Sensitization range
427-816 deg C / 800-1500 deg F is the cited chromium-carbide precipitation range for 18-8 austenitic stainless steels
Time, prior cold work, welding cycle, and service environment influence the practical risk.
Stainless steel / UNS S30403
Stainless Steel 304L / UNS S30403 Material Data for Flanges and Pipe Fittings
A controlled material-authority page for procurement teams and materials engineers specifying low-carbon 304L stainless steel flanges, wrought pipe fittings, forged fittings, and related process components where weldability, intergranular-corrosion control, traceability, and a correctly defined product standard matter.
Quick technical snapshot
Verified facts first, project assumptions second.
The snapshot is published only from controlled structured data. Anything that needs review stays out of the authoritative display.
Low-carbon welding benefit
The 304L carbon limit extends the time required for harmful carbide precipitation and supports welded-condition corrosion resistance
It does not replace a qualified welding procedure or the project's heat-treatment and corrosion requirements.
Design-temperature control
Allowable stress, pressure rating, flange class, wall thickness, and service approval must come from the governing design code and ordered product standard
| Specification | Verified value | Unit |
|---|---|---|
| UNS | S30403 | - |
| ASTM specifications | ASTM A240, A312, A182 F304L, A403 WP304L, A276, A479The applicable standard depends on whether the order covers flat product, pipe, flanges, wrought fittings, forged fittings, bar, or machined components. | - |
| Alloy family | Low-carbon chromium-nickel austenitic stainless steel | - |
| Density | 7.90Published ATI and Outokumpu flat-product reference value. | g/cm3 |
| General corrosion characteristics | General-purpose Cr-Ni stainless grade with improved resistance to weld-related intergranular corrosion compared with higher-carbon 304; chloride pitting and stress-corrosion cracking still require caution | - |
| Temperature considerations | Prolonged exposure in the 427-816 deg C / 800-1500 deg F sensitization range requires review; low carbon delays harmful carbide precipitation but does not remove every time-temperature risk | - |
| Typical industries | Food and beverage, pharmaceutical, chemical equipment, storage, heat exchange, utilities, fabricated process systems, and general industrial piping | - |
Products and size range
Standard scope for a more complete RFQ.
Each material has its own controlled capability record, giving buyers standard dimensional context before final RFQ specification review.
Flanges
Standard dimensional coverage, pressure-class architecture, facing options, and bore review.
Butt-weld fittings
Standard NPS / DN architecture, fitting geometry, schedule or wall, and end preparation control.
Forged fittings
Socket-weld and threaded fitting architecture with class and end-connection review.
| Nominal size | DN | Product | Standard | RFQ review |
|---|---|---|---|---|
| 1/2" | DN 15 | Flange | ASME B16.5 | |
| 3/4" | DN 20 | Flange | ASME B16.5 | |
| 1" | DN 25 | Flange | ASME B16.5 | |
| 1-1/4" | DN 32 | Flange | ASME B16.5 | |
| 1-1/2" | DN 40 | Flange | ASME B16.5 | |
| 2" | DN 50 | Flange | ASME B16.5 | |
| 2-1/2" | DN 65 | Flange | ASME B16.5 | |
| 3" | DN 80 | Flange | ASME B16.5 | |
| 4" | DN 100 | Flange | ASME B16.5 | |
| 5" | DN 125 | Flange | ASME B16.5 | |
| 6" | DN 150 | Flange | ASME B16.5 | |
| 8" | DN 200 | Flange | ASME B16.5 | |
| 10" | DN 250 | Flange | ASME B16.5 | |
| 12" | DN 300 | Flange | ASME B16.5 | |
