KR101058872B1 - High concentration molybdenum-containing zirconium alloy composition having excellent corrosion resistance and creep resistance, preparation method thereof and use thereof - Google Patents

Abstract

The present invention relates to a high-concentration molybdenum-containing zirconium alloy composition having excellent corrosion resistance and creep resistance, a preparation method thereof, and a use thereof, more specifically, 0.55-0.8 wt% molybdenum (Mo); 0.2-0.4 weight percent niobium (Nb); 0.2-0.4 weight percent tin (Sn); The total content of at least one element selected from the group consisting of iron (Fe), chromium (Cr) and copper (Cu) is 0.1-1.0 wt%; And a zirconium alloy composition having excellent corrosion resistance and creep resistance, including a zirconium (Zr) balance, a method of preparing the same, and a use thereof. In the zirconium alloy composition according to the present invention, when molybdenum having a high melting point is added to zirconium in a high concentration, segregation is locally formed without dissolving in the alloy and thus lacks manufacturability. It is manufactured from an intermetallic compound (Mo ₂ Nb) in which the ratio of molybdenum and niobium is 2: 1, and then pulverized and added to the nanopowder, so that fine powder can be easily dissolved in zirconium to secure manufacturability. It is useful for nuclear fuel coating pipes, support grids, core structures, etc., which is composed of zirconium alloys used in high combustion / long cycle operation, because it provides superior corrosion resistance and excellent creep resistance compared to commercially available zircaloy-4. Can be used.

Description

High concentration molybdenum-containing zirconium alloy composition having excellent corrosion resistance and creep resistance, a method for producing the same and its use {High molybdenum-contained zirconium alloy composition having excellent corrosion and creep resistance, manufacturing method

The present invention relates to a high concentration molybdenum-containing zirconium alloy composition having excellent corrosion resistance and creep resistance, a preparation method thereof, and a use thereof.

Due to the high temperature and high pressure corrosion environment and neutron irradiation, the deterioration of performance due to deterioration of nuclear power plant causes the safety and economic efficiency of the reactor. Particularly, zirconium alloy parts such as fuel cladding and support lattice used in nuclear fuel assembly in nuclear reactors are very important because alloy composition is accompanied by deterioration of integrity due to oxide growth and creep deformation due to corrosion reaction. Accordingly, the zirconium alloys having the low neutron absorption cross-sectional area and excellent mechanical strength and corrosion resistance have been widely used in domestic Pressurized Water Reactor (PWR) reactors for decades. Representative alloys of zirconium alloys for pressurized light reactor fuel assemblies developed in the related art are Zircaloy-4 (Zircaloy-4, 1.20-1.70 wt% tin, 0.18-0.24 wt% iron, 0.07-1.13 wt% chromium, 900-1500 ppm oxygen). , Zirconium balance).

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-4 is used as the fuel cladding material, the problem of fuel corrosion is increasing.

Therefore, the development of a material that can be used as a high-combustion / long-cycle fuel assembly with excellent corrosion resistance against the high temperature and high pressure cooling water and water vapor is very urgent. Therefore, many studies to develop a zirconium alloy with improved corrosion resistance are needed. Are being performed. Since the corrosion resistance of the zirconium alloy is greatly influenced by the kind of additive element added, processing conditions, heat treatment conditions, etc., it is most important to establish an optimum condition having excellent corrosion resistance.

Zirconium is used as a reactor material because its thermal neutron absorption area is the smallest among metals and maintains corrosion and mechanical resistance at high temperatures. In general, zirconium is stable at room temperature and increases corrosion reactivity and creep deformation at high temperatures. Alloy zircaloys having a small amount of tin, iron, chromium, etc. added to zirconium have high corrosion resistance, and other alloys containing zirconium also exhibit excellent corrosion resistance.

Niobium (Nb) is a silver-white gloss metal, but it looks blue because of its oxide film, and its specific gravity and hardness are similar to copper, but it is resistant to corrosion and easy to deform. It has a very high melting point of 2468 ° C. and has good heat resistance, thermal conductivity and stone resistance. If niobium is added to the zirconium alloy, the corrosion resistance is improved, but if it is added above the solid solution limit, the corrosion resistance may be greatly changed by heat treatment.

