Primary Structure and Graphite Nodules in Thin-Walled High-Nickel Ductile Iron Castings
Abstract
:1. Introduction
2. Materials and Methods
3. Results
3.1. Microstructure
3.2. Macrostructure
4. Discussion
5. Conclusions
- The fading effects of grain refinement and inoculation of the primary structure and eutectic are accompanied by changes in the morphology and number of austenite dendrites and eutectic grains.
- The refining process of the primary and eutectic grains is unstable and requires strict metallurgical control.
- Under non-refined conditions, the solidification of SGI in thin-walled castings is dominated by the presence of large (columnar) austenite primary grains.
- Additions of Ti to the melt (Series II) can modify the primary structure in thin-walled castings, resulting in the transformation of the exogenous to endogenous crystallization of the austenite dendrites.
- Additions of Zr and Nb to the melt (Series III and IV) does not modify the primary structure in thin-walled castings as in the case of Ti.
- The EBSD study shows that there are numerous boundaries dividing the grain into many small areas within a single dendritic grain. It is found that the graphite nodules are in contact with the boundaries developed inside the primary grains. This most likely resulted from crystallization of highly branched dendrites that pushed the graphite nodules into the interdendritic regions during their growth. This in turn strongly affects the graphite nodule distribution, and it may also contribute to the occurrence of graphite alignment.
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Series No. | Element, wt.% | |||||||||
---|---|---|---|---|---|---|---|---|---|---|
C | Si | Ni | Mg | Mn | S | Ti | Nb | Zr | Fe | |
I | 2.55 | 2.15 | 23.50 | 0.050 | 0.85 | 0.010 | 0.00 | 0.00 | 0.00 | Balance |
II | 2.43 | 2.28 | 22.84 | 0.037 | 0.81 | 0.008 | 0.13 | 0.00 | 0.00 | Balance |
III | 2.50 | 2.10 | 25.85 | 0.040 | 0.98 | 0.020 | 0.00 | 0.00 | 0.10 | Balance |
IV | 2.51 | 2.05 | 24.66 | 0.042 | 1.00 | 0.003 | 0.00 | 0.11 | 0.00 | Balance |
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Górny, M.; Kawalec, M.; Sikora, G.; Olejnik, E.; Lopez, H. Primary Structure and Graphite Nodules in Thin-Walled High-Nickel Ductile Iron Castings. Metals 2018, 8, 649. https://doi.org/10.3390/met8080649
Górny M, Kawalec M, Sikora G, Olejnik E, Lopez H. Primary Structure and Graphite Nodules in Thin-Walled High-Nickel Ductile Iron Castings. Metals. 2018; 8(8):649. https://doi.org/10.3390/met8080649
Chicago/Turabian StyleGórny, Marcin, Magdalena Kawalec, Gabriela Sikora, Ewa Olejnik, and Hugo Lopez. 2018. "Primary Structure and Graphite Nodules in Thin-Walled High-Nickel Ductile Iron Castings" Metals 8, no. 8: 649. https://doi.org/10.3390/met8080649