Welding then forming 409SS problems

[gilley29]

Weld seam cracks after roll forming a flange.

Process: Rolling a cylindrical tank with 14 ga 409SS sheet and
using SAW for the butt weld seam. Filler is ER309LSI and flux is
ST-100. After the seam weld, a .4" deep flange (rough cross
section below) is roll formed on the top edge of the tank. The
weld is so brittle it cracks at the stressed corners. I am getting
mixed info on pre- and post-weld heating. One says to use low
heat input during welding and form at room temp without
annealing. Another expert suggested pre- and post-weld
treatment. If heat treatment is recommended, can heating with a
dull grinder be effective? Any other suggestions? It would be
nice if a ductile filler for 409 and 304 could be found. Thanks in
advance. SCOTT

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[gdodd]

We use 308 or 309 austenitic grade welding wire to successfully join our exhaust components which are either 409, 304 stainless steel or ACMS. I suggest you may have residual stresses introduced in your part by the roll forming operation and it may be necessary to stress relieve the part before welding, but not with a dull grinder.

 

[Rob45]

No doubt your cracks are being caused by forming stresses from the flanging operation, but I'd also try using a different weld filler material. For example, try a ferritic filler wire with Cb stabilization. It'll help you avoid intergranular corrosion if the end product is ever exposed to salt.