What is 304L Stainless Steel? (304 vs 304L Differences Explained)
- By Nicoo Tong
- Last Updated: September 8, 2026
Quick Summary：
304L stainless steel is a low-carbon variant of 304 stainless steel, with a maximum carbon content of 0.03%. The “L” stands for “Low Carbon.” This reduction prevents harmful carbide precipitation during welding, providing superior intergranular corrosion resistance in heavy-gauge welded applications without the need for post-weld annealing.
What is 304L Stainless Steel?
304L stainless steel is an extra-low-carbon austenitic stainless steel grade within the T-300 series family. Featuring 18% chromium and 8% nickel, it offers exceptional corrosion resistance, high ductility, and superior weldability—making it essential for high-temperature filtration like sintered wire mesh elements.
Chemical Composition (ASTM A240, wt‑% max) of 304L Stainless Steel
| Element | 304L |
|---|---|
| Carbon (C) | 0.03 |
| Chromium (Cr) | 18.0‑20.0 |
| Nickel (Ni) | 8.0‑12.0 |
| Manganese | 2.00 |
| Silicon | 1.00 |
Key Mechanical and Physical Properties of 304L Stainless Steel [1]
| Property / Feature | 304L Stainless Steel |
|---|---|
| Yield Strength (0.2% Proof) | ~170 MPa |
| Tensile Strength | ~485 MPa |
| Elongation | ~40 % |
| Hardness | 88–92 HRB |
| Weldability | Excellent (No post-weld annealing required) |
| Max Operating Temp | Up to 800°C (best for welded parts) |
| Intergranular Corrosion Risk | Very Low |
What is the Difference Between 304 and 304L Stainless Steel?
Comparison Summary：
The primary difference between 304 and 304L stainless steel is carbon content: 304 contains up to 0.08% carbon, while 304L contains a maximum of 0.03%. This lower carbon level eliminates carbide precipitation during welding, making 304L better for heavy welding, whereas 304 offers slightly higher mechanical strength and temperature limits.
1. Carbon Content and Carbide Precipitation (Sensitization)
What is Sensitization in Welding?
Direct Answer: Sensitization is a metallurgical reaction occurring in standard 304 stainless steel when heated to 425°C–860°C (800°F–1500°F). At these temperatures, carbon binds with chromium to form chromium carbide at the grain boundaries, depleting the metal’s protective chromium layer in the Heat-Affected Zone (HAZ).
During welding or high-heat fabrication, standard 304 stainless steel undergoes thermal cycles. In the critical temperature range of 425°C to 860°C, carbon rapidly combines with chromium, forming chromium carbide precipitates (Cr23C6).
Because chromium is the primary element responsible for passivation (rust resistance), this precipitation leaves the surrounding boundaries chromium-deficient, leaving the Heat-Affected Zone (HAZ) highly vulnerable to localized decay.
How 304L Prevents Intergranular Corrosion
Direct Answer: By capping maximum carbon content at 0.03%, 304L limits the amount of available carbon to form chromium carbides. This low-carbon chemistry prevents intergranular corrosion in welded joints without requiring costly post-weld heat treatment.
In 304L (“L” stands for Low Carbon), restricting carbon to ≤ 0.03% stops carbide precipitation before it starts. The metal retains at least 10.5% free chromium across all grain boundaries during welding, maintaining a continuous protective oxide layer that resists aggressive corrosive media, acids, and chemical fluids.
2. Weldability and Heat-Affected Zone (HAZ) Performance
Direct Answer: 304L offers superior weldability compared to standard 304 because it eliminates the need for post-weld annealing on thick-gauge welded parts, significantly reducing manufacturing costs and assembly turnaround times.
When fabricating heavy-gauge equipment (typically parts thicker than 6 mm or 0.25 inches):
Standard 304: Requires post-weld heat treatment (annealing) to redissolve chromium carbides and restore corrosion resistance in the HAZ.
Grade 304L: Can be welded in heavy cross-sections in the as-welded condition while maintaining full structural and corrosion integrity.
For polymer filtration and wire mesh manufacturing, using 304L streamlines production when fabricating heavy-duty extruder screen packs by skipping post-weld furnace annealing operations.
