304L
Typical reasons to choose 304L
Welded tanks, architectural fabrication, food equipment and general corrosive service.
Stainless steel grade comparison
304L vs 317L Stainless Steel
Compare 304L and 317L stainless steel by chemistry, microstructure, corrosion resistance, fabrication, product form, governing standard and procurement priorities.
Quick answer: Choose 304L where low-carbon weldability and general corrosion resistance are sufficient. Choose 317L where molybdenum is needed for a stronger localized-corrosion margin in chloride-containing service.
The alloying and microstructure difference behind the selection decision
304L
EN 1.4307 · UNS S30403- C0.02%
- Cr18.1%
- Ni8.1%
- Mo—
317L
EN 1.4438 · UNS S31703- C0.02%
- Cr17.2%
- Ni10.1%
- Mo2.1%
Technical basis: Outokumpu Core 304L/4307 and Supra 317L/317L/4438 reference material. Final composition and properties must follow the applicable specification and mill test certificate.
M03 · Decision summary
304L or 317L: which one should you specify?
Both grades are low-carbon austenitic stainless steels. The central distinction is the 2% molybdenum addition in 317L, not a simple difference in weldability.
| Decision factor | 304L stainless steel | 317L stainless steel | |
|---|---|---|---|
| Corrosion resistance | 304L — Low-carbon austenitic Cr-Ni | 317L — Low-carbon austenitic Cr-Ni-Mo | Service environment controls the decision. |
| Welding and fabrication | State thickness, weld route and required corrosion performance. | State thickness, weld route and required corrosion performance. | Do not use grade name alone. |
| Magnetic behavior | Confirm delivery condition and cold-work exposure. | Confirm delivery condition and cold-work exposure. | Microstructure can matter to the design. |
| Supply condition | Define product form, finish, dimensions and certificate scope. | Define product form, finish, dimensions and certificate scope. | Quote to the finished requirement. |
| Selection priority | Welded tanks, architectural fabrication, food equipment and general corrosive service. | Process equipment, chloride-exposed fabrication, marine-adjacent systems and more demanding cleanability. | Start from service evidence, not price alone. |
Neither grade should be specified as universally seawater-proof. Crevices, deposits, temperature and chloride concentration can require duplex or higher-alloy review.
M04 · Technical data
304L vs 317L Stainless Steel properties
Typical chemistry is shown as an engineering reference. Mechanical properties must be compared only under the same product standard and delivery condition.
Typical chemical composition
Reference values by mass, not guaranteed purchase limits.
| Element / indicator | 304L | 317L | Selection significance |
|---|---|---|---|
| C | 0.02% | 0.02% | Confirm final chemistry against the governing material standard and MTC. |
| Cr | 18.1% | 17.2% | Confirm final chemistry against the governing material standard and MTC. |
| Ni | 8.1% | 10.1% | Confirm final chemistry against the governing material standard and MTC. |
| Mo | — | 2.1% | Molybdenum materially changes localized-corrosion performance. |
Material and fabrication behavior
Use these points to frame a condition-specific technical review.
| Property | 304L | 317L | Procurement interpretation |
|---|---|---|---|
| Microstructure | Low-carbon austenitic Cr-Ni | Low-carbon austenitic Cr-Ni-Mo | Defines the main fabrication and service behavior. |
| Heat treatment | Specify delivery condition; this comparison does not imply a hardening route. | Specify delivery condition; this comparison does not imply a hardening route. | Confirm finished property requirements. |
| General fabrication | Use the applicable welding/forming procedure. | Use the applicable welding/forming procedure. | Process route matters as much as grade. |
| Corrosion review | Define chlorides, chemicals, temperature, deposits and crevices. | Define chlorides, chemicals, temperature, deposits and crevices. | Higher-alloy review may be required. |
Engineering caution: Neither grade should be specified as universally seawater-proof. Crevices, deposits, temperature and chloride concentration can require duplex or higher-alloy review.
M05 · Product form matrix
Product forms and supply routes for 304L and 317L
Both grades can be supplied in common stainless product forms, but availability, finish and certification are product-specific. Confirm the exact grade and delivery condition in the RFQ.
