KR100754477B1 - Zr-based Alloys Having Excellent Creep Resistance - Google Patents

Abstract

The present invention relates to a zirconium alloy composition having excellent creep resistance, and more particularly, 0.8 to 1.8 wt% of niobium (Nb) subjected to final heat treatment so as to have a recrystallization of 40 to 70% to improve creep resistance; Tin (Sn) 0.38-0.50 wt%; And / or at least one element selected from 0.1 to 0.2 wt% of iron (Fe), 0.05 to 0.15 wt% of copper (Cu), and 0.12 wt% of chromium (Cr); Oxygen (O) 0.10 to 0.15 wt%; 0.006% to 0.010% carbon (C); 0.006% to 0.010% silicon (Si); 0.0005 to 0.0020% by weight of sulfur (S); and zirconium alloy composition containing the balance zirconium (Zr). The zirconium alloy prepared by the composition of the present invention is very excellent in creep resistance than the conventional zircaloy-4, and can be very useful as a fuel coating pipe, a support grid, and an internal structure in a nuclear reactor reactor reactor reactor reactor core.

Zirconium Alloy, Zircaloy, Creep Resistance

Description

Zr-based Alloys Having Excellent Creep Resistance

1 is a recrystallization diagram of a zirconium alloy according to the present invention; And

2 is a graph showing creep strain according to the recrystallization of the zirconium alloy according to an embodiment of the present invention.

The present invention relates to a zirconium alloy composition having excellent creep resistance, and more particularly, 0.8 to 1.8 wt% of niobium (Nb) subjected to final heat treatment so as to have a recrystallization of 40 to 70% to improve creep resistance; Tin (Sn) 0.38-0.50 wt%; And / or at least one element selected from 0.1 to 0.2 wt% of iron (Fe), 0.05 to 0.15 wt% of copper (Cu), and 0.12 wt% of chromium (Cr); Oxygen (O) 0.10 to 0.15 wt%; 0.006% to 0.010% carbon (C); 0.006% to 0.010% silicon (Si); 0.0005 to 0.0020% by weight of sulfur (S); and zirconium alloy composition containing the balance zirconium (Zr).

Nuclear power plant fuel cladding is one of the key core components that traps fuel and prevents fission products from entering the cooling water. The outside of the fuel cladding tube is exposed to 320 ° C. cooling water under about 15 MPa pressure. Nuclear fuel cladding pipes are widely used because zirconium alloys are very important because alloy composition is accompanied by deterioration of mechanical properties due to embrittlement and growth due to high temperature / high pressure corrosion environment and neutron irradiation. That is, a zirconium alloy (eg, Zircaloy-4) developed in the early 1960's is used because the zirconium alloy has excellent mechanical strength, creep resistance, corrosion resistance, thermal conductivity, and low neutron absorption at high temperatures. .

However, due to high combustion, long cycle operation, high temperature coolant and high pH operation to increase the economics of nuclear power plants, it is difficult to continue to use the existing Zircaloy-4 cladding as a fuel cladding.

Therefore, in order to improve the safety and economic efficiency of the reactor, a new fuel cladding tube having greatly improved reliability and thermal margin is required. For this purpose, a new alloy cladding tube having improved corrosion resistance and creep resistance has been developed. Newly developed new alloys for cladding tubes tend to add Nb to reduce or eliminate the Sn content which adversely affects the corrosion resistance.

U.S. Patent No. 5,832,050 discloses a zirconium alloy composition and manufacturing process that improves corrosion resistance and creep resistance by adding 8 to 100 ppm of sulfur to a zirconium alloy containing at least 96% (hereinafter,% means% by weight). Doing. The alloy composition referred to in this patent claims the following eight alloys as dependent claims, claiming Zr alloys containing 96% or more of sulfur added by 8-100 ppm (preferably 8-30 ppm) as independent claims. That is, alloy 1: Zr alloy with Sn 1.2 to 1.7%, Fe 0.18 to 0.25%, Ni 0.05 to 0.15%, Cr 0.05 to 0.15%;

Alloy 2: Zr alloy having Sn 1.2 to 1.7%, Fe 0.07 to 0.2%, Ni 0.05 to 0.15%, Cr 0.05 to 0.15%;

Alloy 3: Zr alloy with Nb 0.7-1.3%, O 900-1600 ppm;

Alloy 4: Zr alloy with Sn 0.3-1.4%, Fe 0.4-1%, V 0.2-0.7%, O 500-1800 ppm;

Alloy 5: Zr alloy with Nb 0.7-1.3%, Sn 0.8-1.5%, Fe 0.1-0.6%, Cr 0.01-0.2%, O 500-1800 ppm;

Alloy 6: Zr alloy with Nb 0.1-0.3%, Sn 0.7-1.25%, Fe 0.1-0.3%, Cr 0.05-0.2%, Ni 0.01-0.02%, O 500-1800 ppm;

Alloy 7: Zr alloy having Nb of 2.2 to 2.8%; And

Alloy 8: Zr alloys with 0.3 to 0.7% Sn, 0.3 to 0.7% Fe, 0.1 to 0.4% Cr, 0.01 to 0.04% Ni, 70 to 120 ppm Si, and 500 to 1800 ppm O are disclosed.

