A stress relief annealing process suitable for large-size high-temperature titanium alloy curved surface or flat plate components

Abstract

The present invention belongs to the field of hot processing of titanium-based materials, and specifically relates to a stress relief annealing process suitable for large-sized high-temperature titanium alloy curved surfaces or flat plate components. The process includes components such as the applicable annealing times, annealing temperatures, holding time, and cooling methods. The use of the technology of the present invention to perform stress relief annealing during CNC machining of high-temperature titanium alloy forgings can achieve efficient elimination of internal stress while maximizing the stability of the material's microstructure and mechanical properties, providing technical support and guarantee for CNC machining of complex-shaped, high-dimensional precision parts such as aircraft wall panels, and can also be promoted and applied to stress relief annealing during CNC machining of complex structural parts such as integral blade disks and casings of engines made of the same material, meeting the application requirements of lightweight, high-temperature-resistant, large-sized high-temperature titanium alloy parts in high-tech fields such as aerospace.

Description

Technical Field

[0001] The invention belongs to the field of thermal processing of titanium-based materials, and in particular relates to a stress relief annealing process suitable for large-size high-temperature titanium alloy curved surfaces or flat plate components. Background Art

[0002] High-temperature titanium alloy is a type of titanium-based material with specific uses that developed in the 1950s along with aero-engine technology. The current mature high-temperature titanium alloy has a use temperature range of 350°C to 600°C. Compared with other types of titanium alloys, the most notable feature of high-temperature titanium alloys is the introduction of endurance and creep performance requirements. Under creep or endurance test conditions above 500°C, the material deformation mechanism is dominated by diffusion-controlled dislocation climb. Therefore, the higher the design and use temperature of the titanium alloy, the higher the diffusion activation energy of its alloying elements. The purpose is to reduce the element diffusion capacity and achieve high endurance and creep performance.

[0003] Another characteristic of high-temperature titanium alloys is that the control requirements for microstructure are very strict in order to achieve a good match of many mechanical properties such as tensile strength, durability, creep, fatigue, fracture, thermal stability, etc. To this end, there are strict control requirements for material composition, hot processing technology and heat treatment technology. The three must be within the process technology window required by the material. The resulting problem is that the part preparation process must adapt to the basic material process.

[0004] like Figure 1 As shown in the figure, the schematic diagram of the traditional heat treatment process curve includes three stages: heating, insulation and cooling, with charging temperature T 01～n , set heat treatment temperature T1, set furnace temperature T f There are temperature control points such as heating time τ1, insulation end time τ2 after reaching temperature and cooling time. The cooling time corresponds to various cooling methods such as water quenching, oil quenching, wind cooling, air cooling, furnace cooling, temperature controlled cooling, etc.

[0005] High-temperature titanium alloy forging products are the main application export of this type of alloy, such as: integral blade disc forgings, casing ring forgings, wall plate forgings, etc. The common feature of these products is that they need to be processed into finished parts by CNC machining. The machining removal of these parts is often greater than 93%, so there is an order of magnitude difference between the characteristic size of the parts (generally thickness) and the size of the forging blanks. For example, the thickness of the blades of the integral blade disc parts is ~2mm, while the thickness of the integral blade disc forging blanks is tens to hundreds of millimeters. High-temperature titanium alloys use elements with stronger bonding force with titanium atoms as strengthening elements, allowing the precipitation of intermetallic compounds such as Ti3Al, and belong to the category of difficult-to-process alloys. Under the superposition of the residual stress existing in the forging blank itself and the residual stress generated by the machining process, the blanks at different processing stages will be deformed to varying degrees; if not strictly controlled, it will lead to over-size of parts, difficulty in assembly, and even scrapping, resulting in huge losses. Therefore, for thin-walled and complex-shaped parts of high-temperature titanium alloys, the machining stress relief annealing process is crucial. Summary of the invention

[0006] In view of the application requirements of the aerospace field for fine and complex structures such as high-temperature titanium alloy integral blades, casings, wall panels, etc., the purpose of the present invention is to provide a stress relief annealing process suitable for large-size high-temperature titanium alloy curved surfaces or flat plate components. Through 2 or more stress relief annealing measures, the deformation of the forging blank during CNC machining is controlled within the allowable range, and the last step of part preparation is completed to meet the application requirements to the greatest extent.

