Preparation method of high-uniformity titanium alloy large-thickness forgings

Abstract

This invention relates to the field of titanium alloy forging technology, and particularly to a method for preparing a thick titanium alloy forging with high uniformity. The method includes: S100, initial forging; S200, low-temperature forging and high-temperature annealing; S300, low-temperature reforging I; S400, low-temperature reforging II; S500, forming forging; and S600, heat treatment. The advantages of this method are: rational use of reheating measures in the furnace reduces the number of surface treatments between forging cycles, significantly shortens the process flow, effectively improves the uniformity of the microstructure, reduces the likelihood of cracking during deformation, eliminates the need for surface grinding to remove surface oxidation and cracks between forging cycles, simplifies the forging process of thick forgings, reduces costs, shortens the cycle time, reduces the difference in microstructure between the surface and core, and lowers the risk of surface cracking.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy forging technology, and in particular to a method for preparing thick titanium alloy forgings with high uniformity. Background Technology

[0002] Titanium and titanium alloys possess characteristics such as high specific strength, corrosion resistance, non-magnetic properties, sound transmission, and excellent weldability, making them widely used in aerospace, shipbuilding, marine, and petrochemical industries. In recent years, as my country's equipment has continuously developed towards high performance and large size, extremely high requirements have been placed on the dimensional specifications and uniformity of microstructure and properties of titanium alloy forgings. However, titanium alloy forging processes suffer from deformation "dead zones" and poor forging penetration, especially for thick forgings, where significant differences in microstructure and properties exist at different locations. This has an extremely adverse impact on the future service performance of structural components.

[0003] Currently, to improve the uniformity of microstructure and properties of thick forgings, the common methods are to increase the number of forging passes and change the cooling method. For example, Chinese invention patent CN119368653A discloses a method for manufacturing a large-size Ti-6Al-4V titanium alloy forging with high uniformity, comprising the following preparation steps: S1. Providing a powder metallurgy sintered Ti-6Al-4V titanium alloy billet, the cross-sectional thickness of which is 120mm or more; S2. Heating the billet to 1030℃~1060℃ using a heating device, holding it at that temperature, and then forging it, with a forging deformation of 30%~38%, to obtain a large-size titanium alloy forging. However, due to the active chemical properties of titanium alloys, they readily react with oxygen, nitrogen, hydrogen, and carbon in the air, and have poor plasticity and high resistance, making them prone to cracking during deformation. Surface grinding is required between each forging pass to remove surface oxidation and cracks, resulting in a complex, costly, and time-consuming forging process for thick forgings. In addition, due to the poor hardenability of titanium alloys, high-temperature water cooling will increase the difference in microstructure between the surface and the core, and at the same time increase the risk of surface cracking. Summary of the Invention

[0004] In view of this, the present invention aims to provide a method for preparing thick titanium alloy forgings with high uniformity. Based on the characteristics of titanium alloys, and utilizing the basic principle of recrystallization microstructure refinement, a forging process of "high-low deformation + high-temperature annealing + low-low deformation" is designed. The method also rationally utilizes reheating measures in the furnace to reduce the number of surface treatments between forging cycles, significantly shortening the process flow. Simultaneously, special deformation methods such as reversal, diagonal drawing, and flattening are used to effectively improve microstructure uniformity. Finally, through a reasonable heat treatment process, the preparation of thick titanium alloy forgings with high uniformity is achieved. This invention solves the problems of titanium alloys being chemically active and easily reacting with oxygen, nitrogen, hydrogen, and carbon in the air, having poor plasticity and high resistance, and being prone to cracking during deformation. It also addresses the need for surface grinding between each forging cycle to remove surface oxidation and cracks, resulting in complex forging processes, high costs, and long cycles for thick forgings. Furthermore, the poor hardenability of titanium alloys means that high-temperature water cooling increases the microstructure difference between the surface and core, while also increasing the risk of surface cracking.

[0005] To address the above problems, this invention provides a method for preparing a large, thick titanium alloy forging with high uniformity, comprising:

[0006] S100, forging:

[0007] After coating the ingots with an anti-oxidation coating, they are loaded into the furnace, and the furnace temperature is raised to the first temperature T during the first forging process. d1 The heat retention coefficient is 0.6~1.0 min / mm, and the final forging temperature is not lower than 800℃;

[0008] After being reheated in the furnace, it is at the second temperature T. d2 The second forging is then carried out, T d1 >T d2 >T β , among which, T β The phase transformation point temperature has a holding coefficient of 0.3–0.6 min / mm, and the final forging temperature is not lower than 800℃.