Iron is the most common industrial material and contains carbon or other elements and is classified as steel or steel. Adding iron to the zirconium alloy improves the corrosion resistance.

Chromium (Cr) is very stable at room temperature and does not interfere with air and water. Hydrochloric acid and dilute sulfuric acid dissolve while generating hydrogen to form a solution of chromium (II) salt, which is rapidly oxidized to chromium (III) by oxygen in the air. When chromium is immersed in oxidizing acids such as nitric acid, chromic acid, phosphoric acid, chloric acid, perchloric acid, and aqua regia, a solid thin film layer of oxide is formed on the metal surface, which becomes passive and does not dissolve. These properties make chromium and chromium alloys corrosion resistant.

Since tin (Sn) does not change well in air, it is used for surface treatment of iron, steel, copper, and the like. The addition of tin to zirconium alloys has the property of increasing creep resistance while reducing corrosion resistance.

Molybdenum (Mo) is an element having a BCC crystal structure and having a very high melting point (2617 ° C.) and has a property of improving corrosion resistance when a small amount is added to a zirconium alloy. However, since the molten point of molybdenum is very high, when added to the zirconium alloy by more than about 0.5% by weight, molybdenum does not easily dissolve and segregates, thus making it impossible to manufacture the alloy.

U.S. Patent No. 4,775,508 discloses an alloy composition consisting of 0.05-0.4 wt% niobium, 0.1-0.4 wt% tin, 0.05-0.2 wt% iron, 0.25 wt% chromium or nickel, 300-700 ppm oxygen and the balance of zirconium. To improve the corrosion resistance.

U.S. Patent No. 4,810,461 discloses an alloy composition and manufacturing process consisting of 1.0-2.0 wt% tin, 0.2-0.35 wt% iron, 0.05-0.15 wt% chromium, 0.03-0.16 wt% nickel, and zirconium balance. To reduce the corrosiveness of the composition.

U.S. Patent No. 5,023,048 discloses an alloy composition consisting of 0.25-0.35 wt% niobium, 0.35-0.65 wt% tin and the balance of zirconium as an alloy to maintain mechanical properties according to a decrease in tin content.

As described above, efforts have been made to improve the corrosion resistance and mechanical properties of zirconium alloys used as nuclear fuel assembly materials in nuclear power plants.However, in order to improve the economic efficiency of the power plant, the fuel cycle length is long and the target combustion degree is increased. Considering the increasing trend of high combustion / long cycle operation, the zirconium alloy having excellent corrosion resistance to secure nuclear fuel health in high combustion / long cycle operation is continuously required.

Accordingly, the present inventors conducted a study to improve the corrosion acceleration phenomenon and creep resistance which are the most problematic under high combustion / long cycle operation of a nuclear fuel coating tube, a support grid, and a structure made of a zirconium alloy. In particular, zirconium alloys containing 0.2 to 0.5% by weight of niobium, tin, and iron are excellent in corrosion resistance but very poor in creep resistance. It was confirmed that creep resistance was improved without making it.

However, when molybdenum having a high melting point is added at a high concentration, it is not easily dissolved in zirconium. In the present invention, in order to solve this problem, niobium having the same BCC crystal structure as molybdenum was prepared from molybdenum and a mother alloy and then added in a nanopowder form. From these studies, niobium 0.2-0.4 wt%; 0.2-0.4 wt% tin; The total content of any one or more elements of iron, chromium, copper or elements is 0.1-1.0 wt%; And by adding 0.55 to 0.8% by weight of molybdenum to the zirconium alloy composition containing the zirconium balance, it was confirmed that significantly improved creep resistance while maintaining the corrosion resistance and completed the present invention.

An object of the present invention is to provide a molybdenum-containing zirconium alloy composition excellent in corrosion resistance and creep resistance.

In addition, another object of the present invention to provide a method for producing the zirconium alloy composition.

