Calculation of the kinetics of the crystallization front of iron-carbon alloys in mold cylindrical forms

Processy litʹâ, 2021, Tom 144, №2, p.23-30

Abstract

Received 21.03.2021

UDK 621.746.62

The aim of the work is to digitize experimental thermographic studies of solidification processes in the chill mold of cylindrical castings made of iron-carbon alloys, their interpolation in the range of carbon content 0.1...4.83 % and the development of a graphic-analytical technique for constructing the kinetics of the advance of the isosolidus front. Modern analytical calculations of solidification and cooling of castings by the method of integral heat balance, Stefan-Schwartz, A. I. Veinik, N. I. Khvorinov does not allow to establish the influence of the chemical composition of the alloy, the air gap between the solidified metal layer and the chill mold, the degree of surface blackness, the expansion of the chill mold upon heating, shrinkage of the casting metal and the dependence of the thermophysical coefficients on temperature. Computer simulation programs for solidification processes increase the accuracy of calculations only if they are adapted to the results of experimental measurements of solidification temperatures of castings with a specific chemical composition. In this work, the results of nine experimental studies of the solidification processes of cylindrical castings from Fe-C alloys obtained by B. B. Gulyaev, O. N. Magnitsky, L. M. Postnov in the coordinates of the parametric criterion (τ/R2) and the relative thickness (x/R) of the solidified metal layer (x). The obtained dependences of crystallization of 100 % solid phase with a step of 0.05 x/R were interpolated in the range of carbon content 0.04 ... 4.83 %. Examples of calculating the solidification duration of cylindrical castings in a chill mold are given, and according to the hypothesis of the reduced thickness of N.I. Khvorinov, it is possible to establish in a first approximation the duration of solidification of castings in the form of a ball and plate. The obtained results are recommended to be used to assess the accuracy of computer modeling of the solidification processes of the reference Fe-C alloys and to further correct the thermophysical coefficients adopted in the calculations. The kinetics of the advance of the isosolidus front is constructed for the Fe-0.3 % C alloy, which is cooled in a cylindrical mold, and its total solidification duration is calculated. Using the graphs in the coordinates τ / R2 and х/R, it is possible to calculate the duration of crystallization of castings of various sizes, the minimum time for safe movement of the mold with the ingot from the caisson to the casting cooling section to perform the technology of hot fit of the ingot into a thermal furnace, implement the technology of influencing liquid metal in the foundry form or gas-dynamic pressure during crystallization of the liquid phase.