321 / 321H Stainless Steel (1.4541 / 1.4878)

Designed for durability under heat and stress, 321/321H stainless steel is built for high-performance applications.

321/321H Stainless Steel

321 stainless steel is a titanium-stabilised austenitic alloy known for its excellent resistance to intergranular corrosion, particularly after exposure to high temperatures. It is part of the 300-series family and widely used in industries requiring strength and stability in elevated heat conditions.

321H stainless steel is the high-carbon version of standard 321. The “H” indicates increased carbon content, which enhances high-temperature strength and creep resistance. Both grades are corrosion-resistant and capable of withstanding long-term thermal stress, but 321H is specifically suited to heavy-duty applications such as pressure vessels, heat exchangers, and furnace components.

Thanks to its durability, weldability, and resistance to high temperatures, stainless steel 321 is commonly used to produce components such as pipework for heat exchangers, sheets and plates for furnace linings, and tubing and round bar for structural or pressure-bearing applications. Its adaptability across these forms makes it ideal for fabrication in aerospace, petrochemical, and industrial heating systems.

AVAILABLE FORMS

Intamet offers 321/321h stainless steel in a wide range of forms, including the below:

Tubes & Pipes

Fitting & Flanges

Round Bars

Sheet & Plate

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What is the Chemical Composition of 321 / 321H Stainless Steel?

321 stainless steel (1.4541 / UNS S32100) contains:

Carbon (C): ≤ 0.08%
Manganese (Mn): ≤ 2.00%
Silicon (Si): ≤ 1.00%
Phosphorus (P): ≤ 0.045%
Sulfur (S): ≤ 0.03%
Chromium (Cr): 17.0–19.0%
Nickel (Ni): 9.0–12.0%
Titanium (Ti): ≥ 5×C
Iron (Fe): Balance

321H stainless steel (1.4878 / UNS S32109) typically includes:

Carbon (C): 0.04–0.10%
Nitrogen (N): 0.10–0.25%
Titanium (Ti): 5×(C+N), max 0.70%
Other elements (Mn, Si, Cr, Ni, P, S, Fe): similar to 321

321H may also contain trace amounts of columbium and tantalum to enhance high-temperature stability.

What are the Physical Properties of 321 / 321H Stainless Steel?

Physical properties shared by both grades include:

Density: 7.99 g/cm³
Melting Point: 1399–1454 °C
Specific Heat: 0.5 J/g·K
Thermal Conductivity: ~16 W/m·K
Thermal Expansion: ~16 × 10⁻⁶/K
Modulus of Elasticity: 193 GPa

These thermal and physical properties allow 321 stainless steel sheet, plate, and pipe to maintain structural integrity under high temperatures, making the material ideal for use in exhaust systems, furnace parts, and thermal barriers.

Are There Variants of 321 Stainless Steel?

There are several variants designed for specific operational needs:

321H: High-carbon version for improved high-temperature strength
321L: Low-carbon version offering greater weldability and corrosion resistance
321F: Machinable version stabilised with titanium
321Ti: Titanium-stabilised alternative, sometimes used interchangeably with 321F
321LN: Low-carbon, nitrogen-strengthened version for improved toughness

These options ensure that 321 stainless steel can be tailored for precise mechanical, chemical, or fabrication performance.

What are the Mechanical Properties of 321 / 321H Stainless Steel?

Both 321 stainless steel and 321H offer strong mechanical properties suitable for structural and high-temperature applications. Typical values include:

Tensile Strength: 620 MPa (90 ksi)
Yield Strength: 310 MPa (45 ksi)
Elongation: 40%
Hardness: Rockwell B95
Impact Strength: 27 J (20 ft-lb)
Density: 7.99 g/cm³
Melting Point: 1399–1454 °C (2550–2650 °F)

321H exhibits higher mechanical strength and better creep resistance compared to standard 321, making it preferable for components under prolonged stress and heat.

Where is 321 / 321H Stainless Steel Used?

Due to its excellent strength and heat resistance, 321 / 321H stainless steel is widely used in:

Aerospace and aviation — engine components, exhaust manifolds

Petrochemical & oil and gas — pipelines, processing equipment

Power generation — heat exchangers, boiler tubes

Industrial heating — furnace parts, kilns, and burners

Automotive & marine — exhaust systems and structural components

Available in forms such as 321H stainless steel tubes & pipes, round bar, sheets & plates, it is a preferred alloy for fabrications involving welding and thermal exposure.

321 / 321H Stainless Steel (1.4541 / 1.4878)