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Author Topic: Attaching different metals - brazing?  (Read 2270 times)
milamber
Deck Hand
*
United Kingdom United Kingdom


« on: December 04, 2013, 12:18:15 pm »

Hi.

First off my apologies as this has bound to have been asked many times, but I've had a good look through and can find loads of advice on technique, but my question is probably a bit more basic than that.

Looking to do a couple of projects over the winter, firstly a rocket pack. This will be mostly bolted or riveted and I'm fairly experienced at soldering copper plumbing materials. Also I have a hankering for trying to make a few weird and wonderful animals from scrap bolts, cutlery, old tools etc etc, particularly a steampunked parrot for my shoulder.......

Whilst I can probably get away with physical attachment and soldering for the rocket pack, the scrap animals will mean attaching small pieces of different types of metal together - brass, copper, steel, stainless steel etc. I'm assuming a welder is both overkill and not practical for the small sizes and variety of metals. Also my only attempt at welding in the distant past left assorted welding rods attached to bits of metal all over the workshop.

Is silver soldering the answer? I solder the plumbing materials with a blowtorch and 'normal' solder. Is silver soldering broadly the same technique with a different type of solder? Is 'brazing' just another name for silver soldering? Or should I stick to Araldite?

Again apologies if this has been asked a zillion times.

Thanks
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Narsil
Immortal
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United Kingdom United Kingdom



WWW
« Reply #1 on: December 04, 2013, 09:35:54 pm »


Yes silver soldering is basically a type of brazing, there is pretty much a continuum from soft soldering to hard soldering, brazing, braze welding etc. The terminology does vary a bit between particular industries

An yes it's a pretty good way to join dissimilar metals, for most practical purposes the joint should be as strong as a welded joint. The most important thing is that you design and prepare your joints properly, brazing, like soldering, is much less tolerant of gaps and poor joint preparation than welding, it's also important that the joint is properly supported before during and after brazing as it doesn't achieve any kind of strength until it is properly cool.

Another thing to be aware of is that you need to get the whole joint up to the correct temperature or it simply won't work, depending on what you're attempting a blowtorch may or may not be adequate. Having said that a proper brazing torch is still significantly less expensive than even quite cheap and nasty welding kit.

« Last Edit: December 24, 2013, 08:06:04 pm by Narsil » Logged







A man of eighty has outlived probably three new schools of painting, two of architecture and poetry and a hundred in dress.
Lord Byron
milamber
Deck Hand
*
United Kingdom United Kingdom


« Reply #2 on: December 05, 2013, 12:00:31 am »

Thanks - much appreciated. I'll just have a play with some scrap first Smiley
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Narsil
Immortal
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United Kingdom United Kingdom



WWW
« Reply #3 on: December 24, 2013, 08:25:09 pm »


There are really four key things to bear in mind with brazing

- Fist select a brazing rod and flux which are appropriate to the metals you are using, many common ones are pretty general purpose but it is well worth checking that you have got the right ones for the job.

-Joint design : brazing tends to work best when you have two flat (or flat relative to each other like one tube closely fitting inside another) surfaces in good contact with each other, an excellent example of this is old, good quality bicycle  frames which are often made from brazed chrome-moly steel, these often have quite intricate lugs at the joints which are designed to give a large joint surface area.

-Heat : it is vital that the whole joint is heated to the correct temperature before you apply the filler, you shouldn't need to directly heat the filler ros at all, the heat of the joint, combined with the action of the flux  should suck the filler into the joint by capillary action. If you get blobs of filler/solder then it isn't hot enough. The joint should naturally form a neat, clean looking,  fillet without you having to poke it.

-Clean surfaces : all mating surfaces should be thoroughly cleaned of oxides, oils and grease and any other contaminants, and foreign matter on the surface will impede the flow of the solder and result in a  weak joint

In many ways brazing and soldering is technically a lot easier than welding as it's all down to deliberate preparation but on teh other hand it's a lot more difficult to fudge as brazed joints tend to be ether good or failed with not much inbetween,
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thomasedwin
Swab

United States United States


« Reply #4 on: January 08, 2014, 02:29:10 am »


Yes silver soldering is basically a type of brazing, there is pretty much a continuum from soft soldering to hard soldering, brazing, braze welding etc. The terminology does vary a bit between particular industries

An yes it's a pretty good way to join dissimilar metals, for most practical purposes the joint should be as strong as a welded joint. The most important thing is that you design and prepare your joints properly, brazing, like soldering, is much less tolerant of gaps and poor joint preparation than welding, it's also important that the joint is properly supported before during and after brazing as it doesn't achieve any kind of strength until it is properly cool.

Another thing to be aware of is that you need to get the whole joint up to the correct temperature or it simply won't work, depending on what you're attempting a blowtorch may or may not be adequate. Having said that a proper brazing torch is still significantly less expensive than even quite cheap and nasty welding kit.


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Keith_Beef
Snr. Officer
****
France France


« Reply #5 on: January 08, 2014, 11:04:19 am »

Another thing to be aware of is that you need to get the whole joint up to the correct temperature or it simply won't work, depending on what you're attempting a blowtorch may or may not be adequate. Having said that a proper brazing torch is still significantly less expensive than even quite cheap and nasty welding kit.

A propane or butane torch is also a very flexible and useful tool, when you fit different burners, and not all that expensive. I've used mine for hard soldering and brazing, but also
  • for heating up jammed screw-fittings to loosen them,
  • for stripping paint,
  • for hardening and tempering steel blades (with a small kiln made of a dozen firebricks),
  • as a very quick way of getting a charcoal BBQ up to cooking heat.

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--
Keith
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