317L Stainless Steel (UNS S31703): Properties, Corrosion Resistance & Applications
ASTM A240 / UNS S31703 · Published: 2026-08-10 · Updated: August 2026
317L (UNS S31703) is a low-carbon austenitic stainless steel with 18-20% chromium, 11-15% nickel, and 3-4% molybdenum — significantly higher molybdenum than 316L (2-3%). This additional molybdenum content increases the Pitting Resistance...
317L (UNS S31703) is a low-carbon austenitic stainless steel with 18-20% chromium, 11-15% nickel, and 3-4% molybdenum — significantly higher molybdenum than 316L (2-3%). This additional molybdenum content increases the Pitting Resistance Equivalent Number (PREN) to 29-33, compared to 24-28 for 316L, providing superior resistance to chloride pitting and crevice corrosion. 317L is the preferred material for chemical processing equipment handling sulfuric acid, phosphoric acid, and chloride-containing environments where 316L has insufficient corrosion resistance. The low carbon content (0.03% max) prevents chromium carbide precipitation during welding, eliminating the need for post-weld heat treatment.
Quick Facts
| Category | Stainless Steel |
| Standard | ASTM A240 / UNS S31703 |
| Density | 8.0 g/cm³ |
| Yield Strength | 205 MPa (30 ksi) |
| Tensile Strength | 515-690 MPa (75-100 ksi) |
Detailed Mechanical Properties
| Elongation | 40% minimum |
| Hardness | 85 HRB max |
| Charpy V Notch | Excellent impact toughness at cryogenic temperatures |
Physical Properties
| Melting Point | 1370-1400 °C |
| Thermal Conductivity | 14.4 W/m·K at 100°C |
| Electrical Resistivity | 0.000079 Ω·cm |
| Specific Heat | 500 J/kg·K |
Global Equivalents & Cross-Reference
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Frequently Asked Questions
What is the main difference between 317L and 316L stainless steel?
317L contains 3-4% molybdenum versus 2-3% in 316L, providing approximately 20% higher PREN (29-33 vs 24-28). This translates to significantly better pitting and crevice corrosion resistance in chloride environments. 317L costs approximately 15-25% more than 316L.
Is 317L stainless steel weldable?
Yes. The low carbon content (0.03% max) makes 317L highly weldable without risk of sensitization. Standard filler metals (ER317L, ER316L) are used. No post-weld heat treatment is required.
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).