JPS6111302B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing spongy metal zirconium by adding carbon and oxygen to spongy metal zirconium.

To industrially produce spongy metal zirconium, a method generally referred to as the Kroll method is used.

In the Kroll method, solid or liquid metal magnesium is first charged into a reduction reaction vessel, purified zirconium tetrachloride vapor is introduced under an inert gas atmosphere, and then the following reaction is carried out at high temperature. In this method, a reduction reaction is carried out according to the reaction formula to produce spongy metal zirconium.

ZrCl ₄ + 2Mg = Zr + 2MgCl ₂ Zirconium produced in this way has a small thermal neutron absorption cross section, so it has attracted attention as a nuclear reactor material. Zircaloy-2, Zircaloy-4 with small amounts of chromium, nickel, etc. added.
It is used as an alloy called niobium or as a zirconium-niobium alloy containing niobium.

Since these alloys are also exposed to high-temperature, high-pressure steam inside a nuclear reactor, improvements in heat resistance, corrosion resistance, and high strength have always been desired.

For this purpose, it has been found that these properties can be significantly improved by increasing the content of carbon and oxygen in zirconium.

As a method to increase the content of carbon and oxygen,
First, in an attempt to increase the carbon content, zirconium carbide and oil-covered return material were added in the raw material preparation stage before vacuum melting, and in an attempt to increase the oxygen content, zirconium oxide was added. , it was not possible to raise the carbon and oxygen content to a sufficiently high level.

In particular, when zirconium oxide is added, the melting point of this zirconium oxide is as high as 2715℃, so
A problem arose in that it could not be completely dissolved during melting, causing segregation.

In view of this point, the present inventors have developed the crawl method.
During the smelting process of metallic zirconium, we have developed a method for producing metallic zirconium in which carbon dioxide or carbon monoxide is supplied together with purified zirconium tetrachloride onto metallic magnesium, and carbon and oxygen are added to the produced metallic zirconium.

This method uses the fact that metallic zirconium reacts with carbon dioxide gas or carbon monoxide at high temperatures to become zirconium carbide and zirconium oxide as shown in the following formula, and increases carbon and oxygen in the process of producing sponge-like metallic zirconium. It is something that makes you

2Zr＋CO ₂ →ZrC＋ZrO ₂ 3Zr＋2CO→2ZrC＋ZrO _2This allows oxygen and carbon to be added uniformly and at a high content into the zirconium sponge, making it easy to produce metallic zirconium and zirconium alloys, which are extremely effective as nuclear reactor structural materials. Now I can get it. Note that the amount of oxygen and carbon is O in order to improve the yield strength at high temperatures;
1000 ppm or more, C: 100 ppm or more is added.

Next, an example will be described.

Example 1 During the reduction reaction process by the Kroll method, zirconium tetrachloride vapor was supplied at 60 kg/hr, and carbon dioxide gas was mixed with this at a rate of 10/hr at a reaction temperature of 800°C. The reaction is exothermic. Approximately 1,500 kg of reaction product is taken out and the by-product magnesium chloride is removed in vacuo at approximately 1,000°C. The oxygen and carbon analysis results of the spongy metal zirconium thus obtained were as follows.

Oxygen: 1450 ppm Carbon: 180 ppm Example 2 During the reduction reaction process by Kroll method, zirconium tetrachloride vapor was supplied at 60 kg/hr, and carbon monoxide was mixed and supplied at a rate of 12/hr. Approximately 1500
Kg of reaction product is taken out and further placed in vacuum.
By-product magnesium chloride was removed at 1000°C.

The analysis results of oxygen and carbon in the obtained spongy metal zirconium were as follows.

Oxygen 1257ppm Carbon 290ppm Comparison Since the contents of oxygen and carbon in the sponge-like metallic zirconium obtained by the conventional Kroll method are 900ppm and 30ppm, respectively, the content of oxygen and carbon in the sponge-like metal zirconium obtained by the method of the present invention is It can be seen that oxygen and carbon in the metal zirconium were contained very effectively, with oxygen being slightly less than twice as much and carbon being 6 to 9 times as much.

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Claims (1)

[Claims] 1. A method for producing metallic zirconium in which carbon dioxide or carbon monoxide is supplied together with purified zirconium tetrachloride onto metallic magnesium in the process of smelting metallic zirconium by the Kroll method, and carbon and oxygen are added to the produced metallic zirconium.