What is Stainless Steel & What is it Used For?

Stainless steel is a strong, corrosion-resistant alloy essential in industries ranging from construction and automotive to oil and gas and medical equipment. Its versatility and durability make it an irreplaceable material for applications in extreme and everyday environments.

In this guide, we’ll explore the types, properties, and grades of stainless steel, its manufacturing process, and the benefits of high-performance stainless steels for demanding applications.

What is Stainless Steel?

Stainless steel is a type of iron-based alloy containing at least 10.5% chromium, which forms a protective layer on its surface, preventing rust and corrosion. Other elements, such as nickel, molybdenum, carbon, and nitrogen, enhance its performance, making it suitable for a variety of environments.

With its superior mechanical properties and resistance to extreme temperatures, stainless steel is often chosen for both structural and decorative applications.

Key Properties of Stainless Steel:

• Corrosion resistance: Withstands exposure to moisture, acids, and chemicals.
• High tensile strength: Greater than regular steel, making it ideal for structural applications.
• Hygienic and easy to clean: Suitable for food and medical environments.
• Aesthetic appeal: Polished, sleek finish for architectural and consumer use.

Learn about stainless steel’s composition and how key elements enhance its performance.

The History of Stainless Steel

Stainless steel is a new phenomenon in the world of metallurgy, unlike iron which has been around for over a thousand years. Stainless steel was first discovered in 1913 by Harry Brearley of Sheffield, England, during experiments to create a material resistant to gun barrel erosion. Since then, it has become synonymous with Sheffield’s industrial history and global innovation.

There had been many attempts to create ‘rustless steel’ without any luck. Then Brierley discovered how to make stainless steel while trying to solve the problem of erosion in gun barrels in the First World War. After the initial discovery, improvements have happened at a rapid pace and stainless steel is now one of the most commonly used commercial alloys.

Commercial History of Stainless Steel

• 1919-1923: stainless steel is used to manufacture surgical scalpels, tools, and cutlery in Sheffield.
• 1925: a stainless steel tank is used to store nitric acid, cementing its position as corrosion-resistant.
• 1926: the first stainless steel surgical implants are used.
• 1928: stainless steel shows its hygiene benefits by fermenting beer in a specialised vessel, it’s now widely used by the food and hygiene industry.
• 1930s: the first stainless steel trains are made.
• 1931: the first stainless steel aircraft was built.
• 1935: stainless steel is commonly used in kitchens.
• 1954: the first stainless steel underwater camera was manufactured.
• 1966: the first tidal power station with stainless steel turbine blades was completed in France.
• 1980s: the biggest movable flood barrier in the world is built using stainless steel.
• 2010: global production of steel reaches 31 million tonnes.

Is Stainless Steel an Alloy?

Yes, stainless steel is an alloy consisting of iron, chromium, nickel, and other metals or non-metals. Its key component, chromium, is what gives it its corrosion-resistant properties. Nickel and molybdenum further enhance this protection, making stainless steel suitable for use in marine, chemical, and industrial applications.

Key Alloying Elements and Their Roles:

• Chromium: Protects against corrosion by forming a passive oxide layer
• Nickel: Adds toughness and resistance to high temperatures
• Molybdenum: Increases pitting and crevice corrosion resistance
• Nitrogen: Enhances mechanical strength and corrosion resistance

What is the Difference Between Steel and Stainless Steel?

Steel is prone to rust and corrosion, whereas stainless steel doesn’t stain or rust easily. Both types of steel contain their base metal which is iron, plus carbon and some other trace elements. The difference in the makeup of stainless steel is the addition of chromium, nickel, nitrogen and molybdenum, which makes it less prone to corrosion and rust.

Steel is made by removing impurities from iron such as manganese, sulfur and silicon. Steel is magnetic while most forms of stainless steel aren’t.

Stainless Steel Advantages and Disadvantages

Cleanliness

Steel is easy to clean, which is why it’s popular in the medical and food industries who adhere to strict food hygiene standards. It’s impact resistance means little crevices or dents can’t appear in the steel, meaning dirt and germs have nowhere to hide.

Durability

Stainless steel is a durable alloy; its strength and corrosion-resistant characteristics make it a popular choice for businesses from various industries. It also has high-temperature resistance and takes impact to its structure well. If you maintain stainless steel (which isn’t too difficult), you can count on it lasting a long time.

Corrosion Resistance

The main reason stainless steel was developed was to combat corrosion in regular steel, be it rust-based or other types of corrosion. However, certain environments can be damaging, so it’s important to consult with a specialist beforehand.

Holds Value

Because it doesn’t damage or corrode quickly, stainless steel can hold its value over a long period. If you’re using steel as an interim, you can resell it on and recoup some of the money you paid for it.

Cost

The initial cost of stainless steel can be higher than other metals like aluminium. However, if the resale value stays high, you can recoup some of the cost if you do sell.

Dirt

While steel is easy to clean, it is a magnet for dirt and dust, so it’ll need to be cleaned regularly.

Stainless Steel Properties

Stainless Steel Corrosion

As we’ve already mentioned, stainless steel is known for its corrosion-resistant properties; it’s what separates it from regular steel. The chromium in the alloy gives the steel an oxide layer, which is what gives it its corrosion-resistant property. The oxide layer is self-healing, and even if the surface is damaged, it will still be resistant to corrosion.

In contrast, carbon steels are protected via coatings like galvanising. Unfortunately, any damage to the surface will expose the steel and leave it open to corrosion, so it can cause issues with its full lifetime value.

Different grades of steel have varying resistance, and chloride accelerates corrosion in some grades. Grades with nickel, chromium and molybdenum are the most resistant to corrosion.

