Steel vs Ductile Iron

WHY IS DUCTILE IRON COST LOWER THAN STEEL?

Two factors determine this significant difference in cost:

1- Temperature required

First, steel must be poured at a much higher temperature than ductile iron, which demands greater energy expenditure for an equivalent part.

2- Shrinkage

Another reason of this substantial cost difference is caused by what is called shrinkage. When a metal cools, it shrinks. To avoid creating porosity due to shrinkage, smelters use risers containing metal that will remain in fusion longer than the actual part, providing it with the metal necessary to avoid creating porosity. Using these risers necessitate melting more metal thus using more energy.

With ductile iron, the needed risers are much smaller thanks to the graphite precipitation phenomenon. This brings the cost of ductile iron cast lower than one made of steel.