KR101779128B1 - Alumina-forming duplex stainless steels as accident resistant fuel cladding materials for light water reactors - Google Patents

Abstract

The present invention relates to a nuclear fuel cladding pipe having a duplex organization and a manufacturing method thereof. By including 35-65 wt% of iron (Fe), 15-30 wt% of chromium (Cr), 15-30 wt% of nickel (Ni) and 5-10 wt% of aluminum (Al), essential processability and mechanical toughness can be retained as a thin nuclear fuel cladding pipe by forming the duplex organization in which an austenite phase with excellent ductility and a ferrite phase with excellent strength are mixed. Critical accident resistance which is dramatically improved can be provided because stable alumina is generated in a high temperature vapor environment which is expected under a high temperature nuclear accident.

Description

Technical Field [0001] The present invention relates to a stainless steel fuel cladding tube having a duplex structure excellent in light-water reactor accident resistance and a method of manufacturing the cladding tube,

The present invention relates to a duplex stainless steel nuclear fuel cladding tube having excellent mechanical properties and capable of providing a stable oxide film in a pressurized light water reactor water chemistry and high temperature water vapor environment, thereby providing excellent oxidation resistance in a normal operation of a light water reactor and an accident environment, and a method for manufacturing the same.

Alloy composition is very important because the nuclear fuel cladding, support grid and reactor structures used in nuclear fuel assemblies are subject to high temperature / high pressure corrosive environment and neutron irradiation, which leads to deterioration of mechanical properties due to embrittlement and corrosion growth. Thus, zirconium alloys having low neutron absorption cross sections and excellent mechanical strength and corrosion resistance have been widely applied in PWR (Pressurized Water Reactor) and Boiling Water Reactor (BWR) reactors for decades.

Among the zirconium alloys developed so far, Zircaloy-2 (tin 1.20-1.70 wt%, iron 0.07-0.20 wt%) containing tin (Sn), iron (Fe), chromium (Cr) (Zircaloy-4, tin 1.20-1.70 wt.%, Iron 0.18-0.24 wt.%, Chromium (Cr), chromium 0.05-1.15 wt.%, Nickel 0.03-0.08 wt.%, Oxygen 900-1500 ppm, zirconium balance) 0.07-1.13 wt%, oxygen 900-1500 ppm, nickel <0.007 wt%, zirconium remainder) alloy is the most widely used.

These zirconium-based alloy materials have very small neutron absorption cross-sectional area, excellent corrosion characteristics under steady-state operating conditions, good mechanical properties and excellent manufacturability, and have been used as nuclear fuel cladding in light-water nuclear reactors.

However, unlike normal operating conditions, when the reactor core loses its cooling ability in the event of an accident such as a loss of coolant accident, the zirconium metal cladding undergoes a rapid high temperature oxidation reaction in a high temperature water vapor environment due to the rapidly rising temperature of the nuclear fuel itself, And as a result, internal fuel and fission products may be discharged to the outside.

In addition, when a large amount of hydrogen, which is a byproduct of high-temperature oxidation reaction, is generated, damage to a reactor containment building due to atmospheric hydrogen explosion is damaged, thereby increasing loss.

Therefore, it is required to develop a new concept of oxidation resistant cladding for safety of cladding tube itself and for eliminating loss of hydrogen explosion etc.

Korean Patent No. 1595436 Korean Patent No. 0916642

It is an object of the present invention to provide a duplex structure in which austenite phase and ferrite phase are mixed to form a duplex structure, thereby providing excellent mechanical properties and producing a stable oxide film in a pressurized water reactor water chemistry and high temperature steam environment, To provide a duplex stainless steel fuel cladding which is capable of providing excellent oxidation resistance.

It is another object of the present invention to provide a method of manufacturing the fuel cladding.

In order to achieve the above object, the fuel cladding tube having a duplex structure according to the present invention comprises 35 to 65% by weight of iron (Fe), 15 to 30% by weight of chromium (Cr), 15 to 30% by weight of nickel (Ni) ) 5 to 10% by weight.

