Difference Between Ductile Iron and Cast Iron (With Table)

Nowadays, Iron Casting Industries have advanced in terms of their techniques and machinery used. Casting is the term used to describe the manufacturing of an element by pouring a liquid substance into the mould, which results in the formation of a solid substance when kept for some time. This process is carried out using heat treatment which involves finishing the solidified substance.

Ductile Iron vs Cast Iron

The difference between Ductile Iron and Cast Iron is that Ductile is less brittle, i.e. it does not break quite easily, whereas, Cast iron is comparatively more brittle. Ductile iron has an amazing bending capability over Cast iron. Cast iron surpasses Ductile iron in terms of vibration damping, which adjusts the natural vibration of a substance quite well.

Ductile iron, otherwise known as spheroidal graphite iron, has become one of the most popular iron alloys these days. It has some interesting properties and capabilities that set its bar high. It is less brittle in comparison and can be bent easily. Also, it does not fracture very easily.

On the other hand, Cast iron is such an iron alloy that it has been there for a long time now. It comes in various types as well. It is harder and brittle. The graphite molecules are an important part of the cast iron since these molecules provide iron its properties.

Comparison Table Between Ductile Iron and Cast Iron

Parameters of ComparisonDuctile Iron Cast Iron
OriginDuctile iron got discovered in 1943. Cast iron got discovered during the 5th Century BC.
TextureIt is relatively softer in texture. It is harder.
Composition Along with Carbon as the primary element, it contains Silicon, Manganese, Magnesium etc. It contains Carbon and Silicon as the primary composition.
BrittleIt is less brittle.It is more brittle in comparison.
ElongationIt can result in around 18 per cent elongation. It only has around 0.5 per cent elongation.
Tensile StrengthIt has more tensile strength. The tensile strength of Cast iron is less.
MachinabilityIt has decent machinability. It has a good one.
WeldabilityIts weldability ranges from low to medium depending on the procedure. It has medium weldability.
PricingIt has priced at higher rates. It has a lower price in comparison.

What is Ductile Iron?

Ductile Iron is a type of Cast Iron that is rich in graphite. It was first discovered by Keith Millis in 1943. But its production didn’t start until 1949. On the 25th of October of that year, Keith Millis, along with Albert Paul and Norman Boden Pilling, got a US patent for iron production. The production was carried out through magnesium treatment.

Ductile iron is one of the most commonly produced iron varieties in the world today. It is composed of Carbon, Silicon and Manganese as primary contents. While Magnesium, Phosphorus, Sulfur and Copper are also present but in negligible amounts. As known, graphite is found in abundance in ductile iron.

The term ‘Ductile’ means a substance that can be easily moulded into a thin wire. This is what ductile iron is. In addition to this, it is less brittle and is capable of tolerating impacts and does not fracture easily. Ductile iron is made to have these features right from the time it comes out of the mould.

The primary application of Ductile iron is for automotive components. Others include diesel trucks, agricultural tractors, oil well pumps etc. Most of the ductile iron is made into ductile iron pipes for water lines in cities as well as localities.

What is Cast Iron?

Cast Iron started to be used for making artefacts in the 5th Century BC. It is a type of iron that has been there for years and has expanded into several varieties over time. A Cast iron is nothing but an iron-type that is first melted and solidified in a mould instead of just being heated and shaped with tools. However, the production of cast iron began unintentionally during a copper smelting session utilising iron ore as flux.

Carbon covers the highest percentage of Cast iron’s composition. The remaining part is covered by Silicon. Silicon is used for stabilizing the graphite molecules in order to maintain the properties of cast iron. Moreover, other elements are added while producing the iron in melted form. But these elements burn out of the molten iron and are not present in the final composition.

There are several varieties of Cast iron, including Malleable Cast iron, White Cast iron and Grey Cast iron. Cast iron is generally brittle, but malleable cast iron remains an exception. Low melting point, great machinability, castability, wear resistance are some of the brownie points of cast iron.

Cast iron is very popularly used as an engineering substance. It has resistance from oxidation damage. Therefore, it is used for various things like pipes, the automotive industry, i.e. cylinder blocks, heads etc. Other machines are also made from Cast iron.

Main Differences Between Ductile Iron and Cast Iron

  1. Ductile Iron is relatively newer in the market when compared to Cast Iron.
  2. Ductile Iron is softer and more flexible than Cast Iron.
  3. Cast Iron is more brittle than Ductile Iron.
  4. Machinability and Weldability of Cast Iron are better in comparison.
  5. Ductile iron has more tensile strength than Cast iron.
  6. Ductile Iron is costlier than Cast Iron.

Conclusion

Iron Casting has been a job for ages. Various types of iron are being produced through this process and are used to make several machines and products in return. Ductile Iron and Cast Iron are the two most common iron types in the market today.

Both these types of iron cater to different needs. Ductile iron can be bent way more easily than Cast iron. It is also less brittle and has better flexibility. However, Cast iron does a better job at machinability, capability and resisting capacity. Cast iron is resistant to Oxidation.

Even Ductile iron is a type of Cast iron, which has some advantages over the previously discovered varieties of Cast iron. It is very similar to Malleable Cast iron. The only difference is that Ductile iron provides the same features at a lower price.

References

  1. https://link.springer.com/article/10.1007/s00170-016-8510-y
  2. https://www.jstage.jst.go.jp/article/isijinternational1989/41/4/41_4_372/_article/-char/ja/
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