ODS-FeCrAl alloy thin-wall pipe and preparation method thereof

Abstract

The invention provides an ODS-FeCrAl alloy thin-wall pipe and a preparation method thereof, and relates to the field of metallurgy. The preparation method of the ODS-FeCrAl alloy thin-wall pipe comprises the following steps: mechanically alloying yttrium oxide and FeCrAl alloy powder, and screening to obtain the ODS-FeCrAl alloy powder; and the ODS-FeCrAl alloy powder is sequentially subjected to air exhaust treatment, hot isostatic pressing solidification, double-gradient temperature heat treatment, hot extrusion, post-heat treatment, cold rolling and annealing treatment, and then four-die rotary swaging is conducted to obtain the ODS-FeCrAl alloy thin-wall pipe. The thin-wall pipe is an alloy which has a double-peak grain size and is reinforced by double-size nano oxide particles, so that the strength and the plasticity of the alloy are synchronously improved.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, and particularly relates to an ODS-FeCrAl alloy thin-walled tube and its preparation method. Background Technology

[0002] Due to its sufficiently high thermal stability (creep), excellent strength, and outstanding resistance to radiation damage, ODS-FeCrAl alloy has become a key structural material for fourth-generation mainstream reactor types such as supercritical pressurized water reactors (SCPWs) and sodium-cooled fast reactors (SFRs). However, the nano-oxide particles in ODS-FeCrAl alloys, being hard particles incompatible with matrix deformation, result in poor plastic forming ability of the alloy tubing. Furthermore, due to neutron economy constraints, the thickness of ODS-FeCrAl tubing is typically limited to around 0.4 mm. This further amplifies the difficulty in manufacturing ODS-FeCrAl tubing. Achieving a balance between high strength and high plasticity, as well as defect-free fabrication of thin-walled tubing, has become a major technical challenge for the engineering application of ODS-FeCrAl alloys.

[0003] In view of this, the present invention is hereby proposed. Summary of the Invention

[0004] The purpose of this invention is to provide an ODS-FeCrAl alloy thin-walled tube and its preparation method to solve the above-mentioned problems.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing ODS-FeCrAl alloy thin-walled tubing, comprising: Yttrium oxide and FeCrAl alloy powder were mechanically alloyed under an argon atmosphere and then sieved to obtain ODS-FeCrAl alloy powder. The ODS-FeCrAl alloy powder is subjected to sequential processes including degassing, hot isostatic pressing, dual-gradient temperature heat treatment, hot extrusion, post-heat treatment, cold rolling, and annealing. Then, it is subjected to four-die rotary forging to obtain the ODS-FeCrAl alloy thin-walled tube.

[0006] Preferably, the amount of yttrium oxide used is 0.25wt%-1wt% of the total mass of the yttrium oxide and the FeCrAl alloy powder.

[0007] Preferably, the mechanical alloying includes: Ball milling was performed at a rotation speed of 250-350 r / min and a ball-to-material ratio of (5-15):1 for 35-50 h. Preferably, the ball milling process involves a 10-minute pause after every 20 minutes.

[0008] Preferably, the FeCrAl alloy powder has a particle size of 20-60 μm; And / or, The particle size of the ODS-FeCrAl alloy powder is 20-100 μm.

[0009] Preferably, the temperature of the air extraction process is 200-600℃ and the time is 20-30h.

[0010] Preferably, the temperature of the hot isostatic pressing consolidation is 1000-1300℃, the pressure is 120-180 MPa, and the holding time is 2-4 hours. And / or, The dual-gradient temperature heat treatment includes: After the hot isostatic pressing consolidation is completed, the temperature and pressure are reduced. When the temperature drops to 950-1050℃, it is held for 10-50 minutes; when the temperature drops to 750-850℃, it is held for 30-90 minutes.

[0011] Preferably, the hot extrusion temperature is 900-1100 ℃, and the extrusion ratio is 8-14; And / or, The temperature of the post-heat treatment is 800-1000℃.

[0012] Preferably, the cold rolling speed is 40-60 times / min, the cycle feed is 2-4 mm, the rotation angle is 53-59°, the cross-sectional area deformation per pass is 10-30%, and the number of rolling passes is 5-15. And / or, The annealing temperature is 700-1000℃, and the holding time is 0.5-15h.

[0013] Preferably, the rotary forging is performed after the wall thickness of the rolled tube is less than or equal to 1.5 mm. And / or, The forging temperature is 300-500℃, and the deformation is 15-30%.

[0014] This application also provides an ODS-FeCrAl alloy thin-walled tube, which is prepared using the method described above.

