Nonmetallic inclusions in rails made of electro-steel alloyed with chromium

Type, relative concentration and size of most characteristic non-metallic inclusions for the elements of rails (head, web) from electro-steel of E79KhF and E90KhАF grades were determined on the basis of metallographic (with a microscope “OLYMPUS GX-51”) and spectral (using spectrometer “ARL iSpark” method “Spark-DAT”) analyses. It was found that the highest relative concentration of manganese sulfides (MnS) is 30.8 – 43.4 ppm. At the same time, 60 – 100 % of inclusions of this type are of small sizes (less than 4 μm), and it does not allow them to be detected using standard metallographic analysis with 100-fold magnification. The revealed high relative concentration of sulfide inclusions directly correlates with the established positive sulfur liquation in considered rail elements, which is up to 40 %. Despite the high concentration of manganese sulfides, their influence on the quality of rails can be considered not dangerous, taking into account their high ductility during hot deformation and the established prevalence of inclusions of this type with small size (less than 4 μm). Among inclusions of a silicate type, SiO₂ inclusions (3.4 – 14.9 ppm) have a significant concentration. All detected inclusions of this type have a size not exceeding 4 μm. It was found that the concentration of complex inclusions containing alumina (Al₂O₃ – CaO – MgO, Al₂O₃ – CaO – MgO – CaS, Al₂O₃ – CaO, Al₂O₃ – MgO) is insignificant: in total it does not exceed 3.1 ppm and 1.6 ppm for individual types. The concentration of corundum (Al₂O₃) is also insignificant and does not exceed 0.3 ppm. In this case, alumina inclusions of small size (less than 6 μm) prevail. Due to the low contamination (taking into account the relative concentration and size of inclusions) with non-plastic silicate and alumina non-metallic inclusions, their influence on the quality of the rails was not significant. It is confirmed by the absence of defects detected during ultrasonic testing.

1. Zhang H., Liu C., Lin Q., Wang B., Liu X., Fang Q. Formation of plastic inclusions in U71Mnk high-speed heavy-rail steel refined by CaO–SiO2–Al2O3–MgO slag. Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science. 2019, vol. 50, no. 1, pp. 459–470.

2. Kalisz D., Gerasin S., Bobrowski P., Zak P.L., Skowronek T. Computer simulation of microsegregation of sulphur and manganese and formation of MnS inclusions while casting rail steel. Archives of Metallurgy and Materials. 2016, vol. 61, no. 4, pp. 1939–1944.

3. Zhao K.-w., Zeng J.-h., Wang X.-h. Nonmetallic inclusion control of 350 km/h high speed rail steel. Journal of Iron and Steel Research International. 2009, vol. 16, no. 3, pp. 20–26.

4. Garber A.K., Arsenkin A.M., Grigorovich K.V., Shibaev S.S., Kushnarev A.V., Petrenko Yu.P. Analysis of various versions of the deoxidation of rail steel at OAO NTMK. Russian Metallurgy (Metally). 2009, vol. 2009, no. 7, pp. 581–586.

5. Grigorovich K.V., Shibaev S.V. Influence of smelting technology on steel purity by non-metallic inclusions. In: Nemetallicheskie vklyucheniya v rel’sovoi stali: sb. nauch. tr. [Non-metallic inclusions in rail steel: Coll. of sci. works]. Ekaterinburg: izd. UIM, 2005, pp. 74–86. (In Russ.).

6. Dobuzhskaya A.B., Smirnov L.A., Mukhranov N.V., Fomichev M.S., Belokurova E.V. Composition of non-metallic inclusions in rails. Stal’. 2015, no. 5, pp. 82–86. (In Russ.).

7. Yur’ev A.B., Godik L.A., Devyatkin Yu.D., Kozyrev N.A., Tokarev A.V. Reduction of rail steel by calcium carbonate. Steel in Translation. 2008, vol. 38, no. 4, pp. 312–314.

