Zirconium-based alloy pipe manufacturing method

Abstract

The present invention relates to the field of nuclear engineering and to the production of tubular products from zirconium alloys, which can be used as structural elements in the core of a water-cooled nuclear reactor. The method of producing tubular products from zirconium-based alloys of the present invention comprises melting an ingot by vacuum arc remelting, mechanically treating the ingot, heating the ingot, subjecting the ingot to multi-stage hot forging to produce a forged workpiece, subsequently mechanically treating the forged workpiece to produce a billet with a circular profile, producing a tubular billet, quenching and tempering it, applying a protective coating to the tubular billet and heating it to a hot pressing temperature, hot pressing, removing the protective coating, performing a vacuum heat treatment, and performing a multi-pass cold rolling to produce a tubular product, wherein a vacuum heat treatment is performed after each cold rolling pass, and a final vacuum heat treatment is performed at the final size, followed by a finishing operation. The technical effect is to provide the material with machinability in all steps of the hot working and cold working processes, as well as to provide a tubular product with high strength properties and good corrosion resistance.

Description

Technical Field

[0001] The invention relates to the field of nuclear technology, and in particular to a method for manufacturing a zirconium alloy tube, wherein the tube is used as a structural element of a water-cooled nuclear reactor core, in particular for water-water type and PWR type nuclear pressurized water reactors. Background Art

[0002] Zirconium alloys have very small thermal neutron absorption cross sections and good physical and mechanical properties, i.e., they are structural components of nuclear reactor cores. Higher requirements are placed on components made of zirconium alloys for reactor cores in terms of corrosion resistance, hydrogen absorption, strength, irradiation growth, thermal creep, and irradiation thermal creep under high-temperature water and steam stress. The material must also have high technical properties. The performance and manufacturability of products made of this alloy depend not only on the alloy composition, but also on its preparation method, including smelting ingots, hot and cold processing, heat treatment methods for intermediate and finished sizes, and finishing operations.

[0003] There is a method for producing tubular products from zirconium alloys (optional) RU2123065C1 (published on March 12, 1997, grade C22F / 1 / 18), in which the preparation of a multi-component zirconium alloy includes the following steps: preliminary hot deformation of an alloy ingot, forming a tube blank (extrusion) by hot working, quenching, machining and tempering, cold forming, with hot working in between, and then final annealing.

[0004] The disadvantage of this method is that no protective coating is applied to the tube blank before hot extrusion, which will cause oxidation of the metal during the manufacturing process and reduce the processability of the tube production; it does not include finishing treatment to remove residual production contaminants on the surface of the tube and reduce surface roughness, resulting in reduced corrosion resistance of the product.

[0005] The existing "Method for Producing Products with Zirconium Alloys" RU 2110600C1 (published on May 10, 1998, C22F / 1 / 18 grade), includes hot forming (extruding) the alloy ingot into an original billet, then hot forming the intermediate billet, quenching and tempering the cut billet, hot forming and tempering, and then cold rolling.

[0006] The disadvantage of this method is that no protective coating is applied to the tube blank before hot extrusion, which will cause oxidation of the metal during the manufacturing process and reduce the processability of the tube production; it does not include finishing treatment to remove residual production contaminants on the surface of the tube and reduce surface roughness, resulting in reduced corrosion resistance of the product.

[0007] Existing "Zirconium alloy pipe and its manufacturing method" RU 2298042C2 (published on April 27, 2004, C22F / 1 / 18C21D1 / 18, C22C16 / 00 grades). The manufacturing method includes homogenizing the extruded sleeve, quenching it in water, stress relief annealing, and two-stage cold rolling with intermediate and final annealing.

[0008] The disadvantage of this patent is that no protective coating is applied to the ingot before hot extrusion, which causes oxidation of the metal during extrusion, resulting in reduced manufacturability of tube production. The method of using a two-stage cold rolling process in the (α+β) region and a final homogenization treatment can obtain a high-strength product, while annealing in the (α+β) region will produce a metastable β-Zr phase in the product structure, which has a negative impact on the corrosion of zirconium alloys. The technical solution does not include finishing operations to remove residual technical contaminants on the surface of tubular products and reduce surface roughness, thereby reducing the corrosion resistance of the product.

