Organizational differences lead to huge differences in performance:
Gray cast iron is a flake graphite matrix, which is easy to cause stress concentration, brittleness and good damping performance. It is mainly used for the production of various high strength unnecessary cabinet/base, mainly bear compression stress.
Nodular cast iron is a spherical graphite matrix. The splitting between grains is minimized and the stress concentration is minimized. Therefore, the strength is high, and the same as medium carbon steel. It can give full play to the properties of the matrix, with a certain degree of plasticity. Good toughness. It is commonly used to make parts with high toughness and complex shapes, such as crankshaft/chain joints for internal combustion engines. Ductile iron can usually also be heat treated for strength, while gray iron is usually not heat treated for strength (the effect of flake graphite).
Malleable cast iron is a ferrite (F) + aggregate graphite (G) matrix that can be used to generate shock or vibration and torsional loads. It is commonly used in the manufacture of rear axles, spring supports, low pressure valves, pipe fittings, tool wrenches.