[0007] The technical solution of the present invention is:

[0008] A stress relief annealing process suitable for large-sized high-temperature titanium alloy curved surface or flat plate components, including the stress relief annealing times, annealing temperature, time and cooling method components. The stress relief annealing times are 2 to 3 times, the annealing temperature is in the range of 550°C to 760°C, the single annealing time is 1 to 6 hours, and the annealing treatment is followed by furnace cooling or temperature control cooling.

[0009] The stress relief annealing process is suitable for large-sized high-temperature titanium alloy curved surface or flat plate components, and the curved surface or flat plate components are large-sized forged or forged+rolled blanks of high-temperature titanium alloy.

[0010] The stress relief annealing process suitable for large-sized high-temperature titanium alloy curved surface or flat plate components, when the annealing temperature is in the range of 680°C to 750°C, after the insulation time is over, it needs to be transferred to a heat treatment furnace with a temperature in the range of 600°C to 660°C for furnace or temperature-controlled cooling.

[0011] The stress relief annealing process is suitable for large-sized high-temperature titanium alloy curved surface or flat plate components. The stress relief annealing process is combined with the material low-temperature aging or annealing heat treatment process. The sum of the heat treatment + stress relief annealing time τ 总 The following relationship must be satisfied: 总 =2τ 750℃ +τ 700℃ +1 / 6τ 650℃ +1 / 12τ 630℃ +1 / 50τ 550～600℃ ≤7.0h, τ 750℃ , τ 700℃ , τ 650℃ , τ 630℃ and τ 550 ~ 600℃ They are the holding time of parts at 750℃, 700℃, 650℃, 630℃ and 550-600℃ respectively.

[0012] The stress relief annealing process is suitable for large-sized high-temperature titanium alloy curved surface or flat plate components. The stress relief annealing is performed twice and the total annealing time is τ 总 ≤6.0h; the first annealing temperature is 700~750℃, the annealing time is 1~5h, after the annealing treatment, it is transferred to a heat treatment furnace with a temperature of 600℃~660℃ and cooled with the furnace or with temperature control; the second annealing temperature is 630±30℃, the annealing time is 2h~6h, after the annealing treatment, it is cooled with the furnace or with temperature control.

[0013] The stress relief annealing process is suitable for large-sized high-temperature titanium alloy curved surface or flat plate components. The stress relief annealing times are 3 times and the total annealing time is τ 总 ≤6.5h; the first annealing temperature is 700℃±20℃, the annealing time is 1~3h, the second annealing temperature is 700±20℃, the annealing time is 1~4h. After the annealing treatment, it is necessary to transfer to a heat treatment furnace with a temperature of 600℃~660℃ and cool it with the furnace or with temperature control; the third annealing temperature is 600±50℃, the annealing time is 3~6h, and it is cooled with the furnace or with temperature control after annealing.

[0014] The design idea of ​​the present invention is:

