CN1125885C - Zirconium based alloy - Google Patents

Abstract

A zirconium-based alloy containing (percentage by weight): niobium, 0.5-3.0; tin, 0.5-2.0; iron, 0.3-1.0; chromium, 0.002-0.2; carbon, 0.003-0.04; 0.002-0.15; 0.001-0.4 for tungsten, molybdenum or vanadium; the balance is zirconium. The microstructure of the alloy is characterized by particles of Zr(Nb, Fe) ₂ -type iron-containing and niobium-containing intermetallic compounds and α solid solution with a size not exceeding 0.3 μm. The alloy structure can also have Zr[Nb, Fe(W or Mo or V)] ₂ , Zr[Fe, Cr, Nb(W or Mo or V)] ₂ , [Zr, Nb( W or Mo or V)] ₂ Fe, Zr(Fe, Cr, Nb) ₂ , (Zr, Nb) ₂ Fe-type iron-containing and niobium-containing intermetallic compound particles and α solid solution.

Description

Zirconium based alloy

technical field

This invention relates to metallurgy and in particular to zirconium-based alloys.

Background technique

Considerable demands are placed on the above-mentioned alloys such as corrosion resistance in water and high-temperature water vapor, strength properties and resistance to oxidation, hydrogenation resistance, radiation growth resistance and creep resistance. Furthermore, since the alloy is primarily aimed at the manufacture of thin-walled tubes for fuel cladding and other components of the working flow channels of nuclear reactors and their radioactive cores, it must have high machinability.

Hitherto, a prior art zirconium-based alloy and its preparation process and method of manufacturing products therefrom are known (see US Pat. No. 4,649,023). The alloy contains the following components in the following proportions (by weight): niobium, 0.5-2.0; tin, 0.9-1.5; one element among iron, chromium, molybdenum, vanadium, copper, nickel, tungsten, 0.09-0.11; The balance is zirconium.

However, products produced from this alloy by known methods are characterized by an insufficiently broad spectrum of corrosion resistance, including an insufficiently high resistance to nodulation corrosion in boiling water. The reduction in the iron content of the obtained product prevents obtaining a fixed ratio between the various iron-containing intermetallic compounds, thereby adversely affecting the strength and corrosion resistance of the alloy.

Another zirconium-based alloy is known to contain (percentage by weight): niobium, 0.5-2.0; tin, 0.7-1.5; at least one element in iron, chromium, nickel, 0.07-0.28; the balance is zirconium (see U.S. Patent US5125985).

However, said alloys suffer from poor machinability because, at an early stage of processing, elongated large particles of stable intermetallic compounds such as ZrFe ₃ are formed in the alloy structure, which adversely affect This limits the crack resistance of products made from the alloy, which in turn prevents the use of intense cold working in the final stages of processing and substantially limits the manufacture of large components used in the radioactive core of nuclear reactors.

Another zirconium-based alloy is known to contain (by weight percent): niobium, 0.5-1.5; tin, 0.9-1.5; iron, 0.3-0.6; chromium, 0.005-0.2; carbon, 0.005-0.04; oxygen, 0.05-0.15 ; silicon, 0.005-0.15, the alloy structure is a metal matrix hardened by niobium-containing and iron-containing intermetallic compounds, said intermetallic compounds have such a total volume ratio of intermetallic compounds, that is, Zr(Fe, Nb) ₂ +Zr(Fe, Cr, Nb)+(Zr, Nb) ₃ Fe accounts for at least 60% of the total amount of iron-containing intermetallic compounds with a gap equal to 0.32±0.09 μm (see US Pat. No. 2,032,759).

This alloy, which is closest in technical substance to the alloys described herein, was chosen as the prototype.

Products made from this prototype alloy exhibit high strength properties, resistance to boiling water corrosion, and resistance to radiative growth and creep.

However, people need to use alloys with high strength characteristics, creep resistance and radiation growth resistance under long-term radiation close to 350°C for the manufacture of some products used in nuclear reactor radioactive cores, such as guide slots or work. Runner tube.

Summary of the invention

The object of the present invention is to provide a zirconium-based alloy, the product made of said alloy is characterized by its high strength and resistance to radiation growth and creep resistance at 300°C-350°C, because A defined microstructure is established in the product without affecting its strong corrosion resistance and fracture resistance.

