South Ural State University, Chelyabinsk, Russia:

A. A. Tokarev, Postgraduate Student, Dept. of Pyrometallurgical and Foundry Technologies, e-mail: 151@nppgroup.ru
A. V. Kalyaskin, Postgraduate Student, Dept. of Pyrometallurgical and Foundry Technologies, e-mail: 155@nppgroup.ru

SPE Research and Development Center Ltd., NPP Tekhnologiya Ltd., Chelyabinsk, Russia:
A. V. Barkhatov, Leading Metallurgical Engineer, e-mail: 181@nppgroup.ru

Novotroitsk branch of NUST MISIS, Novotroitsk, Russia:
E. V. Bratkovsky, Cand. Eng., Associate Professor, Dept. of Metallurgical Technologies and Equipment, e-mail: evbratk@yandex.ru

The article presents the results of evaluating the impact of late inoculation on formation the microstructure of thin-wall castings from ductile iron. Existing hypotheses about the mechanism of formation and growth of graphite inclusions in the iron are analyzed. The analysis of the existing theories makes it possible to predict the high efficiency of inoculation treatment as close as possible to melt crystallization. It is noted that idea of late treatment is in introducing of inoculants into the iron melt in the pre-crystallization period, what make it is possible to provide high inoculation impact on the molten metal by creating additional crystallizing nuclei of graphite. Presented type of inoculation treatment makes it possible to obtain the required shape and diameter of nodular graphite, its uniform distribution, increase the area of graphite inclusions, reduce risk of shrinkage defects, and prevent the formation of cementite. In the presented research work the late inoculation was carried out by integrating of solid inserts of the INOCSIL^® series produced by NPP Technology Company in the gating feeding system of the mould on the existing foundry factory. It is given the results of metallographical tests of samples from the castings obtained both by the current inoculation treatment of iron and by late inoculation treatment technology. The analysis of results of metallographical research showed the high efficiency of late inoculation compare with the existing technology of ladle treatment on the foundry. The use of late inoculation treatment technology made it possible to improve the microstructure of metal and increase the elongation by more than two times.

1. Stefanescu D. M., Ruxanda R. Lightweight iron castings-can they replace aluminum castings. Foundryman. 2003. No. 9. pp. 221–224.
2. Borrajo J. M., Martínez R. A., Boeri R. E., Sikora J. A. Shape and count of free graphite particles in thin wall ductile iron castings. ISIJ International. 2002. Vol. 42. No. 3. pp. 257–263.

3. Delprete C., Sesana R. Experimental characterization of a Si – Mo – Cr ductile cast iron. Materials and Design. 2014. Vol. 57. pp. 528–537.
4. Gorny M., Lelito J., Kawalec M., Sikora G. Thermal conductivity of thin walled compacted graphite iron castings. ISIJ International. 2015. Vol. 55. No. 9. pp. 1925–1931.
5. Çelik G. A., Tzini M. T., Polat, Ş. et al. Thermal and microstructural characterization of a novel ductile cast iron modified by aluminum addition. International Journal of Minerals, Metallurgy and Materials. 2020. Vol. 27. pp. 190–199.
6. Belyakov А. I., Zhukov А. А. Production of castings from ductile iron with nodular graphite. Moscow: Mashinostroenie, 2010. 712 p.
7. Shamelkhanova N. A., Uskenbayeva A. M., Volochko A. T., Korolyov S. P. The study of the role of fullerene black additive during the modification of ductile cast iron. Materials Science Forum. 2017. Vol. 891. pp. 235–241.
8. Rahmadi F. D. Effect of strontium addition in graphite morphology and nodularization of hypoeutectic cast iron. Materials Science Forum. 2020. Vol. 1000. pp. 454–459.
9. Korovin V. А., Leushin I. О., Gerotsky V. А. Improvement of the process of modifying high strength iron. Chernye Metally. 2009. No. 7. pp. 1–7.
10. Sluzov P. А., Sedunov V. К., Korovin V. А., Leushin I. О. Progressive technology of modification of high-strength iron. Chernye Metally. 2014. No. 11. pp. 1–18.
11. Lerner Y. S, Riabov M. V. Iron inoculation: an Overview of methods. Modern casting. 1999. No. 6. pp. 37–41.
12. Csenka J. M. Ductile iron trends: reducing costs, improving quality. Modern casting. 2002. No. 5. pp. 27–29.
13. Mikhaylovsky V. М., Korolev S. P., Konstantinovich О. А., Sheshko А. G. Late in-mould graphitizing modification is an effective way to prevent chill in cast iron. Lityo i metallurgiya. 2010. No. 1–2. pp. 95–97.
14. Lia B.-G., Sim K.-H., Kim R.-C. Effect of Sb – Ba – Ce – Si – Fe post inoculants on microstructural and mechanical properties of As – cast pearlitic ductile iron. Steel research international. 2019. Vol. 90. p. 1800530.
15. Bublikov V. B. Increasing the modifying effect on the structure formation of ductile iron. Liteynoe proizvodstvo. 2003. No. 8. pp. 20–22.
16. Mohamed M. M., Shimaa E.-H., Mervat M. I., Adel A. N. Effect of processing parameters on the mechanical properties of heavy section ductile iron. Journal of Metallurgy. 2015. Vol. 9. pp. 1–11.
17. Olsen S. O., Skaland T., Hartung K. Modification of gray and high-strength cast irons. Comparison of nucleation sites and some practical recommendations for modification. Liteyshchik Rossii. 2011. No. 2. pp. 1–6.
18. Skaland T., Grong T. A. A model for graphite formation in ductile iron. Metallurgical Transactions A. 2013. Vol. 24, Iss. 10. pp. 2347–2353.
19. Boldyrev D. А., Popova L. I., Prasolov S. G., Muratkin G. V. Key parameters of modification processes in the production of gray and ductile irons. Liteynoe proizvodstvo. 2021. No. 5. pp. 4–8.
20. Zenkin R. N. Mechanism and varieties of modification of high-strength cast iron. Izvestiya Tulskogo gosudarstvennogo universiteta. Tekhnicheskie nauki. 2014. No. 1. pp. 1–9.
21. Makarenko K. V. Method for refinement of graphite inclusions in high-strength cast iron. Patent RF. No. 2402317. Applied: 10.04.2010. Published: 27.10.2010. Bulletin No. 30.
22. GOST 1497–84. Metals. Methods of tension test. Introduced: 01.01.1986. Moscow: Izdatelstvo standartov, 1984.
23. GOST 3443–87. Cast iron castings with graphite of different form. Methods of structure determination. Introduced: 01.07.1988. Moscow: Izdatelstvo standartov, 1987.