Steel and Hardend Steel

[kermit911]

What is the difference between steel, and hardend steel? Why can steel bend but hardend steel breaks?

[jake-the-peg]

There are many different types of steel not just hardened and mild steel.

The amount of carbon in the steel is important but there are a lot of other factors such as so how quickly it was cooled.

http://www.answers.com/topic/carbon-steel-2 

[stevie21]

My miniscule amount of knowledge on the subject is that adding carbon makes it harder but more brittle.

[Peter Pedant]

Oh Good question, i wanna know as well:

what makes something brittle?

[jidboy85]

Your correct about the "brittle-ness" of steel being asociated with its carbon content.
When steel is first produced, it has a higher carbon content than that of treated steel. This initial steel is not so useful structurally as when tension, torsion is applied to it, it breaks instead bends. Because of this, the steel is treated to produce a lower carbon steel which is more useful as it is less brittle. As mentioned also by jake, the way in which steel is cooled will affect how brittle the metal is as some cooling procedures allow for carbon to be taken back into the metal, which should be avoided.
In the case of metals both "natural" and manufactured alloys, the carbon content of the metal affects its purity and how brittle the metal is. This is why many metals undergo a purification process to remove excess carbon before being used industrially.
Hope this helps.