The nuclear fuel cladding tube comprises 0.1 to 2 parts by weight of niobium (Nb), 0.5 to 1.5 parts by weight (Mn) of manganese (Mn) based on 100 parts by weight of the mixture of iron (Fe), chromium (Cr), nickel , 0.3 to 1.0 part by weight of silicon (Si), 0.01 to less than 0.01 part of phosphorus (P), and 0.01 part or less of sulfur (S) can do.

The fuel cladding tube may comprise 30 to 60 vol% of the austenite phase and 30 to 60 vol% of the ferrite phase.

In another aspect of the present invention, there is provided a method of manufacturing a nuclear fuel cladding tube comprising the steps of: (A) preparing a fuel clad comprising 35 to 65% by weight of Fe, 15 to 30% by weight of Cr, 15 to 30% By weight of aluminum and 5 to 10% by weight of aluminum (Al) to prepare an ingot; (B) subjecting the produced ingot to hot rolling at 1100 to 1200 ° C for 5 to 10 times; (C) performing solution annealing of the alloy subjected to the hot rolling step at 1000 to 1300 占 폚; (D) pickling the surface of the alloy subjected to the solution annealing step; And (E) subjecting the pickled alloy to cold rolling at room temperature.

0.1 to 2 parts by weight of niobium (Nb) and 0.5 to 1.5 parts by weight of manganese (Mn) are added to 100 parts by weight of the mixture of iron (Fe), chrome (Cr), nickel (P) 0.01 parts by weight or less and 0.01 part by weight or less of sulfur (S), based on 100 parts by weight of at least one member selected from the group consisting of In addition, the ingot can be manufactured.

The fuel cladding tube of the present invention is a duplex stainless steel containing aluminum in an amount of 5 wt% or more. It can provide a stable oxide film containing alumina in a high temperature water vapor environment under a high temperature nuclear accident, Have excellent corrosion behavior in water chemistry environments.

In addition, since the fuel cladding tube of the present invention uses iron as a main material in place of zirconium used as a cladding material in the prior art, the production cost can be lowered to enhance the competitiveness.

In addition, the fuel cladding tube of the present invention has excellent mechanical properties by forming a duplex structure containing a mixture of austenite phase and ferrite phase.

1 is a photograph of a microstructure surface of an alloy produced according to Example 1 by SEM / BSE.
2 is a SEM / BSE photograph of a microstructure surface of an alloy prepared according to Example 2. FIG.
FIG. 3A is a photograph of the cross section of the alloy taken by SEM / BSE after exposing the alloy produced according to Example 1 for 72 hours under a steam of 1038 DEG C, FIG. 3B is a photograph of the alloy prepared according to Comparative Example 2 at 1038 DEG C Of SEM / BSE after exposure for 72 hours under water vapor.
FIGS. 4A and 4B are photographs of the surface of the alloy by SEM / BSE after exposing the alloy prepared in Example 1 for 45 days in a normal operating environment (360.degree. C., 190 bar controlled water chemistry) 4c is a photograph of the exposed cross section taken by FIB ion milling followed by 52 ^o tilted FIB / SEM, and FIG. 4D is a photograph of the same photograph taken in FIG.
5 is a graph showing stress-strain curves of an alloy prepared according to Example 1, Example 2 and Comparative Example 1 at room temperature micro tensile test.

The present invention relates to a duplex stainless steel nuclear fuel cladding tube having excellent mechanical properties and capable of providing a stable oxide film in a pressurized light water reactor water chemistry and high temperature water vapor environment, thereby providing excellent oxidation resistance in a normal operation of a light water reactor and an accident environment, and a method for manufacturing the same.

The present invention has been completed with stainless steel containing 5 wt% or more of aluminum so as to have excellent mechanical properties and oxidation resistance based on iron (Fe) to lower the production cost.

Hereinafter, the present invention will be described in detail.

The fuel cladding tube having a duplex structure according to the present invention includes iron (Fe), chromium (Cr), nickel (Ni), and aluminum (Al), and includes niobium Nb, manganese Mn, carbon C, Si), phosphorus (P), and sulfur (S).

Specifically, iron (Fe) reduces the manufacturing cost of the fuel cladding and is used with Cr, Ni and Al to form austenite phase and ferrite phase together An existing duplex organization can be implemented.

The iron (Fe) is used in an amount of 35 to 65% by weight, preferably 42 to 53% by weight. When the content of iron is less than the lower limit, the cost is not more efficient than the conventional cladding tube. If the content of iron is less than the lower limit, the duplex structure is not formed and the mechanical properties may be deteriorated.

