JPH0441628A - Manufacture of nb-zr alloy - Google Patents

Abstract

PURPOSE:To stably obtain an Nb-Zr alloy in which impurities are sufficiently suppressed at high Zr yield by subjecting the mixture of Nb2O3 and ZrO2 with KClO3 or NaClO3 to alumithermit reduction, subjecting the obtd. Nb-Zr-Al alloy metal stock to electron beam melting and removing and refining Al and other impurities. CONSTITUTION:The mixture of Nb2O3 and ZrO2 is mixed with KClO3 or NaClO3 in the ration of about 4 to 5% to the amt. of (Nb2O5+ZrO2). Furthermore, the amt. of ZrO2 to be blended in the mixed raw material is preferably regulated to about 20% by the ratio of [ZrO2/(Nb2O5+ZrO2)], and, if required, the whole of the series is heated to a room temp. to 400 deg.C. At the time of subjecting the Nb-Zr-Al metal stock obtd. by the alumithermit reduction of the mixture of Nb2O5 and ZrO2 to electron beam melting, Al and other impurities are easily volatilized away without causing excessive loss of Zr to form an Nb-Zr alloy of high quality.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides low-cost and industrially stable Nb −
The present invention relates to a method for manufacturing Zr alloy.

Technical background In general, high-temperature chemical reaction plants require materials that exhibit high corrosion resistance against high-temperature acids as reactor liner materials. Base alloys etc. are used. but,
Since Ta, Nb, and alloys based on these exhibit superior corrosion resistance against high-temperature acids, they will be indispensable for future high-temperature chemical reaction plants that require even better performance. It is expected that this material will not be used.

In particular, although Nb has overall inferior corrosion resistance compared to Ta, it is cheap and its stability against molten alkali metals and alkali metal vapor is comparable to Ta, so depending on the manufacturing method, it may not be suitable for current use in terms of cost. This material is considered to be a sufficient substitute for materials for high-temperature chemical reaction plants. Also, Nb
It also has the characteristic of having a small thermal neutron absorption cross section, and is a material that is attracting attention as a material for nuclear power-related components.

Among them, Nb-lXZr alloy (
Hereinafter, % representing the component ratio is expressed as weight %) is pure Nb.
In addition to the above-mentioned properties, the mechanical strength at high temperatures is higher than that of pure Nb, and the addition of alloying elements (Zr) makes the crystal grains finer and exhibits good workability. It is also used as pipe sealing caps, vacuum evaporation equipment parts, structural materials for nuclear reactors, aerospace equipment parts, etc., and demand in this field is expected to increase further in the future.

<Prior art and its problems> By the way, the following method has been known as a means for producing Nb-Zr alloy.

(a) A method in which pure Nb powder and pure Zr powder are mechanically mixed and compression-molded, alloyed by electron beam melting, and then homogenized by vacuum arc melting.

At the same time as electron beam melting of pure Nb, the melted Nb
A method of alloying by adding granular Zr to b.

(C) A method in which a mixture of niobium oxide and zirconium oxide is reduced with carbon at high temperature and under vacuum to obtain a crude Nb-Zr alloy metal, and then purified by electron beam melting.

However, although the method in item (a) is currently being practiced industrially and has a proven track record, it is expensive because it uses expensive "pure metal" as a raw material and requires a multi-step and long process. It could not be said to be an industrially advantageous method.

Furthermore, in the method described in item ('b) above, the composition of the alloy tends to be non-uniform, so re-melting is required, and the vapor pressure of Zr is considerably higher than that of Nb, so the addition of Zr is necessary. There is a problem of poor yield. For this reason, it is possible to prevent the evaporation of Zr by using an Nb round rod with a Zr rod as the core, or by using an electrode with a Zr band attached to the back of the Nb rod, so that the electron beam can directly hit the Zr. Consideration has been given to modifying the electrodes to avoid collisions, but in both cases the problem is the manufacturing cost of the electrodes when the scale is increased.
Industrial adoption was hesitant.

On the other hand, in the method of item +01 above, C that invades in the reduction step
It has been difficult to remove Nb-Zr alloys with desired characteristics, making it difficult to stably produce Nb-Zr alloys with desired properties.

Therefore, the object of the present invention was to establish an industrial means for stably producing a homogeneous NbZr alloy with excellent properties through a relatively simple process.

