It is an alloy made from 96%-98% iron, 2%-4% carbon, and small amounts of silicone. It has impressive temperature tolerance, with some cast iron capable of handling temperatures over 2100F (1150C). When it comes to pressure, cast iron's strength depends on its pressure class.
Ductile iron is less brittle than other cast iron, even before heat treatment. It does not fracture as easily with impact. Being ductile allows the iron to bend. In comparison, gray cast iron is harder.