DE1188301B - Process for the removal of gases from titanium, zirconium, hafnium or thorium taken up in interstitial spaces - Google Patents

Description

Process for extracting gases absorbed at interstitial sites made of titanium, zirconium, hafnium or thorium. The invention relates to extraction gases absorbed at interstitial spaces, in particular nitrogen and / or oxygen, of titanium, zirconium, hafnium or thorium in the form of pieces, at least of which one dimension is significantly smaller than one of the other dimensions, such as wire, Tape and the like

Oxygen and nitrogen can be easily extracted from these metals Way, while maintaining the shape of the metal pieces to be treated, remove. So prolonged annealing in a vacuum remains unsuccessful. Nor does it succeed through a simple one reducing treatment in the solid state e.g. B. to withdraw oxygen from zirconium.

If in a mixture of gaseous or vaporous components, in which a constituent is present in a smaller amount, a temperature gradient occurs, differences in concentration arise due to diffusion. When the molecular weight If this constituent is greater than that of the others, diffusion occurs from the warmer to colder places, and if the molecular weight is smaller, it takes place Diffusion in the opposite direction. This diffusion phenomenon is called the Ludwig-Soret-Effect known.

It is also known that carbon and nitrogen are found in iron exhibit such thermal diffusion in the solid state. It moves the carbon or nitrogen in the direction of the places with higher temperatures.

Tests that led to the invention have shown that that in interstitial spaces absorbed gases in titanium, zirconium, hafnium or Thorium in the solid state under the action of a temperature gradient at temperatures Diffuse over about 1000 ° C for parts that are at the lower temperatures are located, and so quickly that this diffusion phenomenon is advantageous can be used for the above stated purpose.

According to the invention, when withdrawing is taken at interstitial spaces Gases, in particular oxygen and / or nitrogen, made of titanium, zirconium, hafnium or thorium in the form of pieces of wire, pieces of tape or the like in a vacuum at temperatures above about 1000 ° C, but below the temperature of these metal-gas systems at which Eutectics or peritectics occur in the longitudinal direction of the pieces a temperature gradient of at least about 50 ° C per centimeter. The temperatures will be then sustained until the gases taken up in the interstitial lattice dissolve through diffusion have concentrated in the parts that are at a lower temperature, whereupon these parts were separated. It is important that the im to be treated Pieces of occurring temperatures should not be selected too low, so that the diffusion can be done quickly enough.

A zone in which the Temperature gradient is generated and diffusion occurs in the longitudinal direction the pieces are moved.

The required heating of the pieces can be carried out by the passage of current. In this case, the desired temperature gradient can be achieved by local cooling or by lower heating in places, e.g. B. by appropriate dimensioning of the Power supply, are brought about. Heating can also be used inductively will.

The invention is illustrated by a few examples in the table below explained.

In these cases, the heating was carried out by alternating current, including the Pieces to be treated attached to electrodes made of molybdenum tape by spot welding are. The heating is in a high vacuum of about 10-7 mm Hg on zirconium tape carried out with a length of 65 mm, a width of 5 mm and different thicknesses been.

When heated with alternating current, only diffusion takes place according to the Ludwig Soret Effect. When using direct current can be simultaneously, as per se known, a diffusion under the action of the electrical occurring Field.

The oxygen and nitrogen contents given in the table were determined by hardness measurements. The course of hardness with the content of this For this purpose, gases were measured beforehand on zirconium tape, which was homogenized up to 1358 ° C in a vacuum was and in which different precisely dosed amounts of gas by heating to about l200 ° C were recorded.

The temperature difference given for the examples was over realized a length of 20 to 30 mm.

The table shows the thickness of the treated pieces of zirconium strip in millimeters and the original oxygen or nitrogen content in atomic percent. Furthermore, the applied temperature difference is given in degrees Celsius, the treatment time in hours and the minimum and maximum oxygen or nitrogen content reached in places, also in atomic percent. No. Thickness Original grade Temperature difference Duration Minimum grade Maximum grade mm atomic percent o C in hours atomic percent atomic percent 1 0.1 3.2 oxygen 1100 to 1450 18 1.0 6.2 2 0.2 3.8 oxygen 1000 to 1460 20 0.3 8.3 3 0.14 6.4 oxygen 1000 to 1225 21 2.0 7.4 4 0.14 4 oxygen 1400 to 1700 17 0.3 5.4 5 0.2 2 nitrogen 1100 to 1450 20 0.5 2.5

Claims (1)

Claim: Method for extracting interstitial spaces Gases, in particular oxygen and / or nitrogen, made of titanium, zirconium, hafnium or thorium in the form of pieces of wire, pieces of tape and the like, marked by d u r c h, that in a vacuum at temperatures above about 1000 ° C, but below the temperature of this Metal-gas systems, in which eutectics or peritectics occur, in the longitudinal direction the pieces created a temperature gradient of at least about 50 ° C per centimeter and temperatures are maintained until the gases diffuse through concentrated in the parts at lower temperatures, on what these parts are separated. Publications considered: M. H a n s e n, "Constitution of Binary Alloys", 1958, pp. 990, 996, 1069 and 1079.