I. MIHALIC POKOPEC et al.: EFFECT OF INOCULATION ON THE FORMATION OF CHUNKY GRAPHITE ...
275–281
EFFECT OF INOCULATION ON THE FORMATION OF CHUNKY
GRAPHITE IN DUCTILE-IRON CASTINGS
VPLIV MODIFIKACIJE NA NASTANEK GRUDASTEGA GRAFITA
V ULITKIH IZ GNETLJIVEGA @ELEZA
Ivana Mihalic Pokopec1, Primo` Mrvar2, Branko Bauer1
1University of Zagreb, Faculty of Mechanical Engineering and Naval Architecture, Ivana Lucica 5, 10002 Zagreb, Croatia
2University of Ljubljana, Faculty of Natural Science and Engineering, Lepi pot 11, 1000 Ljubljana, Slovenia
branko.bauer@fsb.hr
Prejem rokopisa – received: 2015-12-23; sprejem za objavo – accepted for publication: 2016-02-22
doi:10.17222/mit.2015.355
Chunky graphite is one of the most deleterious graphite degenerations in thick-walled ductile-iron castings. This defect
normally appears in the thermal center of a casting and dramatically decreases the mechanical properties. Chunky-graphite
formation is primarily caused by a reduction in the cooling rate and melt composition. An addition of subversive elements (Bi,
Sb, Pb, Sn,...) associated with a small amount of Ce is known to be beneficial to avoid chunky graphite. In this study, the effects
of Bi and Ce additions at different cooling rates on the graphite morphology and mechanical properties of ductile-cast iron
EN-GJS-400-18-LT were investigated. Y-blocks with wall thicknesses of 25 mm and 75 mm and cylindrical blocks with a
diameter of 200 mm and a height of 300 mm were cast. The presence of chunky graphite in the thermal center of the cylindrical
blocks and a decrease in the mechanical properties were revealed, regardless of the presence of Bi.
Keywords: chunky graphite, cooling rate, graphite morphology, thick-walled ductile-iron castings
Grudast grafit je ena od najbolj {kodljivih degeneracij grafita v debelostenskih ulitkih iz gnetljivega `eleza. Ta napaka se
obi~ajno pojavi v toplotnem sredi{~u ulitka in mo~no zmanj{a mehanske lastnosti. Nastanek grudastega grafita je posledica
zmanj{anja hitrosti ohlajanja in sestave taline. Dodatek {kodljivih elementov v sledovih (Bi, Sb, Pb, Sn,...) v povezavi z
majhnim dodatkom Ce je poznan kot ugoden za prepre~itev nastanka grudastega grafita. V tej {tudiji je bil prou~evan vpliv
dodatka Bi in Ce pri razli~nih hitrostih ohlajanja na morfologijo grafita in mehanske lastnosti gnetljivega litega `eleza
EN-GJS-400-18-LT. Uliti so bili Y-kosi z debelino stene 25 mm in 75 mm ter cilindri~ni kosi s premerom 200 mm in visoki
300 mm. Odkriti sta bili prisotnost grudastega grafita v toplotnem sredi{~u cilindri~nih kosov ter zmanj{anje mehanskih
lastnosti, neodvisno od prisotnosti Bi.
Klju~ne besede: grudast grafit, hitrost ohlajanja, morfologija grafita, debelostenski ulitki iz gnetljivega `eleza
1 INTRODUCTION
Chunky graphite, CHG, is one of the most deleterious
graphite degenerations in thick-walled ductile-iron cast-
ings. CHG normally appears in the thermal center of
large castings, and decreases the mechanical properties,
in particular the tensile and fatigue strength and elonga-
tion. Local, cell-type accumulations of compact graphite
forms are characteristic for CHG.1 On the macro-scale, it
is optically visible on cut or machined surfaces as a
black spot. Microscopic observation shows that CHG
consists of large cells of highly branched and intercon-
nected graphite strings. A graphite nodule can usually be
observed at the end of these strings. CHG grows along
the c-axis with a spiral growth mechanism. Although the
mechanism of growth is the same as with spheroidal
graphite, its driving forces are different.2
A great number of studies have been conducted to
describe the CHG formation, but a clear understanding
of its appearance and a safe mastering of the metal
preparation to avoid CHG are not yet available.
