A high-purity and high-performance aluminum alloy seamless pipe for nuclear industry and its preparation method

Abstract

The invention discloses a high-purity and high-performance aluminum alloy seamless pipe for nuclear industry, wherein the content of each element in the aluminum alloy ingot used by the invention is measured by mass percentage, and comprises the following components: Si 0.4%-0.8%, Cu 0.15%-0.4%, Mg 0.8%-1.2%, Cr 0.15%-0.35%, Fe≤0.5%, Zn≤0.04%, Ti≤0.04%, Mn≤0.04%, Ga≤0.04%, Li≤0.0006%, Cd≤0.001%, B≤0.001%, Co≤0.001%, single impurity≤0.02%, total impurity≤0.15%, total content of U and Th≤0.0002%, and the balance is aluminum. The invention also discloses a manufacturing method of the high-purity and high-performance aluminum alloy seamless pipe for nuclear industry. The aluminum alloy seamless pipe produced by the present invention has extremely low contents of Li, Cd, B, Co and radioactive U and Th elements, and has extremely small influence of atoms on nuclear fuel in the reactor. The deformed structure is uniform, the strength and elongation are medium, the wall thickness of the pipe is uniform, and the eccentricity does not exceed 5%. The inner surface of the pipe is smooth without defects such as peeling and scratching, and the mechanical properties are excellent, so the pipe is suitable for use in nuclear industry reactor fuel assemblies.

Description

Technical Field

[0001] The invention relates to the technical field of metal manufacturing, and in particular to a method for preparing a high-purity and high-performance aluminum alloy seamless pipe for nuclear industry. Background Art

[0002] Aluminum alloy materials are mainly composed of aluminum, magnesium, manganese, silicon and other elements, and are manufactured through a special seamless pipe production process. In industrial production, aluminum alloy seamless pipes are widely used in various fields, such as aerospace, shipbuilding, automobiles, petrochemicals, construction, etc. Aluminum alloy is an alloy material composed of aluminum and other metal or non-metal elements, with the following advantages: 1. Lightweight and high strength: Aluminum alloy has a lower density and is lighter than ordinary steel, but its strength is higher than many steels. 2. Corrosion resistance: A layer of oxide film can be formed on the surface of aluminum alloy, which can effectively prevent aluminum alloy from contacting with corrosive media such as oxygen and moisture in the environment, thereby improving the corrosion resistance of aluminum alloy. 3. Good thermal conductivity: Aluminum alloy has excellent thermal conductivity and can quickly transfer heat, so it has great application in the manufacture of radiators. 4. Good machinability: Aluminum alloy seamless pipes can be processed by various processing techniques, such as cold drawing, hot rolling, forging, etc., which can meet the requirements of different fields for materials. In short, as a high-performance metal material, aluminum alloy seamless pipes have broad application prospects in industrial production and scientific research technology.

[0003] Aluminum alloy materials also have disadvantages: 1. Not resistant to high temperatures: Aluminum alloy has a low melting point and is easily deformed after heating. In high temperature environments, the strength and hardness of aluminum alloys will decrease. 2. Easy to wear: The hardness of aluminum alloys is relatively low and they are easily scratched or worn. 3. Relatively poor rigidity: The rigidity of aluminum alloys is not as good as that of metal materials such as steel, so it may not be appropriate to use aluminum alloys in situations where high strength and rigidity are required. In general, aluminum alloys have the advantages of light weight, high strength, and corrosion resistance, but they are easy to deform in high temperature environments and have relatively poor rigidity, so they need to be selected according to specific usage scenarios.

[0004] With the vigorous development of the nuclear industry, the demand for aluminum alloy seamless pipes for the nuclear industry is also increasing. Aluminum alloy seamless pipes used for low and medium temperature water-cooled nuclear reactor fuel assemblies require a small absorption cross section of thermal neutrons, good resistance to dynamic water corrosion, high plasticity and easy forming. Therefore, they have been widely used in water-cooled nuclear reactors. In the specific manufacturing and processing, it is required to strictly control the harmful and impurity elements of the pipe, have medium strength, good plasticity, smooth and clean inner wall, and good welding performance. Therefore, in the specific manufacturing, the composition of the elements in the aluminum alloy pipe, the amount of each element, and the specific processing conditions will affect the performance of the aluminum alloy seamless pipe. How to adjust and optimize the element composition and ratio of aluminum alloy, as well as the manufacturing process of aluminum alloy seamless pipes becomes the key. Summary of the invention

