Abstract
This paper suggest a mathematical interpretation of the influence of the basic chemical composition over the mechanical characteristics (the hardness on the rolling surface and on the necks of the rolls) of this nodular irons, resulting the equations of the hyper surface in the four and three dimensional space, the average values and mean average square deviation of the dependencies. For the statistical and mathematical analysis, there were used some industrial cases. The values processing was made using Matlab program, which can generate multi-component correlations, enounced by mathematical formulas. The resulting surfaces, belonging to the three-dimensional space, can be represented and, therefore, interpreted by technologists. Also, the level curves can be interpreted by engineers. Knowing the level curves allows the correlation of the values of the twos independent variables so that the hardness can be obtained inside the requested limits. It is presented, in graphical form, the influence of the basic chemical composition upon the hardness, which is measured on the necks and the core of the rolls, respectively on the working surface (body) of these very important rolling mill components. The performed study had in view to obtain correlations between the hardness of the cast iron rolls (on the necks and on the working surface) and its chemical composition, defined by basic chemical elements (C, Si, Mn).