[0015] The beneficial effects of this invention are: This application provides an ODS-FeCrAl alloy thin-walled tube and its preparation method. By combining hot isostatic pressing and gradient temperature heat treatment, the ODS-FeCrAl alloy powder is solidified, achieving a bimodal grain structure and a dispersed distribution of dual-size nano-oxide particles. Specifically, powder densification is achieved at high temperatures, while the size of the nano-oxide particles and the volume fraction of coarse grains are controlled by holding at lower temperatures, simultaneously improving the alloy's strength and ductility. To avoid cold-rolling cracks in thin-walled ODS-FeCrAl alloy tubes, which could lead to manufacturing failure, the Pilger cold rolling process is optimized to medium-temperature rotary forging when the tube wall thickness is below a certain value. This effectively avoids the problem of cracking during cold rolling of thin-walled ODS-FeCrAl alloy tubes. Furthermore, the grain refinement level and uniform deformation characteristics of the ODS-FeCrAl alloy tubes prepared by rotary forging are significantly superior to those of traditional cold rolling. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 Here is an EBSD image of the microstructure of the alloy after the two-stage aging treatment in Example 1; Figure 2 The images show TEM images of the microstructure and the number density statistics of the alloy after the two-stage aging treatment in Example 1. Figure 3 This is a photograph of the tube blank obtained by hot extrusion in Example 1; Figure 4 This is a photograph of the actual surface of the pipe obtained in Example 1; Figure 5 This is a photograph of the actual surface of the pipe obtained in Comparative Example 1; Figure 6 This is a photograph of the actual surface of the pipe obtained in Example 2; Figure 7 This is a photograph of the actual surface of the pipe obtained in Comparative Example 2; Figure 8 This is a photograph of the actual surface of the pipe obtained in Comparative Example 3; Figure 9 This is a photograph of the actual surface of the pipe obtained in Comparative Example 4; Figure 10 This is a photograph of the actual surface of the pipe obtained in Comparative Example 5; Figure 11 This is a photograph of the actual surface of the pipe obtained in Comparative Example 6; Figure 12 This is a photograph of the actual surface of the pipe obtained in Comparative Example 7; Figure 13 EBSD image of the microstructure of the alloy after two-stage aging treatment, Comparative Example 8; Figure 14 TEM images showing the microstructure of the alloy after the two-stage aging treatment in Comparative Example 8; Figure 15 EBSD image of the microstructure of the alloy after two-stage aging treatment, Comparative Example 9; Figure 16 TEM images of the microstructure of the alloy after the two-stage aging treatment in Comparative Example 9; Figure 17 EBSD microstructure of the alloy after two-stage aging treatment, Comparative Example 10; Figure 18 TEM images showing the microstructure of the alloy after two-stage aging treatment, Comparative Example 10; Figure 19 This is a photograph of the actual surface of the pipe obtained in Comparative Example 11; Figure 20 EBSD image of the microstructure of the alloy after single-temperature aging treatment in Comparative Example 12; Figure 21 The surface morphology of the alloy obtained by processing in Comparative Example 13; Figure 22 The surface morphology of the alloy obtained by processing in Comparative Example 14 is shown. Detailed Implementation

[0018] To better illustrate this application, the technical solution provided in this application will first be described in its entirety, as follows: A method for preparing ODS-FeCrAl alloy thin-walled tubing, comprising: Yttrium oxide and FeCrAl alloy powder were mechanically alloyed under an argon atmosphere and then sieved to obtain ODS-FeCrAl alloy powder. The ODS-FeCrAl alloy powder is subjected to sequential processes including degassing, hot isostatic pressing, dual-gradient temperature heat treatment, hot extrusion, post-heat treatment, cold rolling, and annealing. Then, it is subjected to four-die rotary forging to obtain the ODS-FeCrAl alloy thin-walled tube.

[0019] Currently, the production of ODS-FeCrAl alloy pipes begins with the traditional mechanical alloying process to prepare FeCrAl alloy powder containing Y2O3, followed by consolidation through hot isostatic pressing or sintering. ODS-FeCrAl alloys produced using this method contain small-sized (approximately 10 nm), high-density nano-oxide particles, and the alloy grains are refined to submicron size due to the pinning effect of these nano-oxide particles. However, the fine grain size reduces the alloy's work hardening energy and deformation stability, which is detrimental to the rolling of ODS-FeCrAl pipes. Furthermore, the rolling of ODS-FeCrAl pipes still primarily relies on Pilger cold rolling. Due to the poor plastic forming ability of ODS-FeCrAl alloys, it typically requires more than ten rolling passes to achieve the final dimensions, with vacuum stress-relief annealing at approximately 900℃ between each pass to improve the pipe's formability. ODS-FeCrAl alloy pipes produced using traditional methods not only have a long production cycle, but the nano-oxide particles in the alloy are also prone to coarsening during high-temperature annealing, leading to a decline in the pipe's service performance.

[0020] Based on this, this solution is proposed.

