BU DUCTILE CI is spheroidal graphite (nodular) ductile iron. Ductile irons differ from the grey irons in that the graphite occurs as spheroids or nodules instead of flakes. The resulting material has generally higher strength than grey iron, is ductile rather than brittle, tough and readily machined. Grade is an essentially ferritic grade, having high elasticity and resistance to impact, suitable for applications involving thermal and mechanical shock. It can be welded but cannot be readily flame or induction hardened.