By the way, if you follow the technical reports to date, you will find an experimental example stating that ``Nb or Nb alloy can be obtained when niobium oxide (NbzOs) is reduced to aluminum thermite.'' I can do it. What is this “alumithermite reduction”?A
This is a high-temperature reduction method of metal oxides using l, which reduces the oxides through an exothermic reaction that occurs when AI powder and metal oxides are mixed and ignited, and the metals that melt and are separated due to the high temperature are collected. Needless to say, this is a method to do so.

In other words, the reduction of Nb2 OS to aluminium chloride occurs according to the following reaction, and the amount of heat generated (ΔH°) at 298'K at this time is - ΔH' z,s (Aj! 20 : +) - ΔH'
zze(NbzOs) = -214,2kcal, which results in the production of Nb coarse metal (N
b-AJ! alloy) is obtained.

However, metals can be stably extracted from raw material oxides by aluminum thermite reduction only when the amount of heat generated by the reduction reaction is sufficient, and as a result, there are only a limited number of materials to which this method can be applied industrially. It was just a thing.

For example, oxide of Zr (Zr
Regarding ZrO2, the reduction reaction of ZrO2 by M is also an exothermic reaction. However, the amount of heat generated in this reaction (ΔH') is due to the fact that the free energy of formation of Zr0z is 81
Since it is almost equal to □03, it is only about 2% of the case of 80 029B-4,2kcal and NbzO5, and therefore,
Even if zirconium oxide (ZrO□) is used as the material to be reduced, aluminum thermite reduction does not actually proceed.

Therefore, the reduction of ZrO2 to alumithermite has never been intended, and for example, NbzOs containing a large amount of Zr0h and Zr0
It was unexpected that the aluminum thermite reduction of the mixture raw material of t.

However, the inventors fully recognized the advantages of the aluminum thermite reduction method, which can use inexpensive oxides as raw materials and require a small number of steps. As a result of repeated basic experiments on reduction and exploring the possibility of producing Nb-1χZr alloy by this process, we found that especially potassium chlorate (KCj!Oi) or sodium chlorate ( When aluminum thermite reduction is performed by also mixing Na (JO+), the heat generated by the reduction reaction of potassium chlorate or sodium chlorate effectively compensates for the reaction heat, and the Zr content can be reduced with a high Zr recovery rate. It was confirmed that a high Nb-Zr-M alloy coarse metal can be obtained.

Moreover, the crude metal obtained by reducing aluminothermite from such KCZO or a mixed raw material of NbzOs and Zr0z to which NaClO3 is added (excluding impurities, NbZr
-Aj! Zr alloy) is electron beam melted.
Effective volatilization removal of M and other impurities is achieved without significant loss of M and other impurities, such as the A37M standard.

No. B 393 Com+*ercial Gra
de RO4216 (Zr: 0.8~1.2χ, Al
It was also found that it is possible to stably manufacture not only Nb-Zr alloys having a Zr content of less than 0.0051), but also NbZr alloys having a much higher Zr content than this.

The present invention has been made based on the above-mentioned findings and the like. and Nb-Zr-A1
After obtaining a crude alloy metal, it is electron beam melted to remove and refine M and other impurities, thereby producing a Nb-Zr alloy with a high Zr yield and sufficiently suppressed impurities in a stable manner at a low cost. A major feature of this system is that it has been made possible to do so.

In addition, as mentioned above (Nb2O5, ZrO, in the aluminum thermite reduction of the mixture, the amount of heat generated is insufficient and good slag and metal separation cannot be obtained. Therefore, in the method of the present invention, KC70
3 or Na (J 03 is also added to supplement the heat amount, but the amount of KClO3 or NaClO3 added to the raw material mixture is 4 to 5 in the ratio to the amount of (Nb20.+zrO□).
% is appropriate. Here, K[ljO, or Na
(j Thermal guarantee by adding Ox is K[170,
+2Ai'=KC/+A1zOzΔH"!911=
This is supported by an exothermic reaction such as 410 kcal, but for that reason, the amount of M used is Nb2
o6. In addition to the amount necessary for reducing Zr0z, the value should be at least the equivalent of KC703 or Na (JO).

In addition, as the amount of excess M increases, the Zr concentration in the metal obtained by thermite reduction also increases, and the Zr yield decreases to 20%.
It has also been confirmed that it can be increased to about %. and,
The appropriate amount of excess M is approximately 40% of the amount that can stoichiometrically reduce the total amount of NbzOs and ZrO.

Figure 2 shows “N” when the excess M amount is 15%.
bz O5 + Zr Oz The Zr concentration in the crude metal achieved by Chirmint reduction is defined as the (Nb + Zr concentration in the raw material)
This graph is organized according to the ratio of the amount of Zr to the amount of
It can be confirmed that the Zrfli degree in the crude metal increases steadily as the blending amount increases.

