Ductile Iron Casting and its Development
Ductile iron castings are spherical
graphite through spheroidizing treatment, which are of relatively
high mechanical properties, plasticity and toughness, therefore
ductile iron is better than carbon steel in strength.
Chemical composition of ductile iron
carbon content is 3.5~4.0%, silicon content is 2.1~3.1%, the
contents of manganese, phosphorus and sulfur are not more than 1.7%,
and proper amount of rare earth and magnesium.
There are many classifications of ductile iron castings,
according to molding
1. Ordinary sand casting includes green sand mold, dry sand mold and
chemically solidifying sand mold. Ductile iron castings require
relatively high hardness as bearings, thus the castings after
quenching and tempering in low temperature are of high hardness and
toughness, retained lubrication performance of the graphite, and
improved wear resistance.
2. Special casting according to molding materials can be divided
into the natural mineral sand and gravel as the main form of special
casting material (such as investment casting, cement casting,
foundry shell casting, vacuum casting, solid casting, ceramic
casting, etc.) and metal as the main cast of special casting
material (such as metal casting, pressure casting, continuous
casting, low pressure casting, centrifugal casting, etc.).
Production research and development of ductile iron casting
1. Pearlite ductile iron cast crankshaft and ferrite ductile iron
car base indicate that China’s ductile iron production reaches a
high level. Meanwhile the applications of outsourcing
desulfurization, double melting method, instantaneous birth, audio
analysis and fast thermal analysis narrow the gap between Chinese
automotive castings technology and international advanced
2. The process of forced cooling, solidification and delayed birth
can prevent graphite distortion in the center of ductile iron and
3. In the early of 1970s, austenitic-bainitic ductile iron has been
used, and the tensile strength of this material can be reach
1000MPa, thus it is widely used in gear and structural parts, and
has higher economic and social benefits.
4. The ductile iron pipe foundry whose annual production gets to 90
tons gives to birth and the casting production line of ductile iron
pass inspections by the state inspection center.
5. According to the mechanical properties researches of rare earth
magnesium ductile iron, it is of high stress-strain properties,
shock resistance and fracture toughness, therefore it is widely put