317L stainless steel (UNS S31703) is a low-carbon austenitic grade with more molybdenum (3–4 %), chromium and nickel than 316L. It is used where 316L is borderline for pitting or for certain acids, such as in pulp and paper, flue gas desulfurisation and chemical processing.
Chemical limits are from ASTM A554-26 Table 1. Tensile values are from ASTM A312/A312M-24b Table 4.
317L chemical composition
| Element, % | 317L (S31703) | 316L (S31603) for comparison |
|---|---|---|
| Carbon, max | 0.030 | 0.030 |
| Manganese, max | 2.00 | 2.00 |
| Phosphorus, max | 0.045 | 0.045 |
| Sulfur, max | 0.030 | 0.030 |
| Silicon, max | 0.75 | 0.75 |
| Chromium | 18.0–20.0 | 16.0–18.0 |
| Nickel | 11.0–15.0 | 10.0–14.0 |
| Molybdenum | 3.0–4.0 | 2.00–3.00 |
| Nitrogen, max | 0.10 | 0.10 |
Mechanical properties (A312)
| Grade | Tensile, min | Yield, min |
|---|---|---|
| TP317L (S31703) | 75 ksi [515 MPa] | 30 ksi [205 MPa] |
| TP316L (S31603) | 70 ksi [485 MPa] | 25 ksi [170 MPa] |
317L vs 316L vs 904L
Using PREN = Cr + 3.3 Mo + 16 N on the minimum chromium and molybdenum, 316L gives about 23, 317L about 28 and 904L about 32. 317L is the step between them: more pitting resistance than 316L at a cost well below the high-alloy grades. These are ranking values only; real performance depends on temperature, chlorides and surface condition.
Ordering
317L is listed as TP317L in ASTM A312 (pipe) and in A249 (welded heat-exchanger tube). Confirm molybdenum on the mill test certificate; PMI separates it from 316L by molybdenum and chromium. TeCarve supplies 317L seamless and welded tube and pipe on request.
Frequently asked questions
What is 317L stainless steel?
A low-carbon austenitic stainless steel, UNS S31703, with 18–20 % chromium, 11–15 % nickel and 3–4 % molybdenum (ASTM A554).
Is 317L better than 316L?
For pitting and some acids, yes: it has about one point more molybdenum and two points more chromium. For mild service 316L is usually sufficient.
What is the strength of 317L pipe?
ASTM A312 requires 75 ksi [515 MPa] minimum tensile and 30 ksi [205 MPa] minimum yield strength for TP317L.