[0015] High-temperature titanium alloy elements have high diffusion activation energy, and there is a temperature threshold for achieving efficient stress relief: if the annealing temperature is lower than this threshold, the stress relief annealing time needs to be significantly extended, which will become economically unacceptable; if the annealing temperature is too high, it will cause the precipitated phase to grow significantly or other microstructural changes, which will have an adverse effect on the mechanical properties of the material, especially the strength of the forging. To this end, the present invention proposes the following design ideas: ① Considering that high-temperature titanium alloy forgings need to be aged or annealed at around 700°C, the machining stress relief annealing and the forging aging or annealing process are comprehensively considered; ② During the cooling process after aging or annealing, the difference in cooling rate at different positions of the forging will lead to the generation of new residual stresses, so it is necessary to reduce the cooling rate after annealing. The present invention adopts furnace cooling or temperature-controlled cooling process; ③ Furnace cooling or temperature-controlled cooling means that the insulation time at high temperature is extended, and strengthening phases of different scales will continue to precipitate, reducing the plastic reserve of the material, so it is necessary to optimize the cooling method and strictly control it, see Attachment Figure 1 and Figure 2 ;④ Heat treatment of high-temperature titanium alloy at 650℃~750℃ mainly affects the formation and growth of precipitated phases such as α2 and silicide. The number and size of these two precipitated phases depend on the heat treatment temperature and time, among which the influence of heat treatment temperature is much greater than that of heat treatment time. To this end, another important feature of the present invention is that the annealing or aging time of forgings needs to be adjusted accordingly according to the conditions of stress relief annealing, so that the comprehensive effect of forging aging or annealing treatment + stress relief annealing treatment does not exceed the limit of high-temperature titanium alloy's control requirements for precipitated phases, thereby achieving the premise of meeting the efficient stress relief annealing effect and minimizing the adverse effects on the mechanical properties of the forgings. For this purpose, τ is set 总 =2τ 750℃ +τ 700℃ +1 / 6τ 650℃ +1 / 12τ 630℃ +1 / 50τ 550～600℃ ≤7.0h constraint, where τ 750℃ , τ 700℃ , τ 650℃ , τ 630℃ and τ 550 ~ 600℃ They are the holding time of the forging blank at 750℃, 700℃, 650℃, 630℃ and 550-600℃ respectively.

[0016] The advantages and beneficial effects of the present invention are:

[0017] 1. The present invention can effectively control the dimensional accuracy of large-sized and super-large-sized high-temperature titanium alloy parts during CNC machining, meeting the production and application needs of such parts;

[0018] 2. The present invention adopts 2 to 3 times of stress relief annealing process, and the first annealing process is comprehensively considered with the high-temperature titanium alloy aging or annealing process, which shortens the process flow, reduces the cost, simplifies the process, and has low requirements on equipment.

[0019] 3. Within the annealing process window of the present invention, the internal stress can be eliminated efficiently while the microstructure and mechanical properties of the material before and after stress relief annealing are kept stable to the maximum extent. The annealing treatment has no obvious adverse effect on the mechanical properties of the forgings, especially the strength and plasticity.

[0020] 4. The present invention is for weight more than 800kg and projection area 2m 2 Forgings with machining removal rate above 95% have higher applicability.

[0021] 5. The present invention provides technical support and guarantee for the CNC machining of large-sized, complex-shaped, and high-dimensional precision parts such as aircraft wall panels, and can be widely used in aircraft engine integral blades, casings and other parts to meet the application needs of high-temperature titanium alloy parts in high-tech fields such as aerospace.

[0022] 6. The materials applicable to the present invention include high-temperature titanium alloys such as TA32, TA33, TA37, TA38, etc., whose second annealing temperature is ≥ 600°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of traditional heat treatment process curve.

[0024] Figure 2 It is a schematic diagram of the heat treatment process curve of the present invention. DETAILED DESCRIPTION

[0025] In the specific implementation process, the present invention proposes a stress relief annealing process suitable for large-sized high-temperature titanium alloy curved surface or flat plate components, including the annealing times, annealing temperature, time and cooling method (cooling rate) and other components, including the following steps:

[0026] 1) The processing object is large-size forging or forging + rolling blanks of high-temperature titanium alloy, suitable for projection size 0.4m 2 ~8.0m 2 Stress relief annealing treatment of parts within the scope;

[0027] 2) Stress relief annealing is performed 2 to 3 times, the annealing temperature is within the range of 550℃ to 760℃, the single annealing time is 1 to 6 hours, and the annealing is followed by furnace cooling or temperature control cooling;

[0028] For forgings with smaller projection area or higher symmetry, the specification size range is: 0.4m 2 ~1.1m 2, adopting two stress relief annealing processes. Among them, the first annealing treatment temperature is 700℃~750℃, the furnace is loaded at 500℃ or below, and the heat is kept for 2~5h after heat through. After the heat preservation is completed, the power is turned off, and the forging is transferred to a heat treatment furnace with a temperature of 600℃~660℃, and it is cooled to below 400℃ with the furnace or temperature control before being taken out of the furnace; the second annealing treatment temperature is 550℃~660℃, the furnace is loaded at the temperature or below the target temperature, and the heat is kept for 2~6h after heat through. After the heat preservation is completed, the power is turned off, and the forging is cooled to below 400℃ with the furnace or temperature control before being taken out of the furnace;

