Stainless Steel Composition
Stainless steel is made from a blend of elements that enhance its resistance to corrosion. The key component in all stainless steel is chromium, which must be at least 10.5% of the composition.
The most common type is austenitic stainless steel, which includes grades 304 and 316. This type is known for its excellent corrosion resistance due to its high chromium and nickel content.
Another popular type is ferritic stainless steel, which includes grade 430. While it doesn’t offer the same level of corrosion resistance as austenitic steel, it’s a cost-effective option often used in the catering industry.
Martensitic stainless steel contains lower levels of chromium, resulting in less corrosion resistance but higher strength. This makes martensitic steel suitable for applications where strength is essential.
Below is a table detailing the chemical composition of various stainless steel grades supplied by Solitaire Steel. If the grade you need isn’t listed or if you need more information, please check our mechanical properties page or our stainless steel data sheets.
Stainless Steel Composition and Characteristics
| Type | Cr | Ni | Cmax | Other Elements | Major Characteristics |
|---|---|---|---|---|---|
| 303 | 17.00-19.00 | 8.00-10.00 | 0.15 | S 0.15 min | † Free-machining modification of Type 302 |
| 303 Se | 17.00-19.00 | 8.00-10.00 | 0.15 | Se 0.15 min | † Free-machining version of Type 302. Produces better surface finish than Type 303. |
| 304 | 18.00-20.00 | 8.00-10.00 | 0.08 | – | † Low carbon variation of Type 302. Minimizes carbide precipitation during welding |
| 304L | 18.00-20.00 | 8.00-10.00 | 0.03 | – | † Extra-low carbon content eliminates harmful carbide precipitation due to welding |
| 309 | 22.00-24.00 | 12.00-15.00 | 0.20 | – | † High strength and resistance to scaling at high temperatures |
| 310 | 24.00-26.00 | 19.00-22.00 | 0.20 | – | † Higher alloy content improves basic characteristics of Type 309 |
| 316 | 16.00-18.00 | 10.00-14.00 | 0.08 | Mo 2.00-3.00 | † Mo improves general corrosion and pitting resistance and high temperature strength over that of Type 302 |
| 316L | 16.00-18.00 | 10.00-14.00 | 0.20 | Mo 2.00-3.00 | † Extra-low carbon version of Type 316. Eliminates harmful carbide precipitation due to welding |
| 317 | 18.00-20.00 | 11.00-15.00 | 0.08 | Mo 3.00-4.00 | † Higher alloy content improves basic advantages of Type 316 |
| 321 | 17.00-19.00 | 9.00-12.00 | 0.08 | Ti 5 x C. min | † Stabilized to permit use in 800-1500°F temperature range without harmful carbide precipitation |
| 347 | 17.00-19.00 | 9.00-13.00 | .008 | Cb + Ta 10 x C. min | † Characteristics similar to Type 321. Stabilized by Cb and Ta. |
| 348 | 17.00-19.00 | 9.00-13.00 | 0.08 | Ta 0.10 max Cb 0.20 maxCb + Ta 10 x C min | † Similar to Type 347 but Ta reduced for atomic energy applications |
| 410 | 11.50-13.50 | – | 0.15 | – | ¥ Lowest cost general purpose stainless steel. Wide use where corrosion is not severe. |
| 416 | 12.00-14.00 | – | 0.15 | S 0.15 min | ¥ Free-machining version of Type 410. |
| 420 | 12.00-14.00 | – | 0.15 min | – | ¥ Similar variation of Type 410 but higher carbon produces higher strength and hardness. |
| 430 | 14.00-18.00 | – | 0.12 | – | * Most popular of the chromium types. Combines good corrosion and heat resistance and mechanical properties. |
| 430 F | 14.00-18.00 | – | 0.12 | S 0.15 min | * Free-machining version of Type 430. |
| 440A440B440C | 16.00-18.0016.00-18.0016.00-18.00 | – | 0.60-0.750.75-0.950.95-1.20 | – | ¥ Series of high carbon types. Some basic composition with varying carbon content. Higher carbon produces higher strength and hardness but lower toughness. All Type 440 versions are corrosion resistant only in the hardened condition. |
| 446 | 23.00-27.00 | – | 0.20 | – | * Similar to Type 442 but Cr increased to provide maximum resistance to scaling. |
| 15-5 PH | 14.00-15.50 | 3.50-5.50 | 0.07 | Cu 2.50-4.50 | • Similar in properties and characteristics to 17-4 PH but has superior transverse ductility and toughness. |
| PH 15-7 Mo | 14.00-16.00 | 6.50-7.75 | 0.09 | Mo 2.00-3.00Al 0.75-1.50 | •• Special type similar to 17-7 PH but with higher strength. |
| 17-4 PH | 15.50-17.50 | 3.00-5.00 | 0.07 | Cu 3.00-5.00 | • Special type that combines excellent corrosion resistance…high strength and hardness… low temperature hardening and good fabrication characteristics. |
| 17-7 PH | 16.00-18.00 | 6.50-7.75 | 0.09 | AL 0.75-1.25 | •• Special ultra-high strength type with good formability and excellent fabricating characteristics. |
