Method for controlling dimensional precision and surface quality in superplastic forming process of TC4 titanium alloy

Abstract

The invention discloses a dimensional precision and surface quality control method in a TC4 titanium alloy superplastic forming process, which is characterized by comprising the following steps of: performing two-phase region forming forging on a TC4 titanium alloy cast ingot after a high-low high upsetting and drawing process to obtain a blank; the blank is subjected to isothermal forging forming, the height of the blank is monitored in real time, the deformation stage is judged to be the mold filling stage, the compaction stage and the shaping stage according to the height of the blank, the hot initial forging condition is adopted in the mold filling stage, the hot intermediate forging condition is adopted in the compaction stage, the hot forming forging condition is adopted in the shaping stage, and finally a forge piece is obtained; and the forge piece is subjected to solution treatment and aging heat treatment. According to the method, the change of the monitored height is combined with the real-time adjustment of forging process parameters, so that the anisotropy in a microstructure is minimum, crystal grains are finest and uniform, the comprehensive performance is optimal, and meanwhile, the precision control and the surface quality improvement are achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of titanium alloy preparation, and particularly relates to a size precision and surface quality control method in a superplastic forming process of TC4 titanium alloy. BACKGROUND

[0002] Titanium alloy is widely used in key fields such as aerospace and medical devices due to its high specific strength, corrosion resistance and high temperature performance. The precision forming of titanium alloy faces the problems of size and surface quality control of complex thin-walled structural parts and high-precision parts. The traditional constant pressure or simple pressure curve process is easy to cause uneven material flow and stress concentration, resulting in defects such as underfilling and surface microcracks. The high temperature oxidation sensitivity and deformation resistance of titanium alloy have strict requirements for temperature-pressure synergistic control, and the narrow process window further aggravates the difficulty of forming precision control.

[0003] In the prior art, patent CN 119158968 A proposes a high-temperature titanium alloy (Ti60) variable-curvature thin-walled conical member forming method and device, which finally achieves a ±0.3mm surface precision and Ra≤0.8μm surface finish through hot forming of the skin, welding of the split skin, symmetrical mold design, double size scaling compensation and segmented pressure control + pressure setting, and temperature-pressure synergistic control. However, the differentiated needs of rate for different forming stages (such as filling, compaction and setting) are not considered.

[0004] Another patent CN 118287578 A solves the problem of springback in hot forming of large shell parts by using the core process of isothermal synchronous heating + staged pressing and pressure setting + gradient cooling, which can be used to prepare large shell parts with a thickness of more than 50mm. Finally, the size precision of the large shell part is ≤0.5mm, and the surface quality reaches Ra≤1.6μm. However, the influence of the real-time changes of height, pressure, rate and temperature on the forming precision of the forging is not considered. In addition, the contradiction between the poor hardenability of TC4 alloy and the increase in size of the integral blade disc (height exceeding 200mm) is highlighted, and the traditional isothermal forging cannot meet the demand. It is urgent to develop a new superplastic forming process that takes into account the forming precision and surface integrity. SUMMARY

[0005] In view of the problem in the prior art that the superplastic forming process of titanium alloy cannot take into account the forming precision and surface integrity, the purpose of the present application is to provide a size precision and surface quality control method in a superplastic forming process of TC4 titanium alloy, which can improve the size precision and surface quality of the forging.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0007] The application discloses a size precision and surface quality control method in a superplastic forming process of TC4 titanium alloy.

[0008] The TC4 titanium alloy ingot is subjected to a high-low-high pier pulling process and then is formed and forged in a two-phase zone to obtain a blank;

[0009] The blank is isothermally forged to form a forging piece, and the height of the blank is monitored in real time; the deformation stage is determined as a filling stage, a compaction stage and a shaping stage according to the height of the blank; the hot initial forging condition is adopted in the filling stage, the hot intermediate forging condition is adopted in the compaction stage, and the hot forming forging condition is adopted in the shaping stage.

[0010] The forging piece is subjected to solid solution treatment and aging heat treatment.

[0011] Further, the diameter of the TC4 titanium alloy ingot is 800-1200 mm, and the TC4 titanium alloy ingot is obtained through at least three times of vacuum self-consumption smelting.

[0012] Further, the diameter of the blank with the equiaxed structure is 450-600 mm.

[0013] Further, the conditions of the high-low-high pier pulling process are as follows: the deformation amount of each fire is 50-80 %, and the upsetting and piercing temperature in the single-phase zone is 1000-1200 DEG C; the piercing temperature in the two-phase zone is 940-980 DEG C.

[0014] Further, if the real-time height H1 of the blank is Hx (0.6-1.0), H1 is the real-time height of the blank, the unit is mm, and H is the height of the blank, the unit is mm, the hot initial forging condition is adopted for forging;

[0015] If the real-time height H1 of the blank is Hx (0.3-0.6), the hot intermediate forging condition is adopted for forging;

[0016] If the real-time height H1 of the blank is Hx (0.3 and below), the hot forming forging condition is adopted for forging.