Furthermore, another object of the present invention is to provide a use of a zirconium alloy having the above composition.

In order to achieve the above object, the present invention is molybdenum (Mo) 0.55-0.8% by weight; 0.2-0.4 weight percent niobium (Nb); 0.2-0.4 weight percent tin (Sn); The total content of at least one element selected from the group consisting of iron (Fe), chromium (Cr) and copper (Cu) is 0.1-1.0 wt%; And it provides a high concentration molybdenum (Mo) containing zirconium alloy composition having excellent corrosion resistance and creep resistance comprising a zirconium (Zr) balance.

In addition, in the present invention, when molybdenum having a high melting point is added to zirconium at a high concentration, molybdenum and niobium are not dissolved in the alloy, and segregation is locally formed, thus lacking in manufacturability. A method of preparing a zirconium alloy composition in which the ratio is 2: 1 and prepared by intermetallic compound (Mo ₂ Nb) and then pulverized and added to the nanopowder so that the fine powder can be easily dissolved in zirconium. to provide.

Furthermore, the present invention provides a nuclear fuel cladding tube, a support grid, and a core structure used during high combustion / long cycle operation using a zirconium alloy having the above composition.

The high-concentration molybdenum-containing zirconium alloy composition according to the present invention provides a zirconium alloy exhibiting superior corrosion resistance and excellent creep resistance compared to conventional zircaloy-4, which has been used conventionally, and thus, zirconium used during high combustion / long cycle operation It can be usefully used for nuclear fuel cladding, support lattice, and core structure made of alloy.

Molybdenum (Mo) 0.55-0.8 wt%; 0.2-0.4 weight percent niobium (Nb); 0.2-0.4 wt% tin (Sn); The total content of at least one element selected from the group consisting of iron (Fe), chromium (Cr) and copper (Cu) is 0.1-1.0 wt%; And it provides a high concentration molybdenum (Mo) containing zirconium alloy composition having excellent corrosion resistance and creep resistance comprising a zirconium (Zr) balance.

Hereinafter, the present invention will be described in more detail.

The zirconium alloy composition according to the present invention is molybdenum (Mo) 0.55-0.8 wt%; 0.2-0.4 weight percent niobium (Nb); 0.2-0.4 weight percent tin (Sn); Iron (Fe) 0.1-1.0 wt%; And zirconium (Zr) balance.

In addition, the zirconium alloy composition according to the present invention is molybdenum (Mo) 0.55-0.8 wt%; 0.2-0.4 weight percent niobium (Nb); 0.2-0.4 weight percent tin (Sn); 0.1-1.0 wt.% Chromium (Cr); And zirconium (Zr) balance.

Furthermore, the zirconium alloy composition according to the present invention is molybdenum (Mo) 0.55-0.8 wt%; 0.2-0.4 weight percent niobium (Nb); 0.2-0.4 weight percent tin (Sn); 0.1-1.0 weight percent copper (Cu); And zirconium (Zr) balance.

In addition, the zirconium alloy composition according to the present invention is molybdenum (Mo) 0.55-0.8 wt%; 0.2-0.4 weight percent niobium (Nb); 0.2-0.4 weight percent tin (Sn); 0.1-1.0 weight percent of iron (Fe) and chromium (Cr); And zirconium (Zr) balance.

Furthermore, the zirconium alloy composition according to the present invention is molybdenum (Mo) 0.55-0.8 wt%; 0.2-0.4 weight percent niobium (Nb); 0.2-0.4 weight percent tin (Sn); 0.1-1.0 weight percent of iron (Fe) and copper (Cu); And zirconium (Zr) balance.

In addition, the zirconium alloy composition according to the present invention is molybdenum (Mo) 0.55-0.8 wt%; 0.2-0.4 weight percent niobium (Nb); 0.2-0.4 weight percent tin (Sn); 0.1-1.0 wt% chromium (Cr) and copper (Cu); And zirconium (Zr) balance.

In the zirconium alloy composition according to the present invention, the metal element used is molybdenum (Mo); Niobium (Nb); Tin (Sn); At least one element selected from the group consisting of iron (Fe), chromium (Cr) and copper (Cu); And zirconium (Zr) balance.

