CN110835716B - Preparation method of FeCrAl-based ODS alloy for nuclear reactor core - Google Patents

Abstract

The invention discloses a preparation method of FeCrAl-based ODS alloy for a nuclear reactor core, which is characterized by smelting Fe, 7-10% of Cr, 1.0-2.5% of W, 3.5-5.5% of Al, 0-1.2% of Nb, 0-0.5% of Ti and 0-0.3% of V according to a FeCrAl-based ODS alloy component formula to obtain alloy, and preparing the alloy after smelting into alloy powder; mixing the alloy powder with 0.4-1.0% of Zr and 0.25-0.5% of Y₂O₃Carrying out mechanical alloying ball milling treatment on the powder; sintering and densifying the ball-milled powder by hot isostatic pressing; forging the alloy blank obtained after hot isostatic pressing; 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 normal-temperature and high-temperature mechanical properties and excellent high-temperature oxidation resistance and corrosion resistance.

Description

Preparation method of FeCrAl-based ODS alloy for nuclear reactor core

Technical Field

The invention relates to the technical field of nuclear reactor cladding materials, in particular to a preparation method of FeCrAl-based ODS alloy for a nuclear reactor core.

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: when the contents of Cr and Al are reduced to prepare the FeCrAl-based ODS alloy, how to enable the FeCrAl-based ODS alloy to have good mechanical property and high-temperature oxidation resistance simultaneously is provided.

The invention is realized by the following technical scheme:

a preparation method of FeCrAl-based ODS alloy for a nuclear reactor core 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: 7% -10%, W: 1.0% -2.5%, Al: 3.5% -5.5%, Ti: 0% -0.5%, V: 0% -0.3%, Nb: 0% -1.2%, Zr: 0.4% -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 11 percent.

Further, the total weight percentage content of the W, Nb, Ti, Zr and V 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 1100-1150 ℃ at a heating rate of 2-10 ℃/min and preserving the heat for 2 h.

Further, in the step 4, the forging temperature is 1050 ℃, 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 with the weight percentage of (7-10)% Cr, (1.0-2.5)% W, (3.5-5.5)% Al, (0-0.3)% V, (0-0.5)% Ti, (0-1.2)% Nb, (0.4-1.0)% 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 11 percent, so that better high-temperature oxidation performance and corrosion resistance can be maintained; by adding 0.25-0.5% 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, which are uniformly dispersed in a matrix phase, the particle size is 10-40 nm, and the particles are treated at high temperature (650 ℃ and 20 hours), so that the remarkable phenomenon of grain growth or particle agglomeration does not occur, the thermal stability is good, and a very good effect is generated, 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 property of the alloyStrength and toughness at room temperature and high temperature, and thermal stability of 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.

Example 1

The embodiment provides a preparation method of FeCrAl-based ODS alloy for a nuclear reactor core, which comprises the following specific steps:

step 1, smelting Fe, Cr, W, Al, Ti, Nb and V elements according to a FeCrAl-based ODS alloy component formula, mixing industrial pure iron and high-purity alloy with the purity of more than 99.9% according to a formula shown in a table 1, and smelting by using a vacuum induction smelting furnace; and (3) obtaining alloy powder with the mesh number of 50-200 meshes from the smelted alloy by adopting an atomization powder preparation technology, wherein the oxygen content of the atomized alloy powder is controlled to be below 0.05 wt.%.

Step 2, mixing the alloy powder with Zr and Y₂O₃Carrying out mechanical alloying ball milling treatment on the powder; the specific ball milling mode is dry milling, the ball milling time is 30 hours, the ball-to-material ratio is 10:1, and the size of the powder obtained after ball milling is 65-130 mu m.

Step 3, sealing the ball-milled powder in a steel sheath, and sintering and densifying the powder through hot isostatic pressing; the pressure of hot isostatic pressing treatment is 150 MPa-190 MPa, the sintering temperature is 1050 ℃ to 1120 ℃, and the heat preservation time is 2 h-3 h.

Step 4, obtaining a cylindrical alloy blank after the hot isostatic pressing sample vehicle is subjected to canning removal, and forging the alloy blank; the forging process is to heat up to 1050 ℃ under the condition of the heating rate of 10 ℃/min, and to keep the temperature for 1-3 h, wherein the forging ratio is 3: 1.

And 5, turning the surface of the forged sample, loading at the temperature of no more than 800 ℃, quickly taking out and rolling the sample after the temperature of the sample is stable, and carrying out large deformation and small deformation. The total deformation is 66-74%, and the final thickness is 8-10 mm.

The formulation of the FeCrAl-based ODS alloy composition is shown in Table 1 by weightNumber 1^#As shown.

