Ductile iron
From Wikipedia, the free encyclopedia
| Iron alloy phases |
|---|
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Austenite (γ-iron; hard) |
| Types of Steel |
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Plain-carbon steel (up to 2.1% carbon) |
| Other Iron-based materials |
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Cast iron (>2.1% carbon) |
Ductile iron, also called nodular cast iron, is one type of cast iron. It was invented in 1942 by Keith Millis[1].
A typical chemical analysis of this material is:
- Carbon 3.3 to 3.8%
- Silicon 2.2 to 2.8%
- Manganese 0.1 to 0.5%
- Sulfur 0.005 to 0.02%
- Phosphorus 0.005 to 0.04%
- Magnesium 0.03 to 0.05%
- balance (i.e., 100% minus the above elements) is the element Iron.
Other elements such as copper, tin may be added intentionally to increase tensile and yield strength while simultaneously reducing elongation.
The unique characteristic of ductile iron is that the graphite forms into a spherical shape, instead of irregular flakes. Sometimes this is referred to as a "nodular" shape. Ductile iron may also be called "nodular iron". This can be achieved by addition of "nodulizers" into the melt. Yttrium was studied as one of the options.
Castings made of ductile iron are used in numerous applications. Examples are in automobile construction, industrial machinery, wind turbine electrical energy generation, valves, air conditioning machinery, lawn & garden equipment, agricultural products and many other types of castings.
For corrosion resistant applications 15% to 30% of the Iron in the alloy may be replaced with varying amounts of Nickel and/or Copper and/or Chromium.
A recent development in ductile iron metallurgy is Austempered Ductile Iron where the metallurgical structure is manipulated through a sophisticated heat treat process.
A large percentage of the annual tonnage of ductile iron produced is used in water and sewer lines. This is called cast ductile iron pipe. Ductile iron pipe is stronger, easier to tap, requires less support and provides greater flow area compared to other materials. In difficult terrain it may be a better choice than PVC, concrete, polyethylene or steel pipe.
[edit] External links
Non-Commercial sites:
de:Gusseisen mit Kugelgraphit it:Ghisa duttile pl:Żeliwo sferoidalne sk:Tvárna liatina
