Stainless Steel 317
Stainless Steel 317 (UNS S31700) has comparatively higher molybdenum content than the 316 series, which is a minimum of 3.0%, with chromium at 18-20% and nickel at 11-15%. The higher alloy content gives this material noticeably better pitting and crevice corrosion resistance, suited to aggressive reducing acid and chloride-bearing chemical process environments.
1. Chemical Composition
The table given below shows the chemical composition ranges for Stainless Steel 317. The higher molybdenum content and broader chromium-nickel range produce a higher PREN than 316 or 316L grades.
| Grade | C | Mn | P | S | Si | Cr | Ni | Mo | Other |
| TP317 | ≤ 0.080 | ≤ 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 below lists minimum ambient-temperature mechanical properties for Stainless Steel 317 in the annealed condition, consistent with ASTM A312 and A213 requirements for austenitic pipe and tube products.
| Grade | Condition | Tensile Strength Min, MPa (ksi) | Yield Strength Min, MPa (ksi) | Elongation Min, % | Heat Treatment Temp |
| TP317 | Annealed | 515 (75) | 205 (30) | 35 | 1040°C (1900°F) min |
3. Equivalent Grade
This table cross-references Stainless Steel 317 with its international designations. The European and Japanese counterparts are closely aligned by composition and are used in similar process industry applications.
| GRADE | UNS | GB | JIS | ISO | DIN/EN | GOST | |
| ISC | NEW | ||||||
| 317 | S31700 | S31708 | 06Cr19Ni13Mo3 | SUS317 | - | 1.4449 | - |
3. Key Technical Advantages
- Higher PREN Than 316 Series: This grade has a minimum 3% Mo and 18-20% Cr. This is why the PREN of 317 reaches approximately 28-33 (4-5 PREN units above 316/316L). This means it can handle more concentrated chloride environments and higher-temperature pitting conditions than 316.
- Resistance to Sulfurous Acid and Kraft Pulping Liquors: The higher molybdenum level improves resistance to sulfurous acid (H2SO3), bisulfite solutions, and black liquor in kraft pulping processes. This is one of the main industrial reasons for choosing 317 over 316.
- Improved Resistance to Reducing Acids: In dilute-to-moderate concentration sulfuric acid and phosphoric acid environments, the extra molybdenum in 317 lowers corrosion rates compared to 316. Components last longer in acid plant and fertiliser processing equipment as a result.
- Broad Corrosion Resistance Profile: By combining elevated Cr, Ni, and Mo, Grade 317 resists both oxidising and reducing corrosion environments. This makes it a practical choice when process conditions shift between the two, such as in mixed acid service.
Technical Note: For severe pitting or crevice corrosion environments that exceed the capability of 317, consider 317L (low-carbon variant) or super-austenitic grades such as 317LMN (UNS S31726).
4. Common Manufacturing Standards
- ASTM A312: Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes — TP317 designation.
- ASTM A213: Standard Specification for Seamless Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes — TP317 designation.
- ASTM A269: Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for General Service.
- ASTM A249: Standard Specification for Welded Austenitic Steel Boiler, Superheater, Heat-Exchanger, and Condenser Tubes.
- ASTM A358: Standard Specification for Electric-Fusion-Welded Austenitic Chromium-Nickel Stainless Steel Pipe for High-Temperature and General Corrosive Service.
- DIN EN 10216-5: Seamless steel tubes for pressure purposes — stainless steel (1.4449).
- DIN EN 10217-7: Welded steel tubes for pressure purposes — stainless steel (1.4449).
- JIS G3459: Stainless Steel Pipes (SUS317).
- JIS G3463: Stainless Steel Boiler and Heat Exchanger Tubes.
- GB/T 14976: Seamless stainless steel tubes for fluid transport (06Cr19Ni13Mo3).
Manufacturing Standards Comparison Table:
| Standard | ASTM | EN/DIN | JIS | GB/T | GOST |
| Seamless Pipe | A312 (TP317) | EN 10216-5 (1.4449) | G3459 (SUS317) | 14976 | - |
| Welded Pipe | A312 (TP317) | EN 10217-7 (1.4449) | G3459 (SUS317) | - | - |
| Heat Exchanger Tube | A213 (T317) / A249 | EN 10216-5 | G3463 | 13296 | - |
| General Service Tube | A269 | EN 10216-5 | G3463 | 14976 | - |
5. Primary Applications
- Pulp and Paper Industry: Digesters, evaporators, and washers in kraft and sulfite pulping operations where sulfite, bisulfite, and black liquor attack 316 at unacceptable rates.
- Sulfuric Acid Plant Equipment: Heat exchanger tubes, gas cooling systems, and absorption tower internals in contact with dilute-to-moderate H2SO4 and sulfur trioxide at elevated temperatures.
- Flue Gas Desulfurization (FGD) Systems: Absorber tower liners, ductwork, and slurry piping in coal-fired power plant desulfurization units where chloride concentrations in scrubber liquor exceed what 316L can handle.
- Dye and Textile Chemical Processing: Reactor vessels and transfer piping handling complex organic acids, dye intermediates, and bleaching chemicals in speciality chemical manufacturing.
- Phosphoric Acid and Fertiliser Plants: Evaporators, heat exchangers, and piping in wet-process phosphoric acid production where high phosphate and fluoride concentrations at elevated temperature demand more Mo content than 316 provides.