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Borax and forge floor

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As I continue reading through the threads on forge building, I am wondering about the affects of flux (borax, specifically) on the refractory.  I understand it tears it up over time, but the question is what sort of time period are we talking?  I understand this is relative. 

If I use Kasolite as the refractory and I were forging, say, a pattern welded billet with borax flux 2-3 times per week, what sort of time frame could I expect the forge to last?  Sure, there are other factors, but just trying to get an idea...are we talking a week, a month, a year? (Trying to gauge just how damaging the borax is over time).

Would casting some Kasolite forge floors in a form that could be removed and replaced be the ticket, or is Kasolite too brittle in thin (1/4", 3/8" thick) "plates"?

 

 

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As is true with so many things, the devil is in the details.  Kastolite 30 is not impervious to flux.  If coated with something like Matrikote or some kiln washes it will last a lot longer.  If you are forging large billets and tend to be "flux happy"  you'll see more damage sooner.  What I've seen on both "regular" (not high alumina) kiln shelf and Kastolite is the flux makes a dark gooey sticky mess at forge welding temperatures. When it cools down it hardens into a dark glossy surface that will effectively cement pieces together if it gets between them.  So, if you use a sacrificial floor you want to make sure the flux doesn't go to the edges of the sacrificial piece.

Now, if you use a minimal amount of flux to begin with and brush off excess flux frequently and you coat your sacrificial piece with something with high flux resistance you'll get a lot more welding sessions before you have to replace the piece than if you use lots of flux and don't coat the floor.  I know that's not a definitive answer, but the range is between one welding session if you are crazy with the flux and are welding a large billet to dozens of sessions if you are careful with the flux and use a resistant coating.

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Makes sense, at least that gives me an idea of the nastiness of borax in general (I was just trying to determine how nasty it can be).  I guess I was trying to determine if it was more like the effect of hydrochloric acid vs vinegar on metals. 

Considering the price of high alumina kiln shelf, would it be worth the effort to cast kasolite floors to shape, wash them and use those than paying for sacrificial kiln shelf and, assumingly wash those as well?  At least with the Kastolite, I have control over a "custom shape"...could build up edges or give it a dish shape to help keep flux from running over the edges?. I guess it's an exercise in economics.  I mean, if the kiln shelf material is so much more impervious it might be worth the cost, but I don't know the difference between it and Kastolite in that respect.  I wouldn't mind spending the time and effort to make a mold and do the casting if it's saves money down the road.  Time I have, money not so much, but I like to balance that where ever possible.

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Kiln shelf is expensive.  My floor is hard firebrick and I built the forge so it's easy to replace.

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