ASSESSMENT OF THE INFLUENCE OF CARBON ON THE STRUCTURE OF ROLLS

Abstract

Introduction. The urgency of forecasting the mechanical properties of cast iron rolls is dictated by the complex periodic technology of their production. The forecast of quality criteria of rolls, as the review of literature sources shows, is possible in the presence of the system approach. The systems approach includes the analysis of the most important parameters influencing mechanical and service indicators of massive rolls. Such parameters certainly include their chemical composition and structure. It is proposed to investigate the influence of carbon on the structure and properties of cast iron rolls using fractal theory. Materials and methods. Varietal rolled cast iron rolls with a pearlitic matrix were studied. The rolls included carbides (up to 25 %) and the inclusion of spherical graphite (up to 2,5 %) due to the addition of magnesium within the experiment from 0.038 to 0.054 %. The following modifiers were used in the manufacture of СШХН rolls: Foundrisil, Elmag-600, Elmag-900, Vl 57 (M), Barinoc, Elgraf. The structure of the rolls was studied at a magnification of 200 times. The results of the experiment. Determination of the fractal dimension of the elements of the structure of cast iron rolls was performed by a patented method, which is based on the determination of cellular and point fractional dimensions. It has been observed that with increasing magnesium content, the fractal dimension of spherical graphite increases to its topological dimension 2. With increasing strength and toughness and decreasing hardness values, the carbon content and fractal dimension of carbides decrease. By comparing the values of the fractal dimension of spherical graphite, carbides in the form of cementite ledeburite eutectic with the values of carbon and mechanical properties (strength, toughness and hardness) obtained regression equations with correlation coefficients R2 = 0,82… 0,94. These equations can be represented in the form of models for predicting the mechanical properties of cast iron rolls СШХН. Conclusions. The value of the results is determined by the established relationships between carbon content, structure and properties of cast iron. Using a fractal approach, linear models for estimating the mechanical properties of СШХН rolls are constructed. The maximum and minimum values of the relative error of the prediction of properties are in the range of values 2,4… 7,8 %.