317L Stainless Steel
317L is a low-carbon, high-molybdenum austenitic stainless steel for aggressive corrosion conditions. Compared with 316L, it typically carries higher molybdenum and nickel, which can improve resistance to pitting and crevice corrosion in chloride exposure and support stronger performance in some acidic media.
Many buyers specify 317L for welded fabrication and long service life. The low carbon limit helps reduce sensitization risk in heat-affected zones, which is a key consideration for process equipment in corrosive duty.
Alloy focus
High Mo (3–4%)
Stronger localized corrosion resistance versus common 316L.
Low-carbon stability
C ≤ 0.03%
Helps reduce weld-zone sensitization risk in many applications.
Typical equivalents
EN 1.4438 / SUS317L
Order to the governing standard and product form.
Magnetism
Non-magnetic (annealed)
Slight magnetism may appear after cold work or forming.
317L is selected when corrosion margin is a key driver. It is commonly used in chemical processing, marine and coastal systems, and industrial equipment that sees acids, chlorides, or both. It is often considered a practical upgrade when 316L is close to its limit.
- Chemical processing: heat exchangers, reactors, evaporators, and process piping
- Marine and coastal: condensers, pumps, valve parts, and seawater-related systems
- Pulp and paper: digesters, bleaching lines, and corrosion-critical vessels
- Pollution control: scrubbers, absorption towers, and wet gas handling
- Food and specialty service: tanks and parts where higher corrosion resistance is specified
317L may appear under different naming systems. Equivalents help for cross-reference, but the purchase order should be written to the target standard and product form.
| System | Designation | Note |
|---|---|---|
| ASTM / AISI | 317L | Common grade name in many specifications |
| UNS | S31703 | Used for identification and MTC |
| EN | 1.4438 | Often referenced in European project documentation |
| DIN / ISO style | X2CrNiMo18-15-4 | Common European naming format |
| JIS | SUS317L | Japanese designation |
| GB / regional | Common equivalents by spec | Confirm exact mapping by your governing standard |
- Corrosion resistance: improved localized corrosion resistance in chloride exposure compared with common 316L.
- Acid service: often chosen for certain sulfuric and organic acid duties when specified.
- Weld reliability: low carbon helps reduce sensitization risk in heat-affected zones.
- Fabrication fit: good ductility supports forming, bending, and standard welding routes.
Values below are typical specification limits used in many orders. Always confirm the final delivered chemistry on the Mill Test Certificate.
| Element | Typical limit / range | Role |
|---|---|---|
| C | ≤ 0.03% | Low carbon supports weld-zone corrosion stability |
| Cr | 18.0–20.0% | Base corrosion resistance and passivation |
| Ni | 11.0–15.0% | Toughness and austenitic structure stability |
| Mo | 3.0–4.0% | Improves pitting/crevice resistance and acid performance |
| Mn / Si | Mn ≤ 2.0%, Si ≤ 1.0% | Supports processing and deoxidation control |
| P / S | P ≤ 0.045%, S ≤ 0.03% | Impurity control for quality and performance |
| Fe | Balance | Base metal |
Properties vary by product form and thickness. For design work, use code tables and the governing specification.
| Property | Typical value | Note |
|---|---|---|
| Tensile strength | ≥ 515 MPa | Reference for annealed condition |
| Yield strength (0.2%) | ≥ 205 MPa | Reference for annealed condition |
| Elongation | ≥ 40% | Supports forming and fabrication |
| Hardness | ≤ 217 HBW | Typical maximum in many specifications |
317L can be supplied in a wide range of industrial forms. Availability depends on requested tolerances, finish, and inspection scope. If you share your standard, size, quantity, and destination, LYH Steel can advise the best supply route.
| Form | Typical size range | Notes |
|---|---|---|
| Sheet (cold rolled) | Thickness 0.3–6.0 mm, width 1000–2000 mm | Common for fabrication and cladding |
| Plate (hot rolled) | Thickness 3–100 mm, width 1000–2000 mm | Used for pressure parts and heavy equipment |
| Coil (cold rolled) | Thickness 0.3–6.0 mm, width 1000–2000 mm | Slitting and cut-to-length available |
| Strip | Width 7–600 mm, thickness 0.3–10 mm | Often used in fabrication and parts production |
| Pipe / tube | Seamless and welded options (OD/WT per standard) | Specify NDT, hydrotest, and surface requirements |
| Bars and shapes | Round/flat/angle/channel (size per request) | Common for machining and frames |
- Machining: similar to 316L; stable results typically require controlled speeds, sharp tooling, and proper coolant.
- Welding: use a disciplined procedure, clean surfaces, and controlled heat input. Match filler selection to the service environment.
- Forming: generally suitable for standard cold forming and bending with proper tooling and radius planning.
- Heat treatment: solution anneal is commonly used for best corrosion performance, followed by rapid cooling.
- Finishing: compatible with pickling, passivation, and polishing when specified.
317L is often selected as an upgrade from 316L when corrosion margin is needed. It is also a common replacement for 317 in weld-heavy projects, because the low carbon level helps reduce sensitization risk in heat-affected zones.
| Topic | 316L | 317L |
|---|---|---|
| Typical Mo range | Lower | Higher (often 3–4%) |
| Localized corrosion margin | Very good | Improved for demanding duty |
| Weld-heavy fabrication | Common | Common when higher corrosion margin is required |
| 317 comparison | N/A | Often preferred vs 317 due to lower carbon limit |
Use these internal tools to confirm equivalents, estimate weight, and plan tolerances before you issue an RFQ.
What is 317L stainless steel used for?
It is commonly used in chemical processing, marine and coastal systems, pollution control equipment, and other corrosive service where extra corrosion margin is required.
Why choose 317L instead of 316L?
317L typically includes higher molybdenum and nickel, which can improve resistance to pitting and crevice corrosion in chloride exposure and support stronger performance in certain acids.
Is 317L stainless steel magnetic?
In the annealed condition, it is generally non-magnetic. Slight magnetism can appear after cold work or forming.
Why is the low carbon level important?
The low carbon limit helps reduce sensitization risk in weld heat-affected zones, which can improve long-term corrosion stability in many corrosive services.
