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. But is steel the strongest material to use for common applications? Yes, there are exotic metals that are stronger but they have more limited uses due to availability and cost. When looking for a viable competitor to steel, consider the strength of ductile iron.
If you compare ductile iron and cast 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
- yield strength
- shock absorption
- abrasion resistance
- corrosion resistance
- impact resistance
When it comes to tensile strength – how much stress a material can handle before it breaks, steel and ductile iron are so close, the differences are irrelevant.
Yield strength (or elasticity) is how much a material can be bent or stretched before it experiences plastic deformation. Here, ductile iron has a slight edge at approximately 40 ksi versus 36 ksi for steel.
When it comes to shock absorption, ductile iron is the clear winner. Ductile iron’s shock absorption capabilities are over six times greater than those of steel.
Ductile iron is used for a number of applications such as crankshafts because it is extremely resistant to abrasion, much more so than steel. The main reason for this is the higher graphite content. As the ductile iron wears away, it creates graphite dust that acts as a lubricant, just like when a Cub Scout puts a little graphite dust on the axel of his pinewood derby car.
Cast steel is far superior when it comes to weldability. Welding steel is fairly simple for anyone with a bit of training in the trade. Ductile iron is more prone to cracking while welding and cooling than is steel. Special training is needed before it can be safely welded. Most of the precautions needed to weld ductile iron center around temperature control to minimize the risk or cracking. The most important of these is ensuring the metal is preheated. Foundries like Faircast Inc. are experts at welding cast iron and know how to handle melding, and what the heat requirements are.
When it comes to corrosion resistance, ductile iron has good properties for most applications but they are roughly equivalent to most kinds of steel. There are different alloys and corrosion-resistant coatings the can be applied to ductile iron that will help to improve resistance high corrosion environments.
Impact resistance is the ability of a material to withstand a large amount of force in a very short amount of time, i.e. to get hit really hard. Ductile iron is actually slightly less impact resistant than steel, making the latter the preferred material for high-intensity applications.
A byproduct of some of the above qualities is the fact that ductile iron dampens vibrations better than steel. This results in a smoother and quieter operation of machinery that makes use of ductile iron versus steel parts.
Some of the best benefits of ductile iron include:
- Lower costs – Always a plus
- Improved cast-ability – Making it easier to use in a variety of applications
- Greater vibration dampening – For quieter operation
- Better corrosion resistance – When treated appropriately
- Superior compressive yield strength – Far superior to steel
- Elasticity – Thanks to those graphite nodules
- Abrasion Resistance – Thanks to its higher graphite content
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.