Cast iron is classified into several distinct metallurgical grades based on its micro-structure, carbon distribution, and mechanical performance characteristics. The primary categories include Gray Cast Iron, characterized by graphite flakes that provide superior vibration damping; Ductile (or Nodular/Spheroidal Graphite) Iron, where spheroidal graphite nodules deliver enhanced tensile strength and ductility; Malleable Iron, produced through heat-treatment annealing; White Cast Iron, known for extreme surface hardness and wear resistance; and Compacted Graphite Iron, which bridges the thermal and mechanical properties of gray and ductile irons.