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Post by Garry Coles on Sept 13, 2014 15:46:46 GMT
Hi
I have just been looking up brazing rods and what's in them. I see that Silver-flo 55 contains 55% silver, 2% tin, 22% zinc and 21% copper.
Now I know that you must not use brass bushes on boilers because of the zinc content, So why is it okay to use a brazing rod with zinc in it to braze in bronze bushes.
Also can some tell me please the best flux to use with Comsol hi melt solder.
Thanks
Garry
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Post by suctionhose on Sept 14, 2014 1:54:42 GMT
Somehow the addition of tin changes the game. We talked about this at the club too.
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waggy
Statesman
Posts: 744
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Post by waggy on Sept 14, 2014 16:29:47 GMT
Garry,
The only flux I've had success with for Comsol is Baker's Fluid. I cut the solder into approx. 1/32" slices and place them on the joint, refluxing after placement. Doing so holds the solder in place as the joint is heated (most of the time anyway!)
Good luck,
Waggy.
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Post by cupalloys on Sept 17, 2014 8:12:24 GMT
The presence of silver (a relatively inert metal) in the alloy offers a higher level of corrosion resistance preventing de-zincification and porosity in the joint. One of the main justifications for using such an expensive filler metal is the corrosion resistance of the joint.
The presence of the tin is to reduce the melting temperature and increase the fluidity of cadmium free solders. All the common cadmium free alloys contain tin.
regards
Keith
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Post by suctionhose on Sept 17, 2014 12:23:34 GMT
Keith,
You're knowledge of these products is far superior to mine.
My response re "addition of tin" was based on Tobin Bronze which the Australian Code allows for brazed joints on copper eg barrel to throatplate if you don't want to flange and other internal structural parts that are never accessible once the boiler is closed up.
Tobin Bronze is essentially Brass - copper + zinc - with a splash of Tin (1%). Apparently, where Brass will dezincify the addition of 1% Tin stops that from happening.
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