JPS59208044A - Corrosion-resistant hafnium alloy - Google Patents

Abstract

PURPOSE:To provide excellent nodular corrosion resistance and to prevent hydrogen embrittleness by incorporating a specific ratio of Nb and Zr into Hf and precipitating a martensite crystal in the alloy texture. CONSTITUTION:At least one kind of 0.01-14.8wt% Nb and >=0.01wt% Zr are incorporated into Hf and the total amt. of these added alloy elements is made <=40wt%. The Hf alloy is quickly cooled from the beta region or alpha+beta region to precipitate the martensite crystal structure in the alloy structure. After the precipitation of the martensite crystal structure, the alloy is annealed at about 800 deg.C and is quench hardened, by which strain is relieved therefrom. The alloy having excellent strength and a remarkable effect as a control rod for a nuclear reactor is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention applies NU to a corrosion-resistant hafnium-based alloy used as a material that requires corrosion resistance, such as control rods for nuclear reactors.

[Technical background of 5';'J' and its problems] Hafnium does not necessarily have a large thermal neutron absorption cross section, but
It has many peaks in the resonance energy region, and therefore has nuclear properties that make it useful as a control rod for nuclear reactors, and it also has good corrosion resistance even in difficult processing and high-temperature, high-pressure steam. It is something. Furthermore, in recent years, the use of hafnium as control rods for nuclear reactors has become a focus for reasons such as the failure of light water reactors and the increasing production of hafnium as a by-product of zirconium production.

However, if hafnium is loaded in a nuclear reactor and used as a control rod for a long period of time, at the end of its use, white corrosion products due to a corrosion reaction called so-called nodular corrosion will form on its surface in spots. Chiru.

This is because...funium reacts with high-temperature water, and the generated hydrogen accumulates between the base material and the oxide film on the surface, forming corrosion products. This large amount of product accumulates on the surface over time, and if it eventually peels off from the surface, there is a risk that the strength of the control rod will be reduced.

When the still-formed hydrogen penetrates into the interior of the metal, a hafnium hydride is formed, which, when formed perpendicular to the surface, forms the so-called hydrogen Ir1 due to successive hydrides.
It is thought that a problem of s-ness will occur.

Moreover, (='・il r=':Q L 7'ko113
Eclipse formation'1 Of course, it will reduce the neutron absorption capacity, so if it floats in the cooling water, it will not be able to absorb neutrons, leading to a decrease in the reactor metal's own strength and making it difficult to control. be done.

[Purpose of Jihaku jJ]

The present theory is based on such a conventional method;
It is made of a conium-based alloy that has 1:llj horn sea corrosion resistance and has 16% strength against hydrogen embrittlement. [Shiru 1゜ and Motomei's) already 2] The present Komyo et al.
1b eclipse (・yo, zonomoto or α phase (h -c-p'
It is confirmed that i3 is generated with /'. In order to stop the formation of this α phase, the α phase is formed by rapid cooling from the high temperature β region with a b-c-c crystal (curved shape). A martensitic structure with different martensitic structures is formed.It was discovered that this crystal structure has excellent hydrogen embrittlement properties with nodular coronoyons 1↑ and 1iiij, and the present invention was made based on this knowledge. be.

That is, in the present invention, 0.01 to 14.0% of niobium is added to the hafnium group.
Coordination 8 (hereinafter CH indicates weight proportion), zirconium 0.01
% or more of 1a, and the total amount of these alloying addition elements is 40% or less, and is characterized by having a martenzite crystal structure in the solute.

Explaining Akira Honji in detail below, first of all, among the alloying elements, niobium is a solid solution in hafnium, stabilizes the β phase and σαα+β phase, and has the effect of promoting the expression of martenzite crystal structure. be. The reason why the amount added was limited to the above range was less than 0.01% (β phase and α+
The stabilizing effect of the β phase is small, and 14. If more than 8% of niobium is added, niobium cannot be completely dissolved and becomes a two-phase state, resulting in a decrease in mechanical strength and corrosion resistance. Specified within the range of cracks/C.
・Also, norconium is in the same position as niobium, and IM is in hafnium.
It has the function of stabilizing the "I i'i'; ``The amount of addition of kagome/koso''
The reason why it is limited to the range of ij is that if the coefficient OO is below 1, the stabilizing effect of the β phase and α+β phase will be small. Further, since zirconium and hafnium are dissolved in solid solution at a total rate of 2'-A and 1A, there is no particular upper limit for zirconium.