[0021] In an optional embodiment, the amount of yttrium oxide used is 0.25wt%-1wt% of the total mass of the yttrium oxide and the FeCrAl alloy powder.

[0022] Optionally, the amount of yttrium oxide can be any value between 0.25wt%, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, 0.5wt%, 0.55wt%, 0.6wt%, 0.65wt%, 0.7wt%, 0.75wt%, 0.8wt%, 0.85wt%, 0.9wt%, 1wt%, or 0.25wt%-1wt% of the total mass of the yttrium oxide and the FeCrAl alloy powder.

[0023] In an optional implementation, the mechanical alloying includes: Ball milling was performed at a rotation speed of 250-350 r / min and a ball-to-material ratio of (5-15):1 for 35-50 h. In one optional implementation, the ball milling process is interrupted by a 10-minute pause every 20 minutes.

[0024] Optionally, the rotation speed can be any value between 250 r / min, 300 r / min, 350 r / min or 250-350 r / min, the ball-to-material ratio can be any value between 5:1, 10:1, 15:1 or (5-15):1, and the time can be any value between 35h, 40h, 45h, 50h or 35-50h.

[0025] In one optional embodiment, the FeCrAl alloy powder has a particle size of 20-60 μm; And / or, The particle size of the ODS-FeCrAl alloy powder is 20-100 μm.

[0026] The addition of Y2O3 was to introduce high-density, dispersed nano-oxide particles into the alloy matrix. To reduce the contamination rate of the alloy powder and improve the sintering density, the ODS-FeCrAl alloy powder prepared by mechanical alloying was mechanically sieved, and alloy powder with a size of 20-100 μm was selected for subsequent hot isostatic pressing.

[0027] Optionally, the particle size of the FeCrAl alloy powder can be any value between 20μm, 30μm, 40μm, 50μm, 60μm or 20-60μm; the particle size of the ODS-FeCrAl alloy powder can be any value between 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm or 20-100μm.

[0028] In one optional embodiment, the temperature of the air extraction process is 200-600°C, and the time is 20-30 hours.

[0029] Optionally, the temperature of the air extraction process can be any value between 200℃, 300℃, 400℃, 500℃, 600℃ or 200-600℃, and the time can be any value between 20h, 25h, 30h or 20-30h.

[0030] In an optional embodiment, the temperature of the hot isostatic pressing consolidation is 1000-1300℃ (which can be any value between 1000℃, 1100℃, 1200℃, 1300℃ or 1000-1300℃), the pressure is 120-180MPa (which can be any value between 120MPa, 130MPa, 140MPa, 150MPa, 160MPa, 170MPa, 180MPa or 120-180MPa), and the heat and pressure holding time is 2-4h (which can be any value between 2h, 3h, 4h or 2-4h).

[0031] In an optional embodiment, the dual-gradient temperature heat treatment includes: after the hot isostatic pressing consolidation is completed, reducing the temperature and pressure; when the temperature is reduced to 950-1050℃ (which can be any value between 950℃, 1000℃, 1050℃ or 950-1050℃), holding at that temperature for 10-50 min (which can be any value between 10 min, 20 min, 30 min, 40 min, 50 min or 10-50 min); when the temperature is reduced to 750-850℃ (which can be any value between 750℃, 800℃, 850℃ or 750-850℃), holding at that temperature for 30-90 min (which can be any value between 30 min, 60 min, 90 min or 30-90 min).

[0032] Hot isostatic pressing (HIP) induces the precipitation of Y-Al-O nano-oxide particles in the alloy, forming dual-size nano-oxide particles in the alloy.

[0033] In one optional embodiment, the hot extrusion temperature is 900-1100 ℃ and the extrusion ratio is 8-14; And / or, The temperature of the post-heat treatment is 800-1000℃.

[0034] Optionally, the hot extrusion temperature can be any value between 900℃, 1000℃, 1100℃ or 900-1100℃, and the extrusion ratio can be any value between 8, 9, 10, 11, 12, 13, 14 or 8-14; the post-heat treatment temperature can be any value between 800℃, 900℃, 1000℃ or 800-1000℃.

[0035] The ODS-FeCrAl alloy prepared by hot isostatic pressing was machined, and hot extrusion was used to further improve the density of the material and prepare a raw tube blank of a certain size.

[0036] In one optional embodiment, the cold rolling speed is 40-60 times / min (any value between 40, 50, 60, or 40-60 times / min), the cycle feed is 2-4 mm (any value between 2 mm, 3 mm, 4 mm, or 2-4 mm), the rotation angle is 53-59° (any value between 53°, 54°, 55°, 56°, 57°, 58°, 59°, or 53-59°), the cross-sectional area deformation per pass is 10-30% (any value between 10%, 20%, 30%, or 10-30%), and the number of rolling passes is 5-15 (any value between 5, 10, 15, or 5-15). And / or, The annealing temperature is 700-1000℃, and the holding time is 0.5-15h.

