Stainless steel is one of the most widely used metals across various industries, from construction and automotive to food processing and medical applications.
But what exactly is stainless steel made of? As an alloy, stainless steel is composed of multiple elements that enhance its durability, corrosion resistance, and mechanical properties.
At Speciality Metals, we supply a range of stainless steel products, including stainless steel sheet metal, box section, angle, flat bar, and U channel, making us a trusted supplier for both professionals and DIY enthusiasts.
Understanding what stainless steel is an alloy of can help you make informed decisions when selecting the right material for your project.
In this article, we’ll explore:
- The primary elements that make up stainless steel.
- How different alloying elements affect its properties.
- The various grades of stainless steel and their applications.
- Why stainless steel is a preferred choice over other metals.
By the end of this guide, you’ll have a clearer understanding of stainless steel’s composition and which type is best suited for your specific needs.
What Is Stainless Steel an Alloy Of?
Stainless steel is primarily an iron-based alloy that contains at least 10.5% chromium, which gives it its signature corrosion resistance.
However, additional elements are added to improve its strength, durability, and resistance to environmental factors. The most common elements found in stainless steel alloys include:
1. Chromium (Cr) – The Key to Corrosion Resistance
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Chromium is the defining element of stainless steel, forming a thin passive oxide layer on the surface that prevents rust and corrosion.
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The higher the chromium content, the greater the corrosion resistance. For example, 316 stainless steel, commonly used in marine environments, contains 16-18% chromium for enhanced protection.
2. Nickel (Ni) – Improving Strength and Ductility
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Nickel enhances the formability, toughness, and corrosion resistance of stainless steel.
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Austenitic stainless steels like 304 stainless steel contain 8-10.5% nickel, making them highly resistant to oxidation and acids.
3. Carbon (C) – Influencing Hardness
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Carbon is added in small amounts to increase hardness and strength.
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Low-carbon stainless steel, such as 304L, has better weldability and reduced carbide precipitation, making it ideal for fabrication.
4. Molybdenum (Mo) – Enhancing Resistance to Pitting
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Found in 316 stainless steel, molybdenum improves resistance to pitting and crevice corrosion, particularly in saltwater or chemical environments.
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This is why 316 stainless steel box sections and flat bars are commonly used in marine and industrial applications.
5. Manganese (Mn) – Strengthening the Alloy
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Manganese improves toughness and wear resistance, particularly in stainless steels used in heavy-duty applications.
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It also stabilises austenitic structures in steels that contain low nickel.
6. Silicon (Si) – Improving Oxidation Resistance
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Helps prevent oxidation at high temperatures, making stainless steel ideal for heat exchangers, industrial ovens, and exhaust systems.
7. Nitrogen (N) – Strength and Pitting Resistance
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Nitrogen enhances mechanical properties and is commonly found in duplex stainless steels, used in offshore and structural applications.
These elements combine to create various grades of stainless steel, each designed for different environments and applications.
Types of Stainless Steel and Their Alloying Elements
Stainless steel comes in several categories, each with its own unique composition and performance characteristics.
1. Austenitic Stainless Steel (Most Common – 304 & 316 Grades)
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Contains high levels of chromium (16-26%) and nickel (6-22%).
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Excellent corrosion resistance, formability, and weldability.
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Example: 304 Stainless Steel Flat Bar – Used in construction and fabrication.
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Example: 316 Stainless Steel Box Section – Ideal for marine applications due to added molybdenum.
2. Ferritic Stainless Steel (430 Grade)
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Contains 10.5-27% chromium but low nickel content.
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Magnetic, with good corrosion resistance but lower ductility than austenitic grades.
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Example: 430 Stainless Steel Sheet Metal – Used in kitchen appliances and automotive trim.
3. Martensitic Stainless Steel (410 & 420 Grades)
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Higher carbon content for increased hardness and strength.
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Less corrosion-resistant but ideal for cutting tools, medical instruments, and turbine blades.
4. Duplex Stainless Steel (2205 Grade)
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A mix of austenitic and ferritic structures, offering higher strength and corrosion resistance.
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Used in chemical plants, bridges, and pressure vessels.
Comparison of Stainless Steel Grades & Alloying Elements
Grade | Chromium (Cr) | Nickel (Ni) | Molybdenum (Mo) | Carbon (C) | Common Applications |
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304 | 18-20% | 8-10.5% | 0% | ≤0.08% | Kitchen equipment, structural fabrication, tubing |
316 | 16-18% | 10-14% | 2-3% | ≤0.08% | Marine environments, chemical processing, medical implants |
430 | 16-18% | ≤0.75% | 0% | ≤0.12% | Automotive trim, appliances, decorative panels |
410 | 11.5-13.5% | ≤0.75% | 0% | 0.15-0.40% | Cutlery, turbine blades, medical tools |
2205 | 22-23% | 4.5-6.5% | 3-3.5% | ≤0.03% | Bridges, offshore platforms, pressure vessels |
Why Choose Stainless Steel from Speciality Metals?
At Speciality Metals, we supply a range of high-quality stainless steel products, ensuring that our customers get the right grade and form for their projects. Whether you need:
- 304 Stainless Steel Flat Bar for structural fabrication.
- 316 Stainless Steel Box Section for marine and industrial use.
- 430 Stainless Steel Sheet for decorative and automotive applications.
We offer cut-to-size services, allowing you to purchase stainless steel in the exact dimensions required, reducing waste and improving efficiency.
Stainless steel is an alloy of iron, chromium, nickel, and other elements, giving it its signature corrosion resistance, strength, and durability. With various grades available, from 304 and 316 for general use to duplex and martensitic grades for specialised applications, choosing the right stainless steel is crucial.
At Speciality Metals, we provide premium stainless steel sheet metal, box sections, flat bars, and more, ensuring our customers have access to the highest-quality materials for their projects.
Explore our stainless steel range at smetals.co.uk and contact us today for expert guidance on selecting the best metal for your needs.
As always, thank you for checking out our blog. We hope that this helps you with your project.
Please also check out the other articles in our helpful guide series. We have written about aluminium sheeting and checker plate recently to name but two of our articles.
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If you have any further questions, feel free to contact us.
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