Saint-Petersburg State Polytechnic University (St. Petersburg, Russia):

V. M. Golod, K. I. Emelyanov, I. G. Orlova

E-mail: cheshire@front.ru

The paper reviews the publications concerning dependence of dendrite arm spacings of iron-based industrial alloys from the conditions of solidification. It was noted that the used thermal parameters which characterize the conditions of dendrite formation — the rate of solidification, the temperature gradient and the cooling rate — quite often are determined with significant experimental errors, are estimated on the basis of approximate relationships and often mutually correlated. It was established that the published empirical power-type models of dendrite arm spacing for carbon and low-alloy steels are characterized by a lot of the types of the parameters predictors and by scatters of their values, do not consider the effect of the alloys composition and slightly suitable for prediction of the dendritic structure. For objective assessment of uncertainties arising from the use of insufficiently large data sets and simplified method of estimation for model parameters the procedures of statistical analysis of the models adequacy for their correction and/or rejection were proposed. The comparison of results of computer modeling for a steel slabs (250 mm thickness) with 0.006, 0.06 and 0.6% C are used for analysis the evolution during solidification of the rate of crystallization and the temperature gradient under various intensity of heat extraction and natural convection of the melt. It was deduced that a radical increase in the accuracy of the analysis of the conditions of formation of the dendritic structure is provided using a developed computer model of the non-equilibrium solidification of ingots and castings on the base the thermal properties of alloys, determined by means of thermodynamic modeling, with obligatory taking into account the intense convective heat transfer in the melt.

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