阅读说明：本技术 一种核反应堆耐事故燃料元件包壳用FeCrAl基ODS合金的制备方法 (Preparation method of FeCrAl-based ODS alloy for nuclear reactor accident-resistant fuel element cladding ) 是由 孙永铎 张瑞谦 周张健 邱绍宇 姚力夫 尹春雨 唐奇 于 2019-12-05 设计创作，主要内容包括：本发明公开了一种核反应堆耐事故燃料元件包壳用FeCrAl基ODS合金的制备方法,包括以下步骤：按照FeCrAl基ODS合金成分配方将Fe、Cr、W、Al、Nb、Ti、V元素进行熔炼获得合金,将熔炼后的合金采用雾化制粉技术获得目数小于200目的合金粉末；将合金粉末与Zr和Y<Sub>2</Sub>O<Sub>3</Sub>粉末进行机械合金化球磨处理；球磨后的粉末封入钢制包套中通过热等静压进行烧结致密化；热等静压后获得合金坯,将合金坯进行锻造处理；锻造后的样品经热轧处理获得FeCrAl基ODS合金。本发明通过优化组分及控制工艺获得的FeCrAl集ODS合金具有良好的高温力学性能、以及优异的高温抗氧化和耐腐蚀性能。(The invention discloses a preparation method of FeCrAl-based ODS alloy for nuclear reactor accident-resistant fuel element cladding, which comprises the following steps: smelting Fe, Cr, W, Al, Nb, Ti and V elements according to a FeCrAl-based ODS alloy component formula to obtain an alloy, and obtaining alloy powder with the mesh number of less than 200 by adopting an atomization powder preparation technology for the smelted alloy; mixing the alloy powder with Zr and Y 2 O 3 Carrying out mechanical alloying ball milling treatment on the powder; the powder after ball milling is sealed in a steel sheath for sintering densification through hot isostatic pressing; obtaining an alloy blank after hot isostatic pressing, and forging the alloy blank; and hot rolling the forged sample to obtain FeCrAl-based ODS alloy. The FeCrAl set ODS alloy obtained by optimizing the components and controlling the process has good high-temperature mechanical property and excellent high-temperature oxidation resistance and corrosion resistance.)

1. A preparation method of FeCrAl-based ODS alloy for nuclear reactor accident-resistant fuel element cladding is characterized by comprising the following steps:

step 1, smelting Fe, Cr, W, Al, Nb, Ti and V elements according to a FeCrAl-based ODS alloy component formula to obtain an alloy, and obtaining alloy powder with the mesh number of less than 200 by adopting an atomization powder preparation technology for the smelted alloy;

step 2, mixing the alloy powder with Zr and Y₂O₃Carrying out mechanical alloying ball milling treatment on the powder;

step 3, sealing the ball-milled powder in a steel sheath, and sintering and densifying the powder through hot isostatic pressing;

step 4, obtaining an alloy blank after hot isostatic pressing, and forging the alloy blank;

step 5, carrying out hot rolling treatment on the forged sample to obtain FeCrAl-based ODS alloy;

the formula of the FeCrAl-based ODS alloy comprises the following components in parts by weight: cr: 12% -14%, W: 1.5% -3.0%, Al: 4.5% -5.5%, Ti: 0% -0.5%, V: 0% -0.3%, Nb: 0-0.9%, Zr: 0.3% -1.0%, Y₂O₃: 0.25 to 0.5 percent of the total weight of the iron-based alloy, less than or equal to 0.008 percent of C, less than or equal to 0.008 percent of N and the balance of iron and impurities, wherein the content of the residual impurities meets the standard of commercial industrial pure iron and ferritic stainless steel.

2. The method for preparing FeCrAl-based ODS alloy for nuclear reactor emergency fuel element cladding as recited in claim 1, wherein the total content of Cr and Al alloying elements is 16% or more, and the content of Cr is 12.5% or more.

3. The method for preparing FeCrAl-based ODS alloy for nuclear reactor crash-resistant fuel element cladding as recited in claim 1, wherein the total weight percentage content of W, Nb, V, Ti and Zr alloying elements is not less than 3.0%.

4. The method of claim 1, wherein in step 1, the grain size of the atomized alloy powder is 50-200 mesh, and the oxygen content of the atomized alloy powder is controlled to be less than 0.05 wt.%.

5. The method of claim 1, wherein in the step 2, the size of the powder obtained after ball milling is 50 μm to 150 μm.

6. The method for preparing FeCrAl-based ODS alloy for nuclear reactor crash-resistant fuel element cladding as recited in claim 1, wherein in step 2, dry milling is performed, the ball milling time is 30h, and the ball-to-material ratio is 10: 1.

7. The method for preparing FeCrAl-based ODS alloy for nuclear reactor accident-resistant fuel element cladding as recited in claim 1, wherein in step 3, the pressure of hot isostatic pressing treatment is 100 MPa-200 MPa, the sintering temperature is 1050 ℃ -1150 ℃, and the holding time is 2 h-3 h.

