What are the process characteristics of high frequency induction heating equipment heat treatment for iron castings?

The structure of cast iron and steel is very different. In addition to the amount of carbon contained in cementite, a large amount of carbon exists in the form of graphite in different forms. Therefore, its organizational structure and various properties are different from those of steel. Because the chemical composition and structure of cast iron are quite different from those of steel, especially the presence of graphite in different forms, cast iron has certain characteristics when it is heat treated by high-frequency induction heating equipment.

1. Due to the high silicon content in cast iron, the eutectoid transformation temperature increases and the austenitization temperature increases. Therefore, when cast iron is heat treated, its heating temperature is relatively high. At the same time, a higher heating temperature is conducive to the dissolution of phosphorus eutectic structure in cast iron and reduces the brittleness of cast iron.

2. The heat treatment of high-frequency induction heating equipment can only change the matrix structure of cast iron, but cannot change the shape and distribution of graphite.

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

4. Due to the high silicon content in cast iron, it can prevent the diffusion of carbon. Therefore, the tempering stability of cast iron is good. To obtain the same hardness, a slightly higher tempering temperature and a slightly longer holding time are required than steel parts, which is conducive to reducing its internal stress.

5. In order to prevent cracks and reduce deformation of castings during quenching, medium with too fast cooling rate should not be used during cooling.

6. By changing the heating temperature and holding time of ductile iron, the carbon content in austenite can be adjusted, and then the ratio of ferrite and pearlite after cooling can be improved, so as to meet different performance requirements.

Regarding the heat treatment process characteristics of these high-frequency induction heating equipment for cast iron, most of the differences from steel are in terms of process parameters. In addition to these, almost all heat treatment methods for steel (annealing, normalizing quenching, tempering, etc.) can be Used in different types of cast iron.