Vacuum high-temperature creep correction method for castings

Abstract

The application discloses a kind of castings vacuum high temperature creep shape correction method, comprising: the three-dimensional scanning of deformed casting is carried out, and the deformation position and deformation of casting are determined according to scanning result;According to the deformation position and deformation of casting, the shape correction tooling that is adapted therewith is made, and the shape correction tooling is assembled on casting;The shape correction tooling and casting assembled together are put into vacuum heating furnace as a whole, and the vacuum degree is less than or equal to 5Pa, and high temperature creep shape correction is carried out in the way of sectional heating;After shape correction is completed, the shape correction tooling and casting are cooled to room temperature in the way of sectional cooling, and the casting of size correction qualified is obtained by removing shape correction tooling.The method effectively solves the problem that titanium and titanium alloy, zirconium alloy deformed casting is difficult to repair.

Description

Technical Field

[0001] This invention belongs to the field of casting processing technology, and specifically relates to a method for vacuum high-temperature creep correction of castings. Background Technology

[0002] Titanium and titanium alloys have advantages such as light weight, high specific strength and good corrosion resistance, and are widely used in the manufacturing of high-end equipment such as aerospace. Zirconium alloys, with their excellent high-temperature resistance, strong resistance to acid and alkali corrosion, good thermal stability, and unique nuclear mechanical properties, are core special materials in the nuclear industry, high-end chemical industry, and deep-sea equipment manufacturing, and their application scenarios are becoming increasingly critical. However, in the actual industrial production and processing stage, titanium and titanium alloy thin-walled parts, thick-walled structural parts, and various precision structural parts of zirconium alloys are prone to deformation, contour distortion, and dimensional deviations during hot isostatic pressing and high-temperature stress processing, resulting in a low finished product qualification rate. For deformed and scrapped titanium and titanium alloy and zirconium alloy castings, the existing cold straightening process has obvious technical shortcomings. Not only are there defects such as large springback after straightening and easy cracking of castings, but for zirconium alloy castings with special plasticity and complex stress release rules, there is also a high risk of residual straightening stress. The lack of precision in repairing deformed castings generally leads to a high scrap rate, resulting in economic losses of expensive titanium and zirconium materials. Therefore, the industry urgently needs a way to accurately repair defects in deformed castings. Summary of the Invention

[0003] To address the aforementioned problems in the existing technology, this invention provides a vacuum high-temperature creep correction method for castings. The technical problem to be solved by this invention is achieved through the following technical solution:

[0004] A method for vacuum high-temperature creep correction of castings includes:

[0005] Step 1: Perform a 3D scan on the deformed casting and determine the deformed parts and the amount of deformation based on the scan results;

[0006] Step 2: Fabricate a matching straightening fixture according to the deformed part and the amount of deformation of the casting, and assemble the straightening fixture onto the casting;

[0007] Step 3: Place the assembled calibration fixture and casting into a vacuum heating furnace with a vacuum degree ≤5Pa, and perform high-temperature creep calibration using a segmented heating method;

[0008] Step 4: After the calibration is completed, the calibration fixture and the casting are cooled to room temperature by segmented cooling. The calibration fixture is then removed to obtain a casting with qualified dimensions.

[0009] Furthermore, the calibration fixture includes a bottom support lower mold, a pressure-bearing correction upper mold, and a counterweight. During assembly, the casting is placed on the bottom support lower mold and its deformed part is completely fitted with the bottom support lower mold. The pressure-bearing correction upper mold is placed on top of the deformed part of the casting and is completely fitted with the top. A counterweight adapted to the deformation amount of the casting is placed on the upper end of the pressure-bearing correction upper mold.

[0010] Furthermore, the calibration fixture also includes an inner cavity limiting support core mold. When the deformed part has a cavity, the inner cavity limiting support core mold is placed in the cavity.

[0011] Furthermore, when the deformation of the deformed part of the casting is 1~2mm, the counterweight weight is 10~25kg; when the deformation of the deformed part of the casting is 3~4mm, the counterweight weight is 25~50kg; when the deformation of the deformed part of the casting is 4~6mm, the counterweight weight is 50~100kg.

[0012] Furthermore, in step 3, the segmented heating process is as follows:

[0013] First, heat the vacuum heating furnace to 350~400℃ and hold for 100~140 minutes; then heat to 600~700℃ and hold for 80~100 minutes; finally heat to 900~950℃ and hold for 2~4 hours.

