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Jason Fry

Kast o Lite

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Anyone with experience know the difference in function between Kast o lite 25 and Kast o lite 30?  Local refractory supplier recommended a Plibrico LWI 24 insulating refractory, which google fu says is more like the Kast o lite 25 than the 30 that's often recommended.  

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Makes sense, but does that change its function as a forge liner?  Any ideas how the material reacts to flux?

I can tell you all about alloy elements in knife steel, but don't know how the different constituents of refractory products impact overall function.

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Is the Plibrico product a high alumina or silicate based refractory? Hot borax based fluxes are very caustic at welding temperatures and dissolve silicates. Lastly 2,500f isn't too hard to exceed with a well tuned propane burner, you CAN get one to exceed 3,000f but it's a PITA, unnecessary and makes for an oxidizing atmosphere in a forge.  BAD things.

If it's not too hard to get, I tend to buy products that exceed my expected needs, I'd be using Kastolite 90 if it wasn't crazy expensive up here. Kast-O-Lite-30 is becoming the preference by consensus for good reasons. 3,000 f., high alumina, concrete hard at 3,000 f. and structurally strong is hard to beat for what we need. That it's also a moderately effective insulator that'll extend the life of the ceramic blanket outer liner / insulation is gravy. 

With Kast-O-Lite products a kiln wash isn't actually necessary but one improves the efficiency and better still the effectiveness of your forge.

There are a lot of refractory products that'll work just fine, the important things to remember are the working temp needs to be higher than your expected max forge temp and 3,000 f. is a common industry standard max working spec for refractories and if you want to do any forge welding it needs to withstand HOT caustics. High alumina fills the bill and is also an industry standard for furnaces that need to withstand hot caustics. 

That's my reasoning.

Frosty The Lucky.

 

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Thanks, Frosty, that's a good step in the right direction. 

Here's the SDS.... I don't know if these numbers are "high" alumina or not.

http://plibrico.com/uploads/MSDS/sds Plicast LWI 24.pdf

My inclination at the moment is to cast my shells in this stuff, then put in a coating layer or two of other things.  Maybe a layer of satanite, then a matrikote/plistix/itc/your veegum mix type infrared reflective. 

I'm glad I make knives and not forges....

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I would not go with just a high alumina refractory. Kast-O-lite 30 is somewhat insulating too. If you use the Pilbrico product, you would do well to buy glass mini bubbles, and mix them in for insulation. If your hot-face refractory doesn't insulate better than straight high alumina refractory than don't expect your ceramic blanket to last very well; one of the many reasons we suggest using Kast-O-lite 30.

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I'm really not trying to be argumentative, just to learn... 

The Plicast LWI 24 is sold as a "lightweight" insulating refractory and comes in at 80 pounds per cubic foot.  Google says mizzou, for example, runs 141 pounds per cubic.

I should have listened to the forge building experts, not the guy who sells refractory for a living.  I would have thought that the rep would know his product better.

So back to my original question....  If I've got a 2500 degree "insulating" castable refractory that's 40% alumina and 40% silica, what do I lose by using it?  I mean, what are the tradeoffs?

I'm assuming a 2" wool/1/2" Kast o lite 30 forge as you guys have developed would be "more efficient" on fuel to some degree, which makes sense.  Any idea what kind of margin we're talking?  10% more propane use?  20%? 

Is a 40% alumina content high or low relative to the terms you've been using?  For example, "high carbon" steel has as little as .6 and as much as 1.2 percent carbon, which proportionally isn't very high relative to the other elements.  Help me understand the terms, please.  Again by comparison, google shows mizzou at 60% alumina and 32% silica.

I'm a hobby knifemaker.  Time is money, also, even though money is money as well.  I want a forge that I don't have to take a few days to rebuild once a year.  A day's work costs hundreds.  20% more propane in exchange for durability is a reasonable tradeoff to me. 

