bike frames welded vs soldered question.

[Sen]

So you got welded frames, and hard soldered frames, but now my question is, do soldered frames give problems when you cut em and weld em back together?
Here at school, I was planning on really chopping my frame, but the "workshop manager" said that this is not a good idea because the soldered connections might come loose and weaken the frame. For this build I solved the problem by just inverting the frame, but it's good to know this for future projects.

 

[yoothgeye]

I guess soldered is a way some people say brazing.

I've welded on frames that were originally brazed and I've seen people on this site braze on bikes that have been brazed. I don't see it weakening anything as long as you check your work afterwords.

Maybe what he was thinking was that the heat from welding close to a brazed joint could loosen that joint, but you'd have to hold A LOT of heat near a brazed joint to make it come apart, and if it did, you'd know it and you could weld it back.

 

[724wd]

could be i don't remember exactly, but i seem to recall that if you're going to weld (MiG) something that has been brazed in the past, you need to remove ALL the bronze or bad juju ensues. wouldn't effect something that was close, but if you hit the bronze with the MiG wire, it'd pop something fierce?

 

[frameteam2003]

Some Hi-End road bikes are silver solidered--and yes heating them would be a bad idea.
brazed frames like old schwinns you should not have a problem with--again some hi-end road frames the tubing should not be heated.low end bikes like we norminally use--not a problem

 

[Dethklok]

brazing and soldering are not the same although very similar processes.

If you are welding, it does create heat that is higher than silver solder or brazing rods melting points so it can cause either imperfections (weaknesses) or re-flow (melt) them again. This is not always the case, as said before recheck the previous bonds to make sure theyre ok, also moving in small sections and allowing to metal to recool after small portions so the heat doesnt spread can help or using something to soak up and draw away the exces heat.