SS 304H Chemical Composition: Chromium, Nickel, and Carbon

What is SS 304H Chemical Composition: Chromium, Nickel, and Carbon

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

Gangsteel focuses on the chemical composition of SS 304H, emphasizing the roles of chromium, nickel, and carbon, for applications like boilers, heat exchangers, and SA 240 GR 304 pipe. For inquiries, contact us at admin@gangsteel.com or explore our ASME SA240 Stainless sheet offerings.

Chemical Composition of 304H Stainless Steel

The chemical composition of 304H stainless steel, as specified by ASME SA 240 and ASTM A240, ensures its suitability for high-temperature service:

Analysis of Key Elements

• Carbon: The elevated carbon content (0.04-0.10%) is the defining feature of 304H stainless steel, improving creep resistance at temperatures above 800°F (427°C). It increases allowable stress (e.g., 25.5 ksi at 1000°F) compared to 304 (18.6 ksi) and 304L (14.9 ksi). However, it risks sensitization (carbide precipitation) in the 797°F-1580°F range, potentially reducing corrosion resistance in weld zones unless annealed.
• Chromium: Provides excellent corrosion resistance, outperforming lower-grade alloys like SS204 vs SS 304, but lacks molybdenum, limiting chloride resistance compared to sa240 gr 316l.
• Nickel: Ensures a stable austenitic structure, maintaining non-magnetic properties and enhancing formability for applications like plat SS 304 3mm.
• Comparison: Unlike sa240 gr 321 (titanium-stabilized), 304H relies on carbon for high-temperature strength, and unlike sa240 gr 317l, it lacks molybdenum for chloride environments.

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

Mechanical Properties Supporting Composition

The chemical composition supports robust mechanical properties for annealed plates (8-75 mm thick):

• High-Temperature Strength: Carbon content boosts creep resistance, with allowable stress of 25.5 ksi at 1000°F, ideal for high-temperature applications.
• Comparison: Stronger than sa240 gr 304l but similar to sa240 gr 304.

Physical Properties Supporting Composition

The chemical composition contributes to physical properties:

• 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 high-temperature processing.
• Thermal Conductivity: 16.2 W/m·K at 100°C.
• Coefficient of Thermal Expansion: 17.2 × 10⁻⁶/K (20-100°C).
• Service Temperature: Continuous up to 1500°F (815°C); intermittent up to 1600°F (871°C).

These properties support high-heat stability, unlike ferritic grades like sa240 gr 430.

Corrosion Resistance

304H stainless steeloffers corrosion resistance in:

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

Higher carbon increases sensitization risk in weld zones (797°F-1580°F), requiring annealing. For chloride-heavy environments, see sa240 gr 316ln.

Weldability

Weldability is fair using ER308H fillers. Higher carbon risks sensitization, necessitating low heat input (<2.0 kJ/mm) or post-weld annealing (1870-2100°F). For better weldability, see sa240 gr 304l.

Applications

304H stainless steelis used in:

• Boilers and pressure vessels.
• Heat exchangers.
• Power generation (superheaters, reheaters).
• Chemical processing (vessels, SA 240 GR 304 pipe).
• High-temperature piping.

For cost-effective options, see sa240 gr 201.

Pricing and Availability

As of October 19, 2025, 304H stainless steel plate prices (2B finish, 3-6mm) range from $1.60-$3.50/kg. Gangsteel offers $1.60/kg FOB (MOQ 1 ton) for sa240 gr 304h. Contact admin@gangsteel.com or visit astm a 240 stainless plate.

FAQ on 304H Chemical Composition

What is the carbon content of 304H stainless steel?

0.04-0.10%, higher than 304 (≤0.08%) and 304L (≤0.03%), enhancing creep strength but increasing sensitization risk during welding.

How does chromium contribute to 304H stainless steel properties?

Chromium (18-20%) forms a passive oxide layer, providing corrosion resistance in mild acids and atmospheric conditions, similar to 304.

Why is nickel important in 304H stainless steel?

Nickel (8-10.5%) stabilizes the austenitic structure, ensuring non-magnetic properties and enhancing formability for high-temperature applications.

How does 304H compare to 304L in chemical composition?

304H has higher carbon (0.04-0.10% vs. ≤0.03%) for high-temperature strength, while 304L prioritizes weldability with lower carbon.

What applications benefit from 304H’s chemical composition?

The high carbon and chromium/nickel content make 304H ideal for boilers, heat exchangers, and piping requiring creep resistance up to 1500°F.