Austenitic Grades
| Grade | EN Specification | Carbon (C) | Silicon (S) | Manganese (Mn) | Phosphorus (P) | Sulfur (S) | Chromium (Cr) | Molybdenum (Mo) | Nickel (Ni) | Nitrogen (N) | Iron (Fe) |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 301 | 1.4310 | 0.05 – 0.15 | 2.00 | 2.00 | 0.045 | 0.015 | 16.0 – 19.0 | 0.80 | 6.0 – 9.5 | 0.10 | Balance |
| 304 | 1.4301 | 0.07 | 1.00 | 2.00 | 0.045 | 0.015 | 17.5 – 19.5 | – | 8.0 – 10.5 | 0.1 | Balance |
| 304L | 1.4307 | 0.03 | 1.00 | 2.00 | 0.045 | 0.015 | 17.5 – 19.5 | – | 8.0 – 10.5 | 0.1 | Balance |
| 201 | 1.4372 | 0.15 | 1.00 | 5.5 – 7.5 | 0.045 | 0.015 | 16.0 – 18.0 | – | 3.5 – 5.5 | 0.05 – 0.25 | Balance |
| 316 | 1.4401 | 0.07 | 1.00 | 2.00 | 0.045 | 0.015 | 16.5 – 18.5 | 2.0 – 2.5 | 10.0 – 13.0 | 0.1 | Balance |
| 316L | 1.4404 | 0.03 | 1.00 | 2.00 | 0.045 | 0.015 | 16.5 – 18.5 | 2.0 – 2.5 | 10.0 – 13.0 | 0.1 | Balance |
Ferritic Grades
| Grade | EN Specification | Carbon (C) | Silicon (Si) | Manganese (Mn) | Phosphorus (P) | Sulfur (S) | Chromium (Cr) | Titanium (Ti) | Niobium (Nb) | Molybdenum(Mo) | Nickel (Ni) |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 409 | 1.4512 | 0.030 | 1.00 | 1.00 | 0.040 | 0.015 | 10.5 – 12.5 | [6 x (C + N)] to max 0.65 | – | – | – |
| 430 | 1.4016 | 0.080 | 1.00 | 1.00 | 0.040 | 0.015 | 16.0 – 18.0 | – | – | – | – |
| 434 | 1.4113 | 0.080 | 1.00 | 1.00 | 0.040 | 0.015 | 16.0 – 18.0 | – | – | – | – |
| 439 | 1.4510 | 0.050 | 1.00 | 1.00 | 0.040 | 0.015 | 16.0 – 18.0 | [4 x (C + N) + 0.15] to max 0.8 | (3 x C + 0.3) to max 1 | – | – |
| 4509 | 1.4509 | 0.030 | 1.00 | 1.00 | 0.040 | 0.015 | 17.5 – 18.5 | 0.1 – 0.6 | – | – | – |
| 436 | 1.4513 | 0.025 | 1.00 | 1.00 | 0.040 | 0.015 | 16.0 – 18.0 | [4 x (C + N) + 0.15] to max 0.8 | – | 0.80 – 1.40 | 0.020 |
Martensitic Grades
| Grade | EN Specification | Carbon (C) | Silicon (S) | Manganese (Mn) | Phosphorus (P) | Sulfur (S) | Chromium (Cr) | Nickel (Ni) | Nitrogen (N) | Iron (Fe) |
|---|---|---|---|---|---|---|---|---|---|---|
| 410 | 1.4006 | 0.08 – 0.15 | 1.00 | 1.50 | 0.040 | 0.015 | 11.5 – 13.5 | 0.75 | – | Balance |
| 420 | 1.4021 | 0.16 – 0.25 | 1.00 | 1.50 | 0.040 | 0.015 | 12.0 – 14.0 | – | – | Balance |
| 420 | 1.4031 | 0.07 | 1.00 | 2.00 | 0.045 | 0.015 | 17.5 – 19.5 | 8.0 – 10.5 | 0.1 | Balance |
What is Stainless Steel?
Stainless steel is a type of metal that contains at least 10.5% chromium, which gives it its unique properties. The most common example grades of stainless steel are 304 and 430. Each grade includes different alloying elements, which influence its characteristics like corrosion resistance, strength, and flexibility.
Due to its low cost, attractive appearance, high corrosion resistance, and durability, stainless steel is a popular choice for many applications
Why is it Called Stainless?
The term “stainless” means that the metal doesn’t stain easily. This is because of the chromium content, which reacts with oxygen in the air to create a protective layer of chromium oxide on the surface.
Even if this layer gets scratched or damaged by harsh chemicals, it can repair itself when exposed to air again, ensuring that the protective coat remains intact.
Summary: Stainless Steel Composition
Stainless steel is an alloy primarily composed of at least 10.5% chromium, which enhances its corrosion resistance. The most common types are austenitic stainless steels, such as grades 304 and 316, known for their high corrosion resistance due to their chromium and nickel content. Ferritic stainless steels, like grade 430, offer a cost-effective alternative with lower corrosion resistance, commonly used in the catering industry. Martensitic steels have low chromium content but provide high strength, making them suitable for demanding applications. Each grade features different alloying elements that contribute to its unique properties.
FAQs
Stainless steel is primarily composed of iron and carbon, containing at least 10.5% chromium and less than 1.2% carbon. Additional alloying elements may include nickel, molybdenum, manganese, and others to enhance specific properties.
The best composition of stainless steel is often considered to be 304 stainless steel, which contains approximately 18% chromium and 8% nickel. It lacks molybdenum but is highly resistant to atmospheric corrosion, water, and various chemicals, making it versatile and widely used.
Steel is an alloy of iron and carbon, with carbon content up to 2%. Higher carbon content defines cast iron. Steel is essential for infrastructure and industries, used in applications from sewing needles to oil tankers.
