What Does the H Stand for in 304H?

What Does the H Stand for in 304H?

At Gangsteel, a leading manufacturer and exporter of stainless steel products, we supply premium 304H stainless steel plates compliant with ASME SA 240 and ASTM A240 standards. 304H stainless steel, 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). The "H" in 304H stands for "High Carbon", indicating its elevated carbon content (0.04-0.10%) compared to standard 304 (≤0.08% C) or 304L (≤0.03% C). This guide explains the meaning of "H" in 304H, its properties, and applications for uses 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.

The Meaning of "H" in 304H Stainless Steel

The "H" in 304H stainless steel denotes High Carbon, a designation used in AISI and ASME standards to indicate a variant of 304 with increased carbon for improved high-temperature performance. Specifically, the high carbon content (0.04-0.10%) enhances creep and stress rupture strength, making 304H suitable for continuous service up to 1500°F (815°C). This distinguishes it from:

• 304: Balanced carbon (≤0.08%) for general-purpose applications.
• 304L: Low carbon (≤0.03%) for superior weldability and corrosion resistance in mild environments.

The "H" classification ensures 304H meets the needs of high-heat applications like boilers and heat exchangers, where standard 304 may underperform. See sa240 gr 304h for stock.

Chemical Composition of 304H Stainless Steel

The chemical composition emphasizes the high carbon content:

• Carbon: The "H" factor, providing creep resistance at high temperatures.
• Chromium: 18-20% for corrosion resistance.
• Nickel: 8-10.5% for non-magnetic austenitic structure (SA 240 304 non magnetic).

Mechanical Properties

• High-temperature: Allowable stress 25.5 ksi at 1000°F (538°C).

Physical Properties

• Density: 8.00 g/cm³.
• Melting Point: 1400-1450°C.
• Thermal Conductivity: 16.2 W/m·K.
• Coefficient of Thermal Expansion: 17.2 × 10⁻⁶/K.
• Max Service Temperature: 1500°F (815°C) continuous.

Corrosion Resistance

304H stainless steel resists mild acids and atmospheric conditions, outperforming SS204 vs SS 304. Higher carbon risks sensitization in welds; anneal for protection. See sa240 gr 316l for chlorides.

Weldability

Fair with ER308H fillers; low heat input (<2.0 kJ/mm) and annealing required. See sa240 gr 304l.

Applications

304H stainless steel is used in:

• Boilers and pressure vessels.
• Heat exchangers.
• Power generation piping.
• High-temperature chemical processing.

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 Stainless Steel

What is the difference between 304 and 304H stainless steel?

304 has ≤0.08% carbon for general use; 304H has 0.04-0.10% carbon for enhanced high-temperature strength up to 1500°F.

How does 304H compare to 304L in carbon content?

304H has higher carbon (0.04-0.10% vs. ≤0.03%) for creep resistance, while 304L prioritizes weldability.

What is the maximum service temperature for 304H stainless steel?

Continuous up to 1500°F (815°C), with excellent creep resistance for boilers and heat exchangers.

What is the tensile strength of 304H stainless steel?

Minimum 515 MPa (75 ksi), ensuring robust performance at high temperatures.

Why is 304H stainless steel non-magnetic?

Its austenitic structure, stabilized by 8-10.5% nickel, ensures non-magnetic properties in the annealed state.