U.S. Patent Application Publication No. 2004/0118491 discloses the following alloy-based compositions and manufacturing processes that have undergone recrystallization heat treatment and limited the composition and size of precipitates to improve corrosion resistance.

(Fe 0.03-0.25%) + (Cr, V, Nb 0.8-1.3%, Sn <2000 ppm, O 500-2000 ppm, C <100 ppm, S 3-35 ppm, Si <50 ppm) Zr alloy.

In addition, J. Nucl . Mater . , vol. 255 (1998) p.78 mentions Zr-1.0% Nb and Zr-0.5% Sn-0.6% Fe-0.4% V alloys by adding sulfur to improve thermal creep resistance, the same magazine vol.304 ( 2002. p.246 explains the correlation between the precipitated phase and the corrosion characteristics produced by adding up to 850 ppm of sulfur to unalloyed-Zr.

In addition to the prior art, US Pat. No. 5,254,308 added Nb and Fe to maintain the mechanical properties of the alloy due to Sn reduction. This alloy contains 0.45 to 0.75% Sn (preferably 0.6%), 0.4 to 0.53% Fe (preferably 0.45%), 0.2 to 0.3% Cr (preferably 0.25%), 0.3 to 0.5% Nb (preferably Is 0.45%), 0.012-0.03% Ni (preferably 0.02%), 50-200 ppm Si (preferably 100 ppm), and 1000-2000 ppm oxygen (preferably 1600 ppm). At this time, Fe / Cr = 1.5, and the amount of Nb was determined according to the amount of Fe affecting the hydrogen absorption, and the alloys had excellent corrosion resistance and strength by controlling the amount of Ni, Si, C, and O added. It was. U.S. Patent 5,334,345 discloses 1.0-2.0% Sn, 0.07-0.70% Fe, 0.05-0.15% Cr, 0.16-0.40% Ni, 0.015-0.30% Nb (preferably to improve corrosion resistance and hydrogen absorption resistance). 0.015-0.20%), 0.002-0.05% Si (preferably 0.015-0.05%), and 900-1600 ppm oxygen. U.S. Patent No. 5,366,690 mainly controlled the amount of Sn, N, Nb addition, 0 to 1.5% Sn (preferably 0.6%), 0 to 0.24% Fe (preferably 0.12%), 0 to 0.15% Cr ( Preferably 0.10%), 0-2300 ppm N, 0-100 ppm Si (preferably 100 ppm), 0-1600 ppm oxygen (preferably 1200 ppm), 0-0.5% Nb (preferably 0.45%) An alloy composition consisting of U.S. Patent No. 5,211,774 mentions a zirconium alloy composition developed for the purpose of improving ductility, creep strength and corrosion resistance in neutron irradiation environments. In this case, the alloy is Sn 0.8-1.2%, Fe 0.2-0.5% (preferably 0.35%), Cr 0.1-0.4% (preferably 0.25%), Nb 0-0.6%, Si 50-200 (preferably 50ppm), O 900 ~ 1800 ppm (preferably 1600ppm) composition, and the amount of Si was changed to reduce the change in corrosion resistance according to hydrogen absorption and process differences.

European Patent No. 195,155 proposes a Duplex cladding tube, the zirconium alloy containing 0.1 to 0.3% Sn, 0.05 to 0.2% Fe, 0.05 to 0.4% Nb, one or two of Cr and Ni. 0.03% to 0.1%. At this time, the content of Fe + Cr + Ni should not exceed 0.25% and included oxygen 300 ~ 1200ppm. European Patent No. 468,093 or U.S. Patent No. 5,080,861 show 0-0.6% Nb, 0-0.2% Sb, 0-0.2% Te, 0.5-1.0% Sn, 0.18- to improve the corrosion resistance of the alloy at high combustion. A zirconium alloy consisting of 0.24% Fe, 0.07 ~ 0.13% Cr, 900 ~ 2000ppm O, 0 ~ 70ppm Ni, 0 ~ 200ppm C is proposed. At this time, the size of the precipitate was limited to 1200 ~ 1800 하였고 and Bi may be added up to 0.2% instead of Te or Sb. Similar zirconium alloy compositions have been proposed in European Patent No. 345,531, which contains Nb 0 to 0.6%, Mo 0 to 0.1%, Sn 1.2 to 1.70%, Fe 0.07 to 0.24%, Cr 0.05 to 0.13%, Ni 0 ~ 0.08%, O 900 ~ 1800 ppm composition. EP 532,830 describes a composition for improving corrosion resistance, irradiation stability, mechanical strength, and creep resistance of an alloy, including Nb 0 to 0.6%, Sn 0.8 to 1.2%, Fe 0.2 to 0.5% (preferably 0.35%). Zirconium alloys with 0.1 to 0.4% Cr (preferably 0.25%), Si 50 to 200 ppm (preferably 100 ppm) and O 900 to 1800 ppm (preferably 1600 ppm) are proposed. In French Patent No. 2,624,136, a zirconium alloy in which Nb and V are added together, Fe 0.1 to 0.35%, V 0.1 to 0.4%, O 0.05 to 0.3%, Sn 0 to 0.25%, Nb 0 to 0.25%, V / Fe A composition of> 0.5 and an optimum alloy manufacturing process using this composition are suggested.

