ESTUDO SOBRE A NUCLEAÇÃO E CRESCIMENTO DE NÓDULOS DE GRAFITA EM FERROS FUNDIDOS NODULARES
STUDY ON NUCLEATION AND GROWTH OF NODULAR GRAPHITE PARTICLES IN DUCTILE CAST IRON
André de Albuquerque Vicente, Victor Bridi Telles, Amilton Barbosa Botelho Junior, Susana Marraccini Giampietri Lebrão, Denise Crocce Romano Espinosa, Jorge Alberto Soares Tenório
Foram estudadas três corridas comerciais de ferro fundido nodular. Para produção das corridas, partiu-se do mesmo metal base e utilizou-se a mesma liga nodularizante. Cada uma das corridas foi feita com inoculantes diferentes. Os percentuais em peso de inoculante e liga nodularizante foram, respectivamente, 1,0% e 1,3%. Estudou-se a nucleação e o crescimento dos nódulos de grafita. Várias técnicas complementares de análise microestrutural foram utilizadas, tais como microscopia óptica, microscopia eletrônica de varredura (MEV) e espectroscopia de raios-X por dispersão de energia (EDS). Observou-se a sequência de crescimento dos nódulos de grafita, evidenciando-se a formação de silicatos complexos ricos em alumínio, cálcio e bário ao redor dos núcleos, gerando uma interface favorável à solidificação heterogênea de grafita a partir destas partículas de tamanho superior ao raio crítico.
Three commercial ductile cast iron heats were studied. The same base metal and nodularization alloy were used. Each of the heats was made with different inoculants. The weight percentage of inoculant and nodularization alloy were respectively 1.0% and 1.3%. The nucleation and growth of the nodular graphite particles were studied. Several complementary techniques for microstructural analysis were used, such as optical microscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). It was observed the growth sequence of spheroid nodular graphite particles, demonstrating the formation of complex silicates rich in aluminium, calcium and barium around the core, creating a supportive interface to the heterogeneous solidification of graphite from these particles larger than the critical radius
1 Karsay SI. Ductile iron – production and practice. USA: American Foundry Society; 1985.
2 Edneral FP. Electrometallurgical of steel and ferro alloys. Vol. 2. Moscow: Mir Publishers; 1979.
3 Olsen SO, Skaland T, Hartung C. Inoculation of grey and ductile iron: a comparison of nucleation sites and some practical advises. In Proceedings of the World Foundry Congress; 2004; Turkey. Istanbul, Foundrymen’s Association of Turkey; 2004.
4 Olsen SO, Hartung C. Recovery of magnesium in a ductile iron process. Kristiansand: Elkem; 2001. Elkem Technical Information Sheets, Elkem Foundry Products.
5 Skaland T. A new method for chill and shrinkage control in ladle treated ductile iron. In: Proceedings of the World Foundry Congress; 2004; Turkey. Hilton Head: American Foundry Society; 2004.
6 Skaland T. A model for the graphite formation in ductile cast iron [thesis]. Norway: The University of Trondheim; 1992.
7 Skaland T. A New Method for Chill and Shrinkage Control in Ladle Treated Ductile Iron. In: Keith Millis Symposium on Ductile Iron, Las Vegas, EUA. 2003.
8 Skaland T. Nucleation mechanisms in ductile iron. In: Proceeding of the AFS Cast Iron Inoculation Conference; Schaumburg, Illinois; 2005 September. Schaumburg: American Foundry Society; 2005.
9 Skaland T. Ductile iron production - a comparison of alternative treatment methods. Kristiansand: Elkem; 1999. Metal Casting and Surface Finishing, Elkem Technical Information Sheets, Elkem Foundry Products.
10 Skaland T. ductile iron shrinkage control through graphite nucleation and growth. elkem technical information. sheets. Kristiansand: Elkem Foundry Products; 2002.
