Authoritative comparison of 304 vs. 304L vs. 304N stainless steels

1. Introduction

Austenitic stainless steels in the 300-series rank among the most versatile alloys in modern industry.

In particular, Type 304 serves as a workhorse, balancing corrosion resistance, formability, and cost.

Yet, applications requiring extensive welding or enhanced strength have driven the evolution of two derivatives: low-carbon 304L and nitrogen-strengthened 304N.

Consequently, engineers must distinguish among these grades to ensure reliability and longevity in service.

This article delivers an original, data-driven analysis—spanning composition, metallurgy, mechanical behavior, corrosion performance, fabrication, heat treatment, applications, and equivalents—to guide informed material selection.

2. Chemical Composition & Metallurgy

Element	304 (S30400)	304L (S30403)	304N (S30453)
Cr	18.0–20.0 wt%	18.0–20.0 wt%	18.0–20.0 wt%
Ni	8.0–10.5 wt%	8.0–12.0 wt%	8.0–10.5 wt%
C	≤ 0.08 wt%	≤ 0.03 wt%	≤ 0.04 wt%
N	≤ 0.10 wt%	≤ 0.10 wt%	0.10–0.16 wt%
Mn	≤ 2.0 wt%	≤ 2.0 wt%	≤ 2.0 wt%
Si	≤ 1.0 wt%	≤ 0.75 wt%	≤ 1.0 wt%

Firstly, carbon drives strength but also sensitization.

Standard 304 permits up to 0.08 wt% C, which elevates yield strength to ≈ 215 MPa, yet encourages chromium‐carbide precipitation in the 450–850 °C sensitization window.

By contrast, 304L limits C to 0.03 wt%, reducing sensitization risk nearly to zero during typical cooling cycles.

Moreover, 304N introduces 0.10–0.16 wt% nitrogen, capitalizing on N’s strong solid‐solution strengthening and austenite stabilization:

Nitrogen raises yield strength by up to 20% (to ≈ 260 MPa) and refines grain size by about 10–15%, without compromising toughness.

Furthermore, nitrogen enhances pitting resistance: each 0.01 wt% N adds roughly 1 PREN (Pitting Resistance Equivalent Number = Cr + 3.3 Mo + 16 N).

Thus, 304N’s PREN climbs from ≈ 18 in 304 to ≈ 20, translating into higher chloride thresholds before pitting initiates.

3. Mechanical Properties of 304 vs. 304L vs. 304N

Property	304	304L	304N
Yield Strength (Rp0.2)	~215 MPa	~205 MPa	~260 MPa
Tensile Strength (Rm)	505–735 MPa	485–680 MPa	530–760 MPa
Elongation (A%)	≥ 40 %	≥ 45 %	≥ 35 %
Charpy V-Notch @ –40 °C	≥ 30 J	≥ 35 J	≥ 25 J
Work-Hardening Exponent (n)	0.25	0.28	0.22

At ambient temperatures, 304N outperforms both 304 and 304L in yield strength, owing to nitrogen’s lattice‐distortion effect.

In addition, 304L achieves the highest elongation (≥ 45 %), which proves beneficial in deep‐drawing and stretch‐forming operations.

Transitioning to impact behavior, 304L delivers an average Charpy toughness of 40 J at –40 °C, whereas 304 and 304N record 35 J and 30 J, respectively—underscoring 304L’s superior low-temperature toughness.

When temperatures exceed 200 °C, all three grades retain roughly 80% of their room-temperature tensile strength up to 400 °C.

However, 304N maintains creep resistance marginally better—approximately 15% lower creep rate in constant-load tests at 300 °C—thanks to nitrogen’s suppression of grain-boundary sliding.

Finally, fatigue tests in 10⁶–10⁷ cycles reveal that nitrogen’s presence in 304N increases the fatigue strength limit by about 5%, while 304L matches 304’s baseline fatigue performance.

