Hello fellow welders,

Found this forum and decided to pick yall's brains..........lol
I work for a large heat exchanger/condenser manufacturer and we are in the process of obtaining our Nuke stamp again (we used to do nuke work years ago but it faded out).

We landed a large Naval Nuke Submarine condenser contract and Im the "LUCKY" welder chosen to qualify the welding procedures. I have 20+ years of welding experience ranging from HVAC welding all the way to military aircraft, and materials ranging from tin all the way to magnesium. So im a fairly experienced welder throughout the spectrum.

Ive been working for the past few weeks with 2 of our welding engineers (one is VERY experienced at 40+ years, the other is quite green as he just graduated a year or 2 ago) We are trying to establish a procedure for the following:

70/30 MIL spec CuNi to CuNi 1" thick X 24" length coupon,double V groove 37.5 degree, 3G position ,GTAW, pure argon @ 30 cfm, ceriated 3/32" tungsten, welding amperage restricted to 250 amps max because of torch capabilities. Max interpass temp @ 300F. RN67 Mil spec 3/32" filler.

70/30 MIL spec CuNi to HY80 MIL spec 1" thick X 24" length coupon,double V groove 37.5 degree, 3G position ,GTAW, pure argon @ 30 cfm, ceriated 3/32" tungsten, welding amperage restricted to 250 amps max because of torch capabilities. Max interpass temp @ 300F, RN60 Mil spec 3/32" filler .

Ive welded both coupons and failed RT for lack of fusion or voids pretty severely on the CuNi to CuNi. The CuNi to HY80 wasnt nearly as bad, but still a FAILURE no the less. Ive gave it another shot this week after tweaking a few techniques (grinding entire surface of each pass to remove all the oxides) but im awaiting RT results on the 2nd try.(fingers crossed)

When I qualified to weld CuNi in the 1G and 2G positions years ago, I had no problems what-so-ever. But that was on 1/2" single bevel plate.
Im trying to convince the engineers that I need a bigger powersource (300+ amp TIG and torch) for such thick base material. (tried preheating but it didnt seem to make a difference) The 1" coupons plus the 2" test fixture jig is just a HUGE heatsink sucking all the heat away from the weld pool! And this material welds like mud to begin with. In the 3G position on heavy plate................. its a nightmare!

Anyone have any tips or tricks on how to weld this sludge on heavy plate in 3G? Im thinking 300+ amps, 1/8" tungsten, 1/8" filler, argon/hydrogen sheilding gas, and maybe a single bevel instead of a double bevel? Someone has to know how to weld this on heavy material......... any help with be greatly appreiciated! Thanks in advance......