A method for heat treatment of a super-large whole frame

Abstract

The application relates to the technical field of heat treatment, and particularly discloses a heat treatment method for a super-large whole frame. The method comprises the following steps: preliminary annealing: placing a titanium alloy whole frame on a hollowed-out type tray, and keeping the temperature at 850 DEG C + / - 10 DEG C for 3-4 hours; pre-air cooling: transferring to an air cooling area within 150 seconds, and rapidly cooling to 600 DEG C through four corner air blowers and middle air blowers of four sides; strong air cooling: transferring to an air cooling rack, and forcibly cooling through circumferential air outlets of a middle air outlet platform; stress relief annealing: pressure block annealing at 560 DEG C + / - 10 DEG C; slow cooling: furnace cooling at <= 30 DEG C / h to below 300 DEG C, and then slow cooling to room temperature at <= 15 DEG C / h in an adiabatic box. Through stage cooling, tooling cooperation and block deformation inhibition, the application solves the warping problem of the titanium alloy whole frame, the warping amount is reduced by more than 90%, and the room temperature and high temperature mechanical properties are better than the technical standard.

Description

Technical Field

[0001] This invention relates to the field of heat treatment technology, specifically to a heat treatment method for an extra-large integral frame. Background Technology

[0002] With the upgrading of equipment, the size of the fuselage frame has gradually increased, with the current dimensions of an extra-large titanium alloy frame measuring 5700×2500×300mm. During the heat treatment process after forging, ordinary annealing followed by air cooling is generally used. However, due to its large size, the enormous cross-sectional dimensions inevitably lead to a huge temperature gradient during heating / cooling, resulting in significant thermal stress. The large size also causes a significant asynchrony in the phase transformation times of the surface and core during cooling, generating substantial structural stress. Existing processes (ordinary annealing + air cooling) cannot achieve uniform cooling of such large workpieces, further amplifying the aforementioned temperature gradient and stress inhomogeneity. The complex superposition of thermal stress, structural stress, residual stress, and stress caused by its own weight makes it highly susceptible to exceeding the yield limit of the material at high temperatures and low strength, leading to irreversible warping, which is difficult to correct through subsequent straightening processes. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a heat treatment method for extra-large frames to reduce the impact of stress on titanium alloy frames.

[0004] The technical solution adopted by this invention to solve its technical problem is a heat treatment method for extra-large whole frames, including the following steps:

[0005] S1: Place the entire titanium alloy frame on a hollowed-out tray and transfer it to a heat treatment furnace for preliminary annealing. The preliminary annealing temperature is 850℃±10℃, and the temperature is maintained for 3-4 hours.

[0006] S2: After the initial annealing is completed, the hollow material tray and the titanium alloy frame are transferred to the air-cooling area together using a transfer tool within 150 seconds. Multiple blowers are used to pre-cool the hollow material tray and the titanium alloy frame. The distance between the blowers and the titanium alloy frame is ≤2m until the surface temperature of the titanium alloy frame drops to 600℃.

[0007] S3: After pre-cooling is completed, the titanium alloy frame is transferred from the hollow material tray to the air-cooled material rack. An air outlet is set in the middle of the air-cooled material rack, and an air outlet is set around the circumference of the air outlet for strong air cooling to room temperature. The strong air cooling wind speed is ≥15m / s.

[0008] S4: After the strong air cooling is completed, the titanium alloy frame is placed in the heating furnace for stress relief annealing. The stress relief annealing temperature is 560℃±10℃, and a pressure block is placed on top of the titanium alloy frame during stress relief annealing.

[0009] S5: After stress-relief annealing, furnace cool to below 300℃ at a rate of ≤30℃ / h before unloading.

[0010] Furthermore, the pre-cooled blower layout in step S2 is at the four corners and the center of the four sides, and the blower outlet forms an angle of 30°-45° with the surface of the titanium alloy frame.

[0011] Furthermore, the air outlet platform is provided with multiple support plates around its perimeter, each support plate having mounting holes, a lifting mechanism being installed within the mounting holes, and rollers being installed on the top of the lifting mechanism.

[0012] Furthermore, in step S5, after the furnace is cooled to 300°C, the entire titanium alloy frame is moved to an insulated box for slow cooling to room temperature, with a slow cooling rate of ≤15°C / h.

