The success of this investigation will rely on the comple- tion of extensive experimental work that will provide critical data required in the understanding of casting skin formation and elimination. The developed correlations be- tween process variables, casting skin quality and mechani- cal 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 the influence of skin formation on fatigue will be determined. Also, potential actions to reduce or eliminate skin forma- tion will be investigated.


Status Update: Papers resulting from Phase I were presented at the 2011 Metalcasting Congress. Phase II has begun with test specimens for fatigue testing cast at OSU’s new metalcasting lab. Those wishing further information on the project should contact Prof. Doru Stefanescu, The Ohio State University, at stefanescu.1@osu.edu.


Ductile Iron Structure/Property Optimization & Enhancement—Phase II (10-11#02) Phase I (09-10#02)—Complete


Coordinator: Element Materials Technology, 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 has not been conducted to de- termine what is required to consistently achieve such proper- ties with this extent of ferrite. It is known that strengthening mechanisms in metal include solid solution strengthening with both substitutional and interstitial elements. Work hardening is another means to strengthen metals. Phase transformation, pre- cipitation hardening and grain refinement are still other mecha- nisms utilized to strengthen metals.


This study will characterize the graphite and other fac- tors that control the matrix mechanical properties that are independent of nodule count, size and morphology. The characterization will include tensile and compression test- ing of sections from example casting and test bars, as well as impact testing. The impact test temperature will be at room temperature and -30C (-20F), as required in GGG 40.3, for example. The ductile to brittle transitions temper- ature determination could also be made for select samples. The microstructure of the test bars will be evaluated us-


ing quantitative metallography. Optical microscopy will be used to determine ferrite grain size. Chemical analysis will also be required. It will be essential to procure castings 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 deter- mine how the different factors interact with the mechani- cal 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 includes DOE tests to reproduce these results.


Status Update: Phase II is underway and starting with DOE heats and validation of improved properties. The project re- sults continue to be reviewed during updates given to con- sortium members and the steering committee. Information on the project is limited to the consortium members and will be released at a later date to AFS corporate members. Those wishing to participate should contact John Tartaglia, Element Materials Technology, at John.Tartaglia@element.com.


Effects of Varying SiC Purity on Cupola Performance (09-10#03)


Coordinator: Grede, S. Katz Associates and AFS Melting Methods & Materials Division (8)


Nearly 8 million tons of cast iron products were produced in the U.S. in 2007. This required the production of about 16 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 com- position (~2.5% Si). To meet this level of demand, cupolas consume about 4x105 10% is oxidized (4x104


only a large added cost to the foundry ($40x106 a large waste of energy.


tons of silicon/year, of which about tons of Si). This loss represents not /year), but also


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 final report is being written and should be available shortly. The work is being monitored by the AFS Melting Methods & Materials Cupola Committee (8F). Those wishing to participate should contact Jim Cree, Grede, at JCree@grede.com.


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International Journal of Metalcasting/Winter 2012


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