The main causes of a CHG formation are a slower
cooling rate and the melt composition.3,4 With slower
cooling rates and increasing section thicknesses, the size
of the spherulites increases and their count per unit of
area decreases. In such zones, CHG frequently develops
as a result of graphite degeneration.1,5 A high carbon
equivalent, approx. >4.1 % of mass fractions, and in-
creasing contents of the elements such as Ni, Si, Cu, Ce,
Ca, Al, P, Mg promote the formation of CHG.1,2,6,7
The CHG formation is also affected by the presence
of low-level elements in the melt. It has been well do-
cumented that the presence of either subversive ele-
ments, such as Pb, Bi, Sb and As, or excessive RE
amounts cause the degeneration of graphite spheriods,
i.e., the CHG formation. However, the co-existence of
subversive elements and RE in appropriate ratios will
result in the retention of spheroidal graphite.8,9
It was found that small amounts of bismuth added to
the melt promote the formation of spheroidal graphite.
However, when its content exceeds the critical value, Bi
is known as a detrimental element, which can cause
degeneration of a good nodular graphite structure. This
effect was attributed to the interaction between Bi and
Mg, which blocks the spheroidization effect of Mg to a
certain extent. This negative effect of Bi is mostly
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UDK 67.017:621.039.532.2:669.11 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 51(2)275(2017)
neutralized with RE additions, especially Ce. The
interaction effect between RE and Bi is achieved with the
formation of various types of intermetallic compounds,
e.g., Bi3Ce4, BiCe3, etc. Intermetallic compounds delete
the effect of subversive elements, and also serve as
nuclei for the graphite formation.5,9,10 According to
reference11, adding 0.002–0.006 % of mass fraction of Bi
with a certain amount of Ce, increases the nodule count
and prevents the CHG formation in thick sections. But,
when the amount of RE exceeds the value required for
neutralization of the subversive elements, CHG may
form.5
In reference10, it was found that a Ce/Bi ratio of
0.8–1.1 was sufficient to achieve a complete neutraliza-
tion of the castings with a relatively long solidification
time (e.g., 3200 s), while Ce/Bi ratios in excess of 1.1
were required for the castings with very short solidifica-
tion times (e.g., 100 s).
P. Ferro et al.5 studied the effects of an inoculant se-
quence and inoculant chemical composition on a casting
heavy-section microstructure. An in-stream inoculation
with an inoculant containing RE and Bi was found to
drastically reduce the formation of CHG. This result was
attributed to the major fading resistance of such an
inoculant compared to the standard ones. They found
that Bi is suppressing or reducing the CHG formation by
reducing the undercooling, which is considered the main
reason for the CHG formation. In this case, Bi behaves in
a similar way like Sb, whose effect was confirmed by
P. Larrañaga et al.12 Bismuth also has the function to
remove the oxygen absorbed at the interface between
graphite and liquid iron, thus reducing the oxygen
absorption and preventing the formation of CHG.5
Although it is known that the correlation between the
ratio of RE/subversive elements and the appearance of
chunky graphite in thick-walled ductile-iron castings
exists, this area is still not fully investigated. More work
is needed to provide a correct balancing of the RE/Bi
ratio that would prevent the formation of chunky gra-
phite.
In the present work, the solidification behavior of
large ductile-iron blocks with or without an addition of
Bi and the same amount of Ce are compared by means of
a microstructure observation and measuring of mecha-
nical properties. Bi and Ce were supplied from different
inoculants.
2 EXPERIMENTAL PART
The test castings used in this study were Y blocks,
25 mm and 75 mm in size and cylindrical blocks with a
diameter of 200 mm and a height of 300 mm, Figure 1,
to enable the investigation of the influence of different
solidification times on the chunky graphite formation.
The thermal modulus, i.e., the relation between the vol-
ume and the cooling surface area (V/A) of a cylinder was
3.75 cm.
Two moulds (M1, M2), with the same test castings,
were produced from sodium silicate bonded sand.
With the aim to limit the number of the parameters,
all the samples were cast using the same melt. The melt
was produced in a 5.6 t capacity medium-frequency
induction furnace. The charge material consisted of grey
pig iron (Sorelmetal®), steel scrap and returns as listed in
Table 1. In order to increase the carbon and silicon con-
tent and the nucleation ability of the melt, SiC (~92 % of
the mass fractions of SiC) was added into the furnace
with the metallic charge. Once the melting was finished,
the chemical composition of the metal was adjusted
according to the carbon and silicon evaluation obtained
with a thermal analysis and spectrometric analysis
carried out on the coupon for the other elements.
