Silv-solder SST pipe threads

Tue, 31 Aug 2021 15:35:32 GMT

go to see Welding Machine for Silv-solder SST pipe threads

I failed to get the silver solder into the threads. In this thread I was looking at the issue of whether I needed to solution sak my SST parts (pictures of the parts are in that thread)  http://weldingweb.com/vbb/showthread.php?t=44412Half inch NPT  throughout 304 SST  plumbing  fittingsI shined 'em up nice and pretty and then did some pressure testing.   Out of ten. six leaked like sprinklers.So I took 'em apart.  I wire brushed 'em with  a SST  rotary brush, I soaked 'em in Muriatic (to get any burnt on crap off)  then passivated 'em in Citric acid then tumbled 'em in abrasive micro beads.Taking them apart I learned that the flux on the Harris rods failed to penetrate the threads.   That mean there  was no flow to the threads. I also realized I was using way far too much heat. So this time I pre-tinned the  threads.  I only  tinned the male threads, but I used a high temp brush on silver brazing flux  on everything where I wanted the braze to flow. Then I watched my heat with greater care.  when pressure tested: The parts I re-brazed did not leak. BUT~!!!!!!!!! I think I ought to heat up and  take apart all the welded up assemblies that passed the  first pressure test, because I can't know whether the putative seal is due to brazing flux or the brazing metal.  What do you think?
Reply:I was interested in responses to this thread, too.  Is it common practice to braze threaded fitting?Aren't there some sealants that would work well?
Reply:I agree you should rebraze the first set since you found that brazing process unreliable.Then I think you should seriously consider investing in TIG welder if you are going to contimue making brew system components for yourself and others.  These fittings could quickly and easily be seal welded with TIG.  I get that these are made for home brewers to make their own kettle from a keg with no welding on their part, but if you're making your own kettle, again better to just TIG weld a nipple to the kettle rather than having the threads and O-ring arrangement that would need to be dissasembled and cleaned.
Reply:Originally Posted by tapwelderIs it common practice to braze threaded fitting?
Reply:I took 'em apart. What a crappy job~!! There was so bloody little silver braze where it needed to be.I'm going to use fluxless wire and  have got two kinds of flux: High temp black and conventional  white silver brazing flux. Oddly the black  flux is not black it's a white paste. Why do they call it black?
Reply:Here.http://weldingweb.com/vbb/showthread.php?t=44169You will need to get the flux that puts up with this kind of heat..White is better.....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by zapsterHere.http://weldingweb.com/vbb/showthread.php?t=44169You will need to get the flux that puts up with this kind of heat..White is better.....zap!
Reply:[QUOTE=Raul;420042]I failed to get the silver solder into the threads. brazing  relies on capillary action to get metal into a gap. threaded joints    relies on a metaltometal fit, hence no gap. brazing a threaded fitting is inherently at odds with itself. you will get the braze metal into the gap only sodeep, when the gap gets smaller than the minimal gap that will allow capillary action to work, no flow, no metal and a  void . how much pressure does this gotta hold?
Replyon't understand why you are doing this job that way. Locktite or one of many sealers would provide excellent sealing properties. Why Silver solder, if you don't mind me asking? Enquiring minds got to know!
Reply:I was taught that NPT pipe threads need teflon tape or pipe thread sealant to seal properly. (steel, stainless steel, cast iron etc.)The only exception was for brass which I was taught was soft enough to deform and seal by itself when threaded together and tightened securely. (teflon tape or pipe thread sealant couldn't hurt here either)I am also curious why you feel you need to silver solder or braze the NPT joints."The reason we are here is that we are not all there"SA 200Idealarc TM 300 300MM 200MM 25130a SpoolgunPrecision Tig 375Invertec V350 ProSC-32 CS 12 Wire FeederOxweld/Purox O/AArcAirHypertherm Powermax 85LN25
Reply:Been a while since I was on this thread.Why silver solder the threads? Because  using a female coupling an o ring and a close coupling with a hex nut is a workable solution to having a pipe threaded bulkhead fitting and needing the thing to be made from SST without spending a hundred dollars per fitting. .  Threads mating (especially pipe threads(  never achieve a perfect fit so there is always a gap for things like solder.  Anyway it all came together in the end. And now I have a welder to do this right if I gotta make more
Reply:I use black flux when silver brazing (higher temperature tolerance).  Also, 50N has the strongest capillary action.  I typically have no problem getting it to penetrate 100%.Here is an example of a flange I made using 3/8ths plate and a 1/2 inch pipe coupling.  All brazing was done from the reverse side this shows the capillary action of 50N alloy.