Grey Iron Cylinder Inoculant Float

1. Grey Iron Cylinder Inoculant Float Joe Licavoli Aaron Lueker Dan Seguin Paul Nelson Terri Mullen Andrew Zeagler

2. 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

3. 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.

4. 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

5. Our Group’s Problems to solve

6. 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.

7. 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

8. 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

9. Effect of Pour Temperature Notice: Not very temperature dependent

10. 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

11. 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

12. 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

13. 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)

14. 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

15. Simulated Inoculant Mixing

16. 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

17. 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

18. 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)

19. Flotation cont. • Figure F.1 • In this figure the critical particle radius is found as the length of the cylinder is increased

20. Flotation Results • Flotation problems • -Most of the particles floated to the surface without reacting with the grey iron melt

21. Dissolution • Changes in particle diameter may influence flotation time • Dissolution equation derived from analogous heat transfer equations in Gaskell

22. Dissolution cont’d. • Equations derived from Gaskell lead to solution for mass transfer coefficient hD

23. Problems with Result • Calculations do not agree with experiment • Unavailable ternary phase diagram forced approximation from binary phase diagram • Viscosity difference is unknown Particle radius ~tenths of mm ΔR = .2363 mm/s

24. 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.

25. 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.

26. 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

27. 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.

28. Questions ?????