Grey Iron Cylinder Inoculant Float

Joe LicavoliAaron LuekerDan SeguinPaul NelsonTerri 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:

• Time comes out to be 8.9 minutes

t s T p M Q t T p 2

T m T o 2 22 A

2 M2

Effect of Pour TemperatureTp 1300K 1301K 1999K

1400 1600 1800520

530

540

ts Tp

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 qVm

C Metal T p T m A m1

H f Metal

time

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 Ferro-Silicate

• 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-

• Also the critical radius for flotation can be found by

R T p L x 9 v t T p L x

2 Metal Inoculent g

.5

v t T p L x L xt s T p L

Flotation cont’d.• With this data we can also find the Reynolds

number which will show whether the flow is laminar or turbulent

• The Reynolds number will be less than 0.1, exhibiting laminar flow. (This confirms that our equation for terminal velocity is valid)

R e T p L x 2 R T p L x v t T p L x Metal

Flotation cont.

• Figure F.1• In this figure the

critical particle radius is found as the length of the cylinder is increased 0 0.1 0.2 0.3 0.4 0.5

5 106

1 105

1.5 105

2 105

2.5 105

2.325 105

9.181 106

R T p L x

0.60.015 L

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

atSI

Dissolution cont’d.

• Equations derived from Gaskell lead to solution for mass transfer coefficient hD

hD

2 .4 Re Tp L x 0.5 .06 Re Tp L x 2

3

1

poise

2.4 109

.4

s

.25

2 R Tp L x

DSi

s

Problems with Result

• Calculations do not agree with experiment• Unavailable ternary phase diagram forced

approximation from binary phase diagram• Viscosity difference is unknown

hD

2 .4 Re Tp L x 0.5 .06 Re Tp L x 2

3

1

poise

2.4 109

.4

1

1

.25

2 R Tp L x

DSi

R t

h D Isi Lsi

atSI

Particle radius ~tenths of mm

ΔR = .2363 mm/s

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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