[Des]

Hi all,

When welding ss 321 where the finished structure is being used at prolonged elevated temperatures,( in the 425 to 850 °C), it is required to use filler rod 321 or 347.
321 filler rod is restricted for tig welding only, since the stabilising agent used in this rod (Ti) would mostly deteriorate when transfered to the base metal via an arc.
When I use the tig melding procedure I thus have an option to use filler rod 321 or 347...but is there a preference?
Where 321 filler rod wil match perfect the base metal composition, whereas 347 where the stabilising agent is niobium, will there be any difference in the finished weld quality?

Best regards and many thanks in advance,
Des.

[Coldman]

Hi Des,
interesting application.
We know that titanium is going to be stable during welding and under high temperature service so it's a given that 321 is an appropriate choice for filler here.
Niobium is also stable but I have in my mind that it may also increase hardness a little in dilution which may be an issue at high temperature. I don't have any supporting evidence as I am out of town for a while, it's just a niggle at the back of my head.

[kiwi2wheels]

347 has always been the filler material used to build 321 exhaust systems for race cars.

http://corp.burnsstainless.com/componen ... ld-quality

http://corp.burnsstainless.com/technica ... l-overview

[Coldman]

Well that clears it up. 347 it is.


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[Poland308]

http://www.harrisproductsgroup.com/~/me ... ection.pdf

There is a foot note on the chart that says use the top listed number first( likely will give the best results) but sometimes you choose a different filler for its specific properties.
308 would also be an acceptable choice and maybe more cost effective if it’s for practice.