The duplex structure includes a mixture of austenite phase and ferrite phase. In the present invention, the austenite phase is contained in an amount of 30 to 60% by volume, preferably 45 to 55% by volume, The ferrite phase is contained in an amount of 30 to 60% by volume, preferably 45 to 55% by volume, and the phase of the austenite phase and other phases other than the ferrite phase may be included. In this case, the uniform distribution of the two phases through the post-heat treatment is required to have desirable high temperature steam resistance and excellent toughness characteristics.

 When the content of the austenite phase is less than the lower limit value, the machinability may be deteriorated due to the decrease in ductility. When the content exceeds the upper limit value, the ferrite phase is decreased It is possible to cause a defect according to the irradiation drop.

When the content of the ferrite phase is less than the lower limit value, the ferrite phase may not satisfy the tensile strength and toughness characteristics required as the cladding tube. If the ferrite phase content exceeds the upper limit value, Is not excellent in the preparation of the cladding tube, and may cause deterioration of mechanical properties due to thermal brittleness.

Moreover, the austenite phase and the ferrite phase coexist at a volume ratio of 1: 0.5 to 1, preferably 1: 0.8 to 1. If the content of the ferrite phase is less than the lower limit value, the strength may be lowered. If the content of the ferrite phase is higher than the upper limit value, the preparation may not be excellent and mechanical properties may be deteriorated.

The chromium (Cr) is used together with nickel (Ni), aluminum (Al) and iron (Fe) to realize a preferable duplex structure. In addition, chromium (Cr) and aluminum So that a stable oxide film is formed in a high-temperature water vapor environment expected under accident conditions. In addition, in the normal operation condition of the nuclear power plant, chromium forms an oxide film which is a main component and has excellent corrosion behavior.

 The content of chromium (Cr) is 15 to 30 wt%, preferably 17 to 25 wt%, more preferably 20 to 24 wt%. If the content of chromium is less than the lower limit value, a preferable duplex structure is not controlled and tensile strength and toughness may be lowered, and a stable alumina oxide film may not be formed under high temperature steam. If the content of chromium exceeds the upper limit, The austenite phase and the ferrite phase distribution are not formed, which may lead to problems such as deterioration of workability and heat brittleness.

In addition, the nickel (Ni) may be used with Cr (Cr), Al (Al) and Fe (Fe) to form a duplex structure so that austenite phase and ferrite phase are formed in the present invention. have.

The content of nickel (Ni) is 15 to 30% by weight, preferably 20 to 24% by weight. When the content of nickel is less than the lower limit value, the duplex texture distribution suggested by the present invention may not be formed due to a decrease in austenite phase. If the content is higher than the upper limit value, the tensile strength and toughness it is possible to cause a defect in the toughness property and irradiation embrittlement.

Further, the aluminum (Al) is used with Cr and Ni to form a stable oxide film in a high temperature steam environment and can be used with Fe to improve the mechanical strength.

The content of the aluminum (Al) is 5 to 10% by weight, preferably 5 to 8% by weight. When the content of aluminum is less than the lower limit, the alumina oxide film is not efficiently formed when exposed to the high-temperature water vapor environment of the present invention. If the aluminum content is above the upper limit, the duplex structure distribution suggested by the present invention may not be formed. Secondary phase formation and solid-solution hardening which adversely affect the workability of the steel sheet.

The nuclear fuel cladding tube of the present invention may further contain 0.1 to 2 parts by weight of niobium (Nb), 0.5 to 2 parts by weight of manganese (Mn) 0.5, and the like, based on 100 parts by weight of iron (Fe), chromium (Cr), nickel (P) 0.01 parts by weight or less and 0.01 part by weight or less of sulfur (S), based on 100 parts by weight of carbon (C), 0.03 to 0.2 parts by weight of carbon (C), 0.3 to 1.0 parts by weight of silicon . The phosphorus may preferably be contained in an amount of 0.001 to 0.01 part by weight, respectively.