Japanese Patent No. 62,180,027 proposes a Zr alloy with Nb 1.7-2.5%, Sn 0.5-2.2%, Fe 0.04-1.0% in order to improve the mechanical strength and nodular corrosion resistance of the alloy. The addition amount of Fe + Mo was limited to 0.2 ~ 1.0%. Japanese Patent No. 2,213,437 also proposes an alloy containing Nb, including a Zr-Sn-Fe-V alloy, in order to improve nodular corrosion resistance. That is, an alloy composition consisting of Zr 0.25-1.5%, Nb 0.15-1.0%, Fe and Zr 0.25-1.5%, Nb 0.5-1.0%, Sn 0.05-0.15%, Ni was proposed. Japanese Patent No. 62,207,835 proposes a ternary alloy consisting of Zr 0.2-2.0%, Nb 0.5-3.0%, Sn 900-2500 ppm, O. Japanese Patent No. 62,297,449 proposes an alloy composition of Nb 1 to 2.5%, Sn 0.5 to 2.0%, Mo 0.1 to 1.0%, and Mo + Nb 1.5 to 2.5% to improve corrosion resistance, ductility and strength. In the β or β region, a manufacturing process by a solution treatment method is proposed, and Japanese Patent No. 62,180,027 has a similar composition except that Fe is added, that is, Nb 1.7-2.5%, Sn 0.5-2.2%, The composition of Fe 0.04 ~ 1.0%, Mo 0.2 ~ 1.0%, Fe + Mo 0.2 ~ 1.0% was presented.

U.S. Patent Nos. 4,863,685, 4,986,975, 5,024,809, and 5,026,516 have proposed Zr alloys containing 0.5-2.0% Sn and approximately 0.5-1.0% of other solute atoms. These alloys also contain between 0.09 and 0.16% oxygen. Specifically, the alloy of US Pat. No. 4,863,685 included Mo, Te, mixtures thereof or Nb-Te, Nb-Mo as solute atoms other than Sn. The alloy composition of U. S. Patent No. 4,986, 975 contained Cu, Ni, Fe, etc. as a solute atom, its content was limited to 0.24-0.40%, and Cu was added at least 0.05%. In US Pat. Nos. 5,024,809 and 5,026,516, Mo, Nb, Te, and the like were added as solute atoms, and the amount thereof was limited to 0.5 to 1.0%, similar to US Pat. No. 4,863,685, and Bi or Bi + Sn was 0.5 to 2.5. % Was added.

In US Patent No. 4,938,920, an attempt was made to develop an alloy with improved corrosion resistance by improving the conventional Zircaloy-4, reducing the amount of Sn added to 0 to 0.8% and 0 to 0.3% V and 0 to 1% Nb was added. At this time, the amount of Fe added was 0.2 ~ 0.8%, the amount of Cr was 0 ~ 0.4%, the amount of Fe + Cr + V was limited to 0.25 ~ 1.0%. In addition, the addition amount of oxygen was 1000-1600 ppm. 0.8% Sn-0.22% Fe-0.11% Cr-0.14% O, 0.4% Nb-0.67% Fe-0.33% Cr-0.15% O, 0.75% Fe-0.25% V-0.1% O or 0.25% Sn-0.2% When the corrosion test was performed on an alloy having a composition of Fe-0.15% V-0.1% O for 200 days in a steam atmosphere at 400 ° C., the corrosion amount was about 60% of Zircaloy-4 and the tensile strengths of Zircaloy-4 Similar.

