Anyone here with experience of TIG welding copper-nickel alloys?
I'm planning to make a miniature 1:8 scale locomotive boiler of Cu-Ni, with copper tubes, and TIG (GTAW) weld it all together.
(More about my trains on http://www.saunalahti.fi/animato/steam )
I have ordered a 160 Amp pulsed DC TIG inverter with HF arc start, and a bottle of pure argon gas, but am a little unsure how to best protect the reverse side of the weld - shielding gas not being practical in a hobby environment (too expensive to have another gas type & tank - almost as expensive as the welder itself).
Has anybody used some special adhesive tape, or brush-on stuff for this purpose? I've heard rumors of such, but have no specific info.
I already made a test welding 3/8" copper staybolts to the 1/8" CuNi sheet, and when trying to pull out a bolt (by tightening a nut), the staybolt sheared at the thread, not at the weld, so the welding works well there.
But it's the long seams in the boiler that I'm concerned about, leaving them unprotected on the back during welding will invite all kinds of problems with the seam - oxidation, porosity, you name it...
Suggestions?
Greetings,
Jan-Eric from Finland
Hello Jan-Eric, there is a flux that is mixed with rubbing alcohol, brushed on the backside of the weld joint and used for backing certain stainless welds, it is called Solar Flux. I'm not sure if this would work for this particular purpose, when I checked the label for application and use it only list stainless steel. Since you are in the experimentation mode you might give this a try and see what your results end up being. Best of luck and Regards, aevald
Jan Eric
What Alloy of Cu-Ni are you wanting to weld?
90/10 or 70/30.
I have found that you can successfully weld the 90/10 (90% Cu; 10% Ni) alloy using the following consumable ER CuNi with the same alloy split 90/10.
I have successfully qualified procedures using the following:
PreHeat : 93°C Min.
Interpass: 176 °Max.
Sheilding gas: Industrial grade pure Argon (15 - 20 L/min)
Purging: Same gas as sheilding.
The purging is essential to solve the oxidation problem of the "root" area.
I hope this is of help to you.
Go to the welding supplyer and order a "Splitter" for innert gasses . You'll need another flow meter and maybe a plug to block off any end of the splitter that you aren't useing . The splitters come in three-way and six-way . We use these at school so that we save money on bottle rental . We also use this set up for running a back purge and trailing sheild . Mine was $35 . I tried to use a "Y" connecter off of the same flow meter that the torch was hooked to but I couldn't get it to work right .
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