Well known for its versatility and sustainability, stainless steel is a commonly used material, easily recognized and present in many homes and industries. The name “stainless steel” is a broad term, applying to any metal with a minimum of 10.5% chromium content. There are many types of stainless steel, each given a numerical grade and organized under one of four general groups. These grades are based on the steel’s composition, properties, and uses. Familiarity with grade numbers and groups give quick insight into the steel’s makeup and applications.

The four general groups of stainless steel are austenitic, ferritic, duplex, and martensitic.

Austenitic

As the most frequently used type, austenitic stainless steels possess high chromium and nickel content. Their weldability, strength, and corrosion resistance make them a metal used both for household kitchen cutlery and structural components in the aerospace industry. Unlike ferritic types, austenitic stainless steels are not magnetic.

Types of austenitic stainless steel: 304V, 316LVM, 330, Biodur108, Nitronic 60.

Ferritic

An often magnetic, low nickel material with good corrosion resistance, ferritic stainless steels are a popular material for indoor applications. They are commonly chosen for their resistance to stress corrosion and cracking, particularly in situations that require contact with other corrosive materials. These uses include cookware and car components. Ferritic stainless steel’s cost effectiveness and decreased malleability differentiate them from austenitic types.

Types of ferritic stainless steel: 430, 430FR.

Duplex

Named for its nearly 50/50 composition of austenitic and ferritic, this hybrid is stronger than either of its alloys of origin. This strength gives duplex stainless steels improved corrosion and cracking resistance. Additionally, due to its high ferritic content, it is magnetic. Duplex stainless steels are relatively weldable and well suited for saltwater corrosive conditions, making them useful for the underwater oil industry.

Types of duplex stainless steel: S31803, S32205.

Martensitic

With a structure similar to ferritic, martensitic stainless steels stand apart with their higher carbon content (1%) and greater hardening capabilities. With their high strength and average resistance to corrosion, martensitic stainless steels have a wide range of uses, ranging from surgical instruments to turbine parts.

Types of martensitic stainless steel: 15-5PH, 17-4PH, 416, 420F, 420 MOD, 455, 465.

Stainless steel is well known and frequently used due to its strength, versatility, and recyclability. The four general categories assist in beginning to outline the many compositions and uses for the material.

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Stainless Steel: The 4 Main Types

'Stainless steel' is an umbrella term that covers a range of alloys. To be considered a stainless steel an iron-based alloy must meet the single criterion of containing a minimum of 10.5% chromium. Varying this amount or adding other substances produces different types of stainless steel, each with correspondingly different properties and applications.

Generally speaking, all variations of stainless steel are divided into one of four groups. In this edition of our blog, we present a short guide to these different groups.

• AUSTENITIC. This group contains the most common types of stainless steel. Austenitic stainless steels contain, as compared to other types, a high content of nickel, chromium, molybdenum and chromium. Renowned for their high levels of malleability, strength and corrosion resistance, the austenitic steels are particularly versatile with many thousands of applications.
• FERRITIC. Carbon consistencies in ferritic stainless steel are low, usually not exceeding 0.1%. Primarily consisting of chromium but sometimes with additives such as molybdenum, ferritic stainless steels are magnetic and display excellent resistance to stress corrosion cracking. 
• DUPLEX. Essentially a combination of austenitic and ferritic stainless steels, duplex is stronger than either. It is also extremely resistant to corrosion, making it the material of choice for a number of applications in offshore oil and gas facilities.
• MARTENSITIC. Though structurally similar to ferritic stainless steel, martensitic stainless steel contains much more carbon (around 1%). This difference in carbon percentage gives rise to the key difference: martensitic stainless steels can be hardened to a massive degree, imbuing them with extremely high strength.

Our expert team here at BS Stainless can provide you with all of the information you require when it come to selecting the most appropriate type of stainless steel for any given application: simply get in touch with us for clear, authoritative advice. To stay in touch with all the latest industry news from BS Stainless, please subscribe to our newsletter and follow us on social media (facebook, twitter, linkedin).

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