[0037] Optionally, the annealing temperature can be any value between 700℃, 800℃, 900℃, 1000℃ or 700-1000℃, and the holding time can be any value between 0.5h, 1h, 5h, 10h, 15h or 0.5-15h.

[0038] In an optional embodiment, the rotary forging is performed after the wall thickness of the rolled tube is less than or equal to 1.5 mm. And / or, The forging temperature is 300-500℃, and the deformation is 15-30%.

[0039] Compared to Pilger cold rolling, dynamic loading at moderate temperatures promotes dynamic recrystallization of the material, preventing cracking caused by dislocation buildup during cold rolling of thin-walled tubes. Furthermore, moderate temperatures release some work hardening, reducing residual stress in the deformed tube, and eliminate the need for additional annealing.

[0040] Optionally, the temperature of the rotary forging can be any value between 300℃, 400℃, 500℃ or 300-500℃, and the deformation amount can be any value between 15%, 20%, 25%, 30% or 15-30%.

[0041] This application also provides an ODS-FeCrAl alloy thin-walled tube, which is prepared using the method described above.

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Example 1 This embodiment provides an ODS-FeCrAl alloy thin-walled tube, the preparation method of which is as follows: (1) Mechanical alloying process: 0.5 wt% Y2O3 is mechanically alloyed with 20-40 μm FeCrAl alloy powder. The ball milling time is 45 h, the rotation speed is 300 r / min, the ball-to-material ratio is 10:1, and the protective atmosphere is high-purity argon gas with a purity greater than 99.99%. To avoid overheating of the powder, there is a 10-min interval after every 20 min of ball milling.

[0044] (2) Hot isostatic pressing process: The ODS-FeCrAl alloy powder was subjected to a vacuum treatment at 400℃ for 24 h, and then the powder was packaged. The hot isostatic pressing temperature was 1150℃, the pressure was 150 MPa, and the holding time was 3 h.

[0045] (3) Dual-gradient temperature heat treatment: To optimize heat treatment efficiency, a dual-gradient heat treatment was immediately implemented after the hot isostatic pressing (HIP) holding stage. The specific process parameters were as follows: the first stage heat treatment was held at 1000℃ for 30 min; followed by the second stage heat treatment at 800℃ for 60 min. Finally, the ODS-FeCrAl alloy material with both high strength and high plasticity was obtained by furnace cooling. At room temperature, its tensile strength was 890.10 MPa, its yield strength was 732.52 MPa, and its elongation was 35.23%. At high temperature (650 ℃), its tensile strength was 227.77 MPa, its yield strength was 209.10 MPa, and its elongation was 88.07%. Figure 1 The image shows the microstructure of the alloy after two-stage aging treatment. After heat treatment, large grains (>5 μm) account for 53% of the alloy matrix. Figure 2 The images show TEM images (a) and number density statistics (b) of the alloy after two-stage aging treatment. The alloy matrix contains both small nanoparticles (6.9 nm and large nanoparticles (15.87 nm), with an overall number density of 2.6 × 10²² / m². 3 .

[0046] (4) Hot extrusion processing: The temperature is 1000 ℃, and the extrusion ratio is 12. The hot-extruded tube blank is heat-treated at 900℃ to obtain an ODS-FeCrAl alloy tube blank with a bimodal grain structure. Actual product as shown... Figure 3 As shown.

[0047] (5) Pilger cold rolling process: A three-roll Pilger cold rolling mill is used in conjunction with intermediate heat treatment for the initial rolling of the tube. The dimensions of the rolls and mandrel are matched according to the outer diameter and deformation of the tube. The rolling speed is 50 times / min, the cycle feed is 2mm, the rotation angle is 57°, the cross-sectional area deformation per pass is 15-25%, and the rolling passes are 10. After each pass of rolling, the alloy tube is vacuum annealed at 900 ℃ for 0.5h. The specifications of the tube after Pilger cold rolling are φ11.95×0.5 mm.

[0048] (5) Medium-temperature rotary forging process: The final thin-walled pipe is prepared by a four-die rotary forging process at 400℃. The pipe is heated to 400℃ in a heating furnace and held for 10 min before rotary forging begins. The pipe is fed into the main rotary forging machine at a speed of 1.5 mm / s, moving forward axially while rotating, and simultaneously the four hammers are applied to the billet at a frequency of 20 Hz. During the entire forging process, the pipe diameter reduction is 0.65 mm, the wall thickness reduction is 0.1 mm, and the deformation is 23.84%. The surface of the processed pipe is as follows: Figure 4 As shown.

