CN115717215B - A kind of stainless steel cladding tube material for lead-bismuth fast reactor fuel assembly and its preparation method - Google Patents

Abstract

The invention discloses a stainless steel cladding tube material for lead-bismuth fast reactor fuel assembly and a preparation method thereof; the cladding tube material includes elements Fe, Cr, Ni, Mn, Ti, Mo, Al, C, Si, B, wherein Their mass percentages in the material are: 0.04%≤C≤0.08%, 15.0%≤Cr≤17.0%, 14.0%≤Ni≤16.0%, 0.3%≤Si≤0.5%, 1.0%≤Mn≤1.2%, 0.2%≤Ti≤0.5%, 1.3%≤Mo≤1.5%, 0.003%≤B≤0.004%, 0≤Al≤0.3%, and the mass percentage ratio of Ti and C, Ti/C, is (4‑6 ): 1; the balance is Fe; preparation method: obtain an alloy ingot through vacuum induction melting and vacuum arc consumable remelting, then forge and roll it to obtain a stainless steel cladding tube. The stainless steel cladding tube material proposed by the invention has good room temperature and high temperature mechanical properties and excellent lead-bismuth liquid metal corrosion resistance.

Description

A kind of stainless steel cladding tube material for lead-bismuth fast reactor fuel assembly and its preparation method

Technical field

The invention relates to the technical field of nuclear materials, and in particular to a stainless steel cladding tube for a lead-bismuth fast reactor fuel assembly and a preparation method thereof.

Background technique

The fuel assembly is one of the most core components of lead-based reactors and has a harsh working environment. Because it is in direct contact with liquid lead-based coolant, the fuel assembly structural materials must not only be resistant to high temperatures and radiation, but also have excellent resistance to liquid metal corrosion. The 15Cr-15Ni series of Ti-containing austenitic stainless steels have good structural stability, excellent processing performance, high operating temperature, and can withstand radiation damage up to 150dpa. They have good application prospects and are the main candidates for lead-based fast reactor cladding tubes. One of the structural materials. However, most of the current application experience of 15-15Ti alloy comes from sodium-cooled fast reactors. The coolant used in lead-based fast reactors (lead and lead-bismuth eutectic alloy) is more corrosive than sodium-cooled fast reactors. Therefore, if used as a lead-based fast reactor cladding tube material, the liquid metal corrosion resistance of 15-15Ti alloy needs to be further optimized and improved.

In order to improve the corrosion resistance of 15-15 Ti austenitic stainless steel, it is generally improved by adjusting or adding alloy elements such as Si, Ti, Mn, and Al. Material composition design to improve lead-bismuth corrosion performance often affects other important properties of the material such as mechanical properties, irradiation tissue stability, etc. The composition range of 15-15Ti has not yet been unified at home and abroad. It is necessary to develop a material that meets the requirements of corrosion resistance, uniform structure and surface quality for lead-based reactor fuel assemblies without affecting mechanical properties, welding performance and other important structural material properties. Excellent stainless steel cladding pipe material and preparation method thereof.

Contents of the invention

The technical problem to be solved by the present invention is to provide a stainless steel cladding tube for lead-bismuth fast reactor fuel assembly and a preparation method thereof in view of the above-mentioned defects of the prior art.

The technical solution adopted by the present invention to solve the technical problem is: a stainless steel cladding tube material for lead-bismuth fast reactor fuel assembly, including elements Fe, Cr, Ni, Mn, Ti, Mo, Al, C, Si, B, Their mass percentages in the material are: 0.04%≤C≤0.08%, 15.0%≤Cr≤17.0%, 14.0%≤Ni≤16.0%, 0.3%≤Si≤0.5%, 1.0%≤Mn≤1.2% , 0.2%≤Ti≤0.5%, 1.3%≤Mo≤1.5%, 0.003%≤B≤0.004%, 0≤Al≤0.3%, and the mass percentage ratio of Ti and C Ti/C is (4- 6):1; the balance is Fe.

Preferably, the total mass percentage of all impurity elements in the stainless steel cladding tube material is not higher than 0.03%; among the impurity elements, the mass percentage of P is not higher than 0.01%, the mass percentage of N is not higher than 0.003%, The mass percentage of S is not higher than 0.0015%, and the mass percentage of O is not higher than 0.0015%.

A method for preparing stainless steel cladding tube materials for lead-bismuth fast reactor fuel assemblies, including the following steps:

S1. Weighing materials: Polycrystalline silicon, nickel plate, pure iron, molybdenum strips, metal chromium, carbon, metal aluminum, metal manganese, boron iron alloy and sponge titanium are used as raw materials. The mass percentage of boron element in the boron iron alloy is 15-20%. ; The ratio of raw materials meets the mass percentage of their elements: 0.04% ≤ C ≤ 0.08%, 15.0% ≤ Cr ≤ 17.0%, 14.0% ≤ Ni ≤ 16.0%, 0.3% ≤ Si ≤ 0.5%, 1.0% ≤ Mn ≤1.2%, 0.2%≤Ti≤0.5%, 1.3%≤Mo≤1.5%, 0.003%≤B≤0.004%, 0≤Al≤0.3%, and the mass percentage ratio of Ti and C is Ti/C: (4-6): 1; the balance is Fe; the mass percentage of polysilicon is 0.3-0.5%;

S2. Vacuum induction melting: Polycrystalline silicon is added in two steps. First, put part of the polycrystalline silicon, nickel plate, pure iron, molybdenum strips and metal chromium into the reaction vessel, evacuate and refine; then add carbon and metal aluminum, and wait until they are melted. Then stop the power supply, introduce protective gas, re-power on, add the remaining polycrystalline silicon, metallic manganese, boron ferroalloy and sponge titanium at the first preset temperature, stir and adjust the temperature of the molten steel to the second preset temperature and push it into the mold. Pouring to obtain the primary alloy ingot;

S3. Vacuum arc consumptive remelting: remove the shrinkage cavity of the preliminary alloy ingot obtained in the step S2, and perform vacuum arc consumptive remelting to obtain a consumable remelted ingot;

S4. Forging: The consumable remelted ingot obtained in step S3 is subjected to upsetting-drawing and homogenization processing to obtain an alloy forged rod;

S5. Pipe rolling: The alloy forged rod obtained in step S4 is processed into a pipe blank, and subjected to multiple passes of cold rolling and heat treatment, and finally pre-deformation cold rolling is performed to obtain a stainless steel cladding pipe.