[0014] Furthermore, in step 4, the segmented cooling process is as follows:

[0015] First, the vacuum heating furnace is cooled to 550~650℃ and held at that temperature for 25~35 minutes; then it is cooled to room temperature along with the furnace.

[0016] Furthermore, the calibration tooling is made of high-purity graphite.

[0017] Furthermore, the casting is a titanium or titanium alloy, or a zirconium alloy casting.

[0018] The beneficial effects of this invention are:

[0019] 1. This invention adopts the principle of vacuum high-temperature creep correction, and uses appropriate graphite tooling to fully constrain and shape the casting. It utilizes the creep characteristics of metal at high temperature to achieve plastic deformation correction, avoiding microcracks, springback and stress residue problems caused by cold correction. The dimensional accuracy after correction can be controlled within the design tolerance range, and the pass rate is significantly improved.

[0020] 2. A three-stage stepped heating process is adopted to gradually release the residual casting stress, avoiding thermal shock cracking. A segmented slow cooling temperature control process is used to release the secondary stress generated by high-temperature correction. The entire correction process does not damage the mechanical properties of the casting matrix, and the corrected casting still meets the original design performance requirements.

[0021] 3. The calibration tooling is made of high-purity graphite, which has excellent dimensional stability under high temperature and vacuum, and no softening or deformation problems. The tooling can be reused for the same product specifications, which greatly reduces the tooling cost of the calibration process.

[0022] 4. The calibration process of this invention is simple and easy to promote in industrial applications; the overall process flow is clear, no complex equipment is required, and it can be achieved by relying on a conventional vacuum heating furnace. It can be applied in batches to the deformation repair of titanium and titanium alloy, zirconium alloy valve bodies, pump bodies, irregular structural parts and similar structural castings, and has good engineering application value.

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0024] Figure 1 This is a photograph of the calibration tooling of Example 1 being assembled onto the Zr-5 zirconium alloy valve body casting;

[0025] Figure 2 This is a three-dimensional scanning chromatographic deviation comparison image of the Zr-5 zirconium alloy valve body casting in Example 1;

[0026] Figure 3 This is a photograph of the calibration tooling assembled onto the TA1 pure titanium valve body casting in Example 2;

[0027] Figure 4 This is a photograph of the calibration tooling assembled onto the TA2 pure titanium pump body casting in Example 3;

[0028] Figure 5 This is a three-dimensional scanning chromatographic deviation comparison diagram of the TA2 pure titanium pump body casting in Example 3;

[0029] Figure 6 This is a photograph of the calibration tooling assembled onto the TC4 titanium alloy cylindrical casting in Example 4;

[0030] Figure 7 This is a three-dimensional scan of the TC4 titanium alloy cylindrical casting in Example 4;

[0031] Figure 8 This is a three-dimensional scanning chromatographic deviation comparison diagram of the TC4 titanium alloy cylindrical casting in Example 4;

[0032] Figure 9 This is a photograph of the alignment tooling being assembled onto the TA15 titanium alloy irregular casting in Example 5.

[0033] Explanation of reference numerals in the attached figures:

[0034] 1- Bottom support lower mold; 2- Inner cavity limiting support core mold; 3- Pressure bearing and correction upper mold; 4- Counterweight; 5- Pad block. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0036] Example 1

[0037] This embodiment provides a vacuum high-temperature creep correction method for Zr-5 zirconium alloy valve body castings, which specifically includes the following steps:

[0038] Step 1: Perform a 3D scan on the deformed Zr-5 zirconium alloy valve body casting, and determine the deformed part of the valve body casting as the intermediate flange based on the scan results. The radial deformation is 5mm, and the wall thickness of the intermediate flange hole is 50mm.

[0039] Step 2: Based on the intermediate flange structure and deformation of the Zr-5 zirconium alloy valve body casting, fabricate a matching calibration fixture and assemble the calibration fixture onto the Zr-5 zirconium alloy valve body casting as required.

