Chilled cast iron. Iron-carbon alloy with low graphitization factor so that chill occurs forming a graphite-free structure.
In order to achieve chilling, the silicon content is set to a low level depending on the wall thickness of the casting; the carbon content is approx. 2.5 to 3.8%.
Cobalt improves strength at high temperatures and magnetic permeability.
Increases hardness, also allows for higher quenching temperatures (during the heat treatment procedure). Intensifies the individual effects of other elements in more complex steels. Co is not a carbide former, however adding Cobalt to the alloy allows for higher attainable hardness and higher red hot hardness.