Prediction of Ferrite-Pearlite Ratios The diffusion coefficient of carbon in ferrite,
form of the first-order exponential3 (2)
Therefore, the % ferrite vs. cooling rate (ε)data for an unal- loyed ductile iron was also fit to a first order exponential decay of the form:
(3) As shown in Figure 2, the first order exponential fit is excellent.
Predicting Ferrite-Pearlite Ratios in Castings , is in the
ProCAST, a finite element-based casting simulation pack- age was used to determine the cooling rates at the different sections of the casting (end, middle, and near riser). The cooling rate used to calculate the % ferrite was assumed to be the average cooling rate in that section between 773o (1423o
C F) and 550o C (1022o C/min (360o tion temperature for a cooling rate of 2o
F ), the ferrite-start transforma- C/min (3.6o
and pearlite-end transformation temperature for a cooling rate of 200o
F/min) F/min). The first-order exponen-
tial fit and the cooling rates calculated from the simulation were used to predict the ferrite contents in the three sec- tions of the castings.
Table 2. Comparison of Percent Ferrite from Metallographic Analysis and Predicted from Exponential Fit
Figure 2. Percent ferrite vs. cooling rate plot showing excellent first order exponential fit.
International Journal of Metalcasting/Winter 10
73
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85