Table 1: Charge materials used for melting
Tabela 1: Vlo`ki, uporabljeni za pretaljevanje
total mass
(kg)
pig iron
(kg)
steel scrap
(kg)
returns
(kg)
SiC
(kg)
5600 4026 448 1120 6
72 (w/%) 8 (w/%) 20 (w/%) 0.1 (w/%)
For both moulds, the spheroidising treatment was
carried out in a dedicated ladle with a capacity of 200 kg
by adding ~2 % of the mass fractions of the FeSiMg
alloy (44–48 % of the mass fraction of Si, 3.5–3.8 % of
mass fraction of Mg, 0.9–1.1 % of the mass fraction of
Ca, 0.5–1.2 % of the mass fraction of Al, 0.6–0.8 % of
the mass fractions of RE, and Fe bal.) using the sand-
wich method at ~1480 °C. The FeSiMg alloy was
positioned at the bottom of the casting ladle and then
covered with steel scrap before pouring the iron from the
furnace. 0.7 % of the mass fraction of Ni was also added
to the casting ladle. The source of Ni is 99.9 % of the
mass fractions of the Ni pure metal. In this type of
industrial alloy, it is not possible to sustain the requested
95 % of the mass fraction of the ferritic matrix in the
as-cast state, so it has to be heat treated. Ni is added to
assure the requested tensile strength (above 400 N/mm2)
and to improve the low-temperature ductility after the
heat treatment of this alloy.
Simultaneously with the spheroidising treatment, the
first inoculation (preconditioning) was carried out by
adding 0.2 % of the mass fraction of commercial
inoculant I1. After the treatment, slag was removed from
the melt surface and the melt was poured into the mould.
The holding time was ~3 min. The second inoculation
(in-stream) during the pouring of the mould was per-
formed by adding 0.2 % of the mass fraction of inoculant
I2, containing Ce, at ~1380 °C. The Mg recovery was
about 75 %.
In order to investigate the influence of the Bi-con-
taining inoculant in the second mould, inoculation was
additionally performed by adding commercial inoculant
I3, in the form of a block fixed with the foundry adhesive
to the bottom of the downsprue, as indicated in Figure 1.
I. MIHALIC POKOPEC et al.: EFFECT OF INOCULATION ON THE FORMATION OF CHUNKY GRAPHITE ...
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MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
The chemical composition of the used inoculants is
reported in Table 2. The pouring temperature for both
moulds was 1380 °C and the pouring time was 27 s.
Just before pouring the melt to the mould, the chilled
coupon was analysed with an optical emission spectro-
meter (ARL 3460). The C and Si contents were deter-
mined from the results of the thermal analysis using the
ATAS® system. The chemical compositions are listed in
Table 3.
Each cylindrical block was afterwards sectioned
along the vertical symmetry plane to evaluate the zone
affected by CHG. As illustrated in Figure 2, the zone
affected by CHG was easily located as the darker zone in
the thermal center of the casting. Zones 1 and 2 were
from the CHG area and zone 3 was from the border of
the CHG area. Also, the samples obtained from these
zones were prepared for the metallographic analysis;
samples S1, S2 and S3 as shown in Figure 2. The
metallographic analysis was done with an optical
microscope (Olympus GX 51), equipped with a system
for automatic image processing (Analysis® Materials
Research Lab). All the metallographic parameters such
as nodularity, nodule count, nodule size, area fraction of
graphite, graphite particle size class distribution, graphite
shape classification and ferrite/pearlite ratio were
evaluated according to the Standard EN-ISO 945-1 2010.
Finally, tensile-test bars were machined out from the
core of each cylindrical block as indicated in Figure 2.
Y blocks of 25 mm and 75 mm were also machined
to obtain tensile-test bars. The samples for the
metallographic analysis of the Y blocks were collected
from the heads of the tensile-test bars.
The microstructure in the vicinity of the fracture
surface of the tensile-test bars was investigated under an
optical microscope.
The samples for the metallographic analysis were
prepared with the standard methods of grinding,
polishing and etching in 5 % nital. The microstructures
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Figure 1: Pattern used in the experiment
Slika 1: Vzorec, uporabljen pri preizkusu
Table 2: Chemical compositions of inoculants
Tabela 2: Kemijska sestava modifikatorjev
Inoculant
Chemical composition, (w/%)
Si Mg Ca Al Ce Ba RE Bi S O Fe
I1 64–70 – 1.0–2.0 0.8–1.5 – 2.0–3.0 – – – – bal.
I2 70–76 – 0.75–1.25 0.75–1.25 1.5–2.0 – – – (<1%) (<1%) bal.