RFQ rule: grade, product form, dimensions, tolerance, finish, governing standard, quantity, destination and certificate scope.
| Product form / route | 304L | 317L | Procurement note |
|---|---|---|---|
| Cold-rolled coil, strip and sheet | Common route | Common route | Confirm thickness, width, finish and edge. |
| Plate and fabricated components | Available | Available | State fabrication and inspection requirements. |
| Bar / mechanical component | Program dependent | Program dependent | Use the correct long-product standard and condition. |
| Welded fabrication | Procedure review | Procedure review | State joint design, filler, post-weld treatment and service. |
M06 · Grade selector
Screen 304L and 317L against the service conditions
This is a preliminary routing tool, not a substitute for governing specification review.
Preliminary result
Define the controlling requirement
Select the conditions that apply to your component.
Send conditions to an engineer01Define environment
02Define fabrication
03Define final condition
04Confirm standard
M08 · Applications & limitations
Where 304L works, where 317L is justified, and where a further review is needed
The relevant choice is the one that meets the finished-component and service requirement with defined specification evidence.
317L
Typical reasons to choose 317L
Process equipment, chloride-exposed fabrication, marine-adjacent systems and more demanding cleanability.
Review
Conditions needing a different alloy review
Neither grade should be specified as universally seawater-proof. Crevices, deposits, temperature and chloride concentration can require duplex or higher-alloy review.
Fabrication and service comparison
Use these points to define the RFQ.
| Requirement | 304L | 317L | Selection effect |
|---|---|---|---|
| Corrosion resistance | 304L — Low-carbon austenitic Cr-Ni | 317L — Low-carbon austenitic Cr-Ni-Mo | Service environment controls the decision. |
| Welding and fabrication | State thickness, weld route and required corrosion performance. | State thickness, weld route and required corrosion performance. | Do not use grade name alone. |
| Magnetic behavior | Confirm delivery condition and cold-work exposure. | Confirm delivery condition and cold-work exposure. | Microstructure can matter to the design. |
| Supply condition | Define product form, finish, dimensions and certificate scope. | Define product form, finish, dimensions and certificate scope. | Quote to the finished requirement. |
| Selection priority | Welded tanks, architectural fabrication, food equipment and general corrosive service. | Process equipment, chloride-exposed fabrication, marine-adjacent systems and more demanding cleanability. | Start from service evidence, not price alone. |
Important: Neither grade should be specified as universally seawater-proof. Crevices, deposits, temperature and chloride concentration can require duplex or higher-alloy review.
Material image comparison
Reserved positions for approved product imagery showing each material option. These blocks can be replaced directly with Media Library images later.
Reserved image position
Use an approved product-form or surface-detail image.
Reserved image position
Use an approved product-form or application image.
M10 · Standards & equivalence
304L and 317L stainless steel grade designations
304L and 317L are low-carbon austenitic grades. Confirm the product form, delivery condition and governing standard before purchase.
