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(Redirected from Grey iron)
'Gray iron' or 'grey iron' was the original "cast iron". It is relatively easy and inexpensive to make. Compared to the more modern engineered irons, gray iron has a lower tensile strength and lower ductility. In other words, it will fail more easily, and its mode of failure will be sudden fracture (it will not bend). It is used for housings where tensile strength is non-critical, such as engine blocks, pump housings, valve bodies, electrical boxes and decorative castings.
In grey cast iron, a large part or all of the carbon is in the form of flakes or nodules of graphites. Graphitic cast iron has a dark gray or almost black fracture. Upon small degree of super cooling, graphite is formed when the cast iron solidifies from its liquid state. Slow cooling promotes graphitisation. Rapid cooling partly or completely suppresses graphitisation and leads to formation of cementite.