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Thread: CuNi 70/30 3g?

  1. #1
    Join Date
    May 2012
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    Default CuNi 70/30 3g?

    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......

  2. #2
    Join Date
    Aug 2010
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    Los Angeles
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    Default

    Just a couple of observations.

    250 amps is pretty light for 30 cfh argon.

    You say your limited on ampt because of torch. I would consider a larger torch, and a cup size of a least# 10 to accomodate that amount of gas flow. In fact, I would just move up to a # 12 cup.

    Good Stuff, let us know how you fare.
    Nothing welded, Nothing gained

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  3. #3
    Join Date
    Nov 2010
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    Default

    Quote Originally Posted by DirtyDan View Post
    Hello fellow welders,



    Anyone have any tips or tricks on how to weld this sludge on heavy plate in 3G? Thanks in advance......
    If your company is manufacturing a condenser based on a similar SubNuc design then I would recommend looking at the NavSea technical notes that are included with those designs. Also, the NRC has very specific requirements for its primary and secondary systems that must be followed...

  4. #4
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    Just for reference I had to qualify a procedure for a turret weldment that was 1/4" cyl to 5/8" base plate. Minimum amps for remote current control GTAW was 300 amps. We qualified it at 350 amps.

    AWS has prequalifed procedures in the thicknesses you are doing. Although not the same alloys, the thickness ranges will suggest amperages.

    I agree with you, more horsepower is needed. What power supply are you currently running?
    Last edited by shovelon; 05-19-2012 at 11:41 AM.
    Nothing welded, Nothing gained

    Miller Dynasty700DX
    3 ea. Miller Dynasty350DX
    Miller Dynasty200DX
    ThermalArc 400 GTSW
    MillerMatic350P
    MillerMatic200 with spoolgun
    MKCobraMig260
    Lincoln SP-170T
    Linde UCC305 (sold 2011)
    Hypertherm 1250
    Hypertherm 800
    PlasmaCam CNC cutter
    Fadal Toolroom CNC Mill
    SiberHegner CNC Mill
    2 ea. Bridgeport
    LeBlond 15" Lathe
    Haberle 18" Cold Saw
    Doringer 14" Cold Saw
    6 foot x 12 foot Mojave granite

  5. #5

    Default

    I would also go with a machine with more amps (300+) and a water cooled torch and 1/8 tung. Would Heli-Argon give you more heat?

  6. #6
    Join Date
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    greenfield new hampshire
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    Default

    This is why i like this forum, top notch questions, from educated people with interesting work.

  7. #7
    Join Date
    May 2012
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    14

    Default

    Quote Originally Posted by Dipsomaniac View Post
    If your company is manufacturing a condenser based on a similar SubNuc design then I would recommend looking at the NavSea technical notes that are included with those designs. Also, the NRC has very specific requirements for its primary and secondary systems that must be followed...
    Thanks Dipso...........

    Unfortunately, the only documentation I have available to me as a welder is a pre-requisite procedure sheet that only suggests a 300F interpass temp. (info provided by the filler wire manufacturer I assume) I work night shift, so I only have a few mins a day to communicate with the day shift weld engineers.........and all I ever get is "just weld it, your already qualified in 1g and 2g, it shouldnt be a problem". I think im on my own on this one......

  8. #8
    Join Date
    May 2012
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    Quote Originally Posted by shovelon View Post
    Just for reference I had to qualify a procedure for a turret weldment that was 1/4" cyl to 5/8" base plate. Minimum amps for remote current control GTAW was 300 amps. We qualified it at 350 amps.

    AWS has prequalifed procedures in the thicknesses you are doing. Although not the same alloys, the thickness ranges will suggest amperages.

    I agree with you, more horsepower is needed. What power supply are you currently running?
    I agree shovelon, need a lil more umphh!
    I always use a Miller Pipeworx 400 at work. (but they only have CK flexneck 250 amp torches connected to them) Although, they have several Miller Dynasty 700's available as well. I just hate using that HUGE freaking torch, as im a finesse welder more than a brute-force welder. Im thinking that Im gonna have to make an exception on this qualification. Thanks for your input.

  9. #9
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    Quote Originally Posted by browniethewelder View Post
    I would also go with a machine with more amps (300+) and a water cooled torch and 1/8 tung. Would Heli-Argon give you more heat?
    I used a Tri-A mix (helium,argon,CO2) to qualify the gmaw-pulse procedure 2G on these materials with no problems. But from the little info that I could find on the web, it suggests that I use a argon/hydrogen mix for heavy base metal. I have no idea, as I have never used it before.The 250 amp torch Im using now is water cooled.........they are just junk. I keep blowing them at least twice a week. (all the welders that work here do) But Im thinking that 1/8" tungsten should help out alot. Thanks for the concurrence..........Anyone else have any suggestions?

  10. #10
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    May 2012
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    Quote Originally Posted by kevin View Post
    This is why i like this forum, top notch questions, from educated people with interesting work.
    Thanks Kevin..............

    I make GREAT money and LOVE my job most of the time. But the simple fact is, im NOT a weld engineer and im not making a weld engineer's salary. (wish I was) Im just a "highly" qualified welder thats had this responsibility "pushed" on me. It seems that im taking on the responsibilities of the engineers to make this process work. But telling that to management is like negotiating with a stone wall. I think I know how to get this done............I just need some comfirmation from someone who has had expierence with CuNi before I proceed to waste any more time on these HUGE test plates.

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