First TIG braze.

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First TIG braze.

Postby LikkerSheWillLoveIt » Wed Sep 30, 2020 8:43 am

So I stopped by my local welding supply shop yesterday, I use them for work, and I got some Silicone Bronze brazing wire.

It’s a bit different to TIG welding but I got it. Damn strong join. This is only some scrap I had laying around. I did 4 joins.

I found that using a lay wire technique, Then doing a second pass with no wire, once everything is hot, I got a fairly smooth braze with no penetration into either of the parent materials. First pass was at 48 amps, second down to 40 amps as everything was hot. It’s strong, I did a destruction test, the copper tore about 8mm from the join. Freshly annealed copper will do that.

If anyone can give me some tips, I’ll happily take any and all criticism.
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LikkerSheWillLoveIt
 
Posts: 189
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Location: Tweed Heads. Northern NSW
equipment: Home made 50L keg boiler. PID controlled. Stainless Column dual valved reflux still.

Re: First TIG braze.

Postby 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.
/list]

Could you describe you setup (gas type and flow, electrode type, current, strike settings)? Did you purge?

Thanks for sharing
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Re: First TIG braze.

Postby Dude » Sun Dec 06, 2020 12:22 pm

I have decided to go the same route for my build but I have been having a heap of trouble with the "weld" area especially the copper oxidizing and then the braze wont flow to the joint. Via trial and error I have discovered that I have been running the amps too low, I was trying at 40A and have just raised it to 60A and got a much better looking job and the material flowed much better. The down side is that it is easy to blow thru from overheating so speed from the get go is important.

Hope this helps someone.
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Re: First TIG braze.

Postby LikkerSheWillLoveIt » Sun Dec 06, 2020 1:38 pm

I’ve got a 320amp water cooled unimig.

I was running 53amps, 2% Thoriated Tungsten, 2.4mm sharpened to a very fine point. Hf start and downslope set to about 1.5 seconds
Gas flow was set at 14-15 L/min, no purge, with 3 seconds of pre and post flow gas running a number 12 Pyrex cup with twin diffusers

Cleaned everything with my manual polisher then cleaned with isopropyl alcohol immediately before welding.

I laid the wire on the join, not something I do very often, silicone bronze rod 1.6mm I think

I know all about galvanic corrosion, oxidization, I’m not overly concerned on a still that is kept really really clean. Couldn’t be bothered polishing it yet, I will one day.

On the topic of heat stress causing cracks in the stainless, not likely on 2mm wall thickness stainless with only 53 amps thrown at it, also considering it is a static join with no movement or vibration, I’m pretty sure that join will be good for the next decade or so.

It was a very interesting new technique to learn.
LikkerSheWillLoveIt
 
Posts: 189
Joined: Fri Sep 25, 2020 11:16 am
Location: Tweed Heads. Northern NSW
equipment: Home made 50L keg boiler. PID controlled. Stainless Column dual valved reflux still.


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