“Chepetsky Mechanical Plant” JSC, Glazov, Russia

A. V. Aleksandrov, Head of a Group of Central Scientific and Research Laboratory, e-mail: post@chmz.net

E. V. Ilyenko, Head of Central Scientific and Research Laboratory

“Leading Scientific-Research Institute of Chemical Technology” JSC, Moscow, Russia

M. L. Kotsar, Head of Laboratory

S. L. Kochubeeva, Scientific Secretary

Hafnium raw materials are used for iodide refining (recycled Hf – Ni master alloy, recycled Hf melted tablets, initial fine Hf cutting (width is less than 5 mm) and coarce Hf cutting (width is more than 5 mm), initial Hf sheet shearings and recycled Hf pieces). Researches of temperature and time modes of degassing process of hafnium raw materials were carried out in polythermal regime in the temperature range of 20–1200 ^oС and residual pressure of (2.7–8.0)·10^–3 Pa. Laboratory electric pit-type resistor furnace SShVE-1.2,5/25 (СШВЭ-1.2,5/25) was used for these researches. Sample of the researched material (50–100 g) was placed in the kiln feeder. The furnace was vacuumized to the residual pressure of 1.33.10^–2–1.33.10^–3 Pa. The material was heated with a rate of ~300 degr/h. Temperature and residual pressure in the furnace were controlled during the heating process. Separation of gas from the material was measured during 5 minutes at the temperature from 200 ^oC and further at intervals of 200 ^oC, with closed vacuum lock between the chamber of the furnace and diffusion pump. All types of researched raw materials can be divided into three groups, according to the temperature range of maximum gas separation:
1. Initial raw materials (fine and coarse Hf cutting), with maximum specific gas separation at the temperature of 400 ^oC and distinct specific gas separation at the temperature of up to 900 ^oC;
2. Recycled raw materials (Hf–Ni master alloy HFN-10 and Hf melted tablets) with maximum specific gas separation at the temperature of 600 ^oC and distinct specific gas separation at the temperature of up to 825 ^oC;
3. Сompact raw materials (initial Hf sheet shearings and recycled Hf pieces) with a “diffused” maximum in the temperature range of 400–600 ^oC.
There were calculated the specific rates of separation of gas from all types of the considered raw materials. The obtained data about gas separation makes it possible to draw the following conclusions:
1. It is possible to carry out the degassing process of recycled materials (especially, recycled master alloy), using the stage increasing of temperature with soakings at the peaks of gas separation.
2. Heating of raw material for its effective degassing before the process of iodide Hf refining should be carried out in the temperature range of 600–850 ^oС. The formula for calculation of weight of raw materials charging into the degassing unit is given, taking into account the used vacuum system on experimentally specified rates of gas separation.

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