Higher-Molybdenum Austenitic Stainless for Aggressive Chemical Service
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UNS NUMBER
S31700
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ALLOY FAMILY
Austenitic (Mo-bearing)
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STRUCTURE
100% Austenite
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UTS (MIN)
≥515 MPa
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MAX TEMP
~870°C
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DENSITY
7.99 g/cm³
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Stainless Steel 317 (UNS S31700) is the higher-molybdenum version of 316, with 3–4% Mo (vs 2–3% in 316) lifting pitting and crevice resistance (PREN ~30) for more aggressive chemical and pulp/paper service. Carbon runs up to 0.08% like 316; for welded fabrications use 317L.
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Cr
18–20%
Oxidation resistance
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Ni
11–15%
Austenite stabilizer
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Mo
3–4%
Higher pitting / crevice than 316
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N
≤0.10%
Minor
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UTS
≥515 MPa
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YS 0.2%
≥205 MPa
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Elong.
≥35%
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Service
-196~870°C
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What is Stainless Steel 317?
317 is a modified 316 with extra molybdenum (3–4%) and a slightly wider nickel range (11–15%). That extra molybdenum raises PREN from ~26 (316) to ~30, giving better resistance to pitting, crevice corrosion, and a broader range of process chemicals — the reason it appears in pulp bleaching, FGD, and aggressive acid service.
Carbon runs up to 0.08%, so like 316 it can sensitize in the 425–815°C range after welding. For welded equipment that cannot be post-weld annealed, 317L (C ≤ 0.030%) is the correct choice. Where chloride levels are extreme (seawater, warm brine), the super-austenitics 904L, AL6XN, and 254SMO take over.
Chemical Composition (Weight %)
| Element |
Min (%) |
Max (%) |
Role in Alloy |
| Chromium (Cr) |
18.0 |
20.0 |
Oxidation resistance |
| Nickel (Ni) |
11.0 |
15.0 |
Austenite stabilizer |
| Molybdenum (Mo) |
3.0 |
4.0 |
Higher pitting / crevice than 316 |
| Carbon (C) |
— |
0.08 |
Kept low; risks sensitization |
| Manganese (Mn) |
— |
2.00 |
Deoxidizer |
| Silicon (Si) |
— |
1.00 |
Deoxidizer |
| Phosphorus (P) |
— |
0.045 |
Impurity |
| Sulfur (S) |
— |
0.030 |
Impurity |
| Nitrogen (N) |
— |
0.10 |
Minor |
| Iron (Fe) |
Balance |
— |
Matrix former |
★ Molybdenum 3–4% (vs 2–3% in 316) is the key upgrade, raising PREN to ~30. Carbon up to 0.08% means welded fabrications can sensitize; use 317L where PWHT is impractical.
Mechanical Properties
Values are for the solution-annealed condition per ASTM A240, A182 (F317), and A312 (TP317).
| Condition / Form |
UTS (MPa) |
YS 0.2% (MPa) |
Elong. % (min) |
Hardness (max) |
| Minimum (ASTM A240 / A182 F317) |
≥515 |
≥205 |
35 |
217 HBW (95 HRB) |
| Typical mill-annealed |
515–690 |
205–350 |
40–50 |
155–200 HBW |
Modulus of Elasticity 193 GPa. Cold work raises strength. Not hardenable by heat treatment. 317 has slightly better creep strength than 316 due to higher Mo/Ni.
Physical Properties
| Property |
Value |
Note |
| Density |
7.99 g/cm³ |
~316 |
| Melting Range |
1371–1421°C |
Solidus ~1371°C |
| Thermal Conductivity (20°C) |
16.2 W/m·K |
Comparable to austenitics |
| Thermal Expansion (20–100°C) |
16.0 ×10⁻⁶ /K |
Higher than carbon steel |
| Specific Heat |
0.12 kcal/kg·°C |
~500 J/kg·K |
| Electrical Resistivity |
74 µΩ·cm |
At room temp |
| Magnetic Property |
Non-magnetic* |
*Slight after cold work |
| PREN (Pitting Resistance) |
~30 |
PREN = %Cr + 3.3×%Mo + 16×%N |
Corrosion Resistance
Pitting & Crevice Corrosion
The 3–4% molybdenum gives PREN ~30, better than 316 in chloride and bromide environments. Still limited in warm/stagnant seawater; for aggressive chloride use 904L or 254SMO.
