Volgograd State Technical University, Volgograd, Russia:

N. A. Kidalov, Dr. Eng., Prof., Head of the Dept. of Machinery and Technology of Foundry
N. V. Grigoryeva, Lecturer of the Dept. of Machinery and Technology of Foundry
A. A. Belov, Cand. Eng., Lecturer of the Dept. of Machinery and Technology of Foundry, e-mail: aa-belov@bk.ru
N. I. Gabelchenko, Cand. Eng., Associate Prof. of the Dept. of Machinery and Technology of Foundry

A study of the effect of thermal-oxidative degradation of a carbon-containing additive on the formation of the binder film structure and the residual strength of sand-liquidglass mixtures after various calcination temperatures is presented. Pyrolyzed industrial carbon (pyrocarbon) of P324 grade was used as an additive. The methods of differential thermal and thermogravimetric analyzes were used to study the physical and chemical processes that occur with the investigated carbon-containing material when heated to a temperature characteristic of the heating of the surface layer of the core (molding) mixture in contact with liquid steel. This made it possible to reveal the temperature ranges of the degradation of the carbon-containing additive, which lead to a violation of the integrity of the sodium silicate film and a decrease in the residual strength of the sand-liquid-glass mixture. For a comparative analysis of the structure of silicate binder films and the residual strength of sand-liquid-glass mixtures after calcination at temperatures of 453, 673, 873, and 1073 K (180, 400, 600, and 800 °C), standard cylindrical samples from reference (quartz sand of 1K2O303 grade and liquid glass with a silicate modulus of 2.8, a density of 1490 kg/m³ as a binder) and experimental (with the introduction of pyrolytic carbon in the amount of 2 % (wt.)) mixtures have been prepared. As a result of the study, it was found that the residual strength of the studied sand-liquid-glass mixtures depends on the morphological features of the surface of the silicate binder film, expressed by the presence of carbonaceous formations (soot), pores and crystals of sodium carbonates (stress concentrators in the binder film).

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