U.S. Patent No. 4,963,323 or Japanese Patent No. 1,188,646 modified the alloy components in the existing Zircaloy-4 to develop a fuel cladding material having improved corrosion resistance. That is, the content of Sn was reduced, and Nb was added to compensate for the decrease in strength due to the reduction of Sn, and the amount of nitrogen was made 60 ppm or less. Specifically, Sn 0.2 ~ 1.15%, Fe 0.19 ~ 0.6% (preferably 0.19 ~ 0.24%), Cr 0.07 ~ 0.4% (preferably 0.07 ~ 0.13%), Nb 0.05 ~ 0.5%, N ≤ 60 ppm Zr alloy. In addition, U.S. Patent No. 5,017,336 added Nb, Ta, V, Mo to control the existing alloy components of Zircaloy-4, specifically, 0.2 to 0.9% Sn, 0.18 to 0.6% Fe, 0.07 to 0.4% Cr Zr alloys composed of Nb 0.05-0.5%, Ta 0.01-0.2%, V 0.05-1%, Mo 0.05-1% were presented. U.S. Patent No. 5,196,163 or Japanese Patent No.63,035,751 also discloses Zr alloys in which Zir alloys are added in addition to Sn, Fe, Cr as well as Ta and optionally added Nb in conventional Zircaloy-4 alloy components, that is, Sn 0.2 to 1.15%, Fe An alloy composition consisting of 0.19 to 0.6% (preferably 0.19 to 0.24%), Cr 0.07 to 0.4% (preferably 0.07 to 0.13%), Ta 0.01 to 0.2%, Nb 0.05 to 0.5%, and N ≤ 60 ppm Presented. French Patent No. 2,769,637 suggested a Zr alloy of similar composition, specifically, Sn 0.2 ~ 1.7%, Fe 0.18 ~ 0.6%, Cr 0.07 ~ 0.4%, Nb 0.05 ~ 1.0%, optionally Ta 0.01 ~ 0.1% , N <60ppm, and also presented the heat treatment parameters according to the composition.

U.S. Patent 5,560,790 discloses an alloy consisting of 0.5-1.5% Nb, 0.9-1.5% Sn, 0.3-0.6% Fe, 0.005-0.2% Cr, 0.005-0.04% C, 0.05-0.15% O, 0.005-0.015% Si. The composition is presented. At this time, the distance between the precipitated phases containing Sn or Fe (Zr (Nb, Fe) ₂ , Zr (Fe, Cr, Nb), (Zr, Nb) ₃ Fe) was 0.20 to 0.40 µm, and Fe was The precipitated phase contained was limited to 60% by volume of the total precipitated phase.

Japanese Patent No. 5,214,500 proposes an alloy composition and a size of precipitated phases to improve corrosion resistance. Specifically, the alloy composition is composed of 0.5 to 2.0% Sn, 0.05 to 0.3% Fe, 0.05 to 0.3% Cr, 0.05 to 0.15% Ni, 0.05 to 0.2% O, 0 to 1.2% Nb and the balance Zr, the average of the precipitate The size was limited to 0.5 μm or less. In Japanese Patent No. 8,086,954, the heat treatment parameters introduced during hot / cold processing in the α-region are presented, and Sn 0.4 to 1.7%, Fe 0.25 to 0.75%, Cr 0.05 to 0.30%, Ni 0 to 0.10%, and Nb 0 A Zr alloy composed of ˜1.0% is presented. Japanese Patent No. 8,114,688 discloses Sn-Fe-Cr- containing Nb 0.05 to 0.75% and Si 0 to 0.02% to reduce secondary corrosion of the alloy due to stress corrosion cracking and hydrogen absorption at high temperatures. A Zr alloy of dual structure with inner layer made of Ni was presented. Japanese Patent No. 9,111,379 consists of 0.5-1.7% Sn, 0.1-0.3% Fe, 0.05-0.02% Cr, 0.05-0.2% Cu, 0.01-1.0% Nb, 0.01-0.20% Ni to prevent nodule corrosion Zr alloy is presented. Japanese Patent No. 10,273,746 proposes a Zr alloy composed of Sn 0.3 to 0.7%, Fe 0.2 to 0.25%, Cr 0.1 to 0.15%, and Nb 0.05 to 0.20% in order to improve the processability and corrosion resistance of the alloy.

European Patent No. 198,570 limits the Nb content to 1 to 2.5% in binary alloys composed of Zr-Nb, and presents the heat treatment temperature introduced during the alloy manufacturing process. At this time, the second phase including Nb should be uniformly distributed and its size should be maintained at 800 Hz or less. U.S. Patent No. 5,125,985 proposes an alloy having at least one of 0.5 to 2.0% Nb, 0.7 to 1.5% Sn, Fe, Ni, and Cr at 0.07 to 0.28%, and adjusts the creep properties of the material using various manufacturing processes. Said that. At this time, one of the characteristics of the manufacturing process is to introduce a β-quench heat treatment in the middle.

As described above, the zirconium alloy has been studied in various directions such as zircaloy-4. However, current nuclear power plants have severe operating conditions in order to improve economic efficiency, and fuel cladding tubes made of conventional zircaloy-4 have reached their service limits, and new zirconium alloys with better creep resistance are needed. Do.

Therefore, the present inventors have diligently studied to develop a new zirconium alloy with better creep resistance, and found that the creep resistance of the zirconium alloy can be improved by developing a zirconium alloy with a new composition with appropriate recrystallization. The invention was completed.

Accordingly, the present invention provides a zirconium alloy having excellent creep resistance that can double safety and economical efficiency compared to conventional commercial materials by minimizing creep deformation during operation when used as a fuel cladding tube and core part material in light and heavy water reactors. Its purpose is to.

