“Chepetsky Mechanical Plant” JSC, Glazov, Russia

A. A. Talanov, Leading Engineer of the Central Scientific and Research Laboratory, e-mail: taalek@rambler.ru
E. V. Ilenko, Head of the Central Scientific and Research Laboratory
V. L. Kiverin, Head of a Project
R. T. Abashev, Master of Calcium Production

Leading Scientific and Research Institute of Chemical Technology, Moscow, Russia

M. L. Kotsar, Head of Laboratory

This article describes the usage of equipment materials in electrolytic method of obtaining of metallic calcium. This method includes the electrolysis of calcium chloride with obtaining of copper-calcium alloy at temperature from 680 to 720 ^оС, and the following vacuum distillation of calcium from this alloy at temperature from 1100 to 1200 ^оС. In spite of the fact that the specified temperatures exceed maximum values, which are recommended by normative documents, there is shown the possibility of usage of materials after the changing of their structure and properties at operating conditions of equipment. The steel 35Kh23N7SL (35Х23Н7СЛ) is recommended to be used instead of cast iron SCh18 (СЧ18), as a cathode material for calcium electrolyzers. The service life of this grade of steel accounted more than 5 years, according to its full-scale tests in calcium manufacturing at “Elektrostal engineering plant” JSC. Results of the tests, which were held at the distillation stage, showed, that the steel 20Kh23N18 (20Х23Н18) has low resistance to the temperature cycling under load. This steel is recommended for the muffles manufacturing with development of distillation devices with countervacuum. The violation reasons of leak resistance of loading containers, made of steel St3ps (Ст3пс), were found out at the distillation stage. Interaction of steel with calcium containing melt was shown along with the growth of the cracks, caused by silicate inclusions. For the purpose of increasing of service life of loading containers, there was recommended to change their design and to stabilize the composition of residual of calcium in “poor” copper-calcium alloy at the level of 20–22%. There was defined an additional direction of increasing of durability of loading containers due to the usage of high-quality low-alloyed steels, deoxidated by calcium. Alloying elements of such steels do not react with calcium melt, for example: 15 Kh (15Х), 15KhF (15ХФ), 12 KhM (12ХМ).

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