I3 71.33 0.79 3.96 1.20
Table 3: Chemical compositions of the melts, (w/%)
Tabela 3: Kemijska sestava talin, (w/%)
C Si Mn P S Mg Ni
M1 3.68 1.65 0.13 0.034 0.01 0.049 0.741
M2 3.67 1.62 0.13 0.032 0.011 0.043 0.761
Figure 2: Central sections of cast cylindrical blocks M1 and M2
(zones 1, 2 and 3)
Slika 2: Sredinski del cilindri~nih kosov M1 in M2 (podro~ja 1, 2 in 3)
were analysed according to the Standard EN ISO
945-1:2008.
Tensile tests were carried out on a tensile-testing
machine (Fritz Heckert ZD-20) at room temperature on
five samples taken from the Y blocks and two samples
taken from the cylindrical blocks. The yield strength,
tensile strength and elongation were determinated
according to the Standard EN 1563.
3 RESULTS
3.1 Macro- and microstructures
Usually CHG is easily detected after sectioning a
casting. The presence of CHG is visible as a localized
darkening of the surface, often revealed without any need
of chemical etching. In Figure 2, the CHG macrostruc-
tures of the cross-sections of the cylindrical blocks are
clearly visible. CHG appeared in the thermal centers due
to the slowest cooling rates, in both blocks, with and
without Bi. The solidification time in the centre was
5140 s, determined from the results of the simulation in
the ProCAST® software. Evident differences in the
proportion of the areas affected by CHG in these two
cast blocks were observed, as shown in Figures 2 and 3.
The diameter of the area affected by CHG at the top
of zone 1 for M1 was 129 mm, and 78 mm for M2,
Figure 3. The area affected by CHG appeared in an
ellipsoid shape in the cross-section along the vertical
symmetry plane, for both blocks. The CHG zone for M1
starts 58 mm from the bottom of the block, and 87 mm
for M2, as can be seen in Figure 2.
An addition of Bi caused a significant reduction of
the CHG-affected zone, at the lower cooling rates in the
centre of a block.
The microscopic observation showed that CHG
occurred locally, having typical cell-type structures,
Figure 4. These cells were relatively large, with the
apparent diameter in the range of 0.5–1.5 mm, with a
sharp transition between the non-affected and the
affected zones, Figures 4 and 5. Inside the CHG area,
zones with spherical graphite were found. Distribution of
CHG is generally not uniform within the affected zone.
The samples with a Bi addition showed a pronounced
eutectic growth in zones 1 and 3, while in the samples
without a Bi addition, it was more difficult to distinguish
specific cells in zones 1 and 2, Figure 4. The nodules
around the CHG area in zones 1 and 2 showed a regular
shape, while in zone 3 more degenerated nodules were
found.
As can be seen from Table 4, after long solidification
times, from 3670 s to 5140 s, a significant graphite
deterioration occurred with the graphite nodularity in the
vicinity of 50 %, and a very low nodule count, below 50
I. MIHALIC POKOPEC et al.: EFFECT OF INOCULATION ON THE FORMATION OF CHUNKY GRAPHITE ...
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Figure 3: Cross-sections of cast blocks at the top of zone 1:
a) M1 without Bi, b) M2 with Bi
Slika 3: Prerez ulitega kosa na vrhu podro~ja 1: a) M1 brez Bi,
b) M2 z Bi
Table 4: Graphite-microstructure data for cylindrical blocks in CHG area according to EN-ISO 945-1
Tabela 4: Podatki o mikrostrukturi grafita v cilindri~nih kosih v podro~ju CHG, skladno z EN-ISO 945-1
Mould
Zone
(Figure
2)
Shape Size
Nodula-
rity
(%)
Nodule
count
(mm–2)
Area
frac. of
graphite
(%)
Size distribution
3
(max.
500 μm)
4
(max.
250 μm)
5
(max.
120 μm)
6
(max.
60 μm)
7
(max.
30 μm)
8
(max.
15 μm)
M1
1 V,III(35 %) 6 47 65 10.7 0 3 107 426 789 1284
2 V,II (35 %) 5 48 38 10.8 2 11 87 330 473 741
3 IV 6 51 47 11.1 1 8 67 392 753 1287
M2
1 V,II (40 %) 6 45 25 10.4 0 5 105 472 729 807
2 6 49 42 8.9 0 12 99 365 463 396
3 V,II (45 %) 6 40 43 10.3 0 10 135 459 788 694
nodules/mm2 (except in zone 1 of M1). The obtained
nodule count was substantially below the recommended
minimum nodule count for heavy-section castings, which
is more than 60 nodules/mm2. The results were slightly
inferior for the samples with the Bi addition. The results
of the nodule count cannot be related with the solidi-
fication time. The lowest nodule count was observed for
cylindrical block M2. With the decrease in the nodule
count for the cylinders, the size of the nodules increased,
Figure 4. Also, the Bi addition reduced the amount of
ferrite, from approx. 90 to 80 %, Table 5.
