JPS5825467A - Manufacture of zirconium base alloy-clad pipe - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a cladding tube made of a zirconium-based alloy for a fuel rod in a carving furnace.

Thin-walled zirconium-based alloy tubes known as Jintong Zircaloy are used as cladding tubes for fuel rods in nuclear reactors. These alloys include alloying materials such as tin, iron, nickel, etc. In the case of Zircaloy, the C phase is stable at temperatures below 790°C and the β phase is stable at temperatures above 950°C.
Occurs between 0°C and 950°C. In the normal phase, zirconium atoms are arranged in a hexagonal canned lattice, and in the β phase, they are arranged in a body-centered cubic lattice. In so-called β-quenching of Zircaloy to obtain desired properties such as improving corrosion properties, the material is heated to a temperature in the β-phase region and rapidly cooled to a temperature in the β-phase region.

When manufacturing conventional Zircaloy clad pipes.

After forging into an input V-rod, β-quenching is performed. After the production of Ronde's extruded billet, the billet is extruded to a single-phase state at a temperature below 680°C, and then this extrudate is cold-rolled in several stages, allowing subsequent cold rolling between successive cold-rolling steps. 625'-700℃ to adjust
Annealed, intermediate annealing %: Applicable. Cooling of the extrudate after each intermediate annealing takes place relatively slowly at a rate of up to 6° C. per minute in a temperature range just below the annealing temperature and without the use of any coolant. After the final cold rolling step, a final annealing process imparts the desired properties to the material. This final annealing is 400°
It is carried out at temperatures from 700°C to 700°C.

Tubes made from silicaloy under conventionally employed conditions have proven to have sufficient resistance to corrosion under the operating conditions commonly applied to VcWL child furnaces. However, the evolving situation is such that the operating time of the fuel assembly becomes even longer. Therefore, the cladding material is exposed to corrosive water for a longer period of time than before, increasing the risk of corrosion damage. It is therefore desirable to obtain good corrosion properties from the alloy used without undesirable changes in its mechanical properties.

In particular, as already known from US Pat. No. 4,238,251, the resistance of the pipe to so-called accelerated nodular corrosion in water and high-pressure steam can be improved by quenching the finish of silicalloy. As is clear from U.S. Pat. No. 3,865,655, it is possible to obtain a Zircaloy tube with better mechanical properties by subjecting the extrudate to β quenching before subjecting it to a final cold rolling step. I can do it.

The exact reason why β-quenching achieves improved resistance to accelerated nodular corrosion has not yet been fully determined. However, the improvements appear to be related to the size of the intermetallic compounds as well as their distribution in the material.

The so-called second phase of the intermetallic compound is composed of a compound containing mainly iron, chromium, and nickel in addition to zirconium, and has a granular form. Due to the dissolution and precipitation achieved by β quenching, the particle size decreases and redistribution from uniformly distributed grains to grains with an arrangement of % S at the grain boundaries of 5 grains formed uniquely by β phase change is obtained. Beta quenching of the finished cladding tube reduces the ductility of the tube and this results in drawbacks of the manufacturing process. Beta-quenching the extrudate to its final dimensions before cold abrasion reduces deterioration of the mechanical properties of the finished tube. However, β-quenching, whether it is done on the finished tube or before the final cold rolling process, increases the amount of scrap and even more! The yield is reduced due to the formation of an oxide layer on the surface that must be removed.

In accordance with the present invention, it is possible to produce cladding tubes for fuel rods for nuclear reactors that have good resistance to nodular corrosion and better ductility than at least the best cladding tubes previously known. has been proven. Compared to previously known methods of manufacturing clad tubes that use β-quenching after extrusion, the use of the present invention, which also uses β-quenching, allows for the production of tubes on small surfaces rather than carrying out β-quenching early in the manufacturing process. Since the formed oxides can be removed, production yields are improved due to less scrap and less material loss.

The present invention provides a method for manufacturing silicone-based alloy cladding tubes for nuclear reactor fuel rods, in which the silicone-based alloy is extruded and the extrudate is subjected to cold rolling and at least one annealing process. A method of undergoing intermediate annealing during inter-rolling and β-quenching before final cold rolling, wherein β-quenching is carried out before cold rolling, and then at least one intermediate annealing is carried out at a temperature of 500-610°C. The method is characterized in that: The preferred temperature for intermediate annealing is 50
0-610°C, particularly preferably 550-600°C.

Extrusion is carried out in a one-phase region at any temperature.

After the final cold rolling, the extrudate is subjected to a final annealing at a temperature of 400-675°C, preferably 400-610°C, preferably 550-500°C.

For β quenching of extruded products, the temperature in the β phase region is suitably 950-12.
It is carried out by heating to a temperature of 50°C, preferably 1000-1150°C, and then rapidly cooling to a temperature in the apophase region. Next, cooling is performed at a rate of 20-400°C per second from the temperature used in the β phase region to a temperature of 790°C.
℃ to 500 ℃ or less at a rate of 5 ℃ or more per minute.

In manufacturing the clad tube of the present invention, the size of the second phase particles in the finished tube is considerably smaller than that in the case of conventional glued two-layer tube manufacturing that does not involve β quenching after extrusion, such as when β quenching is used. is known. however,
β It is the case after rapid cooling. It may be the small size of the second phase particles and their uniform distribution achieved by the present invention that provides a suitable combination of good resistance to nodular corrosion and good mechanical properties.

