What is Stainless Steel?
Stainless steel is a corrosion-resistant alloy of iron, chromium and, in some cases, nickel and other metals.
Completely and infinitely recyclable, stainless steel is the “green material” par excellence. In fact, within the construction sector, its actual recovery rate is close to 100%. Stainless steel is also environmentally neutral and inert, and its longevity ensures it meets the needs of sustainable construction. Furthermore, it does not leach compounds that could modify its composition when in contact with elements like water.
In addition to these environmental benefits, stainless steel is also aesthetically appealing, extremely hygienic, easy to maintain, highly durable and offers a wide variety of aspects. As a result, stainless steel can be found in many everyday objects. It also plays a prominent role in an array of industries, including energy, transportation, building, research, medicine, food and logistics.
Composition of Stainless Steel
Steel is an alloy of iron and carbon. Stainless steels are steels containing at least 10.5% chromium, less than 1.2% carbon and other alloying elements. Stainless steel’s corrosion resistance and mechanical properties can be further enhanced by adding other elements, such as nickel, molybdenum, titanium, niobium, manganese, etc.
Reaction to Contact with Air, Humidity or Water
On contact with oxygen, a chromium oxide layer is formed on the surface of the material. This passive layer protects it and has the unique ability to repair itself.
General Properties of Stainless Steel
Stainless Steel Families
With five categories of stainless steels available – each differentiated by the alloying elements added to iron, carbon and chromium – we offer a complete range of solutions.
- Austenitics or 300 series
0.015 to 0.10% carbon, 16 to 21% chromium, 6 to 26% nickel, 0 to 7% molybdenum. The presence of nickel improves corrosion resistance in certain media and makes stainless steel more ductile. The presence of molybdenum further enhances the resistance to corrosion in an acid medium. The most common grades are 304/304L and 316/316L.
Boiler market, aeronautics, electronic components, railway equipment, tubes, chemical tanks and food vats, marine applications, containers, etc.
- Heat resistant steel applications
Heating systems, resistor jackets, furnace equipment.
- Austenitics with manganese or 200 series
These are chromium manganese steels, with a low nickel content (always below 5%).
Asphalt tankers, tubes, food containers, silos, conveyor chains, safety soles, etc.
- Ferritics or 400 series: the KARA ferritic offer
0.02 to 0.06% carbon, 10.5 to 30% chromium, 0 to 4% molybdenum. Commonly used internally, these grades are now being developed for envelope and structural products.
- KARA is the Aperam brand for ferritic stainless steels
Unlike other stainless steels, the KARA range doesn’t contain nickel and is thus immune from the erratic price fluctuations of this alloying element. As a result, prices are more stable over time, giving KARA a strong argument in the construction sector where project cost and economic design are key elements.
Car exhaust systems, conveyor chains, cooking utensils, boilers, domestic appliances, trim, dishware, heating, hot water tanks, tubes, etc.
- Austeno-ferritics or Duplex
0.02% carbon, 0 to 4% molybdenum, 1 to 7% nickel and 21 to 26% chromium. These stainless steels not only offer excellent quality, because of their low nickel content – a material that suffers from highly speculative prices – they are also very cost effective.
Oil, gas, pulp and paper, desalination sectors, chemical industry, etc.
0.1% carbon, 10.5 to 17% chromium.
Cutlery, cutting tools, hand tools, springs, etc.