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Brazing Materials

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Nick Clarke 325/07/2019 13:18:55
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While today cadmium free silver solder is the only material advised for boiler making and steel fabrications may, with modern equipment be easily welded or bronzewelded (eg SifBronze) Several other materials were written about in old copies of ME that have aroused my curiosity and any more information on them would interest me.

While true brazing with brass wire is obvious, but what were easy running strip and granulated spelter? Are they still available?

Is this what was meant? **LINK**

Many materials and techniques recommended in the past are not so today. I am thinking of Sifbronzing coal fired boilers and at least one well known design where boiler plates are unflanged and joined with the self fluxing alloy Silbralloy - so this is a request purely out of interest, not for use!

Jeff Dayman25/07/2019 13:52:24
2221 forum posts
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Not sure about the easy running strip and the granulated spelter, but sheets of thin brazing metal are still available for attaching carbide tips to steel shanks. Fine-ground brazing metal powder suspended in a flux paste is widely used for furnace brazing assemblies like heat exchangers, fuel pickup tubes, etc for cars and trucks.

I still use flux coated round bronze rod for oxy acetylene bronze welding of all sorts of machine repairs on steel or bar iron parts (NOT boiler work) where electric arc welding would be too hot or imprecise. Bronze welding works great on cast iron parts not exposed to high heat. This rod can also be used to repair mid to large bronze valves and fire hose couplings and nozzles. Heat control when bronze welding bronze is VERY fussy - 20 degrees too cold and there is no fusion, 20 degrees too hot and it all falls apart in front of you! With much practice, and a few dirty tricks, it is very possible.

Keith Hale25/07/2019 14:10:21
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Hi Nick,

Here we go again............

Don't understand the "true brazing" bit! Brazing is a process of joining metal and its success depends on capillary flow. Brazing has nothing to do with the filler metal used! You can braze with copper, silver, gold, palladium, and nickel alloys

You can use sifbronze on your boiler, you just need heating equipment that will give you the extra 250 deg C to melt it compared to using a silver bearing brazing alloy.

You will probably need an oxy acetylene torch working alongside your propane torch.

You will probably need to enter contracts, bottle hire agreements, increased storage issues to satisfy your gas supplier.

But yes, it can be used. It's just easier with a silver brazing alloy. OK it's more expensive but easier. You pay your money and take your choice.

UNDER NO CIRCUMSTANCES USE A SILBRALLOY TYPE MATERIAL IN A COAL FIRED BOILER. IT'S CHEAP AND WILL PRODUCE STRONG JOINTS BETWEEN COPPER COMPONENTS WITHOUT THE NEED FOR A SEPARATE FLUX.. SULPHUR FROM THE COAL WILL RENDER THE JOINT POROUS AND IT WILL FAIL.

Spelter is an old word used to refer to a brazing alloy. Who knows what "easy running strip" is? Probably a name adopted on a shop floor in the antiquities of time!

As for the cheap stuff on your link - why not ask the supplier? Let the buyer beware!

For more information see my book based on 50 years experience in the brazing business. Or talk to CuP Alloys. They will tell you.

Regards

Keith

Nick Clarke 325/07/2019 14:51:07
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Hi Keith, Thanks for your reply - My query was a purely intellectual question as any boiler work will be based on modern practise, including that kindly given by yourself here, and also face to face at the last Bristol show where a great deal was explained to me.

My comment on true brazing was based on a mention in one of Tubal Cain's articles and the OED also defines 'braze' as "Form, fix, or join by soldering with an alloy of copper and zinc at high temperature"

There have frequently been published letters and comments regarding the dezincification of Sifbronze in boiler use, so your experience is useful here.

LBSC frequently referred to granulated spelter and free running strip in his writings and my question was 'what are these' - I see from your reply they are not obvious today. The only reason to include the link was because it appeared to be a low temperature strip (not a rod) as a possible explanation. I do not know!

The reference to Silbralloy is after reading the description of the 'Twin Sisters' boiler by J. Austen-Walton in ME Jan 29th 1953 - a published design, of which some may still be running. Interestingly LBSC decried the used of this or similar alloys and non flanged plates in an article that same year.

As someone who enjoys collecting and reading old magazines there are many terms that are no longer in use, and though I hope to take full advantage of modern methods and experience, I would still like to find out what was meant a long time ago.

Thanks,

Nick

Ian S C25/07/2019 15:30:59
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7468 forum posts
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Mum's father was a plumber in Scotland, and when he came to NZ on holiday in 1952 among the tools and stuff he brought with him was what dad said was easy flow/silver solder, it was a strip about 6 mm x 1.5 mm section, there was about 1 metre of it, and it worked well with borax as a flux using a petrol blow lamp.

