Tesco Steel & Engineering manufactures SS 317 & 317L flanges — the high-molybdenum austenitic upgrade from 316L (ASTM A182 F317 / F317L, UNS S31700 / S31703, EN 1.4449 / 1.4438). Their 3–4% molybdenum (vs 2–3% in 316L) delivers markedly better resistance to chloride pitting, crevice corrosion and reducing acids like sulphuric acid — a PREN of ~32 vs ~25 for 316L. The low-carbon 317L (C ≤ 0.03%) avoids weld sensitisation without PWHT. Available in weld neck, slip-on, blind, socket-weld, threaded, lap-joint, orifice and long weld neck types to ASME B16.5 / B16.47. Class 150 to 2500, NPS 1/2″ to 24″. ISO 9001:2015 certified. Made in India.
SS 317 / 317L (ASTM A182 F317L) Flanges
SS 317L Weld Neck & Blind Flanges
Tesco Steel & Engineering manufactures SS 317 / 317L flanges per ASTM A182 F317 / F317L and ASME B16.5, in all flange types from weld neck to blind, Class 150 to 2500 — supplied with EN 10204 3.1 mill test certificates (3.2 / third-party inspection on request). Explore the wider stainless steel flange range, SS 316L flanges, duplex steel flanges, and the flange dimension charts.
| Element | SS 317 (S31700 / 1.4449) | SS 317L (S31703 / 1.4438) | SS 316L (S31603) | Role in Alloy |
|---|---|---|---|---|
| Carbon (C) | ≤ 0.080% | ≤ 0.030% | ≤ 0.030% | Low C prevents sensitisation during welding |
| Chromium (Cr) | 18.0 – 20.0% | 18.0 – 20.0% | 16.0 – 18.0% | Passive film, oxidation resistance |
| Nickel (Ni) | 11.0 – 15.0% | 11.0 – 15.0% | 10.0 – 14.0% | Austenite stabiliser, SCC resistance |
| Molybdenum (Mo) | 3.0 – 4.0% | 3.0 – 4.0% | 2.0 – 3.0% | Key differentiator — pitting & crevice resistance |
| Manganese (Mn) | ≤ 2.00% | ≤ 2.00% | ≤ 2.00% | Austenite stabiliser |
| Silicon (Si) | ≤ 1.00% | ≤ 1.00% | ≤ 1.00% | Deoxidiser |
| Phosphorus (P) | ≤ 0.045% | ≤ 0.045% | ≤ 0.045% | Residual — kept low for toughness |
| Sulphur (S) | ≤ 0.030% | ≤ 0.030% | ≤ 0.030% | Residual — low S improves corrosion resistance |
| Nitrogen (N) | ≤ 0.10% | ≤ 0.10% | ≤ 0.10% | Strengthens austenite, raises PREN |
| Property | SS 317 (F317) | SS 317L (F317L) | Unit |
|---|---|---|---|
| Tensile Strength (UTS) | 515 min | 515 min | MPa (74.7 ksi) |
| Yield Strength (0.2% offset) | 205 min | 205 min | MPa (29.8 ksi) |
| Elongation in 2″ | 30 min | 30 min | % |
| Reduction in Area | 50 min | 50 min | % |
| Hardness (max) | 217 HB / 96 HRB | 217 HB / 96 HRB | Brinell / Rockwell B |
| Density | 8.0 | 8.0 | g/cm³ |
| Modulus of Elasticity | 193 | 193 | GPa |
| ASME B16.5 Material Group | 2.2 | 2.2 | — |
| Property | SS 316L (S31603) | SS 317L (S31703) | SS 317LMN (S31726) |
|---|---|---|---|
| Mo content | 2.0–3.0% | 3.0–4.0% | 4.0–5.0% |
| Cr content | 16.0–18.0% | 18.0–20.0% | 17.0–20.0% |
| N content | ≤ 0.10% | ≤ 0.10% | 0.10–0.20% |
| Typical PREN | ~25 | ~32 | ~36 |
| UTS (MPa) | 515 min | 515 min | 515 min |
| Yield (MPa) | 205 min | 205 min | 240 min (N-strengthened) |
| H₂SO₄ resistance | Adequate for dilute, mild | Good for dilute–moderate | Excellent — near 904L |
| Relative cost | Baseline | ~20% above 316L | ~35% above 316L |
| ASTM Forging Grade | A182 F316L | A182 F317L | A182 F317LMN |
| Flange Type | Standard | Size Range | Class | Typical Application |
|---|---|---|---|---|
| Weld Neck | ASME B16.5 | 1/2″–24″ NB | 150–2500 | High-pressure process piping, acid plant headers |
| Slip-On | ASME B16.5 | 1/2″–24″ NB | 150–600 | Low-pressure headers, FGD ductwork connections |
| Blind | ASME B16.5 | 1/2″–24″ NB | 150–2500 | Line isolation, tank/vessel manholes |
