Copper thickness & TIG

[Jedd Haas]

I have been fabricating a few test components out of copper. I'm curious about what everyone recommends as the minimum thickness for copper fabrication. My test pieces are roofing copper, 24 gauge, which is .02" and it gets thinner when stretched. Wall thickness for 3/4" type L copper pipe is .07", so I'm thinking of going to 14 gauge sheet copper, which is .062".

With these thicknesses in mind, what minimum current rating and duty cycle would be recommended for TIG fusion welding the copper? Any suggestions on filler rod thickness and details for brand/type?

[Chip Tate]

I have been fabricating a few test components out of copper. I'm curious about what everyone recommends as the minimum thickness for copper fabrication. My test pieces are roofing copper, 24 gauge, which is .02" and it gets thinner when stretched. Wall thickness for 3/4" type L copper pipe is .07", so I'm thinking of going to 14 gauge sheet copper, which is .062".

With these thicknesses in mind, what minimum current rating and duty cycle would be recommended for TIG fusion welding the copper? Any suggestions on filler rod thickness and details for brand/type?

Roofing copper it normally not the best choice since it's C11000 (electrolytic tough pitch) which does not weld very well. C12000 (phosphorus deoxidized copper) is the best choice for TIG welding, but C10200 (oxygen free copper) works fairly well too. Thickness depends on what you're making, but I normally use 1/8"- 1/4" thickness for most production distillery pieces. Like welding titanium, you want a surgical level of cleanliness in the weld zone before you start. High temp flux is a good idea too (Harris black brazing flux is ideal). Amperage depends as much on the size of the piece as the thickness. I also use pulsing a lot to help control penetration on sheet metal, so the following amperages are peak values (50% of time at max A, 45-55% of max amps at minimum amps). Typically, 180-250 amps will do it for 1/8" thick. Most of the 1/4" thick I've welded was on large pieces, so you may need less, but 340-450 amps is typical. Get a good preheat too. A bevel and gap (~1/2 the width of your rod) is also a good idea for good penetration on the thicker stuff. You'll often want to weld both sides to penetrate thoroughly. Straight argon is fine, but a mix with helium will give you a hotter arc. 50% Ar, 40% He, 10% CO2 is ideal, but is less convenient for quick tank swaps at you local shop. Hope this helps.

CT

[Jedd Haas]

Thanks Chip, great details. Do you think this something like this unit, http://products.esabna.com/EN/home/arc_welding_equipment/arc_eq_category_page/q/display_id.id43628b95ba83a2.84035793/category_id.1743 would cut it for 1/8" or thinner?

[Chasin' Tales]

Thanks Chip, great details. Do you think this something like this unit, http://products.esabna.com/EN/home/arc_welding_equipment/arc_eq_category_page/q/display_id.id43628b95ba83a2.84035793/category_id.1743 would cut it for 1/8" or thinner?

I have this unit and used it sucessfully on 1/8" copper: http://www.millerwelds.com/products/tig/product.php?model=M00152

It looks similar to the ESAB unit you listed.

I have also found that these brazing rods make great TIG filler rods and flow wonderfully. I haven't used them on a still, so not sure if the 7% phosphorus would be an issue or not. : http://www.weldfabulous.com/Filler-Metals/SolderFlux/Phos-Copper-0/Weldcote-0-332-x-20-36-Phos-p8876381.html

Best of luck!