Preparation Process of High-Precision Copper-Chromium-Zirconium Tube with High Heat Load Bearing Capacity for Fusion Reactors

Abstract

The present invention provides a preparation process for high-precision copper-chromium-zirconium tubes with high heat load bearing capacity for nuclear fusion reactors, which is characterized by including the steps of preparing copper-chromium-zirconium ingots, forging round bars, first heat treatment, machining and drilling, first cold rolling, cleaning and intermediate inspection, second heat treatment, pickling, second cold rolling, vacuum annealing, and inspection. By using the divertor designed and manufactured according to the present invention for nuclear fusion devices, the heat transfer capacity can be significantly improved, the high heat load brought by the plasma of the nuclear fusion device to the divertor can be quickly removed, the technical problems of high surface temperature and excessive temperature gradient under the high heat load condition of the divertor of the fusion device, which cause high thermal stress, can be effectively solved, and the service life of the divertor can be extended; the present invention also has good sealing performance and fracture toughness. In addition to filling the gap in the field of nuclear fusion devices in China, the present invention can also meet the technical requirements for heat exchange in special fields such as deep space exploration and aerospace, and has good application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of non-ferrous metal processing, relates to the divertor of a nuclear fusion device, and particularly relates to a preparation process of a high-precision chromium-zirconium copper cooling tube with high heat load bearing capacity for a divertor. Background Art

[0002] Chromium-zirconium copper alloy materials have the characteristics of good electrical and thermal conductivity, high hardness, wear resistance, explosion resistance, good uprightness, and easy processability of not bending when making thin sheets. They are commonly used as heat-conducting and electrically-conducting components such as electrical contact blocks, electrodes, and molds, and are widely used in the fields of power electronics, welding, etc. In recent years, copper-chromium-zirconium alloy materials for high-speed railways meet the requirements of high tensile strength, high electrical conductivity, and high elongation. In addition to the element ratio, the existing preparation process of copper-chromium-zirconium tubes mainly includes processes such as drawing and rolling, which are difficult to meet the usage requirements of the present invention.

[0003] The existing processing techniques mainly include: 1. Vacuum melting + extrusion process. Due to the inherent structure of the vacuum induction furnace, its production method is only limited to products with periodic operations. The single-piece casting weight or length is limited by the capacity of the crucible, and it is impossible to produce products with a large weight or theoretically infinite length, and the production cost is relatively high. 2. Non-vacuum melting + continuous casting + extrusion process: The disadvantage of this kind of process is that the composition in the alloy is difficult to control, and it is also impossible to produce products with a large weight or theoretically infinite length like the vacuum melting + extrusion process. Since chromium and zirconium have extremely strong affinity with oxygen under high-temperature melting and casting conditions, they are extremely easy to oxidize and volatilize during the melting and casting processes, and the production difficulty is relatively large. Generally, vacuum melting and casting methods need to be adopted to reduce oxidation and volatilization and ensure that the product finally has the required chemical composition. Nevertheless, the tubes made of the existing copper-chromium-zirconium alloy materials have extremely poor resistance to low-temperature and high-temperature shocks and low load bearing capacity, and cannot meet the requirements of the reliability and safe use performance of "high-temperature and high-temperature shocks and super-large load bearing capacity" of a nuclear fusion device (reactor).

[0004] The experimental research of the International Nuclear Fusion Experimental Device (ITER) is one of the major issues in the world today, and one of its core issues is how to design and manufacture a divertor with efficient cooling, which is a global problem that needs to be overcome urgently. In the International Nuclear Fusion Experimental Reactor, the high heat load from the plasma affects the safety and reliability of the fusion reactor divertor. The high heat load on the divertor needs to be discharged, which requires the design of a heat transfer element that can work under high temperature and high pressure conditions of the divertor. The divertor cooling method mainly adopts coolants such as water cooling and helium cooling. From the perspective of coolant flow channels, different cooling structures have different effects on the heat load bearing capacity of the cooling divertor. According to experimental tests, the coolant flow channels of different cooling structures are inseparable from the structural setting of high-precision copper-chromium-zirconium tubes (including straight tubes and coils), and the medium flowing in the tubes takes away the heat to ensure the normal operation of the nuclear fusion device. In addition, the study shows that under asymmetric high temperature and high heat load conditions, for the heat transfer and flow characteristics requirements of a specific supercooled flow boiling flow field, the existing internally smooth chromium-zirconium copper tubes have improved enhanced heat transfer characteristics with the increase of heat flux density and mass flow rate. In addition, with the increase of heat flux density, the onset of nucleate boiling (ONB) and the fully developed boiling point (FDB) appear earlier and earlier. At this time, compared with other material components, the innermost copper-chromium-zirconium tube is damaged first, posing a fatal unsafe factor.

