KR100916652B1 - High Fe contained zirconium alloy compositions having excellent corrosion resistance and preparation method thereof - Google Patents

Abstract

The present invention relates to a high-concentration iron-containing zirconium alloy composition having excellent corrosion resistance and a method for producing the same, specifically, 0.5 to 1.0% by weight of iron (Fe), 0.25 to 0.5% by weight of chromium (Cr), and 0.06 to 0.18 of oxygen (O). It has excellent corrosion resistance composed of one or more elements selected from 0.20 to 0.5% by weight of tin (Sn), 0.1 to 0.3% by weight of niobium (Nb), and 0.05 to 0.3% by weight of copper (Cu) and the balance of zirconium (Zr). It relates to a high concentration iron-containing zirconium alloy composition and a method for producing the same. Since the zirconium alloy of the present invention has excellent corrosion resistance, it can be used as a fuel cladding tube, a support grid, and an in-structure structure material used in fuel assemblies of light and heavy water reactors.

Iron, copper, tin, niobium, oxygen, zirconium alloys, fuel cladding, corrosion resistance

Description

High concentration iron containing zirconium alloy compositions having excellent corrosion resistance and preparation method thereof

The present invention relates to a high concentration iron-containing zirconium alloy composition having excellent corrosion resistance and a method for producing the same.

The composition of the alloy is very important because the fuel cladding, support lattice, and reactor structures used in the nuclear fuel assembly are accompanied by deterioration of mechanical properties due to embrittlement and corrosive growth due to high temperature / high pressure corrosion environment and neutron irradiation. . Accordingly, zirconium alloys having a low neutron absorption cross-sectional area and excellent mechanical strength and corrosion resistance have been widely applied in pressurized water reactor (PWR) and boiling water reactor (BWR) reactors for decades. Of the zirconium alloys developed to date, Zircaloy-2, 1.20 to 1.70 wt% of tin (Sn), iron (Fe), chromium (Cr) and nickel (Ni), and 0.07 to 0.20 wt. %, 0.05-1.15 wt% chromium, 0.03-0.08 wt% nickel, 900-1500 ppm oxygen, balance of zirconium) and zircaloy-4 (Zircaloy-4, 1.20-1.70 wt% tin, 0.18-0.24 wt% iron, chromium) 0.07 to 1.13% by weight, 900 to 1500 ppm oxygen, nickel <0.007% by weight, zirconium balance) alloys are most widely used.

However, as part of improving the economic efficiency of nuclear reactors, high-combustion / long-cycle operation is used to increase the replacement cycle of nuclear fuel in order to reduce the cycle cost of nuclear fuel. When the reaction time is extended and the existing Zircaloy-2 and Zircaloy-4 are used as the fuel cladding material, there is a problem of intensifying the corrosion of the fuel.

Therefore, it is very urgent to develop a material that can be used as a high-combustion / long-cycle nuclear fuel assembly due to its excellent corrosion resistance to the high temperature, high pressure cooling water and water vapor, and thus, many studies for developing a zirconium alloy with improved corrosion resistance are needed. Are being performed. At this time, since the corrosion resistance of the zirconium alloy is greatly influenced by the kind addition amount of the element added, processing conditions, heat treatment conditions, etc., it is most important to establish the optimum conditions having excellent corrosion resistance.

Looking at major patents related to high-burning / long-cycle fuel assemblies registered after the mid-1980s, zirconium alloys contain most of the iron that can improve corrosion resistance even when added in small amounts. In addition, the iron-containing zirconium alloy composition has a tendency to increase the amount of addition of iron and to add other elements that affect the improvement of corrosion resistance. That is, the zirconium alloy for high-combustion / long-cycle nuclear fuel is required to add a high concentration of iron, and the optimum manufacturing process is set to exhibit excellent performance.

U.S. Patent No. 5,648,995 discloses a method for producing a zirconium alloy consisting of 0.005 to 0.025 weight percent iron, 0.8 to 1.3 weight percent niobium, 0.16 weight percent or less oxygen, 0.02 weight percent or less carbon, 0.012 weight percent or less silicon, and zirconium balance. In one, the iron content was controlled in a very low range to improve creep resistance.