[0009] S200, low-temperature forging and high-temperature annealing:

[0010] At the third temperature T d3 The third forging will be carried out next, T d3 <T β The heat retention coefficient is 0.6~1.0 min / mm, and the final forging temperature is not lower than 750℃;

[0011] After the third forging, at the annealing temperature T t Annealing is performed at the specified temperature, T t >T β ;

[0012] S300, Low-Temperature Forging I: At the fourth temperature T d4 The fourth forging will be carried out next, T d4<T β The heat retention coefficient is 0.6~1.0 min / mm, and the final forging temperature is not lower than 750℃;

[0013] After being reheated in the furnace, at the fifth temperature T d5 The fifth forging was carried out, T d5 <T d4 The heat retention coefficient is 0.3~0.6min / mm, the billet is drawn into a flat square shape, and the final forging temperature is not lower than 750℃;

[0014] S400, Low-Temperature Forging II: At the sixth temperature T d6 The sixth forging will be carried out below, T d6 ≤T d5 The heat retention coefficient is 0.6~1.0 min / mm, and the final forging temperature is not lower than 750℃;

[0015] After the sixth forging, the furnace is reheated with a holding coefficient of 0.3–0.6 min / mm at T. d6 Upsetting and preforming are carried out at a certain temperature, and the final forging temperature is not lower than 750℃;

[0016] S500, Forming and Forging: In T d6 Forging is carried out at a temperature and a holding coefficient of 0.6–1.0 min / mm, with the forging ratio controlled at 1.5–2.0. The final forging temperature is not lower than 750℃. One to two reheating cycles are allowed during the forming process. The heating temperature is T. β -(30~50)℃, thermal insulation coefficient 0.3~0.6min / mm;

[0017] S600, heat treatment: annealing is carried out in an atmospheric atmosphere at a temperature of 700-1000℃. The furnace is placed at the temperature and the time is recorded. The holding coefficient is 0.4-1.0 min / mm.

[0018] Furthermore, in steps S100 to S500, the furnace loading temperature is 800 to 850°C, the preheating time is 60 to 120 minutes, and then the temperature continues to rise to the respective forging temperatures.

[0019] Furthermore, between steps S100 and S500, the billet undergoes 100% inspection and grinding to remove forging defects such as surface oxidation, cracks, and folds. The width to depth ratio of the grinding pits is ≥10:1.

[0020] Furthermore, in steps S100 to S400, each forging process requires reversing upsetting 1 to 2 times.

[0021] Furthermore, the upsetting-drawing ratio is controlled between 1.0 and 2.0 for each iteration.

[0022] Furthermore, in steps S100 to S400, during each forging step, a preset shape is formed after each forging, and the overall forging process forms at least two shapes.

[0023] Furthermore, in step S100, after forging, the billet is formed into an octagon by diagonal drawing;

[0024] In step S200, after forging, the billet is formed into a hexagon by diagonal drawing;

[0025] In step S300, after the fourth forging, the billet is formed into an inverted octagon, and after the fifth forging, the billet is drawn into a flat rectangle.

[0026] In step S400, after forging, the billet is formed into an octagon by diagonal drawing.

[0027] Furthermore, the titanium alloy is an α-type titanium alloy, a near-α-type titanium alloy, or an α+β-type titanium alloy.

[0028] Furthermore, the thick forging is a titanium alloy plate, titanium alloy bar, or titanium alloy disc.

[0029] Furthermore, the tensile strength differences in the transverse and longitudinal directions and between different thickness layers of the prepared titanium alloy thick forgings are within 20 MPa.

[0030] Compared with existing technologies, the method for preparing a large, thick titanium alloy forging with high uniformity described in this invention has the following advantages:

[0031] The advantages of this technical solution lie in its design of a forging process based on the characteristics of titanium alloys and the fundamental principle of recrystallization for microstructure refinement. This process involves "high-low deformation + high-temperature annealing + low-low deformation," and the rational use of reheating measures in the furnace reduces the number of surface treatments between heat treatments, significantly shortening the process flow. Furthermore, special deformation methods such as reversal, diagonal drawing, and flattening effectively improve microstructure uniformity. Finally, a reasonable heat treatment process enables the preparation of highly uniform, thick titanium alloy forgings. These forgings are less prone to cracking during deformation, and surface grinding to remove surface oxidation and cracks is unnecessary between heat treatments. This simplifies the forging process for thick forgings, reduces costs, shortens the cycle time, minimizes the microstructure differences between the surface and core, and lowers the risk of surface cracking. Attached Figure Description