[0017] Further, the hot initial forging condition is as follows: the initial temperature of the blank is 940-960 DEG C, the preheating temperature of the die is 930-960 DEG C, the lower pressure of the press is 20-30 MN, and the lower pressing speed is 1-3 mm / s;

[0018] The hot intermediate forging condition is as follows: the initial temperature of the forging piece is 930-950 DEG C, the preheating temperature of the die is 950-970 DEG C, the lower pressure of the press is 40-50 MN, and the lower pressing speed is 1-2.5 mm / s;

[0019] The hot forming forging conditions are that the initial temperature of the forging is 930-950 DEG C, the preheating temperature of the die is 960-980 DEG C, the down pressure is 50-60 MN, the down pressure speed is 1-2 mm / s, and the pressure maintaining time is 10 min.

[0020] Further, the blank is heated to the initial temperature and then is loaded into the heat-insulated forging die within 10-20 s.

[0021] Further, after the isothermal forging forming is completed, the forging is water-cooled within 20 s, and the cooling rate is 5-10 DEG C / min.

[0022] Further, the temperature of the solid solution treatment is 930-960 DEG C, the heat preservation time is 2-5 h, and then water cooling is carried out, and the cooling rate is 5-10 DEG C / min.

[0023] Further, the temperature of the aging treatment is 650-750 DEG C, the heat preservation time is 2-5 h, and then air cooling is carried out to room temperature.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] The present application aims at the size precision and surface quality control problem of large-scale TC4 titanium alloy in large-scale aviation forgings. The equiaxed structure is obtained through the high-low-high process and the two-phase zone forming process, the high plasticity is utilized to improve the filling uniformity and reduce the non-mold defect. The equiaxed alpha phase combined with the beta matrix can inhibit excessive creep, reduce the springback amount by 30%-50% compared with the lamellar structure, and relieve the deformation caused by the release of residual stress. The large-scale TC4 titanium alloy forgings obtained by the present application can be directly applied in the aviation field, and the material utilization rate can be improved from 28% of the traditional process to 48%, the size precision and surface quality of the forgings are improved, thereby further expanding the processing and application potential of titanium alloy and enriching the application field of titanium alloy. The present application monitors the height change and adjusts the forging process parameters in real time, so that the anisotropy in the microstructure is minimized, the grain is the smallest and most uniform, the comprehensive performance is optimal, and the precision control and surface quality improvement are achieved.

[0026] Further, the TC4 titanium alloy blank and the forging die are both heated and heat-insulated to the range of 20 DEG C-80 DEG C below Tbeta. Because the deformation resistance of the material is negatively correlated with the temperature, the blank and the die do not have temperature drop during the long-time contact process, so the deformation resistance of the blank is very small and the plasticity is good, and the high plasticity characteristics under low strain rate are fully utilized to realize the large forming of each pass in the forging process of the large-scale integral blisk.

[0027] Further, the application combines the isothermal forging process with the segmented pressure control combined with the pressure holding process, innovatively introduces the temperature-pressure synergistic attenuation algorithm and accurate control of the rate in the forging process segment; at the same time, through laser scanning real-time monitoring of the height change of the blank and accurate control of the pressure holding time, temperature and rate range in the later forming stage, promoting dislocation rearrangement and grain boundary sliding, reducing lattice distortion energy, making the residual stress distribution tend to be uniform; further, while inhibiting the rebound deformation, the microstructure and surface state are optimized, which provides a process closed-loop solution for the high-precision and high-surface integrity forming of TC4 titanium alloy.

[0028] Further, the overall forging forming large-size TC4 titanium alloy forgings have a diameter of 800-1500mm and a thickness of 200-350mm, which solves the technical problem that the increase of the size causes the difficulty of the forging organization and size control to increase by several times, which easily leads to forging rebound, filling deficiency and non-compliance with the use requirements.

[0029] Further, the application innovatively uses large-size TC4 to replace TC17 titanium alloy, solving the poor working condition adaptability problem caused by the insufficient plasticity of the latter. After the size of the blank increases to more than Φ800mm, higher requirements are put forward for the synergistic control of temperature-pressure-rate. Through dynamic heating of the die to compensate for the temperature drop in real time, the temperature difference between the blank and the die and the surface cooling rate are reduced, effectively inhibiting the sharp increase of deformation resistance and filling defects. Precise control of the pressure holding time promotes stress release, and synchronous realization of the synergistic optimization of the forging size precision ≤0.3mm and the surface roughness Ra≤0.6μm.

