Brazing question

Submitted: Wednesday, Aug 02, 2017 at 15:44
ThreadID: 135327 Views:1760 Replies:5 FollowUps:1
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I hope someone can help me. I am making a water-heated towel rail out of 20mm copper fittings and want to attach some heavy brackets to keep it on the wall. Brass bar 6mm x 75mm is the preferred choice to make the bracket and it would be attached to the copper tube by fusing it along the 75 x 6 edge to the bar, along its length. .
The options to join them are are silver solder or brazing. It is going into a little off road caravan and I am wondering if anyone can tell me which is the strongest way to attach - silver solder or brazing?
Many thanks
Keith
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Reply By: bobsabobsa - Wednesday, Aug 02, 2017 at 17:33

Wednesday, Aug 02, 2017 at 17:33
I have always used silver solder in the fridgy trade 15% rods and you will need a number 2 flux ,make sure you clean the flux off well . using bronze it can be a bit brittle
will work but you have to get it much much hotter to flow
bob
AnswerID: 612826

Follow Up By: Shaker - Wednesday, Aug 02, 2017 at 17:42

Wednesday, Aug 02, 2017 at 17:42
He could also use silicone bronze, either gas or TIG with filler rods, or MIG with silicone bronze wire.
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Reply By: Member - Rob S (NSW) - Wednesday, Aug 02, 2017 at 17:49

Wednesday, Aug 02, 2017 at 17:49
Hi Brazing will be stronger but probably no where as neat as silver solder.
If i was doing something like that i would use silver solder.
And use the correct silver solder, there are many different types ,basically the silver content changes,but just use a general purpose silver solder.

Plus the bracket design to the rail with a good surface area for solder.
75 x6mm bar will certainly strong enough, 3mm would be adequate?

You could use soft solder, if you drilled a 20mm hole through the 75 mm plate to put the tube through, and solder, look at car radiators they are soft soldered and go for years of service.

All depends on your fabrication and soldering skills!
Rob
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AnswerID: 612827

Reply By: Ron N - Thursday, Aug 03, 2017 at 11:21

Thursday, Aug 03, 2017 at 11:21
I found 45% silver solder is great to work with (provided you clean the surfaces properly and use the right flux) and gives a high-strength weld.

Used this rod to solder up high pressure (2000-3000psi) hydraulic fittings on construction equipment for decades, and never had a failure.
In addition to pressure, the soldered hydraulic fittings have to cope with serious vibration, particularly on bulldozers.

Good soldering results always require spotlessly-clean surfaces to be joined, no matter what the type of solder used.
Lastly, close-fitting tolerances of the components to be joined, also assists in final strength.

Cheers, Ron.
AnswerID: 612832

Reply By: Michael ( Moss Vale NSW) - Thursday, Aug 03, 2017 at 18:06

Thursday, Aug 03, 2017 at 18:06
Gday Keith, Ron is spot on, 45 % silver solder produces strong neat joints that can be made with lower process temperatures. $15 to $20 will get you a stick of 2.0 mm x1000 (Blue tip) . Regards, Michael
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AnswerID: 612837

Reply By: Keith B2 - Saturday, Aug 05, 2017 at 06:54

Saturday, Aug 05, 2017 at 06:54
Thanks everyone for your advice. I didn't realise that a tight fit was so important, so I think I'll get the 6x75 surface machined to the pipe radius and get a pro to silver solder these joints.
AnswerID: 612867

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