Anyone for Brazing?

[Cursitor Doom]

Sometimes I need to join a couple of pieces of metal that are too much for solder yet too delicate for arc welding. For those odd times, brazing would be useful, but the standard propane torch I use for plumbing is hopeless; the flame just isn't precise enough. Can anyone recommend a brazing torch that would meet my requirements? Something I could find in BnQ ideally. And should I be using propane, butane, or some other gas? The 'metal' concerned is typically some form of steel - mild, stainless, HT or HSS.

Cheers,

cd.

[Nightjar]

I used to have a jeweller's torch, which electrolysed water to produce a very hot, very fine, oxy-hydrogen flame, which was ideal for very fine silver soldering. I've long since forgotten the name though.

Colin Bignell

[stanhvac1]

You can use a map torch which is simmler to a propane torch however, the map gas burns at 1200 F. degrees. You can use 6% flux brazing rods, 15% or 45% silver solder also with this torch. In addition you can use regular propane tanks with the map torch tip. The map torch heads are much stronger than a regular propane head and most of the better one have a built in puch button spark ignitor. I think you can get one at Lowe's or Home Depo. We get ours from HVAC distributors.

[harryagain]

Brazing or hard soldering is carried out at temperatures below that of the metals being joined so think of it as a soldering process using a copper based alloy instead of lead. Brazing is a lot stronger than "soft" soldering because the copper alloy (usually brass) is stronger than lead. One of the few methods of joining/repairing cast iron.

Welding actually melts the metals being joined. So a fine point flame i snot required, just hotter and maybe bigger.

[Stephen]

As a materials scientist with a doctorate in materials processing, I can offer the following:

You are quite right that welding involves the melting of one or both of the parent metals with or without a filler metal.

As far as soldering and brazing are concerned, they are one and the same process. They do NOT involve melting the parent metals at all, just the melting of a filler metal.

The only difference between soldering and brazing is that if the temperature of the joining process is below 450°C its called soldering. If the temperature is above 450°C, its called brazing....

Hardness or softeness does not come into it.

So if you wish to carry out brazing instead of soldering, you need a hotter torch, most likely different fluxes (because you are now working with different parent metals and different filler metals as well as at a higher temperature.)

[Richard]

Damn! Apple has the mucus market now?

[Andrew Mawson]

I would just add to Stephens wise words though that when brazing, often the parent metal will migrate, presumably by dissolving, into the braze metal, markedly altering it's characteristics. It can happen that having brazed something satisfactorily with a particular torch it becomes impossible to unbraze it with the same set up as the melting point of the braze has now changed.

Being in possession of oxy-acetylene means that I rarely have problems getting things 'done or undone' but a marginal torch can be a nightmare. I did once have one of those jewellers oxy-hydrogen set ups mentioned in a previous post - seem to remember that the gases were bubbled through alcohol to add to the fuel mix. Very much under powered for my jobs, but then I'm not a jeweller :)

Andrew

[harryagain]

"Hard" and "soft" soldering are terms used in industry. Referring to the difference beween lead and copper alloys. So yes it does come into it.

[Nightjar]

On 23/04/2014 07:03, Stephen wrote: ...

Apart, of course, from the fact that hard soldering is a common alternative name for brazing (aka silver soldering, particularly when non-copper alloys are used).

Colin Bignell

[Nightjar]

On 23/04/2014 08:05, Andrew Mawson wrote: ...

...

That can happen when working silver, even with soft solders, but there are special alloys that resist the migration.

Colin Bignell

[Nightjar]

On 23/04/2014 08:32, harryagain wrote: ...

Except, of course, that the real difference is in the temperatures at which they melt, not the material of the alloys. There are plenty of lead-free soft solders about and many copper-free hard solders.

Colin Bignell

[Huge]

That's a pity, since it would be ideal for repairing our Russell-Hobbs electric kettle. Every few years, the spout, which is silver soldered on, falls off and we end up having to buy a new one, a purchase which irks my "make do and mend" bump.

[Huge]

Fascinating, and useful to a greater or lesser extent, and thank you, but you are aware that this newsgroup is UK based? Oh, and it's "MAPP", not "MAP".

MAPP gas is a trademarked name belonging to Linde Group, previously to Dow, for a fuel gas based on a stabilized mixture of methylacetylene and propadiene. The name comes from the original chemical composition: methylacetylene-propadiene propane. ...

[Nightjar]

I think the Model 30 here was the device:

It will be cheaper to keep replacing the kettles, if that is your only use for it. :-)

Colin Bignell

[Bob Minchin]

ROTFL excellent!!

[Dave Plowman (News)]

I have a small jeweller's blowlamp bought from B&Q some time back badged BernzOmatic which produces a very small hot flame. Uses ordinary lighter gas re-fills. Have used it for brazing small items. And for soldering things too large for a soldering iron - like lugs to starter cable - where the small accurate flame is easier to direct and prevent damage to the insulation than a normal blowlamp

[Chris J Dixon]

Cheaper still to select a different kettle.

Chris

[Huge]

Holy Shit, yes. OTOH, the MAPP gas option looks viable. And experience teaches me that tools bought for one job frequently turn out to be useful for all kinds of other things.

[Huge]

Quite possibly, but we do not select items simply on the single criterion of cheapness.

[newshound]

This is something similar, I find them surprisingly good

I also regularly do silver soldering on ironwork with an ordinary plumbers gas torch (on separate propane bottles), the only problem is heat loss on larger sections preventing you reaching the good red heat which you need. Loads of stuff on Google and easy-flo or similar fluxes are readily available on eBay.

I have a selection of vermiculite "fire bricks" which I use to build a suitable brazing hearth. This is an expensive and not very good example