(a)
(b)
(c)
(d)
Figure 5. (a, c) Eutectic cell, N and nodule count, Nn as a function undercooling ∆Tm = 1250o
0.11 J/(cm2 o C s1/2 ).
Equations (8 and 11 or 12) are plotted using the data given in Tables 1 and 2 and they are shown in Fig. 5. Notice from this figure that as CE increases, the cell count also increases for a given degree of undercooling (Fig. 5a), or for a given casting modulus (Fig. 5b). A similar trend is found in ductile iron for the influence of CE on the nodule count (See Figs.5c, d).
In particular, notice from Fig. 5 that there is an excellent agreement between the experimental and the calculated re- sults. In a similar way, the influence of various elements can be predicted, as long as the graphite nucleation coefficients are known. Figure 6 shows the influence of CE on the exper- imentally determined eutectic cell density or nodule count. Notice that as CE increases the cell count in non-inoculated flake graphite iron increases while the cell count in inocu- lated cast iron decreases (Fig. 6a). In addition, it is worth
40 , and (b,
d) as a function casting modulus, M for various carbon equivalent values (CE). Continuous lines are based on Eqns. (8), (11) and (12) and Tables 1 and 2 for Ti
C (2282F) and a =
mentioning that the largest effects in increasing cell count in inoculated cast iron (when compared with the base cast iron) are found in castings of strongly hypoeutectic composition. Figure 6b shows the effect of CE on the nodule count in ductile iron. In general, it is found that as the CE increases, the nodule count also increases.
From the foundry practice it is found that phosphorus29 free sulfur in solution30,31
and increase the cell count in non-in-
oculated cast iron, while the opposite is true for free manga- nese in solution.30
Moreover, the intensity of the influence of
carbon and silicon depends on their relative contents. At low carbon levels, Si additions have a strong effect on increas- ing the cell count (Fig. 7). Yet, this effect is significantly reduced with increasing carbon and it becomes negligible at carbon contents above 3.5 %C. Alternatively, increasing Si levels reduce the carbon influence on the cell count.
International Journal of Metalcasting/Summer 10
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