US Pat. No. 5,112,573 discloses 0.07-0.14 weight percent iron, 0.5-2.0 weight percent niobium, 0.7-1.5 weight percent tin, 0.03-0.14 weight percent nickel, or chromium having a higher iron content than US Pat. No. 5,648,995, A process for producing a zirconium alloy consisting of 0.022% by weight or less of carbon and the zirconium balance is disclosed.

U.S. Patent No. 5,125,985 and U.S. Patent No. 5,266,131 relate to a manufacturing process that introduces a "Late stage" beta quenching process during cold working on zirconium alloys of the same composition as U.S. Patent No. 5,112,573. And to improve corrosion resistance.

U.S. Patent No. 5,940,464 discloses about 0.02 to 0.4% by weight of iron, 0.8 to 1.8% by weight of niobium, 0.2 to 0.6% by weight of tin, and 30 to 180 ppm of carbon, about 20 times the weight of iron compared to U.S. Patent No. 5,648,995. An alloy composition and manufacturing process including 10 to 120 ppm of silicon, 600 to 1800 ppm of oxygen and the balance of zirconium are disclosed, and to improve corrosion resistance and creep resistance.

U.S. Patent No. 5,211,774 discloses 0.2 to 0.5 wt% iron, 0.8 to 1.2 wt% tin, 0.1 to 0.4 wt% chromium, 0 to 0.6 wt% niobium, 50 to 200 ppm silicon, 900 to 1800 ppm oxygen, and zirconium balance. An alloy composition and a manufacturing process are disclosed, and the amount of silicon in the zirconium alloy is changed to reduce the hydrogen absorption and the corrosiveness due to the process difference.

In US Patent No. 5,254,308, an alloy for maintaining mechanical properties according to a decrease in tin content, high concentrations of iron 0.4 to 0.53% by weight, tin 0.45 to 0.75% by weight, chromium 0.2 to 0.3% by weight, and niobium 0.3 to 0.5% by weight An alloy composition consisting of 0.012 to 0.03 weight percent nickel, 50 to 200 ppm silicon, 1000 to 2000 ppm oxygen, and zirconium balance was disclosed. At this time, the iron / chromium ratio was 1.5, and the amount of niobium added was determined according to the amount of iron affecting the hydrogen absorption, and the amount of niobium, silicon, carbon, and oxygen was configured to have excellent corrosion resistance and mechanical strength.

U.S. Patent No. 5,560,790 discloses 0.3-0.6 wt% iron, 0.5-1.5 wt% niobium, 0.9-1.5 wt% tin, 0.005-0.2 wt% chromium, 0.005-0.04 wt% carbon, 0.05-0.15 wt% oxygen and silicon An alloy composition consisting of 0.005 to 0.015% by weight is presented. In the above patent, the distance between niobium or iron-containing precipitated phases (Zr (Nb, Fe) ₂ , Zr (Fe, Cr, Nb), (Zr, Nb) ₃ Fe) is set to 0.20 to 0.40 μm, and The precipitated phase containing was limited to a volume of 60% of the total precipitated phase.

European Patent No. 198,570 limits the niobium content to 1.0 to 2.5% by weight in a binary alloy composed of zirconium-niobium, and suggests that the corrosion resistance can be improved by presenting a heat treatment temperature introduced during the manufacturing process of the alloy.

U.S. Patent No. 5,125,985 proposes an alloy comprising 0.5 to 2.0% by weight of niobium, 0.7 to 1.5% by weight of tin, and 0.07 to 0.28% of at least one element of iron, chromium and niobium, and using various manufacturing processes. It is said that the creep resistance of the material can be controlled.

As such, efforts are being made to improve the corrosion resistance and mechanical properties of zirconium alloys used as nuclear fuel assembly materials in nuclear power plants. In view of the trend of high combustion / long cycle operation, there is a continuing need for a zirconium alloy having excellent corrosion resistance to ensure the integrity of nuclear fuel in high combustion / long cycle operation.

