even more preferably 50%-65%; the deformation amount of each upsetting process can be the same or different, without any special restrictions. In this invention, it is preferred that the deformation amount of each upsetting process gradually decreases during the upsetting and drawing forging; the forging strain rate of the upsetting and drawing process is preferably gradually decreased, and the forging strain rate of the first upsetting and drawing process is preferably 0.15-0.2S. -1 More preferably, it is 0.15 to 0.18S. -1 The preferred forging strain rate for the final upsetting is 0.05–0.1 s. -1 More preferably, it is 0.08 to 0.09S. -1The final forging temperature is preferably not lower than 850℃, more preferably 860℃~950℃, and even more preferably 880℃~900℃. After forging, it is preferred to rapidly cool to room temperature with water. After water cooling, it is also preferred to perform surface mold repair treatment to obtain the forged billet after opening.

[0030] In this step, the ingot is heated to between 1100℃ and 1200℃ and subjected to repeated upsetting and drawing deformation in one heat. The purpose is to homogenize the microstructure of the ingot during high-temperature holding, and then fully break down and refine the coarse original β-grain structure of the ingot. Unlike conventional upsetting and drawing deformation of titanium alloys, this invention presses the forging blank into a flat square after each upsetting, then performs upsetting deformation along the streamline direction of the flat square, and finally performs traditional drawing deformation. Using this forging process, the forging blank is deformed in both directions parallel and perpendicular to the streamline direction in a single upsetting and drawing process, achieving the combined process effect of traditional upsetting and drawing and reverse upsetting and drawing. This significantly improves the microstructure uniformity of the forging blank, further reduces the difference in microstructure in different regions of the forging blank, and effectively eliminates the anisotropy that may occur in the forging blank. By controlling the amount of upsetting deformation and the forging strain rate of upsetting and drawing, a comprehensive balance between dynamic recrystallization and grain nucleation and growth of the titanium alloy microstructure is achieved. Considering the relatively poor process plasticity of titanium alloy, the number of upsetting and drawing is strictly controlled to not exceed three upsetting and three drawing operations. Rapid water quenching after forging suppressed the coarsening of the elongated α phase precipitated within the grains during the cooling process, resulting in a fine and uniform lamellar structure.

[0031] The forged billet after initial forging is heated to 1000℃~1100℃ and subjected to one-pass forging. The number of upsetting and drawing operations in this pass does not exceed two upsetting and two drawing operations, and the upsetting deformation in a single pass is 45%~60%. Then, recrystallization annealing is performed to obtain the first intermediate forging billet. In this invention, the forged billet after initial forging is preferably heated to 1030℃~1090℃, more preferably to 1050℃~1070℃, and subjected to one-pass forging. The number of upsetting and drawing operations in this pass does not exceed two upsetting and two drawing operations, and the upsetting deformation in a single pass is preferably 50%~60%. The deformation in each upsetting operation can be the same or different, without any particular limitation. When the upsetting and drawing is one upsetting and one drawing operation, the forging strain rate during upsetting and drawing is preferably 0.05~0.1S. -1 More preferably, it is 0.06 to 0.09S. -1 When the forging and pulling process involves two forging and pulling operations, the forging strain rate during the first forging and pulling operation is preferably gradually reduced, with the forging strain rate during the first forging and pulling operation preferably being 0.08–0.1 s. -1 More preferably, it is 0.08 to 0.09S. -1 The preferred forging strain rate for the second upsetting and pulling is 0.05–0.07 s. -1 More preferably, it is 0.06 to 0.07S. -1The final forging temperature is preferably not lower than 850℃, more preferably 860℃~950℃, even more preferably 860℃~900℃, and even more preferably 860℃~880℃. After forging, it is preferable to directly perform recrystallization annealing treatment. The recrystallization annealing treatment temperature is preferably 800℃~950℃, more preferably 830℃~930℃, even more preferably 850℃~900℃, and most preferably 850℃~880℃. The recrystallization annealing treatment time is preferably 120~300min, more preferably 150~260min, and even more preferably 160~260min. After recrystallization annealing treatment, it is preferable to cool in air, more preferably to cool in air to room temperature. After cooling, it is preferable to also perform surface mold repair treatment to obtain the first intermediate forging billet.

