Siberian State Industrial University (Novokuznetsk, Russia)

V. E. Gromov, Dr. Phys.-Math., Prof., Head of the Dept. of Natural Sciences named after prof. V. M. Finkel, e-mail: gromov@physics.sibsiu.ru
M. A. Porfiryev, Researcher, e-mail: mporf372@gmail.com
R. E. Kryukov, Cand. Eng., Associate Prof., Dept. of Metallurgy of Ferrous Metals, e-mail: rek_nzrmk@mail.ru
V. V. Shlyarov, Postgraduate Student, Dept. of Natural Sciences named after prof. V. M. Finkel, e-mail: shlyarov@mail.ru

The level of microscopic internal long-range stress fields &l on the rolling surface and the working fillet is determined for two categories of rails with a carbon content of 0.74 wt. % and 0.91 wt. %. DT350 for general purpose and DT400IK of increased wear resistance and contact endurance after the passed tonnage of 1,770 mln. t (for DT350) and 187 mln. t DT400IK (1) and 234 mln. t of DT400IK (2). For this purpose, the bending extinction contours were analyzed by means of transmission electron diffraction microscopy, the parameters of which were used in calculating σ_l. The presence of excess extinction contours indicates the bending-torsion of the lattice, which is characterized by the excess density of dislocations. A comparison is made with other methods for measuring internal stress fields at the meso- and macro levels. It is shown that the parameters of the bending extinction contours are the most informative and allow one to control the locality of the measurement σ_l. Sources of internal stress fields in rail steels are noted. An increase in the level of σ_l was revealed in DT400IK rails in comparison with DT350 rails. The growth of the passed tonnage for rails of category DT400IK leads to an increase in σ_l, the values of internal stresses on the fillet surface exceed the corresponding values on the rolling surface. The physical causes of the observed changes are discussed.

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