[0029] For forgings with larger projected areas, the specification size range is: 1.1m 2 ~8.0m 2 , using two or more stress relief annealing processes. Its main features are that the first and second annealing temperatures are both 700-750℃, the furnace is loaded at 500℃ or below, the heat preservation time is 1-3h after heat through, the power is turned off after the heat preservation is over, and the heat treatment furnace is transferred to a temperature of 600℃-660℃, and the furnace is cooled to below 400℃ with the furnace or temperature control before being taken out of the furnace; the third annealing temperature is 550℃-660℃, the furnace is loaded when the temperature reaches or is below the target temperature, the heating rate is ≤3℃ / min, the temperature is kept for 3-6h after reaching the temperature, and the furnace is cooled to below 400℃ with the furnace or temperature control after the heat preservation is over.

[0030] In the above stress relief annealing scheme, the first stress relief annealing treatment is combined with the high temperature titanium alloy aging or annealing heat treatment process.

[0031] like Figure 2 As shown in the figure, the heat treatment process curve diagram of the present invention is similar to the attached Figure 1 The biggest difference is: 1) The control range of heating and cooling rate is narrowed, such as the heating curve is narrowed to T 03 → Near T1, the cooling rate is controlled between S3 and S4; 2) The end time of heat preservation is τ3≤τ2; 3) After the heat preservation is completed, it is transferred to the heat treatment furnace with a set temperature of T2 (T2≤T1), and then Figure 1 Cooling speed in the range of S3 to S4 to the specified temperature (T f ) is released; 4) requires T f ≤400℃.

[0032] The characteristics and novelty of the above preparation method are reflected in the following aspects: 1) The first high temperature stress relief annealing is in the range of 680℃~750℃, which is combined with material aging or low temperature annealing treatment; 2) After the first stress relief annealing in the range of 700℃~750℃ is completed, it is transferred to a heat treatment furnace with a temperature of 600℃~660℃ for cooling along with the furnace or temperature control; 3) When the stress relief annealing temperature is in the range of 550℃~650℃, after the insulation is completed, it is cooled along with the furnace or temperature control to a temperature point below a certain point and then taken out of the furnace for air cooling; 4) The sum of all stress relief annealing times τ总 The following constraints must be met: 总 =2τ 750℃ +τ 700℃ +1 / 6τ 650℃ +1 / 12τ 630℃ +1 / 50τ 550～630℃ ≤7.0h, τ 750℃ , τ 700℃ , τ 650℃ , τ 630℃ and τ 550 ~ 630℃ They are the holding time of the forging blank in the range of 750℃, 700℃, 650℃, 630℃ and 550-630℃ (excluding 630℃) under furnace cooling or temperature-controlled cooling conditions.

[0033] Below, the present invention is further described in detail by examples.

[0034] Embodiment 1:

[0035] The experimental material is TA38 alloy forging blank, the blank size is 3200mm×660mm×85mm, the weight is 780kg, the nominal composition is Ti-5.8Al-4.0Sn-3.5Zr-0.5Mo-0.4Si-0.3Nb-1.5Ta-1.0W-0.06C (wt%). The process route involves the first stress relief annealing, rough machining, dimensional inspection, second stress relief annealing, fine milling and other steps. The total time of stress relief annealing is equivalent to 4.1h:

[0036] 1) First stress relief annealing: Annealing temperature is 750℃, and heating is carried out in an electric furnace conforming to GJB 904A III. The furnace is loaded at 300℃, and after the temperature rises to 750℃, the heat-through time is 50min, and the heat preservation time is 120min; after the heat preservation is completed, it is transferred to a heat treatment furnace at a temperature of 660℃, and the temperature is controlled and cooled to 350℃ at a speed of 1℃ / min, and then air-cooled to room temperature after being taken out of the furnace;

[0037] 2) Rough machining: Use a three-axis CNC gantry milling machine to rough-machine the forging blank, remove 80% of the weight during rough machining, and then perform dimensional inspection;

[0038] 3) Second stress relief annealing: annealing temperature is 600℃, heating is carried out in an electric furnace conforming to GJB 904A III, the furnace is loaded at 450℃, the temperature is increased to 600℃ at a rate of 5℃ / min, the heat-through time is 30min, and the heat preservation time is 300min; after the heat preservation is completed, the power is turned off, and the steel is cooled to 350℃ with the furnace, and then air-cooled to room temperature after being taken out of the furnace;

[0039] 4) Finishing milling: Use a five-axis CNC gantry milling machine to perform finishing milling on the forging blank until the final size, and then the size is finally measured.

