The method of obtaining the finer elements of the alloy based on zirconium and plate, obtained by this method

 

The invention relates to nuclear technology. The essence of the invention: a method of obtaining a thin flat elements lies in the fact that form a billet of an alloy containing also zirconium and unavoidable impurities of 0.8-1.3 wt.% niobium, 500-2000 ppm of oxygen and 5-35 ppm sulfur, with a possible total concentration to 0.25 wt.% iron, chromium, vanadium, and up to 300 ppm tin. Spend it hardening up-condition and hot rolling to obtain a preform, which is rolled in a cold state, in at least three passes with intermediate heat treatments in the form of annealing. One of these intermediate heat treatments or preliminary heat treatment prior to the first pass of the cold rolling, hold for a long time, at least for 2 hours at a temperature of from 520 to 600°C. All possible subsequent heat treatment is carried out at a temperature below 620°C for no more than 15 minutes. A method of obtaining a thin plate to grid for nuclear fuel assemblies is that gives a subtle element, and that element is cut and punched plate. Advantages of the invention consist in the elimination of the education phase

The invention relates to a method for producing a thin elements from an alloy based on zirconium for nuclear reactors with water cooling, among the latter, in particular, for reactors cooled by pressurized water.

The invention is particularly widely used in the production of thin strip material from which cut the workpiece to obtain structural elements for the frame of the nuclear fuel Assembly, in particular for the manufacture of plates for gratings with a transverse relationship to the fuel rods.

Such structural elements are required at the same time good resistance to the cooler, consisting of a high temperature water environment, minor random growth with a large element size, and low creep loaded elements. Furthermore, the method for thin elements should not be characterized by a high rate of marriage.

The aim of the invention in particular is to provide a method that allows you to achieve the solution of these problems is avoiding the presence of phaseZr, adverse effects, in an oxidizing substance. Its additional purpose of yavlyaetsya not only with the water environment, but with fuel.

Has been proposed (EP-A-0 720 177) pipe from an alloy based on zirconium content of 50-250 ppm of iron, 0.8 to 1.3 wt.% niobium, less than 1600 ppm oxygen, less than 200 ppm of carbon and less than 120 ppm silicon. This alloy is first subjected to drawing, then rolled in a cold state, in at least four passes (the term "rolling" mean in relation to the tubular material transmission on the mandrel, to which the workpiece is pressed covering rollers) or in multiple passes with intermediate heat treatments at a temperature of 560-620°C.

At such relatively low temperatures that are optimal from the point of view of corrosion resistance to recrystallization of the alloy, which is necessary for carrying out the subsequent rolling in a single pass in the optimal mode, requires considerable time.

The method according to the invention allows to obtain thin and flat structural elements and are able to apply on a continuous line. This way we obtain a billet of an alloy based on zirconium, in addition to containing inevitable impurities also of 0.8-1.3 wt.% niobium, 500-200 ppm oxygen and 5-35 ppm sulfur, as well as on the choice of Fe, Cr, and V in a total content of less than 0.25 wt.% and the tin content less than 300 ppm. Harvesting after temper the ore, in three passes with intermediate heat treatments in the form of annealing, and one such intermediate heat treatments or pre-cooking prior to the first pass of the cold rolling is carried out for a long time, at least for 2 hours at a temperature below 600°With all the necessary heat treatment, following a lengthy heat treatment is carried out at a temperature of, generally, from 610 to 620°C for no more than 15 minutes, usually within 2-10 minutes

Often the oxygen content is: 1100-1800 ppm sulfur 10-35 ppm.

Interest in the conduct of short-term heat treatments for a period of not more than 15 minutes due to the fact that they may be in the through-type furnaces. However, they may be present temperature, causing the appearance of phaseZr, which eliminated the "long" treatment.

In the first variant of the method according to the invention, the number of passes during cold rolling is only three. The first intermediate heat treatment is carried out at temperatures above 620°C, in which you receive phaseZr, within a short period of time, corresponding to the presence of the workpiece in the entrance of the furnace. the leaves of less than 600°C for more than 2 hours, and it may be held in the cover furnace. This operation eliminates almost completely the phaseZr. Processing, in particular at temperatures below 560°With the possible, but with a duration in excess of 5 hours.

In the second variant of the method according to the invention, carrying cold rolling in four passes with a short intermediate anneals between the first two or three passes at a temperature that causes the appearance of phaseZr. Then phaseZr removed by prolonged annealing (for more than 2 hours) at temperatures below 600°C before the last or the penultimate rolling, depending on the circumstances. Annealing for 5 hours at a temperature of less than 560°C, you can achieve a similar result.

In one embodiment, the method provides for cold rolling four passes (or more) and prolonged heat treatment at a temperature of less than 600°With (often at a temperature of less than 560°C) immediately after hot rolling. All subsequent annealing is carried out at a temperature of less than 620°C, they are short (less than 15 min) and occur in the entrance of the furnace.

