Wind Chapman

Disodium Borate, a new flux?

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I watched Brian demo this flux here in Ontario and was impressed. I suspect it has to do with the iron POWDER not fillings. I like anti-borax flux (contains anhydrous borax) for things like drop the tongs welds, but it can leave nasty lumps from the iron filings in things like basket twists. Brian sold the whole box of flux bottles after demoing it, I got the last bottle but have not had a chance to try it yet.

I was talking to Leo who worked in the blacksmith shop at one of the local steel mills about flux. Years ago they used to buy the anti-borax by the 45 gallon drum. That was a couple of months supply.

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One suggestion as to why some filings work, and some don't: Most of the metal we work with today is STEEL, not pure iron; and it's possible (I'm a chemist, not a metallurgist, so I say POSSIBLE) that the carbon and other alloying elements can interfere with the iron's adding to the weld. "Back in the day", plain iron was more common.

I've never been very good at forge-welding, but last year, I made up a home-brew of 90% borax and 10% (40 mesh) laboratory-grade iron filings that I got from Fisher Scientific. Measurements are by volume, btw.

It works like a charm, and I haven't screwed up a weld since (and clearly, the NEXT one will be a disaster!) I haven't tried it at low temperatures, though.. just at normal welding heat. But if I get it on the surrounding metal, I have to file off the resulting iron granules. If I can score some iron powder, I'll try that too.

Ooops... I see that I've repeated what someone else wrote. Oh, well...

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fluxes do behave differently from one another and behave very differently at different temperatures.
There are many things that iron powder can do in a welding environment. the most likely is that the iron powder acts as a sacrificial sponge for available oxygen. ie it oxydises in preference to the parent metal due to its greater surface area and absence of carbon. pure iron has a very high melting point not a low one so if it is pure iron then it is unlikely to be melting into the weld.
I have used fluxes with ground cast iron in them as the cast iron does lower the melting point of the parent material (be it steel or iron), I have used it to cast iron forge braze pieces together, carbon migration will then allow the piece to be forge welded or manipulated at forge welding heat with out coming apart.
I weld flux less or with a few different fluxes and different temperatures depending on situations materials etc
there is no best way, unless you are being very specific about material and welding situations , then there may well be a few best ways for any one particular circumstance....
so a readily available commercial flux for a tricky welding material sounds good to me . I will probably grab some if I ever come across it and give it a try.
All the best Owen

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I remember some smiths using brake turnings to help weld up "nasty" billets. Probably safer now that asbestos in the brake shoes is out! (about 20 years ago I once welded up a piece of chainmaille and thought I was doing good until Quad-State that year where a fellow had welded up lathe swarf into a knife...)

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