The above objects are achieved by the fact that the zirconium-based alloy of the present invention containing niobium, tin, iron, chromium, carbon, oxygen, silicon also contains another element selected from one of tungsten, molybdenum and vanadium, the composition of which is The percentages are like this (by weight): Niobium, 0.5-3.0; Tin, 0.5-2.0; Iron, 0.3-0.1; Chromium, 0.002-0.2; Carbon, 0.003-0.04; 0.15; tungsten, molybdenum or vanadium, 0.001-0.4; the balance is zirconium.

Products made from this alloy are practical because firstly the work of pretreating the alloy to form large intermetallic grains is eliminated, and secondly because considerable deformation can be used in its infancy The process extension limit of the billet in the cold working section is wider. The use of a large amount of deformation makes the material structure more uniform and helps to form a fixed composition, degree of dispersion and uniformity of the dispersion of the secondary phase particles in the zirconium matrix, thereby obtaining higher processing characteristics at a temperature close to 350 °C , including strength, corrosion resistance, crack resistance, radiation growth resistance and creep resistance.

According to the present invention, the microstructure of the alloy is characterized in that it has particles of Zr(Nb, Fe) ₂ -type iron-containing and niobium-containing intermetallic compounds and alpha solid solutions with a size smaller than 0.2-0.3 μm, and it may also have a size smaller than 0.2 - 0.3 μm of Zr[Nb, Fe(W or Mo or V)] ₂ , Zr[Fe, Cr, Nb(W or Mo or V)] ₂ , [Zr, Nb(W or Mo or V)] ₂ Fe , Zr(Fe, Cr, Nb) ₂ , (Zr, Nb) ₂ Fe-type iron-containing and niobium-containing intermetallic compound particles and α solid solution.

The sum of the above-mentioned intermetallic compounds in the total amount of isolated components of the secondary phase exceeds 80% (volume percentage).

Adding an element selected from one of tungsten, molybdenum and vanadium to the alloy in an amount of 0.001% to 0.4% by weight increases the strength of the alpha-zirconium matrix, whereby by sealing iron, chromium and Compared with the prototype, the content of niobium, tin and iron is increased without forming large β-zirconium phase particles and binary intermetallic compounds of zirconium and iron and zirconium and chromium in the final product, thereby preventing intermetallic compounds containing iron and chromium Compound condensation, said binary intermetallic compound reduces the corrosion resistance of the material, causing disintegration of the final product and making it less machinable.

The amount of added material between 0.001% and 0.4% by weight is selected based on the fact that when the content of tungsten, molybdenum or vanadium in the material is less than 0.001% by weight, the alpha zirconium matrix is appreciably reduced and the iron-containing metal The intercompounds are no longer strengthened, decomposed and stabilized during the manufacturing process, and as a result, the corrosion resistance of the material is adversely affected.

This leads to the formation of large particle clusters of bimetallic compounds (zirconium and iron or zirconium and chromium) and other iron and niobium whose interparticle gaps exceed 0.3 μm when the content of said element in the alloy exceeds 0.4 wt. The secondary phase particles are excessively coagulated. As a result, poorer machinability of the material during cold working and crack resistance of the final product is obtained.

Tungsten, molybdenum and vanadium also form part of the iron- and niobium-containing intermetallic compounds, thereby increasing their dispersion and density.

All of the aforementioned factors related to the manufacture of products used in the radioactive core of nuclear reactors from the aforementioned materials contribute to the formation of a uniform fine-grained alpha-zirconium matrix in the final product, which is characterized by a high density and dispersion of intermetallic compounds containing iron and niobium , the vast majority of these intermetallic compounds are characterized by a particle size of less than 0.1 μm-0.3 μm and a particle gap of 0.1 μm-0.3 μm. The total amount of more than 80% of the particles shows intermetallic compounds, such as Zr(Nb, Fe) ₂ and Zr[Nb, Fe(W or Mo or V)] ₂ , Zr[ Fe, Cr, Nb(W or Mo or V)] ₂ , [Zr, Nb(W or Mo or V)] ₂ Fe, Zr(Fe, Cr, Nb) ₂ , (Zr, Nb) ₂ Fe.

