Construction of gas forge

[(M)]

I have my shell-propane tank, i'm going to cut it down to 8" and weld the rounded ends back on.  I dry-fitted the kaowool as shown.  That is a split concrete brick and a steel pipe as spacers.  Im gonna add a flat floor make of kaowool to the inside layer so that will make up the extra insulation.  

[Buzzkill]

Are you going to cut the tank lengthwise and have the forge body resting on a flat floor, or cast a flat floor without cutting the tank?   If you're going to cast it without cutting then it's easier to put kaowool where you have the bricks and pipe.  A little extra insulation on the bottom won't hurt anything and I can't think of any real advantage to other options. 

[Frosty]

The concrete brick won't survive long though the blanket above it should prevent pieces fro flying around the shop when it spalls to bits. It will however probably destroy the blanket while it's blowing itself to pieces. Portland cement concrete has no place inside a forge, heck they have to use a special mix in fireplaces and BBQs.

The pipe? Shouldn't hurt anything but you'll have a more efficient forge if you use ceramic blanket to make the floor. Remember to wear a mask and wet it down when cutting and stripping the edges to make smooth transition from floor to walls. Rigidize and cure of course before adding the flame face hard refractory inner liner.

Except for the concrete it looks good so far, you're on the right track.

Frosty The Lucky.

 

[(M)]

I'm not cutting the tank or casting a flat bottom, i want a mostly round chamber with a small flat floor.  I figure i might do a clamshell or something when i re-line it next.  I am going to make a flat kaowool flooor inside the round profile shown, providing the full 2" of kaowool for the floor, protecting thr concrete from any heat.  I figured it didnt really matter what i used for the spacer considering it is fully insulated like the rest of the tank.  I would use kaowool but i'm afraid i wont have enough to close off the one end and make an insulated door.  

Should i just do a small casting with the mizzou i have?? The issue here is that it needs to be like a circumference not like a chord if you get what i mean.  I still want a round chamber.  Maybe i should just buy some more kaowool and have 3" of insulation on the bottom... 

[Buzzkill]

Unless you line the rigidized kaowool with something that can handle hot steel and tongs poking it or dragging across it I think you'll find that the floor gets damaged quickly.  Two inches of kaowool should protect from most of the heat for sure.  After an hour or so of use I can usually touch my hand to the outer surface of the forge shell without burning myself, but it's too hot to rest my hand on it comfortably.  I cut my tank lengthwise and gave myself a clamshell option, but I mostly use it the conventional way.  I used perlite (because I happened to have some) in the bottom section to create a flat surface and support for the fiber blanket. After that it was two layers of one inch thick blanket followed by about 3/4 inch of Kastolite 30 (a half inch of Kastolite would probably have been enough).  That's not the only way to go, but it's a reasonably good way to go.  Perlite cannot handle the temperatures in the forge chamber itself, but it can easily deal with the heat that bleeds through the kastolite and two inches of fiber blanket.

If you plan to forge weld I highly suggest a removable flat floor piece, such as kiln shelf.  I didn't do that and let's just say that the flat floor is no longer flat due to the effects of the flux.  Granted I used too much flux at first and was a bit sloppy, but if you don't have experience forge welding with flux you may do something similar.

If you have some kiln shelf  you can probably press it into the fiber blanket on the floor after you wet it with rigidizer.  I'm guessing (but don't know for sure) that if you fire the forge with the shelf in place the rigidized blanket will stick to the kiln shelf, but if the blanket holds the shape of the shelf when fired then that could make a little "tray" to set it in and be easily removed/replaced as needed.  I may need to try that on my next forge or rebuild.

[(M)]

I'm lining everything including the kaowool floor with a solid 1/2" of mizzou, and i might get a kiln shelf if it doesnt stand up to use and possibly flux if i end up using it.  I might just pour mizzou in the bottom then, because i have it and obviously it can withstand temperature.  I might use sonotube( those concrete pillar pouring thingies)  as a form. Thanks!  Im just going with a simple round forge for now, and if i have something really big that wont fit then i'll probably use my JABOD or a stoked campfire.  

