Stainless Steel Types

Stainless steel is a common name given to a number of steels with anti-corrosive and anti-staining properties. Right from home, especially kitchen appliances, to the field of construction, stainless steel is a popular choice of metal that does not wear off quickly with rust. It is because stainless steel has a minimum of 10.5% of chromium unlike other steel types. And that 10.5% or more of chromium is what makes the difference, as it prevents corrosion by reacting with oxygen to form a thin and invisible, yet tough layer of chromium oxide film on the surface of the original steel.

Now if you are wondering what if that thin chromium film or coating gets damaged, it repairs itself as long as it reacts with oxygen. Although we are emphasizing on a well-known and much boasted property of stainless steel, we must not ignore the fact that even this alloy can corrode, if it doesn't get enough oxygen to react and form that layer that protects it from corroding and rusting. This could happen with storing of foods in a stainless steel container for a prolonged time, as it prevents the contact from oxygen and results in corrosion. Some of the other common elements that are used in making this alloy include nickel, molybdenum and nitrogen.

Properties and Types of Stainless Steel

There are mainly five types of this metal alloy and more of it has been discussed below.

Austenitic Stainless Steel
This is the most commonly used type and is derived with a mix of nickel, nitrogen and manganese. It is also known for its flexibility that is achieved with the use of at least 7% of nickel content. The properties of stainless steel can further be modified with the addition of elements such as titanium, copper and molybdenum. The structure makes it more suitable for welding etc and can be used to make kitchen sinks, food processing equipment, doors and windows, for roofing, in ovens and making chemical tanks, etc.

Ferritic Stainless Steel
The only major alloying element used to make ferritic stainless steel is chromium wherein the chromium content ranges from 10.5 to 18%. This composition of iron and chromium is found not suitable for fabrication purposes and are more appropriate as a corrosion resistant steel. Ferritic stainless stee is also magnetic and are used to make cooking utensils, domestic or home appliances, vehicle exhausts etc.

Precipitation Hardening Grades
Precipitation hardening grades of stainless steel is mostly used for industrial purposes such as in making aerospace applications, mechanical components, turbine blades and paper industry etc. This grade consists of nickel and chromium both and has a considerably small percentage of copper and niobium in it.

Martensitic Stainless Steel
Martensitic stainless steel types are magnetic but, they are not suitable for welding purposes and can be considered all right when it comes to being corrosion resistant. To name a few typical martensitic stainless steel products would include cutlery, shafts, surgical instruments etc.

Duplex Stainless Steel
Duplex stainless steel has properties of both austenitic and ferritic varieties and therefore the name. It contains a higher percentage of chromium than the nickel content. Duplex stainless steel that contains both austenitic and ferritic steel properties are suitable for tough industrial applications such as in making chemical plants, petrochemical plants, heat exchangers, oil and gas installations, etc.

So these were some basic points on this alloy and I hope the types and properties mentioned in the articles can help you identify and distinguish the different types of stainless steel from each other.