4. Corrosion Resistance

Environment	304	304L	304N
General Corrosion (Neutral pH)	Excellent	Excellent	Excellent
Seawater Spray (3.5 % NaCl)	Fair (0.2 % pits)	Fair (0.2 % pits)	Good (0.3 % pits)
Pitting Potential (Epit, mV SCE)	+200	+220	+260
Intergranular Corrosion (HAZ)	Susceptible	Resistant	Resistant
Chloride SCC Threshold	≤ 100 °C	≤ 120 °C	≤ 130 °C

In neutral or mildly acidic media, all three grades exhibit corrosion rates below 0.1 mm/year.

Conversely, in chloride-rich environments, 304N’s elevated PREN pushes its critical pitting potential (Epit) to +260 mV SCE,

compared to +200 mV for 304 and +220 mV for 304L—translating to lower pit density and delayed onset.

Likewise, 304L and 304N effectively eliminate weld-zone intergranular attack common to 304, thanks to minimal carbide precipitation and nitrogen’s role in stabilizing chromium in solution.

Moreover, in accelerated SCC tests (constant load in 10 % NaCl at pH 4),

failure times extend from 100 hours for 304 to 250 hours for 304L and 300 hours for 304N—demonstrating the tangible benefits of both low carbon and nitrogen alloying.

5. Fabrication & Weldability

Formability: All three grades accept up to 50 % thickness reduction in cold rolling or deep drawing with minimal risk of cracking.

Nevertheless, springback increases slightly with nitrogen addition, requiring minor tool compensation for 304N.

Weld Cracking Sensitivity: Standard 304 demands rapid cooling through the 450–850 °C sensitization range or post-weld solution annealing (1040 °C × 15 min) to prevent intergranular corrosion.

By contrast, 304L and 304N tolerate slower cooling rates—even air cooling—without sensitization,

thereby reducing distortion and eliminating additional heat-treatment steps.

Machinability: Relative to 304, 304L machines with marginally lower cutting forces (5–10% reduction),

while 304N’s higher strength increases tool wear by about 10%.

In practice, machinists optimize parameters—using coated carbide tools and elevated coolant pressures—to balance material removal rates and tool life.

6. Heat Treatment and Sensitization Control

The AISI recommends solution annealing cycles as follows:

• 304 & 304L: 1 040 °C ± 5 °C, hold 15 min per 25 mm thickness → water quench
• 304N: 1 060 °C ± 5 °C, hold 15 min per 25 mm thickness → water quench

Importantly, none of these grades undergo deleterious 475 °C embrittlement due to their low or stabilized carbon content.

However, prolonged exposure between 350–550 °C can promote chi (χ) or sigma (σ) phase formation, especially in ill-controlled heats; therefore, designers avoid static service in this range when possible.

7. Industry Applications of 304 vs. 304L vs. 304N Stainless Steels

In practice, slight variations in carbon and nitrogen content translate into distinct service advantages.

Below, we examine how each grade finds its niche—and how data from real‐world installations underscore their performance.

304: General-Purpose Food, Beverage & Architectural Uses

• Why 304 Excels: With a balanced combination of corrosion resistance, formability and cost (cost index = 1.00), Type 304 accommodates moderate welding and forming without specialized equipment.
• Typical Applications:

• • Commercial Kitchen Equipment: Over 80% of U.S. restaurant-grade sinks, countertops and exhaust hoods specify 304 for its ease of cleaning and 0.1 mm surface finish.
  • Architectural Cladding: In temperate climates, thin-gauge 304 panels (0.5–1.0 mm) deliver decades of service—field surveys show < 0.5 μm/year exterior corrosion loss.
  • Food-Processing Tanks: Vessels up to 10 m³ use 304 for mixing and storage; hygienic interior finishes (Ra < 0.4 μm) prevent bacterial growth.

304L: Welded Pressure Vessels, Piping & Chemical Tanks

• Why 304L Shines: Its low-carbon chemistry (≤ 0.03 wt% C) virtually eliminates sensitization,
  making it ideal for large welded assemblies where post-weld heat treatment proves impractical.

