Engineering Nucleation Kinetics of Graphite Nodules in Inoculated Cast Iron for Reducing Porosity
- 90 Downloads
Inoculation of cast iron with spherical graphite (SGI) controls nucleation kinetics of graphite nodules and is used for improving casting performance and eliminating solidification micro-porosity. In this study, thermodynamic simulations were used to design inoculants. Thermal and chemical stability of different potential heterogeneous nuclei formed in the melt above the liquidus temperature and in the mushy zone during solidification was predicted. Several inoculation treatments of SGI were performed in laboratory heats. An automated SEM/EDX analysis was applied to examine the graphite nodule size distribution and the family of the non-metallic inclusions in the experimental castings. The data were used to reconstruct a relative graphite nodule nucleation rate in the castings. It was shown that the graphite nodule nucleation kinetics in the castings were significantly different from those predicted by classical nucleation models. In inoculated SGI, the observed bi-modal distribution of graphite nodules was related to a continuous nucleation that occurred towards the end of solidification. The origin of the continuous nucleation and the possibility of engineering graphite nodules nucleation kinetics to control SGI casting soundness by inoculation are discussed.
The author thank Dr. David Robertson for discussion and suggestions, Ph.D. student Obinna Adaba and undergrad students Michael Khayat for help with experimental heat and sample preparation.
- 4.M. Chisamera, I. Riposa, S. Stan, and M. Barstow: AFS Proceedings, 2012, Paper 12-071.Google Scholar
- 6.S. Lekakh, J. Qing, V. Richards, and K. Peaslee: AFS Transactions, 2013, paper13-1321, pp.1–8.Google Scholar
- 9.G. Alonso, D.M. Stefanescu, R. Larranaga, R. Suarez, and E. De la Fuente: AFS Proceedings, 2017, Paper 17-031.Google Scholar
- 14.P. Kainzinger, C. Guster, M. Severing, and A. Wolf: Proceedings 13th Inter. Conference on Fracture, Beijing, China, 2013, pp. 1–9.Google Scholar
- 16.C.A. Bhaskaran and D.J. Wirth: AFS Transactions, 2002, Paper 02-003.Google Scholar
- 17.P. Larranaga, J.M. Gutierres, A. Loizaga, J. Sertucha, and R. Suarez: AFS Transactions, 2008, Paper 08-008.Google Scholar
- 18.D.M. Stefanescu, M. Morgan, S. Boonmee, and W.L. Guesser: AFS Proceedings, 2012, Paper 12-045.Google Scholar
- 22.Factsage software, www.factsage.com.
- 24.SE-FIT Software, Portland State University, www.se-fit.com.
- 27.M. Harris, O. Adaba, S. Lekakh, R. O’Malley, and V. Richards: AISTech Proceedings, 2015, pp. 3315–25.Google Scholar