Low-Carbon 18/8 Austenitic Stainless Steel for Welded Fabrications
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UNS NUMBER
S30403
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ALLOY FAMILY
Austenitic (18/8)
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STRUCTURE
100% Austenite
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UTS (MIN)
≥485 MPa
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MAX TEMP
~870°C
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DENSITY
7.93 g/cm³
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Stainless Steel 304L (UNS S30403) is the low-carbon version of 304, with carbon capped at 0.030% so welded structures resist intergranular corrosion without post-weld heat treatment. It keeps the same 18/8 corrosion profile and is the most common grade for tanks, piping, and welded process equipment.
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Cr
18–20%
PREN contributor; oxidation
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Ni
8–12%
Austenite stabilizer
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Mo
— (none)
Not added in 304L
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C
≤0.030%
Low carbon, weld-friendly
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UTS
≥485 MPa
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YS 0.2%
≥170 MPa
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Elong.
≥40%
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Service
-196~870°C
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What is Stainless Steel 304L?
304L carries the same chromium-nickel balance as 304 but restricts carbon to 0.030% maximum. That single change removes the sensitization mechanism: there is too little carbon to form chromium carbides at the grain boundaries during welding, so the material stays corrosion-resistant as-welded. This is why 304L dominates in fabricated equipment.
The trade-off is a slightly lower strength floor (485 MPa UTS, 170 MPa yield versus 515/205 for 304). In practice most buyers accept this because welded assemblies rarely need 304's extra margin, and dual certification (304/304L) is common so a single heat can meet either spec. Where chloride exposure is expected, step up to 316L for the molybdenum benefit.
Chemical Composition (Weight %)
| Element |
Min (%) |
Max (%) |
Role in Alloy |
| Chromium (Cr) |
18.0 |
20.0 |
Oxidation resistance; PREN contributor |
| Nickel (Ni) |
8.0 |
12.0 |
Austenite stabilizer; toughness |
| Carbon (C) |
— |
0.030 |
Low carbon prevents sensitization |
| Manganese (Mn) |
— |
2.00 |
Deoxidizer |
| Silicon (Si) |
— |
1.00 |
Deoxidizer |
| Phosphorus (P) |
— |
0.045 |
Impurity |
| Sulfur (S) |
— |
0.030 |
Impurity |
| Nitrogen (N) |
— |
0.10 |
Minor |
| Iron (Fe) |
Balance |
— |
Matrix former |
★ Carbon ≤ 0.030% is the defining limit. 304L is immune to carbide sensitization in the 425–815°C range that affects standard 304, so post-weld annealing is not required for corrosion integrity.
Mechanical Properties
Values are for the solution-annealed condition per ASTM A240, A182 (F304L), and A312 (TP304L).
| Condition / Form |
UTS (MPa) |
YS 0.2% (MPa) |
Elong. % (min) |
Hardness (max) |
| Minimum (ASTM A240 / A182 F304L) |
≥485 |
≥170 |
40 |
201 HBW (92 HRB) |
| Typical mill-annealed |
515–680 |
205–330 |
50–60 |
150–185 HBW |
Modulus of Elasticity 193 GPa; Shear Modulus 77 GPa; Poisson's Ratio 0.29. Cold work raises strength; note that some specs only certify 304L in the annealed condition for corrosion service.
Physical Properties
| Property |
Value |
Note |
| Density |
7.93 g/cm³ |
Same as 304 |
| Melting Range |
1400–1450°C |
Solidus ~1400°C |
| Thermal Conductivity (100°C) |
16.2 W/m·K |
Comparable to austenitics |
| Thermal Expansion (20–100°C) |
17.2 ×10⁻⁶ /K |
Higher than carbon steel |
| Specific Heat |
500 J/kg·K |
At 21°C |
| Electrical Resistivity |
0.72 µΩ·m |
At 21°C |
| Magnetic Property |
Non-magnetic* |
*Slight after cold work |
| PREN (Pitting Resistance) |
~19 |
PREN = %Cr + 3.3×%Mo + 16×%N |
Corrosion Resistance
Welded Structures
304L is the standard for welded tanks and piping because it stays resistant to intergranular attack after welding. No post-weld annealing is needed for corrosion service.