[0032] Figure 1-1 This is a transverse-surface microstructure diagram of the TA31 forged plate described in Embodiment 1 of this application;

[0033] Figure 1-2 This is a transverse-core microstructure diagram of the TA31 forged plate described in Embodiment 1 of this application;

[0034] Figure 1-3 This is a longitudinal-surface microstructure diagram of the TA31 forged plate described in Embodiment 1 of this application;

[0035] Figure 1-4 This is a longitudinal-core microstructure diagram of the TA31 forged plate described in Embodiment 1 of this application;

[0036] Figure 2-1 This is a transverse-surface microstructure diagram of the TA31 bar described in Embodiment 2 of this application;

[0037] Figure 2-2 This is a transverse-core microstructure diagram of the TA31 bar described in Embodiment 2 of this application;

[0038] Figure 2-3 This is a longitudinal-surface microstructure diagram of the TA31 bar described in Embodiment 2 of this application;

[0039] Figure 2-4 This is a longitudinal-core microstructure diagram of the TA31 bar described in Embodiment 2 of this application;

[0040] Figure 3-1 This is a transverse-surface structure diagram of the TC4 cake material described in Embodiment 3 of this application;

[0041] Figure 3-2 This is a transverse-core microstructure diagram of the TC4 disc material described in Embodiment 3 of this application;

[0042] Figure 3-3 This is a longitudinal-surface microstructure diagram of the TC4 cake material described in Embodiment 3 of this application;

[0043] Figure 3-4 This is a longitudinal-core microstructure diagram of the TC4 disc material described in Embodiment 3 of this application;

[0044] Figure 4-1 This is a transverse-surface microstructure diagram of the TA31 forging billet described in Comparative Example 1 of this application;

[0045] Figure 4-2 This is a transverse-core microstructure diagram of the TA31 forging billet described in Comparative Example 1 of this application;

[0046] Figure 5-1 This is a transverse-surface microstructure diagram of the TC4 forged plate described in Comparative Example 2 of this application;

[0047] Figure 5-2 This is a transverse-core microstructure diagram of the TC4 forged plate described in Comparative Example 2 of this application. Detailed Implementation

[0048] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0049] In this invention, the terms "first," "second," "upper," and "lower," etc., are used for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," "upper," or "lower" may explicitly or implicitly include at least one of those features. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. Where the technical solutions of the embodiments can be combined, they are all within the scope of protection claimed by this invention.

[0050] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0051] A method for preparing a large, thick titanium alloy forging with high uniformity, comprising:

[0052] S100, Forging of billets: After the ingot is coated with an anti-oxidation coating, it is loaded into the furnace at a loading temperature of 800-850℃ and a preheating time of 60-120 minutes. Then, the temperature is increased to the first temperature T. d1 First temperature T d1 Above the phase transition point, i.e., T d1 =T β +(100~200)℃, holding coefficient 0.6~1.0min / mm, reverse upsetting and drawing 2~3 times, each upsetting and drawing forging ratio controlled between 1.0 and 2.0, the billet is finally drawn diagonally into an octagon, and the final forging temperature is not lower than 800℃. After forging, it is reheated in the furnace 1~2 times, and the heating temperature is raised to the second temperature T. d2 =T β +(50~100)℃, heat preservation coefficient 0.3~0.6min / mm, upsetting and drawing number 1~2 times per heat, upsetting and drawing ratio controlled between 1.0 and 2.0 each time, billet is finally turned into an octagon, and the final forging temperature is not lower than 800℃.

[0053] S200, low-temperature forging and high-temperature annealing: furnace loading temperature 800-850℃, preheating time 60-120min, then continue heating to the third temperature T. d3 Below the phase transition point T d3 =T β -(30~50)℃, heat preservation coefficient 0.6~1.0min / mm, reverse upsetting and drawing 1~2 times, single upsetting and drawing ratio controlled between 1.0 and 2.0, the billet is finally drawn diagonally into a hexagon, and the final forging temperature is not lower than 750℃. After forging, the billet is cooled to below 700℃ and subjected to high-temperature annealing in the single-phase region, heated to the annealing temperature, i.e., T t =T β+(30~50)℃, heat preservation coefficient 0.3~0.6min / mm, air cool to room temperature after taking out of the furnace.

