The thermal conductivity in cast irons is known to be highly affected by the graphite morphology. However, the metal matrix is also known to affect the thermal conductivity and it is therefore important to analyze how all microstructure constituents influence the thermal conductivity. Compacted graphite iron (CGI) is a cast iron material that has gained much attention due to its attractive material properties which are intermediate between those of gray and ductile cast iron.

The microstructure analysis and the thermal conductivity measurements were all based on 76 compacted graphite iron materials with metal matrices containing various fractions of ferrite, pearlite and carbides. The thermal conductivity was measured using the laser flash technique at seven temperatures between 35°C and 600°C.

The investigation revealed that the thermal conductivity value was highly affected by the ferrite constituent as well as the addition of carbon and silicon. The nodularity is known to influence the thermal conductivity and that was also confirmed. Carbides usually have a negative influence on the thermal conductivity but in this experiment the low fraction of carbides made it hard to confirm.

A mathematical model, taking into account the above mentioned material parameters, was developed for calculation of the thermal conductivity at various temperatures. The accuracy of the model was validated by comparing calculated thermal conductivity values with measured thermal conductivity values from the literature.