[0030] Further, the application innovatively introduces the real-time monitoring and multi-parameter dynamic control technology based on the height change of the blank, uses high temperature + low strain rate in the forming process, promotes α / β phase boundary sliding, speeds up dynamic recrystallization and inhibits grain coarsening. Through the closed-loop feedback system, the die heating temperature and the hydraulic press reduction and rate are adjusted in real time, so that the material is always in the peak value interval (m≥0.3) of the strain rate sensitivity index (m value), realizing the precise control of the size and surface quality. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a schematic diagram for the implementation of the application;

[0032] Figure 2 is a high magnification microstructure photo of the Φ450mm TC4 titanium alloy blank in Example 1 of the application;

[0033] Figure 3 is a microstructure photo of the core of the forging in Example 1 of the application;

[0034] Figure 4 is a high magnification microstructure photo of the Φ800mm large-size TC4 titanium alloy blank obtained in Example 2 of the application;

[0035] Figure 5 Microstructure photograph of the core of the forging in Example 2 of the present application

[0036] Figure 6 Microstructure photograph of the core of the forging in Comparative Example 1 of the present application DETAILED DESCRIPTION

[0037] In order to facilitate the understanding of the present application, the present application will be described in more detail below with reference to the relevant drawings. The preferred embodiments of the present application are shown in the drawings. However, the present application can be realized in various different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0038] In the present application, a size precision and surface quality control method in the superplastic forming process of TC4 titanium alloy, comprising the following steps:

[0039] S1) preparing a titanium alloy ingot;

[0040] The titanium alloy ingot is a TC4 titanium alloy ingot with a diameter of Φ800-1200mm, obtained by at least three times of vacuum consumable melting;

[0041] S2) preparing a blank

[0042] The TC4 titanium alloy ingot obtained in step S1) is subjected to high-low-high pierc ing process and then two-phase zone forming forging to obtain a blank with an equiaxed structure with a diameter of Φ450-600mm; the deformation amount per fire is 50-80%, the upsetting and piercing temperature in the single-phase zone is 1000-1200℃; the upsetting and piercing temperature in the two-phase zone is 940-980℃;

[0043] S3) precision forming

[0044] The blank of step S2) is subjected to isothermal forging forming, and a TC4 titanium alloy bar is formed during the isothermal forging forming process, and a forging is obtained after the isothermal forging forming is completed; laser scanning is used to monitor the thickness change in real time, and then the process parameters are adjusted, comprising the following steps:

[0045] Preferably, in step S3), the height of the blank is monitored in real time by laser scanning, and then the precision forming is realized by adjusting the forging pressure rate and temperature. The specific operation is: the height change rate of the blank is tracked in real time by a high-precision displacement sensor to determine the deformation stage (filling → compaction → sizing), i.e. the temperature-pressure collaborative attenuation algorithm is used for isothermal forging forming.

[0046] S31) The real-time height H1 of the blank is H x (0.6-1.0), H1 is the real-time height of the blank, unit, mm; H is the height of the blank in step S2), unit, mm; hot preliminary forging is adopted: the initial temperature of the blank is 940-960℃, the preheating temperature of the die is 930-960℃, the down pressure of the press is 20-30MN, and the down speed is 1-3mm / s;

[0047] S32) The real-time height H1 of the blank is H x (0.3-0.6), H1 is the real-time height of the blank, unit, mm; hot intermediate forging is adopted: the initial temperature of the forging is 930-950℃, the preheating temperature of the die is 950-970℃, the down pressure of the press is 40-50MN, and the down speed is 1-2.5mm / s;

[0048] S33) The real-time height H1 of the blank is H x (0.3 and below), H1 is the real-time height of the blank, unit, mm; hot forming forging is adopted: the initial temperature of the forging is 930-950℃, the preheating temperature of the die is 960-980℃, the down pressure is 50-60MN, and the down speed is 1-2mm / s, and the pressure is kept for 10min;

[0049] Preferably, the heated TC4 titanium alloy blank is loaded into the preheated forging die within 10-20s in step S3).

[0050] Preferably, the TC4 titanium alloy forging is water-cooled within 20s after the pre-forging forging is completed in step S3), and the cooling rate is 5-10℃ / min.

[0051] S4) Solid solution and aging heat treatment

[0052] The plasticity and strength of the forging obtained in step S3) are comprehensively improved after the solid solution and aging heat treatment.

[0053] Preferably, the temperature of the solid solution treatment in step S4) is 930-960℃, and the temperature is kept for 2-5h, and then the TC4 titanium alloy integral forging is water-cooled, and the cooling rate is 5-10℃ / min.

[0054] Preferably, the temperature of the aging treatment in step S4) is 650-750℃, and the temperature is kept for 2-5h, and then the TC4 titanium alloy forging is air-cooled to room temperature.

[0055] The application is further described below in combination with the embodiments and the drawings.

