Thanks, Brian,
I wasn't going to step into the jungle of the various types of CI. Ductile is a common varient as are proprietary recipes like Mehanite, Austempered ductile iron, malleable iron, Ni-hard. Then there is good old fashioned white iron and there are even more. Suffice to say that in the realm of cast metals, cast iron is still king. At least in terms of tonnage poured.
Much of the iron pipe is centrifugally cast and that is an interesting process in its own right.
Likewise the family tree of steels is pretty bushy as well.....