What is Ductile Iron ?
Ductile iron, also known sometimes as nodular iron or
spheroidical graphite (SG) iron, has now been universally
accepted as an engineering material as it combines high
strength to weight ratio, toughness and good machinability.
The spheroidal graphite cast iron manhole cover is around
30% lighter than the gray cast iron.
In 1943, in an
effort to create an iron with better mechanical properties
Keith Dwight Millis made a ladle addition of magnesium (as a
copper-magnesium alloy) to cast iron while working in the
International Nickel Company Research Laboratory. The
resulting castings contained not flakes, but nearly perfect
spheres of graphite. This discovery opened the door to
dramatic new possibilities in metal applications. Ductile
iron offers versatility and high performance at low costs.
Ductile Iron castings have proven to be an effective, lower
cost alternative to malleable iron castings, steel forgings
and steel fabrications. It appears Ductile Iron was invented
with the designer in mind. High Tensile Strength, yield
strength and elongation combine to give Ductile Iron a
superior strength to weight ratio that adds up to more
strength for less expense.
Currently, 80% of automobile crankshafts are ductile iron
castings and this is only the beginning as this portion
represents a fraction of its numerous applications.
addition of magnesium at the molten stage transforms the
microstructure of conventional grey iron of thin flakes to
spheroidical form providing tensile strength that is at
least twice that of grey iron.
formation of graphite during solidification causes an
internal expansion of Ductile Iron as it solidifies. This
property of Ductile iron reduces requirements for feed metal
as well as material and energy requirements, resulting in
substantial cost savings. The use of the most common grades
of Ductile Iron "as-cast" eliminates heat treatment costs,
offering a further advantage.
Ductile Iron Production
castings currently has the capacity to produce 5,000 tons of
ductile iron castings per year. Casting sizes range from
0.500 lb to 2,200 lbs. EDcons foundries produce all standard
grades of ductile iron, from