Chemical & Pulp Service
317 resists a broader range of acids and oxidizing chlorides than 316, so it is used in pulp bleaching, FGD scrubbers, and aggressive process streams.
General Atmospheric & Aqueous
Comparable to 316 in fresh water and atmospheric service, with extra margin in mildly aggressive media.
Weld Sensitization
Carbon up to 0.08% means welded thick sections can sensitize in the 425–815°C range. Use 317L for as-welded fabrications.
Stainless Steel 317 vs Similar Grades — Selection Guide
| If you need... |
Choose... |
Why |
| Aggressive chemical, >316 need |
317 / 317L |
Mo 3–4%, PREN ~30 |
| Welded vessel not PWHT |
317L |
C ≤ 0.030% avoids sensitization |
| Warm seawater / extreme Cl⁻ |
904L / 254SMO |
PREN 36–45 |
| General chloride |
316L |
Lower cost |
| FGD / pulp bleach |
317L / 904L |
Acid + chloride |
Applicable Standards
| Standard |
Product Form |
| ASTM A240 |
Plate, sheet, strip |
| ASTM A182 F317 |
Forged flanges & fittings |
| ASTM A312 TP317 |
Seamless & welded pipe |
| ASTM A403 WP317 |
Butt-weld fittings |
| ASTM A276 / A479 |
Bar, rod, forging stock |
| EN 1.4449 |
European equiv. |
HT PIPE Supply — Stainless Steel 317 Product Forms
| Product Form |
Specifications |
HT PIPE Supply |
| Seamless Pipe |
ASTM A312 TP317 |
✅ Available |
| Forged Flanges |
ASTM A182 F317, ASME B16.5 |
✅ In stock |
| Butt-Weld Fittings |
ASTM A403 WP317 |
✅ Available |
| Plate / Sheet |
ASTM A240 |
✅ Available |
| Bar / Rod |
ASTM A276 / A479 |
✅ Available |
| Welded Pipe |
ASTM A312 TP317 |
✅ Available |
HT PIPE supplies 317 (and 317L) in pipe, flanges, fittings, plate, and bar for aggressive chemical and pulp/paper service, with full MTRs.
Project Experience — Stainless Steel 317
HT PIPE supplies 317 for pulp/paper, FGD, and aggressive chemical process systems.
| Project |
Product |
Specification |
| Pulp Bleaching Plant (Europe) |
317L Pipe + Fittings |
A312, A403 |
| FGD Scrubber (Asia) |
317L Plate + Forgings |
A240, A182 |
| Aggressive Acid Process (China) |
317 Flanges + Pipe |
A182 F317, A312 |
We advise 317 vs 317L and provide PMI verification for chloride/acid service.
| FREQUENTLY ASKED QUESTIONS |
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FAQ — Stainless Steel 317
| What is the difference between 317 and 316? |
| 317 has more molybdenum (3–4% vs 2–3%) and a wider nickel range, raising PREN from ~26 to ~30. That gives better pitting/crevice resistance and a broader chemical range — at a higher cost. |
| What is the difference between 317 and 317L? |
| 317L caps carbon at 0.030% (vs up to 0.08% for 317) to avoid weld sensitization. Use 317L for welded fabrications that will not be post-weld annealed. |
| Is 317 good in seawater? |
| Better than 316 (PREN ~30) but still not enough for warm/stagnant seawater. For aggressive chloride use 904L, AL6XN, or 254SMO. |
| What filler is used for 317? |
| ER317 / E317 for matching chemistry. For welded joints in the sensitizing range use ER317L. |
| Where is 317 typically used? |
| Pulp bleaching, FGD scrubbers, and aggressive acid/oxidant process streams where 316 would corrode too quickly. |
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Need Stainless Steel 317 for Aggressive Service?
HT PIPE supplies 317 seamless pipe, butt-weld fittings, forged flanges, and plate with full MTR documentation. Contact our technical team for material selection and welding advice.
Request a Quote |
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