Nosov Magnitogorsk State Technical University (Magnitogorsk, Russia):

A. S. Savinov, Dr. Eng., Prof., Associate Prof., Director of Metallurgy, Mechanical Engineering And Material Processing Institute, mcm@magtu.ru
V. N. Selivanov, Cand. Eng., Prof., the Chair of Material Science and Foundry Production
O. S. Zhelezkov, Dr. Eng., Prof., the Chair of Mechanics
A. S. Tuboltseva, Senior Lecturer, the Chair of Mechanics

The paper examines the problem of rejected material appearance during fabrication of shaped casting “Track link” manufactured on the base of Mechanical and Repair Complex that is a part of Magnitogorsk Iron and Steel Plant (MMK) in Magnitogorsk. Hot cracks are considered to be the main cause of rejects for such castings. These cracks are arising due to force interaction between casting and mould, as a result of development of shrinkage processes during cooling of a casting. The main methods of evaluation of hot brittleness of a cast billet are displayed, the scientists from Russian and foreign scientific schools that have conducted researches in this area are mentioned. The technology of fabrication of the casting “Track link” is considered in the work. It is noted that the casting material (steel 110G13L) is characterized by low mechanical properties at high temperatures, large casting shrinkage and low heat conductivity; thereby these material parameters can be concluded to be a cause of high hot brittleness. Thermal interaction between casting and mould is examined using the numerical methods for solving the problems of heat conductivity. Influence of geometry and technological factors (such as wall thickness, pouring temperature, yielding of foundry mould) on development of stress-strain state of cast billet wall is determined. The dynamics of varying of arising stresses depended on geometry variation as well as on technological factors of casting fabrication (pouring temperature and mix yielding) is shown. Quantitative evaluation of the effect of each separate factor is calculated. It is displayed that wall thickness of a cast billet has the most strong effect on its stress-strain state. Recommendation for varying of wall thickness of a cast billet by 3 mm is given. It led to calculated lowering of stresses by 27.62% and, consequently, to absence of metal rejects caused by hot cracks during fabrication of pilot series of castings.

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