[0049] Comparative Example 1 Unlike Example 1, this example uses Pilger cold-rolled tubing with a specification of φ11.95×0.5 mm. The final thin-walled tubing is prepared using a four-die rotary forging process at 400℃. The tubing is heated to 400℃ in a furnace and held for 10 minutes before rotary forging begins. The tubing is fed into the main rotary forging mill at a speed of 3 mm / s, rotating axially while simultaneously being loaded onto the billet by four hammers at a frequency of 20 Hz. During the entire forging process, the tubing diameter reduction is 0.65 mm, the wall thickness reduction is 0.15 mm, and the deformation is 33.05%. The surface of the processed tubing is as shown in the image. Figure 5 As shown.

[0050] Compared with Example 1, this shows that the deformation amount of rotary forging should not be too large.

[0051] Example 2 Unlike Example 1, this example uses Pilger cold-rolled tubing with a specification of φ11.95×0.5 mm. The final thin-walled tubing is prepared using a four-die rotary forging process at 400℃. The tubing is heated to 400℃ in a furnace and held for 10 minutes before rotary forging begins. The tubing is fed into the main rotary forging mill at a speed of 4.5 mm / s, rotating axially while simultaneously being loaded onto the billet by four hammers at a frequency of 20 Hz. During the entire forging process, the tubing diameter reduction is 0.65 mm, the wall thickness reduction is 0.05 mm, and the deformation is 11.71%. The surface of the processed tubing is as shown in the image. Figure 6 As shown.

[0052] Comparative Example 2 Unlike Example 1, this example uses Pilger cold-rolled tubing with a specification of φ11.95×0.5 mm. The final thin-walled tubing is prepared using a four-die rotary forging process at 200℃. The tubing is heated to 200℃ in a furnace and held for 10 minutes before rotary forging begins. The tubing is fed into the main rotary forging mill at a speed of 1.5 mm / s, rotating axially while simultaneously being loaded onto the billet by four hammers at a frequency of 20 Hz. During the entire forging process, the tubing diameter reduction is 0.65 mm, the wall thickness reduction is 0.05 mm, and the deformation is 11.07%. The surface of the processed tubing is as shown in the image. Figure 7 As shown.

[0053] Comparative Example 3 Unlike Example 1, this example uses Pilger cold-rolled tubing with a specification of φ11.95×0.5 mm. The final thin-walled tubing is prepared using a four-die rotary forging process at 200℃. The tubing is heated to 200℃ in a furnace and held for 10 minutes before rotary forging begins. The tubing is fed into the main rotary forging mill at a speed of 3 mm / s, rotating axially while simultaneously being loaded onto the billet by four hammers at a frequency of 20 Hz. During the entire forging process, the tubing diameter reduction is 0.65 mm, the wall thickness reduction is 0.1 mm, and the deformation is 23.84%. The surface of the processed tubing is as shown in the image. Figure 8 As shown.

[0054] Comparative Example 4 Unlike Example 1, this example uses Pilger cold-rolled tubing with a specification of φ11.95×0.5 mm. The final thin-walled tubing is prepared using a four-die rotary forging process at 200℃. The tubing is heated to 200℃ in a furnace and held for 10 minutes before rotary forging begins. The tubing is fed into the main rotary forging mill at a speed of 4.5 mm / s, rotating axially while simultaneously being loaded onto the billet by four hammers at a frequency of 20 Hz. During the entire forging process, the tubing diameter reduction is 0.65 mm, the wall thickness reduction is 0.15 mm, and the deformation is 33.05%. The surface of the processed tubing is as shown in the image. Figure 9 As shown.

[0055] Comparative Examples 2, 3, and 4 show that if the forging temperature is too low, qualified products cannot be obtained.

[0056] Comparative Example 5 Unlike Example 1, this example uses Pilger cold-rolled tubing with a specification of φ11.95×0.5 mm. The final thin-walled tubing is prepared using a four-die rotary forging process at 600℃. The tubing is heated to 600℃ in a furnace and held for 10 minutes before rotary forging begins. The tubing is fed into the main rotary forging mill at a speed of 1.5 mm / s, rotating axially while simultaneously being loaded onto the billet by four hammers at a frequency of 20 Hz. During the entire forging process, the tubing diameter reduction is 0.65 mm, the wall thickness reduction is 0.15 mm, and the deformation is 33.05%. The surface of the processed tubing is as shown in the image. Figure 10 As shown.

[0057] Comparative Example 6 Unlike Example 1, this example uses Pilger cold-rolled tubing with a specification of φ11.95×0.5 mm. The final thin-walled tubing is prepared using a four-die rotary forging process at 600℃. The tubing is heated to 600℃ in a furnace and held for 10 minutes before rotary forging begins. The tubing is fed into the main rotary forging mill at a speed of 3 mm / s, rotating axially while simultaneously being loaded onto the billet by four hammers at a frequency of 20 Hz. During the entire forging process, the tubing diameter reduction is 0.65 mm, the wall thickness reduction is 0.05 mm, and the deformation is 11.71%. The surface of the processed tubing is as shown in the image. Figure 11 As shown.