[0056] Example 1

[0057] An aero-engine blisk (the blisk comprises a disc body and blades), a required forging weight is 560 kg, a diameter is 1000 mm, a thickness is 250 mm, a beta phase transition temperature Tβ=1000℃, and a manufacturing method comprises the following steps:

[0058] S1) preparing a titanium alloy ingot;

[0059] A Φ800 mm TC4 titanium alloy ingot is obtained through three vacuum consumptions;

[0060] S2) preparing a blank;

[0061] After the TC4 titanium alloy ingot obtained in step S1) is subjected to a high-low-high pierce drawing process, an equiaxed structure blank of Φ450 mm*1000 mm is obtained through two-phase zone forming forging; a deformation amount of each fire is 50%, a single-phase zone upsetting and drawing temperature is 1000℃, and a high-multiple structure is as shown in the figure. Figure 2

[0062] S3) precision forming;

[0063] The blank in step S2) is heated at a furnace temperature of 940℃, and after 10s of heat preservation, the blank is moved into a die, the die temperature is 930℃, the lower pressure of a press machine is 20MN, and the lower pressing speed is 3mm / s;

[0064] When the real-time height H1 of the blank is 1000-600mm, the blank temperature is real-time controlled to be 940℃ by controlling the die temperature;

[0065] When the real-time height H1 of the blank is 300-600mm (not including 600mm), the blank temperature is real-time controlled to be 940℃ by controlling the die temperature, the die temperature is 950℃, the lower pressure of the press machine is 40MN, and the lower pressing speed is 2.5mm / s; the blank temperature is real-time controlled to be 940℃ by controlling the die temperature throughout the whole process;

[0066] When the real-time height H1 of the blank is less than 300 (not including 300mm), the blank temperature is real-time controlled to be 940℃ by controlling the die temperature, the die temperature is 960℃, the lower pressure of the press machine is 50MN, and the pressure is kept for 10min, the lower pressing speed is 1.5mm / s; the blank temperature is real-time controlled to be 940℃ by controlling the die temperature throughout the whole process; and the blank is water-cooled within 20s after being taken out, and the cooling speed is 10℃ / min;

[0067] S4) solid solution and aging heat treatment;

[0068] The forging after step S3) is subjected to solid solution and aging heat treatment.

[0069] ​The temperature of the solution treatment is 930℃, and the holding time is 2h. Then the TC4 titanium alloy integral blisk forging is water-cooled, and the cooling rate is 10℃ / min.

[0070] The temperature of the aging treatment is 650℃, and the holding time is 2h. Then the TC4 titanium alloy forging is air-cooled to room temperature to obtain the forging. The core microstructure of the forging is shown in Figure 3 , and the parameters are shown in Table 1. The mechanical properties are shown in Table 2.

[0071] Example 2

[0072] An aero-engine integral blisk (the blisk includes a disc body and blades), the required forging weight is 800kg, the diameter is 1500mm, the thickness is 300mm, and the beta phase transition temperature Tβ is 995℃. The manufacturing method includes the following steps:

[0073] S1) preparing a titanium alloy ingot;

[0074] A Φ1200mm TC4 titanium alloy ingot is obtained by three times of vacuum consumable melting;

[0075] S2) preparing a blank;

[0076] After the TC4 titanium alloy ingot obtained in step S1) is subjected to high-low-high piercings and extrusions, two-phase zone forming forging is performed to obtain a Φ600mm×1500mm blank with equiaxed structure. The deformation amount of each fire is 80%, the single-phase zone upsetting and extrusion temperature is 1200℃, and the high-magnification structure is shown in Figure 4 .

[0077] S3) precision forming;

[0078] The blank in step S2) is heated in a heating furnace at a furnace temperature of 960℃, and after holding for 20s, it is moved into a mold. The mold temperature is 955℃, the press machine lower pressure is 30MN, and the lower pressing rate is 2.5mm / s.

[0079] When the real-time height H1 of the blank is 900-1500mm, the blank temperature is real-time controlled to 955℃ by controlling the mold temperature;

[0080] When the real-time height H1 of the blank is 450-600mm (excluding 900mm), the blank temperature is real-time controlled to 950℃ by controlling the mold temperature, the mold temperature is 960℃, the press machine lower pressure is 50MN, and the lower pressing rate is 2mm / s. The blank temperature is real-time controlled to 950℃ by controlling the mold temperature throughout the process.

[0081] When the real-time height H1 of the blank is < 450 (not including 450mm), the blank temperature is controlled to be 950℃ in real time by controlling the mold temperature, the mold temperature is 980℃, the press down pressure is 60MN, and the pressure is maintained for 10min, and the down pressure rate is 1mm / s; the blank temperature is controlled to be 950℃ in real time through the mold temperature control during the whole process; and water cooling is carried out within 10s after taking out, and the cooling rate is 5℃ / min;

[0082] S4) solid solution and aging heat treatment;

[0083] The forged piece treated in step S3) is subjected to solid solution and aging heat treatment.

[0084] The temperature of the solid solution treatment is 960℃, and the temperature is maintained for 5h, then the TC4 titanium alloy integral blisk forged piece is water cooled, and the cooling rate is 5℃ / min.

