SS 321

347 Bob

For welding 321 to 321, use 321 or 347 filler.

321 and 347 are almost identical to 304. each has a little added alloy to make the alloy heat stable.

Here is a great write up of them both

For 321 to 304, use 3321 or 347 again. If the 304 is being used in a hot area at least use 304L.

where can i get 347 or 321 tig filler online? my local Airweld shop gave me a funny face when i asked for 321 filler...

Not sure about the 321, but TIG Depot has 347

I have found it in the past on eBay.

Although 321 filler metal does exist, it is much less common than 347 filler metal. Type 347 filler metal is normally used to weld either

321 or 347 base metals.

321 and 347 are typically used for higher temperature applications and have the compositions adjusted to prevent carbide precipitation during long term exposures to high temperatures (more than 600 deg F). 321 has a small amount of titanium added while 347 has niobium (aka columbium) added to provide this "stabilization" effect. As an electode filler metal, the titanium does not transfer very effectively across the weld arc (and, therefore, the staibilizing effect is lost) whereas there is no problem with the niobium, therefore, the preference for 347 filler metal. This is primarily true for MIG and stick and sub-arc welding processes. For TIG, the filler rod is being added directly to the weld pool so this problem of loss of the titanium is not significant.

In summary, you can find 321 TIG filler metals (e.g. from Washington Alloy) but the 347 will be much more widely available from many more sources (and, I would guess, possibly be a little cheaper).

Tom D.

Ernie Leimkuhler wrote:

AWS A5.9: ER 347Si