The metal element used in the zirconium alloy composition according to the present invention is a type of metal element except zirconium in order to prevent an unexpected zirconium precipitate phase is formed in the zirconium base during the neutron irradiation due to the excess of the kind to reduce the corrosion resistance of zirconium And is limited to a maximum of four or five.

Hereinafter, the role and effect of the element added to the high concentration molybdenum-containing zirconium alloy composition according to the present invention.

1) Molybdenum (Mo)

In order to secure excellent corrosion resistance and creep resistance, the zirconium alloy composition according to the present invention considers molybdenum (Mo), vanadium (V), tungsten (W), etc. having the lowest diffusion rate in the zirconium base, among which neutron absorption Contains the lowest molybdenum. Since the molybdenum has an eutectoid temperature with zirconium of 738 ° C., the heat treatment introduced into the processing after the solution treatment is performed at 700 ° C. or less to generate a ZrMo ₂ precipitated phase, thereby improving strength and creep resistance. Therefore, in the zirconium alloy composition according to the present invention, if the content of the molybdenum is less than 0.55% by weight, there is a problem that the improvement of creep resistance does not reach the zircaloy-4, which is a commercial cladding tube, and exceeds 0.8% by weight. There is a problem in that the creep resistance improving effect on the amount is insufficient, and the manufacturability decreases due to the formation of cracks during alloy production.

2) niobium (Nb)

Niobium serves to greatly improve the corrosion resistance of zirconium alloys. However, if it is added less than 0.2% by weight, it is difficult to secure excellent corrosion resistance. If it is added so that 0.4% by weight is added, 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]. Therefore, the content of niobium preferably contains 0.2-0.4% by weight.

3) Tin (Sn)

Tin is known as an α-phase stabilizing element in zirconium alloys, and serves to improve mechanical strength by solid solution strengthening. The tin is preferably added at 0.2-0.4% by weight, which does not significantly affect the corrosion resistance. If less than 0.2% by weight, there is a problem that the effect of increasing the corrosion resistance is weak, and when it exceeds 0.4% by weight, there is a problem of reducing the corrosion resistance.

4) Iron (Fe), Chromium (Cr) and Copper (Cu)

Iron is an element added to improve the corrosion resistance of zirconium alloys, and it is reported that corrosion resistance is improved when 0.3 wt% or more is added [A. Seibold er al .; Proceedings, International KTGENS Topical Meeting on Nuclear Fuel, TOPFUEL 95, Wurzburg, Germany, 12-15 March 1995, vol 2, p. 117]. Chromium, like iron, is a major element that increases the corrosion resistance of alloys. Garzarolli et al. ASTM-STP 1245 (1994) p. 709]. Moreover, copper is an element which improves the corrosion resistance of a zirconium alloy when adding a trace amount. Iron, chromium, and copper do not play a significant role in improving creep resistance because the zirconium alloy has a very low solid solution and thus forms precipitated phases by adding only 0.1% by weight and coarsens the precipitated phases. Therefore, in the present invention, creep resistance can be added by adding molybdenum which greatly suppresses diffusion in order to prevent this. In view of not reducing the effect of increasing creep resistance by the addition of molybdenum (Mo), the iron (Fe), chromium (Cr), copper (Cu) or a mixture thereof has a total added amount of 0.1-1.0 wt% It is preferable.

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

A forging step (step 2) of forging the ingot prepared in step 1 in the beta phase region;

A quenching step (step 3) of quenching the ingot forged in the step 2 after the solution heat treatment in the β phase region;

A hot working step of hot extruding the β-sintered ingot in step 3 (step 4);

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

Cold working and intermediate heat treatment of the extruded body heat-treated in step 5 (step 6); And

After cold working the intermediate product prepared in step 6, and performing a final heat treatment (step 7); provides a method for producing a zirconium alloy composition containing a high concentration molybdenum comprising.