[0013] The beneficial effects of this invention are as follows: By using a multi-angle blower layout at the four corners and the center of the four sides, the temperature can be rapidly and uniformly reduced to 600°C within 150 seconds, suppressing β-phase coarsening and reducing thermal stress accumulation; the circumferential air outlet of the central air outlet of the air-cooled material rack forms a high-speed circumferential airflow, which forcibly penetrates the hollow area of ​​the titanium alloy frame, eliminates the temperature difference between the core and the surface, and reduces structural stress; the annealing at 560°C±10°C simultaneously applies vertical pressure to counteract the tendency of self-weight deformation under high temperature plasticity. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the present invention;

[0015] Figure 2 yes Figure 1 A cross-sectional view along AA.

[0016] Reference numerals: 1-Titanium alloy frame; 2-Air-cooled material rack; 3-Air outlet platform; 4-Air outlet; 5-Bearing plate; 6-Mounting hole; 7-Lifting mechanism; 8-Roller. Detailed Implementation

[0017] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0018] This invention discloses a heat treatment method for an extra-large frame, comprising the following steps:

[0019] S1: Place the titanium alloy frame 1 on a hollowed-out tray and transfer it to a heat treatment furnace for preliminary annealing. The preliminary annealing temperature is 850℃±10℃, and the temperature is held for 3-4 hours. By allowing the titanium alloy frame 1 to recrystallize above the β phase transformation point, the forging stress is eliminated, the structure is homogenized, and deformation caused by the superposition of initial stress during subsequent cooling is avoided.

[0020] S2: After the initial annealing is completed, within 150 seconds, the hollowed-out material tray and the titanium alloy frame 1 are transferred to the air-cooling area using a transfer tool. Multiple blowers are used to pre-cool the hollowed-out material tray and the titanium alloy frame 1. The distance between the blowers and the titanium alloy frame 1 is ≤2m until the surface temperature of the titanium alloy frame 1 drops to 600℃. By pre-cooling, the surface temperature of the titanium alloy frame 1 drops to 600℃, quickly passing through the brittle zone of the titanium alloy, preventing cracks caused by the brittle zone, reducing thermal stress accumulation, and inhibiting β grain coarsening. At the same time, the pre-cooling cools the surface of the titanium alloy frame 1 and locks in the shape of the titanium alloy frame 1.

[0021] See Figure 1 S3: After pre-air cooling is completed, the titanium alloy frame 1 is transferred from the hollow material tray to the air-cooled material rack 2. The air-cooled material rack 2 is equipped with an air outlet 3 in the middle, and the air outlet 3 is equipped with an air outlet 4 in the circumference for strong air cooling to room temperature. The strong air cooling wind speed is ≥15m / s. The air-cooled material rack 2 is rectangular, and its outer contour dimension is larger than that of the titanium alloy frame 1. The air outlet 3 is located in the middle of the air-cooled material rack 2, and its outer contour dimension is smaller than that of the inner contour dimension of the titanium alloy frame 1. This allows the air outlet 4 on the air outlet 3 to face the inner surface of the titanium alloy frame 1. An air outlet pipe can be set at the center of the air outlet 3. One end of the air outlet pipe is connected to the air outlet 4, and the other end is connected to the output end of the air outlet mechanism. The air outlet 3 of the air-cooled material rack 2 provides circumferential air outlets, realizing forced convection cooling of the core of the titanium alloy frame 1, eliminating the core-surface temperature difference, and reducing structural stress.

[0022] S4: After the strong air cooling is completed, the titanium alloy frame 1 is placed in the heating furnace for stress-relief annealing. The stress-relief annealing temperature is 560℃±10℃, and a pressure block is placed above the titanium alloy frame 1 during stress-relief annealing. The stress-relief annealing time is 2-4 hours. The pressure block can be a long strip or a rectangular block. The pressure block applies vertical pressure to compensate for the self-weight deformation in the high-temperature plastic state, suppress warping during the annealing process, and eliminate residual stress.

[0023] S5: After stress-relief annealing, furnace cool to below 300℃ at a rate of ≤30℃ / h before unloading. Slow cooling avoids secondary phase transformation stress and prevents deformation and springback at the end of cooling.

[0024] To better achieve pre-air cooling, the pre-air cooling blower layout in step S2 is further configured at the four corners and the center of the four sides, with the blower outlet forming a 30°-45° angle with the surface of the titanium alloy frame 1. This 30°-45° angle between the blower outlet and the surface of the titanium alloy frame 1 eliminates cooling dead zones and ensures uniform airflow coverage; simultaneously, the inclined airflow enhances turbulence on the surface of the titanium alloy frame 1, improving heat exchange efficiency.

