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Efeito da Pre Inoculação com SiC

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and in 3-mm
plates-32%, as expected. This may be explained as a result of excessive residual magnesium served as an iron carbides
stabilizer in ductile iron pre-inoculated with SiC.
AFS Transactions 01-064 (Page 8 of 15)
Microstructure Evaluation. Area of graphite, nodules count, and nodularity were evaluated during the first stage of
microstructural analysis. The second stage of microstructural analysis comprised of evaluating metallic matrix: iron carbides
and ferrite/pearlite ratio.
Graphite morphology. Results of this study are presented in Figures 8 and 9 that illustrate average nodule count and
area of graphite in plates with thickness 1.5; 2 and 3 mm. Data obtained on 1 mm plates has been disregarded due to
significant amounts of iron carbides in their structure.
As can be seen (Figure 8), all 1.5 mm plates had the highest and 3 mm plates had the lowest nodule count regardless
of the type of inoculant and amount of FeSiMg masteralloy used. The nodule count at the edges of the plates was always
found higher than in the center of the plates. However, ductile iron plates, pre-inoculated with SiC and treated with reduced
additions of FeSiMg (1.4% / 3.5 lb) with residual magnesium 0.029%, produced the highest nodule count. The lowest nodule
count was found in ductile iron plates pre-inoculated with FeSi75 and SiC and treated with standard additions of FeSiMg
(1.8% / 4.5 lb) having residual magnesium 0.032% and 0.039% respectively. In ductile iron plates pre-inoculated with SiC
and treated with reduced additions of FeSiMg (1.6% / 4.0 lb) nodule count was intermediate.
Area of graphite in thin wall ductile plates (Figure 9) was always higher in 3 mm plates. The highest area of
graphite was observed in plates pre-inoculated with SiC and treated with reduced additions of FeSiMg (1.6% / 4.0 lb). Thin
wall ductile plates pre-inoculated with FeSi75 or SiC and treated with standard additions of FeSiMg (1.8% / 4.5 lb) had the
lowest area of graphite.
Nodularity in all experimental samples, regardless of the thickness of plates, type of pre-inoculant used, and amount
of FeSiMg-masteralloy added, was more than 95%.
Metallic matrix. Percentage of iron carbides (Figure 10) in 1-mm plates in all series of experiments was much
higher (varied from 57 to 42%) than in 1.5, 2, 3-mm plates. In all 2-mm and 3-mm ductile iron plates, regardless type of pre-
inoculant and amount of FeSiMg-master alloy, inverse chill along the center of fracture was found. In plates pre-inoculated
with SiC and treated with standard FeSiMg additions the percentage of iron carbides was the highest, having the highest
residual Mg. The lowest iron carbides content has been found in those heats pre-inoculated with SiC and treated with 1.6%
and 1.4% FeSiMg-masteralloy additions.
The percentage of ferrite (Figure 11) in metallic matrix was the highest in 3-mm plates and the lowest in 1-mm
plates, regardless which pre-inoculant was used. In plates pre-inoculated with FeSi75 the percentage of ferrite was higher in
comparison with thin wall plates pre-inoculated with SiC and treated with the same amount of FeSiMg-master alloy. All
experimental heats, where iron was pre-inoculated with SiC and treated with reduced FeSiMg-masteralloy additions (1,6% or
1.4%) had almost the same ferrite content as observed in ductile iron plates pre-inoculated with FeSi75 and treated with the
standard FeSiMg additions.
AFS Transactions 01-064 (Page 9 of 15)
0
10
20
30
40
50
60
 Top Middle Bottom
L
e
n
g
th
 o
f 
p
la
te
, 
m
m
Pre-inoculated with FeSi75, standard (1.8%/4.5 lb.) additions of FeSiMg (0.032% residual Mg)
Pre-inoculated with SiC, standard (1.8%/4.5 lb.) additions of FeSiMg (0.039% residual Mg)
Pre-inoculated with SiC, reduced (1.6%/4.0 lb.) additions of FeSiMg (0.033% residual Mg)
Pre-inoculated with SiC, reduced (1.4%/ 3.5 lb.) additions of FeSiMg (0.029% residual Mg)
Figure 6. Average castability of 1-mm ductile iron plates pre-inoculated with FeSi75 and SiC.
AFS Transactions 01-064 (Page 10 of 15)
0
10
20
30
40
50
60
70
80
1.5 2 3
Thickness of plates, mm
C
h
ill
e
d
 a
re
a
, 
%
Pre-inoculated with FeSi75, standard (1.8%/4.5 lb.) additions of FeSiMg (0.032% residual Mg)
Pre-inoculated with SiC, standard (1.8%/4.5 lb.) additions of FeSiMg (0.039% residual Mg)
Pre-inoculated with SiC, reduced (1.6%/4.0 lb.) additions of FeSiMg (0.033% residual Mg)
Pre-inoculated with SiC, reduced (1.4%/ 3.5 lb.) additions of FeSiMg (0.029% residual Mg)
Figure 7. Chill tendency in thin wall ductile iron plates pre-inoculated with FeSi75 and SiC
as a ratio of the chill to the whole fracture area.
AFS Transactions 01-064 (Page 11 of 15)
0
100
200
300
400
500
600
700
800
900
1.5 m m 2 m m 3 m m
Plate thickness, m m
N
o
d
u
l
e
 
