Experimental investigation on the effect of copper upon eutectoid transformation of as-cast and austenitized spheroidal graphite cast iron

Copper is known as a pearlite promoter in cast iron and has been used as such for a long time, most often together with low amounts of manganese. Literature data, however, has shown that these two elements act differently on the ferritic and pearlitic transformations. In order to provide more insight in the role of this element on the solid-state transformation of spheroidal graphite (SG) cast iron, this paper investigates the effect of adding copper in small step increments, from 0.11 to 1 wt. % Cu, to SG irons containing about 0.15 wt. % Mn.
The characteristic temperatures for the stable and metastable eutectoid transformations as recorded during cooling after solidification in standard cups and after austenitizing are presented together with microstructure information. It is found that a copper content of about 0.6 wt. % is the upper limit over which only small amounts of ferrite could be obtained except at very low cooling rates. This is tentatively related to the lowering of the temperature for ferrite and the associated decreased kinetics for austenite decomposition in the stable system.