Preferably, in the step S2, vacuum is evacuated to a vacuum degree ≤ 5.0 Pa, and refining is performed at 1300-1700°C for 10-20 minutes.

Preferably, in step S2, the protective gas is argon; the first preset temperature is 1350-1400°C; and the second preset temperature is 1500-1550°C.

Preferably, in step S3, 50-80mm is removed from the shrinkage cavity area.

Preferably, in the S4 step, 20-40% upsetting-drawing pre-deformation and homogenization treatment are performed first, and then upsetting-drawing is performed 2-5 times, and the final deformation amount is 30-40%; wherein, The temperature of the homogenization treatment is 1150-1200°C, and the heat preservation time of the homogenization treatment is 11-12 hours.

Preferably, in step S4, the diameter of the alloy forged rod is 45-55mm; in step S5, the outer diameter of the tube blank is 40-50mm, and the wall thickness is 4-5mm.

Preferably, in step S5, the tube blank is subjected to solution treatment before cold rolling, wherein the temperature of the solution treatment is 1050-1100°C, and the time of the solution treatment is 20-40 min. .

Preferably, in step S5, the number of cold rolling passes is 8-15; the deformation amount of the pre-deformation cold rolling is 15-25%, and the feeding amount is 1-2mm/min.

Preferably, in step S5, the heat treatment includes intermediate heat treatment and final heat treatment; wherein, the temperature of the intermediate heat treatment is 1050-1100°C, the time of the intermediate heat treatment is 10-30 min; the temperature of the final heat treatment is The temperature is 1030-1080°C, and the final heat treatment time is 8-15 minutes.

Beneficial effects of the present invention:

The present invention proposes a stainless steel cladding tube material for lead-bismuth fast reactor fuel assembly. By reducing the Mn content, adjusting the Al content and strictly controlling the N content, the structural uniformity of the alloy ingot is improved, and the oxidation resistance of the stainless steel cladding tube material is improved. properties and reduce inclusions in the material.

The present invention proposes a method for preparing stainless steel cladding tube materials for lead-bismuth fast reactor fuel assemblies. This method can more accurately control the chemical element content of the stainless steel cladding tube material, better reduce the content of impurity elements, and improve the material's Microstructure uniformity and hot and cold processing properties. Among them, multiple pier deformation and homogenization treatments are used for forging to ensure the elimination of segregation during the solidification process of the ingot and obtain an excellent deformation structure without banding structures and macroscopic defects. The stainless steel cladding tube material of the present invention has good room temperature and high temperature mechanical properties and excellent lead-bismuth liquid metal corrosion resistance, and can better meet the material selection requirements for lead-bismuth fast reactor fuel components.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and examples. In the accompanying drawings:

Figure 1 is a microstructure diagram of the alloy forged rod in Example 1 of the present invention;

Figure 2 is a microstructure diagram of the alloy forged rod in Example 2 of the present invention;

Figure 3 is a microstructure diagram of the stainless steel cladding tube in Embodiment 1 of the present invention;

Figure 4 is a microstructure diagram of the stainless steel cladding tube in Embodiment 2 of the present invention;

Figure 5 is a graph showing the lead-bismuth corrosion test results of Example 1 of the present invention;

Figure 6 is a diagram of the lead-bismuth corrosion test results of Example 2 of the present invention;

Figure 7 shows the lead-bismuth corrosion test results of stainless steel 15-15Ti.

Detailed ways

In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the present invention will be further described in detail below with reference to examples. This example is only used to explain the present invention and does not constitute a limitation on the protection scope of the present invention.

A stainless steel cladding tube material for lead-bismuth fast reactor fuel assembly, including elements Fe (iron), Cr (chromium), Ni (nickel), Mn (manganese), Ti (titanium), Mo (molybdenum), Al (aluminum) ), C (carbon), Si (silicon), B (boron), where their mass percentages in the material are: 0.04% ≤ C ≤ 0.08%, 15.0% ≤ Cr ≤ 17.0%, 14.0% ≤ Ni ≤ 16.0 %, 0.3%≤Si≤0.5%, 1.0%≤Mn≤1.2%, 0.2%≤Ti≤0.5%, 1.3%≤Mo≤1.5%, 0.003%≤B≤0.004%, 0≤Al≤0.3%, and The ratio of mass percentages of Ti and C, Ti/C, is (4-6):1; the balance is Fe.

It should be noted that the mass percentage ratio of Ti to C is (4-6):1, that is, Ti/C can be 4:1, 4.5:1, 4.67:1, 5:1, 5.6:1, 6:1, etc., which is not limited here. In addition, the remaining elements refer to the elements other than Cr, Ni, Mn, Ti, Mo, Al, C, Si and B in the stainless steel raw material, that is, the basic metal element Fe of the stainless steel cladding tube material.

The total mass percentage of all impurity elements in the stainless steel cladding tube material is not higher than 0.03%; among the impurity elements, the mass percentage of P (phosphorus) is not higher than 0.01%, and the mass percentage of N (nitrogen) is not higher than 0.003%. , the mass percentage of S (sulfur) is not higher than 0.0015%, and the mass percentage of O (oxygen) is not higher than 0.0015%. Among them, the mass percentages of P, N, S and O only need to be controlled within the corresponding ranges, and are not specifically limited here.

