Peter the Great St.Petersburg Polytechnic University (St. Petersburg, Russia):

A. A. Kazakov, Dr. Eng., Prof., e-mail: kazakov@thixomet.ru
A. I. Zhitenev, Engineer,
M. A. Salynova, Engineer

Modern methods of metallographic evaluation of nonmetallic inclusions (NMIs) in wheel steels has been discussed. It has been shown that large single nonmetallic inclusions cannot be estimated when only one plane of a section is analyzed by the stereological methods used in industry today. For an assessment of such inclusions in standard ASTM E 2283 it is offered to investigate four different planes of the section and to process the obtained results by means of the mathematical tools of extreme values statistics. The results of such processing allow to predict the size of the largest NMI in wheel steel. On an example of the specimens which have been cut out from industrial railway wheels it is shown that the results of the ASTM E 2283 evaluation have predictive features: analysis of 24 specimens planes has not reveal large nonmetallic inclusions exceeding the critical sizes, but the forecast made on these data has allowed to predict the presence of such large NMIs. The results of factory acceptance tests of the same metal on other planes of the section have confi rmed the presence of large inclusions exceeding the critical size. The developed technique has been implemented as a plug-in of the Thixomet Pro Image Analyzer, and its use in the final control of wheel and other high performance steels can serve as a basis for improving the steelmaking technology as well as will allow to calculate reasonably a resource of products manufactured from them.

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