STAINLESS STEEL OVERVIEW: TUTORIAL
How is it made?
Stainless steel is produced in an electric arc furnace where carbon electrodes contact recycled stainless scrap and various alloys of chromium (and nickel, molybdenum etc. depending on the stainless type). A current is passed through the electrode and the temperature increases to a point where the scrap and alloys melt. The molten material from the electric furnace is then transferred into an AOD (Argon Oxygen Decarbonization) vessel, where the carbon levels are reduced (remember stainless has a much lower carbon level than mild steel) and the final alloy additions are made to make the exact chemistry. Exhibit 1 shows the process from melting and casting either into ingots or continually cast into a slab or billet form. Then the material is hot rolled or forged into its final form. Some material receives cold rolling to further reduce the thickness as in sheets or drawn into smaller diameters as in rods and wire.
Most stainless steels receive a final annealing (a heat treatment that softens the structure) and pickling (an acid wash that removes furnace scale from annealing and helps promote the passive surface film that naturally occurs).