Application of cooling curve analysis in solidification pattern and structure control of grey cast irons
Commercial cast iron is a typical multi-phase, natural metal matrix composite, including a ferrous matrix at different alloying grade and several phases, each having varying levels of carbon and other elements present, such as carbide, graphite and nitride. It was found that some active elements, such as S, O, Al, Ca, Ba and RE (rare earth), are important to control carbide/graphite phase formation. A major purpose of the present paper was to investigate the solidification pattern and structure of un-inoculated and inoculated cast irons, with intentionally critical conditions for graphite nucleation, typical for electric melted iron, by thermal (cooling curve) analysis technique; this is especially pertinent to the production of thin section iron castings. Increased chill (carbides formation), undercooled graphite amount, eutectic cells count and relative density correlate well with the degree of eutectic undercooling, at the beginning of eutectic reaction and at the end of solidification. Inoculation application led to decrease of ∆Tm and increase of ∆T1 (it became positive) and ∆T3 (less negative) parameters, at higher influencing power on ∆T1 parameter (narrow variation range). Higher inoculant addition rate gives better cooling curve analysis parameters. ∆T1 appears to be the recommended cooling curve analysis parameter to characterize the specifics of solidification pattern and structure formation on the entire solidification range.
KeywordsGrey cast iron Solidification Eutectic undercooling Inoculation Thermal analysis Cooling curves Structure Carbides Graphite Eutectic cells
This work was partially financed by a grant of the Romanian National Authority for Scientific Research and Innovation, CNCS/CCCDI–UEFISCDI, project number PN-III-P2-2.1-PED-2016-1793, within PNCDI III.
- 1.Riposan I, Chisamera M, Stan S. New developments in high quality grey cast irons. China Foundry. 2014;11(4):351–64.Google Scholar
- 2.Riposan I, Skaland T. Modification and Inoculation of Cast Iron. In: In D.M. Stefanescu, Volume Editor, Cast Iron Science and Technology Handbook. 2017. pp. 160–176, American Society of Materials.Google Scholar
- 3.Sparkman D, Bhaskaram CA. Chill measurement by thermal analysis. AFS Trans. 1996;104:969–76.Google Scholar
- 4.Sillen, RV. Optimizing Inoculation Practice by means of Thermal Analysis. In: AFS International Inoculation Conference, 6–8 Apr.1998, Rosemont, Illinois,USA.Google Scholar
- 8.Sillen RV. Novacast Technologies, www.novacast.se, 2006.
- 9.Chisamera M, Stan S, Riposan I, Costache G, Barstow M. Solidification pattern of in-mold and ladle inoculated low sulfur hypoeutectic gray cast irons. AFS Trans. 2008;116:641–52.Google Scholar
- 10.Stan S, Chisamera M, Riposan I, Stefan E, Barstow M. Solidification pattern of un-inoculated and inoculated gray cast irons in wedge test samples. AFS Trans. 2010;118:295–309.Google Scholar
- 11.Sparkman D. Microstructure by Thermal Analysis. AFS Trans. 2011; Paper 11-068:413–419.Google Scholar
- 13.Stefanescu DM, Moran M, Boonmee S. The use of combined liquid displacement and cooling curve analysis in understanding the solidification of cast iron. AFS Trans. 2012;120:365–74.Google Scholar
- 15.Alonso G, Stefanescu DM, Suarez R. Understanding graphite expansion during the eutectic solidification of cast iron through combined linear displacement and thermal analysis. Int Foundry Res. 2014;66(4):2–12.Google Scholar
- 16.Riposan I, Stefan IC, Firican MC, Stan S. Thermal Analysis to Optimize and Control the Cast Iron Solidification Process. In: Proc 6th Int Conf. Advanced Materials and Structures–AMS ‘13, 16–17 Oct. 2015, Timisoara, Romania.Google Scholar
- 20.Chisamera M, Riposan I, Stan S, Skaland T. Effects of calcium and strontium undercooling, chill and microstructure in grey irons of varying sulphur and oxygen contents. In: Proc. 64th World Foundry Congress, 2000, Paris, France, Paper No. 62.Google Scholar
- 21.Riposan I, Chisamera M, Stan S, Skaland T, Onsoien MI. Analyses of possible nucleation sites in Ca/Sr overinoculated grey irons. AFS Trans. 2001;109:1151–62.Google Scholar
- 22.Riposan I, Chisamera M, Stan S, SkalandT. Graphite nucleants (microinclusions) characterization in Ca/Sr inoculated grey irons. Int J Cast Metal Res. 2003; 16(1–3):105–111.Google Scholar
- 26.Gundlach R. observations on structure control to improve the properties of cast irons. The honorary cast iron lecture, Div.5, 112nd AFS Metalcasting Congress, Atlanta, Georgia, USA; 2008. Paper 08–158.Google Scholar
- 33.Alonso G, Stefanescu DM, Larranaga P, De la Fuente F, Suarez R. On the Nucleation of Graphite in Lamellar Graphite Cast Iron. AFS Trans. 2016; 124:Paper 16–020.Google Scholar
- 34.American Society for Testing of Materials, Standard A367–85: Standard Test Methods of Chill Testing of Cast Iron, 1. West Conshohocken. USA: PA; 2000. p. 151–4.Google Scholar