tig welding inconel tube root and stick filer pass amperage/also porosity on carbon tube on filler passes on start up

by Lance Knight
(monroe, la)

i am taking a test this week on an inconel tube and ive never touched the stuff....i really could use some tips on amperage for the more common tig wire and filler rods and any other tips like gap and how quickly to walk the cup or take my time.....also, for some reason, in the last year i have been experiencing porosity on my tubes on start up on the bottom of heavy wall carbon tube, 6g position....i consider myself to be a great stick and tig welder on carbon and this is frustrating because ive never had this problem b4 this past year and ive tried everything......i even failed my first tube test last week because of one of my straps of the 4 had 2 little pin holes i believe was caused by the porosity i just didnt grind out enough.....sorry this was so long but any help would be appreciated....thanks!!!!! Boilermaker Local 74

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Sorry about being late on this post.

amperage for a root pass on inconel depends on bevel angle, gap, and land, and filler wire diameter but generally anywhere between 55-75 can work with the right technique.
I like about a 1/8" gap and dip with a 3/32 wire.
there are so many different grades of inconel and all run a little bit different.

if the porosity is happening on the root pass, it is probably a combination of cup size, gas flow, and gap creating a vortex and sucking air.