Table 5: Ferrite/pearlite ratio of cylindrical blocks in CHG area
according to EN-ISO 945-1
Tabela 5: Razmerje ferit/perlit v cilindri~nih kosih v podro~ju CHG,
skladno z EN-ISO 945-1
Mould Zone(Figure 2)
Ferrite area
%
Pearlite area
%
M1
1 91.4 8.6
2 91.8 8.2
3 90.6 9.4
M2
1 85.3 14.7
2 81.4 18.6
3 79.8 20.2
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Figure 5: Fracture surface of a test bar (M1-2)
Slika 5: Prelom preizkusne palice (M1-2)
Figure 4: Microstructures from zones 1, 2, 3 from blocks M1 and M2
Slika 4: Mikrostrukture iz razli~nih podro~ij 1, 2, 3, iz kosov M1 in
M2
Figure 6: Microstructures of Y-blocks, 25 mm: a) M1 without Bi, b)
M2 with Bi
Slika 6: Mikrostrukturi Y-kosa, 25 mm: a) M1 brez Bi, b) M2 z Bi
In the Y blocks of 25 mm and 75 mm, CHG did not
appear, Figure 6. The nodule count of the Y blocks was
in a range from 74 to 405 nodules/mm2. The nodularity
was from 60 % to 73 %. The bismuth addition negatively
affected the microstructure regarding the nodule count,
while the nodularity was positively affected.
3.2 Tensile test
Table 6 gives the tensile-test results for the CHG area
in the cylindrical blocks. The samples containing CHG
were characterized by a significant reduction in the elon-
gation and tensile strength compared to the CHG-free
samples from the Y blocks. The samples from the Y
blocks showed elongation values in the vicinity of 18 %,
while the samples containing CHG achieved elongation
values in a range of 3.5–7.5 %. The tensile strength
values for the CHG area were reduced by 20–25 %,
while the yield strength was reduced by 10 %. Hardness
was hardly affected at all.
Table 6: Mechanical properties in the CHG area
Tabela 6: Mehanske lastnosti v podro~ju CHG
Mould Specimen RmN/mm2
Rp0,2
N/mm2
A5
% HB
M1
1 323 269 4.2 140
2 317 269 3.5 -
M2
1 345 249 7.5 123
2 331 259 5.5 -
The effect of the Bi addition on the mechanical
properties can be seen. In the CHG area, the Bi addition
resulted in better elongation and tensile-strength proper-
ties, while the yield strength and hardness were slightly
reduced, Table 6. In the Y blocks, the Bi addition posi-
tively influenced the elongation properties, while the
strength properties were reduced.
Visual testing of the fracture surfaces of the tensile-
test bars pointed out local dark areas of various sizes.
The macroscopic observation of CHG corresponded very
well with the microscopic observations, Figure 5. On the
fracture surface, eutectic cells of chunky graphite sur-
rounded with normal spheroidal graphite were detected.
4 DISCUSSION
High concentrations of Ce, Ca, Si and Ni are the
usual reasons of the CHG formation. Excessive Ce, in
the absence of subversive elements in heavy-section
ductile iron will almost always cause a CHG formation.
In thin-section castings, the risk of a CHG formation is
minimum due to short solidification times.
Most MgFeSi alloys contain some level of RE,
especially Ce, to promote a high nodule count, improve
nodularity and counteract the effects of anti-nodularising
elements. This is usually good for thin-section parts, but
it is a problem for the sections thicker than 50 mm.
There is a unified opinion found in the literature that an
addition of Bi (up to about 0.003 % of mass fraction) can
prevent the formation of degenerated graphite in thick-
section castings.14 To eliminate the detrimental effect of
RE, the most important task to do is to achieve the right
balance between the presence of RE and the subversive
elements.1,7 Note also that the amount of Bi required to
counteract the detrimental effect of RE (Ce) is casting
section-size dependent.
In this study the Bi addition did not totally suppress
the CHG formation, but the added amount reduced the
area affected with CHG. The amount of Bi was too low
and the presumption is that the right balance between Ce
and Bi would prevent the formation of CHG.
