Stainless Steel Alloy 309

Stainless steel alloy 309 is known for its strength, ability to resist corrosion and withstand high temperatures of up to 2000 F. It is these attributes, but its ability to resist oxidation that makes it preferred over 304 for some applications.

The ability to withstand continuous high temperatures makes it ideal for high heat applications such as: oven and boiler linings, furnaces, wood stoves and fire box sheets.

For machinability it is similar to stainless steel alloy 304. It does harden rapidly and produce stringy chips during machining. Therefore it is necessary to employ chip breakers and to avoid starts and stops in the tool cutting.

Like most austenitic alloys, alloy 309 is easily welded. The fusion or resistance welding methods are the best, but the oxyacetylene method should be avoided.

High working temperatures are required for stainless steel alloy 309. The optimal temperature for working is 2150 F. At 1800 degrees F it is necessary to initiate reheating to continue working. When the work is finished the part should be rapidly cooled by water quenching.

While it has a high rate with work hardening, 309 does respond well to some cold work, such as; stamping, and can be headed, drawn and upset. This alloy of stainless steel requires full annealing, at 1900 to 2050 F water quenching. This will alleviate internal stress once the cold work is finished.

When it comes to hardening, stainless steel alloy 309 has a negative response to heat treatment. However, for hardness and strength, cold work is the best method.

For more information about the actual chemical composition of Stainless Steel Alloy 309.

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