[0040] Embodiment 2:

[0041] The experimental material is TA38 alloy forging blank, the blank size is 2800mm×1000mm×90mm, the weight is 1160kg, and the nominal composition is Ti-5.8Al-4.0Sn-3.5Zr-0.5Mo-0.4Si-0.3Nb-1.5Ta-1.0W-0.06C (wt%). The process route involves the first stress relief annealing, rough machining, dimensional inspection, the second stress relief annealing, semi-finishing milling and the third stress relief annealing, finishing milling and other steps. The total time of stress relief annealing is equivalent to 230min:

[0042] 1) First stress relief annealing: Annealing temperature is 700℃, and heating is carried out in an electric furnace conforming to GJB 904A III. The furnace is loaded at 450℃, and after the temperature rises to 700℃, the heat-through time is 50min, and the heat preservation time is 180min; after the heat preservation is completed, the steel is taken out of the furnace and transferred to a heat treatment furnace at a temperature of 650±10℃ while it is still hot. After cooling to 350℃, the steel is taken out of the furnace and air-cooled to room temperature;

[0043] 2) Rough machining: Use a three-axis CNC gantry milling machine to rough-machine the forging blank, remove 70% of the weight during rough machining, and then perform dimensional inspection;

[0044] 3) Second stress relief annealing: annealing temperature is 650℃, heating is carried out in an electric furnace conforming to GJB 904A III, the furnace is loaded at 450℃, the heating rate is 3℃ / min to 650℃, the heat-through time is 30min, and the heat preservation time is 180min; after the heat preservation is completed, the power is turned off, and the steel is taken out of the furnace after cooling to 350℃, and air-cooled to room temperature;

[0045] 4) Semi-finishing milling: Use a five-axis CNC gantry milling machine to perform semi-finishing milling on the forging blank. Based on the weight of the rough forging, semi-finishing milling removes 55% of the weight, and then the size is inspected;

[0046] 5) Third stress relief annealing: annealing temperature is 630℃, heating is carried out in an electric furnace conforming to GJB 904A III, the furnace is loaded at 400℃, the temperature is increased to 630℃ at a rate of 3℃ / min, the heat-through time is 10min, and the holding time is 240min; after the holding time is completed, the power is turned off, the furnace is cooled to 350℃, and then taken out of the furnace and air-cooled to room temperature;

[0047] 6) Finishing milling: Use a five-axis CNC gantry milling machine to perform finishing milling on the forging blank until the required size is reached, and then the size is finally measured.

[0048] Embodiment 3:

[0049] The experimental material is TA38 alloy forging billet, with dimensions of 3100mm×1600mm×85mm, weight of 1770kg, and nominal composition of Ti-5.8Al-4.0Sn-3.5Zr-0.5Mo-0.4Si-0.3Nb-1.5Ta-1.0W-0.06C (wt%). The process route involves the first stress relief annealing, rough machining, dimensional inspection, the second stress relief annealing, semi-finishing milling, and the third stress relief annealing, finishing milling, etc. The total time of stress relief annealing is equivalent to 4.1h:

[0050] 1) First stress relief annealing: Annealing temperature is 700℃, and heating is carried out in an electric furnace conforming to GJB 904A III. The furnace is loaded at 450℃, and after the temperature rises to 700℃, the heat-through time is 50min, and the heat preservation time is 100min; after the heat preservation is completed, it is transferred to a heat treatment furnace at a temperature of 630℃ and cooled to 350℃ at a speed of 1℃ / min, and then air-cooled to room temperature after being taken out of the furnace;

[0051] 2) Rough machining: Use a three-axis CNC gantry milling machine to rough-machine the forging blank, remove 65% of the weight during rough machining, and then perform dimensional inspection;