[0058] Comparative Example 7 Unlike Example 1, this example uses Pilger cold-rolled tubing with a specification of φ11.95×0.5 mm. The final thin-walled tubing is prepared using a four-die rotary forging process at 600℃. The tubing is heated to 600℃ in a furnace and held for 10 minutes before rotary forging begins. The tubing is fed into the main rotary forging mill at a speed of 4.5 mm / s, rotating axially while simultaneously being loaded onto the billet by four hammers at a frequency of 20 Hz. During the entire forging process, the tubing diameter reduction is 0.65 mm, the wall thickness reduction is 0.1 mm, and the deformation is 23.84%. The surface of the processed tubing is as shown in the image. Figure 12 As shown.

[0059] Comparative Examples 5, 6, and 7 show that even with excessively high forging temperatures, qualified products cannot be obtained.

[0060] Comparative Example 8 (1) Mechanical alloying process: 0.25 wt% Y2O3 and 20-40 μm FeCrAl alloy powder were mechanically alloyed. The ball milling time was 45 h, the rotation speed was 300 r / min, the ball-to-material ratio was 10:1, and the protective atmosphere was high-purity argon gas with a purity greater than 99.99%. In order to avoid overheating of the powder, the ball milling was interrupted for 10 min after every 20 min.

[0061] (2) Hot isostatic pressing process: The ODS-FeCrAl alloy powder was subjected to a vacuum treatment at 400℃ for 24 h, and then the powder was packaged. The hot isostatic pressing temperature was 1150 ℃, the pressure was 150 MPa, and the holding time was 3 h.

[0062] (3) Dual-gradient temperature heat treatment: To optimize heat treatment efficiency, a dual-gradient heat treatment was immediately implemented after the hot isostatic pressing (HIP) holding stage. The specific process parameters were as follows: the first stage heat treatment was held at 1000 ℃ for 30 min; followed by the second stage heat treatment at 800 ℃ for 60 min. Finally, the ODS-FeCrAl alloy material with both high strength and high plasticity was obtained by furnace cooling. At room temperature, its tensile strength was 840.77 MPa, its yield strength was 713.49 MPa, and its elongation was 29.24%. At high temperature (650 ℃), its tensile strength was 172.23 MPa, its yield strength was 130.20 MPa, and its elongation was 74.45%. Figure 13 The image shows the microstructure of the alloy after two-stage aging treatment. After heat treatment, large grains (>5 μm) account for 72% of the alloy matrix. Figure 14 The image shows a TEM image of the microstructure of the alloy after two-stage aging treatment. After heat treatment, the number of nano-oxide particles in the alloy matrix is ​​3.91 × 10²² m. -3 Compared to the 0.5 wt% Y2O3 alloy, this alloy has lower high-temperature strength, which does not meet the requirements for subsequent pipe manufacturing.

[0063] Comparative Example 9 (1) Mechanical alloying process: 0.75 wt% Y2O3 and 20-40 μm FeCrAl alloy powder were mechanically alloyed. The ball milling time was 45 h, the rotation speed was 300 r / min, the ball-to-material ratio was 10:1, and the protective atmosphere was high-purity argon gas with a purity greater than 99.99%. In order to avoid overheating of the powder, the ball milling was interrupted for 10 min after every 20 min.

[0064] (2) Hot isostatic pressing process: The ODS-FeCrAl alloy powder was subjected to a vacuum treatment at 400℃ for 24 h, and then the powder was packaged. The hot isostatic pressing temperature was 1150 ℃, the pressure was 150 MPa, and the holding time was 3 h.

[0065] (3) Dual-gradient temperature heat treatment: To optimize heat treatment efficiency, a dual-gradient heat treatment was immediately implemented after the hot isostatic pressing (HIP) holding stage. The specific process parameters were as follows: the first stage heat treatment was held at 1000 ℃ for 30 min; followed by the second stage heat treatment at 800 ℃ for 60 min. Finally, the ODS-FeCrAl alloy material with both high strength and high plasticity was obtained by furnace cooling. At room temperature, its tensile strength was 882.41 MPa, its yield strength was 722.03 MPa, and its elongation was 29.46%. At high temperature (650 ℃), its tensile strength was 212.10 MPa, its yield strength was 203.80 MPa, and its elongation was 51.99%. Figure 15 The image shows the microstructure of the alloy after two-stage aging treatment. After heat treatment, large grains (>5 μm) account for 36% of the alloy matrix. Figure 16 The image shows a TEM image of the microstructure of the alloy after two-stage aging treatment. After heat treatment, the number of nano-oxide particles in the alloy matrix is ​​2.23 × 10²² m. -3 The alloy exhibits low strength at high temperatures, which does not meet the requirements for subsequent pipe manufacturing. Furthermore, the number of nanoparticles, low-temperature strength, high-temperature strength, and elongation of this alloy are lower than those of 0.5 wt% Y₂O₃, which also fails to meet the requirements for subsequent pipe manufacturing.

