Types of Stainless Steel

What is Stainless Steel?

Stainless steel, a kind of steel, is an alloy of iron and chromium. The presence of chromium in stainless steel makes it stainless. It is widely used in constructions as well as in kitchens. As it contains chromium, stainless steel is resistant to stains, rust and corrosion. There are several physical properties of stainless steel. As stainless steel can be easily melted and recycled, it is also environmental friendly. As it is ductile, long lasting and considerably inexpensive as compared to other metals, stainless steel has various applications. Due to this, there are different grades of stainless steel. Let us look at the most common types of stainless steel.

Types of Stainless Steel

According to the chemical properties of stainless steel, it can be divided into five major types and applications.

• Austenitic: Austenitic stainless steel, also known as the 300 series, is the most common and abundantly used steel. It contains 0.15% carbon and 16% chromium, along with other elements like nickel, nitrogen and manganese. It is ductile and also highly resistant to corrosion. Type 304 or T304 is the most commonly used type of stainless steel. It is the classic 18/8 stainless steel. This type of stainless steel is used for making shafts, pumps, etc.
• Martensitic: It is a high carbon containing steel, having a higher carbon level (nearly 1%) and 18% chromium. It also contain other elements like nickel and molybdenum. It can be hardened by heat and also possesses magnetic properties. It is resistant to corrosion but is less durable than austenitic steel. It is mostly used in making molds, surgical instruments and cutlery.
• Ferritic: Both ferritic and martensitic stainless steel types are known as the 400 series. Ferritic steel contains 10.5% carbon and up to 27% chromium. It is less ductile, cannot be hardened by heating, but possesses magnetic properties. It is not tough and less durable than austenitic stainless steel. Ferritic steel can be effectively used in sea water as it is highly resistant to corrosion. It is also used in washing machines and even boilers.
• Duplex: This type of stainless steel is a mixture of microstructures of austenitic and ferritic steel (in a 50/50 percentage ). It contains a higher amount of chromium and a lower amount of nickel. As it is a mixture of the two types of stainless steel, it is tough, resistant to corrosion, stress and may also show some magnetic properties. 'Superduplex' is the best quality of stainless steel and is widely used as it has the highest corrosion resistive properties among all types of stainless steel.
• Precipitation Hardening: This type of stainless steel hardens at a relatively lower temperature. In the initial stage, it is austenitic. Sometimes other elements are added to it in order to make it tougher. Among all the types of stainless steels, precipitation hardened stainless steel can be transformed into different shapes by heating. It is as corrosion resistant as austenitic stainless steel. Although it is prominently used in making aircraft components, it is also used in making shafts and pumps.

Based on these types, stainless steel is graded in about 150 grades, viz. from 100 series up to 600 series. The 300 and 400 series have various types and are widely used. Using and cleaning stainless steel is extremely simple and comfortable. As it has literally no maintenance costs and is highly durable, stainless steel is found nearly everywhere, in every field, be it at home, commercial areas or in industries.