SUS321 vs SUS304: Titanium-Stabilized Grade Differences

Key Differences

Stabilization: SUS321 has titanium (Ti) added, which binds with carbon to form stable titanium carbides, preventing chromium depletion at grain boundaries. SUS304 lacks this stabilization.

High-Temperature Performance: SUS321 excels in temperatures from 425°C to 900°C (800°F–1650°F) due to its resistance to carbide precipitation and creep, unlike 304, which is prone to "weld decay" in these conditions.

Corrosion Resistance: Both offer good corrosion resistance, but SUS321's titanium stabilization provides superior resistance to intergranular corrosion after welding or heating, a key advantage over standard 304.

Applications: SUS304 is great for general, ambient-temp use (food, beverage). SUS321 is for high-temp parts like aircraft exhausts, heat exchangers, furnace components, and chemical processing equipment.

Cost: SUS321 is typically more expensive (10-15%) than SUS304 due to the added titanium.

When to Choose Which

Choose SUS304 for cost-effective, general-purpose applications in moderate environments where high heat or extensive welding isn't a major concern.

Choose SUS321 when the application involves high temperatures, thermal cycling, or welding, requiring enhanced stability and prevention of weld decay.