Metallurgy and Roman swords

[XorX]

steel is today defined as Fe + 0,2-2% C, everything with more than 2% C is cast iron (which can not be forged but transferred to steel with the proper technique) so, technically, the romans used steel because most of the "iron" contained more than 0,2%C. no blacksmith with some knowledge in the Fe-C-diagram would use steel with more than 1%C (and no other (modern) alloys contained) for a long thin blade. why should one? the "ideal" C-content for hardening is around 0,8% C (if you have the skills to work with such a material which is not that easy), most blacksmiths use steel with 0.6-0,7%C which is a bit, but not much, over the average C content in early imperial blades. the way of producing the material might have changed but the physical and chemical parameters have not