[0005] The technical problem to be solved by the present invention is: in view of the shortcomings of the prior art, a high-purity and high-performance aluminum alloy seamless pipe of T6061 T6 series specifications for nuclear industry and a preparation method thereof are provided. The present invention effectively adjusts and optimizes the dosage of each element in the aluminum alloy ingot and the process conditions during the preparation of the pipe without using grain refining elements (such as titanium, boron, etc.) that are harmful to the application of pipes for nuclear industry. The obtained aluminum alloy seamless pipe has medium strength and elongation, uniform wall thickness, eccentricity not exceeding 5%, smooth inner and outer surfaces, and no defects such as peeling, abrasions, wrinkles, overlaps, cracks, corrosion spots, etc.

[0006] In order to solve the above technical problems, the technical solution of the present invention is:

[0007] A high-purity and high-performance aluminum alloy seamless pipe for nuclear industry, wherein the content of each element in the aluminum alloy ingot used in the preparation of the aluminum alloy seamless pipe is measured by mass percentage and comprises the following components:

[0008] Si 0.4%-0.8%, Cu 0.15%-0.4%, Mg0.8%-1.2%, Cr0.15%-0.35%, Fe≤0.5%, Zn≤0.04%, Ti≤0.04%, Mn≤0.04%, Ga≤0.04%, Li≤0.0006%, Cd≤0.001%, B≤0.001%, Co≤0.001%, single impurity≤0.02%, total impurities≤0.15%, the total content of U and Th≤0.0002%, the balance is aluminum.

[0009] In order to better understand the above technical problems, the present invention also provides the following technical solutions:

[0010] A method for preparing a high-purity and high-performance aluminum alloy seamless pipe for nuclear industry comprises the following steps:

[0011] (1) Smelting: Weigh a certain amount of Al99.996 refined aluminum ingot, 2202 industrial silicon, cathode copper, Mg ingot, RJ-6 refining agent, AlTi3C 0.15As raw materials, first put Al99.996 refined aluminum ingots into a smelting furnace. When the smelting furnace is heated to 750±5℃, add 0.5-0.7% of the total raw material input of 2202 industrial silicon and 0.2-0.3% of the total raw material input of cathode copper, stir manually for 10-20min, and then stir electromagnetically for 20-30min. Add 0.8-1.2% of the total raw material input and 99.95% purity Mg ingots into the smelting furnace, supplemented by mechanical stirring and manual stirring; realize dynamic grain refinement, ensure uniformity of organization, and no dead corners; then use 0.15-0.25% of the total raw material input of RJ-6 refining agent, refine for 20-30min, and then fill the smelting furnace with high-purity argon gas and refine for 30-40min; remove the slag, take samples for analysis, and let it stand. After the sampling and analysis are qualified, the smelting is completed, and the temperature is controlled at 740±5℃ to obtain a smelting material solution;

[0012] (2) Casting: 0.01-0.02% of the total raw material input AlTi3C is added to the smelting material solution in the furnace through a wire feeder. 0.15 , then the smelt solution passes through the online refining device, and then undergoes 30+50PPi double-stage filtration, and slowly flows into the casting plate. The flow rate of the melt is controlled by the inclination of the baffle, so that the melt flow rate of the casting plate crystallizer is controlled at 50%, so as to extend the time of the melt in the degassing box and achieve the best degassing effect; when the height of the smelt solution in the casting plate exceeds the required liquid level height of 5cm, the hydrogen content is detected to ensure that the hydrogen content of the smelt solution is <0.1ml / 100g, and then the car casting is started to obtain an aluminum alloy ingot, and the grain size of the aluminum alloy ingot reaches level 1. The speed of the wire feeder is controlled at 1.5±0.2m / min, and double-strand wire feeding is adopted; the wire refining device adopts argon for online refining and degassing, and the degassing is carried out at an electromagnetic stirring speed of 200-300 rpm, the argon gas source pressure is controlled at 0.3Mpa-0.6Mpa, the argon working pressure is controlled at 0.2Mpa, and the total argon flow rate is controlled at 4.5-5m 3 / h; the starting casting adopts hot top casting to prepare aluminum alloy ingots, the casting speed is 50-70mm / min, and the cooling water flow rate is controlled at 100-130m 3 / h; the diameter of the aluminum alloy ingot is Φ275-277mm; in the casting process, the casting temperature is controlled at 740±5℃; the cooling water temperature is 20-25℃; flow rate: initial 20m 3 / h, normal 100m 3 / h, the interval from the initial flow rate to the normal flow rate is 160±10 seconds; casting speed: starting at 15mm / min, normal at 50mm / min, the interval from the initial flow rate to the normal flow rate is 160±10 seconds;

