This Wiki about steel should give you a brief overview into pig iron production and subsequent steel production.
The exact date when people developed the technique of melting iron and produced usable metal is unknown.
Iron and Steel
Steel is a mixture of iron with other elements. These elements are called alloying elements and the resulting product is an alloy.
Pig Iron Production
Iron ore and coke are needed to produce pig iron in the blast furnace. Iron ore can contain admixtures.
After leaving the blast furnace, the pig iron still contains many impurities.
After production, the steel usually does not yet have the properties required for the intended use.
Die Friedrich Krupp AG meldete im Jahr 1912 ein Patent für einen Stahl an, der besonders für die Herstellung von korrosionsbeständigen Produkten geeignet war.