In the present paper, the change in strength caused by the difference in the form of cast iron was examined by using round, square and triangular bars with the same sectional area.
It was found that the strength increased in order of round, square and triangular form.
On the assumptions that (1) the cooling rate in casting depends on the ratio of the surface area to the volume of the castings and (2) the mechanical strength is closely associated with the cooling rate, the following expression was obtained for the tensile strength.
σB=K(1/V/S)n
where, S is the surface of the cast iron, V is the volume and K and n are experimental constants.
Furthermore, microstructural observations were made to understand the above phenomena. In the case of the bars with small sectional area, the graphite structure of E type, appearad in all the bars. The change in mechanical strength caused by the difference in form can mainly be explained from the size, form and distribution pattern of the graphite appearing in cast iron.