Here, regarding the amount of ZrO□ blended into the mixed raw material, C
Zr Oz/ (Nbz○s+Zro2)) ratio: 20%
The front and rear are appropriate.

Moreover, if necessary, the entire system can be heated to a temperature of [room temperature to 400'C:l] to facilitate the reaction.

When the Nb-Zr-Al crude metal obtained by aluminum thermite reduction of the NbzOs and ZrO□ mixture is subjected to electron beam melting, M and other impurities are easily removed by volatilization without causing excessive loss of Zr. High quality Nb −
It becomes a Zr alloy.

Next, the present invention will be explained in more detail based on Examples.

<Example> stl First, niobium pentoxide (NbzOs) powder was used as a raw material for producing Nb-Zr alloy: purity 99%.

Zirconium oxide (ZrOz) powder: 99% purity.

Pure M powder: purity 99%.

KCl0z: purity 98% prepared.

Next, from the above raw materials NbzO5=1620 g.

Zr　Oz　-380g Pure M...soo g.

KCl0ff...94g was weighed and mixed, and as shown in Figure 3, this mixed powder (1) was poured into a bed of alumina sand with a depression (
2) Place the alumina refractory tube (3) on top! ! After charging the container into a container and compacting it lightly, the nichrome wire (
4) was ignited to cause a thermite reaction.

When the state after the completion of the aluminum chill mint reduction reaction was investigated, as shown in Figure 4, the crude metal (5) and slag (6) were completely separated, and the crude metal (5) was separated from the slag (6).
6) had solidified and accumulated under it.

The composition of this coarse metal is “Nb 1.1XZr~
15χAj! ” was confirmed.

Next, when the crude metal was subjected to electron beam melting treatment, it was confirmed that the resulting alloy had a uniform composition of "Nb-1,4XZr" and the M content was 50 ppm or less.

Otsuka group-■ From the raw materials shown in Example 1 Nb! O,...1230g.

ZrO,...770 g.

Pure M...814g.

114 g of Kctos was weighed and mixed, and this mixture was reduced with aluminum chillmint in the same manner as in Example 1 to obtain a crude metal.

When we analyzed the components of this crude metal, we found that its composition was “
Nb-7,5χZr-22χAn''.

Next, when the crude metal was subjected to electron beam melting treatment, it was confirmed that the resulting alloy had a uniform composition of "Nb-10χZr" and the M content was 50 ppm or less.

Summary of Effects> As explained above, the method for producing the Nb-Zr alloy according to the present invention has the following advantages: fa) The raw material is an inexpensive oxide.

Cb) The process is simple (as a crude metal with a uniform composition can be obtained in advance by aluminum chill mint reduction, there is no need to re-melt and homogenize after electron beam melting and purification).

fcl It is very easy to remove M used as the reduction side by electron beam melting, and it is possible to prevent it from remaining in the alloy as much as possible, so it is possible to use high-grade Nb-Zr with few impurities.
fdl alloy obtained Nb-Zr alloy with high Zr content can be stably obtained with good Zr yield (Zr is alloyed in advance during aluminum thermite reduction, so the vapor pressure is low and the electron (Less Zr volatilization during beam melting and refining).

Therefore, according to the present invention,
This brings about extremely excellent industrial effects, such as making it possible to stably produce a high-quality Nb-Zr alloy at low cost.

[Brief explanation of drawings]

FIG. 1 is a flow diagram illustrating the manufacturing process of the Nb-Zr alloy according to the present invention. FIG. 2 is a graph showing the relationship between "the ratio of Zr to the amount of (Nb + Zr) in the raw material" and "1 degree of Zr in the reduced crude metal" in aluminum thermite reduction in the presence of excess M. FIG. 3 is a conceptual diagram illustrating the method of aluminum thermite reduction employed in the examples. FIG. 4 is a schematic diagram showing the "state inside the reaction vessel" after the aluminum chill mint reduction in Example is completed. In the drawing, ■... Mixed powder of raw materials. 2...Alumina sand head. 3... Alumina refractory tube. 4... Nichrome wire. 5... Coarse metal. 6...Slag.

Claims (1)

[Claims] A mixture of niobium oxide and zirconium oxide and potassium chlorate or sodium chlorate is reduced to alumitermite to obtain a crude Nb-Zr-Al alloy metal, which is then electron beam melted to remove Al and other impurities. A method for producing a Nb-Zr alloy, which comprises refining the alloy.