c
o
u
n
t
 
p
e
r
 
m
Pre-inoculated with FeSi75, standard (1.8% / 4.5 lb.) additions of FeSiM g (0.032% residual M g)
Pre-inoculated with SiC, standard (1.8% / 4.5 lb.) additions of FeSiM g (0.039% residual M g)
Pre-inoculated with SiC, reduced (1.6% / 4.0 lb.) additions of FeSiM g (0.033% residual M g)
Pre-inoculated with SiC, reduced (1.4% / 3.5 lb.) additions of FeSiM g (0.029% residual M g)
Figure 8. Average nodule count in thin wall ductile iron plates: C – in the center of a plate, E – in the edge of a plate.
 C
 E
 E
 C
 E
 C
 E
 C
AFS Transactions 01-064 (Page 12 of 15)
0
2
4
6
8
10
12
1.5 m m 2 m m 3 m m
Plate thickness, m m
A
r
e
a
 
o
f
 
g
r
a
p
h
i
t
Pre-inoculated with FeSi75, standard (1.8% / 4.5 lb.) additions of FeSiM g (0.032% residual M g)
Pre-inoculated with SiC, standard (1.8% / 4.5 lb.) additions of FeSiM g (0.039% residual M g)
Pre-inoculated with SiC, reduced (1.6% / 4.0 lb.) additions of FeSiM g (0.033% residual M g)
Pre-inoculated with SiC, reduced (1.4% / 3.5 lb.) additions of FeSiM g (0.029% residual M g)
Figure 9. Area of graphite in the center of thin wall ductile iron plates.
AFS Transactions 01-064 (Page 13 of 15)
0
10
20
30
40
50
60
70
Ir
o
n
 c
a
rb
id
e
s,
 %
Edge of plate pre-inoculated with FeSi75, standard (1.8%/4.5 lb.) additions of
FeSiMg (0.032% residual Mg)
Edge of plate pre-inoculated with SiC, standard (1.8%/4.5 lb.) additions of FeSiMg
(0.039% residual Mg)
Edge of plate pre-inoculated with SiC, reduced (1.6%/4.0 lb.) additions of FeSiMg
(0.033% residual Mg)
Edge of plate pre-inoculated with SiC, reduced (1.4%/ 3.5 lb.) additions of FeSiMg
(0.029% residual Mg)
Center of plate pre-inoculated with FeSi75, standard (1.8%/4.5 lb.) additions of
FeSiMg (0.032% residual Mg)
Center of plate pre-inoculated with SiC, standard (1.8%/4.5 lb.) additions of FeSiMg
(0.039% residual Mg)
Center of plate pre-inoculated with SiC, reduced (1.6%/ 4.0 lb.) additions of FeSiMg
(0.033% residual Mg)
Center of plate pre-inoculated with SiC, reduced (1.4%/ 3.5 lb.) additions of FeSiMg
(0.029% residual Mg)
Figure 10. Percentage of iron carbides in microstructure of 1-mm ductile iron plates
pre-inoculated with FeSi75 and SiC.
AFS Transactions 01-064 (Page 14 of 15)
0
5
10
15
20
25
30
1 1.5 2 3
Thickness of plates, mm
F
e
rr
ite
, 
%
Pre-inoculated with FeSi75, standard (1.8%/4.5 lb.) additions of FeSiMg (0.032% residual Mg)
Pre-inoculated with SiC, standard (1.8%/4.5 lb.) additions of FeSiMg (0.039% residual Mg)
Pre-inoculated with SiC, reduced (1.6%/4.0 lb.) additions of FeSiMg (0.033% residual Mg)
Pre-inoculated with SiC, reduced (1.4%/ 3.5 lb.) additions of FeSiMg (0.029% residual Mg)
Figure 11. Percentage of ferrite in microstructure of thin wall ductile iron plates pre-inoculated with FeSi75 and SiC.
AFS Transactions 01-064 (Page 15 of 15)
Based on the results of the study, pre-inoculation with SiC in production of thin wall ductile iron plates provides better
magnesium recovery, less chill tendency, and high castability, when residual magnesium content is at the same level as in
iron pre-inoculated with FeSi75.
SUMMARY AND CONCLUSIONS
The obtained results