Effect of Cooling Rate on Eutectic Cell Count, Grain Size, Microstructure, and Ultimate Tensile Strength of Hypoeutectic Cast Iron

This article describes a series of microstructural and strength studies performed on hypoeutectic cast iron, which was sand cast using a variety of end chills (metallic, nonmetallic, water-cooled, and subzero, respectively). The effects of cooling rate on the eutectic cell count (ECC), grain size, and the ultimate tensile strength (UTS) were evaluated. Attempts were also made to explain these effects and to correlate the UTS with ECC. It was found that subzero chilled and water-cool, chilled cast iron exhibit severe undercooling compared to normal sand cast iron. It was concluded from this investigation that nucleation conditions are completely altered but growth conditions prevail as usual, Therefore, undercooling during solidification is considered to be responsible for variation in ECC, grain size, microstructure, and tensile strength.