At least three kinds selected from the group consisting of niobium (Nb), manganese (Mn), carbon (C), silicon (Si), phosphorus (P) and sulfur (S) can improve the mechanical properties, And the extent to which it participates in the formation of duplex structure is insufficient and the extent to oxidation behavior is also insufficient. Therefore, when the respective contents of niobium (Nb), manganese (Mn), carbon (C), silicon (Si), phosphorus (P) and sulfur (S) are out of the above range, desired microstructure and mechanical properties none.

The present invention also provides a method of manufacturing a stainless steel fuel cladding tube having a duplex structure.

Recently developed accident-resistant fuel cladding tubes have been manufactured in a multi-layered structure using an alloy layer (coating) on the surface of conventional cladding tubes. The nuclear fuel cladding tube of the present invention has excellent mechanical properties such as a zirconium alloy through casting and heat- And is manufactured in a bulk metal casting type having oxidation resistance.

(A) 35 to 65 wt% of iron (Fe), 15 to 30 wt% of chromium (Cr), 15 to 30 wt% of nickel (Ni), and 5 to 10 wt% of aluminum % To produce an ingot; (B) subjecting the produced ingot to hot rolling at 1100 to 1200 ° C for 5 to 10 times; (C) performing solution annealing of the alloy subjected to the hot rolling step at 1000 to 1300 占 폚; (D) pickling the surface of the alloy subjected to the solution annealing step; And (E) subjecting the alloy subjected to the pickling treatment to cold rolling at room temperature.

In step (A), 35 to 65% by weight of iron, 15 to 30% by weight of chromium (Cr), 15 to 30% by weight of nickel (Ni) and 5 to 10% The ingot is manufactured. At this time, three or more selected from niobium (Nb), manganese (Mn), carbon (C), silicon (Si), phosphorus (P) and sulfur (S) can be further added to produce an ingot.

The ingot is preferably manufactured by a vacuum induction melting (VIM) method. Specifically, the ingot is heated in an inert gas atmosphere such as argon at a temperature of from 1150 to 1300 DEG C under a pressure of 500 Torr or less by using a vacuum induction melting furnace After dissolving for 2 to 3 hours, the ingot is cooled to produce an ingot in a capacity of 40 to 50 kg. After the air furnace heat treatment at 1100 to 1200 ° C for 3 hours for casting tissue destruction and microstructure homogenization treatment, the final 25 to 35 mm thick block form is processed for the subsequent rolling process.

At this time, it is preferable to dissolve the impurities repeatedly 3-5 times to prevent segregation of the impurities or uneven distribution of the alloy composition in the ingot. It is desirable to cool the specimen by injecting an inert gas such as argon in order to prevent oxidation phenomenon on the specimen surface during the cooling process.

Next, in the step (B), the ingot produced in the step (A) is subjected to a hot rolling process at 1100 to 1200 ° C for 5 to 10 times.

The ingot produced in the step (A) is rolled 5 to 10 times at 1100 to 1200 캜 under an inert gas atmosphere, and hot rolling is performed until the thickness becomes 2.5 to 3.5 mm.

When the temperature and the process are out of the above range during the hot rolling, even if iron, chromium, nickel and aluminum are used in the content of the present invention, a desired amount of austenite phase and ferrite phase are secured And may cause product defects such as plate thickness irregularity due to slip during the rolling process due to the solid-solution hardening effect of aluminum.

Next, the alloy subjected to the hot rolling step (C) is subjected to solution annealing at 1000 to 1300 ° C, preferably at 1030 to 1280 ° C for 2 to 4 hours.

In solution annealing, for example, austenitic steel is heated to a high temperature of 1030 DEG C or higher, and the compound is dissolved in the austenite. When air cooling is performed at the high temperature, Improves toughness.

In the present invention, the alloy subjected to the hot rolling step is subjected to solution annealing at 1000 to 1300 ° C to form a mixture of carbide and other compounds in austenite phase and ferrite phase, followed by air cooling, Control microstructure and improve machinability and processability for subsequent cladding fabrication.

Next, in step (D), the surface of the alloy subjected to the hot rolling process is chemically pickled with at least one pickling solution selected from the group consisting of nitric acid, hydrofluoric acid mixture, sulfuric acid and hydrochloric acid mixture, and hydrogen peroxide. After wrapping the pickled alloy, the material is stored and transported at room temperature.

