317L Stainless Steel (UNS S31703)
Austenitic (high-Mo, low carbon) · ASTM A240/A240M · Density 7.98 g/cm³
317L (UNS S31703) is a low-carbon austenitic stainless steel with 3–4% molybdenum — one full step above 316L in pitting and crevice corrosion resistance. It is specified where 316L shows attack but duplex or 6Mo grades would be overkill: flue-gas desulfurization scrubbers, pulp bleach plants and process equipment handling hot acidic, chloride-bearing liquors.
Chemical Composition (wt%)
| C | Mn | Si | Cr | Ni | Mo | P | S | N |
|---|---|---|---|---|---|---|---|---|
| ≤0.030 | ≤2.00 | ≤0.75 | 18.0–20.0 | 11.0–15.0 | 3.0–4.0 | ≤0.045 | ≤0.030 | ≤0.10 |
Single values are maximums unless a range is shown. Balance: Fe. Per ASTM A240/A240M.
Mechanical Properties
| Tensile strength | ≥515 MPa (75 ksi) |
|---|---|
| Yield strength (0.2%) | ≥205 MPa (30 ksi) |
| Elongation (50 mm) | ≥40% |
| Hardness | ≤217 HBW |
Room-temperature minimum values are summarized for annealed flat product under ASTM A240/A240M unless a condition is named in the property label; product form and thickness can change the requirement.
Physical Properties & Structure
| Density | 7.98 g/cm³ |
|---|---|
| Magnetic response | Essentially non-magnetic after solution annealing; cold work can introduce a measurable magnetic response. |
| Microstructure | Austenitic (high-Mo, low carbon) |
Corrosion Resistance & Limits
- General corrosion resistance comes from the chromium-rich passive film; nickel, molybdenum, nitrogen and copper change performance by grade.
- Check chlorides, temperature, crevices, deposits, process chemistry and cleaning conditions. A grade designation alone is not a service-life guarantee.
Fabrication & Heat Treatment
| Welding | Generally weldable with a qualified procedure and matching or over-alloyed filler where required; remove heat tint when corrosion service demands it. |
|---|---|
| Forming | Good ductility is typical, but rapid work hardening increases forming load and springback; bend radius and intermediate annealing depend on grade and reduction. |
| Machining | Use rigid tooling, positive feeds and controlled heat because the material work-hardens; free-machining grades require separate corrosion and welding review. |
| Heat treatment | Solution annealing and rapid cooling restore the intended condition where applicable. Austenitic grades are not hardened by conventional quench-and-temper treatment. |
Equivalent Grades
The closest international equivalents of 317L Stainless Steel are 1.4438 (X2CrNiMo18-15-4) in the EN system, SUS317L in the JIS system, 022Cr19Ni13Mo3 in the GB system.
These are common corresponding designations, not unconditional substitutes. Verify chemistry, mechanical properties, product standard, delivery condition, dimensions and project approval before changing designation.
| System | Designation |
|---|---|
| UNS | S31703 |
| EN | 1.4438 (X2CrNiMo18-15-4) |
| JIS | SUS317L |
| GB | 022Cr19Ni13Mo3 |
Reference Product Forms & Dimensional Ranges
Common reference product forms for 317l stainless steel: Sheet / Plate, Coil / Strip, Pipe / Tube, Bar.
| Finishes | No.1, 2B, BA |
|---|---|
| Sheet / coil thickness | 0.5–6.0 mm |
| Plate thickness | 6–60 mm |
Common surface and delivery options: No.1, 2B, BA or mechanically polished finish when supported by the product route; Annealed and pickled, descaled or polished tube finish as specified; Hot rolled, peeled, bright drawn, ground or polished bar condition according to tolerance.
These published ranges are engineering references, not a live-stock or production-capability promise. Confirm the required product form, dimensions, condition, finish and supply route in the quotation.
Typical Applications
- Flue-gas desulfurization (FGD) scrubbers
- Pulp and paper bleach washers
- Chemical process vessels and columns
- Condenser and heat-exchanger tubing
- Textile dyeing and finishing equipment
Frequently Asked Questions
How much better is 317L than 316L?
The extra molybdenum lifts the pitting resistance equivalent number (PREN) from roughly 24–26 for 316L to 29–33 for 317L. In practice that means 317L tolerates higher chloride concentrations and temperatures before pitting starts — often the difference between annual repairs and a full service life in scrubber duty.
Is 317L usually dual-certified like 304/304L?
Dual certification is possible when the heat meets both 317 and 317L requirements. For welded process equipment, order the required L designation and confirm both chemistry and mechanical requirements on the MTC.
When should I move from 317L up to duplex or 6Mo grades?
If chlorides or temperature keep rising, the next steps are duplex 2205 (similar corrosion resistance with double the strength) or super-austenitic S31254 with 6% Mo for seawater-level chlorides. 317L remains the economical choice when 316L is marginal rather than clearly failing.
317L Compared With Other Grades
Organizational author: Tsingshan (Shandong) Iron & Steel Co., Ltd..Review method, status and limitations.
Other stainless steel grades:
304304L316316L201321310S4104302205202301309S316Ti347904L409L4204394414442507303254 SMO440C17-4 PH2304
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