Stainless Steel 409

Principal Design Features

409 is an alloy designed principally for the automotive exhaust industry, although it has been used successfully in other industrial applications. It combines good elevated temperature corrosion resistance with medium strength, good formability and overall cost. In recent years, however, and with the upcoming US government requirement for a 100,00 mile exhaust capability, other alloys have been becoming more prevalent.


Automobile mufflers, catalytic converters, tailpipes, farm equipment, structural supports and hangers, transformer cases, diamond tread plate and shipping containers.


Machining this alloy produces tough, draggy chips with heavy build-up. While this alloy can be machined in the annealed condition, it tends to perform better in the cold drawn or heat treated condition.


This alloy is quite ductile in the annealed condition and can be easily formed using all commonly employed practices. Experienced fabricators report that it is similar in formability to soft carbon steel.


Can be successfully welded employing SMA, GMA and GTA processes. When not used in a high temperature environment, filler metal AWS ER309 is acceptable for use. For stronger, more resilient welds at high temperature, use weld filler such as 409 Cb, AWS ER430 or W18 Cr-Cb.

Hot Working

Heat to 1500-1600 F(816-871 C) then rapidly heat to 1900-2050 F(1038-1121 C). Do not soak at this temperature and do not work at temperatures below 1500 F(816 C). Air cool forgings.

Cold Working

Despite a rather low work hardening rate, this alloy can be easily formed using most common methods.


Soak material at 1200-1400 F(649-760 C) and air cool.


This alloy is not hardenable by heat treatment.

Density: 0.278

Specific Gravity: 7.68

Specific Heat: 0.11

MoETensile: 29


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