8. The method for preparing FeCrAl-based ODS alloy for nuclear reactor accident-resistant fuel element cladding as recited in claim 7, wherein the hot isostatic pressing treatment comprises the steps of controlling the temperature rise rate to be below 5 ℃/min, raising the temperature to 800 ℃, and starting pressurizing to 120 MPa-200 MPa at 800 ℃; then heating to 1050-1150 ℃ at a heating rate of 2-10 ℃/min and preserving the heat for 2 h.

9. The method for preparing FeCrAl-based ODS alloy for nuclear reactor emergency fuel element cladding according to claim 1, wherein in step 4, the forging temperature is 1130 ℃, the holding time is 1-3 h, and the forging ratio is 3: 1.

10. The method for preparing FeCrAl-based ODS alloy for nuclear reactor crash-resistant fuel element cladding as recited in claim 1, wherein in said step 5, the hot rolling temperature is not more than 800 ℃, the total deformation is 60-80%, and the thickness of the final alloy material is 8-10 mm.

Technical Field

The invention relates to an accident-resistant cladding material of a nuclear reactor, in particular to a preparation method of FeCrAl-based ODS alloy for cladding of an accident-resistant fuel element of a nuclear reactor.

Background

The fuel element is the core component of the nuclear power reactor core, and the performance of the fuel element is directly related to the safety and the economical efficiency of the operation of the nuclear reactor. The zirconium alloy is the only cladding material adopted by the commercial nuclear power light water reactor fuel element at present. However, in an emergency (such as a fukushima nuclear accident, a pressurized water reactor water loss accident and the like), the zirconium alloy cladding reacts violently with high-temperature coolant water, and a large amount of heat and explosive gas hydrogen are released, so that the mechanical property of the cladding material is deteriorated, and nuclear catastrophic results such as reactor hydrogen explosion, leakage of a large amount of radioactive products and the like are generated. Therefore, compared with the existing nuclear zirconium alloy cladding material, the cladding material for the fuel element for the next generation and future advanced nuclear pressurized water reactor must have better high-temperature steam oxidation resistance, high-temperature strength and high-temperature stability, can provide larger safety margin within a certain time and avoid potential serious core melting accidents, and is also called accident-resistant cladding material. The accident-resistant cladding material is required to be capable of keeping a very low oxidation rate (at least 2 orders of magnitude lower than that of zirconium alloy) within a few hours (the longer the time is, the better the rescue time is) in a steam environment at about 800-1000 ℃, and meanwhile, the cladding material has mechanical strength meeting short-period reliability under a high-temperature condition (not lower than 800 ℃), so that the safety margin of a reactor core accident can be improved when the design basic accident is exceeded. Under the promotion of the strong demand background, the nuclear power countries in the world carry out a great deal of high-temperature oxidation performance research on a plurality of candidate accident-resistant cladding materials, and the most representative materials comprise Zr-2, Zr-4, SiC, 304SS, 310SS, FeCrAl-based alloy and the like. The research result shows that: the FeCrAl-based alloy has good radiation resistance and high-temperature oxidation resistance, and the strength of the FeCrAl-based ODS alloy at high temperature can be enhanced by Oxide Dispersion Strengthening (ODS), so the FeCrAl-based ODS alloy is an ATF cladding material with potential.

Most of the current commercial FeCrAl-based alloy materials have high Cr and Al contents (15-30 percent of Cr and 5-15 percent of Al), and although the high-temperature oxidation resistance is obvious, the alloy is easy to age harden and radiation embrittle when running in a reactor due to the high Cr and Al contents, thereby bringing great potential safety hazard to the running of the reactor. Furthermore, the high temperature strength of the existing FeCrAl alloys still does not fully meet the ATF fuel element cladding requirements.

The ODS steel is a novel heat-resistant steel prepared by a powder metallurgy method. A large amount of ultra-fine particles which are dispersed and distributed can not only improve the high-temperature mechanical property of the material, but also enhance the irradiation stability of the material by blocking dislocation movement. In the case of ferritic ODS steel, a major problem restricting the development thereof is the relatively poor corrosion resistance. In general, the oxidation resistance of the material is improved by increasing the Cr content, but the material has an enriched Cr element region in a long-term service environment, so that the mechanical property of the material is seriously deteriorated. Although Al can improve the strength and inhibit the generation of an enrichment region, the addition of Al influences the types of dispersed particles, and the size and the number density of the dispersed particles play a crucial role in the material performance.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the invention provides a preparation method of FeCrAl-based ODS alloy for cladding of nuclear reactor accident-resistant fuel elements, which solves the problems.

