Obrabotka Metallov 2014 No. 1

ОБРАБОТКА МЕТАЛЛОВ № 1 (62) 2014 45 МАТЕРИАЛОВЕДЕНИЕ Abstract The relationship between the size of structural elements, the grain direction and the level of the strength and reliability of hardened low-carbon sheet steel 12Х2Г2НМФТ is investigated. Methods of metallographic analysis, transmission and scanning microscopy, a uniaxial tension tests and three-point bending impact were used. It is established that there is a deviation from the Hall-Petch relationship with the achievement of the nanocrystalline state of lath martensite in the steel under consideration. The dependence of fracture toughness (KCT) and the fracture structure on the structure dispersion of the steel under consideration is largely determined by the by the fiber direction with respect to the applied load. The grain direction relative to the applied load largely determines the dependence of the impact toughness (KCT) and the structure of the fracture on the dispersion of the structure of investigated steel. The impact toughness (KCT) began to increase with the dispersed austenite grain less than 40 microns on samples cut lengthwise to the rolling direction, at the same time the destruction took across the fiber in the tests. And the micromechanism of destruction varies from quasi-chip to tough in the preparation of nanostructured state with the size of the lath of 96 nm. In transverse samples dispersion of structure has almost no effect on the level of impact toughness (KCT), but the fibrous structure significantly influence the level of impact toughness (KCT). Keywords: impact toughness, low-carbon martensite steel, lath martensite, structure of dispersion, micromechanism of destruction . References 1. Grange R.A. Strengthening steel by austenite grain refinement. ASM Transactions Quarterly. 1966, Vol. 59, pp. 26–47. 2. Porter L.F., Dabkowski D.S. Grain-size control by thermal cycling . In: Burke J.J., Weiss V. (eds) Ultra-fine Grain Metals . Syracuse University Press, New York, 1970 (Russ. ed.: Porter L.F., Dabkowski D.S. Regulirovanie razmera zerna putem termociklirovanija . Sverhmelkoe zerno v metallah . Moscow, Metallurgija, 1973. pp. 135– 164.) 3. Morito S., Yoshida H., Makic T., Huang X. Effect of block size on the strength of lath martensite in low carbon steels. Materials Science and Engineering A. 2006, Vol. 438–440, pp. 237–240. 4. Georgiev M.N. Vjazkost’malouglerodistyh stalej [The viscosity of low-carbon steels]. Moscow, Metallurgija, 1973. 234 p. 5. Simonov Yu.N. Uslovija poluchenija struktury paketnogo martensita pri zamedlennom ohlazhdenii nizkouglerodistogo austenita [Conditions of the formation of lath martensite from low-carbon austenite upon slow cooling]. Fizika metallov i metallovedenie – The Physics of Metals and Metallography , 2004, Vol. 97, no. 5, pp. 77–81. 6. Klejner L.M., Tolchina I.V., Arhipov V.M., Jefron L.I., Tishaev S.I., Usikov M.P., Nekrasov V.K., Pilikina L.D. Stal’ [A steel]. Patent USSR, no. 1790622, 1993. 7. Bykova P.O., Zajac L.C., Panov D.O. Zavodskaja laboratorija. Diagnostika materialov , 2008, no. 6, pp. 42–45. 8. IvanovYu. F. Vlijanie tehnologicheskih parametrov na razmernuju odnorodnost’paketnogo martensita [Influence of technological parameters on size homogeneity of packet martensite]. Fizika metallov i metallovedenie – The Physics of Metals and Metallography , 1992, no. 9, pp. 57–63. 9. Koneva N.A., Kozlov Je.V., Popova N.A. Fundamental’nye problemy sovremennogo materialovedenija , 2010, Vol. 7, no. 1, pp. 64-70. 10. Orlova E.N., Panov D.O. Nauchnoe obozrenie , 2012, no. 5, pp. 51–55.