| 14" | DN 350 | Flange | ASME B16.5 | |
| 16" | DN 400 | Flange | ASME B16.5 | |
| 18" | DN 450 | Flange | ASME B16.5 | |
| 20" | DN 500 | Flange | ASME B16.5 | |
| 22" | DN 550 | Flange | ASME B16.5 | |
| 24" | DN 600 | Flange | ASME B16.5 |
| Nominal size | DN | Product | Standard | RFQ review |
|---|---|---|---|---|
| 1/2" | DN 15 | Butt-weld fitting | ASME B16.9 | |
| 3/4" | DN 20 | Butt-weld fitting | ASME B16.9 | |
| 1" | DN 25 | Butt-weld fitting | ASME B16.9 | |
| 1-1/4" | DN 32 | Butt-weld fitting | ASME B16.9 | |
| 1-1/2" | DN 40 | Butt-weld fitting | ASME B16.9 | |
| 2" | DN 50 | Butt-weld fitting | ASME B16.9 | |
| 2-1/2" | DN 65 | Butt-weld fitting | ASME B16.9 | |
| 3" | DN 80 | Butt-weld fitting | ASME B16.9 | |
| 4" | DN 100 | Butt-weld fitting | ASME B16.9 | |
| 5" | DN 125 | Butt-weld fitting | ASME B16.9 | |
| 6" | DN 150 | Butt-weld fitting | ASME B16.9 | |
| 8" | DN 200 | Butt-weld fitting | ASME B16.9 | |
| 10" | DN 250 | Butt-weld fitting | ASME B16.9 | |
| 12" | DN 300 | Butt-weld fitting | ASME B16.9 | |
| 14" | DN 350 | Butt-weld fitting | ASME B16.9 | |
| 16" | DN 400 | Butt-weld fitting | ASME B16.9 | |
| 18" | DN 450 | Butt-weld fitting | ASME B16.9 | |
| 20" | DN 500 | Butt-weld fitting | ASME B16.9 | |
| 22" | DN 550 | Butt-weld fitting | ASME B16.9 | |
| 24" | DN 600 | Butt-weld fitting | ASME B16.9 | |
| 26" | DN 650 | Butt-weld fitting | ASME B16.9 | |
| 28" | DN 700 | Butt-weld fitting | ASME B16.9 | |
| 30" | DN 750 | Butt-weld fitting | ASME B16.9 | |
| 32" | DN 800 | Butt-weld fitting | ASME B16.9 | |
| 34" | DN 850 | Butt-weld fitting | ASME B16.9 | |
| 36" | DN 900 | Butt-weld fitting | ASME B16.9 | |
| 38" | DN 950 | Butt-weld fitting | ASME B16.9 | |
| 40" | DN 1000 | Butt-weld fitting | ASME B16.9 | |
| 42" | DN 1050 | Butt-weld fitting | ASME B16.9 | |
| 44" | DN 1100 | Butt-weld fitting | ASME B16.9 | |
| 46" | DN 1150 | Butt-weld fitting | ASME B16.9 | |
| 48" | DN 1200 | Butt-weld fitting | ASME B16.9 |
Material overview
Stainless Steel 304L material data for engineering review.
The narrative supports specification review without replacing the engineer's design basis, corrosion review, or purchase standard.
Stainless Steel 304L / UNS S30403 is the low-carbon 304 route used where fabrication and welding make resistance to chromium-carbide sensitization an important material-selection consideration. The UNS designation should remain attached to the applicable product grade on the RFQ and MTC.
304L is widely used for general process and hygienic equipment, but it is not a universal chloride-service grade. Fluid chemistry, temperature, deposits, crevices, residual stress, cleaning media, and fabrication condition must be reviewed before final approval.
For RTI component enquiries, the product route must be explicit: ASTM A182 F304L for applicable forged flanges and forged fittings, ASTM A403 WP304L for applicable wrought pressure-piping fittings, and the relevant dimensional standard, class, schedule, facing, inspection, and document scope stated separately.
Chemical composition
Published chemistry reference.
The published chemistry values are structured data and must be reconciled against the actual material certificate for every supplied lot.
| Element | Verified composition | Basis |
|---|---|---|
| Chromium | 17.5-19.5 | Mass % |
| Nickel | 8.0-12.0 | Mass % |
| Manganese | 2.00 max | Mass % |
| Silicon | 0.75 max | Mass % |
| Nitrogen | 0.10 max | Mass % |
| Phosphorus | 0.045 max | Mass % |
| Carbon | 0.030 max | Mass % |
| Sulfur | 0.030 max | Mass % |
| Iron | Balance | Mass % |
Mechanical properties
Verified property data.
