Preface: I know this is a quite broad question both because the medieval period is a very long period of history and Europe is a freaking continent but I'm interested in all the info I can get (including timelines)
Reason for the question: I am writing fantasy novel in which the protagonist works at a forge for some time. While I don't plan on describing the minute details of their work there I do want to properly represent what actions I do write as they talk or think there.
Question and sub questions: I'm mostly asking for the process from ores arriving at the forge (I assume the smith is the one to refine it) to when it is made into bars/ingots. I'm familiar with the steps after that of heating it until it's white hot and hammering it into shape as well as the quenching process but going from iron ore to steel ingots is baffling me. What tools and machines could they use? What was the most popular method? When were each methods introduced and taken to popularity? Were there risks with any of these? Side effects such as high temperature, dust in the air etc. Which of those would you assume is used in a generic fantasy world (Tolkien inspired fantasy)? Anything else you think I should know about the process or any references I could read?
Little note: Though I only need the general info my curiosity is unquenchable so the more info I get the happier I'll be.
Thanks ahead of time for all of you willing to help here! :)
Hi! I'm a blacksmith and classicist who studies ancient arms and armor, so I have suffered through the pre-renaissance process of making steel. Steel was refined from ore for much the same way (outside of India and Central Asia) from the beginning of the iron age through to the late middle ages.
Basically, you build a big tube on the ground out of clay, fill it with coal, light it up, keep air flowing through it, and dump in the ore. The heat separates the iron from the impurities in the metal, while also absorbing carbon (to make steel). The process is incredibly imprecise and requires the smelters (yes, plural. It takes tons of manpower) to then take the refined iron (now called a "bloom") and put it into a forge. The iron is heated to near melting temperatures ("welding temperature") and hit with hammers to squeeze out more impurities (called "slag") and turn it into a "billet."
The process involves purging the metal of slag and folding it over on itself multiple times while heating it back up to welding temperature to weld it back onto itself.
Often the higher carbon steel (the good stuff for swords, armor, etc) is separated from the lower quality stuff (wrought iron, low carbon steel).
In Central Asia and India, a different process was developed thanks in part to the particular types of clay that allowed them to create crucibles that could handle the heat necessary to bring iron up to a fully liquid temperature. By bringing it to a liquid, the impurities separate from the now VERY high carbon and therefore VERY brittle iron much the same way oil and water separate. Then, the "puck" of steel (called wootz steel by some) is forged out into a bar or whatever shape is needed.
There are plenty of youtube videos detailing both bloomery furnaces (the medieval way) and Wootz steel methods for a more step by step look.
My, have I got the resource for you, as a fellow fantasy writer. You will love the answers listed on u/WARitter's profile here, in particular the ones underneath 'The Manufacture of Armour and Weapons'. Period note, though, he focuses largely on the Late Middle Ages, more plate armour than mail, but there should be enough material there for you to work with.
Apart from the material by u/WARitter mentioned by u/DanKensignton below, you might find some interesting information in the recent response about the 13-14th century metalworking by u/LordIndica in this thread.