[0005] Based on the above problems, the present invention studies the characteristics of heat conduction area, thermodynamic dryness, cavitation fraction and temperature distribution of smooth tubes under different heat flux density conditions, and studies and trial-produces high-precision and high-performance copper-chromium-zirconium cooling tubes with high heat load bearing capacity, which well meet the stringent requirements of nuclear fusion on copper-chromium-zirconium tube accuracy, thermodynamic properties and eddy current flaw detection, and fills the gap in my country's high-precision and high-performance copper-chromium-zirconium tubes for nuclear fusion devices. Summary of the invention

[0006] In order to overcome the above technical problems, the present invention intends to provide a high-performance and high-precision copper-chromium-zirconium tube preparation process for nuclear fusion reactors with high heat load resistance. The copper-chromium-zirconium tube manufactured by the present invention not only fills the gap in the field of nuclear fusion device technology in my country, but also can meet the technical requirements of heat exchange in deep space exploration and special aerospace environments, and has good application prospects. The specific technical solution of the present invention is:

[0007] The preparation process of a high-precision copper-chromium-zirconium tube with high heat load resistance for a nuclear fusion reactor is characterized by comprising the steps of preparing a copper-chromium-zirconium ingot, forging a round bar, a first heat treatment, machining and drilling, a first cold rolling, cleaning and intermediate inspection, a second heat treatment, pickling, a second cold rolling, vacuum annealing, and inspection, specifically:

[0008] Step 1: Preparation of copper-chromium-zirconium ingots

[0009] a) Stock preparation: Select Cu, Cr, and Zr lump materials with a particle size of 5 - 45 mm. Among them, Cr (wt%): 0.6% - 0.9%; Zr (wt%): 0.07% - 0.15%; the rest is Cu and unavoidable impurities,

[0010] The total content of the impurity elements < 0.15%, where the total of the impurity elements Fe, Al, Si, C, Pb, Nb, Ta < 0.12%, and O < 0.002%;

[0011] b) Vacuum melting:

[0012] Place the copper block at the bottom of the graphite crucible;

[0013] Vacuumize the graphite crucible and heat it electrically to ≥ 1270 °C. Stop vacuumizing when the copper block starts to melt, and fill it with argon gas at 0.01 - 0.02 MPa until the copper block is completely melted;

[0014] After the copper block is completely melted, heat it up to 1920 ± 10 °C, and add chromium blocks batch by batch to avoid inclusions. Wait until the previous batch of chromium blocks is completely melted, then add the next batch of chromium blocks. After the chromium blocks are completely melted, add zirconium blocks batch by batch. Wait until the previous batch of zirconium blocks is completely melted, then add the next batch of zirconium blocks;

[0015] c) After all the zirconium blocks are added, refine the whole furnace for 20 - 25 min, adjust the temperature to 1250 - 1330 °C, pour it into the ingot mold for forming. When it cools to form a copper - chromium - zirconium ingot block, directly transfer it to the forging process while it is still hot;

[0016] Step 2: Forge a round bar: The forging temperature is 920 ± 5 °C. Use a 2500 - ton precision forging machine to forge the ingot block into a round bar with a diameter × length value of Φ160 × L;

[0017] Step 3: Manufacture a tube blank:

[0018] a) Machine - process the tube blank: Machine - process the Φ160 mm × L mm copper - chromium - zirconium round bar into a rough tube blank with an outer diameter × inner diameter × length value of Φ148 (±0.1) mm × Φ38 (±0.1) mm × 450 (±1) mm;

