soldering stainless steel

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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?

Re: soldering stainless steel


"Patrick"  wrote...
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You have the correct solder/flux (Stay-Brite). Do not use the paste flux.
I'd suggest that you clean the surfaces with Bar Keepers Friend and
then wash and dry them well. Warm the area with the propane
torch and then apply the liquid flux.  Do not apply the heat directly
to the soldering area. Allow the heat to conduct to the joint. This
will prevent it from being overheated. When you apply the solder
it should melt on/in the joint _not_ in the flame. If it does not
easily coat the metal, apply more flux and continue.

You should be able to get an excellent result. I use that solder
flux combination all the time.



Re: soldering stainless steel


PJ wrote:
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Why not?


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I believe, as you indicate, that I am probably overheating the work.
Then I guess the chemicals in the flux get used up and the protective
oxides form again on the surface.

I'm thinking that an application of paste is going to have a lot more
oxide-removing chemicals than the thin film of liquid flux, so that it
will keep working even if the work stays hot a long time.  Also wouldn't
the paste help by keeping the air away?

Re: soldering stainless steel



"Patrick" wrote...
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Try it.. Then let us know how it works. Be careful with the torch. The
paste flux will burn easily.



Re: soldering stainless steel


Soldering is more an 'art' than a 'science'. Perhaps viewing the below
reference YouTube video will be helpful ->




Re: soldering stainless steel


Billy wrote:
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Thanks, that video really hits the spot.  I am trying to do once almost
exactly what that guy seems to have done dozens of times.

What kind of torch is he using?

So I need only solder on one side of the bulkhead, it seems.

Re: soldering stainless steel



: Billy wrote:
: > Soldering is more an 'art' than a 'science'. Perhaps viewing the
below
: > reference YouTube video will be helpful ->
: >
: > :
:
: Thanks, that video really hits the spot.  I am trying to do once
almost
: exactly what that guy seems to have done dozens of times.
:
: What kind of torch is he using?
:
: So I need only solder on one side of the bulkhead, it seems.

@ Patrick,

The person in the referenced YouTube video is using an Oxy/Acetylene
torch - he explains how to adjust the Oxygen to obtain a Neutral Flame.


Billy



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