Composition[edit]
| Fe | C | Si | Ni | Mn | Mg | Cr | P | Cu |
|---|---|---|---|---|---|---|---|---|
| Balance | 3.0–3.7 | 1.2–2.3 | 1.0 | 0.25 | 0.07 | 0.07 | 0.03 | 0.1 |
Other ductile iron compositions often have a small amount of sulfur as well.
Carbon, 3.2–3.60%
Silicon, 2.2–2.8%
Manganese, 0.1–0.2%
Magnesium, 0.03–0.04%
Phosphorus, 0.005–0.04%
Sulfur, 0.005–0.02%
Copper, <0.40%
Iron, balance
Elements such as copper or tin may be added to increase tensile and yield strength while simultaneously reducing ductility. Improved corrosion resistance can be achieved by replacing 15–30% of the iron in the alloy with varying amounts of nickel, copper, or chromium.
Silicon as a graphite formation element can be partially replaced by aluminum to provide better oxidation protection.[9]
Applications[edit]
Much of the annual production of ductile iron is in the form of ductile iron pipe, used for water and sewer lines. It competes with polymericmaterials such as PVC, HDPE, LDPE and polypropylene, which are all much lighter than steel or ductile iron; being softer and weaker, these require protection from physical damage.
Ductile iron is specifically useful in many automotive components, where strength must surpass that of aluminum but steel is not necessarily required. Other major industrial applications include off-highway diesel trucks, class 8 trucks, agricultural tractors, and oil well pumps. In the wind power industry ductile iron is used for hubs and structural parts like machine frames. Ductile iron is suitable for large and complex shapes and high (fatigue) loads.
Ductile iron is used in many grand piano harps (the iron plates to which high-tension piano strings are attached).
