317L stainless steel – UNS S31703
Low-carbon Cr-Ni-Mo (3–4% Mo) austenitic stainless steel
Austenitic stainless with more Cr, Ni and Mo than 316L, which improves resistance to pitting, crevice corrosion and sulfuric and acetic acids. Low carbon for welding without sensitization. Widely used in flue gas scrubbers (FGD) and pulp and paper.
Designations and equivalents
| System | Designation |
|---|---|
| UNS | S31703 |
| W.Nr./EN | ≈ 1.4438 (X2CrNiMo18-15-4) |
| DIN | X2CrNiMo18-15-4 |
| JIS | SUS317L |
| Trade names | AISI 317L |
| Others | 317LMN (S31726) is the N-bearing version |
Standards by product form
| Form | Standard |
|---|---|
| Bar | ASTM A276 |
| Forging/flange | ASTM A182 F317L |
| Plate | ASTM A240 |
| Tube | ASTM A312 TP317L |
Tolerances and HS codes
- Forged bars (round and square): machining allowance from 2 mm (Ø 6–16 mm) to 24 mm (Ø 400–500 mm) on the diameter. E.g. Ø 100–125 mm finished: +7 mm, tolerance +6 / −0 (length up to 3,500 mm).
- Forged discs: allowance of 4 to 9 mm on the diameter and 3 to 11 mm on the height, plus-only tolerance.
- Cutting and machining: band saw −0 / +5 to +15 mm on length; waterjet +10 % of thickness on the diameter (min. 2 mm); machined parts −0 / +2 to +5 mm on the diameter. See the full tables (INF 002 and INF 003, the same for every alloy).
| Form | NCM (Brazil, 8 digits) | HS (international, 6 digits) | HTS (USA, 10 digits)* | CN (European Union, 8 digits)* |
|---|---|---|---|---|
| Forged bar | 7222.30.00 | 7222.30 | 7222.30.0024 | 7222 30 51 |
| Hot-rolled bar | 7222.11.00 | 7222.11 | 7222.11.0059 | 7222 11 11 |
| Plate (> 10 mm, width ≥ 600 mm) | 7219.21.00 | 7219.21 | 7219.21.0020 | 7219 21 10 |
| Seamless pipe | 7304.41.90 | 7304.41 | 7304.41.6045 | 7304 41 00 |
| Welded pipe | 7306.40.00 | 7306.40 | 7306.40.5085 | 7306 40 80 |
| Flange and fitting | 7307.21.00 | 7307.21 | 7307.21.5000 | 7307 21 00 |
Tariff class: stainless steel (by chemical composition, under the Chapter 72 Notes and Section XV Note 5).
*: US and EU codes for reference. NCM per current legislation (General Rules of Interpretation, Notes to Chapters 72, 74 and 75 and Section XV Note 5). Confirm the final code with your customs broker according to the item size and finish. HS = first 6 digits of the NCM.
Chemical composition (%)
ASTM A182 F317L / A240
| Element | Range (%) |
|---|---|
| C | ≤ 0.030 |
| Mn | ≤ 2.00 |
| P | ≤ 0.045 |
| S | ≤ 0.030 |
| Si | ≤ 1.00 (A240: ≤ 0.75) |
| Cr | 18.0 – 20.0 |
| Ni | 11.0 – 15.0 |
| Mo | 3.0 – 4.0 |
| N | ≤ 0.10 |
| Fe | balance |
Mechanical properties
Solution annealed (A182 F317L; A240 in parentheses)
| Property | Value |
|---|---|
| Yield strength (0.2%) | ≥ 170 MPa (A240: ≥ 205) |
| Tensile strength | ≥ 485 MPa (A240: ≥ 515) |
| Elongation | ≥ 30% (A240: ≥ 40%) |
| Reduction of area | ≥ 50% |
| Hardness | ≤ 217 HB (A240) |
Typical physical properties
| Property | Value |
|---|---|
| Density | 8.0 g/cm³ |
| Melting range | 1,375 – 1,400 °C |
| Modulus of elasticity | 200 GPa |
| Thermal conductivity (20 °C) | ≈ 14 W/m·K |
| Thermal expansion (20–100 °C) | ≈ 16.0 µm/m·K |
Heat treatment, welding and machining
| Item | Usual practice |
|---|---|
| Service temperature | Cryogenic up to ≈ 425–450 °C under load; oxidation ≈ 870 °C. |
| Heat treatment | Solution annealing 1,040 – 1,150 °C with rapid water quench. |
| Welding | Good. Consumable AWS ER317L / E317L; in very aggressive media use an over-alloyed consumable (ER385 or ERNiCrMo-3) to compensate for Mo segregation in the weld bead. |
| Machining | Machinability lower than carbon steel: it work hardens quickly; use sharp tools, positive rake, constant feed without 'rubbing' and abundant coolant. |
Filler metal for welding
The wire composition is usually not identical to the material: each page explains why.