[0025] To better achieve cooling of the lower surface of the titanium alloy frame 1, further, see... Figure 1 and Figure 2 The air outlet platform 3 is surrounded by multiple support plates 5. Each support plate 5 has mounting holes 6, and a lifting mechanism 7 is installed within each mounting hole 6. Rollers 8 are mounted on the top of the lifting mechanism 7. For better explanation, here we combine... Figure 1 The upper and lower support plates 5 are symmetrically arranged, as are the left and right support plates 5. The upper support plate 5 and the left support plate 5 are perpendicular. Mounting holes 6 are located on the upper surface of the support plates 5. It should be noted that there are gaps between the support plates 5, allowing the cold air from the air outlet 4 to remove heat from the lower surface of the titanium alloy frame 1, thus cooling the lower surface. Mounting holes 6 can be set on all support plates 5, or on a few of them. For example, if there are four support plates 5 on each side, mounting holes 6 can be set on the first and fourth support plates 5, or on the second and third support plates 5. The lifting mechanism 7 can be a hydraulic cylinder or an electric push rod. Two opposing mounting plates are set on the top of the lifting mechanism 7, with rollers 8 positioned between them. It can rotate relative to the mounting plate; after a period of strong air cooling, the lifting mechanism 7 can be used to lift the entire titanium alloy frame 1. Here, an alternating lifting method is adopted, that is, after the lifting mechanisms 7 on the left and right sides are lifted, the entire titanium alloy frame 1 moves up and down. After the movement is completed, the lifting mechanisms 7 on the left and right sides retract, and the lifting mechanisms 7 on the upper and lower sides are lifted, causing the entire titanium alloy frame 1 to move left and right. After the movement is completed, the lifting mechanisms 7 on the upper and lower sides retract. The position of the entire titanium alloy frame 1 can be moved manually, or the drive motor can be used to rotate the rollers 8, so that the position that was previously in contact with the bearing plate 5 can be moved between the two bearing plates 5. This can better achieve cooling of the lower surface of the entire titanium alloy frame 1.

[0026] Furthermore, in step S5, after furnace cooling to 300°C, the titanium alloy frame 1 is moved to an insulated box for slow cooling to room temperature at a rate ≤15°C / h. The slow cooling at ≤15°C / h after furnace cooling to 300°C further releases residual stress and simultaneously suppresses dimensional drift caused by low-temperature phase transformation.

[0027] Example 1

[0028] The dimensions of the titanium alloy frame 1 are 5700×2500×300mm;

[0029] S1: Place the titanium alloy frame 1 on the hollowed-out tray and transfer it to the heat treatment furnace for preliminary annealing. The preliminary annealing temperature is 850±10℃ and the holding time is 3 hours.

[0030] S2: After the initial annealing is completed, within 150 seconds, the hollow material tray and the titanium alloy frame 1 are transferred to the air-cooling area using a forklift. Eight blowers are used to pre-cool the hollow material tray and the titanium alloy frame 1. The blowers are 2m away from the titanium alloy frame 1, and the blowers are opposite to the four corners and the middle of the four sides of the titanium alloy frame 1. The blowers are turned on to cool down the titanium alloy frame 1 until the surface temperature of the titanium alloy frame 1 drops to 600℃.

[0031] S3: After pre-cooling is completed, the titanium alloy frame 1 is transferred from the hollow material tray to the air-cooled material rack 2. The air-cooled material rack 2 is provided with an air outlet 3 in the middle, and the air outlet 3 is provided with an air outlet 4 around its circumference. Strong air cooling is carried out to room temperature, and the strong air cooling wind speed is 15m / s. During the strong air cooling process, the temperature of the titanium alloy frame 1 is monitored by an infrared thermometer. For every 50°C drop in temperature, the lifting mechanism 7 lifts the titanium alloy frame 1 and moves the titanium alloy frame 1 a certain distance, so that the position that was previously in contact with the bearing plate 5 is moved between the two bearing plates 5.

[0032] S4: After the strong air cooling is completed, the titanium alloy frame 1 is placed in the heating furnace for stress relief annealing. The stress relief annealing temperature is 560℃±10℃ and the stress relief annealing time is 2 hours. During the stress relief annealing, a pressure block is placed on top of the titanium alloy frame 1.

[0033] S5: After stress-relief annealing, furnace cooling is carried out at a rate of 30℃ / h to 280℃. Then, the titanium alloy frame 1 is transferred to an insulated box for slow cooling to room temperature at a rate of 15℃ / h.

[0034] Example 2

[0035] The dimensions of the titanium alloy frame 1 are 5700×2500×300mm;

[0036] S1: Place the titanium alloy frame 1 on the hollowed-out tray and transfer it to the heat treatment furnace for preliminary annealing. The preliminary annealing temperature is 850±10℃ and the holding time is 4 hours.

