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.

[JasonB]

On JasonB Said:

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.

Hi Jason,

Great idea, will definitely try that – silver solder paste is really expensive,

Thank you,

Chris

[Bazyle]

On Bazyle Said:

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.

Never even considered that Bazyle, I’m rethinking the procurement of the powder anyway based on the responses from you guys here. I think there is scope here from some testing though, I will add a post if I get the chance to do it.

Cheers,

Chris

[Clive Foster]

On Clive Foster Said:

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

Hi Clive – you clearly have a lot of experience doing this, I only have flux paste at present although I have watched a few YT videos such as https://www.youtube.com/watch?v=0ti2VQbn_A0 and wondered if the powder mixed into paste was a good idea or a sales push by Solpro. I suspect I’ll buy some and try it,

Thanks for your input, much appreciated,

Chris

[bernard towers]

On bernard towers Said:

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.

Thank you Bernard, duly noted – really useful info regarding CuP Alloys too (I hope Keith is fit and well),

Kind regards,

Chris

 

[Bill PhinnParticipant @billphinn90025]

I’m not sure why you want to bronze braze as opposed to silver braze. Can you explain?

Silver brazing/soldering is adequate for delicate components. All my silver jewellery work was done with silver solder of various temperature grades: hard, medium, easy, and extra easy. For non-hallmarking silver soldering I generally use Johnson Matthey Silverflo 55 solder with Easy Flo 2 flux powder mixed into a paste. On bigger work I also feed with rods, as Jason suggests. Dipping a heated rod into dry flux powder (at the right temp. the powder will stick to the rod) means you don’t need to apply flux paste to the joint at all.

I reserve bronze brazing for repairing or joining steel components subject to heavy usage, though these are not necessarily big components. I use two different kinds of bronze rod: silicon bronze rods and manganese bronze rods. The first has better gap filling characteristics, the latter better flow characteristics.

For bronze brazing I generally use Sif Bronze flux powder, though I’ve also used Easy Flo 2 successfully.

BTW, the flux paste mix shown in the video is too watery for most purposes, even after the demonstrator has added several dollops of extra powder.

[JasonBModerator @jasonb]

You can also get other pastes depending on the job you want to do but as these are mostly used by industry getting hold of small amounts is difficult, hence why I linked to CuP as they do it in small amounts.

If you look at someone like JM then they do quite a range, the Argo-Braze being closer to a bronze but if you look at the composition they are not that far from the silver solder ones and all contain a fair proportion of silver (Ag) hence the cost.

[Bill Phinn]

On Bill Phinn Said:

I’m not sure why you want to bronze braze as opposed to silver braze. Can you explain?

Silver brazing/soldering is adequate for delicate components. All my silver jewellery work was done with silver solder of various temperature grades: hard, medium, easy, and extra easy. For non-hallmarking silver soldering I generally use Johnson Matthey Silverflo 55 solder with Easy Flo 2 flux powder mixed into a paste. On bigger work I also feed with rods, as Jason suggests. Dipping a heated rod into dry flux powder (at the right temp. the powder will stick to the rod) means you don’t need to apply flux paste to the joint at all.

I reserve bronze brazing for repairing or joining steel components subject to heavy usage, though these are not necessarily big components. I use two different kinds of bronze rod: silicon bronze rods and manganese bronze rods. The first has better gap filling characteristics, the latter better flow characteristics.

For bronze brazing I generally use Sif Bronze flux powder, though I’ve also used Easy Flo 2 successfully.

BTW, the flux paste mix shown in the video is too watery for most purposes, even after the demonstrator has added several dollops of extra powder.

Hi Bill,

I would say generally, ignorance and a lack of knowledge – I guess if I knew what I was doing I wouldn’t have reached out to creatives and engineers in here to be honest.

I’m using gasless mig which brings it’s own difficulties, transitioning from 6mm plate and 1 inch diameter bars and box sections to attempting fiddly pieces like small lengths of 3-6mm rod, ball bearings and assorted scrap parts needs some thought. I’ve been asked if I’d try and make some small figures/sculptures and so I needed to tap into those with experience as my learning curve is almost vertical.

You’ve given me plenty to think about and research here for which I’m grateful,

Thanks very much

Chris

[noel shelleyParticipant @noelshelley55608]

Going back to where the OP started eg Mig welding. Many machines use 0.8mm wire, this is fine for general fabrication work, or 1mm for heavy stuff. Simply looking at the sectional area or volume of wire, 0.6mm wire will do much lighter work, needing a much lower heat input ! Depending on the cost/ quality of the MIG welding machine the wire feeder is the MOST important part of the set up, a cheap unit will have simple control of a toy car motor and a molded plastic block, where as an expensive model will have complexted control of the feeder, with pre gas, ramp up,feed, burn back, post gas, a special motor, a cast block and geared feed rollers, or even 4 rollers. All this gives a very steady control of the wire feed which is vital. Very light work can be done with the right wire and a good machine. OR use a TIG torch on the MIG power supply and set up a gas supply. Just a few thoughts ! Noel.

Having just read your reply, your NOT using MIG, The G stands for GAS ! And I assume that it is a cheap machine and you do not want the expense of using proper MIG with Co2 or an Argon or Argon mix. From the above you may understand why you are failing to get success using your set up. If you wish to braze, then a brazing hearth and small MAPP gas torch may work IF you can get enough heat. small brazing rods eg 1 or 1.2mm rods and a tin of brazing flux are worth a try. If your near me (Kings Lynn ) I can let you have a short rod and some flux to play with ? Noel.