In any case providine the emergence phaseZr, i.e., at temperatures below 620°C.

Received this thin element is a thin strip of the material before its use is not subjected to a more chernometallurgicheskie processing, and passes only the operations such as edit, decamerone, control and cutting.

In the manufacturing process can be applied annealing furnace through-type for all short heat treatments at elevated temperatures. Only annealing to remove phaseZr has a duration of several hours, typically from 5 to 15 hours at a temperature of 520-580°With, for example, in the cover furnace.

Complex heat treatments carried out in an atmosphere of inert gas or in vacuum.

The presence of sulfur in a small amount of reduces creep at high temperatures in the aquatic environment. The oxygen content in the range from 1000 to 1600 ppm is optimal. It can be carefully regulated and controlled by the addition of Zirconia.

Used alloy is also suitable for the manufacture of shells, the method comprising rolling in several passes on the roller pilgeram mill with intermediate prolonged heat treatment at a sufficiently low is ASCII 5-35 ppm sulphur (in particular 10-35 ppm), also allows you to obtain ingots of the same composition as the flat elements cut out from a thin strip of material, and a tubular sheath or guide tubes for nuclear fuel assemblies.

The above and other features and more are explained below in the description and private methods of the invention, given as non-limiting examples. The description refers to the attached drawings, which represent:

- Fig.1-3 organigram of manufacturing a thin strip of materials for plate grids for nuclear fuel assemblies;

- Fig.4 schematically fragment plate lattice, obtained according to the invention.

Way, the stages of which are shown in the drawings, was used to obtain a thin strip of material of thickness from 0.4 to 0.6 mm for the manufacture of cutting and stamping on the press plates for grids with holes for the spring, as shown in Fig.4. However, springs can serve as a stamped part plates.

The method of manufacture involves first the casting of an ingot of the corresponding composition. In some cases, heterogeneity produce ingot, some parts of which, particularly the ends, sometimes periphery Sea.

Investigated product represent particular examples in which the obtained content of niobium was from 1.01 to 1.03 wt.%, the sulfur content of 15 to 28 ppm and the oxygen content from up to 1280 1390 ppm. For all other elements present as impurities, the content was less than the following values:

From an ingot was obtained by rolling a thick tutuncu, the thickness of which in the studied case was 100 mm After hot rolling 10 conducted usually at a temperature of from 930 to 960°C, the thickness of the in was 30 mm After rolling the product is subjected to hardening 12 tostate, usually with a temperature of 1000 to 1200°C, and received the workpiece. Then the workpiece is again subjected to hot rolling, 14, usually at a temperature of from 770 to 790°C.

All operations are common to all methods of carrying out the invention.

Example 1 (Fig.1).

In this case, was carried out by cold rolling in three passes. After hot rolling 14 was conducted cold rolling 161and 162in the first two passes, in between which were annealed 181in the annealing furnace pass-through type, which provides temperature provide the best high temperature, made from 690 to 710°C, i.e. above the temperature of transition/,. The transition to these higher temperatures leads to phaseZr, who subsequently must be almost completely removed to increase the resistance of a thin strip of the material to oxidation.

Annealing 181was carried out at about 700°C for about 4 minutes.

But the annealing 20 to remove phaseZr was conducted in Kolpakova oven for 10-12 hours out of the production line, at a nominal temperature of 550°C.

After the final cold rolling 163conducted recrystallization annealing 24 at temperatures below 620°With the aim of preventing the occurrence of phaseZr in large numbers. In practice, this annealing may be conducted at the entrance of the furnace when the exposure time from two to ten minutes at a temperature of 610-620°C.

Thin strip material obtained after annealing 24, was used without additional heat treatment. He was subjected to the usual operations, such as decamerone and control, then, if necessary, cut and stamped to izgotovlena.

Example 2 (figure 2).

The method, according to example two, involves cold rolling in four passes. It was used for the production of thin strip material thickness 0,425 and 0.6 mm

To obtain these two thicknesses conducted cold rolling 160, 161, 162, 163in four passes. Intermediate anneals 180and 182was held in the entrance of the furnace at 700°C. However, in this time of prolonged heat treatment 26 at low temperature (below 560°C) preceded both the last cold rolling passes 162and 163. Annealing 182was carried out at a temperature of below 620°With, for example, at a nominal temperature of 610°C for several minutes. The final recrystallization annealing, namely heat treatment 24, may be conducted at 615°C for a few minutes at the entrance of the furnace.

All operations specified in a in Fig.2, are the same for both the finite thickness. Subsequent passes of cold rolling was carried out at the respective degrees of compression.

In an embodiment, after cold rolling 162were annealed to the almost complete destruction of phaseZr. To this end, the annealing is carried out at temperatures below 620°C. the variants. The number of passes during cold rolling can be increased. Annealing 26 to remove phaseZr may be conducted at a temperature that is lower the longer the annealing time.