[0054] S300, Low-Temperature Forging I: Furnace loading temperature 800-850℃, preheating time 60-120min, then continue heating to the fourth temperature T. d4 The fourth forging was carried out at the fourth temperature T. d4 Below the phase transition point, i.e., T d4 =T β -(10~30)℃, heat preservation coefficient 0.6~1.0min / mm, reverse upsetting and drawing 1~2 times, single upsetting and drawing forging ratio controlled between 1.0 and 2.0, billet finally turned into an octagon, final forging temperature not lower than 750℃. After forging, reheat in the furnace 1~2 times, heating temperature to the fifth temperature T. d5 That is, T d5 =T β -(20~40)℃, heat preservation coefficient 0.3~0.6min / mm, 1~2 times of reverse upsetting and drawing per heat, single upsetting and drawing forging ratio controlled between 1.0 and 2.0, the billet is finally drawn into a flat square shape, and the final forging temperature is not lower than 750℃.

[0055] S400, Low-Temperature Forging II: Furnace loading temperature 800-850℃, preheating time 60-120min, then continue heating to the sixth temperature T. d6 The sixth temperature T d6 Below the phase transition point, i.e., T d6 =T β -30~50)℃, heat preservation coefficient 0.6~1.0 min / mm, reverse upsetting and drawing 1~2 times, single upsetting and drawing forging ratio controlled between 1.0 and 2.0, the billet is finally drawn diagonally into an octagon, and the final forging temperature is not lower than 750℃. After forging, it is reheated in the furnace 1~2 times, and the heating temperature is raised to the sixth temperature T. d6 =T β -(30~50)℃, heat preservation coefficient 0.3~0.6min / mm, for upsetting and drawing preforming, final forging temperature not lower than 750℃.

[0056] S500, forming and forging: furnace loading temperature 800~850℃, preheating time 60~120min, then continue heating to below the phase transformation point T. β -30~50)℃, heat preservation coefficient 0.6~1.0min / mm, forging is carried out, the forging ratio is controlled at 1.5~2.0, the final forging temperature is not lower than 750℃, and 1~2 reheating in the furnace are allowed during the forming process, with heating temperature T β -(30~50)℃, heat preservation coefficient 0.3~0.6min / mm, final forging temperature not lower than 750℃.

[0057] S600, heat treatment: annealing is carried out in an atmospheric atmosphere at a temperature of 700-1000℃. The furnace is placed at the temperature and the time is recorded. The holding coefficient is 0.4-1.0 min / mm.

[0058] Furthermore, between steps S100 and S500, the billet undergoes 100% inspection and grinding to remove forging defects such as surface oxidation, cracks, and folds. The ratio of grinding pit width to depth is ≥10:1.

[0059] Based on the properties of titanium alloys, this invention utilizes the fundamental principle of recrystallization for microstructure refinement and designs a process of "high-low deformation + high-temperature annealing + low-low deformation" (where "high" refers to the phase transformation point T). β Above, "low" refers to the phase transition point T. β The following forging process was adopted, and the reheating measures were reasonably utilized to reduce the number of surface treatments between heat treatments, which greatly shortened the process flow. At the same time, special deformation methods such as reversal, diagonal drawing, and flattening were used to effectively improve the uniformity of the structure. Finally, through reasonable heat treatment, the preparation of high-uniformity titanium alloy thick forgings was achieved.

[0060] This invention has the following innovations and advantages: ① It employs a forging process of "high-low deformation + high-temperature annealing + low-low deformation," along with special deformation methods such as reversal, diagonal drawing, and flattening, to develop a method for preparing thick titanium alloy forgings with high uniformity and low anisotropy. ② This method rationally utilizes furnace reheating and high-temperature annealing, which not only ensures surface quality and microstructure properties but also reduces the number of surface treatments, significantly shortening the process flow and production cycle, and lowering production costs. ③ This method is applicable to the preparation of thick titanium alloy forgings such as plates, bars, and discs of most α, near-α, and α+β microstructure types, demonstrating its versatility. ④ It adopts conventional forging production methods, has strong process applicability, requires no additional equipment, and features simple equipment and operation, enabling mass production.

[0061] The preparation method of this application is illustrated below with several specific embodiments.

[0062] Example 1:

[0063] Prepared from 160mm thick TA31 forged plate, with a measured phase transformation point of 995℃.

