· Fundición ·
R Källbom *, K Hamberg ** and L-E Björkegren *
*Swedish Foundry Association, ** Chalmers University of Technology. Sweden.
Non-spherical graphite morphology is detrimental on the mechanical
properties of ductile iron castings. This includes the branched and
interconnected chunky graphite that occasionally occurs in the thermal
center of castings. In this work the graphite morphology in ferritic ductile
iron that contained chunky graphite was studied. Chunky graphite was
shown to be a progressively degenerated morphology of spherical
graphite. Attempts to investigate the presence and segregation patterns of
elements that might play a role in the still concealed formation and growth
mechanism of chunky graphite were made. No macro segregation was
detected. The possible role of micro segregation of trace elements was
discussed but could not be determined. The graphite nucleation potential
seemed to be low in the chunky graphite areas due to the lack of available
oxygen and/or sulphur.