[0019] b) Extrude the tube blank: Heat the rough tube blank to 880 ± 10 °C, keep it warm for 120 min, and extrude it into a medium - sized tube blank with an outer diameter × wall thickness × length value of Φ55 × 9 × L; Immediately cool it in water after extrusion;

[0020] Step 4: First heat treatment: Heat it up. Raise the solution heat treatment temperature of the medium - sized tube blank to 890 ± 5 °C, keep it warm for 60 min, then cool it with flowing water, and transfer it to drilling;

[0021] Step 5, Machining and Drilling: Use a deep-hole drilling machine to process and ream the hole. After machining, use a manual flaw detector to measure the internal surface finish to be ≤1.6, and control the wall thickness deviation to be ≤0.5 mm;

[0022] Step 6, First Cold Rolling: Roll using an LG45 rolling mill. Check whether all parts of the rolling mill are normal, and whether the voltage and current are normal. Roll the medium tube billet after the first heat treatment into a thin tube billet with an outer diameter × wall thickness value of Φ25 mm × 4.2 mm;

[0023] Step 7, Cleaning and Intermediate Inspection: Clean the thin tube billet using kerosene and a degreasing agent; after cleaning, check the inner and outer surfaces, and inspect that the stress is qualified, then transfer to the second heat treatment;

[0024] Step 8, Second Heat Treatment: Solution heat the thin tube billet to 880 ± 1 °C, hold for 60 min, and then cool with cold water;

[0025] Step 9, Pickling: Mix hydrochloric acid and sulfuric acid to wash away the residual oxide scale of copper oxide on the inner and outer surfaces of the tube, making the inner and outer surfaces bright and free of any defects;

[0026] Step 10, Second Cold Rolling;

[0027] Perform cold rolling using an LD40 rolling mill; check that all parts of the rolling mill are normal. Roll into a tube with an outer diameter × wall thickness × length value of Φ15 mm × 1.5 mm × L mm. Take samples from each tube to check the dimensions, straightness, and detect and clean the inner and outer surfaces using flaw detection;

[0028] Step 11, Vacuum Annealing: Perform annealing aging treatment using a vacuum furnace. The vacuum degree is 10 - 2 Pa. Heat to 480 °C, hold for 3 h, cool with the furnace, and carry out protective measures when taking out of the furnace to prevent surface scratches, and ensure that the surface has no oxide scale and no oil stain;

[0029] Step 12, Inspection: Perform flaw detection (ultrasonic and eddy current) on each tube one by one, and store in the warehouse after passing the batch inspection.

[0030] Further improvement lies in that the total content of impurity elements < 0.15%, among which the total content of impurity elements: Fe, Al, Si, C, Pb, Nb, Ta < 0.12%, and O < 0.002%.

[0031] Further improvement lies in that the kerosene in Step 7 uses pure kerosene, and the degreasing agent uses hot water with a concentration of 8% and a temperature of 45 °C.

[0032] Further improvement lies in that for the pickling in Step 9: Use hydrochloric acid and sulfuric acid in a ratio of 1:1 to wash away the residual oxide scale of copper oxide on the inner and outer surfaces, making the inner and outer surfaces bright and free of any defects.

[0033] Further improvements include an extrusion deformation of 92%, an extrusion speed of 50 mm / min, and a wall thickness deviation of the extruded tube blank of less than 1 mm.

[0034] Compared with the prior art, the technical effects of the present invention are as follows:

[0035] 1. The heat sink effect of the chromium-zirconium copper tube of the present invention is more obvious. It can quickly transfer heat to the coolant and also has good sealing performance and fracture toughness.

[0036] 2. By using the present invention to design and manufacture the divertor of a nuclear fusion device (reactor), the heat transfer capacity is significantly improved. It can quickly remove the high heat load brought by the plasma of the nuclear fusion device to the divertor, effectively solve the technical problems of high surface temperature and large temperature gradient caused by high heat load conditions of the divertor of the fusion reactor, and extend the service life of the divertor.

[0037] 3. The inner surface of the chromium-zirconium copper tube of the present invention has high smoothness and high precision. With the increase of heat flux density and mass flow rate, the heat transfer enhancement characteristics are significantly improved, and the service life of the copper-chromium-zirconium tube is significantly extended, overcoming the fatal unsafe factor of easy corrosion and failure.

