What is 321 stainless steel pipe?

321 stainless steel is an austenitic stainless steel known for its exceptional high-temperature stress rupture strength and creep resistance. Compared to 304 stainless steel, it offers enhanced mechanical properties under high-temperature conditions. Stabilized with titanium (Ti), 321 stainless steel prevents intergranular corrosion when exposed to temperatures ranging from 425-850°C. This makes it an excellent choice for applications requiring oxidation resistance, high strength, and phase stability in high-temperature environments up to 900°C.

1. Material Composition

321 stainless steel belongs to the Ni-Cr-Mo austenitic stainless steel family. Its composition is similar to 304 stainless steel, but the addition of titanium significantly improves its resistance to intergranular corrosion and enhances its high-temperature strength. The titanium content effectively suppresses the formation of chromium carbide, thereby maintaining corrosion resistance.

Chemical Composition of TP321 Stainless Steel:

2. Performance Characteristics

a. High-Temperature Resistance & Intergranular Corrosion Prevention

Titanium stabilization prevents intergranular corrosion by inhibiting chromium carbide formation along grain boundaries.

Exhibits superior stress rupture strength and creep resistance at elevated temperatures.

Resistant to oxidation, wear, and structural brittleness under extreme heat conditions like flue gas and steam environments.

b. Exceptional Mechanical Strength

Can withstand tensile, bending, and impact stresses without deformation or rupture.

Maintains good plasticity, toughness, rigidity, elasticity, and fatigue resistance under prolonged stress conditions.

Offers high stress resistance without requiring excessive strain or exhibiting permanent deformation.

3. Applications of 321 Stainless Steel Pipes

Due to its superior high-temperature strength and intergranular corrosion resistance, 321 stainless steel pipes are widely used in:

Chemical heating furnaces

Boiler pressure vessels

Combustion furnaces

Diesel engines

Drying equipment

These applications often involve high temperatures and exposure to aggressive environments, making corrosion resistance a critical factor. Intergranular corrosion can be particularly dangerous, as it weakens the bonding force between grains without visible surface damage, leading to mechanical failure and potential safety hazards.

4. Does 321 Stainless Steel Rust?

Although 321 stainless steel has excellent corrosion resistance, it is not entirely immune to rust. Corrosion can occur under certain environmental conditions, influenced by:

Medium concentration

pH level

Operating temperature

For instance, prolonged exposure to the sensitization temperature range (450-850°C) can lead to intergranular corrosion due to chromium depletion. This happens when carbon (C) reacts with chromium (Cr) at the grain boundary, forming Cr23C6 precipitates, reducing the available Cr content below 12%, which increases susceptibility to corrosion.

Conclusion

321 stainless steel stands out for its high-temperature performance, excellent mechanical properties, and strong resistance to intergranular corrosion. While it is widely used in high-risk, high-temperature industrial applications, factors like temperature, pH, and environmental exposure must be considered to maintain its long-term durability and performance.