What is Stainless Steel?

Among the most requested and used materials in the world of manufacturing screws, bolts, and fasteners, stainless steel is an iron-based alloy particularly resistant to corrosion. Also known as stainless steel, it is a material composed of 50% iron, nickel, chromium, and molybdenum.

Although the term stainless is used to generally define this material, not all steel is the same. In the following paragraphs, we will define the substantial differences and types that can be found.

What is the difference between steel and stainless steel?

The main difference to underline is between steel and stainless steel. This distinction mainly depends on the composition of the steel and, therefore, the percentage of elements that make up the material. For example, the composition of stainless steel is characterized, as already mentioned, by 50% iron and 12% chromium.

The latter is the main component from which the material's resistance to corrosion derives, a fundamental reason for its wide use and advantages.

During production, indeed, the addition of chromium among the elements creates a protective surface that prevents moisture and air from oxidizing the material. From this process derives the appellation of stainless.

How many types of stainless steel are there?

Different compositions among the elements mean different grades of stainless steel (there are over 100), classified into 5 main types:

Ferritic, corrosion-resistant type, is used, for example, in internal architecture works.
Martensitic, very strong and durable type, though less resistant to corrosion, is used for producing turbine blades and knives.
Duplex, a type that combines ferritic and austenitic steel, is a material widely used in the paper, shipbuilding, and cellulose industries.
Semi-austenitic, also known as precipitation hardening, is very strong since it is composed of an aluminum, niobium, and copper alloy.
Austenitic, the most used type for its temperature management capability, finds application in construction, shipbuilding, architecture, and the production and installation of industrial pipelines. This steel is also known for the two most commercially widespread types: A2 and A4 stainless steel, materials with a non-corrosive nature and very broad applicability, which we talked about in a previous article.

What is the difference between 304 and 316 steel?

When discussing the different types and characteristics of stainless steel, a necessary deep dive is between 304 and 316 steel, the two main types of stainless steel and among the most sought after. Thanks to the presence of 2-3% molybdenum, they are highly resistant to corrosion and provide anti-rust protection.

In detail, stainless steel AISI 304 can be used both indoors and outdoors and is generally considered the most common austenitic steel. As for 316 stainless steel, it can be used in challenging environments, such as the sea or pools, but may rust if not regularly maintained. One type is not better than the other, but the right choice depends on the field of application: each steel, for heat and corrosion resistance, has a very specific destination.

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