[0052] 3) Second stress relief annealing: Annealing temperature is 700℃, and heating is carried out in an electric furnace conforming to GJB 904A III. The furnace is loaded at 500℃, and after the temperature rises to 700℃, the heat-through time is 20min, and the heat preservation time is 140min; after the heat preservation is completed, it is transferred to a heat treatment furnace at a temperature of 650℃ and cooled to 350℃ at a speed of 1℃ / min, and then air-cooled to room temperature after being taken out of the furnace;

[0053] 4) Semi-finishing milling: Use a five-axis CNC gantry milling machine to perform semi-finishing milling on the forging blank. Based on the weight of the rough forging, semi-finishing milling removes 50% of the weight, and then the size is inspected;

[0054] 5) Third stress relief annealing: Annealing temperature is 600℃, and heating is carried out in an electric furnace conforming to GJB 904A III. The furnace is loaded at 450℃, and the temperature is increased to 600℃ at a rate of 3℃ / min, with a heat-through time of 10min and a heat-holding time of 300min. After the heat-holding is completed, the power is turned off and the steel is removed from the furnace after cooling to below 300℃.

[0055] 6) Finishing milling: Use a five-axis CNC gantry milling machine to perform finishing milling on the forging blank until the required size is reached, and then the size is finally measured.

[0056] Embodiment 4:

[0057] The experimental material is TA38 alloy forging billet, with dimensions of 3100mm×1600mm×85mm, weight of 1770kg, and nominal composition of Ti-5.8Al-4.0Sn-3.5Zr-0.5Mo-0.4Si-0.3Nb-1.5Ta-1.0W-0.06C (wt%). The process route involves the first stress relief annealing, rough machining, dimensional inspection, the second stress relief annealing, semi-finishing milling, and the third stress relief annealing, finishing milling, etc. The total time of stress relief annealing is equivalent to 6.35h:

[0058] 1) First stress relief annealing: Annealing temperature is 750℃, and heating is carried out in an electric furnace conforming to GJB 904A III. The furnace is loaded at 450℃, and after the temperature rises to 750℃, the heat-through time is 50min, and the heat preservation time is 180min; after the heat preservation is completed, the material is taken out of the furnace, and then transferred to a heat treatment furnace at a temperature of 660℃ while hot, and cooled to 350℃ at a speed of 1℃ / min, and then air-cooled to room temperature after being taken out of the furnace;

[0059] 2) Rough machining: Use a three-axis CNC gantry milling machine to rough-machine the forging blank, remove 70% of the weight during rough machining, and then perform dimensional inspection;

[0060] 3) Second stress relief annealing: Annealing temperature is 630℃, and heating is carried out in an electric furnace conforming to GJB 904A III. The furnace is loaded at 450℃, and the temperature is increased to 630℃ at a rate of 3℃ / min, with a heat-through time of 30min and a heat-holding time of 180min. After the heat-holding is completed, the power is turned off, and the furnace is cooled to 300℃, and then air-cooled to room temperature after being taken out of the furnace;

[0061] 4) Semi-finishing milling: Use a five-axis CNC gantry milling machine to perform semi-finishing milling on the forging blank. Based on the weight of the rough forging, semi-finishing milling removes 55% of the weight, and then the size is inspected;

[0062] 5) Third stress relief annealing: Annealing temperature is 550℃, heated by electric furnace conforming to GJB 904A III. Load the furnace at 400℃, and heat up to 550℃ at a rate of 3℃ / min, heat-through time is 10min, and heat preservation time is 300min; after the heat preservation is completed, the circuit is turned off, and the furnace is cooled to 300℃, and air-cooled to room temperature after being taken out of the furnace;

[0063] 6) Finishing milling: Use a five-axis CNC gantry milling machine to perform finishing milling on the forging blank until the required size is reached, and then the size is finally measured.

[0064] The stress relief annealing process of Examples 1 to 4 was adopted, and the mechanical properties of the forgings are shown in Tables 1 and 2. The comparative examples in the table are forgings that were not subjected to stress relief treatment, and it can be seen that the stress relief annealing system of the present invention has little effect on the tensile strength.

[0065] Table 1 shows the room temperature tensile properties

[0066] Sample status <![CDATA[R m ,MPa]]> <![CDATA[R p0.2 ,MPa]]> A，％ Z，％ Example 1 1090 1001 6.0 9 Example 2 1085 1005 8.0 11 Example 3 1044 954 9.0 17 Example 4 1083 1000 9.5 14 Comparative Example 1079 998 10.0 16

[0067] Table 2 shows the tensile properties at 650℃

[0068] Sample status <![CDATA[R m ,MPa]]> <![CDATA[R p0.2 ,MPa]]> A，％ Z，％ Example 1 617 481 15.0 26 Example 2 611 484 11.5 28 Example 3 618 477 14.5 37 Example 4 625 486 20.0 30 Comparative Example 623 492 11.5 30

[0069] In summary, based on the theoretical analysis and experimental research on material properties, the present invention proposes a stress relief annealing process suitable for large-size high-temperature titanium alloy curved surfaces or flat plate components according to the application requirements of the fields of aviation and aerospace for TA38 and other high-temperature titanium alloy precision and complex forgings. This method is used to minimize the deformation of parts during CNC machining, and to achieve rough machining and fine milling of high-temperature titanium alloy forging blanks with large removal volumes. The mechanical properties of the parts remain stable before and after stress relief annealing, and the part can be used for the production of high-temperature resistant structural parts for aircraft or aerospace vehicles, and has broad prospects for promotion and application.

Claims

1. A stress relief annealing process suitable for large-sized high-temperature titanium alloy curved surface or flat plate components, characterized in that: It includes the stress relief annealing times, annealing temperature, time and cooling method. The stress relief annealing times are 2 to 3 times, the annealing temperature is in the range of 550℃ to 760℃, the single annealing time is 1 to 6 hours, and the annealing is followed by furnace cooling or temperature control cooling. When the annealing temperature is in the range of 680℃~750℃, after the holding time is over, it needs to be transferred to a heat treatment furnace with a temperature in the range of 600℃~660℃ for cooling along with the furnace or temperature control; The stress relief annealing process is considered together with the material low temperature aging or annealing heat treatment process. The sum of the heat treatment + stress relief annealing time is τ 总 The following relationship must be satisfied: 总 =2τ 750℃ +τ 700℃ +1 / 6τ 650℃ +1 / 12τ 630℃ +1 / 50τ 550～600℃ ≤7.0h, τ 750℃ , τ 700℃ , τ 650℃ , τ 630℃ and τ 550 ~ 600℃ They are the holding time of parts at 750℃, 700℃, 650℃, 630℃ and 550~600℃ respectively; The high temperature titanium alloy is TA32, TA33, TA37 or TA38.

2. The stress relief annealing process for large-sized high-temperature titanium alloy curved surface or flat plate components according to claim 1, characterized in that: The curved surface or flat plate component is a large-size forged or forged+rolled blank of a high-temperature titanium alloy.

3. The stress relief annealing process for large-sized high-temperature titanium alloy curved surface or flat plate components according to claim 1, characterized in that: Stress relief annealing times: 2 times, total annealing time: τ 总 ≤6.0h; the first annealing temperature is 700~750℃, the annealing time is 1~5h, after the annealing treatment, it is transferred to a heat treatment furnace with a temperature of 600℃~660℃ and cooled with the furnace or with temperature control; the second annealing temperature is 630±30℃, the annealing time is 2h~6h, after the annealing treatment, it is cooled with the furnace or with temperature control.

4. The stress relief annealing process for large-sized high-temperature titanium alloy curved surface or flat plate components according to claim 1, characterized in that: Stress relief annealing times: 3 times, total annealing time: τ 总 ≤6.5h; the first annealing temperature is 700℃±20℃, the annealing time is 1~3h, the second annealing temperature is 700±20℃, the annealing time is 1~4h. After the annealing treatment, it is necessary to transfer to a heat treatment furnace with a temperature of 600℃~660℃ and cool it with the furnace or with temperature control; the third annealing temperature is 600±50℃, the annealing time is 3~6h, and it is cooled with the furnace or with temperature control after annealing.

Images