However, when used as a nuclear reactor material f::, it is essential that l() has a large absorption capacity for medium+S+- molecules, so how should niobium and turconium be combined? , at least one of them may be added alone, but it is necessary that the total amount of alloying addition elements does not exceed 40φ.

To explain the method for manufacturing 'i7ζhonshi■22a gold coating, the method for producing gold coating is as follows: By rapidly cooling a conium alloy of the above composition from the β phase region or α+β phase region), alloy 1i11
1x'; Martenzite crystal + m weave can be exposed in C. In this case, water cooling, oil cooling, forced air cooling, or the like is used as the rapid cooling method. After the martensitic crystal structure is completely developed, it is preferable to anneal the material at a temperature of around 800° C. to remove distortion caused by rapid quenching.

In this way, the alloy of the present invention has b-c-
The crystal groove structure shown in c is obtained, but when this is rapidly cooled, symmartinsite crystal threads are exposed, and these are distributed in a network shape at grain boundaries or sub-grain boundaries, resulting in a ζ alloy; That is, when rapidly cooled from the β region, the crystal orientation U ratio of the present invention alloy is (110) b, c, c, / (0001) h, c, p.

[111) b, c, c, /C1120] h, c, p.

becomes.

The corrosion-resistant hafnium-based alloy of the present invention obtained in this way has a martenzite crystal structure, so it has excellent nodular corrosion properties and
Since almost no corrosion occurs, the generation of hydrogen can also be suppressed to a very low level, and the generation of water accumulation due to hydrides can also be prevented. Is it possible to make niobium-containing materials even more erodible by incorporating them into the entire alloy as a solid solution? It is.

Hafnium has a high melting point of ~2,200°C and a transformation humidity of ~1,740°C, but by adding niobium and zirconium, the melting point and rhombic crystalline ratio are lowered.

In particular, the temperature drop is remarkable, so the β phase and α+β phase stably exist at low temperatures.
7- I can do something.

In addition, martenzite rn products and i'L1 woven fabrics have improved hardness, and those containing niobium must be quenched! ＞ IRI's effect can be changed and the strength is increased.
- to do. Therefore, when used as a control line for a nuclear reactor, the 11
In addition to having the above-mentioned corrosion resistance for a long period of time, it can also maintain effective neutron absorption capacity.

[Embodiments of the invention]

A hafnium-based alloy consisting of 3% niobium, 8% zirconium, and the balance hafnium was heated to about 1750'C and cooled with water to obtain a corrosion-resistant hafnium-based alloy having a martenzite crystal structure.

In order to investigate the nodular corrosion properties of the alloy samples of the present invention thus obtained, an accelerated m-corrosion test was conducted in a steam atmosphere. This test: The test conditions are 500℃, 105
The test was carried out using high-temperature, high-pressure water and air at a rate of 2 kg/kg.

In order to compare with the alloy of the present invention, hafnium for nuclear power use, which contains impurities such as zirconium and has a purity of 98 and has not been subjected to any heat treatment, was also subjected to an accelerated corrosion test in a steam atmosphere in the same manner as in the example. I did it.

The test results are shown in the drawings, and the alloy of the present invention is shown in the figure 'AI'J.
As shown in '-a, the curve of weight increase due to corrosion is gentle, and test 1. No solar coronation was observed in the surface observation after 0 days. On the other hand, hafnium for nuclear power use, which does not have martensitic crystal bile, suddenly increases in weight after 50 days, as shown in the drawing with a curved edge. I',...
In the state after 00 days of "IL" mini, nodular corrosion was easily occurring.

[Nv 1jJJ Nozu's power question:b]Hj:1
It is related to 'I Kakarari' Rakana Like, Pilot'! According to the base alloy, it has excellent anti-corrosion resistance and is superior to f1 in terms of hydrogen embrittlement prevention. 11
, 1 word; ', il 4:4 It has a remarkable power!
: It is something to be shouldered.

41Σl ifu III
This is a graph of the coil conduction I, ↑, (compared to ii', &L,) of the 11-5 meal obtained by the Tsunonilla corrosion test of the k1 main brother 4 alloy and the nuclear-grade No. 7 nium.

Deno, I+fI Jindai Chojin Patent Attorney Suzue Takehiko Koro B Agoma (El)

Claims (1)

[Claims] Hafnium group, 0.01 to 14.8 weight of niobium, 0.01 weight of zirconium) jE 5' or more
An opening hafnium-based alloy containing martenzite crystalline gauze in the alloy structure containing F, 1lIf and having a martenzite crystal structure in the alloy structure in which the total number of purple needles added to these alloys is 40% by weight or less.