SS 304H Material: What Does 304H Stand For?

SS 304H Material: What Does 304H Stand For?

At Gangsteel, a premier manufacturer and exporter of stainless steel products, we supply high-quality SS 304H material plates compliant with ASME SA 240 and ASTM A240 standards. SS 304H material, also known as AISI 304H, UNS S30409, or EN 1.4948, is a high-carbon variant of the 304 austenitic stainless steel family, engineered for superior strength and creep resistance in high-temperature environments up to 1500°F (815°C).

The designation "304H" distinguishes it from standard 304 and 304L, with the "H" indicating a higher carbon content for enhanced performance in applications like boilers, heat exchangers, and SA 240 GR 304 pipe. This comprehensive guide explains the meaning of 304H, its properties, specifications, and applications. For inquiries, contact us at admin@gangsteel.com or explore our ASME SA240 Stainless sheet offerings.

What Does 304H Stand For in SS 304H Material?

The "304H" in SS 304H material stands for "high carbon," referring to its carbon content of 0.04-0.10%, which is higher than standard 304 (≤0.08% C) and 304L (≤0.03% C). Specified under ASME SA 240 as SA 240 GR 304H, this grade is designed for pressure vessels and high-temperature service, offering improved creep and stress rupture strength. The austenitic structure ensures non-magnetic properties in the annealed state, often noted as SA 240 304 non magnetic. SS 304H material is ideal for demanding applications where thermal stability is critical, unlike 304L, which prioritizes weldability. For related grades, see our sa240 gr 304 and sa240 gr 304l pages.

Chemical Composition of SS 304H Material

The chemical composition of SS 304H material enhances its high-temperature performance while maintaining corrosion resistance:

• Carbon: Higher content (0.04-0.10%) improves creep resistance at elevated temperatures but increases sensitization risk during welding.
• Chromium: Provides corrosion resistance via a passive oxide layer, effective in mild acids and atmospheric conditions.
• Nickel: Maintains the austenitic structure, ensuring non-magnetic properties.
• Comparison: Lacks molybdenum (unlike sa240 gr 316l) and titanium (unlike sa240 gr 321), optimizing it for non-chloride high-heat environments.

For detailed specifications, refer to our SS 304 data sheet.

Mechanical Properties of SS 304H Material

The mechanical properties of SS 304H material for annealed plates (8-75 mm thick) support its use in high-temperature structural applications:

• High-Temperature Strength: SS 304H material offers superior creep resistance, with an allowable stress of 25.5 ksi at 1000°F (538°C) compared to 18.6 ksi for 304 and 14.9 ksi for 304L, making it ideal for elevated-temperature service.
• Comparison: Stronger than 304L (485 MPa tensile, 170 MPa yield) but similar to 304, with enhanced performance above 800°F (427°C).
• Cold-Working: Can increase tensile strength (up to 900 MPa) but reduces ductility, suitable for applications like plat SS 304 3mm.

Physical Properties of SS 304H Material

The physical properties of SS 304H material ensure its suitability for high-temperature environments:

• 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, supporting high-temperature processing.
• Thermal Conductivity: 16.2 W/m·K, moderate for heat transfer.
• Coefficient of Thermal Expansion: 17.2 × 10⁻⁶/K (20-100°C), stable across temperature ranges.
• Electrical Resistivity: 0.72 × 10⁻⁶ Ω·m, suitable for non-conductive applications.
• Maximum Service Temperature: 1500°F (815°C) for continuous service; 1600°F (871°C) for intermittent exposure, with scaling onset at ~1200°F (649°C).

These properties make SS 304H material ideal for high-temperature applications, unlike ferritic grades like sa240 gr 430.

Corrosion Resistance of SS 304H Material

SS 304H materialprovides corrosion resistance similar to standard 304:

• Environments: Excellent in atmospheric conditions, freshwater, and mild acids (e.g., food-grade applications), outperforming SS204 vs SS 304 due to higher nickel content.
• Limitations: Less resistant to chloride-induced pitting compared to molybdenum-enhanced grades like sa240 gr 316l. Higher carbon content increases sensitization risk in the 797°F-1580°F (425°C-860°C) range, potentially reducing corrosion resistance in weld zones unless annealed.

For chloride-heavy environments, consider sa240 gr 317l for enhanced pitting resistance.

Weldability of SS 304H Material

• Weldability: Fair, using ER308H or ER308 fillers. The higher carbon content (0.04-0.10%) increases the risk of sensitization (chromium carbide precipitation), which can compromise corrosion resistance in welded areas. Controlled heat input (<2.0 kJ/mm) or post-weld annealing at 1870-2100°F (1020-1149°C) is recommended.
• Comparison: Less weldable than SA 240 GR 304L due to higher carbon; for critical welds, consider sa240 gr 304l or titanium-stabilized sa240 gr 321 for high-temperature welding.

Applications of SS 304H Material

SS 304H materialis widely used in high-temperature applications, including:

• Boilers and Pressure Vessels: Steam drums and headers requiring creep resistance.
• Heat Exchangers: Tubes and shells for elevated-temperature service.
• Power Generation: Superheaters and reheaters operating up to 1500°F.
• Chemical Industry: Vessels and SA 240 GR 304 pipe for mild corrosives at high temperatures.
• Piping and Fittings: High-temperature systems, including flanges and fittings compliant with astm a 312/a 312m stainless pipe.

For lower-temperature or highly corrosive applications, explore sa240 gr 201 for cost savings or sa240 gr 904l for extreme corrosion resistance.

Pricing and Availability at Gangsteel

As of October 19, 2025, SS 304H material plate prices for 2B finish (3-6mm thick) range from $1.60-$3.50/kg globally, influenced by nickel prices (~$15,325/t). Gangsteel offers competitive pricing starting at $1.60/kg FOB (MOQ 1 ton) for standard sizes (e.g., 4’x8’, 5’x10’) and custom cuts like plate 2 mm SUS 304, with finishes like 2B, No.1, and polished. Our SS 304 plate price is 5-10% below market averages, and dual-certified SA 240 TP 304/304L plates are available for flexibility. For pricing details, contact admin@gangsteel.com or visit our sa240 gr 304h page.

Why Choose Gangsteel for SS 304H Material?

Gangsteel provides certified SS 304H material with consistent properties and competitive pricing. Our 600+ ton inventory supports global delivery for applications from high-temperature pressure vessels to heavy plates. For quotes or to learn more about SS 304H material, visit our astm a 240 stainless plate page or email admin@gangsteel.com.