During the casting process, the iron castings have different cooling rates from the surface to the inside, forming the casting internal stress. If it is not eliminated, it will deform or even crack the parts during cutting and use. To relieve stress, artificial aging and natural aging are often used. The casting is heated to about 500~560℃ for a certain period of time, and then the casting is taken out with the furnace to cool down. This aging is artificial aging; the natural aging is to store the cast iron outdoors for 6 to 18 months to let the stress release naturally. Aging can partially relieve the stress, but because of the long time and low efficiency, it has not been adopted. In order to improve the overall performance of cast iron parts, white-mouth annealing is often used, ductile iron annealing to improve toughness, normalizing and quenching to increase the strength of ductile iron.