[0066] Comparative Example 10 (1) Mechanical alloying process: 1.0 wt% Y2O3 and 20-40 μm FeCrAl alloy powder are mechanically alloyed. The ball milling time is 45 h, the rotation speed is 300 r / min, the ball-to-material ratio is 10:1, and the protective atmosphere is high-purity argon with a purity greater than 99.99%. To avoid overheating of the powder, there is a 10-min interval after every 20 min of ball milling.

[0067] (2) Hot isostatic pressing process: The ODS-FeCrAl alloy powder was subjected to a vacuum treatment at 400℃ for 24 h, and then the powder was packaged. The hot isostatic pressing temperature was 1150 ℃, the pressure was 150 MPa, and the holding time was 3 h.

[0068] (3) Dual-gradient temperature heat treatment: To optimize heat treatment efficiency, a dual-gradient heat treatment was immediately implemented after the hot isostatic pressing (HIP) holding stage. The specific process parameters were as follows: the first stage heat treatment was held at 1000 ℃ for 30 min; followed by the second stage heat treatment at 800 ℃ for 60 min. Finally, the ODS-FeCrAl alloy material with both high strength and high plasticity was obtained by furnace cooling. At room temperature, its tensile strength was 904.3 MPa, its yield strength was 735.73 MPa, and its elongation was 27.01%. At high temperature (650 ℃), its tensile strength was 225.47 MPa, its yield strength was 216.92 MPa, and its elongation was 54.67%. Figure 17 The image shows the microstructure of the alloy after two-stage aging treatment. After heat treatment, large grains (>5 μm) account for 36% of the alloy matrix. Figure 18 The image shows a TEM image of the microstructure of the alloy after two-stage aging treatment. After heat treatment, the number of nano-oxide particles in the alloy matrix is ​​1.68 × 10²² m. -3 The alloy exhibits low strength at high temperatures, which does not meet the requirements for subsequent pipe manufacturing. While its low-temperature and high-temperature strengths are comparable to 0.5 wt% Y₂O₃, its nanoparticle count and elongation are significantly lower compared to the 0.5 wt% Y₂O₃ alloy.

[0069] Comparative Example 11 This comparative example uses a 0.5 wt% Y₂O₃ alloy tube blank. The tube, after being cold-rolled by Pilger mill, has a specification of φ11.95×0.5 mm. The next rolling pass is performed using a Pilger cold rolling mill. The rolling speed is 50 times / min, the cycle feed is 2 mm, the rotation angle is 57°, and the cold rolling deformation is 15.92%. The surface of the finished tube is as shown. Figure 19 As shown.

[0070] Comparative Example 12 (1) Mechanical alloying process: 0.25 wt% Y2O3 and 20-40 μm FeCrAl alloy powder were mechanically alloyed. The ball milling time was 45 h, the rotation speed was 300 r / min, the ball-to-material ratio was 10:1, and the protective atmosphere was high-purity argon gas with a purity greater than 99.99%. In order to avoid overheating of the powder, the ball milling was interrupted for 10 min after every 20 min.

[0071] (2) Hot isostatic pressing process: The ODS-FeCrAl alloy powder was subjected to a vacuum treatment at 400℃ for 24 h, and then the powder was packaged. The hot isostatic pressing temperature was 1150 ℃, the pressure was 150 MPa, and the holding time was 3 h.

[0072] (3) Single temperature heat treatment: The specific process parameters for heat treatment are: hold at 1000 ℃ for 90 min; obtain ODS-FeCrAl alloy material by furnace cooling. Figure 20 The images show the EBSD microstructure of the alloy after a single-temperature aging treatment. After heat treatment, the grain size within the alloy matrix is ​​significantly larger than 5 μm, indicating the absence of small-sized grains. This alloy exhibits low plasticity, which does not meet the requirements for subsequent pipe fabrication.

[0073] Comparative Example 13 (1) Mechanical alloying process: 0.25 wt% Y2O3 and 20-40 μm FeCrAl alloy powder were mechanically alloyed. The ball milling time was 45 h, the rotation speed was 300 r / min, the ball-to-material ratio was 10:1, and the protective atmosphere was high-purity argon gas with a purity greater than 99.99%. In order to avoid overheating of the powder, the ball milling was interrupted for 10 min after every 20 min.

