Siberian Federal University (Krasnoyarsk, Russia):

Babkin V. G., Dr. Eng, Prof.
Leonov V. V., Dr. Chem, Prof.
Gilmanshina T. R., Cand. Eng., Associate Prof., e-mail: gtr1977@mail.ru
Stepanova T. N., Senior Lecturer

Penetration of the melt into the pores of the mold is accompanied by the processes of chemical interaction of the alloy components and the molding mixture. Therefore, the aim of this work was to study the changes in the phase composition of a water-based anti-garnish coating based on graphite of different quality during heating and their effect on the surface quality of cast iron castings. For the research methods of thermal and X-ray phase analysis were chosen. The natural graphite of the Kurey deposit, mechanically activated, chemically activated and chemically mechanically activated graphites were used as filler. Mechano-activation of graphite was carried out in a planetary-centrifugal mill, chemical activation — according to bichromatic technology. Chemical-mechanical activation is the chemical activation of graphite, followed by its mechano-activation. As a binder in the coating included technical lignosulfonate, as a stabilizer — bentonium. In the course of the work, possible chemical processes occurring in the atmosphere of the mold at the boundary «graphite coating — iron melt» are investigated. It is shown that the use of chemical and chemical-mechanical activation makes it possible to improve the quality of the surface of cast iron castings by reducing the amount of coke on their surfaces (from 4,503–5,465 to 600–700 μm using chemically activated graphite and up to 20–25 μm when using chemically-mechanically activated graphite). This is due to the fact that the iron (III) sulfate graphite formed during the chemical activation decomposes into iron (III) oxide and sulfur oxide (II) at a temperature above 600 °C. In the process of casting the cast iron form, the iron (III) oxide formed in the carbonaceous medium will be reduced to iron, thereby preventing the formation of a coke and increasing the purity of the surface of the castings. At the same time, as the results of studies have shown, similar reactions can occur with heating of bentonite and technical lignosulfonate present in the coating composition.

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