Accordingly, the present inventors have focused on improving the corrosion acceleration phenomenon, which is the most problematic under high combustion / long cycle operation of nuclear fuel coating tubes, support grids, and structures made of zirconium alloys, and contain 0.5 to 1.0 wt% of iron. The present invention was completed by confirming that the zirconium alloy composition prepared by changing the type of added elements and optimizing the manufacturing process has superior corrosion resistance than conventional zircaloys.

It is an object of the present invention to provide a composition of a high concentration iron-containing zirconium alloy having excellent corrosion resistance that can be used as a material for fuel cladding tubes, support grids and structures used during high combustion / long cycle operation.

In order to achieve the above object, the present invention provides 0.5 to 1.0% by weight of iron, 0.25 to 0.5% by weight of chromium, 0.06 to 0.18% by weight of oxygen, 0.2 to 0.5% by weight of tin, 0.1 to 0.3% by weight of niobium, and 0.05 to 0.3% by weight of copper. It provides a high concentration of iron-containing zirconium alloy composition having excellent corrosion resistance, including at least one of and zirconium balance.

In addition, the present invention comprises the steps of dissolving a mixture of the zirconium alloy composition elements to produce an ingot (step 1);

Forging the ingot prepared in step 1 in the β-phase region (step 2);

Quenching the ingot forged in the step 2 after the solution heat treatment in the β-phase region (step 3);

Extruding the ingot cooled in step 3 (step 4);

Performing an initial heat treatment on the extruded body extruded in step 4 (step 5);

Cold working the intermediate heat treatment and the intermediate heat treatment several times in step 5 to produce a zirconium alloy composition (step 6); And

It provides a method of producing a high concentration of iron-containing zirconium alloy composition comprising a; performing a final heat treatment (step 7) to the zirconium alloy composition prepared in step 6.

The high-concentration iron-containing zirconium alloy composition according to the present invention exhibits excellent corrosion resistance by appropriately adjusting the type and amount of added elements and improving the corrosion resistance through heat treatment, so that nuclear fuel coating pipes, support grids, core structure materials of nuclear power reactors and heavy water reactors It may be usefully used as such.

Hereinafter, the present invention will be described in detail.

Zirconium alloy composition according to the invention is iron 0.5 to 1.0% by weight; Chromium 0.25-0.5 wt%; Oxygen 0.06-0.18 weight percent; Any one or more elements selected from the group consisting of 0.2-0.5 wt% tin, 0.1-0.3 wt% niobium and 0.05-0.3 wt% copper; And zirconium balance, preferably 0.54 to 0.8 wt% iron; Chromium 0.27-0.40 weight percent; Oxygen 0.1 to 0.15 weight percent; Any one or more elements selected from the group consisting of 0.2-0.5 wt% tin, 0.1-0.3 wt% niobium and 0.05-0.3 wt% copper; And zirconium residues.

The most important problem to be solved in high fuel / long cycle fuel assemblies is the rapid increase in surface corrosion due to high heat flux and increased exposure time in reactor conditions. Increasing the amount of corrosion means an increase in the brittle oxide film and further increases the amount of hydrogen introduced into the branch metal, thereby deteriorating the structural integrity of the nuclear fuel rod. Therefore, development of the cladding tube material excellent in corrosion resistance can directly contribute to the improvement of the economics and safety of light and heavy water reactors. In the present invention, a high concentration of iron, which is known to directly contribute to the improvement of corrosion resistance of zirconium alloy, is considered to suppress corrosion in a high combustion / long cycle operation environment, and an additional amount of tin, copper, and niobium is added to improve corrosion resistance. It was.

Hereinafter, each component element of the zirconium alloy composition according to the present invention will be described in detail.