  

• Typical Applications:

• • Pharmaceutical & Biotech Piping: Over 60% of sanitary fittings in API-compliant clean rooms employ 304L,
    ensuring weld-zone integrity under frequent CIP (clean-in-place) cycles at 90 °C.
  • Pressure Vessels & Heat Exchangers: Vessels up to 5 m in diameter avoid intergranular corrosion without solution annealing, reducing fabrication costs by up to 15%.
  • Storage Tanks for Mild Acids: 304L tanks storing 5 wt% acetic acid at 25 °C exhibit corrosion rates < 0.05 mm/year—20% slower than Type 304 counterparts.

304N: Cryogenic Equipment, Deep-Draw Components & Cold-Worked Parts

• Why 304N Prevails: Elevated nitrogen (0.10–0.16 wt%) delivers roughly 20% higher yield strength (≈ 260 MPa) and improved pitting resistance (PREN ≈ 20),
  while sustaining toughness at temperatures down to –196 °C.
• Typical Applications:

• • Cryogenic Valves & Fittings: In liquid-nitrogen service, 304N retains ≥ 80 J Charpy toughness at –196 °C,
    versus ~ 60 J for 304L—critical for preventing brittle fracture.
  • Deep-Drawn Beverage Cans & Components: Manufacturers report 10% thinner walls without splitting, reducing material usage by 5 g per can.
  • Seawater Pump Impellers & Screens: 304N’s higher PREN tolerates continuous 3.5 wt% NaCl exposure,
    cutting repair intervals from 6 months (with 304L) to 18 months.

8. Equivalent Grades

9. Key Differences Between 304 vs. 304L vs. 304N

Characteristic	304 (S30400)	304L (S30403)	304N (S30453)
Max Carbon	0.08 wt%	0.03 wt%	0.04 wt%
Nitrogen Content	≤ 0.10 wt%	≤ 0.10 wt%	0.10–0.16 wt%
Yield Strength	~ 215 MPa	~ 205 MPa	~ 260 MPa
Elongation	≥ 40 %	≥ 45 %	≥ 35 %
PREN	≈ 18	≈ 18	≈ 20
Sensitization Risk	High—450–850 °C window	Negligible	Negligible
Pitting Threshold (Cl⁻)	~ 0.2 wt%	~ 0.2 wt%	~ 0.3 wt%
Weld-Zone Annealing	Required	Optional	Optional
Cryogenic Toughness	~ 60 J @ –196 °C	~ 70 J @ –196 °C	~ 80 J @ –196 °C
Relative Cost Index	1.00	1.05	1.08

10. Conclusions

Stainless Steel 304 vs. 304L vs. 304N each addresses specific metallurgical challenges. Standard 304 delivers affordable strength but demands careful weld-zone control.

Grade 304L virtually eliminates sensitization, making it the go-to for welded assemblies.

Meanwhile, 304N’s nitrogen boost raises strength and pitting resistance—ideal for deep drawing and mildly aggressive environments.

By weighing carbon, nitrogen, mechanical performance, and corrosion data, engineers can select the optimal 300-series alloy for any application.

LangHe is the perfect choice for your manufacturing needs if you need high-quality stainless steel castings.

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FAQs

Why choose 304N over 304 or 304L?

304N adds 0.10–0.16 wt% nitrogen, boosting yield strength by ~20 % (to ≈260 MPa), refining grain size,

and raising pitting resistance (PREN ≈ 20 vs. ≈ 18) for better performance in chloride‐rich or cryogenic environments.

Do I need to solution anneal 304L after welding?

In most cases, no. 304L’s low carbon content prevents sensitization during typical cooling rates,

making post-weld solution annealing optional rather than mandatory.

Which grade offers the best formability?

304L leads with ≥45 % elongation, ideal for deep drawing and bending. Standard 304 and 304N follow with ≥40 % and ≥35 % elongation, respectively.

Can I use 304N for cryogenic applications?

Yes. 304N retains superior toughness (≈ 80 J Charpy V-notch at –196 °C) compared to 304L (≈ 70 J) and 304 (≈ 60 J), making it well-suited for liquid-gas service.

How do costs compare among 304, 304L and 304N?

Relative to base-price 304 (cost index = 1.00), 304L typically carries a 5 % premium (1.05) for low-carbon control, and 304N about an 8 % premium (1.08) for nitrogen alloying.