Stainless Steel Austenitic Grades
Austenitic stainless steel is the most widely used and preferred type among manufacturers, primarily including SS 304 and SS 316 grades. These grades offer excellent corrosion resistance, thanks to their high chromium levels combined with nickel content.
| Grade | EN Specification | Carbon (C) | Silicon (S) | Manganese (Mn) | Phosphorus (P) | Sulfur (S) | Chromium (Cr) | Molybdenum (Mo) | Nickel (Ni) | Nitrogen (N) | Iron (Fe) |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 301 | 1.431 | 0.05 - 0.15 | 2 | 2 | 0.045 | 0.015 | 16.0 - 19.0 | 0.8 | 6.0 - 9.5 | 0.1 | Balance |
| 304 | 1.4301 | 0.07 | 1 | 2 | 0.045 | 0.015 | 17.5 - 19.5 | - | 8.0 - 10.5 | 0.1 | Balance |
| 304L | 1.4307 | 0.03 | 1 | 2 | 0.045 | 0.015 | 17.5 - 19.5 | - | 8.0 - 10.5 | 0.1 | Balance |
| 201 | 1.4372 | 0.15 | 1 | 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 | 2 | 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 | 2 | 0.045 | 0.015 | 16.5 - 18.5 | 2.0 - 2.5 | 10.0 - 13.0 | 0.1 | Balance |
Austenitic stainless steels are among the most widely used stainless steel types due to their excellent corrosion resistance, formability, and weldability. The most commonly used grades include 301, 304, 304L, 201, 316, and 316L, each with a unique chemical composition suited for different applications.
Grade 301 (EN 1.431) contains between 0.05–0.15% carbon, 2% silicon, 2% manganese, and a chromium range of 16.0–19.0%. It has 6.0–9.5% nickel, a small 0.8% of molybdenum, and 0.1% nitrogen, with iron as the balance. This grade is known for its high strength and work-hardening ability, although its corrosion resistance is slightly lower than that of 304.
Grade 304 (EN 1.4301) is the most widely used stainless steel grade, with 0.07% carbon, 1% silicon, 2% manganese, 17.5–19.5% chromium, and 8.0–10.5% nickel. The presence of 0.1% nitrogen further enhances its strength. This grade offers a well-balanced combination of corrosion resistance, durability, and weldability, making it ideal for a wide range of applications.
Grade 304L (EN 1.4307) is the low-carbon variant of 304, with only 0.03% carbon content. The rest of its chemical composition remains almost identical to 304. The lower carbon level improves its resistance to intergranular corrosion, especially in welded structures, making it suitable for pressure vessels and food processing equipment.
Grade 201 (EN 1.4372) is a cost-effective alternative to 304, containing 0.15% carbon, 1% silicon, and significantly higher manganese (5.5–7.5%). Its chromium content is 16.0–18.0%, while nickel ranges from 3.5–5.5%. Nitrogen ranges between 0.05–0.25%, enhancing strength. While it is more affordable, its corrosion resistance is lower, so it is typically used in indoor or mildly corrosive environments.
Grade 316 (EN 1.4401) offers enhanced corrosion resistance due to the addition of 2.0–2.5% molybdenum. Its composition includes 0.07% carbon, 1% silicon, 2% manganese, 16.5–18.5% chromium, and 10.0–13.0% nickel, along with 0.1% nitrogen. This grade is particularly suitable for marine, chemical, and coastal environments where resistance to chlorides is essential.
Grade 316L (EN 1.4404) is the low-carbon version of 316, with only 0.03% carbon content. Like 304L, it offers better resistance to welding-related corrosion (intergranular corrosion) while retaining the same superior corrosion resistance of 316, especially in harsh industrial and marine conditions.
In summary, 304 and 316 are the most preferred grades for general and corrosion-critical applications, respectively. The L variants are ideal for welding and sensitive environments. 201 offers affordability for lighter-duty applications, while 301 provides high strength for more demanding mechanical use. These stainless grades are selected based on the desired balance between strength, corrosion resistance, cost, and environmental suitability.
Mechanical Properties of Austenitic Stainless Steel Grades
The Mechanical Properties of Stainless Steel vary depending on the chemical composition of each grade.
| Grade | EN Specification | Form | Max Thickness (mm) | 0.2% - Proof Strength (min MPa)a | 1% - Proof Strength (min MPa)a | Tensile Strength (MPa) |
|---|---|---|---|---|---|---|
| 304 | 1.4301 | Cold rolled strip | 6 | 230 | 260 | 540 - 750 |
| 304 | 1.4301 | Hot rolled strip | 13.5 | 210 | 250 | 520 - 720 |
| 304 | 1.4301 | Hot rolled plate | 75 | 210 | 250 | 520 - 720 |
| 304L | 1.4307 | Cold rolled strip | 6 | 220 | 250 | 520 - 700 |
| 304L | 1.4307 | Hot rolled strip | 13.5 | 200 | 240 | 520 - 700 |
| 304L | 1.4307 | Hot rolled plate | 75 | 200 | 240 | 500 - 700 |
| 316 | 1.4401 | Cold rolled strip | 6 | 240 | 270 | 530 - 680 |
| 316 | 1.4401 | Hot rolled strip | 13.5 | 220 | 260 | 530 - 680 |
| 316 | 1.4401 | Hot rolled plate | 75 | 220 | 260 | 520 - 670 |
| 316L | 1.4404 | Cold rolled strip | 6 | 240 | 270 | 530 - 680 |
| 316L | 1.4404 | Hot rolled strip | 13.5 | 220 | 260 | 530 - 680 |
| 316L | 1.4404 | Hot rolled plate | 75 | 220 | 260 | 520 - 670 |
Austenitic stainless steels such as 304, 304L, 316, and 316L are known not only for their excellent corrosion resistance but also for their robust mechanical strength, making them ideal for a wide range of structural and industrial applications. The table provides a comparison of these grades in different forms—cold rolled strips, hot rolled strips, and hot rolled plates—based on their maximum thickness, proof strength, and tensile strength.
Grade 304 (EN 1.4301) in cold rolled strip form, up to 6mm thick, offers a minimum 0.2% proof strength of 230 MPa, a 1% proof strength of 260 MPa, and a tensile strength between 540–750 MPa. When produced as a hot rolled strip (up to 13.5mm), the strength slightly reduces, with a 0.2% proof strength of 210 MPa and tensile strength between 520–720 MPa. For thicker hot rolled plates (up to 75mm), the mechanical values remain similar.
Grade 304L (EN 1.4307), a low-carbon version of 304, provides slightly lower strength values. In cold rolled form, it offers a 0.2% proof strength of 220 MPa and tensile strength up to 700 MPa. For hot rolled strips and plates, the values drop marginally, with proof strengths around 200–240 MPa and tensile strength ranging from 500–700 MPa. This grade is commonly chosen for welded components due to its reduced risk of intergranular corrosion.
Grade 316 (EN 1.4401), which contains molybdenum for enhanced corrosion resistance, also delivers superior mechanical properties. In cold rolled strip form, it achieves a 0.2% proof strength of 240 MPa and tensile strength between 530–680 MPa. The hot rolled variants show slightly lower values but remain suitable for load-bearing and corrosive environments.
Grade 316L (EN 1.4404) is the low-carbon variant of 316, with nearly identical mechanical performance. Cold rolled strips offer a 0.2% proof strength of 240 MPa and a tensile strength of up to 680 MPa. For hot rolled plates and strips, the proof strength is around 220–260 MPa and tensile strength ranges from 520–670 MPa. This grade is preferred in marine, pharmaceutical, and chemical processing industries due to its excellent weldability and chloride resistance.
