In addition to correctly purchasing the preferred components of iron castings to determine the structure, heat treatment is also an effective way to further adjust and improve the structure of the matrix material to improve the performance of cast iron. The heat treatment of cast iron has similarities and differences with the heat treatment of steel. Heat treatment of cast iron generally does not allow the appearance and diffusion of graphite in the initial structure. For gray cast iron, the effect caused by a large amount of graphite and stress is the leading role of the cast iron performance, so the effect of heat treatment applied to gray cast iron is far less obvious than that of steel and ductile iron. Therefore, the heat treatment process of excellent cast iron is mostly annealing, quenching and so on. For ductile iron, since the graphite is spherical, the isolation effect of the matrix is released. According to the heat treatment, the efficiency of the matrix structure can be fully utilized, and then obvious spherical mechanical properties can be obtained. Therefore, ductile iron, like steel, has heat treatment processes such as annealing, quenching, tempering, multi-temperature quenching, induction heating quenching and surface chemical heat treatment.

Due to the uneven thickness of the casting, during heating, cooling, and phase transformation, forces and tissue stresses occur. In addition, large parts are also prone to residual stresses inside them after the production of iron castings, all these thermal stresses. Stress relief annealing is usually heated at a temperature of 500 to 550 ° C, and the holding time is 2 to 8 hours, followed by cooling in the furnace (gray iron) or air cooling (ductile iron). Using this process can make the thermal stress of the casting reach 90-95%, but the structure of the cast iron will not change. If the temperature exceeds 550 ℃ or the holding time is too long, it will cause graphitization and reduce the strength and hardness of the casting.