Stainless Steel 309

Chemical Analysis
C Carbon
Mn Manganese
2.00 max
P Phosphorus
0.045 max
S Sulfur
0.030 max
Si Silicon
1.00 max
Cr Chromium
22.00 – 24.00
Ni Nickel
12.00 – 15.00

General characteristics of Stainless Steel 309

Type 309, thanks to its higher chromium and nickel contents than the 18/8 austenitic steels, has somewhat better heat and corrosion resistance and may be used in continuous service at temperatures up to 2000ºF (1090ºC.)

Applications of Stainless Steel 309

The alloy is used for furnace parts, firebox sheets, high temperature containers and welding wire. It may be further used in numerous applications that will take advantage of its heat resisting properties.

Forging Stainless Steel 309

Type 309 should be forged at a temperature of about 2150ºF (1175ºC) and not forged much below 1800ºF (980ºC.) Small forgings should be rapidly air cooled or water quenched straight after forging. For optimum corrosion resistance parts should be annealed after forging.

Heat treatment


Anneal at 1900/2050ºF (1040/1120ºC) and water quench.


Type 309 machines like other 18/8 types, giving tough, stringy chips. Maximum feeds and slow speeds will give best machinability. A small amount of cold work on bars will improve the surface finish after machining.


Type 309 can be welded by shielded fusion and resistance methods, but oxyacetylene welding should be avoided to prevent carbon pick up in the welds. There is little risk of cracking in the welds. Should filler metal be required, 309 or 309L rods are recommended. A post weld anneal will prevent the occurrence of intergranular corrosion.


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