[0032] In this step, the forging billet is first repeatedly upsetting and drawing in the streamline direction to further break down and refine the grains. After forging, the billet is directly subjected to recrystallization annealing. The purpose is to transform the relatively coarse deformed grains caused by the large deformation in the first two forging cycles back into undistorted grains through static recrystallization, further refining the grain structure and improving process plasticity. By directly recrystallizing and annealing the forged billet, the production process of cooling and reheating the billet is simplified, reducing workload, increasing production efficiency, and lowering production costs.

[0033] The first intermediate forging billet is heated to 20°C–50°C below the β phase transformation temperature and forged in 2–3 passes, with each pass involving no more than two upsetting and two drawing operations, and a single upsetting deformation of 35%–50%, to obtain the second intermediate forging billet. In this invention, it is preferable to heat the first intermediate forging billet to 20°C–40°C below the β phase transformation temperature, more preferably to 20°C–35°C below the β phase transformation temperature, and even more preferably to 25°C–35°C below the β phase transformation temperature, forging in 2–3 passes; each pass involving no more than two upsetting and two drawing operations, and a single upsetting deformation preferably of 40%–50%; when each pass involves one upsetting and one drawing operation, the forging strain rate during upsetting and drawing is preferably 0.03–0.1 s. -1 More preferably, it is 0.05 to 0.09S. -1 The preferred value is 0.05–0.08S. -1 When each forging and drawing operation consists of two forging and two drawing operations, the forging strain rate during the forging and drawing processes should preferably decrease gradually, with the forging strain rate of the first forging and drawing operation preferably being 0.08–0.1 s. -1 More preferably, it is 0.08 to 0.09S. -1 The preferred forging strain rate for the second upsetting and pulling is 0.03–0.06 s. -1 More preferably, it is 0.05 to 0.06S. -1The final forging temperature is preferably not lower than 800℃, more preferably 800℃~900℃, even more preferably 820℃~850℃, and most preferably 820℃~840℃. After each forging cycle, if no cracks appear in the forging billet, the hot material can be returned to the furnace for the next heating forging cycle. After forging, it is preferred to cool in air, more preferably to cool in air to room temperature, to obtain two intermediate forging billets.

[0034] This step involves forging the ingot 2 to 3 times at a temperature 20°C to 50°C below the β phase transformation point. The purpose is to further refine and homogenize the microstructure. Due to the low deformation temperature, cracks are avoided during the deformation process. Therefore, the number of upsetting and drawing operations per forging operation is strictly controlled to not exceed two upsettings and two drawing operations. At the same time, by controlling the amount of upsetting deformation and the forging strain rate of upsetting and drawing, the microstructure of the titanium alloy undergoes repeated dynamic recrystallization to obtain titanium alloy bars with uniform microstructure and properties.

[0035] The second intermediate forging billet is heated to 30°C–60°C below the β phase transformation temperature and subjected to single-pass forging to obtain large-diameter titanium alloy bars. In this invention, it is preferable to heat the second intermediate forging billet to 40°C–60°C below the β phase transformation temperature, more preferably to 40°C–50°C below the β phase transformation temperature. The forming forging is preferably a rounding forging. The forging strain rate of the forming forging is preferably 0.05–0.01 s. -1 More preferably, it is 0.04 to 0.01S. -1 The preferred value is 0.04–0.02S. -1 The final forging temperature is preferably not lower than 800℃, more preferably 800℃~850℃, and even more preferably 810℃~820℃. After forging, it is preferred to cool in air, more preferably to cool in air to room temperature, to obtain large-size titanium alloy bars.

[0036] Based on the inherent good fracture toughness and excellent machinability of titanium alloys, this invention employs large deformation, repeated upsetting and drawing, flat square upsetting and drawing, and recrystallization annealing processes to achieve uniform deformation of the core, edges, and multiple directions of thick cross-section forging billets. It also matches the forging strain rate during each upsetting and drawing process, controlling the comprehensive balance between dynamic recrystallization, static recrystallization, and grain nucleation and growth. Thus, it successfully addresses the technical challenges of homogenizing and refining the microstructure of titanium alloy bars with fewer forging passes. While ensuring the excellent mechanical properties of titanium alloys, it reduces forging process costs, meeting the needs of various aerospace, weaponry, and other fields for low-cost, high-performance titanium alloy structural components.