[0085] The temperature of the aging treatment is 700℃, and the temperature is maintained for 5h, then the TC4 titanium alloy forged piece is air cooled to room temperature to obtain the forged piece, and the core microstructure photo of the forged piece is shown in Figure 5 , and the mechanical properties are shown in Table 2.

[0086] Comparative Example 1

[0087] The aviation engine integral blisk has a weight of 800kg, a diameter of 1500mm, a thickness of 300mm, and a beta phase transformation temperature Tβ=995℃, and the manufacturing method comprises the following steps:

[0088] S1) preparing a titanium alloy ingot;

[0089] The TC4 titanium alloy ingot with a diameter of Φ1200mm is obtained by three times of vacuum consumable melting;

[0090] S2) preparing a blank;

[0091] After the TC4 titanium alloy ingot obtained in step S1) is subjected to high-low-high pierc ing and drawing process, an equiaxed structure blank with a diameter of Φ600mm and a length of 1500mm is obtained by two-phase zone forming forging; the deformation amount of each fire is 80%, the single-phase zone upsetting and drawing temperature is 1200℃, and the two-phase zone upsetting and drawing temperature is 980℃.

[0092] S3) precision forming;

[0093] The blank in step S2) is heated in a heating furnace with a temperature of 960℃, and after heat preservation, the blank is moved into a mold in 20s, the mold temperature is 960℃, the press down pressure is 60MN, the down pressure rate is 2.5mm / s, and water cooling is carried out within 10s after taking out, and the cooling rate is 5℃ / min;

[0094] S4) solid solution and aging heat treatment;

[0095] The forging after the treatment of step S3) is subjected to solid solution treatment and aging heat treatment.

[0096] The temperature of the solid solution treatment is 960℃, and the holding time is 5h, after which the TC4 titanium alloy blisk forging is water-cooled, and the cooling rate is 5℃ / min.

[0097] The temperature of the aging treatment is 700℃, and the holding time is 5h, after which the TC4 titanium alloy forging is air-cooled to room temperature to obtain the forging, and the core microstructure of the forging is as shown in Figure 6 , and the mechanical properties are as shown in Table 2.

[0098] Example 3

[0099] An aero-engine blisk (the blisk comprises a disc body and blades), the required forging weight is 560kg, the diameter is 1000mm, the thickness is 250mm, the beta phase transition temperature Tβ=1000℃, and the manufacturing method comprises the following steps:

[0100] S1) preparing a titanium alloy ingot;

[0101] A Φ1200mm TC4 titanium alloy ingot is obtained through three times of vacuum consumable melting;

[0102] S2) preparing a blank;

[0103] After the TC4 titanium alloy ingot obtained in step S1) is subjected to high-low-high piercings and extrusions, two-phase zone forming forging is performed to obtain a Φ600mm×1000mm blank with equiaxed structure; the deformation amount of each fire is 80%, the single-phase zone upsetting and extrusion temperature is 1000℃, and the high-magnification structure is as shown in Figure 2 .

[0104] S3) precision forming;

[0105] The blank in step S2) is heated in a heating furnace at a furnace temperature of 950℃, and after holding for 15s, it is moved into a die, the die temperature is 940℃, the press machine lower pressure is 20MN, and the lower pressing rate is 1mm / s;

[0106] When the real-time height H1 of the blank is 1000-600mm, the blank temperature is real-time controlled to be 950℃ by controlling the die temperature;

[0107] When the real-time height H1 of the blank is 300-600mm (not including 600mm), the blank temperature is real-time controlled to be 950℃ by controlling the die temperature, the die temperature is 960℃, the press machine lower pressure is 45MN, and the lower pressing rate is 1mm / s; the blank temperature is real-time controlled to be 950℃ by controlling the die temperature throughout the whole process;

[0108] When the real-time height H1 of the blank is < 300 (not including 300 mm), the blank temperature is controlled in real time to be 930℃ by controlling the mold temperature, the mold temperature is 960℃, the press down pressure is 50 MN, and the pressure is maintained for 10 min, and the down pressure rate is 1 mm / s; the blank temperature is controlled in real time to be 930℃ by controlling the mold temperature throughout the process. Water cooling is carried out within 10 s after taking out, and the cooling rate is 5℃ / min;

[0109] S4) solid solution and aging heat treatment;

[0110] The forged piece treated in step S3) is subjected to solid solution and aging heat treatment.

[0111] The temperature of the solid solution treatment is 930℃, and the temperature is maintained for 5 h, and then the TC4 titanium alloy integral blisk forged piece is water cooled, and the cooling rate is 10℃ / min.

[0112] The temperature of the aging treatment is 650℃, and the temperature is maintained for 5 h, and then the TC4 titanium alloy forged piece is air cooled to room temperature to obtain the forged piece.

