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I'm working on a diy project which requires a tiny L bracket attached to a tinbox. I have tried several adhesive techniques such as super glue and metal epoxy but the smooth surface of the tin box does not permit proper adhesion. I'm thinking of either using welding or soldering to attach these two pieces together. What would you guys suggest for a cost effective yet quality outcome?

Correction: the L bracket is nickel plated steel whereas the tin box is just steel with tin plating.

Tried apply some heat but it caused massive discolouration to the tin box surface (heat stains). blackened tin box

Will soldering/ welding require so much heat as to result in such discolouration?

Thanks

Ler Ws
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  • Silver solder works well with stainless. This requires oxygen/ acetylene gas mix. If you can find one of the small pre filled torch kits you may have a small enough flame at a high enough temp for it to work. butane and mapp gas don't get hot enough in my experience. – Ed Beal Aug 18 '16 at 12:54
  • What about using an electric arc? I think it is pretty hard to obtain the gases from where I come from. – Ler Ws Aug 18 '16 at 13:07
  • A spot welder may be the best choice for a small device. 2 electrodes pinch the metal together then push the power button for a second and the current welds the 2 together. An auto repair shop or machine shop may have one and will do it for a couple of bucks. This is how they assemble battery packs holds quite well. Arc welding even wire welders are hard to make tiny welds. A shop that has a TIG may also do it this is a form of welding that can be very small. – Ed Beal Aug 18 '16 at 13:17
  • http://sg.element14.com/ettinger/14-86-313/mounting-brackets-m3-10x11x7-2/dp/1466883 these are the mounting brackets I wish to weld/ solder. Will the screw holes on the bracket affect the spot welding process? – Ler Ws Aug 18 '16 at 13:29
  • I looked for micro oxygen/ acetylene. this looks like an old version of one I had it worked quite well. – Ed Beal Aug 18 '16 at 13:46
  • Hmm so far I've only managed to find butane gas micro torches. Will a butane torch and solder like this http://www.monotaro.sg/g/00186505/ work? – Ler Ws Aug 18 '16 at 13:57
  • Have you considered something like pop rivets as an alternative? – BrownRedHawk Aug 18 '16 at 15:18
  • I don't think butane will get hot enough Mapp gas unless mixed with oxygen dosen't get hot enough – Ed Beal Aug 18 '16 at 18:27
  • Are you sure these are stainless steel? The specs for the link you've provided show they are nickel plated. Rarely is there a need to nickel plate stainless steel, while ordinary carbon steel takes well to the plating, providing some rust resistance. If they are magnetic, they are either ordinary steel or very poor quality stainless. If they are not stainless, your options increase and temperature requirements are lowered as well. – fred_dot_u Aug 18 '16 at 19:49
  • Hmm according to the specs it is steel with nickel plating. And the tin box is steel with tin plate coating – Ler Ws Aug 18 '16 at 23:02

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The major trick with soldering stainless steel is using the correct type of flux, which needs to be very aggressive to remove the oxide layer which is what makes stainless steel "stainless."

You will require a flux specifically made for that, and then you will need to carefully clean the flux residue off when you are done soldering. This can be done with ordinary low temperature solders, no particular need to pull out the oxy-acetylene torch. It may also help to wire-brush with the flux in place, so that the brush mechanically abrades the oxide layer and the flux coating keeps it from re-oxidizing.

If that proves to be too weak, silver brazing (commonly misnomered as silver soldering, which is even more confusing in the era of silver-bearing low-temperature lead-free solders) or "normal" bronze brazing is considerably stronger. Bronze will have a color mis-match, which matters to some folks.

95-5 Tin-Antimony is a low-temperature solder that might be a touch stronger than some others, and which works well on stainless IMPE.

Ecnerwal
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  • Correction, the bracket is just steel with nickel plating whereas the tin box is steel with tin plating. – Ler Ws Aug 18 '16 at 23:05
  • As the bracket is steel, not stainless, this answer for brazing is a valid one. Research shows that it is necessary to remove the nickel plating for the best bond. MAPP gas is higher temperature than propane or butane and works well, combined with suitable flux coated welding rods.

    Be sure to get both items up to temperature before applying the rod. The rod will melt and be pulled into the interface between the parts. If the part is too cold, the melted rod will not go as far as it should. If you apply the rod around the perimeter of all four edges, you'll have a strong bond.

     – fred_dot_u Aug 19 '16 at 15:14
  • I wanted to test the tin box's response to heat and thus I used a butane torch and to try and heat up its surface. So far the tin box has been very discoloured as shown in the picture above. Won't this happen if I use MAPP gas as well? – Ler Ws Aug 20 '16 at 05:49