TITLE:
Effect of Silicon Content and Shake-Out Time on Hardness and Grain Size Properties of GL 250 Cast Iron
AUTHORS:
P. Atanda, G. Oluwadare, O. Oluwole
KEYWORDS:
Shake-out time; Silicon content; Hardness; Grain-Size; GL 250 C.I
JOURNAL NAME:
Journal of Minerals and Materials Characterization and Engineering,
Vol.10 No.3,
March
5,
2011
ABSTRACT: The properties of cast iron grade GL 250 are dependent on the microstructures developed during
casting. These microstructures are in turn dependent on the composition of the alloy, type of
mould and other numerous casting practice variables such as shake-out time, pouring
temperature, mould ambient conditions and inoculating technique.
In this work, the effect of silicon content and shake-out time on the grain size (GS) and hardness
properties of GL 250 cast iron was studied using a pouring temperature of 1400℃ and sand
mould casting. Using charge materials consisting of pig iron and other additives, GL 250
castings containing silicon contents of 1.7, 2.1 and 2.7% were casted using a constant pouring
temperature of 1400℃, molding sand of specified properties and ambient mould temperature of
32℃.
Results showed that type A flake type was obtained at 30mins shakeout time for all samples for
the C.I composition under study. Increasing shake-out time decreased hardness and increased
carbide grain size. Increasing silicon content was observed to increase grain size and reduce
free graphite but with resultant decrease in hardness. Two mathematical relationships were
derived. One related grain-size to silicon content and shakeout time while the second related
Brinnel Hardness to Silicon content and shake-out time. They are: Grain Size=0.40
Si+0.17Shake-out Time-0.15 and BHN=-60.53Si-7.15Shake-out Time+329.35 at 1400℃ pouring
temperature in a molding sand of specified properties and sand mould ambient temperature of
32℃.