Transcript Grey Iron Cylinder Inoculant Float

Grey Iron Cylinder Inoculant
Float
Joe Licavoli
Aaron Lueker
Dan Seguin
Paul Nelson
Terri Mullen
Andrew Zeagler
Process
• Grey Iron was cast into many
different cylindrical molds with
varying height; 6,12, and 20in
• Inoculant was added to the
melt to initiate nucleation
sites for graphite flakes to
form in the solid
• The uniformity of flakes
affects the mechanical
properties of the material
Type D/E Flakes 20μm Scale Bar
Type A/B Flakes 20μm Scale Bar
Initial Defective Iron Sample
• The hollow area
inside of the solidified
iron sample is where
the Ferro-Silicate
inoculant coagulated,
leaving it un-reacted
with the iron.
Considerations for the Grey Iron
Casting Process
• Solidification - The cylinder may take too long to
solidify, giving the inoculant the opportunity to
float
• Flotation - The inoculant may flow almost
completely to the surface before reacting with
the melt
• Dissolution - The radius of the inoculant affects
its flotation. Since dissolution affects radius,
dissolution may, in turn, affect flotation
Our Group’s Problems to solve
Grey Iron Cylinder
problems
Solidification
Flotation
Dissolution
Solidification
• Chvorinov’s rule used to determine
solidification time.
• Solidification from top determined using
Newton’s Law of cooling.
• Inconsistencies in calculation with reality.
• Did not account heat flow from sides through
top.
Solidification from Mold Walls
• Calculate energy conducted away from the
metal to the mold during solidification
• Excess energy had two sources
– From the phase transformation
– From superheating
• This energy had to be conducted away from
the metal through mold surfaces
Solidification from the Mold Wall
• Chvorinov’s rule yields the following equation
for time through Fourier’s Law of Conduction:
 
t s T p 
    Q T  2 
M t p 

T m  T o  2  A
2 2
2
 M
2
• Time comes out to be 8.9 minutes
  1 30
0K  1 30 1K Temperature
1 99 9K
EffectTp of
Pour
540
 
t s T p 530
520
1400
1600
1800
Tp
Notice: Not very temperature dependent
Solidification from Top
• Heat dissipated by convection through top of mold
• Modeled using Newton’s Law of Cooling
– Heat flux found, multiplied by solidification time and
energy liberated to find depth of solidification as a
function of pour temperature
 
D sol T p
Vm


1
q 

  time
C
 T  T m A m H f  Metal
 Metal  p

D sol(1773K)
.529m
Inconsistencies
• The calculated solidification distance from
the top was inconsistent with actual results
– 1.5-2.5” in reality
• Rough estimate from casting
– Did not account for heat flow from sides
through top
– Limited models for heat transfer coefficient in
calculating heat flux
Magmasoft Simulations
•
•
•
Modeled solidification to
understand where inoculants
would have the most time to float
Limitations of the universities
version of Magmasoft did not
allow for the modeling of the Iron
containing inoculant particles
Knowing the temperature and
geometries of the un-solidified
sections as time passes could
allow for a more accurate
calculation of final inoculant
distribution
Cooling Rate Control of Flake Spacing
• Flake spacing is controlled by
cooling rate
• Since the cylinder has a constant
cooling rate, there is uniform flake
spacing throughout the cylinder
• This would be a good medium to
attempt an experiment to
determine the relationship of
inoculant mixing time vs. flake
spacing (i.e. fade)
Predicted Porosity
• The simulated regions of
porosity without taking into
account flotation of FerroSilicate
• Indicates that any other
regions of high porosity are
completely due to inoculant
concentrations
Simulated Inoculant Mixing
Flotation
• The inoculant is mixed in with the liquid
grey iron as it is poured into the transfer
crucible
• From here it is poured into the desired
mold
• As the mold solidifies, the particles of
inoculant begin to float because they are
less dense than the grey iron
Flotation cont’d.
• The following calculations were used from
example 3.3 (Gaskell)
• Terminal Velocity-


L x
v t T p  L x 
t s T p L


• Also the critical radius for flotation can be
found by


 

RT p  L x 
 2  Metal   Inoculent g 
9   v t T p  L x
.5
Flotation cont’d.
• With this data we can also find the Reynolds
number which will show whether the flow is
laminar or turbulent

Re T p
2 R T p  L x  v t T p  L x   Met al

 L x  


• The Reynolds number will be less than 0.1,
exhibiting laminar flow. (This confirms that our
equation for terminal velocity is valid)
Flotation cont.
• Figure F.1
• In this figure the
critical particle
radius is found as
the length of the
cylinder is
increased
2.5 10
5
2.32510
5
2 10
5


R T p  L  x1.5 10 5
1 10
5
6
9.18110 5 10 6
0
0.015
0.1
0.2
0.3
L
0.4
0.5
0.6
Flotation Results
•
•
Flotation problems
-Most of the particles
floated to the
surface without
reacting with the
grey iron melt
Dissolution
• Changes in particle diameter may influence
flotation time
• Dissolution equation derived from analogous
heat transfer equations in Gaskell
R t  


h D  Isi   Lsi
 at SI
Dissolution cont’d.
• Equations derived from Gaskell lead to
solution for mass transfer coefficient hD
.4
1 
2 

    .25
  
p
oi
se
0.5
3
  s 
2   .4 Re Tp  L x
 .0 6 Re Tp  L x   


9
 
2 .4 1 0  

hD  
 2 RTp  L x 


DSi


Problems with Result
• Calculations do not agree with experiment
• Unavailable ternary phase diagram forced
approximation from binary phase diagram
• Viscosity difference is unknown
R t  


h D  Isi   Lsi
 at SI
Particle radius ~tenths of mm
ΔR = .2363 mm/s
1 
2 


  
p
oi
se
0.5
3

2   .4 Re Tp  L x
 .0 6 Re Tp  L x   


9
2 .4 1 0 

hD  
 2 R Tp  L x 


DSi


.4
1
  
 1
.25
A More Likely Explanation
• Interfacial resistance may account for
differences
• Solidification at inoculant surface may
serve as a barrier to further atomic
diffusion
• Conclusion: Better numbers and
consideration of interfacial resistance
could accurately model dissolution.
Conclusions
• Based on solidification model in conjunction with
flotation model, inoculant particles in our
particular application would have ample time to
float.
• The flotation of incoculant did in fact lead to the
numerous pores located on the surface of the
cylinder.
• Dissolution could be a huge factor in removing
inoculant from the molten iron before it floated,
but interfacial considerations need to be taken to
understand the complete dynamics.
Proposed Solutions and Extensions
• Adjustment of Inoculant Particle
Size/Amount (Size might not be most
economically feasible).
• Adjust Length of Cylinder (might not be
possible for an application)
• Consideration of Nucleation Rates
• Innoculant Mixing Time
• Develop model for heat transfer coefficient
for such a situation
References
Metal Casting Handbook For MY4130 by
Karl B. Rundman
David R. Gaskell “An Introduction to
Transport Phenomena in Materials
Engineering”
SAH Free Consulting Firm “Bring all your
problems to me, I’ll help ya out…. unless
yer a union guy”
The offices of Lord Chadwick Boyle III & Sir
Chester Fairfax.
Questions
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