[Latticino]

In my experience Mizzou is fairly flux resistant, possibly not quite as much as greencast 97, but certainly adequate if you don't got crazy with the flux. Actually for most gas forges I recommend going with an oxide bearing flux made with anhydrous borax (Black Magic is the one I use) rather then bog standard 20 mule team.  It sticks in place better,  so you use less.  Of course fluxless is always an option. 

If cast a Mizzou cylinder,  make sure to allow for shrinkage as drying. 

[(M)]

Thanks! What dimension of shrinking should i watch out for?  It will be like a     "(" in shape, so will it decrease in diameter or length or just overall? 

[Latticino]

Diameter shrinking is where you may get cracking if you inner form does not allow for that (not to mention the difficulty of removing the form).  Casting a 1" thickness of mizzou can be a bit of a challenge in any case as you will need to tamp it down to fill the annulus.  Might be worth considering casting it in sections, a bit thicker, or using an inner form that will give a bit (I have successfully used rolled up vinyl flooring material in the past, or a tapered inner form that got removed once the castable has started to setup).

Sorry, I don't have info on shrinkage rates, but the manufacturer surely does.

Good luck and please continue to report on your progress.

[Frosty]

Do you use Greencast 97 currently? I picked up a bag before I discovered Kast-O-Lite 30. While more expensive it has to be about 2x as tough as the KastOLite. I liked it for being easier to use and work with, it's smoother with a less sharp aggregate and has a longer working time.

My first pipe forge had a rammed liner and the trick using Sono tube for forms is to remove them after the refractory sets but and let it cure in open air. I don't know about Mizzou but Greencast and Kastolite high alumina refractories don't dry, they set and cure just like Portland cement concrete, the binder is a calcium compound and behaves the same.

Once the refractory is set, give it a couple few hours and just peal the Sonotube like opening "Poppen Fresh Bisquits". Slitting the inner tube with a utility knife will make it easier.

Once stripped you want to keep the humidity at 100% for ideal cure strength. You can follow the same rules you would for concrete structures. Heck you could put it underwater for a week and only make it stronger. 

Frosty The Lucky.

[jeremy k]

3 minutes ago, Frosty said:

 Heck you could put it underwater for a week and only make it stronger. 

Frosty The Lucky.

Hummmm. Underwater forging.....never thought of that.

[JHCC]

7 minutes ago, jeremy k said:

Hummmm. Underwater forging.....never thought of that.

Best done with air-quenching steels.

[(M)]

This sounds like really a lot of work when i could just buy 5$ more kaowool.  Ill probably do that or see if what i have could work.  Thanks for the input, i'll keep you posted.

[Latticino]

1 hour ago, Frosty said:

Do you use Greencast 97 currently

Been almost 20 years since I used it last.  Thanks for prompting my memory.  Might have been the high temp insulating castable that I had trouble with on the molds, so go figure.  Ignore potential shrinkage warnings

[Frosty]

I'd have to go look in the bucket I have the Greencast in and sift the aggregate to see if it's rounded or crusher run. It was however WAY easier to work than KastOLite. I've sifted the aggregate out of the KastOLite so I could mix it with Zircopax and make a smooth flame face. The aggregate is all sharp crushed down to the sand, I used a loupe to take a look. I can't say about the fines but that's not as much a factor. Naw, I don't carry a loupe around like some kind of goofy Sherock Holmes but there's one in the top box I picked up for $10 at a shop sale. I sifted out the binder to experiment with making Kaowool structural enough to serve as the heart of a partition wall. Mixed with Zircopax it worked nicely as a flame face/ kiln wash.

If you mix the KastOLite as dry as recommended it's a real PITA to work and makes me understand why you see people hammering it on a flat surface then wrapping the form. 

Seeing as the last forge I built with the multiple orifice burners is too large I'll be making another when it warms up. I'm building that one in sections so I can hammer the KastOLite into a mostly flat form. It doesn't react to vibration very well unless it's really wet. Another sharp aggregate thing.

Who would've thought time in the soil's lab would be useful 40 years later. It's a good example of the old axiom, "there's no useless information" but . . . Grandma's . . . stories?