Iron (Fe) is the main element added to improve the corrosion resistance of zirconium alloys, when the addition of more than 0.3% by weight has been studied to improve the corrosion resistance [A. Seibold er al .; Proceedings, International KTGENS Topical Meeting on Nuclear Fuel, TOPFUEL 95, Wurzburg, Germany, 12-15 March 1995, vol 2, p. 117]. In the present invention, the iron content is added to the zirconium alloy composition in more than 0.5% by weight. However, when the iron content exceeds 1.0% by weight, there is a problem in workability, so the iron content of the zirconium alloy of the present invention is preferably 0.5 to 1.0% by weight.

Chromium (Cr), like iron, is a major element that increases the corrosion resistance of alloys. It is known that corrosion resistance is improved when added at least 0.2% [F. Garzarolli et al. ASTM-STP 1245 (1994) p. 709].

On the other hand, the ratio of iron and chromium affects the corrosion resistance, and it is known that the corrosion resistance is improved especially when the iron / chromium ratio is increased [C.M. Eucken et al., ASTM STP 1023 (1989) p. 113]. At this time, it is preferable to add so that the ratio of iron / chromium is 1.5 ~ 3. If the iron / chromium ratio is less than 1.5 or more than 3, there is a problem that the corrosion resistance is lowered. Therefore, the content of chromium in the present invention is preferably 0.25 to 0.5% by weight.

Oxygen (O) improves mechanical strength by solid solution strengthening. However, it is preferable to limit the amount to 0.06 to 0.18% by weight because the addition of excessive amount causes processing problems.

Tin (Sn) is known as an α-phase stabilizing element in zirconium alloys, and serves to improve mechanical strength by solid solution strengthening. However, if the addition amount is excessively added, the corrosion resistance is reduced, and therefore, it is preferable to add 0.2 to 0.5% by weight, which does not significantly affect the corrosion resistance.

Niobium (Nb) serves to greatly improve the corrosion resistance of the zirconium alloy. However, if it is added at a high concentration (0.3%) or more, it is necessary to control the size and composition of the precipitate by introducing a specific heat treatment temperature and time to improve the corrosion resistance [Y.H. Jeong et al. J. Nucl Mater. vol 317 p. 1]. In consideration of this, the content of niobium preferably contains 0.1 to 0.3% by weight.

Copper (Cu), like iron and chromium, is a major element added to improve the corrosion resistance of alloys, especially when the trace amount is added [B.O. Choi et al. J. Kor. Inst. Met. & Mater. vol 42 (2004) p. 178]. Therefore, it is preferable that it is 0.05 to 0.3 weight% in this invention.

In addition, in the present invention, a method for producing a high concentration iron-containing zirconium alloy composition,

Dissolving a mixture of zirconium alloy composition elements to produce an ingot (step 1);

Forging the ingot prepared in step 1 in the β-phase region (step 2);

Quenching the ingot forged in the step 2 after the solution heat treatment in the β-phase region (step 3);

Extruding the ingot cooled in step 3 (step 4);

Performing an initial heat treatment on the extruded body extruded in step 4 (step 5);

Cold-working and intermediate heat treatment of the extruded heat-treated in step 5 are repeated several times to prepare a zirconium alloy composition (step 6); And

Performing a final heat treatment to the zirconium alloy composition prepared in step 6 (step 7); can be prepared by a method comprising a.

Hereinafter, the manufacturing method of the present invention will be described in detail step by step.

First, step 1 is a step of preparing an ingot made by melting the mixture of the zirconium alloy composition elements.

The ingot is preferably manufactured by a vacuum arc remelting (VAR) method, specifically, after maintaining the vacuum state in the chamber to 1 × 10 ^-5 torr, argon (Ar) gas 0.1 ~ 0.3 torr The ingot is injected into the flask, dissolved by applying a current of 500 to 1000 A, and then cooled to prepare an ingot in the form of a button or the like.

At this time, it is preferable to dissolve repeatedly three to five times in order to prevent impurities from segregation or uneven distribution of the alloy composition in the ingot. In the cooling process, in order to prevent the occurrence of oxidation on the surface of the specimen, it is preferable to cool by injecting an inert gas such as argon.

