by OzDistilling » Fri Nov 27, 2020 9:45 pm
TIG Brazing has almost completely replaced all other forms of welding, soldering and brazing for commercial still builders. You can do (with the correct setup and skills, as you have) braze almost anything to anything. Most importantly it removes the age old problem with copper to copper welding and contamination.
But.. consider Ferrous to Non-Ferrous brazing challenges;
[list]As the non ferrous metals (copper) anneal with the heat, the ferrous (stainless) harden. Thermal stress cracking is common in the stainless parts. Consider heat Normalising the weld
Bonding of dissimilar metals often leads to all sorts of galvanic corrosion problems, any assembly with CU/Stainless brazing joints should employ a sacrificial anode, especially of they are pipe work transferring water
Chemical cleaning of the heat spoils (marks) is hard. As one chemical cleans the stainless it corrodes the copper, and vice versa. Mechanical polishing is the best.
With your example (and a superb braze I would say) consider the spiggot to be the same Stainless grade as the column, and then use a mechanical (compression fitting) to convert from Stainless to copper?
Where this technique really shines is brazing the large still pot dome heads, swan necks and copper pipework to stronger stainless flanges, couplings and fittings. Traditionally these would be brass, or bronze.
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Could you describe you setup (gas type and flow, electrode type, current, strike settings)? Did you purge?
Thanks for sharing