We have already seen a lot about Ductile Iron also called SG iron, spheroidal graphite, nodular cast iron, spheroidal graphite cast iron a cast iron type created in 1943 by Keith Millis in our previous blogs. Many types of cast iron are brittle, but Ductile Iron (DI) shows a high level of fatigue and impact resistance because of its nodular graphite additions. The most basic application of ductile iron is in the area of manufacture of water and sewer lines, but there is a range of applications of ductile iron castings in varied market segments. It can also take on polymeric materials including polypropylene, PVC, LDPE and HDPE which are comparatively light-weight than ductile iron or steel. As it is more flexible, these need extra protection and coverage from physical damage or loss.

Chemical Make-Up of Ductile Iron
Ductile Iron isn’t a single material but made of a number of materials that can be produced using an array of properties by controlling their microstructure. A common characteristic that defines this material group is the structure of graphite. In SG iron, graphite assumes the structure of nodules instead of flakes as in the case of grey iron. Whilst the sharp graphite flakes can produce stress concentration points within the material matrix, the rounded nodules in SG iron prevent the formation of cracks, therefore offering an increased ductility that lends its name.

Addition of modulizing elements, generally magnesium (note magnesium’s boiling point is 1100°C and the melting point of iron is 1500°C) and, not that frequently now, cerium (normally in Mischmetal form) leads to nodule formation. Tellurium has also been applied.

Check out for “magnesium fade” when making nodular iron castings. Nodularity depends upon time, and therefore the timing of the addition of the inoculant to the molten metal to when the metal cast is imperative for the maintenance of the required metal properties.

The “Austempered Ductile Iron” (ADI) was developed in the 1950’s but was later commercialized in the marketplace. In Austempered Ductile Iron, the metallurgical structure is subjected to manipulation through a high-level heat-treatment process. The name’s “aus” portion is referred to as ‘austenite'.

We are one of the leading Foundries in India dealing with a number of industrial applications using Grey Iron and SG Iron castings. Talk to us for any enquiries.