Transcript Dynamic Inoculation

ATAS Dynamic Inoculation
Adding the optimal amount of inoculant as a function of the nucleation properties in
the base iron
Version: 020131
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Why dynamic inoculation?
• Too much inoculant increases risk for shrinkage in grey
iron and slag defects
• Too little inoculant increases risk for chill and shrinkage
in ductile iron
• Amount and type of inoculant influences the precipitation
of eutectic graphite
• The nucleation properties can vary considerably even
with constant chemistry
• Reduces cost for inoculants
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Efficient inoculation is essential!
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Most frequently used treatment to cast iron
Provide initial nucleation sites
Control crystallization
Influence nodule count / cell size
Control chill and intercellular carbides
Influence shrinkage tendency
Influence physical properties
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Problem 1 - Selecting Inoculant
• Influencing factors: Base iron status, type of
graphite (flake, CG, DI), pouring temperature,
casting modulus, quality requirement, price etc.
• At least 20 different basic types of inoculants to
choose from
Question: How to select and evaluate?
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Problem 2 - How much to add?
Too much:
• increases cost
• increases shrinkage in grey iron
• increases endogenous slag a.o.
Too little:
• decreases cell size / nod. count
• increases chill tendency
• reduces some physical properties
Question: How to evaluate?
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Chemistry is not enough!
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Weight % of each element - that´s all !!!
No info about compounds
No info about oxides, silicates or nitrates
No info about amount or size of graphite
No info about interactions
No info about behaviour during solidification
In summary no info about nucleation!
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ATAS shows the integrated effects of
all components!
A spectrometer analysis shows the elemental amount of each element, so e.g. 0.04% Mg can mean different things!
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White eutectic temperature
1% Si reduces TE approx 12 C
1% P reduces TE approx 30 C
1% Cr increases TE approx 27 C
The white eutectic temperature shows the “silicon equivalent”, which is the
lower limit for chill formation.
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Grey eutectic temperature
The grey eutectic temperature (TElow) shows the actual, lowest
temperature during the eutectic part of solidification.
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Factors influencing Metallurgical
Quality
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Chemical composition
Charge materials and mixture (Combined & Free C)
Charging sequence and temperature / time ratios
Iron handling and treatment practice
Pouring temperature and inoculation practice
Presence and amount of reaction products
Thermal properties of alloy, mould and core(s)
Mould / core hardness / weighting
Methoding (gating, feeding, feeding paths, etc.)
Shake-out time
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Nucleation properties
Nucleation properties in the base iron do vary although chemistry is
constant!
Variation Recalescence & R-rate
14,0
1165,0
12,0
1160,0
Low1155,0
eutectic temperature
8,0
1130,0
19
17
15
13
11
9
1145,0
1140,0
1135,0
19
17
15
13
11
9
7
5
3
1130,0
1
5
3
7
Test #
Test #
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19
1150,0
0,0
17
1135,0
15
1155,0
13
2,0
11
1140,0
9
1160,0
7
4,0
5
1145,0
1
1165,0
TE_low C
6,0
3
1150,0
1
C
10,0
White and grey curves
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Under cooling
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Chill & Inverse Chill
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Chill
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Inverse Chill
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Effects of inoculation
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Can reduce TL
Increase TElow
Increase TEhigh
Reduce recalescence
Increase GRF 1
Decrease GRF 2
Deeper dT/dt_TS
Conclusion: Different applications require different inoculants!
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0.08% Inoculant
Sample taken from the QuikCup. Note R and GRF 2
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Recalescence - R
Inoculation Index = Undercooling uninoculated sample / Undercooling inoculated.
Undercooling = TEgray - TElow (actual)
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Testing Inoculants
The effect of different
inoculants can easily
be studied using
ATAS and the most
optimal inoculant for
the actual application
can be selected.
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Dynamic Inoculation
The optimal amount of inoculant during a day as evaluated by ATAS. Without ATAS the
foundry had to add 0.3% all the time in order to take the ”worst” case into account.
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Dynamic Inoculation
In most cases the iron
is over-inoculated (often
30-40%) as the
chemical analysis does
not give any indication
of the nucleation status.
ATAS can measure the
nucleation status and
suggest optimal
additions of inoculants.
The dynamic
inoculation approach
reduces problems with
micro shrinkage, chill,
slag and reduces costs.
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Calibration
The Dynamic Inoculation
module in ATAS is calibrated
by taking samples from
uninoculated iron and iron
with different amounts of
inoculant. A formula for
inoculation is created based
on these data.
The main factors influenced
by inoculation are:
TL, TElow, R, GRF1, GRF 2,
TS and dT/dt_TS
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Alloy Database - Learning
The results from all
tests are stored and
used with a
statistical method to
fine-tune the
threshold values.
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Alloy Database - Limits
The threshold values
for different alloys
and/or casting
categories are stored
in a database.
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Alloy Database Inoculation
The system can be
used “off-line” where
the recommended
amount is displayed
on the screen or “online” connected to an
inoculation dosing
device.
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Benefits with ATAS Dynamic Inoculation
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Reduced shrinkage problems
Reduced chill problems
Reduced expansion penetration
Less variations in cell size
Less variations in Brinell Hardness
Less variations in machinability
Less consumption of inoculant
SPC test of base iron
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