Mechanical values are presented with product-form context. Flanges and fittings still follow the ordered ASTM or ASME route.
| Product form and basis | 0.2% yield strength | Tensile strength | Elongation / hardness |
|---|---|---|---|
| ATI 304L plate, sheet, and strip - published minimum | 170 MPa / 25 ksi | 485 MPa / 70 ksi | 40% min; 92 HRB max |
| Outokumpu Core 304L/4307 cold-rolled flat product - EN 10088-2 | 220 MPa | 520-700 MPa | 45% min |
Corrosion behaviour
Selection guidance for the corrosion mechanism, not just the alloy name.
These notes are intentionally conservative because medium chemistry, temperature, stress, crevices, fabrication, and cleaning practice govern final suitability.
General corrosion
304L is a general-purpose austenitic stainless grade used across many clean and moderately corrosive environments. Actual concentration, contaminants, temperature, aeration, deposits, and cleaning chemistry can change suitability and must be reviewed.
Intergranular corrosion after welding
The low carbon limit reduces chromium-carbide precipitation during welding compared with higher-carbon 304 and is the principal reason for selecting 304L for many as-welded fabrications. Long exposure in the sensitization range can still require evaluation.
Pitting and crevice corrosion
304L does not contain the molybdenum addition used in 316L. Chloride concentration, temperature, stagnant crevices, deposits, and surface condition should therefore be reviewed before approving 304L for chloride-bearing service.
Chloride stress-corrosion cracking
ATI identifies 304-series susceptibility when halides, tensile stress, and temperatures above about 49 deg C / 120 deg F occur together. Welding and cold work can introduce residual stress, so hot chloride service requires engineering review.
Welding and fabrication control
Use a qualified welding procedure, the approved filler-metal route, controlled heat input, and agreed cleaning or passivation requirements. Low carbon supports weld-zone corrosion resistance but does not replace fabrication qualification or final inspection.
Available RTI products
Flanges and pipe fittings routed by material standard.
The page template separates product form, material route, dimensional standard, inspection, and final release documents.
Flanges
304L flange enquiries should identify ASTM A182 F304L / ASME SA182 F304L where applicable, then state flange form, ASME dimensional route, pressure class, facing, bore, heat traceability, PMI, and certificate requirements.
Pipe Fittings
Applicable wrought 304L elbows, tees, reducers, caps, and stub ends should be defined to ASTM A403 WP304L / ASME SA403 WP304L and ASME B16.9. Forged socket-weld or threaded fittings require the separate A182 F304L and B16.11 route.
Relevant standards
Standards are supply routes, not decoration.
Each enquiry should identify which standard controls the product form, which standard controls dimensions, and which documents prove conformance.
ASTM A182 F304L / ASME SA182 F304L
Applicable forged or rolled stainless flanges, forged fittings, valves, and pressure-system parts
ASTM A403 WP304L / ASME SA403 WP304L
Applicable wrought austenitic stainless pressure-piping fittings, with class and construction details stated in the order
ASTM A312 / ASME SA312
Seamless, welded, and heavily cold-worked austenitic stainless pipe reference route
ASTM A240 / ASME SA240
Chromium and chromium-nickel stainless plate, sheet, and strip reference route
ASTM A276 / A479
Stainless bar and shape routes used for applicable machined or pressure-component feedstock
ASME B16.5 / B16.47
Flange dimensions, pressure classes, facings, tolerances, and large-diameter series where applicable
ASME B16.9 / B16.11
Applicable wrought butt-weld fitting and forged socket-weld or threaded fitting dimensional routes
Applications
Where procurement conversations usually begin.
Applications are signals for engineering review, documentation scope, and grade comparison.
Typical industries
Built for severe-service buying environments.
The same grade can behave differently by industry because service media, inspection plans, and owner specifications change.
Quality and inspection
Document control from the first quotation.
