Because the chemical composition and structure of cast iron are quite different from that of steel, Yinuo reminds that when designing the heat treatment process of cast iron in a walking heating furnace, it is necessary to pay attention to determining the heating parameters.

Heat treatment can only change the matrix structure of cast iron, but not the shape and distribution of graphite. Due to the higher silicon content in cast iron, the eutectoid transformation temperature and the austenitizing temperature are increased. Therefore, when cast iron is heat treated, its heating temperature is relatively high. At the same time, higher heating temperature is conducive to the dissolution of phosphorus eutectic structure in cast iron and reduces the brittleness of cast iron.

Due to the large amount of graphite in cast iron, the heat transfer rate is slowed down. Therefore, the heating rate of cast iron should be reduced during heat treatment, especially for the more complex structure of cast iron, it is better to slowly heat, and the holding time should be appropriately extended, in order to obtain a more uniform austenite structure.

In order to prevent cracks and reduce deformation of cast irons in walking heating furnaces during quenching, it is not advisable to use excessively fast cooling media during cooling.

Due to the high silicon content in cast iron, it has the effect of preventing carbon diffusion. Therefore, the tempering stability of cast iron is good. To obtain the same hardness, a slightly higher tempering temperature and a longer holding time than steel parts should be used, which is beneficial to reduce its internal stress.

It is recommended to adjust the carbon content in austenite by changing the heating temperature and holding time of ductile iron to improve the ratio of ferrite and pearlite after cooling, so as to meet different performance requirements.