3. Mechanical Strength and Temperature Resistance
Direct Answer: 304L has approximately 5% to 15% lower yield strength and tensile strength than standard 304 due to its reduced carbon content. However, this minor strength reduction is negligible for the vast majority of industrial and structural applications.
Carbon acts as an interstitial strengthening agent in austenitic stainless steels. According to certified ASTM A240 standards and data from the AZoM Materials Database, the mechanical property comparison is as follows:
Yield Strength (0.2% Offset): 304 requires a minimum of 205 MPa (30 ksi), while 304L requires 170 MPa (25 ksi).
Tensile Strength: 304 requires a minimum of 515 MPa (75 ksi), while 304L requires 485 MPa (70 ksi).
Maximum Operating Temperature: Standard 304 handles continuous service up to 870°C (1600°F), whereas 304L is recommended up to 800°C (1472°F) in continuous oxidation environments.
For woven wire mesh, filter discs, and general pressure piping, 304L’s mechanical strength is more than adequate for high-pressure operations.
Comparison Table: 304 vs 304L Stainless Steel
| Property / Feature | 304L Stainless Steel | 304 Stainless Steel |
|---|---|---|
| Carbon Content (Max) | 0.03% (Low Carbon) | 0.08% |
| Chromium Content | 17.5% - 19.5% | 17.5% - 19.5% |
| Nickel Content | 8.0% - 12.0% | 8.0% - 10.5% |
| Yield Strength (0.2% Proof) | ~170 MPa | ~205 MPa |
| Tensile Strength | ~485 MPa | ~515 MPa |
| Weldability | Excellent (No post-weld annealing required) | Good (Requires annealing for heavy sections) |
| Intergranular Corrosion Risk | Very Low | Moderate (in high-heat conditions) |
| Max Operating Temp | Up to 800°C (best for welded parts) | Up to 870°C |
When to Choose 304L vs 304 Stainless Steel?
Choose 304L Stainless Steel If:
Your application involves heavy welding or thick-gauge material (over 6mm).
The finished component cannot undergo post-weld heat treatment.
The product operates in highly corrosive environments (e.g., chemical processing, marine filtration, woven wire mesh for corrosive fluids).
You require maximum resistance to intergranular corrosion.
Choose Standard 304 Stainless Steel If:
The components require higher mechanical strength or pressure resistance at elevated temperatures.
Welding is minimal, thin-gauge, or non-existent.
Cost optimization is required for high-volume, non-welded stamped parts
Our Suggestion:
When welding stainless steel filter elements, 304L grade reduces the risk of intergranular corrosion, as defined under ASTM A240/A240M‑24b.
In our filter workshop, we notice that many buyers confuse 304 and 304L. If final parts require laser welding, we always recommend 304L to avoid intergranular corrosion after high‑temperature welding.
Nicoo Tong
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FAQ on Sintered Wire Mesh Alloy Selection
Is 304L stronger than 304 stainless steel?
No, 304L is slightly weaker than standard 304 in terms of ultimate tensile strength (485 MPa vs. 515 MPa) and yield strength (170 MPa vs. 205 MPa) due to its lower carbon content. However, this minor strength difference is negligible for most structural and industrial applications.
Can you weld 304 to 304L?
Yes, 304 and 304L stainless steel can be welded together seamlessly using standard filler metals such as ER308L. Using a low-carbon filler wire ensures the weld joint maintains maximum corrosion resistance without sensitization.
Does 304L stainless steel rust?
304L stainless steel is highly corrosion-resistant and will not rust under normal atmospheric conditions. However, prolonged exposure to aggressive chloride environments, such as seawater or heavy chemical solutions, can cause localized pitting over time.
Is 304L stainless steel magnetic?
In the annealed state, 304L stainless steel is virtually non-magnetic due to its austenitic crystal structure. However, it may exhibit weak magnetism after undergoing heavy cold working, forming, or welding operations.
Is 304L stainless steel more expensive than standard 304?
No, 304L and standard 304 stainless steel typically cost the same. Modern refining processes, such as Argon Oxygen Decarburization (AOD), allow mills to produce low-carbon grades efficiently without adding manufacturing premiums.
References
- Stainless Steel Grade 304L Properties https://www.azom.com/article.aspx?ArticleID=965