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

Step 1: Ingot Manufacturing

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 a vacuum state of 1 × 10 ^-5 torr in the chamber, high purity (99.99%) of argon (Ar) ) The gas is injected at 0.1-0.3 torr, 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.

In the dissolving step of the mixture of the alloying elements, the molybdenum element having a high melting point is first prepared in the form of an intermetallic compound (Mo ₂ Nb) in which the ratio of molybdenum and niobium is 2: 1, and then nanopowder (100 nm). It is preferable to grind | pulverize to below), and then add and mix and dissolve it with other composition elements. When molybdenum with high melting point of 2617 ℃ is added directly to zirconium at high concentration of 0.55 wt% or more, it is not dissolved in the alloy and segregation is formed locally, which is difficult to secure the shape of the product due to lack of manufacturability. to be.

At this time, it is preferable to dissolve the alloy composition element mixture three to five times in order to minimize the segregation of impurities 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.

Step 2: β-forging

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 produced ingot, preferably the forging can be carried out at 1000-1200 ℃. If the forging temperature is less than 1000 ℃, there is a problem that the ingot structure is not easily destroyed, if the temperature exceeds 1200 ℃ there is a problem that the heat treatment cost increases.

Step 3: β-Annealing

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 heats the ingot in the β phase region in order to obtain fine precipitates. At this time, the specimen is sealed with a stainless steel sheet in order to prevent oxidation of the specimen, and preferably, heat treatment at 1000-1200 ° C, more preferably 1050-1100 ° C. At this time, the heat treatment time is preferably about 10-30 minutes, more preferably 10-20 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. The tissue of the ingot prepared by quenching is formed of martensite tissue or widmanstatten tissue.

Step 4: Hot Machining

Next, step 4 is a step of hot extrusion of the β-sintered ingot in step 3.

The β-sintered ingot in step 3 may be manufactured into an extruded shell suitable for cold working as an intermediate product after hot extrusion after processing into a hollow billet. In this step, the extrusion time is preferably 20-40 minutes, more preferably 30 minutes. It is preferable that extrusion temperature is 630-670 degreeC. If it is out of this temperature, it is difficult to obtain an extruded body suitable for the processing of the next step.

Step 5: Initial Heat Treatment

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

The heat treatment temperature is set to 600 ° C or less. Specifically, the extruded intermediate product is preferably subjected to heat treatment at 570-590 ° C. for 2-4 hours. If the initial heat treatment temperature is less than 570 ° C., there is a problem in workability. If the initial heat treatment temperature is higher than 590 ° C., there is a problem that corrosion resistance is lowered due to the formation of coarse precipitated phase.

Step 6: cold working and intermediate heat treatment

Next, step 6 is to perform a cold working and an intermediate heat treatment for the intermediate product heat-treated in step 5.

The cold working and the intermediate heat treatment of step 6 may be repeated one or more times if necessary. That is, the intermediate product heat-treated in step 5 may be cold worked 1 to 5 times, and the intermediate heat treatment may be performed 1 to 4 times between the cold processes. At this time, the intermediate heat treatment is preferably performed for 3 to 5 hours at 570-590 ℃. If the heat treatment temperature is less than 570 ° C., there is a problem in workability, and if it exceeds 590 ° 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 to 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.

Step 7: Final Heat Treatment

Next, step 7 is a final heat treatment of the cold and intermediate heat-treated intermediate product. It is carried out to increase the creep resistance through cold working of the intermediate product. At this time, the final heat treatment is preferably made in a vacuum, it is preferably carried out at 500-520 ℃ for 2-10 hours. If the temperature is less than 500 ° C., there is a problem that creep resistance is reduced, and if it is more than 520 ° C., there is a problem that the mechanical strength is lowered. 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.

The present invention further provides a nuclear fuel cladding tube for use during high combustion / long cycle operation with the zirconium alloy composition.

The present invention also provides a support grid for use during high combustion / long cycle operation with the zirconium alloy composition.

Furthermore, the present invention provides a core structure for use during high combustion / long cycle operation with the zirconium alloy composition.

