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Forge weld flux


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Adding sand to borax will make it a poorer flux. Adding boric acid to borax will improve it---boric acid $$$ at the pharmacy or *cheap* at the hardware store as "Roach Pruf"

Clean Quartz sand was the traditional flux for real wrought iron which can be welded at a much higher temperature than modern alloys *and* did not need as aggressive a flux as modern steels either.

(I started a billet Saturday at the Festival of the Cranes, 21 layers of band saw blade and pallet strapping: did the first tricky weld, drew it out---used dividers to locate the center line, notched and folded and did the second weld. Then had to let the coal forge cool.)

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At high temps I don't think borax is alkaline. Buying a pound of roach Pruf locally for $5 seems a better deal. If you are going though 20 pounds of flux in a year you are going way beyond my usage! Roach Pruf is 98% boric acid and 2% colouring.


Borax and boric acid supposedly both break down to boron trioxide at high temps, and that's what dissolves the metal oxides that interfere with forge welding (and probably the oxides that most forge linings are made from). It kinda makes you wonder if mixing the two really accomplishes anything. I have experimented with using straight Hot Shot boric acid roach killer as a welding flux, but only on a very limited basis.
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At high temps I don't think borax is alkaline. Buying a pound of roach Pruf locally for $5 seems a better deal. If you are going though 20 pounds of flux in a year you are going way beyond my usage! Roach Pruf is 98% boric acid and 2% colouring.


its posted on another thread, but has a Ph of 2.2 at our typical welding temps.
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Well thats interesting info about the degradation to Boron Trioxide and the ph. I will have to see what happens in practice.

I looked for roach powder in my town but couldn't find it so I bought from ebay. If the roaches ever show up in my house they will be xxxx sorry! :)

I add brake drum chips to my borax and find it really helps. Just another recipe in the Black Art of Forge Welding.

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  • 3 months later...

He simply sprayed WD40 between the layers and heated to welding temp and press welded the layers into a 1" billet (30 ton press). His technique produced the cleanest, inclusion free weld possible.

He cut a cross-section of the resulting 1" billet and we were all amazed at how clean and solid the interior of the billet was - simply beautiful.


I'll try that this weekend. I'm working on a length of chain (first forge-welding project). Would the weld set if I could get it pressed in a table vise quick enough, or would schmucking it with a hammer work too?

I'm very new to forge-welding, and I've only been able to get one to set, and that was pure dumb luck. Wish me well!
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