When used in radioactive cores of nuclear reactors, the formation of such a microstructure in the end product ensures its high operational stability and thereby the pursuit of high corrosion resistance and especially nodulation corrosion resistance, high strength and fracture resistance properties as well as creep resistance and radiation growth resistance at temperatures close to 450°C.

BEST MODE FOR CARRYING OUT THE INVENTION

In order to facilitate the understanding of the invention, some specific exemplary embodiments of the invention are given below.

example 1

The alloys of the present invention are formed into ingots by vacuum arc melting. Next, the ingot was forged at a temperature between 1070°C and 900°C, resulting in a 5-fold reduction in the diameter of the ingot, while the forged billet was heated to 1050°C and subjected to water quenching. Once the surface gas-saturated layer was removed, the quenched billets were cut to length and one hole was drilled in each billet and annealed at 620°C. Next, the cut-to-length blanks with holes are press-formed at 620°C. Then, the pressure-formed tube blank is quenched at a speed of 500 °C/s starting from 950 °C and annealed at 425 °C, and the annealed billet is pressed in multiple passes in the first rolling pass and subsequent rolling passes. The lower rolling system accepts cold forging with a total reduction rate of 50 (in terms of wall thickness and billet diameter), and accepts intermediate annealing at 620°C. Final annealing after cold rolling was performed at 580°C. After finishing, a finished tube with an outer diameter of 9.15 mm and a wall thickness of 0.65 mm was obtained.

Example 2

The alloys of the present invention are formed into ingots by vacuum arc melting. Next, the ingot was forged at a temperature of 1070° C. to 900° C., resulting in a 1.6-fold reduction in the diameter of the ingot. Subsequently, the forging blank is heated to 1050°C and subjected to water quenching. Once the surface gas-saturated layer has been removed, the quenched billet is cut to length into sections and a hole is drilled into each billet. Next, the perforated cut-to-length blanks were press-formed at 735°C ± 10°C and annealed at 620°C for two hours. Next, the billets were subjected to two repeated cold rolling cycles and a two-hour intermediate anneal at 630° C., followed by a final cold rolling to defined dimensions at a reduction of 20%-25%. Final annealing after cold rolling is performed at 580°C-590°C. The trimming operation resulted in a finished tube with an outer diameter of 88 mm and a wall thickness of 4 mm to be used as working runner tube in a nuclear reactor.

The examples listed in Tables 1 and 2 have shown examples in accordance with the present invention, wherein Table 1 shows the composition of the alloy of the present invention and according to the prototype (No. 10), the sample composition (No. 11) with an over-limit content value, and the microscopic Composition of tissue properties. Table 2 shows the material properties: fuel jacket at 350°C (example 1) and working runner tube of nuclear reactor radioactive core at 300°C (example 2).

Table 1 Sample serial number alloy composition Characteristics of secondary phase particles in finished pipe niobium tin iron chromium carbon oxygen silicon tungsten molybdenum vanadium Average grain gap μm Ratio of Zr(Nb, Fe, W/Mo/V) ₂ , Zr(Fe, Cr, Nb, W/Mo/V) secondary phase particles 1 2 3 4 5 6 7 8 9 10 11 12 13 example 1 1 0.5 0.5 1.0 0.003 0.003 0.05 0.003 0.4 0.16 91 2 3.0 2.0 0.3 0.2 0.04 0.15 0.15 0.001 0.21 80* 3 1.5 1.3 0.8 0.1 0.01 0.12 0.1 0.01 0.19 85* 4 1.5 1.3 0.8 0.1 0.02 0.1 0.1 0.4 0.17 90 5 2.0 1.0 0.7 0.08 0.03 0.09 0.009 0.001 0.22 80* 6 1.0 1.7 0.9 0.15 0.08 0.07 0.07 0.01 0.18 87 7 1.5 1.3 0.8 0.1 0.02 0.1 0.1 0.4 0.17 90 8 2.0 1.0 0.7 0.08 0.03 0.09 0.009 0.001 0.22 81* 9 1.0 1.7 0.9 0.15 0.08 0.03 0.09 0.01 0.19 82* 10 1.5 1.2 0.3 0.2 0.04 0.15 0.15 0.28 72 11 0.4 2.2 1.2 0.22 0.002 0.004 0.002 0.43 0.38 60 Example 2 12 1.5 1.3 1.0 0.1 0.01 0.1 0.1 0.05 0.17 85* 13 1.0 1.7 0.9 0.15 0.02 0.07 0.07 0.01 0.19 87* 14 2.0 1.7 0.9 0.15 0.02 0.07 0.07 0.01 0.20 81* 15 2.8 1.0 0.4 0.2 0.003 0.007 0.4 0.2 0.19 87 16 0.7 0.7 1.2 0.18 0.005 0.14 0.008 0.3 0.18 89 17 2.8 1.0 0.4 0.2 0.003 0.007 0.4 0.01 0.21 81* *The structure is characterized by Zr(Nb, Fe) type ₂ intermetallic compound