The siliconium-based alloy is preferably a siliconium-tin alloy, such as the alloys known under the trade names Silicaloy 2 and Silicaloy 4, which have a tin content of 1.
2-1.7%% iron with 0.07-0.24 Ls, Rio
-hte0.05-0.151 nickel o -o, o
It is within the range of s o s, the remainder being silicone as well as the usual existing impurities, which are stated in units of units per weight like the other units mentioned in the text. Silicaloy 2 is 1.2-1.7% tin.

Contains 0.07-0.20% iron, 0.05-0.15% chromium and 0.3-0.08% nickel. Ji! J force o (4t! 1.2-1.711b)
Tin, 0.18-0.24% Iron, 0.07-0.13
Contains chromium and does not contain nickel.

The siliconium-based alloy is preferably subjected to a beta quench treatment prior to extrusion, ie, heated to a temperature in the beta phase region and rapidly cooled to a temperature in the direct phase region. However, β
It can be used without quenching. Beta quenching prior to extrusion is carried out by heating the alloy suitably to a temperature of 950 DEG-1250 DEG C., preferably 1000 DEG-1150 DEG C., and rapidly cooling it to a temperature in the 18 Im range. Then, the cooling of the β-phase region from the working temperature to a temperature of 750°C is omitted at a rate of 1-50°C per second, and the cooling from 790°C to 500°C or less is
Cooling to E is preferably carried out at a rate of greater than 5° C. per minute.

Next, the present invention will be explained in detail with reference to examples thereof.

Forged into a Zircaloy 2 Inborator diameter 150-200 diameter rod. This rod piece was heated to 1050℃ for 1
β-quenching treatment is performed by heating for 5 minutes and cooling to room temperature at a rate of 5-10°C per second. Made from extruded billet rod. These billets are extruded at temperatures of 700-740°C, ie in the one-phase range. The extruded product is then subjected to a six-stage cold rolling process, which gives the tube an R of 11 and a final outer diameter of 12.
It becomes 3111.

Between the first and second rolling and between the second and last rolling the extrudate is annealed to a temperature of 700° C. for 1 hour.

After each intermediate annealing, the extrudates are cooled in a helium-filled furnace at a cooling rate of 10°C per minute at the annealing temperature, i.e., in the temperature range from 700°C to 650°C. After the final cold rolling, the tube is finally annealed at a temperature of 565°C. Both intermediate and final annealing are performed in a vacuum furnace. In the finished tube, the second phase particles are 'x 0.01-0.2
In clad tubes manufactured by American methods and not subjected to beta quenching in the finished or early extruded state, with sizes in the pm range and average particle size of about 0.1 pm, the second phase particles are 'f with a size range H of 0.1-0.6 pm and an average particle size of about 0.3 am.

Clad pipes made according to the present invention were tested during corrosion tests that have been shown to closely simulate nuclear reactor operating conditions.
This is only a fraction of what can be obtained by conventional manufacturing without β-quenching treatment after extrusion, and shows a weight gain of about the same magnitude as that obtained by manufacturing with special treatment by β-quenching treatment after extrusion, and in the case of the present invention, the weight gain is 50%. -10011717 am” and 350-4000”j in conventional manufacturing without β quenching
'/dm2 is 0. The fly resistance of the clad tube made according to the present invention is better than that of a tube that has undergone β quenching in the finished state and is better than that of a tube that has undergone β quenching immediately before final cold rolling. It is.

The above corrosion tests were carried out in a steam pressure vessel at a pressure of 9.8 MPa and a temperature of 500°C.

Weight gain indicates the degree of corrosion that the tube has undergone.

Agent Asamura Hao 4 other people

Claims (1)

[Scope of Claims] (1) A method of manufacturing a silicone-based alloy cladding tube for a nuclear reactor fuel rod, wherein the silicone-based alloy is extruded, and the extrudate is subjected to cold rolling and at least one annealing process. , an intermediate annealing in two successive cold rolling volumes as well as a β quench before the last cold rolling, wherein the β quench is carried out before the cold rolling and is followed by at least one intermediate annealing of 500 A manufacturing method characterized in that it is carried out at a temperature of -675°C. (2. The manufacturing method according to claim 1, wherein the intermediate annealing is carried out at a temperature of 500-610°C, preferably 550-600°C. (3) 411' In the manufacturing method according to either the first or second term of the Ffil requirement, the silicone-based alloy contains 1.2-1.7% tin per 'N' amount and 0 per lid.
．． 0.07-0.241 iron and 0.05-0.1 per weight
5% of chromium and o - o, o s s of nickel by weight, the remainder being silicone and any existing impurities of the common type. (4) A manufacturing method according to any one of claims 1 to 3, characterized in that the siliconium-based alloy used during extrusion is β-quenched. (5) Range of Permissible Percentage Percentage Percentage per cent of the manufacturing method according to any one of paragraphs 1 to 4, in which the extruded product undergoes a final annealing at a temperature of 400-675°C after the final cold rolling.
Manufacturing method for making images.