FGD scrubbers
Absorber internals, ducts and spray piping in wet, acidic, chloride-laden slurry.
Austenitic stainless · low-carbon Mo grade · UNS S31703 · EN 1.4438
SS 317L stainless steel for welded, chloride-rich equipment
In short: SS 317L pairs 3–4% molybdenum with carbon held to 0.030%, so it resists pitting better than SS 316L and stays sound after welding without heat treatment. That combination makes it a standard choice for scrubbers, bleach plants and welded chemical equipment.
Overview
SS 317L in brief
- Low carbon for welded construction
- PREN about 28–30
- Step up from SS 316L for pitting and crevice resistance
- Common in FGD and pulp and paper equipment
SS 317L combines the higher molybdenum of SS 317 with 0.030% maximum carbon, so welded assemblies resist intergranular corrosion without post-weld annealing. It's one of the most common "next step up" grades when SS 316L shows pitting in service.
Typical users are FGD scrubbers, pulp and paper digesters and bleach washers, chemical plants handling acetic or phosphoric acid, and condensers. For severe chloride conditions, designers often compare SS 317L with SS 904L, duplex 2205 and 6Mo grades on a cost-per-PREN basis.
Available as
SS 317L product forms
Select a form for its specification, sizes and weights.
Where it's used
Industries that specify SS 317L
Typical services
Welded, wet and full of chlorides
Bleach plants
Washers and piping in chlorine-dioxide bleaching stages.
Process equipment
Reactors, condensers and heat exchangers handling organic acids and chlorides.
Chemistry
Composition of SS 317L
- UNS
- S31703
- EN / W.Nr.
- 1.4438 · X2CrNiMo18-15-4
- Density
- 8 g/cm³
- PREN
- 28 – 30
| Element | Limit, % | Why it matters |
|---|---|---|
| C | 0.030 max | 0.030% max: weldable without sensitising |
| Mn | 2.00 max | |
| P | 0.045 max | |
| S | 0.030 max | |
| Si | 0.75 max | |
| Cr | 18.0 – 20.0 | |
| Ni | 11.0 – 15.0 | |
| Mo | 3.0 – 4.0 | 3–4%: pitting and crevice resistance |
| N | 0.10 max |
Limits per ASTM A240; other product forms and specifications differ slightly. Your order's specification and edition govern.
Mechanical properties
Room-temperature minimums
515 MPa (75 ksi)Tensile strength (min. unless max)
205 MPa (30 ksi)Yield strength (0.2%) (min. unless max)
40%Elongation (min. unless max)
217 HBW / 95 HRBHardness (min. unless max)
ASTM A240: room-temperature specification values for the annealed condition.
Welding SS 317L
Use filler with molybdenum at least equal to the base metal, often an over-alloyed type, because weld metal segregates and can pit first.
Pickle and passivate welds in chloride service. See surface finishes.
Supply
SS 317L by product form
| Product form | Specification and designation |
|---|---|
| SS 317L pipes | ASTM A312 / ASME SA312 TP317L (seamless & welded); A358 EFW |
| SS 317L tubes | ASTM A213 TP317L (seamless); A249 / A269 TP317L (welded) |
| SS 317L plates | ASTM A240 / ASME SA240 317L |
| SS 317L sheets | ASTM A240 / ASME SA240 317L |
| SS 317L bars | ASTM A276 / A479 317L |
| SS 317L fittings | ASTM A403 WP317L (butt-weld); A182 F317L (forged) |
| SS 317L flanges | ASTM A182 / ASME SA182 F317L |
- Grade 317L with 0.030% max carbon
- Molybdenum 3.0% minimum confirmed on the certificate
- Over-alloyed filler if welding consumables are included
- Surface condition: pickled and passivated
- Matching fittings and flanges in SS 317L
Ordering
What to put on an order for SS 317L
Getting these on the enquiry avoids the usual back-and-forth and makes sure the certificate matches your specification.
SS 317L questions
Answers about SS 317L
Where is SS 317L used?
Flue gas desulphurisation (FGD) scrubbers, pulp and paper bleach plants, condensers, and chemical process equipment that is welded and handles chlorides or acids beyond what SS 316L tolerates.
SS 317L or SS 316L?
SS 317L has 3–4% molybdenum against 2–3% in SS 316L, so a pitting number of about 28–30 against about 23–25, at higher cost. Both keep carbon at 0.030% max for welding.[1] Compare SS 316L vs SS 317L.
Does SS 317L need post-weld heat treatment?
No. Low carbon prevents sensitisation in normal welding. Use filler with at least matching molybdenum (often over-alloyed) so weld metal isn't the weak point.
What is the EN equivalent of SS 317L?
1.4438 (X2CrNiMo18-15-4) is the usual EN counterpart; composition ranges are close but not identical.
Which specifications cover SS 317L?
Pipe: ASTM A312 / ASME SA312 TP317L (seamless & welded); A358 EFW. Tube: ASTM A213 TP317L (seamless); A249 / A269 TP317L (welded). Plate: ASTM A240 / ASME SA240 317L.
Sources
References
Composition limits from current ASTM editions; confirm against the edition on your order.
Need SS 317L?
Send sizes and service conditions. Matching fittings and flanges in SS 317L can ship together.