The Mn element is an element that stabilizes austenite. It can stabilize the single-phase austenite matrix of the alloy and improve the tensile plasticity of the alloy. However, the Mn element is highly volatile and is prone to composition fluctuations during the smelting process. The content is inappropriate. Too high. Therefore, in order to improve the structural uniformity of the alloy ingot without affecting its alloy properties, the mass percentage of the Mn element in the present invention is 1.0-1.2%.

In order to improve the oxidation resistance of the stainless steel cladding pipe material, the present invention adds Al element, and its mass percentage is 0-0.3%.

N element is the main source of TiN inclusions. The N content in the present invention is strictly controlled below 0.003% by mass, reducing the number of inclusions and thereby improving the performance of stainless steel cladding pipe materials.

A method for preparing the stainless steel cladding tube material for the lead-bismuth fast reactor fuel assembly, including the following steps:

S1. Weighing materials: polycrystalline silicon, nickel plate, pure iron, molybdenum bar, metallic chromium, carbon, metallic aluminum, metallic manganese, ferroboron alloy and sponge titanium are used as raw materials. The ratio between the raw materials meets the mass percentage of their elements: 0.04%≤C≤0.08%, 15.0%≤Cr≤17.0%, 14.0%≤Ni≤16.0%, 0.3%≤Si≤0.5%, 1.0%≤Mn≤1.2%, 0.2%≤Ti≤0.5%, 1.3%≤Mo≤1.5%, 0.003%≤B≤0.004%, 0≤Al≤0.3%, and the mass percentage ratio of Ti to C is Ti/C (4-6):1; the balance is Fe.

Among them, the mass percentage of boron element in the boron iron alloy is 15-20%; when calculating the amount of pure iron, first calculate the amount of boron iron alloy based on the mass percentage of boron in the stainless steel cladding tube material being 0.003-0.004%, and then determine the boron The content of iron element in ferroalloy, and finally the amount of pure iron is calculated.

The mass percentage of polysilicon is 0.3-0.5%.

S2. Vacuum induction melting: Polycrystalline silicon is added in two steps. First, put part of the polycrystalline silicon, nickel plate, pure iron, molybdenum strips and metal chromium into the reaction vessel, evacuate and refine; then add carbon and metal aluminum, and wait until they are melted. Then stop the power supply, introduce protective gas, re-power on, add the remaining polycrystalline silicon, metallic manganese, boron ferroalloy and sponge titanium at the first preset temperature, stir and adjust the temperature of the molten steel to the second preset temperature and push it towards the mold. Internal casting is performed to obtain the primary alloy ingot.

Preferably, in the above steps, after the raw materials are added for the first time, the vacuum can be evacuated to a vacuum degree ≤ 5.0 Pa and refined at 1300-1700°C for 10-20 minutes. After the material is added again, argon gas can be introduced as a protective gas, and the first preset temperature can be 1350-1400°C, and the second preset temperature can be 1500-1550°C.

Specifically, vacuum induction melting: polysilicon is added in two times. First, part of the polysilicon, nickel plate, pure iron, molybdenum strips and chromium are placed in the crucible of the vacuum induction furnace, and the furnace is evacuated until the vacuum degree is ≤5.0Pa (here Vacuum degree ≤ 5.0Pa, no limit), refining at 1300-1700°C for 10-20 minutes; then add carbon and aluminum, stop powering after they melt, add protective gas argon, and power again. Add the remaining polycrystalline silicon, manganese, ferroboron alloy and titanium sponge at 1350-1400°C, stir and adjust the temperature of the molten steel to 1500-1550°C, and pour it into the mold to obtain a preliminary alloy ingot.

During the smelting process, polysilicon is added in two steps. The first addition is for deoxidation, and the second addition is to better control the Si content in the stainless steel material. In order to avoid the reaction of metal raw materials during the smelting process, inert gas is selected as the protective gas. Considering the smelting effect and economy, the present invention selects argon gas as the protective gas. In the state of argon gas and a lower first preset temperature (1350-1400°C), the loss of metal raw materials is small and oxidation is not easy to occur; and due to the high environmental pressure, the molten steel is not easy to overflow, making it easy to control the content of stainless steel.

S3. Vacuum arc consumptive remelting: The shrinkage cavity of the preliminary alloy ingot obtained in step S2 is removed, and vacuum arc consumptive remelting is performed to obtain a consumable remelted ingot.

Preferably, in the above steps, 50-80mm is removed from the shrinkage cavity area.

Specifically, vacuum arc consumable remelting: cut off 50-80mm of the shrinkage cavity of the preliminary alloy ingot obtained in step S2, and use it as a remelting electrode to perform vacuum arc consumable remelting in a consumable furnace to obtain consumable remelting. Remelted ingot. After the ingot is cooled, the head and tail are removed, the surface is skinned and cut into pieces. The purpose of head and tail resection is to remove shrinkage cavities and non-dense parts of the steel ingot. The surface defects are peeled off to provide good conditions for subsequent forging. The segmentation process is to facilitate forging and obtain a more uniform deformation structure. Head and tail resection, surface peeling and segmentation are all existing technologies and will not be described in detail here.

S4. Forging: The consumable remelted ingot obtained in step S3 is subjected to upsetting-drawing and homogenization processing to obtain an alloy forged rod.

Preferably, in the above steps, 20-40% upsetting-drawing pre-deformation and homogenization treatment are performed first, and then upsetting-drawing is performed 2-5 times, and the final deformation amount is 30-40%; wherein, homogenization The temperature of the treatment is 1150-1200°C, and the holding time of the homogenization treatment is 11-12 hours.