11 Skaland T. A new approach to ductile iron inoculation. EUA: AFS Transaction; 2001.
12 Skaland T. A new method for chill and shrinkage control in ladle treated ductile iron. Kristiansand: Elkem; 1999. Elkem Technical Information Sheets, Elkem Foundry Products.
13 Skaland T. Developments in cast iron metallurgical treatments. Kristiansand: Elkem; 2001. Elkem Technical Information Sheets, Elkem Foundry Products.
14 Onsoien MI, Grong O, Gurdersen O, Skaland T. A process model for microstructure evolution in ductile cast iron - Part I - The Model. Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science. 1999;30(4):1053-1068.
15 Onsoien MI, Grong O, Gurdersen O, Skaland T. A process model for microstructure evolution in ductile cast iron - Part II - Applications of the Model - The Model. Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science. 1999;30(4):1069-1079.
16 Onsoien MI, Grong O, Skaland T, Jorgensen K. Mechanisms of graphite formation in ductile cast iron containing rare earth metals, materials science and technology. Journal Materials Science and Technology. 1999;15(3):253-259.
17 Onsoien MI, Grong O, Rorvik G, Nordmark A, Skaland T. Design and development of treatment alloys for ductile cast iron. International Journal Cast Metals Research. 1997;10(1):17-26.
18 Skjegstad NT, Skaland T. Inoculation of grey and ductile iron. In: Proceedings of the Bombay Foundry Congress; 1996 May 24-25; Indian; Bombay: The Institute of Indian Foundrymen; 1996.
19 Skjegstad NT, Skaland T. Inoculation of grey and ductile iron - a comparison of nucleation sites and some practical advises. In: Proceedings of the Bombay Foundry Congress; 1996 May 24-25; Indian. Bombay: The Institute of Indian Foundrymen, 1996.
20 Ecob CM. Review of common metallurgical defects in ductile cast iron. Kristiansand: Elkem; 1998. Elkem Technical Information Sheets, Elkem Foundry Products.
21 Gerghu R, Åberg LM, Lacaze J. A possible mechanism for the formation of exploded graphite in nodular cast irons. Materials Science Forum, 2014;790-791:435-440.
22 Lacaze J, Sertucha J, Åberg LM. Microstructure of as-cast ferritic-pearlitic nodular cast irons. ISIJ International, 2016;56(9):1606-1615.
23 Zhu M, Zhang L, Zhao H, Stefanescubc DM. Modeling of microstructural evolution during divorced eutectic solidification of spheroidal graphite irons. Acta Materialia. 2015;84(1):413-425.
24 Stefanescu DM, Alonso G, Larrañaga P, De la Fuente E, Suarez R. On the crystallization of graphite from liquid ironcarbon-silicon melts. Acta Materialia. 2016;107:102-126.
25 Stefanescu DM, Alonso G, Larrañaga P, Suarez R. On the stable eutectic solidification of iron–carbon–silicon alloys. Acta Materialia. 2016;103:103-114.
26 Riposan I, Chisamera M, Uta V, Stan S, Naro R, Williams D. The importance of rare earth contribution from nodulizing alloys and their subsequent effect on the inoculation of ductile iron. International Journal of Metalcasting. 2014;8(2):65-80.
27 Colpaert H. Metalografia dos produtos siderúrgicos comuns. 4. ed. São Paulo: Editora Blucher; 2008.
28 TurnBull D, Vonnegut R. Nucleation Catalysis. Industrial & Engineering Chemistry. 1952;44(10):2265- 1952.
29 American Society for Testing And Materials. ASTM A536: Standards specific for ductile iron casting. West Conshohocken: ASTM; 1997.
30 Minkoff I. The physical metallurgy of cast iron. New York: John Wiley & Sons; 1983.
31 American Society for Testing and Materials. ASTM A247A: Adjunct to A247A Iron Casting Graphite Microstructure Rating Wall Chart. West Conshohocken: ASTM; 2010.
32 Xue W, Li Y. Pretreatments of gray cast iron with different inoculants. Journal of Alloys and Compounds. 2016;689:408-415.