| Socket Weld | ASME B16.5 | 1/2″–4″ NB | 150–2500 | Instrument connections, small-bore corrosive service |
| Threaded | ASME B16.5 | 1/2″–4″ NB | 150–2500 | Gauge connections, instrument taps |
| Lapped Joint | ASME B16.5 | 1/2″–24″ NB | 150–2500 | Frequent dismantling, stub-end connections |
| Long Weld Neck | ASME B16.5 / B16.47 | 1/2″–24″ NB | 150–2500 | Pressure vessel nozzles, reactor flanges |
| Spectacle Blind | ASME B16.48 | 1/2″–24″ NB | 150–1500 | Isolation / bypass in acid process systems |
| Orifice Flanges | ASME B16.36 | 1″–16″ NB | 300–2500 | Flow measurement in corrosive acid lines |
| Plate / Flat | DIN 2573 / EN 1092-1 | DN 15–DN 600 | PN 6–PN 100 | European piping, pump connections |
| Corrosive Environment | SS 316L | SS 317L | Notes |
|---|---|---|---|
| Sulphuric Acid H₂SO₄ (<30% at <60 °C) | Acceptable | Good | 317L preferred; higher Mo lowers corrosion rate |
| Sulphuric Acid H₂SO₄ (30–60% at <60 °C) | Marginal | Acceptable | 317L significantly outperforms 316L |
| Phosphoric Acid H₃PO₄ (up to 85%) | Acceptable (impure) | Good | 317L preferred for wet-process phosphoric acid |
| Nitric Acid HNO₃ (dilute) | Good | Good | Both adequate; 304L also acceptable for nitric only |
| Hydrochloric Acid HCl (any conc.) | Not recommended | Not recommended | Use Hastelloy C276 or Titanium Gr.2 for HCl |
| Chloride pitting (seawater, brines) | Moderate (PREN ~25) | Better (PREN ~32) | 317L suits higher chloride concentrations |
| Crevice corrosion (chlorides) | Moderate risk >40 °C | Lower risk — higher Mo | T&G face reduces crevice risk at gasket |
| Chloride stress-corrosion cracking | Susceptible >60 °C | Susceptible >60 °C | Use duplex or nickel alloy for SCC service |
| Caustic (NaOH/KOH) — dilute | Good | Good | Avoid concentrated hot caustic |
| FGD wet scrubbers (SO₂ + Cl⁻ + H₂O) | Insufficient | Good | 317L is standard for FGD scrubber flanges |
| Pulp bleach plant (ClO₂, Cl₂) | Insufficient | Good | 317L standard in Kraft bleach sequence flanges |
| Parameter | SS 317 (Standard Carbon) | SS 317L (Low Carbon) |
|---|---|---|
| Filler wire (AWS A5.9) | ER317 or ER317L | ER317L (mandatory for corrosive service) |
| Electrode (AWS A5.4) | E317-16 / E317-15 | E317L-16 / E317L-15 |
| Preheat required | None | None |
| Post-Weld Heat Treatment | May be required for thick sections | Not required — low C prevents sensitisation |
| Max inter-pass temperature | 175 °C (350 °F) | 175 °C (350 °F) |
| Sensitisation risk | Present at 425–870 °C (C ≤ 0.08%) | Negligible — low C prevents Cr₂₃C₆ |
| Weld process | GTAW, GMAW, SMAW, SAW | GTAW, GMAW, SMAW, SAW |
| Shielding gas | Argon or Ar/He mix | Argon or Ar/He mix |
| Industry | Application | Why 317L Over 316L |
|---|---|---|
| Sulphuric Acid Plants | Absorber tower flanges, weak-acid condensers, dilution piping | Higher Mo resists dilute-to-moderate H₂SO₄ |
| Phosphoric Acid Processing | Wet-process plant pipe flanges, evaporator nozzles | 317L handles impure phosphoric acid where 316L corrodes |
| FGD / Flue Gas Desulphurisation | Wet scrubber inlet/outlet flanges, absorber nozzles, slurry piping | SO₂ + Cl⁻ environment demands PREN >30 |
| Pulp & Paper / Kraft | Bleach plant flanges, ClO₂ generator connections, white liquor headers | Chlorine dioxide and oxidising bleach attack 316L |
| Chemical Processing | Mixed-acid reactors, chloride + acid service, pharma intermediates | Broader resistance across mixed environments |
| Petrochemical | Sour-crude fractionation, amine scrubbing, acetic acid plants | Mild reducing acid + chloride needs PREN >30 |
