EVALUATION OF MATERIAL QUALITY BY NON-DESTRUCTIVE METHOD
Keywords:chemical composition; structure; mechanical properties; forecast equations
Introduction. Different approaches are used to assess the quality of metal by non-destructive methods. These include ultrasound, X-ray, optical and electron microscopy, and mathematical prediction. The latter differ in the ability to improve the obtained models by adjusting the arguments (in this case, the studied parameters of technology). This problem is especially acute when assessing the quality criteria for solid metal castings, which include cast iron rolls. Materials and methods. As a material for the study, high-grade rolled cast iron of СПХН was selected to study the effect of its chemical composition on mechanical properties (HB hardness; tensile strength σB; flexural strength σзгин). The structure of the working layer of cast iron barrels (up to 50 mm from the surface) consisted of a pearlite matrix (70… 85 %), ledeburite eutectic cementite (13… 28 %) and plate-shaped graphite (up to 2,5 %). The results of the experiment. Using the matrix of experimental planning, mathematical models of forecasting the selected quality criteria of cast iron depending on the influence of elements of chemical composition on them are obtained. In order to increase the results of the forecast of mechanical properties, a symbiosis of expert and experimental evaluations was used in the work. The application of this approach has made it possible to reduce the cost of conducting mechanical examinations, which is relevant for the considered periodic technology. The values of the rows of the planning matrix, where there were not enough experimental estimates of mechanical properties, were replaced by expert estimates. Rows 6 and 13−16 of the matrix provide expert assessments. The pairwise correlation coefficients of the obtained regression equations vary in the range of 0,71…0,83, which allows them to be used for practical purposes to predict and adjust the mechanical characteristics in the process of manufacturing cast iron rolls. Conclusions. The influence of elements of chemical composition (carbon, silicon, manganese, phosphorus, sulfur, chromium and nickel) of rolled cast iron of SPHN performance on its mechanical properties: σB, σзгин and HB is investigated. It is recommended to apply the obtained equations of estimation of mechanical properties at the enterprise ДЗПВ of Dnipro for their operative forecast.
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