[0009] The closest to this method is the patent "Zirconium alloy with high corrosion resistance for producing fuel element cladding and its manufacturing method" (US2016 / 0307651A1, published on October 20, 2016, G21C 3 / 07, B22D 21 / 00, B22D7 / 00, C22C 16 / 00, C22F 1 / 18 grade). This patent points out the composition of the corrosion-resistant zirconium alloy and the method of using it to make fuel element cladding, which includes: melting ingots, covering the ingots with steel protective sleeves, heat treatment of the ingots with sleeves before hot rolling, hot rolling, removing the steel protective sleeves, heat treatment of hot-rolled tubes, three rounds of cold rolling, intermediate heat treatment after each rolling, and final heat treatment.

[0010] The disadvantage of this method is that the use of carbon steel sleeves interacts with zirconium alloys at hot rolling temperatures and forms carbides. Hot rolling of the ingot does not ensure uniform processing of the cast structure, which is characterized by axial porosity of the billet. The number and size of the pores increase from the periphery to the center of the billet, which leads to a deterioration in the machinability of the material. The low temperatures of the intermediate annealing (570-590°C in the first pass, 560-580°C in the second pass, 560-580°C in the third pass), with a selected deformation manufacturing scheme (30-40% in the first and third deformations, (50-60)% in the second stage of cold deformation) are not enough to relieve residual stresses and recrystallization processes, which have a negative impact on the manufacturability of the material and its creep resistance and radiation growth. The use of three-stage long final hot rolling annealing (first stage from 460°C to 470°C, second stage from 510°C to 520°C, third stage from 580°C to 590°C) can obtain a stronger material, while the creep resistance and radiation growth resistance are deteriorated, mainly due to the recrystallization process. In addition, the use of a small amount of cold deformation stage and a lower annealing temperature in the hot rolling at a temperature of T = 630-650°C cannot complete the crushing and decomposition of the metastable β-zr phase, resulting in a decrease in the corrosion resistance of the product. This technical solution does not include finishing operations to remove residual technical contaminants on the surface of tubular products and reduce surface roughness, thereby reducing the corrosion resistance of the product. Summary of the invention

[0011] The technical problem to be solved by the present invention is to develop a method for manufacturing a tube material used as a structural element of a water-cooled nuclear reactor core, in particular for water-water type and PWR type nuclear pressurized water reactors.

[0012] The technical achievement of the present invention is to ensure the processability of the material and the high strength and corrosion resistance of the pipe in each stage of cold pressing and hot pressing when manufacturing the pipe.

[0013] The technical achievement is achieved by a method for manufacturing a zirconium-based alloy pipe, wherein the weight percentage of the zirconium alloy is: 0.9-1.7% niobium, 0.5-2.0% tin, 0.3-1.0% iron, 0.002-0.200% chromium, 0.003-0.040% carbon, 0.04-0.15% oxygen, 0.002-0.15% silicon, and the balance of zirconium, using a vacuum consumable arc furnace to perform multi-stage smelting to melt the ingot, machining the ingot, heating, performing multi-stage hot forging on the ingot to obtain a forging, and then Mechanical processing of forgings, obtaining round billets, obtaining tube billets, then quenching and tempering, applying a copper protective layer on the tube billet, heating it to the hot pressing temperature, hot pressing, removing the copper protective layer therefrom, vacuum heat treatment, and then repeatedly cold rolling, each time the comprehensive deformation is 25.6-56.8%, the pipeline coefficient Q=1.0-6.4, obtaining a tube, and after each cold rolling, intermediate vacuum heat treatment, vacuum heat treatment when the required shape is obtained, and then final finishing operation.

[0014] The alloy ingot is subjected to multi-stage hot forging in the range of 980°C to 720°C, with a comprehensive deformation of 93%, and is heated multiple times in the range of 890°C to 850°C.

[0015] An axial center hole is drilled on a round billet cut into a certain length, and then an axial center hole is bored to obtain a tube billet.

[0016] Quenching is carried out at a temperature of 1050 to 1100°C, and tempering is carried out at a temperature of 450 to 600°C.

[0017] The hot pressing treatment of the tube blank is carried out in the range of 640°C to 600°C and the stretching degree μ=8.5-9.0.

[0018] In the time interval between hot pressing and cold rolling, the tube blank is vacuum heat treated at a temperature of 605-630°C.