Table 2 Sample serial number Finished Pipe Properties ultimate strength Weight gain in autoclave water mg/dm ² Creep rate σ＝100MPa×3000h.10 ^-5 %/h Radiation growth deformation % under the influence of 5.4×10 ^-26 m ^-2 (E>0.1MeV)

Example 1 (350°C)

1 360 46 1.5 0.31

2 390 48 1.65 0.32

3 390 45 1.4 0.30

4 380 48 1.55 0.31

5 370 51 1.6 0.33

6 350 46 1.5 0.30

7 380 47 1.55 0.33

8 350 51 1.6 0.34

9 360 48 1.5 0.32

10 280 55 1.7 0.35

11 - - - -

Example 2 (300℃)

12 510 16 1.15 0.30

13 490 18 1.25 0.32

14 520 15 1.27 0.33

15 520 16 1.21 0.31

16 480 17 1.2 0.32

17 550 16 1.28 0.32

As shown in the previous examples, the use of the alloy ensures the formation of a product with a uniformly finely divided structure and a uniform distribution of secondary phase particles, 80% by volume of which is composed of Zr (Nb, Fe) ₂ intermetallic compound particles. Due to the formation of such a microstructure, the final product is characterized by high strength, crack resistance, corrosion resistance, creep resistance and radiation growth resistance.

For comparison, Tables 1 and 2 (Sample No. 11) show alloys whose constituent contents exceed their content limits in the alloy of the present invention and prototype alloys (Sample No. 10).

All products made from Sample No. 11 failed due to the formation of microcracks when subjected to flaw detection. The addition of tungsten, molybdenum or vanadium as alloy components (unlike sample No. 10) to the proposed alloy ensures higher strength, creep resistance and radiation growth resistance, while strong corrosion resistance and fracture resistance are not affected by Influence.

Industrial Applicability

The invention may be most applicable when used in the manufacture of products used in the radioactive core of nuclear reactors, such as thin-walled tubes for fuel containment, as well as large items such as working flow tubes and other components used in the radioactive core of nuclear reactors. In addition, the alloy can also be used in the fields of chemical industry, medicine and other engineering fields that require strong corrosion resistance, crack resistance, extended high temperature resistance service life and strong radiation resistance.

Claims (3)

1. zirconium base alloy, it contains niobium, tin, iron, chromium, carbon, oxygen, silicon, it is characterized in that, and it also contains the element that another kind is selected from one of tungsten, molybdenum and vanadium, and its composition weight percent is such: niobium, 0.5-3.0; Tin, 0.5-2.0; Iron, 0.3-1.0; Chromium, 0.002-0.2; Carbon, 0.003-0.04; Oxygen, 0.04-0.15; Silicon, 0.002-0.15; Tungsten, molybdenum or vanadium, 0.001-0.4; Surplus is a zirconium.

2. zirconium base alloy as claimed in claim 1 is characterized in that, the characteristics of this alloy microtexture be it have size be no more than 0.3 μ m Zr (Nb, Fe) ₂The type iron content contains the particle and the αGu Rongti of the intermetallic compound of niobium.

3. zirconium base alloy as claimed in claim 1 is characterized in that, the characteristics of this alloy microtexture are that it has the Zr[Nb of size less than 0.2 μ m-0.3 μ m, Fe (W or Mo or V)] ₂, Zr[Fe, Cr, Nb (W or Mo or V)] ₂, [Zr, Nb (W or Mo or V)] ₂Fe, Zr (Fe, Cr, Nb) ₂, (Zr, Nb) ₂Fe type iron content contains the particle and the αGu Rongti of the intermetallic compound of niobium.