My steel broke

[Kyle Hayden]

I'm fairly new to blacksmithing, but I've worked with a few types of metal already. Most of them worked very well, but last week I attempted to make a knife out of some sort of steel I found under a bridge (I know, already not the best place to be looking for metal). I heated it up to about a cherry red, because there was a bend that I wanted to flatten out and I figured that would be hot enough just for that. When I hit it, the steel just compleately broke apart, as if I had hit some pottery or something.

The steel was very low carbon (I know from a spark test I did). Could this be the source of the problem? It was also cold that day, so maybe the contract of air and metal temperature made it brittle, although I've never heard of this being the case. Could it just be due to impurities in the steel? 

[ThomasPowers]

Can you tell the difference in a spark test from very low carbon steel and cast iron or wrought iron? (how old is this bridge and the road that uses it?)  It may have had cracks already due to the bending---and why were you trying to make a knife from a low carbon steel in the first place?  Would you practice making pies making mud pies?  Practicing using an alloy suitable for knives is what you need to do.

If you lived in the USA there is a lot of places you can get such alloys free.  Shoot stop by my shop and I'll give you some!

[Daswulf]

Kyle, what Thomas said, and pictures would help. 

My guess is what Thomas mentioned, could have been cast iron or wrought iron. 

[ThomasPowers]

I've found wrought iron buried in the muck under a bridge that served a road that was several hundred years old...the bridge was much newer...

[Will W.]

I have no experience whatsoever with wrought, but it sounds like it could have been cast iron, IMO. 

I second that, Daswulf, pictures would help.