The high-concentration molybdenum-containing zirconium alloy of the composition according to the present invention exhibits superior corrosion resistance as well as superior corrosion resistance as compared to conventional commercially used coating tube, Zircaloy-4, and exhibits excellent creep resistance by containing molybdenum. Able to know. In addition, it can be seen that there is a significant difference in creep resistance, depending on the degree of content even in the presence or absence of molybdenum (see Experimental Example 1 and Experimental Example 2).

Therefore, the zirconium alloy having a high concentration molybdenum-containing zirconium alloy composition according to the present invention can be usefully used for nuclear fuel cladding, support lattice, core structure, etc. used during high combustion / long cycle operation.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are merely to illustrate the invention, but the content of the present invention is not limited by the following examples.

Example 1 Preparation of High Molybdenum-Containing Zirconium Alloy 1

Step 1: Ingot Manufacturing

Vacuum arc dissolution (VAR) method for compositions comprising 0.55% molybdenum (Mo), 0.3% niobium (Nb), 0.3% tin (Sn), 0.2% iron (Fe), and zirconium (Zr) balance. Ingot was prepared using the 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. At this time, the addition of the molybdenum element having a high melting point / high concentration is prepared in the form of molybdenum and niobium 2: 1 intermetallic compound (Mo ₂ Nb), and then pulverized into a nano powder (100 nm or less) and then the remaining composition elements To the field.

In order to prevent impurities from segregation or uneven distribution of alloy composition, four times of dissolution were performed. In order to prevent oxidation during dissolution, vacuum was sufficiently maintained in the chamber to 1 × 10 ^-5 torr and then high purity 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 (99.99%) of argon gas.

Step 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.

Step 3: β-Annealing

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.

Step 4: Hot Machining

The β-sintered material was processed into a hollow billet and then preheated at 630 to 670 ° C. for 15 minutes, followed by hot extrusion to prepare an intermediate product suitable for cold working.

Step 5: Initial Heat Treatment

The hot extruded material was subjected to initial heat treatment at 580 (± 10) ° C for 3 hours.

Step 6: cold working and intermediate heat treatment

The first intermediate product was cold worked, and the intermediate heat treatment was performed for 3 hours at 580 (± 10) ° C.

Step 7: Final Heat Treatment

The intermediate product after the intermediate heat treatment was cold worked, and the final heat treatment for 3 hours at 510 (± 10) ℃ in a vacuum state to prepare a high concentration molybdenum-containing zirconium alloy according to the present invention.

Example 2-6 Preparation of High Molybdenum-Containing Zirconium Alloys 2-6

Except for the chemical composition constituting the zirconium alloy composition, was carried out in the same manner as in Example 1 to prepare a zirconium alloy having the excellent corrosion resistance. The chemical composition constituting the zirconium alloy composition is shown in Table 1 below.

Comparative Example 1-4 Preparation of Zirconium Alloy 1-4

The alloy of Comparative Example 1-3 was carried out in the same manner as in Example 1 except for the chemical composition constituting the zirconium alloy composition to prepare a zirconium alloy. The alloy of Comparative Example 4 was prepared according to the composition and manufacturing process of a commercial Zircaloy-4 alloy. The chemical composition constituting the zirconium alloy composition is shown in Table 1 below. The alloy of Comparative Example 2 was attempted to be prepared without adding molybdenum as the niobium and intermetallic compound in the dissolving step, but many cracks occurred in the manufacturing step after dissolution, and thus it was impossible to prepare a specimen for evaluating corrosion and creep performance.

division Chemical composition molybdenum
(weight%) Niobium
(weight%) Remark
(weight%) iron
(weight%) chrome
(weight%) Copper
(weight%) zirconium
(weight%) Example 1 0.55 0.3 0.3 0.3 - - Remainder Example 2 0.8 0.3 0.3 0.3 - - Remainder Example 3 0.55 0.3 0.3 - 0.2 - Remainder Example 4 0.8 0.3 0.3 - 0.2 - Remainder Example 5 0.55 0.3 0.3 - 0.1 0.1 Remainder Example 6 0.55 0.3 0.3 0.2 0.2 0.2 Remainder Comparative Example 1 - 0.3 0.3 0.3 - - Remainder Comparative Example 2 0.45 0.3 0.3 0.3 - - Remainder Comparative Example 3 - 0.3 0.3 0.2 0.2 0.1 Remainder Comparative Example 4 - - 1.5 0.2 0.1 - Remainder