The microstructure analysis of the CHG area in the
cylindrical blocks showed similar results with and
without a Bi addition. The present results indicate that
the addition of Bi to heavy-section ductile-iron castings
exhibited a beneficial effect of a decreasing CHG area as
reported in other works.5,13,14
5 CONCLUSION
Based on the results obtained in this study, the
following main conclusions can be drawn:
• CHG occurred in the thermal center of a heavy-
section ductile-iron casting;
• a Bi addition has a positive influence on the CHG
suppression in thick-section areas, while maintaining
good mechanical properties in thin-section areas;
• the Bi addition also improved the tensile strength and
elongation in the CHG area;
• for the investigated section size, the addition of Bi
was too low to totally suppress the CHG formation.
Acknowledgements
This work was partially supported by the foundry
MIV d.d., Vara`din.
6 REFERENCES
1 H. Löblich, Effect of nucleation conditions on the development of
chunky graphite in heavy ductile iron castings, Giessereiforschung,
58 (2006) 3, 28–41
2 O. Knustad, L. Magnusson Åberg, Chunky graphite, effects and
theories on formation and prevention, 14th Inter. Foundry Confe-
rence, Opatija, Croatia, 2014
3 R. Källbom, K. Hamberg, M. Wessen, L.-E. Björkegren, On the
solidification sequence of ductile iron castings containing chunky
graphite, Materials Science and Engineering A, 413–414 (2005),
346–351, doi:10.1016/j.msea.2005.08.210
4 J. Lacaze, L. Magnusson, J. Sertucha, Review of microstructural
features of chunky graphite in ductile cast irons, Keith Millis Symp.
on Ductile Cast Iron, Nashville, USA, 2013, 360–368
5 P. Ferro, A. Fabrizi, R. Cervo, C. Carollo, Effect of inoculant con-
taining rare earth metals and bismuth on microstructure and
mechanical properties of heavy-section near-eutectic ductile iron
castings, Journal of Materials Processing Technology, 213 (2013),
1601–1608, doi:10.1016/j.jmatprotec.2013.03.012
I. MIHALIC POKOPEC et al.: EFFECT OF INOCULATION ON THE FORMATION OF CHUNKY GRAPHITE ...
280 Materiali in tehnologije / Materials and technology 51 (2017) 2, 275–281
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
6 K. Hartung, O. Knustad, K. Wardenaer, Chunky graphite in ductile
cast iron castings – Theories and examples, Indian Foundry Journal,
55 (2009), 25–29
7 R. Källbom, K. Hamberg, L. E. Björkegren, Chunky Graphite -
Formation and Influence on Mechanical Properties in Ductile Cast
Iron, Proc. of Gjutdesign 2005, Espoo, Finland, 2005
8 S. Mendez, D. Loper, I. Asenjo, P. Larrañaga, J. Lacaze, Improved
analytical method for chemical analysis of cast iron, Application to
castings with chunky graphite, ISIJ International, 51 (2011),
242–249
9 P. C. Liu, C. R. Loper Jr., T. Kimura, H. K. Park, Study of chunky
graphite in heavy section ductile iron, AFS Transactions, 83–51
(1983), 119–126
10 E. N. Pan, C. Y. Chen, Effects of Pb and solidification conditions on
the graphite structure of heavy-section ductile cast iron, AFS
Transactions, 103 (1995), 265–273
11 M. Koch, Chunky Graphite, Effects and theories on formation and
prevention, 2013 Keith Millis Symp. on Ductile Cast Iron, Nashville,
USA, 2013
12 P. Larrañaga, I. Asenjo, J. Sertucha, R. Suarez, I. Ferrer, J. Lacaze,
Effect of Antimony and Cerium on the Formation of Chunky Gra-
phite during Solidification of Heavy-Section Castings, Metallurgical
and Materials Transactions A, 36A (2009), 654–661, doi:10.1007/
s11661-008-9731-y
13 E. N. Pan, C. Y. Chen, Effects of Bi and Sb on graphite structure of
heavy-section ductile cast iron, AFS Transactions, 104 (1996),
845–858
14 J. Riposan, M. Chisamera, S. Stan, Performance of heavy ductile iron
castings for windmills, China Foundry, 7 (2010) 2, 163–170
I. MIHALIC POKOPEC et al.: EFFECT OF INOCULATION ON THE FORMATION OF CHUNKY GRAPHITE ...
Materiali in tehnologije / Materials and technology 51 (2017) 2, 275–281 281
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS