Stainless Steel-321

321 stainless steel should be considered for applications which require freedom from intergranular corrosion in moderately corrosive environments. General atmospheric and oxidation resistance is excellent, similar to Type 304 and even better once annealed and subjected to elevated temperature service. The product also provides improved creep and stress rupture characteristics when compared to 304 stainless steel.

Alloy 321 (UNS S32100) is a titanium-stabilized austenitic stainless steel with good general corrosion resistance. It has excellent resistance to intergranular corrosion after exposure to temperatures in the chromium carbide precipitation range of 800–1500°F (427–816°C). The alloy resists oxidation to 1500°F (816°C) and has lower creep and stress rupture properties than alloys 304 and 304L. It also possesses good low-temperature toughness.

Alloy 321 cannot be hardened by heat treatment; it can only be hardened by cold working. The alloy can be easily welded and processed by standard shop fabrication practices.

Corrosion Resistance

Alloy 321 exhibits good general corrosion resistance that is comparable to 304. It can be developed for use in the chromium carbide precipitation range of 800–1500°F (427–816°C), where un-stabilized alloys such as 304 are subject to intergranular attack.
The alloy can be used in most diluted organic acids at moderate temperatures and in pure phosphoric acid at lower temperatures and up to 10% diluted solutions at elevated temperatures. Alloy 321 resists polythionic acid stress corrosion cracking in hydrocarbon service. It can also be utilized in fluoride or chloride free caustic solutions at moderate temperatures.

Alloy 321 does not perform well in chloride solutions, even in small concentrations, or in sulfuric acid.
Fabrication Data

Welding

Alloy 321 can be easily welded and processed by standard shop fabrication practices.

Machining

The cold work hardening rate of 321 makes it less machinable than 410 stainless steel, but similar to 304. The table below provides relevant machining data.

Hot Forming

Working temperatures of 2100–2300°F (1149–1260°C) are recommended for forging, upsetting, and other hot working processes. Do not work this alloy at temperatures below 1700°F (927°C). Material must be water quenched or fully annealed after working to re-attain maximum corrosion resistance.

Cold Forming

The alloy is quite ductile and forms easily.