“Metallurgical technologies” Chair, St. Petersburg State Polytechnic University (St. Petersburg, Russia):

Kazakov A. A., Dr. Eng., Prof., Head of the Chair, e-mail: kazakov@thixomet.ru
Lyubochko D. A., Engineer
Ryaboshuk S. V., Assistant
Chigintsev L. S., Engineer

The capability of automated X-ray microanalysis for the evaluation and development of nonmetallic inclusion identification and rating of steel are demonstrated on HSLA steel as the example. A large number of nonmetallic inclusions were chemically analyzed and compared with the overall inclusion quantity determined by light optical microscopy image analysis methods within an area of 25 mm². This combination of techniques gave reliable information not only about the size and volume fraction, but also about the composition of each of the inclusions that were analyzed. All of these inclusions were divided into categories according to basic composition. Each of these categories can be associated with the corresponding formation nature and particularities of nonmetallic inclusion evolution during the steelmaking processing. Thus, an inverse problem of thermodynamic modeling in terms of local equilibrium has been solved. The concentrations of reagents in steel melt (where inclusions have been formed) were determined by an average composition of the inclusions inside each group. The novelty of this approach is that the databases of inclusion compositions obtained, together with number of analyzed particles and thermodynamic modeling methods, allows the steelmaker to determine the specific nature of inclusions created taking into account the thermal, hydrodynamic and physical-chemical processes occurring in the liquid and the solidifying steel. The data obtained about the volume fraction, size and composition of inclusions provides an adequate description of the processes of deoxidation and subsequent modification during the steelmaking processing that can be used for reasonable improvement of this technology.

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