# Silicon Bronze for Torch Brazing



## BentChainring (Jul 10, 2008)

Howdy all,

Does anyone use Silicon Bronze (AWS A5.7 ERCuSil-A) rod for torch brazing? I ran a few fillets the other day and it flowed REALLY well, even without flux (didnt have any on hand). Normally, I would just compare it with Brass brazing rod, but I dont have any of that either, so I cant look up what my comparable rod would be.

Thanks.


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## Walt (Jan 23, 2004)

*I'm not an expert, but...*

I have messed with Si-Bronze with my TIG torch, since it doesn't require any flux. Fun stuff - you can stick stuff together without melting the parent metal, without a sticky mess.

BUT, I'm told by folks who know a lot more than me that it's not safe for fillets because it tends to have cracking problems when it cools. I think it's sometimes used to join stainless equipment for brewing, and for sheet metal repairs on classic cars, but those are the only applications I know about.

-Walt



BentChainring said:


> Howdy all,
> 
> Does anyone use Silicon Bronze (AWS A5.7 ERCuSil-A) rod for torch brazing? I ran a few fillets the other day and it flowed REALLY well, even without flux (didnt have any on hand). Normally, I would just compare it with Brass brazing rod, but I dont have any of that either, so I cant look up what my comparable rod would be.
> 
> Thanks.


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## BentChainring (Jul 10, 2008)

Walt said:


> I have messed with Si-Bronze with my TIG torch, since it doesn't require any flux. Fun stuff - you can stick stuff together without melting the parent metal, without a sticky mess.
> 
> BUT, I'm told by folks who know a lot more than me that it's not safe for fillets because it tends to have cracking problems when it cools. I think it's sometimes used to join stainless equipment for brewing, and for sheet metal repairs on classic cars, but those are the only applications I know about.
> 
> -Walt


Thanks...

I _Should_ know more about this... I am in a welding engineering program, with much focus on brazing and a welding/materials engineer... but using alloys for things not in handbooks frequently just requires doing it, and finding out how it worked.

I am thinking about somethign Bicycle related for my capstone Masters project (pseudo-thesis)... just not sure what yet.

Also... I have a distaste for TIG brazing. We do TONS of it at work, frequently with Gold based alloys that run in the $1000/rod price range for dissimilar metal joining. Ive performed tig brazes many times, but just dont like the 'feel'... hard to describe.


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## j-ro (Feb 21, 2009)

I use quite a bit of silicon-bronze for TIG in my shop for various things, mostly in a 'hot-glue 'sense for little jigs and fixtures. It does flow really really well and it is easy to control the amount of penetration that you wish it to achieve. As mentioned above , it works well with sheet metal, I use it on galvanized sheet metal with great success due in part to the zinc present in the rod and also on the sheet metal. it flows well and leaves a smooth finish. 
Several times I have tried to use it in framebuilding but cannot convince myself to do it after testing practice joints. I recently wanted to use it on a ST-BB junction weld that was tight due to the bb had chainstay ports on it and it would be hard to get in there. I regularly pierce my BB to allow the seattube full drainage and a much smaller profile tig bead due to the subsequent joint design. This I did in practice and it failed under load completly, cracking at the point of highest stress and shearing the rest once momentum was reached, The only part of the joint that was left was the very start of the weld where fusion was achieved before filler metal was added. 
I have heard people say that It is too soft to use but I think that it is the opposite with it being too brittle. I was introduced to it as "everdur" and it is often used to build things up where they need a durable wear surface., like a press brake punch that was dented,can easily be built up at a fairly low temperture and ground smooth again.

You could totally use it for non structural stuff like braze ons or bridges, etc. but I would not use it for any strutural main tube joint that would be susceptable to shear loads. The one exception I made was on my sons bike where I used it on the chainstays at the bottom bracket end, due again to tight conditions but he is just a little guy and would outgrow the bike before it became and issue if ever.


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## HomeGrownSS (Jan 18, 2006)

i dont even arc-weld, yet i know the answer to this bc its been covered so many times. SEARCH function, people.


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## AZ (Apr 14, 2009)

HomeGrownSS said:


> i dont even arc-weld, yet i know the answer to this bc its been covered so many times. SEARCH function, people.


I searched and it came up exactly one time in the frame forum , I humbly suggest that revisiting this subject is not out of line . :thumbsup:


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## HomeGrownSS (Jan 18, 2006)

AZ.MTNS said:


> I searched and it came up exactly one time in the frame forum , I humbly suggest that revisiting this subject is not out of line . :thumbsup:


my apologies!

since i have been reading this forum, frameforum, and the framebuilders email list for the past few years i have seen this topic come up time and time again, with walt and mbudd chiming in on the topic frequently.
:thumbsup:


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## AZ (Apr 14, 2009)

HomeGrownSS said:


> my apologies!
> 
> since i have been reading this forum, frameforum, and the framebuilders email list for the past few years i have seen this topic come up time and time again, with walt and mbudd chiming in on the topic frequently.
> :thumbsup:


No apologies neccesary . :thumbsup:


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