[0064] S100, Initial Forging: After the ingot is coated with an anti-oxidation coating, it is loaded into the furnace at a temperature of 800℃ for 60 minutes. The temperature is then increased to 1150℃ with a holding coefficient of 0.6 min / mm. Two reverse upsetting and drawing operations are performed. The initial upsetting ratio is 2.0, and subsequent upsetting and drawing ratios are 1.5. The ingot is finally drawn diagonally into an octagon, with a final forging temperature not lower than 800℃. After forging, a reheating process is performed once at 1050℃ with a holding coefficient of 0.3 min / mm. Two reverse upsetting and drawing operations are performed again. The initial upsetting ratio is 2.0, and subsequent upsetting and drawing ratios are 1.5. The ingot is finally shaped into an octagon, with a final forging temperature not lower than 800℃.

[0065] S200, Low-Temperature Forging and High-Temperature Annealing: Furnace loading temperature 800℃, preheating time 60min, then continue heating to 960℃, holding coefficient 0.6min / mm, two reverse upsetting and drawing operations, initial upsetting ratio 2.0, subsequent upsetting and drawing ratio 1.5, billet finally drawn diagonally to 16 square, final forging temperature not lower than 750℃. After forging, the billet is cooled to below 700℃ and subjected to single-phase high-temperature annealing, heating temperature 1030℃, holding coefficient 0.3min / mm, and air-cooled to room temperature after exiting the furnace.

[0066] S300, Low-Temperature Forging I: Furnace loading temperature 800℃, preheating time 60min, then continue heating to 980℃, holding coefficient 0.6min / mm, two reverse upsetting and drawing operations, initial upsetting ratio 2.0, subsequent upsetting and drawing ratio 1.5, billet finally drawn into an octagon, final forging temperature not lower than 750℃. After forging, one reheating operation is performed, heating temperature 970℃, holding coefficient 0.3min / mm, one reverse upsetting and drawing operation, initial upsetting ratio 2.0, subsequent upsetting and drawing ratio 1.5, billet finally drawn into a flat square, final forging temperature not lower than 750℃.

[0067] S400, Low-Temperature Forging II: Furnace loading temperature 800℃, preheating time 60min, then continue heating to 970℃, holding coefficient 0.6min / mm, two reverse upsetting and drawing operations, the first upsetting ratio 2.0, and the subsequent upsetting and drawing ratios 1.5. The billet is finally drawn diagonally into an octagon, with a final forging temperature not lower than 750℃. After forging, a reheating process is performed once, with a heating temperature of 960℃ and a holding coefficient of 0.3min / mm, for upsetting and drawing pre-forming, with a final forging temperature not lower than 750℃.

[0068] S500, Forming and Forging: Furnace temperature 800℃, preheating time 60min, then continue to heat to 950℃, holding coefficient 0.6min / mm, for forming and forging, forging ratio 2.0, final forging temperature not lower than 750℃, one return to the furnace for reheating during the forming process, heating temperature 950℃, holding coefficient 0.3min / mm, final forging temperature not lower than 750℃.

[0069] S600, Heat treatment: Annealing is carried out in an atmospheric atmosphere at a temperature of 980℃. The furnace is placed at the temperature and the time is recorded. The holding coefficient is 1.0 min / mm.

[0070] Furthermore, between steps S100 and S500, the billet undergoes 100% inspection and grinding to remove forging defects such as surface oxidation, cracks, and folds. The ratio of grinding pit width to depth is ≥10:1.

[0071] The microstructure and properties of the cross-sections and longitudinal sections of the prepared 160mm thick TA31 forging billet are shown in the figures below. Figure 1-1-Figure 1-4 And Table 1.

[0072] Table 1

[0073]

[0074] Example 2:

[0075] 400mm diameter TA31 bar stock was prepared, with a measured phase transition point of 1000℃.

[0076] S100: After the ingot is coated with an anti-oxidation coating, it is loaded into the furnace at a temperature of 850℃ and a preheating time of 120 min. The temperature is then increased to 1170℃ with a holding coefficient of 1.0 min / mm. Two reverse upsetting and drawing processes are performed. The initial upsetting roughing ratio is 1.0, and subsequent upsetting and drawing ratios are 1.7. The billet is finally drawn diagonally into an octagon, with a final forging temperature not lower than 800℃. After forging, a reheating process is performed once at 1050℃ with a holding coefficient of 0.6 min / mm. Two reverse upsetting and drawing processes are performed, with the upsetting and drawing ratio controlled at 1.7 each time. The billet is finally shaped into an octagon, with a final forging temperature not lower than 800℃.

