Effect of inoculation, cooling rate and charge composition on gray iron microstructure

  • 1 University of Zagreb, Faculty of Metallurgy, Sisak, Croatia


This paper analyses the effect of different charge compositions for melt production, cooling rate (i.e. casting wall thickness) and inoculation on the gray iron microstructure. In this study, three gray iron melts were produced that had almost the same chemical composition. The proportions of steel scrap (SS), pig iron (PI), gray iron return (GIR) and SiC in charge were as follows: melt 1 (10 % SS, 39.4 % PI, 49.2 % GIR, 0.6 % SiC), melt 2 (38.8 % SS, 9.9 % PI, 47.9 % GIR, 1.6 % SiC) and melt 3 (0 % SS, 0 % PI, 99.2 % GIR, 0.06 % SiC). One uninoculated and one inoculated stepped test casting with walls thicknesses of 5, 10, 20, 45 and 65 mm was casted from each melt. The inoculant was added in the melt stream during pouring in the mould in an amount of 0.23 wt.%. The type, size and distribution of graphite flakes in the analysed walls did not significantly depend on the charge compositions. The structure of the metal matrix, carbides precipitation and type, size and distribution of graphite flakes were largely dependent on the wall thickness. As the wall thickness increased, the cooling rate decreased and the type of graphite flakes changed, from D and E through B to A type. Carbide formation has occurred in the edge region of the 5 mm thick walls. With the decrease of the cooling rate and increasing the proportion of D and E type graphite flakes, the ferrite content in the metal matrix increased. The carbide content in the edge region of the 5 mm thick walls was significantly reduced by inoculation. Inoculation increased the proportion of A type graphite flakes in the middle of 5 mm thick wall and in walls with a thickness from 10 to 65 mm. In addition, inoculation significantly reduced the proportion of B, D and E type graphite flakes or were completely eliminated. Wall thickness has affected this effect.



  1. T. Fugal, G.M. Goodrich, V. Patterson, M. Mroczek, J. Ward, G. Goodrich, C. Callison, C.A. Bhaskaran, L. Helm, A. Shturmakov, J. Way, Introduction to Gray Cast Iron Processing, American Foundry Society, Des Plaines, Illinois, SAD 2000.
  2. D.B. Craig, M.J. Hornung, T.K. McCluhan, Gray Iron, chapter in ASM Handbook, Volume 15, Casting, ASM International, Metals Park Ohio, 1998., 1365 - 1404.
  3. J.R. Brown, Foseco Ferrous Foundryman’s Handbook, Butterworth-Heinemann, Oxford, 2000.
  4. E. Weiss, G. Fedorko, P. Futáš, A. Pribulová, I. Vasková, Dependence of Quality Properties for Grey Iron on Used Raw Materials, Metalurgija 48(2009) 1, 43 - 45.
  5. …, The Use of Foundry Pig Iron in Grey Iron Castings, https://www.metallics.org/assets/files/Public-Area/Fact- Sheets/_7_Foundry_Pig_Iron_Fact_Sheet_rev3.pdf (Accessed: June 19, 2019)
  6. D. Bartocha, K. Janerka, J. Suchoń, Charge Materials and Technology of Melt and Structure of Gray Cast Iron, Journal of Materials Processing Technology 162–163 (2005), 465– 470.
  7. K.B. Rundman, Metal Casting, Reference Book for MY4130, Michigan Tech. University, 1986.
  8. J. Dawson, S. Maitra, Recent Research On the Inoculation of Cast Iron. British Foundryman 60(1967) 4, 117 - 127.
  9. M. Jacobs, T. Law, D. Melford, M. Stowell, Basic Processes Controlling the Nucleation of Graphite Nodules in Chill Cast Iron, Metals Technology 1(1974) 1, 490 -500.
  10. T. Elbel, J. Senberger, A. Zadera, J. Hampl, Behaviour of Oxygen in Cast Irons, Archives of Materials Science and Engineering 33(2008) 2, 111 - 116.
  11. J. Campbell, A Hypothesis for Cast Iron Microstructures, Metallurgical and Materials Transactions B 40(2009) 6, 786 - 801.
  12. M. Chisamera, I. Riposan, S. Stan, C. Militaru, I. Anton, M. Barstow, Inoculated Slightly Hypereutectic Grey Cast Irons, Journal of Materials Engineering and Performance 21(2012) 3, 331 – 338.
  13. I. Riposan, M. Chisamera, S. Stan, T. Skaland, A New Approach to Graphite Nucleation Mechanism in Gray Irons, Proceedings of the AFS Cast Iron Inoculation Conference, September, 29-30, 2005, Schaumburg, Illinois, 31 – 41.
  14. W. Weis, The Metallurgy of Cast Iron, Proceedings of the Second International Symposium on the Metallurgy of Cast Iron, The Metallurgy of Cast Iron, eds. B. Lux, I. Minkoff, F. Mollard, Georgi Publishing, Geneva, Switzerland, 29 – 31 May 1974., 69 – 79.
  15. D.M. Stefanescu, Science and Engineering of Casting Solidification, Kluwer Academic/Plenum Publishers, New York, 2002.
  16. … Overview of Alloying Elements and their Effects in Grey Iron, Tehnical Information 12A, Elkem ASA, Oslo, Norway, 2011. http://foundrygate.com/upload/artigos/7ZmcrE9zgVGm6iKw HxeNNjbEdqt1.pdf. (Accessed: June 19, 2019).
  17. M.I. Onsoinen, T. Skaland: Preconditioning of Gray Iron Melts Using Ferrosilicon or Silicon Carbide, AFS Transactions 109(2001), Paper 01-093.
  18. …, Preseed Preconditioner, Elkem, Foundry Products, Oslo, 2012. https://www.yumpu.com/en/document/view/32276377/presee dtm-preconditioner-elkem (Accessed: June 19, 2019).
  19. Z. Glavaš, F. Unkić, J. Martišković, Predobrada i metalurška kvaliteta talina sivih željeznih ljevova, Ljevarstvo 51(2009) 2, 47 - 56.
  20. I. Riposan,M. Chisamera, S. Stan, Enhanced Quality in Electric Melt Grey Cast Irons, ISIJ International 53(2013) 10, 1683 – 1695.

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