The normal temperature means a temperature of 23 to 27 ° C.

Next, in step (E), the pickled alloy is subjected to cold rolling at room temperature so that a thickness of 1.2 to 2.4 mm, which is 20 to 60% reduced compared to the alloy produced in step (B) do.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention. Such variations and modifications are intended to be within the scope of the appended claims.

Example  1. Fe- Cr - Ni -Al alloy

(Fe), 47.5 wt% of iron (Fe), 23 wt% of chromium (Cr), 24 wt% of nickel (Ni) 0.48 parts by weight of Nb, 1.01 parts by weight of Mn, 0.12 parts by weight of C and 0.31 parts by weight of Si were dissolved in an argon atmosphere of 450 Torr using a vacuum induction melting furnace at a temperature of 1150 to 1300 DEG C for a total of 3 hours After cooling, the ingot was taken out and air-cooled by air-cooling at 1200 ° C for 3 hours for casting structure destruction and homogenization in an air furnace to produce a 30 mm thick block, followed by hot rolling at 1150 ° C for 8 times To prepare an alloy having a thickness of 3 mm. The alloy thus obtained was subjected to solution annealing at 1120 ° C. for 3 hours, washed with a nitric acid and hydrofluoric acid mixed acid solution in a bath, washed with water and then cold-rolled at room temperature to give a 1.2 mm- Was prepared.

Example 2. Fe-Cr-Ni-Al alloy

(Fe), chromium (Cr) 20 wt%, nickel (Ni) 21 wt%, aluminum (Al) 5.5 wt%, iron (Fe) 0.48 parts by weight of Nb, 1.01 parts by weight of Mn, 0.12 parts by weight of C and 0.31 parts by weight of Si were added to 100 parts by weight of a mixture of nickel (Ni) and aluminum (Al).

Example 3. Fe-Cr-Ni-Al alloy

(Fe), chromium (Cr), 16% by weight of nickel (Ni), 24.8% by weight of aluminum (Ni) 1.00 parts by weight of Nb, 1.11 parts by weight of Mn, 0.11 parts by weight of C and 0.33 parts by weight of Si, based on 100 parts by weight of a mixture of nickel (Ni) and aluminum (Al)

Comparative Example 1

In the United States, a plate-type (1.4 mm thick) single ferrite phase stainless steel Kanthal APM used as a reference material for the development of accident resistant stainless steel (ATF FeCrAl) was used for similar purposes. The quantified chemical composition values are shown in Table 1 below.

Comparative Example 2

Among the commercially available stainless steel 300 series, 310S, which is known to form a chromia oxide film at a high temperature due to a high Cr content, was used. The quantified chemical composition values are shown in Table 1 below.

< Test Example >

Test Example 1. Development Alloy Microstructure SEM / BSE Analysis

Table 1 below shows the chemical composition values of alloys used in Examples and Comparative Examples.

Chemical composition
(wt.%) Fe Ni Cr Al Nb Mn C Si Ti Example 1 Honey. 24.15 23.64 5.54 0.48 1.01 0.12 0.31 0.0080 Example 2 21.48 20.96 5.50 0.52 1.04 0.12 0.32 0.0056 Example 3 20.9 16.3 4.20 1.40 1.11 0.11 0.33 0.002 Comparative Example 1 - 21.99 5.81 - 0.16 0.033 0.28 0.038 Comparative Example 2 19.1 24.7 - - 0.87 0.06 0.69 -

The alloys produced according to Examples 1 to 3 of the present invention all have a duplex structure, Comparative Example 1 is a single ferrite stainless steel containing aluminum, Comparative Example 2 is a single austenite containing no aluminum (Austenite ) Stainless steel was used as a comparative material.

FIG. 1 is a photograph of a microstructure surface of an alloy prepared according to Example 1 by SEM / BSE, and FIG. 2 is a SEM / BSE photograph of a microstructure surface of an alloy prepared according to Example 2. FIG.

As shown in Figs. 1 and 2, the Fe-Cr-Ni-Al alloy produced according to the produced Embodiments 1 and 2 of the present invention has an austenite phase represented by a light gray portion and a (Ferrite) phase shown in Fig. Also, it was confirmed that the rounded image with black shades was a NiAl phase (B2) composed of nickel (Ni) and aluminum (Al).