[0113] Example 4

[0114] An aero-engine integral blisk (the blisk includes a disc body and blades), the required forged piece weight is 560 kg, the diameter is 1000 mm, the thickness is 250 mm, the beta phase transition temperature Tβ is 1000℃, and the manufacturing method includes the following steps:

[0115] S1) preparing a titanium alloy ingot;

[0116] A Φ900 mm TC4 titanium alloy ingot is obtained by five times of vacuum consumable melting;

[0117] S2) preparing a blank;

[0118] After the TC4 titanium alloy ingot obtained in step S1) is subjected to high-low-high pierc ing and drawing process, an equiaxed structure blank of Φ500 mm*1000 mm is obtained by two-phase zone forming forging; the deformation amount of each fire is 60%, the single-phase zone upsetting and drawing temperature is 1100℃, and the two-phase zone pierc ing and drawing temperature is 940℃, and the high-magnification structure is as shown in Figure 2 .

[0119] S3) precision forming;

[0120] The blank in step S2) is heated in a heating furnace at a furnace temperature of 960℃, and after heat preservation, the blank is moved into a mold after 20 s, the mold temperature is 950℃, the press down pressure is 25 MN, and the down pressure rate is 3 mm / s;

[0121] When the real-time height H1 of the blank is 1000-600 mm, the blank temperature is controlled in real time to be 960℃ by controlling the mold temperature;

[0122] When the real-time height H1 of the blank is 300-600 mm (not including 600 mm), the blank temperature is controlled to be 970 ℃ in real time by controlling the mold temperature, the mold temperature is 970 ℃, the pressing force of the press is 50 MN, and the pressing speed is 2 mm / s; the blank temperature is controlled to be 970 ℃ in real time by controlling the mold temperature throughout the process;

[0123] When the real-time height H1 of the blank is <300 (not including 300 mm), the blank temperature is controlled to be 950 ℃ in real time by controlling the mold temperature, the mold temperature is 980 ℃, the pressing force of the press is 55 MN, and the pressing speed is 2 mm / s; the blank temperature is controlled to be 950 ℃ in real time by controlling the mold temperature throughout the process. Water cooling is carried out within 15 s after taking out, and the cooling speed is 7 ℃ / min;

[0124] S4) solid solution and aging heat treatment;

[0125] The forged piece treated in step S3) is subjected to solid solution and aging heat treatment.

[0126] The temperature of the solid solution treatment is 960 ℃, and the holding time is 2 h, and then the TC4 titanium alloy integral blisk forged piece is water cooled, and the cooling rate is 10 ℃ / min.

[0127] The temperature of the aging treatment is 660 ℃, and the holding time is 3 h, and then the TC4 titanium alloy forged piece is air cooled to room temperature to obtain the forged piece.

[0128] Example 5

[0129] An aero-engine integral blisk (the blisk includes a disc body and blades), the required forged piece has a weight of 560 kg, a diameter of 1000 mm, a thickness of 250 mm, and a beta phase transformation temperature Tβ=1000 ℃, and a manufacturing method thereof includes the following steps:

[0130] S1) preparing a titanium alloy ingot;

[0131] A Φ1000 mm TC4 titanium alloy ingot is obtained by four times of vacuum consumable melting;

[0132] S2) preparing a blank;

[0133] After the TC4 titanium alloy ingot obtained in step S1) is subjected to high-low-high pierc ing and drawing process, an equiaxed structure blank with a diameter of Φ450 mm and a length of 1000 mm is obtained by two-phase zone forming forging; the deformation amount of each fire is 70%, the upsetting and drawing temperature in the single-phase zone is 1200 ℃, and the upsetting and drawing temperature in the two-phase zone is 980 ℃, and the high-magnification structure is as shown in Figure 2 .

[0134] S3) precision forming;

[0135] The blank in step S2) is heated in a heating furnace at a furnace temperature of 960 DEG C, and after holding for 10s, is moved into a mold, the mold temperature is 960 DEG C, the press down pressure is 30MN, and the press down rate is 3mm / s;

[0136] When the real-time height H1 of the blank is 1000-600mm, the blank temperature is controlled in real time to be 960 DEG C by controlling the mold temperature;

[0137] When the real-time height H1 of the blank is 300-600mm (not including 600mm), the blank temperature is controlled in real time to be 960 DEG C by controlling the mold temperature, the mold temperature is 970 DEG C, the press down pressure is 42MN, the press down rate is 2.5mm / s, and the blank temperature is controlled in real time to be 960 DEG C throughout the process by controlling the mold temperature;

[0138] When the real-time height H1 of the blank is less than 300 (not including 300mm), the blank temperature is controlled in real time to be 940 DEG C by controlling the mold temperature, the mold temperature is 960 DEG C, the press down pressure is 60MN, the holding time is 10min, the press down rate is 1.5mm / s, and the blank temperature is controlled in real time to be 960 DEG C throughout the process by controlling the mold temperature; and after being taken out, water cooling is carried out within 20s, and the cooling rate is 8 DEG C / min;

[0139] S4) solid solution and aging heat treatment;

[0140] The forged piece after step S3) is subjected to solid solution and aging heat treatment.

