National University of Science and Technology MISIS (Moscow, Russia)

L. D. Мiteva, Postgraduate Student of the Department of Casting Technologies and Artistic Processing of Materials, miteva.ld@misis.ru
А. Yu. Titov, Associate Professor of the Department of Casting Technologies and Artistic Processing of Materials, Candidate of Technical Sciences, titov.ay@misis.ru
Т. А. Bazlova, Associate Professor of the Department of Casting Technologies and Artistic Processing of Materials, Candidate of Technical Sciences, Associate Professor, bazlova.ta@misis.ru
М. М. Dudareva, Student of the Department of Casting Technologies and Artistic Processing of Materials, dmm.846@list.ru
А. А. Nikitina, Senior Lecturer of the Department of Casting Technologies and Artistic Processing of Materials, a.nikitina@misis.ru
V. D. Belov, Professor of the Department of Casting Technologies and Artistic Processing of Materials, Doctor of Technical Sciences, Professor, vdbelov@mail.ru

This paper presents the results of an investigation into the upward stepwise continuous casting of BrO10S2N3 tin bronze billets with a diameter of 50 mm. The influence of casting parameters, primarily the casting speed, on the formation of the microstructure and macrostructure, hardness, and mechanical properties of the alloy has been investigated. It has been established that the formation of internal cavity defects in 50 mm diameter billets is caused by the low heat extraction rate after the formation of an air gap between the graphite mold and the solidifying billet. An optimum casting temperature regime has been selected to produce high-quality billets free from shrinkage porosity and internal defects. A nonlinear relationship between the volume fraction of the γ-Cu₃Sn intermetallic phase and the casting speed has been revealed. The maximum volume fraction (4.80 ± 0.29%) is achieved at a casting speed of 12 mm/min, which is attributed to nonequilibrium solidification. A further increase in casting speed results in a lower intermetallic phase content due to the partial homogenization of the billet within the mold. The optimum casting parameters have been determined as follows: casting speed of 15 mm/min (forward stroke – 3 mm, dwell time – 8 s, backward stroke – 1 mm). These conditions ensure a high surface quality of the billets and provide superior mechanical properties, including an ultimate tensile strength of 353 MPa and hardness exceeding the requirements of OST 1 90054–72. A correlation has been established between the casting speed, the volume fraction of the intermetallic phase, and the mechanical properties, enabling the targeted control of the structure and properties of cast billets.

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