[0074] (2) Spark plasma sintering preparation process. ODS-FeCrAl alloy powder was placed in a graphite mold and heated to 1050 ℃ at a heating rate of 100 ℃ / min under a pressure of 40 MPa. The temperature was then held for 5 min and cooled by furnace cooling. The surface morphology of the processed alloy is as follows: Figure 21 As shown, the alloy density decreases significantly. At room temperature, its tensile strength is 762.6 MPa, its yield strength is 705.6 MPa, and its elongation is 5.93%, which does not meet the plasticity requirements for subsequent processing.

[0075] Comparative Example 14 (1) Mechanical alloying process: 0.25 wt% Y2O3 and 20-40 μm FeCrAl alloy powder were mechanically alloyed. The ball milling time was 45 h, the rotation speed was 300 r / min, the ball-to-material ratio was 10:1, and the protective atmosphere was high-purity argon gas with a purity greater than 99.99%. In order to avoid overheating of the powder, the ball milling was interrupted for 10 min after every 20 min.

[0076] (2) Hot isostatic pressing (HIP) process: ODS-FeCrAl alloy powder was subjected to a vacuum treatment at 400℃ for 24 h, and then the powder was encapsulated. The HIP temperature was 1150℃, the pressure was 150 MPa, the holding time was 3 h, and the powder was cooled by furnace cooling. The surface morphology of the processed alloy is as follows: Figure 22 As shown, at room temperature, its tensile strength is 807.6 MPa, its yield strength is 725.6 MPa, and its elongation is 10.31%, which does not meet the plasticity requirements for subsequent processing.

[0077] The tube forming results obtained from the examples and comparative examples were statistically analyzed, and the results are shown in Table 1.

[0078] Table 1. Pipe Rolling Process and Forming Conditions

[0079] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing ODS-FeCrAl alloy thin-walled tubing, characterized in that, include: Yttrium oxide and FeCrAl alloy powder were mechanically alloyed under an argon atmosphere and then sieved to obtain ODS-FeCrAl alloy powder. The ODS-FeCrAl alloy powder is subjected to sequential processes including degassing, hot isostatic pressing, dual-gradient temperature heat treatment, hot extrusion, post-heat treatment, cold rolling, and annealing. Then, it is subjected to four-die rotary forging to obtain the ODS-FeCrAl alloy thin-walled tube.

2. The method for preparing ODS-FeCrAl alloy thin-walled tubing according to claim 1, characterized in that, The amount of yttrium oxide used is 0.25wt%-1wt% of the total mass of the yttrium oxide and the FeCrAl alloy powder.

3. The method for preparing ODS-FeCrAl alloy thin-walled tubing according to claim 1, characterized in that, The mechanical alloying includes: Ball milling was performed at a rotation speed of 250-350 r / min and a ball-to-material ratio of (5-15):1 for 35-50 h. Preferably, the ball milling process involves a 10-minute pause after every 20 minutes.

4. The method for preparing ODS-FeCrAl alloy thin-walled tubing according to claim 1, characterized in that, The FeCrAl alloy powder has a particle size of 20-60 μm; And / or, The particle size of the ODS-FeCrAl alloy powder is 20-100 μm.

5. The method for preparing ODS-FeCrAl alloy thin-walled tubing according to claim 1, characterized in that, The temperature of the air extraction process is 200-600℃, and the time is 20-30h.

6. The method for preparing ODS-FeCrAl alloy thin-walled tubing according to claim 1, characterized in that, The hot isostatic pressing consolidation temperature is 1000-1300℃, the pressure is 120-180 MPa, and the heat and pressure holding time is 2-4h. And / or, The dual-gradient temperature heat treatment includes: After the hot isostatic pressing consolidation is completed, the temperature and pressure are reduced. When the temperature is reduced to 950-1050℃, it is held for 10-50 minutes. When the temperature drops to 750-850 ℃, keep it warm for 30-90 minutes.

7. The method for preparing ODS-FeCrAl alloy thin-walled tubing according to claim 1, characterized in that, The hot extrusion temperature is 900-1100 ℃, and the extrusion ratio is 8-14; And / or, The temperature of the post-heat treatment is 800-1000℃.

8. The method for preparing ODS-FeCrAl alloy thin-walled tubing according to claim 1, characterized in that, The cold rolling speed is 40-60 times / min, the cycle feed is 2-4 mm, the rotation angle is 53-59°, the cross-sectional area deformation per pass is 10-30%, and the number of rolling passes is 5-15. And / or, The annealing temperature is 700-1000℃, and the holding time is 0.5-15h.

9. The method for preparing the ODS-FeCrAl alloy thin-walled tube according to any one of claims 1-8, characterized in that, When the wall thickness of the rolled tube is less than or equal to 1.5 mm, the rotary forging is performed. And / or, The forging temperature is 300-500℃, and the deformation is 15-30%.

10. An ODS-FeCrAl alloy thin-walled pipe, characterized in that, The ODS-FeCrAl alloy thin-walled tube was prepared using the method described in any one of claims 1-9.

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