Study of the Eutectoid Transformation in the As-Cast Spheroidal Graphite Cast Iron with 'in Situ' Dilatation Analysis – Method for Quality Control

Abstract:

The eutectoid transformation of the spheroidal graphite cast iron (S.G.I.) has been investigated with “in situ” dilatometer, which was made for the investigation of the cast iron alloys. The investigation of the eutectoid transformation has been taking place by evaluation of the “insitu” dilatation curves in connection with metallographic examinations, chemical analyses and thermodynamic calculations of the phase equilibriums. By dilatometric curves it is possible to follow the exact eutectoid transformation of austenite. On a basis of numerous quantitative relations, as the relation between the ferrite and pearlite fractions in the as-cast SGI, which was determined by the analysis of the dilatometric curves and the composition, the ratio between ferrite and pearlite in the microstructure could be determined in a very short time. From the kinetics of austenite transformation and temperature dependence of the ferrite or pearlite growth the following characteristic temperatures of the eutectoid transformation have been established: the ferrite nucleation o Tα , the beginning of the ferrite growth Tα , and pearlite growth Tp , respectively. Kinetic curves, which show the fraction of the single microstructure constituents in the microstructure in dependence of the transformation time for mainly ferrite SGI, are good represented by the physical sigmoidal Boltzmann model.

• Periodical: Materials Science Forum (Volume 508)
• Pages: 287-294
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.508.287
• Online since: March 2006
• Authors: Primož Mrvar, Milan Tribžan, Jožef Medved, Alojz Križman
• Keywords: Eutectoid Transformation, Fe-C-Si-Cu-Mn Alloys, In Situ Dilatation Analyses, Kinetic, Quenching Experiments, Sigmoidal Boltzmann Models, Spheroidal Graphite Cast Iron

References

[1] Stefanescu D. Ductile Iron Handbook, American Foundrymen´s Society, Inc.: 1993: 1 - 19.

[2] Guo X, Stefanescu D. AFS, Inc., 101st World Casting Congress (1997).

[3] Hasse S. Duktiles Gußeisen, Schiele & Sch�n, Berlin, 1996: 211-216.

[4] Lacaze J, Ford S, Wilson C, Dubu E. Scandinavian Journal of Metallurgy 1993: 22: 300-309.

[5] Lacaze J, Wilson C, Bak C. Scandinavian Journal of Metallurgy 1994: 23: 151-163.

[6] Askeland DR, Gupta SS. AFS Transactions, 1975: 83: 313 - 320.

[7] Mrvar P, Trbižan M, Medved J. Scandinavian Journal of Metallurgy: 2002: 31: 393-400.