[TheForge] Strengthening castable refractory

[theforge@mailman.qth.net]

I think I read somewhere that castable refractory is reinforced with 
short pieces of stainless steel wire that are put into the mix before 
casting.  I'd call a field rep from the info below and ask them how to 
reinforce the dome.

Everyone probably knows by  now that A.P. Green, North American 
Refractories, and Harbison-Walker are now all owned by some 
European company.  I use the website www.hwr.com that is a great 
site for locating nearest distributor, technical datasheetsl, product 
information, etc.

In the castable forge that I'm still messing with I used Mizzou 3000 
but was interested in reducing its thermal conductivity.  Mizzou has 
a number of 7.4 for thermal conductivity at 2000 degrees and the 
insulating castable (Kastolite 30 LI, for one) has a conductivity of 
4.4 at the same temperature which I think is quite a bit less but still 
no doubt much greater than an insulating blanket like Durablanket.  
I called a field rep and mentioned that I had heard that people  
make their own insulating refractory by adding perlite and/or 
vermiculite to the Mizzou.  I was surprised that he didn't pooh pooh 
the idea and said that he had heard the same thing and it might be 
worth a try.  Mizzou weighs 140 lbs per cu. ft. and Kastolite weighs 
90 lbs. per cu. ft. so I just added perlite and vermiculite (I forget the 
proportiions that were recommended to me) until I got about the 
density I wanted (90 lbs per cu. ft).  For all I know both additives 
may just create air space in the mix after the heat gets to them.

What the hell this long post has to do with the subject, I'll never 
know.  But personally, I wouldn't worry too much about damaging 
the castable in a reasonably sized dome unless the forge is 
dropped, etc. Anyone who has a castable forge with the experience 
of it would know much better than I would.

Sorry the post is so long.

Norm Larson