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(a)


modulus, M for two melt treatments (Table 2). Continuous lines are predicted results based on Eqns. (8) and (12) and Tables 1 and 2 for a = 0.10 J/cm2 o (2354F) in melts 1 (3.69 %C, 2.63 %Si) and 2 (3.72 %C, 2.66 %Si).


Figure 11. (a) Nodule count, Nn as a function undercooling ∆Tm C s1/2


and (b) the casting and Ti = 1290o


C


(b)


(a) ), Ti = 1234o


(b)


Continuous line (Fig. 12a) includes predicted results based on Eqn. (11), and Tables 1 and 2 for a = 0.10 J/(cm2 o 2.08 %Si.


C (2253F) and M = 0.5 cm in a melt with 3.16 %C and


nucleation are dissolved or deactivated due to vari- ous reactions including coagulation. As a result, the cell or nodule count continually decrease with time. The effect of time, t after inoculation in flake graphite iron on the nucleation coefficients is given in the equation found in Table 2. Using Eqn. 11 and the data from Tables 1 and 2 the fading can be calculated (Fig. 12a) and compared with the ex- perimental results. In particular, notice from Fig. 12a that the fading velocity is very high during the first 5 minutes. Similar effects are found in ductile iron (Fig. 12b).


44 •


Figure 12. (a) Eutectic cell, N and (b) nodule count, Nn as a function of time after inoculation. C s1/2


Influence of charge materials, type of furnace, fur- nace atmosphere, holding time, bath superheating and preconditioning


1. The charge materials have distinct carbon carrying capacities. Charge materials which contain carbon in the form of graphite (pig iron and gray cast iron scrap) provide high numbers of graphite nucleation sites and thus ensure high cell and nodule counts. In contrast, charge materials containing carbon in the form of Fe3


C (white cast iron scrap, Table 3) provide relatively low graphite nucleation sites. International Journal of Metalcasting/Summer 10


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