Test Example  2. Oxidation weight measurement under high temperature steam

 After forming the open loop type pure water vapor environment at 1038 캜, the alloys (5 kinds, each 2 pieces) prepared in Examples and Comparative Examples were exposed for 72 hours to measure the weight before and after exposure to high temperature steam. The values in Table 2 are average and standard deviation values obtained by subtracting the weight value before the apparatus from the weight value after leaving the apparatus.

division Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Weight change
(mg / cm ²⁾ 0.128 + 0.02 0.108 ± 0.01 1.28 ± 0.48 0.318 ± 0.12 1.457 ± 0.09

As shown in Table 2, it was confirmed that the alloys prepared according to Examples 1 and 2 of the present invention showed almost no increase in oxidation weight even after prolonged exposure under high temperature steam, and thus were excellent in oxidation resistance in high temperature steam environment. In other words, accidental resistance can be improved by minimizing the thickness thinning due to high temperature steam oxidation of the medium - and - high temperature notched cladding tube and by delaying the time to reach the radiation exposure by rapid melting of the covering material.

On the other hand, the alloys of Example 3 and Comparative Examples 1 and 2 were found to be susceptible to high temperature oxidation because the weight increase value was larger than those of Examples 1 and 2. Particularly, in Comparative Examples 2 and 3 containing less than the lower limit of aluminum suggested in the present invention, a very high weight increase value of more than ten times was shown.

Test Example 3. Analysis of SEM / BSE oxide film after exposure to high temperature steam

FIG. 3A is a photograph of a section of the alloy taken by SEM / BSE after exposing the alloy produced according to Example 1 for 140 hours under water vapor for 72 hours, FIG. 3B is a photograph of the alloy prepared according to Comparative Example 2 at a temperature of 1038.degree. SEM / BSE images of the cross section of the alloy after exposure to steam for 72 hours.

The alloys of Example 1 and Comparative Example 2 were similarly exposed to open-loop type pure water vapor environment at 1038 캜 for 72 hours after the composition.

As shown in FIG. 3A, the alloy prepared according to Example 1 of the present invention was found to have an alumina oxide film having a thickness of 3 μm on the surface of the alloy after being left under the steam of 1038 ° C. for 72 hours.

On the other hand, as shown in FIG. 3B, when the alloy of Comparative Example 2 was allowed to stand for 72 hours under steam of 1038 ° C., internal oxidation occurred, and silicon dioxide (SiO ₂ ) of 20 μm thickness was generated as internal oxides, It was confirmed that a 8 μm thick surface chromia oxide film thicker than the alumina oxide film of Example 1 was also produced. This is in accordance with the result that the weight of oxidation shown in Test Example 2 is much increased and that the alloy of Comparative Example 2 containing less than the lower limit of aluminum suggested in the present invention is vulnerable to the nuclear accident condition (high temperature steam oxidation) .

Test Example 4. Surface FIB / SEM Oxide Film Analysis After Exposure to Normal Operating Environment of Pressurized Light Water Reactor

4A and 4B are photographs of the surface of the alloy taken by SEM / BSE after exposure of the alloy prepared in Example 1 at 360 ° C and 190 bar for 45 days (1080 hours) and the cross-sectional pictures taken 52 ^o inclined (tilted) to the FIB / SEM of the alloy, Figure 4d is a schematic view showing this picture and pictures taken to expand the same picture Figure 4c. 4D is a schematic representation of the structure of the above FIB / SEM photograph.

The alloy prepared according to Example 1 was tested for water chemistry (7.1 pH), temperature (360 ° C), pressure (190 bar), and pressure at a closed loop system in order to simulate the pressurized water reactor primary environment. , And dissolved oxygen (3 ppm) for 45 days (1080 hours).

As shown in Figs. 4A and 4B, in the normal operating environment, the alloy of Example 1 is expected to have an oxide film mainly composed of chromium on the surface thereof, and to have excellent oxidation behavior even in a long-term operation in a core as a cladding.

Further, as shown in Figs. 4C and 4D, the corrosion behavior of the alloy of Example 1 is similar to ordinary stainless steels, and thus can have better or equal oxidation resistance than zirconium clad tubes at present.

