Stoutstien
lunk
Melted iron was well within the technology well before any time that is commonly considered medieval. The largest limiting factor was actually the formation of workable iron stock. the smelting techniques at the time were so inefficient the loss of materials during the process made iron a very precious commodity. Iron itself is actually workable at a relatively low temperature.'Just'?
Melting iron is beyond standard medieval technology.
Then there is the fact there is nothing historically relevant about the level of technology in any DND setting.