1. Heat treatment of gray cast iron.
In order to achieve different purposes, gray cast iron can be heat treated differently after casting. In the valve production, the heat treatment processes for the ANSI Valve Body and other parts after casting are: heat aging to eliminate casting stress and high temperature annealing to eliminate free cementite. Thermal aging is a necessary process. High temperature annealing is only used when casting, because of the improper control of chemical composition and casting cooling rate, it is used to replace the thermal aging when there is primary cementite in the microstructure after casting.
2. Heat treatment of carbon cast steel.
Steel castings have large casting residual stresses after casting, sometimes the structure of the steel castings is coarse, and even superheated structures appear. These all affect the dimensional stability of the steel castings, reduce the mechanical properties of the steel and are not conducive to the cutting process. In order to eliminate casting stress, refine the structure, improve the mechanical properties and improve the machinability, the parts such as Customized ANSI Valve Body are often annealed or normalized + tempered after casting.