In order to achieve the above object, the present invention is niobium (Nb) 0.8 ~ 1.8% by weight; Tin (Sn) 0.38-0.50 wt%; And / or at least one element selected from 0.1 to 0.2 wt% of iron (Fe), 0.05 to 0.15 wt% of copper (Cu), and 0.12 wt% of chromium (Cr); Oxygen (O) 0.10 to 0.15 wt%; 0.006% to 0.010% carbon (C); 0.006% to 0.010% silicon (Si); It provides a zirconium alloy composition containing 0.0005 to 0.0020% by weight of sulfur (S); and residual zirconium (Zr).

Hereinafter, the present invention will be described in detail.

The present invention includes a zirconium alloy composition.

The zirconium alloy composition is preferably, 0.8 to 1.8% by weight niobium; 0.05-0.15 weight percent copper; 0.10 to 0.15 weight percent oxygen; 0.006-0.010 weight percent carbon; 0.006 to 0.010 weight percent silicon; Sulfur 0.0005-0.0020 wt%; And the balance zirconium.

Moreover, the zirconium alloy composition of this invention is 0.8-1.8 weight% of niobium; 0.38-0.50 weight percent tin; 0.10 to 0.15 weight percent oxygen; 0.006-0.010 weight percent carbon; 0.006 to 0.010 weight percent silicon; Sulfur 0.0005-0.0020 wt%; And the balance zirconium.

In the zirconium alloy composition of the present invention, in addition to the composition, it may further contain one or more elements selected from 0.1 to 0.2% by weight of iron, 0.05 to 0.15% by weight of copper and 0.12% by weight of chromium. More preferably, it may further contain one or more elements selected from 0.1 to 0.2% by weight of iron, 0.05 to 0.15% by weight of copper and 0.12% by weight of chromium.

In the zirconium alloy composition of the present invention, a zirconium alloy having excellent creep resistance is produced by using the above zirconium alloy composition in which the recrystallization degree according to the present invention is maintained in the range of 40 to 70% by optimally adjusting the final vacuum heat treatment conditions. can do.

Hereinafter, the role of each alloying element used in the alloy composition of the present invention and the reason for limiting the composition ratio will be described in detail.

Niobium (Nb) serves to improve the corrosion resistance of the zirconium alloy. However, in the case of adding the solid solution (about 0.3 ~ 0.6%) or more, the composition and size of the precipitate must be controlled to improve the corrosion resistance. It is known that the addition of Nb above the solubility has a good effect on the mechanical properties by precipitation strengthening. However, the alloy performance is very sensitive to heat treatment conditions when the concentration of Nb is increased to form a large amount of precipitates. Therefore, in the present invention, the content of Nb is limited to 1.8% by weight or less and contained in the range of 0.8 to 1.8% by weight.

Tin (Sn) is known as the α-phase stabilizing element in zirconium alloys and serves to improve mechanical strength by solid solution strengthening. However, if Sn is not added at all, it may show a very rapid acceleration under LiOH corrosion conditions. Therefore, in the present invention, the content of Sn is adjusted according to the content of Nb and preferably contained in the range of 0.38 to 0.50% by weight, which does not significantly affect the corrosion resistance.

Iron (Fe) is the main element added to improve the corrosion resistance of the alloy, in the present invention is preferably added in the range of 0.05 to 0.2% by weight, more preferably limited to 0.1 to 0.2% by weight.

Chromium (Cr), like Fe, is a major element that increases the corrosion resistance of the alloy. In the present invention, the preferred content of Cr is limited to 0.05 to 0.2 wt%, more preferably 0.12 wt%.

Copper (Cu), like Fe and Cr, is a major element added to improve the corrosion resistance of the alloy, and especially when the trace amount is added, the effect is excellent. Therefore, the present invention is limited to 0.05 to 0.2 wt%, more preferably 0.05 to 0.15 wt%.

Oxygen (O) plays a role in improving mechanical strength and creep resistance by solid solution strengthening. However, it is contained in the present invention at 1000 to 1500 ppm (0.1 to 0.15% by weight), because excessive amounts cause processing problems.

Carbon (C) and silicon (Si) reduce hydrogen absorption and delay the transition time of corrosion rate, and also contain 60 to 100 ppm (0.006 to 0.010% by weight) of impurity elements related to corrosion resistance.

Sulfur (S) is an impurity element that contributes to creep resistance improvement without affecting the corrosion characteristics below 30 ppm. If more than 0.0020% by weight of sulfur is added, the amount of creep deformation no longer decreases. Therefore, the preferred content of S added to improve creep resistance in the present invention is 6 to 20 ppm (0.0006 to 0.0020% by weight).

The zirconium alloy excellent in creep resistance of the present invention can be prepared by adjusting the recrystallization in the range of 40 to 70%.