[0019] For tube products with fixed cross-section, the tube blank is repeatedly cold rolled, with a total deformation of 41.8-56.8% in each pass and a tube coefficient Q=1.0-1.6.

[0020] For pipe products with variable cross-sections, the pipe blank is repeatedly cold rolled, with a total deformation of 25.6-56.5% in each pass and a pipe coefficient Q=1.0-6.4.

[0021] During the time interval between cold rolling, the tube blank is vacuum heat treated at a temperature of 570-630°C.

[0022] The final vacuum heat treatment of the tube is carried out in the range of 535℃ to 545℃.

[0023] The final vacuum heat treatment of the tube is carried out in the range of 600℃ to 620℃.

[0024] The residual pressure in the furnace for vacuum heat treatment of pipes shall not exceed 1.10 -4 -1·10 -5 mmHg.

[0025] After the tube has been formed to its final dimensions, its surface is treated chemically and mechanically.

[0026] The specified alloy component ratio embodiment of the zirconium alloy ensures the processing performance, corrosion resistance, stable mechanical properties and deformation resistance of the pipe.

[0027] The advantage of the above invention for producing pipes is that the hot deformation process ensures that the casting structure can be uniformly processed along the length and cross-section of the ingot; the use of the copper protective layer prevents gas saturation and excludes diffusion interaction between the coating and the blank. This process ensures that the produced pipe has the highest fracture toughness and plasticity of this component ratio embodiment. Repeated cold rolling, the total deformation of each pass is 25.6-56.8%, the pipeline coefficient Q=1.0-6.4, and the result of intermediate vacuum heat treatment is that a material structure with minimal residual stress and recrystallization process is formed during reorganization, which improves the manufacturability of the pipe product. According to the requirements for the strength of the pipe, the final vacuum heat treatment is carried out in two different temperature ranges. The first range (535-545℃) ensures the formation of a uniform partially recrystallized (recrystallization degree is not less than 40%) structure, and the second range (600-620℃) ensures the formation of a uniform recrystallized structure (recrystallization degree is 100%).

[0028] Finishing can make the roughness Ra of the inner and outer surfaces less than 0.8 microns, thereby improving the stability of corrosion performance. DETAILED DESCRIPTION

[0029] The embodiments of the invention are as follows:

[0030] Example 1

[0031] According to the technical solution protected by the present invention, the technology for manufacturing zirconium tubular products includes the following operations. Melting alloy ingots, composed of the following components by weight percentage: niobium 1.05-1.07%, tin 1.24-1.27%, iron 0.31-0.34%, chromium 0.0025-0.003%, carbon 0.011-0.019%, oxygen 0.064-0.065%, silicon 0.0025-0.0035%, and zirconium balance. The alloy components are uniformly mixed with electrolytic zirconium powder, pressed into consumable electrodes, and melted twice in a vacuum consumable arc furnace. The side of the ingot is machined. The ingot is heated to a temperature of 980°C. The first step of the multi-stage hot forging of the ingot is carried out at a temperature of 980°C, the last step is carried out at a temperature of 720°C, and the temperature range of the intermediate heating is 890°C to 850°C.

[0032] The total deformation (∑ε) during the hot forging of the ingot was 93%. The ingot was heated and intermediate heated in a resistance furnace. Round billets with a diameter of mm are made by machining forgings.

[0033] An axial center hole is drilled on a round billet cut into a certain length, and then an axial center hole is bored to obtain a tube billet.

[0034] Quenching is carried out at a temperature of 1050 to 1100°C, and tempering is carried out at a temperature of 450 to 600°C. The roughness of the tube surface does not exceed Ra equal to 2.5 microns. Subsequently, a copper coating is applied to the tube (for example, a copper protective layer is used after copper plating) to prevent gas saturation during subsequent heating and hot pressing.

[0035] The ingot is heated in a resistance furnace before hot pressing. The heating temperature of the tube blank before pressing is between 640°C and 600°C. The elongation μ = 8.9. Then, the copper coating is removed.

[0036] Subsequently, the tube billet is sent to vacuum heat treatment at a treatment temperature of T = 605-630 ° C. The tube billet is cold rolled on XΠT, XΠTP, and KPW cold rolling mills for 5 times, with a total deformation ∑ε of 41.8 to 56.5% each time, and the tube coefficient Q is in the range of 1.00-1.6, and a tube with a fixed cross-section is obtained. The intermediate vacuum heat treatment is carried out in a temperature range of 570 ° C to 610 ° C. The final vacuum heat treatment is carried out at T = 535-545 ° C or T = 600-620 ° C. The vacuum degree of the vacuum furnace used is at least 1·10 -4 -1·10 -5 mmHg.

[0037] After annealing and straightening, the tubes undergo a series of operations, namely: jet etching, alkali treatment, and surface grinding.

[0038] The zirconium alloy tube with a diameter of 12.60×11.24 mm manufactured according to the technical solution has the following characteristics (Table, Example 1).

[0039] Example 2

[0040] The implementation method is similar to that of Example 1. The melting component ratio percentage is: niobium 0.94-0.97%, tin 1.15-1.20%, iron 0.40-0.46%, chromium 0.004-0.005%, carbon 0.008-0.009%, oxygen 0.10-0.11%, silicon 0.0055-0.0060%. The original alloy components are mixed with zirconium magnesium hot sponge to form a consumable electrode, which is remelted by double vacuum arc.

[0041] The zirconium alloy tube with a diameter of 12.60×10.90 mm manufactured according to the present technical solution has the following characteristics (Table, Example 2).

[0042] Example 3

[0043] The implementation method is similar to that of Example 1. The melting component ratio percentage is: niobium 0.90-0.93%, tin 1.18-1.22%, iron 0.82-0.87%, chromium 0.008-0.009%, carbon 0.010-0.011%, oxygen 0.082-0.086%, silicon 0.0052-0.0058%. The original alloy components are mixed with zirconium magnesium hot sponge to form a consumable electrode, which is remelted by double vacuum arc.

[0044] The zirconium alloy tube with a diameter of 13.00×11.00 mm manufactured according to the present technical solution has the following characteristics (Table, Example 3).

[0045] Example 4

[0046] According to the technical solution protected by the present invention, the technology for manufacturing zirconium tubular products includes the following operations. Melting alloy ingots, composed of the following components by weight percentage: niobium 1.06-1.09%, tin 1.28-1.30%, iron 0.65-0.68%, chromium 0.009-0.011%, carbon 0.009-0.010%, oxygen 0.008-0.009%, silicon 0.009-0.010%. The alloy components are uniformly mixed with electrolytic zirconium powder, pressed into consumable electrodes, and melted twice in a vacuum consumable arc furnace. The side of the ingot is machined. The ingot is heated to a temperature of 980°C. The multi-stage hot forging of the ingot is carried out at a temperature of 980°C to 720°C, and the temperature range of the intermediate heating is 890°C to 850°C.

[0047] The total deformation (∑ε) during the multi-stage hot forging of the ingot was 93%. The ingot was heated and intermediately heated in a resistance furnace. The round billet with a diameter of mm is made by machining forgings. An axial center hole is drilled on the round billet cut into a certain length, and then an axial center hole is bored to obtain a tube billet. The roughness of the tube billet surface does not exceed Ra equal to 2.5 microns. Quenching is carried out at a temperature of 1050 to 1100 ° C, and tempering is carried out at a temperature of 450 to 600 ° C.

[0048] The tube blank is then coated with a copper coating to prevent gas saturation during the subsequent heating and hot pressing process.

[0049] The ingot is heated and intermediate heated in a resistance furnace. The heating temperature of the tube before pressing is between 640°C and 600°C. At the elongation μ=8.9. Then, the copper coating is removed.

[0050] Subsequently, the tube blank is sent to vacuum heat treatment at a temperature of T = 605-630 ° C. The obtained tube blank is cold rolled on XΠT, XΠTP, and KPW cold rolling mills for 6 times, and the tube coefficient Q is in the range of 1.00-6.4 each time. The combined stepped mandrel with a total deformation amount ∑ε = 25.6-56.5% is required to form a variable cross-section of the tube blank.

[0051] The intermediate vacuum heat treatment is carried out in the temperature range of 575°C to 590°C. The final vacuum heat treatment is carried out at T = 535°C or T = 610°C according to different strength requirements. The vacuum degree of the vacuum furnace used is at least 1.10 -4 -1·10 -5 mmHg.