Specifically, forging: the consumable remelted ingot obtained in step S3 is first subjected to 20-40% upsetting-drawing pre-deformation, and then homogenized at 1150-1200°C, with a heat preservation time of 11-12 hours. Repeat pier drawing 2-5 times, the final deformation of pier drawing is 30%-40%, and an alloy forged rod with a diameter of 45-55mm is obtained; the forged rod does not have strip-like distributed carbide and fine-grained band structures. And the grain size is greater than level 3.

S5. Pipe rolling: The alloy forged rod obtained in step S4 is processed into a pipe blank, and subjected to multiple passes of cold rolling and heat treatment, and finally pre-deformation cold rolling is performed to obtain a stainless steel cladding pipe.

Preferably, the alloy forged rod is processed into a tube blank with an outer diameter of 40-50 mm and a wall thickness of 4-5 mm. In the above steps, the number of cold rolling passes is 8-15; the deformation amount of pre-deformation cold rolling is 15-25%, and the feeding amount is 1-2mm/min; and the heat treatment includes intermediate heat treatment and final heat treatment, wherein, The temperature of the intermediate heat treatment is 1050-1100℃, and the time of the intermediate heat treatment is 10-30min; the temperature of the final heat treatment is 1030-1080℃, and the time of the final heat treatment is 8-15min.

Furthermore, before cold rolling, the tube blank will also be subjected to solution treatment, where the temperature of solution treatment is 1050-1100°C and the time of solution treatment is 20-40 minutes.

Specifically, pipe rolling: process the alloy forged rod obtained in step S4 into a tube blank with an outer diameter of 40-50mm and a wall thickness of 4-5mm, and solidify it at 1050-1100°C in an atmosphere protective furnace. Solution treatment, the treatment time is 20-40min; followed by 8-15 passes of cold rolling deformation, the intermediate heat treatment temperature is 1050-1100°C, the time is 10-30min, the final heat treatment is carried out in an atmosphere-protected roller continuous heat treatment furnace. The temperature is 1030-1080℃, the time is 8-15min; the deformation amount of pre-deformation cold rolling is 15-25%, the feed rate is 1-2mm/min, and finally a stainless steel package with an average grain size of 7-9 is obtained shell tube. The size of the stainless steel cladding pipe is selected and set according to actual needs and is not limited here.

The preparation method of the present invention adopts vacuum induction melting and vacuum arc consumable remelting processes to obtain alloy ingots, and then uses the forging method of multiple piercing deformations and high-temperature homogenization treatment to carry out ingot blanking to obtain alloy forged bars. Then the tube blank is prepared by machining, followed by multiple passes of cold rolling and heat treatment. Finally, the cold rolling process is used to apply 15-25% cold working pre-deformation to produce a stainless steel cladding tube.

The austenitic stainless steel materials used in lead-bismuth fast reactors prepared by the existing technology, such as austenitic stainless steel 15-15 Ti, have unsatisfactory lead-bismuth corrosion resistance, and the existing technology does not conduct research on the alloying elements in the preparation process of stainless steel materials. Accurate control, especially trace elements such as nitrogen and carbon.

The invention can accurately control the element content in the stainless steel cladding tube material. By reducing the Mn content, adjusting the Al content and strictly controlling the N content, the structural uniformity of the ingot is improved, the number of inclusions is reduced, and the oxidation resistance and resistance of the material are improved at the same time. Hot and cold processing properties. The invention can ensure the elimination of solidification segregation of the ingot and obtain an excellent deformation structure without striped structures and macroscopic defects. Compared with similar stainless steels, the stainless steel cladding tube material prepared by the invention has good room temperature and high temperature mechanical properties and excellent lead-bismuth liquid metal corrosion resistance, and can better meet the material selection requirements for lead-bismuth fast reactor fuel components.

The following is explained through specific examples:

Example 1

A stainless steel cladding tube material for a lead-bismuth fast reactor fuel assembly, including the elements Fe, Cr, Ni, Mn, Ti, Mo, C, Si, and B, wherein their mass percentages in the material are respectively: C 0.06%, Cr 16.00%, Ni 15.00%, Mn 1.20%, Ti 0.36%, Mo 1.50%, Si 0.40%, B 0.003%, Fe 65.477%. The total mass percentage of all impurity elements in the stainless steel cladding tube material is not higher than 0.03%; among the impurity elements, the mass percentage of P is not higher than 0.01%, the mass percentage of N is not higher than 0.003%, and the mass percentage of S is not higher than 0.003%. Higher than 0.0015%, the mass percentage of O is not higher than 0.0015%.

A method for preparing the stainless steel cladding tube material for the lead-bismuth fast reactor fuel assembly, including the following steps:

S1. Weighing materials: Polycrystalline silicon, nickel plate, pure iron, molybdenum strips, metal chromium, carbon, metal aluminum, metal manganese, boron iron alloy and sponge titanium are used as raw materials, of which the mass percentage of boron element in the boron iron alloy is 17%; raw materials The proportions between them meet the mass percentages of their elements: C 0.06%, Cr 16.00%, Ni 15.00%, Mn 1.20%, Ti 0.36%, Mo 1.50%, Si 0.40%, B0.003%, Fe 65.477%.

S2. Vacuum induction melting: Polycrystalline silicon is added in two times. First, some polycrystalline silicon, nickel plate, pure iron, molybdenum strips and chromium are placed in the crucible of the vacuum induction furnace. The furnace is evacuated until the vacuum degree is ≤5.0Pa. At 1500℃ Refining for 15 minutes; then add carbon and aluminum, stop powering after they melt, pass in protective gas argon, power again, add the remaining polycrystalline silicon, manganese, boron ferroalloy and sponge titanium at 1370°C, stir and adjust the steel The liquid temperature is 1525°C and poured into the mold to obtain a preliminary alloy ingot.

