304H Hardness Brinell and Rockwell Values

What is 304H Hardness: Brinell and Rockwell Values

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). This guide focuses on the hardness properties of 304H stainless steel, specifically Brinell and Rockwell values, 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.

Hardness of 304H Stainless Steel

The hardness of 304H stainless steel measures its resistance to indentation, critical for machinability and formability in high-temperature applications. For annealed plates (8-75 mm thick), as specified by ASME SA 240 and ASTM A240, the hardness values are:

• Brinell Hardness (HB): ≤ 201 HB
• Rockwell B Hardness (HRB): ≤ 92 HRB

These values ensure 304H stainless steel is soft enough for machining and forming (e.g., plat SS 304 3mm or plate 2 mm SUS 304) while maintaining strength for high-temperature service. The moderate hardness is comparable to SA 240 GR 304 and slightly softer than sa240 gr 316l (≤217 HB), reflecting the austenitic structure and higher carbon content (0.04-0.10%).

Importance of Hardness

• Machinability: ≤201 HB allows easy cutting, drilling, and shaping, critical for fabricating complex components like pressure vessels.
• Formability: Low hardness supports high elongation (40%), enabling forming without cracking.
• High-Temperature Performance: Hardness remains stable up to 1500°F, unlike ferritic grades like sa240 gr 430 (≤183 HB).
• Cold-Working: Hardness can increase significantly (e.g., up to 300 HB) with cold-working, enhancing strength but reducing ductility.

Chemical Composition Supporting Hardness

The chemical composition of 304H stainless steel influences its hardness:

The higher carbon content (0.04-0.10%) compared to 304 (≤0.08%) and 304L (≤0.03%) contributes to slightly higher hardness potential after cold-working, but annealing keeps hardness at ≤201 HB. For comparison, see sa240 gr 304.

Mechanical Properties Supporting Hardness

The hardness values complement other mechanical properties for annealed plates:

• Hardness and Strength: The low hardness (≤201 HB) ensures machinability while supporting tensile strength (515 MPa) and yield strength (205 MPa), ideal for high-temperature applications.
• Creep Resistance: Allowable stress of 25.5 ksi at 1000°F (538°C) benefits from controlled grain structure and moderate hardness, outperforming sa240 gr 304l.

Physical Properties Supporting Hardness

• 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).

Moderate hardness ensures stability at high temperatures, unlike harder martensitic grades like sa240 gr 410.

Corrosion Resistance

304H stainless steeloffers excellent corrosion resistance in:

• Atmospheric conditions, freshwater, and mild acids (food-grade).
• General environments, outperforming SS204 vs SS 304 due to higher nickel (8-10.5%).

Higher carbon (0.04-0.10%) increases sensitization risk in weld zones (797°F-1580°F), requiring annealing. For chloride-heavy environments, see sa240 gr 317l.

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 321.

Applications Leveraging Hardness

The moderate hardness (≤201 HB) of 304H stainless steel supports:

• Boilers and pressure vessels (machinability for fabrication).
• Heat exchangers (forming complex shapes).
• Power generation (superheaters, reheaters).
• Chemical processing (vessels, SA 240 GR 304 pipe).
• High-temperature piping and fittings.

For cost-effective alternatives, 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 Hardness

What are the Brinell and Rockwell hardness values for 304H stainless steel?

Brinell hardness is ≤201 HB, and Rockwell B is ≤92 HRB, ensuring good machinability and formability in the annealed state.

How does 304H hardness compare to 304L?

Both have similar hardness (≤201 HB), but 304H’s higher carbon (0.04-0.10%) allows greater hardness potential after cold-working compared to 304L (≤0.03% C).

Why is low hardness important for 304H stainless steel?

Low hardness (≤201 HB) supports easy machining and forming for complex components like pressure vessels, while maintaining high-temperature strength.

How does 304H hardness compare to 316L?

304H (≤201 HB) is slightly softer than 316L (≤217 HB) due to the absence of molybdenum, offering better machinability but less chloride resistance.

What applications benefit from 304H’s hardness?

Boilers, heat exchangers, and SA 240 GR 304 pipe leverage low hardness for fabrication ease and high-temperature durability.