Stainless Steel Magnetism

Magnetism is the attraction of steel to a magnet. Austenitic grades are not usually magnetic, although magnetism can be achieved with cold working. Grades with high nickel content will also be non-magnetic, and ferritic steels are magnetic.

Stainless Steel Tensile Strength

When compared with mild steel, stainless steel has more tensile strength, and duplex stainless steel has better tensile strength than austenitic stainless steel.

However, the highest tensile steel is seen in martensitic steel and can have strengths higher than that of the steel above.

Stainless Steel Cryogenic Resistance

At sub-zero temperatures, the toughness and ductility of austenitic stainless steel are increased, whereas ferritic and martensitic stainless steel should not be used at these temperatures.

Discover more about Stainless Steel Properties.

How is Stainless Steel Made?

1. Melting and Casting

The raw materials are melted together in a furnace, which usually requires about 8-10 hours of intense heat. When the steel is liquidised, it’s cast into semi-finished forms such as blooms, billets and slabs, rods and tube rounds.

2. Forming

The steel is heated and passed through huge rolls. Blooms and billets are formed into bar and wire ,and slabs are formed into plate, strip and sheet which are all available in different sizes.

3. Heat Treatment

After the stainless steel is formed, it needs to be annealed. Annealing is a process where the metal is heated and cooled to relieve internal stressors and soften the metal. The process is delicate as the steel is sensitive to different cooling rates and temperatures.

For example, a rapid cooling process can increase the strength of steel without affecting toughness. Different types of steel receive different treatments.

4. Descaling

Annealing causes a scale or build-up on the steel, which can be removed with several processes. Pickling uses a nitric-hydrofluoric acid bath to clean the steel. Electrocleaning applies an electric current to the surface of the steel using a cathode and phosphorous acid. The descaling process will depend on the type of steel.

5. Cutting

Cutting is usually required to get the desired shape or size before the steel is finished. Mechanical cutting is done with a variety of methods, such as straight shearing with guillotine knives, circular shearing with circular knives, sawing using high-speed blades, blanking and nibbling. Stainless steel can also be cut using flame cutting and plasma jet cutting.

6. Finishing

Surface finish is important in steel manufacturing, especially if the material is going to be customer-facing. In addition, steel is also easier to clean with a surface finish. There are several different types of finish, which include a dull finish, a bright finish, a reflective finish, and a mirror finish.

Once the steel has been through this process, it’s ready to be sold.

Types of Stainless Steel

Stainless steel comes in four main types: austenitic, ferritic, martensitic, and duplex. Each type has unique properties and is used for different applications, based on its composition and microstructure.

1. Austenitic Stainless Steel

• Most common type known for its excellent corrosion resistance, ductility, and weldability.
• Common Uses: Food processing equipment, medical devices, and chemical plants.
• High Performance: Enhanced nickel content protects against pitting in harsh environments.

2. Ferritic Stainless Steel

• Affordable and magnetic, with good corrosion resistance for indoor or general applications.
• Common Uses: Car exhausts, kitchen appliances, and sinks.
• Cost-Effective: Contains little to no nickel, making it cheaper than austenitic grades.

3. Martensitic Stainless Steel

• Strong and wear-resistant, making it ideal for high-stress applications.
• Common Uses: Surgical instruments, cutlery, and aerospace components.
• High Strength: Harder and tougher than austenitic and ferritic grades but with lower corrosion resistance.

4. Duplex Stainless Steel

• A 50/50 mix of austenitic and ferritic properties, offering high strength and superior resistance to corrosion.
• Common Uses: Oil and gas pipelines, pressure vessels, and marine structures.
• Heavy-Duty Applications: Ideal for environments prone to stress corrosion cracking and chloride exposure.

Stainless Steel Grades

There are numerous ways to grade steel which vary from country to country; we’re going to use the SAE steel grading series as it’s what we use for our steel and is recognised worldwide.

• Series 100 Steel
• Series 200 Steel – austenitic chromium-nickel-manganese alloys.
• Series 300 Steel – austenitic chromium-nickel alloys.
• Series 400 Steel – ferritic and martensitic chromium alloys.
• Series 500 Steel – heat-resisting chromium alloys.
• Series 600 Steel – created for proprietary alloys (which are no longer graded by the SAE).
• Series 900 Steel – austenitic chromium-molybdenum alloys.

For a more in-depth look, check out our guide on stainless steel types and grades.

What is Stainless Steel Used For?

Stainless steel is part of everyday life. Whether it’s the knife and fork you use or the oil you put in your car, steel has probably had a direct or indirect impact on what you do.

Most industries use steel in some form, but some industries have a more active interest in the product, such as manufacturers that need parts for machinery or production.

• Automotive industry – catalytic converters, exhaust systems, and structural purposes. Steel helps to reduce long-term maintenance costs, lifetime value and environmental impact.
• Construction industry – facades, cladding and roofing. Stainless steel is known for its anti-vandalism properties and is popular for public equipment like ticket machines.
• Mining & materials – stainless steel has played a part in many large-scale projects, with improved tools and better facilities for workers to live in.
• Railway industry – stainless steel is corrosion-resistant and offers excellent mechanical properties, which is ideal for the railway industry. Austenitic stainless steel has been used for carriages, and ferritic stainless steel is used for freight wagons.
• Oil and gas industries – stainless tanks, pipes, pumps and valves. The oil and gas industry relies on steel due to its corrosion-resistant properties.

Stainless steel is used in various industries, such as medical equipment, food processing, pulp and paper, power plants, civil engineering, bridge building and shipbuilding.

Read more about stainless steel applications.

NeoNickel Steel Manufacturing

All of our steels go through this manufacturing process, so we can give you the type and grade of steel that suits your project. If you’d like to learn more about our stainless steel, contact us, and we’ll answer any questions you have.