S3. Vacuum arc consumable remelting: Cut off 60mm of the shrinkage cavity of the preliminary alloy ingot obtained in step S2, and use it as a remelting electrode in a consumable furnace to perform vacuum arc consumable remelting to obtain a consumable remelted ingot. . After the ingot is cooled, the head and tail are removed, the surface is skinned and cut into pieces.

S4. Forging: Heat the consumable remelted ingot obtained in step S3 to 1200°C and keep it for 2 hours, then perform 40% upsetting-drawing pre-deformation, and then perform homogenization treatment at 1200°C. The holding time is 12 hours. Repeat the pier drawing twice, and the final deformation of the pier drawing is 40%, and an alloy forged rod with a diameter of 50 mm is obtained.

S5, tube rolling: the alloy forged rod obtained in the step S4 is processed into a tube blank with an outer diameter of 42 mm and a wall thickness of 4.5 mm, and a solid solution treatment is carried out at 1080° C. in an atmosphere protection furnace for 30 min; then 10 cold rolling deformations are carried out, the intermediate heat treatment temperature is 1080° C., the time is 20 min, and the final heat treatment is carried out in an atmosphere protection roller continuous heat treatment furnace at a treatment temperature of 1060° C. for 12 min; the deformation amount of the pre-deformation cold rolling is 20%, and the feed amount is 1.5 mm/min, to obtain a stainless steel clad tube.

Example 2

A stainless steel cladding tube material for a lead-bismuth fast reactor fuel assembly, including the elements Fe, Cr, Ni, Mn, Ti, Mo, Al, C, Si, and B, wherein their mass percentages in the material are respectively: C 0.06 %, Cr 16.00%, Ni 15.00%, Mn1.20%, Ti 0.36%, Mo 1.50%, Al 0.2%, Si 0.40%, B 0.003%, Fe 65.277%. The total mass percentage of all impurity elements in the stainless steel cladding tube material is not higher than 0.03%; among the impurity elements, the mass percentage of P is not higher than 0.01%, the mass percentage of N is not higher than 0.003%, and the mass percentage of S is not higher than 0.003%. Higher than 0.0015%, the mass percentage of O is not higher than 0.0015%.

A method for preparing the stainless steel cladding tube material for the lead-bismuth fast reactor fuel assembly, including the following steps:

S1. Weighing materials: Polycrystalline silicon, nickel plate, pure iron, molybdenum strips, metal chromium, carbon, metal aluminum, metal manganese, boron iron alloy and sponge titanium are used as raw materials, of which the mass percentage of boron element in the boron iron alloy is 17%; raw materials The ratio between them satisfies the mass percentage of their elements: C 0.06%, Cr 16.00%, Ni 15.00%, Mn 1.20%, Ti 0.36%, Mo 1.50%, Al 0.2%, Si0.40%, B 0.003%, Fe 65.277%.

S2. Vacuum induction melting: Polysilicon is added in two times. First, some polysilicon, nickel plate, pure iron, molybdenum strips and chromium are placed in the crucible of the vacuum induction furnace. The furnace is evacuated until the vacuum degree is ≤5.0Pa. At 1500℃ Refining for 15 minutes; then add carbon and aluminum, stop powering after they melt, pass in protective gas argon, power again, add the remaining polycrystalline silicon, manganese, boron ferroalloy and sponge titanium at 1370°C, stir and adjust the steel The liquid temperature is 1525°C and poured into the mold to obtain a preliminary alloy ingot.

S3. Vacuum arc consumable remelting: Cut off 60mm of the shrinkage cavity of the preliminary alloy ingot obtained in step S2, and use it as a remelting electrode in a consumable furnace to perform vacuum arc consumable remelting to obtain a consumable remelted ingot. . After the ingot is cooled, the head and tail are removed, the surface is skinned and cut into pieces.

S4. Forging: Heat the consumable remelted ingot obtained in step S3 to 1200°C and keep it for 2 hours, then perform 40% upsetting-drawing pre-deformation, and then perform homogenization treatment at 1200°C. The holding time is 12 hours. Repeat the pier drawing twice, and the final deformation of the pier drawing is 40%, and an alloy forged rod with a diameter of 50 mm is obtained.

S5. Pipe rolling: Process the alloy forged rod obtained in step S4 into a tube blank with an outer diameter of 42mm and a wall thickness of 4.5mm, and perform solid solution treatment at 1080°C in an atmosphere protective furnace. The treatment time is 30min; followed by 12 passes of cold rolling deformation, the intermediate heat treatment temperature is 1080°C, the time is 20min, the final heat treatment is carried out in an atmosphere-protected roller continuous heat treatment furnace, the treatment temperature is 1060°C, the time is 12min; pre-deformation cold rolling The deformation amount is 20%, the feeding amount is 1.5mm/min, and a stainless steel cladding tube is obtained.

Example 3

A stainless steel cladding tube material for lead-bismuth fast reactor fuel assembly, including elements Fe, Cr, Ni, Mn, Ti, Mo, Al, C, Si, B, wherein their mass percentages in the material are respectively: C 0.04 %, Cr 15.00%, Ni 14.00%, Mn1.00%, Ti 0.20%, Mo 1.30%, Al 0.10%, Si 0.30%, B 0.004%, Fe 68.056%. The total mass percentage of all impurity elements in the stainless steel cladding tube material is not higher than 0.03%; among the impurity elements, the mass percentage of P is not higher than 0.01%, the mass percentage of N is not higher than 0.003%, and the mass percentage of S is not higher than 0.003%. Higher than 0.0015%, the mass percentage of O is not higher than 0.0015%.

