Are new model copper boilers soft?

I have a short length of approx 1/8" wall thickness copper tube 6" diameter by 12" long and have earmarked it for an ambitious attempt (for me) boiler project. My first attempt though will be with something a bit smaller just to get my eye in, 2.5" x 6" probably.

Something I have often wondered though - due to the amount of heat applied to the copper when silver soldering and the annealing effect thereof, does this leave a newly completed copper boiler soft? If yes, will it work harden after use / pressurisation?

Rik

a) Yes, completely annealed.

b) No, to work-harden, the material must be mechanically deformed. This might happen very locally on a micro scale when pressurised but not to a significant degree.

In my work old vehicles, copper pipework often needs to be renewed, and new or adjusted bends usually require annealing. But old pipe always seems to be hard, so I suggest that this is die to age and vibration, not just deformation.

If you need an annealed surface to be harder, you might try planishing - find a steel former to match (+/-) the inner surface, and a properly smooth hammer, and cover the surface with even taps all over. Old hand-made silver will give you the idea (but modern pseudo-planishing won't).

Cheers, Tim

Yes, soft on completion (hence the advice when testing to increase pressure gradually)

Yes, it will harden in service, not strictly work harden as it won't be deformed beyond the yield (hopefully!) but it will harden due to stress / temperature cycles.

Paul.

Thanks Paul - just the info I was looking for. It's as I suspected.

Rik

Edited By Rik Shaw on 10/08/2020 18:16:57