[0141] The solid solution temperature is 950 DEG C, the holding time is 3h, then the TC4 titanium alloy integral blade disc forged piece is water cooled, and the cooling rate is 10 DEG C / min.

[0142] The aging temperature is 750 DEG C, the holding time is 2h, then the TC4 titanium alloy forged piece is air cooled to room temperature to obtain the forged piece.

[0143] Table 1 is the forged piece parameters of examples 1-2 and comparative example 1

[0144]

[0145] Table 2 is the mechanical properties of examples 1-2 and comparative example 1

[0146]

[0147] The forged piece parameters and finished product properties of the examples of the application are shown in Table 1-Table 2.

[0148] Comparative analysis of the integral blade disc forged piece structures of example 1, example 2 and comparative example 1.

[0149] See Figure 2 ,Figure 3 、 Figure 4 With Figure 5 The microstructure of the forging of the embodiment 1 of the application is shown in the figure, which is a typical two-phase zone structure, the content of the primary alpha phase is in the range of 40-50%, the size of the alpha phase is basically consistent and uniformly distributed, the size is ≤20 μm, the secondary alpha phase is fine and in the form of sheet with a certain length-width ratio; in combination with the mechanical properties in table 2, each part has high strength and plasticity, and has excellent comprehensive performance.

[0150] Referring to Figure 6 The microstructure of the forging of the comparative example is shown in the figure, the comparative example 1 is a two-phase zone structure, the content of the primary alpha phase and the equiaxed degree are obviously not as good as those of the embodiment 1 and the embodiment 2, there is obvious difference in the structure, the structure has obvious grain orientation preference, which causes unstable performance and does not meet the use requirement.

[0151] In the method of the application, the segmented pressure and temperature control and speed control and water cooling process after solid solution heat treatment are adopted, which avoids the grain growth caused by slow cooling to a certain extent, controls the uniformity of the structure and reduces the difference in each water cooling process; at the same time, the high-temperature beta phase is transformed into martensite in the multi-pass rapid water cooling process, the structure contains a lot of dislocations and twins, which has serious pinning effect on slip, thereby improving the strength performance of the material.

[0152] In the application, the TC4 titanium alloy blank and the forging die are both heated and kept at 20-80 ℃ below Tβ, because the deformation resistance of the material is negatively correlated with the temperature, the blank and the die will not have temperature drop during the long-time contact, so the deformation resistance of the blank is very small and the plasticity is good, the high plasticity characteristics at low strain rate are fully utilized to realize large forming of each pass in the forging process of the large-size integral blisk forging.

[0153] Compared with the patent CN 119259905 A, the patent proposes an isothermal near-net forming method of TC4 titanium alloy aero-engine blisk, but the method in the patent fails to realize precise size and surface quality control of TC4 titanium alloy, and also fails to consider real-time regulation under different deformation amounts in isothermal forging process and temperature change of the blank after deformation. Meanwhile, multiple forging is needed for the forging piece with complex shape. In the present application, the forging pressure parameters are regulated by laser real-time monitoring of the height change of the blank, effectively avoiding abnormal grain growth and coarsening caused by excessive deformation amount in the forging process; meanwhile, the uneven organization refinement and mechanical property deterioration caused by insufficient recrystallization degree due to insufficient deformation amount are avoided. By precisely controlling the deformation amount, temperature, forging rate and pressure, precise control of the forging piece and avoidance of underfilling are realized, so that the comprehensive performance of the forging piece is improved. In addition, the present application adopts one-time precision forming, effectively improving the production efficiency and material loss, and the performance and size precision are also improved.

[0154] Compared with the patent CN 119259906 A, the patent proposes a high-efficiency short forging. The method of TC4 titanium alloy fan integral blade disk forging superplastic forming, the method in the patent realizes one-time near-net forming forging with 95% ultra-large deformation. However, the problem of grain growth and coarsening after recrystallization during the forming process is not considered. In the present application, the pressure control and moderate deformation are adopted. When the one-time deformation of the forging is more than 85%, the grains will grow and coarsen, resulting in performance deterioration. The pressure control refers to controlling the pressure and deformation during the forging process to make the material uniformly deform under specific conditions. The following advantages are obtained by adopting 50%-80% deformation: (1) uniform and refined structure: pressure control can ensure uniform deformation of the material during forging, avoiding local stress concentration, thereby obtaining a uniformly refined structure. Uniform and refined structure can improve the mechanical properties (such as strength, plasticity and toughness) of the material and reduce anisotropy. (2) reduce internal defects: moderate deformation can reduce the risk of cracks, cavities and other defects in the material. Reducing internal defects can improve the reliability and service life of the material. (3) control grain size: 50%-80% deformation can effectively control the grain size, avoiding excessive grain growth or excessive small grain size. Moderate grain size helps to balance the strength and plasticity of the material. (4) reduce energy consumption and die wear: moderate deformation can reduce energy consumption and die wear during forging. Reducing production cost and prolonging die life. (5) avoid overheating of the material: pressure control can avoid local overheating of the material due to excessive deformation during forging. Prevent the material from being coarsened or the performance of the material from being deteriorated due to overheating. Therefore, by adopting 50%-80% deformation with pressure control, the following comprehensive benefits can be achieved: obtaining a uniformly refined structure, improving the mechanical properties of the material, reducing the risk of internal defects, improving the reliability of the material, achieving moderate grain size, balancing the strength and plasticity of the material, reducing energy consumption during forging, reducing production cost, reducing die wear, prolonging die life, and preventing the material from being coarsened or the performance of the material from being deteriorated due to local overheating.

