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Stainless Steel

Stainless Steel


Stainless steels are corrosion-resistant, high-performance alloys that contain at least 11% chromium. A passive chromium-rich oxide film forms naturally on the surface of the steel, protecting the metal from a wide range of corrosive media. The film’s ability to quickly self-restore in the presence of oxygen allows any damage by abrasion, cutting or machining to be quickly repaired.

Production

Stainless steel is produced in an electric arc furnace (EAF). A current is passed through carbon electrodes, which contact the recycled stainless scrap and various alloys, causing the temperature to rise to a point where the scrap and alloys melt. The molten material is then transferred to an argon oxygen decarbonisation vessel, where the carbon levels are reduced and the finishing alloys are introduced to create the precise chemistry. Next, the product is either cast into ingots, or slab or billet form, followed by a hot-rolling process. Some material receives cold rolling to reduce the thickness of the sheets even further, or is drawn into smaller diameters to produce rod and wire products.

Most stainless steel receives a final heat treatment called annealing to ‘soften’ the structure. The final process is pickling, an acid wash that removes surface impurities and helps foster the inert chromium film that coats the surface of stainless steel.

Sustainability Credentials

Stainless steel is attractive, and boasts excellent corrosion resistance, good mechanical properties, low maintenance requirements and long life. If the appropriate stainless steel and surface finish are selected the material will maintain functionality over the service life of an engineering structure, which can span more than a century. Over the past 50 years, the use of stainless steel has grown at an average rate of almost 6% per year. Globally, close to 20 million tonnes of stainless steel are consumed annually – approximately 12% of this by the building and construction industry.

At the end of its useful life, stainless steel is fully recyclable – scrap is fed back into the EAF for remelting back into stainless steel, a process that can continue indefinitely. It is estimated that 80% of stainless steel is recycled at the end of its life. The EAF is highly efficient at processing scrap stainless, ensuring that new stainless steel has an average recycled content of more than 60%. The EAF also has a low environmental impact in terms of both CO2 and other emissions.