| Designation / standard | 304L | 317L | Procurement caveat |
|---|---|---|---|
| ASTM / AISI type | 304L | 317L | Use the exact grade identity. |
| UNS | S30403 | S31703 | Use UNS where grade identity matters. |
| EN material number | 1.4307 | 1.4438 | Do not rely on informal equivalence alone. |
| Alloy family | Low-carbon austenitic Cr-Ni | Low-carbon austenitic Cr-Ni-Mo | Molybdenum provides a higher chloride-corrosion margin. |
| Typical product route | A240 / A276 as applicable | A240 / A276 as applicable | Confirm dimensions, finish and delivery condition. |
| EN grade name | X2CrNi18-9 | X2CrNiMo18-15-4 | Both are low-carbon austenitic grades; molybdenum distinguishes the 317L route. |
| JIS reference | SUS304L | SUS317L | Confirm the governing JIS product standard and exact chemistry. |
| ASTM / ASME flat-product route | ASTM A240 / ASME SA-240 where applicable | ASTM A240 / ASME SA-240 where applicable | Confirm thickness range, finish and current edition. |
| ASTM long-product route | ASTM A276 / A479 as applicable | ASTM A276 / A479 as applicable | Bar, billet, forging and pressure-service requirements are product-specific. |
| EN flat-product reference | EN 10088-2 where applicable | EN 10088-2 where applicable | Use the exact delivery condition and product form. |
| EN long-product reference | EN 10088-3 where applicable | EN 10088-3 where applicable | Long-product properties must be checked separately from flat-product data. |
| Material certificate | EN 10204 3.1 when specified | EN 10204 3.1 when specified | State certificate, testing and traceability requirements in the RFQ. |
| Delivery condition | 304L: commonly solution annealed; state finish and dimensions. | 317L: commonly solution annealed; state finish and dimensions. | Do not assume a common condition across forms, dimensions or suppliers. |
| Selection input | State chloride exposure, fabrication route and required documentation. | Use the governing specification for final acceptance. | |
304L · S30403Low-carbon austenitic stainless steel.
304L · 1.4307EN low-carbon Cr-Ni designation.
317L · S31703Low-carbon higher-molybdenum austenitic grade.
317L · 1.4438EN low-carbon Cr-Ni-Mo designation.
Grade equivalence is not permission to substitute. Confirm chemistry, product form, dimensions, finish, delivery condition, standard revision and mill test certificate before changing material.
M11 · Direct answers
304L vs 317L Stainless Steel FAQ
Answers to the main purchasing and engineering questions behind this comparison.
What is the main difference between 304L and 317L stainless steel?
Both grades are low-carbon austenitic stainless steels. The central distinction is the 2% molybdenum addition in 317L, not a simple difference in weldability.
Which grade has the stronger corrosion-resistance starting point?
317L has the stronger chloride-resistance starting point because it includes molybdenum. Both are low-carbon grades, so the actual welding procedure, thickness and corrosive service should be specified.
What should be included in an RFQ for this comparison?
State grade, product form, dimensions, finish, standard, quantity, service environment, weld route and required certificate or inspection level.
Can one grade replace the other simply to reduce cost?
No. A grade change can alter corrosion resistance, fabrication behavior, magnetic response, heat treatment and certification requirements. Compare the finished component and actual service.
When should a higher-alloy stainless steel be reviewed?
Neither grade should be specified as universally seawater-proof. Crevices, deposits, temperature and chloride concentration can require duplex or higher-alloy review.
M13 · Sources & technical review
Technical basis for this 304L vs 317L comparison
This page distinguishes manufacturer typical chemistry from final purchase specification. It does not make a live-inventory or fixed-price claim.
Primary technical references
- Outokumpu product-range informationOutokumpu Core 304L/4307 and Supra 317L/317L/4438 reference material.
- ASTM A240/A240MCommon flat-product specification family; confirm the applicable edition and delivery condition.
- EN 10088 seriesEuropean stainless-steel designation and product-condition reference.
- Mill test certificateFinal chemistry and properties must be confirmed against the supplied heat and purchase specification.
Page accountability
AuthorStainless Steel Market technical content team
Material-selection and procurement guidance for buyer review.
Technical reviewSupplier confirmation required for final acceptance
Confirm product form, standard, condition and MTC for each enquiry.
Review date24 September 2026
Checked against current manufacturer reference material.
Update log
2026-09-24 — Initial T09 comparison prepared with technical tables, selector, FAQ and RFQ routing.
M14 · Ask an engineer
Still deciding between 304L and 317L?
Send the product form, service environment, fabrication route, dimensions and governing specification for a condition-specific material review.
- 304L, 317L or alternative grade under consideration
- Product form, dimensions, tolerance and finish
- Chlorides, chemicals, temperature and cleaning conditions
- Welding, forming, machining and final condition
- Required standard, MTC, inspection and destination
- Quantity, timing and commercial requirements
Send your material requirement
For a useful review, include product form, dimensions, service conditions, fabrication route, required standard, quantity and documentation needs.