The influence of copper on microstructure and mechanical properties of compacted graphite iron

The influence of copper content (0.26 to 1.31 wt-%) on microstructure formation and mechanical properties of compacted graphite iron (CGI) has been evaluated through standard metallographic analysis, colour etching techniques and tensile testing of machined test bars. The properties investigated are yield strength, tensile strength and elongation. The castings were made in an industrial environment from a combination of CGI returns, pig iron, cast iron- and steel scrap. A total of four heats were cast in specially designed sampling cups (3 different cooling rates), chill wedges as well as tensile test bars machined from sand moulded cylinders (20, 45 and 85 mm in diameter). The results clearly illustrate the combined effect of copper and cooling rate on nodularity, chilling tendency as well as pearlite content. A discussion concerning the effect of graphite morphology on the ferrite growth is also included.