What is Stainless Steel?- Types, Properties, 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.

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.

  • Properties
  • Corrosion Resistance.
  • Cryogenic (Low Temperature) Resistance.
  • Work Hardening.
  • Hot Strength.
  • Ductility.
  • High Strength.
  • Magnetic Response

What are the types of stainless steel?

Types of Stainless Steel:

  • Austenitic Stainless Steel
  • Ferritic Stainless Steel
  • Duplex Stainless Steel
  • Martensitic Stainless Steel

What metal is stainless steel?

Stainless steel is a corrosion-resistant alloy of iron, chromium and, in some cases, nickel and other metals. Completely and infinitely recyclable, stainless steel is the “green material” par excellence.

Is stainless steel good quality?

Stainless steel is a durable and affordable metal that is used for a wide variety of purposes. It’s strong, making it perfect for construction purposes, and its corrosion-resistant, so it can last a long time without being replaced or breaking.

What are the 3 types of stainless steel?

The Three Primary Types of Stainless Steel

  • Austenitic stainless steel. There are two main characteristics of this type of stainless steel.
  • Ferritic Stainless Steel. This type of stainless steel is the second most common type of alloy and is also magnetic.
  • Martensitic Stainless Steel.

Can stainless steel rust?

In summary, stainless steel does not rust because it is sufficiently reactive to protect itself from further attack by forming a passive corrosion product layer. Other important metals such as titanium and aluminum also rely on passive film formation for their corrosion resistance.

What is the purpose of stainless steel?

Stainless steel is popularly used for cookware, kitchen utensils and cutlery. This is because it’s hardwearing, corrosion-resistant, and it doesn’t affect the flavor of the food when used for food storage or production. Due to the resistance level, foods with high acidity won’t cause damage.

Is stainless steel man made or natural?

Steel is what is known as an alloy, meaning it is not naturally found but instead is man-made, composed from a combination of different materials and metals.

What is difference between steel and stainless steel?

The difference between steel and stainless steel is that during the process of making steel into stainless steel, chromium, nickel, nitrogen, and molybdenum is added to make stainless steel. Stainless steel is resistant to corrosion, and steel is prone to stains and rust.

Is stainless steel toxic?

Please note that stainless steel does not contain hexavalent chromium (VI), which is a highly toxic carcinogen. Manganese is an essential trace nutrient in all forms of life. The form of manganese used in industrial applications is considered toxic at levels above 500 micrograms.

What is the highest quality steel?

304 stainless steel is the most common form of stainless steel used around the world due to its excellent corrosion resistance and value. 304 can withstand corrosion from most oxidizing acids. That durability makes 304 easy to sanitize, and therefore ideal for kitchen and food applications.

Which stainless steel is cheapest?

Common ferritic grades include the proprietary grade 430 stainless steel and the cheapest stainless steel, grade 409 stainless steel. 409 stainless steel is the material of choice for automotive exhausts due to its combination of low price, corrosion resistance and excellent formability.

What’s the strongest stainless steel?

Even among steel alloys, grade 304 stainless steel is noteworthy for its high tensile strength—roughly 621 MPa (90 ksi). Like most stainless steel, grade 304 has a high maximum operating temperature (about 870˚C).

Is stainless steel or aluminum better?

Aluminum is about one-third of the weight of stainless steel – hence the reason it’s used in industries such as airplane and bicycle manufacturing. You’ll also find aluminum sheets widely used in the automotive sector. So, although Stainless steel is stronger, the strength-to-weight ratio of aluminum is much better.

Can stainless steel scratch?

It’s an excellent choice for cookware, kitchen appliances, sinks, fixtures, and other items around the house and workplace. Unfortunately, whether it’s a microwave, dishwasher or refrigerator, stainless steel can become scratched. You don’t have to live with scuffed up steel forever, though!

Can stainless steel go in water?

Stainless steel is waterproof and lasts longer than other metals used as jewelry. When you’re caught in the rain, you don’t need to fret. It won’t rust or get tarnished. All you need to do is to wipe up the water with a soft lint-free cloth.

Does stainless steel turn green?

Stainless steel will not tarnish and turn your finger green as long as the materials are of high quality and it’s made with at least 12% chromium. Not all rings are up to such standards, so be careful where you buy your jewelry.

Why stainless steel does not rust?

Stainless steel is a steel alloy that contains a minimum chromium content of 10.5%. The chromium reacts with the oxygen in the air and forms a protective layer that makes stainless steel highly resistant to corrosion and rust.

Who invented stainless steel?

Harry Brearley, Elwood Haynes, Robert Forester Mushet, and that’s how Harry Brearley discovered stainless steel well, not quite. During the 5-year period between 1908 and Brearley’s discovery in 1913, many other scientists and metallurgists have potential claims to Brearley’s title.

Which is stronger titanium or steel?

When compared to steel in a strength-to-weight ratio, titanium is far superior, as it is as strong as steel but 45% lighter. In fact, titanium has the highest strength-to-weight ratio of all known metals.

How can you tell if its stainless steel?

If you grind a bit of the item in question on a grinding wheel and it throws a “glow” of sparks, then it is steel. If it is non-magnetic and gives off sparks, the item is most likely made of a 300-series grade of stainless steel.