Entrainment Defects in Cast Iron
Castings were made of two types of cast iron, flake grey iron (FGI) and spheroidal graphite iron (SGI), in test bar moulds having both turbulent and quiescent filling systems. The different filling system designs did not seem to affect the scatter of values of the ultimate tensile strength (UTS) in FGI. On the other hand, the turbulently filled moulds had increased scatter of UTS values in the case of the FGI more than in the case of the SGI. Slag particles and ternary eutectic phosphide defects were identified as responsible for the fracture of FGI test bars. Two types of defects, (classified as type I and II), symmetrical on either side of the fracture surfaces of tensile test bars, were found in the SGI test bars, but not the FGI test bars. Scanning electron microscopy and EDX analysis of defects suggested that type I was a thin film of magnesium silicate and type II consisted of folded-over carbon-rich films containing magnesium oxide. These defects are similar in form and structure to the double oxide film defects found in Al and Mg alloys.
KeywordsCast iron Flake grey cast iron Spheroidal graphite cast iron Weibull Entrainment defects Bifilms Oxide films
I would like to express my sincere thanks to Mr. Adrian Caden for his careful assistance with the experimental work.
I would also like to extend my gratitude to Grainger and Worrall foundry represented by Tim Garwood and Keith Dunham for their continuous help in producing the castings and allowing me to join them for industrial training.
- 2.Campbell J (2015) Complete casting handbook: metal casting processes, metallurgy, techniques and design, 2nd edn. Butterworth-Heinemann, AmesterdamGoogle Scholar
- 4.Divandari M, Campbell J (2001) Mechanisms of bubble trail formation in castings. Transactions of American Foundry Society 109:433–442Google Scholar
- 10.BSI (2011) BS EN 1561:2011 founding. Grey cast irons, LondonGoogle Scholar
- 11.BSI (2018) BS EN 1563:2018 founding. Spheroidal graphite cast irons, LondonGoogle Scholar
- 12.ASTM International (2016) Standard test methods for tension testing of metallic materialsGoogle Scholar