Stainless steel is an immensely popular steel alloy that is highly prized for its resistance to corrosion and used in a variety of ways, including cutlery, medicine and jewelry. There are different types of stainless steel and the type will depend on what has been added to it. The fact that different varieties can be formed gives this an alloy an immense versatility which explains its popularity and suitability for a wide number of applications.
Austenitic stainless steel can also be referred to as the 300 series and is formed by adding 18% chromium and 8% nickel. Over 70% of stainless steel production is for austenitic steel and it is popularly used in kitchens and food processing equipment due to its excellent hygiene properties.
Ferritic stainless steels are usually cheaper and often have better engineering qualities than austenitic. They can contain up to 27% chromium and their high resistance to corrosion means they can be used in severe environments, such as being submerged in seawater for prolonged periods of time, although austenitic is still more durable.
Less durable than ferritic and austenitic steels, martensitic was one of the first to be commercially produced and is still very strong. It contains up to 18% chromium with a very low amount of nickel and molybdenum. High temperatures can make it harder and it has commonly been used in cutlery, as well as pins and surgical instruments.
Duplex stainless steels are a mix of austenitic and ferritic, or at least the components that make them. The mix is usually half and half, although it can be slightly more weighted to in a 60/40 split, and has a high chromium content of up to 32% as well as low nickel and usually around 5% molybdeneum. The best qualities of each type show up in this version, which is highly resistant to corrosion, more so than any other variety, as well as strong and sometimes magnetic. Standard duplex is the variety most widely used but super duplex also exists which is considered the very best quality of stainless steel.