[0052] After the final vacuum heat treatment of the tube is completed, a series of finishing operations will be carried out, namely: jet etching, alkali treatment, and surface grinding.

[0053] Different parts of the variable cross-section tube blank have different degrees of cumulative deformation. The tube blank is used to form a variable cross-section tube, so the thin-wall and thick-wall parts of the finished tube will be subjected to approximately the same degree of cumulative deformation, ensuring that the tube product has uniform mechanical properties after the final vacuum heat treatment.

[0054] The zirconium alloy tube with a diameter of 12.60×11.24 (10.1) mm manufactured according to the present technical solution has the following characteristics (Table, Example 4).

[0055] Example 5

[0056] The implementation method is similar to that of Example 4

[0057] The zirconium alloy tube with a diameter of 12.60×10.90 (8.8) mm manufactured according to the present technical solution has the following characteristics (Table, Example 5).

[0058] Industrial Applicability

[0059] In summary, the above pipe manufacturing scheme ensures the high strength and corrosion resistance of the pipe.

[0060]

[0061]

[0062]

Claims

1. A method for manufacturing a zirconium-based alloy ingot pipe, wherein the zirconium-based alloy ingot components are as follows: 0.9-1.7 niobium, 0.5-2.0 tin, 0.3-1.0 iron, 0.002-0.200 chromium, 0.003-0.040 carbon, 0.04-0.15 oxygen, 0.002-0.15 silicon, and the remainder zirconium, the method comprising: The ingot is melted by multiple smelting in a vacuum consumable arc furnace. Machining of ingots, heating, The ingot is subjected to multi-stage hot forging to obtain forgings. The forging is then machined to obtain a round billet. The round billet is machined to obtain a tube billet. Then the tube is quenched and tempered. A protective layer is applied to the tube to prevent gas saturation, and the tube is heated to hot pressing temperature. Heat pressing, Remove the protective layer from the tube blank, It is subjected to vacuum heat treatment and then repeated cold rolling, with each comprehensive deformation of 25.6-56.8%, and the pipeline coefficient Q=1.0-6.4 to obtain a pipe. Among them, for the tube products with fixed cross-section, the tube blank is repeatedly cold rolled, and the total deformation of each pass is 41.8-56.8%, and the tube coefficient Q = 1.0-1.6, For variable cross-section tube products, the tube blank is repeatedly cold rolled, with a total deformation of 25.6-56.5% in each pass and a tube coefficient of Q = 1.0-6.

4. After each cold rolling, an intermediate vacuum heat treatment is performed, and After the final vacuum heat treatment of the tube, the final finishing operation is carried out.

2. The method according to claim 1, characterized in that Multi-stage hot forging is carried out by multi-stage forging or spiral rolling in the temperature range of 980°C to 720°C, with a total deformation of 93% and an intermediate heating temperature of 890°C to 850°C.

3. The method according to claim 1, characterized in that: The tube blank is obtained by drilling and subsequently drilling an axial center hole in a round blank cut to length after multi-stage hot forging.

4. The method according to claim 1, characterized in that Quenching is carried out at a temperature of 1050°C to 1100°C, and tempering is carried out at a temperature of 450°C to 600°C.

5. The method according to claim 1, characterized in that The hot pressing of the tube blank is carried out at a heating temperature of 640°C to 600°C, and the elongation μ=8.9-9.

0.

6. The method according to claim 1, characterized in that The temperature of the tube blank vacuum heat treatment in the interval between hot pressing and cold rolling is 605℃-630℃.

7. The method according to claim 1, characterized in that At a temperature of 570°C-630°C, the tube blank is subjected to intermediate vacuum heat treatment between cold rolling operations.

8. The method according to claim 1, characterized in that: The pipe is subjected to a final vacuum heat treatment at a temperature of 535°C-545°C.

9. The method according to claim 1, characterized in that: The pipe is subjected to a final vacuum heat treatment at a temperature of 600°C-620°C.

10. The method according to claim 6, 7, 8, 9, characterized in that: The residual pressure in the furnace for vacuum heat treatment of pipes shall not exceed 1.10 -4 -1·10 -5 mmHg.

11. The method according to claim 1, characterized in that At the final dimensions of the tube, its surface is chemically and mechanically treated.

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