| Marine & Offshore | Seawater pipe flanges, offshore process headers, desalination pre-treatment | Higher PREN reduces pitting in warm seawater (>35 °C) |
| Food & Beverage | Acidic food lines, CIP with acidic cleaning agents | Better resistance to organic acid + cleaning chemicals |
| Power Generation | Condenser water boxes, seawater cooling-water flanges | Higher Mo prevents pitting in chloride-bearing water |
| Category | Standard | Scope |
|---|---|---|
| Flange Dimensions | ASME B16.5 | Pipe flanges Class 150–2500, 1/2″–24″ NB |
| Flange Dimensions | ASME B16.47 Series A & B | Large-diameter flanges, NPS 26–60 |
| Flange Dimensions | EN 1092-1 | European metric flanges, PN 2.5–400 |
| Flange Dimensions | MSS SP-44 | Steel pipeline flanges |
| Material — Forgings | ASTM A182 F317 / F317L | Stainless forgings for piping — standard flange material |
| Material — Bar | ASTM A276 / A479 | SS 317/317L bar for machined or small-bore flanges |
| Material — Plate | ASTM A240 Type 317 / 317L | Plate for slip-on and plate flanges |
| Material — European | EN 10222-5 | Pressure-vessel forgings — 1.4449 (317) / 1.4438 (317L) |
| Material — Japanese | JIS G4303 | SUS317 / SUS317L stainless bar |
| Inspection | EN 10204 3.1 / 3.2 | Mill test certificate — works (3.1) or TPI witness (3.2) |
| Piping Code | ASME B31.3 | Process piping — 317L in Material Group 2.2 |
| Weld Filler / Electrode | AWS A5.9 ER317L / A5.4 E317L-16 | Wire & electrode for welding 317L flanges |
| Standard | SS 317 | SS 317L |
|---|---|---|
| UNS (USA) | S31700 | S31703 |
| ASTM A182 (USA) | F317 | F317L |
| EN / DIN (Europe) | 1.4449 / X5CrNiMo17-13-4 | 1.4438 / X2CrNiMo18-15-4 |
| JIS (Japan) | SUS317 | SUS317L |
| BS (UK) | 317S16 | 317S12 |
| Common trade name | SS 317 | SS 317L |
3–4% Mo gives PREN ~32 — resists chloride pitting, crevice corrosion and reducing acids where 316L fails.
Low carbon (≤0.03%) eliminates weld sensitisation — no PWHT needed, full HAZ corrosion resistance.
WNRF, SORF, blind, socket-weld, threaded, lap-joint, LWN, orifice and plate — in RF, FF, RTJ and T&G faces.
EN 10204 3.1 / 3.2 MTC, PMI, ASTM A262 IGC and third-party inspection on request.
SS 317/317L flange prices run ~15–25% above equivalent 316L items due to the higher molybdenum and nickel content, and also depend on size, class, flange type and quantity. Tesco Steel & Engineering offers competitive factory-direct pricing backed by ISO-certified quality and full material traceability. Click Ask for Quote or message us on WhatsApp at +91 92233 66922 with grade (317 or 317L), flange type, size (NB), pressure class, quantity and documentation requirements — our team responds within 24 hours.
Q1. What is SS 317 / 317L stainless steel?
SS 317 (UNS S31700) and SS 317L (UNS S31703) are austenitic stainless steels containing 18–20% Cr, 11–15% Ni, and 3–4% Mo. The higher molybdenum (3–4% vs 2–3% in 316L) gives significantly better resistance to chloride pitting, crevice corrosion and reducing acids like sulphuric acid. 317L is the low-carbon variant (C ≤ 0.030%) that avoids sensitisation during welding without requiring post-weld heat treatment.
Q2. What is the difference between SS 317 and SS 317L flanges?
SS 317 has a maximum carbon of 0.080%; SS 317L limits carbon to 0.030%. The low carbon in 317L prevents chromium carbide precipitation at grain boundaries during welding (sensitisation), making it the preferred choice for field-welded flanges. Mechanical properties are virtually identical (UTS 515 MPa, Yield 205 MPa min). For flanges used as-forged without welding, either grade is acceptable.