The zirconium alloy having excellent creep resistance of the present invention may be prepared by a conventional method in the field of the present invention, but more preferably after the β-heat treatment and cold working, the final heat treatment while adjusting the recrystallization to 40 to 70% It can be prepared by performing the.

Specifically, the method for preparing a zirconium alloy composition of the present invention comprises the steps of: forging each zirconium alloy ingot having the composition of the present invention in a β region to destroy the ingot structure; Β-quenching step in which the solution heat treatment is performed in the β region and then quenched to homogenize the alloy composition, wherein the β-quenching process is performed to uniformly distribute and control the size of the precipitate in the base metal. ; Hot rolling the β-quenched material; Performing vacuum heat treatment between four cold workings and cold working; And performing a final vacuum heat treatment while adjusting the recrystallization to 40 ~ 70%. The final vacuum heat treatment step for improving the creep resistance is preferably carried out for 3 to 8 hours in the temperature range of 470 ~ 570 ℃ so that the recrystallization is 40 ~ 70% through the recrystallization monitoring of the metal.

The zirconium alloy composition of the present invention can improve the creep resistance by adjusting the recrystallization to 40 to 70%. Therefore, the zirconium alloy composition according to the present invention has excellent creep resistance. As such, by minimizing creep deformation, it is possible to double safety and economical efficiency compared to conventional commercial materials. Therefore, the zirconium alloy composition according to the present invention can be usefully used as a fuel cladding tube, a support grid and a structure material in the reactor core of a light water reactor and a heavy water reactor type nuclear power plant. In addition, by using the zirconium alloy composition according to the present invention as the material of the structure as described above it is possible to ensure the integrity of the nuclear fuel rod in the atomic core of high combustion degree / long cycle operation.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited or limited by the following examples.

< Example  1-13> Preparation of Zirconium Alloy of the Present Invention

Example alloys varying the Nb content from 0.8% to 1.8% Nb (①Zr-0.8% Nb-0.07% Cu-0.14% O-0.008% C-0.008% Si-0.002% S, ②Zr-1.1 % Nb-0.07% Cu-0.14% O-0.008% C-0.008% Si-0.002% S, ③Zr-1.5% Nb-0.07% Cu-0.14% O-0.008% C-0.008% Si-0.002% S, ④Zr -1.8% Nb-0.07% Cu-0.14% O-0.008% C-0.008% Si-0.002% S);

Zr-1.5% Nb-0.4% Sn alloy (⑤ Zr-1.5% Nb-0.4% Sn-0.14% O-0.008% C-0.008% Si-0.002% S);

Four examples of alloys in which one or more elements of Cu, Fe, and Cr were added to the Zr-1.5% Nb-0.4% Sn alloy (6 Zr-1.5% Nb-0.4% Sn-0.1% Cu-0.14% O-0.008 % C-0.008% Si-0.002% S, ⑦Zr-1.5% Nb-0.4% Sn-0.1% Fe-0.14% O-0.008% C-0.008% Si-0.002% S, ⑧Zr-1.5% Nb-0.4% Sn -0.1% Cu-0.1% Fe-0.14% O-0.008% C-0.008% Si-0.002% S, ⑨Zr-1.5% Nb-0.4% Sn-0.2% Fe-0.1% Cr-0.14% O-0.008% C -0.008% Si-0.002% S); And

Example alloys in which the amount of sulfur added was changed from 0.0005% to 0.005% (⑩Zr-1.1% Nb-0.07% Cu-0.14% O-0.008% C-0.008% Si-0.0005% S, ⑪Zr-1.1% Nb-0.07 % Cu-0.14% O-0.008% C-0.008% Si-0.0010% S, ⑫Zr-1.1% Nb-0.07% Cu-0.14% O-0.008% C-0.008% Si-0.0020% S, ⑬Zr-1.1% Nb A total of 13 example alloy compositions of -0.07% Cu-0.14% O-0.008% C-0.008% Si-0.0050% S) are summarized in Table 1 below, where% means wt%.

Zirconium Alloy Composition Example Alloy Composition ratio (wt%) Remarks Example 1 Zr-0.8Nb-0.07Cu-0.14O-0.008C-0.008Si-0.002S PRX Example 2 Zr-1.1Nb-0.07Cu-0.14O-0.008C-0.008Si-0.002S PRX Example 3 Zr-1.5Nb-0.07Cu-0.14O-0.008C-0.008Si-0.002S PRX Example 4 Zr-1.8Nb-0.07Cu-0.14O-0.008C-0.008Si-0.002S PRX Example 5 Zr-1.5Nb-0.4Sn-0.14O-0.008C-0.008Si-0.002S PRX Example 6 Zr-1.5Nb-0.4Sn-0.1Cu-0.14O-0.008C-0.008Si-0.002S PRX Example 7 Zr-1.5Nb-0.4Sn-0.1Fe-0.14O-0.008C-0.008Si-0.002S PRX Example 8 Zr-1.5Nb-0.4Sn-0.1Cu-0.1Fe-0.14O-0.008C-0.008Si-0.002S PRX Example 9 Zr-1.5Nb-0.4Sn-0.2Fe-0.1Cr-0.14O-0.008C-0.008Si-0.002S PRX Example 10 Zr-1.1Nb-0.07Cu-0.14O-0.008C-0.008Si-0.0005S PRX Example 11 Zr-1.1Nb-0.07Cu-0.14O-0.008C-0.008Si-0.0010S PRX Example 12 Zr-1.1Nb-0.07Cu-0.14O-0.008C-0.008Si-0.0020S PRX Example 13 Zr-1.1Nb-0.07Cu-0.14O-0.008C-0.008Si-0.0050S PRX Zircaloy-4 Zr-1.38Sn-0.2Fe-0.1Cr-0.12O