Next, step 2 is a step of forging the ingot prepared in step 1 in the β-phase region.

In this step, it can be achieved by forging in the β-phase region of 1000 ℃ or more in order to break the cast structure in the prepared ingot, wherein the forging is preferably performed at 1000 ~ 1200 ℃. If the forging temperature is less than 1000 ℃, there is a problem that the ingot structure is not easily broken, if the temperature exceeds 1200 ℃ there is a problem that the heat treatment cost increases.

Next, step 3 is a step of quenching the ingot forged in the step 2 after the solution heat treatment in the β-phase region.

This step homogenizes the alloy composition in the ingot and cools and melts the ingot in the β region to obtain fine precipitates. At this time, after the specimen is sealed with a stainless steel sheet in order to prevent oxidation of the specimen, preferably heat treatment at 1000 ~ 1200 ℃, more preferably 1050 ~ 1100 ℃. At this time, the heat treatment time is preferably about 30 to 90 minutes, more preferably 50 to 70 minutes. After the heat treatment, water is preferably cooled to a temperature of 400 ° C. or lower, preferably 300 to 400 ° C. in the β-phase region.

Next, step 4 is a step of extruding the ingot cooled in step 3.

The ingot cooled in step 3 is processed into a hollow billet and then hot extrusion to produce an extruded shell suitable for cold working. In this step, the extrusion time is preferably 20 to 40 minutes, more preferably 30 minutes. It is preferable that extrusion temperature is 550-700 degreeC. If it is out of this temperature, it is difficult to obtain an extruded body suitable for the processing of the next step.

Next, step 5 is a step of performing an initial heat treatment of the extruded body extruded in step 4.

The heat treatment temperature is set to 700 ° C or less. Specifically, the extruded extruded body is preferably heat treated at 550 to 700 ° C. for 1 to 5 hours, and more preferably at 2 to 4 hours at 560 to 690 ° C. If the initial heat treatment temperature is less than 550 ° C., there is a problem in workability, and if it exceeds 700 ° C., there is a problem that corrosion resistance is lowered due to the formation of coarse precipitated phase.

Next, step 6 is a step of manufacturing a zirconium alloy composition by repeatedly performing cold working and intermediate heat treatment several times for the extruded body heat-treated in step 5.

The cold working and the intermediate heat treatment of step 6 may be performed by cold working the extruded body heat-treated in step 5 two to five times, and performing one to four intermediate heat treatments between the cold workings. At this time, the intermediate heat treatment is preferably performed for 3 to 5 hours at 550 ~ 700 ℃. If the heat treatment temperature is less than 550 ° C., there is a problem in workability, and if it exceeds 700 ° C., there is a problem that corrosion resistance is lowered due to the formation of coarse precipitated phase. In addition, the cold working amount when performing the cold working is preferably 20 ~ 85%. Specifically, the primary cold working amount is more preferably 20 to 80%, the secondary cold working amount is 30 to 85%, and the third cold working amount is 35 to 85%. If the cold working amount is less than 20%, there is a problem that a product of a desired thickness cannot be obtained, and if it exceeds 85%, there is a problem in workability.

Next, step 7 is a step of performing a final heat treatment of the composition of the prepared zirconium alloy.

 In order to increase creep resistance through cold working of the composition. At this time, the final heat treatment is preferably made in a vacuum, it is preferably carried out for 2 to 10 hours at 450 ~ 580 ℃. If the temperature is less than 450 ℃ creep resistance is reduced, there is a problem that the mechanical strength is lowered if it exceeds 580 ℃. In addition, when the heat treatment time is less than 2 hours, there is a problem that the processed structure remains, and when more than 10 hours, the precipitated phase becomes coarse and corrosion resistance is deteriorated.

Hereinafter, the present invention is described in detail by way of examples. However, the following examples are only examples of the present invention, and the scope of the present invention is not limited to the following examples.

