[Bill Douglas]

At high school we had a full on engineering class. We had lathes that had been used for making heavy artillery guns in WW2, new lathes, milling machines, welding equipment and a forge.

Teacher had us heating bright mild steel in the forge, hammering it out on anvils and then dipping it into a container of carbon. This was case hardening schoolboy style. Just like the Chinese (must be bad AI - my apologies Japan ) did with their sammy swords but folded it lots of times.

The carbon was some product specifically for the steel type.