[0038] 4. The present invention well meets the stringent requirements of nuclear fusion for the precision, thermodynamic properties and eddy current flaw detection of copper-chromium-zirconium tube materials, filling the gap in nuclear fusion devices in China.

[0039] 5. The present invention can also meet the technical requirements of the efficient heat exchange environment for drastic temperature changes in special environment fields such as deep space exploration, aviation, and aerospace aircraft, which is of great significance and has a large application prospect. Specific Embodiments

[0040] In this embodiment, a preparation process of a high-precision copper-chromium-zirconium tube with high heat load bearing capacity for a nuclear fusion reactor will be further described to facilitate understanding and implementation by those skilled in the art. It is characterized by including the steps of preparing a copper-chromium-zirconium ingot, forging a round bar, the first heat treatment, machining and drilling, the first cold rolling, cleaning and intermediate inspection, the second heat treatment, pickling, the second cold rolling, vacuum annealing, and inspection, specifically as follows:

[0041] Step 1. Prepare a copper-chromium-zirconium ingot

[0042] a) Prepare materials: Select copper Cu, chromium Cr, and zirconium Zr block materials with a particle size of 5 - 45 mm. Among them, Cr (wt%): 0.6% - 0.9%; Zr (wt%): 0.07% - 0.15%; the rest are Cu and unavoidable impurities;

[0043] The total content of the impurity elements is controlled < 0.15%. Among them, the total content of impurity elements Fe, Al, Si, C, Pb, Nb, Ta < 0.12%, and O < 0.002%;

[0044] b) Vacuum melting:

[0045] Place the copper block at the bottom of the graphite crucible;

[0046] Vacuumize the graphite crucible and heat it electrically to ≥1270 °C. Stop vacuumizing when the copper block starts to melt, and fill it with argon gas at 0.01 - 0.02 MPa until the copper block is completely melted;

[0047] After the copper block is completely melted, heat it up to ≥1920 ± 10 °C, and add chromium blocks batch by batch. To avoid inclusions, wait until the previous batch of chromium blocks is completely melted before adding the next batch of chromium blocks. After the chromium blocks are completely melted, add zirconium blocks batch by batch. Wait until the previous batch of zirconium blocks is completely melted before adding the next batch of zirconium blocks;

[0048] c) After all the zirconium blocks are added, refine the whole furnace for 20 - 25 minutes, adjust the temperature to 1250 - 1330 °C, cast it into an ingot mold to form, and when it cools to form a copper-chromium-zirconium ingot block, transfer it directly to the forging process while it is still hot;

[0049] Step 2: Forge a round bar: The forging temperature is 920 ± 5 °C, and use a 2500-ton precision forging machine to forge the ingot block into a round bar with a diameter × length value of Φ160 × L;

[0050] Step 3: Manufacture a tube blank:

[0051] a) Machine-process the tube blank: Machine-process the Φ160mm × L mm copper-chromium-zirconium round bar into a rough tube blank with an outer diameter × inner diameter × length value of Φ148 (±0.1) mm × Φ38 (±0.1) mm × 450 (±1) mm;

[0052] b) Extrude the tube blank: Heat the rough tube blank to 880 ± 10 °C, keep it warm for 120 minutes, and extrude it into a medium tube blank with an outer diameter × wall thickness × length value of Φ55 mm × 9 mm × L mm; The extrusion deformation amount is 92%, the extrusion speed is 50 mm / min, the wall thickness deviation of the extruded tube blank is less than 1 mm, and it is immediately cooled in water after extrusion;

[0053] Step 4: First heat treatment: Heat up, raise the solution heating temperature of the medium tube blank to 890 ± 5 °C, keep it warm for 60 minutes, then cool it with running water, and transfer it to drilling;

[0054] Step 5: Machine-process and drill holes: Use a deep-hole drilling machine to process and ream the holes. After machining, use a manual flaw detector to measure that the inner surface finish reaches ≤1.6, and control the wall thickness deviation ≤0.5 mm;

