I am modifying a water distiller by adding a tube nipple to the side of the boiler, to use for filling and draining the boiler.
I need some advice about choosing a combination of solder, flux, and torch.
The boiler is 22 ga. (0.031") 304 stainless, and I want to solder a two-inch length of 3/8" 304 tube (wall thickness 0.020") into a 3/8" hole I will drill in the boiler.
I got some 22 ga. 304 sheet to practice on. I am able to drill 3/8" holes in the practice sheet, and I can cut lengths of tube.
However the result was abysmal when I tried to solder the tube in the hole.
I hope to use my propane torch, and I don't see why I should need anything hotter. The joint is not going to suffer much mechanical stress, so I expect a soldered joint to be more than strong enough. The temperature will be up to the boiling point and down to say 55 degF, but again I wouldn't expect that to be very stressful.
I did not use a wire brush to clean the tube for my first (failed) attempts. Should I have?
I used the NSF-approved Radnor Stay-Brite Silver solder Kit # 54001776 by Harris. That is a combo of 3/64" solder and a 1/2 oz. bottle of Stay-Clean Flux (liquid).
The first thing I noticed is that the flux did not want to stick to anything---it would not easily soak into the flux brush, and it beaded up on the metal. I guess I was able to get the metal wet to some degree and I did get solder to stick in some places.
I desoldered the joint and tried again with Oatey Sta-Flo 95/5 1/8" solder, and the result was at least as bad.
There is a paste version of the Stay-Clean flux. Do you think maybe I should be using that instead?
I have some experience soldering electronics and copper tube. Stainless seems to be about a hundred times more difficult. What am I doing wrong?