A method for preparing the stainless steel cladding tube material for the lead-bismuth fast reactor fuel assembly, including the following steps:

S1. Weighing materials: Polycrystalline silicon, nickel plate, pure iron, molybdenum strips, metal chromium, carbon, metal aluminum, metal manganese, boron iron alloy and sponge titanium are used as raw materials, of which the mass percentage of boron element in the boron iron alloy is 17%; raw materials The ratio between them satisfies the mass percentage of their elements: C 0.04%, Cr 15.00%, Ni 14.00%, Mn 1.00%, Ti 0.20%, Mo 1.30%, Al 0.10%, Si0.30%, B 0.004%, Fe 68.056%.

S2. Vacuum induction melting: Polycrystalline silicon is added in two times. First, some polycrystalline silicon, nickel plate, pure iron, molybdenum strips and chromium are placed in the crucible of the vacuum induction furnace. The furnace is evacuated until the vacuum degree is ≤5.0Pa. At 1300℃ Refining for 20 minutes; then add carbon and aluminum, stop powering after they melt, pass in protective gas argon, power again, add the remaining polycrystalline silicon, manganese, boron ferroalloy and sponge titanium at 1350°C, stir and adjust the steel The liquid temperature is 1500°C and poured into the mold to obtain a preliminary alloy ingot.

S3. Vacuum arc consumable remelting: Cut off 50mm of the shrinkage cavity of the preliminary alloy ingot obtained in step S2, and use it as a remelting electrode in a consumable furnace to perform vacuum arc consumable remelting to obtain a consumable remelted ingot. . After the ingot is cooled, the head and tail are removed, the surface is skinned and cut into pieces.

S4. Forging: Heat the consumable remelted ingot obtained in step S3 to 1150°C and keep it for 2.5 hours, then perform 20% upsetting-drawing pre-deformation, and then perform homogenization treatment at 1150°C. The holding time is 11.5 hours. h, repeat the pier drawing 3 times, the final deformation of the pier drawing is 30%, and obtain an alloy forged rod with a diameter of 45mm.

S5. Pipe rolling: Process the alloy forged rod obtained in step S4 into a tube blank with an outer diameter of 40mm and a wall thickness of 4mm, and perform solid solution treatment at 1050°C in an atmosphere protective furnace for 40 minutes. ; Subsequently, 8 passes of cold rolling deformation are carried out. The intermediate heat treatment temperature is 1050°C and the time is 30 minutes. The final heat treatment is carried out in an atmosphere-protected roller continuous heat treatment furnace. The treatment temperature is 1030°C and the time is 15 minutes. Deformation of pre-deformation cold rolling The amount is 15%, the feeding amount is 1.0mm/min, and a stainless steel cladding tube is obtained.

Example 4

A stainless steel cladding tube material for a lead-bismuth fast reactor fuel assembly, including the elements Fe, Cr, Ni, Mn, Ti, Mo, Al, C, Si, and B, wherein their mass percentages in the material are respectively: C 0.08 %, Cr 16.00%, Ni 16.00%, Mn1.10%, Ti 0.48%, Mo 1.40%, Al 0.30%, Si 0.50%, B 0.004%, Fe 64.136%. The total mass percentage of all impurity elements in the stainless steel cladding tube material is not higher than 0.03%; among the impurity elements, the mass percentage of P is not higher than 0.01%, the mass percentage of N is not higher than 0.003%, and the mass percentage of S is not higher than 0.003%. Higher than 0.0015%, the mass percentage of O is not higher than 0.0015%.

A method for preparing the stainless steel cladding tube material for the lead-bismuth fast reactor fuel assembly, including the following steps:

S1. Weighing materials: Polycrystalline silicon, nickel plate, pure iron, molybdenum strips, metal chromium, carbon, metal aluminum, metal manganese, boron iron alloy and sponge titanium are used as raw materials, of which the mass percentage of boron element in the boron iron alloy is 17%; raw materials The ratio between them satisfies the mass percentage of their elements: C 0.08%, Cr 16.00%, Ni 16.00%, Mn 1.10%, Ti 0.48%, Mo 1.40%, Al 0.30%, Si0.50%, B 0.004%, Fe 64.136%.

S2. Vacuum induction melting: Polycrystalline silicon is added in two times. First, some polycrystalline silicon, nickel plate, pure iron, molybdenum strips and chromium are placed in the crucible of the vacuum induction furnace. The furnace is evacuated until the vacuum degree is ≤5.0Pa. At 1700℃ Refining for 10 minutes; then add carbon and aluminum, stop powering after they melt, pass in the protective gas argon, power again, add the remaining polycrystalline silicon, manganese, boron ferroalloy and sponge titanium at 1400°C, stir and adjust the steel The liquid temperature is 1550°C and poured into the mold to obtain a preliminary alloy ingot.

S3. Vacuum arc consumable remelting: Cut off 80mm of the shrinkage cavity of the preliminary alloy ingot obtained in step S2, and use it as a remelting electrode in a consumable furnace to perform vacuum arc consumable remelting to obtain a consumable remelted ingot. . After the ingot is cooled, the head and tail are removed, the surface is skinned and cut into pieces.

S4. Forging: Heat the consumable remelted ingot obtained in step S3 to 1180°C and keep it for 1.5 hours, then perform 30% upsetting-drawing pre-deformation, and then perform homogenization treatment at 1180°C, with a holding time of 12 hours. , repeat the pier drawing 5 times, the final deformation of the pier drawing is 35%, and an alloy forged rod with a diameter of 55mm is obtained.