[0077] S200, Low-Temperature Forging and High-Temperature Annealing: Furnace loading temperature 850℃, preheating time 120min, then continued heating to 970℃, holding coefficient 1.0min / mm, 2 reverse upsetting and drawing cycles, single upsetting and drawing ratio 1.5, the billet is finally drawn diagonally into a hexagon, and the final forging temperature is not lower than 750℃. After forging, the billet is cooled to below 700℃ and subjected to high-temperature annealing in the single-phase region, heating temperature 1030℃, holding coefficient 0.6min / mm, and then air-cooled to room temperature after being removed from the furnace.

[0078] S300, Low-Temperature Forging I: Furnace loading temperature 850℃, preheating time 120min, then continue heating to 980℃, holding coefficient 1.0min / mm, two reverse upsetting and drawing, single upsetting and drawing forging ratio 1.5, billet finally drawn into an octagon, final forging temperature not lower than 750℃. After forging, one reheating in the furnace, heating temperature 980℃, holding coefficient 0.6min / mm, two reverse upsetting and drawing, single upsetting and drawing forging ratio 1.5, billet finally drawn into a flat square, final forging temperature not lower than 750℃.

[0079] S400, Low-Temperature Forging II: Furnace loading temperature 850℃, preheating time 120min, then continue heating to 970℃, holding coefficient 1.0min / mm, two reverse upsetting and drawing, single upsetting and drawing forging ratio 1.5, the billet is finally drawn diagonally into an octagon, the final forging temperature is not lower than 750℃. After forging, two reheating in the furnace are performed, heating temperature 970℃, holding coefficient 0.6min / mm, for upsetting and drawing pre-forming, the final forging temperature is not lower than 750℃.

[0080] S500, forming forging: furnace loading temperature 850℃, preheating time 120min, then continue heating to 960℃, holding coefficient 1.0min / mm, perform round forming forging, forging ratio 1.7, final forging temperature not lower than 750℃, the forming process is reheated twice in the furnace, heating temperature 960℃, holding coefficient 0.6min / mm, final forging temperature not lower than 750℃.

[0081] S600, Heat treatment: Atmospheric annealing, annealing temperature 950℃, furnace entry at the specified temperature, holding coefficient 0.4min / mm.

[0082] Furthermore, between steps S100 and S500, the billet undergoes 100% inspection and grinding to remove forging defects such as surface oxidation, cracks, and folds. The ratio of grinding pit width to depth is ≥10:1.

[0083] The microstructure and properties of the cross and longitudinal sections of the prepared Φ400mm diameter TA31 bars are shown in the figures below. Figures 2-1 to 2-4 And Table 2.

[0084] Table 2

[0085]

[0086] Example 3:

[0087] Φ650*200mm TC4 disc material was prepared, with a measured phase transition point of 998℃.

[0088] S100, Initial Forging: After the ingot is coated with an anti-oxidation coating, it is loaded into the furnace at a temperature of 800℃ for 120 minutes, then heated to 1150℃ with a holding coefficient of 0.8 min / mm. Two reverse upsetting and drawing operations are performed. The initial upsetting ratio is 1.2, and subsequent upsetting and drawing ratios are 1.8. The ingot is finally drawn diagonally into an octagon, with a final forging temperature not lower than 800℃. After forging, two reheating operations are performed at 1080℃ / 1050℃ with a holding coefficient of 0.4 min / mm. Two reverse upsetting and drawing operations are performed per heat cycle, with a forging ratio of 1.6 per upsetting and drawing operation. The ingot is finally shaped into an octagon, with a final forging temperature not lower than 800℃.

[0089] S200, Low-Temperature Forging and High-Temperature Annealing: Furnace loading temperature 800℃, preheating time 120min, then continued heating to 970℃, holding coefficient 0.8min / mm, two reverse upsetting and drawing, single upsetting and drawing ratio 1.6, the billet is finally drawn diagonally into a hexagon, the final forging temperature is not lower than 750℃. After forging, the billet is cooled to below 700℃, and then subjected to high-temperature annealing in the single-phase region, heating temperature 1030℃, holding coefficient 0.4min / mm, and air-cooled to room temperature after exiting the furnace.

[0090] S300, Low-Temperature Forging I: Furnace loading temperature 800℃, preheating time 120min, then continue heating to 980℃, holding coefficient 0.8min / mm, two reverse upsetting and drawing, single upsetting and drawing forging ratio 1.6, billet finally drawn into an octagon, final forging temperature not lower than 750℃. After forging, two reheating cycles are performed, heating temperature 980℃, holding coefficient 0.4min / mm, two reverse upsetting and drawing cycles per heat, single upsetting and drawing forging ratio 1.6, billet finally drawn into a flat square, final forging temperature not lower than 750℃.