< Example  1> Preparation of Zirconium Alloy Composition

(One) ingot  Produce

0.6 wt% iron, 0.3 wt% chromium, 0.12 wt% oxygen, 0.05 wt% copper and the balance of zirconium were prepared by vacuum arc melting (VAR) method. The zirconium used was a nuclear grade sponge zirconium as specified in ASTM B349, and the alloy element was a high purity product of 99.99% or more. In addition, silicon and oxygen were first dissolved with sponge zirconium to prepare a mother alloy, and then added at the time of ingot melting according to a desired amount of addition. In order to prevent impurities from segregation or uneven distribution of alloys, four times of dissolution were performed. In order to prevent oxidation during dissolution, the vacuum was kept sufficiently up to 1 × 10 ^-5 torr in order to maintain high purity (99.99%). ) The ingot was prepared in a water-cooled copper crucible having a cooling water pressure of 1 kgf / cm ² and a diameter of 60 mm by applying an applied current of 500 A while injecting argon gas.

(2) β-forging

Forging was performed in the β phase region at 1100 ° C. in order to break the cast structure in the prepared ingot.

(3) β- Hardening

The solution heat treatment was performed for 15 minutes in the β-phase region of 1050 ℃ to break the cast structure in the prepared ingot. After the heat treatment was completed, the ingot was quenched by dropping it into a water-filled water bath at room temperature to form martensite tissue or widmanstatten tissue.

(4) hot working

The β-sintered material was processed into a hollow billet and then hot extruded at 600 ° C. for 30 minutes to prepare an extruded body suitable for cold working.

(5) initial heat treatment

The hot extruded material was subjected to initial heat treatment at 600 ° C. for 2 hours.

(6) cold working and intermediate heat treatment

The extruded body was cold worked and subjected to intermediate heat treatment at 570 ° C. for 2 hours in a vacuum. The heat-treated extruded body was then subjected to secondary cold working and subjected to intermediate heat treatment at vacuum and 570 ° C. for 2 hours. Thereafter, the heat treated extruded body was subjected to third cold working. In the cold working, the first cold working amount is 30%, the second cold working amount is 40%, the third cold working amount is 60%.

(7) final heat treatment

The high iron-containing zirconium alloy composition was subjected to a final heat treatment at 470 ° C. for 3 hours in vacuum.

< Example  2>

The content of the zirconium alloy composition was carried out in the same manner as in Example 1, except that 0.2 wt% of niobium was added instead of copper.

< Example  3>

0.1 wt% of copper was added in the content of the zirconium alloy composition, and the heat treatment was performed in the same manner as in Example 1 except that the heat treatment was performed at a final heat treatment temperature of 490 ° C.

< Example  4>

The same method as in Example 3 was carried out except that 0.4 wt% tin was added instead of copper in the content of the zirconium alloy composition.

< Example  5>

It was carried out in the same manner as in Example 3, except that 0.2 wt% of niobium was added instead of copper in the content of the zirconium alloy composition.

< Example  6>

It was carried out in the same manner as in Example 3, except that 0.4 wt% tin and 0.2 wt% niobium were added instead of copper in the content of the zirconium alloy composition.

< Example  7>

The content of the zirconium alloy composition was added in the same manner as in Example 1 except that 0.2 wt% tin was added instead of copper and the heat treatment was performed at a final heat treatment temperature of 510 ° C.

< Example  8>

It was carried out in the same manner as in Example 7, except that 0.2 wt% of niobium was added instead of tin in the content of the zirconium alloy composition.

< Example  9>

Example 1 except that 0.1% by weight of copper and 0.2% by weight of tin were added instead of copper in the content of the zirconium alloy composition, and the heat treatment was performed at 680 ° C. for the hot working and initial heat treatment and 630 ° C. for the intermediate heat treatment. It was carried out in the same manner as in the method.

< Example 10>

The same method as in Example 9 was conducted except that 0.2 wt% of niobium was added instead of copper and tin in the content of the zirconium alloy composition.

