Brass/Bronze vs. 38% Silver?

[tnort...@gmail.com]

So I am in the process of building frame #3 a touring frame. Using a lugged BB and I  am fillet brazing the balance. After lots of practice fillet brazing  samples I  was quite please with my progress.

As I ha e time to try some different things I ordered some 38% silver from Gasflux with my recent Flux order. I heard it is a good replacement for Fillet Pro. I mocked up a section of 14mm tube,to simulate a SS on a section of ST and did a fillet with 38%. After cooling I really tried to rip it off!  But no luck!😀

I notice that I was able to get a smoother fillet with 38%. Is this typical? 

So thoughts on where to use 38%? And yes I am aware of the $ difference. 

Thanks!

Tom

NE Ohio 

[m-gineering]

Peeling strenght of silver is less than brass, and it is possible to get
fractures in the solidifiying fillet because it cools so slow.
So I started out with silver fillets and have progressed to brass.

To me the difference is if you crash the frame, the bronze filleted one
will be bent, the silver one might have come apart. Both will be toast,
but the bronze one doesn't need explaning.

I keep the silver for stainless

--
Marten Gerritsen
Kiel Windeweer
Netherlands

[AJ XOXO]

56% silver is very thin and runny.  That makes it good for places you can deal with it being so runny.  Places where you have a really tight fit like lugs.

45% silver is a little less runny, so it’s good for lugs too but it’s not as runny as 56% silver.

38% silver is even less runny than 45% silver, so it’s better than 45% silver in places where there are larger gaps.  I’ve heard that Ceewsy sells something very similar to 38% in the UK, and that some European builders have used it successfully on fillet-brazed frames.

[Alex Meade]

Some data on various brazing alloys in the high 30% range:

The alloy Ceeway sells, mentioned by AJ XOXO, is Sif-39, with the following nominal composition:

Ag 38%

Cu 32%

Zn 28%

Sn 2%

I think "Sif" is is a UK or EU designation - I really don't know.  And I don't know the manufacturing tolerances on the composition of Sif-39.

In the US, there are two alloys that are close to this. BAg-34 could be an exact match to Sif-39, based on where the composition lies in the allowable tolerance range.   The nominal of BAg-34 is identical to the nominal of Sif39.  However, the allowable manufacturing tolerances, at least based on this website for BAg-34 are:

Ag 37-39

Cu 31-33

Zn 26-30

Sn 1.5-2.5

There's another alloy that's close, and I believe used for filleting stainless steel, and it's BAg-28, with nominal composition in the midrange of these tolerances, these numbers being from the aforementioned website:

Ag 39-41

Cu 29-31

Zn 26-30

Sn 1.5-2.5

If you look at, for example, the Aufhauser website, you'll see the percentages for these alloys listed as being the midpoint of the ranges above. Aufhauser doesn't show their tolerance range, though I'm sure they'd tell us if asked.

My own analytical results suggest the manufacturers use the tolerance range, so it's entirely possible that batches of BAg-28 and BAg-34 could be exactly the same.  My analytical results suggest they skew toward the low end of the range for the expensive elements, silver and copper, so on the other hand I'm guessing you won't find a sample of BAg-34 with 39% silver, but you might find a sample of BAg-28 with 39%.

I've never tried BAg-28 and BAg-34 side by side, so I can't offer any real world comparison.  All of this is just published data plus some analytical work I had done once.  I'm hoping someone else knows more about the real-world tolerances in composition of silver brazing alloys than I.

I hope this information is useful to someone!

Alex

www.alexmeadetools.com

[Dan Chambers]

" I think "Sif" is is a UK or EU designation " 

SIF is the UK-based manufacturer's brand name: (https://www.weldability-sif.com/products/?Search=Brazing). They used to be an independent company, but have been swallowed up by Weldability, a more general welding supply company. The brazing side seems to be going a little quiet recently, but they do still have a couple of alloys specifically for TIG-brazing, which can be useful.

In the UK, we also have access to the far more extensive Metabraze range (https://www.meta-braze.com/products/silver-brazing-alloys/silver-brazing-alloys#more-info-1465117-link). For anything non-capilliary I use Metabraze 130, which is 30%Ag, and find that it handles similarly to SIF #39, but at 1/2 the cost and only slightly higher temps (SIF #39 650-728°C, MB 130 665-755°C).

These ranges (and most standard European brazing alloys) are made to European Norm EN1044, so +/-1% on the Ag content. Full pdf of EN1044 attached. It's from 1999, but I doubt anything has changed (and I'm not paying $150-300 to find out ;-).

The naming system globally is a nightmare, when even ISO and DIN each have had two different naming schemes: 

All the best,
Dan Chambers