[0037] To further illustrate the present invention, the following describes in detail a forging method for large-diameter titanium alloy bars provided by the present invention, in conjunction with embodiments.

[0038] All reagents used in the following examples are commercially available. The ingots used in the examples can be Φ380mm~Φ980mm in size, and the mechanical property testing standard is GB / T 228.1-2010.

[0039] Example 1

[0040] This embodiment describes a 5-forging process to obtain a low-cost, high-performance 200mm TC32 titanium alloy bar, specifically including the following steps:

[0041] Step 1: Heat the qualified TC32 low-cost, high-performance titanium alloy Φ530mm ingot to 1180℃ and perform a single-pass, three-upsetting, three-drawing forging process. The deformation amount in the first upsetting and drawing pass is 60%, and the forging deformation rate is controlled at 0.15s. -1 The aspect ratio of the flattened material after upsetting is 1:3; the second upsetting and drawing deformation is 55%, and the forging deformation rate is controlled at 0.1 s. -1 The aspect ratio of the flattened pier after roughing is 1:3; the third pier extraction deformation is 50%, and the pier extraction deformation rate is 0.08 s. -1 The flat square billet, after being upsetting and pressed, has a height-to-width ratio of 1:2.5; the final forging temperature is 900℃, followed by rapid cooling to room temperature by immersion in water, and then surface grinding to obtain the forging billet.

[0042] Step 2: Heat the forging billet described in Step 1 to 1070℃ and perform a single-pass, two-upsetting, two-drawing forging process. The deformation amount in the first upsetting and drawing pass is 60%, and the forging deformation rate is controlled at 0.08 s. -1 The second forging pass deformation was 50%, and the forging deformation rate was controlled at 0.06 s. -1 The final forging temperature is 860℃. The forged billet is then placed directly into a heating furnace for recrystallization annealing at 860℃. After holding at this temperature for 160 minutes, it is cooled in air and then surface-ground.

[0043] Step 3: Heat the forging billet from Step 2 to 25°C below the β-phase transformation temperature and perform two-pass forging, each pass consisting of two upsetting and two drawing operations. The deformation amount in the first pass is 45% for both upsetting and drawing, and the forging deformation rate is controlled at 0.09 s. -1 The deformation amount in the second forging pass was 40%, and the forging deformation rate was controlled at 0.05 s. -1 The final forging temperature is 820℃, and the forged billet is obtained after air cooling.

[0044] Step 4: Heat the forging billet described in Step 3 to 50°C below the β phase transformation temperature, and perform a single-pass forging process to form the bar stock, controlling the forging deformation rate to be 0.04 s. -1 The final forging temperature was 810℃, and after air cooling, a bar with uniform microstructure and properties was obtained.

[0045] The mechanical properties of the 200mm TC32 low-cost, high-performance titanium alloy bars prepared in this embodiment after heat treatment at room temperature are shown in Table 1, and the microstructure is as follows. Figure 1 As shown in Table 1 and Figure 1 It can be concluded that it meets the relevant technical standards requirements.

[0046] Table 1. Mechanical properties of TC32 low-cost, high-performance titanium alloy Φ200mm bars in Example 1

[0047]

[0048] Example 2

[0049] This embodiment describes a 5-forging process to obtain a low-cost, high-performance 300mm TC32 titanium alloy bar, specifically including the following steps:

[0050] Step 1: Heat the qualified TC32 low-cost, high-performance titanium alloy Φ620mm ingot to 1190℃ and perform a single-pass, three-upsetting, three-drawing forging process. The deformation amount in the first upsetting and drawing pass is 65%, and the forging deformation rate is controlled at 0.18s. -1 The aspect ratio of the flattened material after upsetting is 1:3; the deformation amount in the second upsetting and drawing stage is 60%, and the forging deformation rate is controlled at 0.12 s. -1 The aspect ratio of the flattened pier after roughing is 1:2.5; the third pier pull-out deformation is 55%, and the pier pull-out deformation rate is 0.09 s. -1 The flat square billet, after being upsetting and pressed, has a height-to-width ratio of 1:2; the final forging temperature is 890℃, followed by rapid cooling to room temperature by immersion in water, and then surface grinding to obtain the forging billet.

