The figure shows the effect of scrap content on the hardness and tensile strength of gray cast iron. It can be seen from the figure that the hardness and tensile strength of grey cast iron increased with the increase of scrap content, while the hardness and tensile strength of grey cast iron with 100% scrap increased significantly.
This fully proves that the microstructure of gray cast iron has a decisive effect on its mechanical properties under the condition of constant composition. Gray cast iron is mainly composed of pearlite matrix and flake graphite. The formation of graphite (especially flake graphite) splits the pearlite matrix, which has the most obvious effect on the mechanical properties of cast iron. Pearlite content, distribution uniformity and refinement degree also have a very important impact on the mechanical properties of gray cast iron.