Stainless Steel 321

Stainless Steel 321 is a titanium-stabilized austenitic alloy, similar to 304 but with Ti (5×C–0.70%). It prevents intergranular corrosion at 425–815°C, ideal for welded or high-heat equipment needing corrosion resistance.

Chemical Composition (Key, % ASTM A240)

C: ≤0.08; Cr: 17.0–19.0; Ni: 9.0–12.0

Ti: 5×C–0.70 (min 0.10)

Mechanical Properties (Annealed)

Tensile Strength: ≥515 MPa; Yield Strength: ≥205 MPa

Elongation: ≥40%; Hardness: ≤217 HB

Performance & Uses

Advantages: Resists intergranular corrosion, weldable without post-treatment, works at 870°C.

Applications: Aircraft exhausts, heat exchangers, boiler parts, food ovens.

Equivalent Grades

EN 1.4541, JIS SUS321, DIN X6CrNiTi18-10

Q&As

How does Ti stabilize it?Ti binds carbon before it forms Cr carbides (which deplete Cr and cause corrosion). Even in welded heat zones, Ti locks carbon, keeping Cr evenly distributed-no weld decay (unlike 304).

Compare to 316Ti?316Ti has Mo (2–3%) for chloride resistance (marine use) and more Ni (10–14%). 321 has no Mo (worse in saltwater) but is cheaper. Choose 321 for dry high heat (exhausts); 316Ti for chlorides.

Cryogenic use?Yes. Austenitic structure stays ductile below -196°C (liquid nitrogen). Ti doesn't harm low-temp performance-retains ≥40% elongation. Good for rocket fuel tanks, but 304 is cheaper for pure cryo use.

What is weld decay?It's intergranular corrosion in welded 304: heat zones form Cr carbides, corroding easily. 321's Ti prevents this-welds stay corrosion-resistant, no post-weld annealing needed.

Heat treatment tips?Anneal at 925–1100°C (30–60 mins/25mm thickness) to soften and form Ti carbides. Quench in water (slow cooling causes Cr carbides). Avoid overheating >1100°C (dissolves Ti carbides).