Formation of a Pearlite Border in Cast Iron Castings.

A pearlite border in cast iron castings is formed under decarburizing conditions. The possibility of graphite precipitation is reduced not only as a result of total dissolution of graphite inclusions in the surface layer during decarburization, but also by partial dissolution of these inclusions, when pores form around the inclusions and contact between the graphite and the matrix is lost. Difficulties in graphite precipitation lead to eutectoid decomposition of austenite into ferrite and cementite and the formation of pearlite in the decarburized layer.