[0040] The tooling used in this calibration process is made of high-purity graphite with a density of 1.68 g / cm³, a tensile strength of 25.25 MPa, a compressive strength of 61.27 MPa, and a coefficient of thermal expansion of 1.5 × 10⁻⁻⁻⁶ at 500℃. 6 / ℃, the coefficient of thermal expansion at 1000℃ is 4.4×10⁻ 6 / ℃. In summary, the calibration tooling made of this high-purity graphite material exhibits high thermochemical stability and refractoriness, high strength, and a low coefficient of thermal expansion. It shows no thermal expansion deformation or high-temperature softening and collapse under high-temperature vacuum conditions, demonstrating excellent stability.

[0041] Specifically, such as Figure 1 As shown, the calibration fixture includes a bottom support lower mold, an inner cavity limiting support core mold, a pressure-bearing calibration upper mold, and a counterweight. The bottom support lower mold is positioned at the bottom of the Zr-5 zirconium alloy valve body casting and must be completely fitted to the bottom of the intermediate flange, ensuring effective support for both ends of the Zr-5 zirconium alloy valve body casting and the bottom of the intermediate flange. The inner cavity limiting support core mold is embedded in the inner hole of the intermediate flange to support the intermediate flange cavity, and a 0.5mm springback allowance is required. The pressure-bearing calibration upper mold is placed on top of the intermediate flange to ensure normal pressure transmission during calibration without damaging the casting. Specifically, the shape of the pressure-bearing calibration upper mold can be designed to conform to the shape of the top of the intermediate flange, as long as it ensures normal pressure transmission during calibration. The counterweight is positioned at the upper end of the pressure-bearing calibration upper mold to apply pressure to the intermediate flange. In this embodiment, a 70kg counterweight is used.

[0042] Step 3: Place the assembled calibration fixture and Zr-5 zirconium alloy valve body casting into a vacuum heating furnace with a vacuum degree ≤5Pa, and perform high-temperature creep calibration using a segmented heating method.

[0043] The specific process of segmented heating is as follows: First, the vacuum heating furnace is heated to 400℃ and held for 135 minutes. This stage mainly removes water vapor and impurities from the high-purity graphite shaping tooling to prevent thermal stress cracking of the casting caused by rapid heating. Then, the temperature is raised to 700℃ and held for 100 minutes. This stage mainly releases the residual casting stress of the valve body casting slowly and reduces the temperature difference between the inside and outside of the casting. Finally, the temperature is raised to 900℃ and held for 3 hours. In this stage, under the action of high temperature and counterweight, the hole wall of the valve body intermediate flange undergoes creep deformation. Relying on the constraints of the bottom support lower mold, the inner cavity limit support core mold, the pressure-bearing correction upper mold and counterweight, the valve body casting finally achieves the required shape and size.

[0044] Step 4: After the calibration is completed, the calibration fixture and the Zr-5 zirconium alloy valve body casting are cooled to room temperature by segmented cooling, and the calibration fixture is removed to obtain the Zr-5 zirconium alloy valve body casting with the intermediate flange dimensions corrected.

[0045] The specific process of segmented cooling is as follows:

[0046] First, the vacuum heating furnace is cooled to 650℃ and held for 35 minutes. This stage mainly releases the secondary stress generated by the high-temperature shaping on the valve body casting. Then, the casting is cooled to room temperature with the furnace, and the counterweight, bottom support lower mold, inner cavity limiting support core mold, and pressure-bearing correction upper mold are removed. Figure 2 As shown, the dimensional accuracy of the intermediate flange of the Zr-5 zirconium alloy valve body casting meets the target requirements after 3D scanning inspection.

[0047] Example 2

[0048] This embodiment provides a vacuum high-temperature creep correction method for TA1 pure titanium valve body castings, which specifically includes the following steps:

[0049] Step 1: Perform a 3D scan on the deformed TA1 pure titanium valve body casting, and determine the deformed part of the valve body casting as one end of the intermediate flange, i.e. the closed end, based on the scan results; the axial deformation is 4mm, and the thickness of this end of the intermediate flange is 25mm.

[0050] Step 2: Based on the structure and deformation of both ends of the intermediate flange of the TA1 pure titanium valve body casting, fabricate a matching calibration fixture, and assemble the calibration fixture onto the TA1 pure titanium valve body casting as required. The material and performance of this calibration fixture are the same as in Example 1, and will not be repeated here.

