Is Ductile Iron Stronger than Steel?

When we think of strength, we think of steel. Superman, the Man of Steel. To steel, yourself means to gather your strength. So, are there materials that are stronger than steel? It depends on what you’re using the material for. When comparing ductile iron vs steel, ductile iron might be better (stronger) for the job at hand.

If you compare ductile iron vs steel, based on their unique properties you should be able to make a determination as to which alloy is better for what application. Let’s consider the following elements that allow us to compare and contrast the capabilities of both steel and ductile iron.

  • tensile strength
  • shock absorption
  • abrasion resistance
  • weldability
  • corrosion resistance
  • impact resistance

Let’s look at each of these elements and properties of both.

Tensile Strength – Ductile Iron vs Steel

Ductile Iron has the edge when it comes to tensile strength. While the difference is marginal, when it comes to tensile strength, ductile iron has the greater yield strength – 40 KSI. However, the difference is not great.  Cast steel can only reach 36 KSI yield strength.

Something to note is that as the strength of ductile iron increases it’s ductility decreases

Shock Absorption

When it comes to shock absorption, ductile iron is the clear winner. Ductile iron has far superior shock absorption than does steel.  The damping capacity for ductile iron is 6.6 times greater than SAE 1018 steel on average. So, that’s a significant difference.

Abrasion Resistance

Ductile iron is a great choice when in use one mechanisms that have a higher abrasive wear factor.   It offers higher abrasion resistance than cast steel and is typically used for things like engine crankshafts when the wear factor is very important for the longevity of the part. This abrasion resistance can be explained, in large part, to the high volume percentage of graphite in ductile iron which creates a kind of graphitic lubricant.

So, when the need is higher for abrasion resistance for abrasive wear mechanisms, austenitic ductile iron grades are the better choice for wear resistance as well as greater strength.

Weldability

Okay, so when it comes to weldability, cast steel is the better choice.  To properly weld ductile iron, you have to be aware of the proper welding techniques. Foundries like Faircast Inc. are experts at welding cast iron and know how to handle melding, and what the heat requirements are.

Corrosion Resistance

When it comes to corrosion resistance, ductile iron is superior to unalloyed steel, and, depending on the environment at hand, can even be superior to highly alloyed steel.  The corrosion resistance of ductile iron can be improved when the corrosion mechanism is understood and when alloying the material properly.

Impact Resistance – Ductile Iron vs Steel

In general, when considering Ductile Iron vs Steel, ductile irons offer good impact resistance but the impact resistance properties of ductile iron are dependent on its microstructure. Its impact resistance depends on the degree of ferritization in the microstructure. So, it’s important to know that Type A395 ductile iron is fully ferritic. However, cast steel would be more consistent because of its homogeneous microstructure.

Here are some more engineered applications where ductile iron is the best choice due to it’s greater strength and ductility:

  • Pumps
  • Cable drums
  • Gearboxes
  • Frames

Some of the best benefits of ductile iron include:

  • Lower costs (everyone loves that) – Considered superior to steel
  • Improved cast-ability – Considered superior to steel
  • Greater vibration dampening – Considered superior to steel
  • Better corrosion resistance – Considered superior to steel
  • Superior compressive yield strength – Far superior to steel
  • Elasticity – Considered slightly superior to steel
  • Corrosion Resistance – Considered superior to steel
  • Wear Resistance – Can be superior to steel dependent on wear mechanisms

When considering using ductile iron for any project or application, please contact our representatives at Faircast Inc. Our engineers are always happy to speak with you and get you on the right track.

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