[0037] S2: After the initial annealing is completed, within 150 seconds, the hollow material tray and the titanium alloy frame 1 are transferred to the air-cooling area using a forklift. Eight blowers are used to pre-cool the hollow material tray and the titanium alloy frame 1. The distance between the blowers and the titanium alloy frame 1 is 1.5m. The blowers are opposite to the four corners and the middle of the four sides of the titanium alloy frame 1. The blowers are turned on to cool down the titanium alloy frame 1 until the surface temperature of the titanium alloy frame 1 drops to 600℃.

[0038] S3: After pre-cooling is completed, the titanium alloy frame 1 is transferred from the hollow material tray to the air-cooled material rack 2. The air-cooled material rack 2 is provided with an air outlet 3 in the middle. The air outlet 3 is provided with an air outlet 4 around its circumference. Strong air cooling is carried out to room temperature with a strong air cooling wind speed of 20m / s. During the strong air cooling process, the temperature of the titanium alloy frame 1 is monitored by an infrared thermometer. For every 50°C drop in temperature, the lifting mechanism 7 lifts the titanium alloy frame 1 and moves it a certain distance so that the position that was previously in contact with the bearing plate 5 is moved between the two bearing plates 5.

[0039] S4: After the strong air cooling is completed, the titanium alloy frame 1 is placed in the heating furnace for stress relief annealing. The stress relief annealing temperature is 560℃±10℃ and the stress relief annealing time is 4 hours. During the stress relief annealing, a pressure block is placed on top of the titanium alloy frame 1.

[0040] S5: After stress-relief annealing, furnace cooling is carried out at a rate of 20℃ / h to 250℃. Then, the titanium alloy frame 1 is transferred to an insulated box for slow cooling to room temperature at a rate of 10℃ / h.

[0041] Comparative Example 1

[0042] The dimensions of the titanium alloy frame 1 are 5700×2500×300mm;

[0043] The titanium alloy frame 1 is placed on a hollowed-out tray and transferred to a heat treatment furnace for preliminary annealing. The preliminary annealing temperature is 850±10℃ and the holding time is 4 hours. After annealing, it is air-cooled.

[0044] The table below shows the room temperature performance of the titanium alloy frame under different heat treatment methods.

[0045]

[0046] The table below shows the high-temperature performance of the titanium alloy frame under different heat treatment methods.

[0047]

[0048] As can be seen from the table above, the performance of the titanium alloy frame treated by this method is significantly improved.

[0049] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A heat treatment method for an extra-large integral frame, characterized in that, Includes the following steps, S1: Place the titanium alloy frame (1) on the hollowed-out tray and transfer it to the heat treatment furnace for preliminary annealing. The preliminary annealing temperature is 850℃±10℃ and the temperature is maintained for 3-4 hours. S2: After the initial annealing is completed, within 150 seconds, the hollow material tray and the titanium alloy frame (1) are transferred together to the air-cooling area using a transfer tool. Multiple blowers are used to pre-cool the hollow material tray and the titanium alloy frame (1). The distance between the blower and the titanium alloy frame (1) is ≤2m until the surface temperature of the titanium alloy frame (1) drops to 600℃. The blower used for pre-cooling is opposite to the four corners and the middle of the four sides of the titanium alloy frame (1), and the outlet of the blower is at an angle of 30°-45° to the surface of the titanium alloy frame (1). S3: After the pre-air cooling is completed, the titanium alloy frame (1) is transferred from the hollow material tray to the air-cooled material rack (2). The air-cooled material rack (2) is provided with an air outlet (3) in the middle. The air outlet (3) is provided with an air outlet (4) in the circumference. The strong air cooling is carried out to room temperature. The strong air cooling wind speed is ≥15m / s. S4: After the strong air cooling is completed, the titanium alloy frame (1) is placed in the heating furnace for stress relief annealing. The stress relief annealing temperature is 560℃±10℃, and a pressure block is set on the titanium alloy frame (1) during stress relief annealing. S5: After stress-relief annealing, furnace cool to below 300℃ at a rate of ≤30℃ / h before unloading.

2. The heat treatment method for an extra-large frame according to claim 1, characterized in that: The air outlet platform (3) is provided with multiple support plates (5) around its perimeter. The support plates (5) are provided with mounting holes (6). The mounting holes (6) are provided with lifting mechanisms (7). The top of the lifting mechanisms (7) is provided with rollers (8).

3. The heat treatment method for an extra-large frame according to claim 1, characterized in that: In step S5, after the furnace is cooled to 300°C, the titanium alloy frame (1) is moved to an insulated box and slowly cooled to room temperature at a rate of ≤15°C / h.

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