S5. Pipe rolling: Process the alloy forged rod obtained in step S4 into a tube blank with an outer diameter of 50mm and a wall thickness of 5mm, and perform solid solution treatment at 1100°C in an atmosphere protective furnace for 20 minutes. ; followed by 15 passes of cold rolling deformation, the intermediate heat treatment temperature is 1100°C, the time is 10min, the final heat treatment is carried out in an atmosphere protected roller continuous heat treatment furnace, the treatment temperature is 1080°C, the time is 8min; deformation of pre-deformation cold rolling The amount is 25%, the feeding amount is 2.0mm/min, and a stainless steel cladding tube is obtained.

Comparative Test:

Compare the performance of Example 1 and Example 2 of the present invention with the 15Cr-15Ni series Ti-containing austenitic stainless steel (hereinafter referred to as 15-15Ti) currently commonly used in lead-based fast reactor cladding tubes. The composition range of -15Ti has not yet been unified. The chemical composition of 15-15Ti used in the present invention is: Cr 16wt.%, Ni 15wt.%, Mn 1.5wt.%, Ti0.36wt.%, Mo 2.1wt.%, Si 0.40 wt.%. The main difference between 15-15Ti and the stainless steel cladding tube material of the present invention is that the Mn content is not reduced, the Al content is not required, and the N content is not strictly controlled.

1. Component testing

Test instruments: oxygen, nitrogen and hydrogen analyzer, carbon and sulfur analyzer, optical microscope

Test steps: The chemical composition of the consumable remelted ingots of Example 1 and Example 2 was tested, and the alloy forged rods produced after forging of the consumable remelted ingots were microscopically observed. The composition detection results are as shown in Table 1. shows, the microscopic observation results of the forged rod are shown in Figures 1 and 2. Among them, O, N, H, C, and S elements are detected by elemental analyzers, and other elements are detected by chemical methods. Component detection usually does not target basic metal elements. The basic metal element of the self-consumable remelted ingot of the present invention is Fe. Therefore, there is no need to detect Fe element.

2. Quality inspection

Test instruments: ultrasonic non-destructive flaw detector, optical microscope

Test steps: Conduct ultrasonic flaw detection and microscopic observation on the stainless steel cladding tubes of Example 1 and Example 2. The results of microscopic observation are shown in Figures 3 and 4.

3. Tensile test, high temperature endurance test

Testing instrument: Universal tensile testing machine

Test steps: Conduct room temperature and high temperature tensile tests and 650°C, 1000h high temperature endurance tests on the stainless steel cladding tubes prepared in Example 1, Example 2 and 15-15Ti respectively. The test results are shown in Table 2.

4. Lead-bismuth corrosion test

Test equipment: optical microscope

Test steps: The stainless steel cladding tubes prepared in Example 1, Example 2 and 15-15Ti were subjected to static lead-bismuth liquid metal corrosion at 600°C for 500h, and then observed under a microscope. The test results are shown in Figure 5-7 .

Table 1 Detection results of components of consumable remelted ingots of Example 1 and Example 2

Table 2 Performance comparison between Example 1, Example 2 and 15-15Ti

As can be seen from Table 1, the total content of all impurity elements in the consumable remelted ingot of the present invention is less than 0.03%, and the content is relatively low, which indicates that the content of impurity elements is well controlled; the content of other elements is consistent with the elemental composition of the raw materials. The ratio is very close, which indicates that the composition of the stainless steel cladding tube material is well controlled. In addition, as can be seen from Figures 1 and 2, the alloy forged rod of the present invention has an excellent deformation structure, without striped carbides and macroscopic defects; the solidification segregation of the ingot is eliminated, and the grain size is greater than level 3. In addition, the ultrasonic flaw detection quality test results of the stainless steel cladding tube of the present invention are qualified, and it can be seen from Figures 3 and 4 that the microstructure of the cladding tube is well controlled, the grain structure is uniform, and the grain size is level 7-8. It can be seen that the material structure of the stainless steel cladding tube of the present invention is uniform and the surface quality of the material is excellent.

As can be seen from Table 2, the stainless steel cladding pipe material of the present invention has good room temperature and high temperature tensile strength and tensile plasticity, and the high temperature durable strength is equivalent to that of stainless steel 15-15Ti. It can be seen that the stainless steel cladding pipe material of the present invention has good room temperature and high temperature resistance. High temperature mechanical properties.

It can be seen from Figure 5-7 that after static lead-bismuth corrosion at 600°C and 500 hours, the oxide layer thickness of the cladding tube in Example 1 is 42 μm, the oxide layer thickness of the cladding tube in Example 2 is 35 μm, and the 15-15Ti cladding tube The oxide layer thickness is 83μm. Therefore, after the stainless steel cladding tube material of the present invention is corroded by lead and bismuth, the thickness of the oxide layer generated is smaller than that of similar austenitic stainless steel 15-15Ti. It can be seen that the stainless steel cladding tube material of the present invention has excellent lead-bismuth liquid metal resistance. Corrosion properties.

In summary, the present invention proposes a stainless steel cladding tube material for lead-bismuth fast reactor fuel assembly. By reducing the Mn content, adjusting the Al content and strictly controlling the N content, the structural uniformity of the alloy ingot is improved, and the stainless steel cladding tube material is improved. oxidation resistance and reduce inclusions in materials.

The present invention proposes a method for preparing stainless steel cladding tube materials for lead-bismuth fast reactor fuel assemblies. This method can more accurately control the chemical element content of the stainless steel cladding tube material, better reduce the content of impurity elements, and improve the material's Microstructure uniformity and hot and cold processing properties. Among them, multiple pier deformation and homogenization treatments are used for forging to ensure the elimination of segregation during the solidification process of the ingot and obtain an excellent deformation structure without banding structures and macroscopic defects. The stainless steel cladding tube material of the present invention has good room temperature and high temperature mechanical properties and excellent lead-bismuth liquid metal corrosion resistance, and can better meet the material selection requirements for lead-bismuth fast reactor fuel components.