General & Atmospheric Service
Same broad resistance as 304 in fresh water, food, and mild chemicals. It is the workhorse of sanitary and process piping.
Pitting & Crevice Corrosion
Still PREN ~19 with no molybdenum, so 304L pits in chloride environments just like 304. For seawater or coastal service, move to 316L or higher.
Acids & Temperature
Good in nitric and many organic acids; poor in hydrochloric or hot reducing sulfuric. Oxidation resistance is comparable to 304, not a high-temperature grade.
Stainless Steel 304L vs Similar Grades — Selection Guide
| If you need... |
Choose... |
Why |
| Welded tank / pipe, no PWHT |
Stainless Steel 304L |
Low carbon avoids sensitization |
| General food, water, architectural |
304L |
Cheapest safe welded choice |
| Chloride or seawater exposure |
316L |
Molybdenum raises PREN to ~26 |
| High-temp furnace service |
310S / 253MA |
Better oxidation resistance |
| Aggressive seawater + acid |
904L / 254SMO |
PREN 36–45 |
Applicable Standards
| Standard |
Product Form |
| ASTM A240 |
Plate, sheet, strip |
| ASTM A182 F304L |
Forged flanges & fittings |
| ASTM A403 WP304L |
Butt-weld fittings |
| ASTM A312 TP304L |
Seamless & welded pipe |
| ASTM A213 / A269 |
Tube |
| ASTM A276 / A479 |
Bar, rod, forging stock |
HT PIPE Supply — Stainless Steel 304L Product Forms
| Product Form |
Specifications |
HT PIPE Supply |
| Seamless Pipe |
ASTM A312 TP304L |
✅ Available |
| Welded Pipe |
ASTM A312 TP304L |
✅ Available |
| Forged Flanges |
ASTM A182 F304L, ASME B16.5/B16.47 |
✅ In stock |
| Butt-Weld Fittings |
ASTM A403 WP304L |
✅ Available |
| Plate / Sheet |
ASTM A240 |
✅ Available |
| Bar / Rod |
ASTM A276 / A479 |
✅ Available |
HT PIPE stocks 304L (and dual-certified 304/304L) in pipe, fittings, and flanges, supplied solution-annealed with full MTRs.
Project Experience — Stainless Steel 304L
HT PIPE supplies 304L for welded process, food, and water systems where as-welded corrosion resistance matters.
| Project |
Product |
Specification |
| Pharmaceutical Process Skid (China) |
304L Pipe + BW Fittings |
A312, A403 |
| Food-Grade Storage Tanks (Europe) |
304L Plate + Forgings |
A240, A182 |
| Potable Water Reticulation (Africa) |
304L Flanges + Pipe |
A182 F304L, A312 |
Our team supports welding procedure specification (WPS) and PMI verification for 304L fabrications.
| FREQUENTLY ASKED QUESTIONS |
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FAQ — Stainless Steel 304L
| Why choose 304L over 304? |
| 304L's carbon is capped at 0.030% so welded joints do not sensitize and do not need post-weld annealing. Choose it whenever the component is welded and cannot be heat-treated afterward. |
| Is 304L weaker than 304? |
| Marginally. Minimum UTS is 485 MPa and yield 170 MPa versus 515/205 for 304. In welded structures that difference is rarely decisive, and dual certification covers both. |
| Can 304L be used in seawater? |
| No. Like 304 it has no molybdenum (PREN ~19) and pits quickly in chlorides. Use 316L for ambient seawater and 904L/254SMO for aggressive seawater. |
| What filler for 304L welding? |
| ER308L / E308L keeps the weld deposit low-carbon and matching. Avoid plain 308 if the joint may sit in the sensitizing temperature range. |
| Does 304L need post-weld heat treatment? |
| For corrosion integrity, no. The low carbon content prevents sensitization. PWHT is only considered for stress relief in special cases, not for carbide control. |
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Need Stainless Steel 304L for Your Project?
HT PIPE supplies 304L seamless pipe, butt-weld fittings, forged flanges, and plate with full MTR documentation. Contact our technical team for welding and material selection advice.
Request a Quote |
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