Experimental Example 1 Corrosion Resistance Experiment

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

After preparing the zirconium alloys of Examples 1-6 and Comparative Examples 1-4 into specimens of 25 × 15 × 1 mm in length, the volume ratio of water (H ₂ O): nitric acid (HNO ₃ ): hydrofluoric acid (HF) was Dipping in a solution of 50:40:10 removes impurities on the surface and microscopic defects on the surface. The surface treated specimens were measured for surface area and initial weight just prior to loading into the autoclave. After corrosion for 270 days in 360 ℃ cooling water, 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 2 and FIG. 1.

As shown in Table 2, Example 1-6 consisting of a zirconium alloy composition according to the present invention is 33-38 mg / dm ² weight increase in the cooling water environment, 34 ~ 39 mg / dm of Comparative Examples 1-3 ² is similar to that of Comparative Example 4 (85 mg / dm ² ), and thus, the weight increase amount is about half, and thus the corrosion resistance is much better than that of Commercial Zircaloy-4 of Comparative Example 4.

Experimental Example 2 Creep Resistance Experiment

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

In the creep test, the zirconium alloys of Examples 1-6 and Comparative Examples 1-4 were prepared as creep characteristics evaluation specimens, and then the deformation amount was measured for 10 days under constant load conditions of 380 ° C. and 120 MPa. The creep test results are shown in Table 2 and FIG. 1.

As shown in Table 2, Example 1-6 consisting of a zirconium alloy composition according to the present invention was evaluated for 10 days at 380 ℃, 120 MPa stress conditions, the creep deformation was measured in the range of 0.95% to 1.13%. On the other hand, the creep deformation amount of the alloy of Comparative Example 1-4 showed the smallest creep deformation amount of 1.21% in the commercial cladding tube of Comparative Example 4, and showed a creep deformation amount of up to 1.56%. In particular, the alloy of Comparative Example 2 had a content of molybdenum of 0.45%, except that the composition was adjusted in the same manner as in Examples 1 and 2 except that the difference was different from that of Examples 1 and 2, It can be seen that there is a significant difference.

division Weight increase (mg / dm ² ) Creep Strain (%) 360 ° C, cooling water (270 days) 380 ° C, 120 MPa (10 days) Example 1 33.76 1.13 Example 2 35.97 0.98 Example 3 37.18 1.10 Example 4 34.23 0.95 Example 5 35.83 1.06 Example 6 34.17 1.01 Comparative Example 1 33.12 1.56 Comparative Example 2 34.89 1.26 Comparative Example 3 35.15 1.39 Comparative Example 4 85.02 1.21

In addition, Figure 1 shows the results of Experimental Examples 1 and 2 for Examples 1-6 and Comparative Examples 1-4 according to the present invention, corrosion resistance of iron, chromium and copper alloys in niobium, tin of low concentration (■) is excellent, but creep resistance (●) is reduced (Comparative Example 1-4), and when molybdenum is added, it is superior to Comparative Example 1-4 including commercial coating pipe of Comparative Example 4 while maintaining excellent corrosion resistance. It can be confirmed that the creep resistance is secured. In this case, it can be seen that it is preferable to add 0.55% or more of molybdenum in order to secure better creep resistance than commercial coating pipes.

1 is a graph showing the corrosion resistance (■) of the Experimental Example 1 and the creep resistance (●) of the Experimental Example 2 for the zirconium alloys of Examples 1-6 and Comparative Examples 1-4 according to the present invention.

