>>8985
>There could be difference between ore and ore but after they're transformed into iron bars how can anyone say that there's a difference between the Fe atoms forming those bars?

Oh, this is very serious question. German in >>8987 said mostly true things, although different phases not really related to internal tensions as is, it is mostly about crystallic structure, size of grain etc.

Using term "iron" is incorrect, it is all about steel. Steel is actually an alloy, where iron and carbon are required, and other elements, even in small amounts, can do very serious shift in properties. And processing method, temperatures, speed of cooling/heating, time etc - all this can change property of metal seriously.

This was known in past, but not fully, so smiths often got best results by luck and intuition.

t. metallurgy pro