Brazing parts – bronze equivalent to solder paste

[migmanParticipant @migman]

Hi All,

My background is electronics but in latter years have been messing about with a mig welder.

Recently I have been trying to join more delicate components that simply won’t tolerate that level of heat and have therefore invested in a modest brazing torch and some cans of MAPP gas. It’s often a fiddly task trying to hold/clamp small parts whilst fluxing and heating and generally trying to keep one’s eyebrows in tact, my question is this, has anyone here used or experimented with bronze paste (if indeed there is such a thing)? My experience of flow soldering makes me wonder if there is an equivalent for brazing – is it possible to add some material (similar to a flow solder paste) in between parts and let the heat work it’s magic, the bronze paste flowing at the prescribed temperature.

I am aware that you can buy bronze powder (ground to a fine mesh size 240-350 Microns), but cannot find it mixed in a compound – could it be mixed with some brazing flux and wiped in between parts?

Any thoughts would be appreciated,

Thanks very much

[JasonBModerator @jasonb]

Silver solder paste is available which can be used for small parts.

Myself I don’t have  aproblem fluxing the work and then feeding in a rod when things are hot enough. You can get thinner section silver solder rod or just beat a larger rod flat and cut into strips with tin snips.

[BazyleParticipant @bazyle]

I think regular bronze dust will have a lot of oxidised surface area so will carry a lot of dross into the joint. Perhaps get a new uncontaminated file, degrease it, and file some bronze as needed under a layer of flux paste so it never sees air. Try it on a test piece and let us know if it works.

[Clive FosterParticipant @clivefoster55965]

Clipping off small pieces of silver solder and placing them in the joint before fluxing and final assembly ready to heat works well. Because silver solder follows the heat it’s relatively easy to get the solder going the right way into the joint rather than coating the hottest part. The small pieces method is more economical with silver solder too. Like many folk who only silver solder occasionally I tend to over do things when simply introducing a rod leaving excess silver solder to be cleaned off.

With small parts the most troublesome thing is the way the flux / water mix can lift and shift things as it bubbles up to working temperature. Using flux powder direct is more predictable but harder to get full coverage.

Once a year (or less) just isn’t enough to keep my skills hot.

Clive

[bernard towersParticipant @bernardtowers37738]

If you mix flux with meths it does not bubble up so doesn’t spread where you dont need it so generally you need a lot less and if it doesn’t spread neither does your silver solder (less expense). And as Keith Hale (CuP Alloys) always said the silver solder you can see is not doing any work its the stuff you cant see that makes the joint. By the way how are you keeping Keith.

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