The role of manganese and copper in the eutectoid transformation of spheroidal graphite cast iron
- Ecole Nationale Superieure de Chimie de Toulouse (France). Equipe Metallurgie Physique
- Univ. do Porto (Portugal). Dept. de Engenharia Metalurgia
The decomposition of austenite to ferrite plus graphite or to pearlite in spheroidal graphite (SG) cast iron is known to depend on a number of factors among which are the nodule count, the cooling rate, and the alloying additions (Si, Mn, Cu, etc.). This study was undertaken in order to deepen the understanding of the effect of alloying with Mn and/or Cu on the eutectoid reaction. For this purpose, differential thermal analyses (DTAs) were carried out in which samples were subjected to a short homogenization treatment designed to smooth out the microsegregations originating from the solidification step. The effect of various additions of copper and manganese and of the cooling rate on the temperature of the onset of the stable and metastable eutectoid reactions was investigated. The experimental results can be explained if the appropriate reference temperature is used. The cooling rate affects the temperature of the onset of the ferrite plus graphite growth in the same way as for the eutectic reaction, with a measured undercooling that can be extrapolated to a zero value when the cooling rate is zero. The growth undercooling of pearlite had values that were in agreement with similar data obtained on silicon steels. The detrimental effect of Mn on the growth kinetics of ferrite during the decomposition of austenite in the stable system is explained in terms of the driving force for diffusion of carbon through the ferrite ring around the graphite nodules. Finally, it is found that copper can have a pearlite promoter role only when combined with a low addition of manganese.
- OSTI ID:
- 543476
- Journal Information:
- Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Vol. 28, Issue 10; Other Information: PBD: Oct 1997
- Country of Publication:
- United States
- Language:
- English
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