Q3. What is the PREN of SS 317L and how does it compare to 316L?
PREN = %Cr + 3.3×%Mo + 16×%N. For 317L (typical): ~19 + 3.3×3.5 + 16×0.08 ≈ 32. For 316L (typical): ~17 + 3.3×2.25 + 16×0.05 ≈ 25. This ~7-point advantage means 317L resists chloride pitting in significantly more aggressive environments than 316L.
Q4. What ASTM standard covers SS 317L flanges?
SS 317L flanges are made to ASTM A182 Grade F317L for forgings. The dimensional standard is ASME B16.5 (Class 150–2500, 1/2″–24″ NB) or ASME B16.47 (large diameter, 26″–60″ NB). Composition and mechanical properties are governed by ASTM A182; certification per EN 10204 3.1.
Q5. What is the equivalent grade of SS 317L in European (DIN/EN) standards?
SS 317L (UNS S31703) equals EN/DIN 1.4438 (X2CrNiMo18-15-4); SS 317 (UNS S31700) equals EN/DIN 1.4449 (X5CrNiMo17-13-4). The Japanese equivalent is SUS317L (JIS G4303). All refer to the same alloy family with 3–4% Mo, 18–20% Cr and 11–15% Ni.
Q6. What is the temperature range for SS 317L flanges?
317L is austenitic and retains excellent toughness at cryogenic temperatures without impact testing — suitable down to −196 °C (−320 °F). Per ASME B16.5, 317L flanges (Material Group 2.2) may be used from −196 °C to +538 °C. Above 425 °C in oxidising conditions, use stabilised grades (321, 347) to avoid sensitisation in standard 317.
Q7. Where are SS 317 / 317L flanges used instead of SS 316L?
317/317L is specified over 316L for more aggressive service: (1) sulphuric acid plants (dilute H₂SO₄ 10–70% at elevated temperature); (2) phosphoric acid processing; (3) FGD wet scrubbers (SO₂ + chlorides); (4) Kraft pulp bleach plants (chlorine dioxide); (5) seawater with higher chloride where 316L misses the minimum PREN; (6) chemical processing with combined chloride + acidic conditions.
Q8. What filler wire is used for welding SS 317L flanges?
ER317L filler wire (AWS A5.9 / ISO 14343). This low-carbon filler matches the base chemistry and prevents weld-metal sensitisation. PWHT is not required for 317L. Keep inter-pass temperature below 175 °C (350 °F) to preserve corrosion resistance. ER317L is mandatory for any acidic or chloride service.
Q9. What is the maximum allowable stress for SS 317L flanges at 100 °C?
Per ASME Section II Part D, the allowable stress (S) for UNS S31703 at 100 °C is ~115 MPa (16.7 ksi); at 38 °C, S = 115 MPa; at 200 °C, 109 MPa; at 300 °C, 98 MPa. These govern pressure-vessel and exchanger nozzle-flange design. For piping, ASME B16.5 pressure-class ratings govern flange selection.
Q10. Is SS 317L better than SS 316L for sulphuric acid service?
Yes. The higher molybdenum (3–4% vs 2–3%) improves resistance to reducing acids including sulphuric acid. 317L performs well in dilute-to-moderate H₂SO₄ (up to ~50–60% at ambient). Above ~70% or at elevated temperature, even 317L may be insufficient — use Hastelloy C276 or Alloy 20. For mild service (<30% at <60 °C) both 316L and 317L are adequate; for more demanding concentrations 317L is clearly preferred.
Countries We Export SS 317 / 317L Flanges To: Kuwait, UAE, Germany, Saudi Arabia, West Africa, Iraq, Mexico, Bahrain, Canada, Philippines, Thailand, Kenya, Oman, Malaysia, Turkey, Qatar, Netherlands, Nigeria, Russia, Vietnam, Angola, Indonesia, UK, Yemen, Italy, USA, Venezuela, Spain, Iran, Kazakhstan, Algeria, Jordan, Colombia, Libya, Peru, South Africa, Denmark, Norway, France, Brazil, Poland, Greece, Egypt, New Zealand, Austria, Finland, Czech Republic and 40+ more countries.
Domestic Supply — SS 317 / 317L Flanges in India: Mumbai, Delhi, Bangalore, Hyderabad, Ahmedabad, Chennai, Kolkata, Surat, Pune, Jaipur, Nagpur, Gujarat, Maharashtra, Rajasthan, Tamil Nadu, Telangana, Karnataka, Uttar Pradesh, West Bengal and all major Indian industrial hubs.