Test Example  5. Through microtensile stress-strain curves The tensile strength  And Elongation  Measure

Fig. 5 shows stress-strain curves, which are the result of microtensile tests at room temperature for alloys prepared according to Examples 1 and 2 and Comparative Example 1. Fig.

The alloys prepared according to Examples 1 and 2 were processed in the same manner as in Comparative Example 1 to obtain plate-like microtensile specimens (specimen length 16 mm, gage 5 mm, thickness 0.5 mm), and the strain in the reduced section was 3.33E -4 sec ^-1 (cross-head speed 0.1 mm / min), and the tensile properties of the specimen at room temperature were evaluated.

As shown in FIG. 5, it was confirmed that Examples 1 and 2 exhibited excellent tensile toughness values at room temperature than Comparative Example 1. That is, the result shows that the processability of the present invention material, which is essential for manufacturing a thin nuclear fuel cladding tube, is excellent.

Table 3 below shows the mean and standard deviation values for the Ultimate Tensile Strength (UTS) and elongation shown in the stress-strain curve of FIG. 5.

division The tensile strength
(MPa) Elongation
(%) Comparative Example 1 710.5 ± 29.64 24.0 ± 0.18 Example 1 932.9 ± 10.24 22.2 ± 0.56 Example 2 989.7 ± 0.62 24.5 + 0.02

As shown in the above Table 3, alloys produced according to Examples 1 and 2 of the present invention all have high tensile strength values and elongations similar to those of Comparative Example 1. This is the result of disproving the high toughness characteristics of the present invention.

Claims (6)

A stainless steel nuclear fuel cladding comprising 35 to 65% by weight of iron (Fe), 15 to 30% by weight of chromium (Cr), 15 to 30% by weight of nickel (Ni) and 5 to 10% by weight of aluminum (Al)
The stainless steel fuel cladding tube may be manufactured by (i) dissolving the iron (Fe), chromium (Cr), nickel (Ni) and aluminum (Al) Hot rolled, (iii) subsequently subjecting the hot-rolled alloy to solution annealing at 1000-1300 ° C, and then (iv) exposing the surface of the alloy subjected to the solution annealing process to By pickling treatment and performing cold rolling at room temperature,
Austenite phase, a ferrite phase and a NiAl (B2) phase, wherein the austenite phase and the ferrite phase each comprise 30 to 60% by volume,
Characterized in that the austenite phase and the ferrite phase are formed as 1: 0.5-1 of the secondary skin. The fuel clad tube according to claim 1, wherein the nuclear fuel cladding tube comprises 0.1 to 2 parts by weight of niobium (Nb), manganese (Mn), and manganese (Mn) in 100 parts by weight of a mixture of Fe, Cr, Ni, ), 0.5 to 1.5 parts by weight of carbon (C), 0.03 to 0.2 parts by weight of carbon (C), 0.3 to 1.0 parts by weight of silicon (Si), 0.01 parts by weight of phosphorus (P) Wherein the stainless steel fuel clad further comprises three or more species. delete delete (A) preparing an ingot by dissolving 35 to 65% by weight of iron (Fe), 15 to 30% by weight of chromium (Cr), 15 to 30% by weight of nickel (Ni) and 5 to 10% ;
(B) subjecting the produced ingot to hot rolling at 1100 to 1200 ° C for 5 to 10 times;
(C) performing solution annealing of the hot-rolled alloy at 1000-1300 占 폚;
(D) pickling the surface of the alloy subjected to the solution annealing step; And
(E) performing cold rolling at room temperature on the pickled alloy,
An austenite phase, a ferrite phase and NiAl (B2), wherein the austenite phase and the ferrite phase each comprise 30 to 60% by volume,
Wherein the austenite phase and the ferrite phase are formed to have a bulk density of 1: 0.5-1. The method of claim 5, wherein 0.1 to 2 parts by weight of niobium (Nb) is added to 100 parts by weight of iron (Fe), chromium (Cr), nickel (Ni), and aluminum 0.5 to 1.5 parts by weight of carbon (Mn), 0.03 to 0.2 parts by weight of carbon (C), 0.3 to 1.0 part by weight of silicon (Si), 0.01 parts by weight of phosphorus (P) Wherein the ingot is produced by adding at least three selected from the group consisting of iron and iron.

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