The invention is realized by the following technical scheme:

a preparation method of FeCrAl-based ODS alloy for nuclear reactor accident-resistant fuel element cladding comprises the following steps:

step 1, smelting Fe, Cr, W, Al, Nb, Ti and V elements according to a FeCrAl-based ODS alloy component formula to obtain an alloy, and obtaining alloy powder with the mesh number of less than 200 by adopting an atomization powder preparation technology for the smelted alloy;

step 2, mixing the alloy powder with Zr and Y₂O₃Carrying out mechanical alloying ball milling treatment on the powder;

step 3, sealing the ball-milled powder in a steel sheath, and sintering and densifying the powder through hot isostatic pressing;

step 4, obtaining an alloy blank after hot isostatic pressing, and forging the alloy blank;

step 5, carrying out hot rolling treatment on the forged sample to obtain FeCrAl-based ODS alloy;

the formula of the FeCrAl-based ODS alloy comprises the following components in parts by weight: cr: 12% -14%, W: 1.5% -3.0%, Al: 4.5% -5.5%, Ti: 0% -0.5%, V: 0% -0.3%, Nb: 0-0.9%, Zr: 0.3% -1.0%, Y₂O₃: 0.25 to 0.5 percent of the total weight of the iron-based alloy, less than or equal to 0.008 percent of C, less than or equal to 0.008 percent of N and the balance of iron and impurities, wherein the content of the residual impurities meets the standard of commercial industrial pure iron and ferritic stainless steel.

Further, the total weight percentage content of the Cr and Al alloy elements is more than or equal to 16%, and the content of the Cr is more than or equal to 12.5%.

Further, the total weight percentage content of the W, Nb, V, Ti and Zr alloy elements is more than or equal to 3.0%.

Further, in the step 1, the grain size of the atomized alloy powder is 50 to 200 meshes, and the oxygen content of the atomized alloy powder is controlled to be less than 0.05 wt.%.

Further, in the step 2, the size of the powder obtained after ball milling is 50 μm to 150 μm.

Further, in the step 2, dry milling is adopted, the ball milling time is 30 hours, and the ball-to-material ratio is 10: 1.

Further, in the step 3, the pressure of hot isostatic pressing treatment is 100 MPa-200 MPa, the sintering temperature is 1050-1150 ℃, and the heat preservation time is 2-3 h.

Further, hot isostatic pressing treatment, namely controlling the heating rate to be below 5 ℃/min, heating to 800 ℃, and starting pressurizing to 120-200 MPa at 800 ℃; then heating to 1050-1150 ℃ at a heating rate of 2-10 ℃/min and preserving the heat for 2 h.

Further, in the step 4, the forging temperature is 1130 ℃, the heat preservation time is 1-3 h, and the forging ratio is 3: 1.

Further, in the step 5, the hot rolling temperature is less than or equal to 800 ℃, the total deformation is 60-80%, and the thickness of the final alloy material is 8-10 mm.

The invention has the following advantages and beneficial effects:

the invention prepares a component of (12-14)% Cr, (1.5-3.0)% W, (4.5-5.5)% Al, (0-0.5)% Ti, (0-0.3)% V, (0-0.9)% Nb, (0.3-1.0)% Zr and (0.25-0.5)% Y by a hot isostatic pressing method₂O₃(wherein C and N are lower than 0.008 wt%) of multi-element ferrite ODS alloy material, and through the optimization of alloy element content and the control of processing technology, the obtained FeCrAl-based ODS alloy has high mechanical strength and plasticity suitable for processing at room temperature, and simultaneously has good high-temperature mechanical strength, high-temperature oxidation resistance and corrosion resistance.

Specifically, since the present invention employs preferable Cr, Al, W, Nb, Zr, Ti, V and Y₂O₃The total weight percentage content of Cr and Al alloy elements in the iron-based alloy is not less than 16 percent so as to keep better high-temperature oxidation performance and corrosion resistance; by adding 0.25% >. E0.5% of Y₂O₃Fine, uniform and dispersed oxides are formed, and the mechanical properties of the alloy at room temperature and high temperature are improved; appropriate amount of W, Nb, Ti, Zr and V alloy elements are added so as to precipitate Laves second phase particles and further improve the room temperature mechanical property and high temperature strength of the alloy. And then the processing technologies such as hot isostatic pressing, forging, rolling and the like are combined to obtain Y-Zr-O, Y-Al-O particles with the particle size of less than 100nm, the Y-Zr-O, Y-Al-O particles are uniformly dispersed in a matrix phase, the particle size can reach 50 nm-100 nm, and after high-temperature (800 ℃ and 20 hours) treatment, the remarkable phenomenon of grain growth or particle agglomeration does not occur, so that the high-temperature-resistant aluminum alloy has good thermal stability and produces a very good effect, and the effect is mainly shown in the following aspects: 1) the FeCrAl-based ODS alloy has excellent high-temperature oxidation resistance under the condition of 1000 ℃ steam, and the high-temperature steam oxidation rate is far lower than that of the Zr-4 alloy of the current commercial nuclear power cladding material; 2) the alloy of the invention obtains evenly distributed fine dispersed oxide particles after optimized formulation, mechanical alloying, hot isostatic pressing processing and forging, and obviously improves the mechanical properties (room temperature toughness and high temperature strength) of the alloy and the thermal stability of the alloy structure.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not used as limitations of the present invention.