In this study, gray cast iron ASTM A48 was subjected (1) to testing for effects of cooling rate on its impacts properties; and (2) to assessing the relationship between microstructure and properties. The cooling rate was varied by testing the four cooling methods (1) As-cast; (2) Furnace-cooled; (3) Air-cooled; and 4) Green sand-cooled. It was found that the impacted properties are governed by flat fractures that meet minimum energy density criteria. Thus, we established a correlation between the microstructure and impact properties of GI ASTM A48 for conformance analysis to develop a predictive relationship. These include test specimen size and energy consumption patterns. As a result, the impact properties of GI ASTM A48 are finally predictable. This results in good efficiency and can be applied to heat treatments of some new materials.