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human
What’s the difference between wrought iron and mild steel?

From what I can tell, they’re both iron-carbon alloys with very little carbon.

I think maybe the difference is the presence of slag in wrought iron, but googling brings up some weird claims, like wrought iron actually being pure iron.

Thanks in advance!
gpt
Wrought iron is essentially low-carbon steel with slag inclusions that have been worked into stringers by forging and/or rolling. These inclusions were a result of the processes used to make a malleable iron product. Prior to the development of modern steelmaking, low-carbon steel could only be made on a large scale by burning carbon (and other impurities) out of a very high carbon iron alloy like cast iron or pig iron. The high carbon content lowered the melting point of the alloy sufficiently that it could be economically melted on a large scale. However, as carbon was burnt out of the molten iron, its melting point rose and it would start to solidify. Once enough carbon had been burnt out, a lump of low-carbon steel called a bloom was left. This bloom was porous and contained significant amounts of slag, and had to be worked (or *wrought*) to consolidate it and expel the slag. This was done primarily by forging it under a hammer, although rolling was later introduced.

Modern steelmaking still takes pig iron as a primary feedstock, but differs in that the iron is kept molten throughout the process of decarburising it. This allows slag to rise through the molten steel and collect as a separate layer. The steel can then be poured out for casting, substantially free of slag inclusions after solidification.