Stainless Steel 304L
Stainless Steel 304L (UNS S30403) is the low-carbon variant of Grade 304, with carbon restricted to 0.030% maximum. This lower carbon level prevents carbide precipitation at weld heat-affected zones, making it the preferred grade for heavy-section welded fabrications that will not receive post-weld annealing.
1. Chemical Composition
The table below shows the elemental composition limits for Stainless Steel 304L. The reduced carbon ceiling is what prevents sensitisation during welding and high-temperature exposure.
| Grade | Carbon, max | Manganese, max | Phosphorus, max | Sulfur, max | Silicon, max | Chromium | Nickel | Molybdenum | Titanium | Niobium (Cb) | Nitrogen | Iron |
| TP304L | ≤ 0.035 | ≤ 2.00 | ≤ 0.040 | ≤ 0.030 | ≤ 0.75 | 18.00–20.00 | 8.00–11.00 | — | — | — | — | Bal |
2. Mechanical Properties
The following table gives minimum mechanical property values for Stainless Steel 304L in the annealed condition. The lower carbon content results in slightly reduced yield strength compared to standard 304.
| Grade | UNS | Tensile Min, ksi (MPa) | Yield Min, ksi (MPa) | Elong. Min, % |
| TP304L | S30403 | 70 (485) | 25 (170) | 35 |
3. Equivalent Grade
This table consists of various international equivalent designations of the grade 304L, including UNS, European, Japanese, Chinese, and Russian standards.
| GRADE | UNS | GB | JIS | ISO | DIN/EN | GOST | |
| ISC | NEW | ||||||
| 304L | S30403 | S30403 | 022Cr19Ni10 | SUS304L | X2CrNi19-11 | 1.4307 | 03X18H11 |
3. Key Technical Advantages
- Weld Sensitisation Resistance: Carbon content capped at 0.030% means chromium carbides do not precipitate at grain boundaries during welding. This preserves intergranular corrosion resistance in the as-welded condition.
- ASME Pressure Vessel Qualification: 304L meets ASME Section VIII Division 1 and Division 2 requirements for welded pressure vessel construction without mandatory post-weld heat treatment.
- Corrosion Resistance Equivalence: In non-sensitised form, 304L has corrosion resistance essentially equal to standard 304, making it a direct replacement in most corrosive environments.
- Dual Certification: 304L tubing and pipe are frequently dual-certified to meet both 304 and 304L specifications when chemistry and properties fall within both ranges.
Technical Note: While 304L has a lower minimum yield strength than 304, it is often acceptable at the same wall thickness for most pressure piping systems due to ASME code allowances for low-carbon grades.
4. Common Manufacturing Standards
- ASTM A312: Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes — TP304L designation.
- ASTM A213: Standard Specification for Seamless Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes — TP304L designation.
- ASTM A269: Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for General Service — 304L grade.
- ASTM A249: Standard Specification for Welded Austenitic Steel Boiler, Superheater, Heat-Exchanger, and Condenser Tubes.
- ASTM A376: Standard Specification for Seamless Austenitic Steel Pipe for High-Temperature Central-Station Service.
- DIN EN 10216-5: Seamless steel tubes for pressure purposes — Technical delivery conditions for stainless steel tubes (1.4307).
- DIN EN 10217-7: Welded steel tubes for pressure purposes — stainless steel (1.4307).
- JIS G3459: Stainless Steel Pipes (SUS304L).
- JIS G3463: Stainless Steel Boiler and Heat Exchanger Tubes (SUS304L).
- GB/T 14976: Seamless stainless steel tubes for fluid transport (022Cr19Ni10).
- GOST 9941: Seamless cold- and warm-deformed pipes from corrosion-resistant steel.
Manufacturing Standards Comparison Table:
| Standard | ASTM | EN/DIN | JIS | GB/T | GOST |
| Seamless Pipe | A312 (TP304L) | EN 10216-5 (1.4307) | G3459 (SUS304L) | 14976 | 9941 |
| Welded Pipe | A312 (TP304L) | EN 10217-7 (1.4307) | G3459 (SUS304L) | 12771 | - |
| Heat Exchanger Tube | A213 (T304L) / A249 | EN 10216-5 | G3463 | 13296 | - |
| General Service Tube | A269 | EN 10216-5 | G3463 | 14976 | - |
5. Primary Applications
- Chemical Processing Vessels: Storage tanks and pressure vessels with heavy fillet or butt welds where sensitisation-free performance is needed without post-weld annealing.
- Pulp and Paper Industry: Digesters, bleaching equipment, and wash drums exposed to caustic sulfide liquors and chloride-bearing bleaching chemicals at elevated temperatures.
- Nuclear Auxiliary Systems: Low-pressure piping and heat exchanger circuits in nuclear facilities where low carbon content is mandated by design codes.
- Cryogenic Equipment: Storage and transport vessels for liquefied gases such as nitrogen and CO2, taking advantage of austenitic toughness at temperatures down to -196°C.
- Offshore and Marine Structures: Welded pipe spools and structural members in coastal and offshore environments where sensitised 304 would not perform adequately.