[0091] S400, Low-Temperature Forging II: Furnace loading temperature 800℃, preheating time 120min, then continue heating to 960℃, holding coefficient 0.8min / mm, two reverse upsetting and drawing, single upsetting and drawing forging ratio 1.6, billet finally drawn diagonally into an octagon, final forging temperature not lower than 750℃. After forging, two reheating in the furnace, heating temperature 960℃, holding coefficient 0.4min / mm, upsetting and drawing pre-forming, final forging temperature not lower than 750℃.

[0092] S500, Forming and Forging: Furnace loading temperature 800℃, preheating time 120min, then continue heating to 955℃, holding coefficient 0.8min / mm, forming and forging, forging ratio 1.5, final forging temperature not lower than 750℃, one return to the furnace for reheating during the forming process, heating temperature 955℃, holding coefficient 0.4min / mm, final forging temperature not lower than 750℃.

[0093] S600, Heat treatment: Atmospheric annealing, annealing temperature 700℃, put into the furnace at the temperature and start timing, holding coefficient 1.0min / mm.

[0094] Furthermore, between steps S100 and S500, the billet undergoes 100% inspection and grinding to remove forging defects such as surface oxidation, cracks, and folds. The ratio of grinding pit width to depth is ≥10:1.

[0095] The microstructure and properties of the prepared Φ650*200mm TC4 disc cross sections are shown in the figures below. Figures 3-1 to 3-4 And Table 3.

[0096] Table 3

[0097]

[0098] Corresponding to the above three embodiments, the advantages of the preparation method of this application are illustrated below with two comparative examples.

[0099] Comparative Example 1:

[0100] The 160 mm thick TA31 forging billet has a measured phase transformation point of 1004℃.

[0101] A 160mm thick TA31 forging billet was prepared using a conventional sequential cooling forging process. The initial forging temperature was 1150℃, the high-temperature re-forging temperature was 1050℃ / 1020℃, the low-temperature forging temperature was 980℃ / 980℃ / 960℃, the forming forging temperature was 960℃, and each heat treatment involved 1-2 upsetting and drawing processes with a forging ratio of 1.0-2.0 per upsetting and drawing process. The final heat treatment temperature was 960℃, and surface grinding was performed between each heat treatment process.

[0102] The microstructure and mechanical properties of the prepared TA31 forging billet are shown in the figures below. Figure 4-1 , Figure 4-2 See Table 4. It can be seen that there is a significant difference between the surface and core microstructures, with a tensile strength difference exceeding 50 MPa.

[0103] Table 4

[0104]

[0105] Comparative Example 2:

[0106] TC4 forging billet with a thickness of 180 mm, measured phase transformation point of 995℃.

[0107] Following a conventional forging process with sequentially decreasing temperatures, a 180mm thick TC4 forging billet was prepared. The initial forging temperature was 1170℃, followed by reheating at 1020℃, low-temperature forging at 980℃, and reheating at 980℃. The final forging temperature was 960℃. Each heat treatment involved 2-3 upsetting and drawing operations, with a forging ratio of 1.0-2.0 per upsetting and drawing operation. The final heat treatment temperature was 750℃, and surface polishing was performed between each heat treatment.

[0108] The microstructure and mechanical properties of the prepared TC4 forging billet are shown in the figures below. Figure 5-1 , Figure 5-2 See Table 5. It can be seen that there is a significant difference in the microstructure between the surface and the core, with a tensile strength difference exceeding 45 MPa.

[0109] Table 5

[0110]

[0111] Depend on Figures 1-1 to 1-4 As shown in Tables 1-3, 2-1 to 2-4, 3-1 to 3-4, and Tables 1-3, the thick titanium alloy forgings prepared in Examples 1, 2, and 3 of this invention exhibit uniform microstructure in both transverse and longitudinal directions, as well as in layers of different thicknesses, with minimal differences. The tensile strength differences in both transverse and longitudinal directions, and in layers of different thicknesses, are within 20 MPa, demonstrating good microstructure and property uniformity. Furthermore, compared to the specifications, the performance margin is also relatively large. In contrast, the thick titanium alloy forgings prepared in Examples 1-2 show significant differences in microstructure and properties in layers of different thicknesses, with tensile strength differences exceeding 40 MPa, indicating poor microstructure and property uniformity.

