7 - Time-Temperature Relationships Involved in the Decomposition of Carbides in Ductile Iron

Abstract:

The presence of carbides in ductile iron castings adversely affects their strength, ductility, impact and machining properties. Since it is not always possible to produce carbide free as cast ductile iron castings, it is frequently necessary to heat treat the castings to remove these carbides. This research was done to determine the optimum temperature and time at that temperature for the complete decomposition, or breakdown, of carbides in ductile iron castings of various compositions. The resulting curves are referred to as Time-Temperature-Transformation, or Isothermal Transformation curves for the decomposition of carbide or cementite.