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Post by Geoffrey Levens on Jan 14, 2015 7:46:56 GMT -8
Considering these numbers and ignoring costs
14 firelay -melting point 3,240 °F
fire cement Fire cement (more is fine) -Meerco good to 3000 F
sodium silicate - Melting point 1,990°F
It seems to me with my VERY limited knowledge, that fireclay would hold up the longest under the highest temps found in the core. So what are reasons for using the other binders?
Also - 14 perlite - softening point 1560-1650 °F
1 having considerably lower melt point and I think lower than highest temps we are aiming for (?) is there something that is more robust vs temperature and is a good insulator? Maybe ceramic blanket stiffened from outside with...something?
Of course I am looking for the perfect core materials for high performance and 20 year working lifespan HAH!
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Post by matthewwalker on Jan 14, 2015 8:03:27 GMT -8
Perlite is a good insulator that works in these things, it may break down close to the burn but will still leave voids at that stage, so it's still serving it's function.
Fireclay/perlite is my initial mix. That's the structure and the insulation. My home core was just those two, and it showed no signs of breakdown after 3 seasons of constant use in my home. The addition of the Furnace Cement(used as a cheap easy route to add SoSi and some high alumina content clay to the mix) was just to help things kick off a bit so one could work with the core the next day instead of a month or two later. Without the "hardener" aspect of the SoSi the thing will stay soft for weeks for weeks. I'm not sure the SoSi adds anything long term, but it helps immensely in the initial build. I've always thought of it as a hardener, one that doesn't add much structural support.
I could be wrong about all of this, those are my thoughts and how I got to my mix. Others have different opinions, and Karl can tell us what is really going on. But, yeah, fireclay/perlite is the heart of the core material, the additives are just that, a little help to harden things up initially.
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Post by Geoffrey Levens on Jan 14, 2015 8:59:38 GMT -8
Thanks matt. Makes sense. That sort of covers my background thoughts of figuring out how to mechanically protect the ceramic mat is used in the casting of the firebox part of the core. I am planning on a bell mass, and tearing it apart every few years to rebuild the core was seeming a bit daunting.
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Post by Geoffrey Levens on Jan 14, 2015 10:47:52 GMT -8
Just had a thought....ooooo, there, I had another one!
I a bit hard imagine this actually happening, but then again...someone pulling a nicely functioning core that has seen heavy use and cutting the riser w/ a band saw at approx hottest zone. Looking at cross section might be fascinating. Could well be that inner perlite is gone but that as you move towards the perimeter, there is enough drop in temperature that at some point they are fully intact, with a gradation of damage along the way.
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Post by ericvw on Jan 14, 2015 15:23:30 GMT -8
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Post by Geoffrey Levens on Jan 15, 2015 7:40:29 GMT -8
Eric, OY! My head...it's about to explode. That is just the kind of thing I was thinking of
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