[JasonB]

On JasonB Said:

You can also get other pastes depending on the job you want to do but as these are mostly used by industry getting hold of small amounts is difficult, hence why I linked to CuP as they do it in small amounts.

If you look at someone like JM then they do quite a range, the Argo-Braze being closer to a bronze but if you look at the composition they are not that far from the silver solder ones and all contain a fair proportion of silver (Ag) hence the cost.

Thanks Jason, wowzers, it is pricy https://cupalloys.co.uk/product/455-silver-solder-paste-10g-syringe/

Johnson Matthey, a name I’ve not remembered since 1987 – I worked for an ICI in Runcorn producing military microwave circuits  (missile systems) and used JM products back then.

Just need to pull some bits and pieces together and have a go now,

Thanks again,

Chris

[JasonBModerator @jasonb]

One thing to bear in mind with you mentioning making small figures/sculptures is that Mig and Tig are both very localised be they welding or brazing. Silver soldering be it with rods or paste generally applies the heat to a larger area bringing the parts upto temperature. This means that you will have to be careful about not melting previously soldered joints. There are ways around it such as using heat sinks and solders of different melting points but there is still a risk unlike with welding

You also need quite close fitting joints so unlike welding where the rod can bridge a gap or build up a fillet you only need a thou or two gap for solder to flow, anymore and it won’t fill a gap. This will mean any two parts will need filing or coping to give a close joint.

[noel shelley]

On noel shelley Said:

Going back to where the OP started eg Mig welding. Many machines use 0.8mm wire, this is fine for general fabrication work, or 1mm for heavy stuff. Simply looking at the sectional area or volume of wire, 0.6mm wire will do much lighter work, needing a much lower heat input ! Depending on the cost/ quality of the MIG welding machine the wire feeder is the MOST important part of the set up, a cheap unit will have simple control of a toy car motor and a molded plastic block, where as an expensive model will have complexted control of the feeder, with pre gas, ramp up,feed, burn back, post gas, a special motor, a cast block and geared feed rollers, or even 4 rollers. All this gives a very steady control of the wire feed which is vital. Very light work can be done with the right wire and a good machine. OR use a TIG torch on the MIG power supply and set up a gas supply. Just a few thoughts ! Noel.

Having just read your reply, your NOT using MIG, The G stands for GAS ! And I assume that it is a cheap machine and you do not want the expense of using proper MIG with Co2 or an Argon or Argon mix. From the above you may understand why you are failing to get success using your set up. If you wish to braze, then a brazing hearth and small MAPP gas torch may work IF you can get enough heat. small brazing rods eg 1 or 1.2mm rods and a tin of brazing flux are worth a try. If your near me (Kings Lynn ) I can let you have a short rod and some flux to play with ? Noel.

All understood Noel, I knew I would experience short comings when I bought the welder and even more so as I chose to be gasless. You’re right, it’s a cheap machine which may or may not work out – I’m sure you’ll appreciate how spattery the tack welds can look. Very kind offer of some consumables to me, I’m up in Cheshire so a tad far unfortunately. I have some rods arriving tomorrow so hopefully I can have a play over the weekend.

Kind regards,

Chris

[JasonB]

On JasonB Said:

One thing to bear in mind with you mentioning making small figures/sculptures is that Mig and Tig are both very localised be they welding or brazing. Silver soldering be it with rods or paste generally applies the heat to a larger area bringing the parts upto temperature. This means that you will have to be careful about not melting previously soldered joints. There are ways around it such as using heat sinks and solders of different melting points but there is still a risk unlike with welding

You also need quite close fitting joints so unlike welding where the rod can bridge a gap or build up a fillet you only need a thou or two gap for solder to flow, anymore and it won’t fill a gap. This will mean any two parts will need filing or coping to give a close joint.

The close fit was part of the attraction for joining small parts (at least in my mind), but time will tell if it’s achievable,

Thanks Jason

[Andrew TinsleyParticipant @andrewtinsley63637]

I use brazing instead of silver soldering on many occasions, because it is cheaper! Does take a higher temperature to do the job. As far as paste goes. I have used brass filings mixed with Sif bronze flux and made into a paste with water. gives quite satisfactory results and is a huge amount cheaper than silver solder paste.

Andrew.

[Andrew Tinsley]

On Andrew Tinsley Said:

I use brazing instead of silver soldering on many occasions, because it is cheaper! Does take a higher temperature to do the job.

Cheaper to buy, though not cheaper to use, Andrew, when the extra temperature required is nearly 250 degrees C.

Also, unless you’re using the more expensive manganese bronze rods, you’ll struggle to get joints as neat as with silver solder, all things being equal.

[Andy_GParticipant @andy_g]

wowzers, it is pricy https://cupalloys.co.uk/product/455-silver-solder-paste-10g-syringe/

 

A little does go a long way.

If you don’t like the price of that, just get a length of wire – for example:

https://cupalloys.co.uk/product/1-metre-455-silver-solder-wire-0-5mm-dia/

and the appropriate flux to try it out.

Snip off tiny pieces (pallions) as suggested by @Clive Foster and place them next to the joint after fluxing it up, but prior to heating. A butane torch will provide enough heat for small-ish parts.

 

 

[Andrew TinsleyParticipant @andrewtinsley63637]

Bill,

Not sure about neatness, my sif bronzing is just as neat as my silver soldering, take that whichever way you want! The difference in cost for the extra 200 degrees is nothing compared to the cost of the silver. Anyway I always use oxyacetylene for heating and never even notice the difference in temperature between silver soldering and sif bronzing.

Andrew.

[Author]

Posts