[0112] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for preparing a thick titanium alloy forging with high uniformity, characterized in that, include: S100, forging: After coating the ingots with an anti-oxidation coating, they are loaded into the furnace, and the furnace temperature is raised to the first temperature T during the first forging process. d1 The heat retention coefficient is 0.6~1.0 min / mm, and the final forging temperature is not lower than 800℃; After being reheated in the furnace, it is at the second temperature T. d2 The second forging is then carried out, T d1 >T d2 >T β , among which, T β The phase transformation point temperature has a holding coefficient of 0.3–0.6 min / mm, and the final forging temperature is not lower than 800℃. S200, low-temperature forging and high-temperature annealing: At the third temperature T d3 The third forging will be carried out next, T d3 <T β The heat retention coefficient is 0.6~1.0 min / mm, and the final forging temperature is not lower than 750℃; After the third forging, in T t Annealing is performed at the specified temperature, T t >T β ; S300, Low-Temperature Forging I: At the fourth temperature T d4 The fourth forging will be carried out next, T d4 <T β The heat retention coefficient is 0.6~1.0 min / mm, and the final forging temperature is not lower than 750℃; After being reheated in the furnace, at the fifth temperature T d5 The fifth forging was carried out, T d5 <T d4 The heat retention coefficient is 0.3~0.6min / mm, the billet is drawn into a flat square shape, and the final forging temperature is not lower than 750℃; S400, Low-Temperature Forging II: At the sixth temperature T d6 The sixth forging will be carried out below, T d6 ≤T d5 The heat retention coefficient is 0.6~1.0 min / mm, and the final forging temperature is not lower than 750℃; After the sixth forging, the furnace is reheated with a holding coefficient of 0.3–0.6 min / mm at T. d6 Upsetting and preforming are carried out at a certain temperature, and the final forging temperature is not lower than 750℃; S500, Forming and Forging: In T d6 Forging is carried out at a temperature and a holding coefficient of 0.6–1.0 min / mm, with the forging ratio controlled at 1.5–2.

0. The final forging temperature is not lower than 750℃. One to two reheating cycles are allowed during the forming process. The heating temperature is T. β -(30~50)℃, thermal insulation coefficient 0.3~0.6min / mm; S600, heat treatment: annealing is carried out in an atmospheric atmosphere at a temperature of 700-1000℃. The furnace is placed at the temperature and the time is recorded. The holding coefficient is 0.4-1.0 min / mm.

2. The method for preparing a thick titanium alloy forging with high uniformity according to claim 1, characterized in that, In steps S100 to S500, the furnace loading temperature is 800 to 850°C, the preheating time is 60 to 120 minutes, and then the temperature is increased to the respective forging temperatures.

3. The method for preparing a thick titanium alloy forging with high uniformity according to claim 1, characterized in that, Between steps S100 and S500, the billet is 100% inspected and polished to remove forging defects such as surface oxidation, cracks, and folds. The width to depth of the polishing pit is ≥10:

1.

4. The method for preparing a high-uniformity titanium alloy thick forging according to claim 1, characterized in that, In steps S100 to S400, each forging process requires reversing upsetting 1 to 2 times.

5. The method for preparing a thick titanium alloy forging with high uniformity according to claim 4, characterized in that, The upsetting-drawing-forging ratio is controlled between 1.0 and 2.0 each time.

6. The method for preparing a high-uniformity titanium alloy thick forging according to claim 1, characterized in that, In steps S100 to S400, during each forging step, a preset shape is formed after each forging, and the overall forging process forms at least two shapes.

7. The method for preparing a thick titanium alloy forging with high uniformity according to claim 6, characterized in that, In step S100, after forging, the billet is formed into an octagon by diagonal drawing; In step S200, after forging, the billet is formed into a hexagon by diagonal drawing; In step S300, after the fourth forging, the billet is formed into an inverted octagon, and after the fifth forging, the billet is drawn into a flat rectangle. In step S400, after forging, the billet is formed into an octagon by diagonal drawing.

8. The method for preparing a thick titanium alloy forging with high uniformity according to claim 1, characterized in that, The titanium alloy is an α-type titanium alloy, a near-α-type titanium alloy, or an α+β-type titanium alloy.

9. The method for preparing a thick titanium alloy forging with high uniformity according to claim 1, characterized in that, The thick forging is a titanium alloy plate, titanium alloy bar, or titanium alloy disc.

10. The method for preparing a large, thick titanium alloy forging with high uniformity according to claim 1, characterized in that, The tensile strength differences in the transverse and longitudinal directions and between different thickness layers of the prepared titanium alloy thick forgings are within 20 MPa.

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