The above are only examples of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the content of the description of the present invention, or directly or indirectly applied in other related technical fields, shall be regarded as Likewise, it is included in the patent protection scope of the present invention.

Claims (9)

1. The stainless steel ladle casing pipe material for the lead-bismuth fast reactor fuel assembly is characterized by comprising the following elements Fe, cr, ni, mn, ti, mo, al, C, si, B in percentage by mass: 0.04% or less of C or less than 0.08%, 15.0% or less of Cr or less than 17.0%, 14.0% or less of Ni or less than 16.0%, 0.3% or less of Si or less than 0.5%, 1.0% or less of Mn or less than 1.2%, 0.2% or less of Ti or less than 0.5%, 1.3% or less of Mo or less than 1.5%, 0.003% or less of B or less than 0.004%, 0.1% or less of Al or less than 0.3%, and the ratio of Ti to C by mass percent Ti/C is (4-6): 1; the balance being Fe;

the total mass percentage of all impurity elements of the stainless steel ladle shell and tube material is not higher than 0.03%; among the impurity elements, the mass percent of P is not higher than 0.01%, the mass percent of N is not higher than 0.003%, the mass percent of S is not higher than 0.0015%, and the mass percent of O is not higher than 0.0015%;

the stainless steel ladle shell tube material is prepared by the following preparation method:

s1, weighing: taking polycrystalline silicon, nickel plates, pure iron, molybdenum strips, metallic chromium, carbon, metallic aluminum, metallic manganese, ferroboron and sponge titanium as raw materials, wherein the mass percentage of boron element in the ferroboron is 15-20%; the proportion of the raw materials meets the mass percentage of the elements: 0.04% or less of C or less than 0.08%, 15.0% or less of Cr or less than 17.0%, 14.0% or less of Ni or less than 16.0%, 0.3% or less of Si or less than 0.5%, 1.0% or less of Mn or less than 1.2%, 0.2% or less of Ti or less than 0.5%, 1.3% or less of Mo or less than 1.5%, 0.003% or less of B or less than 0.004%, 0.1% or less of Al or less than 0.3%, and the ratio of Ti to C by mass percent Ti/C is (4-6): 1; the balance being Fe; the mass percentage of the polysilicon is 0.3-0.5%;

s2, vacuum induction melting: adding polysilicon twice, firstly, placing partial polysilicon, nickel plate, pure iron, molybdenum strip and metal chromium into a reaction container, vacuumizing and refining; adding carbon and metal aluminum, stopping power transmission after the carbon and the metal aluminum are melted, introducing protective gas, re-transmitting power, adding the rest polysilicon, metal manganese, ferroboron and sponge titanium at a first preset temperature, stirring, adjusting the temperature of molten steel to a second preset temperature, and pouring into a mold to obtain an alloy ingot casting primary body; the first preset temperature is 1350-1400 ℃; the second preset temperature is 1500-1550 ℃;

s3, vacuum arc consumable remelting: cutting off the shrinkage cavity part of the alloy ingot casting primary body obtained in the step S2, and carrying out vacuum arc consumable remelting to obtain a consumable remelting ingot;

s4, forging: upsetting-drawing and homogenizing the consumable remelting cast ingot obtained in the step S3 to obtain an alloy forging rod;

s5, rolling the pipe: and (3) processing the alloy forging rod obtained in the step (S4) into a tube blank, performing multi-pass cold rolling and heat treatment, and finally performing pre-deformation cold rolling to obtain the stainless steel ladle shell tube.

2. The stainless steel ladle tube material for the lead-bismuth fast reactor fuel assembly according to claim 1, wherein in the step S2, vacuum is pumped to a vacuum degree of less than or equal to 5.0Pa, and refining is carried out for 10-20min at 1300-1700 ℃.

3. The stainless steel ladle tube material for lead bismuth fast reactor fuel assemblies according to claim 1, wherein in the step S2, the shielding gas is argon.

4. The stainless steel ladle tube material for lead bismuth fast reactor fuel assemblies according to claim 1, wherein in the step S3, the shrinkage cavity is cut off by 50-80mm.

5. The stainless steel ladle tube material for the lead bismuth fast reactor fuel assembly according to claim 1, wherein in the step S4, 20-40% upsetting-drawing pre-deformation and homogenization treatment are performed, and then upsetting-drawing is performed for 2-5 times, wherein the final deformation is 30-40%; wherein the temperature of the homogenization treatment is 1150-1200 ℃, and the heat preservation time of the homogenization treatment is 11-12h.

6. The stainless steel ladle tube material for a lead bismuth fast reactor fuel assembly according to claim 1, wherein in the step S4, the diameter of the alloy forging rod is 45-55mm; in the step S5, the outer diameter of the tube blank is 40-50mm, and the wall thickness is 4-5mm.

7. The stainless steel ladle tube material for a lead bismuth fast reactor fuel assembly according to claim 1, wherein in the step S5, the tube blank is subjected to solution treatment before cold rolling, wherein the temperature of the solution treatment is 1050-1100 ℃, and the time of the solution treatment is 20-40min.

8. The stainless steel ladle tube material for the lead bismuth fast reactor fuel assembly according to claim 1, wherein in the step S5, the number of cold rolling passes is 8-15; the deformation amount of the pre-deformation cold rolling is 15-25%, and the feeding amount is 1-2mm/min.

9. The stainless steel ladle tube material for a lead bismuth fast reactor fuel assembly according to claim 1, wherein in the step S5, the heat treatment includes an intermediate heat treatment and a final heat treatment; wherein the temperature of the intermediate heat treatment is 1050-1100 ℃, and the time of the intermediate heat treatment is 10-30min; the temperature of the final heat treatment is 1030-1080 ℃, and the time of the final heat treatment is 8-15min.