Frosty The Lucky.

[(M)]

Here's the near-finished dry-fit.  2" on the back, little shredded chunks to fill the holes that you can see.  Im going to cut a small hole in the back and have a split blanket kaowool to flatten the floor profile.  I forgot to wet it down when shredding the kwool so everything in my garage may be very itchy...

I am planning to have the burner horizontal at the top to induce a vortex so we'll see how that goes.  Started on cutting out the hole in the tank, once i finalize the position, i will cut the wool, weld on the burner holder and i should be off to the races.  

First pic is with just the outer layer, second is with full 2 layers.  

To start, firebricks will be the doors, but once i get more kwool and time i will figure out a swinging door.  

Please continue to critique!

[(M)]

I got the kaowool in, successfully rigidized, and mizzou casted all around pretty much 1/2" around evenly. Curing untill tomorrow afternoon.  It all went pretty smoothly, the burner FINALLY worked when it was in the forge to fire the kaowool.  Thanks for all your help and advice, i put it into practice and i couldnt be happier with the way the forge has turned out so far.  The picture is the firing of the rigidizing of the kaowool.  I will post pictures after the curing.  

@IronDragon Forge & Clay: sorry for ignoring you, the folks weren't comfortable at first with posting the location.  I'm southern ontario, Canada. 

Thanks again everyone !

[(M)]

I Got it all pretty much done! Just got the zirconium in yesterday and did some forging.  No legs yet.  The only problem is it doesnt want to get yellow hot.  Havent gotten anything to welding heat as of yet.  I am working outside so that may affect my colour perception.

 Should i need to max out the pressure on the burner to reach welding temps?

It is still running a bit oxidizing which i will need to fix, and my mig tip may be a tiny bit off centre but im not sure.  

I forged the hot cut and hold down in that forge.  It seems to heat up material quickly, but bright red/orange seems to be the max.   

Any help is appreciated.  

[Irondragon Forge ClayWorks]

On 4/15/2018 at 7:14 PM, (M) said:

I'm southern ontario, Canada. 

We won't remember this after leaving this thread. If you edit your profile to show location, it will show up with every post and we won't have to ask when answers depend upon location.

[(M)]

Done

[Buzzkill]

4 hours ago, (M) said:

 The only problem is it doesnt want to get yellow hot.  Havent gotten anything to welding heat as of yet.  I am working outside so that may affect my colour perception.

 Should i need to max out the pressure on the burner to reach welding temps?

It is still running a bit oxidizing which i will need to fix, and my mig tip may be a tiny bit off centre but im not sure.

Working in sunlight can definitely affect your color perception.  Slightly oxidizing tends to run hotter than slightly reducing though, so getting your burner tuned to neutral or reducing may decrease the heat you reach inside the forge.   Each DIY burner/forge combination is different so it's not likely we'll be able to tell you exactly what pressure you'll need for forge welding temperatures.  For a reference point though, I run about double the pressure to forge weld compared to forging.  That may or may not hold true for your setup.

[(M)]

Thanks Buzzkill! What pressure do you usually run the forge at?  I keep mine just above the point where it sputters for an idle when i take the piece out, and i would guess 10 or 15 psi or lower for forging.  I dont plan on doing much forge welding any time soon to be honest, but i do like to work mild steel at a lemon yellow. 

[Buzzkill]

My forge has a different shaped chamber and volume than yours and I'm running a naturally aspirated ribbon burner powered by a 1/2 inch Frosty T design, so the pressures I use are not in any real way relatable to your setup.  The stock I'm using at the time and my level of patience can also influence the pressure I use.  Having said that, I usually forge in the 7 to 10 psi range and bump up to about 20 psi for forge welding high carbon steels.

[(M)]

Good to know.  Thanks.  it has been interesting working with a propane forge instead of solid fuel for sure, but I really like it.  The heat control and lack of fire management are great.  I can be up and running in 15-20 min including setup compared to the 45 minutes with my charcoal.  Now that the important stuff is done I hope to get it totally finished and experiment with different heats and the like. and of course get on to forging stuff! 

Thanks again everyone!

(M)