[0013] (3) Ingot homogenization treatment: Specifically, the aluminum alloy ingot is heated to 535±5° C., kept at this temperature for 12 to 16 hours, and then cooled naturally;

[0014] (4) Car skin: ensure that the single-side car skin volume is ≥ 2mm, the straightness is ≤ 0.5mm, and the depth of the knife mark is ≤ 0.20mm;

[0015] (5) Extrusion: Preheat the aluminum alloy round cast rod with a length of 300-400mm to 400℃-490℃, and extrude it into a seamless pipe with an outer diameter of Φ35-110mm and a wall thickness of 9-12mm in an extruder using a piercing needle with a two-stage connector connection structure; during the extrusion process, a high-temperature and rapid extrusion process is used to prevent the coarse grains on the surface of the pipe. The mold temperature is 450℃-480℃, the temperature of the extrusion barrel is 430-450℃, the extrusion coefficient is 12-50, the extrusion speed is 1m / min-3m / min, and the extrusion residue is 35-40mm; before extruding each batch of pipes, the extruder dual-drive structure mode two-way cleaning mechanism is used to clean the pressure residue formed on the inner wall of the extrusion barrel during the extrusion process in the radial and axial directions to ensure the surface quality of the pipe, and it is naturally cooled after extrusion.

[0016] (6) Solution quenching and aging treatment: The extruded aluminum alloy pipe is quenched at a temperature of 525℃-530℃ and a holding time of 40-90 minutes; then the rapid quenching furnace lifting system is used for quenching, and the quenching water entry time is less than 12 seconds. Finally, straightening and aging treatments are performed in sequence, at a temperature of 170℃-180℃ and a holding time of 8-12 hours; finally, the obtained seamless aluminum alloy pipe is cut into a certain length according to the needs, and packaged after inspection to obtain a high-purity and high-performance aluminum alloy seamless pipe.

[0017] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0018] The composition of the high-purity aluminum alloy ingot used in the present invention includes the main components of 6061 aluminum alloy national standard Si, Cu, Mg, Cr, and also includes inevitable impurities Fe, Zn, Ti, Mn, Ga, Li, Cd, B, Co, and the balance is Al. The silicon element has a great influence on the performance of aluminum alloy seamless pipes. Adding an appropriate amount of silicon element can increase the solid solution phase in the alloy and form more stable grains, thereby improving the strength; the silicon element has good stability in the aluminum alloy, which can reduce the formation of oxides on the surface of the alloy and inhibit the sensitivity of the alloy surface to the external environment; and the appropriate addition of silicon element can improve the machinability of the aluminum alloy seamless pipe, making it easier to form and process. However, if the amount of silicon element added is too much, it will increase the brittleness of the alloy, thereby reducing the overall performance of the aluminum alloy seamless pipe. Therefore, the addition amount of silicon element in the present invention is controlled to be 0.4%-0.8%.

[0019] The addition of an appropriate amount of copper can improve the tensile strength and yield strength of aluminum alloy seamless pipes. Copper can form solid solution strengthening phases, precipitation hardening phases, etc., and increase the strength of the material by hindering lattice displacement. It can also improve the heat treatment effect of aluminum alloy seamless pipes and promote the precipitation of hardening phases and stable phases, thereby improving the room temperature and high temperature mechanical properties of the alloy; however, excessive addition of copper will increase the difficulty of alloy processing. Therefore, the present invention controls the addition of copper to 0.15%-0.4%. The present invention adds an appropriate amount of magnesium and chromium to the aluminum alloy matrix, which can effectively control the strength and tensile strength of aluminum alloy seamless pipes and improve the plasticity and corrosion resistance of aluminum alloys. The addition of magnesium and chromium in the present invention is controlled to Mg0.8%-1.2% and Cr0.15%-0.35%. Impurity elements such as iron, zinc, titanium, cobalt, manganese, cadmium and gallium should be strictly controlled, and the controlled amounts of impurity elements are: Fe≤0.5%, Zn≤0.04%, Ti≤0.04%, Mn≤0.04%, Ga≤0.04%.