[0155] The above only describes the best embodiments of the present application, but cannot be understood as limiting the claims. The present application is not limited to the above embodiments, and the specific structure allows changes. Any changes made within the protection scope of the independent claims of the present application are within the protection scope of the present application.

[0156] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application herein are only for the purpose of describing the specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

Claims

1. A method for controlling dimensional accuracy and surface quality in a superplastic forming process of a TC4 titanium alloy, characterized in that, The method comprises the following steps: a TC4 titanium alloy ingot is subjected to a high-low-high pierc ing process and then two-phase zone forming forging to obtain a blank; the blank is subjected to isothermal forging forming, and the height of the blank is monitored in real time; the deformation stage is determined to be a filling stage, a compaction stage and a shaping stage according to the height of the blank; the hot preliminary forging condition is adopted in the filling stage, the hot intermediate forging condition is adopted in the compaction stage, and the hot forming forging condition is adopted in the shaping stage, and finally a forged piece is obtained; the forged piece is subjected to solid solution treatment and aging heat treatment.

2. The method of controlling dimensional accuracy and surface quality in a TC4 titanium alloy superplastic forming process according to claim 1, characterized in that, The diameter of the TC4 titanium alloy ingot is Φ800-1200mm, and the TC4 titanium alloy ingot is obtained through at least three times of vacuum consumable melting.

3. The method of controlling dimensional accuracy and surface quality in a TC4 titanium alloy superplastic forming process according to claim 1, characterized in that, The diameter of the blank with equiaxed structure is Φ450-600mm.

4. The method of controlling dimensional accuracy and surface quality in a TC4 titanium alloy superplastic forming process according to claim 1, wherein The conditions of the high-low-high pierc ing process are as follows: the deformation amount of each fire is 50-80%, and the pierc ing temperature in the single-phase zone is 1000-1200℃; the pierc ing temperature in the two-phase zone is 940-980℃.

5. The method of controlling dimensional accuracy and surface quality in a TC4 titanium alloy superplastic forming process according to claim 1, wherein If the real-time height H1 of the blank is H×(0.6-1.0), the real-time height H1 of the blank is in mm, and the height H of the blank is in mm, the hot preliminary forging condition is adopted for forging; If the real-time height H1 of the blank is H×(0.3-0.6), the hot intermediate forging condition is adopted for forging; If the real-time height H1 of the blank is H×(0.3 and below), the hot forming forging condition is adopted for forging.

6. The method of controlling dimensional accuracy and surface quality in a TC4 titanium alloy superplastic forming process according to claim 1, wherein The hot preliminary forging condition is that the initial temperature of the blank is 940-960℃, the preheating temperature of the die is 930-960℃, the lower pressure of the press is 20-30MN, and the lower pressing speed is 1-3mm / s; The hot intermediate forging condition is that the initial temperature of the forged piece is 930-950℃, the preheating temperature of the die is 950-970℃, the lower pressure of the press is 40-50MN, and the lower pressing speed is 1-2.5mm / s; The hot forming forging condition is that the initial temperature of the forged piece is 930-950℃, the preheating temperature of the die is 960-980℃, the lower pressure is 50-60MN, the lower pressing speed is 1-2mm / s, and the pressure is maintained for 10min.

7. The method of controlling dimensional accuracy and surface quality in a TC4 titanium alloy superplastic forming process according to claim 1, wherein After the blank is heated to the initial temperature, it is loaded into the preheated forging die within 10-20s.

8. The method of controlling dimensional accuracy and surface quality in a TC4 titanium alloy superplastic forming process according to claim 1, wherein After the isothermal forging forming is completed, the forged piece is water-cooled within 20s, and the cooling rate is 5-10℃ / min.

9. The method of controlling dimensional accuracy and surface quality in a TC4 titanium alloy superplastic forming process according to claim 1, wherein The temperature of the solid solution treatment is 930-960℃, the holding time is 2-5h, and then water cooling is performed, and the cooling rate is 5-10℃ / min.

10. The method of controlling dimensional accuracy and surface quality in a TC4 titanium alloy superplastic forming process according to claim 1, wherein The temperature of the aging treatment is 650-750℃, the holding time is 2-5h, and then air cooling is performed to room temperature.

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