Quick Answer
Quick Answer
SS 304L (EN 1.4307) is the low-carbon version of 304, with carbon ≤ 0.030 %. The reduced carbon content minimizes chromium carbide precipitation at grain boundaries during welding, eliminating sensitization risk without post-weld annealing. Mechanical strength minimums are slightly lower than standard 304.
Overview
Grade 304L mirrors the role of 316L in the molybdenum-free austenitic family. When 304 components are welded and cannot undergo post-weld solution annealing, 304L provides protection against sensitization-induced intergranular corrosion in the heat-affected zone.
The European equivalent is 1.4307 per EN 10088. Note that this is a different EN number from 1.4301 (standard 304) — a distinction that must be correctly captured on purchase orders and MTCs.
Chemical Composition — SS 304L / 1.4307
| Element | ASTM A240 Type 304L | EN 1.4307 |
|---|---|---|
| Carbon (C) | ≤ 0.030 | ≤ 0.030 |
| Manganese (Mn) | ≤ 2.00 | ≤ 2.00 |
| Silicon (Si) | ≤ 0.75 | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.045 | ≤ 0.045 |
| Sulfur (S) | ≤ 0.030 | ≤ 0.015 |
| Chromium (Cr) | 18.0 – 20.0 | 17.5 – 19.5 |
| Nickel (Ni) | 8.0 – 12.0 | 8.0 – 10.5 |
| Nitrogen (N) | ≤ 0.10 | ≤ 0.11 |
The ASTM A240 304L nickel range extends to 12.0 % (vs 10.5 % for 304). This acknowledges that lowering carbon can require slightly higher nickel to maintain austenite stability.
Mechanical Properties — SS 304L (Annealed Plate)
| Property | ASTM A240 304L | EN 1.4307 (+A) |
|---|---|---|
| Ultimate Tensile Strength (UTS) | 485 MPa (70 ksi) | 480 – 680 MPa |
| 0.2 % Proof Strength (YS) | 170 MPa (25 ksi) | 175 MPa |
| Elongation in 50 mm | 40 % | 45 % |
| Hardness (max) | 217 HBW / 95 HRB | 215 HBW |
Weldability Notes
- Use ER308L or ER308LSi filler for GTAW/GMAW welding of 304L.
- No PWHT required for sensitization prevention in most service conditions.
- Maximum interpass temperature 150 °C for corrosion-critical service.
- Delta ferrite 3–8 FN in weld metal prevents hot cracking.
Dual Certification: 304/304L
Many mills produce plate that is dual-certified to both 304 and 304L because the actual carbon content is typically well below 0.08 %. A dual-certified MTC shows both designations and means the material meets:
- Carbon ≤ 0.030 % (satisfying 304L)
- Mechanical minimums of 304 (≥ 205 MPa YS, ≥ 515 MPa UTS)
Dual certification is acceptable under ASTM, ASME, and most EN applications, but the purchaser should verify that the design calculation does not rely on the higher 304 YS minimum if accepting dual-cert product.
Standards Coverage
| Standard | Product Form | Designation |
|---|---|---|
| ASTM A240 | Plate, sheet, strip | Type 304L |
| ASTM A276 | Bar and shapes | Type 304L |
| ASTM A312 | Seamless and welded pipe | TP304L |
| ASTM A182 | Forgings | F304L |
| ASME SA-240 | Pressure vessel plate | Type 304L |
| EN 10088-2 | Flat products | 1.4307 |
| EN 10088-3 | Long products | 1.4307 |
Applications
304L is the practical default for welded 304-type construction:
- Welded storage vessels and tanks — chemical, water, food
- Piping systems — field-fabricated with no PWHT available
- Pharmaceutical equipment — where 304 chemistry is acceptable but welding is unavoidable
- Cryogenic systems — liquefied gas storage and transfer
- Pulp and paper — digesters and wash equipment
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Try TestCert freeFrequently Asked Questions
Is 304L weaker than 304?
Slightly, by specification minimum. ASTM A240 sets 304L's minimum YS at 170 MPa vs 205 MPa for 304. In practice, actual mill values often fall in the same range because modern steelmaking routinely produces low-carbon material that still meets the higher 304 minimums — hence the prevalence of dual-certified product. If design calculations are tight, verify the actual certified yield strength on the MTC rather than relying on the minimum.
When should I choose 304L over 316L?
Choose 304L when the operating environment does not involve significant chloride concentrations and the cost premium of molybdenum-bearing 316L cannot be justified. 316L provides better pitting and crevice corrosion resistance in chloride-containing media. For fresh water, atmospheric, or mild chemical service where welding is involved, 304L is typically adequate and more economical.
Does EN 1.4307 and ASTM 304L have identical requirements?
Not exactly. EN 1.4307 specifies tighter sulfur limits (≤ 0.015 % vs ≤ 0.030 % in ASTM A240) and slightly different Cr/Ni ranges. Mechanical requirements are also expressed differently (Rm range vs minimum UTS). When cross-referencing an EN-certified material to an ASTM order or vice versa, verify each element and property individually against the applicable standard.
Can TestCert check both ASTM 304L and EN 1.4307 limits for the same MTC?
Yes. TestCert maintains separate composition and property tables for each standard and revision. When an MTC references both ASTM A240-304L and EN 1.4307 (as some European mills do), the platform checks conformance against each standard independently and reports any element that passes one standard but fails the other.