Example 2

The embodiment provides a preparation method of FeCrAl-based ODS alloy for a nuclear reactor core, which comprises the following specific steps:

step 1, smelting Fe, Cr, W, Al, Ti, Nb and V elements according to a FeCrAl-based ODS alloy component formula, mixing industrial pure iron and high-purity alloy with the purity of more than 99.9% according to a formula shown in a table 1, and smelting by using a vacuum induction smelting furnace; and (3) obtaining alloy powder with the mesh number of 50-200 meshes from the smelted alloy by adopting an atomization powder preparation technology, wherein the oxygen content of the atomized alloy powder is controlled to be below 0.05 wt.%.

Step 2, mixing the alloy powder with Zr and Y₂O₃Carrying out mechanical alloying ball milling treatment on the powder; the specific ball milling mode is dry milling, the ball milling time is 30 hours, the ball-to-material ratio is 10:1, and the size of the powder obtained after ball milling is 65-130 mu m.

Step 3, sealing the ball-milled powder in a steel sheath, and sintering and densifying the powder through hot isostatic pressing; the pressure of hot isostatic pressing treatment is 150 MPa-190 MPa, the sintering temperature is 1050 ℃ to 1120 ℃, and the heat preservation time is 2 h-3 h.

Step 4, obtaining a cylindrical alloy blank after the hot isostatic pressing sample vehicle is subjected to canning removal, and forging the alloy blank; the forging process is to heat up to 1050 ℃ under the condition of the heating rate of 10 ℃/min, and to keep the temperature for 1-3 h, wherein the forging ratio is 3: 1.

And 5, turning the surface of the forged sample, loading at the temperature of no more than 800 ℃, quickly taking out and rolling the sample after the temperature of the sample is stable, and carrying out large deformation and small deformation. The total deformation is 66-74%, and the final thickness is 8-10 mm.

The formulation of the FeCrAl-based ODS alloy composition is shown by the number 2 in Table 1^#As shown.

Example 3

The embodiment provides a preparation method of FeCrAl-based ODS alloy for a nuclear reactor core, which comprises the following specific steps:

step 1, smelting Fe, Cr, W, Al, Ti, Nb and V elements according to a FeCrAl-based ODS alloy component formula, mixing industrial pure iron and high-purity alloy with the purity of more than 99.9% according to a formula shown in a table 1, and smelting by using a vacuum induction smelting furnace; and (3) obtaining alloy powder with the mesh number of 50-200 meshes from the smelted alloy by adopting an atomization powder preparation technology, wherein the oxygen content of the atomized alloy powder is controlled to be below 0.05 wt.%.

Step 2, mixing the alloy powder with Zr and Y₂O₃Carrying out mechanical alloying ball milling treatment on the powder; the specific ball milling mode is dry milling, the ball milling time is 30 hours, the ball-to-material ratio is 10:1, and the size of the powder obtained after ball milling is 65-130 mu m.

Step 3, sealing the ball-milled powder in a steel sheath, and sintering and densifying the powder through hot isostatic pressing; hot isostatic pressing treatment, namely controlling the heating rate to be below 5 ℃/min, heating to 800 ℃, and starting pressurizing to 150-190 MPa at 800 ℃; then heating to 1050-1120 ℃ at a heating rate of 5-8 ℃/min, and preserving the heat for 2 h.

Step 4, obtaining a cylindrical alloy blank after the hot isostatic pressing sample vehicle is subjected to canning removal, and forging the alloy blank; the forging process is to heat up to 1050 ℃ under the condition of the heating rate of 10 ℃/min, and to keep the temperature for 1-3 h, wherein the forging ratio is 3: 1.

And 5, turning the surface of the forged sample, loading at the temperature of no more than 800 ℃, quickly taking out and rolling the sample after the temperature of the sample is stable, and carrying out large deformation and small deformation. The total deformation is 66-74%, and the final thickness is 8-10 mm.

The formulation of the FeCrAl-based ODS alloy composition is shown by the number 2 in Table 1^#As shown.

Comparative example 1

The embodiment provides a preparation method of FeCrAl-based ODS alloy for a nuclear reactor core, which is different from the embodiment 2 in that: the formulation of the FeCrAl-based ODS alloy composition is shown by the number 3 in Table 1^#As shown, no Zr element was added.

Comparative example 2

The embodiment provides a preparation method of FeCrAl-based ODS alloy for a nuclear reactor core, which is different from the embodiment 2 in that: the formulation of the FeCrAl-based ODS alloy composition is shown by number 4 in Table 1^#Shown that an excessive amount of Zr element was added。

Comparative example 3

The embodiment provides a preparation method of FeCrAl-based ODS alloy for a nuclear reactor core, which is different from the embodiment 2 in that:

step 1, according to the formula of FeCrAl-based ODS alloy components, smelting and casting Cr, W, Al, V, Nb, Zr, Ti and Y elements, mixing industrial pure iron and high-purity alloy with the purity of more than 99.9% according to the formula in table 1, and smelting and casting by using a vacuum induction smelting furnace.