Ian S C

Neil Wyatt25/07/2019 15:52:33
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I think 'free running strip' was indeed easyflow type silver solder in sheet form cut into strips.

I don't think Sifbronze was exceptionally good for boiler making, but reading between the lines I suspect LBSC got as much free Sifbronze as he ever needed.

There's information about making about granulated spelter here. It seems to be coarsely powdered brass which was mixed with borax as a sort of high temperature brazing flux.

The origin of the word brazing comes from brass, but today is generally taken to mean any soldering process at elevated temperatures.

Neil.

Speedy Builder525/07/2019 16:04:54
2590 forum posts
207 photos

EasyFlow was that lovely silver solder stuff with Cadmium, you could smell the joint - and more that likely no good for us. We used it mainly for stainless steel hydraulic pipe fittings using Tenacity 5 flux

IanT25/07/2019 16:08:37
1984 forum posts
211 photos

" While today cadmium free silver solder is the only material advised for boiler making and steel fabrications may, with modern equipment be easily welded or bronzewelded (eg SifBronze) Several other materials were written about in old copies of ME that have aroused my curiosity and any more information on them would interest me. "

I've mentioned this a few times before - but for anyone interested you can certainly Sifbronze small steel fabrications without the expense and trouble of OxyA kit. However you will need a propane torch capable of the required heat outputs - and the one I have (a Bullfinch 404) can manage this. They are not cheap but are well made and I expect mine will last me my lifetime - I can also silver solder with it and I like the auto-ignition feature.

Why Sifbronze? - well I paid about £20 for 1kg of 1.6mm Sifbronze No 1 (about Qty 60 x I metre lengths) - so it is considerably cheaper than silver solder! I still have quite a few lengths in stock. Using a larger propane tank also saves money over disposable gas bottles.

I've just checked current pricing - 1kg Sifbronze No1 (Approx. 60 x 1.6 x 1 meter rods) is £26.85 (inc VAT) from WeldEquip (not some no-name Ebay supplier) - whilst Qty 5 x 1.5mm x 500mm 524 Silver Solder is £21.77 (inc VAT & Delivery) from CuP.

So if a fabrication is not too big (and made of steel) - I tend to use Sifbronnze but for other (generally non-ferrous) applications I will use my precious (e.g. expensive) 524 silver solder.

Is it worth the extra cost of the Bullfinch 404? Well, certainly it is not for everyone. It will depend on how much small scale steel fabricating you need to do - but I use mine a fair bit and find it very useful.

Regards,

IanT

Side Frame Assembly End Assembly

Edited By IanT on 25/07/2019 16:09:06

SillyOldDuffer25/07/2019 16:43:11
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8469 forum posts
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My Ure's Dictionary of Arts, Manufactures and Mines (1875 edition) identifies:

  • Pewterers' Solder:
    • 2 Bismuth, 4 Lead, 3 Tin or
    • 1 Bismuth, 1 Lead, 2 Tin
  • Coarse Plumbers Solder:
    • 1 Tin, 3 Lead (Melts at about 500°F), or
    • 2 Tin, 1 Lead (Melts at about 360°F)
  • Soft spelter Solder: Equal parts Copper and Zinc.
  • Spelter Solder: 12ozs Zinc to 16ozs Copper.

Anyone wanting to go completely old-school may be interested that Ure's Dictionary identifies welding specifically as the process of joining white-hot Wrought Iron by forging, ie blacksmithing. What we understand as welding is called 'Autogenous Soldering'. Another useless fact from me!

Comment: I think soft spelter is relatively easy to melt, but the joint made is on the weak side. Spelter solder makes a stronger joint, but is much harder to work with. Adding Cadmium and Silver to Brass drops the melting point without weakening the joint, making it possible for us to Braze without doing a seven year apprenticeship first!

There are an awful lot of Brasses available. Various mixes of copper and zinc are suitable for different purposes. The grain structure of a casting made from melted cartridge brass is inferior, and casting alloys are unsuitable for making cartridges. Lead makes Brass more machinable, and a little extra Tin makes Brass better for engraving. Iron, Phosporous and Aluminium all improve strength and corrosion resistance. Although there are many different types I've found most brasses machine reasonably well, and only phosphor bronze has given me bother. Same can't be said of steels: many of these are so unpleasant I only buy known alloys now.

Dave

Edited By SillyOldDuffer on 25/07/2019 16:44:47

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