[0051] Step 2: Heat the forging billet described in Step 1 to 1060℃ and perform a single-pass, two-upsetting, two-drawing forging process. The deformation amount in the first upsetting and drawing pass is 55%, and the forging deformation rate is controlled at 0.09 s. -1 The second forging pass deformation was 50%, and the forging deformation rate was controlled at 0.07 s. -1 The final forging temperature was 880℃. The forged billet was then placed directly into a heating furnace for recrystallization annealing at 850℃. After holding at this temperature for 220 minutes, it was cooled in air and then surface-ground.

[0052] Step 3: Heat the forging billet from Step 2 to 30°C below the β-phase transformation temperature and perform two-pass forging, each pass consisting of two upsetting and two drawing operations. The deformation amount in the first pass is 50% for both upsetting and drawing, and the forging deformation rate is controlled at 0.08 s. -1 The deformation amount in the second forging pass was 45%, and the forging deformation rate was controlled at 0.06 s. -1 The final forging temperature is 830℃, and the forged billet is obtained after air cooling.

[0053] Step 4: Heat the forging billet described in Step 3 to 50°C below the β phase transformation temperature, and perform a single-pass bar rounding forging, controlling the forging deformation rate to be 0.03 s. -1 The final forging temperature was 820℃, and after air cooling, a bar with uniform microstructure and properties was obtained.

[0054] The mechanical properties of the 300mm TC32 low-cost, high-performance titanium alloy bars prepared in this embodiment after heat treatment at room temperature are shown in Table 2, and the microstructure is as follows. Figure 2 As shown in Table 2 and Figure 2 It can be concluded that it meets the relevant technical standards requirements.

[0055] Table 2 Mechanical properties of TC32 low-cost, high-performance titanium alloy Φ300mm bars in Example 2

[0056]

[0057] Example 3

[0058] This embodiment describes a 6-forging process to obtain a low-cost, high-performance 380mm TC32 titanium alloy bar stock, specifically including the following steps:

[0059] Step 1: Heat the qualified TC32 low-cost, high-performance titanium alloy Φ860mm ingot to 1160℃ and perform a single-pass, three-upsetting, three-drawing forging process. The deformation amount in the first upsetting and drawing pass is 60%, and the forging deformation rate is controlled at 0.16s. -1 The aspect ratio of the flattened material after upsetting is 1:3.5; the second upsetting and drawing deformation is 50%, and the forging deformation rate is controlled at 0.1 s. -1 The aspect ratio of the flattened pier after roughing is 1:2.5; the third pier pull-out deformation is 45%, and the pier pull-out deformation rate is 0.08 s. -1 The flat square formed after upsetting has a height-to-width ratio of 1:2; the final forging temperature is 880℃, followed by rapid cooling to room temperature by immersion in water, and then surface grinding to obtain the forging billet.

[0060] Step 2: Heat the forging billet described in Step 1 to 1050℃ and perform a single-pass, two-upsetting, two-drawing forging process. The deformation amount in the first upsetting and drawing pass is 50%, and the forging deformation rate is controlled at 0.08 s. -1 The second forging pass deformation was 50%, and the forging deformation rate was controlled at 0.06 s. -1 The final forging temperature was 870℃. The forged billet was then placed directly into a heating furnace for recrystallization annealing at 880℃. After holding at this temperature for 260 minutes, it was cooled in air and then surface-polished.

[0061] Step 3: Heat the forging billet from Step 2 to 25°C below the β-phase transformation temperature and perform three-pass forging. The first two passes are two-upsetting and two-drawing forgings, and the third pass is one-upsetting and one-drawing. The deformation amount of the first pass is 40% for both upsetting and drawing, and the forging deformation rate is controlled at 0.08 s. -1 The deformation amount in the second forging pass was 45%, and the forging deformation rate was controlled at 0.05 s. -1 The final forging temperature is 840℃, and the forged billet is obtained after air cooling.

[0062] Step 4: Heat the forging billet described in Step 3 to 40°C below the β phase transformation temperature, and perform a single-pass bar rounding forging, controlling the forging deformation rate to be 0.02 s. -1 The final forging temperature was 810℃, and after air cooling, a bar with uniform microstructure and properties was obtained.

