Stainless Steel: Types, Properties, and Application

What is Stainless Steel?

Stainless steel is a group of iron-based alloys that contain a minimum of approximately 11% chromium, a composition that prevents the iron from rusting and also provides heat-resistant properties. Specific types of stainless steel are often designated by a three-digit number, e.g., 304 stainless.

Stainless steel is a corrosion-resistant alloy made from iron, chromium, and in some cases nickel and other metals.

Stainless steel is completely and infinitely recyclable and the “green material” par excellence. In fact, the actual rate of recovery within the construction sector is close to 100%.

Stainless steel is also environmentally neutral and inert, and its durability ensures that it meets the requirements of sustainable building. In addition, it does not leach compounds that could change their composition when they come into contact with elements such as water.

In addition to these environmental advantages, stainless steel is also aesthetically pleasing, extremely hygienic, easy to care for, extremely durable, and offers a multitude of aspects. As a result, stainless steel is found in many everyday objects.

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It also plays a prominent role in a number of industries including energy, construction, research, medicine, food, transportation, and logistics.

Check out another article: What is Steel?

Composition of Stainless Steel

Steel is an alloy of iron and carbon. Stainless steels are steels that contain at least 10.5% chromium, less than 1.2% carbon, and other alloying elements. The corrosion resistance and mechanical properties of stainless steel can be further improved by adding other elements such as nickel, titanium, niobium, molybdenum, manganese, etc.

Reaction to Contact with Air, Humidity, or Water:

On contact with oxygen, a chromium oxide layer is formed on the surface of the material. This passive layer protects it and has the unique ability to repair itself.

Properties of Stainless Steel

1. Aesthetics

Stainless steel has a wide variety of finishes, from matte to bright, including brushed and engraved. It can be embossed or tinted, making stainless steel a unique and aesthetic material. It is widely used by architects for building envelopes, interior design, and street furniture.

2. Mechanical Properties

Compared to other materials, stainless steel has strong mechanical properties at ambient temperatures – after all, it is steel! In particular, it combines ductility, elasticity, and hardness, which allows it to be used in difficult forming modes (deep stamping, flattening, extrusion, etc.) while providing resistance to heavy wear (friction, abrasion, impact, elasticity, etc.). In addition, it offers good mechanical behavior at both low and high temperatures.

Check out the article: Mechanical Properties of material

3. Resistance to Fire

Stainless steel has the best fire resistance of all metallic materials when used in structural applications, having a critical temperature above 800°C. Stainless steel is ranked A2s1d0 for fire resistance with no toxic fume emissivity.

4. Corrosion Resistance

With a minimum chromium content of 10.5%, stainless steel is continuously protected by a passive chromium oxide layer, which naturally forms on the surface through the reaction of chromium with oxygen from air or water. If the surface is scratched, it regenerates itself. This special feature gives stainless steel its resistance to corrosion.

5. Cleanability

Stainless steel objects are easy to clean, common cleaning agents (detergents, soap powder) are sufficient and do not damage the surface. Stainless steel fully meets the requirements of decorative and cooking utensils that require frequent and effective washing.

6. Recycling

Stainless steel is the “green material” and is infinitely recyclable. Within the construction sector, the actual recovery rate is close to 100%. It is environmentally neutral and inert when in contact with elements like water, and it does not release compounds that could change their composition.

These properties make stainless steel ideal for building applications that are exposed to adverse weather conditions, such as roofs, facades, rainwater recovery systems, and service water pipes. The longevity of stainless steel meets the requirements of sustainable building. Effective assembly, installation, and low maintenance guarantee the user an unsurpassed service life.

Types of Stainless Steel

Stainless steel is generally divided into four distinct groups:

  1. Austenitic. The austenitic group includes the most common types of stainless steel. Compared to other types, austenitic stainless steels contain higher contents of chromium, molybdenum, and nickel. They are particularly versatile and known for their excellent strength and malleability.
  2. Ferritic. Ferritic stainless steels contain between 10.5% and 30% chromium and typically have a low carbon consistency of no more than 0.1%. Ferritic stainless steels are magnetic and are selected primarily for their resistance to temperature oxidation and stress corrosion cracking.
  3. Duplex. Duplex stainless steel combines the austenite with the ferrite, resulting in a metal that is stronger than both: this higher strength can result in significant weight reductions. Due to its excellent corrosion resistance even in demanding environments, it is perfect for use in marine applications.
  4. Martensitic. Structurally similar to ferritic stainless steel, but with an increased carbon content (up to 1.2%), martensitic stainless steel can be hardened to a large extent. They are particularly useful for creating medical tools and surgical instruments.

Application of Stainless steel

Most often, stainless steel is used for applications that require the unique properties of steel as well as corrosion resistance. You can find this alloy milled in coils, sheets, plates, rods, wire and tubes. It is the most commonly processed:

  • Culinary uses: Kitchen sinks, Cutlery, Cookware
  • Surgical tools and medical equipment: Hemostats, Surgical implants, Temporary crowns (dentistry)
  • Architecture (pictured above: Chrysler Building): Bridges, Monuments and sculptures, Airport roofs
  • Automotive and aerospace applications: Autobodies, Rail cars, Aircraft

FAQs.

What is stainless steel?

Stainless steel is a group of iron-based alloys that contain a minimum of approximately 11% chromium, a composition that prevents the iron from rusting and also provides heat-resistant properties. Specific types of stainless steel are often designated by a three-digit number, e.g., 304 stainless.

What is the composition of stainless steel?

Stainless steels are steels containing at least 10.5% chromium, less than 1.2% carbon, and other alloying elements. Stainless steel’s corrosion resistance and mechanical properties can be further enhanced by adding other elements, such as nickel, molybdenum, titanium, niobium, manganese, etc.

What are the properties of stainless steel?

These factors mean stainless steel can be more economically viable once service life and life-cycle costs are considered.
1. Properties
2. Corrosion Resistance.
3. Cryogenic (Low Temperature) Resistance.
4. Work Hardening.
5. Hot Strength.
6. Ductility.
7. High Strength.
8. Magnetic Response

What are the types of stainless steel?

Types of Stainless Steel:
1. Austenitic Stainless Steel
2. Ferritic Stainless Steel
3. Duplex Stainless Steel
4. Martensitic Stainless Steel