How to Identify hardened steel compared to mild steel
Hardened steel is very durable, but nearly impossible to work with at home. If you are trying to choose a piece of steel and can't tell if it's hardened or not, you're in luck, because this video contains a quick method for doing so. All you do is try to file an indentation in the steel with a file. If that doesn't make a mark, you've probably got hardened steel.