[0055] Step 6: First cold rolling: Roll with an LG45 rolling mill, check whether all parts of the rolling mill are normal, whether the voltage and current are normal, and roll the medium tube blank after the first heat treatment into a thin tube blank with an outer diameter × wall thickness value of Φ25 mm × 4.2 mm;

[0056] Step 7, Cleaning and Intermediate Inspection: Use kerosene and degreaser to clean the fine tube blanks;

[0057] The kerosene used is pure kerosene;

[0058] The degreaser used is hot water with a concentration of 8% and a temperature of 45°C. After cleaning, check the inner and outer surfaces and conduct intermediate inspection;

[0059] Take a fine tube blank sample with an outer diameter × wall thickness value of Φ25 mm × 4.2 mm × 500 mm for intermediate inspection. The stress inspection results are shown in the "Comparison Table of Intermediate Inspection Test Results of Stress Limits of Copper-Chromium-Zirconium Tubes with Temperature Changes";

[0060] The inspection stress measurement values all show that they are higher than the allowable stress, meeting the design technical requirements, and transfer to secondary heat treatment.

[0061] Step 8, Secondary Heat Treatment: Solution heat the fine tube blanks to 880 ± 1°C, hold for 60 minutes, and then cool with cold water;

[0062] Step 9, Pickling: Use hydrochloric acid and sulfuric acid in a 1:1 ratio to remove the residual oxide scale of copper oxide on the inner and outer surfaces, making the inner and outer surfaces bright and free of any defects;

[0063] Step 10, Secondary Cold Rolling

[0064] Use an LD40 rolling mill for cold rolling; Check that all parts of the rolling mill are normal. Roll to an outer diameter × wall thickness × length value of Φ15 mm × 1.5 mm × L mm, with a tolerance value of Φ15 (±0.05) mm × 1.5 (±0.05) mm × L mm. Take samples from each tube to check the dimensions, straightness, and detect and clean the inner and outer surfaces with flaw detection;

[0065] Step 11, Vacuum Annealing: Use a vacuum furnace for annealing and aging treatment. The vacuum degree is 10 - 2 Pa. Heat to 480°C and hold for 3 hours, then cool with the furnace. Take protective measures when taking out of the furnace to prevent surface scratches, and ensure that the surface has no oxide scale and no oil stain;

[0066] Step 12, Inspection and Warehousing:

[0067] For the copper-chromium-zirconium tubes obtained in Step 11, conduct cleaning, measure the wall thickness of the tubes with an ultrasonic thickness gauge, and conduct flaw detection inspections (ultrasonic and eddy current). The inspection results are ideal and fully meet the technical requirements. Cut the dimensions according to the usage requirements, and store them in the warehouse after passing the inspection or directly deliver them to the customer.

[0068] Comparison Table of Intermediate Inspection Test Results of Stress Values of Copper-Chromium-Zirconium Tubes with Temperature Changes

[0069]

