Materials
Stainless steel is an iron alloy that contains nickel and chromium to protect it against corrosion and rust. Also known as inox steel, this material is remarkably strong and resistant to high temperatures providing optimum performance under severe environmental and chemical conditions. Stainless steel’s inherent physical properties make it ideal for use in the construction, automotive and transportation sectors. Its versatility also makes it a popular material in household items such as kitchen appliances and cutlery.
The demand for stainless steel has doubled in the last ten years, with production increasing to more than 25 million tonnes a year. In this context, the recycling industry has become a vital player in providing a stable supply of quality secondary raw material.
Besides nickel and chromium, other major alloying elements used in combination with steel include; molybdenum, titanium, tungsten and vanadium. These metals are scarce and only available in very few parts of the word, which makes extraction costly and difficult. Recycling is therefore essential to avoid depleting the planet’s natural resources.
Recycling Processes
Most of these special alloys are very similar in appearance. Sophisticated identification technology, including X-ray spectrometry, are used to separate and prepare each type. Recycling stainless steel is a similar process to the one used for other ferrous metals.
Baled metal ready for melting
Trimming shears being used to separate one type of metal from another
- Sorting: Because many forms of stainless steel are non magnetic, this metal cannot be easily separated from other recyclables in a recycling facility with magnetic belts.
- Baling: Stainless steel products are compacted into large blocks to improve ease of handling and transport.
- Shearing: Hydraulic machinery capable of exerting enormous pressure is used to cut thick heavy stainless steel into smaller pieces.
- Media separation: Shredders incorporate rotating magnetic drums to separate ferrous metals from other materials. Further separation is achieved using electrical currents, high-pressure air flow and liquid floating systems.
- Melting: The recovered materials are melted together in a furnace. This process is determined by the level of purity necessary for the future applications of the secondary raw material. The melted stainless steel is then poured into casters and shaped into ingots or slabs. Later on, they can be rolled into flat sheets that are used to manufacture new products.
Applications
Stainless steel is 100% recyclable and loses none of its original physical properties in the process. The most common applications include:
- Construction: The excellent corrosion resistance, strength and malleability allow for the construction of attractive, low maintenance and durable curtain walls and roofs.
- Food storage and production: Stainless steel resists bacteria colonisation, does not alter the taste of foods, and is easily cleaned and sterilised.
- Transport: Passenger rail cars of today's high-speed trains are often constructed of stainless steel which offers structural strength and improved crash protection.
- Healthcare: Most surgical instruments are made of stainless steel because of its strength and resistance to regular cleaning and sterilisation.
- Household: Stainless steel has been traditionally used in cutlery, cookware and appliances.
Recycling Facts
- Recycling one tonne of steel saves 1,100 kilograms of iron ore, 630 kilograms of coal, and 55 kilograms of limestone.
- An average stainless steel object is composed of about 60% recycled material.
- Approximately 90% of end-of-life stainless steel is collected and recycled into new products.
Our Experts
For further information on technical issues, contact our experts working on the Stainless & Special Alloys Commodity Committee: