The mechanical and physical properties of compacted graphite iron

The mechanical and physical properties of compacted graphite iron (CGI) have been studied. While it is known that CGI provides at least 70 % higher tensile strength, 35 % higher elastic modulus and 80 % higher fatigue limits than conventional grey cast iron, the objective of this paper was to determine how the properties change with varying nodularity (graphite shape) and pearlite content. Tensile properties, hardness, damping capacity and thermal conductivity were determined over the range 0-90 % nodularity and 25-100 % pearlite. Compressive properties, wear resistance and fatigue behaviour of CGI are also reported upon. Of greatest importance is the influence of patches of flake graphite in predominantly CGI microstructures. As soon as flake patches appear, which can occur with a loss of as little as 0.001 % active magnesium, the mechanical properties of CGI abruptly decrease by 25-40 %. Proper foundry control technology and quality procedures are therefore required to ensure the reliable production of this improved material.