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Now you did it Jason, made me look up the product! You realize I'm going to have to get you for this don't you? :ph34r:

The guys selling the stuff we use to build forges NEVER know what we need, I suggest never asking their advice. It's not that they don't know their jobs, we're just doing stuff they don't kow anything about. Never NEVER tell the guys at the counter in a HVAC store you're building a propane burner! It's always been a bad move as long as I've been messing with this stuff.

Anyway, 40%  is about what everything not extravagantly expensive has for alumina content. The silicates tend to add up to about that too. It looks good to that point. The insulation is evacuated glass spheres which increases the silicate content. 

If I had the full selection of Plibrico products available I'd be thinking hard about the LWI-28 or 30 for the higher working max temp. 

Insulating with 2" of Kaowool is way more energy efficient than an insulating hard refractory, soft fire brick is a better insulator than insulting castable, it just has low survivability inn a forge. I can't tell you what the numbers are without guessing but I can say it's more efficient. Is it enough? It sure is if you add in the price of fire brick but that's not what we're talking about.

I think it's worth it in faster heat and saved fuel but that's opinion, NOT fact.

Frosty The Lucky.

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I used to sell Kast-0-Lite 26 as well as Kast-0-Lite 30.  There is so little cost difference that I dropped the 26.  I weld in my Ribbon Burner forge at +- 2300 degrees F  with out flux but I find that if I am not careful the temps can get up near 3000 degrees F.

Keep in mind that Kast-0-Lite is resistant to flux.

Let me know if I can help you.  You can find my contact info on my Profiles page.

Wayne

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Thanks for the endorsement of the 24/26 class material, Wayne.  

Google found this....  Looks like a heck of a technical manual of refractory products... Didn't read it diligently, but it's good science. 

http://mha-net.org/docs/Harbison Walker 2005 Handbook.pdf

Also found this... our friend Satan has 60% alumina and 34% silica and a 3200 degree rating.  

https://ssfbs.com/documents/SATANITE.pdf

I've got to try it, at least.  If I don't like it, I'll sell the forge and build another.  It may be like the time I upgraded from a 16 ft to a 19 ft boat, from 85 HP to 150.  The 150 got crap for gas mileage, but it was a better boat to fish out of.  The annoyance of the fuel use was overcome by other features.  

So I'll run the Plibrico 24 as my main insulator.  Throw a 1/8 or 3/16 of Satanite on top for added flux resistance and a bit better temp resistance.  Throw some reflective on top of that, and go for it.  This will be the horizontal forge.  

Then if it works well enough, I'll do the same in the vertical, although I may skip the Satanite since flux only hits the floor, which I plan to use kitty litter or crushed bricks or something else sacrificial.  

When all that bites, I'll sell these forges and build another vertical and switch back to wool, and follow your formula better.  

Just for fun, here's a shot of my current forge.  Wool was somewhat unknown, from a boiler in an oil refinery.  Clearly not rated high enough.  Satanite and ITC on top.  Melted into some green glass stuff.  Even that thin, the satanite coat held till I started breaking it on purpose.  I welded in this setup one time, and everything melted. 

 

IMG_3606.JPG

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5 hours ago, Jason Fry said:

I'm really not trying to be argumentative, just to learn... 

The Plicast LWI 24 is sold as a "lightweight" insulating refractory and comes in at 80 pounds per cubic foot.  Google says mizzou, for example, runs 141 pounds per cubic.

Kast-O-lite 30, which is rated for a further 600 degrees is also the same weight per cubic foot, but just go on ahead and have your druthers.

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Alright, so I'm making another run at the refractory guy to see if he can get the Plibrico products that are better suited to this task. 

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I understand wanting to use a convenient local source of refractory; I'm only suggesting that an additional product, which you can buy cheaply on eBay, would probably make their version of a refractory with a higher temperature rating a more practical choice. 

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Personally I'd order the kastolite from Wayne. It's very tough stuff!  If you go with the other it may fail and you'll be spending way more $ in the long run.  Do you want to spend your time messing with forges or actually forging??

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