321/321H Stainless Steel

General Properties

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 higher creep and stress rupture properties than alloys 304 and 304L. It also possesses good low temperature toughness.

Alloy 321H (UNS S 32109) is the higher carbon (0.04 – 0.10) version of the alloy. It was developed for enhanced creep resistance and for higher strength at temperatures above 1000oF (537°C). In most instances, the carbon content of the plate enables dual certification.

Alloy 321 cannot be hardened by heat treatment, only by cold working. It can be easily welded and processed by standard shop fabrication practices.

Common Applications

• Aerospace – piston engine manifolds
• Chemical Processing
• Expansion Joints
• Food Processing – equipment and storage
• Petroleum Refining – polythionic acid service
• Waste Treatment – thermal oxidizers

ASTM/ASTE: UNS S32100

Corrosion Resistance

• exhibits good general corrosion resistance that is comparable to 304.
• developed for use in the chromium carbide precipitation range of 1800 – 1500°F (427 – 816°C) .
• can be used in most diluted organic acids at moderate temperatures .
• can be used in pure phosphoric acid at lower temperatures.
• can be used in up to 10% diluted solutions at elevated temperatures.
• resists polythionic acid stress corrosion cracking in hydrocarbon service.
•  utilized in chloride or fluoride free caustic solutions at moderate temperatures.
•  does not perform well in chloride solutions, even in small concentrations, or in sulfuric acid service.

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

Hot Forming

• Working temperatures of 2100 – 2300°F (1149 – 1260°C) are recommended for forging, upsetting and other hot working processes.
• Alloy not suitable for work 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

• Quite ductile and forms easily.

Welding

• Readily welded by most standard processes.
• Post weld heat treatment is not necessary

Machining

• Hardening rate of 321 makes it less machinable than 410 stainless steel, but similar to 304

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