304H vs 304L Gasket Material Comparison for Sealing

304L vs 304H Stainless Steel: Key Differences and Uses

At Gangsteel, a leading manufacturer and exporter of stainless steel products, we supply high-quality SA 240 GR 304L and SA 240 GR 304H plates compliant with ASME SA 240 and ASTM A240 standards.

304L(UNS S30403, AISI 304L, EN 1.4306/1.4307) is a low-carbon austenitic stainless steel designed for superior weldability and corrosion resistance in mild environments, while 304H (UNS S30409, AISI 304H, EN 1.4948) is a high-carbon variant optimized for enhanced high-temperature strength and creep resistance up to 1500°F (815°C).

Both are austenitic, non-magnetic in the annealed state (SA 240 304 non magnetic), and have a density of 8.00 g/cm³.

This guide compares 304L vs 304H stainless steel in chemical composition, mechanical properties, corrosion resistance, weldability, cost, and uses for applications like plat stainless 304 and SA 240 GR 304 pipe. For inquiries, contact us at admin@gangsteel.com or explore our ASME SA240 Stainless sheet offerings.

Chemical Composition Comparison

The primary difference between 304L and 304H stainless steel is carbon content, which impacts weldability and high-temperature strength:

• Carbon: 304L’s ultra-low carbon (≤0.03%) prevents carbide precipitation during welding, preserving corrosion resistance in weld zones, making it ideal for chemical and food processing. 304H’s elevated carbon (0.04-0.10%) strengthens the material against creep and stress rupture at temperatures above 800°F (427°C), but requires post-weld annealing to mitigate sensitization risks.
• Chromium/Nickel: Identical ranges ensure comparable corrosion resistance in mild environments, outperforming SS204 vs SS 304 due to higher nickel content. For chloride-heavy environments, see sa240 gr 316l.
• Comparison: 304L lacks the high-temperature strength of 304H, while 304H sacrifices some weldability. For detailed specs, refer to our SS 304 data sheet.

Mechanical Properties Comparison

The mechanical properties of 304L and 304H stainless steel for annealed plates (8-75 mm thick) highlight their distinct design focuses:

• Tensile Strength: 304H’s 515 MPa outperforms 304L’s 485 MPa, particularly at high temperatures, enabling use in boilers and heat exchangers where creep resistance is vital.
• Yield Strength: 304H’s 205 MPa exceeds 304L’s 170 MPa, ensuring better performance under stress in high-temperature environments.
• Elongation: Identical 40% elongation provides excellent formability, but 304H’s higher carbon makes it slightly less forgiving in severe cold-working.
• Hardness: Both have ≤201 HB, supporting machinability, but 304H’s carbon content allows greater hardening potential after cold-working (up to 300 HB).

For comparison with other grades, see sa240 gr 304.

Corrosion Resistance Comparison

Both 304L and 304H stainless steel provide outstanding corrosion resistance in mild environments:

• Atmospheric conditions, freshwater, and mild acids (food-grade).
• General settings, outperforming SS204 vs SS 304 due to high chromium (18-20%) and nickel.

Key Differences:

• 304L: Superior in welded applications, as low carbon (≤0.03%) prevents sensitization, preserving corrosion resistance in weld zones and making it ideal for chemical tanks and piping.
• 304H: Comparable to 304 in mild environments but higher carbon (0.04-0.10%) increases sensitization risk in the 797°F-1580°F (425°C-860°C) range during welding or service, potentially reducing corrosion resistance unless annealed post-weld (1870-2050°F).

Both are less resistant to chloride-induced pitting compared to molybdenum-enhanced grades like sa240 gr 316l.

Weldability Comparison

• 304L: Excellent weldability with ER308L fillers. Low carbon minimizes sensitization, often eliminating the need for post-weld annealing, ideal for welded applications like SA 240 GR 304 pipe or chemical tanks.
• 304H: Fair weldability with ER308H fillers. Higher carbon increases sensitization risk, requiring controlled heat input (<2.0 kJ/mm) or post-weld annealing to restore corrosion resistance. For high-temperature welds, consider sa240 gr 321.

Physical Properties Comparison

Both grades share identical physical properties due to similar compositions:

• Density: 8.00 g/cm³, ideal for lightweight designs (e.g., a 1m x 1m x 3mm plate weighs ~24 kg).
• Melting Point: 1400-1450°C, suitable for processing.
• Thermal Conductivity: 16.2 W/m·K at 100°C.
• Coefficient of Thermal Expansion: 17.2 × 10⁻⁶/K (20-100°C).
• Electrical Resistivity: 0.72 × 10⁻⁶ Ω·m.
• Service Temperature:
  • 304L: Continuous up to ~800°F (427°C), suitable for mild environments.
  • 304H: Continuous up to 1500°F (815°C); intermittent up to 1600°F (871°C), with scaling onset at ~1200°F (649°C).

These properties support 304H’s high-temperature applications and 304L’s weldability. For cost-effective alternatives, see sa240 gr 201.

Cost Comparison

As of October 19, 2025:

Gangsteel offers competitive pricing: $1.50/kg FOB for 304L and $1.60/kg FOB for 304H (MOQ 1 ton).