I was doing some research on the composition of historical blade materials and I found out that a lot of the iron they used contained a lot of phosphorus, between .4 and 1.4%. It also seems like they used it on purpose for pattern welding.
Here's the links to some articles:
So my question is: wouldn't that much phosphorus make the metal extremely brittle? I've read that phosphorus increases hardness but reduces toughness/ductility but I don't know to what extent. I guess what I'm asking is how a high phosphorus (e.g. 1% )steel or iron would compare to other materials and if it's still strong enough to be useful to a blacksmith.