When you put salt into water you no longer have fresh water.

We in the real world make a distinction between fresh water, brackish water and salt, or seawater. They are all water but are different enough to the creatures that live in them to be distinguished. You cannot for example put a cichlid in a marine tank and expect it to survive even though the salt is only in suspension in the water. A fish that breads in the brackish water at the mouth of a tributary can no longer propagate if the flow of runoff to the sea becomes restricted and the water becomes too salty. Their are exceptions to this, like the Salmon but that is not the norm. And even though the human body needs both water and salt to survive, one can not drink salt water.

In today’s world we make distinctions between materials and products with naming conventions. If you take a pound of iron to the recycler you will get a different price than if you take a pound of high carbon steel. We give them different names because they have different properties and are used for different things.

To a new age black smith who, through his art is keeping an ancient tradition and skill alive there is a world of difference between steel and an iron blades.

Beyond the transformation from pig iron to steel there are other processes that change the very nature of steel without changing it more than very slightly on the elemental level. Carbon steel can be case hardened (surface hardened) and with the addition of traces of manganese and silicon can be further hardened by heat treatment.
Steel can be hardened by quenching from high temps in a variety of different bathes, brine, oil etc. It can be aged at very low temperatures to impart different qualities to it like better machining characteristics etc. All these steps change the steel and with every change the nomenclature of the steel changes also.

When we order a tube set for a bike we ask for 4130, Tange, Prestige etc. we don’t ask the supplier for some iron tubes. Even angle iron isn’t really iron, it is low carbon steel.

If you call a steel supplier and say I want steel, they will ask if you want cold rolled or hot rolled steel. If you ask for iron, they will most likely say we don’t carry iron pipe try a pluming supply. If it is a very large supplier and they do carry iron product, the question then becomes do you want cast gray (graphite flakes added for machinability) or cast ductile iron (nodular iron, or SG iron for strength). Cast iron is the nomenclature for Fe that has been alloyed with carbon and silicon and has graphite added. It is supplied as cast.