321/321H Stainless Steel (1.4541/1.4878)

321 and 321H stainless steels offer reliable mechanical strength for demanding high-temperature environments. 321H’s elevated carbon content provides enhanced creep and rupture resistance for pressure-retaining equipment operating at elevated temperatures.

Typical Mechanical Properties:

Tensile Strength: 620 MPa (90,000 psi) – Supports structural loads in thermal systems.

Yield Strength (0.2%): 310 MPa (45,000 psi) – Resists permanent deformation under stress.

Elongation: 40% – Offers excellent ductility, aiding in forming and fabrication.

Hardness: Rockwell B95 – Suitable for machining and moderate wear resistance.

Impact Strength: 27 J (20 ft-lb) – Maintains toughness in dynamic load applications.

Modulus of Elasticity: 193 GPa (28 x 10⁶ psi) – Ensures stiffness in structural assemblies.

These properties support the use of 321H plates, tubes, and pipes in heat exchangers, boilers, and exhaust systems under high-stress thermal cycles.

321 and 321H maintain structural integrity under thermal stress, making them ideal for components exposed to frequent temperature fluctuations.

Typical Physical Properties:

Density: 7.99 g/cm³ – Supports stable mass-to-strength ratio for structural use.

Melting Point: 1399–1454 °C (2550–2650 °F) – Suitable for high-heat service components.

Specific Heat Capacity: 0.5 J/g·K – Enables thermal stability and resistance to rapid temperature changes.

Thermal Conductivity: ~16 W/m·K – Manages heat distribution in industrial systems.

Thermal Expansion: ~16 × 10⁻⁶/K – Delivers dimensional reliability under thermal cycling.

Modulus of Elasticity: 193 GPa – Ensures rigidity in heat-affected load-bearing systems.

These physical characteristics help maintain performance in exhaust manifolds, thermal barrier structures, and furnace linings.

Multiple variants exist to support specific fabrication, welding, and performance requirements:

321: Standard titanium-stabilised alloy for welded and high-temperature service.

321H: High-carbon version with improved creep strength and heat resistance.

321L: Low-carbon version prioritising weldability and corrosion control.

321F: Free-machining titanium-stabilised grade for precision components.

321Ti: Titanium-enhanced variant for oxidation resistance in exhaust systems.

321LN: Low-carbon, nitrogen-strengthened version for higher mechanical strength.

These options ensure 321 stainless steel can be tailored for industrial heating, aerospace assemblies, or chemical processing lines where high-temperature reliability is critical.