And 2, sintering densification is carried out through hot isostatic pressing, wherein the pressure of hot isostatic pressing treatment is 80-90 MPa, the sintering temperature is 900-920 ℃, and the heat preservation time is 1 h. The hiped samples were used for subsequent forging and hot rolling processes.

Comparative example 4

The embodiment provides a preparation method of FeCrAl-based ODS alloy for a nuclear reactor core, which is different from the embodiment 2 in that: the hot isostatic pressed samples were not forged and hot rolled.

Comparative example 5

The embodiment provides a preparation method of FeCrAl-based ODS alloy for a nuclear reactor core, which is different from the embodiment 2 in that:

step 1, smelting Cr, W, Al, Nb, V, Zr, Ti and Y elements according to a FeCrAl-based ODS alloy component formula, mixing industrial pure iron and high-purity alloy with the purity of more than 99.9 percent according to a formula shown in a table 1, and smelting by using a vacuum induction smelting furnace; and (3) obtaining alloy powder with the mesh number of 50-200 meshes from the smelted alloy by adopting an atomization powder preparation technology, wherein the oxygen content of the atomized alloy powder is controlled to be below 0.05 wt.%.

Step 2, carrying out mechanical alloying ball milling treatment on the alloy powder; the specific ball milling mode is dry milling, the ball milling time is 30 hours, the ball-to-material ratio is 10:1, and the size of the powder obtained after ball milling is 65-130 mu m. The rest steps are the same.

TABLE 1 composition ratio of FeCrAl-based alloy example of the invention

FeCrAl alloys prepared in the above examples 1 to 3 and comparative examples 1 to 5 were subjected to a performance test, and the test results are shown in Table 2:

TABLE 2 FeCrAl alloy Performance test data prepared in examples 1-3 and comparative examples 1-5

Remarking:

room temperature mechanical property test conditions: tensile strength unit: MPa; elongation unit: percent; the test was carried out in particular according to GB/T228.2-2015 "tensile test for Metal materials".

High-temperature mechanical property test conditions: 800 ℃; tensile strength unit: MPa; elongation unit: percent; the test was carried out in particular according to GB/T228.2-2015 "tensile test for Metal materials".

High-temperature oxidation resistance: oxidizing in high-temperature steam at 1000 ℃ for 6 h; weight gain unit mg/cm²(ii) a Specifically, the test was carried out according to the zirconium alloy high temperature steam oxidation test protocol (internal protocol).

The FeCrAl set ODS alloy obtained by optimizing the components and controlling the process has good normal-temperature and high-temperature mechanical properties and excellent high-temperature oxidation resistance and corrosion resistance; the tensile strength of the alloy at 800 ℃ reaches 150 MPa-220 MPa, and the elongation is 25% -27%; the normal temperature tensile strength reaches 980 MPa-1040 MPa, and the elongation is 23% -26%; after oxidation at 1000 ℃ for 6h, the oxidation weight gain is only 0.045mg/cm²～0.088mg/cm²。

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (6)

1. A preparation method of FeCrAl-based ODS alloy for a nuclear reactor core 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, carrying out mechanical alloying ball milling treatment on the alloy powder and Zr and Y2O3 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: 7% -10%, W: 1.0% -2.5%, Al: 3.5% -5.5%, Ti: 0% -0.5%, V: 0% -0.3%, Nb: 0% -1.2%, Zr: 0.4% -1.0%, Y2O 3: 0.25 to 0.5 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 impurities meets the standard of commercial industrial pure iron and ferritic stainless steel;

wherein, the dosage of V, Ti and Nb satisfies the following conditions: v is more than 0, Ti is more than 0, and Nb is more than 0;

in the step 3, the pressure of hot isostatic pressing treatment is 120MPa to 200MPa, the sintering temperature is 1100 ℃ to 1150 ℃, and the heat preservation time is 2 hours; wherein the hot isostatic pressing treatment specifically comprises the following steps: firstly, controlling the heating rate to be below 5 ℃/min, heating to 800 ℃, and starting pressurizing to 120-200 MPa at 800 ℃; then heating to 1100-1150 ℃ at a heating rate of 2-10 ℃/min and preserving heat for 2 h;

in the step 4, the forging temperature is 1050 ℃, the heat preservation time is 1-3 h, and the forging ratio is 3: 1;

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.

2. The method for preparing FeCrAl-based ODS alloy for nuclear reactor core according to claim 1, wherein the total weight percentage content of Cr and Al alloying elements is not less than 11%.

3. The method for preparing FeCrAl-based ODS alloy for nuclear reactor core according to claim 1, wherein the total weight percentage content of W, Nb, Ti, Zr and V alloy elements is not less than 3.0%.

4. The method of claim 1, wherein in step 1, the atomized alloy powder has a particle size of 50 mesh to 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 by ball milling is 50 μm to 150 μm.

6. The method for preparing FeCrAl-based ODS alloy for nuclear reactor core as claimed in claim 1, wherein in step 2, dry milling is adopted, the ball milling time is 30h, and the ball-to-material ratio is 10: 1.