PREDICTING FERRITE-PEARLITE RATIOS IN DUCTILE IRON C. Samuel and S. Viswanathan


The University of Alabama, Tuscaloosa, AL, USA


Copyright © 2010 American Foundry Society Introduction


Gleeble dilatometry was used to characterize the Con- tinuous Cooling Transformation (CCT) behavior of unalloyed ductile iron.1


The CCT diagram provides in-


formation on the start and end of transformation, trans- formation kinetics, and the amount of phases formed during cooling. The objective of this work was to use CCT data in conjunction with a casting simulation code and an analytical model to predict ferrite-pearlite ratios in a ductile iron plate casting. Table 1 lists the composi- tion of the ductile iron used in this investigation. Figure 1 shows the CCT diagram1 composition in Table 1.


obtained for the ductile iron


Ferrite Growth Rate Model


In austenite decomposition models, the growth rate of the ferrite shell, dRα


sion of carbon through the ferrite2 (1) and α C


D is the diffusion coefficient of carbon in ferrite, is carbon concentration in austenite at the ferrite-aus-


tenite boundary, and shell and graphite nodule, respectively. and RGr


in the ferrite at the ferrite-austenite and ferrite-graphite boundaries, and Rα


are the carbon concentration are the radius of the ferrite


/dt is assumed to be controlled by the diffu- , where


Table 1. Composition of Ductile Iron Used in This Investigation


Figure 1. CCT for the ductile iron composition in Table 1. F and P indicate the ferrite and pearlite regions, respectively.


72 International Journal of Metalcasting/Winter 10


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