Institute of Metallurgy of Ural Branch of Russian Academy of Sciences, Ekaterinburg, Russia:

S. A. Vokhmentsev, Post-Graduate Student
A. V. Larionov, Researcher, e-mail: a.v.larionov@ya.ru
R. I. Gulyaeva, Senior Researcher
V. M. Chumarev, Chief Researcher

Our article shows the results of X-ray phase and differential-thermal analysis of phase composition and thermal properties of rapidly cooled high-aluminous slags, formed during the aluminothermic smelting of AVTU (Al – V – Ti – C), AKhMK (Al – Cr – Mo – Si) and ATsMO (Al – Zr – Mo – Sn) foundry alloys in copper moulds. The AVTU and AKhMK slags have the following basic phases: Al₂O₃, CaAl₁₂O₁₉ (CA₆) and CaOAl₄O₆ (CA₂). According to the chemical analysis data, CaF2 was found in all slag samples, and a small amount of KCl was found in the AVTU foundry alloy smelting slag. This KCl was entered as halite into the foundry alloy smelting charge. The ATsMO foundry alloy smelting slag revealed the aluminate СaAl₂O₄ (CA) of orthorhombic and monoclinic crystal systems, clacium zirconates CaZrO₃, CaZr₄O₉ and free aluminium oxide α-Al₂O₃.Two modifications of aluminate CaAl₂O₄ in slag are explained by metastability. The X-ray phase analysis showed that a high velocity of slag cooling and presence of small amounts of calcium fluoride and rare metal oxides in this slag have no significant effect on phase formation. The diffractometry data made a conclusion that the main phases of rapidly-cooled slags of ladle aluminothermic smelting of foundry alloys (based on rare refractory metals) are identical to the ones, formed in the equilibrium solidification of foundry alloys based on Al₂O₃ – CaO melts. The amorphism of the investigated slag samples is insignificant. Thermal analysis of the samples of AVTU, AKhMK and ATsMO slags defined the effects of devitrification and “cold” crystallization, confirming the presence of amorphous phases in slags, and endoeffects related to the smelting of their phase terms. The heating thermograms showed that the complete dissolutions of smelting slag of AVTU, AKhMK and ATsMO foundry alloys are in the temperatures of 1879 ^oC, 1881 ^oC and 1773 ^oC, respectively. In comparison with the AVTU and AKhMK slags, lower temperatures of ATsMO slag crystallization are connected with its lesser content of aluminium oxide.
Our research work was carnied out with the financial support of the Program of the Ural Branch of RAS, project No. 15-6-3-30.

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