Ural Federal University named after the first President of Russia B.N. Yeltsin, Nizhny Tagil Technological Institute (branch), Nizhny Tagil, Russia

A. P. Firstov, Cand. Eng., Associate Prof., Dept. of Metallurgical Technologies, e-mail: first55@mail.ru

Single-use molding and core mixtures must have certain mechanical, technological and physical properties in contact with liquid metal. In the “liquid metal – mold surface” contact zone, the mold surface undergoes harsh conditions from the liquid metal side, associated with a large temperature gradient reaching up to 1500 °C and a different density of components, where the density of the metal exceeds the density of the compacted mold by four times. The surface layers of molding and core mixtures must withstand such a severe impact on the casting mold during casting without significant changes in properties. When casting molds with liquid metal (melt), as a rule, a turbulent mode of mold filling is observed. This mode of filling the mold leads to the formation of various vortices in the melt flow, which at the walls of the mold slow down the movement of the liquid metal, leading to the surface destruction of the mold. The resistance of the surface layer of the casting mold during casting is subject to abrasion of the surface layers of the mold, loss of geometric dimensions of the future casting, loss of process water in the mixture, and is characterized by crumbling and reduced surface strength, which, in turn, will affect the ability of surface sand grains to easily separate with little friction. Insufficient surface strength of the mold causes defects in the castings, forming a hollow cast, the appearance of sand shells and blockages, i.e. particles of molding material get into the casting. These factors manifest themselves during casting, especially for complex and massive carriage parts, and as an example, the “Superstructure Beam” casting, made of 20GL steel with a weight of more than 500 kilograms, can serve as an example. Thus, the surface strength of molding and core mixtures is the most important factor in obtaining high-quality casting.

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