InoculationTheories & Reality
Dr. Torbjörn Skaland
Director of TechnologyElkem Foundry DivisionElkem Foundry Division
Kristiansand, Norway
Elkem Foundry SeminarElkem Foundry SeminarWeinheimWeinheim GermanyGermany, 10 , 10 –– 11 September 201211 September 2012
Effects of InoculationEffects of Inoculation
Un inoculated ductile iron Inoculated ductile iron
100X 100X
Un-inoculated ductile iron Inoculated ductile iron
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Inoculation IngredientsgPrimary: Silicon
Calcium Barium StrontiumCalcium, Barium, Strontium
Beneficial: Aluminum, Zirconium, ManganeseBeneficial: Aluminum, Zirconium, ManganeseCerium, Bismuth
Pure inoculantCa = 0
0.8%Ca-inoculantCa = 10 ppmCa 0 Ca 10 ppm
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Heterogeneous Nucleationg
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Mi ti l i D til IMicro-particles in Ductile Iron
100X 1,000X 70,000X
Micro-particles: 100,000 pr mm3
N d l 1 000 3Nodules: 1,000 pr mm3
100 pr mm2
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The Silicate Nucleation ModelThe Silicate Nucleation Model
X = Ca, Sr, or Ba
Hexagonal Ca-, Ba-, and Sr silicatessettle on surface of heterogeneitiesformed during magnesium treatmentg g
Critical role of group IIA elements andSi, S and O described by this model
Important difference between Mg andother elements Ca, Ba, and Sr
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The CaO-Al O -SiO SystemThe CaO-Al2O3-SiO2 System
DeoxidationCaOSiO2
SrOSiO2
BaOSiO2
CaOAl2O32SiO2
SrOAl2O32SiO2
BaOAl2O32SiO2BaO Al2O3 2SiO2
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The Role of CalciumThe Role of Calcium
Ferrosilicon 75%0.5 – 2% Ca (Ba, Sr, etc.)
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Planar Lattice DisregistryPlanar Lattice Disregistry
Inclusion
PhaseOrientation
RelationshipLattice
Disregistry
CaOSiO2 (001)I (001)G 7.5 %
SrOSiO2 (001)I (001)G 3.5 %
BaOSiO2 (001)I (001)G 1.5 %
CaOAl2O32SiO2 (001)I (001)G 3.7 %
SrOAl2O32SiO2 (001)I (001)G 6.2 %
BaO Al O 2SiO (001) (001) 7 1 %BaOAl2O32SiO2 (001)I (001)G 7.1 %
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Nitrides in Ductile IronNitrides in Ductile Iron
Nitride particle TEM EDX Mg, Al, Si, N Crystal [001]-axis
Mg-Al-Si Nitride (AlN-structure)
Mg2.5AlSi2.5N6
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Inoculation of Gray IronInoculation of Gray Iron
100X
Inoculated gray iron
100X
Un-inoculated gray iron
100X
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MnS Particles in Gray IronMnS Particles in Gray Iron
0.04 0.04 –– 0.12 %S0.12 %S
%Mn = %S x 1.7 + 0.3
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Graphite Nucleation in Gray Iron
XO-Al2O3
M S
A graphite A graphiteGraphite
MnS
g p g p
D graphiteD graphite D graphiteD graphite
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Oxides in Gray IronAl Zr
A graphite A graphite
Ti
A graphite A graphite
D graphiteElkem Foundry SeminarElkem Foundry Seminar
WeinheimWeinheim GermanyGermany, 10 , 10 –– 11 September 201211 September 2012
Aluminum in Gray IronAluminum in Gray Iron
<0.001% Al 0.006% Al
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Inoculation MethodsInoculation MethodsTransfer Ladle P i L dl In-streamTransfer Ladle Pouring Ladle In stream
11 3322
4444In-Mold
Position 1 2 3 4Position 1 2 3 4
Addition rate [wt%] 0.3 – 1.0 0.3 – 0.5 0.05 – 0.2 0.04 – 0.2Sizing [mm] 0.5 – 15 0.5 – 10 0.2 – 1 0.5 – 5
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Inoculant Addition RateInoculant Addition Rate
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Fading of Inoculationg
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Inoculation Selection• Casting thickness & size• Nitrogen contentNitrogen content• Shrinkage tendency• Fade time • Required properties• Required properties• Temperature• Inoculation method
M lti
Gray IronGray Iron Ductile IronDuctile Iron
• Melting process
• Base Sulphur• CEV in iron
Gray IronGray Iron• Treatment process• Nodularizer
Ductile IronDuctile Iron
• CEV in iron• Nitrogen
• Nodularizer• Base composition
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Inoculation – Primary Elements
BaBa SrSrCaCa BaBa SrSr
Graphite promotingMost commercial High potency in GI
CaCa
Graphite promoting
Slag conditioning
Fade resistance
Most commercial inoculants
Low potent vs Ba, Sr
High potency in GI
Powerful chill reducer
Effective in small tCost effective vs Ca
Especially effective in DI and low-S GI
Effect fade fast
Critical element in most inoculants
amounts
Low cell count
Reduce shrinkageDI and low S GI Reduce shrinkage
Powerful in low temperature DI
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Inoculation – Beneficial Elements
AlAl ZrZrCeCe MnMnAlAl
Normally
ZrZr
R d hill i
CeCe MnMn
Neutralize Reduce alloyNormally present in FeSi
H-pinholes
Reduce chill in thin sections
High nodule count
Neutralize subversive elements
High nodule
Reduce alloy melting point
Improve dissolution rateHigh level in
mold alloys
Enhance A
Neutralize N
Use with Ca, Sr, Ba
Refine cell
High nodule count in DI
Especially effective in
dissolution rate
May increase pearlite
S (G )graphite
Max. 1.5% is advised
Refine cell structure in GI
effective in converter iron
Low chill and shrink
Neutralize S (GI)
shrink
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Inoculation and Nodule CountInoculant BInoculant BInoculant AInoculant A
5 mm
310300
section
310300
40 mmsection
150 340
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Inoculation Turning off Shrinkageg gInoculant AInoculant A Inoculant BInoculant B Inoculant CInoculant C
150 250 350
Some shrink More shrink Little shrinkSome shrink More shrink Little shrink
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Inoculation and Thermal AnalysisInoculant BInoculant BInoculant AInoculant A
TElow = 1145oCUndercooling = 19oCR l 2 3
TElow = 1139oCUndercooling = 25oCR l 6 2 Recalescence = 2.3Recalescence = 6.2
GRF2 70GRF2 115 GRF2 = 70GRF2 = 115
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Inoculation and Pearlite
Inoculant A :Inoculant A :Inoculant A :Inoculant A :
190 Nodules/mm190 Nodules/mm22
80 % Nodularity80 % Nodularity80 % Nodularity80 % Nodularity
25 % Pearlite25 % Pearlite
Inoculant B :Inoculant B :Inoculant B :Inoculant B :
360 Nodules/mm360 Nodules/mm22
90 % Nodularity90 % Nodularity
13 % Pearlite13 % Pearlite
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Thank You !Thank You !
Any Questions ?
Elkem Foundry SeminarElkem Foundry SeminarWeinheimWeinheim GermanyGermany, 10 , 10 –– 11 September 201211 September 2012