[0051] Specifically, such as Figure 3As shown, the calibration fixture includes a bottom support lower mold, an inner cavity limiting support core mold, a pressure-bearing calibration upper mold, and a counterweight. During calibration, the TA1 pure titanium valve body casting is placed on the bottom support lower mold, with the open end face of the intermediate flange facing downwards and fully fitted to the lower mold, ensuring effective support from the bottom support lower mold for both ends of the casting and the open end of the intermediate flange. The inner cavity limiting support core mold is vertically inserted into the inner hole of the intermediate flange, aligned with the axis of the hole, to support the intermediate flange cavity and prevent other deformations during calibration. In this embodiment, because the counterweight is relatively wide, improper placement may cause deformation of the intermediate flange. Therefore, the pressure-bearing calibration upper mold is divided into two parts, placed on both sides of the top intermediate flange of the valve body casting, and fully fitted to both sides of the top intermediate flange of the valve body casting, while remaining flush with the upper end face of the intermediate flange. The counterweight is coaxially placed on the closed end face of the intermediate flange and fitted to the pressure-bearing calibration upper mold, so that the counterweight can stably and evenly apply pressure to the closed end of the intermediate flange. In this embodiment, a 48kg counterweight is used.

[0052] Step 3: Place the assembled calibration fixture and the TA1 pure titanium valve body casting into a vacuum heating furnace with a vacuum degree ≤5Pa, and perform high-temperature creep calibration using a segmented heating method.

[0053] The specific process of segmented heating is as follows: First, the vacuum heating furnace is heated to 370℃ and held for 125 minutes. This stage mainly removes water vapor and impurities from the high-purity graphite shaping tooling to prevent thermal stress cracking of the casting caused by rapid heating. Then, the temperature is raised to 650℃ and held for 90 minutes. This stage mainly releases the residual casting stress of the valve body casting slowly and reduces the temperature difference between the inside and outside of the casting. Finally, the temperature is raised to 900℃ and held for 2 hours. In this stage, under the action of high temperature and counterweight, the bottom of the valve body intermediate flange undergoes creep deformation. Relying on the constraints of the bottom support lower mold, the inner cavity limit support core mold, the pressure-bearing correction upper mold and counterweight, the valve body casting finally achieves the required shape and size.

[0054] Step 4: After the calibration is completed, the calibration fixture and the TA1 pure titanium valve body casting are cooled to room temperature by segmented cooling, and the calibration fixture is removed to obtain the TA1 pure titanium valve body casting with the bottom dimension of the intermediate flange corrected.

[0055] The specific process of segmented cooling is as follows:

[0056] First, the vacuum heating furnace is cooled to 600℃ and held for 30 minutes. This stage mainly releases the secondary stress generated by the high-temperature shaping on the valve body casting. Then, the casting is cooled to room temperature with the furnace. The counterweight, bottom support lower mold, inner cavity limiting support core mold and pressure-bearing correction upper mold are removed. After 3D scanning inspection, the bottom dimension accuracy of the intermediate flange of the obtained TA1 pure titanium valve body casting meets the target requirements.

[0057] Example 3

[0058] This embodiment provides a vacuum high-temperature creep correction method for TA2 pure titanium pump body castings, which specifically includes the following steps:

[0059] Step 1: Perform a 3D scan on the deformed TA2 pure titanium pump body casting, and determine the deformed part of the pump body casting as the pump body flange connection part based on the scan results. The radial deformation is 3mm, and the wall thickness of the flange connection part is 15mm.

[0060] Step 2: Based on the flange connection structure and deformation of the TA2 pure titanium pump body casting, fabricate a matching calibration fixture, and assemble the calibration fixture onto the TA2 pure titanium pump body casting as required. The material and performance of this calibration fixture are the same as in Example 1, and will not be repeated here.

[0061] Specifically, the calibration fixture includes a bottom support lower mold, a pressure-bearing calibration upper mold, and a counterweight. The bottom support lower mold is used to support the bottom of the TA2 pure titanium pump body casting and the flange connection, and is required to be completely in contact with the bottom of the flange connection. The pressure-bearing calibration upper mold is placed on top of the flange connection of the TA2 pure titanium pump body casting, and is required to be completely in contact with the top of the flange connection, so as to facilitate the normal transmission of pressure during calibration and not damage the casting. The counterweight is set at the upper end of the pressure-bearing calibration upper mold to apply pressure to the flange connection.

[0062] It should be noted that, since the flange hole diameter of the flange connection is relatively large, this part is prone to deformation when the casting is heated as a whole. Therefore, an inner cavity limiting support core mold can be set in the flange hole according to the actual situation. In addition, in order to ensure the stability of the pressure-bearing correction upper mold, pads are set on both sides of its lower end for support.

[0063] During assembly, such as Figure 4 As shown; the bottom of the TA2 pure titanium pump body casting and the flange connection is placed on the bottom support lower mold, and the inner cavity limiting support core mold is embedded in the flange hole for support. The pressure-bearing correction upper mold is placed on the top of the flange connection of the TA2 pure titanium pump body casting, and a 30kg counterweight is placed on the upper end of the pressure-bearing correction upper mold.

[0064] Step 3: Place the assembled calibration fixture and the TA2 pure titanium pump body casting into a vacuum heating furnace with a vacuum degree ≤5Pa, and perform high-temperature creep calibration using a segmented heating method.

[0065] The specific process of segmented heating is as follows: First, the vacuum heating furnace is heated to 400℃ and held for 140 minutes. This stage mainly removes water vapor and impurities from the high-purity graphite shaping tooling to prevent thermal stress cracking of the casting caused by rapid heating. Then, the temperature is raised to 650℃ and held for 100 minutes. This stage mainly releases the residual casting stress of the pump body casting and reduces the temperature difference between the inside and outside of the casting. Finally, the temperature is raised to 910℃ and held for 2 hours. In this stage, the pump body flange connection undergoes creep deformation under the action of high temperature and counterweight. Relying on the constraints of the bottom support lower mold, the inner cavity limit support core mold, the pressure-bearing correction upper mold and counterweight, the pump body casting finally achieves the required shape and size.

[0066] Step 4: After the calibration is completed, the calibration fixture and the TA2 pure titanium pump body casting are cooled to room temperature by segmented cooling, and the calibration fixture is removed to obtain the TA2 pure titanium pump body casting with qualified flange connection dimensions.

[0067] The specific process of segmented cooling is as follows:

[0068] First, the vacuum heating furnace is cooled to 560℃ and held for 25 minutes. This stage mainly releases the secondary stress generated by the high-temperature shaping on the pump body casting. Then, the casting is cooled to room temperature with the furnace, and the counterweight, bottom support lower mold, inner cavity limiting support core mold, and pressure-bearing correction upper mold are removed. Figure 5 As shown, the dimensional accuracy of the flange connection of the TA2 pure titanium pump body casting meets the target requirements after 3D scanning inspection.

[0069] Example 4

[0070] This embodiment provides a vacuum high-temperature creep correction method for TC4 titanium alloy cylindrical castings, which specifically includes the following steps:

[0071] Step 1: Perform a three-dimensional scan on the deformed TC4 titanium alloy cylindrical casting, and determine the deformed parts of the cylindrical casting as the two ends and the middle of the cylindrical casting based on the scan results. The radial deformation is 3mm, and the wall thickness of the cylindrical casting is 16mm.

[0072] Step 2: Fabricate a suitable calibration fixture based on the structure and deformation of the TC4 titanium alloy cylindrical casting, and assemble the calibration fixture onto the TC4 titanium alloy cylindrical casting as required. The material and performance of this calibration fixture are the same as in Example 1, and will not be repeated here.

[0073] Specifically, the calibration fixture includes a bottom support lower mold, an inner cavity limiting support core mold, a pressure-bearing correction upper mold, and a counterweight (not shown in the figure). Since the casting is deformed at both ends and in the middle, the three parts of the calibration fixture are integrally molded for ease of fabrication. The bottom support lower mold is used to support the bottom of the TC4 titanium alloy cylindrical casting and is required to be completely flush with the bottom of the casting. The inner cavity limiting support core mold is used to support the hollow cavity of the TC4 titanium alloy cylindrical casting and is required to allow for a 0.5mm springback allowance. The pressure-bearing correction upper mold is placed on top of the TC4 titanium alloy cylindrical casting and is required to be completely flush with the top of the casting, thus facilitating normal pressure transmission during calibration without damaging the casting. The counterweight is located at the upper end of the pressure-bearing correction upper mold to apply pressure to the cylindrical casting.

[0074] During assembly, such as Figure 6 As shown; the bottom of the TC4 titanium alloy cylindrical casting is placed on the bottom support lower mold, and the inner cavity limiting support core mold is embedded in the hollow cavity of the TC4 titanium alloy cylindrical casting for support. The pressure-bearing correction upper mold is placed on the top of the TC4 titanium alloy cylindrical casting, and a 35kg counterweight is placed on the upper end of the pressure-bearing correction upper mold.

[0075] Step 3: Place the assembled calibration fixture and the TC4 titanium alloy cylindrical casting into a vacuum heating furnace with a vacuum degree ≤5Pa, and perform high-temperature creep calibration using a segmented heating method.

[0076] The specific process of segmented heating is as follows: First, the vacuum heating furnace is heated to 350℃ and held for 100 minutes. This stage mainly removes water vapor and impurities from the high-purity graphite shaping tooling to prevent rapid heating from causing thermal stress cracking in the casting. Then, the temperature is raised to 600℃ and held for 80 minutes. This stage mainly releases the residual casting stress of the cylindrical casting slowly and reduces the temperature difference between the inside and outside of the casting. Finally, the temperature is raised to 920℃ and held for 2 hours. In this stage, under the action of high temperature and counterweight, the hole walls at both ends and the middle of the cylindrical casting undergo creep deformation. Relying on the constraints of the bottom support lower mold, the inner cavity limit support core mold, the pressure-bearing correction upper mold and counterweight, the cylindrical casting finally achieves the required shape and size.

[0077] Step 4: After the calibration is completed, the calibration fixture and the TC4 titanium alloy cylindrical casting are cooled to room temperature by segmented cooling, and the calibration fixture is removed to obtain the TC4 titanium alloy cylindrical casting with qualified dimensions.

[0078] The specific process of segmented cooling is as follows:

[0079] First, the vacuum heating furnace is cooled to 550℃ and held for 25 minutes. This stage mainly releases the secondary stress generated by the high-temperature shaping on the cylindrical casting. Then, the casting is cooled to room temperature with the furnace, and the counterweight, bottom support lower mold, inner cavity limiting support core mold, and pressure-bearing correction upper mold are removed. Figures 7-8 As shown, after 3D scanning inspection, the dimensional accuracy of both ends and the middle of the obtained TC4 titanium alloy cylindrical casting met the target requirements.

[0080] Example 5

[0081] This embodiment provides a vacuum high-temperature creep correction method for TA15 titanium alloy irregular-shaped castings, which specifically includes the following steps:

[0082] Step 1: Perform a 3D scan on the deformed TA15 titanium alloy irregular casting, and determine the deformed part of the irregular casting as the bottom surface based on the scan results. The horizontal deformation is 1mm, and the thickness of the bottom surface of the irregular casting is 5mm.

[0083] Step 2: Fabricate a suitable alignment fixture based on the structure and deformation of the TA15 titanium alloy shaped casting, and assemble the alignment fixture onto the TA15 titanium alloy shaped casting as required. The material and performance of this alignment fixture are the same as in Example 1, and will not be repeated here.

[0084] Specifically, the calibration fixture includes a bottom support lower mold, an inner cavity limiting support core mold, a pressure-bearing calibration upper mold, and a counterweight. The bottom support lower mold is used to support the bottom of the TA15 titanium alloy irregular casting and is required to be completely in contact with the bottom. The inner cavity limiting support core mold is used to support the inner cavity of the irregular casting and is required to allow for a springback dimension of 0.5mm. The pressure-bearing calibration upper mold is placed on the upper surface of the TA15 titanium alloy irregular casting and is required to be completely in contact with the upper surface, which is conducive to the normal transmission of pressure during calibration and does not damage the casting. The counterweight is set at the upper end of the pressure-bearing calibration upper mold and is used to apply pressure to the bottom surface of the irregular casting.

[0085] During assembly, such as Figure 9 As shown (the pressure-bearing correction upper mold and counterweight are not placed in the figure), the bottom surface of the TA15 titanium alloy special-shaped casting is placed on the bottom support lower mold, and the inner cavity limiting support core mold is placed in the inner cavity of the special-shaped casting for support. The pressure-bearing correction upper mold is placed on the upper end surface of the TA15 titanium alloy special-shaped casting, and a 12kg counterweight is placed on the upper end of the pressure-bearing correction upper mold.

[0086] Step 3: Place the assembled straightening fixture and the TA15 titanium alloy special-shaped casting into a vacuum heating furnace with a vacuum degree ≤5Pa, and perform high-temperature creep straightening by segmented heating.

[0087] The specific process of segmented heating is as follows: First, the vacuum heating furnace is heated to 350℃ and held for 100 minutes. This stage mainly removes water vapor and impurities from the high-purity graphite shaping tooling to prevent rapid heating from causing thermal stress cracking in the casting. Then, the temperature is raised to 600℃ and held for 80 minutes. This stage mainly releases the residual casting stress of the irregular casting slowly and reduces the temperature difference between the inside and outside of the casting. Finally, the temperature is raised to 930℃ and held for 3 hours. In this stage, under the action of high temperature and counterweight, the bottom surface of the irregular casting undergoes creep deformation. Relying on the bottom support lower mold, the inner cavity limit support core mold, the pressure-bearing correction upper mold and the constraint of counterweight, the irregular casting finally achieves the required shape and size.

[0088] Step 4: After the calibration is completed, the calibration fixture and the TA15 titanium alloy special-shaped casting are cooled to room temperature by segmented cooling, and the calibration fixture is removed to obtain the TA15 titanium alloy special-shaped casting with qualified bottom dimensions.

[0089] The specific process of segmented cooling is as follows:

[0090] First, the vacuum heating furnace is cooled to 550℃ and held for 25 minutes. This stage mainly releases the secondary stress generated by the high-temperature shaping on the irregular casting. Then, the casting is cooled to room temperature with the furnace. The counterweight, bottom support lower mold, inner cavity limiting support core mold and pressure-bearing correction upper mold are removed. After 3D scanning inspection, the bottom surface dimension accuracy of the obtained TA15 titanium alloy irregular casting meets the target requirements.

[0091] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for vacuum high-temperature creep correction of castings, characterized in that, include: Step 1: Perform a 3D scan on the deformed casting and determine the deformed parts and the amount of deformation based on the scan results; Step 2: Fabricate a matching straightening fixture according to the deformed part and the amount of deformation of the casting, and assemble the straightening fixture onto the casting; Step 3: Place the assembled calibration fixture and casting into a vacuum heating furnace with a vacuum degree ≤5Pa, and perform high-temperature creep calibration using a segmented heating method; Step 4: After the calibration is completed, the calibration fixture and the casting are cooled to room temperature by segmented cooling. The calibration fixture is then removed to obtain a casting with qualified dimensions.

2. The vacuum high-temperature creep correction method for castings according to claim 1, characterized in that, In step 2, the calibration fixture includes a bottom support lower mold, a pressure-bearing correction upper mold, and a counterweight. During assembly, the casting is placed on the bottom support lower mold and its deformed part is completely fitted with the bottom support lower mold. The pressure-bearing correction upper mold is placed on top of the deformed part of the casting and is completely fitted with the top. A counterweight adapted to the deformation amount of the casting is placed on the upper end of the pressure-bearing correction upper mold.

3. The vacuum high-temperature creep correction method for castings according to claim 2, characterized in that, The calibration fixture also includes an inner cavity limiting support core mold. When the deformed part has a cavity, the inner cavity limiting support core mold is placed in the cavity.

4. The vacuum high-temperature creep correction method for castings according to claim 3, characterized in that, When the deformation of the casting part is 1~2mm, the counterweight weight is 10~25kg; when the deformation of the casting part is 3~4mm, the counterweight weight is 25~50kg; when the deformation of the casting part is 4~6mm, the counterweight weight is 50~100kg.

5. The vacuum high-temperature creep correction method for castings according to claim 1, characterized in that, In step 3, the segmented heating process is as follows: first, the vacuum heating furnace is heated to 350~400℃ and held for 100~140 minutes; then the temperature is raised to 600~700℃ and held for 80~100 minutes; finally, the temperature is raised to 900~950℃ and held for 2~4 hours.

6. The vacuum high-temperature creep correction method for castings according to claim 4, characterized in that, In step 4, the segmented cooling process is as follows: first, the vacuum heating furnace is cooled to 550~650℃ and kept at that temperature for 25~35 minutes; then, it is cooled to room temperature along with the furnace.

7. The vacuum high-temperature creep correction method for castings according to claim 1, characterized in that, The calibration tooling is made of high-purity graphite.

8. The vacuum high-temperature creep correction method for castings according to claim 1, characterized in that, The castings are titanium and titanium alloys, and zirconium alloy castings.

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