[0020] In high-purity and high-performance aluminum alloy seamless pipes for nuclear industry, the content of lithium (Li), cadmium (Cd), boron (B), cobalt (Co), uranium (U) and thorium (Th) with large neutron absorption cross-sections, or harmful elements and radioactive elements for nuclear industry pipes must be strictly controlled. Lithium has a large charge density and is easy to polarize other molecules or ions. It has strong reducing properties and is easily nitrided in the air. It burns or explodes violently when it comes into contact with water. Cadmium is highly toxic. Air and food contaminated by cadmium are seriously harmful to the human body. Elemental boron is a reducing agent, oxidizing agent, and brominating agent. When combined with aluminum alloy, it is a neutron absorber or shielding material. Cobalt is a radioactive element with extremely strong and highly toxic nuclides. Uranium and thorium are radioactive elements. If exposed for a long time, the body will suffer irreversible damage. The high-purity and high-performance aluminum alloy seamless pipe for nuclear industry provided by the present invention has Li≤0.0006%, Cd≤0.001%, B≤0.001%, Co≤0.001%, and the sum of U and Th content≤0.0002%, and the pipe has high safety.

[0021] The present invention effectively controls the dosage ratio of each element in the high-purity aluminum alloy ingot and the process conditions for preparing the aluminum alloy seamless pipe. The obtained high-purity and high-performance aluminum alloy seamless pipe has uniform deformation structure, medium strength and elongation, uniform pipe wall thickness, and eccentricity not exceeding 5%. The inner surface of the pipe is smooth without defects such as peeling and scratches. The mechanical properties of the obtained pipe are as follows: tensile strength Rm≥260Mpa, specified non-proportional extension strength Rp0.2≥240Mpa, and post-elongation A(%)≥10%, which is suitable for use in nuclear industry reactor fuel assemblies. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0023] Embodiment 1:

[0024] A high-purity and high-performance aluminum alloy seamless pipe for nuclear industry. The components of the pipe are as follows by mass percentage: Si 0.53%, Cu 0.26%, Mg 0.95%, Cr 0.22%, Fe ≤ 0.01%, Zn ≤ 0.001%, Ti 0.028%, Mn 0.0008%, Ga 0.001%, Li < 0.0002%, Cd < 0.0001%, B 0.0004%, Co < 0.001%, single impurity < 0.02%, total impurities < 0.15%, the total content of U and Th ≤ 0.0002%, and the balance is aluminum.

[0025] The specific manufacturing process of the above-mentioned high-purity and high-performance aluminum alloy seamless pipe for nuclear industry is: smelting → casting → ingot homogenization → car body treatment → extrusion → solution quenching → straightening → artificial aging.

[0026] The specific steps include:

[0027] S1: Smelting process: First put Al99.996 refined aluminum ingot into the furnace. When the temperature reaches 752℃ (the temperature of the whole process is controlled at 750±5℃), add 0.54% 2202 industrial silicon and 0.27% cathode copper, stir manually for 15 minutes, then stir electromagnetically for 20 minutes, then add 1.0% Mg ingot with a purity of 99.95% into the furnace, stir repeatedly; then use 0.20% RJ6 refining agent, refine for 25 minutes, and then use high-purity argon gas for 30 minutes. Remove the slag, take samples for analysis, and let it stand. Wait for the samples to pass before casting, and control the temperature at 740±5℃.

[0028] S2: Casting process: 0.015% AlTi3C of the total raw material input is added to the melt in the furnace through a wire feeder 0.15 , the speed of the wire feeder is controlled at 1.60m / min, and double-strand wire feeding is adopted; then the smelting material melt passes through the online refining device, and then undergoes 30+50PPi double-stage filtration, slowly flows into the casting plate, and the melt is refined and degassed online through the degassing device. Argon gas is used for degassing at a stirring speed of 250 rpm, the argon gas source pressure is controlled at 0.5Mpa, the argon working pressure is controlled at 0.2Mpa, and the total argon flow rate is controlled at 5m 3 / h; slowly put the degassed melt into the crystallizer, and control the melt flow through the flow control plug to control the melt flow of the casting tray crystallizer at 50%. When the height of the molten material in the casting tray exceeds the required liquid level by 5cm, perform hydrogen content detection to ensure that the hydrogen content of the molten material solution is <0.1ml / 100g. The temperature of the melt at the start of casting is 740℃, and the temperature during casting is controlled at 740±5℃. The cooling water temperature is 23℃, and the cooling water flow rate is: initial 20m 3 / h, normal 100m 3 / h, with an interval (climbing) time of 160 seconds; casting speed: starting at 15mm / min, normal 50mm / min, with an interval (climbing) time of 155 seconds, to obtain an aluminum alloy ingot, the grain size of which reaches level 1;