Claims

1. Preparation process of high-precision copper-chromium-zirconium tube with high heat load bearing capacity for nuclear fusion reactor, characterized in that : It includes the steps of preparing a copper-chromium-zirconium ingot, forging a round bar, the first heat treatment, machining and drilling, the first cold rolling, cleaning and intermediate inspection, the second heat treatment, pickling, the second cold rolling, vacuum annealing, and inspection. Specifically: Step 1. Prepare a copper-chromium-zirconium ingot: a) Prepare materials: Select Cu, Cr, and Zr block materials with a particle size of 5 - 45 mm. Among them, Cr (wt%) is 0.6% - 0.9%, Zr (wt%) is 0.07% - 0.15%, and the rest is Cu and a small amount of impurity elements that are difficult to avoid. b) Vacuum melting: Place the copper block at the bottom of the graphite crucible. Vacuumize the graphite crucible and heat it with electricity to ≥1270 °C. Stop vacuumizing when the copper block starts to melt, and fill it with argon gas at 0.01 - 0.02 MPa until the copper block is completely melted. After the copper block is completely melted, heat it up to 1920 ± 10 °C, add chromium blocks batch by batch and completely melt them, then add zirconium blocks batch by batch and completely melt them, and then transfer to refining. c) Refining: Refine the whole furnace for 20 - 25 min, adjust the temperature to 1250 - 1330 °C, cast it into a mold to form, and when it cools into a copper-chromium-zirconium ingot block, directly transfer it to forging while it is still hot. Step 2. Forge a round bar: The forging temperature is 920 ± 5 °C, and use a 2500-ton precision forging machine to forge the ingot block into a round bar with a diameter × length value of Φ160 mm × L mm. Step 3. Manufacture a tube blank: a) Machine the tube blank: Machine the Φ160 mm × L mm copper-chromium-zirconium round bar into a rough tube blank with an outer diameter × inner diameter × length value of Φ148 (±0.1) mm × Φ38 (±0.1) mm × 450 (±1) mm. b) Extrude the tube blank: Heat the rough tube blank to 880 ± 10 °C, keep it warm for 120 min, and extrude it into a medium tube blank with an outer diameter × wall thickness × length value of Φ55 mm × 9 mm × L mm. Immediately cool it in water after extrusion. Step 4. The first heat treatment: Heat up, raise the solution heat treatment temperature of the medium tube blank to 890 ± 5 °C, keep it warm for 60 min, then cool it with flowing water, and transfer to drilling. Step 5. Machine and drill: Use a deep hole drilling machine to process and ream the hole. After machining, use a manual flaw detector to measure the inner surface smoothness to ≤1.6, and control the wall thickness deviation ≤0.5 mm. Step 6. The first cold rolling: Use an LG45 rolling mill to roll, and roll the medium tube blank after the first heat treatment into a thin tube blank with an outer diameter × wall thickness value of Φ25 mm × 4.2 mm. Step 7. Cleaning and intermediate inspection: Clean the thin tube blank with kerosene; after cleaning, check the inner and outer surfaces. After passing the intermediate inspection stress test, transfer to the second heat treatment. Step 8. The second heat treatment: Heat the thin tube blank to 880 ± 1 °C for solution heat treatment, keep it warm for 60 min, then cool it with cold water, and transfer to pickling. Step 9. Pickling: Pickle the thin tube blank to remove the residual oxide scale on the inner and outer surfaces of the tube, make the inner and outer surfaces of the tube bright and defect-free. Step 10. The second cold rolling: Use an LD40 rolling mill for cold rolling; check that all parts of the rolling mill are normal, roll it into a tube with an outer diameter × wall thickness × length value of Φ15 mm × 1.5 mm × L mm, take samples from each tube to check the size, straightness, and detect the inner and outer surfaces with flaw detection, and then clean. Step 11, Vacuum annealing: Annealing aging treatment is carried out in a vacuum furnace with a vacuum degree of 10 - 2 Pa. Heat to 480 °C and hold for 3 h, then cool with the furnace to prevent scratches on the tube surface, and there is no oxide scale and no oil stain on the surface. Step 12, Inspection: Conduct flaw detection on each tube one by one, cut the specified length according to the usage requirements, and store it in the warehouse after passing the inspection.

2. The preparation process of the high-precision copper-chromium-zirconium tube with high heat load bearing capacity for a nuclear fusion reactor according to claim 1, characterized in that, The total content of the impurity elements < 0.15%, among which the total of the impurity elements: Fe, Al, Si, C, Pb, Nb, Ta < 0.12%, and O < 0.002%.

3. The preparation process of the high-precision copper-chromium-zirconium tube with high heat load bearing capacity for a nuclear fusion reactor according to claim 1, characterized in that, The kerosene in Step 7 uses pure kerosene.

4. The preparation process of the high-precision copper-chromium-zirconium tube with high heat load bearing capacity for a nuclear fusion reactor according to claim 1, characterized in that, In the step b) of extruding the tube blank, the extrusion deformation amount is 92%, the extrusion speed is 50 mm / min, and the wall thickness deviation of the extruded tube blank is less than 1 mm.

5. The preparation process of the high-precision copper-chromium-zirconium tube with high heat load bearing capacity for a nuclear fusion reactor according to claim 1, characterized in that, The pickling in Step 9: Use a mixed solution of hydrochloric acid and sulfuric acid in a ratio of 1:1.

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