For critical alloys, inspection and certificate requirements belong in the RFQ, not as an afterthought before dispatch.
PMI
PMI can support segregation between 304L, 316L, duplex, high-alloy stainless, and nickel alloy items when the project or mixed-material package requires grade verification.
MTC
The material certificate should confirm UNS S30403, the ordered product grade, heat or lot identity, chemistry, mechanical results, heat treatment where applicable, and specification marking.
EN 10204 3.1
Specify EN 10204 3.1 where the buyer requires manufacturer-issued inspection certification tied to the supplied material and test results.
TPI
Third-party inspection may cover document review, visual and dimensional checks, marking, traceability, packing, and agreed witness or hold points.
IGC
Intergranular-corrosion testing or review should be stated with the method and acceptance basis when welding history, service, or project specifications require it.
Dimensional and marking control
Reconcile product form, dimensions, class or schedule, facing or ends, heat marking, item identification, and packing list before release.
Material comparison
Compare material considerations before approving substitution.
This section frames substitution as an engineering decision, especially where corrosion mechanism, temperature, weld route, or code requirements change.
| Comparison | Stainless Steel 304L | Alternate route | Procurement consideration |
|---|---|---|---|
| Versus Stainless Steel 304 | Lower carbon limit supports improved resistance to weld-related intergranular corrosion | 304 can be suitable where the applicable product standard, fabrication route, and service do not require the low-carbon grade | Keep 304 and 304L as separate ordered grades unless the governing specification expressly permits a dual-certified route |
| Versus Stainless Steel 316L | General-purpose low-carbon chromium-nickel stainless without a molybdenum addition | 316L adds molybdenum and is commonly reviewed where greater pitting and crevice-corrosion resistance is needed | Compare chlorides, temperature, crevices, cleaning media, weld condition, and the approved piping class before substitution |
| Versus Duplex 2205 | Austenitic route with broad availability, formability, and conventional fabrication familiarity | Duplex 2205 offers higher strength and stronger chloride SCC resistance but requires duplex-specific fabrication and heat-treatment control | Escalate the material review when chloride SCC, strength, wall reduction, or severe process exposure drives the design |
Procurement guidance
The RFQ fields that prevent expensive ambiguity.
A strong alloy enquiry names the grade, standard, dimensions, inspection, documentation, packing, and destination before commercial comparison.
01
State Stainless Steel 304L and UNS S30403 together, then identify the product grade: F304L for applicable A182 flanges or forged fittings and WP304L for applicable A403 wrought fittings.
02
Define product form, NPS or DN, class or schedule, RF or RTJ facing where applicable, bore, end preparation, dimensional standard, quantity, and drawing revision.
03
For welded scope, include fabrication route, WPS/PQR requirements, filler-metal basis, cleaning or passivation, IGC review where specified, and final surface condition.
04
For chloride-bearing or elevated-temperature service, obtain engineering approval rather than treating 304L as a universal corrosion-resistant grade.
05
Specify MTC, EN 10204 3.1, PMI, dimensional inspection, TPI, marking, traceability, packing, and destination requirements before commercial comparison.
Engineering FAQs
Questions buyers and materials engineers should settle early.
FAQ content is unique to each benchmark material and remains tied to verified structured guidance.
Related materials
Continue the grade comparison.
Internal links connect related alloy families, technical guidance, and RFQ preparation.
Stainless Steel 316L / UNS S31603Compare 304L with the molybdenum-bearing austenitic stainless route.Duplex 2205 / UNS S31803-S32205Review the higher-strength duplex route for more demanding chloride conditions.254 SMO / UNS S31254Review a high-alloy austenitic stainless route for severe chloride-service evaluation.
Related technical guides
Procurement knowledge paths.
These connect material selection to document control, testing, quality review, and RFQ completeness.
Grade and product route review
Inspection and certificate planning
Traceable quotation package
Structured RFQ
Prepare a cleaner component enquiry
Capture material, standard, dimensions, quantity, inspection, documentation, packing, and destination before the technical quotation is prepared.
