[TheForge] Castable Refractory

Sat May 17 01:06:01 2003

Hi Norm,

I asked the same question about 2 years ago and navigated through the advice
to end up with a forge I'm just tickled pink about.  I'll throw in a brief
description, hope it helps you decide on your design:

I used a hard castable which varies from 1.25 to 1.75" thick,  backed by 3"
ceramic fiber insulation - kaowool type.  The castable liner is supported
off the ceramic fiber with ceramic chairs you can get from Jay Hayes cheap
(on this list) .   Jay suggested the 3" insulation so I did it.  The outside
shell stays cool enough to touch.

I lined the inside of the ceramic fiber with the castable for durability and
to keep the ceramic fibers from my lungs.  There is an issue with the
castable getting white hot and burning out the flares (after many hot uses).
Openings for the burners flares should be oversized by at least 1/4" to line
with insulation to protect the flares.

The castable liner is a heat sink but also a flywheel if insulated.  It
takes 20 minutes to get it to forging temperature using low to forging
burner settings.  After I work for another half hour the liner starts to get
white hot and one could weld with no problem.  At this point the forge
should get just as hot as one without the castable.  Here's proof that it
gets hot enough to melt steel, anyway:
http://www.geocities.com/edsusenet/forge.html

A note on casting - I was told by the refractory tech. that the longer you
let it sit with, say, heatlamps, the better.  I did it for a couple days.
Then Jay suggested I close the ends with ceramic fiber or fire brick and use
a single burner and slowly increase the flame from lazy on up over a day.
He also warned me about propane's ability to lie low and mix with o2 until
it becomes explosive.  So I kept a sharp eye on the flame but it never went
out.

Also, I'd pick the guy's brains at Mizzou and get the specifics for your
refractory mix.  They may tell you 3" minimum wall thickness, but others on
the list had luck with theirs thin so I tried it too and also had luck.
There is one crack on the top, lengthwise where the burner holes are.  I was
told to put a relief joint in there when I cast it but I probably should
have.  A piece of tagboard would have done the job.  Anyway, the crack
happened right away and is no problem.  It's from tension created from
thermal expansion.

I can see the stainless reinforcing needles added to the mix helping a forge
that's not insulated and does not get white hot on the outside.  But with
the insulation, the castable is sort of in the oven, and I think the
stainless would deteriorate.  I was told by the refractory supplier that
they would, so I skipped it, and I tend to believe them now that I see it in
practice.

I use thin - about 1.25" - bricks for the floor.  I use the soft insulating
type castable to support the bricks at the wide spot in the circular area.
This, rather than a solid half-round,  keeps the mass of refractory to a
minimum and allows the forge to come up to temperature faster.

I cast about 1.5 to 2" soft refractory in the bottom of a 1 gal plastic ice
cream pails to make disks.  Cut them in half with a cheap wood saw, then
fired them like the liner.  They can be easily sanded with an angle grinder
or a rasp to fit, but I would wear a dust mask.  I just put the supports at
the brick joints.    I have recently replaced the floor because the bricks
were black from steel and dying from heat.  This time I had a wet tile saw
and it sure cut the brick nicely with it's diamond blade.

Good luck and have fun,

Ed

----- Original Message -----
From: <[email protected]>
To: <[email protected]>
Sent: Thursday, May 15, 2003 11:18 PM
Subject: [TheForge] Castable Refractory

> I know this has been discussed before on theforge but I didn't pay
> enough attention.  I have an atmospheric forge that works well and is
> lined with 2" of kaowool and then covered with ITC 100.
>
> Now I want to make a forge that is lined with Mizzou castable
> refractory 3000 degree.Just got the refractory today (55 lbs for
> $27.50)  but no info with it or on the bag as far as specifications or
> applications are concerned.  I assume I just mix water with it and not
> make it too soupy--I'll just wait plenty long for it to set up.  What I'm
> wondering is:
>
> Does it help to put a short metal rods, screws, or whatever through
> the sides of the forge to help hold the lining in place once dry?
> What's the best thing to use?
>
> What's the best way to make a removable form to fit the inside of the
> forge to shape the inside opening?
>
> What are the disadvantages and advantages of using castable
> refractory as opposed to kaowool or durablanket type insulation?
>
> Does Mizzou type material make a good floor for  a forge?
>
> I plan to make the forge out of about a 10" or 12" pipe with about a
> .09 wall and form a flat place in the pipe for the bottom of the forge.
>
> Been thinking about making the thickness of the insulation
> somewhere between 1.5 and 2 inches.  Will this be adequate?
>
> Any suggestions or tips anyone has will be truly appreciated.
> Thanks in advance for your help.
>
> Norm Larson
>
>
>
>
> _______________________________________________
> http://mailman.qth.net/mailman/listinfo/theforge
> theforge mail list group photo site is
> http://www.photoaccess.com
> Login:  [email protected]
> password:  anvil
> ___________
>
>
>
>