Stainless Steel 317L
Stainless Steel 317L (UNS S31703) is a low-carbon austenitic grade with elevated molybdenum (3.0-4.0%) and chromium content. It has noticeably better resistance to pitting, crevice corrosion, and general corrosion than standard 316L in aggressive acidic and chloride-containing environments.
1. Chemical Composition
The table below lists the controlled elemental ranges of 317L. These ranges govern its corrosion resistance, weldability, and low-carbon microstructural stability in service.
| Grade | C | Mn | P | S | Si | Cr | Ni | Mo | Other |
| TP317L | ≤ 0.035 | ≤ 2.00 | ≤ 0.045 | ≤ 0.030 | ≤ 1.00 | 18.00–20.00 | 11.00–15.00 | 3.00–4.00 | — |
2. Mechanical Properties
The table given below consists of the mechanical properties of 317L in the annealed condition, as typically required under ASTM specifications for tubes and pipes.
| Grade | Condition | Tensile Strength Min, MPa (ksi) | Yield Strength Min, MPa (ksi) | Elongation Min, % | PREN |
| TP317L | Annealed | 515 (75) | 205 (30) | 35 | 1040°C (1900°F) min |
3. Equivalent Grade
This table maps 317L across major international designation systems. It supports cross-border procurement, third-party inspection, and material verification for global projects.
| GRADE | UNS | GB | JIS | ISO | DIN/EN | GOST | |
| ISC | NEW | ||||||
| 317L | S31703 | 00Cr19Ni13Mo3 | 022Cr19Ni13Mo3 | SUS317L | X2CrNiMo18-15-4 | 1.4438 | 03Х17Н14М3 |
4. Key Technical Advantages
- Better Pitting and Crevice Corrosion Resistance: The elevated molybdenum content (3.0–4.0%) gives 317L a significantly higher Pitting Resistance Equivalent Number (PREN) (28.5–33.2) than 316L (23–28). This makes it suitable for dilute sulfuric acid, phosphoric acid, and warm chloride environments where 316L is inadequate.
- Low Carbon for As-Welded Corrosion Resistance: The carbon ceiling of 0.030% prevents sensitisation and intergranular corrosion in the heat-affected zone during welding. In most fabrication scenarios, post-weld annealing is unnecessary.
- Resistance to Reducing Acids: The combined chromium and elevated molybdenum content provides measurable resistance to reducing environments such as dilute sulfuric and acetic acids found in chemical processing operations.
- Technical Note: For applications requiring resistance to sulfurous acid and sulfate-containing pulp liquors, 317L is a reliable and cost-effective step up from 316L without moving to superaustenitic or duplex grades.
5. Common Manufacturing Standards
- ASTM A312: Standard specification for seamless, welded, and heavily cold-worked austenitic stainless steel pipes, including TP317L designation.
- ASTM A213: Standard specification for seamless ferritic and austenitic alloy-steel boiler, superheater, and heat-exchanger tubes, covering TP317L.
- ASTM A269: Standard specification for seamless and welded austenitic stainless steel tubing for general service, applicable to 317L.
- ASTM A511: Standard specification for seamless stainless steel mechanical tubing, covering MT317L designation.
- DIN EN 10216-5: Seamless steel tubes for pressure purposes — stainless steel (Grade 1.4438 equivalent).
- JIS G3459: Stainless steel pipes — applicable to SUS317L designation.
- GB/T 14976: Seamless stainless steel tubes for fluid transport — covers 022Cr19Ni13Mo4 designation.
Manufacturing Standards Comparison Table:
| Standard | ASTM | EN/DIN | JIS | GB/T | GOST |
| Seamless Pipe | A312 TP317L | EN 10216-5 (1.4438) | G3459 SUS317L | GB/T 14976 | no established GOST equivalent |
| Seamless Tube | A213 TP317L | EN 10216-5 (1.4438) | G3463 SUS317L | GB/T 13296 | no established GOST equivalent |
| Welded Tube | A249 TP317L | EN 10217-7 (1.4438) | G3463 SUS317L | GB/T 12771 | — |
6. Primary Applications
- Pulp and Paper Industry: This industry uses 317L for digesters, bleaching equipment, and liquor lines handling sulfate and sulfite compounds. The grade’s elevated molybdenum content improves the resistance to pitting from process chemicals.
- Chemical Processing: Heat exchangers and process piping exposed to dilute sulfuric acid, acetic acid, and phosphoric acid, environments that rapidly degrade standard 316L.
- Pollution Control Equipment: Flue gas desulfurization (FGD) scrubber components, wet scrubbers, and absorber vessels handling sulfur dioxide-laden condensates.
- Marine and Offshore: Seawater cooling lines and offshore chemical injection systems that need resistance to warm, chloride-rich fluids at elevated temperatures.
- Pharmaceutical Manufacturing: Process vessels and transfer lines handling acidic intermediates and cleaning solutions where contamination from corrosion products must be kept to a minimum.