Claims (11)

Molybdenum (Mo) 0.55-0.8 wt%; 0.2-0.4 weight percent niobium (Nb); 0.2-0.4 weight percent tin (Sn); The total content of at least one element selected from the group consisting of iron (Fe), chromium (Cr) and copper (Cu) is 0.1-1.0 wt%; And dissolving and cooling the mixture of the zirconium alloy composition elements including the zirconium (Zr) balance to produce an ingot (step 1); A forging step (step 2) of forging the ingot prepared in step 1 in a beta phase region of 1000-1200 ° C .; A quenching step (step 3) of rapidly cooling the ingot forged in the step 2 to 300-400 ° C. after the solution heat treatment in the β-phase region of 1000-1200 ° C .; A hot working step of hot extruding the β-sintered ingot in step 3 at 630-670 ° C. (step 4); Performing an initial heat treatment of the extruded hot extruded body in step 4 at 570-590 ° C. (step 5); Cold-processing the extruded body heat-treated at step 5 to 20-85% and intermediate heat treatment at 570-590 ° C. (step 6); And cold working the intermediate product prepared in step 6, and then performing a final heat treatment at 500-520 ° C. (step 7), wherein the dissolution of the mixture of the zirconium alloy composition elements of step 1 comprises molybdenum and A zirconium alloy composition, which is prepared in the form of an intermetallic compound (Mo ₂ Nb) having a niobium ratio of 2: 1, and then pulverized into a nanopowder of 100 nm or less and then mixed with the remaining composition elements to dissolve. Manufacturing method. According to claim 1, wherein the zirconium alloy composition is molybdenum (Mo) 0.55-0.8 wt%; 0.2-0.4 weight percent niobium (Nb); 0.2-0.4 weight percent tin (Sn); Iron (Fe) 0.1-1.0 wt%; And a method of producing a zirconium alloy composition having excellent corrosion resistance and creep resistance comprising a zirconium (Zr) balance. According to claim 1, wherein the zirconium alloy composition is molybdenum (Mo) 0.55-0.8 wt%; 0.2-0.4 weight percent niobium (Nb); 0.2-0.4 weight percent tin (Sn); 0.1-1.0 wt.% Chromium (Cr); And a method of producing a zirconium alloy composition having excellent corrosion resistance and creep resistance comprising a zirconium (Zr) balance. According to claim 1, wherein the zirconium alloy composition is molybdenum (Mo) 0.55-0.8 wt%; 0.2-0.4 weight percent niobium (Nb); 0.2-0.4 weight percent tin (Sn); 0.1-1.0 weight percent copper (Cu); And a method of producing a zirconium alloy composition having excellent corrosion resistance and creep resistance comprising a zirconium (Zr) balance. According to claim 1, wherein the zirconium alloy composition is molybdenum (Mo) 0.55-0.8 wt%; 0.2-0.4 weight percent niobium (Nb); 0.2-0.4 weight percent tin (Sn); 0.1-1.0 weight percent of iron (Fe) and chromium (Cr); And a method of producing a zirconium alloy composition having excellent corrosion resistance and creep resistance comprising a zirconium (Zr) balance. According to claim 1, wherein the zirconium alloy composition is molybdenum (Mo) 0.55-0.8 wt%; 0.2-0.4 weight percent niobium (Nb); 0.2-0.4 weight percent tin (Sn); 0.1-1.0 weight percent of iron (Fe) and copper (Cu); And a method of producing a zirconium alloy composition having excellent corrosion resistance and creep resistance comprising a zirconium (Zr) balance. According to claim 1, wherein the zirconium alloy composition is molybdenum (Mo) 0.55-0.8 wt%; 0.2-0.4 weight percent niobium (Nb); 0.2-0.4 weight percent tin (Sn); 0.1-1.0 wt% chromium (Cr) and copper (Cu); And a method of producing a zirconium alloy composition having excellent corrosion resistance and creep resistance comprising a zirconium (Zr) balance. delete A fuel cladding tube used during a high combustion / long cycle operation having a zirconium alloy composition produced by the method of any one of claims 1 to 7. A support grid used during a high combustion / long cycle operation having a zirconium alloy composition prepared by the method of any one of claims 1 to 7. A core structure used during a high combustion / long cycle operation having a zirconium alloy composition prepared by the method of any one of claims 1 to 7.

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