< Example  11>

In the preparation of zirconium alloy, it was carried out in the same manner as in Example 4 except that the heat treatment is carried out at a final heat treatment temperature of 490 ℃.

< Example  12>

Instead of tin in the content of the zirconium alloy composition, it was carried out in the same manner as in Example 11 except for adding 0.2% by weight of niobium.

< Example  13>

In the same manner as in Example 11, except that 0.4 wt% tin and 0.2 wt% niobium were added instead of tin in the content of the zirconium alloy composition.

< Example  14>

In the preparation of zirconium alloy, it was carried out in the same manner as in Example 10 except that the heat treatment is performed at a final heat treatment temperature of 510 ℃.

< Comparative example  1>

A nuclear grade commercial Zircaloy-4 alloy, which is used as a fuel structural material in nuclear power plants, was used.

* The zirconium alloy composition described above is shown in Table 1.

Chemical composition analysis division Iron (wt%) Chrome (wt%) Oxygen (wt%) Copper (wt%) Tin (% by weight) Niobium (wt%) Zirconium (wt%) Example 1 0.6 0.3 0.12 0.05 - - Balance Example 2 0.6 0.3 0.12 - - 0.2 Balance Example 3 0.6 0.3 0.12 0.1 - - Balance Example 4 0.6 0.3 0.12 - 0.4 - Balance Example 5 0.6 0.3 0.12 - - 0.2 Balance Example 6 0.6 0.3 0.12 - 0.4 0.2 Balance Example 7 0.6 0.3 0.12 - 0.2 - Balance Example 8 0.6 0.3 0.12 - - 0.2 Balance Example 9 0.6 0.3 0.12 0.1 0.2 - Balance Example 10 0.6 0.3 0.12 - - 0.2 Balance Example 11 0.6 0.3 0.12 - 0.4 - Balance Example 12 0.6 0.3 0.12 - - 0.2 Balance Example 13 0.6 0.3 0.12 - 0.4 0.2 Balance Example 14 0.6 0.3 0.12 - - 0.2 Balance Comparative Example 1 (Zircaloy-4) 0.2 0.1 0.12 - 1.5 - Balance

The stepwise preparation temperatures of the compositions are shown in Table 2.

division Hot working temperature (℃) Initial heat treatment (℃) Intermediate heat treatment (℃) Final heat treatment (℃) Example 1 600 600 570 470 Example 2 600 600 570 470 Example 3 600 600 570 490 Example 4 600 600 570 490 Example 5 600 600 570 490 Example 6 600 600 570 490 Example 7 600 600 570 510 Example 8 600 600 570 510 Example 9 680 680 630 470 Example 10 680 680 630 470 Example 11 680 680 630 490 Example 12 680 680 630 490 Example 13 680 680 630 490 Example 14 680 680 630 510 Comparative Example 1 680-720 680-720 680-720 465

< Experimental Example  1> corrosion test

In order to determine the corrosion resistance of the high-concentration iron-containing zirconium alloy composition according to the present invention, the following corrosion experiment was performed.

The zirconium alloys of Examples 1 to 14 and Comparative Example 1 were made into a specimen having a length of 50 mm, and then immersed in a solution having a volume ratio of water: nitric acid: hydrofluoric acid (HF) of 50:40:10, and fined on the surface impurities and the surface. Defects that were present were removed. The surface treated specimens were measured for surface area and initial weight just prior to loading into the autoclave. Then, after corrosion for 500 days in 360 ℃ cooling water and 400 ℃ steam, by measuring the weight increase of the specimen, the degree of corrosion was quantitatively evaluated by calculating the weight increase relative to the surface area. The corrosion test results are shown in Table 3.

 division Weight increase (mg / dm ² ) 360 ℃ cooling water 400 ℃ water vapor Example 1 51 80 Example 2 54 95 Example 3 50 79 Example 4 56 106 Example 5 53 121 Example 6 55 103 Example 7 50 78 Example 8 53 129 Example 9 53 83 Example 10 72 154 Example 11 58 113 Example 12 95 158 Example 13 64 116 Example 14 112 165 Comparative Example 1 137 190

