Good afternoon,
I see with an endoscope camera that the solder joints of Columbus XCR tube connections have been 90% capillarily penetrated all around on the inside after the first soldering pass.
At 10%, I see no yellow solder seam.
I used 30% silver solder for the first soldering pass.
My question is: is it advisable to use liquid 56% solder for the first pass for better capillary penetration, and then 30% for the build-up?
met vr gr
Martin
I don’t know the liquidus temp for the 30% silver filler you have so don’t feel comfy giving a thumb’s up. Generally one wants the “tinning”/capillary filler to have a higher melt point than the follow up fillet filler does.
Was this joint your first brazing attempt? Did you practice with the 30% on a scrap piece first? Do you have the 56% already? If so can you experiment to find out? Do you have access to other silver fillers with different silver %? Do you know the strength of the 30% and how much fillet build up is needed?
Sorry if I have more questions than answers. Andy.
Andrew, thanks for your reply.
As a retiree, I build about one frame a year. So far, about 20, the last 6 XCR.
With Fillet Pro, test joints always ran through completely.
My current solder (Fortargen AF 319 36%) has a liquidus temp of 710°C, a melting range of 630-730°C, and a tensile strength of 360-480 N/mm.
The fillet width is about 8mm and it is concave.
I was actually hoping there would be frame builders with experience with a similar technique.
I have since built up the fillet, using flux on the inside of the downtube and more with the torch on the inside of the head tube; this time it has run through completely.
Martin
Martin (and thanks for using your name here:)) - Your building sounds much like what I’ve done for a few decades, about a frame a year. I just painted my 56th in my new painting space. I did the painting on my first half dozen+ then lost that space and have had over a dozen painters do my “frame a year” paint jobs till recently.
I just looked at Harris’s 56% silver filler (very common here in the US) and see the temp range is lower than the 36% you mention. Ideally one would want the opposite, the fillet filler should have a lower working temp to avoid effecting the tinning/flow filler. But so much of this “what can I do” is skill based. It looks like you’re gaining that skill with the most recent post. Andy.
Hey, i’ve been using silver brazing with 36% silver alloys on Reynolds 853. Only 5 frames in, but have done a fair bit of experimenting too. With an oxy-propane setup i’m building a fairly sizable fillet after a tinning pass. I’m planning an XCR frame in the autumn and for fillet brazing circa 40% silver seems to be the most common alloy used on stainless with appropriate flux. This is what i plan to use.
If I understood correctly that you were loosing silver to the joint? I’ve found this is caused by too much heat either from the torch too hot or just staying over the filter a touch too long. I tend focus on what the silver is doing rather that the flame temperature, as soon as you see it starting to ‘liquify’ come in with rod and allow that to flow and then come off the heat and allow it to solidify. Try not to go back over too much as you can end up causing the silver to flow into the joint.
Hope this is useful and I didn’t misunderstand what u were asking?
Cheers
Dan