Stainless 21-6-9

Annealing Procedure

1800-2150 F (982-1177 C), air cool.

Applications

Aircraft components, steam and autoclave parts, chemical and pollution control equipment.

Cold Workability

Although higher forces will be required when compared with other austenitic stainless steels, this alloy is readily formed employing most of the common methods.

Forgeability

Material can be forged at 1700-1800 F(927-982 C), followed by air or water quenching. {For heavy sections (over 4"), material should be charged at 1600 F(871 C), equalized at 2000 F(1093 C) and soaked at 2200 F(1204 C) for 1 minute for each inch of thickness.}

Formability

The yield strength of this alloy is nearly double that of conventional 304 stainless. This should be taken into consideration when choosing techniques and required forming pressures.

Hardening Procedure

This alloy does not respond to heat treatment. It can only be hardened through cold reduction.

Heat Treatability

Stress relieving should be performed to optimize performance in operating environments below 1300 F (705 C). Care should be taken in choosing the appropriate temperatures for this operation to protect the properties of cold reduced/ hardened parts. Stress relieving at a temperature between 900-1250 F should have little affect on mechanical properties.

Hot Workability

This alloy can be successfully forged, upset and headed at temperatures of 2100-2200 F (1149-1204 C).A post-work annealing is recommended to retain properties.

Machinability

Due to its relatively high work hardening rate, 21-6-9 is more difficult to machine than most of the austenitic/ 300 series stainless grades. It is quite similar to type 316 stainless. Slow speeds, positive feeds and ample cutting fluids are recommended to overcome work hardening.

Principle Design Features

High manganese and nitrogen strengthening result in a combination of high temperature oxidation resistance, excellent toughness at cryogenic temperatures and above average corrosion properties. Maximum temperature for continuous service is less than 1600 F (871 C). This alloy retains excellent toughness down to -423 F(-230 C).

Weldability

TIG, MIG and SMAW methods have been successfully employed. To obtain optimum service performance, AWS E/ER219 filler metal is recommended. Post-weld annealing is required to maximize corrosion resistance.