As shown in Table 3, the zirconium alloys of Examples 1 to 14 of the zirconium alloy composition according to the present invention have a weight increase of 50 to 112 mg / dm ² in a cooling water environment, and zircaloy-4 of Comparative Example 1 (137 mg It can be seen that the weight increase amount is less than that of / dm ² ), and thus the corrosion resistance is excellent.In addition, the weight increase amount is smaller than that of Comparative Example 1 Zircaloy-4 (190 mg / dm ² ), even when the water vapor environment is 78 to 165 mg / dm ² . It can be seen that the corrosion resistance is excellent.

In particular, when comparing the weight gain of Examples 3, 4, 5 and 6, in the element added in addition to iron, chromium and oxygen in the zirconium alloy at the same heat treatment temperature, only the zirconium containing copper (Example 3, weight increase: 50 mg / dm ² ) showed the smallest weight gain, with a small amount of tin (Example 4, weight gain: 56 mg / dm ² ), niobium (Example 5, weight gain: 56 mg / dm ² ) or niobium The combination of tin (Example 6, weight gain: 55 mg / dm ² ) was slightly increased compared to copper, but the corrosion resistance was higher than that of commercial Zircaloy-4 (Comparative Example 1, weight gain: 137 mg / dm ² ). It can be seen that much increase.

In addition, when comparing the Examples 5 and 12 to determine the effect of the corrosion resistance according to the heat treatment temperature, the weight increase amount of the zirconium alloy (Example 5) performed at the hot working and the initial heat treatment temperature 600 ℃, intermediate heat treatment temperature 570 ℃ ( 56 mg / dm ² ) is lower than the zirconium alloy (Example 12, weight gain: 95 mg / dm ² ) carried out at the hot working and the initial heat treatment temperature 680 ℃, intermediate heat treatment temperature 630 ℃. Therefore, it can be seen that the production temperature of the present invention improves the corrosion resistance of the zirconium alloy composition.

In particular, when comparing Example 2 (weight increase: 54 mg / dm ² ) and 8 (weight increase: 53 mg / dm ² ), it can be seen that the size of the weight increase does not increase as the final heat treatment temperature increases. . The small amount of weight increase means that the final heat treatment does not affect the corrosiveness. Therefore, the zirconium alloy may not degrade corrosion resistance even after the final heat treatment performed for the purpose of increasing creep resistance.

Claims (4)

Iron 0.5-1.0 wt%; Chromium 0.25-0.5 wt%; Oxygen 0.06-0.18 weight percent; 0.2 to 0.5 wt% tin; And dissolving the zirconium residue to produce an ingot (step 1); Forging the ingot prepared in step 1 at 1000 ~ 1200 ℃ (step 2); Quenching the ingot forged in step 2 from 300 to 400 ° C. after solution heat treatment at 1000 to 1200 ° C. for 30 to 90 minutes (step 3); Hot extruding the ingot cooled in step 3 for 20 to 40 minutes at 550 to 600 ° C. to produce an extruded body (step 4); Performing an initial heat treatment of the extruded body prepared in Step 4 for 1 to 5 hours at 550 to 600 ° C. (step 5); Cold working the first heat treated extruded body in step 5 and repeating intermediate heat treatment several times for 3 to 5 hours at 550 to 570 ° C. (step 6); And Performing a final heat treatment for 2 to 10 hours at 450 to 580 ° C. after repeatedly performing the cold working and intermediate heat treatment of step 6 several times (step 7); High concentration iron-containing zirconium alloy composition having excellent corrosion resistance prepared, including. The method of claim 1, wherein step 1 is a step of dissolving 0.54 to 0.8% by weight of iron, 0.27 to 0.40% by weight of chromium, 0.1 to 0.15% by weight of oxygen, 0.2 to 0.5% by weight of tin and the balance of zirconium. A high concentration iron-containing zirconium alloy composition having excellent corrosion resistance. delete delete