Typical applications
- Flue gas desulfurization scrubbers (FGD)
- Pulp and paper (bleaching)
- Thermal power plant condensers
- Acetic, formic and dilute sulfuric acids
- Refining: naphthenic acid media
- Paints, dyes and textiles
Alternatives: 316L in less aggressive media; 904L or 6Mo (254 SMO) when chlorides/temperature exceed 317L; 317LMN for a higher PREN without changing family.
317L stainless steel: complete guide
What 317L stainless steel is
317L belongs to the family of austenitic stainless steels and is the natural evolution of 316L for more aggressive media: more chromium (18 – 20%), more nickel (11 – 15%) and, above all, more molybdenum (3 – 4%). The low carbon preserves intergranular corrosion resistance after welding.
Chemical composition and role of the elements
Molybdenum is the element that defines 317L: each additional 1% raises the PREN by 3.3 points and shifts the critical pitting temperature upward. 317L has no nitrogen addition; the combination of molybdenum and nitrogen often attributed to it belongs to 317LMN, which carries 0.10 – 0.20% N.
Mechanical properties
In solution-annealed forgings ASTM A182 (F317L) requires a minimum yield strength of 170 MPa, minimum tensile strength of 485 MPa, minimum elongation of 30% and minimum reduction of area of 50%; in plate (A240) the minimums rise to 205 and 515 MPa, with 40% elongation and a maximum hardness of 217 HBW.
Corrosion and limits of use
With a PREN between 28 and 33, 317L resists chlorides, organic acids, dilute sulfuric acid and the gas scrubbing media where 316L suffers pitting. It is a process steel chosen for corrosion, not for temperature: the ASME code allows the L grade up to about 425 °C, and the 750 – 925 °C range quoted in catalogs is only the scaling limit. For even more severe chlorides, 904L or 254 SMO.
Applications
Flue gas desulfurization absorbers and ducts (FGD), bleaching equipment and pulp digesters, chemical process exchangers and piping, pump and valve shafts and machined parts for chloride media.
Supply forms and Dustre services
Round bars and blocks forged in open die, cut to size on a band saw, with rough or finish machining, solution annealing in our own furnaces and hardness, tensile and impact testing. All material is supplied with a 3.1 inspection certificate and heat traceability.
Frequently asked questions
What is the chemical composition of 317L stainless steel?
Per ASTM A182 F317L / A240: C ≤ 0.030; Mn ≤ 2.00; P ≤ 0.045; S ≤ 0.030; Si ≤ 1.00 (A240: ≤ 0.75); Cr 18.0 – 20.0.
Which standards cover 317L stainless steel?
Bar: ASTM A276. Forging/flange: ASTM A182 F317L. Plate: ASTM A240. Tube: ASTM A312 TP317L.
Up to what temperature can 317L stainless steel be used?
Cryogenic up to ≈ 425–450 °C under load; oxidation ≈ 870 °C.
Which materials can replace 317L stainless steel?
316L in less aggressive media; 904L or 6Mo (254 SMO) when chlorides/temperature exceed 317L; 317LMN for a higher PREN without changing family.
