"Iron is strong, but not that hard and would wear away quickly."
I was simply making a bit of a joke about progress. Why is the bronze age not called the copper age and why is the iron age not called the steel age?
"Tooth enamel is actually harder than steel and very wear resistant." Really? In which case I would like you to take a bite out of any RSJ you care to choose. That's a rolled steel joist which are not hardened but designed to work well as beams.
Material properties are quite tricky. Hard really means errr hard: a diamond is hard - it can scratch glass. Glass is hard, most steels can't scratch glass. Steel is generally not that hard but can be depending on the alloy (mixture with other elements/etc) Then there are the other material properties such as stiffness, ductility and elasticity and the rest.
Iron is generally brittle so if you make a sword out of just iron it will be quite stiff and look lovely until your opponent smacks it and it breaks. I can give you a load of steels with loads of different properties depending on what you need. The difference between iron on its own and steel is amazing. Pop in a bit of chromium and it resists rusting, for example. Steel is much more than just adding carbon.
Please don't bite any of them - they will destroy your teeth.