Ural Federal University, Nizhny Tagil Institute of Technology (branch), Nizhny Tagil, Russia

A. P. Firstov, Cand. Eng., Associate Prof., Dept. of Metallurgical Technologies, e-mail: first55@mail.ru
O. I. Shevchenko, Dr. Eng., Associate Prof., Head of the Dept. of Metallurgical Technologies, e-mail: oleg.shevchenko@urfu.ru

For the safety of the rod during assembly, the sand-oil molding mixture must have a certain raw strength. Stable strength characteristics of molding mixtures based on linseed and sunflower oils can be achieved by purging the tooling with heated atmospheric air. The use of heating to accelerate drying should not exceed a temperature of 200 °C. At a higher temperature, the binding properties of the oil film drop sharply, which begins to decompose. During drying, in addition to removing moisture, oxidation and polymerization occur with the enlargement of molecules. The thickness of the oil layer around the grains of sand is very small, and therefore the oxidation of the oil occurs quickly. The intensification of the oxidative process is possible by heating the hot air passing through the sand-oil mixture. When purged with hot air, the reactivity of the formed allylic free radicals (–CH=CH–CH2–) increases when compared with the activity of most other free radicals. Reacting with the components of the mixture, the free allyl radical, upon meeting with another double bond, forms a new free radical with a branched structure and a larger size, which, in turn, can continue the chain growth stage in the oxidative polymerization reaction. The interaction of the oil components with the oxygen of the air should occur evenly throughout the entire volume of the mixture. For a more intensive course of the curing process throughout the entire volume of the core mixture, it is necessary to achieve an optimal curing regime, taking into account some features, such as a low temperature of the process and full air access throughout the core and rapid withdrawal of it and reaction products from the mixture, with a minimum volume.

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