8. Dhua S.K., Ray A., Sen S.K., Prasad M.S., Mishra K.B., Jha S. Influence of nonmetallic inclusion characteristics on the mechanical properties of rail steel. Journal of Materials Engineering and Performance. 2000, vol. 9, no. 6, pp. 700–709.

9. Grigorovich K.V., Arsenkin A.M., Trushnikova A.S. Non-metallic inclusions: assessment and prediction of the operational stability of rails. In: Nemetallicheskie vklyucheniya v rel’sovoi stali: sb. nauch. tr. [Non-metallic inclusions in rail steel: Coll. of sci. works]. Ekaterinburg: izd. UIM, 2005, pp. 102–115. (In Russ.).

10. Dobuzhskaya A.B., Deryabin A.A., Semenkov V.E., Reikhart V.A. The study of the Composition and sources of non-metallic inclusions that cause the formation of contact-fatigue defects in the rails produced by Nizhny Tagil Metallurgical Plant. Chernaya metallurgiya. Byul. in-ta “Chermetinformatsiya”. 2006, no. 10, pp. 33–36. (In Russ.).

11. Kozyrev N.A. Main development trends for low temperature operate reliability rails production. Izvestiya. Ferrous Metallurgy. 2011, vol. 54, no. 4, pp. 31–34. (In Russ.).

12. Yur’ev A.B., Godik L.A., Nugumanov R.F., Kozyrev N.A., Korneva L.V. Production and quality of rails made of E90AF steel. Izvestiya. Ferrous Metallurgy. 2009, vol. 52, no. 8, pp. 34–37. (In Russ.).

13. Godik L.A., Kozyrev N.A., Korneva L.V. Optimizing the oxygen content in rail steel. Steel in Translation. 2009, vol. 39, no. 3, pp. 240–242.

14. Yur’ev A.B., Godik L.A., Kozyrev N.A., Korneva L.V., Shcheglova A.B. 90AΦ steel rail. Steel in Translation. 2008, vol. 38, no. 7, pp. 589–591.

15. Umanskii A.A., Golovatenko A.V., Temlyantsev M.V., Dorofeev V.V. Experimental studies of ductility and deformation resistance of chromium rail steels. Chernye metally. 2019, no. 6, pp. 24–28. (In Russ.).

16. Umanskii A.A., Golovatenko A.V., Simachev A.S., Oskolkova T.N., Dorofeev V.V. Plasticity and deformation resistance of the alloyed rail steels in rolling temperature interval. Izvestiya. Ferrous Metallurgy. 2019, vol. 60, no. 6, pp. 452–460. (In Russ.).

17. Umansky A.A., Kozyrev N.A., Boykov D.V., Dumova L.V. Improvement of the extra-furnace rail steel processing on the “ladlefurnace” unit in order to increase the operational stability of railway rails. IOP Conference. Series: Materials Science and Engineering. 2018, vol. 411, no. 012078.

18. Kozyrev N.A., Protopopov E.V., Umanskii A.A., Boikov D.V. Improved deoxidation technologies and secondary treatment of rail electric steel in order to improve the quality of railway rolling. Izvestiya. Ferrous Metallurgy. 2015, vol. 58, no. 10, pp. 721–727. (In Russ.).

19. Kuss H., Lüngen S., Müller G. Comparison of spark OES methods for analysis of inclusions. Anal. Bioanal. Chem. 2002, vol. 374, no. 11, pp. 1242–1249.

20. Kuss H.M., Mittelstaedt H., Mueller G. Inclusion mapping and estimation of inclusion contents in ferrous materials by fast scanning laser-induced optical emission spectrometry. Anal. At. Spectrom. 2005, vol. 20, no. 5, pp. 730–735.

21. Bokk D.N., Labusov V.A., Zarubin I.A. Determination of nonmetallic inclusions in metal alloys by atomic emission spectrometry with spark excitation. Zavodskaya laboratoriya. 2015, vol. 81, no. 1, pp. 92–97. (In Russ.).