Effect of sub-zero (cryogenic) and water-cool chilling on solidification and mechanical behavior of cast iron

Abstract

This paper presents the results obtained and the deductions made from a series of microstructural studies (to determine the eutectic cell count (ECC), secondary dendrite arm spacing (DAS), and grain size), ultimate tensile strength (UTS) and fracture toughness tests involving hypoeutectic gray cast iron which was sand cast using sub-zero and water-cooled end chills. The effect of cooling rate on the ECC, DAS, grain size, UTS and fracture toughness were evaluated. It was found that the UTS and fracture toughness is highly dependent on the rate of chilling, which determines the ECC, DAS and grain size of the material. Attempts were also made in this paper to explain these effects and to correlate the UTS and fracture toughness with ECC and DAS. Moreover, it was found that UTS and fracture toughness decreases as DAS increases and UTS and fracture toughness increases as ECC increases. The results are compared with specimens of the same chemical composition, which were sand casts without any chill.