1. Definitions

According to the ROBERT dictionary, a steel is "an alloy of iron and carbon (less than 1.5%) which is given various properties (malleability, strength, etc.) by mechanical or thermal treatment".

According to standard NF EN 10020 (which in June 1989 replaced standard NF A 02-025), "steel is a material in which iron is the predominant element, its carbon content is generally less than 2% and it contains other elements; a limited number of chromium steels may have a carbon content higher than 2%, but this 2% value is the common limit content which separates steel from cast iron".

Reading these two definitions, we can see that the upper limit of carbon content for Fe-C alloys that might be called steels (as opposed to cast irons) is tricky to specify. For this reason, it may be preferable to adopt a more metallurgical point of view, taking into...