[0029] S3: Ingot homogenization: Specifically, the aluminum alloy ingot is heated to 535±5° C., kept at this temperature for 12 hours, and then cooled naturally;

[0030] S4: Car skin treatment: After the high-purity aluminum alloy ingot is cut, the car skin treatment is performed, and the single-side car skin amount is 2.5mm, the straightness is 0.3mm, and the extruded billet with a smooth surface and a knife mark depth of 0.15mm is obtained;

[0031] S5: Extrusion process: The extruded billet prepared as above is subjected to extrusion treatment. During the extrusion treatment, a pipe mold of corresponding specifications is selected, the temperature of the extruded billet is controlled to be 460-470°C, the mold temperature is 450-460°C, the temperature of the extrusion barrel is 430-440°C, the diameter of the extruded seamless pipe is Φ71mm, the wall thickness is 11.5mm, the extrusion coefficient is: 27.8, the extrusion speed is 1.45m / min, the extrusion residue is 38mm, and an extruded pipe with a smooth surface and uniform wall thickness is obtained.

[0032] S6: Solution treatment: The extruded pipe is kept at a temperature of 525-530℃ for 75 minutes, and then quenched using a rapid quenching furnace lifting system. The quenching water entry time is 10 seconds. In order to ensure the quenching cooling speed, 3 sets of movable pulley chain lifting mechanisms are used, and the speed can be increased by 6 times.

[0033] S7: Straightening: The extruded pipe is straightened within 10 hours using an 11-roller vertical straightening machine. The straightness of the straightened pipe is within 1.0 mm / m.

[0034] S8: Artificial aging: The pipe is aged at 170-180℃ for 8 hours. Finally, the obtained seamless aluminum alloy pipe is cut into a certain length according to needs, and packaged after inspection to obtain high-purity and high-performance aluminum alloy seamless pipe.

[0035] The aluminum alloy pipe disclosed in this embodiment was tested for mechanical properties. The results of three tests are shown in Table 1:

[0036] Table 1

[0037]

[0038] Embodiment 2:

[0039] The difference between this embodiment and embodiment 1 is that:

[0040] Ingot homogenization: Specifically, the aluminum alloy ingot is heated to 535±5° C., kept warm for 15 hours, and cooled naturally;

[0041] Car skin treatment: After the high-purity aluminum alloy ingot is cut, the car skin treatment is performed. The single-side car skin amount is 2.1mm, the straightness is 0.45mm, and the extruded billet with a smooth surface and a knife mark depth of 0.12mm is obtained.

[0042] Extrusion process: the extrusion blank prepared as above is subjected to extrusion treatment, and a pipe mold of corresponding specifications is selected during the extrusion treatment, and the temperature of the extrusion blank is controlled to be 470-480°C, the mold temperature is 450-460°C, the temperature of the extrusion barrel is 430-440°C, the diameter of the extruded seamless pipe is Φ82mm, the wall thickness is 9.5mm, the extrusion coefficient is: 26.2, the extrusion speed is 2.0m / min, and the extrusion residue is 40mm, so as to obtain an extruded pipe with a smooth surface and uniform wall thickness;

[0043] Solution treatment: keep the extruded pipe at 525-530℃ for 60 minutes, then use the rapid quenching furnace lifting system for quenching treatment, and the quenching water time is 9 seconds. In order to ensure the quenching cooling speed, 3 sets of movable pulley chain lifting mechanism are used, and the speed can be increased by 6 times;

[0044] Straightening: The extruded pipe is straightened within 7.5 hours using an 11-roller vertical straightening machine. The straightness of the straightened pipe is within 0.9mm / m;

[0045] Artificial aging: The pipe is aged at 170-180℃ for 8.5 hours. Finally, the obtained seamless aluminum alloy pipe is cut into a certain length according to needs, and packaged after inspection to obtain high-purity and high-performance aluminum alloy seamless pipe.

[0046] The other steps and parameters in this embodiment are the same as those in Embodiment 1.