The ingot was dissolved by dissolving the zirconium alloy composed of the above composition, and forging was performed in β region of 1000 to 1200 ° C. in order to destroy the ingot structure in the ingot. After distribution more uniformly, it was quenched to obtain β-quench structure (martensite). The β-sintered material was hot rolled at 590 ° C. at a reduction ratio of 70%, and then subjected to primary cold working at 50% reduction ratio, followed by vacuum heat treatment at 570˜580 ° C. for 3 hours. The vacuum heat-treated specimens were subjected to three cold workings and the intermediate heat treatment between cold workings was carried out in vacuo at 570 ° C. for 2 hours. Then, the final heat treatment was performed for 3 to 8 hours at 510 ℃ to prepare a zirconium alloy sheet form test piece. In addition, some example alloys (Examples 2, 3, 7, 8, and 9) for evaluating creep properties according to the recrystallization degree may be obtained by varying the final heat treatment temperature at 20 ° C intervals from 470 ° C to 570 ° C. Prepared.

In the present invention, the recrystallization was maintained in the range of 40 to 70% by appropriately adjusting the heat treatment temperature and time. The recrystallization was averaged by analyzing an image analyzer of several (at least 5) matrix metal microstructure photographs taken using a transmission electron microscope. The results are shown in Fig. Figure 1 shows the change in recrystallization according to the heat treatment temperature when the final heat treatment temperature in the process of manufacturing zirconium alloy. As the heat treatment temperature was increased at the same time, the recrystallization tended to increase along the S curve.

< Experimental Example 1 > Chemical Composition Analysis

Samples were analyzed from 13 alloys according to the present invention and a reference alloy Zircaloy-4 to analyze chemical composition. The results are shown in Table 2 below.

Example  Composition Analysis of Alloys Chemical composition analysis, wt% Nb Sn Fe Cu Cr O C Si S Zr Example 1 0.82  -  - 0.068  - 0.139 0.0085 0.0082 0.0017       Balance Example 2 0.11 0.081 0.122 0.0077 0.0075 0.0022 Example 3 1.49 0.072 0.133 0.0081 0.0083 0.0019 Example 4 1.77 0.077 0.144 0.0090 0.0089 0.0021 Example 5 1.47 0.45 - -  - 0.133 0.0069 0.0079 0.0016 Example 6 1.53 0.48 0.112 0.144 0.0090 0.0086 0.0018 Example 7 1.50 0.44 0.12 - 0.129 0.0086 0.0092 0.0020 Example 8 1.53 0.39 0.11 0.133 0.135 0.0081 0.0063 0.0019 Example 9 1.49 0.42 0.19 - 0.12 0.147 0.0075 0.0081 0.0021 Example 10 1.12  -  - 0.066  - 0.127 0.0077 0.0088 0.0006 Example 11 1.13 0.073 0.139 0.0072 0.0091 0.0012 Example 12 1.09 0.079 0.150 0.0079 0.0069 0.0019 Example 13 1.08 0.062 0.143 0.0082 0.0078 0.0055 Zircaloy-4 - 1.38 0.21 - 0.10 0.135 - - -

As can be seen from the above results, the analytical values agree very well with the nominal values shown in Table 1. Thus, it can be seen that the alloy composition of all the example alloys was well controlled to meet the test objectives.

< Experimental Example  2> zirconium alloy On recrystallization  According Creep  exam

In order to determine the creep strain of the alloy prepared in Examples 2 to 3 and Examples 7 to 9, a creep test was performed for 192 hours by applying a constant load of 120 MPa to the specimen at 350 ° C. The result is shown in Fig.

The creep strain tended to decrease as the recrystallization increased, and all the alloys showed the minimum creep strain in the range of 40 to 70%. However, the creep strain tended to increase slightly when the recrystallization passed this zone. The creep properties of zirconium alloys were closely related to the potential distribution in the matrix. That is, the resistance to creep deformation was the best when the recrystallization was moderate (about 40 to 70%).

