Study of the Eutectoid Transformation in Grey Cast Irons and its Effect on Mechanical Properties

Abstract:

In this experimental study, six pearlitic grey cast irons with different Cu and Cr content, different section thicknesses and different eutectoid cooling rates have been examined. The eutectoid cooling rate was approximated by casting simulation analysis. The purpose of the experiments was to study the effect of the matrix structure on the overall mechanical properties. An emphasis is put on the pearlite interlamellar spacing because this controls the resulting mechanical properties to a large extent. By keeping the graphite structure constant, the effect of the matrix structure was able to be studied. This was achieved by shake-out at temperatures above the eutectoid transformation range followed by subsequent cooling in air, mould or in a furnace. The pearlite interlamellar spacing ranged from 90 to 330 nm for the matrices studied. Comparing the strength of the fine structured and coarse structured materials, the tensile and yield strength was reduced by almost 50%. Regarding the elastic deformation, a weak increase in the tangent modulus with increasing alloying content was observed. It was also observed that lower cooling rate decreased the tangent modulus. The tangent modulus ranged between 70 and 110 GPa. Analysing the plastic deformation of the materials, in terms of strain hardening exponent, n, and strength coefficient, K, a strong dependence on the pearlite coarseness was observed. It was concluded that the effect of graphite particle length on tensile strength was negligible and the major improvement on the strength was due to refinement of the pearlite.

• Periodical: Key Engineering Materials (Volume 457)
• Pages: 157-162
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.457.157
• Online since: December 2010
• Authors: Torsten Sjögren, Henrik Svensson
• Keywords: Eutectoid Transformation, Pearlite, Pearlite Interlamellar Spacing

References

[1] J. Lacaze, A. Boudot., V. Gerval, D. Oquab. and H. Santos: Met. Mat. Trans. A Vol. 28A (1997), p.2015-(2025).

[2] W.D. Callister: Materials Science and Engineering - An Introduction, 4 ed., (John Wiley & Sons, Inc., New York 1997).

[3] Y. Yang, A. Luovo, and T. Rantala: The effects of alloying and thermal factors on the solidification and mechanical properties of gray iron, (Technical Research Centre of Finland, Espoo 1989).

[4] C.F. Walton (Ed. ): Gray and ductile iron castings handbook, (Gray and Ductile Iron Founders' Society, Cleveland, 1971).

[5] C.E. Bates: AFS Trans. Vol. 94 (1986), pp.889-912.

[6] T. Levin, C.R. Rosenthal, C.R. Loper, and W. Heine: AFS Trans. Vol. 79 (1971), pp.493-514.

[7] F. Mampaey: AFS Trans. Vol 97 (2004), pp.879-897.

[8] European Standard, EN 10 002-1: 2001 E: (European Committee for Standardization, July 2001).

[9] J.H. Hollomon: Trans. AIME Vol. 162 (1945), p.248.

[10] H. Svensson and T. Sjögren: Submitted to Science and Processing of Cast Iron, Egypt, (2010).

[11] D. Holmgren, M. Rinvall and T. Sjögren: Int. Foundry Res. Vol 59 (2007), pp.14-21.

[12] T. Sjögren, P. Vomacka and I.L. Svensson: Int. J Cast Met. Res. Vol 17 (2004), pp.65-71.