[0063] The mechanical properties of the 380mm TC32 low-cost, high-performance titanium alloy bars prepared in this embodiment after heat treatment at room temperature are shown in Table 3, and the microstructure is as follows. Figure 3 As shown in Table 3. Figure 3 It can be concluded that it meets the relevant technical standards requirements.

[0064] Table 3 Mechanical properties of TC32 low-cost, high-performance titanium alloy Φ380mm bars in Example 3

[0065]

Claims

1. A forging method for large-diameter titanium alloy bars, characterized in that, Includes the following steps: S1) Heat the titanium alloy ingot to 1100℃~1200℃ and perform one-time forging. The number of forging upsetting and drawing in this forging process shall not exceed three upsetting and three drawing. The single upsetting deformation amount is 50%~65%, and a forged billet after blanking is obtained. The size of the titanium alloy ingot is Φ380mm~Φ980mm. S2) The forging billet after the initial forging is heated to 1050℃~1070℃ and forged in one heat. The number of forging upsetting and drawing in this heat shall not exceed two upsetting and two drawing. The deformation amount of a single upsetting is 50%~60%. Then, recrystallization annealing treatment is performed and the billet is cooled to room temperature in air to obtain the first intermediate forging billet. S3) Heat the first intermediate forging billet to 25°C to 35°C below the β phase transformation temperature, and perform 2 to 3 forging cycles. The number of upsetting and drawing cycles in each cycle shall not exceed two upsetting and two drawing cycles, and the single upsetting deformation amount shall be 35% to 50%, to obtain the second intermediate forging billet. S4) The second intermediate forging billet is heated to 40°C to 50°C below the β phase transformation temperature and subjected to one-time forming forging. After forging, it is cooled to room temperature in air to obtain a large-size titanium alloy bar. The forming forging is a rounding forming forging. The titanium alloy ingot is a TC32 titanium alloy ingot; In step S1), the forging blank after each upsetting is pressed into a flat square; the height-to-width ratio of the flat square is 1:(1.5~3.5); In step S1), each pier extraction is carried out according to the pier extraction process of axial pier thickening, pressing flat square, flat square pier thickening, and axial elongation. The recrystallization annealing temperature in step S2) is 850℃~880℃; the recrystallization annealing time is 160~260min; In step S1), the forging strain rate during the upsetting and drawing process gradually decreases, with the forging strain rate for the first upsetting and drawing being 0.15–0.2S. -1 The forging strain rate during the final pull-out was 0.05 s. -1 ~0.1S -1 The final forging temperature is 880℃~900℃; after forging, it is rapidly cooled to room temperature by water cooling; after water cooling, the surface is also repaired to obtain the forged billet after opening. In step S2), when the forging and pulling are performed one forging and one pulling operation, the forging strain rate of the forging and pulling operation is 0.05 s. -1 ~0.1S -1 The final forging temperature is 860℃~880℃; after forging, recrystallization annealing is performed directly. In step S2), when the forging and pulling process involves two forging and pulling operations, the forging strain rate gradually decreases, with the forging strain rate of the first forging and pulling operation being 0.08S. -1 ~0.1S -1 The forging strain rate during the second upsetting was 0.05 s. -1 ~0.07S -1 The final forging temperature shall not be lower than 850℃; In step S3), when each forging pass involves one forging pass and one forging pass, the forging strain rate during forging is 0.03 s. -1 ~0.1S -1 The final forging temperature shall not be lower than 800℃; In step S3), when each pass involves two passes and two pulls, the forging strain rate gradually decreases, with the forging strain rate of the first pass being 0.08 s⁻¹. -1 ~0.1S -1 The forging strain rate during the second upsetting was 0.03 s. -1 ~0.06S -1 The final forging temperature is 820℃~840℃; The forging strain rate during forming forging in step S4) is 0.05 s. -1 ~0.01S -1 The final forging temperature is 810℃~820℃.

2. The forging method according to claim 1, characterized in that, After each forging cycle in step S3), if no cracks appear in the forging billet, the hot material is returned to the furnace for the next heating forging cycle.

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