Anyone for Brazing?

[meow2222]

No need to be snotty, the man's trying to help

NT

[Bill Wright]

I did this exact repair successfully with aluminium solder and a blow torch. Got the metal too hot with the torch, let it cool, applied the solder with a soldering iron at the right moment.

Bill

[Dave Plowman (News)]

I'd expect that to have a less concentrated flame? The one I have produces a flame more akin to an oxy-acetylene torch. Sort of sharp edges. ;-)

[Nightjar]

That is what happened with this. It was about the only tool for a particular job (putting precise portions of silver solder at intervals along 0.75mm OD 7x7 cable laid stainless steel wire without discolouring the wire or needing a lot of flux on it) and we later wondered how we had done without it for all sorts of fine jobs. ISTR it was about a quarter of today's price when we bought it though, which was not a problem as the job brought in about £10k pa for the next five years.

Colin Bignell

[newshound]

Depends on the amount of air which is adjustable, the ones I have used can give the classic blue inner cone, not as short as with OA but still very concentrated and hot at the tip.

[Stephen]

I would just like to add to Andrew's wise words too....

what you are describing as migration is atomic diffusion of the parent metal into the molten filler metal and vice versa.

This forms intermetallic compounds. A good example is copper wire with tin based solders, this will form two specific intermetallics:

Cu3Sn and Cu5Sn6

So when a soldered electrical joint is microsectioned and polished and examined under electron microscopy, you will see the joint as:

Pure copper : Cu3Sn : Cu5Sn6 | tin.

The two intermetallic layers will be the order of micrometres thick.

It is the formation of these intermetallics that alter the mechanical properties of the joint leading you to observe the inability to unbraze it..... :-)

Similar things happen with nickel and tin, which is why component leads are sometimes nickel plated instead of "tinned" with solder.

ENIG PCBs (ENIG is Electroless Nickel Immersion Gold) help with solderability as the gold and tin based solders will readily form a gold-tin intermetallic.

[Stephen]

well "hard soldering" may well be the old fashioned name for brazing but I can assure you that the difference between brazing and soldering relates to the process temperature rather than the hardness of the filler metal.

[Stephen]

"hard" & "soft"They are old fashioned terms used to describe brazing vs soldering, not down to the hardness of the filler metal.

[Stephen]

precisely.....

[John Williamson]

When I was studying metalwork ty years ago, there were four ways of joining metal involving heat.

Welding - With or without filler rod. I never did get the trick of it. :-/

Brazing - Brass filler rods with Borax flux when joining steel or iron. My preferred option if a reasonable joint strength was needed.

Silver Soldering - Similar to brazing, with a similar flux, but using a silver alloy with a lower melting point than brass. For when the blowlamp couldn't get the metal hot enough to braze, or the parent metal was something like copper, with a lower melting point than the brazing rods. Handy for model steam engine boilers.

Soft soldering - Using a lead/ tin alloy with either an acid or rosin based flux, depending on what was being joined. The solder varied from what was known as Tinman's solder (Almost pure tin) to almost pure lead, but was mostly near the 63/37 eutectic mixture. The heating varied from a tiddly little electric iron to a flamin' great blowlamp, via a half pound copper bit heated in a gas oven on the workbench until the gas flame was just tinged slightly with green.

[Stephen]

I'm obviously considerably younger than you then, I trained in materials science to masters and doctoral level in late 1990's early 2000's.... What you describe sounds very 1960's or 1970's......

joining technology has moved on considerably since then!

[Nightjar]

You sound like an academic. In the real world, hard soldering and soft soldering are well known and well understood terms. I suspect the derivation has more to do with the metals that they are used on, than the alloys used for joining them: another 'old fashioned' bit of engineering terminology is to call people who work in steel hard metal workers and those who work in copper alloys soft metal workers.

Colin Bignell

[Fredxxx]

One that has spots falling off hardly sounds value for money?

[Stephen]

nope, not an academic... I'm a materials technologist.

[Andrew Mawson]

Stephen,

I endorse Colin's comments. I find it is frequently the case that academic teachings are a world away from every day life. It is necessary to use terms in this context that will be understood by the vast majority of people actually experienced and 'hands on' in industry.

As far as I'm concerned after something like 56 years doing it (*) there is:

'soldering' - using lead based filler or now the 'lead free' dreadful stuff 'silver soldering' - using a silver bearing filler 'brazing' - using a basically brass based filler 'welding' - using any filler compatible with the metals being welded

These terms will be fully understood by most who have actually 'been there and worn the tee shirt' but they may not sit easily with teaching on a material sciences course :)

Andrew

(* my first soldering was using a copper bit heated on the gas ring making a crystal set when I was 9, and yes it did work )

[stanhvac1]

Thank you. I don't guess he ever accidentaly mispelled a word, ie: typo. Sometimes I don't hit the keys just right and fail to post the letter. Anyway, this is not a spelling class, it's about trying to help someone out.

[Vir Campestris]

Ah, I hadn't realised the problem was an infection. It sounds a little like leprosy, but I didn't know spots were one of the symptoms :)

Andy

[Nightjar]

That sounds like a very academic discipline to me.

Colin Bignell

[Andrew Mawson]

Could just be the storeman who says 'nah - not EN8, I'd use a bit of brass, mate ' :)

Andrew

[Clive George]

If you'd done it once, that would be a reasonable excuse. Twice, less so. But every time you wrote it you got it wrong.

And Huge's reply was pretty unsnotty for usenet.