[TheForge] Strengthening castable refractory

[Marc Godbout]

Thanks for the ideas so far about this. I've got some Delta Crete 25
insulating castable refractory. The "25" refers to 2500 degF. My notes
are at work, but I think it's around 60 lbs per cubic foot.

I've tried the home-brew insulating refractory using Portland cement,
perlite, and sand. It comes out pretty light and seems very strong. But
it melts at high forging temperatures. Vermiculite has a lower
temperature, but I've read that it tends to hold water and could cause
problems when curing. Also used is sawdust. That just burns away,
leaving air pockets. I made some of that and it was weak. It also
melted, so the problem was probably the Portland cement.

Since the insulating castable is light enough on its own, I don't think
I'll be adding any other material.

I do like the needles idea and will definitely search for them around
here. Luckily I have a refractory contractor 2 miles from home who's
very nice to deal with. Hopefully he can help with the needles. 

Also, I wasn't thinking of cardboard between the insulation and shell,
though. I was thinking more like expansion joints in concrete,
perpendicular to the slab, or radial in my case. I'm probably
over-thinking this, though. It sounds like this is tough stuff and the
needles will be enough.

-Marc


-- 
Marc Godbout
http://www.ironringforge.com

New England Blacksmiths Membership Director
http://www.newenglandblacksmiths.org