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Welding copper

Posted by scarlettt (My Page) on
Sat, Apr 22, 06 at 17:25

Hey,
I'm planning to use Oxyacetylene to weld copper sheet, and i was wondering of anyone could give me advice on this(or possibly just tell me it's a stupid idea).

My main source of materials will be old hot water tanks and plumbing scrap, i dont know if this is too thin to weld, or too dificult for a begginer?
I have been using an oxyacetylene torch for a while now, to create texure in my sculpture components by burning and melting away parts, but i havnt been able to do any real welding work yet due to problems getting permission to use stuff at college, but i should be able to start soon. One problem though: i only have four weeks to finish it, which doesn't leave me much practice time!

So....can it be done? Any advice would be great

thanks

Scarlett


Follow-Up Postings:

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RE: Welding copper

"...old hot water tanks..."

They better be very old. Steel tanks with a glass (AKA porcelain) lining have been the 'standard' for at least 50 years.
Copper is relatively hard to weld since it conducts heat very well.
Finding rods is also a PITA.


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RE: Welding copper

Why not solder it?


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RE: Welding copper

Hmm..Ive had no dificulty getting hold of copper ones, the one in my house is copper and that was only installed 5 years ago. Maybe we're just behind in England?
I will solder it if i have to, but i would rather not because 1- soldered joins will remelt and fall apart if a nearby area of metal is heated, while surely welded ones have the same srength as the rest of the piece?
and
2-because solder is a contrasting colour to copper i think welding will look far better.
If anyone knows of a readily availible solder which is not lead coloured, it would be a great help, but i'm not aware if anything like that existing.
One option i was considering is brazing, but i havnt tried it before, so i dont know what it's like to use compared to soft or hard soldering.


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RE: Welding copper

Use brazing rod and braze the joints. Almost the same as solder but the rods melt at 800F and higher.
An 85% Cu, 15% Ag, 5% P rod looks very much like copper when cooled.


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RE: Welding copper

5% Phosphorus?


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RE: Welding copper

The phosphorous acts as flux. No other flux is needed with these rods, called 'self fluxing'. Clean the surfaces, heat, and braze.
They are relatively common in refrigeration work with TXVs that would be damagede by the flux residue reamaining inside the pipes.


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RE: Welding copper

Refrigeration brazing rods are commonly made in 15%, 6% and 0% silver. The higher the silver content the lower the melting point, conversely the lower the silver content the stronger the material and also the cheaper the rod.

I typically pay $15/lb for 15%AG while zero percent Silphoz rod is about $6/lb.

The zero percent is a bit more difficult to work with and will require a bit of additional practice to get the feel of it. Back in the mid 80's when silver went to nearly $75/oz the zero percent rod was the norm in refrigeration work because 15% rod was selling for $48/lb.


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