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borax resistant!!
no such thing!
I run my own welding forge from hard fire brick and have tried hi temp 1700C refactory and 1500 refactory (which is the most flux resistant) and they all get eaten , My personal forge is a much bigger heavier and more industrial structure than this takes around 40 mins to reach welding I let the flux gloop build up and have to constantly replace linings bricks it is a work in progress .
I have lined this forge with fire clay used to make hard fire brick and it will resist a little while....
Borax mixed in with oxidised iron is a powerfull corrosive mix , having a dump zone at the bottom of the forge helps stop the gloope getting on your billet and having easily replacable lining is a big advantage.

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  • 2 weeks later...

Using a high phosphate or phosphate bonded refractory will cure the borax problem. Any high silica refractory will dissolve when in contact with a caustic like HOT borax. High alumina like Kaolin is a lot more resistant so ITC-100 or the equivalent helps a lot. High phosphate on the other hand doesn't notice hot hot HOT caustics.

I used to be able to get Pyramid Super air set rammable which had a working temp rating of 4,000f and was used commercially to line 4,000f ammonia atmosphere furnaces. Pyramid is out of business and I don't think anyone is making the super air set. I'm sure someone is making a replacement though, I just haven't seen any.

Frosty The Lucky.

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AP Green sold a plastic rammable product about 25 years ago which was so stiff that it had to be hammered into form. You had to air dry it for about 2 weeks then fire slowly. It turned an orangish red color and became brittle after full fire but would resist welding flux for a long time. I made up several floor tiles that lasted me until a year or so ago, even if only in pieces near the end.

I've also thrown a plate of stainless in the bottom of gas forges since none of mine will get hot enough to melt it. None of the lightweight refractories I've used will resist borax but I've read that high zircon content resists flux.

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