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The paper considers the geometry of cracks in the volume of briquettes made of a slag-forming material widely used in ferrous metallurgy – magnesium oxide MgO. The authors present the results of measuring the geometry and location of cracks in the volume of briquettes obtained by roller briquetting. The possibility of cracks in the volume of briquettes is a technological feature of roll briquetting. This defect affects the strength of the briquettes, as well as the yield (and productivity) in the process of briquetting on roller briquetting machines. The number and angle of inclination of cracks relative to the direction of briquetting are determined from photographs of the briquette side surface using graphic programs.

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Analysis of the process of structure formation due to briquetting of fine materials with participation of a liquid phase (water) and optimization of the process with the help of a mathematical model of formation of strength in artificial structures is of considerable practical interest. Experimental studies and computations are used for constructing two mathematical models of the strength of briquettes, which allow for the composite action of three factors, namely, the diameter of the particles of the material of the structure, its moisture content, and the proportion of the mechanisms of strength formation (capillary, molecular, and propping). The models are adequate for experimental data covering the range of particle sizes from~0.02 to 3 mm and the range of moisture contents from WMH to W MCM. The models make it possible to predict the strength of artificial structures, i.e., briquettes, depending on the particle size of the initial material and on its moisture content within the specified range of variation of initial data.Today briquetting as a method of agglomerating fine materials plays a noticeable role in various branches of industry. In order to analyze the process of structure formation from fine materials with participation of a liquid phase (water) and to optimize this process at commercial scale it is desirable to develop a mathematical model of formation of strength in artificial structures.The experience of designing nonlinear semi-empirical models shows that their application is limited by the accuracy of the mathematical description of the experimental base and frequently requires the use of specific constraints on the initial data.Assuming that the interaction of particles in a structure obeys potential "1 -3" [1], we will show the possibility of the use of a standard cubic equation for describing experimental data in the form of functions s max = f 1 (1/d p ) and s max = f 2 (W ), 2 where s is the ultimate compressive strength and d p and W are the diameter and the moisture content of the material, respectively. It can be seen from Fig. 1 that despite the high values of the correlation coefficients R (in the description of the experimental data used the quantity R varies from 0.679 to 0.980) curves 1 and 2 in Fig. 1a, b hardly reflect the essence of the phenomena. When the signs at the terms of the cubic equations are correct and correspond to the mechanisms of interaction of particles, the values of the ultimate compressive strength computed as a function of the quantity 1/d p can differ in some cases by a factor of 2 or more and the extreme values of the ultimate compressive strength of the structures can be mismatched with respect to the scales of 1/d p and W.In principle, a mathematical model can be constructed using two approaches, namely, -a formal approach with direct use of the discussed experimental functions s max = f 1 (1/d p ) and s max = f 2 (W ); an analysis of these functions made in [2] has already led to an incorrect conclusion that the mechanism of the interaction of particle...