Cast iron properties

[sydneyjongleur]

I am a little confused as to the properties of cast iron.

Generally in materials when the hardness increases there is a reduction in toughness, and vice versa. In cast iron the material is very brittle yet the hardness/tensile is also very low. Can you explian this?

Also, one of the properties associated with cast iron is wear resistance and as it is generally a soft material I was wondering how this could be?

 

[Maui]

You are likely referring to gray cast iron, which is the most common form of cast iron. It is characterized by a microstructure that contains flake (lamellar) graphite embedded in a steel matrix. Gray irons can occupy a range of hypoeutectic and hypereutectic chemical compositions, and the flake morphology of the graphite is what leads to the characteristic brittle behavior in this type of cast iron. The flakes act as microscopic stress risers that can induce crack formation, even if the hardness and tensile strength are relatively low.

The wear resistance of cast irons is a different matter, and the answer depends on the type and application.

Maui

http://www.EngineeringMetallurgy.com

 

[sydneyjongleur]

The reason I asked is that it has been previously specified for a fixturing application which is reasonably large, 1000mm outside diameter and 800mm inside diameter. I only reason I can think why it has been used as it is stable??, but as it would be coming into contact with surfaces of other components I couldnt understand why they would use this for good wear characteristics.

I am talking about grey iron but I wouldnt imagine that they would utilise any special grades, I could be wrong though.

 

[swall]

The short answer on wear resistance is that gray iron, by virtue of the graphite flakes, is self lubricating to a considerable extent. But as Maui noted, there are many other factors that come into play.

 

[KENAT]

Sydney,

You might want to avoid multiple posting, site management frowns upon it and it can confuse responders.

thread404-327620

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​