Quick Answer
Quick Answer
SS 316 (EN 1.4401) is an austenitic stainless steel containing 16–18 % Cr, 10–14 % Ni, and 2–3 % Mo. The molybdenum addition gives it superior pitting and crevice corrosion resistance compared to 304, making it the standard choice for marine, chemical, and pharmaceutical applications.
Overview
Grade 316 is one of the most widely specified austenitic stainless steels in process industries. Its molybdenum content distinguishes it from 304 and provides meaningful resistance to chloride-induced pitting — the failure mode most commonly encountered in marine, offshore, and food-processing environments.
The European equivalent is 1.4401 per EN 10088. In ASME pressure vessel applications the grade appears as SA-240 Type 316. Both designations describe essentially the same composition, though subtle differences in residual element limits and testing requirements can matter for critical applications.
Chemical Composition — SS 316 / 1.4401
The table below presents composition limits from ASTM A240 (latest revision) and EN 10088-2. Values are in weight percent (wt%).
| Element | ASTM A240 Type 316 | EN 1.4401 |
|---|---|---|
| Carbon (C) | ≤ 0.08 | ≤ 0.07 |
| Manganese (Mn) | ≤ 2.00 | ≤ 2.00 |
| Silicon (Si) | ≤ 0.75 | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.045 | ≤ 0.045 |
| Sulfur (S) | ≤ 0.030 | ≤ 0.015 |
| Chromium (Cr) | 16.0 – 18.0 | 16.5 – 18.5 |
| Molybdenum (Mo) | 2.00 – 3.00 | 2.00 – 2.50 |
| Nickel (Ni) | 10.0 – 14.0 | 10.0 – 13.0 |
| Nitrogen (N) | ≤ 0.10 | ≤ 0.11 |
Note: EN 10088 generally specifies tighter sulfur limits and slightly narrower Mo/Ni ranges. When verifying an MTC, always reference the exact standard and revision cited on the certificate.
Mechanical Properties — SS 316 (Annealed Plate)
Minimum mechanical properties per ASTM A240 for annealed flat-rolled product:
| Property | Minimum Value |
|---|---|
| Ultimate Tensile Strength (UTS) | 515 MPa (75 ksi) |
| 0.2 % Proof Strength (YS) | 205 MPa (30 ksi) |
| Elongation in 50 mm (2 in) | 40 % |
| Hardness (max) | 217 HBW / 95 HRB |
For EN 10088-2 hot-rolled plate (condition +A):
| Property | Minimum Value |
|---|---|
| Rp0.2 (YS) | 220 MPa |
| Rm (UTS) | 520 – 720 MPa |
| A80 (Elongation) | 45 % |
Physical Properties
| Property | Typical Value |
|---|---|
| Density | 7.99 g/cm³ |
| Thermal conductivity (20 °C) | 16.3 W/(m·K) |
| Electrical resistivity (20 °C) | 0.74 μΩ·m |
| Modulus of elasticity | 193 GPa |
| Magnetic permeability (annealed) | ≤ 1.02 (non-magnetic) |
Standards Coverage
SS 316 is covered under a broad range of international standards:
| Standard | Product Form | Designation |
|---|---|---|
| ASTM A240 | Plate, sheet, strip | Type 316 |
| ASTM A276 | Bar and shapes | Type 316 |
| ASTM A312 | Seamless and welded pipe | TP316 |
| ASTM A182 | Forgings and fittings | F316 |
| ASME SA-240 | Pressure vessel plate | Type 316 |
| EN 10088-2 | Flat products | 1.4401 |
| EN 10088-3 | Long products | 1.4401 |
| BS 970 | Bar | 316S31 |
Applications
The molybdenum content of 316 makes it the preferred grade wherever chloride concentrations are elevated:
- Marine and offshore structures — hull fittings, deck hardware, subsea fasteners
- Chemical processing — equipment handling acetic acid, sulfurous environments, halide solutions
- Pharmaceutical and food processing — tanks, pipework, and fittings where CIP cleaning with chlorinated compounds is routine
- Heat exchangers — tube bundles in brackish water or process fluid service
- Architectural — coastal facades and structures where 304 would show tea-staining
SS 316 vs 316L — Choosing Between Them
The key distinction is carbon content: 316 allows up to 0.08 % C while 316L is limited to 0.030 %. For welded fabrications that cannot be solution-annealed after welding, 316L is strongly preferred to prevent sensitization and intergranular corrosion. Where no welding is involved, or full post-weld annealing is performed, standard 316 is acceptable. See the SS 316 vs 316L comparison page for a full breakdown.
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What is the PREN of SS 316?
The Pitting Resistance Equivalent Number (PREN = %Cr + 3.3×%Mo + 16×%N) for SS 316 is approximately 24–26, depending on actual composition. This is meaningfully higher than SS 304 (~19–21) due to the molybdenum content, but lower than duplex grades (2205: ~35, 2507: ~43).
Is 316 stainless magnetic?
In the fully annealed condition, 316 is essentially non-magnetic with a magnetic permeability close to 1.0. Cold working can induce a small amount of martensite transformation, slightly increasing permeability. For applications where magnetic permeability is critical (e.g., MRI facilities), specify a maximum permeability value in the purchase order.
What is the maximum service temperature for SS 316?
SS 316 can be used continuously up to approximately 870 °C (1600 °F). However, prolonged exposure in the 425–860 °C sensitization range should be avoided in corrosive environments unless the low-carbon 316L variant is used. Above 870 °C, consider high-temperature grades such as 309 or 310.
How does TestCert validate SS 316 MTC data?
TestCert cross-references every element reported on an uploaded MTC against the composition limits for ASTM A240 Type 316 (or the applicable EN/ASME edition). Out-of-range values are flagged automatically, and the platform captures both heat analysis and product analysis values when both are reported on the certificate.