STANKIN Moscow State Technical University, Moscow, Russia:

E. N. Sosenushkin, Professor at the Department of Plastic Deformation Systems, e-mail: sen@stankin.ru
E. A. Yanovskaya, Associate Professor at the Department of Applied Mathematics
K. N. Ivanov, Student
T. A. Kinzhaev, Student

What differentiates liquid forging from other plastic deformation processes is a solidification process during which crystals form and grow in liquid metal that is cooling down in the die. This structuring stage determines the processability and performance of forgings, which properties are governed by the number of crystals, their growth rate and pattern, and their orientation. High dimensional precision and low surface roughness of the die, which can be attained during manufacturing, allow to produce high-quality forgings. The quite complex thermodynamic processes that are characteristic of the solidification process, can be described with equations of mathematical physics. This paper describes a mathematical model of the solidification process that takes place in a twophase region during liquid forging. A simultaneous solution of the Fourier heat conduction equations for the melt, two-phase region and solid skin helps determine the solidification kinetics, which defines the structure of the forging. The authors analysed the effect of external pressure on the temperature patterns and solidification time constituents in hollow thin-walled forgings. The processing parameters established through calculations were applied in an experimental forging operation to produce hollow axisymmetric forgings. The authors characterised the microstructure and measured microhardness at different sectional regions of the forging. No shrinkage cavities, gas porosity or microcracks were found.

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