316L Stainless Steel (UNS S31603): Low-Carbon Marine-Grade Properties
AISI 316L / ASTM A240 (UNS S31603) · Published: 2026-07-25 · Updated: July 2026
316L stainless steel (UNS S31603) is the low-carbon variant of standard 316, with carbon limited to ≤0.03% (versus ≤0.08% for standard 316). This single chemistry difference is the reason 316L is specified for welded fabrications in corrosive...
316L stainless steel (UNS S31603) is the low-carbon variant of standard 316, with carbon limited to ≤0.03% (versus ≤0.08% for standard 316). This single chemistry difference is the reason 316L is specified for welded fabrications in corrosive service: with ≤0.03% carbon, 316L does not sensitize during welding—carbide precipitation at grain boundaries (which depletes chromium and causes intergranular corrosion in standard 316 weld HAZs) is effectively eliminated. This makes 316L the correct grade specification whenever 316-type stainless will be welded and subsequently exposed to chloride or corrosive environments. Typical applications include pharmaceutical piping (ASME BPE), food and beverage equipment, marine fittings and coastal architecture, offshore platforms, chemical process vessels, surgical implants (ASTM F138), and water treatment equipment. The tradeoff: 316L has marginally lower yield strength (170 MPa vs 205 MPa for standard 316) due to reduced carbon content. For non-welded components or welded components in non-corrosive environments, standard 316 is acceptable and slightly stronger. For the full UNS S31603 data sheet with detailed mechanical and physical properties, see ss316l/">AISI 316L (UNS S31603).
Quick Facts
| Category | Stainless Steel |
| Standard | AISI 316L / ASTM A240 (UNS S31603) |
| Density | 8.00 g/cm³ |
| Yield Strength | 170 MPa (25 ksi) |
| Tensile Strength | 485 MPa (70 ksi) |
Detailed Mechanical Properties
| Elongation | 50% (annealed) |
| Hardness | 70-85 HB (annealed) |
| Charpy V Notch | >100J at -196°C (excellent cryogenic toughness) |
| Modulus Of Elasticity | 193 GPa |
Physical Properties
| Melting Point | 1375-1400 °C |
| Thermal Conductivity | 16.3 W/m·K at 20°C |
| Electrical Resistivity | 0.000074 Ω·cm |
| Specific Heat | 500 J/kg·K |
Global Equivalents & Cross-Reference
| Alternative Standard / Grade | Action |
|---|---|
| AISI 316L | Compare |
| UNS S31603 | Compare |
| EN 1.4404 | Compare |
| SUS316L | Compare |
| 022Cr17Ni12Mo2 | Compare |
| X2CrNiMo17-12-2 | Compare |
Heat Treatment & Processing
| Solution Annealing | 1040-1120°C, water quench |
| Stress Relieving | 400-425°C (do not exceed 425°C to avoid sensitization risk) |
| Note | 316L cannot be hardened by heat treatment; strength is achieved only by cold work. Full annealing after welding restores maximum corrosion resistance. |
Welding & Fabrication
| Preheat | Not required |
| Filler Metal | ER316L (GMAW/GTAW), E316L-16 (SMAW) |
| Interpass Temp | Max 150°C (low interpass essential to prevent distortion) |
| Weldability Rating | Excellent — superior to standard 316 for welded corrosive service due to low carbon |
Related Materials
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Frequently Asked Questions
Why specify 316L instead of 316 for welded applications?
The 'L' designation means ≤0.03% carbon. During welding, standard 316 can develop chromium carbide precipitation at grain boundaries in the heat-affected zone, depleting chromium and causing intergranular corrosion (weld decay). 316L's low carbon prevents this without requiring post-weld solution annealing. Always specify 316L for welded components in corrosive service.
Is 316L stronger than 316?
No, 316L is marginally weaker than standard 316 due to its lower carbon content. 316L yield strength is ~170 MPa vs ~205 MPa for 316 (annealed). For most applications the difference is negligible; for high-strength applications where welding is not required, standard 316 may be preferred. 316L strength can be increased by cold work.
What is PREN and what is 316L's PREN?
PREN (Pitting Resistance Equivalent Number) = %Cr + 3.3×%Mo + 16×%N. 316L has PREN ~24-28, significantly higher than 304's PREN ~18-20. For seawater immersion resistance, PREN >32 is recommended (consider duplex 2205 or super-austenitic 254 SMO).
Can 316L be used for surgical implants?
Yes. 316L (ASTM F138 wrought, F139 cold-finished) is a standard implant alloy for fracture fixation plates, screws, and temporary orthopedic devices. For permanent joint replacement implants, titanium Ti-6Al-4V or cobalt-chromium alloys are preferred for superior biocompatibility and fatigue strength.
Will 316L rust in coastal environments?
316L resists atmospheric corrosion very well in coastal areas, but it can develop cosmetic tea staining within 1-5 km of saltwater. For pristine architectural finishes near the coast, consider electropolishing or passivation, or upgrade to duplex 2205. 316L will pit in continuous seawater immersion—use a higher-PREN alloy for immersion service.
References & International Standards
- ASTM International. Standard Specifications for Steel & Metal Alloys. astm.org
- International Organization for Standardization (ISO). Metallic Materials — Cross-Reference Database. iso.org
- American Iron and Steel Institute (AISI). Steel Grade Designations & Equivalents. steel.org
- European Committee for Standardization (CEN). EN Steel Standards & Numbering System. cencenelec.eu
Stainless & Corrosion-Resistant Steel — Engineering Reference
Stainless steels are defined by their chromium content (minimum 10.5%), which forms a self-healing passive layer of chromium oxide that resists corrosion. Grades are classified by microstructure: austenitic (300 series), ferritic (400 series), martensitic, and duplex.
ASTM A240/A276/A312, EN 10088, JIS G4304/G4305, GB/T 3280/4237
Food processing equipment, medical implants, chemical tanks, architectural cladding, marine hardware, pharmaceutical piping
For welded stainless fabrications, specify the low-carbon variant (304L, 316L) to prevent chromium carbide precipitation at grain boundaries, which causes intergranular corrosion (weld decay).