Example 3 (Fig.3)

In another embodiment of the method according to the invention is provided by cold rolling in four passes. However, the annealing 28 at a low temperature and a long time to remove phaseZr is preceded by cold rolling. In this case, using in particular the following temperatures (base are temperature, refer to Fig.3):

Thin strip material obtained by the method according to the invention, was subjected to metallurgical research and testing.

The distribution of intermetallic inclusions dispersed and uniform. The electron microscope showed the presence of several rows of dischargeNb due to annealing 18. But the highlightZr was present in trace amounts and were isolated.

Factors Cairns obtained for strip material thickness 0,425 mm, was 0.09 in the longitudinal upravlinnyalisovogo of Zircaloy-4. The tests were carried out to determine uniform corrosion under the action of radiation.

The maximum thickness of the oxide layer formed during the decay coefficient (burn-up) 62 GW·day/t, was less than 27 μm, which is less than the values observed for the guide tubes of the recrystallized Zircaloy-4 and for loose strip of material of Zircaloy-4.

Arbitrary increase the passband of the material obtained by the above method, which was measured at 350°C, very close to the alloy Zircaloy-4 under creep about 6.E neutrons cm-2. On the basis of this value was observed phenomenon of saturation, such as arbitrary growth, which amounted to almost half of arbitrary growth of Zircaloy-4 creep 25.E neutrons cm-2.

Improving education hydride compared to Serkalem-4 is also very significant, since the absorption coefficient of hydrogen is reduced approximately by half.

In the case where there is an intention to use the same alloy for the manufacture of shells and plates, preferably in the alloy as a whole of 0.03-0.25 wt.% iron, on the one hand, and at least chromium and vanadium, on the other hand. Preferably, the ratio Fe/is lock in lithium environment.

Obviously, it is possible to apply continuous heat treatment at different stages of the production cycle, provided, however, that there will not be any subsequent processing temperatures, producing the appearance of phaseZr.

Claims

1. A method of obtaining a thin flat elements, which form a billet of an alloy containing also zirconium and unavoidable impurities of 0.8-1.3 wt.% niobium, 500-2000 ppm of oxygen and 5-35 ppm sulfur, with a possible total concentration to 0.25 wt.% iron, chromium, vanadium, and up to 300 ppm tin, holding his hardening to-condition and hot rolling to obtain a preform, which is rolled in a cold state, in at least three passes with intermediate heat treatments in the form of annealing, one of these intermediate heat treatments or preliminary heat treatment prior to the first pass of the cold rolling, hold for a long time, at least for 2 h at a temperature of from 520 to 600°C and all possible treatment that follow this one from the intermediate heat treatments or pre-heat treatment, provodov under item 1, characterized in that the number of passes during cold rolling is three, and the first heat treatment between the passages is carried out at temperatures above 620°C and for short periods of time, while the intermediate heat treatment, immediately prior to the final rolling is carried out at a temperature below 600°C for > 2 hours

3. The method according to p. 2, characterized in that the first heat treatment is carried out at a temperature of from 690 to 710°C for less than 15 minutes

4. The method according to p. 1, wherein the cold rolling of lead in four passes with a short heat treatment before one of the two or three passages in cold rolling at temperatures above 620°C, in which you receive phaseZr, then spend extended intermediate heat treatment for more than 2 hours at a temperature below 600°before the last or the penultimate rolling.

5. The method according to p. 1, characterized in that it includes cold rolling, at least four passes and one intermediate heat treatments or pre-heat treatment at a temperature below 600°To be held immediately after hot rolling.

6. The method according to p. 1, wherein the sufficiently low, to avoid phaseZr.

7. The method according to p. 6, characterized in that the final recrystallization annealing is carried out at a temperature of 610 to 620°C for 2-10 minutes

8. The method according to p. 1, characterized in that the short intermediate heat treatment is carried out in a through-type furnace.

9. The method according to any of the preceding paragraphs, characterized in that the alloy contains 1100-1800 ppm oxygen and 10-35 ppm of sulfur.

10. The method according to p. 1, characterized in that one of these intermediate heat treatments and preliminary heat treatment prior to the first pass of the cold rolling, hold for a long time, at least for 5 h, at temperatures below 560°C.

11. The method according to p. 1, characterized in that the intermediate heat treatment, immediately prior to the final rolling is carried out at temperatures below 560°C for more than 5 hours

12. The method according to p. 1, characterized in that the iron, chromium, vanadium and tin are present only as impurities.

13. A method of obtaining a thin plate to the grid of a nuclear fuel Assembly, wherein the receive subtle element of the method according to any of paragraphs.1-12, and that such element cut out and stamp PLA is

 

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EFFECT: improved quality of valve and increased reliability in operation.

16 cl, 3 tbl, 1 ex, 15 dwg

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