required in the understanding of casting skin formation and elimination. The developed correlations between process variables, casting skin quality and mechanical properties will provide the impetus to further expand the applications of CGI. During Phase I, the mechanism for skin formation and test specimens design was validated. During Phase II fatigue specimens will be cast and influence of skin formation of fatigue will be determined. Also, potential actions to reduce or eliminate skin formation will be investigated.
Status Update: The final report was being written and re- ported in a paper given at CastExpo’10 & Congress. Phase II has begun. Those wishing further information on the project should contact Prof. Doru Stefanescu, The Ohio State Uni- versity, at
stefanescu.1@osu.edu.
Ductile Iron Structure/Property Optimization & Enhancement Phase I (09-10#02)
Coordinator: Stork CRS and AFS Cast Iron Division (5), Ductile Iron Society and Consortium
ASTM A536 contains examples of the yield strength, tensile strength and percent elongation relationships expected in ductile cast iron. Frequently, both castings and test bars will exhibit mechanical properties that are significantly better than the minimums expected as indicated in the ASTM specifica- tion. One example is the information generated by the re- searchers from testing a pearlitic ductile iron expected to have mechanical strength properties that would be consistent with the pearlitic 80-55-06 grade, but exhibiting high ductility of almost 15% elongation.
To our knowledge, research work has not been conducted to determine what is required to consistently achieve such prop- erties with this extent of ferrite. It is known that strengthen- ing mechanisms in metal include solid solution strengthening with both substitutional and interstitial elements. Work hard- ening is another means to strengthen metals. Phase transfor- mation, precipitation hardening and grain refinement are still other mechanisms utilized to strengthen metals.
This study will characterize the graphite and other factors that control the matrix mechanical properties that are independent of nodule count, size and morphology. The characterization will include tensile and compression testing of sections from example casting and test bars as well as impact testing. The im- pact test temperature will be at room temperature as well as -30C (-20F) as required in GGG 40.3 for example. Ductile to brittle transitions temperature determination could also be de- termined for select samples. The microstructure of the test bars will be evaluated using quantitative metallography. Optical mi-
croscopy will be used to determine ferrite grain size. Chemical analysis will also be required. It will be essential to procure cast- ings in this first task that exhibit those properties which both meet as well as exceed the ASTM A536 minimum expectations. The second task will characterize all of the data generated from Task 1 using multiple regression analysis to determine how the different factors interact with the mechanical properties with the intent to isolate those factors that contribute to the high tensile strengths, and yield strengths (and other properties) when the structure is predominantly ferrite. From these results a determination will be made to go to Phase II, which included DOE tests to reproduce these results.
Status Update: The project has begun and initial updates given to consortium members and steering committee. Since infor- mation on the project is limited at first to the consortium members and then at a later date to AFS Corporate mem- bers, those wishing to participate should contact George Goodrich, Stork CRS, at
george.goodrich@us.stork.com.
Effects of Varying SiC Purity on Cuploa Perfor- mance (09-10#03)
Coordinator: Grede, S. Katz Associates and AFS Melting Methods & Materials Division (8)
Nearly eight million tons of cast iron products were produced in the United States in 2007. This required the production of about sixteen million tons of liquid iron. About 60% of the liquid iron was generated in cupola furnaces. The major materials charged to the cupola are cast iron and steel. On average, about 50% of the charge is steel, which makes it necessary to add large amounts of silicon alloy to achieve the desired cast iron composition (~2.5% Si). To meet this level of demand, cupolas consumed about 4x105 tons of silicon/yr of which about 10% was oxidized (4x104
tons
of Si). This loss represents not only a large added cost to the foundry ($40x106
/yr), but also a large waste of energy.
The overall goal of this study is to demonstrate the relative advantages and disadvantages of 36% and 65% SiC so as to provide foundries with the information required to optimize the use of SiC at their facilities. The project will involve sig- nificant in-kind effort by the foundry conducting the work and the steering committee, with AFS support to fund for slag and off-gas analyses and a consultant to assist with data collection and analysis.
Status Update: The plant trial phase of this project is sched- uled to be conducted this summer. The work is being moni- tored by AFS Melting Methods & Materials Cupola (8F) Com- mittee. Those wishing to participate should contact Jim Cree, Grede, at
JCree@grede.com.
International Journal of Metalcasting/Summer 10
77
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