[0047] After testing, the aluminum alloy pipe disclosed in this embodiment was tested for mechanical properties, and the results of three tests are shown in Table 2:

[0048] Table 2

[0049]

[0050] Embodiment 3:

[0051] A high-purity and high-performance aluminum alloy seamless pipe for nuclear industry. The components of the pipe are as follows by mass percentage: Si 0.65%, Cu 0.28%, Mg 1.01%, Cr 0.23%, Fe ≤ 0.01%, Zn ≤ 0.001%, Ti 0.030%, Mn 0.0009%, Ga 0.001%, Li < 0.0002%, Cd < 0.0001%, B 0.0004%, Co < 0.001%, single impurity < 0.02%, total impurities < 0.15%, the total content of U and Th ≤ 0.0002%, and the balance is aluminum.

[0052] The specific manufacturing process of the above-mentioned high-purity and high-performance aluminum alloy seamless pipe for nuclear industry is: smelting → casting → ingot homogenization → car body treatment → extrusion → solution quenching → straightening → artificial aging.

[0053] The specific preparation method comprises the following steps:

[0054] Melting process: First put Al99.996 refined aluminum ingot into the furnace. When the temperature reaches 750℃ (the temperature is controlled at 750±5℃ during the whole process), add 0.66% of the total raw material input of 2202 industrial silicon and 0.29% of the total raw material input of cathode copper, stir manually for 20 minutes, and then stir electromagnetically for 25 minutes. Then add 1.10% of the total raw material input and 99.95% purity Mg ingot into the furnace and stir repeatedly; then use 0.22% of the total raw material input of RJ6 refining agent, refine for 28 minutes, and then use high-purity argon gas for refining for 35 minutes. Remove the slag, take samples for analysis, and let it stand until the samples are qualified before casting. The temperature is controlled at 740±5℃.

[0055] Casting process: 0.020% AlTi3C is added to the melt in the furnace through a wire feeder. 0.15 , the speed of the wire feeder is controlled at 1.55m / min, and double-strand wire feeding is adopted; then the smelting material melt passes through the online refining device, and then undergoes 30+50PPi double-stage filtration, slowly flows into the casting plate, and the melt is refined and degassed online through the degassing device. Argon gas treatment is used for degassing at a stirring speed of 280 rpm, the argon gas source pressure is controlled at 0.5Mpa, the argon working pressure is controlled at 0.2Mpa, and the total argon flow rate is controlled at 4.8m 3 / h; slowly put the degassed melt into the crystallizer, and control the melt flow through the flow control plug to control the melt flow of the casting tray crystallizer at 50%. When the height of the molten material in the casting tray exceeds the required liquid level by 5cm, perform hydrogen content detection to ensure that the hydrogen content of the molten material solution is <0.1ml / 100g. The temperature of the melt at the start of casting is 738℃, the casting temperature is 740±5℃, the cooling water temperature is 25℃, and the cooling water flow rate: initial 20m 3 / h, normal 105m 3 / h, with an interval (climbing) time of 166 seconds; casting speed: starting at 15mm / min, normal at 55mm / min, with an interval (climbing) time of 168 seconds, to obtain an aluminum alloy ingot, the grain size of which reaches level 1.

[0056] Ingot homogenization: Specifically, the aluminum alloy ingot is heated to 535±5° C., kept at this temperature for 14 hours, and then cooled naturally;

[0057] Car skin treatment: After the high-purity aluminum alloy ingot is cut, the car skin treatment is performed. The single-side car skin amount is 2.2mm, the straightness is 0.40mm, and the extruded billet with a smooth surface and a knife mark depth of 0.16mm is obtained.

[0058] Extrusion process: The extruded billet prepared as above is subjected to extrusion treatment. During the extrusion treatment, a pipe mold of corresponding specifications is selected, the temperature of the extruded billet is controlled to be 455-465°C, the mold temperature is 450-460°C, the temperature of the extrusion barrel is 430-450°C, the diameter of the extruded seamless pipe is Φ92mm, the wall thickness is 9.0mm, the extrusion coefficient is: 23.7, the extrusion speed is 2.7m / min, the extrusion residue is 36mm, and an extruded pipe with a smooth surface and uniform wall thickness is obtained.

[0059] Solution treatment: The extruded pipe is kept at a temperature of 525-530℃ for 60 minutes, and then quenched using a rapid quenching furnace lifting system, with a quenching water entry time of 11 seconds. In order to ensure the quenching cooling speed, 3 sets of movable pulley chain lifting mechanisms are used, and the speed can be increased by 6 times.

[0060] Straightening: The extruded pipe is straightened within 9 hours using an 11-roller vertical straightening machine. The straightness of the straightened pipe is within 1mm / m.

[0061] Artificial aging: The pipe is aged at 170-180℃ for 9 hours. Finally, the obtained seamless aluminum alloy pipe is cut into a certain length according to needs, and packaged after inspection to obtain high-purity and high-performance aluminum alloy seamless pipe.

[0062] The aluminum alloy pipe disclosed in this embodiment was tested for mechanical properties. The results of three tests are shown in Table 3:

[0063] Table 3

[0064]

[0065] Embodiment 4:

[0066] The difference between this embodiment and embodiment 3 is that:

[0067] Ingot homogenization: Specifically, the aluminum alloy ingot is heated to 535±5° C., kept at this temperature for 16 hours, and then cooled naturally;

[0068] Car skin treatment: After the high-purity aluminum alloy ingot is cut, the car skin treatment is performed, with a single-side car skin amount of 2.4mm and a straightness of 0.45mm, to obtain an extruded billet with a smooth surface and a knife mark depth of 0.15mm.

[0069] Extrusion process: The extruded billet prepared as above is subjected to extrusion treatment. During the extrusion treatment, a pipe mold of corresponding specifications is selected, the temperature of the extruded billet is controlled to be 440-450°C, the mold temperature is 450-465°C, the temperature of the extrusion barrel is 430-450°C, the diameter of the extruded seamless pipe is Φ102mm, the wall thickness is 10.0mm, the extrusion coefficient is: 19.7, the extrusion speed is 1.3m / min, the extrusion residue is 37mm, and an extruded pipe with a smooth surface and uniform wall thickness is obtained.

[0070] Solution treatment: The extruded pipe is kept at a temperature of 525-530℃ for 75 minutes, and then quenched using a rapid quenching furnace lifting system, with a quenching water entry time of 9 seconds. In order to ensure the quenching cooling speed, 3 sets of movable pulley chain lifting mechanisms are used, and the speed can be increased by 6 times.

[0071] Straightening: The extruded pipe is straightened within 8 hours using an 11-roller vertical straightening machine. The straightness of the straightened pipe is within 1mm / m.

[0072] Artificial aging: The pipe is aged at 170-180℃ for 8 hours. Finally, the obtained seamless aluminum alloy pipe is cut into a certain length according to needs, and packaged after inspection to obtain high-purity and high-performance aluminum alloy seamless pipe.

[0073] The other steps and parameters in this embodiment are the same as those in specific embodiment 3.

[0074] The aluminum alloy pipe disclosed in this embodiment was tested for mechanical properties. The results of three tests are shown in Table 4:

[0075] Table 4

[0076]

[0077] In summary, it can be seen from the test results of Table 1, Table 2, Table 3, and Table 4 that the present invention effectively adjusts the amount of each element in the aluminum alloy and effectively controls the preparation process conditions of the aluminum alloy pipe. The obtained aluminum alloy seamless pipe has uniform deformation structure, medium strength and elongation, uniform pipe wall thickness, and eccentricity not exceeding 5%; the inner surface of the pipe is smooth without defects such as peeling and scratches. The mechanical properties reach: tensile strength Rm ≥ 260Mpa, specified non-proportional extension strength Rp0.2 ≥ 240Mpa, and post-elongation A (%) ≥ 10%, which is suitable for use in nuclear industry reactor fuel assemblies.

[0078] In addition, it should be understood that after reading the contents of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A high-purity and high-performance aluminum alloy seamless pipe for nuclear industry, characterized by: The contents of various elements in the aluminum alloy ingot used in the preparation of the aluminum alloy seamless pipe are expressed in percentage by mass and include the following components: Si 0.4%-0.8%, Cu 0.15%-0.4%, Mg0.8%-1.2%, Cr0.15%-0.35%, Fe≤0.5%, Zn≤0.04%, Ti≤0.04%, Mn≤0.04%, Ga≤0.04%, Li≤0.0006%, Cd≤0.001%, B≤0.001%, Co≤0.001%, single impurity≤0.02%, total impurities≤0.15%, total content of U and Th≤0.0002%, balance is aluminum; The manufacturing process of the high-purity and high-performance aluminum alloy seamless pipe for the nuclear industry is: smelting → casting → ingot homogenization → car skin treatment → extrusion → solid solution quenching → straightening → artificial aging; the artificial aging treatment is: the temperature of the aluminum alloy pipe is 170°C-180°C, and the insulation time is 8-12 hours; the solid solution quenching is: the temperature of the treated aluminum alloy pipe is 525°C-530°C, and the insulation time is 40-90 minutes, and then the rapid quenching furnace lifting system is used for quenching treatment, and the quenching water entry time is <12 seconds.

2. The high-purity and high-performance aluminum alloy seamless pipe for nuclear industry according to claim 1, characterized in that: The smelting process is specifically as follows: weigh a certain amount of Al99.996 refined aluminum ingot, 2202 industrial silicon, cathode copper, Mg ingot, RJ-6 refining agent, AlTi3C 0.15 As raw materials, Al99.996 refined aluminum ingots are first placed in a smelting furnace. When the smelting furnace is heated to 750±5°C, 0.5-0.7% of 2202 industrial silicon and 0.2-0.3% of cathode copper are added to the total raw material input. After manual stirring for 10-20 minutes, electromagnetic stirring is performed for 20-30 minutes. Then, 0.8-1.2% of the total raw material input and 99.95% purity Mg ingots are added to the smelting furnace, assisted by mechanical stirring and manual stirring; then 0.15-0.25% of the total raw material input RJ-6 refining agent is added, refined for 20-30 minutes, and high-purity argon is filled into the smelting furnace and refined for 30-40 minutes. The slag is scraped out, sampled and analyzed, and allowed to stand. After the sampling and analysis are qualified, the smelting is completed, and the temperature is controlled at 740±5°C to obtain a smelting material melt.

3. The high-purity and high-performance aluminum alloy seamless pipe for nuclear industry according to claim 2, characterized in that: The casting process is specifically as follows: adding 0.01-0.02% of AlTi3C4O4 in the total raw material input into the molten material in the furnace through a wire feeder. 0.15 , then the smelt passes through the online refining device, and then undergoes double-stage filtration, and slowly flows into the casting plate. The flow rate of the smelt is controlled by the inclination of the baffle plate, so that the flow rate of the smelt in the casting plate crystallizer is controlled at 50%. When the height of the smelt in the casting plate exceeds the required liquid level by 5 cm, the hydrogen content is detected to ensure that the hydrogen content of the smelt is <0.1 ml / 100 g, and then the casting is started to obtain an aluminum alloy ingot; the speed of the wire feeder is controlled to be 1.5±0.2 m / min, and double-strand wire feeding is adopted; the online refining device adopts argon for online refining and degassing, and the degassing is carried out at an electromagnetic stirring speed of 200-300 rpm, the argon gas source pressure is controlled to be 0.3 MPa-0.6 MPa, the argon working pressure is controlled to be 0.2 MPa, and the total argon flow rate is controlled to be 4.5-5 m 3 / h; the starting casting adopts hot top casting to prepare aluminum alloy ingots, the casting speed is 50-70mm / min, and the cooling water flow rate is controlled at 100-130m 3 / h; the diameter of the aluminum alloy ingot is Φ275-277mm; in the casting process, the casting temperature is controlled at 740±5℃; the cooling water temperature is 20-25℃; flow rate: initial 20m 3 / h, normal 100m 3 / h, the interval time from the initial flow rate to the normal flow rate is 160±10 seconds; casting speed: starting 15mm / min, normal 50mm / min, the interval time from the initial flow rate to the normal flow rate is 160±10 seconds.

4. The high-purity and high-performance aluminum alloy seamless pipe for nuclear industry according to claim 1, characterized in that: The ingot homogenization process is specifically as follows: heating the aluminum alloy ingot to 535±5° C., keeping the temperature for 12 to 16 hours, and then cooling naturally.

5. The high-purity and high-performance aluminum alloy seamless pipe for nuclear industry according to claim 1, characterized in that: When processing car skin, ensure that the single-side car skin volume is ≥2mm, the straightness is ≤0.5mm, and the knife mark depth is ≤0.20mm.

6. The high-purity and high-performance aluminum alloy seamless pipe for nuclear industry according to claim 1, characterized in that: The extrusion process comprises: preheating an aluminum alloy round cast rod with a length of 300-400 mm to 400° C.-490° C., and extruding it into a seamless pipe with an outer diameter of 35-110 mm and a wall thickness of 9-12 mm in an extruder; during the extrusion process, the mold temperature is 450° C.-480° C., the temperature of the extrusion barrel is 430-450° C., the extrusion coefficient is 12-50, the extrusion speed is 1 m / min-3 m / min, the extrusion residue is 35-40 mm, and the aluminum alloy pipe is naturally cooled after extrusion.

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