< Experimental Example  3> according to the content of alloying elements Creep  exam

To determine the recrystallization and creep strain of the 13 alloys prepared according to Examples 1 to 13, a creep test was performed for 192 hours and 7200 hours by applying a constant load of 120 MPa to the specimen at 350 ° C. Table 3 shows.

Example  Recrystallization of the alloy and Creep Strain Recrystallization,% Creep strain,% 350 ℃ / 120 MPa × 192 h 350 ℃ / 120 MPa × 7200 h Example 1 68 0.31 0.62 Example 2 60 0.26 0.53 Example 3 53 0.24 0.51 Example 4 42 0.22 0.48 Example 5 48 0.19 0.45 Example 6 50 0.17 0.43 Example 7 49 0.21 0.46 Example 8 46 0.18 0.45 Example 9 44 0.23 0.47 Example 10 62 0.55 0.82 Example 11 59 0.35 0.67 Example 12 59 0.27 0.54 Example 13 57 0.25 0.52 Zircaloy-4 8 0.72 1.12

As shown in the above results, the creep strain of the alloy having the composition according to Examples 1 to 4 in which the addition content of Nb was changed in the range of 0.8 to 1.8% by weight was 0.22 to 0.31% under the two test conditions (192h, 7200h), 0.48 ~ 0.62%, lower than Zircaloy-4.

In addition, Zr-1.5% Nb-0.4% Sn-based alloy having a composition according to Examples 5 to 9 showed better creep resistance due to the addition of Sn.

In order to examine the effect of sulfur addition on the creep properties, the creep strain of the alloy having the composition according to Examples 10 to 13 of the present invention was observed. As shown in the results of the above table, it was apparent that the amount of creep deformation decreased as the amount of sulfur added increased, and the amount of creep deformation did not decrease any more when 0.002% by weight of sulfur was added. Sulfur added to improve creep resistance was found to be most effective in the range 0.0006 to 0.0020% by weight.

It can be seen that the recrystallization of all 13 alloys of Examples 1 to 13 shown in Table 3 is in the range of 40 to 70%. If the recrystallization is present in the above range it was possible to improve the creep resistance at least 160% or more than the existing Zircaloy-4.

As described above, the zirconium alloy according to the present invention has excellent creep resistance by controlling the final heat treatment temperature and time so as to maintain the recrystallization degree of 40 to 70%, and the conventional commercial fuel cladding material, zircaloy-4 ( Better creep resistance than Zircaloy-4). In addition, the recrystallization proposed in the present invention can be sufficiently utilized to prepare a zirconium alloy having excellent creep properties, and will greatly contribute to improving creep resistance. Therefore, the zirconium alloy according to the present invention can double the safety and economy by minimizing creep deformation under high combustion / long cycle operating conditions, and can maintain the soundness. In addition, it can be very useful as a support grid and furnace structure, and can replace Zircaloy-4, which has been used as a conventional fuel cladding material.

Claims (5)

Niobium 0.8-1.8 wt%; 0.05-0.15 weight percent copper; 0.10 to 0.15 weight percent oxygen; 0.006-0.010 weight percent carbon; 0.006 to 0.010 weight percent silicon; Sulfur 0.0005-0.0020 wt%; And a zirconium alloy composition containing residual zirconium and having excellent creep resistance with a recrystallization of 40 to 70% of the alloy composition. The zirconium alloy composition according to claim 1, further comprising at least one element selected from 0.05 to 0.2% by weight of iron or 0.05 to 0.2% by weight of chromium in addition to the composition, and having an excellent creep resistance of 40 to 70%. . 3. The zirconium alloy composition according to claim 2, wherein the zirconia alloy composition having excellent creep resistance is 0.12% by weight of chromium and has a recrystallization of 40 to 70%. delete i) 0.8-1.8 weight percent niobium; 0.05-0.15 weight percent copper; 0.10 to 0.15 weight percent oxygen; 0.006-0.010 weight percent carbon; 0.006 to 0.010 weight percent silicon; Sulfur 0.0005-0.0020 wt%; And each zirconium alloy ingot having an alloy composition containing the balance zirconium or an alloy composition additionally containing at least one element selected from 0.05 to 0.2% by weight of iron and 0.05 to 0.2% by weight of chromium in addition to the above composition. Forging in the area to destroy the ingot tissue; ii) a β-quenching step of performing quenching heat treatment in the β region at 1015˜1075 ° C. and then quenching to homogenize the alloy composition; iii) hot rolling the β-quenched material at 590 ° C. with a reduction ratio of 70%; iv) The first cold working is performed at 50% reduction rate, the vacuum heat treatment is performed at 570-580 ° C. for 3 hours, the cold heat treatment of the vacuum heat treated test piece is performed three times, and the intermediate heat treatment between the cold workings is 570. Performing at 2 ° C. for 2 hours; And v) a method of producing a good creep resistance zirconium alloy composition comprising the step of performing a final vacuum heat treatment for 3 to 8 hours at 470 ~ 570 ℃ while controlling the recrystallization to 40 to 70%.

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